Photodynamic therapy for treatment of bacterial keratitis

Update in management of microbial keratitis associated with contact lenses

PURPOSE OF REVIEW

The rising prevalence of contact lens wear is associated with increased contact lens-related complications, with one of the most serious being contact lens (CL)-associated microbial keratitis (MK). We describe updated prevention and management strategies of this sight-threatening condition.

RECENT FINDINGS

Poor contact lens hygiene and practices remain the most common predisposing factors for CL-associated MK. Management currently relies largely on antimicrobial therapy guided by culture data; however, increasing antimicrobial resistance is a worldwide concern. Recent studies show early promise for novel broad-spectrum therapies including cross-linking and rose Bengal-photodynamic therapy, povidone iodine, and antimicrobial peptides.

SUMMARY

There has been increased investigation in past years into broad-spectrum nonselective treatments for MK. While these investigations show early promise, prevention of CL-associated MK through education on hygiene practices remains an important healthcare intervention.

Dextran guanidinylated carbon dots with antibacterial and immunomodulatory activities as eye drops for the topical treatment of MRSA-induced infectious keratitis

Bacterial keratitis (BK) develops rapidly and can cause serious consequences, requiring timely and efficient treatment. As the main treatment strategy, antibiotic eye drops are still plagued by bacterial resistance by biofilms and failure to modulate immunity. Herein, dextran guanidinylated carbon dots (DG-CDs) with antimicrobial and immunomodulatory properties were developed. DG-CDs with the graphitized core-like structure with the ordered arrangement of carbon atoms and surface groups of CN, COC, and -OH were thoroughly characterized and modeled as a graphene-like sheet. DG-CDs exhibited strong antimicrobial and anti-biofilm activities with a minimum inhibitory concentration (MIC) of 5 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA). Molecular docking based on well-characterized structures of DG-CDs revealed that DG-CDs had strong affinity for key bacterial proteins including FtsA, IcaA and ArgA, which were confirmed by corresponding RT-qPCR and transcriptomics. Furthermore, DG-CDs regulated macrophage polarization by inhibiting the M1 subtype and promoting the transition to the M2 subtype. In vivo experiments illustrated that DG-CDs used as eye drops significantly attenuated corneal infection, enhanced the expression of anti-inflammatory factors, and effectively promoted corneal repair in MRSA-infected BK. Overall, this study provides a promising antibacterial nanomaterial with clarified properties and acting mechanism for treating BK as eye drops. STATEMENT OF SIGNIFICANCE: Besides bacterial invasion, bacterial keratitis (BK) also suffers from immune imbalance, which further impairs corneal healing. Current antibiotic eye drops are plagued by bacterial resistance and their inability to modulate immunity. Herein, dextran guanidinylated carbon dots (DG-CDs) with dual functions of antimicrobial and immunomodulatory were developed for treating MRSA infected BK. DG-CDs, with clarified structure and surface groups, exhibited strong antimicrobial activity and no detectable resistance. Molecular docking, based on well-characterized structures of DG-CDs, was achieved to reveal the antibacterial mechanism, which was subsequently confirmed by RT-qPCR and transcriptomics. In addition, DG-CDs exhibited an effective healing ability in an MRSA-infected rat keratitis model by exerting antibacterial activity and regulating macrophage polarization from M1 type to M2 type. DG-CDs represent a promising antibacterial nanomedicine with clarified properties and acting mechanism for treating bacterial infection.

Oxygen-supplying nanotherapeutics for bacterial septic arthritis via hypoxia-relief-enhanced antimicrobial and anti-inflammatory phototherapy

Bacterial septic arthritis, an inflammatory disease caused by bacterial infections, is often accompanied by the emergence of multidrug-resistant bacteria, making therapeutic treatment a formidable challenge. With the emergence of antibiotic resistance, research on antimicrobial photodynamic therapy (aPDT) has regained attention. However, insufficient singlet oxygen production due to the hypoxia in the infection microenvironment is recognized as a key limiting the efficacy of aPDT. Hence, in this study, we designed a bacteria-targeted liposomal nanoplatform (MCPL) to alleviate hypoxia in the infectious microenvironment and enhance aPDT for bacterial septic arthritis. The nanoplatform was developed by integrating the phototherapeutic agent CyI and small-sized Pt NPs into thermosensitive liposomes, with modification of maltohexose on the liposome surface. In vitro and in vivo studies showed that MCPL could specifically target bacterial cell membranes and be thermally activated to catalytically convert endogenous hydrogen peroxide (H2O2) in the septic joint, supplementing local O2 reservoirs. This, in turn, supplies additional substrate pools for photodynamic conversion into reactive oxygen species (ROS) with bacterial toxicity. Furthermore, the antibacterial mechanism revealed that MCPL can regulate the HIF-1α and NF-κB signaling pathways in immune cells, acting as an effective modulator of antioxidant and anti-inflammatory pathways in both macrophages and neutrophils. This study demonstrates that MCPL could not induce bacterial multidrug resistance and provide as an innovative approach for treating bacterial septic arthritis.

