NANOSTRUCTURE MEDIATED ENHANCEMENT OF ANTIBACTERIAL POTENTIAL OF SELECTED ANTIBIOTICS

Abstract

This PhD dissertation focusses on antibiotics coated silver and gold nanoparticles (NPs), analysis of their photo-physical and enhanced antibacterial properties. The drug resistant bacteria are increasing day by day due to irrational use of antibiotics. Bacterial resistance towards the existing antibiotics is a global health issue and these drugs are at high risks in this regard. To overcome this problem new methodologies and measurements are dreadfully needed. In this context, the present study was designed to modify some selected antibacterial drugs through nanochemical approach to enhance their antibacterial potential. The beta-lactam antibiotics are most commonly used for the treatment of bacterial infections. Silver and gold NPs stabilized with these antibiotics were successfully synthesized though chemical reduction method. The NPs were characterized with Ultra-Violet visible spectrophotometry, Fourier transform infra-red spectroscopy (FTIR) and atomic force microscopy (AFM). The analysis confirmed the formation of poly-dispersed NPs of size less than 100 nm. The NPs were found stable at high temperature (up to 100oC), at various pH range and in different salt concentrations. The antibacterial potential of conjugated antibiotics were compared with pure antibiotics and unconjugated gold and silver NPs using AFM and conventional techniques such as the agar well diffusion method. Analysis of bacterial cells surface topography was recorded under AFM before and after treating with the antibiotics conjugated with Ag and Au NPs, free antibiotics and bare Ag and Au NPs. Conjugation to AgNPs enhanced the antibacterial activity of Ceftriaxone by 2 times, and conjugation to AuNPs by 6 times. The antibacterial potential of Cefadroxil was enhanced up to 2 and 3 times on conjugation with AgNPs and AuNPs, respectively. Similarly, the antibacterial potential of Cephradine was enhanced up to about 2 times on conjugation with AgNPs and conjugation to AuNPs by about 6 times. It was found that Ampicillin conjugated to Ag and Au NPs are about 5 and 10 times more active than pure Abstract xi Ampicillin, respectively. Similarly, Cefixime conjugated to Ag and Au NPs are about 3 and 8 times more active than pure Cefixime, respectively. The study also explored the improved kinetics of the antibiotics as the drugs coated with the NPs destroyed bacteria more timely than the free drugs. The antibiotics were also encapsulated with polymers to create nanoscale materials. Ceftriaxone and Cefixime were successfully encapsulated with polyethylene glycol (PEG). The polymeric nanosized Ceftriaxone and Cefixime were found more active than their respective free drugs.