Preparation of Poly (dl-Lactide-co-Glycolide) Nanoparticles Encapsulated with Periglaucine A and Betulinic Acid for In Vitro Anti-Acanthamoeba and Cytotoxicity Activities

Nanoparticle-Terpene Fusion: A Game-Changer in Combating Primary Amoebic Meningoencephalitis Caused by Naegleria fowleri

Pathogenic Naegleria fowleri (N. fowleri) are opportunistic free-living amoebae and are the causative agents of a very rare but severe brain infection called primary amoebic meningoencephalitis (PAM). The fatality rate of PAM in reported cases is more than 95%. Most of the drugs used againstN. fowleri infections are repurposed drugs. Therefore, a large number of compounds have been tested againstN. fowleri in vitro, but most of the tested compounds showed high toxicity and an inability to cross the blood-brain barrier. Andrographolide, forskolin, and borneol are important natural compounds that have shown various valuable biological properties. In the present study, the nanoconjugates (AND-AgNPs, BOR-AgNPs, and FOR-AgNPs) of these compounds were synthesized and assessed against both stages (trophozoite and cyst) ofN. fowleri for their antiamoebic and cysticidal potential in vitro. In addition, cytotoxicity and host cell pathogenicity were also evaluated in vitro. FOR-AgNPs were the most potent nanoconjugate and showed potent antiamoebic activity againstN. fowleriwith an IC50 of 26.35 μM. Nanoconjugates FOR-AgNPs, BOR-AgNPs, and AND-AgNPs also significantly inhibit the viability of N. fowleri cysts. Cytotoxicity assessment showed that these nanoconjugates caused minimum damage to human keratinocyte cells (HaCaT cells) at 100 μg/mL, while also effectively reducing the cytopathogenicity of N. fowleri trophozoites to the HaCaT cells. The outcomes of our experiments have unveiled substantial potential for AND-AgNPs, BOR-AgNPs, and FOR-AgNPs in the realm of developing innovative alternative therapeutic agents to combat infections caused by N. fowleri. This study represents a significant step forward in the pursuit of advanced strategies for managing such amoebic infections, laying the foundation for the development of novel and more effective therapeutic modalities in the fight against free-living amoebae.

New strategies in the treatment of diseases caused by Acanthamoeba based on nanoparticles: a systematic review

BACKGROUND

Acanthamoeba is one of the opportunistic parasites with a global prevalence. Currently, due to the side effects and the emergence of drug resistance to this parasite, much research has been performed on the use of nano-drugs to treat Acanthamoeba-caused diseases. Therefore, this systematic review study aims to evaluate new strategies for treating diseases caused by Acanthamoeba based on nanoparticles (NPs).

METHODS

We designed a systematic review based on the articles published in English between 2000 and 2022. Our search strategy was based on syntax and specific tags for each database, including ScienceDirect, PubMed, Scopus, Ovid, and Cochrane. From the articles, those that had inclusion criteria were selected, and their data were extracted and analyzed.

RESULTS

In this study, 26 studies were selected. Metallic nanoparticles were mostly used against the Acanthamoeba species (80.7%). 19.2% of the studies used polymeric nanoparticles, and 3.8% used emulsion nanoparticles. Most studies (96.1%) were performed in vitro, and only one study (3.8%) was carried out in vivo. Silver NPs were the most used metallic nanoparticles in the studies. The best effect of the anti-Acanthamoeba compound was observed for green synthesized nanoparticles based on stabilization by plant gums, loaded with citrus fruits flavonoids hesperidin (HDN) and naringin (NRG) with a 100% growth inhibition at a concentration of 50 μg/mL.

CONCLUSION

This study showed that chlorhexidine and other plant metabolites loaded with silver and gold nanoparticles increase the anti-Acanthambae activity of these nanoparticles. However, green synthesized nanoparticles based on stabilization by plant gums, loaded with citrus fruits flavonoids hesperidin (HDN) and naringin (NRG), showed the best anti-Acanthambae effect. Nevertheless, further studies should be performed to determine their safety for human use.

