Pharmacological Approaches for the Prevention of Breast Implant Capsular Contracture.

Capsular contracture is a common complication associated with breast implants following reconstructive or aesthetic surgery in which a tight or constricting scar tissue capsule forms around the implant, often distorting the breast shape and resulting in chronic pain. Capsulectomy (involving full removal of the capsule surrounding the implant) and capsulotomy (where the capsule is released and/or partly removed to create more space for the implant) are the most common surgical procedures used to treat capsular contracture. Various structural modifications of the implant device (including use of textured implants, submuscular placement of the implant, and the use of polyurethane-coated implants) and surgical strategies (including pre-operative skin washing and irrigation of the implant pocket with antibiotics) have been and/or are currently used to help reduce the incidence of capsular contracture. In this article, we review the pharmacological approaches-both commonly practiced in the clinic and experimental-reported in the scientific and clinical literature aimed at either preventing or treating capsular contracture, including (i) pre- and post-operative intravenous administration of drug substances, (ii) systemic (usually oral) administration of drugs before and after surgery, (iii) modification of the implant surface with grafted drug substances, (iv) irrigation of the implant or peri-implant tissue with drugs prior to implantation, and (v) incorporation of drugs into the implant shell or filler prior to surgery followed by drug release in situ after implantation.

Enhanced field-dependent conductivity and material properties of nano-AlN/micro-SiC/silicone elastomer hybrid composites for electric stress mitigation in high-voltage power modules.

This paper reports an enhancement of the nonlinear conductivity, thermal and mechanical properties of micro-silicon carbide/silicone elastomer (m-SiC/SE) composites by adding nano-aluminum nitride (n-AlN) for power module encapsulation applications. The electrical properties (such as nonlinear conductivity characteristics and transient permittivity obtained from polarization current, and trap distributions obtained from thermally stimulated depolarization current) and material properties (including thermo-gravimetric analysis, coefficient of thermal expansion (CTE), and thermal conductivity, tensile strength, strain at break and Young's modulus) of the pure SE, m-SiC/SE microcomposites, m-SiC/n-AlN/SE hybrid composites are investigated. The effect of the m-SiC fillers and n-AlN fillers on physicochemical properties of the SE matrix is analyzed by FT-IR spectroscopy and crosslinking degree. The measured nonlinear conductivity and transient permittivity are used for electric field simulation under DC stationary and square voltages. It is found that the addition of n-AlN fillers in the SE hybrid composite improves the nonlinear conductivity characteristics and mitigates the electric field under DC stationary and square voltages, compared to the SE microcomposite. Furthermore, the m-SiC/n-AlN/SE hybrid composite has a higher thermal degradation temperature, thermal conductivity, tensile strength, Young's modulus, and crosslinking degree than the SE microcomposite, whereas their CTE and strain at break are lower. It is elucidated that the m-SiC/n-AlN/SE hybrid composite with enhanced nonlinear conductivity and material properties is a promising packaging material for high-voltage power modules.

Omnidirectional Fingertip Pressure Sensor Using Hall Effect.

When grasping objects with uneven or varying shapes, accurate pressure measurement on robot fingers is critical for precise robotic gripping operations. However, measuring the pressure from the sides of the fingertips remains challenging owing to the poor omnidirectionality of the pressure sensor. In this study, we propose an omnidirectional sensitive pressure sensor using a cone-shaped magnet slider and Hall sensor embedded in a flexible elastomer, which guarantees taking pressure measurements from any side of the fingertip. The experimental results indicate that the proposed pressure sensor has a high sensitivity (61.34 mV/kPa) in a wide sensing range (4-90 kPa) without blind spots on the fingertip, which shows promising application prospects in robotics.

Silicone elastomer gel impregnated with 20(S)-protopanaxadiol-loaded nanostructured lipid carriers for ordered diabetic ulcer recovery.

