Nanoformulations for dismantling fungal biofilms: The latest arsenals of antifungal therapy

Globally, fungal infections have evolved as a strenuous challenge for clinicians, particularly in patients with compromised immunity in intensive care units. Fungal co-infection in Covid-19 patients has made the situation more formidable for healthcare practitioners. Surface adhered fungal population known as biofilm often develop at the diseased site to elicit antifungal tolerance and recalcitrant traits. Thus, an innovative strategy is required to impede/eradicate developed biofilm and avoid the formation of new colonies. The development of nanocomposite-based antibiofilm solutions is the most appropriate way to withstand and dismantle biofilm structures. Nanocomposites can be utilized as a drug delivery medium and for fabrication of anti-biofilm surfaces capable to resist fungal colonization. In this context, the present review comprehensively described different forms of nanocomposites and mode of their action against fungal biofilms. Amongst various nanocomposites, efficacy of metal/organic nanoparticles and nanofibers are particularly emphasized to highlight their role in the pursuit of antibiofilm strategies. Further, the inevitable concern of nanotoxicology has also been introduced and discussed with the exigent need of addressing it while developing nano-based therapies. Further, a list of FDA-approved nano-based antifungal formulations for therapeutic usage available to date has been described. Collectively, the review highlights the potential, scope, and future of nanocomposite-based antibiofilm therapeutics to address the fungal biofilm management issue.

Emergence of Nano-Based Formulations for Effective Delivery of Flavonoids against Topical Infectious Disorders

Flavonoids are hydroxylated phenolic substances in vegetables, fruits, flowers, seeds, wine, tea, nuts, propolis, and honey. They belong to a versatile category of natural polyphenolic compounds. Their biological function depends on various factors such as their chemical structure, degree of hydroxylation, degree of polymerization conjugation, and substitutions. Flavonoids have gained considerable attention among researchers, as they show a wide range of pharmacological activities, including coronary heart disease prevention, antioxidative, hepatoprotective, anti-inflammatory, free-radical scavenging, anticancer, and anti-atherosclerotic activities. Plants synthesize flavonoid compounds in response to pathogen attacks, and these compounds exhibit potent antimicrobial (antibacterial, antifungal, and antiviral) activity against a wide range of pathogenic microorganisms. However, certain antibacterial flavonoids have the ability to selectively target the cell wall of bacteria and inhibit virulence factors, including biofilm formation. Moreover, some flavonoids are known to reverse antibiotic resistance and enhance the efficacy of existing antibiotic drugs. However, due to their poor solubility in water, flavonoids have limited oral bioavailability. They are quickly metabolized in the gastrointestinal region, which limits their ability to prevent and treat various disorders. The integration of flavonoids into nanomedicine constitutes a viable strategy for achieving efficient cutaneous delivery owing to their favorable encapsulation capacity and diminished toxicity. The utilization of nanoparticles or nanoformulations facilitates drug delivery by targeting the drug to the specific site of action and exhibits excellent physicochemical stability.

Quercetin-Loaded Polycaprolactone-Polyvinylpyrrolidone Electrospun Membranes for Health Application: Design, Characterization, Modeling and Cytotoxicity Studies

Fibrous membranes of polycaprolactone (PCL)-polyvinylpyrrolidone (PVP) encapsulating 15% wt of quercetin are fabricated by a uniaxial electrospinning technique. Morphological analysis of the electrospun systems proved the fabrication of micrometric fibers (1.58 µm for PCL/PVP and 2.34 µm for quercetin-loaded membrane). The liquid retention degree of the electrospun membranes is evaluated by testing four different liquid media. The contact angle estimation is performed by testing three liquids: phosphate buffer solution, basic solution (pH = 13) and acidic solution (pH = 3), showing high hydrophobicity degree (contact angles > 90°) in all cases. The release of quercetin from the nanofibers in PBS (phosphate buffer solution) and pH = 3 medium, modeled through different models, shows the possibility of a fine tuning of drug release (up to 7 days) for the produced materials. The release profiles attained a plateau regime after roughly 50 h up to 82% and 71% for PBS and pH = 3 media, respectively. Then, since quercetin is known to undergo photooxidation upon UV radiation, release tests after different UV treatment times are carried out and compared with the untreated membrane, demonstrating that the release of the active drug changes from 82% for no-irradiated sample up to 57% after 10 h of UV exposure. The biology activity of released quercetin is evaluated on two human cell lines. The reported results demonstrate the ability of the quercetin-loaded membranes to reduce cell viability of human cell lines in two different conditions: direct contact between cells and quercetin-loaded membranes and cells treatment with culture medium previously conditioned with quercetin-loaded membranes. Therefore, the reported preliminary data confirm the possibility of applying the electrospun quercetin-loaded PCL-PVP membranes for health applications.

