Bioactivity of Nanohybrid: Comprising of Metallosalen Incorporated into Lacunary Polyoxometalate and Encapsulated with Chitosan Biopolymer

Abstract

Biocompatible polymer chitosan has note-worthy applications in biomedical science. Nanohybrids synthesized by using chitosan as an encapsulating unit for polyoxometalates (POMs) and study of its biomedical applications is a fast-emerging field. In this research work, a lacunary polyoxometalate (α-K8SiW11O39) has been synthesized and then alkylsilane has been inserted into its lacunary position. It has been then reacted with 2-hydroxy-1-naphtaldehyde followed by copper metalation and finally encapsulated into chitosan by using the ionotropic gelation technique, in which the chitosan and the POM served as cation and anion, respectively. The bands in UV-Vis spectra at characteristic wavelength indicate that the organosilane is successfully inserted into α-K8SiW11O39 and metalled with Cu. Then its encapsulation into chitosan to synthesize final nanohybrid has been confirmed by UV-Vis spectra. Further, chitosan, POM inserted with organosilane and nanohybrid have been characterized by FT-IR. EDX analysis reveals the presence of all the expected elements in their desired ratios. EDX study was further supported by Inductively Coupled Plasma (ICP) technique. Morphology of nanohybrid has been studied by Scanning Electron Microscope (SEM) imaging. The loading and entrapment efficiency of the prepared nanohybrid was exceptionally excellent and was calculated to be 81.2% and 59.1%, respectively. In vitro drug release study suggested sustainable and pH-modulated release behaviour of the nanohybrid. Further, it is the first time that an organosilane attached to lacunary POM, then metalated with Cu and finally encapsulated into CS has been investigated for drug delivery. The antibacterial activity of POM inserted with organosilane and nanohybrid have been tested against bacterial strains of B. subtilis gram (+)ve and E. coli gram (-)ve. The antibacterial activity of nanohybrid has been improved as compared to bare POM inserted with metallated organosilane and chitosan.