Amphotericin B-conjugated biogenic silver nanoparticles as an innovative strategy for fungal infections

Assessing the Potential of Aconitum Laeve Extract for Biogenic Silver and Gold Nanoparticle Synthesis and Their Biological and Catalytic Applications

The adoption of green chemistry protocols in nanoparticle (NP) synthesis has exhibited substantial potential and is presently a central focus in research for generating versatile NPs applicable across a broad spectrum of applications. In this scientific contribution, we, for the first time, examined the ability of Aconitum Laeve (A. Laeve) crude extract to synthesize silver and gold nanoparticles (AgNPs@AL; AuNP@AL) and explored their potential applications in biological activities and the catalytic degradation of environmental pollutants. The synthesized NPs exhibited a distinctive surface plasmon resonance pattern, a spherical morphology with approximate sizes of 5-10 nm (TEM imaging), a crystalline architecture (XRD analysis), and potential functional groups identified by FTIR spectroscopy. The antibacterial activity was demonstrated by inhibition zones that measured 16 and 14 mm for the AgNPs@AL and AuNP@AL at a concentration of 80 µg/mL against Staphylococcus aureus and 14 and 12 mm against Escherichia coli, respectively. The antioxidant potential of the synthesized NPs was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-Oxide (PTIO), and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. Our findings suggest that the AuNP@AL effectively countered the tested radicals considerably, displaying IC50 values of 115.9, 103.54, and 180.85 µg/mL against DPPH, PTIO, and ABTS, respectively. In contrast, the AgNPs@AL showed IC50 values of 144.9, 116.36, and 95.39 µg/mL against the respective radicals. In addition, both the NPs presented significant effectiveness in the photocatalytic degradation of methylene blue and rhodamine B. The overall observations indicate that A. Laeve possesses a robust capability to synthesize spherical nanoparticles, exhibiting excellent dispersion and showcasing potential applications in both biological activities and environmental remediation.

Conjugates of amphotericin B to resolve challenges associated with its delivery

INTRODUCTION

Amphotericin B (AmB), a promising antifungal and antileishmanial drug, acts on the membrane of microorganisms. The clinical use of AmB is limited due to issues associated with its delivery including poor solubility and bioavailability, instability in acidic media, poor intestinal permeability, dose and aggregation state dependent toxicity, parenteral administration, and requirement of cold chain for transport and storage, etc.

AREAS COVERED

Scientists have formulated and explored various covalent conjugates of AmB to reduce its toxicity with increase in solubility, oral bioavailability, and payload or loading of AmB by using various polymers, lipids, carbon-based nanocarriers, metallic nanoparticles, and vesicular carriers, etc. In this article, we have reviewed various conjugates of AmB with polymers and nanomaterials explored for its delivery to give a deep insight regarding further exploration in future.

EXPERT OPINION

Covalent conjugates of AmB have been investigated by scientists, and preliminary in vitro and animal investigations have given successful results, which are required to be validated further with systematic investigation on safety and therapeutic efficacy in animals followed by clinical trials.

Inorganic Nanoparticles: Tools to Emphasize the Janus Face of Amphotericin B

Amphotericin B is the oldest antifungal molecule which is still currently widely used in clinical practice, in particular for the treatment of invasive diseases, even though it is not devoid of side effects (particularly nephrotoxicity). Recently, its redox properties (i.e., both prooxidant and antioxidant) have been highlighted in the literature as mechanisms involved in both its activity and its toxicity. Interestingly, similar properties can be described for inorganic nanoparticles. In the first part of the present review, the redox properties of Amphotericin B and inorganic nanoparticles are discussed. Then, in the second part, inorganic nanoparticles as carriers of the drug are described. A special emphasis is given to their combined redox properties acting either as a prooxidant or as an antioxidant and their connection to the activity against pathogens (i.e., fungi, parasites, and yeasts) and to their toxicity. In a majority of the published studies, inorganic nanoparticles carrying Amphotericin B are described as having a synergistic activity directly related to the rupture of the redox homeostasis of the pathogen. Due to the unique properties of inorganic nanoparticles (e.g., magnetism, intrinsic anti-infectious properties, stimuli-triggered responses, etc.), these nanomaterials may represent a new generation of medicine that can synergistically enhance the antimicrobial properties of Amphotericin B.

