Amelioration of Acute Radiation Dermatitis in Breast Cancer Patients by a Bioadhesive Barrier-Forming Gel (Episil): A Single-Center, Open, Parallel, Randomized, Phase I/II Controlled Trial

Episil is a bioadhesive barrier-forming liquid gel that can relieve mucositis caused by radiotherapy (RT) and effectively relieve pain. The purpose of this trial is to compare the efficacy and safety of Episil in improving acute radiation dermatitis (ARD) in patients with breast cancer. This study included patients who met the criteria for postoperative RT for breast cancer. The primary end point was the grade of RD during treatment. A total of 102 patients were included in this study. The patients were grouped in a 2:1 ratio using the randomized number table method: 67 patients received Episil combined with conventional skin care (the Episil group), whereas the remaining 35 patients served as the control group and received conventional skin care only (the control group). According to the grading criteria of the Radiation Therapy Oncology Group (RTOG), the skin reaction rate and severity were significantly better in the Episil group than the control group (24.62%, 72.31%, 3.08, 0, 0 vs. 0, 85.71%, 14.29%, 0, 0, 0) across grades 0 to 4 (P < 0.05). The itchiness score exhibited s significant reduction in the Episil group as compared with the control group (P < 0.05). The results of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) showed that the overall health (z = -5.855, P < 0.001) and overall quality of life (z = -6.583, P < 0.001) were better in the Episil group than the control group after RT. Overall, in patients with breast cancer receiving RT, the topical application of Episil may significantly reduce the grading of ARD, alleviate patient symptoms, and improve the patient's overall quality of life.

Assessment of the color stability of two silicone elastomers for maxillofacial prostheses upon exposure to cold beverages

PURPOSE

This study investigated the color stability of different commercially available silicone materials for facial prostheses upon exposure to everyday beverages. It was hypothesized that the beverages would not alter the color of the silicone under conditions simulating daily exposure.

METHODS

Sixty specimens were fabricated using two materials - VST-50 and Silfy - and exposed to commercially available cold mineral water, tea, or coffee. Specimen color was evaluated on days 1 and 15. The color was measured with a spectrophotometer based on CIELab system and color differences were calculated as ΔE. Statistical analysis was performed using the Kruskal-Wallis test and Mann-Whitney U test.

RESULTS

The mean ΔE values after 15 days of exposure to mineral water, cold green tea, and coffee were 1.016, 3.480, and 3.636 for VST-50 and 0.440, 0.798, and 1.425 for Silfy, respectively. Both materials showed significant differences in color, and VST-50 showed a greater color change than Silfy, especially for coffee.

CONCLUSION

Pigmented silicone elastomers have low color stability, leading to an overall color change in silicone prostheses when exposed to pigmented beverages. Color changes in such prostheses can be mitigated by selecting materials with better color stability to extend their longevity.

Complications of foldable intraocular lenses requiring explantation or secondary intervention: 2022 survey with update of long-term trends

PURPOSE

To assess the complications that resulted in the explantation or secondary intervention with foldable intraocular lenses (IOLs).

SETTING

University setting, Salt Lake City, Utah.

DESIGN

Survey study.

METHODS

For the 25th consecutive year, surgeons were surveyed regarding complications associated with foldable IOLs requiring explantation or secondary intervention over the 2022 calendar year. These forms were made available online using the ASCRS and ESCRS websites and a fax-on-demand service. Surgeons completed 1 survey for each foldable IOL requiring explantation or secondary intervention. Further analysis determined complication trends related to specific IOL styles, materials, and types over the past 16 years (2007 to 2022).

RESULTS

103 completed surveys were returned in 2022 contributing to a total of 1627 tabulated surveys since 2007. In the 2022 survey, dislocation/decentration continued to be the most common complication overall. Glare/optical aberrations was a common complication associated with multifocal IOLs continuing a 16-year trend. In addition, hydrophilic acrylic IOLs as well as some silicone lenses in eyes with asteroid hyalosis demonstrated calcification as the most common complication necessitating explantation.

CONCLUSIONS

Dislocation/decentration remains the leading cause of explantation in most IOL types. Glare/optical aberrations continue to be an associated complication of multifocal IOLs suggesting this ongoing issue has yet to be resolved with this type of IOL. In addition, calcification of hydrophilic acrylic lenses and silicone lenses is a rare event but continues to occur.

Adhesive strength of 3 long-term resilient liners to CAD-CAM denture base polymers and heat-polymerized polymethyl methacrylate with thermocycling

STATEMENT OF PROBLEM

Computer-aided design and computer-aided manufacturing (CAD-CAM) technologies have become popular for manufacturing complete dentures. However, the adhesive strength of resilient liners to the polymers used to fabricate CAD-CAM complete dentures is unclear.

PURPOSE

The purpose of this in vitro study was to determine the adhesive strength of 3 long-term resilient liners to CAD-CAM denture base polymers and heat-polymerized PMMA with thermocycling.

MATERIAL AND METHODS

A total of 90 specimens were fabricated, 30 per group of denture base material (Lucitone 199, Ivo Base CAD, Denture Base LP). For each denture base polymer, 10 specimens were relined with 1 of 3 resilient liners (Permasoft, Mucopren Soft, Molloplast-B). Five specimens of each group were thermocycled, and the other 5 specimens were stored in distilled water. Subsequently, the adhesive strength of the specimens was assessed by tensile testing. The resulting data were analyzed by using a 3-way analysis of variance (ANOVA) (α=.05).

RESULTS

After thermocycling, the adhesive strengths of all the resilient liners were found to be statistically different from each other for the same denture base polymer (P≤.012). Mucopren Soft displayed a high mean ±standard deviation adhesive strength to Lucitone 199 (1.78 ±0.32 MPa), followed by Molloplast-B (1.27 ±0.21 MPa) and Permasoft (0.66 ±0.06 MPa). For Ivo Base CAD, Molloplast-B exhibited a high mean ±standard deviation adhesive strength (1.70 ±0.36 MPa), followed by Mucopren Soft (1.11 ±0.16 MPa) and Permasoft (0.53 ±0.04 MPa). Molloplast-B displayed high mean ±standard deviation adhesive strength to Denture Base LP (1.37 ±0.08 MPa), followed by Mucopren Soft (0.68 ±0.20 MPa) and Permasoft (0.32 ±0.04 MPa). The adhesive strength of the majority of resilient liners not exposed to thermocycling was statistically different from each other for the same type of denture base polymer (P<.001). The only exception was the difference between the adhesive strength of Molloplast-B and Mucopren Soft to Lucitone 199 with mean ±standard deviation values of 1.42 ±0.18 and 1.66 ±0.40 MPa, respectively, (P=.067). Without thermocycling, the mean ±standard deviation adhesive strength to Lucitone 199 of Permasoft (0.57 ±0.02 MPa) was statistically different from that of Molloplast-B and Mucopren Soft (P<.001). Molloplast-B displayed a high mean ±standard deviation adhesive strength to Ivo Base CAD (1.83 ±0.25 MPa), followed by Mucopren Soft (1.26 ±0.19 MPa) and Permasoft (0.58 ±0.08 MPa). Molloplast-B displayed a high mean ±standard deviation adhesion to Denture Base LP (1.76 ±0.23 MPa), followed by Mucopren Soft (0.88 ±0.14 MPa) and Permasoft (0.25 ±0.06 MPa). Only Molloplast-B was significantly adversely affected by thermocycling (P=.009).

CONCLUSIONS

Molloplast-B displayed high adhesive strength to both CAD-CAM denture base polymers regardless of the storage conditions. Mucopren Soft displayed high adhesion to Lucitone 199. Permasoft presented moderate adhesion to PMMA-based denture bases and low adhesion to DBLP. Combining Permasoft with Denture Base LP should be considered carefully and limited to short-term use. Thermocycling had a detrimental effect on the adhesive strength of Molloplast-B.

A novel method for the accurate quantification of two isomeric mercapturic acids of 1,3-dichlorobenzene in human urine using isotope dilution online-SPE-LC-MS/MS

1,3-dichlorobenzene (1,3-DCB) is an aromatic solvent that might be formed during thermal decomposition of bis(2,4-dichlorobenzoyl)peroxide used as initiator in silicone rubber production with many workers exposed worldwide. During metabolism of 1,3-DCB, two isomeric mercapturic acids can be formed from ring oxidation of 1,3-DCB in the liver, namely 2,4-dichlorophenylmercapturic acid (24CPhMA) and 3,5-dichlorophenylmercapturic acid (35CPhMA). These urinary mercapturic acids might serve as biomarkers of the toxicologically relevant absorbed dose of 1,3-DCB and have not been determined so far. Thus, we were aimed to develop an analytical method for quantification of these biomarkers. Authentic standards of both mercapturic acids as well as deuterium-labelled analogues were self-synthesized. A method for the quantification of both CPhMAs in human urine using online-SPE LC/MS/MS was developed and validated with an LOQ of 0.1 ng mL-1 for both CPhMAs. The analytes were extracted from urine by online-SPE on a restricted access material phase, transferred to the analytical column and quantified by tandem mass spectrometry. Interday (n = 6) and Intraday (n = 10) precision for both CPhMAs ranged from 1.7 to 4.3 % with accuracies between 99.4 and 109.9 % at concentrations of 0.6 and 3 ng mL-1. We applied the method on post-shift urine samples of 16 workers of the silicone rubber industry with occupational exposure to 1,3-DCB. Both CPhMAs were above LOQ in 15 of 16 urine samples with median levels (range) for 24CPhMA and 35CPhMA of 1.64 ng mL-1 (<0.1 - 8.2 ng mL-1) and 3.98 ng mL-1 (0.36 - 24.1 ng mL-1), respectively. This is the first report on specific urinary mercapturic acids of 1,3-DCB in humans. Our results show that ring oxidation of 1,3-DCB is considered to be a toxicologically relevant metabolic pathway in humans. This might improve risk assessment of 1,3-DCB-emissions in silicone rubber industry.