Inefficient diabetic ulcer healing and scar formation remain a challenge worldwide, owing to a series of disordered and dynamic biological events that occur during the process of healing. A functional wound dressing that is capable of promoting ordered diabetic wound recovery is eagerly anticipated. In this study, we designed a silicone elastomer with embedded 20(S)-protopanaxadiol-loaded nanostructured lipid carriers (PPD-NS) to achieve ordered recovery in scarless diabetic ulcer healing. The nanostructured lipid carriers were prepared through an emulsion evaporation-solidification method and then incorporated into a network of silicone elastomer to form a unique nanostructured lipid carrier-enriched gel formulation. Interestingly, the PPD-NS showed excellent in vitro anti-inflammatory and proangiogenic activity. Moreover, in diabetic mice with full-thickness skin excision wound, treatment with PPD-NS significantly promoted in vivo scarless wound healing through suppressing inflammatory infiltration in the inflammatory phase, promoting angiogenesis during the proliferation phase, and regulating collagen deposition in the remodeling phase. Hence, this study demonstrates that the developed PPD-NS could facilitate ordered diabetic wound recovery via multifunctional improvement during different wound-healing phases. This novel approach could be promising for scarless diabetic wound healing.

Matrix Vaginal Rings for Female Dogs-Effect of Altering Dimensions on Mechanical Properties and Dissolution Characteristics, and In vivo Safety Study.

The vaginal rings research is almost exclusively focused on rings for human medicine, although the dosage form offers improvement of therapeutic effect in other mammals as well. This contribution studied an effect of varying dimension parameters (diameter 20, 30 or 40 mm; height 3, 4 or 5 mm; width of annulus 5, 7.5 or 10 mm) on mechanical properties and dissolution behaviour of silicone vaginal rings with constant drug amount, intended for use in dogs. Results showed that altering dimensions influenced mechanical properties (compressive force, tensile strength and resistance of removal thread), in vitro drug release and water uptake. The removal thread resistance was increasing with increasing height and width. Compression force was higher for the rings with smaller diameter. The total drug release was increasing with decreasing height and rising diameter, surface area and water uptake during dissolution test. The initial dissolution rate was slower for the rings with higher width. As the best candidate for use in model dog subjects, the ring with 30 mm diameter, 3 mm height and 7.5 mm width was found. These drug-free vaginal rings were further tested in in vivo safety study. The results did not show any major deviation from the physiological conditions. Graphical abstract.

Colour Difference Between Caucasian and Afro-Caribbean Skin Tone Silicone Elastomer Moulded in Type II and Type III Dental Stone.

AIM: The colour stability of the silicone is essential for the longevity of facial prostheses. This in vitro study investigates the colour degradation of two different skin shade silicones moulded in Type II and Type III dental stone. METHODS & MATERIALS: Two different types of dental stone were used to fabricate 168 silicone samples (n=42 for each group) using M511 maxillofacial silicone, which was coloured with Spectromatch Procolourants. The polymerisation was carried out at 85°C 1.5 hours. A spectrophotometer was used to record the colour differences (ΔΕ) of each group before and after polymerisation. The CIEL*a*b* formula was used to obtain the measurements and a one-way ANOVA was carried out for the statistical analysis of the data. RESULTS: There is a statistically significant colour difference (ΔΕ) for all groups. For the Afro-Caribbean skin tone, Type III dental stone demonstrated the greatest colour change (ΔΕ = 4.36), whereas, for the Caucasian skin tone, it was the Type II dental stone (ΔΕ = 2.21). CONCLUSION: This study showed that regardless of the investing material, the colour of the silicone lightens after polymerisation. Both types of dental stone resulted in visible colour changes, with a ΔΕ ranging from 1.64 - 4.36.

Vibro-Perception of Optical Bio-Inspired Fiber-Skin.

In this research, based on the principle of optical interferometry, the Mach-Zehnder and Optical Phase-locked Loop (OPLL) vibro-perception systems of bio-inspired fiber-skin are designed to mimic the tactile perception of human skin. The fiber-skin is made of the optical fiber embedded in the silicone elastomer. The optical fiber is an instinctive and alternative sensor for tactile perception with high sensitivity and reliability, also low cost and susceptibility to the magnetic interference. The silicone elastomer serves as a substrate with high flexibility and biocompatibility, and the optical fiber core serves as the vibro-perception sensor to detect physical motions like tapping and sliding. According to the experimental results, the designed optical fiber-skin demonstrates the ability to detect the physical motions like tapping and sliding in both the Mach-Zehnder and OPLL vibro-perception systems. For direct contact condition, the OPLL vibro-perception system shows better performance compared with the Mach-Zehnder vibro-perception system. However, the Mach-Zehnder vibro-perception system is preferable to the OPLL system in the indirect contact experiment. In summary, the fiber-skin is validated to have light touch character and excellent repeatability, which is highly-suitable for skin-mimic sensing.

