A tumor-acidity-activated charge-conversional nanogel as an intelligent vehicle for promoted tumoral-cell uptake and drug delivery

Multi-responsive nanogels containing motifs of ortho ester, oligo(ethylene glycol) and disulfide linkage as carriers of hydrophobic anti-cancer drugs

A family of multi-responsive nanogels with different compositions and crosslinking degrees have been prepared by the miniemulsion copolymerization of monomethyl oligo(ethylene glycol) acrylate (OEGA) and an ortho ester-containing acrylic monomer, 2-(5,5-dimethyl-1,3-dioxan-2-yloxy) ethyl acrylate (DMDEA), with bis(2-acryloyloxyethyl) disulfide (BADS) as a crosslinker. These nanogels are thermoresponsive and labile in the weakly acidic or reductive environments. The thermoresponsive behaviors, acid-triggered hydrolysis, and reduction-induced degradation of these nanogels were studied by means of dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The results indicate that the volume phase transition temperature (VPTT), thermally induced deswelling ratio, and acid-triggered swelling ratio of the nanogels are closely relevant to their compositions and crosslinking degrees. Although these nanogels could be reductively disrupted by dithiothreitol (DTT), single polymer chains with sizes smaller than 20 nm were not detected by DLS. This is probably due to the existence of some unbreakable linkages formed by chain transfer to the disulfide bond during the radical polymerization. These nanogels are capable of encapsulating hydrophobic compounds. The loading capability of the nanogels for Nile Red (NR), paclitaxel (PTX), and doxorubicin (DOX), and the release behaviors of the drug-loaded nanogels were investigated by UV-vis spectrometry and HPLC. As expected, drug release can be greatly accelerated by a cooperative effect of both acid-triggered hydrolysis and DTT-induced degradation. Finally, the PTX-loaded nanogels exhibit a concentration-dependent toxicity to MCF-7 cells while the intact unloaded nanogels are non-toxic, thereby they may be used as potential carriers for hydrophobic anticancer drugs.

Synthesis of poly(acrylic acid) (PAA) modified Pluronic P123 copolymers for pH-stimulated release of doxorubicin

Pluronic P123 was chain-extended at their terminal groups using atom transfer radical polymerization to form poly(acrylic acid) (PAA) tails and obtain the PAA-b-P123-b-PAA (P123-PAA) copolymer. The incorporation of PAA had the effect of increasing the carrier's drug loading capacity of an anti-cancer drug, Doxorubicin (DOX), and also allowed for pH-controlled release of the drug. Drug release assays showed that up to 60% of DOX cargo could be retained in the DOX/P123-PAA complex for 3 days at normal physiological pH (7.4). This was then followed by a secondary burst release of DOX when the environment became more acidic (pH 5). Therefore, it was possible that the more acidic physiological environment of tumor sites could be used to trigger an accelerated release of DOX from the drug carriers. The material was demonstrated for potential application in the delivery of cationic drugs for cancer treatment.