Tannic Acid-Modified Silver Nanoparticles in Conjunction with Contact Lens Solutions Are Useful for Progress against the Adhesion of Acanthamoeba spp. to Contact Lenses.

Acanthamoeba spp. are amphizoic amoebae that are widely distributed in the environment and capable of entering the human body. They can cause pathogenic effects in different tissues and organs, including Acanthamoeba keratitis (AK), which may result in a loss of visual acuity and blindness. The diagnostics, treatment, and prevention of AK are still challenging. More than 90% of AK cases are related to the irresponsible wearing of contact lenses. However, even proper lens care does not sufficiently protect against this eye disease, as amoebae have been also found in contact lens solutions and contact lens storage containers. The adhesion of the amoebae to the contact lens surface is the first step in developing this eye infection. To limit the incidence of AK, it is important to enhance the anti-adhesive activity of the most popular contact lens solutions. Currently, silver nanoparticles (AgNPs) are used as modern antimicrobial agents. Their effectiveness against Acanthamoeba spp., especially with the addition of plant metabolites, such as tannic acid, has been confirmed. Here, we present the results of our further studies on the anti-adhesion potential of tannic acid-modified silver nanoparticles (AgTANPs) in combination with selected contact lens solutions against Acanthamoeba spp. on four groups of contact lenses. The obtained results showed an increased anti-adhesion activity of contact lens solutions in conjunction with AgTANPs with a limited cytotoxicity effect compared to contact lens solutions acting alone. This may provide a benefit in improving the prevention of amoebae eye infections. However, there is still a need for further studies on different pathogenic strains of Acanthamoeba in order to assess the adhesion of the cysts to the contact lens surface and to reveal a more comprehensive picture of the activity of AgTANPs and contact lens solutions.

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

Acanthamoeba keratitis (AK), a severe sight-threatening corneal infection, has become a significant medical problem, especially among contact lens wearers. The disease manifests as eye pain, congestion, blurred vision, lachrymation, and ring-shaped infiltrates of the cornea, and can lead to permanent blindness. Inappropriate habits of contact lens users may result in an increased risk of AK infection. The anti-amoebic efficiency of popular multipurpose contact lens solutions is insufficient to reduce this risk. An effective and non-toxic therapy against AK has not yet been developed. The prevention of AK is crucial to reduce the number of AK infections. Nanoparticles are known to be active agents against bacteria, viruses, and fungi and were also recently tested against protozoa, including Acanthamoeba spp. In our previous studies, we proved the anti-amoebic and anti-adhesive activity of silver nanoparticles against Acanthamoeba castellanii. The aim of this study is to evaluate the activity, cytotoxicity, and anti-adhesive properties of silver nanoparticles conjugated with five commonly used multipurpose contact lens solutions against the Acanthamoeba castellanii NEFF strain. The obtained results show a significant increase in anti-amoebic activity, without increasing the overall cytotoxicity, of Solo Care Aqua and Opti Free conjugated with nanoparticles. The adhesion of Acanthamoeba trophozoites to the contact lens surface is also significantly reduced. We conclude that low concentrations of silver nanoparticles can be used as an ingredient in contact lens solutions to decrease the risk of Acanthamoeba keratitis infection.

Tannic acid-modified silver nanoparticles enhance the anti-Acanthamoeba activity of three multipurpose contact lens solutions without increasing their cytotoxicity.

BACKGROUND: Free-living amoebae of the genus Acanthamoeba are cosmopolitan, widely distributed protozoans that cause a severe, vision-threatening corneal infection known as Acanthamoeba keratitis (AK). The majority of the increasing number of AK cases are associated with contact lens use. Appropriate eye hygiene and effective contact lens disinfection are crucial in the prevention of AK because of the lack of effective therapies against it. Currently available multipurpose contact lens disinfection systems are not fully effective against Acanthamoeba trophozoites and cysts. There is an urgent need to increase the disinfecting activity of these systems to prevent AK infections. Synthesized nanoparticles (NPs) have been recently studied and proposed as a new generation of anti-microbial agents. It is also known that some plant metabolites, including tannins, have anti-parasitic activity. The aim of this study was to evaluate the anti-amoebic activity and cytotoxicity of tannic acid-modified silver NPs (AgTANPs) conjugated with selected multipurpose contact lens solutions. METHODS: The anti-amoebic activities of pure contact lens care solutions, and NPs conjugated with contact lens care solutions, were examined in vitro by a colorimetric assay based on the oxido-reduction of alamarBlue. The cytotoxicity assays were performed using a fibroblast HS-5 (ATCC CRL-11882) cell line. The results were statistically analysed by ANOVA and Student-Newman-Keuls test using P < 0.05 as the level of statistical significance. RESULTS: We show that the NPs enhance the anti-Acanthamoeba activities of the tested contact lens solutions without increasing their cytotoxicity profiles. The activities are enhanced within the minimal disinfection time recommended by the manufacturers. CONCLUSIONS: The conjugation of the selected contact lens solutions with AgTANPs might be a novel and promising approach for the prevention of AK infections among contact lens users.