Super-tough poly(lactic acid)/silicone rubber thermoplastic vulcanizates: The organic and inorganic synergistic interfacial compatibilization

Polymer modification using silicone rubber represents a promising avenue for enhancing physico-mechanical properties. However, achieving optimal performance through direct blending is hindered by the poor interface compatibility between silicone rubber and the matrix. In this study, we prepared super-tough thermoplastic vulcanizates (TPVs) of polylactic acid/silicone rubber through dynamic vulcanization with PLA, methyl vinyl silicone rubber (MVQ), glycidyl methacrylate grafted MVQ (MVQ-g-GMA), and fumed silica nanoparticles (SiO2). The impact of the SiO2 addition in MVQ on the morphology, mechanical properties, crystallization, and thermal properties of the TPVs was investigated. The results showed that MVQ-g-GMA and SiO2 exhibited a synergistic compatibilization effect significantly improving the interfacial adhesion between PLA and MVQ. Therefore, the impact and tensile strength of the TPVs increased from 8.0 kJ/m2 and 22.2 MPa to 62.6 kJ/m2 and 36.7 MPa, respectively. Moreover, the TPVs also presented good low-temperature toughness with a maximum impact strength of 40.4 kJ/m2 at -20 °C. Additionally, improvements in thermal stability and crystallization rate were also observed. Overall, combining organic and inorganic synergistic compatibilization is a feasible and effective method to fabricate outstanding low-temperature toughness to PLA.

Microwave disinfection of facial silicone prostheses, part 2: Mechanical properties

STATEMENT OF PROBLEM

Part 1 of this 2-part study determined that microwave disinfection did not degrade the color stability of facial silicone prostheses. However, investigations on the effects of microwave disinfection on the mechanical properties of different silicone elastomers are lacking.

PURPOSE

The purpose of this in vitro study was to examine the mechanical properties of commonly used colored facial silicone elastomers before and after microwave disinfection over a simulated 1.5-year period.

MATERIAL AND METHODS

Six commonly used facial silicone elastomers: MDX4-4210, MDX4-4210/Type A, M511, A-2186, VST-50, and A-2000 were combined with functional intrinsic silicone pigments and opacifier (red, yellow, blue, and white). A total of 288 specimens were fabricated (n=12). Half of the specimens were tested for mechanical properties as the baseline, while the other specimens were tested after microwave disinfection. Microwave disinfection was performed with 660 W, 6 minutes of exposure time, and microwaved for 18 cycles to simulate 1.5 years of usage (one 6-minute exposure monthly). For mechanical property testing, all specimens were tested for tensile strength and percentage elongation (ASTM D412), tear strength (ASTM D624), and hardness (ASTM D2240). For each property, a 2-way ANOVA (silicone type and microwave disinfection factors) and Tukey multiple comparison test were performed using the R statistical software program (α=.05).

RESULTS

Following microwave disinfection, tensile strength and percentage elongation of A-2000 increased significantly (P<.05). MDX4-4210, MDX4-4210/Type A, and A-2000 showed significant increases in their hardness (P<.001). Tear strength also increased significantly for MDX4-4210 and VST-50 (P<.05). Among the materials tested (ranked from highest to lowest value,=not statistically significant different), for tensile strength, VST-50>A-2186=A-2000>MDX4-4210/Type A=M511=MDX4-4210 (P<.05). For percentage elongation, VST-50>MDX4-4210/Type A>A-2186>M511=A-2000=MDX4-4210=M511 (P<.05). For hardness, A-2000=A-2186>M511=VST-50>MDX4-4210>MDX4-4210/Type A (P<.05). For tear strength, VST-50>A-2186>A-2000>M511>MDX4-4210/Type A=MDX4-4210 (P<.05).

CONCLUSIONS

Overall, the mechanical properties of all the silicones tested were not adversely affected by microwave disinfection. VST-50 showed the best mechanical properties among the materials tested both before and after microwave disinfection. Microwave energy is a safe method of disinfecting the silicone elastomers tested in this study.

Varying material thickness of silicone rubber for tunable nitric oxide release

Silicone rubber (SR), a common medical-grade polymer used in medical devices, has previously been modified for nitric oxide (NO) releasing capabilities. However, the effects of material properties such as film thickness on NO release kinetics are not well explored. In this study, SR is used in the first analysis of how a polymer's thickness affects the storage and uptake of an NO donor and subsequent release properties. Observed NO release trends show that a polymer's thickness results in tunable NO release. These results indicate how crucial a polymer's thickness is to optimize the NO release in an efficient and effective method.

A novel Foley catheter made of high-intensity near-infrared fluorescent silicone rubber for image-guided surgery of lower rectal cancer

BACKGROUND

Urethral injury occurs in 1-6 % of male cases during minimally invasive surgery of lower rectal cancer. A Foley catheter emitting near-infrared (NIR) fluorescence of sufficient intensity has been expected to locate the urethra during image-guided surgery. Although it has been difficult to impart NIR fluorescent properties to biocompatible thermosetting polymers, we have recently succeeded in developing a NIR fluorescent compound for silicone rubber and a NIR fluorescent Foley catheter (HICARL). Here, we evaluated its NIR fluorescence properties and visibility performance using porcine anorectal isolation specimens.

METHODS

The HICARL catheter was made of a mixture of solid silicone rubber and a NIR fluorescent compound that emits fluorescence with a wavelength of 820-880 nm, while a conventional transparent Foley catheter was made of solid silicone rubber only. As a standard for comparison of the intensity of NIR fluorescence, a transparent Foley catheter the lumen of which was filled with a mixture of indocyanine green (ICG) and human plasma was used. As a comparison to assess the visibility performance of the HICARL catheter, a transparent Foley catheter into which a commercially available NIR fluorescent polyurethane ureteral catheter (NIRC) was placed was used.

RESULTS

A NIR fluorescence quantitative imaging analysis revealed that the Foley-NIRC catheter and the HICARL catheter emitted 3.42 ± 0.42 and 6.43 ± 0.07 times more fluorescence than the Foley-ICG catheter, respectively. The location of the HICARL catheter placed in the anorectum with a wall thickness of 3.8 ± 0.1 mm was clearly delineated in its entirety by NIR fluorescence, while that of the Foley-NIRC catheter was faintly or only partially visible.

CONCLUSIONS

The HICARL catheter emitting NIR fluorescence of sufficient intensity is a promising and easy-to-use tool for urethral visualization during image-guided surgery of lower rectal cancer.

Steam disinfection enhances bioaccessibility of metallic nanoparticles in nano-enabled silicone-rubber baby bottle teats, pacifiers, and teethers

Nano-enabled silicone-rubber articles for feeding or chewing could be a source of metallic nanoparticles (NPs) directly exposed to infants and young children. However, the impact of steam disinfection on release of NPs and the related potential risks to children's health are unknown. Here, we investigated contents and form of Ag and Zn in 57 nano-enabled silicone-rubber baby bottle teats, pacifiers, and teethers of seven countries and examined the impacts of steam disinfection on in vitro bioaccessibility (IVBA) of Ag and Zn in the articles. Nearly 89% articles had a mixture of Ag- and Zn-containing NPs and the teethers had relatively high Ag and Zn contents (up to 501 and 254 µg/g, respectively). Steam disinfection caused rubber decomposition into micro(nano)plastics (0.54-15.7 µm) and NP release from the interior of bulk rubber and micro-sized plastics, thus enhancing the IVBA of Ag and Zn by up to 5.5 times. The findings provide insights into mechanisms for NP release by steam disinfection. Though oral exposure risk assessment suggested low health concerns on individual metal release, our study points out the need to assess the potential health risks of child co-exposure to metallic NPs and micro(nano)plastics.

Working viscosity and non-Newtonian behavior of silicone denture liners

PURPOSE

To evaluate flow profile and non-Newtonian behavior of 10 different silicone lining materials.

METHODS

Ten commercially available silicone lining materials were selected for evaluation. The flow profile and non-Newtonian behavior of each material was measured using a shark fin testing method. Fin height and resultant base thickness were measured with a digital caliper and compared with one-way ANOVA and Student-Newman-Keuls post hoc test and fin base by Kruskal-Wallis one-way ANOVA on ranks with Dunn post hoc test with significance at P< 0.05 for both.

RESULTS

Shark fin heights ranged from 9.62 ± 0.86 mm [Reline II (Soft)] to 25.54 ± 0.43 mm [Sofreliner (Medium)]. Shark fin bases ranged from 2.57 ± 0.51 mm [Sofreliner (Medium)] to 10.31 ± 0.57 mm [Reline II (Soft)]. Statistically significant differences were found between certain samples' shark fin heights as well as resultant bases (P< 0.05) indicating different rheological properties.