In Vitro Cytotoxicity of Maxillofacial Silicone Elastomers: Effect of Nano-particles.

PURPOSE: Silicone elastomers are generally used for maxillofacial extraoral prostheses. The purpose of this in vitro study was to evaluate the cytotoxicity of different kinds of nanoparticles added to two types of maxillofacial elastomers. MATERIALS AND METHODS: A-2000 and A-2006 silicone elastomers were used. The silicone specimens were divided into eight groups according to the presence of additional nanoparticles (n = 18). The following represents the groups in the study: Group A: A-2000 silicone (control group); Group B: A-2006 silicone (control group); Group C: A-2000 silicone and the addition of titanium dioxide (TiO2 ); Group D: A-2006 silicone and the addition of TiO2 ; Group E: A-2000 silicone and the addition of fumed silica; Group F: A-2006 silicone and the addition of fumed silica; Group G: A-2000 silicone and the addition of silaned silica; Group H: A-2006 silicone and the addition of silaned silica. A paired sample t-test was used to analyze the cytotoxicity of each group after 24, 48, and 72 hours. RESULTS: Based on the results of the 24-hour analysis, the biocompatibility values of the (A-2006) fumed silica group were higher than those of the control groups. There was no statistically significant difference in A-2006 and A-2000 groups. The cytotoxicity values of the control groups and TiO2 (A-2000 silicone) elastomer groups increased at all test times; however, the cytotoxicity values of the TiO2 (A-2006), fumed silica (A-2006), silaned silica (A-2006), fumed silica (A-2000), and silaned silica (A-2000) groups increased significantly only from 24 to 48 hours. CONCLUSION: Nanoparticles of TiO2 , fumed silica, and silaned silica added to a commercial silicone-based elastomer used for fabrication of maxillofacial prostheses are nontoxic.

Effect of manufacturing and experimental conditions on the mechanical and surface properties of silicone elastomer scaffolds used in endothelial mechanobiological studies.

BACKGROUND: Mechanobiological studies allow the characterization of cell response to mechanical stresses. Cells need to be supported by a material with properties similar to the physiological environment. Silicone elastomers have been used to produce various in vitro scaffolds of different geometries for endothelial cell studies given its relevant mechanical, optical and surface properties. However, obtaining defined and repeatable properties is a challenge as depending on the different manufacturing and processing steps, mechanical and surface properties may vary significantly between research groups. METHODS: The impact of different manufacturing and processing methods on the mechanical and surface properties was assessed by measuring the Young's modulus and the contact angle. Silicone samples were produced using different curing temperatures and processed with different sterilization techniques and hydrophilization conditions. RESULTS: Different curing temperatures were used to obtain materials of different stiffness with a chosen silicone elastomer, i.e. Sylgard 184®. Sterilization by boiling had a tendency to stiffen samples cured at lower temperatures whereas UV and ethanol did not alter the material properties. Hydrophilization using sulphuric acid allowed to decrease surface hydrophobicity, however this effect was lost over time as hydrophobic recovery occurred. Extended contact with water maintained decreased hydrophobicity up to 7 days. Mechanobiological studies require complete cell coverage of the scaffolds used prior to mechanical stresses exposure. Different concentrations of fibronectin and collagen were used to coat the scaffolds and cell seeding density was varied to optimize cell coverage. CONCLUSION: This study highlights the potential bias introduced by manufacturing and processing conditions needed in the preparation of scaffolds used in mechanobiological studies involving endothelial cells. As manufacturing, processing and cell culture conditions are known to influence cell adhesion and function, they should be more thoroughly assessed by research groups that perform such mechanobiological studies using silicone.

Delayed-Onset Edematous Foreign Body Granulomas 40 Years After Augmentation Rhinoplasty by Silicone Implant Combined with Liquid Silicone Injection.