Quercetin nano phytosome: as a novel anti-leishmania and anti-malarial natural product

Leishmaniasis is a vector-borne disease that affects several populations worldwide with the clinical manifestations in skin, mucous membranes, and internal organs and there are not any effective and available vaccines and conventional treatments are highly toxic. Quercetin is a kind of flavonoid with different biological effects including free radical scavenging and anti-microbial activity and this study is aimed to assess the anti-leishmania and anti-malarial effects of quercetin loaded phytosome and quercetin alone. In this experimental study, the in vitro activity of above drugs were measured using microscopically examinations and for evaluation the anti-leishmanial efficacy, the size of lesions were measured. Moreover the cytotoxicity of the treatments was evaluated on WI38 and J774 cell lines. Our results indicated that quercetin loaded phytosome and quercetin alone have acceptable anti-parasitic activity mostly at concentration of 400 µg/ml on both P. falciparium and L. major. The results of cytotoxicity revealed that the mentioned drugs have no effects on human cell lines and also have no hemolytic activity. The drug of choice for the treatment of leishmaniasis, in addition to killing the parasite, should not have a toxic effect on human cells and our results indicated that quercetin can be a valuable candidate for treatment of different kinds of leishmaniasis.

PLA Nanofibers for Microenvironmental-Responsive Quercetin Release in Local Periodontal Treatment

The management of periodontitis remains a vital clinical challenge due to the interplay between the microorganisms of the dental biofilm and the host inflammatory response leading to a degenerative process in the surrounding tissues. Quercetin (QUE), a natural flavonol found in many foods, including apples, onions and tea, has exhibited prolonged and strong antibiofilm and anti-inflammatory effects both in vitro and in vivo. However, its clinical application is limited by its poor stability and water solubility, as well as its low bioavailability. Thus, in the present study, electrospun polylactic acid (PLA) nanofibers loaded with different amounts (5−10% w/w) of QUE were produced to rapidly respond to the acidic microenvironment typical of periodontal pockets during periodontal disease. This strategy demonstrated that PLA-QUE membranes can act as a drug reservoir releasing high QUE concentrations in the presence of oral bacterial infection (pH < 5.5), and thus limiting Pseudomonas aeruginosa PAO1 and Streptococcus mutans biofilm maturation. In addition, released QUE exerts antioxidant and anti-inflammatory effects on P. gingivalis Lipopolysaccharide (LPS)-stimulated human gingival fibroblast (HGFs). The reported results confirmed that PLA-QUE membranes could inhibit subgingival biofilm maturation while reducing interleukin release, thereby limiting host inflammatory response. Overall, this study provided an effective pH-sensitive drug delivery system as a promising strategy for treating periodontitis.

Modified magnetic core-shell mesoporous silica nano-formulations with encapsulated quercetin exhibit anti-amyloid and antioxidant activity