Silver Nanoparticles as a Novel Potential Preventive Agent against Acanthamoeba Keratitis.

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.

In Vitro Activity of Statins against Naegleria fowleri.

Naegleria fowleri causes a deadly disease called primary amoebic meningoencephalitis (PAM). Even though PAM is still considered a rare disease, the number of reported cases worldwide has been increasing each year. Among the factors to be considered for this, awareness about this disease, and also global warming, as these amoebae thrive in warm water bodies, seem to be the key factors. Until present, no fully effective drugs have been developed to treat PAM, and the current options are amphotericin B and miltefosine, which present side effects such as liver and kidney toxicity. Statins are able to inhibit the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which is a key enzyme for the synthesis of ergosterol of the cell membrane of these amoebae. Therefore, the in vitro activity of a group of statins was tested in this study against two types of strains of Naegleria fowleri. The obtained results showed that fluvastatin was the most effective statin tested in this study and was able to eliminate these amoebae at concentrations of 0.179 ± 0.078 to 1.682 ± 0.775 µM depending on the tested strain of N. fowleri. Therefore, fluvastatin could be a potential novel therapeutic agent against this emerging pathogen.

Evaluation of in vitro effect of selected contact lens solutions conjugated with nanoparticles in terms of preventive approach to public health risk generated by Acanthamoeba strains.

INTRODUCTION: Various Acanthamoeba species are free-living organisms widely distributed in the human environment. Amphizoic amoebae as facultative parasites may cause vision-threatening eye disease - Acanthamoeba keratitis, mostly among contact lens wearers. As the number of cases is increasing, and applied therapy often unsuccessful, proper hygienic measures and effective contact lenses disinfection are crucial for the prevention of this disease. Available contact lens solutions are not fully effective against amphizoic amoebae; there is a need to enhance their disinfecting activity to prevent amoebic infections. The use of developing nanotechnology methods already applied with success in the prevention, diagnostic and therapy of other infectious diseases might be helpful regarding amoebic keratitis. This study assesses the in vitro effect of selected contact lens solutions conjugated with nanoparticles against Acanthamoeba trophozoites. MATERIAL AND METHODS: Three selected contact lens solutions conjugated with silver and gold nanoparticles in concentration of 0.25-2.5 ppm were used in vitro against the axenically cultured ATCC 30010 type Acanthamoeba castellanii strain. The anti-amoebic efficacy was examined based on the oxido-reduction of AlamarBlue. The cytotoxicity tests based on the measurement of lactate dehydrogenase (LDH) activity were performed using a fibroblast HS-5 cell line. RESULTS: Enhancement of the anti-amoebic activity of contact lens solutions conjugated with selected nanoparticles expressed in the dose dependent amoebic growth inhibition with a low cytotoxicity profile was observed. CONCLUSIONS: Results of the study showed that conjugation of selected contact lens solutions with silver nanoparticles might be a promising approach to prevent Acanthamoeba keratitis among contact lens users.

Tannic acid-modified silver nanoparticles as a novel therapeutic agent against Acanthamoeba.

Free-living amoebae belonging to Acanthamoeba genus are widely distributed protozoans which are able to cause infection in humans and other animals such as keratitis and encephalitis. Acanthamoeba keratitis is a vision-threatening corneal infection with currently no available fully effective treatment. Moreover, the available therapeutic options are insufficient and are very toxic to the eye. Therefore, there is an urgent need for the development of more effective anti-amoebic agents. Nanotechnology approaches have been recently reported to be useful for the elucidation antimicrobial, antiviral, antifungal and antiprotozoal activities and thus, they could be a good approach for the development of anti-Acanthamoeba agents. Therefore, this study was aimed to explore the activity and cytotoxicity of tannic acid-modified silver nanoparticles, pure silver nanoparticles and pure gold nanoparticles against clinical strains of Acanthamoeba spp. The obtained results showed a significant anti-amoebic effect of the tannic acid-modified silver nanoparticles which also presented low cytotoxicity. Moreover, tannic acid-modified silver nanoparticles were well absorbed by the trophozoites and did not induce encystation. On the other hand, pure silver nanoparticles were only slightly active against the trophozoite stage and pure gold nanoparticles did not show any activity. In conclusion and based on the observed results, silver nanoparticle conjugation with tannic acid may be considered as potential agent against Acanthamoeba spp.