Influence of surface roughness on silicone rubber voice prostheses on in vitro biofilm formation and clinical lifetime in laryngectomised patients

Strategies for Inhibition of Biofilm Formation on Silicone Rubber Voice Prostheses: A Systematic Review

BACKGROUND

Lifetime elongation of the silicone voice rubber prostheses by inhibition of biofilm formation is a primary objective in voice restoration of laryngectomized patients. This systematic review sought to explore the existing strategies in this direction.

MATERIALS

We conducted a systematic search of both in vitro and in vivo literature published in PubMed, Scopus, and Cochrane Central Register of Controlled Trials, until December 31, 2022, for published and unpublished trials assessing the strategies for inhibiting biofilm formation on silicone rubber voice prostheses, and appraised quality assessment with the modified Consolidated Standards of Reporting Trials tool. We analyzed the infection prevention capacity of the included antibacterial and antifungal agents.

RESULTS

The qualitative synthesis showed that both surface modification methods and prophylactic treatment of silicone rubber voice prostheses present adequate antibiofilm activity. Of note, the majority of the suggested prosthetic surfaces were not chronically exposed to both human fluids and biofilm-forming microorganisms.

CONCLUSION

Various experimental methods provide promising antibiofilm activity and, thus, possible lifespan elongation of silicone rubber voice prostheses.

Mechanical deformation of elastomer medical devices can enable microbial surface colonization

Elastomers such as silicone are common in medical devices (catheters, prosthetic implants, endoscopes), but they remain prone to microbial colonization and biofilm infections. For the first time, our work shows that rates of microbial surface attachment to polydimethylsiloxane (PDMS) silicone can be significantly affected by mechanical deformation. For a section of bent commercial catheter tubing, bacteria (P. aeruginosa) show a strong preference for the 'convex' side compared to the 'concave' side, by a factor of 4.2. Further testing of cast PDMS materials in bending only showed a significant difference for samples that were manually wiped (damaged) beforehand (1.75 × 10⁴ and 6.02 × 10³ cells/mm² on the convex and concave sides, respectively). We demonstrate that surface microcracks in elastomers are opened under tensile stress (convex bending) to become 'activated' as sites for microbial colonization. This work demonstrates that the high elastic limit of elastomers enables these microcracks to reversibly open and close, as 'dynamic defects'. Commercial catheters have relatively high surface roughness inherent to manufacturing, but we show that even manual wiping of newly-cast PDMS is sufficient to generate surface microcracks. We consider the implication for medical devices that feature sustained, surgical, or cyclic deformation, in which localized tensile conditions may expose these surface defects to opportunistic microbes. As a result, our work showcases serious potential problems in the widespread usage and development of elastomers in medical devices.

Plant-derived nanotherapeutic systems to counter the overgrowing threat of resistant microbes and biofilms

Since antiquity, the survival of human civilization has always been threatened by the microbial infections. An alarming surge in the resistant microbial strains against the conventional drugs is quite evident in the preceding years. Furthermore, failure of currently available regimens of antibiotics has been highlighted by the emerging threat of biofilms in the community and hospital settings. Biofilms are complex dynamic composites rich in extracellular polysaccharides and DNA, supporting plethora of symbiotic microbial life forms, that can grow on both living and non-living surfaces. These enforced structures are impervious to the drugs and lead to spread of recurrent and non-treatable infections. There is a strong realization among the scientists and healthcare providers to work out alternative strategies to combat the issue of drug resistance and biofilms. Plants are a traditional but rich source of effective antimicrobials with wider spectrum due to presence of multiple constituents in perfect synergy. Other than the biocompatibility and the safety profile, these phytochemicals have been repeatedly proven to overcome the non-responsiveness of resistant microbes and films via multiple pathways such as blocking the efflux pumps, better penetration across the cell membranes or biofilms, and anti-adhesive properties. However, the unfavorable physicochemical attributes and stability issues of these phytochemicals have hampered their commercialization. These issues of the phytochemicals can be solved by designing suitably constructed nanoscaled structures. Nanosized systems can not only improve the physicochemical features of the encapsulated payloads but can also enhance their pharmacokinetic and therapeutic profile. This review encompasses why and how various types of phytochemicals and their nanosized preparations counter the microbial resistance and the biofouling. We believe that phytochemical in tandem with nanotechnological innovations can be employed to defeat the microbial resistance and biofilms. This review will help in better understanding of the challenges associated with developing such platforms and their future prospects.

Assessment of Ceragenins in Prevention of Damage to Voice Prostheses Caused by Candida Biofilm Formation

This study aimed to investigate the potential application of ceragenins (CSAs) as new candidacidal agents to prevent biofilm formation on voice prostheses (VPs). The deterioration of the silicone material of VPs is caused by biofilm growth on the device which leads to frequent replacement procedures and sometimes serious complications. A significant proportion of these failures is caused by Candida species. We found that CSAs have significant candidacidal activities in vitro (MIC; MFC; MBIC), and they effectively eradicate species of yeast responsible for VP failure. Additionally, in our in vitro experimental setting, when different Candida species were subjected to CSA-13 and CSA-131 during 25 passages, no tested Candida strain showed the significant development of resistance. Using liquid chromatography–mass spectrometry (LC-MS), we found that VP immersion in an ethanol solution containing CSA-131 results in silicon impregnation with CSA-131 molecules, and in vitro testing revealed that fungal biofilm formation on such VP surfaces was inhibited by embedded ceragenins. Future in vivo studies will validate the use of ceragenin-coated VP for improvement in the life quality and safety of patients after a total laryngectomy.

