Influences of supra-physiological temperatures on microstructure and mechanical properties of skin tissue

Hybrid Fillers Personal Experience of Premixing Calcium Hydroxylapatite and Hyaluronic Acid for Natural Face Reshaping

OBJECTIVE

This retrospective study evaluates the efficacy and safety of premixed calcium hydroxylapatite (CaHA) and hyaluronic acid (HA) hybrid fillers for facial reshaping and rejuvenation, focusing on natural outcomes with long-term follow-up over 12 months.

METHODS

Forty-six patients (ages 45-65) underwent hybrid filler treatments using a 1:1 premixed formulation of CaHA and HA. Injection techniques targeted specific facial zones using cannulas for subdermal delivery. Standardized 3D imaging and the Merz Aesthetics Scale (CR-MASJ) were used to assess lifting effects and volume restoration. The Global Aesthetic Improvement Scale (GAIS) measured patient satisfaction.

RESULTS

Improvements in skin laxity, volume restoration, and facial contouring were noted as early as 3 months post-treatment and sustained through 12 months. Premixed hybrid fillers demonstrated enhanced biostimulatory effects compared with standalone CaHA or HA, promoting neocollagenesis and providing immediate and lasting results. Adverse events were minimal, with no significant complications reported.

CONCLUSION

Premixing CaHA and HA offers a safe, effective, and reproducible technique for natural facial reshaping and rejuvenation. The combination enhances skin quality while providing immediate volumization and long-term collagen stimulation, meeting the aesthetic expectations of patients seeking minimally invasive anti-aging solutions.

Histopathology of thermal effects in endoscopic ear surgery: An experimental animal study

Objective

The potential risk of thermal damage in the transcanal endoscopic ear surgery has been a concerning issue. This study aimed to investigate the histopathological effects of heat exposure of different durations in external auditory canal (EAC) skin and facial nerve tissues.

Methods

This study was conducted on 20 rabbits assigned equally to five groups according to the endoscope-transmitted heat exposure duration: Control group (no exposure), 2, 10, 15, and 30 min. At the end of the procedure, EAC skin and the tympanic segment of facial nerve tissue samples were taken surgically and histopathologically examined.

Results

Significant histopathological thermal damage findings in external auditory canal skin and facial nerve tissues were observed under endoscope-transmitted heat exposure longer than 15 and 10 min, respectively.

Conclusion

This study demonstrated that prolonged exposure of the endoscope-transmitted heat can cause histopathological thermal damage in EAC skin and facial nerve on rabbit subjects.

A multifunctional Fe2O3@MoS2@SDS Z-scheme nanocomposite: NIR enhanced bacterial inactivation, degradation antibiotics and inhibiting ARGs dissemination

To fight the flourishment of drug-resistant bacteria caused by antibiotics and the dissemination of antibiotic resistance genes (ARGs), it is of great urgency to develop multifunctional non-antibiotic agents with residual antibiotics elimination, and ARGs dissemination inhibition properties. Herein, sodium dodecyl sulfate (SDS) was modified onto the surface of Fe2O3 @MoS2 by ultrasonic method to obtain the Z-scheme, multifunctional Fe2O3 @MoS2 @SDS nanocomposites. The Fe2O3 @MoS2 @SDS (weight ratio of Fe2O3 @MoS2 and SDS was 1:1) was selected as the optimal agent. Under NIR irradiation, the Fe2O3 @MoS2 @SDS had a photothermal conversion efficiency of 45.96%, and could generate plenty of reactive oxygen species (ROS) at the same time. Under the synergy of photothermal and photodynamic, the antibacterial efficiency of Fe2O3 @MoS2 @SDS to E. coli, MRSA and P. aeruginosa could reach 99.95%, 99.97% and 99.58%, respectively, indicating excellent photothermal-photodynamic therapy (PPT) effect. The Fe2O3 @MoS2 @SDS also displayed photocatalytic activity in degradation of tetracycline (TC). The degradation rate of TC could reach 92.3% after 2 h of visible light irradiation. The obtained results indicated that a promising Fe2O3 @MoS2 @SDS composite based multifunctional nanoplatform could be constructed for NIR induced bacterial inactivation, antibiotics degradation and ARGs dissemination inhibition.

