Coenzyme Q (CoQ) is widely used in preventive or curative treatment of cardiovascular diseases. However, CoQ exhibits an extremely low solubility in aqueous medium as well as a poor oral bioavailability. Therefore, solanesyl poly(ethylene glycol) succinate (SPGS) and CoQ were formulated as CoQ-SPGS micelles with a high content of CoQ to improve the bioavailability of CoQ in rat. Findings indicate that, in the CoQ-SPGS micelles, SPGS is self-assembled into stable nanosized micelles with a CoQ loading capacity of more than 39%. The CoQ-SPGS micelles exhibit an enhanced photostability upon exposure to simulated sunlight. In vivo experiments demonstrate that, as compared to that of the coarse suspensions of CoQ, there was three-fold enhancement of oral bioavailability for CoQ-loaded SPGS micelles depending on varying molecular weight of SPGS. In the encapsulation of CoQ by SPGS micelles, the self-assembled nanocarriers with strong muco-adhesive properties lead to increases in the solubility and oral absorption of lipophilic CoQ nanoparticles.

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Biodegradable pH-sensitive amphiphilic block polymer (mPEG-Hyde-PLGA) was synthesized via ring-opening polymerization, initiated from a hydrazone-containing macro-initiator. In this way, a pH-sensitive hydrazone bond was inserted into the backbone of block copolymer, linking hydrophilic poly(ethylene glycol) segment and hydrophobic poly(lactic-co-glycolic acid) segment. The copolymer self-assembled to form stable micelles with mean diameters below 100 nm and served as a drug delivery system for doxorubicin, with drug loading content of 5.3%. pH sensitivity of the hydrazone-containing micelles was investigated by changes in diameter and size distribution observed by dynamic light scattering measurements when the micelles were encountered to acidic medium. Small pieces and larger aggregates were found by transmission electron microscopy resulting from the disassociation of the micelles in acidic conditions. It was also noted that doxorubicin release from the pH-sensitive micelles is significantly faster at pH 4.0 and pH 5.0 compared to pH 7.4, while almost no difference was detected in the case of pH non-sensitive micelles. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays on HepG-2 and MCF-7 cells revealed that doxorubicin-loaded pH-sensitive micelles had higher antitumor activity than pH-insensitive ones. This pH-sensitive drug delivery system based on hydrazonecontaining block copolymer has been proved as a promising drug formulation for cancer therapy.

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