Prospect of nanomaterials as antimicrobial and antiviral regimen

In recent years studies of nanomaterials have been explored in the field of microbiology due to the increasing evidence of antibiotic resistance. Nanomaterials could be inorganic or organic, and they may be synthesized from natural products from plant or animal origin. The therapeutic applications of nano-materials are wide, from diagnosis of disease to targeted delivery of drugs. Broad-spectrum antiviral and antimicrobial activities of nanoparticles are also well evident. The ratio of nanoparticles surface area to their volume is high and that allows them to be an advantageous vehicle of drugs in many respects. Effective uses of various materials for the synthesis of nanoparticles impart much specificity in them to meet the requirements of specific therapeutic strategies. The potential therapeutic use of nanoparticles and their mechanisms of action against infections from bacteria, fungi and viruses were the focus of this review. Further, their potential advantages, drawbacks, limitations and side effects are also included here. Researchers are characterizing the exposure pathways of nano-medicines that may cause serious toxicity to the subjects or the environment. Indeed, societal ethical issues in using nano-medicines pose a serious question to scientists beyond anything.

Biogenic silver nanoparticles as antifungal agents

In recent years, an increase in multidrug-resistant fungal strains has been observed, which, together with the limited number of clinically available antifungal agents, highlights the need for the development of new antifungal agents. Due to the proven antifungal activity of silver nanoparticles (AgNPs), there is a growing interest in their use in the treatment of fungal infections. Nanoparticles are usually synthesised through a variety of physical and chemical processes that are costly and pollute the environment. For this reason, biogenic synthesis is emerging as an environmentally friendly technology and new strategies are increasingly based on the use of biogenic AgNPs as antifungal agents for clinical use. The aim of this review is to compare the antifungal activity of different biogenic AgNPs and to summarise the current knowledge on the mechanisms of action and resistance of fungi to AgNPs. Finally, a general analysis of the toxicity of biogenic AgNPs in human and veterinary medicine is performed.

Orally Administered Amphotericin B Nanoformulations: Physical Properties of Nanoparticle Carriers on Bioavailability and Clinical Relevance

Amphotericin B is an effective polyene antifungal considered as a “gold standard” in the management of fungal infections. Currently, it is administered mainly by IV due to poor aqueous solubility, which precludes its delivery orally. Paradoxically, IV administration is akin to side effects that have not been fully eliminated even with more recent IV formulations. Thus, the need for alternative formulations/route of administration for amphotericin B remains crucial. The oral route offers the possibility of delivering amphotericin B systemically and with diminished side effects; however, enterocyte permeation remains a constraint. Cellular phagocytosis of submicron particles can be used to courier encapsulated drugs. In this regard, nanoparticulate delivery systems have received much attention in the past decade. This review examines the trajectory of orally delivered amphotericin B and discusses key physical factors of nanoformulations that impact bioavailability. The review also explores obstacles that remain and gives a window into the possibility of realizing an oral nanoformulation of amphotericin B in the near future.

A Promising Antifungal and Antiamoebic Effect of Silver Nanorings, a Novel Type of AgNP

Silver nanoparticles (AgNPs) play an important role in the medical field due to their potent antimicrobial activity. This, together with the constant emergence of resistance to antimicrobial drugs, means AgNPs are often investigated as an alternative to solve this problem. In this article, we analyzed the antifungal and antiamoebic effects of a recently described type of AgNP, silver nanorings (AgNRs), and compared them with other types of AgNPs. Tests of the activity of AgNPs against various fungal and amoebic species were carried out. In all cases, AgNPs showed a high biocidal effect, although with fungi this depended on the species involved. Antifungal activity was detected by the conditioning of culture media or water but this effect was not dependent on the release of Ag ions. On the other hand, the proliferation of Acanthamoeba castellanii trophozoites was reduced by silver nanorings (AgNRs) and silver nanowires (AgNWs), with AgNWs being capable of totally inhibiting the germination of A. castellanii cysts. AgNRs constitute a new type of AgNP with an antifungal and antiacanthamoebic activity. These results open the door to new and effective antimicrobial therapies as an alternative to the use of antifungals or antiamoebic drugs, thus avoiding the constant appearance of resistance and the difficulty of eradicating infections.

Activity of poly(methacrylic acid)-silver nanoparticles (PMAA-AgNPs) on fluconazole resistant Candida albicans strains: synergistic and cytotoxic effects

AIMS

To synthesize and evaluate the antifungal activity of poly(methacrylic acid)-silver nanoparticles (PMAA-AgNPs) against nine Candida albicans isolated from clinical specimens.