Applications of photodynamic therapy in keratitis

Keratitis is corneal inflammatory disease which may be caused by several reason such as an injury, allergy, as well as a microbial infection. Besides these, overexposure to ultraviolet light and unhygienic practice of contact lenses are also associated with keratitis. Based on the cause of keratitis, different lines of treatments are recommended. Photodynamic therapy is a promising approach that utilizes light activated compounds to instigate either killing or healing mechanism to treat various diseases including both communicable and non-communicable diseases. This review focuses on clinically-important patent applications and the recent literature for the use of photodynamic therapy against keratitis.

Copper(II)-infused porphyrin MOF: maximum scavenging GSH for enhanced photodynamic disruption of bacterial biofilm

Bacterial biofilm infection is a serious obstacle to clinical therapeutics. Photodynamic therapy (PDT) plays a dynamic role in combating biofilm infection by utilizing reactive oxygen species (ROS)-induced bacterial oxidation injury, showing advantages of mild side effects, spatiotemporal controllability and little drug resistance. However, superfluous glutathione (GSH) present in biofilm and bacteria corporately reduces ROS levels and seriously affects PDT efficiency. Herein, we have constructed a Cu2+-infused porphyrin metal-organic framework (MOF@Cu2+) for the enhanced photodynamic combating of biofilm infection by the maximum depletion of GSH. Our results show that the released Cu2+ from porphyrin MOF@Cu2+ could not only oxidize GSH in biofilm but also consume GSH leaked from ROS-destroyed bacteria, thus greatly weakening the antioxidant system in biofilm and bacteria and dramatically improving the ROS levels. As expected, our dual-enhanced PDT nanoplatform exhibits a strong biofilm eradication ability both in vitro and in an in vivo biofilm-infected mouse model. In addition, Cu2+ can promote biofilm-infected wound closing by provoking cell immigration, collagen sediment and angiogenesis. Besides, no apparent toxicity was detected after treatment with MOF@Cu2+. Overall, our design offers a new paradigm for photodynamic combating biofilm infection.

Photodynamic therapy and associated targeting methods for treatment of brain cancer

Brain tumors, including glioblastoma multiforme, are currently a cause of suffering and death of tens of thousands of people worldwide. Despite advances in clinical treatment, the average patient survival time from the moment of diagnosis of glioblastoma multiforme and application of standard treatment methods such as surgical resection, radio- and chemotherapy, is less than 4 years. The continuing development of new therapeutic methods for targeting and treating brain tumors may extend life and provide greater comfort to patients. One such developing therapeutic method is photodynamic therapy. Photodynamic therapy is a progressive method of therapy used in dermatology, dentistry, ophthalmology, and has found use as an antimicrobial agent. It has also found wide application in photodiagnosis. Photodynamic therapy requires the presence of three necessary components: a clinically approved photosensitizer, oxygen and light. This paper is a review of selected literature from Pubmed and Scopus scientific databases in the field of photodynamic therapy in brain tumors with an emphasis on glioblastoma treatment.

Antimicrobial Resistance: Is There a 'Light' at the End of the Tunnel?

In recent years, with the increases in microorganisms that express a multitude of antimicrobial resistance (AMR) mechanisms, the threat of antimicrobial resistance in the global population has reached critical levels. The introduction of the COVID-19 pandemic has further contributed to the influx of infections caused by multidrug-resistant organisms (MDROs), which has placed significant pressure on healthcare systems. For over a century, the potential for light-based approaches targeted at combatting both cancer and infectious diseases has been proposed. They offer effective killing of microbial pathogens, regardless of AMR status, and have not typically been associated with high propensities of resistance development. To that end, the goal of this review is to describe the different mechanisms that drive AMR, including intrinsic, phenotypic, and acquired resistance mechanisms. Additionally, the different light-based approaches, including antimicrobial photodynamic therapy (aPDT), antimicrobial blue light (aBL), and ultraviolet (UV) light, will be discussed as potential alternatives or adjunct therapies with conventional antimicrobials. Lastly, we will evaluate the feasibility and requirements associated with integration of light-based approaches into the clinical pipeline.

