Chitosan and N, N, N-trimethyl chitosan nanoparticle encapsulation of ocimum gratissimum essential oil: Optimised synthesis, in vitro release and bioactivity

Abstract

Background: The encapsulation of plant essential oils (EOs) with polymeric materials (e.g. chitosan (CS) and N, N, N-trimethyl chitosan (TMC)) and the further reduction of the polymers into their nano sizes are gaining research interest in nanotechnology due to potential applications in medical drug delivery systems as well as the food and pharmaceutical industry. The present study reports a novel approach for the synthesis of Ocimum gratissimum essential oil (OGEO)-loaded CS and TMC nanoparticles with distinct bioactive and physiochemical properties. Methods: The OGEO-loaded CS and TMC nanoparticles were characterised using various microscopic and spectroscopic techniques. The bioactive compounds in Ocimum gratissimum methanolic extract (OG-MeOH) and EOs was evinced with gas chromatography-mass spectrometry (GC-MS). Total phenolic content (TPC) of OGEO and OG-MeOH was determined using the Folin-Ciocalteu method. The in vitro drug release kinetic pattern was ascertained by membrane dialysis, while antioxidant activity was determined by the 2,2-diphenyl-1picrylhydrozyl (DPPH) free radical scavenging method. The disc diffusion method was used for antibacterial activity evaluation, while MTT and a trypan blue dye exclusion assay were used to assess cytotoxic activity on MDA-MB-231 breast cancer cells. Results: GC-MS analysis revealed components that have not been previously reported for Ocimum gratissimum. The maximum OGEO cumulative drug release percentage in vitro was observed at pH 3 for both OGEO-loaded chitosan nanoparticles (OGEO-CSNPs) and OGEOloaded N, N, N-trimethyl chitosan nanoparticles (OGEO-TMCNPs). The antioxidant activity of OGEO-CSNPs and OGEO-TMCNPs never reached a steady state after 75 h. OGEOTMCNPs exhibited antibacterial activity at a lower concentration for both Gram-negative and Gram-positive food pathogens. In vitro cytotoxicity revealed the increased toxicity of OGEO-TMCNPs on MDA-MB-231 breast cancer cell lines. Conclusion: OGEO-loaded CS and TMC nanoparticles were synthesised using a novel material optimisation approach. The synthesised nanoparticles have shown a promising application in the pharmaceutical and food industries.