Silver Nanoparticles as a Novel Potential Preventive Agent against Acanthamoeba Keratitis

Abstract

Free living, cosmopolitan amoebae from Acanthamoeba genus present a serious risk to human health. As facultative human parasites, these amoebae may cause Acanthamoeba keratitis (AK). Acanthamoeba keratitis is a severe, vision-threatening corneal infection with non-specific symptoms. The number of reported AK cases worldwide has been increasing every year. Moreover, 90% of Acanthamoeba keratitis cases are related to contact lens use. Wearing and storage contact lenses not in accordance with the physicians and manufacturers recommendations are the primary key risk factors of this disease. Amoebae can easily adhere to the contact lens surface and transmit to the corneal epithelium. Preventing amoebae adhesion to the contact lens surface could significantly decrease the number of AK infections. Until now, the effective therapy against AK is still under development. Currently proposed therapies are mainly limited to the chlorhexidine digluconate combined with propamidine isethionate or hexamidine applications, which are insufficient and very toxic to the eye. Due to lack of effective treatment, looking for new potential preventive agents is crucial to decrease the number of Acanthamoeba keratitis infections, especially among contact lens users. Nanoparticles have been already included in several novel therapies against bacteria, viruses, fungi, and protist. However, their anti-amoebic potential has not been fully tested yet. The aim of this study was to assess silver nanoparticles (AgNPs) and platinum nanoparticles (PtNPs) anti-amoebic activity and influence on the amoebae adhesion to the surface of four different groups of contact lenses—classified according to the Food and Drugs Administration (FDA) guidelines. The obtained results show that both tested nanoparticles were effective against Acanthamoeba trophozoites and decreased the amoebae adhesion to the contact lens surface. AgNPs showed better anti-amoebic activity to cytotoxicity dependence and reduced amoebae adhesion in a wider spectrum of the tested contact lenses. Our studies also confirmed that ionization next to hydration of the contact lens material is a crucial parameter influencing the Acanthamoeba adhesion to the contact lens surface. In conclusion, silver nanoparticles might be considered as a novel preventive agent against Acanthamoeba keratitis infection.

Silver Nanoparticles Conjugated with Contact Lens Solutions May Reduce the Risk of Acanthamoeba Keratitis

“…By transmission electron microscopy (TEM) using a JEOL JEM-1220 TE microscope at 80 KeV (JEOL Ltd., Tokyo, Japan), with a Morada 11-megapixel camera (Olympus Corporation, Tokyo, Japan), the size and distribution of the AgNPs were defined. Their size was between 15 to 30 nm (average value: 22.3 ± 12.41 nm), as previously mentioned [14].…”

“…It includes a process of disruption of the cell membrane structure, the generation of reactive oxygen species (ROS) to interrupt respiratory chain enzymes inside the cell, the disturbance of the DNA replication process, and the inhibition of ATP-dependent (adenosine triphosphate-dependent) protein synthesis. The recognition of NPs by cells as a cell-surface receptor makes them an ideal drug carrier [ 13 , 14 , 15 ]. In recent years, silver nanoparticles (AgNPs) have been widely tested against a broad range of pathogens.…”

“…The efficacy of AgNPs against Acanthamoeba spp. was described in our previous studies [ 14 ]. We showed that AgNPs possess anti-amoebic properties and the capability to reduce amoebae adhesion to the contact lens surface.…”

“…We showed that AgNPs possess anti-amoebic properties and the capability to reduce amoebae adhesion to the contact lens surface. The cytotoxic effect on human cells was limited [ 14 ]. Other authors showed that conjugations of AgNPs with various drugs and plant extracts might be promising strategies in AK treatment and prevention.…”

Establishment of an Acanthamoeba keratitis mouse model confirmed by amoebic DNA amplification

“…AK patients are often treated with disinfectants and antifungal agents, including propamidine isethionate, polyhexamethylene biguanide, neomycin, chlorhexidine, polymyxin B, miconazole, itraconazole, brolene, diamidine compounds, and chlorhexidine gluconate, although corneal opacity or scarring may sometimes occur after treatment 16 . Recently, Hendiger et al 17 reported silver nanoparticles as a novel potential preventive agent against AK. Many efforts have been made to use silver nanoparticles to treat AK, but there are no effective agents for the treatment of AK.…”