This project involved the synthesis of N-hexanoyl chitosan or simply modified chitosan (MC) stabilized iron oxide nanoparticles (MC-IOPs) and the biological evaluation of MC-IOPs. IOPs containing MC were prepared using conventional methods, and the extent of cell uptake was evaluated using mouse macrophages cell line (RAW cells). MC-IOPs were found to rapidly associate with the RAW cells, and saturation was typically reached within the 24 h of incubation at 37°C. Nearly 8.53 ± 0.31 pg iron/cell were bound or internalized at saturation. From these results, we conclude that MC-IOPs effectively deliver into RAW cells in vitro and we also hope MC-IOPs can be used for MRI enhancing agents in biomedical fields.

The clinical application of natural and synthetic amphipathic peptides (e.g., melittin) for cancer therapy is hindered by their notorious side effect, lysing red blood cells. To safely deliver a therapeutic peptide to the tumor tissue and kill cancer cells, we developed an environment-sensitive peptide delivery system, dual secured nano-sting (DSNS), through the combination of a zwitterionic glycol chitosan and disulfide bonds. Melittin loaded DSNS could kill almost 100% of MCF-7, HCT-116, SKOV-3, and NCI/ADR-RES (multidrug resistant) cancer cells at the concentration of 5 μM, while not showing any hemolytic effect.

The growth of hydroxyapatite (HA) on self-assembled collagen gold nanoparticles is presented for the first time by employing wet chemistry at ambient conditions, and we obtained near-quantitative yields of composite. Transmission electron microscopy reveals that the gold nanoparticles are well dispersed with an average diameter of 4 nm, which was further supported by the strong surface plasmon band (SPB) at 527 nm in the UV-vis spectra. The band broadening, shifting and flattening after the addition of HA precursors suggests the formation of HA aggregates. FT-IR spectroscopy confirms that the characteristic functionalities of collagen are intact even after the conjugation with gold nanoparticles, which renders the formation of randomly aggregated quarter-moon-like HA. Microscopic and crystallographic study at this stage further confirms its crystallographic structure that the HA particles aligned with their crystallographic c-axes preferentially parallel to the orientation of collagen on the gold nanoparticles with an elemental composition resembling that of natural HA. The result showed that gold nanoparticles with collagen form an efficient matrix for the growth of HA and the mineralized collagen can be potentially applied in bone tissue repair and regeneration.

It has been challenging to modify primary cells with non-viral gene delivery. Herein, we developed a ternary nano-formulation for gene delivery to umbilical cord blood and bone marrow derived mesenchymal stem cells (MSC) by using lipid-modified small (1.2 kDa) molecular weight polyethylenimine (PEI1.2). Linoleic acid (LA) was end-capped with carboxyl functionality by coupling with mercaptopropionic acid through thio-ester linkage, and then grafted onto PEI1.2 via N-acylation. The thio-ester LA grafted PEI1.2 (PEI-tLA) displayed a significantly lower (up to 6-fold) DNA binding capability and a higher propensity to dissociate upon polyanionic challenge. The dissociation ability of the complexes was further enhanced by incorporating hyaluronic acid (HA) into plasmid DNA (pDNA) complexes of PEI-tLA. The HA incorporation influenced the surface charge of complexes more so than the hydrodynamic size, but it clearly increased the propensity for dissociation upon a polyanionic challenge. The PEI-tLAs were less toxic on MSC and displayed significantly higher transgene expression in MSC than conventional PEI-LA. Ternary complexes of with HA (pDNA/HA = 2, w/w) further enhanced the efficiency of PEI-tLAs of low (∼2 lipid/PEI) lipid substitution, which was comparable to or higher than commercial transfection reagents. We conclude that PEI-tLA of low lipid substitution can be employed as a gene carrier to design supersensitive nano-formulations.