Silicone Discs Research Articles

Improvement of a low-cost protocol for a simultaneous comparative evaluation of hydrolytic activity between sessile and planktonic cells: Candida albicans as a study model

Candida albicans is often implicated in nosocomial infections with fatal consequences. Its virulence is contributed to hydrolytic enzymes and biofilm formation. Previous research focused on studying these virulence factors individually. Therefore, this study aimed to investigate the impact of biofilm formation on the hydrolytic activity using an adapted low-cost method. Eleven strains of C. albicans were used. The biofilms were formed on pre-treated silicone discs using 24-well plates and then deposited on the appropriate agar to test each enzyme, while the planktonic cells were conventionally seeded. Biofilms were analysed using Raman spectroscopy, fluorescent and scanning electron microscopy. The adapted method provided an evaluation of hydrolytic enzymes activity in C. albicans biofilm and showed that sessile cells had a higher phospholipase and proteinase activities compared with planktonic cells. These findings were supported by spectroscopic and microscopic analyses, which provided valuable insights into the virulence mechanisms of C. albicans during biofilm formation.

Release Control of Biologically Active Substances from Simulation Model of Silicone Liners

Introduction. In modern medicine, the requirements for the quality of used materials are getting stricter. There is serious concern about bacterial and fungal contamination related to the use of silicone polymeric products, especially those that are in direct contact with human tissues and body fluids. In this regard, the issue of impregnating silicone medical products with various biologically active substances (BAS), particularly with antimicrobial properties, appears relevant.Aim. The research studies the relevance of adding BAS into silicone medical devices to improve their quality and prevent negative consequences of their use. The authors of the article aimed at proving prolonged release of the chosen BAS from silicone products during their contact with skin and the bacteriostatic effect emerging as a result of the BAS release. That required verifying the existence of BAS in the washouts from silicone disks, which, in turn, proves the fact that BAS initially distributed evenly in the volume of a silicone disk are capable of diffusing to the surface and then releasing from it under mechanical action, as well as when treating it with alcohol or alcohol-containing solutions.Materials and methods. Symdiol and bisabolol were selected as the BAS for this study due to their proved antibacterial, anti-inflammatory and moisturizing properties. Bisabolol and symdiol were used in the form of Dragosantol 100 and SymDiol 68T preparations correspondingly. Silicone disks (SDs), impregnated with BAS (0,2 % of the volume) were used as a simulation model of silicone liners. The BAS release from silicone liner models was assessed using highly sensitive chromatographic methods of thin-layer and gas-liquid chromatography.Results and discussion. The method of impregnating SDs with BAS was worked out, the optimal concentration of these substances to add them into the silicone base was selected. The release of the impregnated additives, as well as prolonged stable releasing effect, were confirmed. The data obtained during the experiment allows saying with confidence that the impregnated preparation (symdiol and bisabolol) releases from a SD even upon short and low-intensity mechanical contact with skin, which produces stable bacteriostatic effect on a wide range of microorganisms. The process of BAS release from SDs is also facilitated when treating the product periodically with alcohol-containing solutions, which is necessary according to the operating rules. The obtained results of the chromatographic research quite correlate with the data of the previous microbiological experiments regarding the studied topic. Release of the studied BAS from polymer products during their contact with the skin within the period of not less than 3 months justifies feasibility of adding these BAS into the silicone base.Conclusions. The study confirmed the release of biologically active substances from silicone medical products. Adding BAS into silicone liners undoubtedly improves the quality of these medical products, which can be applied in prosthetics and orthoses.