CLINICAL SIGNIFICANCE

Silicone liner materials differ significantly with respect to flow profile and non-Newtonian behavior. While a high flow profile (low viscosity) of an elastomeric impression material improves accuracy, it may be a detriment to a denture lining material that must achieve a critical minimum thickness to provide resilience. Likewise, a low flow profile (high viscosity) material may also pose a disadvantage, requiring excessive compression and possible tissue distortion to achieve the same critical thickness. The results of this study should be considered when selecting the appropriate material for clinical application. Additional studies are indicated to further quantify rheological properties as well as correlate them to physical properties after the complete cure of the material.

Inhalation of gaseous hypochlorous acid and its effect on human respiratory epithelial cells in laboratory model systems

During the disinfection of indoor spaces using gaseous hypochlorous acid (HOCl(g)), inhalation is the most common route of exposure for humans. In this study, an artificial human respiratory tract model was exposed to 12-140 ppb HOCl(g) at an aspiration flow rate of 800 mL/s for 15 h in a 1 m3 chamber. The respiratory tract model was equipped with 5th order bronchi and all gas-contact parts were made of silicone rubber with no other chlorine-consuming substances. The concentration of HOCl(g) reaching the lung pseudo-space was approximately 47.4% of the HOCl(g) concentrations in the chamber and was calculated to be very close to zero when the chamber concentration was less than 20.5 ppb. The disappearance of HOCl(g) during inhalation is likely due to the adsorption of HOCl(g) on the gas-contact silicone rubber surfaces. The cytotoxicity of HOCl(g) on respiratory epithelial cells was also examined using human air-liquid-interface airway tissue models. Human nasal epithelium and bronchiolar epithelium were exposed to 100 ppb and 500 ppb HOCl(g) for 8 h and 5 d, respectively. No significant effects of HOCl(g) on cell viability and ciliary activity were observed in any cell type, indicating that low concentrations of HOCl(g）, less than 500 ppb, had no cytotoxic effect.

A Systematic Review on Maxillofacial Prosthesis with Respect to Their Color Stability

The aim of this systematic review was to identify and analyze the findings of various studies that analyzed the changes in the color stability of maxillofacial prosthetic materials after the addition of various colorants and nanoparticles and assess the change in color after being subjected to either natural or artificial accelerated aging as well as outdoor aging. This systematic review was conducted in accordance with the guidelines of transparent reporting of systematic reviews and meta-analysis (PRISMA Statement). The primary objective of this systematic review was to evaluate the color stability of maxillofacial prosthesis. The secondary objective was to assess the effect of various colorants; pigments; opacifiers; UV absorbers-such as inorganic colorants (dry earth pigments); metal oxides; and organic colorants. The time period of the included studies extended from 2013 to 2023. Electronic database search identified a total of 217 studies. Ten studies were included to meet the research question. All 10 included studies analyzed the effect of various colorants and their exposure to various aging and weathering conditions. It was found that various pigments and nanoparticles had an effect on the color stability. Also weathering and aging conditions had a direct effect on the color stability as well. In terms of disinfection, although there was not much color difference observed, highest change in color stability was observed when rubbing or brushing of the prosthesis was carried out. In conclusion, the color stability of maxillofacial prosthetics is a critical factor that influences both patient satisfaction and the overall cosmetic look. The potential of pigments and nanoparticles to enhance the color stability of silicone-based maxillofacial prosthesis has received much research. By avoiding color fading and discoloration brought on by environmental variables including UV radiation, aging, and chemical exposure, the inclusion of various pigments and nanoparticles has been demonstrated to improve the color stability of silicone maxillofacial prostheses.

Analysis of Individualized Silicone Rubber Bolus Using Fan Beam Computed Tomography in Postmastectomy Radiotherapy: A Dosimetric Evaluation and Skin Acute Radiation Dermatitis Survey

Objective: To investigate the dosimetric effects of using individualized silicone rubber (SR) bolus on the target area and organs at risk (OARs) during postmastectomy radiotherapy (PMRT), as well as evaluate skin acute radiation dermatitis (ARD). Methods: A retrospective study was performed on 30 patients with breast cancer. Each patient was prepared with an individualized SR bolus of 3 mm thickness. Fan-beam computed tomography (FBCT) was performed at the first and second fractions, and then once a week for a total of 5 times. Dosimetric metrics such as homogeneity index (HI), conformity index (CI), skin dose (SD), and OARs including the heart, lungs, and spinal cord were compared between the original plan and the FBCTs. The acute side effects were recorded. Results: In targets' dosimetric metrics, there were no significant differences in Dmean and V105% between planning computed tomography (CT) and actual treatments (P > .05), while the differences in D95%, V95%, HI, and CI were statistically significant (P < .05). In OARs, there were no significant differences between the Dmean, V5, and V20 of the affected lung, V5 of the heart and Dmax of the spinal cord (P > .05) except the V30 of affected lung, which was slightly lower than the planning CT (P < .05). In SD, both Dmax and Dmean in actual treatments were increased than plan A, and the difference was statistically significant (P < .05), while the skin-V20 and skin-V30 has no difference. Among the 30 patients, only one patient had no skin ARD, and 5 patients developed ARD of grade 2, while the remaining 24 patients were grade 1. Conclusion: The OR bolus showed good anastomoses and high interfraction reproducibility with the chest wall, and did not cause deformation during irradiation. It ensured accurate dose delivery of the target and OARs during the treatment, which may increase SD by over 101%. In this study, no cases of grade 3 skin ARD were observed. However, the potential of using OR bolus to reduce grade 1 and 2 skin ARD warrants further investigation with a larger sample size.

Occidiofungin inhibition of Candida biofilm formation on silicone elastomer surface

IMPORTANCE

Candida are opportunistic fungal pathogens with medical relevance given their association with superficial to life-threatening infections. An important component of Candida virulence is the ability to form a biofilm. These structures are highly resistant to antifungal therapies and are often the cause of treatment failure. In this work, we evaluated the efficacy of the antifungal compound, occidiofungin, against Candida biofilms developed on a silicone surface. We demonstrate that occidiofungin eliminated cells at all stages of biofilm formation in a dose-dependent manner. Consistent with our understanding of occidiofungin bioactivity, we noted alterations to actin organization and cell morphology following antifungal exposure. Given the challenges associated with the treatment of biofilm-associated infections, occidiofungin exhibits potential as a therapeutic antifungal agent in the future.

Alternative Techniques To Remove Retained Silicone Oil Droplets On IOLs

BACKGROUND/PURPOSE

To describe several modified approaches to remove retained silicone oil droplets on intraocular lens (IOLs).

METHODS

Four novel techniques for removing retained silicone oil droplets on IOLs were described.

RESULTS

All four techniques led to an improved IOL with a good view to the posterior segment. No intraoperative or long-term postoperative complications have been seen in any of these eyes. These modified approaches are safe, efficient, low cost, and use existing vitreoretinal operating room supplies to add to the vitreoretinal surgeon's armamentarium to clear retained IOL silicone droplets.

CONCLUSION

It is advocated for having multiple techniques at the disposal of the vitreoretinal surgeon to address retained silicone oil on IOLs. Being able to use multiple techniques may not be superior than a single approach but is often necessary to accomplish the surgical goal of removing these adherent droplets.

Effect of titanium dioxide nanocoating on the colour stability of room temperature vulcanizing maxillofacial silicone-an invitro study

OBJECTIVE

The aim of this in vitro study was to evaluate the effect of an oxide nanocoating to prevent colour degradation of maxillofacial silicone elastomers following accelerated ageing.

MATERIAL AND METHODS

Specimens (N = 40) of specified dimensions were fabricated in Factor II room temperature vulcanizing (RTV) silicone and processed according to the manufacturer's instructions. Two groups were classified with 20 specimens each. Specimens in the first group were coated with titanium dioxide (TiO2) by atomic layer deposition technology. The colour stability test was conducted with a UV-VIS spectrometer (Schimadzu) for both titanium dioxide nanocoated and uncoated specimen groups after subjecting them to accelerated ageing. It was analysed using the CIE L*a*b method.

RESULTS

The average colour change was highest for uncoated specimens (2.868), and the average colour change for titanium dioxide-coated specimens was significantly low (1.774). The average colour change of uncoated specimens (2.868) was close to the acceptable threshold value (3), and that of coated specimens (1.774) was far below the acceptable threshold (3).

CONCLUSIONS

The colour change that occurred in titanium dioxide nanocoated specimens following accelerated ageing was significantly lower than that in the uncoated group, showing that the TiO2 nanocoating was effective in reducing the colour degradation of silicone elastomers.

CLINICAL RELEVANCE

Maxillofacial prostheses fabricated from silicone elastomers go through undesirable colour degradation over time. The development of a scientific technique that retards the colour deterioration of silicone prostheses would be of great clinical significance.

SCLERAL SUTURE FIXATION FOR DISLOCATED SILICONE PLATE HAPTIC INTRAOCULAR LENS

PURPOSE

To describe results in two cases of a dislocated silicone plate haptic intraocular lens managed with vitrectomy and repositioning with scleral suture fixation.

METHODS

Small case series.

RESULTS

Two patients presenting with dislocated silicone plate haptic intraocular lens underwent a 23-gauge vitrectomy with a "handshake" maneuver to pass a 9-0 prolene suture through the positioning holes to allow scleral fixation. Best-corrected visual acuity was returned to predislocation Level 2 and 8 months after the vitrectomy.