Hydrothermal Synthesis of β-Nb2ZnO6 Nanoparticles for Photocatalytic Degradation of Methyl Orange and Cytotoxicity Study

β-Nb₂ZnO₆ nanoparticles were synthesized by a hydrothermal process and calcined at two temperatures, 500 °C and 700 °C, and assigned as A and B, respectively. X-ray diffraction, together with transmission electron microscopy, revealed that the β-Nb₂ZnO₆ nanoparticles calcined at 700 °C (B) were more crystalline than the β-Nb₂ZnO₆ calcined at 500 °C (A) with both types of nanoparticles having an average size of approximately 100 nm. The physiochemical, photocatalytic, and cytotoxic activities of both types of β-Nb₂ZnO₆ nanoparticles (A and B) were examined. Interestingly, the photodegradation of methyl orange, used as a standard for environmental pollutants, was faster in the presence of the β-Nb₂ZnO₆ nanoparticles calcined at 500 °C (A) than in the presence of those calcined at 700 °C (B). Moreover, the cytotoxicity was evaluated against different types of cancer cells and the results indicated that both types of β-Nb₂ZnO₆ nanoparticles (A and B) exhibited high cytotoxicity against MCF-7 and HCT116 cells but low cytotoxicity against HeLa cells after 24 and 48 h of treatment. Overall, both products expressed similar EC₅₀ values on tested cell lines and high cytotoxicity after 72 h of treatment. As a photocatalyst, β-Nb₂ZnO₆ nanoparticles (A) could be utilized in different applications including the purification of the environment and water from specific pollutants. Further biological studies are required to determine the other potential impacts of utilizing β-Nb₂ZnO₆ nanoparticles in the biomedical application field.

Emerging trends in the delivery of nanoformulated oxytocin across Blood-Brain barrier

Neurological diseases are related to the central nervous system disorders and considered as serious cases. Several drugs are used to treat neurological diseases; however, to date the main issue is to design a therapeutic model which can cross the blood-brain-barrier (BBB) easily. The delivery of neuropeptides into the brain lays as one of the important routes for treating neurological disorders. Neuropeptides have been demonstrated as potential therapeutics for neurological disorders. Among numerous neuropeptides, the oxytocin (OT) hormone is of particular interest as it serves as a neurotransmitter in the brain as well as its role as a hormone. OT has a wide-range of activities in the brain and has a key role in cognitive, neuroendocrine, and social functions. However, OT does not cross the BBB readily coupled with its half-life in the blood being too short. The current literature reveals that the delivery of OT by nanoparticle-based drug delivery system (DDS) improves its efficacy. Nanoparticle based DDS are considered important tools for the targeted delivery of drugs to the brain as they lower toxicity of the drug and improve the drug efficacy. Nanoparticles are advantageous candidates for biomedical applications due to their distinctive characteristics such as quantum effects, large surface area and their ability to carry and transport the drug to its target site. OT can be delivered through oral and intranasal routes, but the bioavailability of OT inside the brain can further be enhanced by the delivery using nanoparticles. The application of nano-based delivery system not only improves the penetration of OT inside brain but also increases its half-life by the application of encapsulation and extended release. The aim of current review is to provide an overview of nanoparticle-based drug-delivery systems for the delivery of OT inside brain.