METHODS AND RESULTS

The effects of PMAA-AgNPs-fluconazole combination was analyzed by checkerboard methodology. The synergistic potential of PMAA-AgNPs-fluconazole was determined by the fractional inhibitory concentration index (FICI). The inhibition of germ tube formation and the determination of PMAA-AgNPs cytotoxicity were also performed. All C. albicans strains were susceptible to PMAA-AgNPs and resistant to fluconazole. PMAA-AgNPs at sub-inhibitory concentrations restored the susceptibility of resistant C. albicans to fluconazole, whose FICI ranged from 0.3 to 0.5. The synergistic interaction of the combination was observed in eight of nine strains. The PMAA-AgNPs-fluconazole combination was also able to inhibit the germ tube formation. PMAA-AgNPs showed a dose-dependent decrease on viability for cells tested, with 50% cytotoxic concentration (CC₅₀ ) values of 6.5, 4.9 and 6.8 μg ml^-1 for macrophages, fibroblasts and Vero cells, respectively.

CONCLUSIONS

This study demonstrated that in general, PMAA-AgNPs acts synergistically in combination with fluconazole, inhibiting fluconazole-resistant C. albicans strains. PMAA-AgNPs-fluconazole combination was also able to inhibit germ tube formation, an important virulence factor. Inhibitory effect of PMAA-AgNPs alone or in combination was higher in C. albicans than in mammalian cells.

SIGNIFICANCE AND IMPACT OF STUDY

This study shows the potential of poly(methacrylic acid)-silver nanoparticles combined with fluconazole to inhibit fluconazole-resistant Candida albicans strains.

Synergistic Effects Between Metal Nanoparticles and Commercial Antimicrobial Agents: A Review

Nanotechnology has expanded into a broad range of clinical applications. In particular, metal nanoparticles (MNPs) display unique antimicrobial properties, a fundamental function of novel medical devices. The combination of MNPs with commercial antimicrobial drugs (e.g., antibiotics, antifungals, and antivirals) may offer several opportunities to overcome some disadvantages of their individual use and enhance effectiveness. MNP conjugates display multiple advantages. As drug delivery systems, the conjugates can extend the circulation of the drugs in the body, facilitate intercellular targeting, improve drug stabilization, and possess superior delivery. Concomitantly, they reduce the required drug dose, minimize toxicity, and broaden the antimicrobial spectrum. In this work, the common strategies to combine MNPs with clinically used antimicrobial agents are underscored. Furthermore, a comprehensive survey about synergistic antimicrobial effects, the mechanism of action, and cytotoxicity is depicted.

Biogenic Silver Nanoparticles: Synthesis and Application as Antibacterial and Antifungal Agents

The importance and need for eco-oriented technologies has increased worldwide, which leads to an enhanced development of methods for the synthesis of nanoparticles using biological agents. This review de-scribes the current approaches to the preparation of biogenic silver nanoparticles, using plant extracts and filtrates of fungi and microorganisms. The peculiarities of the synthesis of particles depending on the source of biocomponents are considered as well as physico-morphological, antibacterial and antifungal properties of the resulting nanoparticles which are compared with such properties of silver nanoparticles obtained by chemical synthesis. Special attention is paid to the process of self-assembly of biogenic silver nanoparticles.

Bionanofactories for Green Synthesis of Silver Nanoparticles: Toward Antimicrobial Applications

Among the various types of nanoparticles and their strategy for synthesis, the green synthesis of silver nanoparticles has gained much attention in the biomedical, cellular imaging, cosmetics, drug delivery, food, and agrochemical industries due to their unique physicochemical and biological properties. The green synthesis strategies incorporate the use of plant extracts, living organisms, or biomolecules as bioreducing and biocapping agents, also known as bionanofactories for the synthesis of nanoparticles. The use of green chemistry is ecofriendly, biocompatible, nontoxic, and cost-effective. We shed light on the recent advances in green synthesis and physicochemical properties of green silver nanoparticles by considering the outcomes from recent studies applying SEM, TEM, AFM, UV/Vis spectrophotometry, FTIR, and XRD techniques. Furthermore, we cover the antibacterial, antifungal, and antiparasitic activities of silver nanoparticles.

