Potentially Active Fluorescent Drug Polymer Nanoconjugate for Antibacterial Drug Delivery

Synthesis of sulphanilamide-based organic nanoaggregates and their interactions with PEG-6000 were studied using absorption and emission spectroscopy. Size and morphology of sulphanilamide-based organic nanoaggregates and PEG-coated sulphanilamide organic nanoaggregates were determined using dynamic light scattering, scanning electron microscopy and transmission electron microscopy techniques. Dynamic light scattering studies suggested the formation of around 100 nm sized sulphanilamide organic nanoaggregates and 197 nm sized PEG-conjugated sulphanilamide organic nanoaggregates. The effect of pH on hydrolysis of nanoaggregates has shown maximum instability at pH 9, which was stabilized by conjugation of nanoaggregates with PEG. Further interaction studies of PEG-coated nanoaggregates were carried out in aqueous solutions of major electrolytes and organic acids present in biofluids. Results demonstrated that Mg+2 had maximum interactions with PEG-coated sulphanilamide organic nanoaggregates in aqueous solutions of chlorides and sulphates; whereas Na+ showed maximum interactions in aqueous solutions of carbonates and bicarbonates. Similarly, among organic aqueous acid solutions, L-ascorbic acid showed greater interactions than nicotinic acid with PEG-conjugated sulphanilamide organic nanoaggregates. Antibacterial activities of sulphanilamide, sulphanilamide organic nanoaggregates and PEG-coated sulphanilamide organic nanoconjugates were evaluated against four strains of Gram-positive and Gram-negative bacteria. Minimum inhibitory concentration profile suggested that sulphanilamide PEG nanoconjugates showed highest antibacterial activity against Staphylococcus aureus after 72 h of treatment. Scanning electron microscopy studies performed before and after the treatment of sulphanilamide PEG nanoconjugates, indicated accumulation of cytoplasm of bacterial cell and formation blebs, which ultimately led to cell death. Sulphanilamide PEG nanoconjugate demonstrated greater antibacterial activity compared to that of sulphanilamide.