Targeted tissue drug delivery is a challenge in contemporary nanotechnologically driven therapeutic approaches, with the interplay interactions between nanohost and encapsulated drug shaping the ultimate properties of transport, release and efficacy of the drug at its destination. Prompted by the need to pursue the synthesis of such hybrid systems, a family of modified magnetic core-shell mesoporous silica nano-formulations was synthesized with encapsulated quercetin, a natural flavonoid with proven bioactivity. The new nanocarriers were produced via the sol-gel process, using tetraethoxysilane as a precursor and bearing a magnetic core of surface-modified monodispersed magnetite colloidal superparamagnetic nanoparticles, subsequently surface-modified with polyethylene glycol 3000 (PEG3k). The arising nano-formulations were evaluated for their textural and structural properties, exhibiting enhanced solubility and stability in physiological media, as evidenced by the loading capacity, entrapment efficiency results and in vitro release studies of their load. Guided by the increased bioavailability of quercetin in its encapsulated form, further evaluation of the biological activity of the magnetic as well as non-magnetic core-shell nanoparticles, pertaining to their anti-amyloid and antioxidant potential, revealed interference with the aggregation of β-amyloid peptide (Aβ) in Alzheimer's disease, reduction of Aβ cellular toxicity and minimization of Aβ-induced Reactive Oxygen Species (ROS) generation. The data indicate that the biological properties of released quercetin are maintained in the presence of the host nanocarriers. Collectively, the findings suggest that the emerging hybrid nano-formulations can function as efficient nanocarriers of hydrophobic natural flavonoids in the development of multifunctional nanomaterials toward therapeutic applications.

Three Dimensional Quercetin-Functionalized Patterned Scaffold: Development, Characterization, and In Vitro Assessment for Neural Tissue Engineering

Regeneration of injured neuronal areas is a big challenge owing to the complex structure and function of the nervous system along with the limited regeneration capacity of neural cells. Recent reports show that patterned and functionalized scaffolds could control neural cell directional growth. In this study, aligned nanofibers (ANFs) were fabricated using a versatile and cost-effective approach, electrospinning, and further processed to make a patterned hybrid scaffold (HANF). The patterned scaffold had circular rings of ANFs reinforced in a biocompatible gellan-gelatin hydrogel matrix to provide adequate mechanical strength and contact guidance for adhesion and growth of neural cells in vitro. Quercetin was loaded into the nanofibrous scaffold to provide a functional agent that supported regeneration of neural cells. The reinforced ANFs enhanced the mechanical strength of the scaffold and provided a cylindrical nerve conduit structure to support neuronal cell growth. The influence of scaffold topology on cell behavior was assessed in in vitro cell culture conditions that revealed that the functionalized patterned scaffolds favored directed neurite cell growth/extension with favored cell culture morphology and showed no cytotoxicity toward neural cells. The results ultimately indicated that the fabricated scaffold has potential for guiding nerve tissue growth and can be used as nerve regeneration scaffolds.

Could Flavonoids Compete with Synthetic Azoles in Diminishing Candida albicans Infections? A Comparative Review Based on In Vitro Studies

Flavonoids are polyphenolic compounds with already confirmed various health benefits. This review will shed light on flavonoids as potential antifungals in Candida albicans infections. C. albicans is an opportunistic pathogen able to cause serious health issues due to numerous virulence factors amplifying its pathogenicity. One of the most important virulence factors is Candida ability to form biofilms which are highly resistant to the treatment of antifungal drugs; making diminishing of this pathogen even more challenging. This review will focus on current knowledge on individual flavonoid compounds having the potential to deal with C. albicans in vitro, with special turn on antibiofilm potential and insight into the mode of action, where available. Majority of the commercial drugs for the treatment of candidiasis belong to azole class, so the activity of flavonoids will be compared with the activity of newly synthetized azole compounds, as well as with azole drugs that are already on the market as official therapeutics. This literature review will provide pros and cons for pushing future research towards exploring novel synthetic azoles or further examination of a wide pallet of natural flavonoids.

Phenolic composition and medicinal usage of Psidium guajava Linn.: Antifungal activity or inhibition of virulence?

Psidium guajava is a Myrtaceae plant whose medicinal properties are recognized in several locations. The use of teas and tinctures prepared from their leaves has been used to combat infections caused by fungi of the genus Candida. In this study, aqueous extracts of leaves and hydroethanolic were tested to verify the antifungal potential and its chemical composition has been investigated. The microbiological assays were performed by broth microdilution to determine the minimum inhibitory concentration (MIC) and from these the minimum fungicidal concentration was performed (MFC) by subculturing on solid media. A cell viability curve was obtained for demonstration of inhibition of fungal growth of strains of Candida albicans and Candida tropicalis. Tests to check morphological changes by the action of the extracts were performed in microcultive cameras depleted environment at concentrations of MIC/2, MIC and MIC × 2. Extracts analyzed by high performance liquid chromatography demonstrated flavonoids and phenolic acids. The extracts showed fungistatic effect and no fungicide with MIC >8192 μg/mL, MFC above 8192 μg/mL. The IC50 was calculated ranging from 1803.02 to 5623.41 μg/mL. It has been found that the extracts affect the morphological transition capability, preventing the formation of pseudohyphae and hyphae. Teas and tinctures, therefore, have the potential antifungal, by direct contact, causing inhibition of fungal multiplication and its virulence factor, the cell dimorphism, preventing tissue invasion. Further studies are needed to elucidate the biochemical pathways and genes assets involved in these processes.