Phytoassisted synthesis and characterization of palladium nanoparticles (PdNPs); with enhanced antibacterial, antioxidant and hemolytic activities

With increasing demand for the treatment of microbial resistance around the globe, it is necessary to develop metallic nanoparticles , ideally by the use of nontoxic medium i.e. plant constituents, that could arrest the microbial growth. For this reason, small and highly crystalline PdNPs were effectively synthesized by using Eryngium caeruleum leaf extract as both the reducing and capping agent. During the synthesis of PdNPs, the size and shape were made controlled by using different solvents i.e., ethanol, methanol and aqueous extract of Eryngium caeruleum. A series of physicochemical characterizations were applied to inquire the synthesis, crystal structure, particles size, and surface morphology of PdNPs. Furthermore, the PdNPs demonstrated excellent potential for the inactivation of gram-positive and gram-negative bacteria, where the methanol-PdNPs exhibited maximum growth inhibition zones against tested bacteria as compared to ethanol-PdNPs and aqueous-PdNPs. Besides, PdNPs showed better antioxidant activity to effectively scavenge 2, 2 diphenyl-1-picrylhydrazyl (DPPH). More importantly, the synthesized PdNPs are not only active for ROS generation but also show no hemolytic activity. We believe that this greener approach uncovered the useful and efficient applications of highly active PdNPs and their biocompatibility.

Striking Back against Fungal Infections: The Utilization of Nanosystems for Antifungal Strategies

Fungal infections have become a major health concern, given that invasive infections by Candida, Cryptococcus, and Aspergillus species have led to millions of mortalities. Conventional antifungal drugs including polyenes, echinocandins, azoles, allylamins, and antimetabolites have been used for decades, but their limitations include off-target toxicity, drug-resistance, poor water solubility, low bioavailability, and weak tissue penetration, which cannot be ignored. These drawbacks have led to the emergence of novel antifungal therapies. In this review, we discuss the nanosystems that are currently utilized for drug delivery and the application of antifungal therapies.

Dissolvable carboxymethyl cellulose/polyvinylpyrrolidone microneedle arrays for transdermal delivery of Amphotericin B to treat cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is a significant public health problem caused by different species of Leishmania parasites. Due to low skin permeability, the development of an effective system for delivery of Amphotericin B (AMB), the common effective drug for leishmaniasis treatment, is required to replace the unpleasant and problematic injections. To overcome this problem, a dissolvable microneedle (MN) patch was developed, using biodegradable polymers (a mixture of polyvinylpyrrolidone and carboxymethyl cellulose) for AMB's transdermal delivery. Scanning electron microscopy and fluorescent images showed successful fabrication of the MNs and homogeneous dispersion of the drug into the needles. MNs showed good mechanical properties with the ability to penetrate the rat skin and reach the lower layers. After insertion to the skin, the MNs were rapidly dissolved to release the encapsulated drug, and the resulted micropores in the skin were quickly resealed within 30 min. MN patches showed non-toxicity as exposed to HT-29 cell line. Flow cytometry results showed a potent in vitro leishmanicidal activity of AMB-loaded MN patches against the Leishmania parasites (up to 86% of the parasites' death). Taken together, MN patches might represent a new, efficient and clinically translational approach for transdermal AMB delivery to treat CL.

Recent developments in biomolecule-based nanoencapsulation systems for antimicrobial delivery and biofilm disruption

Biomolecules are very attractive nanomaterial components, generally, due to their biocompatibility, biodegradability, abundance, renewability, and sustainability, as compared to other resources for nanoparticle-based delivery systems. Biomolecule-based nanoencapsulation and nanodelivery systems can be designed and engineered for antimicrobial cargos in order to surmount classical and current challenges, including the emergence of multi-drug resistant strains of microorganisms, the low effectiveness and limitations in the applicability of the present antimicrobials, and biofilm formation. This feature article highlights the recent applications and capabilities of biomacromolecule-based nanomaterials for the delivery and activity enhancement of antimicrobials, and disruption of biofilms. Unique properties of some nanomaterials, arising from specific biomacromolecules, were also emphasized. We expect that this review will be helpful to researchers in engineering new types of antimicrobial nanocarriers, hybrid particles and colloidal systems with tailored properties.

Nanoparticles as a Tool for Broadening Antifungal Activities

Fungal infections are diseases that are considered neglected although their infection rates have increased worldwide in the last decades. Thus, since the antifungal arsenal is restricted and many strains have shown resistance, new therapeutic alternatives are necessary. Nanoparticles are considered important alternatives to promote drug delivery. In this sense, the objective of the present study was to evaluate the contributions of newly developed nanoparticles to the treatment of fungal infections. Studies have shown that nanoparticles generally improve the biopharmaceutical and pharmacokinetic characteristics of antifungals, which is reflected in a greater pharmacodynamic potential and lower toxicity, as well as the possibility of prolonged action. It also offers the proposition of new routes of administration. Nanotechnology is known to contribute to a new drug delivery system, not only for the control of infectious diseases but for various other diseases as well. In recent years, several studies have emphasized its application in infectious diseases, presenting better alternatives for the treatment of fungal infections.