Disinfection Ability of Aqueous Ocimum sanctum (Tulsi) Extract against Candida albicans and Staphylococcus aureus Inoculated on Maxillofacial Silicone - An In Vitro Study

Abstract Background: Patients who use maxillofacial prostheses often encounter difficulties cleaning them thoroughly daily. Traditional cleaning methods may not work and could change the prostheses’ physical properties. Therefore, it is essential to look for alternative disinfection methods. Aim: The aim of this study was to evaluate the efficacy of aqueous extract of Ocimum sanctum (tulsi) against Candida albicans and Staphylococcus aureus inoculated on maxillofacial silicone. Materials and Methods: One hundred and twenty silicone discs, 5 mm diameter, 2 mm thick, were made with maxillofacial Factor II A-2000. Samples were divided into four main groups, each with three subgroups of 10 samples. Each subset was inoculated with C. albicans, S. aureus clinical strains, and the American Type Culture Collection (ATCC) strains. The specimens were incubated at 37°C for 72 h and then soaked in three disinfectant solutions: a neutral soap solution for 30 s, 0.2% chlorhexidine for 10 min, and aqueous tulsi for 10 min. The disinfection ability was determined based on the number of surviving cells by methoxy-nitro-sulfophenyl-tetrazolium carboxanilide assay, and the results were analyzed using a one-way analysis of variance and the post hoc Tukey’s test. Results: There were no significant differences in the ability to disinfect between neutral soap, 0.2% chlorhexidine, and tulsi extract when tested against clinical and ATCC C. albicans and clinical S. aureus. The P > 0.05 indicates that the differences between the disinfection abilities were not statistically significant. However, the 0.2% chlorhexidine disinfectant showed better results when used on Staphylococcus ATCC strains, with a P < 0.001. Conclusion: A 10% aqueous extract of tulsi can be used as a disinfectant for clinical and ATCC strains of C. albicans and the clinical strain of S. aureus.

Atmospheric Plasma Sources as Potential Tools for Surface and Hand Disinfection

Good hand hygiene has proven to be essential in reducing the uncontrolled spread of human pathogens. Cold atmospheric plasma (CAP) may provide an alternative to disinfecting hands with ethanol-based handrubs when handwashing facilities are unavailable. CAP can be safely applied to the skin if the energy is well controlled. In this study, radio frequency (RF) and direct current (DC) plasma sources were built with a pin-to-mesh electrodes configuration inside a fused silica tube with a 5 mm inner diameter. Microbiological assays based on EN 13697:2015+A1:2019 using Escherichia coli DSM 682 or Staphylococcus epidermidis DSM 20044 were used to examine the antimicrobial effect of various plasma conditions. Metal and silicone disks that model skin were used as inoculation matrices. The prototype air RF CAP achieved significant disinfection in the MHz range on stainless steel and silicone substrates. This is equivalent to half the performance of direct current CAP, which is only effective on conductive substrates. Using only electricity and air CAP could, with further optimization to increase its efficacy, replace or complement current hand disinfection methods, and mitigate the economic burden of public health crises in the future.

THE EFFECT OF THE PRE-HEATING PROCESS ON SURFACE ROUGHNESS OF COMPOMER

Aim: In pediatric dentistry, where fast finishing processes are of great importance to reduce the roughness in order to obtain an ideal restoration surface. In restorative materials, differences in surface roughness may occur with the pre-heating process. Therefore, the aim of the study is to compare the surface roughness of the compomer prepared at four different temperatures.
 Materials and Methods: In this study, discs prepared from light-cured compomer prepared at four different temperatures were evaluated and their surface roughnesses were compared. Compomer, which was brought to pre-heat values using a composite heating device to bring it to 39 ºC and 55 ºC, was placed on silicone discs with a diameter of 10 mm and a thickness of 2 mm. The surface roughness was measured with a profilometer device. Statistical analysis was performed with One Way ANOVA and t-test.
 Results: The surface roughness value of the compomer was the highest at 4 °C and the lowest at 55 °C. A statistically significant difference was found between the roughness value of compomer at 4 °C and the roughness values at 23 °C and 55 °C (p

Comparing the efficacy of antimicrobial pocket-irrigation protocols in an in vivo breast implant infection model