Despite the widespread application of augmentation rhinoplasty in Asia, reports on the interaction between alloplastic implants and injectable filler are scarce. This paper reports on a patient with delayed-onset edematous foreign body granuloma that had been caused by augmentation rhinoplasty performed using a silicone implant in conjunction with a liquid silicone injection 40 years earlier. This is the longest reported duration between initial rhinoplasty and the exacerbation of foreign body granuloma. This case report also presents intraoperative findings pertaining to the interlocking structures between silicone implants and injected liquid silicone. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Effect of vulcanization temperature and dental stone colour on colour degradation of maxillofacial silicone elastomers.

BACKGROUND: Colour degradation is a major problem in maxillofacial silicone elastomers. Recent studies have focused on colour stability and the mechanical properties of the silicone elastomers. A colour match is also essential for the acceptance of the prosthesis by the patient. The aim of this study is to assess the colour degradation of the silicone elastomer after being moulded in different colours of dental stones at two different vulcanization temperatures. METHODS: Five different colours of dental stones were used to fabricate a total of 120 silicone blocks using a Cosmesil M511 maxillofacial silicone elastomer. Vulcanization was completed at two different temperatures (25 and 100° Celsius). Colour measurements were obtained with a Conica Minolta spectrophotometer. The CIEDE2000 formula was used to calculate the colour differences (∆E00). Two-way ANOVA, one-way ANOVA with Bonferroni corrected post-hoc p values and independent samples t-test were used for the statistical analyses. RESULTS: High temperature vulcanization causes lightening of the maxillofacial silicone elastomers without regard to the dental stone colour (p = 0.001). Specimens moulded in green stone lightened least at room temperature (p = 0.999). Compared to the control group, at high temperature, all specimens moulded in coloured dental stones darkened significantly (p < 0.001 for white, blue and yellow; p = 0.006 for green; p = 0.045 for reddish-brown). In the high temperature group, the shift to a green chroma was significant in the white, yellow and green dental stones groups (p = 0.001, p = 0.002, p < 0.001, respectively). The mean b* of the high temperature control group was higher than that of the room temperature control group (p < 0.001). The only ∆E00 score lower than the perceptibility threshold for dental materials (∆E00 = 1.30) was between the room temperature control group and the room temperature green dental stone group (∆E00 = 0.96). CONCLUSIONS: Green and blue dental stones cause less colour degradation in silicone elastomers. Reddish-brown dental stones cause the most colour degradation in silicone elastomers. At 100 °C, the colour of the silicone elastomer lightens and yellows even if the elastomer is vulcanized in a stainless steel mould. White, yellow and reddish-brown dental stones make the silicone elastomer appear more yellow even if the elastomer is vulcanized at room temperature.

A spectrophotometric analysis of extraoral aging conditions on the color stability of maxillofacial silicone.

CONTEXT: Surveys have reported color fading as the most frequent reasons patients given for disliking their prostheses. AIM: The aim of the study is to compare the color variation between two maxillofacial silicone elastomers after subjecting them to extraoral aging conditions. SUBJECTS AND METHODS: A total of 80 samples were made from M511 Maxillofacial Rubber (Part A: Part B = 10:1) and Z004 Platinum Silicone Rubber (Part A: Part B = 1:1) and divided into two main Groups A and B (40 each). These main groups were then subdivided into five subgroups (A1B1, A2B2, A3B3, A4B4, and A5B5) (n = 8); outdoor weathering, acidic perspiration, sebum (for 6 months), and neutral soap and disinfectant (for 30 h), respectively. Baseline L*a*b* values were recorded. The samples were subjected to the extraoral aging conditions, and the L* a*b* values were recorded after the aging period using a spectrophotometer. STATISTICAL ANALYSIS: The intergroup comparison was done by Kruskal-Wallis test, whereas the intragroup comparison was done by Mann-Whitney test. RESULTS: All groups exhibited visually detectable, mean color differences that ranged from 3.06-5.21, except for A4B4. There was no statistical significance between the two materials when subjected to extraoral aging conditions. CONCLUSIONS: Visually perceptible and clinically unacceptable color changes occur when exposed to various extraoral aging conditions except for neutral soap solution immersion, for which values of Δ E* were clinically acceptable (ΔE < 3). It can be said for all practical purposes, clinically, the choice between M511 Maxillofacial Rubber (Part A: Part B = 10:1) and Z004 Platinum Silicone Rubber (Part A: Part B = 1:1) would yield more or less the same results, with unacceptable norms in terms of color stability under extraoral aging conditions.

