Effect of Antimicrobial Contact Lenses on Corneal Infiltrative Events: A Randomized Clinical Trial

Antifouling Efficacy on S. epidermidis of Nano-Au Surfaces Functionalized with Polyethylene Glycol (PEG)-Tethered Antimicrobial Peptides

Cationic antimicrobial peptides (cAMPs) kill bacteria in solution by membrane lysis; however, translating cAMPs into a covalently attached antibacterial coating is challenging since it remains unclear how the specifics of the conjugation impact the antifouling efficacy. Furthermore, studies have typically assessed cAMP coatings with a high and homogeneous surface coverage, although this may be difficult to implement in practice of the materials commonly used in medicine. Herein, we investigate the antifouling efficacy of fractional surface coatings made from poly(ethylene glycol) (PEG)-tethered cAMPs presented on gold nanoparticles (AuNPs) deposited onto surfaces. For all tested cAMPs, the antifouling efficacy increases exponentially with the 2D surface coverage of the coating. However, although the cAMPs have a similar primary sequence and display similar potency against Staphylococcus epidermidis in solution, the cyclic peptide is much more potent after tethering to the AuNPs than the linear counterparts. The attachment of the cyclic cAMPs also led to an unexpected shrinkage of the modified PEG-brush by more than 50%, indicating a restricted mobility of the tethering PEG chains. The shrinkage increased the closeness of the peptide on the AuNP and may thus enable cooperative actions of the grafted cAMPs such as the formation of nanosized peptide clusters that were previously found to enhance cAMP potency in solution. These findings pave the way for antibacterial coatings that cover only a subfraction of a material while remaining active in a clinical setting.

Mel4-coated hyaluronic acid-laden etafilcon A contact lenses: Improved wettability with retained antimicrobial properties

Soft contact lenses are a common mode of vision correction used worldwide. However, contact lens wearers often experience discomfort and are at risk of developing microbial infections. To address these issues, we designed Mel4-coated hyaluronic acid-laden etafilcon contact lenses to improve wettability while providing antimicrobial properties. The process involved the interaction of the etafilcon lens, which carries a net negative charge, with positively charged Mel4 (a cationic antimicrobial peptide). This was followed by interaction with hyaluronic acid (a negatively charged polymer). The components were then crosslinked using EDC-NHS [N-(3-dimethyl aminopropyl)-N'-ethyl carbodiimide hydrochloride and N-Hydroxy succinimide] to form amide bonds between the compounds and the lens. In this study, four batches of lenses were prepared: the first consisted of conventional HA-soaked lenses (SM-HA-L), the second consisted of lenses soaked in Mel4 and HA (SM-Mel4-HA-L), the third batch consisted of HA crosslinked with the lens (HA-Cr-L), and the fourth consisted of lenses soaked in Mel4 and HA, followed by crosslinking (Mel4-HA-Cr-L). During the washing and sterilization steps, SM-HA-L lenses showed high leaching compared to SM-Mel4-HA-L lenses, while HA-Cr-L and Mel4-HA-Cr-L lenses showed no leaching. A hyaluronidase breakdown assay revealed 5.37 μg, 9.28 μg, 8.04 μg, and 6.07 μg of HA per lens for SM-HA-L, SM-Mel4-HA-L, HA-Cr-L, and Mel4-HA-Cr-L, respectively. The wettability (contact angle) of SM-Mel4-HA-L lenses was improved compared to HA-Cr-L and Mel4-HA-Cr-L lenses. In vitro release studies showed no leaching of HA, indicating permanent entrapment or binding of HA to the contact lens surface. Both the SM-Mel4-HA-L lenses and crosslinked Mel4-HA-Cr-L lenses could significantly reduce the adhesion of Pseudomonas aeruginosa 6294 and Staphylococcus aureus 31 to the lenses. In conclusion, the presence of HA improved wettability, while Mel4 retained its antimicrobial activity, highlighting its potential to advance existing contact lens technology with improved wettability and antimicrobial properties.