Breast implant infection and biofilm formation are major concerns in reconstructive and esthetic breast surgery, with significant medical and economic consequences. Staphylococcus is the common pathogen, with rapidly increasing rates of methicillin-resistant Staphylococcus aureus (MRSA). There is no consensus on prevention practices. This study compares the effect of several pocket irrigation and antibiotic prophylaxis regimens on implant colonization and biofilm formation in an established rat model of MRSA-infected silicone breast implants. Silicone discs were inserted in a sub-pectoral pocket in 57 rats (114 implants). Implant infection was induced by injection of free planktonic MRSA into the surgical pocket. Rats were allocated to study groups treated by different antimicrobial protocols: pocket irrigation with vancomycin, povidone-iodine, or saline. Each group was divided into subgroups treated with or without additional peri-operative systemic vancomycin. Implant colonization or overt infection was assessed at post-operative day 14 both clinically and by cultures. Pocket irrigation with vancomycin prevented contamination in 87% of implants. Irrigation and systemic vancomycin prevented contamination in 100% of implants with no difference between a single preoperative dose and a 48-h regimen. Systemic vancomycin alone or irrigation with povidone-iodine alone resulted in 100% contamination rates. In this in vivo model, combination of systemic vancomycin with vancomycin pocket irrigation was the most effective regimen, preventing contamination in 100% of implants. Continuation of post-operative antibiotic treatment showed no added advantage.

18. Tissue Microenvironment Affects Fibrotic Capsules Formed during Foreign Body Response

PURPOSE: Foreign body response (FBR) is a common surgical complication, wherein a fibrotic capsule forms around an implant. Though it is posited that FBR has mechanistic overlap with normal wound healing, the specific cell populations responsible for this phenomenon remain elusive. Our group previously demonstrated that En1 positive fibroblasts (EPFs) predominate in murine dorsal wounds, and showed that these cells are responsible for scar formation within the wound bed. This observation led us to explore the role of EPFs and other fibroblast subpopulations during FBR. METHODS: En-1Cre transgenic driver mice were crossed with R26mTmG reporter mice, generating En-1Cre; Rosa26mTmG (En1+) mice. In this mouse line, cells expressing En1 also express GFP, while all others express RFP. Silicone discs were surgically implanted below the subcutaneous layer of En1+ mice dorsi, and fibrotic capsules surrounding the implants were harvested at POD28. Immunohistochemistry and flow cytometry (FACS) analysis were utilized to evaluate the cellular characteristics of the En1+ cells. A subset of fibrotic capsules placed in C57BL/6J for 28 days was also prepared for single-cell RNA sequencing. Software packages in R and Python were used to identify and define subtypes of fibroblasts present within fibrotic capsules. Crosstalk and signaling pathways were further identified via network analysis platforms. RESULTS: Immunohistochemistry and FACS analysis confirmed that En1+ cells predominate in the fibrotic capsule, and that GFP+ cells also expressed pro-fibrotic markers, including Col-1 and α-SMA. As these cells were also negative for the endothelial and immune cell markers CD41 and CD45, respectively, these data indicate that En+ cells within capsules were primarily of fibroblast origin. Interestingly, basic histology highlighted that capsule thickness (p < 0.0001; n = 4) and collagen deposition (p = 0.0016; n = 4) were higher in the capsule adjacent to the subcutaneous tissue (subcutaneous capsule) in comparison to that adjacent to muscle tissue (muscle capsule). In parallel, our transcriptional dataset revealed that the distribution of fibroblast subpopulations present in subcutaneous capsule to that in muscle capsule differed. Notably, cell clustering, cell-cell interaction, and gene ontology analyses underscored that fibroblasts in the subcutaneous capsules were more fibrotic in nature relative to those present in muscle capsule. CONCLUSION: These data strongly suggest that, as with normal wound healing in which EPFs are diffusely present within a healing scar, En1 appears to play a key role in fibrotic capsule formation. Further, the presence of multiple subpopulations of fibroblasts revealed by our transcriptional analysis underscores the significant function fibroblasts may have in FBR, and that the tissue microenvironment may play a role in the fibrotic response. Deeper understanding of the mechanism behind fibroblasts’ involvement and the effect the tissue microenvironment may have on fibrotic capsule formation may offer potential therapeutic targets to reduce FBR post surgical implantation in the future.

In Vitro Antibacterial Activity of Silver Nanoparticles Conjugated with Amikacin and Combined with Hyperthermia against Drug-Resistant and Biofilm-Producing Strains.