Mechanical Properties and Simulated Aging of Silicone Maxillofacial Elastomers: Advancements in the Past 45 Years.

PURPOSE: To identify and discuss the findings of publications on mechanical behavior of maxillofacial prosthetic materials published since 1969. METHODS: Original experimental articles reporting on mechanical properties of maxillofacial prosthetic materials were included. A two-stage search of the literature, electronic and hand search, identified relevant published studies up to May 2015. An extensive electronic search was conducted of databases including PubMed, Embase, Scopus, and Google Scholar. Included primary studies (n = 63) reported on tensile strength, tear strength, and hardness of maxillofacial prosthetic materials at baseline and after aging. RESULTS: The search revealed 63 papers, with more than 28 papers being published in the past 10 years, which shows an increased number of publications when compared to only 6 papers published in the 1970s. The increase is linear with significant correlation (r = 0.85). Such an increase reflects great awareness and continued developments and warrants more research in the field of maxillofacial prosthetic materials properties; however, it is difficult to directly compare results, as studies varied in maxillofacial prosthetic materials tested with various silicone elastomers being heavily investigated, standards followed in preparing test specimens, experimental testing protocols, and parameters used in setting simulated aging conditionings. CONCLUSION: It is imperative to overcome the existing variability by establishing unified national or international standards/specifications for maxillofacial prosthetic materials. Standardization organizations or bodies, the scientific community, and academia need to be coordinated to achieve this goal. In the meantime and despite all of these theoretically significant alternatives, clinical practice still faces problems with serviceability of maxillofacial prostheses.

Inhibition of Candida albicans adhesion on medical-grade silicone by a Lactobacillus-derived biosurfactant.

AIMS: The study aimed at investigating the ability of biosurfactant (BS) produced by a Lactobacillus brevis isolate (CV8LAC) to inhibit adhesion and biofilm formation of Candida albicans on medical-grade silicone elastomeric disks (SEDs). METHODS AND RESULTS: Biosurfactant activity was evaluated at physiological conditions, by means of co-incubation and precoating assays. Additionally, BS extract was tested for antifungal susceptibility against C. albicans in both planktonic and sessile form. Biofilm covered surface and hyphae and blastospores occurrence were quantified by scanning electron microscopy (SEM) and image analysis. BS did not inhibit growth of C. albicans in both planktonic and sessile form. Nevertheless, co-incubation with 2000 µg ml(-1) BS significantly reduced biofilm formation on SEDs surface by 89, 90 and 90% after 24, 48 and 72 h of incubation. Fungal adhesion and biofilm formation to precoated SEDs was reduced by 62, 53, 50 and 44% after 1.5, 24, 48 and 72 h. SEM showed a significant reduction of biofilm covered surface in precoated disks but no differences in the production of hyphae or blastospores, except at 1.5 h of incubation. CONCLUSIONS: This study demonstrated that CV8LAC BS has the ability to counteract significantly the initial deposition of C. albicans to silicone surfaces and to effectively slow biofilm growth. SIGNIFICANCE AND IMPACT OF THE STUDY: The anti-adhesive properties of the CV8LAC BS suggest a potential role of the coating for preventing fungal infection associated to silicone medical devices.

Effect of Incorporation of Nano-Oxides on Color Stability of Maxillofacial Silicone Elastomer Subjected to Outdoor Weathering.

