Glucose cryoprotectant affects glutathione-responsive antitumor drug release from polysaccharide nanoparticles

The aim of this work was to prepare polysaccharide-based nanoparticles (NPs) sensitive to glutathione (GSH), and to elucidate the effect of the concentration of glucose used as cryoprotectant during freeze-drying on the GSH-responsiveness. NPs were obtained via ionic interaction between negatively charged polysaccharides, chondroitin sulfate and dermatan sulfate, and the positively charged thiolated chitosan (CSSH), and crosslinking of CSSH before or after the nanoparticles formation with a disulfide-bond containing crosslinker, N,N'-bis(acryloyl)cystamine (BAC). NPs were freeze-dried with glucose at two different concentrations (0.5 and 5.0%w/w) and then characterized as methotrexate delivery systems, studying the effect of GSH concentration on drug release, efficacy against tumor cells and cellular internalization. Non-loaded NPs were highly compatible with murine fibroblasts and showed a suitable size for being used in anticancer therapy. When methotrexate-loaded NPs were freeze-dried with the highest glucose concentration, they lost their responsiveness to GSH concentration in vitro. Drug-loaded NPs were shown to inhibit the growth of tumor cells (HeLa and CHO-K1) with greater efficiency than free methotrexate, disregarding the concentration of glucose used for freeze-drying. Nevertheless, confocal microscopy studies revealed that cellular internalization of NPs freeze-dried with 5.0% glucose is more difficult than for NPs freeze-dried with lower glucose concentration. Thus, concentration of glucose cryoprotectant should be taken into account during development of NPs intended to release the drug as a function of GSH levels, due to the specific interactions of glucose with GSH.