In view of the current increase and spread of antimicrobial resistance (AMR), there is an urgent need to find new strategies to combat it. This study had two aims. First, we synthesized highly monodispersed silver nanoparticles (AgNPs) of approximately 17 nm, and we functionalized them with mercaptopoly(ethylene glycol) carboxylic acid (mPEG-COOH) and amikacin (AK). Second, we evaluated the antibacterial activity of this treatment (AgNPs_mPEG_AK) alone and in combination with hyperthermia against planktonic and biofilm-growing strains. AgNPs, AgNPs_mPEG, and AgNPs_mPEG_AK were characterized using a suite of spectroscopy and microscopy methods. Susceptibility to these treatments and AK was determined after 24 h and over time against 12 clinical multidrug-resistant (MDR)/extensively drug-resistant (XDR) isolates of Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The efficacy of the treatments alone and in combination with hyperthermia (1, 2, and 3 pulses at 41°C to 42°C for 15 min) was tested against the same planktonic strains using quantitative culture and against one P. aeruginosa strain growing on silicone disks using confocal laser scanning microscopy. The susceptibility studies showed that AgNPs_mPEG_AK was 10-fold more effective than AK alone, and bactericidal efficacy after 4, 8, 24, or 48 h was observed against 100% of the tested strains. The combination of AgNPs_mPEG_AK and hyperthermia eradicated 75% of the planktonic strains and exhibited significant reductions in biofilm formation by P. aeruginosa in comparison with the other treatments tested, except for AgNPs_mPEG_AK without hyperthermia. In conclusion, the combination of AgNPs_mPEG_AK and hyperthermia may be a promising therapy against MDR/XDR and biofilm-producing strains. IMPORTANCE Antimicrobial resistance (AMR) is one of the greatest public health challenges, accounting for 1.27 million deaths worldwide in 2019. Biofilms, a complex microbial community, directly contribute to increased AMR. Therefore, new strategies are urgently required to combat infections caused by AMR and biofilm-producing strains. Silver nanoparticles (AgNPs) exhibit antimicrobial activity and can be functionalized with antibiotics. Although AgNPs are very promising, their effectiveness in complex biological environments still falls below the concentrations at which AgNPs are stable in terms of aggregation. Thus, improving the antibacterial effectiveness of AgNPs by functionalizing them with antibiotics may be a significant change to consolidate AgNPs as an alternative to antibiotics. It has been reported that hyperthermia has a large effect on the growth of planktonic and biofilm-producing strains. Therefore, we propose a new strategy based on AgNPs functionalized with amikacin and combined with hyperthermia (41°C to 42°C) to treat AMR and biofilm-related infections.

An improved Chemcatcher-based method for the integrative passive sampling of 44 hydrophilic micropollutants in surface water – Part A: Calibration under four controlled hydrodynamic conditions

When monitoring water quality with hydrophilic integrative passive sampling devices, it is crucial to use accurate sampling rates (RS) that account for exposure conditions such as hydrodynamics. This study aims at calibrating Chemcatcher-like passive samplers – styrene-divinylbenzene reverse phase sulfonate (SDB-RPS) extraction disk covered by a polyethersulfone (PES) membrane – at four water flow velocities (5 to 40 cm s−1) in a channel system. First, the four hydrodynamic conditions were characterized by measuring the mass transfer coefficients of the water boundary layer (kw) at the surface of the samplers using the alabaster dissolution method. Then, fifty-six samplers were deployed in the channels and exposed for 7 different intervals varying from 1 to 21 days. Thus, RS were determined at four different kw for 44 hydrophilic compounds, ranging from 0.015 to 0.115 L day−1. Relationships were established between kw and RS using models for mixed rate control by the membrane and the water boundary layer. The estimated parameters of those relationships are suitable for the determination of accurate RS when kw is measured in situ, for example by co-deploying silicone disks spiked with performance and reference compounds (PRC) as implemented in Part B.