CONCLUSION

Silicone plate haptic intraocular lens can be managed with scleral suture fixation using this adapted technique, avoiding removal and exchange techniques. These are the first reported cases of silicone plate haptic intraocular lens managed with scleral suture repositioning.

[Gentle Method to Elevate Left Liver Lobe in Robot Assisted Gastrectomy]

Robot-assisted gastrectomy with the Davinci XiTM has been performed in our department since August 2019. This technique requires elevation of the left liver lobe. In order to prevent perioperative liver injury and expansion of postoperative subcutaneous emphysema, we use a silicone disc(HAKKO MEDICAL Co., Ltd.)and thread to elevate the liver. After docking the Davinci system, we move the needle as follows:(ⅰ). left side peritoneum near the left triangular ligament, (ⅱ). silicone rubber(, ⅲ). center of crus(, ⅳ). silicone rubber(, ⅴ). hepatic cirrus, and(ⅵ). right side peritoneum. Both ends of the thread are guided out of the abdominal cavity from both hepatic circumflex by end-close, forming a V-shape with the center of crus at the bottom, which provides a stable and effective view of the liver. Fifty-three cases were performed after introduction of this elevation technique. Median AST and ALT on postoperative day 1 were 37(14-1,556)IU/L and 30(10- 1,676)IU/L, respectively, although small subcutaneous emphysema confined to the anterior chest and upper abdominal wall was observed in 2 patients(3.8%). No cases of extensive subcutaneous emphysema involving the neck or extremities were observed. This elevation technique protects the liver and may reduce the incidence of postoperative subcutaneous emphysema.

An investigation of the effects of topical sunscreen protection products under natural weather conditions on intrinsic color stability in maxillofacial silicones

Aim

The relatively short lifespan of maxillofacial prostheses (ranging from 3-24 months) is mostly a result of colour instability of silicone elastomers caused by ultraviolet (UV) radiation, requiring frequent remakes. An improvement in colour preservation could result in fewer remakes, thus saving time and money for both clinician and patient. In the quest for a suitable colour protection method, sunscreen protection products were considered; the most recent study on this subject was carried out in 1994, albeit using a low protection factor. The aim of this research was to determine if there is value in using topical sun protection products on extraoral silicone prostheses to prevent colour degradation.

Settings and Design

This was an in vitro quantitative study.

Materials and Methods

Three commercially available sunscreen products were studied, Riemann P20, Boots Soltan, and Garnier Ambre Solaire all with a sun protection factor of 50. A total of 144 silicone elastomer samples were produced using a Caucasian (light) shade 1.2 (n = 72) and dark skin shade 3.2 (n = 72) from the Technovent Ltd. Reality Shade range. Each shade group (n = 72) was divided into three groups to be subjected to outdoor weathering (n = 24), indoor (n = 24), and dark storage (n = 24). Within each environmental group, samples were divided into groups of six samples (n = 6) to receive the three sunscreens plus a control group with no sunscreen. The CIEL* a* b* formula was used to obtain the color measurements.

Statistical Analysis Used

One way ANOVA test and Tukey's HSD test for multiple comparisons was used to analyse the data.

Results

The ΔE values had changed for all samples throughout the aging process.

Conclusion

Soltan showed promising results in protecting the dark-shaded samples in the outdoor environment only.

The impact of zirconium dioxide nanoparticles on the color stability of artificially aged heat-polymerized maxillofacial silicone elastomer

The limited service life of craniofacial prostheses due to degradation and color instability is a significant challenge. This in vitro study aimed to determine how zirconium dioxide (ZrO2) nanoparticles affect the color stability of M511 heat temperature vulcanizing (HTV) maxillofacial silicone elastomers after artificial aging. ZrO2 nanoparticles were added at concentrations of 1, 2, and 3 wt% to M511 HTV silicone elastomer. Two intrinsic silicone pigments were used (red and mocha). Silicone with pigment and without ZrO2 nanoparticles were used as the control. Eighty disk-shaped specimens were fabricated and divided into eight experimental groups, each containing ten specimens (n = 10). All specimens were subjected to artificial aging, and color changes were recorded at 252, 504, and 1008 h intervals. The L*a *b * values were measured using a colorimeter and the CIE-Lab system. To interpret the recorded color differences, a 50:50 percent perceptibility threshold (ΔE* = 1.1) and acceptability threshold (ΔE* = 3.0) were implemented. A one-way analysis of variance and Tukey's post hoc test at a significance level of 0.05 were used for the statistical analysis. We found that every evaluated specimen group exhibited a chromatic change (ΔE* > 0). The ΔE* values for the mocha pigments with and without ZrO2 nanoparticles were below the perceptible threshold (1.1 units). The ΔE* values of the red pigment with and without ZrO2 nanoparticles were significantly higher than the acceptable threshold (P < 0.000). According to the findings of this in vitro study, all the specimens underwent color changes (ΔE* > 0). The red pigment exhibited highly significant chromatic alterations. In contrast, mocha pigments with and without ZrO2 nanoparticles exhibited the least color change and were below the perceptible threshold. ZrO2 nanoparticles provided important protection and showed a reduction in color change.

Aphid-Inspired and Thermally-Actuated Soft Gripper Using 3D Printing Technology

Herein, a thermo-actuated aphid-inspired dry adhesive (TADA) that offers tunable and reversible adhesion is reported. It is easily fabricated through 3D printing using a polylactic acid (PLA) filament and silicone elastomer, avoiding the use of unfavorable methods for micro- and nanofabrication and unwanted particles for actuation. The tunable adhesive system mimics aphid biology to achieve adhesion switchability. Switching between adhesion states is enabled by the thermo-actuated PLA, which has shape memory properties. Additionally, silicone elastomer enables adherence to flat substrates such as glass, silicon wafers, and acrylic plates. The detachment time of the TADA can be controlled by changing the printing layer height, which is a 3D-printing parameter that results in a short detachment time when the printing layer height is small. The adhesion strength is measured by applying different preloads and varying the size of the adhesive area. The reversibility between the adhesion-on and adhesion-off states, revealing good repeatability with similar adhesion strengths is also demonstrated. The TADA has potential applications in transferring silicon wafers. In addition, it can be printed to fit a flat plate of any shape, enabling it to grip the plate stably.

Soft contact lens options in the management of pediatric aphakia - A quantitative and qualitative assessment

BACKGROUND

The main contact lens for pediatric aphakia has historically been a silicone elastomer lens (Silsoft SuperPlus). Due to supply chain disruption, many aphakic children required an alternative lens. We performed quantitative and qualitative comparisons between Silsoft SuperPlus and alternative aphakic soft contacts.

METHOD

Sixty-nine aphakic eyes of 49 patients wearing Silsoft SuperPlus lenses underwent the refitting process into an alternative soft contact. Data collected included lens parameters, visual acuity, keratometry, horizontal visible iris diameter, and over-refraction. A 6-question survey assessing the patients'/guardians' experience with Silsoft SuperPlus versus the alternative lens was conducted at initial fit and 1-3 months post-fit.

RESULTS

Twenty-four patients (49 %), 4(8 %), and 1(2 %) were refit into Flexlens Definitive 74, Biofinity XR, and Intelliwave Pro Toric lenses, respectively. Sixteen patients (34 %) remained in Silsoft SuperPlus due to personal lens surplus or inability to handle the new lens while 2(4 %) opted for glasses. Silsoft SuperPlus was typically successful in eyes with average keratometry (AveK) 7.4-7.6 mm. Flexlens Definitive 74 required a base curve 0.4 mm steeper than the AveK. Patients'/guardias' reported a trend toward greater comfort with handling Silsoft SuperPlus, however, patients experienced less adverse side effects with the alternative soft contact lenses.

CONCLUSIONS

Flexlens Definitive 74 was an adequate alternative to Silsoft SuperPlus in aphakic children, however lens parameters must be steepened. Keratometry streamlined the contact lens fitting process. Alternative soft lenses are a cost-effective alternative to Silsoft contact lenses.

Physicochemical considerations in the formulation development of silicone elastomer vaginal rings releasing 5-nitroimidazole drugs for the treatment of bacterial vaginosis

Bacterial vaginosis (BV) is a common dysbiosis of the human vaginal microbiota characterized by depletion of hydrogen peroxide and lactic acid-producing Lactobacillus bacteria and an overgrowth of certain facultative anaerobic bacteria. Although short-term cure rates following treatment with frontline antibiotics (most notably oral metronidazole (MNZ), clindamycin vaginal cream, and MNZ vaginal gel) are generally high, longer-term recurrence rates are an issue. The development of vaginal formulations offering continuous/sustained administration of antibiotic drugs over one or more weeks might prove useful in reducing recurrence. Here, we report the manufacture and preclinical testing of matrix-type vaginal rings offering sustained release of four 5-nitroimidazole antimicrobial drugs either being used clinically or having potential in treatment of BV - MNZ, tinidazole (TNZ), secnidazole (SNZ) and ornidazole (ONZ). All four drugs showed good compatibility with a medical-grade addition-cure silicone elastomer based upon thermal analysis experiments, and matrix-type rings containing 250 mg (3.125 %w/w) of each drug were successfully manufactured by reaction injection molding. 28-day in vitro drug release studies demonstrated root-time kinetics, with daily release rates of 25, 22, 9 and 6 mg/day½ for SNZ, ONZ, MNZ and TNZ, respectively. The rank order of drug release from rings correlated with the simple molecular permeability parameter S/V, where S is the measured drug solubility in silicone fluid and V is the drug molecular volume. The relative merits of SNZ and ONZ over MNZ (the current reference treatment) are discussed. The data support development of vaginal rings for sustained release of 5-nitroimidazole compounds for treatment of BV.