Emerging antimicrobial therapies for Gram-negative infections in human clinical use

The growing problem of multi-drug resistance (MDR) is prevalent in Gram-negative infections, and the significant decline in antibiotic development poses a critical threat to global public health. Many emerging non-antibiotic therapies have been proposed, including phage therapy, anti-virulence agents, antimicrobial peptides, plasmapheresis, and immunotherapy options. To identify the therapies most likely to be the next immediate step in treatment for MDR Gram-negative infections, this review highlights emerging therapeutics that have either been successfully used for compassionate care or are currently undergoing clinical trials.

The effect of immobilisation strategies on the ability of peptoids to reduce the adhesion of P. aeruginosa strains to contact lenses

AIM

Previous studies have demonstrated that contact lenses coated with the antimicrobial cationic peptide Mel4, a derivative of melimine, can reduce the occurrence of keratitis. However, the antimicrobial activity of Mel4 weakened over time due to its susceptibility to proteolytic degradation. Oligo-N-substituted glycine peptoids such as TM5 and TM18 possess antimicrobial properties and are resistant to proteolytic breakdown. This study focused on exploring methods for covalently attaching these peptoids to contact lenses to enhance their durability and performance in vitro.

METHODS

The peptoids TM5 and TM18 were covalently attached to etafilcon lenses via carbodiimide chemistry (EDC/NHS), oxazoline plasma, and plasma ion immersion implantation (PIII). The lenses were analysed using X-ray photoelectron spectroscopy (XPS), surface charge, and hydrophobicity. Inhibition of adhesion of multidrug-resistant Pseudomonas aeruginosa and cytotoxicity on corneal epithelial cells were evaluated. The impact of moist heat sterilization on activity was also assessed.

RESULTS

XPS confirmed peptoid binding to lenses. Peptoid coatings slightly increased contact angles (≤23°) without affecting overall charge. Peptoids, bound via carbodiimide, inhibited P. aeruginosa adhesion by over 5 log10 CFU per lens, outperforming melimine, which required six times the concentration for a 3 log10 reduction. Peptoids attached via oxazoline or PIII reduced adhesion by > 5 log10 CFU. All covalent methods significantly reduced bacterial adhesion compared to untreated lenses (P < 0.0001). Peptoid-bound lenses were non-toxic to corneal epithelial cells. Sterilization did not affect carbodiimide-treated lenses but reduced the activity of oxazoline and PIII surfaces by 1-2 log10 CFU.

CONCLUSION

Peptoids TM5 and TM18 effectively reduced P. aeruginosa adhesion on lenses, with carbodiimide-bound surfaces retaining activity post-sterilization, showing promise for the development of antimicrobial contact lenses.

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.

Protecting Orthopaedic Implants from Infection: Antimicrobial Peptide Mel4 Is Non-Toxic to Bone Cells and Reduces Bacterial Colonisation When Bound to Plasma Ion-Implanted 3D-Printed PAEK Polymers

Even with the best infection control protocols in place, the risk of a hospital-acquired infection of the surface of an implanted device remains significant. A bacterial biofilm can form and has the potential to escape the host immune system and develop resistance to conventional antibiotics, ultimately causing the implant to fail, seriously impacting patient well-being. Here, we demonstrate a 4 log reduction in the infection rate by the common pathogen S. aureus of 3D-printed polyaryl ether ketone (PAEK) polymeric surfaces by covalently binding the antimicrobial peptide Mel4 to the surface using plasma immersion ion implantation (PIII) treatment. The surfaces with added texture created by 3D-printed processes such as fused deposition-modelled polyether ether ketone (PEEK) and selective laser-sintered polyether ketone (PEK) can be equally well protected as conventionally manufactured materials. Unbound Mel4 in solution at relevant concentrations is non-cytotoxic to osteoblastic cell line Saos-2. Mel4 in combination with PIII aids Saos-2 cells to attach to the surface, increasing the adhesion by 88% compared to untreated materials without Mel4. A reduction in mineralisation on the Mel4-containing surfaces relative to surfaces without peptide was found, attributed to the acellular portion of mineral deposition.

