Introduction: Pullulan, a water-soluble natural polysaccharide, has attracted considerable attentions in biomedical applications because of its high biocompatibility, biodegradability, non-immunogenicity, and excellent blood compatibility. It has been reported that pullulan shows a specific affinity to hepatocytes through the asialoglycoprotein receptor (ASGP-R)[1]. Therefore, nanoparticles derived from pullulan provide a valuable pathway in delivering anti-cancer drugs to liver tumors due to the specific uptake by hepatocytes[2]. In this work, pH- and redox-responsive pullulan nanoparticles with selective cellular uptake by hepatoma cells were developed. These nanoparticles with pullulan surface could not only significantly improve the stability and achieve active hepatoma targeting, but also control the drug release inside hepatoma cells. They are promising to enhance the therapeutic efficacy of the drugs, and to depress the probability of drug resistance in cancer cells.
Materials and Methods: Anti-cancer drug doxorubicin (DOX) was chemically coupled to pullulan (MW 0.2 MDa) through acid-breakable hydrazone bond or physically encapsulated in reduction-responsible pullulan-cholesterol conjugates to prepared the nanoparticles.
Pyrrolidinedithiocarbamate (PDTC) was encapsulated into the nanoparticles through the hydrophobic interaction between DOX and PDTC. The influence of molecular structure on the characteristics and drug loading properties of the nanoparticles were investigated. The cytotoxicity and anti-cancer effect of the nanoparticles were investigated in vitro and in vivo in cell culture and animal experiments.
Results and Discussion: These pullulan nanoparticles were around 100 nm in diameter. Their characteristics depended much on the substitute degree of hydroazone or disulphide bonds. Benefited by the hydrophobic interaction and π−π stacking of aromatic structure in DOX, stable core-shell structured nanoparticles with high drug loading content more than 50 wt/wt % could be achieved. Drugs released from the nanoparticles in pH- or redox-sensitive manner. DOX-encapsulated nanoparticles effectively inhibited the growth of HepG2 cells in vitro. In animal model, the nanoparticles showed much stronger accumulation in HepG2 tumors than DOX∙HCl, and reduced distribution in other main organs.
The antitumor effect of the nanoparticles was significantly better than that of DOX∙HCl.
Co-delivery of DOX and PDTC increased the cellular uptake and therapeutic effect of nanoparticles on DOX-resistant HepG2/ADR cells.
Conclusions: Pullulan nanoparticles encapsulated with DOX improved the bioavailability of the drugs through the accumulation in hepatoma, and greatly decreased organ damage due to cancer cell wild growth and metastasis, and depressed the toxicity of DOX on the heart and other organs. The synergistical co-delivery of DOX/PDTC is more effective than single-drug delivery both in vitro and in vivo, especially on drug-resistant heptoma.
This study was supported by Natural Science Foundation of China (Grant No. 21174090, 51573113).
References:
[1] H Li, et al.; "Reduction breakable cholesteryl pullulan nanoparticles for targeted hepatocellular carcinoma chemotherapy". J Mater Chem B, 2014, 2, 3500
[2] H Li, et al.; "Efficient delivery of DOXto nuclei of hepatic carcinoma cells in subcutaneous tumor model using pH-sensitive pullulan-DOX conjugates". ACS App Mater & Int, 2015, 7, 15855