Novel silicone elastomer contact lenses designed for simultaneous viewing of distance and near eye displays

SIGNIFICANCE

As technology advances, there is a need for a safe and well-fitting contact lens that can be utilized to carry embedded components without concerns of decreasing oxygen permeability to the eye.

PURPOSE

The purpose of this study was to assess fitting characteristics, vision and performance of a novel ultra-high Dk silicone elastomer contact lens having a fully encapsulated two-state polarizing filter and a high-powered central lenslet that allows viewing at distance and viewing of a near eye display, while managing the concomitant high water vapor permeability of the material.

METHODS

15 participants were fit with the silicone elastomer study lenses. Biomicroscopy was conducted before and after lens wear. Visual acuity with manifest refraction and visual acuity with an over-refraction while wearing the plano-powered study lenses were measured. Participants wore spectacles with micro-displays at the focal length of the lenslet on each eye. Lens fit was assessed including ease of lens removal. Subjective assessments of viewing the micro-displays were completed on a 1(unable) to 10(immediate/profound/stable) scale.

RESULTS

Biomicroscopy revealed no eyes had moderate or severe corneal staining after study lens wear. Mean (±standard deviation) LogMAR acuity for all eyes was -0.13(0.08) with best corrected refraction and -0.03(0.06) with the study lenses and over-refraction. Mean spherical equivalent of the manifest refraction for both eyes was -3.12 D and was -2.75 D over the plano study lenses. Subjective assessments revealed a mean score of 7.67(1.91) for ease of obtaining fusion; 8.47(1.30) for ease of observing three-dimensional vision, and 8.27(1.49) for stability of the fused binocular display vision.

CONCLUSION

The silicone elastomer study lenses with a two-state polarizing filter and central lenslet allow for vision at distance and on spectacle mounted micro-displays.

Effect of core layer parameters on the mechanical properties of biomimetic foamed silicone rubber sandwich structures against low-velocity impact

In this paper, a red-eared slider turtle is used as a prototype for the bionic design of the foamed silicone rubber sandwich structure, and the effect of core layer parameters on the low-velocity impact resistance of the foamed silicone rubber sandwich structure is studied by the finite element method. A numerical model with porosity of the foamed silicone rubber intrinsic model and a three-dimensional Hashin fiber plate damage model were used to verify the validity of the model in comparison with the test. On this basis, finite element simulations were performed by varying the core layer density and thickness. The results show that from the perspective of energy absorption, the sandwich structure has better impact resistance with core density of 750 kg/m3∼850 kg/m3 and core thickness of 20 mm-25 mm; from the perspective of structural lightweight requirements, the sandwich structure is more in line with the structural lightweight requirements with core density of 550 kg/m3∼650 kg/m3 and core thickness of 5 mm-10 mm. Therefore, the adoption of suitable core density and thickness is of great significance to the engineering practice.

Cytotoxicity, endocrine disrupting activity, and chemical analysis of 42 food contact silicone rubber products

After migration in 95 % ethanol (food simulant) at 70 °C for 2 h (accelerated conditions), the cytotoxicity and endocrine-disruption activity of 42 food contact silicone products (FCSPs) obtained from the Chinese market were studied. Of 31 kitchenwares, 96 % showed mild or above cytotoxicity (relative growth rate < 80 %) using the HeLa neutral red uptake test; and 84 % showed estrogenic (64 %), anti-estrogenic (19 %), androgenic (42 %), and anti-androgenic (39 %) activities by the Dual-luciferase reporter gene assay. The mold sample induced late phase HeLa apoptosis as detected by Annexin V-FITC/PI double staining flow cytometry, in addition, the migration of mold sample has a higher risk of endocrine disruption at high temperature usage. Encouragingly, 11 bottle nipples had neither cytotoxic nor hormonal activity. Utilizing multiple mass spectrometry techniques, non-intentionally added substances (NIASs) in 31 kitchenwares were analyzed, and the migration levels of 26 organic compounds and 21 metals were quantified, furthermore, the safe risk of single migrant was evaluated through their special migration limit (SML) or threshold of toxicological concern (TTC). Using "nchoosek" statement and Spearman's correlation analysis in MATLAB, the migration of 38 compounds or combinations including metals, plasticizers, methylsiloxanes, and lubricants, had strong correlation with cytotoxicity or hormonal activity. The coexistence of various chemical substances in migrants leads to complex biological toxicity of FCSPs, so it is very important to detect the toxicity of the final products. The combination of bioassays and chemical analyses are valuable tools to facilitate the identification and analyses of FCSPs and migrants that have potential safety risks.

Conformable Electrode Arrays for Wearable Neuroprostheses

Wearable electrode arrays can selectively stimulate muscle groups by modulating their shape, size, and position over a targeted region. They can potentially revolutionize personalized rehabilitation by being noninvasive and allowing easy donning and doffing. Nevertheless, users should feel comfortable using such arrays, as they are typically worn for an extended time period. Additionally, to deliver safe and selective stimulation, these arrays must be tailored to a user's physiology. Fabricating customizable electrode arrays needs a rapid and economical technique that accommodates scalability. By leveraging a multilayer screen-printing technique, this study aims to develop personalizable electrode arrays by embedding conductive materials into silicone-based elastomers. Accordingly, the conductivity of a silicone-based elastomer was altered by adding carbonaceous material. The 1:8 and 1:9 weight ratio percentages of carbon black (CB) to elastomer achieved conductivities between 0.0021-0.0030 S cm^-1 and were suitable for transcutaneous stimulation. Moreover, these ratios maintained their stimulation performance after several stretching cycles of up to 200%. Thus, a soft, conformable electrode array with a customizable design was demonstrated. Lastly, the efficacy of the proposed electrode arrays to stimulate hand function tasks was evaluated by in vivo experiments. The demonstration of such arrays encourages the realization of cost-effective, wearable stimulation systems for hand function restoration.

Using deep learning approaches for coloring silicone maxillofacial prostheses: A comparison of two approaches

Aim

This study aimed to compare the performance of two deep learning algorithms, attention-based gated recurrent unit (GRU), and the artificial neural networks (ANNs) algorithm for coloring silicone maxillofacial prostheses.

Settings and Design

This was an in vitro study.

Materials and Methods

A total of 21 silicone samples in different colors were produced with four pigments (white, yellow, red, and blue). The color of the samples was measured with a spectrophotometer, then the LFNx01, aFNx01, and bFNx01 values were recorded. The relationship between the LFNx01, aFNx01, and bFNx01 values of each sample and the amount of each pigment in the compound of the same sample was used as the training dataset, entered into each algorithm, and the prediction models were obtained. While generating the prediction model for each sample, the data of the corresponding sample assigned as the target color were excluded. LFNx01, aFNx01, and bFNx01 values of each target sample were entered into the obtained models separately, and recipes indicating the ratios for mixing the four pigments were predicted. The mean absolute error (MAE) and root mean square error (RMSE) values between the original recipe used in the production of each silicone and the recipe created by both prediction models for the same silicone were calculated.

Statistical Analysis Used

Data were analyzed with the Student t-test (α=0.05).

Results

The mean RMSE values and MAE values for the ANN algorithm (0.029 ± 0.0152 and 0.045 ± 0.0235, respectively) were found significantly higher than the attention-based GRU model (0.001 ± 0.0005 and 0.002 ± 0.0008, respectively) (P < 0.001).

Conclusions

Attention-based GRU model provided better performance than the ANN algorithm with respect to the MAE and RMSE values.

A comparative study of invariant-based hyperelastic models for silicone elastomers under biaxial deformation with the virtual fields method

Silicone elastomers have been widely used for biomedical applications. A variety of hyperelastic models have been proposed to describe this type of materials in the past few decades. The assessment of the quality of the proposed models is mostly based on stress-strain data obtained from uniform deformation, but very little work has been done to investigate model performances with heterogeneous deformation fields and full-field characterization methods. In this study, thirteen hyperelastic models are evaluated using the virtual fields method combined with full-field deformation data obtained from biaxial tests. The quality of these models is assessed by their capabilities to predict the mechanical responses of silicone elastomers, and the influences of the first and second invariants on modeling of elastomers are investigated through comparative studies between models. The results indicate that for elastomers under finite biaxial deformation, Yeoh model performs the best among selected models; the first invariant plays an important role in constitutive modeling; the second invariant does not have obvious influence on improving the fitting performance. This study provides a full-field method to calibrate and compare hyperelastic models of silicone elastomers under biaxial loading conditions.