Medical Device-Associated Healthcare Infections: Sterilization and the Potential of Novel Biological Approaches to Ensure Patient Safety

Healthcare-associated infections caused by multi-drug-resistant pathogens are increasing globally, and current antimicrobial options have limited efficacy against these robust species. The WHO details the critically important bacterial and fungal species that are often associated with medical device HAIs. The effective sterilization of medical devices plays a key role in preventing infectious disease morbidity and mortality. A lack of adherence to protocol and limitations associated with each sterilization modality, however, allows for the incidence of disease. Furthermore, issues relating to carcinogenic emissions from ethylene oxide gas (EtO) have motivated the EPA to propose limiting EtO use or seeking alternative sterilization methods for medical devices. The Food and Drug Administration supports the sterilization of healthcare products using low-temperature VH2O2 as an alternative to EtO. With advances in biomaterial and medical devices and the increasing use of combination products, current sterilization modalities are becoming limited. Novel approaches to disinfection and sterilization of medical devices, biomaterials, and therapeutics are warranted to safeguard public health. Bacteriophages, endolysins, and antimicrobial peptides are considered promising options for the prophylactic and meta-phylactic control of infectious diseases. This timely review discusses the application of these biologics as antimicrobial agents against critically important WHO pathogens, including ESKAPE bacterial species.

Antimicrobial Peptidomimetics Prevent the Development of Resistance against Gentamicin and Ciprofloxacin in Staphylococcus and Pseudomonas Bacteria

Bacteria readily acquire resistance to traditional antibiotics, resulting in pan-resistant strains with no available treatment. Antimicrobial resistance is a global challenge and without the development of effective antimicrobials, the foundation of modern medicine is at risk. Combination therapies such as antibiotic-antibiotic and antibiotic-adjuvant combinations are strategies used to combat antibiotic resistance. Current research focuses on antimicrobial peptidomimetics as adjuvant compounds, due to their promising activity against antibiotic-resistant bacteria. Here, for the first time we demonstrate that antibiotic-peptidomimetic combinations mitigate the development of antibiotic resistance in Staphylococcus aureus and Pseudomonas aeruginosa. When ciprofloxacin and gentamicin were passaged individually at sub-inhibitory concentrations for 10 days, the minimum inhibitory concentrations (MICs) increased up to 32-fold and 128-fold for S. aureus and P. aeruginosa, respectively. In contrast, when antibiotics were passaged in combination with peptidomimetics (Melimine, Mel4, RK758), the MICs of both antibiotics and peptidomimetics remained constant, indicating these combinations were able to mitigate the development of antibiotic-resistance. Furthermore, antibiotic-peptidomimetic combinations demonstrated synergistic activity against both Gram-positive and Gram-negative bacteria, reducing the concentration needed for bactericidal activity. This has significant potential clinical applications-including preventing the spread of antibiotic-resistant strains in hospitals and communities, reviving ineffective antibiotics, and lowering the toxicity of antimicrobial chemotherapy.

Contact lenses and ocular dysbiosis, from the transitory to the pathological

Normal ocular microbiota is composed of different Gram-negative and positive bacterial communities that act as commensals on the ocular surface. An imbalance in the homeostasis of the native species or dysbiosis triggers functional alterations that can eventually lead to ocular conditions, indicating the use of contact lenses as the most relevant predisposing factor. Through a bibliographic review that added scientific articles published between 2018 and 2022, the relationship between healthy ocular microbiota and dysbiosis associated with the use of contact lenses that trigger ocular conditions was analyzed. The ocular microbiota in healthy individuals is mainly composed of bacteria from the phyla: Proteobacteria, Actinobacteria and Firmicutes. These bacterial communities associated with the use of contact lenses develop dysbiosis, observing an increase in certain genera such as Staphylococcus spp. and Pseudomonas spp., which under normal conditions are commensals of the ocular surface, but as their abundance is increased, they condition the appearance of various ocular conditions such as corneal infiltrative events, bacterial keratitis and corneal ulcer. These pathologies tend to evolve rapidly, which, added to late detection and treatment, can lead to a poor visual prognosis. It is suggested that professionals in the ophthalmology area learn about the composition of the communities of microorganisms that make up this ocular microbiota, in order to correctly distinguish and identify the causative agent, thereby providing a adequate and effective treatment to the user.