An improved Chemcatcher-based method for the integrative passive sampling of 44 hydrophilic micropollutants in surface water – Part B: Field implementation and comparison with automated active sampling

Integrative passive sampling is particularly useful in the monitoring of hydrophilic contaminants in surface water, but the impact of hydrodynamics on contaminant uptake still needs to be better considered. In part A (Glanzmann et al., 2023), Chemcatcher-like hydrophilic samplers (i.e., SDB-RPS extraction disks covered by PES microporous membranes) were calibrated to determine the sampling rates RS of 44 hydrophilic contaminants (pesticides, pharmaceuticals, industrial products) taking into account the hydrodynamic conditions. In this study, Chemcatcher-like passive sampling devices that allowed co-deploying hydrophilic samplers and performance reference compounds (PRC)-spiked silicone disks were tested in a Swiss river with intermediate water velocities (5–50 cm s−1, 23 cm s−1 on average) during 11 consecutive 14-day periods. The PRC dissipation from silicone disks – combined with the calibration data from part A – allowed to determine in-situ RS that took into account hydrodynamic conditions. The obtained aqueous time-weighted average (TWA) concentrations were found to be robust with good concordance between duplicates (mean quotient of 1.16 between the duplicates). For most measurements (76 %), TWA concentrations showed no major difference (<factor 2) from concentrations obtained with automated sampling (14-day composite samples). This observation was also valid for TWA concentrations calculated with extrapolated RS at infinite water velocity (RS,MAX), revealing that the added value of using in-situ RS compared to RS,MAX is limited above intermediate water velocities (>20 cm s−1). RS from the literature (RS,LIT) – obtained at water velocities between 8 and 37 cm s−1 – were also shown to provide comparable TWA concentrations in the studied hydrodynamic conditions (average water velocity of 24 cm s−1). The estimated errors due to the use of RS,MAX or RS,LIT rather than in-situ RS are given as a function of the water velocity to determine in which conditions the developed method is required (or not) in monitoring programs.

Application of survival analysis to model proliferation likelihood of Escherichia coli biofilm following laser-induced hyperthermia treatment.

Eighty percent of bacterial infections associated with living tissue and medical devices are linked to drug-resistant biofilms, leading to lengthy and costly recoveries. Laser-induced hyperthermia can disrupt cell proliferation within biofilms and increase susceptibility to antibiotics. However, there can be bacterial survival differences dependent upon laser irradiation times, and prolonged time at elevated temperature can damage healthy tissue. The objective of this study was to use survival analysis to model the impact of temperature increases on reducing viable biofilm bacteria. In vitro biofilms of Escherichia coli were grown on silicone discs or silicone doped with photothermal poly(3,4-ethylenedioxythiophene) hydrate (PEDOT) nanotubes, and subjected to laser-induced hyperthermia, using a 3W continuous wave laser at 800nm for varying times. The number of colony forming units per milliliter (CFU/mL) and maximum temperature were measured after each trial. Survival analysis was employed to estimate bacterial cell proliferation post-treatment to provide a quantitative framework for future studies evaluating photothermal inactivation of bacterial biofilms. The results demonstrate the first application of survival analysis for predicting the likelihood of bacterial cell proliferation based on temperature.

Engrailed-Positive Fibroblasts: The Primary Cell Type Present in Fibrotic Capsules During Foreign Body Response

Introduction: We have recently shown that En1 positive fibroblasts (EPFs) predominate in wounds and are responsible for scar formation. Meanwhile, foreign body response (FBR) is a common surgical complication whereby a fibrotic capsule forms around an implant. Though believed to have some mechanistic overlap with normal wound healing, the specific cell populations responsible are unknown. Methods: En1Cre transgenic driver mice were crossed with R26mTmG reporter mice, generating En1Cre; Rosa26mTmG (En1+) mice. In these mice, cells that express En1 also express GFP, while all other cells express RFP. Silicone discs were surgically implanted below the subcutaneous layer of En1+ mice dorsi, and fibrotic capsules surrounding the implants were harvested at POD30. Immunohistochemistry and flow cytometry (FACS) analysis were used to evaluate the cellular characteristics of the En1+ cells. Results: Using immunohistochemistry, En1+ cells were found to be more prevalent in the fibrotic capsule relative to unwounded tissue (*P < 0.05, n = 6). Furthermore, immunofluorescence staining and FACS revealed that GFP+ cells within the fibrotic capsules expressed pro-fibrotic markers such as Col-I, a-SMA, and Col-III. These cells were also negative for CD41 and CD45, endothelial and immune cell markers, respectively. These data indicate that En1+ cells seen within fibrotic capsules were primarily of fibroblast origin. Conclusion: As with normal wound healing, where EPFs are prevalent within a healing scar, our findings strongly suggest that En1 plays a key role in fibrotic capsule formation. Further understanding of the mechanisms that drive En1 positive fibroblasts towards fibrosis may offer potential therapeutic targets to prevent fibrotic capsule formation.