Synthesis and characterization of polyhydroxybutyrate-co-hydroxyvalerate nanoparticles for encapsulation of quercetin

Polyhydroxybutyrate- co-hydroxyvalerate has been identified as a useful polymer for biomedical application due to its biocompatibility and processability. Polyhydroxybutyrate- co-hydroxyvalerate nanoparticles loaded with quercetin, an antimicrobial, anti-inflammatory, and antiviral polyphenol with limited solubility, were obtained using a high-speed double-emulsion technique. The nanoparticle size and the dissolution of quercetin were controlled simultaneously through high-speed stirring (15,000 r/min) in the emulsification process. The size range of quercetin-loaded polyhydroxybutyrate- co-hydroxyvalerate nanoparticles was between 250 and 650 nm. Spherical shape with no aggregation of nanoparticles was confirmed by electron microscopy. Loaded nanoparticles showed less thermal degradation than unloaded nanoparticles. An encapsulation efficiency of 51% was found. Most of the quercetin was released from the nanoparticles within the first 5 h of water immersion. A biocompatibility analysis of the nanoparticles showed no cytotoxicity and no significant difference between loaded and unloaded nanoparticles.

A controlled release system for quercetin from biodegradable poly(lactide-co-glycolide)–polycaprolactone nanofibers and its in vitro antitumor activity

Quercetin is a potent natural antioxidant but has limited therapeutic applications due to its short half-life in body fluids. In order to improve the efficacy of quercetin and overcome its shortcomings, quercetin-encapsulated electrospun poly(lactic-co-glycolic acid)–poly(ε-caprolactone) nanofibrous controlled release system was developed using electrospinning technique. Fourier transform infrared spectroscopy, thermogravimetric, and X-ray diffraction analysis suggested the incorporation, thermal stability, and existence of encapsulated quercetin in semicrystalline state in the nanofibers. The release profiles of quercetin from the poly(lactide-co-glycolide)–polycaprolactone nanofibers in phosphate-buffered saline showed controlled release of quercetin up to 120 h. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed an evident inhibition effect of quercetin-encapsulated nanofibers against human hepatocellular carcinoma (HepG2), and the inhibition rate of 29%, 72%, and 80.1% were recorded for 1%, 2%, and 4% quercetin-encapsulated nanofibers, respectively. The formulated drug delivery system could be potentially used as an implantable anticancer drug in clinical applications in the future.

Biomedical applications of ferulic acid encapsulated electrospun nanofibers

Ferulic acid is a ubiquitous phytochemical that holds enormous therapeutic potential but has not gained much consideration in biomedical sector due to its less bioavailability, poor aqueous solubility and physiochemical instability. In present investigation, the shortcomings associated with agro-waste derived ferulic acid were addressed by encapsulating it in electrospun nanofibrous matrix of poly (d,l-lactide-co-glycolide)/polyethylene oxide. Fluorescent microscopic analysis revealed that ferulic acid predominantly resides in the core of PLGA/PEO nanofibers. The average diameters of the PLGA/PEO and ferulic acid encapsulated PLGA/PEO nanofibers were recorded as 125 ± 65.5 nm and 150 ± 79.0 nm, respectively. The physiochemical properties of fabricated nanofibers are elucidated by IR, DSC and NMR studies. Free radical scavenging activity of fabricated nanofibers were estimated using di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) assay. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay confirmed the cytotoxicity of ferulic acid encapsulated nanofibers against hepatocellular carcinoma (HepG2) cells. These ferulic acid encapsulated nanofibers could be potentially explored for therapeutic usage in biomedical sector.