CONJUGATION WITH SILVER NANOPARTICLES ENHANCES ANTI-ACANTHAMOEBIC ACTIVITY OF KAPPAPHYCUS ALVAREZII

Nanomedicine has the potential in enhancing the efficacy and bioavailability of anti-infective agents. Here we determined whether conjugation of the Malaysian cultivated seaweed Kappaphycus alvarezii with silver-conjugated nanoparticles enhanced anti-acanthamoebic properties. Silver-conjugated K. alvarezii were successfully synthesized, followed by characterization with Fourier transform infrared spectroscopy, ultraviolet-visible spectrophotometry, and transmission electron microscopy. Amoebicidal effects were evaluated against Acanthamoeba castellanii, and cytotoxicity assays were performed using HaCaT cells. Viability assays revealed that silver nanoparticles conjugated with K. alvarezii extract exhibited significant antiamoebic properties (P < 0.05). Nano-conjugates induced the production of reactive oxygen species. Importantly, silver-conjugated extract inhibited amoeba-mediated host cell damage as established by lactate dehydrogenase release. Neither the nano-conjugates nor the extract showed cytotoxicity against human cells in vitro. Liquid chromatography and mass spectroscopy revealed several molecules, including 2,6-nonadien-1-ol, N-desmethyl trifluoperazine, dulciol B, lucidumol A, acetoxolone, 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)phenol, C16 sphinganine, 22-tricosenoic acid, and β-dihydrorotenone, of which dulciol B and C16 sphinganine are known to possess antimicrobial activities. In summary, marine organisms are an important source of bioactive molecules with anti-acanthamoebic properties that can be enhanced by conjugating with silver nanoparticles. Natural products combined with nanotechnology using multifunctional nanoparticle complexes can deliver therapeutic agents effectively and hold promise in the development of new formulations of anti-acanthamoebic agents.

Silver Nanocolloids Loaded with Betulinic Acid with Enhanced Antitumor Potential: Physicochemical Characterization and In Vitro Evaluation

Betulinic acid (BA), a natural compound with various health benefits including selective antitumor activity, has a limited applicability in vivo due to its poor water solubility and bioavailability. Thus, this study focused on obtaining a BA nano-sized formulation with improved solubility and enhanced antitumor activity using silver nanocolloids (SilCo and PEG_SilCo) as drug carriers. The synthesis was performed using a chemical method and the physicochemical characterization was achieved applying UV-Vis absorption, transmission electron microscopy (TEM), Raman and photon correlation spectroscopy (PCS). The biological evaluation was conducted on two in vitro experimental models-hepatocellular carcinoma (HepG2) and lung cancer (A549) cell lines. The physicochemical characterization showed the following results: an average hydrodynamic diameter of 32 nm for SilCo_BA and 71 nm for PEG_SilCo_BA, a spherical shape, and a loading capacity of 54.1% for SilCo_BA and 61.9% for PEG_SilCo_BA, respectively. The in vitro assessment revealed a cell type- and time-dependent cytotoxic effect characterized by a decrease in cell viability as follows: (i) SilCo_BA (66.44%) < PEG_SilCo_BA (72.05%) < BA_DMSO (75.30%) in HepG2 cells, and (ii) SilCo_BA (75.28%) < PEG_SilCo_BA (86.80%) < BA_DMSO (87.99%) in A549 cells. The novel silver nanocolloids loaded with BA induced an augmented anticancer effect as compared to BA alone.

Anti-amoebic potential of azole scaffolds and nanoparticles against pathogenic Acanthamoeba

Acanthamoeba spp. are free living amoeba (FLA) which are widely distributed in nature. They are opportunistic parasites and can cause severe infections to the eye, skin and central nervous system. The advances in drug discovery and modifications in the chemotherapeutic agents have shown little improvement in morbidity and mortality rates associated with Acanthamoeba infections. The mechanism-based process of drug discovery depends on the molecular drug targets present in the signaling pathways in the genome. Synthetic libraries provide a platform for broad spectrum of activities due to their desired structural modifications. Azoles, originally a class of synthetic anti-fungal drugs, disrupt the fungal cell membrane by inhibiting the biosynthesis of ergosterol through the inhibition of cytochrome P450 dependent 14α-lanosterol, a key step of the sterol pathway. Acanthamoeba and fungi share the presence of similar sterol intermediate, as ergosterol is also the major end-product in the sterol biosynthesis in Acanthamoeba. Sterols present in the eukaryotic cell membrane are one of the most essential lipids and exhibit important structural and signaling functions. Therefore, in this review we highlight the importance of specific targeting of ergosterol present in Acanthamoebic membrane by azole compounds for amoebicidal activity. Previously, azoles have also been repurposed to report antimicrobial, antiparasitic and antibacterial properties. Moreover, by loading the azoles into nanoparticles through advanced techniques in nanotechnology, such as physical encapsulation, adsorption, or chemical conjugation, the pharmacokinetics and therapeutic index of the drugs can be significantly improved. The current review proposes an important strategy to target Acanthamoeba using synthetic libraries of azoles and their conjugated nanoparticles for the first time.

