Photo-crosslinkable cyanoacrylate bioadhesive: Shrinkage kinetics, dynamic mechanical properties, and biocompatibility of adhesives containing TMPTMA and POSS nanostructures as crosslinking agents

Microfluidic encapsulation of DNAs in liquid beads for digital PCR application

Droplet-based microfluidics and digital polymerase chain reaction (PCR) hold significant promise for accurately detecting and quantifying pathogens. However, existing droplet-based digital PCR (ddPCR) applications have been relying exclusively on single emulsion droplets. Single emulsion droplets may not be suitable for applications such as identifying the source and pathways of water contamination where the templates must be protected against harsh environmental conditions. In this study, we developed a core-shell particle to serve as a protective framework for DNAs, with potential applications in digital PCR. We employed a high-throughput and facile flow-focusing microfluidic device to generate liquid beads, core-shell particles with liquid cores, which provided precise control over process parameters and consequently particle characteristics. Notably, the interfacial interaction between the core and shell liquids could be adjusted without adding surfactants to either phase. As maintaining stability is essential for ensuring the accuracy of digital PCR (dPCR), we investigated parameters that affect the stability of core-shell droplets, including surfactants in the continuous phase and core density. As a proof of concept, we encapsulated a series of human faecal DNA samples in the core-shell droplets and the subsequent liquid beads. The core-shell particles ensure contamination-free encapsulation of DNA in the core. The volume of the core droplets containing the PCR mixture is only 0.12 nL. Our experimental results indicate that the liquid beads formulated using our technique can amplify the encapsulated DNA and be used for digital PCR without interfering with the fluorescence signal. We successfully demonstrated the ability to detect and quantify DNA under varying concentrations. These findings provide new insights and a step change in digital PCR that could benefit various applications, including the detection and tracking of environmental pollution.

Smart Bandaid Integrated with Fully Textile OECT for Uric Acid Real-Time Monitoring in Wound Exudate

Hard-to-heal wounds (i.e., severe and/or chronic) are typically associated with particular pathologies or afflictions such as diabetes, immunodeficiencies, compression traumas in bedridden people, skin grafts, or third-degree burns. In this situation, it is critical to constantly monitor the healing stages and the overall wound conditions to allow for better-targeted therapies and faster patient recovery. At the moment, this operation is performed by removing the bandages and visually inspecting the wound, putting the patient at risk of infection and disturbing the healing stages. Recently, new devices have been developed to address these issues by monitoring important biomarkers related to the wound health status, such as pH, moisture, etc. In this contribution, we present a novel textile chemical sensor exploiting an organic electrochemical transistor (OECT) configuration based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) for uric acid (UA)-selective monitoring in wound exudate. The combination of special medical-grade textile materials provides a passive sampling system that enables the real-time and non-invasive analysis of wound fluid: UA was detected as a benchmark analyte to monitor the health status of wounds since it represents a relevant biomarker associated with infections or necrotization processes in human tissues. The sensors proved to reliably and reversibly detect UA concentration in synthetic wound exudate in the biologically relevant range of 220-750 μM, operating in flow conditions for better mimicking the real wound bed. This forerunner device paves the way for smart bandages integrated with real-time monitoring OECT-based sensors for wound-healing evaluation.

Polymerization Enhancers for Cyanoacrylate Skin Adhesive

Cyanoacrylate glues are a renowned synthetic tissue sealant that cures rapidly through polymerization at room temperature, felicitating medical glues to treat skin wounds and surgical openings. Despite a wide range of cyanoacrylates available, only 2-octyl cyanoacrylates (OCA) provides the best biocompatibility. In this study, the polymerization and adhesive properties of 2-octyl cyanoacrylates (OCA) are explored in the presence of a highly biocompatible and biochemically inert polymer, poly(ethylene glycol) polyhedral oligomeric silsesquioxane (PEG-POSS). The effect of PEG-POSS on the polymerization of OCA is examined on a plastic surface and over pig skin. A peel-test is performed to evaluate the strength of OCA adhesive properties between two pieces of pig skin samples. Additionally, thin films of OCA are prepared using different fillers and evaluated for tear test. The results reveal that when applied on the plastic or pig skin, PEG-POSS initiated polymerization in OCA yields a high molecular weight OCA polymer with much better adhesive properties compared to commercially available cyanoacrylate adhesives. The relative change in the molecular weights of OCA compared to commercially available cyanoacrylate bioadhesives such as Dermaflex is much higher. The pig skin peeling test shows that OCA needs higher peeling force than Dermaflex.

Effects of ethanol concentrations of acrylate-based dental adhesives on microtensile composite-dentin bond strength and hybrid layer structure of a 10 wt% polyhedral oligomeric silsesquioxane (POSS)-incorporated bonding agent

Background

The aim of this study was to assess for the first time the effects of different amounts of ethanol solvent on the microtensile bond strength of composite bonded to dentin using a polyhedral oligomeric silsesquioxane (POSS)-incorporated adhesive.