PURPOSE: The aim of this study was to evaluate the effect of incorporation of two compositions of nano-oxides on color stability of intrinsically colored maxillofacial silicone elastomer subjected to outdoor weathering. MATERIALS AND METHODS: Ninety Cosmesil M511 silicone elastomer specimens were fabricated. The control group was incorporated with intrinsic coloring agents (umber, brown, yellow), group A was incorporated with intrinsic coloring agents and nanosized titanium oxide (TiO2 ), and group B was incorporated with intrinsic coloring agents and nanosized zinc oxide (ZnO). For outdoor weathering, specimens were mounted on a treated plywood rack, and the assembly was weathered for 6 months. A GretagMacbeth Spectrolino spectrophotometer was used to determine the CIELAB (L*a*b*) parameter before and after weathering of each specimen, and the values were noted. The color change (∆E) values were analyzed by one-way ANOVA, Tukey's post hoc test, and paired t-test. RESULTS: The color change (ΔE*) for groups were control group > group A > group B. The control group (0.76 ± 0.32) and group A (0.47 ± 0.19) showed significant difference in the color change before and after weathering (p < 0.00001). Group B (0.03 ± 0.05) showed no significant difference in color change before and after weathering (p = 0.08). CONCLUSIONS: The present findings suggest that incorporation of nano-oxides improved the color stability of Cosmesil M511 silicone elastomer and also acted as an opacifier. ZnO-incorporated Cosmesil M511 specimens showed minimal or no color change and proved to be most color stable after being subjected to outdoor weathering.

Pre-clinical development of a combination microbicide vaginal ring containing dapivirine and darunavir.

OBJECTIVES: Combination microbicide vaginal rings may be more effective than single microbicide rings at reducing/preventing sexual transmission of HIV. Here, we report the pre-clinical development and macaque pharmacokinetics of matrix-type silicone elastomer vaginal rings containing dapivirine and darunavir. METHODS: Macaque rings containing 25 mg dapivirine, 100 mg dapivirine, 300 mg darunavir or 100 mg dapivirine+300 mg darunavir were manufactured and characterized by differential scanning calorimetry. In vitro release was assessed into isopropanol/water and simulated vaginal fluid. Macaque vaginal fluid and blood serum concentrations for both antiretrovirals were measured during 28 day ring use. Tissue levels were measured on day 28. Ex vivo challenge studies were performed on vaginal fluid samples and IC50 values were calculated. RESULTS: Darunavir caused a concentration-dependent reduction in the dapivirine melting temperature in both solid drug mixes and in the combination ring. In vitro release from rings was dependent on drug loading, the number of drugs present and the release medium. In macaques, serum concentrations of both microbicides were maintained between 10(1) and 10(2) pg/mL. Vaginal fluid levels ranged between 10(3) and 10(4) ng/g and between 10(4) and 10(5) ng/g for dapivirine and darunavir, respectively. Both dapivirine and darunavir showed very similar concentrations in each tissue type; the range of drug tissue concentrations followed the general rank order: vagina (1.8 × 10(3)-3.8 × 10(3) ng/g)  > cervix (9.4 × 10(1)-3.9 × 10(2) ng/g)  > uterus (0-108 ng/g)  > rectum (0-40 ng/g). Measured IC50 values were >2 ng/mL for both compounds. CONCLUSIONS: Based on these results, and in light of recent clinical progress of the 25 mg dapivirine ring, a combination vaginal ring containing dapivirine and darunavir is a viable second-generation HIV microbicide candidate.

Effect of Organic and Inorganic Nanoparticles on Colour Stability and Mechanical Properties of Heat Vulcanised Maxillofacial Silicone Elastomer: a Comparative Study.

Objectives: The purpose of this comparative study in vitro was to evaluate the effect of organic and inorganic nanoparticles on colour stability, tear strength and hardness of maxillofacial silicone elastomer at baseline and when subjected to outdoor weathering for 6 months. Material and Methods: A total of 240 specimens were fabricated using M511 platinum silicone which were divided into total 4 groups (n = 60) based on the type of nanoparticles (control, polytetrafuoroethylene [PTFE], titanium dioxide [TiO2], zinc oxide [ZnO]) added and each group was further divided into 3 subgroups (n = 20) for colour, tear strength (TS) and hardness (H) testing. The tests were conducted and data was obtained both before and after outdoor weathering of 6 months. Results: Minimum colour change after weathering was observed in PTFE group (∆E = 2.23). TiO2 group showed maximum TS (12.01 N/mm) followed by PTFE group (10.85 N/mm) before weathering. After weathering, maximum TS was shown by TiO2 group (12.9 N/mm) and PTFE group (12.54 N/mm). TiO2 group showed maximum hardness (24.15 shore A) before weathering and PTFE group showed maximum hardness (33.43 shore A) after weathering. Conclusions: Within the limitations of this study, it can be concluded that the addition of polytetrafuoroethylene nanoparticles to the polymer enhances both the optical as well as mechanical properties and can be considered favourable for the extended life of the prosthesis.