Development and characterisation of hybrid composite skin simulants based on short polyethylene fibre and bioactive glass particle-reinforced silicone

Silicone elastomers are widely recognised as artificial skins for medical prosthesis and cranial injury assessment. Since silicone is not an ideal skin simulant due to the lack of mechanical stiffness and a fibrous structure, the present study aimed to tailor the mechanical and structural characteristics of silicone by integrating biocompatible reinforcements (namely, short polyethylene fibres and bioglass particles) to develop suitable bio-integrative skin simulant candidates. The influences of short polyethylene fibres and bioglass particles in the selected platinum silicone on the mechanical properties of silicone-based composite skin simulants were investigated with various factors, including filler concentration, KMnO4 surface treatment of the polyethylene fibre, and particle size. A comprehensive assessment of the tensile, compressive, and hardness properties of the examined composites was conducted, and they were compared with the properties of human biological skin. The results exhibited that the elastic moduli and the hardness of all composites increased with the concentration of both reinforcements. While integrating only the bioglass particles had the advantage of an insignificant effect on the hardness change of the silicone matrix, the composite with polyethylene fibres possessed superior tensile elastic modulus and tensile strength compared to those of the bioglass reinforced composite. The composites with 5% untreated polyethylene fibres, KMnO4 surface-treated fibres, and bioglass reinforcements enhanced the tensile elastic moduli from the pure silicone up to 32%, 44%, and 22%, respectively. It reflected that the surface treatment of the fibres promotes better interfacial adhesion between the silicone matrix and the fibres. Moreover, the smaller bioglass particle had a greater mechanical contribution than the larger glass particle. Systematically characterised for the first time, the developed composite skin simulants demonstrated essential mechanical properties within the range of the human skin and constituted better skin alternatives than pure silicone for various biomedical applications.

Contamination of food crops by unintentionally released PCB 47, PCB 51 and PCB 68 in the vicinity of silicone production sites and their relevance for human health assessment

Since it was shown that silicone rubber production can unintentionally release PCBs, these production sites have become a focus of investigation. The use of the cross-linking agent bis(2,4)-dichlorobenzoylperoxide (2,4-DCBP) can lead to emissions of the PCB congeners PCB 47, PCB 51 and PCB 68 into the environment and cause their accumulation e. g. in food crops. To determine the presence and extent of this uptake, we used the newly developed method dandelion screening. Samples were taken from wild dandelion plants near nine production sites in North Rhine-Westphalia, Germany, and analysed for PCBs. In some cases, the regional orientation values for the maximum background level (OMB) were exceeded by up to nine times. Overall, background levels were exceeded at seven of the nine sites investigated and mitigation measures were initiated at the production sites. In order to validate the dandelion screening results, kale was exposed, which allowed for a health assessment. A wide-ranging consumption recommendation was then issued in four out of nine study areas. At this point in the investigations, risk reduction measures had already been implemented at all production sites investigated, so it can be assumed that the exposures at sites not yet in focus are significantly greater. This is a globally relevant problem, as 2,4-DCBP is used in many countries.

High-Sensitive Wearable Strain Sensors Based on the Carbon Nanotubes@Porous Soft Silicone Elastomer with Excellent Stretchability, Durability, and Biocompatibility

Wearable strain sensors can transfer human physical motions into digital features and connect the real world to the virtual world. However, there is still a huge challenge to prepare breathable strain sensors with good sensitivity, stretchability, softness, durability, and biocompatibility, simultaneously. Herein, we employ the soft silicone elastomer as a highly stretchable substrate and propose a new strain sensor based on the carbon nanotubes@porous soft silicone elastomer (CNTs@PSSE) by salt-template-assisted and dip-coating methods. The CNTs (conductive fillers) are firmly embedded in the PSSE. The obtained sensors exhibit excellent sensitivity up to 2845.1 and a large sensing strain range of 186%. Notably, the CNTs@PSSE sensors also possess strong robustness, which can resist ultrasonic deterioration and carry out more than 10,000 high-frequency stretch-relax cycles in the presence of an obvious notch caused by the scissor. Moreover, the excellent biocompatibility indicates that the sensors can be safely attached to human skin for precisely detecting full-range human motions and being configured on smart wireless gloves for synchronous control of the bionic hand robot.

Effects of NiO, SnO2, and Ni-doped SnO2 semiconductor metal oxides on the oxygen sensing capacity of H2TPP

Improving the performance of optical oxygen sensors can be accomplished by adding metal oxide semiconductors (MOSs) additives to the composition comprising an oxygen-sensing agent immobilized in a polymeric thin film. For several decades, MOSs have attracted great interest in gas sensors due to their high sensitivity to many target gasses. Herein, meso-tetraphenylporphyrin (H₂TPP) dye was immobilized into the poly(1-trimethylsilyl-1-propyne) (poly(TMSP)) silicone rubber in the presence of NiO, SnO₂, Ni:SnO₂ metal oxide particles as additives, and their thin films were prepared to investigate oxygen-sensitive optical chemical sensor properties. The characterizations of the synthesized metal oxide powders were carried out through XPS, XRD, FT-IR, PL spectroscopy and SEM methods. Intensity-based spectra and decay kinetics of H₂TPP-based thin films were investigated for the concentration range of 0%-100% [O₂]. The oxygen sensitivity (I₀/I₁₀₀) of the porphyrin was calculated as 70%. Whereas the relative signal intensity values of H₂TPP-based sensor slides were measured as 75%, 80%, and 88% in the presence of NiO, SnO₂, Ni:SnO₂ additives, respectively. The H₂TPP in combination with Ni:SnO₂ semiconductor provided a higher I₀/I₁₀₀ value, larger response range, higher Stern-Volmer constant (K_SV) value, and faster response time compared to the undoped form, and also NiO and SnO₂ additive-doped forms of H₂TPP. The response and the recovery times of the porphyrin-based sensing slide along with Ni:SnO₂ additives have been measured as 12 and 50 s. These results make the H₂TPP along with the MOSs promising candidates as oxygen probes.

Emissions of Fungal Volatile Organic Compounds in Residential Environments and Temporal Emission Patterns: Implications for Sampling Methods

Currently, little is known about the occurrences of fungi-derived microbial volatile organic compounds (mVOCs) in various indoor materials and their detection in residential environments, despite mVOCs being linked to several acute health effects. We identified various mVOCs emitted from fungi grown on PVC wallpaper, silicone rubber, and malt extract agar. We also investigated mVOCs temporal emission and whether fungi-derived VOCs concentration can be used to estimate fungal concentration in the air using active and passive air sampling methods. Among the three fungal growth media included in this study, silicone rubber produced the most variety of mVOCs: 106 compounds (from Aspergillus niger), 35 compounds (from Alternaria alternata), and 85 compounds (from Penicillium chrysogenum). We also found the emission patterns of eight chemical classes (i.e., aromatics, ethers, aliphatics, alcohols, ketones, aldehydes, chlorides, and nitrides) from the three different fungi. From the results of our field experiments in 11 residential environments, passive air samplers led to higher correlations coefficients (0.08 to 0.86) between mVOCs' air concentrations and airborne fungal concentrations, compared with active air samplers, which showed negative correlation coefficients (-0.99 to -0.02) for most compounds. This study elucidated the occurrence and temporal emission patterns of fungal VOCs in residential environments.

Airlift two-phase partitioning bioreactor for dichloromethane removal: Silicone rubber stimulated biodegradation and its auto-circulation

Solid non-aqueous phases (NAPs), such as silicone rubber, have been used extensively to improve the removal of volatile organic compounds (VOCs). However, the removal of VOCs is difficult to be further improved because the poor understanding of the mass transfer and reaction processes. Further, the conventional reactors were either complicated or uneconomical. In view of this, herein, an airlift bioreactor with silicone rubber was designed and investigated for dichloromethane (DCM) treatment. The removal efficiency of Reactor 1 (with silicone rubber) was significantly higher than that of Reactor 2 (without silicone rubber), with corresponding higher chloride ion and CO₂ production. It was found that Reactor 1 achieved a much better DCM shock tolerance capability and biomass stability than Reactor 2. Silicone rubber not only enhanced the mass transfer in terms of both gas/liquid and gas/microbial phases, but also decreased the toxicity of DCM to microorganisms. Noteworthily, despite the identical inoculum used, the relative abundance of potential DCM-degrading bacteria in Reactor 1 (91.2%) was much higher than that in Reactor 2 (24.3%) at 216 h. Additionally, the silicone rubber could be automatically circulated in the airlift bioreactor due to the driven effect of the airflow, resulting in a significant reduction of energy consumption.

Electrical Insulation and Radar-Wave Absorption Performances of Nanoferrite/Liquid-Silicone-Rubber Composites

Novel radar-wave absorption nanocomposites are developed by filling the nanoscaled ferrites of strontium ferroxide (SrFe12O19) and carbonyl iron (CIP) individually into the highly flexible liquid silicone rubber (LSR) considered as dielectric matrix. Nanofiller dispersivities in SrFe12O19/LSR and CIP/LSR nanocomposites are characterized by scanning electronic microscopy, and the mechanical properties, electric conductivity, and DC dielectric-breakdown strength are tested to evaluate electrical insulation performances. Radar-wave absorption performances of SrFe12O19/LSR and CIP/LSR nanocomposites are investigated by measuring electromagnetic response characteristics and radar-wave reflectivity, indicating the high radar-wave absorption is dominantly derived from magnetic losses. Compared with pure LSR, the SrFe12O19/LSR and CIP/LSR nanocomposites represent acceptable reductions in mechanical tensile and dielectric-breakdown strengths, while rendering a substantial nonlinearity of electric conductivity under high electric fields. SrFe12O19/LSR nanocomposites provide high radar-wave absorption in the frequency band of 11~18 GHz, achieving a minimum reflection loss of −33 dB at 11 GHz with an effective absorption bandwidth of 10 GHz. In comparison, CIP/LSR nanocomposites realize a minimum reflection loss of −22 dB at 7 GHz and a remarkably larger effective absorption bandwidth of 3.9 GHz in the lower frequency range of 2~8 GHz. Radar-wave transmissions through SrFe12O19/LSR and CIP/LSR nanocomposites in single- and double-layered structures are analyzed with CST electromagnetic-field simulation software to calculate radar reflectivity for various absorbing-layer thicknesses. Dual-layer absorbing structures are modeled by specifying SrFe12O19/LSR and CIP/LSR nanocomposites, respectively, as match and loss layers, which are predicted to acquire a significant improvement in radar-wave absorption when the thicknesses of match and loss layers approach 1.75 mm and 0.25 mm, respectively.

