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Porous microspheres have enormous specific surface area due to the presence of micropores. This makes them suitable for all applications that involves surface adsorption e.g. chromatographic separation of biomolecules, catalytic reactions and drug delivery. The surface property may further be tuned up by functionalization of microsphere surface with different nanoparticles like silver nanoparticle and carbon dot (CD). In this study porous chitosan microsphere (PCM) was synthesized by 'phase inversion of emulsion' technique. Silver nanoparticle (AgNP) was synthesized, insitu during the process of surface modification, using silver nitrate solution. CD was synthesized by solvothermal method using urea and EDTA. PCM, AgNP and CD were of ∼9 μm, ∼27 nm and ∼14 nm diameter, respectively. From FTIR study it was confirmed that the amino group of chitosan backbone was responsible for reduction of Ag + ion to Ag°species which were clustered as AgNP and attached to the surface of PCM. The same amino group of chitosan molecule was also responsible for conjugation of CD to the microparticle surface. The optimized AgNP functionalized PCM had 5.36×10 11 AgNP per mg dried mass. The release of AgNP was triggered at pH4.5. The CD functionalized PCM had 56.82±2.8 % conjugation efficiency and 7.83±1.7 % quantum yield with respect to quinine sulphate.

Introduction: Gastroretentive Drug Delivery System like floating tablets out performs traditional dosing forms. When compared to conventional tablets, floating tablets have higher bioavailability, higher drug concentration in the systemic circulation, and lower frequency of dose. Metronidazole floating tablets were formulated using a variety of polymer combinations by the direct compression process. Polyvinyl pyrrolidone (PVP K132), Guar gum, and Xanthum gum are the polymers employed in the composition. Materials and Methods: The drug-excipient compatibility was determined by FTIR Spectroscopy and a total of nine formulations of floating tablets have been prepared. Among these, an appropriate formulation was chosen. The angle of repose, Bulk, and tapped density of metronidazole tablet mixes were previously evaluated. Carr's index, Hauser's ratio, physical appearance, hardness, weight fluctuation, friability, floating qualities, and in-vitro dissolving testing were used to characterize the tablets. Results: The flow properties were found optimum in all the pre-compression parameters and hence suitable for the direct compression method. The evaluation of tablets showed a good floating effect of about 4-7 hr in almost all the formulations. The floating tablets showed drug release of more than 92% after 6 hr and hence gastric retention was achieved. The study findings revealed that formulation 13 was the best, with a floating lag time of less than a minute and more than 7 hr of retention in the gastric pH with optimum floating behavior and drug release in the stomach. Conclusion: Hence, the prepared floating system involving a combination of polymers was found to be a reliable tool for gastric retention.

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