Exploring the Biofilm Inhibition Potential of a Novel Phytic Acid-Crosslinked Chitosan Nanoparticle: In Vitro and In Vivo Investigations.

The primary factor underlying the virulence of Candida albicans is its capacity to form biofilms, which in turn leads to recurrent complications. Over-the-counter antifungal treatments have proven ineffective in eliminating fungal biofilms and the inflammatory cytokines produced during fungal infections. Chitosan nanoparticles offer broad and versatile therapeutic potential as both antifungal agents and carriers for antifungal drugs to combat biofilm-associated Candida infections. In our study, we endeavoured to develop chitosan nanoparticles utilising chitosan and the antifungal crosslinker phytic acid targeting C. albicans. Phytic acid, known for its potent antifungal and anti-inflammatory properties, efficiently crosslinks with chitosan. The nanoparticles were synthesised using the ionic gelation technique and subjected to analyses including Fourier transform infrared spectroscopy, dynamic light scattering, and zeta potential analysis. The synthesised nanoparticles exhibited dimensions with a diameter (Dh) of 103 ± 3.9 nm, polydispersity index (PDI) of 0.33, and zeta potential (ZP) of 37 ± 2.5 mV. These nanoparticles demonstrated an antifungal effect with a minimum inhibitory concentration (MIC) of 140 ± 2.2 µg/mL, maintaining cell viability at approximately 90% of the MIC value and reducing cytokine levels. Additionally, the nanoparticles reduced ergosterol content and exhibited a 62% ± 1.2 reduction in biofilm susceptibility, as supported by colony-forming unit (CFU) and XTT assays-furthermore, treatment with nanoparticles reduced exopolysaccharide production and decreased secretion of aspartyl protease by C. albicans. Our findings suggest that the synthesised nanoparticles effectively combat Candida albicans infections. In vivo studies conducted on a mouse model of vaginal candidiasis confirmed the efficacy of the nanoparticles in combating fungal infections in vivo.

Melianone inhibits Secreted Aspartic Proteases (SAP), a Virulence Factor During Hyphal Formation in Candida albicans.

BACKGROUND & OBJECTIVE: Candida albicans (C.-P. Robin) Berkhout, the pathogenic yeasts' ability to transform from yeast to hyphal forms in the bloodstream is essential during systemic infections. Among the several virulence factors studied, secreted aspartic proteinases (SAPs) involved in hyphal penetration are targets of putative hyphal inhibitors. Upregulation of SAP6 gene, (two-to 31- fold high) during budded to hyphal transition and lack of studies on its inhibition, prompted us to investigate this particular protein using in silico tools. RESULTS: Hyphal inhibition of germinating yeast cells by melianone, a triterpenoid, from Swietenia mahagoni (L.) Jacq. (Meliaceae) was observed at 0.1 µM (IC50). One of the targets of putative hyphal inhibitors, SAP, was assayed and for the first time, 50 % of the biological SAP activity was found to be inhibited by melianone at 0.125 µM. This data on SAP inhibition led us to analyse the 3-dimensional structure for SAP6 protein that was constructed through a combination of homology modelling and ab-initio method (Phyre2) and validated before performing Induced Fit Docking (IFD). Melianone formed H-bond and hydrophobic interactions with the crucial residues (ASP108, TYR160, ALA161, ASP162, ASP294, THR297, ASP379) in the catalytic site of SAP6 with a glide energy (-)54.9327 kcal/mol upon Induced Fit Docking (IFD). CONCLUSION: We report here for the first time on the SAP inhibitory ability of melianone at 0.125 uM. Being a small molecular mass inhibitor, binding with high affinity to the S3 pocket sites of SAP proteins provides evidence for pre-clinical testing of such compounds against fungal pathogens. The study is a valuable insight for further research on novel and effective inhibitors targeting SAP.

Functionality of the human antibody response to Candida albicans.

Candida albicans is a common commensal on human mucosal surfaces, but can become pathogenic, e.g. if the host is immunocompromised. While neutrophils, macrophages and T cells are regarded as major players in the defense against pathogenic C. albicans, the role of B cells and the protective function of their antibodies are less well characterized. In this study, we show that human serum antibodies are able to enhance the association of human THP-1 monocyte-like cells with C. albicans cells. Human serum antibodies are also capable of inhibiting the adherence and damage dealt to epithelial cells. Furthermore, human serum antibodies impair C. albicans invasion of human oral epithelial cells by blocking induced endocytosis and consequently host cell damage. While aspartic proteases secreted by C. albicans are able to cleave human IgG, this process does not appear to affect the protective function of human antibodies. Thus, humans are equipped with a robust antibody response to C. albicans, which can enhance antifungal activities and prevent fungal-mediated epithelial damage.