PhotoElasticFinger: Robot Tactile Fingertip Based on Photoelastic Effect

The sense of touch is fundamental for a one-to-one mapping between the environment and a robot that physically interacts with the environment. Herein, we describe a tactile fingertip design that can robustly detect interaction forces given data collected from a camera. This design is based on the photoelastic effect observed in silicone matter. Under the force applied to the silicone rubber, owing to the stress-induced birefringence, the light propagating within the silicone rubber is subjected to the angular phase shift, where the latter is proportional to the increase in the image brightness in the camera frames. We present the calibration and test results of the photoelastic sensor design on a bench using a robot arm and with a certified industrial force torque sensor. We also discuss the applications of this sensor design and its potential relationship with human mechano-transduction receptors. We achieved a force sensing range of up to 8 N with a force resolution of around 0.5 N. The photoelastic tactile fingertip is suitable for robot grasping and might lead to further progress in robust tactile sensing.

Natural Weathering Effects on the Mechanical, Rheological, and Morphological Properties of Magnetorheological Elastomer (MRE) in Tropical Climate

Magnetorheological elastomer (MRE) materials have the potential to be used in a wide range of applications that require long-term service in hostile environments. These widespread applications will result in the emergence of MRE-specific durability issues, where durability refers to performance under in-service environmental conditions. In response, the outdoor tropical climatic environment, combined with the effects of weathering, will be the primary focus of this paper, specifically the photodegradation of the MRE. In this study, MRE made of silicone rubber (SR) and 70 wt% micron-sized carbonyl iron particles (CIP) were prepared and subjected to mechanical and rheological testing to evaluate the effects under natural weathering. Magnetorheological elastomer samples were exposed to the natural weathering conditions of a tropical climate in Kuala Lumpur, Malaysia, for 30 days. To obtain a comprehensive view of MRE degradation during natural weathering, mechanical testing, rheology, and morphological evaluation were all performed. The mechanical and rheological properties test results revealed that after 30 days of exposure and known meteorological parameters, Young’s modulus and storage modulus increased, while elongation at break decreased. The degradation processes of MRE during weathering, which are responsible for their undesirable change, were given special attention. With the help of morphological evidence, the relationship between these phenomena and the viscoelastic properties of MRE was comprehensively defined and discussed.

Self-Healable, Self-Repairable, and Recyclable Electrically Responsive Artificial Muscles

Elastomers with high dielectric permittivity that self-heal after electric breakdown and mechanical damage are important in the emerging field of artificial muscles. Here, a one-step process toward self-healable, silicone-based elastomers with large and tunable permittivity is reported. Anionic ring-opening polymerization of cyanopropyl-substituted cyclic siloxanes yields elastomers with polar side chains. The equilibrated product is composed of networks, linear chains, and cyclic compounds. The ratio between the components varies with temperature and allows realizing materials with largely different properties. The silanolate end groups remain active, which is the key to self-healing. Elastomeric behavior is observed at room temperature, while viscous flow dominates at higher temperatures (typically 80 °C). The elasticity is essential for reversible actuation and the thermoreversible softening allows for self-healing and recycling. The dielectric permittivity can be increased to a maximum value of 18.1 by varying the polar group content. Single-layer actuators show 3.8% lateral actuation at 5.2 V µm^-1 and self-repair after a breakdown, while damaged ones can be recycled integrally. Stack actuators reach an actuation strain of 5.4 ± 0.2% at electric fields as low as 3.2 V µm^-1 and are therefore promising for applications as artificial muscles in soft robotics.

Long-Term Storage Stability and Nitric Oxide Release Behavior of (N-Acetyl-S-nitrosopenicillaminyl)-S-nitrosopenicillamine-Incorporated Silicone Rubber Coatings

Physical incorporation of nitric oxide (NO) releasing materials in biomedical grade polymer matrices to fabricate antimicrobial coatings and devices is an economically viable process. However, achieving long-term NO release with a minimum or no leaching of the NO donor from the polymer matrix is still a challenging task. Herein, (N-acetyl-S-nitrosopenicillaminyl)-S-nitrosopenicillamine (SNAP-SNAP), a penicillamine dipeptide NO-releasing molecule, is incorporated into a commercially available biomedical grade silicone rubber (SR) to fabricate a NO-releasing coating (SNAP-SNAP/SR). The storage stabilities of the SNAP-SNAP powder and SNAP-SNAP/SR coating were analyzed at different temperatures. The SNAP-SNAP/SR coatings with varying wt % of SNAP-SNAP showed a tunable and sustained NO release for up to 6 weeks. Further, S-nitroso-N-acetylpenicillamine (SNAP), a well-explored NO-releasing molecule, was incorporated into a biomedical grade silicone polymer to fabricate a NO-releasing coating (SNAP/SR) and a comparative analysis of the NO release and S-nitrosothiol (RSNO) leaching behavior of 10 wt % SNAP-SNAP/SR and 10 wt % SNAP/SR was studied. Interestingly, the 10 wt % SNAP-SNAP/SR coatings exhibited ∼36% higher NO release and 4 times less leaching of NO donors than the 10 wt % SNAP/SR coatings. Further, the 10 wt % SNAP-SNAP/SR coatings exhibited promising antibacterial properties against Staphylococcus aureus and Escherichia coli due to the persistent release of NO. The 10 wt % SNAP-SNAP/SR coatings were also found to be biocompatible against NIH 3T3 mouse fibroblast cells. These results corroborate the sustained stability and NO-releasing properties of the SNAP-SNAP in a silicone polymer matrix and demonstrate the potential for the SNAP-SNAP/SR polymer in the fabrication of long-term indwelling biomedical devices and implants to enhance biocompatibility and resist device-related infections.

Light responsive plasmonic silicone elastomer/hydrogel soft actuator

Soft robots offer unique advantages in their ability to interact with fragile organisms. Light responsive soft actuators are promising for the development of the untethered soft robots. However, this requires a mechanism for converting the externally applied light into mechanical actuation. We designed, fabricated, and tested a light responsive soft actuator consist of silicone elastomer with plasmonic metal nanoparticle embedment and temperature sensitive hydrogel. We found that the selection of the carrier solvent for the metal nanoparticle embedment in silicone elastomer to be crucial. The fabricated soft actuator showed a relatively fast response time (< 5 min) under light illumination.

Exploring Silicone Rubber Skin with Embedded Customizable Shape Capacitive Sensors to Enable Haptic Capabilities on Upper Limb Prosthetics

Commercially available electromechanical prosthetic devices still lack touch-sensing capabilities, and there is a huge gap between research devices and commercially available ones. There is a need for small flexible touch sensors with high accuracy and sensitivity for this type of device. Touch sensors in prosthetic devices are needed for feedback mechanisms to the user and to achieve high dexterity in control schemes for fragile objects. A brief review of prosthetic touch sensors is presented, addressing desirable characteristics for touch sensing. In this paper, a custom shape flexible capacitive touch sensor is designed and characterized, meeting prosthetic sensors needs, such as thickness, power consumption, accuracy, repeatability, and stability. The designed sensor presented the capability to distinguish up to 0.5N steps with good stability. The sensor accomplished a full sensing range between 5N and 100N with reasonable accuracy, and hysteresis analysis achieved an average of 8.8 %. Clinical Relevance- The custom shape capacitive sensors proposed in this paper contribute to the development of tactile sensors for prosthetic devices as more accurate and sensitive sensor interfaces are required to detect and improve manipulating capabilities.

Decomposition Products of the Initiator Bis(2,4-dichlorobenzoyl)peroxide in the Silicone Industry: Human Biomonitoring in Plasma and Urine of Workers

Bis(2,4-dichlorobenzoyl)peroxide (2,4-DCBP) is used as an initiator for silicone rubber production. During hot curing, 2,4-DCBP decomposes into 2,4-dichlorobenzoic acid, 1,3-dichlorobenzene, and the polychlorinated biphenyl (PCB) congeners PCB-47, PCB-51, and PCB-68. The extent of occupational exposure to these decomposition products has not been investigated yet. We determined for the first time the corresponding internal exposure of employees (n = 104) of a German silicone rubber facility by human biomonitoring in plasma and urine. Collected samples were investigated by gas chromatography/mass spectrometry for levels of PCBs in plasma and by liquid chromatography/tandem mass spectrometry for urinary post-shift levels of 2,4-dichlorobenzoic acid (2,4-DCBA) and the metabolites 3,5-dichlorocatechol (3,5-DCK), 2,4-dichlorophenol (2,4-DCP), and 3,5-dichlorophenol (3,5-DCP). PCB-47 and PCB-68 levels correlated significantly and were found in >97% of all samples with maximum values of 4.43 and 0.77 μg/L, respectively. 2,4-DCBA, 3,5-DCK, 2,4-DCP, and 3,5-DCP were quantified in >80% of all urine samples with maximum levels of 1.46; 26.92; 7.68; and 0.39 mg/L, respectively. There is a considerable uptake of decomposition products of 2,4-DCBP in workers of a silicone rubber facility, affecting employees in all work areas. Individual levels depended on the work task. Considering the carcinogenic potential of PCBs, the workers' additional exposure to PCB-47 and PCB-68 might be of concern.