Green Synthesis of Silver Nanoparticles Using the Lotus lalambensis Aqueous Leaf Extract and Their Anti-Candidal Activity against Oral Candidiasis

Oral candidiasis is widely spread in both humans and animals, which is caused mainly by Candida albicans. In this study, we aimed to biosynthesize silver nanoparticles (AgNPs) for the first time using the Lotus lalambensis Schweinf leaf extract (L-AgNPs) and investigated their anti-candidal potency alone or in combination with the leaf extract of L. lalambensis (L-AgNPs/LL) against C. albicans. The biosynthesized L-AgNPs were characterized by imaging (transmission electron microscopy, TEM), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The results of the disk diffusion method showed the potent synergistic anti-candidal activity of L-AgNPs/LL (24 mm inhibition zone). L-AgNPs/LL completely inhibited the morphogenesis of C. albicans and suppressed the adhesion and the formation of the biofilm of C. albicans by 82.5 and 78.7%, respectively. Further, L-AgNPs/LL inhibited the production of antioxidant enzymes of C. albicans by 80%. SEM and TEM revealed deteriorations in the cell wall ultrastructure in L-AgNPs/LL-treated C. albicans. Interestingly, L-AgNPs/LL showed less than 5% cytotoxicity when examined with either the primary bone marrow derived mesenchymal stem cell (BMSCs) or MCF-7 cell line at MIC values of L-AgNPs/LL. In conclusion, we identified L-AgNPs/LL as a potential biosynthesized-based drug for oral candidiasis in humans and animals.

Current applications and prospects of nanoparticles for antifungal drug delivery

Currently, the significance of fungi as human pathogens is not medically concealed in the world. Consequently, suitable recognition and treatment of such infections are of great importance and necessitate the need for comprehensive information in this regard. The introduction of new antifungals and their use today, especially in the last two decades, have revolutionized the treatment of fungal infections. On the other hand, increasing drug resistance in the world has overshadowed such developments. The use of NPs results in the treatment of fungal infections and owing to their specific properties, these particles, unlike the pure antibiotics, can exert a greater inhibitory power although with less concentration compared with conventional drugs. Important reasons that have led to the use of antifungal drugs in delivery systems include reduced drug efficacy, limited penetration through tissue, poor aqueous solubility, decreased bioavailability, and poor drug pharmacokinetics. It is therefore hoped that unfavorable properties of antifungal drugs be mitigated via their incorporation into different types of NPs. This review summarizes the different types of NPs as delivery systems of antifungal as well as their advantages over pure drugs.

Current and promising pharmacotherapeutic options for candidiasis

Introduction: Candida spp. are commensal yeasts capable of causing infections such as superficial, oral, vaginal, or systemic infections. Despite medical advances, the antifungal pharmacopeia remains limited and the development of alternative strategies is needed.Areas covered: We discuss available treatments for Candida spp. infections, highlighting advantages and limitations related to pharmacokinetics, cytotoxicity, and antimicrobial resistance. Moreover, we present new perspectives to improve the activity of the available antifungals, discussing their immunomodulatory potential and advances on drug delivery carriers. New therapeutic approaches are presented including recent synthesized antifungal compounds (Enchochleated-Amphotericin B, tetrazoles, rezafungin, enfumafungin, manogepix and arylamidine); drug repurposing using a diversity of antibacterial, antiviral and non-antimicrobial drugs; combination therapies with different compounds or photodynamic therapy; and innovations based on nano-particulate delivery systems.Expert opinion: With the lack of novel drugs, the available assets must be leveraged to their best advantage through modifications that enhance delivery, efficacy, and solubility. However, these efforts are met with continuous challenges presented by microbes in their infinite plight to resist and survive therapeutic drugs. The pharmacotherapeutic options in development need to focus on new antimicrobial targets. The success of each antimicrobial agent brings strategic insights to the next phased approach in treatingCandida spp. infections.

Rod-shaped gold nanoparticles exert potent candidacidal activity and decrease the adhesion of fungal cells

Aim: To investigate the fungicidal activity of rod-shaped gold nanoparticles (AuR NPs) against Candida strains isolated from hematooncological patients and representative strains of filamentous fungi. Methods: Colony-counting assays, colorimetric and fluorometric methods and atomic force microscopy were employed. Results: AuR NPs were characterized by their potent fungicidal activity against all tested isolates, regardless of the species or drug susceptibility, at concentrations that are nontoxic to the host cells. The membrane-permeabilizing properties of AuR NPs and induction of reactive oxygen species were recognized as crucial for fungicidal activity. Conclusions: The results provide a rationale for the development of nonspherical Au NPs as effective antifungals or drug-delivery carriers to improve therapy for fungal infections.