Nanoparticles based therapeutic efficacy against Acanthamoeba: Updates and future prospect

Acanthamoeba sp. is a free living amoeba that causes severe, painful and fatal infections, viz. Acanthamoeba keratitis and granulomatous amoebic encephalitis among humans. Antimicrobial chemotherapy used against Acanthamoeba is toxic to human cells and show side effects as well. Infections due to Acanthamoeba also pose challenges towards currently used antimicrobial treatment including resistance and transformation of trophozoites to resistant cyst forms that can lead to recurrence of infection. Therapeutic agents targeting central nervous system infections caused by Acanthamoeba should be able to cross blood-brain barrier. Nanoparticles based drug delivery put forth an effective therapeutic method to overcome the limitations of currently used antimicrobial chemotherapy. In recent years, various researchers investigated the effectiveness of nanoparticles conjugated drug and/or naturally occurring plant compounds against both trophozoites and cyst form of Acanthamoeba. In the current review, a reasonable effort has been made to provide a comprehensive overview of various nanoparticles tested for their efficacy against Acanthamoeba. This review summarizes the noteworthy details of research performed to elucidate the effect of nanoparticles conjugated drugs against Acanthamoeba.

PLGA nanoparticles loaded with Gallic acid- a constituent of Leea indica against Acanthamoeba triangularis

Acanthamoeba, a genus that contains at least 24 species of free-living protozoa, is ubiquitous in nature. Successful treatment of Acanthamoeba infections is always very difficult and not always effective. More effective drugs must be developed, and medicinal plants may have a pivotal part in the future of drug discovery. Our research focused on investigating the in vitro anti- acanthamoebic potential of Leea indica and its constituent gallic acid in different concentrations. Water and butanol fractions exhibited significant amoebicidal activity against trophozoites and cysts. Gallic acid (100 µg/mL) revealed 83% inhibition of trophozoites and 69% inhibition of cysts. The butanol fraction induced apoptosis in trophozoites, which was observed using tunnel assay. The cytotoxicity of the fractions and gallic acid was investigated against MRC-5 and no adverse effects were observed. Gallic acid was successfully loaded within poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles with 82.86% encapsulation efficiency, while gallic acid showed 98.24% in vitro release at 48 hours. Moreover, the gallic acid encapsulated in the PLGA nanoparticles exhibited 90% inhibition against trophozoites. In addition, gallic acid encapsulated nanoparticles showed reduced cytotoxicity towards MRC-5 compared to gallic acid, which evidenced that natural product nanoencapsulation in polymeric nanoparticles could play an important role in the delivery of natural products.

Curcuma longa ethanol extract and Curcumin inhibit the growth of Acanthamoeba triangularis trophozoites and cysts isolated from water reservoirs at Walailak University, Thailand