Making a Painless Drain: Proof of Concept

Chest tubes account for a large proportion of postoperative pain after cardiothoracic operations. The objective of this study was to develop a novel, cost-effective, easy-to-use, lidocaine-eluting coating to reduce pain associated with postoperative chest tubes. A lidocaine-eluting hydrogel was developed by dispersing lidocaine-loaded nanoparticles in an aqueous solution containing gelatin (5%). Glutaraldehyde (1%) was added to crosslink the gelatin into a hydrogel. The hydrogel was dehydrated, resulting in a thin, stable polymer. Sterile lidocaine hydrogel-coated silicone discs and control discs were prepared and surgically implanted in the subcutaneous space of C57B6 mice. Using von Frey filaments, mice underwent preoperative baseline pain testing, followed by pain testing on post-procedure day 1 and 3. On post-procedure day 1, mice implanted with control discs demonstrated no change in pain tolerance compared to baseline, while mice implanted with 20 mg and 80 mg lidocaine-loaded discs demonstrated a 2.4-fold (P = 0.36) and 4.7-fold (P = 0.01) increase in pain tolerance, respectively. On post-procedure day 3, mice implanted with control discs demonstrated a 0.7-fold decrease in pain tolerance compared to baseline, while mice implanted with 20 mg and 80 mg lidocaine-loaded discs demonstrated a 1.8-fold (P = 0.88) and 8.4-fold (P = 0.02) increase in pain tolerance, respectively. Our results demonstrate successful development of a lidocaine-eluting chest tube with hydrogel coating, leading to improved pain tolerance in vivo. The concept of a drug-eluting drain coating has significant importance due to its potential universal application in a variety of drain types and insertion locations.

Efficacy of Povidone Iodine Against Microbial Biofilms in Breast Implants With Different Textures: Results From an in vitro Study.

BackgroundIn the practice of breast augmentation and reconstruction, implant irrigation with various solutions has been widely used to prevent infection and capsular contracture, but to date, there is no consensus on the optimal protocol to use. Recently, application of povidone iodine (PI) for 30 min has shown in vitro to be the most effective irrigating formula in reducing contamination in smooth breast implants. However, as 30 min is not feasible intraoperatively, it is necessary to determine whether shorter times could be equally effective as well as to test it in both smooth and textured implants.MethodsWe tested the efficacy of 10% PI at 1′, 3′, and 5′ against biofilms of 8 strains (2 ATCC and 6 clinical) of Staphylococcus spp. on silicone disks obtained from Mentor® and Polytech® implants of different textures. We analyzed the percentage reduction of cfu counts, cell viability and bacterial density between treatment (PI) and control (sterile saline, SS) groups for each time of application. We consider clinical significance when > 25% reduction was observed in cell viability or bacterial density.ResultsAll textured implants treated with PI at any of the 3 exposure times reduced 100% bacterial load by culture. However, none of the implants reached enough clinical significance in percentage reduction of living cells. Regarding bacterial density, only 25–50 μm Polytxt® Polytech® implants showed significant reduction at the three PI exposure times.ConclusionPI is able to inhibit bacterial growth applied on the surface of breast implants regardless of the exposure time. However, no significant reduction on living cells or bacterial density was observed. This lack of correlation may be caused by differences in texture that directly affect PI absorption.

Modeling and simulation of composite materials used for permanent dental fillings

The aim of this paper was to determine the roughness and Vickers hardness of popular composite materials used for direct tooth fillings. The tests were carried out on the surfaces of samples previously polished with traditional silicone polishing rubbers and discs used in dentistry. The testing methodology and software used for statistical analysis is important to the validity of engineering tests. Measurement systems use sophisticated computer algorithms that are part of the equipment. Analysis of measurement data requires very complex algorithms often based on artificial intelligence. A model and procedure were also prepared to simulate the composite itself under near real-world conditions.

