Chitosan-coated magnetite nanoparticles loaded with polar extracts of Osbeckia octandra leaf

Abstract

Targeted drug delivery improves drug bioavailability and safety, particularly in cancer chemotherapy. When drug-loaded magnetite nanoparticles (MNPs) are employed, the rate of drug release can be controlled by an external magnetic field. The present study aims to synthesize chitosan-coated magnetite nanoparticles (CMNPs) loaded with leaf extracts of Osbeckia octandra; chitosan, a linear copolymer polysaccharide derived from chitin, confers biocompatibility to magnetic nanoparticles. The plant O. octandra, which is endemic to Sri Lanka, is known for its anticancer, antidiabetic, and hepato-protective properties. The dry leaf powder of O. octandra was extracted sequentially with hexane, dichloromethane, methanol, and water using Soxhlet extraction. The antioxidant capacity of the sequential extracts was determined using 2,2- diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays; antioxidants prevent free radical damage associated with cancer development. To evaluate the toxicity of the extracts toward healthy cells, the extracts were subjected to in vitro cell viability studies on Vero 76 cells. The polar extracts (methanol and water) displayed the highest antioxidant capacity comparable to that of ascorbic acid and the highest cell viability (100%) on Vero 76 cells. Accordingly, the methanol and water extracts were treated with CMNPs to obtain the corresponding extract-loaded nanoparticles, MCMNPs and WCMNPs, respectively; MNPs were prepared by the co-precipitation method and CMNPs by surface coating of MNPs with chitosan. The presence of magnetite in each type of magnetic nanoparticles was confirmed by powder X-ray diffractometry and Fourier transforms infrared (FTIR) spectroscopy. Scanning electron microscopy revealed the average particle size of MNPs, CMNPs, MCMNPs, and WMNCPs as 34.19±9.34, 32.67±7.21, 42.89±8.73, and 41.49±8.21 nm, respectively. The incorporation of chitosan into CMNPs was indicated by FTIR, and thermogravimetric analysis (TGA) revealed that 20.4% of the MNP was coated with chitosan. Methanol and water extracts were loaded onto CMNPs with encapsulation efficiencies of 81% and 70%, respectively.