Tetraphenylethene-modified polysiloxanes: Synthesis, AIE properties and multi-stimuli responsive fluorescence.

Herein, polysiloxane-based aggregation-induced emission (AIE) polymers and rubbers were prepared which display interesting multi-stimuli responsive fluorescence. TPE-modified polydimethylsiloxanes (PDMS-TPE) as polysiloxane-based AIE polymers were synthesized through Heck reaction of bromo-substituted tetraphenylethene (TPE-Br) and vinyl polysiloxanes. As expected, TPE moiety endows the modified polysiloxane with typical AIE behavior. However, limited by the long polymer chains, the aggregation process of PDMS-TPE shows obvious differences compared with the small molecule TPE-Br. The fluorescence of PDMS-TPE in THF/H2O starts to increase when the H2O fraction (fw) is 70% while TPE-Br is nearly non-luminous until the fw is up to 99%. The fluorescence intensity ratio (I/I0) of PDMS-TPE in the aggregated state and dispersed state is over 1300, greater than that of TPE-Br (I/I0 = 380). More importantly, the exceptional thermal motion of Si-O-Si chains and AIE characteristic of TPE moiety work together, enabling PDMS-TPE to show specific temperature-dependent fluorescence with a wider response range of room temperature to 190°C, which is distinguished from TPE-Br. And such fluorescence responsiveness possess good fatigue-resistance. Furthermore, fluorescent silicone rubbers, r-PDMS-TPE were prepared by using PDMS-TPE as additive of the base gum. They display interesting solvent-controllable fluorescence and higher tensile strength (4.42 MPa) than the control sample without TPE component (1.96 MPa). Notably, a unique stretching-enhanced emission (SEE) phenomenon is observed from these TPE-modified silicone rubbers. When being stretched, the rubbers' fluorescent emission intensity could increase by 143%.

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.

Assessment of the antibacterial effect of Barium Titanate nanoparticles against Staphylococcus epidermidis adhesion after addition to maxillofacial silicone.

Background: Maxillofacial silicones are the most popular and acceptable material for making maxillofacial prostheses, but they are not perfect in every sense. To enhance their effectiveness, more improvements to their properties are required, such as their antimicrobial efficiency. This study assess the antibacterial effect of barium titanate nanoparticles in various percentages against staphylococcus epidermidis biofilm adhesion after addition to maxillofacial silicone. Methods: Barium titanate nanoparticles were added into VST-50 platinum silicone elastomer in four weight percentages (0.25wt%, 0.5wt%, 0.75wt% and 1wt%). 50 specimens were prepared and categorized into five groups; one control group and four experimental groups. All conducted data was statistically analyzed using (one-way ANOVA) analysis of variance, and Games-Howell multiple comparison test (significant level at p < 0.05). Shapiro-Wilk and Levene's tests were used, respectively, to evaluate the normal distribution and homogeneity of the data. Result: One-way ANOVA test revealed a highly significant difference between all groups, and Games-Howell test revealed a highly significant difference between the control group and the four experimental groups. The 0.25wt% and 0.5wt% groups revealed a highly significant difference between them and with the (0.75%wt and 0.1%wt) groups. While the 0.75wt% group revealed a significant difference with 1wt% group. Conclusions: The addition of barium titanate to VST-50 maxillofacial silicone enhanced the antibacterial activity of silicon against Staphylococcus epidermidis, and this activity seems to be concentration dependent. FTIR analysis demonstrated no chemical interaction between the Barium Titanate and the VST-50 maxillofacial silicone elastomer. SEM pictures show that the barium titanate nanopowder was effectively dispersed inside the maxillofacial silicone matrix.