Comparative Evaluation of Pseudomonas aeruginosa Adhesion to a Poly-(2-Methacryloyloxyethyl Phosphorylcholine)-Modified Silicone Hydrogel Contact Lens

Pseudomonas aeruginosa is the most common causative agent associated with microbial keratitis. During contact lens wear, pathogens may be introduced into the ocular environment, which might cause adverse events. Lehfilcon A is a recently developed contact lens with a water gradient surface composed of polymeric 2-methacryloyloxyethyl phosphorylcholine (MPC). MPC is re-ported to impart anti-biofouling properties onto modified substrates. Therefore, in this in vitro experimental study, we tested the capability of lehfilcon A to resist adhesion by P. aeruginosa. Quantitative bacterial adhesion assays using five strains of P. aeruginosa were conducted to compare the adherence properties of lehfilcon A to five currently marketed silicone hydrogel (SiHy) contact lenses (comfilcon A, fanfilcon A, senofilcon A, senofilcon C, and samfilcon A). Compared to lehfilcon A, we observed 26.7 ± 8.8 times (p = 0.0028) more P. aeruginosa binding to comfilcon A, 30.0 ± 10.8 times (p = 0.0038) more binding to fanfilcon A, 18.2 ± 6.2 times (p = 0.0034) more binding to senofilcon A, 13.6 ± 3.9 times (p = 0.0019) more binding to senofilcon C, and 29.5 ± 11.8 times (p = 0.0057) more binding to samfilcon A. These results demonstrate that, for various strains of P. aeruginosa, lehfilcon A reduces bacterial adhesion compared to other contact lens materials.

Evaluation of Serratia marcescens Adherence to Contact Lens Materials

Bacterial keratitis is a risk associated with the use of contact lenses for cosmetic purposes or vision correction. In this in vitro experimental study, we examined the ability of the ocular pathogen Serratia marcescens to adhere to monthly or biweekly replacement contact lenses. We performed quantitative adhesion assays to evaluate the adherence of S. marcescens to seven contact lens materials: comfilcon A, senofilcon A, omafilcon B, fanfilcon A, balafilcon A, senofilcon C, and lehfilcon A. Lehfilcon A is a newly marketed silicon hydrogel contact lens with a surface modification of poly-(2-methacryloyloxyethyl phosphorylcholine) (PMPC). PMPC has previously been demonstrated to be an effective anti-biofouling treatment for numerous surfaces. We observed low S. marcescens adherence to lehfilcon A compared to other materials. We demonstrate the use of the fluorescent dye 5(6)-Carboxytetramethylrhodamine succinimidyl ester to covalently stain live cells prior to material adhesion studies.

Effect of Deposition and Protease Digestion on the Ex Vivo Activity of Antimicrobial Peptide-Coated Contact Lenses

A clinical study of antimicrobial contact lenses containing the cationic peptide Mel4 was conducted. The few adverse events that occurred with this lens occurred on or after 13 nights of wear. The current study examined whether the Mel4 contact lenses lost activity during wear and the mechanism of this loss. Participants wore contact lenses for up to 13 nights. Lenses were tested for their ability to reduce the adhesion of Pseudomonas aeruginosa and Staphylococcus aureus. The amount of protein and lipid extracted from lenses was measured. The ability of trypsin to affect the antimicrobial activity of Mel4-coated contact lenses was measured. Mel4-coated contact lenses lost their antimicrobial activity at six nights of wear for both bacteria. The amount of lipids (13 ± 11 vs. 21 ± 14 μg/lens at 13 nights wear) and proteins (8 ± 4 vs. 10 ± 3 mg/lens at 13 nights of wear) extracted from lenses was not different between Mel4-coated and uncoated lenses, and was not different after three nights when antimicrobial activity was maintained and thirteen nights when they had lost activity (lipid: 25 ± 17 vs. 13 ± 11, p = 0.2; protein: 8 ± 1 vs. 8 ± 4 mg/lens, p = 0.4). Trypsin digestion eliminated the antimicrobial activity of Mel4-coated lenses. In summary, Mel4-coated contact lenses lost antibacterial activity at six nights of wear, and the most likely reason was proteolytic digestion of the peptide. Future studies will design and test proteolytically stable peptide mimics as coatings for contact lenses.