Advances in Biomaterials for the Prevention and Disruption of Candida Biofilms

Candida species can readily colonize a multitude of indwelling devices, leading to biofilm formation. These three-dimensional, surface-associated Candida communities employ a multitude of sophisticated mechanisms to evade treatment, leading to persistent and recurrent infections with high mortality rates. Further complicating matters, the current arsenal of antifungal therapeutics that are effective against biofilms is extremely limited. Antifungal biomaterials are gaining interest as an effective strategy for combating Candida biofilm infections. In this review, we explore biomaterials developed to prevent Candida biofilm formation and those that treat existing biofilms. Surface functionalization of devices employing clinically utilized antifungals, other antifungal molecules, and antifungal polymers has been extremely effective at preventing fungi attachment, which is the first step of biofilm formation. Several mechanisms can lead to this attachment inhibition, including contact killing and release-based killing of surrounding planktonic cells. Eliminating mature biofilms is arguably much more difficult than prevention. Nanoparticles have shown the most promise in disrupting existing biofilms, with the potential to penetrate the dense fungal biofilm matrix and locally target fungal cells. We will describe recent advances in both surface functionalization and nanoparticle therapeutics for the treatment of Candida biofilms.

Nanosystems against candidiasis: a review of studies performed over the last two decades

The crescent number of cases of candidiasis and the increase in the number of infections developed by non-albicans species and by multi-resistant strains has taken the attention of the scientific community, which has been searching for new therapeutic alternatives. Among the alternatives found the use of nanosystems for delivery of drugs already commercialized and new biomolecules have grown, in order to increase stability, solubility, optimize efficiency and reduce adverse effects. In view of the growing number of studies involving technological alternatives for the treatment of candidiasis, the present review came with the intention of gathering studies from the last two decades that used nanotechnology for the treatment of candidiasis, as well as analysing them critically and pointing out the future perspectives for their application with this purpose. Different studies were considered for the development of this review, addressing nanosystems such as metallic nanoparticles, mesoporous silica nanoparticles, polymeric nanoparticles, liposomes, nanoemulsion, microemulsion, solid lipid nanoparticle, nanostructured lipid carrier, lipidic nanocapsules and liquid crystals; and different clinical presentations of candidiasis. As a general overview, nanotechnology has proven to be an important ally for the treatment against the diversity of candidiasis found in the clinic, whether in increasing the effectiveness of commercialized drugs and reducing their adverse effects, as well as allowing exploring more effectively properties therapeutics of new biomolecules.

New avenues of controlling microbial infections through anti-microbial and anti-biofilm potentials of green mono-and multi-metallic nanoparticles: A review

Nanoparticles synthesized through the green route deserve special mention because this green technology is not only energy-efficient and cost-effective but also amenable to the environment. Various biological resources have been used for the generation of these 'green nanoparticles'. Biological wastes have also been focused in this direction thereby promoting the value of waste. Reports indicate that green nanoparticles exhibit remarkable antimicrobial activitiesboth singly as well as in combination with standard antibiotics. The current phenomenon of multi-drug resistance has resulted due to indiscriminate administration of high-doses of antibiotics followed by significant toxicity. In the face of this emergence of drug-resistant microbesthe efficacy of green nanoparticles might prove greatly beneficial. Microbial biofilm is another hurdle in the effective treatment of diseases as the microorganismsbeing embedded in the meshwork of the biofilmevade the antimicrobial agents. Nanoparticles may act as a ray of hope on the face of this challenge tooas they not only destroy the biofilms but also lessen the doses of antibiotics requiredwhen administered in combination with the nanoparticles. It should be further noted that the resistance mechanisms exhibited by the microorganisms seem not that relevant for nanoparticles. The current review, to the best of our knowledgefocuses on the structures of these green nanoparticles along with their biomedical potentials. It is interesting to note how a variety of structures are generated by using resources like microbes or plants or plant products and how the structure affects their activities. This study might pave the way for further development in this arena and future work may be taken up in identifying the detailed mechanism by which 'green' synthesis empowers nanoparticles to kill pathogenic microbes.

A review of the antimicrobial potential of precious metal derived nanoparticle constructs

The field of nanotechnology is rapidly growing. The promise of pharmacotherapeutics emerging from this vast field has drawn the attention of many researchers. However, with the increase in the prevalence of antibiotic resistant microorganisms, the manifestations of these promises are needed now more than ever. Many have postulated the antimicrobial potential of nanoparticle constructs derived from precious metals/noble metals nanoparticles (NMNPs), such as silver nanoparticles that show activity against multidrug resistant bacteria. In this review we will evaluate the current studies and explore the data to obtain a clear picture of the potential of these particles and the validity of the claims of drug resistant treatments with NMNPs.