[Clinical effect of digital impression combined with all-ceramic denture on restoration of 60 patients with dental defects]

PURPOSE

To analyze the clinical effect of digital impression combined with all-ceramic denture restoration on patients with dental defects.

METHODS

A study was conducted on 120 patients with dental defects admitted to Dongfeng Stomatological Hospital from June 2018 to June 2020. The two groups of patients were randomly divided into digital imprinting modules and silicone rubber imprinting modules using a random number table method. There were 60 cases in each group. The silicone rubber imprint module used traditional silicone impression combined with all-ceramic denture restoration, while the digital imprint module used digital impression combined with all-ceramic denture restoration.The clinical efficacy of the two groups was observed. Gingival index (GI), periodontal index (PI) before dental restoration, during dental restoration and 6 monthes after dental restoration were compared. The adjacent surface contact conditions, occlusion and adverse reactions of the two groups were compared. SPSS 22.0 software package was used for statistical analysis.

RESULTS

The two groups of patients selected grade A and grade B for the evaluation of the restoration when the restoration was completed. The number of patients who chose grade A for the digital imprint module was more than that of the silicone rubber imprint module,but there was no significant difference(P＞0.05). Six months after the tooth was worn, GI and PI indexes of the two groups of patients increased. GI and PI indexes of the silicone rubber stamping module were significantly higher than those of the digital stamping module(P＜0.05). When dental restoration was completed and 6 months after the tooth was replaced, the pass rate of contact between the adjacent surfaces of the imprinting module patients was significantly higher than that of the silicone rubber imprinting module(P＜0.05). When dental restoration was completed, the occlusion of the digital imprinting module patients was significantly better than that of the silicone rubber imprinting module(P＜0.05). Six months after wearing the denture, there was no significant difference in occlusion between the two groups of patients(P＞0.05). When dental models of the two groups of patients were taken, the incidence of adverse reactions in patients with digital imprints was significantly lower than that of silicone rubber imprints(P＜0.05).

CONCLUSIONS

The use of digital impressions combined with all-ceramic restorations to repair patients with dental defects can effectively improve the treatment effect, improve prognostic GI and PI indexes of the patients, increase the pass rate of the adjacent surface contact and occlusion of the tooth, and reduce the process of dental restoration. The incidence of adverse reactions are minimal, with good prognostic effects. It is worthy of clinical application.

Silicone-Textile Composite Resistive Strain Sensors for Human Motion-Related Parameters

In recent years, soft and flexible strain sensors have found application in wearable devices for monitoring human motion and physiological parameters. Conductive textile-based sensors are good candidates for developing these sensors. However, their robust electro-mechanical connection and susceptibility to environmental factors are still an open challenge to date. In this work, the manufacturing process of a silicone-textile composite resistive strain sensor based on a conductive resistive textile encapsulated into a dual-layer of silicone rubber is reported. In the working range typical of biomedical applications (up to 50%), the proposed flexible, skin-safe and moisture resistant strain sensor exhibited high sensitivity (gauge factor of −1.1), low hysteresis (maximum hysteresis error 3.2%) and ease of shaping in custom designs through a facile manufacturing process. To test the developed flexible sensor, two applicative scenarios covering the whole working range have been considered: the recording of the chest wall expansion during respiratory activity and the capture of the elbow flexion/extension movements.

Development and dosimetric verification of 3D customized bolus in head and neck radiotherapy

The commercial flat bolus cannot form perfect contact with the irregular surface of the patient's skin, resulting in an air gap. The purpose of this study was to evaluate the feasibility of using a 3D customized bolus from silicone rubber. The silicone rubber boluses were studied in basic characteristics. The 3D customized bolus was fabricated at the nose, cheek and neck regions. The point dose and planar dose differences were evaluated by comparing with virtual bolus. The hardness, thickness, density, Hounsfield unit (HU) and dose attenuation of the customized bolus were quite similar to a commercial bolus. When a 3D customized bolus was placed on the RANDO phantom, it can significantly increase buildup region doses and perfectly fit against the irregular surface shape. The average point dose differences of 3D customized bolus were -1.1%, while the commercial bolus plans showed -1.7%. The average gamma results for planar dose differences comparison of 3D customized bolus were 93.9%, while the commercial bolus plans were reduced to 91.9%. Overall, A silicone rubber bolus produced the feasible dosimetric properties and could save cost compared to a commercial bolus. The 3D printed customized bolus is a good buildup material and could potentially replace and improve treatment efficiency.

Plasma levels of unintentionally produced non-Aroclor polychlorinated biphenyl (PCB) congeners in workers from the silicone rubber industry

The unintentional release of non-Aroclor-PCBs 47, PCB 68 and PCB 51 by a silicone manufacturing company in North Rhine-Westphalia, Germany, due to the use of bis-(2,4-dichlorobenzoyl)peroxide (2,4-DCBP) as an initiator has raised serious concerns about the possible uptake of these congeners by workers in silicone rubber production. We have conducted a pilot study in Germany to quantify these congeners in plasma samples of employees working in and handling silicone rubber during production and electrical cable manufacturing. A total of 117 plasma samples were collected from workers in 7 companies and 84 plasma samples from control subjects not working in silicone industry. PCB 47 and PCB 68 were detected in plasma above the limit of quantification (0.01 μg/L) in 84% and 66% of the silicone industry workers, respectively, whereas both congeners were undetectable in plasma of the control group. The maximum levels for PCB 47 were 2.56 μg/L and for PCB 68 were 0.42 μg/L. PCB 51 could not be determined in any plasma sample. Plasma samples of workers making electric cables had in general lower levels than those from workers making silicone rubber. Due to the high persistence of PCBs and the poorly defined toxicological properties of PCB 47 and PCB 68, a replacement of 2,4-DCBP as initiator in silicone rubber production should be considered. Given the large market for silicone products, our results might have a global impact on silicone industry.

Probing Covalent Interactions at a Silicone Adhesive/Nylon Interface

Covalent bonding is one of the most robust forms of intramolecular interaction between adhesives and substrates. In contrast to most noncovalent interactions, covalent bonds can significantly enhance both the interfacial strength and durability. To utilize the advantages of covalent bonding, specific chemical reactions are designed to occur at interfaces. However, interfacial reactions are difficult to probe in situ, particularly at the buried interfaces found in well-bonded adhesive joints. In this work, sum frequency generational (SFG) vibrational spectroscopy was used to directly examine and analyze the interfacial chemical reactions and related molecular changes at buried nylon/silicone elastomer interfaces. For self-priming elastomeric silicone adhesives, silane coupling agents have been extensively used as adhesion promoters. Here with SFG, the interfacial chemical reactions between nylon and two alkoxysilane adhesion promoters with varied functionalities (maleic anhydride (MAH) and epoxy) formulated into the silicone were observed and investigated. Evidence of reactions between the organofunctional group of each silane and reactive groups on the polyamide was found at the buried interface between the cured silicone elastomer and nylon. The adhesion strength at the nylon/cured silicone interfaces was substantially enhanced with both silane additives. SFG results elucidated the mechanisms of organo-silane adhesion promotion for silicone at the molecular level. The ability to probe and analyze detailed interfacial reactions at buried nylon/silicone interfaces demonstrated that SFG is a powerful analytical technique to aid the design and optimization of materials with desired interfacial properties.

Frontalis Sling Using a Silicone Rod for Ptosis in Third Nerve Palsy: Cosmesis Versus Safety

Purpose

To evaluate the results of the frontalis sling operation using a silicone rod for the correction of ptosis in patients with third nerve palsy with a focus on corneal safety.

Methods

Patients with third nerve palsy who underwent the frontalis sling operation using a silicone rod between 2008 and 2019 were included in this study. The medical records of all patients were reviewed, and their clinical characteristics and postoperative outcomes were analyzed. In this retrospective, interventional case series, the main outcome measures were eyelid contour, eyelid height by margin reflex distance, and corneal status.

Results

Twenty-four eyes of 18 patients (12 male and six female patients) were included. The mean age at the time of surgery was 35.1 years (range, 5–64 years). Twelve patients underwent a unilateral ptosis operation, and six patients received a bilateral ptosis operation. The mean follow-up period was 32.1 months (range, 2–87 months). Most patients (21 of 24 eyes, 88%) showed poor Bell’s phenomenon on preoperative examination. Satisfactory eyelid height and eyelid contour were achieved in almost all patients (mean postoperative margin reflex distance, +1.2 mm) postoperatively. Although corneal erosions were detected for several months in eight of 24 eyes after surgery, these findings were well controlled medically with artificial tear eye drops and ointments.

Conclusions

Frontalis sling surgery using a silicone rod can safely and effectively correct ptosis without severe corneal complications in patients with third nerve palsy. Our study outlines a new method to define the postoperative safety outcome by specifically focusing on categorized corneal status.