Antiproliferative activity of ferulic acid-encapsulated electrospun PLGA/PEO nanofibers against MCF-7 human breast carcinoma cells

Ferulic acid (FA) is a polyphenolic phytonutrient which possesses strong antiproliferative effect; however, it has limited therapeutic applications due to its physiochemical instability and low bioavailability at the tumor site. In present study, these shortcomings associated with FA were overcome by fabricating FA-encapsulated poly(d,l-lactide-co-glycolide)/polyethylene oxide (PLGA/PEO) blend nanofibers using electrospinning technique. FESEM and fluorescence microscopic analysis imitates the smooth morphology and even distribution of FA within the polymeric nanofibers at optimum 2 wt% concentration of FA. The average diameters were recorded to be 150 ± 47.4 and 200 ± 79 nm for PLGA/PEO and FA-encapsulated PLGA/PEO nanofibers, respectively. The encapsulation, compatibility, and physical state of FA within the nanofibers were further confirmed by FTIR, TGA and XRD analysis. In vitro drug delivery studies demonstrated initial burst liberation of FA within 24 h followed by a sustained release for the subsequent time. MTT assay revealed the effectiveness of FA-encapsulated nanofibers against human breast carcinoma cells (MCF-7) cells as compared to control. FESEM and fluorescence microscopic analysis further confirmed the apoptotic effect of FA-encapsulated PLGA/PEO nanofibers against MCF-7. These fabricated nanofibers hold enormous potential to be used as a therapeutic agent for various biomedical applications.

Quercetin sensitizes fluconazole-resistant candida albicans to induce apoptotic cell death by modulating quorum sensing

Quorum sensing (QS) regulates group behaviors of Candida albicans such as biofilm, hyphal growth, and virulence factors. The sesquiterpene alcohol farnesol, a QS molecule produced by C. albicans, is known to regulate the expression of virulence weapons of this fungus. Fluconazole (FCZ) is a broad-spectrum antifungal drug that is used for the treatment of C. albicans infections. While FCZ can be cytotoxic at high concentrations, our results show that at much lower concentrations, quercetin (QC), a dietary flavonoid isolated from an edible lichen (Usnea longissima), can be implemented as a sensitizing agent for FCZ-resistant C. albicans NBC099, enhancing the efficacy of FCZ. QC enhanced FCZ-mediated cell killing of NBC099 and also induced cell death. These experiments indicated that the combined application of both drugs was FCZ dose dependent rather than QC dose dependent. In addition, we found that QC strongly suppressed the production of virulence weapons-biofilm formation, hyphal development, phospholipase, proteinase, esterase, and hemolytic activity. Treatment with QC also increased FCZ-mediated cell death in NBC099 biofilms. Interestingly, we also found that QC enhances the anticandidal activity of FCZ by inducing apoptotic cell death. We have also established that this sensitization is reliant on the farnesol response generated by QC. Molecular docking studies also support this conclusion and suggest that QC can form hydrogen bonds with Gln969, Thr1105, Ser1108, Arg1109, Asn1110, and Gly1061 in the ATP binding pocket of adenylate cyclase. Thus, this QS-mediated combined sensitizer (QC)-anticandidal agent (FCZ) strategy may be a novel way to enhance the efficacy of FCZ-based therapy of C. albicans infections.

Polyurethane–extracellular matrix/silver bionanocomposites for urinary catheters

Polyurethane–extracellular matrix membranes with bionanocomposites or coatings containing a small amount of biocompatible polymers such as hydrolyzed collagen, elastin, hyaluronic acid or chondroitin sulfate, and silver were obtained by solvent casting or electrospinning/electrospraying of the polyurethane–extracellular matrix–Ag formulations onto pure polyurethane membrane in order to achieve improved antibacterial biomaterials for urinary catheters. Using Fourier transform infrared spectroscopy, the interaction of the incorporated silver nanoparticles with polyurethane–extracellular matrix was found, while X-ray photoelectron spectroscopy and X-ray diffraction analyses ws used to determine the presence of metallic Ag for polyurethane membrane and Ag only in oxidized state for polyurethane–extracellular matrix membranes due to the stabilizing effect of polymeric components. The in vitro antimicrobial tests against Escherichia coli, Salmonella typhymurium, and Listeria monocytogenes were used for the evaluation of the antimicrobial efficiency.