Polysaccharide-Based Bilayer Coatings for Biofilm-Inhibiting Surfaces of Medical Devices.

Chitosan (Chi) and 77KS, a lysine-derived surfactant, form polyelectrolyte complexes that reverse their charge from positive to negative at higher 77KS concentrations, forming aggregates that have been embedded with amoxicillin (AMOX). Dispersion of this complex was used to coat polydimethylsiloxane (PDMS) films, with an additional layer of anionic and hydrophilic hyaluronic acid (HA) as an outer adsorbate layer to enhance protein repulsion in addition to antimicrobial activity by forming a highly hydrated layer in combination with steric hindrance. The formed polysaccharide-based bilayer on PDMS was analyzed by water contact angle measurements, X-ray photoelectron spectroscopy (XPS), and surface zeta (ζ)-potential. All measurements show the existence and adhesion of the two layers on the PDMS surface. Part of this study was devoted to understanding the underlying protein adsorption phenomena and identifying the mechanisms associated with biofouling. Thus, the adsorption of a mixed-protein solution (bovine serum albumin, fibrinogen, γ-globulin) on PDMS surfaces was studied to test the antifouling properties. The adsorption experiments were performed using a quartz crystal microbalance with dissipation monitoring (QCM-D) and showed improved antifouling properties by these polysaccharide-based bilayer coatings compared to a reference or for only one layer, i.e., the complex. This proves the benefit of a second hyaluronic acid layer. Microbiological and biocompatibility tests were also performed on real samples, i.e., silicone discs, showing the perspective of the prepared bilayer coating for medical devices such as prostheses, catheters (balloon angioplasty, intravascular), delivery systems (sheaths, implants), and stents.

Comparing the Antimicrobial Effect of Silver Ion-Coated Silicone and Gentamicin-Irrigated Silicone Sheets from Breast Implant Material.

Post-operative infection is a significant complication of breast implant surgery that may require extensive use of antibiotics and surgical interventions. Here, we developed a biomaterial coating that is chemically bonded to silicone implants which delivers antimicrobial ions over time. After coating the silicone implants with a "mediator" polymer (γ-PGA), the implants were impregnated with silver (Ag) ions. Antimicrobial effects of these implants were assayed with modified Kirby-Bauer disk diffusion method. The silicone disks were transferred to a plate with fresh bacteria. Control was intended to simulate an intra-operative wash. The Ag-γ-PGA coated silicone demonstrated antimicrobial effects against the most common etiological agents of breast implant infections, including Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Klebsiella pneumoniae. There was no effect of inhibition of bacterial growth around the control silicone or the silicone coated only with γ-PGA. The zone of inhibition was generally larger around the Ag-γ-PGA coated silicone as compared to the silicone irrigated with gentamicin, and continued antibacterial effect was also observed at 48 hours in the Ag-γ-PGA coated silicone for all bacteria groups with the exception of P. aeruginosa. Gentamicin-irrigated silicone did not inhibit bacterial growth at 48 hours. The observed antibacterial performance of the Ag-γ-PGA coating as compared to simulated intra-operative antibiotic wash is promising and should be further evaluated to develop the next generation of implants with diminished risk for post-operative implant infections.

Inhibitory Effects of Lipopeptides and Glycolipids on C. albicans-Staphylococcus spp. Dual-Species Biofilms.

