“Drug-free” oligochitosan nanoparticles and their fatty acid derivatives as inhalable cancer therapeutics

Lung cancer has the highest mortality incidence about 1.8 million deaths in 2020. Use of chemotherapeutics inhibits the growth of proliferative cancer cells but causes severe adverse systemic effects. Oligochitosan has been shown to exert anti-proliferative activities in several cancers in vitro and in vivo. Fatty acids, on the other hand, could be a cancer promoter or inhibitor as a function of its physicochemical attributes. Both chitosan/oligochitosan and fatty acid are pharmaceutical excipients which receive a widespread application in the pharmaceutical sector as binder, mucoadhesive, permeation enhancer and/or controlled-release agent. The conjugation of oligochitosan with fatty acids and their translation into nanoparticles is envisaged to promote the delivery aspects of a nanoparticulate system for cancer treatment such as binding to cancer cells and increased membrane permeability for transcellular transport of nanoparticles into the cancer cells. Their anti-cancer potential however can be dubious. This study aimed to investigate oligochitosan and oligochitosan-fatty acid conjugates in the form of nanoparticles as a potential anti-non-small cell lung cancer nanotherapeutic from the perspectives of pulmonary delivery and bioactivity. The conjugates of oligochitosan-fatty acid were synthesised by carbodiimide reaction with the conjugation status being evaluated by FTIR and 1HNMR spectroscopy techniques. They were developed into nanoparticles by means of nanospray drying method. Their size, zeta potential, morphology, crystallinity and contact angle were characterized. When required, oligochitosan-polyethylene glycol (PEG) conjugate nanoparticles were produced as a control sample. The nanoparticles were subjected to two studies: (1) soft agglomeration of nanoparticles with chitosan microparticles for pulmonary aerosolization and inhalation; (2) cancer cytotoxicity, cellular internalization, cancer cells-nanoparticles interaction, endocytic pathway, cancer molecular biology and in vivo pharmacodynamics performance assessment. The oligochitosan nanoparticles and their fatty acid conjugate nanoparticles were deliverable into the lung in the form of soft agglomerates with low molecular weight chitosan microparticles (size = 1.18 ± 0.01 urn, span = 1.48 ± 0.10, aspect ratio = 1.00 ± 0.14, surface roughness = 57.12 ± 10.77 nm, crystallinity = 7.40 ± 0.26 %) as the nanoparticle carrier that admixed the nanoparticles by gentle blending. The inhaled fine particle fraction of the nanoparticles was promoted by their hydrophobicity, surface roughness, off-spherical shape and amorphous particulate structure. The oligochitosan nanoparticles were an effective anti-cancer therapeutic in vitro and in vivo. Conjugation of fatty acid/PEGonto oligochitosan generally reduced its cancer cytotoxicity. The oligochitosan linoleate conjugate nanoparticles and oligochitosan linoleneate conjugate nanoparticles however expressed tumour suppressor potential and increased immune activity that could benefit cancer control. Oligochitosan nanoparticles induced cell death through inhibiting cell growth via cell cycle arrest at the Go/Gi phase, intrinsic and extrinsic apoptosis, mitigating metastasis tendency and sustaining immune responses. The anti-cancer effects of oligochitosan nanoparticles were mediated via the suppression of MAPK/ERK and Akt/mTOR/4E-BPl signalling pathways. The oligochitosan nanoparticles were taken up predominatly by lung cancer cells via caveolae- and lipid-raft mediated endocytic pathways following their interaction with the domains of the plasma membrane of the cancer cells. The oligochitosan nanoparticles were able to reduce the tumour burden, repair damaged lung tissues and restored deteriorated liver function in rats. They are potentially a therapeutic agent for lung cancer.