Sterilization of sealed PVDF pouches containing decellularized scaffold by electrical stimulation

A terminal sterilization process for tissue engineering products, such as allografts and biomaterials is necessary to ensure complete removal of pathogenic microorganisms such as the bacteria, fungi and viruses. However, it can be difficult to sterilize allografts and artificial tissue models packaged in wet conditions without deformation. In this study, we investigated the sterilization effects of electrical stimulation (ES) and assessed its suitability by evaluating sterility assurance levels in pouches at a constant current. Stability of polyvinylidene fluoride pouches was determined by a sterility test performed after exposure to five microorganisms (Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans) for 5 days; the sterility test was also performed with decellularized human dermal tissues inoculated with the five microorganisms. Sterilization using ES inactivated microorganisms both inside and outside of sealed pouches and caused no damage to the packaged tissue. Our results support the development of a novel system that involves ES sterilization for packaging of implantable biomaterials and human derived materials. This article is protected by copyright. All rights reserved.

Intraoperative thermal safety of endoscopic ear surgery utilizing a holder

PURPOSE

Despite the ever-growing popularity of endoscopic ear surgery (EES), there are still concerns regarding the potential thermal risk associated with the use of light sources and also questions raised about the thermal safety of extended stationary applications of endoscopes with holders that allow the use of both hands in the middle ear. The temperature changes witnessed during EES when using different calipers on static endoscopes fitted with camera holders during true operations were measured, and effects of varying light source intensities, as well as the cooling effect of irrigation and suction, were investigated.

METHODS

This study included 12 patients with chronic otitis who were scheduled to undergo myringoplasty surgery. Two of five different endoscopes with xenon light sources (4 mm-0°, 3 mm-0°, 2.7 mm-0°, 3 mm-45° and, 2.7 mm-30°) were used on each patient. Following irrigation and aspiration, gradually increasing heat measurements were recorded at two-minute intervals using a thermocouple thermometer for the entire period the endoscope remained in the ear. Three measurements obtained within the final 6 min, all of which were the same and reached a plateau, were considered to be the peak heat value. Measurements were repeated twice in each patient at 100% and 50% light intensities.

RESULTS

The highest heat was recorded by the 4 mm-0° endoscope, with heats at 100% and 50% light intensity recorded as 48.4 °C and 43.2 °C, respectively. The highest heat was measured by the 2.7 mm-0° endoscope, and heats recorded at 100% and 50% light intensities were 37.8 °C and 35.3 °C, respectively.

CONCLUSION

Stationary use of endoscopes with 3 mm and smaller calipers without irrigation or aspiration, the heat in the middle ear would appear to be safe, and at a level that does not cause thermal trauma to tissue. The present study demonstrates that frequent aspiration or intermittent irrigation may prevent potential thermal damage, even in procedures performed using endoscopes of a 4 mm caliper. Light intensity settings of 50% can be adopted as a further safety measure against potential thermal risk without compromising visual acuity.

Skin aging as a mechanical phenomenon: The main weak links

From a mechanical point of view, human skin appears as a layered composite containing the stiff thin cover layer presented by the stratum corneum, below which are the more compliant layers of viable epidermis and dermis and further below the much more compliant adjacent layer of subcutaneous white adipose tissue (sWAT). Upon exposure to a strain, such a multi-layer system demonstrates structural instabilities in its stiffer layers, which in its simplest form is the wrinkling. These instabilities appear hierarchically when the mechanical strain in the skin exceeds some critical values. Their appearance is mainly dependent on the mismatch in mechanical properties between adjacent skin layers or between the skin and sWAT, on the adhesive strength and thickness ratios between the layers, on their bending and tensile stiffness as well as on the value of the stress existing in single layers. Gradual reduction of elastic fibers in aging significantly reduces the skin's ability to bend, prompting an up to 4-fold reduction of its stability against wrinkling, thereby explaining the role of these fibers in skin aging. While chronological and extrinsic aging differently modify these parameters, they lead to the same end result, reducing the critical strain required for the onset of instabilities. Comparing of mechanical properties of the skin presented as a bi-, tri- or tetra-layer structure demonstrates the particular importance of the papillary dermis in skin aging and provides the arguments to consider the undulations on the dermal-epidermal and dermal-sWAT interfaces as the result of mechanical bifurcation, leading to structural instabilities inside of the skin. According to this model, anti-aging strategies should focus not as much on the reinforcement of the dermis, but rather aim to treat the elastic mismatch between different adjacent layers in the skin and sWAT as well as the adhesion between these layers.

