The Photodynamic Antifungal Activity of Immobilized Xanthene and Thiazine Dyes on Electrospun Nano Nylon 6, 6

Aspergillus niger, Aspergillus fumigatus, Trichoderma viride, Penicillium funiculosum, and Chaetomium globosum are the most common indoor fungal species which are opportunistic human pathogens resulting in aspergillosis and pneumocytosis in immunosuppressed patients and allergy, rhinitis in healthy humans. Magnaporthe grisea and Phytophthora cinnamomi (Oomycetes) are plant pathogens inducing, respectively, rice blast resulting in serious crop loss globally and root rot and canker on Eucalyptus. This study analyzed the antifungal effect of photosensitizers, such as rose bengal (RB), phloxine B (PB), azure A (AA), and toluidine Blue O (TBO), which are grafted on fabrics consisting of nanofibers (nano fabrics) or microfibers (micro fabrics). In order to increase graft yield of photosensitizer onto fabrics, poly(acrylic acid-co-styrene sulfonic acid-co-vinyl benzyl RB or PB) and AA or TBO-grafted-poly(acrylic acid) were polymerized and then grafted to electrospun nano and micro fabrics. Additionally, photobleaching rates and aggregation concentrations of solutions and the relative concentrations of grafted fabrics were compared. Three types of antifungal tests were conducted, broth microdilution of aqueous solutions, inhibition zone, and quantitative antifungal assay of micro and nano fabrics grafted with photosensitizers. Broth microdilution showed RB displayed the lowest minimum inhibition concentration (MIC) at 15.6 microM on P. cinnamoni and 31.25 microM on T. viride. M. grisea showed the highest resistance resulting in MIC at 125 microM for RB, and at 250 microM for PB, AA, and TBO. The inhibition zone test showed the nano fiber grafted with RB and PB displayed no growth on the fabrics, but micro fabrics grafted with AA and TBO had little effectiveness at all concentrations on all 7 types of pathogens. These two methods were limited due to visual observation and low diffusivity of photosensitizers. Thus, the third method was quantitatively analyzed according to time, showing inhibition rate and taking into consideration other factors such as photobleaching. In the results, increased irradiation time and higher concentrations such as nano fabrics grafted with RB resulted in up to a 92% reduction in growth with a high inhibition rate. RB has the largest inhibition rate (ks) on P. cinnamomi and T. viride of up to 3.70 x 10-2 and 3.51 x10-2 l micromol-1 min-1 while on M. grisea with the lowest inhibition rate of 1.42 x10-2 l micromol-1 min-1. The antifungal activity exhibited depended on the quantum yield, lipophilicity, charge, and aggregated concentrations of photosensitizers. Furthermore activity is related to fungal morphologies and lipid composition of the cell membranes. P. cinnamomi has a high amount of arachidonic acid and eicosapentaenoic acid, which are good targets for photooxidation by singlet oxygen, while filamentous ascomycota fungi have ergosterol instead. M. grisea has the largest spore size with diameters of 3.87 microm with multi cells separated by two septa inside conidia and exhibits the highest resistance to singlet oxygen due to inactivation by a multi-hit process with singlet oxygen. Finally, I conclude that the results showed the increasing inhibition percentage in the order of AA < TBO