Synthesis, characterization, and mechanistic studies of a gold nanoparticle-amphotericin B covalent conjugate with enhanced antileishmanial efficacy and reduced cytotoxicity

Background

Amphotericin B (AmB) as a liposomal formulation of AmBisome is the first line of treatment for the disease, visceral leishmaniasis, caused by the parasite Leishmania donovani. However, nephrotoxicity is very common due to poor water solubility and aggregation of AmB. This study aimed to develop a water-soluble covalent conjugate of gold nanoparticle (GNP) with AmB for improved antileishmanial efficacy and reduced cytotoxicity.

Methods

Citrate-reduced GNPs (~39 nm) were functionalized with lipoic acid (LA), and the product GNP-LA (GL ~46 nm) was covalently conjugated with AmB using carboxyl-to-amine coupling chemistry to produce GNP-LA-AmB (GL-AmB ~48 nm). The nanoparticles were characterized by dynamic light scattering, transmission electron microscopy (TEM), and spectroscopic (ultraviolet–visible and infrared) methods. Experiments on AmB uptake of macrophages, ergosterol depletion of drug-treated parasites, cytokine ELISA, fluorescence anisotropy, flow cytometry, and gene expression studies established efficacy of GL-AmB over standard AmB.

Results

Infrared spectroscopy confirmed the presence of a covalent amide bond in the conjugate. TEM images showed uniform size with smooth surfaces of GL-AmB nanoparticles. Efficiency of AmB conjugation was ~78%. Incubation in serum for 72 h showed <7% AmB release, indicating high stability of conjugate GL-AmB. GL-AmB with AmB equivalents showed ~5-fold enhanced antileishmanial activity compared with AmB against parasite-infected macrophages ex vivo. Macrophages treated with GL-AmB showed increased immunostimulatory T_h1 (IL-12 and interferon-γ) response compared with standard AmB. In parallel, AmB uptake was ~5.5 and ~3.7-fold higher for GL-AmB-treated (P<0.001) macrophages within 1 and 2 h of treatment, respectively. The ergosterol content in GL-AmB-treated parasites was ~2-fold reduced compared with AmB-treated parasites. Moreover, GL-AmB was significantly less cytotoxic and hemolytic than AmB (P<0.01).

Conclusion

GNP-based delivery of AmB can be a better, cheaper, and safer alternative than available AmB formulations.

Prospects for the Use of New Technologies to Combat Multidrug-Resistant Bacteria

The increasing use of antibiotics is being driven by factors such as the aging of the population, increased occurrence of infections, and greater prevalence of chronic diseases that require antimicrobial treatment. The excessive and unnecessary use of antibiotics in humans has led to the emergence of bacteria resistant to the antibiotics currently available, as well as to the selective development of other microorganisms, hence contributing to the widespread dissemination of resistance genes at the environmental level. Due to this, attempts are being made to develop new techniques to combat resistant bacteria, among them the use of strictly lytic bacteriophage particles, CRISPR-Cas, and nanotechnology. The use of these technologies, alone or in combination, is promising for solving a problem that humanity faces today and that could lead to human extinction: the domination of pathogenic bacteria resistant to artificial drugs. This prospective paper discusses the potential of bacteriophage particles, CRISPR-Cas, and nanotechnology for use in combating human (bacterial) infections.

Green synthesis of silver nanoparticles: biomolecule-nanoparticle organizations targeting antimicrobial activity

Since discovery of the first antibiotic drug, penicillin, in 1928, a variety of antibiotic and antimicrobial agents have been developed and used for both human therapy and industrial applications. However, excess and uncontrolled use of antibiotic agents has caused a significant growth in the number of drug resistant pathogens. Novel therapeutic approaches replacing the inefficient antibiotics are in high demand to overcome increasing microbial multidrug resistance. In the recent years, ongoing research has focused on development of nano-scale objects as efficient antimicrobial therapies. Among the various nanoparticles, silver nanoparticles have gained much attention due to their unique antimicrobial properties. However, concerns about the synthesis of these materials such as use of precursor chemicals and toxic solvents, and generation of toxic byproducts have led to a new alternative approach, green synthesis. This eco-friendly technique incorporates use of biological agents, plants or microbial agents as reducing and capping agents. Silver nanoparticles synthesized by green chemistry offer a novel and potential alternative to chemically synthesized nanoparticles. In this review, we discuss the recent advances in green synthesis of silver nanoparticles, their application as antimicrobial agents and mechanism of antimicrobial mode of action.