In vitro Inhibition of Biofilm Formation on Silicon Rubber Voice Prosthesis: Α Systematic Review and Meta-Analysis

INTRODUCTION

Biofilm formation on voice prostheses is the primary reason for their premature implant dysfunction. Multiple strategies have been proposed over the last decades to achieve inhibition of biofilm formation on these devices. The purpose of this study was to assess the results of the available in vitro biofilm inhibition modalities on silicone rubber voice prostheses.

METHODS

We conducted a systematic search in PubMed, Embase, and the Cochrane Central Register of Controlled Trials databases up to February 29, 2020. A total of 33 in vitro laboratory studies investigating the efficacy of different coating methods against Candida, Staphylococcus, Streptococcus, Lactobacilli, and Rothia biofilm growth on silicone rubber medical devices were included. Subgroup analysis linked to the type of prevention modality was carried out, and quality assessment was performed with the use of the modified CONSORT tool.

RESULTS

Data from 33 studies were included in qualitative analysis, of which 12 qualified for quantitative analysis. For yeast biofilm formation assessment, there was a statistically significant difference in favor of the intervention group (standardized mean difference [SMD] = -1.20; 95% confidence interval [CI] [-1.73, -0.66]; p < 0.0001). Subgroup analysis showed that combined methods (active and passive surface modification) are the most effective for biofilm inhibition in yeast (SMD = -2.53; 95% CI [-4.02, -1.03]; p = 0.00001). No statistically significant differences between intervention and control groups were shown for bacterial biofilm inhibition (SMD = -0.09; 95% CI [-0.68, 0.46]; p = 0.65), and the results from the subgroup analysis found no notable differences between the surface modification methods. After analyzing data on polymicrobial biofilms, a statistically significant difference in favor of prevention methods in comparison with the control group was detected (SMD = -2.59; 95% CI [-7.48, 2.31]; p = 0.30).

CONCLUSIONS

The meta-analysis on biofilm inhibition demonstrated significant differences in favor of yeast biofilm inhibition compared to bacteria. A stronger inhibition with the application of passive or combined active and passive surface modification techniques was reported.

The Vaginal Microbiota, Bacterial Biofilms and Polymeric Drug-Releasing Vaginal Rings

The diversity and dynamics of the microbial species populating the human vagina are increasingly understood to play a pivotal role in vaginal health. However, our knowledge about the potential interactions between the vaginal microbiota and vaginally administered drug delivery systems is still rather limited. Several drug-releasing vaginal ring products are currently marketed for hormonal contraception and estrogen replacement therapy, and many others are in preclinical and clinical development for these and other clinical indications. As with all implantable polymeric devices, drug-releasing vaginal rings are subject to surface bacterial adherence and biofilm formation, mostly associated with endogenous microorganisms present in the vagina. Despite more than 50 years since the vaginal ring concept was first described, there has been only limited study and reporting around bacterial adherence and biofilm formation on rings. With increasing interest in the vaginal microbiome and vaginal ring technology, this timely review article provides an overview of: (i) the vaginal microbiota, (ii) biofilm formation in the human vagina and its potential role in vaginal dysbiosis, (iii) mechanistic aspects of biofilm formation on polymeric surfaces, (iv) polymeric materials used in the manufacture of vaginal rings, (v) surface morphology characteristics of rings, (vi) biomass accumulation and biofilm formation on vaginal rings, and (vii) regulatory considerations.

Efficacy of A Poly(MeOEGMA) Brush on the Prevention of Escherichia coli Biofilm Formation and Susceptibility

Urinary tract infections are one of the most common hospital-acquired infections, and they are often associated with biofilm formation in indwelling medical devices such as catheters and stents. This study aims to investigate the antibiofilm performance of a polymer brush—poly[oligo(ethylene glycol) methyl ether methacrylate], poly(MeOEGMA)—and evaluate its effect on the antimicrobial susceptibility of Escherichia coli biofilms formed on that surface. Biofilms were formed in a parallel plate flow chamber (PPFC) for 24 h under the hydrodynamic conditions prevailing in urinary catheters and stents and challenged with ampicillin. Results obtained with the brush were compared to those obtained with two control surfaces, polydimethylsiloxane (PDMS) and glass. The polymer brush reduced by 57% the surface area covered by E. coli after 24 h, as well as the number of total adhered cells. The antibiotic treatment potentiated cell death and removal, and the total cell number was reduced by 88%. Biofilms adapted their architecture, and cell morphology changed to a more elongated form during that period. This work suggests that the poly(MeOEGMA) brush has potential to prevent bacterial adhesion in urinary tract devices like ureteral stents and catheters, as well as in eradicating biofilms developed in these biomedical devices.