Synthesis, characterization and functionalization of chitosan and gelatin type B nanoparticles to develop novel highly biocompatible cell-penetrating agents

Nowadays, nanoparticles (NPs) are used to make safe and more effective biomedical technologies for applications in highly targeted therapeutics and drug-delivery vehicles. This helps avoid low cellular penetration and accumulation of the drug in endosomal intracellular compartments that are not of interest for a particular therapy. A way to enhance the therapeutic efficiency is through nanoparticle loading systems, for which the aim of this study is to develop both low molecular (LMW) and high molecular weight (HMW) chitosan, as well as type B gelatin NPs. To enhance cell-penetration, the NPs were interfaced with the translocating peptide Buforin II. The obtained nanobioconjugates were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), confocal microscopy and transmission electron microscopy (TEM). Their size and surface zeta potential were estimated via DLS (Zetasizer Nano). Furthermore, to visualize their endosomal escape, the NPs were marked with the fluorophore Rhodamine B and imaged with the aid of the confocal microscope. The FTIR results showed bands corresponding to the polymers and to Buforin II after conjugation. The average NPs diameters were of about 250nm. The zeta potential of the chitosan NPs approached neutrality, which may be problematic due to low colloidal stability, while gelatin zeta potential of -7mV was closer to the value required for colloidal stability, i.e., ±10 mV. SEM microscopy of LMW and HMW chitosan NPs showed a round-shape and oval morphology, respectively, while the gelatin NPs had a filamentous morphology. SEM also shows agglomerates of the NPs. TEM microscopy results confirmed the LMW chitosan NPs morphology and showed that their nominal size was 5-10 nm.