CURCUMA LONGA

(C. longa) rhizome extract has been traditionally used to treat many infections. Curcumin, a pure compound isolated from the plant, has been documented to possess a wide spectrum of pharmacological effects. The present study aimed to investigate the effects of Thai medicinal plant extracts including C. longa extract and Curcumin on Acanthamoeba triangularis, a causative agent of human Acanthamoeba keratitis. The parasite was isolated from the recreational reservoir at Walailak University, Thailand. The organism was identified as A. triangularis using morphology and 18S rDNA nucleotide sequences. The pathogen was tested for their susceptibility to ethanol extracts of Thai medicinal plants based on eye infection treatment. The ethanol C. longa extract showed the strongest anti-Acanthamoeba activity against both the trophozoites and cysts, followed by Coscinium fenestratum, Coccinia grandis, and Acmella oleracea extracts, respectively. After 24 h, 95% reduction of trophozoite viability was significantly decreased following the treatment with C. longa extract at 125 µg/mL, compared with the control (P < 0.05). The extract at 1,000 µg/mL inhibited 90% viability of Acanthamoeba cyst within 24 h, compared with the control. It was found that the cysts treated with C. longa extract at 500 µg/mL demonstrated abnormal shape after 24 h. The MIC values of C. longa extract and Curcumin against the trophozoites were 125 and 62.5 µg/mL, respectively. While the MICs of the extract and curcumin against the cysts were 500 and 1,000 µg/mL, respectively. The results suggested the potential medicinal benefits of C. longa extract and Curcumin as the alternative treatment of Acanthamoeba infections.

Antiamoebic activity of plant-based natural products and their conjugated silver nanoparticles against Acanthamoeba castellanii (ATCC 50492)

Acanthamoeba spp. are the causative agent of Acanthamoeba keratitis and granulomatous amoebic encephalitis (GAE). The current options to treat Acanthamoeba infections have limited success. Silver nanoparticles show antimicrobial effects and enhance the efficacy of their payload at the specific biological targets. Natural folk plants have been widely used for treating diseases as the phytochemicals from several plants have been shown to exhibit amoebicidal effects. Herein, we used natural products of plant or commercial sources including quercetin (QT), kolavenic acid (PGEA) isolated from plant extracts of Polyalthia longifolia var pendula and crude plant methanolic extract of Caesalpinia pulcherrima (CPFLM) as antiacanthamoebic agents. Furthermore, these plant-based materials were conjugated with silver nanoparticles (AgNPs) to determine the effects of the natural compounds and their nanoconjugates against a clinical isolate of A. castellanii from a keratitis patient (ATCC 50492) belonging to the T4 genotype. The compounds were conjugated with AgNPs and characterized by using ultraviolet visible spectrophotometry and atomic force microscopy. Quercetin coated silver nanoparticles (QT-AgNPs) showed characteristic surface plasmon resonance band at 443 nm and the average size distribution was found to be around 45 nm. The natural compounds alone and their nanoconjugates were tested for the viability of amoebae, encystation and excystation activity against A. castellanii. The natural compounds showed significant growth inhibition of A. castellanii while QT-AgNPs specifically exhibited enhanced antiamoebic effects as well as interrupted the encystation and excystation activity of the amoebae. Interestingly, these compounds and nanoconjugates did not exhibit in vitro cytotoxic effects against human cells. Plant-based compounds and extracts could be an interesting strategy in development of alternative therapeutics against Acanthamoeba infections.

Encapsulation of Low Metronidazole Dose in Poly (D,L-lactide-co-glycolide) (PLGA) Nanoparticles Improves Giardia intestinalis Treatment

Background

The present study was designed to investigate the antigiardial efficacy of low metronidazole dose loaded-D.L-lactide-co-glycolide (LMD-PLGA) nanoparticles (NPs) and to compare it with the standard high dose of metronidazole either free (HMD) or loaded on PLGA (HMD-PLGA).

Materials and Methods

PLGA NPs were prepared by single emulsification method, metronidazole (MTZ) was loaded in low and high doses. The nanoparticles were evaluated in vivo for mice model. The Giardia intestinalis infected mice were treated by LMD and HMD either free or PLGA NPs loaded, the parasitic load and ployclonal antigiardial serum antibodies (IgG and IgA) were recorded. Histopathological studies on intestinal and liver sections were applied.