Materials and Methods

This experimental study was performed on 120 specimens divided into six groups (in accordance with the ISO TR11405 standard requiring at least 15 specimens per group). Occlusal dentin of thirty human molar teeth was exposed by removing its enamel. Five teeth were assigned to each of six groups and were converted to 20 microtensile rods (with square cross-sections of 1 mm × 1 mm) per group. The "Prime and Bond NT" (as a common commercial adhesive) was used as the control group. Experimental acrylate-based bonding agents containing 10 wt% POSS were produced with five concentrations of ethanol as solvent (0, 20, 31, 39, and 46 wt%). After application of adhesives on dentin surface, composite cylinders (height = 6 mm) were bonded to dentin surface. The microtensile bond strength of composite to dentin was measured. The fractured surfaces of specimens were evaluated under a scanning electron microscope to assess the morphology of hybrid layer. Data were analyzed using one-sample t-test, one-way analysis of variance (ANOVA), and Tukey tests (α = 0.05).

Results

the mean bond strength in the groups: "control, ethanol-free, and 20%, 31%, 39%, and 46% ethanol" was, respectively, 46.5 ± 5.6, 29.4 ± 5.7, 33.6 ± 4.1, 59.0 ± 5.5, 41.9 ± 6.2, and 18.7 ± 4.6 MPa. Overall difference was significant (ANOVA, P < 0.0001). Pairwise differences were all significant (Tukey P < 0.05) except those of "ethanol 0% versus 20%" and "20% versus 31%." All groups except "0% and 46% ethanol" had bond strengths above 30 MPa (t-test P < 0.05).

Conclusion

Incorporation of 31% ethanol as solvent into a 10 wt% POSS-incorporated experimental dental adhesive might increase the bond strength of composite to dentin and improve the quality and morphology of the hybrid layer. However, higher concentrations of the solvent might not improve the bond strength or quality of the hybrid layer.

Cure kinetic study of methacrylate-POSS copolymers for ocular lens

Abstract

The physical, mechanical and biological properties of multicomponent acrylate-based hard lenses are directly influenced by degree of conversion achieved during copolymerization. In this research, polyhedral oligomeric silsesquioxane (POSS) acrylate is introduced into the polymer backbone in combination with hydroxyethyl methacrylate, dimethyl itaconate, methyl methacrylate, 3-(trimethoxysilyl) propyl methacrylate and triethylene glycol dimethacrylate in free-radical bulk polymerization. Kinetics of curing process was investigated by two techniques: differential scanning calorimetry and FTIR spectroscopy. Reaction kinetics in free-radical bulk polymerization of the system was studied by isothermal DSC performed at 65, 75, 85, and 95 °C using different quantities of initiator. Three compounds were prepared in different concentrations (0.2, 0.4 and 0.6 mol%) of 2,2′-azobisisobutyronitrile as initiator. Conversion rate was calculated as a function of time using data obtained from DSC measurements. The kinetic parameters of the reaction such as reaction constants, reaction orders and activation energies were obtained from the isothermal DSC data according to the autocatalytic model developed by Kamal and Sourour. The results showed that the experimental values were in good agreement with theoretically estimated values and our results may suggest that the polymerization reaction of this system is well described by Kamal’s model. Cytotoxicity results, performed on extracts 28 days after PBS incubation, showed no toxicity of the materials extracted from the lenses indicating that they can be considered as safe materials in ocular lens applications. The viability and proliferation of L929 fibroblast cells in extracting media were followed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and they may have a great potential as ideal supporting lens in people who suffer from keratoconus disease.

Graphical abstract

The effect of acrylate-based dental adhesive solvent content on microleakage in composite restorations

Background:

This study aimed to evaluate the effect of different percentages of ethanol solvent of an experimental methacrylate-based dentin bonding agent containing polyhedral oligomeric silsesquioxanes (POSS) on the microleakage of resin composite restorations.

Materials and Methods:

In this experimental study, 42 extracted human premolar teeth used and 84 standard Class V cavities were prepared on the buccal and lingual surfaces of the teeth. The teeth were divided into 6 groups of 7. Experimental bonding agents with different percentages of solvent were used in 5 groups and Single Bond^® as a control. The teeth were restored with resin composite and subjected to thermal cycling test. Teeth were then immersed in a solution of 2% basic fuchsine dye for 24 h and sectioned buccolingually and scored using stereomicroscope with ×32 magnification. Microleakage data were analyzed using the Kruskal–Wallis, Mann–Whitney U, and Wilcoxon tests.

Results:

There were significant differences between the microleakage enamel margins (P = 0.036) and dentinal margins (P = 0.008) in all the groups. These significant differences were seen between the control group and groups containing 46 wt% solvent (P = 0.011), 46 wt% and 31 wt% solvent in dentinal (P = 0.027), 31 wt% and 0 wt% in enamel (P = 0.021), also 0 wt% and control in enamel (P = 0.039), and dentinal margins microleakage (P = 0.004). The microleakage in dentinal margins was higher than enamel margins (P < 0.001). In the groups with 46 wt% solvent (P = 0.103), 0 wt% (P = 0.122), and control group (P = 0.096), however, this difference was not significant.

Conclusion:

The adhesive containing 31 wt% solvent showed the least marginal microleakage, presence of POSS filler may also result in the reduction of microleakage.