Microbial biofilms strongly resist host immune responses and antimicrobial treatments and are frequently responsible for chronic infections in peri-implant tissues. Biosurfactants (BSs) have recently gained prominence as a new generation of anti-adhesive and antimicrobial agents with great biocompatibility and were recently suggested for coating implantable materials in order to improve their anti-biofilm properties. In this study, the anti-biofilm activity of lipopeptide AC7BS, rhamnolipid R89BS, and sophorolipid SL18 was evaluated against clinically relevant fungal/bacterial dual-species biofilms (Candida albicans, Staphylococcus aureus, Staphylococcus epidermidis) through quantitative and qualitative in vitro tests. C. albicans–S. aureus and C. albicans–S. epidermidis cultures were able to produce a dense biofilm on the surface of the polystyrene plates and on medical-grade silicone discs. All tested BSs demonstrated an effective inhibitory activity against dual-species biofilms formation in terms of total biomass, cell metabolic activity, microstructural architecture, and cell viability, up to 72 h on both these surfaces. In co-incubation conditions, in which BSs were tested in soluble form, rhamnolipid R89BS (0.05 mg/ml) was the most effective among the tested BSs against the formation of both dual-species biofilms, reducing on average 94 and 95% of biofilm biomass and metabolic activity at 72 h of incubation, respectively. Similarly, rhamnolipid R89BS silicone surface coating proved to be the most effective in inhibiting the formation of both dual-species biofilms, with average reductions of 93 and 90%, respectively. Scanning electron microscopy observations showed areas of treated surfaces that were free of microbial cells or in which thinner and less structured biofilms were present, compared to controls. The obtained results endorse the idea that coating of implant surfaces with BSs may be a promising strategy for the prevention of C. albicans–Staphylococcus spp. colonization on medical devices, and can potentially contribute to the reduction of the high economic efforts undertaken by healthcare systems for the treatment of these complex fungal–bacterial infections.

Inhibition of bacterial adherence to biomaterials by coating antimicrobial peptides with anionic surfactant

Medical devices are widely used in modern medicine, but their utilities are often limited by the biofilm formation of bacteria that are tolerant to most antibiotics. In this report, antimicrobial peptides (AMPs) were coated onto biomaterials by the aid of surfactant through hydrophobic interactions. To increase the coating efficiency, stability of AMPs in body fluids and spectrum of antimicrobial activity, pairs of AMPs were coated simultaneously onto various substrates, such as silicone, polyurethane and titanium, which are commonly used components of biomedical devices. These coated AMPs exhibited very low cytotoxicity and hemolytic activities because they were gradually released into urine or serum. The AMP pairs, such as T9W + SAAP159 and T9W + RRIKA, coated onto the silicone discs were able to inhibit in vitro bacterial adherence in urine. Most importantly, AMP pairs coated onto the silicone tubing by surfactant SDBS could prevent bacterial adherence to mouse bladder and the silicone tubing implanted within it. These results provide a promising approach towards circumventing urinary catheter-associated infections caused by bacterial adherence.

Production of Mannosylerythritol Lipids (MELs) to be Used as Antimicrobial Agents Against S. aureus ATCC 6538

Antimicrobial resistance (AMR) is a current major health issue, both for the high rates of resistance observed in bacteria that cause common infections and for the complexity of the consequences of AMR. Pathogens like Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Mycobacterium tuberculosis among others are clear examples of antibiotic-resistant threats. Biosurfactants have recently emerged as a potential new generation of anti-adhesive and anti-biofilm agents; mannosylerythritol lipids (MELs) are biosurfactants produced by a range of fungi. A range of structural variants of MELs can be formed and the proportion of each isomer in the fermentation depends on the yeast used, the carbon substrate used for growth and the duration of the fermentation. In order to allow assessment of the possible functions of MELs as antimicrobial molecules, small quantities of MEL were produced by controlled fermentation. Fermentations of the yeast Pseudozyma aphidis using rapeseed oil as a carbon source yielded up to 165 gMELs/kgSubstrate. The MELs formed by this strain was a mixture of MEL-A, MEL-B, MEL-C and MEL-D. The MELs produced were tested against S. aureus ATCC 6538 on pre-formed biofilm and on co-incubation biofilm experiments on silicone discs; showing a disruption of biomass, reduction of the biofilm metabolic activity and a bacteriostatic/bactericidal effect confirmed by a release of oxygen uptake p_{{{text{O}}_{2} }}, the reduction of citrate synthase activity and scanning electron microscopy. The results show that MELs are promising antimicrobial molecules for biomedical technological applications that could be studied in detail in large-scale systems and in conjunction with animal tissue models.