Results

MTZ-PLGA NPs was successfully prepared with 81.68% encapsulation efficiency and with an average particle size of approximately 228.00 ± 43.19 nm and -32.28 ± 0.07 mV Zeta potential. Experimentally, it was observed that Giardia intestinalis infected animals administered with LMD-PLGA had completely eliminated cyst shedding and trophozoite count compared with Giardia-infected mice. Further, it was found that animals belonging to LMD-PLGA group had significantly reduced levels of antigiardial IgA (0.99 ± 0.05) antibodies in serum compared with Giardia-infected. Histopathologyically, also animals belonging to LMD-PLGA treated group had intact mucosal epithelium lining, and normal villi with no detection of G. intestinalis trophozoites. In addition to the less toxic effect on the liver tissue compared to free HMD, HMD-PLGA and infected-untreated groups using Ishak grading system.

Conclusion

Our study showed that PLGA nanoparticles could be atrial delivery systems for antigiardial drugs to improve their therapeutic efficacy and minimize their side effects that results from frequent dosing.

Acanthamoeba in Southeast Asia - Overview and Challenges

Acanthamoeba, one of free-living amoebae (FLA), remains a high risk of direct contact with this protozoan parasite which is ubiquitous in nature and man-made environment. This pathogenic FLA can cause sight-threatening amoebic keratitis (AK) and fatal granulomatous amoebic encephalitis (GAE) though these cases may not commonly be reported in our clinical settings. Acanthamoeba has been detected from different environmental sources namely; soil, water, hot-spring, swimming pool, air-conditioner, or contact lens storage cases. The identification of Acanthamoeba is based on morphological appearance and molecular techniques using PCR and DNA sequencing for clinico-epidemiological purposes. Recent treatments have long been ineffective against Acanthamoeba cyst, novel anti-Acanthamoeba agents have therefore been extensively investigated. There are efforts to utilize synthetic chemicals, lead compounds from medicinal plant extracts, and animal products to combat Acanthamoeba infection. Applied nanotechnology, an advanced technology, has shown to enhance the anti-Acanthamoeba activity in the encapsulated nanoparticles leading to new therapeutic options. This review attempts to provide an overview of the available data and studies on the occurrence of pathogenic Acanthamoeba among the Association of Southeast Asian Nations (ASEAN) members with the aim of identifying some potential contributing factors such as distribution, demographic profile of the patients, possible source of the parasite, mode of transmission and treatment. Further, this review attempts to provide future direction for prevention and control of the Acanthamoeba infection.

Efficient therapeutic effect of Nigella sativa aqueous extract and chitosan nanoparticles against experimentally induced Acanthamoeba keratitis

Acanthamoeba keratitis (AK) is a devastating, painful corneal infection, which may lead to loss of vision. The development of resistance and failure of the currently used drugs represent a therapeutic predicament. Thus, novel therapies with lethal effects on resistant Acanthamoeba are necessary to combat AK. In the present study, the curative effect of Nigella sativa aqueous extract (N. sativa) and chitosan nanoparticles (nCs) and both agents combined were assessed in experimentally induced AK. All inoculated corneas developed varying grades of AK. The study medications were applied on the 5th day postinoculation and were evaluated by clinical examination of the cornea and cultivation of corneal scraps. On the 10th day posttreatment, a 100% cure of AK was obtained with nCs (100 μg/ml) in grades 1 and 2 of corneal opacity as well as with N. sativa 60 mg/ml-nCs 100 μg/ml in grades 1, 2, and 3 of corneal opacity, highlighting a possible synergistic effect. On the 15th day posttreatment, a 100% cure was reached with N. sativa aqueous extract (60 mg/ml). Moreover, on the 20th day posttreatment, N. sativa (30 mg/ml) provided a cure rate of 87.5%, while nCs (50 μg/ml) as well as N. sativa 30 mg/ml-nCs 50 μg/ml yielded a cure rate of 75%; the lowest percentage of cure (25%) was obtained with chlorhexidine (0.02%), showing a non-significant difference compared to the parasite control. The clinical outcomes were in agreement with the results of corneal scrap cultivation. The results of the present study demonstrate the effectiveness of N. sativa aqueous extract and nCs (singly or combined) when used against AK, and these agents show potential for the development of new, effective, and safe therapeutic alternatives.

