School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UNITED KINGDOM.
Sunlight-driven water disinfection system could help provide clean water to some of the world’s poorest regions where contaminated surface water is a major public health problem and bright solar irradiation is available for free. In this work, photosensitiser - 5, 10, 15, 20-tetrakis (1-methyl-4-pyridinio) porphyrin tetra p-toluene sulfonate (TMPyP) was chosen and immobilised onto chitosan nanofiber mats and chitosan membranes for photodynamic disinfection of water since preliminary studies with TMPyP in solution showed it caused a high rate of photodynamic inactivation (PDI) of model viral organisms (bacteriophages MS2 and Qβ, murine norovirus and bovine enterovirus 2). Native gel electrophoresis, SDS-PAGE and western blotting, TEM and DLS were used to analyse pre- and post-PDI samples of the model viruses. The rate of PDI in model viruses was in the order MS2 > phage Qβ > murine norovirus > bovine enterovirus 2. Our data showed that PDI caused aggregation of MS2 particles and crosslinking of MS2 coat protein. However, the aggregation and crosslinking did not correlate to the rate of PDI we observed in MS2. Using sequence specific antibodies raised against MS2 A-protein (host attachment protein), our results suggest that the rate of PDI is relative to loss of antigenicity of sites on the A-protein. The differences in the rate of PDI were compared to amino acid compositions and surface accessibility of host attachment proteins/sites of the model viruses. Possible modes of action are discussed as a means to gaining insight to the targets and mechanisms of PDI of viruses. Chitosan electrospun nanofibers and chitosan membranes were modified by pyromellitic dianhydride in order to introduce carboxyl groups and facilitate adsorption of the cationic TMPyP. The physico-chemical properties of these modified nanofibers and membranes were investigated by microscopy, absorption spectroscopy, Fourier-transform infrared spectroscopy and Midland surface blotting approaches. The chitosan nanofiber/membrane-TMPyP composite showed photodynamic inactivation of MS2 and E. coli BL21.