Bioreducible micelles self-assembled from amphiphilic hyperbranched multiarm copolymer for glutathione-mediated intracellular drug delivery

Self-assembly of a diblock copolymer with pendant disulfide bonds and chromophore groups: a new platform for fast release

An amphiphilic block copolymer comprising poly(ethylene glycol) (PEG) and poly(2-(methacryloyl)oxyethyl-2'-hydroxyethyl disulfide) (PMAOHD) blocks was synthesized by atom transfer radical polymerization (ATRP). Pyrenebutyric acid was conjugated to the block copolymer by esterification, and a block copolymer with pendant disulfide bonds and pyrenyl groups (PEG-b-P(MAOHD-g-Py)) was obtained. (1)H NMR and gel permeation chromatography (GPC) results demonstrated the successful synthesis of the block copolymer. The cleavage of the disulfide bonds and the degrafting of the pyrenyl groups were investigated in THF and a THF/methanol mixture. Fluorescence spectroscopy, GPC, and (1)H NMR results demonstrated fast cleavage of the disulfide bonds by Bu(3)P in THF. Fluorescence results showed the ratio of the intensity of the excimer peak to the monomer peak decreased rapidly within 20 min. GPC traces of the block copolymer moved to a long retention time region after addition of Bu(3)P, indicating the cleavage of the disulfide bonds and the degrafting of the pyrenyl groups. PEG-b-P(MAOHD-g-Py) can self-assemble into micelles with poly(MAOHD-g-Py) cores and PEG coronae in a mixture of methanol and THF (9:1 by volume). The dissociation of the micelles in the presence of Bu(3)P was investigated. After cleavage of the disulfide bonds in the micellar cores, a pyrene-containing small molecular compound and a block copolymer with pendant thiol groups were produced. Transmission electron microscopy (TEM), dynamic light scattering (DLS), and (1)H NMR were employed to track the dissociation of the polymeric micelles. All the techniques demonstrated the dissociation of the micelles and the fast release of pyrenyl groups from the micelles.

Hyperbranched polydiselenide as a self assembling broad spectrum anticancer agent

This work presents a highly efficient, broad spectrum and self-delivery anticancer agent, which is the hyperbranched polydiselenide (HPSe) consisting of alternative hydrophobic diselenide groups and hydrophilic phosphate segments in the backbone framework. The data of systematic evaluations demonstrate that HPSe is very potent to inhibit the proliferation of many forms of cancer cell. The dose of HPSe required for growth inhibition of 50% (IC(50)) in all of the tested cancer cell lines is within the concentration range between 1 and 2.5 μg mL(-1) with the incubation time of 72 h. Furthermore, the amphiphilic HPSe can self-assembly into nanomicelles with an average diameter of 50 nm and spontaneously enter into tumor cells by the enhanced permeability and retention (EPR) effect. Besides, other hydrophobic anticancer drugs such as doxorubicin (DOX) can be encapsulated into HPSe micelles for combining therapy.

Approaches for the preparation of non-linear amphiphilic polymers and their applications to drug delivery

Amphiphilic polymers are particularly useful for drug delivery because of their ability to self-assemble into discrete aggregates. While this behavior has been studied in depth for simple linear block copolymer amphiphiles, recent advances in synthetic methodologies have provided efficient routes to amphiphilic polymers with more complex architecture, including dendrimers, hyperbranched polymers, star polymers, and cyclic polymers. These architectures can impart unique advantages, such as increased stability, on their micellar aggregates. Herein the different strategies for preparing these complex amphiphiles are described, and the application of their assemblies towards drug delivery are summarized.