Oleic acid-conjugated silver nanoparticles as efficient antiamoebic agent against Acanthamoeba castellanii

Acanthamoeba castellanii belonging to the T4 genotype is an opportunistic pathogen which is associated with blinding eye keratitis and rare but fatal central nervous system infection. A. castellanii pose serious challenges in antimicrobial chemotherapy due to its ability to convert into resistant, hardy shell-protected cyst form that leads to infection recurrence. The fatty acid composition of A. castellanii trophozoites is known to be most abundant in oleic acid which chemically is an unsaturated cis-9-Octadecanoic acid and naturally found in animal and vegetable fats and oils. This study was designed to evaluate antiacanthamoebic effects of oleic acid against trophozoites, cysts as well as parasite-mediated host cell cytotoxicity. Moreover, oleic acid-conjugated silver nanoparticles (AgNPs) were also synthesized and tested against A. castellanii. Oleic acid-AgNPs were synthesized by chemical reduction method and characterized by ultraviolet-visible spectrophotometry, atomic force microscopy, dynamic light scattering analysis, and Fourier transform infrared spectroscopy. Viability, growth inhibition, encystation, and excystation assays were performed with 10 and 5 μM concentration of oleic acid alone and oleic acid-conjugated AgNPs. Bioassays revealed that oleic acid alone and oleic acid-conjugated AgNPs exhibited significant antiamoebic properties, whereas nanoparticle conjugation further enhanced the efficacy of oleic acid. Phenotype differentiation assays also showed significant inhibition of encystation and excystation at 5 μM. Furthermore, oleic acid and oleic acid-conjugated AgNPs also inhibited amoebae-mediated host cell cytotoxicity as determined by lactate dehydrogenase release. These findings for the first time suggest that oleic acid-conjugated AgNPs exhibit antiacanthamoebic activity that hold potential for therapeutic applications against A. castellanii.

Antimicrobial activities of green synthesized gums-stabilized nanoparticles loaded with flavonoids

Herein, we report green synthesized nanoparticles based on stabilization by plant gums, loaded with citrus fruits flavonoids Hesperidin (HDN) and Naringin (NRG) as novel antimicrobial agents against brain-eating amoebae and multi-drug resistant bacteria. Nanoparticles were thoroughly characterized by using zetasizer, zeta potential, atomic force microscopy, ultravoilet-visible and Fourier transform-infrared spectroscopic techniques. The size of these spherical nanoparticles was found to be in the range of 100–225 nm. The antiamoebic effects of these green synthesized Silver and Gold nanoparticles loaded with HDN and NRG were tested against Acanthamoeba castellanii and Naegleria fowleri, while antibacterial effects were evaluated against methicillin-resistant Staphylococcus aureus (MRSA) and neuropathogenic Escherichia coli K1. Amoebicidal assays revealed that HDN loaded Silver nanoparticles stabilized by gum acacia (GA-AgNPs-HDN) quantitatively abolished amoeba viability by 100%, while NRG loaded Gold nanoparticles stabilized by gum tragacanth (GT-AuNPs-NRG) significantly reduced the viability of A. castellanii and N. fowleri at 50 µg per mL. Furthermore, these nanoparticles inhibited the encystation and excystation by more than 85%, as well as GA-AgNPs-HDN only completely obliterated amoeba-mediated host cells cytopathogenicity. Whereas, GA-AgNPs-HDN exhibited significant bactericidal effects against MRSA and E. coli K1 and reduced bacterial-mediated host cells cytotoxicity. Notably, when tested against human cells, these nanoparticles showed minimal (23%) cytotoxicity at even higher concentration of 100 µg per mL as compared to 50 µg per mL used for antimicrobial assays. Hence, these novel nanoparticles formulations hold potential as therapeutic agents against infections caused by brain-eating amoebae, as well as multi-drug resistant bacteria, and recommend a step forward in drug development.