pH and Redox Dual Responsive Nanoparticle for Nuclear Targeted Drug Delivery

To mimic the clinic dosing pattern, initially administering high loading dose and then low maintenance dose, we designed a novel poly­(2-(pyridin-2-yldisulfanyl)­ethyl acrylate) (PDS) based nanoparticle delivery system. Side chain functional PDS was synthesized by free radical polymerization. Polyethylene glycol and cyclo­(Arg-Gly-Asp-d-Phe-Cys) (cRGD) peptide was conjugated to PDS through thiol–disulfide exchange reaction to achieve RPDSG polymer. RPDSG/DOX, RPDSG nanoparticle loaded with doxorubicin, was fabricated by cosolvent dialysis method. The size of the nanoparticles was 50.13 ± 0.5 nm in PBS. The RPDSG/DOX nanoparticle is stable in physiological condition while quickly releasing doxorubicin with the trigger of acidic pH and redox potential. Furthermore, it shows a two-phase release kinetics, providing both loading dose and maintenance dose for cancer therapy. The conjugation of RGD peptide enhanced the cellular uptake and nuclear localization of the RPDSG/DOX nanoparticles. RPDSG/DOX exhibits IC₅₀ close to that of free doxorubicin for HCT-116 colon cancer cells. Due to the synergetic effect of RGD targeting effect and its two-phase release kinetics, RPDSG/DOX nanoparticles display significantly higher anticancer efficacy than that of free DOX at concentrations higher than 5 μM. These results suggest that RPDSG/DOX could be a promising nanotherapeutic for tumor-targeted chemotherapy

Asialoglycoprotein Receptor-Mediated Gene Delivery to Hepatocytes Using Galactosylated Polymers

Highly efficient, specific, and nontoxic gene delivery vector is required for gene therapy to the liver. Hepatocytes exclusively express asialoglycoprotein receptor (ASGPR), which can recognize and bind to galactose or N-acetylgalactosamine. Galactosylated polymers are therefore explored for targeted gene delivery to the liver. A library of safe and stable galactose-based glycopolymers that can specifically deliver genes to hepatocytes were synthesized having different architectures, compositions, and molecular weights via the reversible addition–fragmentation chain transfer process. The physical and chemical properties of these polymers have a great impact on gene delivery efficacy into hepatocytes, as such block copolymers are found to form more stable complexes with plasmid and have high gene delivery efficiency into ASGPR expressing hepatocytes. Transfection efficiency and uptake of polyplexes with these polymers decreased significantly by preincubation of hepatocytes with free asialofetuin or by adding free asialofetuin together with polyplexes into hepatocytes. The results confirmed that polyplexes with these polymers were taken up specifically by hepatocytes via ASGPR-mediated endocytosis. The results from transfection efficiency and uptake of these polymers in cells without ASGPR, such as SK Hep1 and HeLa cells, further support this mechanism. Since in vitro cytotoxicity assays prove these glycopolymers to be nontoxic, they may be useful for delivery of clinically important genes specifically to the liver