Photosensitizers for Photodynamic Therapy of Brain Cancers-A Review

On average, there are about 300,000 new cases of brain cancer each year. Studies have shown that brain and central nervous system tumors are among the top ten causes of death. Due to the extent of this problem and the percentage of patients suffering from brain tumors, innovative therapeutic treatment methods are constantly being sought. One such innovative therapeutic method is photodynamic therapy (PDT). Photodynamic therapy is an alternative and unique technique widely used in dermatology and other fields of medicine for the treatment of oncological and nononcological lesions. Photodynamic therapy consists of the destruction of cancer cells and inducing inflammatory changes by using laser light of a specific wavelength in combination with the application of a photosensitizer. The most commonly used photosensitizers include 5-aminolevulinic acid for the enzymatic generation of protoporphyrin IX, Temoporfin-THPC, Photofrin, Hypericin and Talaporfin. This paper reviews the photosensitizers commonly used in photodynamic therapy for brain tumors. An overview of all three generations of photosensitizers is presented. Along with an indication of the limitations of the treatment of brain tumors, intraoperative photodynamic therapy and its possibilities are described as an alternative therapeutic method.

Medical Applications and Advancement of Near Infrared Photosensitive Indocyanine Green Molecules

Indocyanine green (ICG) is an important kind of near infrared (NIR) photosensitive molecules for PTT/PDT therapy as well as imaging. When exposed to NIR light, ICG can produce reactive oxygen species (ROS), which can kill cancer cells and pathogenic bacteria. Moreover, the absorbed light can also be converted into heat by ICG molecules to eliminate cancer cells. In addition, it performs exceptionally well in optical imaging-guided tumor therapy and antimicrobial therapy due to its deeper tissue penetration and low photobleaching properties in the near-infrared region compared to other dyes. In order to solve the problems of water and optical stability and multi-function problem of ICG molecules, composite nanomaterials based on ICG have been designed and widely used, especially in the fields of tumors and sterilization. So far, ICG molecules and their composite materials have become one of the most famous infrared sensitive materials. However, there have been no corresponding review articles focused on ICG molecules. In this review, the molecular structure and properties of ICG, composite material design, and near-infrared light- triggered anti-tumor, and antibacterial, and clinical applications are reviewed in detail, which of great significance for related research.

Corneal Crosslinking: Present and Future

Keratoconus is a progressive corneal thinning disorder that can lead to vision loss. In the last 2 decades, corneal crosslinking (CXL) has emerged as an effective method to halt the progression of keratoconus and reduce the number of patients requiring keratoplasty. The procedure has been adopted globally and has evolved to become a part of combination treatments to regularize the cornea and improve visual outcomes. CXL has even been extrapolated in managing other ocular pathologies such as progressive myopia, infectious keratitis, and bullous keratopathy. This review aims to summarize the current role of CXL in keratoconus and its alternative uses, and provide insights into future developments in this fast-developing field.

Gelatin/Chitosan Films Incorporated with Curcumin Based on Photodynamic Inactivation Technology for Antibacterial Food Packaging

Photodynamic inactivation (PDI) is a new type of non-thermal sterilization technology that combines visible light with photosensitizers to generate a bioactive effect against foodborne pathogenic bacteria. In the present investigation, gelatin (GEL)/chitosan (CS)-based functional films with PDI potency were prepared by incorporating curcumin (Cur) as a photosensitizer. The properties of GEL/CS/Cur (0.025, 0.05, 0.1, 0.2 mmol/L) films were investigated by evaluating the surface morphology, chemical structure, light transmittance, and mechanical properties, as well as the photochemical and thermal stability. The results showed a strong interaction and good compatibility between the molecules present in the GEL/CS/Cur films. The addition of Cur improved different film characteristics, including thickness, mechanical properties, and solubility. More importantly, when Cur was present at a concentration of 0.1 mM, the curcumin-mediated PDI inactivated >4.5 Log CFU/mL (>99.99%) of Listeria monocytogenes, Escherichia coli, and Shewanella putrefaciens after 70 min (15.96 J/cm2) of irradiation with blue LED (455 ± 5) nm. Moreover, Listeria monocytogenes and Shewanella putrefaciens were completely inactivated after 70 min of light exposure when the Cur concentration was 0.2 mM. In contrast, the highest inactivation effect was observed in Vibrio parahaemolyticus. This study showed that the inclusion of Cur in the biopolymer-based film transport system in combination with photodynamic activation represents a promising option for the preparation of food packaging films.