Host Defense Peptides at the Ocular Surface: Roles in Health and Major Diseases, and Therapeutic Potentials

Sight is arguably the most important sense in human. Being constantly exposed to the environmental stress, irritants and pathogens, the ocular surface – a specialized functional and anatomical unit composed of tear film, conjunctival and corneal epithelium, lacrimal glands, meibomian glands, and nasolacrimal drainage apparatus – serves as a crucial front-line defense of the eye. Host defense peptides (HDPs), also known as antimicrobial peptides, are evolutionarily conserved molecular components of innate immunity that are found in all classes of life. Since the first discovery of lysozyme in 1922, a wide range of HDPs have been identified at the ocular surface. In addition to their antimicrobial activity, HDPs are increasingly recognized for their wide array of biological functions, including anti-biofilm, immunomodulation, wound healing, and anti-cancer properties. In this review, we provide an updated review on: (1) spectrum and expression of HDPs at the ocular surface; (2) participation of HDPs in ocular surface diseases/conditions such as infectious keratitis, conjunctivitis, dry eye disease, keratoconus, allergic eye disease, rosacea keratitis, and post-ocular surgery; (3) HDPs that are currently in the development pipeline for treatment of ocular diseases and infections; and (4) future potential of HDP-based clinical pharmacotherapy for ocular diseases.

Antimicrobial Peptide Expression at the Ocular Surface and Their Therapeutic Use in the Treatment of Microbial Keratitis

Microbial keratitis is a common cause of ocular pain and visual impairment worldwide. The ocular surface has a relatively paucicellular microbial community, mostly found in the conjunctiva, while the cornea would be considered relatively sterile. However, in patients with microbial keratitis, the cornea can be infected with multiple pathogens including Staphylococcus aureus, Pseudomonas aeruginosa, and Fusarium sp. Treatment with topical antimicrobials serves as the standard of care for microbial keratitis, however, due to high rates of pathogen resistance to current antimicrobial medications, alternative therapeutic strategies must be developed. Multiple studies have characterized the expression and activity of antimicrobial peptides (AMPs), endogenous peptides with key antimicrobial and wound healing properties, on the ocular surface. Recent studies and clinical trials provide promise for the use of AMPs as therapeutic agents. This article reviews the repertoire of AMPs expressed at the ocular surface, how expression of these AMPs can be modulated, and the potential for harnessing the AMPs as potential therapeutics for patients with microbial keratitis.

Biocompatibility and Comfort during Extended Wear of Mel4 Peptide-Coated Antimicrobial Contact Lenses

(1) Purpose: This study aimed to investigate the effects of Mel4 antimicrobial contact lenses (MACL) on the ocular surface and comfort during extended wear. (2) Methods: A prospective, randomised, double-masked, contralateral clinical trial was conducted with 176 subjects to evaluate the biocompatibility of contralateral wear of MACL. The wearing modality was 14-day extended lens wear for three months. The participants were assessed at lens dispensing, after one night, two weeks, one month and three months of extended wear and one month after study completion. (3) Results: There were no significant differences (p > 0.05) in ocular redness or palpebral roughness between Mel4 and control eyes at any of the study visits. There was no significant difference (p > 0.05) in corneal staining between Mel4 and control eyes. There were no significant differences in front surface wettability or deposits or back surface debris (p > 0.05). No statistically significant differences (p > 0.05) were found in comfort, dryness, CLDEQ-8 scores lens or edge awareness. There was no evidence for delayed reactions on the ocular surface after cessation of lens wear. (4) Conclusion: The novel MACLs showed similar comfort to control lenses and were biocompatible during extended wear. Thus, these lenses were compatible with the ocular surface.