Nanoparticles and Controlled Delivery for Bioactive Compounds: Outlining Challenges for New "Smart-Foods" for Health

Nanotechnology is a field of research that has been stressed as a very valuable approach for the prevention and treatment of different human health disorders. This has been stressed as a delivery system for the therapeutic fight against an array of pathophysiological situations. Actually, industry has applied this technology in the search for new oral delivery alternatives obtained upon the modification of the solubility properties of bioactive compounds. Significant works have been made in the last years for testing the input that nanomaterials and nanoparticles provide for an array of pathophysiological situations. In this frame, this review addresses general questions concerning the extent to which nanoparticles offer alternatives that improve therapeutic value, while avoid toxicity, by releasing bioactive compounds specifically to target tissues affected by specific chemical and pathophysiological settings. In this regard, to date, the contribution of nanoparticles to protect encapsulated bioactive compounds from degradation as a result of gastrointestinal digestion and cellular metabolism, to enable their release in a controlled manner, enhancing biodistribution of bioactive compounds, and to allow them to target those tissues affected by biological disturbances has been demonstrated.

Amphotericin B-conjugated polypeptide hydrogels as a novel innovative strategy for fungal infections

The present work is focused on the design and development of novel amphotericin B (AmB)-conjugated biocompatible and biodegradable polypeptide hydrogels to improve the antifungal activity. Using three kinds of promoting self-assembly groups (2-naphthalene acetic acid (Nap), naproxen (Npx) and dexamethasone (Dex)) and polypeptide sequence (Phe-Phe-Asp-Lys-Tyr, FFDKY), we successfully synthesized the Nap-FFDK(AmB)Y gels, Npx-FFDK(AmB)Y gels and Dex-FFDK(AmB)Y gels. The AmB-conjugated hydrogelators are highly soluble in different aqueous solutions. The cryo-transmission electron microscopy and scanning electron microscopy micrographs of hydrogels afford nanofibres with a width of 20-50 nm. Powder X-ray diffraction analyses demonstrate that the crystalline structures of the AmB and Dex are changed into amorphous structures after the formation of hydrogels. Circular dichroism spectra of the solution of blank carriers and the corresponding drug deliveries further help elucidate the molecular arrangement in gel phase, indicating the existence of turn features. The in vitro drug releases suggest that the AmB-conjugated hydrogels are suitable as drug-controlled release vehicles for hydrophobic drugs. The antifungal effect of AmB-conjugated hydrogels significantly exhibits the antifungal activity against Candida albicans. The results of the present study indicated that the AmB-conjugated hydrogels are suitable carriers for poorly water soluble drugs and for enhancement of therapeutic efficacy of antifungal drugs.

Antifungal Therapy: New Advances in the Understanding and Treatment of Mycosis

The high rates of morbidity and mortality caused by fungal infections are associated with the current limited antifungal arsenal and the high toxicity of the compounds. Additionally, identifying novel drug targets is challenging because there are many similarities between fungal and human cells. The most common antifungal targets include fungal RNA synthesis and cell wall and membrane components, though new antifungal targets are being investigated. Nonetheless, fungi have developed resistance mechanisms, such as overexpression of efflux pump proteins and biofilm formation, emphasizing the importance of understanding these mechanisms. To address these problems, different approaches to preventing and treating fungal diseases are described in this review, with a focus on the resistance mechanisms of fungi, with the goal of developing efficient strategies to overcoming and preventing resistance as well as new advances in antifungal therapy. Due to the limited antifungal arsenal, researchers have sought to improve treatment via different approaches, and the synergistic effect obtained by the combination of antifungals contributes to reducing toxicity and could be an alternative for treatment. Another important issue is the development of new formulations for antifungal agents, and interest in nanoparticles as new types of carriers of antifungal drugs has increased. In addition, modifications to the chemical structures of traditional antifungals have improved their activity and pharmacokinetic parameters. Moreover, a different approach to preventing and treating fungal diseases is immunotherapy, which involves different mechanisms, such as vaccines, activation of the immune response and inducing the production of host antimicrobial molecules. Finally, the use of a mini-host has been encouraging for in vivo testing because these animal models demonstrate a good correlation with the mammalian model; they also increase the speediness of as well as facilitate the preliminary testing of new antifungal agents. In general, many years are required from discovery of a new antifungal to clinical use. However, the development of new antifungal strategies will reduce the therapeutic time and/or increase the quality of life of patients.