Curcumin-loaded poly(l-lactide-co-D,l-lactide) electrospun fibers: Preparation and antioxidant, anticoagulant, and antibacterial properties

Fibrous materials of poly(l-lactide- co-d,l-lactide), poly(l-lactide- co-d,l-lactide)/poly(ethylene glycol), and curcumin were prepared by electrospinning. The incorporation of poly(ethylene glycol) in the fibers caused a decrease in the mean fiber diameters down to 700 nm and in the water contact angle value, the latter being equal to 0 at poly(l-lactide- co-d,l-lactide)/poly(ethylene glycol) 60/40 weight ratio. The water contact angle values of poly(l-lactide- co-d,l-lactide)/curcumin fibrous materials considerably exceeded those of films of the same composition (approximately 120° as compared to approximately 95°, for electrospun mats and solution-cast films, respectively). Curcumin affected the thermal stability of the fibrous materials and the crystallinity degree of the polymers. The mechanical properties of the electrospun materials also depended on the composition of the polymer matrix and the amount of curcumin therein. In the curcumin-containing fibers, curcumin was found in the amorphous state, while higher antioxidant activity was exhibited by poly(l-lactide- co-d,l-lactide)/poly(ethylene glycol)/curcumin fibrous materials. In vitro determination of the activated partial thromboplastin time and prothrombin time showed that poly(l-lactide- co-d,l-lactide)/curcumin fibrous materials displayed anticoagulant activity. Antibacterial effect toward Staphylococcus aureus was manifested by the curcumin-containing mats.

Electrospun antibacterial nanofibrous polyvinylpyrrolidone/cetyltrimethylammonium bromide membranes for biomedical applications

Nanoscale structures with large surface area-to-volume ratios are used as biomaterial scaffolds for vascular grafts, wound dressings, and air purifying filters. Using electrospinning, nanofibers containing an antibacterial agent, cetyltrimethylammonium bromide, were prepared for wound healing application. Polyvinylpyrrolidone, known as a biocompatible additive in food and drug industries, has been used as fiber processing agent with the organic active ingredient, cetyltrimethylammonium bromide. A series of samples with different polyvinylpyrrolidone/ cetyltrimethylammonium bromide ratios were successfully prepared by this method. The morphology and electroactive characteristics of nanofibers were investigated using scanning electron microscopy, atomic force microscopy, and electrochemical impedance spectroscopy. Fiber diameters and charge transfer resistances were found to decrease with salt content, while the double-layer capacitance increased with no apparent effect on the specific capacitance providing favorable conditions for the fabrication of biomaterials. In addition, the quaternary ammonium compound (cetyltrimethylammonium bromide) with a minimum ratio of 2.5 wt% showed reduction in bacterial activity of Klebsiella pneumonia, Staphylococcus aureus, and Escherichia coli.

Polymeric prodrugs of ampicillin as antibacterial coatings

A novel ampicillin prodrug containing two carboxylic acid functionalities was synthesized by reacting ampicillin with acyl chloride in the presence of base. This prodrug was subsequently converted into a poly(anhydride-amide) via solution polymerization. The polymer, which chemically incorporates the ampicillin prodrug into the polymeric backbone, was developed as a film to prevent infections associated with medical devices by controlled, localized release of antimicrobials. The robust polymer coatings exhibiting strong adhesion to stainless steel were produced under elevated temperature and reduced pressure. The in vitro hydrolytic degradation of the polymer into the ampicillin prodrug was measured and the antibacterial activity of polymer-derived coatings was examined using a Gram-positive bacterium, Staphylococcus aureus. Furthermore, the polymer cytotoxicity was screened using fibroblasts. The ampicillin prodrug demonstrated antibacterial activity and the polymer demonstrated no cytotoxic effects on fibroblasts. Based on these results, the biodegradation of the antimicrobial-based poly(anhydride-amide) into the prodrug displays substantial promise as an implant or implant coating to reduce device failure resulting from bacterial infections.