Role of adipose tissue in facial aging

Age-dependent modification of the facial subcutaneous white adipose tissue (sWAT) connected with reduction of its volume, modification of collagen content and adhesion between dermal and adipose layers can significantly influence mechanical stability of the skin and cause the development of aging symptoms such as wrinkles. Typical aging appearance in facial skin is at least partly connected with special phenotypical features of facial preadipocytes and mature adipocytes. In this paper, we have discussed the possible roles of local inflammation, compartmental structure of facial sWAT and trans-differentiation processes such as beiging of white adipocytes and adipocyte-myofibroblast transition in facial skin aging.

Acute changes in histopathology and intravascular imaging after catheter-based renal denervation in a porcine model

OBJECTIVES

We first aimed to identify the histopathological changes occurring immediately after renal denervation (RDN) with radiofrequency energy, and then to assess the feasibility of determining procedural success using currently available clinical intravascular imaging techniques.

BACKGROUND

Catheter-based RDN has been used as an alternative therapy for hypertension. However, no practical endpoint to determine procedural success during treatment has been established.

METHODS

A total of 39 ablation lesions were induced in vivo in eight porcine renal arteries and a total of 15 ablation lesions were induced ex vivo in five excised porcine renal arteries with a radiofrequency delivery device. Acute histological changes and appearance on intravascular imaging of the lesions were investigated with light microscopy, transmission electron microscopy, intravascular ultrasound (IVUS), and optical frequency domain imaging (OFDI).

RESULTS

Marked changes were noted in media, adventitia, and perirenal-arterial nerves immediately after in vivo ablation. Changes visualized on IVUS were characterized by focal adventitial thickening comprising a relatively echogenic layer around a heterogeneously hypoechoic interior region, and on OFDI as disappearance of the external elastic membrane signals with high scattering of signals in the surface layer. The changes after ex vivo ablation were histopathologically identical to those from in vivo ablation. There were statistically significant positive correlations in measured dimensions (area, depth, width, and diameter) of ablation lesions between histopathology and IVUS/OFDI findings (Pearson correlation coefficients = 0.69-0.77).

CONCLUSIONS

These findings suggest that observation of treated renal arteries by IVUS or OFDI immediately after RDN improves the success rate of RDN.

Development of chitosan/β-glycerophosphate/glycerol hydrogel as a thermosensitive coupling agent

This work develops a dual-function thermosensitive hydrogel to prevent overheating, a side effect of focused ultrasound therapy. The proposed hydrogel has the components of chitosan, β-glycerophosphate, and glycerol. Its thermosensitive sol-to-gel transition gives an instant signal of overheating without the need of any awkward sensing device. Impacts of varying component concentrations on the sol-to-gel temperature, rate, and degree of transparency are also investigated. Chemical structures and ultrasonic coefficients after heating are obtained with a Fourier transform infrared spectroscopy and ultrasonic measurement, respectively. Optimized formula of the proposed hydrogel is 0.5% chitosan, 5% β-glycerophosphate, and 25% glycerol. This hydrogel has a high acoustic impedance (Z=1.8 Mrayl) close to that of human skin, high ultrasonic transmission (T=99%, which is normalized to water) from 25 to 55°C, and low attenuation coefficient (α=4.0Np/m). These properties assure the success of dual functions of the hydrogel developed in this work.

Measurements of the thermal coefficient of optical attenuation at different depth regions of in vivo human skins using optical coherence tomography: a pilot study

We present detailed measurement results of optical attenuation's thermal coefficients (referenced to the temperature of the skin surface) in different depth regions of in vivo human forearm skins using optical coherence tomography (OCT). We first design a temperature control module with an integrated optical probe to precisely control the surface temperature of a section of human skin. We propose a method of using the correlation map to identify regions in the skin having strong correlations with the surface temperature of the skin and find that the attenuation coefficient in these regions closely follows the variation of the surface temperature without any hysteresis. We observe a negative thermal coefficient of attenuation in the epidermis. While in dermis, the slope signs of the thermal coefficient of attenuation are different at different depth regions for a particular subject, however, the depth regions with a positive (or negative) slope are different in different subjects. We further find that the magnitude of the thermal coefficient of attenuation coefficient is greater in epidermis than in dermis. We believe the knowledge of such thermal properties of skins is important for several noninvasive diagnostic applications, such as OCT glucose monitoring, and the method demonstrated in this paper is effective in studying the optical and biological properties in different regions of skin.