Preparation And Characterization Of Controllable Redox-responsive Prodrug-loaded Nanocarriers

The majority of anticancer drugs are water insoluble with poor selectivity, short half-life and drug resistance, resulting in undesirable side effects. The incorporation of anticancer drugs into nanoparticles not only has the potential to decrease their adverse cytotoxic effects, but also in many cases may increase the accumulation of the drug in the tumor vasculature, a phenomenon known as enhanced permeability and retention (EPR). Consequently, this paper aims at developing a prodrug micelles with controllable redox-responsive drug release mechanism for intracellular drug delivery, in order to make the drug carriers more widely distribute within the tumor lesions and targeted delivery, substantially realize controlled drug release and improve the treating effect.Firstly, preparation and characterization of redox-responsive prodrug micelles, doing the test of in vitro drug release and cell viability.This work introduced a redox-responsive prodrug design of MTX covalently linked to a polymer MTX-SS-PEG-SS-MTX and PEG-SS-MTX-SS-PEG by chemical synthesis. The amphiphilic property enables them to self-assemble into micelles in aqueous solution by dialysis method. These micelles were composed of a PEG shell and MTX core, characterized by fluorescence spectrophotometry, DLS and TEM, and the polymers self-assembled in micelles with an average diameter of235nm, CMC of52.48μg·mL-1, which were spherical, smooth and well-dispersed with no aggregation.Additionally, the micelles could serve as carriers of other anticancer drugs, such as DOX, for combination therapy. While the cleavable disulfide linkers allowed the conjugated MTX to exert its therapeutic activity when exposed to high GSH level. The in vitro drug release studies showed that65%of MTX was released from PEG-SS-MT-SS-PEGX/DOX prodrug micelles in the presence of10mM glutathione(GSH) at pH7.4, in10h. Under the same conditions,80.51%of MTX,24.76%of DOX were released from PEG-SS-MTX-SS-PEG/DOX prodrug micelles in72h. These results indicated that PEG-SS-MTX-SS-PEG/DOX prodrug micelles exhibited GSH triggered drug release behavior. Cytotoxicity experiments revealed that, cell viability was55.09%which trained with PEG-SS-MTX-SS-PEG/DOX prodrug micelles, whereas the cell viability was only39.41%which trained with the DOX-loaded PEG-SS-MTX-SS-PEG/DOX prodrug micelles, leading to a synergetic cytotoxicity to HepG2cells. Secondly, preparation and characterization of controllable redox-responsive prodrug micelles, doing the test of in vitro drug release.The pluronic F127(PEO98-PPO67-PEO98) and PEG-SS-MTX-SS-PEG polymeric mixed micelles (F127/PEG-SS-MTX-SS-PEG) were fabricated by dialysis method, and then physically entrapped DOX into mixed micelles(F127/PEG-SS-MTX-SS-PEG/DOX). These micelles were characterized by fluorescence spectrophotometry, DLS and TEM, and the polymers self-assembled in micelles with an average diameter of295.8nm, CMC of42.72μg·mL-1, which were spherical, smooth and well-dispersed with no aggregation. While the cleavable disulfide linkers allowed the conjugated MTX to exert its therapeutic activity when exposed to high GSH level.The in vitro release studies showed that18.48%of MTX were released from F127/PEG-SS-MTX-SS-PEG/DOX prodrug micelles in the presence of10mM GSH at pH7.4, in72h. Under the same conditions,28.33%of DOX were released from F127/PEG-SS-MTX-SS-PEG/DOX prodrug micelles in72h. These results indicated that F127/PEG-SS-MTX-SS-PEG/DOX prodrug micelles exhibited GSH triggered drug release behavior, simultaneously suppressed premature rapid release and realized the combination therapy.