L-Threonine-modified chitosan nanoparticles as efficient gene carriers with enhanced pDNA binding and low cytotoxicity

Aims This study aimed to develop L-threonine-modified chitosan (Chi-LT) nanoparticles as a biocompatible non-viral gene delivery platform with improved solubility, enhanced plasmid DNA (pDNA) binding, and efficient transfection performance.Materials & methods Chitosan was conjugated with L-threonine via carbodiimide-mediated coupling and characterized by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC). Chi-LT nanoparticles were prepared by ionotropic gelation with sodium tripolyphosphate (TPP). Their physicochemical properties, morphology, mucin interaction, pDNA complexation, cytotoxicity in HEK293T cells, and transfection efficiency using pEGFP-N1 plasmid were evaluated.Results L-threonine modification improved chitosan solubility at physiological pH and supported nanoparticle formation. The selected n1Chi-LT formulation showed a particle size of 102.35 ± 8.98 nm, polydispersity index of 0.16 ± 0.05, and zeta potential of 28.55 ± 0.64 mV. Complete pDNA retardation was achieved at a nanoparticle:pDNA weight ratio of 2:1. n1Chi-LT showed no cytotoxicity in HEK293T cells and reached 66.5 ± 10.61% transfection efficiency at a 10:1 ratio.Conclusions L-threonine modification improved the physicochemical and biological performance of chitosan, supporting Chi-LT nanoparticles as promising non-viral gene carriers.