The influence of lens material and lens wear on the removal and viability of Staphylococcus epidermidis

Rational design of antibiotic-free antimicrobial contact lenses: Trade-offs between antimicrobial performance and biocompatibility

Microbial keratitis associated with contact lenses (CLs) wear remains a significant clinical concern. Antibiotic therapy is the current standard of care. However, the emergence of multidrug-resistant pathogens necessitates the investigation of alternative strategies. Antibiotic-free antimicrobial contact lenses (AFAMCLs) represent a promising approach in this regard. The effectiveness of CLs constructed with a variety of antibiotic-free antimicrobial strategies against microorganisms has been demonstrated. However, the impact of these antimicrobial strategies on CLs biocompatibility remains unclear. In the design and development of AFAMCLs, striking a balance between robust antimicrobial performance and optimal biocompatibility, including safety and wearing comfort, is a key issue. This review provides a comprehensive overview of recent advancements in AFAMCLs technology. The focus is on the antimicrobial efficacy and safety of various strategies employed in AFAMCLs construction. Furthermore, this review investigates the potential impact of these strategies on CLs parameters related to wearer comfort. This review aims to contribute to the continuous improvement of AFAMCLs and provide a reference for the trade-off between resistance to microorganisms and wearing comfort. In addition, it is hoped that this review can also provide a reference for the antimicrobial design of other medical devices.

A novel biocompatible antibacterial product: Nanoliposomes loaded with poly(hexamethylene biguanide chloride)

In this study, nanoliposome-loaded poly(hexamethylene biguanide) is introduced as a novel biocompatible antibacterial product with higher activity than microliposomes. Soy lecithin as a clean product was used to prepare various nanoliposomes through sonication, high-pressure homogenizer, and normal homogenizer and also microliposomes through two methods of lipid film hydration and incubation methods. The nanoliposomes were formed under sonication with the size of 50 nm. The prepared liposomes were then loaded with poly(hexamethylene biguanide chloride) and the inclusion percentage was measured. The release profile of liposomes in buffer showed a release of 92% for poly(hexamethylene biguanide) during 24 h. The loaded liposomes were characterized with particle size analyzer, nuclear magnetic resonance, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The antibacterial properties of different micro and nanoliposomes were investigated against a Gram-negative ( Escherichia coli) and a Gram-positive ( Staphylococcus aureus) bacteria. The poly(hexamethylene biguanide)–loaded nanoliposomes indicated higher antibacterial activities than microliposomes. Nanoliposomes have the potential to entrap lower poly(hexamethylene biguanide) dosages while retaining optimum therapeutic efficacy in the target site having lower cytotoxicity with lower side effects. The cytotoxicity of poly(hexamethylene biguanide) entrapped in liposomes was studied in human dermal fibroblasts and compared with free poly(hexamethylene biguanide) and blank liposomes. The maximum cytotoxicity was observed for free poly(hexamethylene biguanide) that is substantially decreased through loading within liposomes structure. Overall, the encapsulation of poly(hexamethylene biguanide) in liposomes improved the biocompatibility and safety of the product introducing a useful biocompatible antibacterial polymer for treatments of infectious diseases.

Lens material and formulation of multipurpose solutions affects contact lens disinfection

PURPOSE

To assess the disinfection efficacy of multipurpose solutions (MPS) against different bacterial species adhered either to silicon hydrogel or to conventional hydrogel contact lenses (CLs). The influences of the MPS formulation and the chemical composition of the lens material were investigated.

METHODS

This investigation followed the standard 14729, which establishes the guidelines for assessing CL disinfecting solutions. Two commercially available (Opti-Free(®) Express(®) and Renu(®) Multiplus) solutions and one recalled solution (Complete(®) MoisturePlus™) were used in this study. After disinfection, the number of survivors was estimated by the colony forming units' method.

RESULTS

The lens material appears to influence disinfection. The conventional hydrogel polymacon exhibited the highest disinfection scores, a fact that should be related with the lack of electrostatic attraction towards the biocides and its hydrophilicity. The MPS formulation appears to have influence in disinfection efficacy as well. For most adhered bacteria, Opti-Free(®) was capable of reducing cell concentration in 4-log.

CONCLUSION

Disinfection results from multivariate factors and this study confirmed that the lens material and the MPS play a very important role in the disinfection efficacy of CL.

A three-phase in-vitro system for studying Pseudomonas aeruginosa adhesion and biofilm formation upon hydrogel contact lenses

Background

Pseudomonas aeruginosa is commonly associated with contact lens (CL) -related eye infections, for which bacterial adhesion and biofilm formation upon hydrogel CLs is a specific risk factor. Whilst P. aeruginosa has been widely used as a model organism for initial biofilm formation on CLs, in-vitro models that closely reproduce in-vivo conditions have rarely been presented.

Results

In the current investigation, a novel in-vitro biofilm model for studying the adherence of P. aeruginosa to hydrogel CLs was established. Nutritional and interfacial conditions similar to those in the eye of a CL wearer were created through the involvement of a solid:liquid and a solid:air interface, shear forces and a complex artificial tear fluid. Bioburdens varied depending on the CL material and biofilm maturation occurred after 72 h incubation. Whilst a range of biofilm morphologies were visualised including dispersed and adherent bacterial cells, aggregates and colonies embedded in extracellular polymer substances (EPS), EPS fibres, mushroom-like formations, and crystalline structures, a compact and heterogeneous biofilm morphology predominated on all CL materials.

Conclusions

In order to better understand the process of biofilm formation on CLs and to test the efficacy of CL care solutions, representative in-vitro biofilm models are required. Here, we present a three-phase biofilm model that simulates the environment in the eye of a CL wearer and thus generates biofilms which resemble those commonly observed in-situ.