Preparation of Pendant Group-Functionalized Diblock Copolymers with Adjustable Thermogelling Behavior

Receptor-Mediated In Vivo Targeting of Breast Cancer Cells with 17α-Ethynylestradiol-Conjugated Silica-Coated Gold Nanoparticles

Efficient therapies for breast cancer remain elusive because of the lack of strategies for targeted transport and receptor-mediated uptake of synthetic drug molecules by cancer cells. Conjugation of nanoparticles (NPs) with active targeting ligands enabling selective molecular recognition of antigens expressed on the surface of cancer cells is promising for localization and treatment of malignant cells. In this study, covalent attachment of synthetic estrogen 17α-ethynylestradiol on the silica (SiO₂) shell of silica-gold NPs (SiO₂@Au) was undertaken to improve the cancer-targeting ability of the nano-biotags. Chemical and structural analysis of the bioconjugates examined in solution (UV-vis and ξ-potential) and solid state (Fourier transform infrared spectroscopy, X-ray diffractometry, and transmission electron microscopy) confirmed the identity of the carrier particles and surface-bound ligands. The mesoporous silica shell served as a reservoir for anticancer drugs (doxorubicin and quercetin) and to facilitate covalent attachment of receptor molecules by click chemistry protocols. The chemoselective recognition between the nanoconjugates and cell membranes was successfully demonstrated by the accumulation of nanoprobes in the tumor tissue of mice with subcutaneous breast cancer, whereas healthy cells were unaffected. The drug release studies showed sustained release kinetics over several weeks. These findings elaborate the exceptional selectivity and potential of estrogen-coated nano-biolabels in efficient diagnosis and detection of breast cancer cells.

Thermoresponsive and Biodegradable Amphiphilic Block Copolymers with Pendant Functional Groups

BACKGROUND

To develop the biodegradability and thermoresponsive hydrogel, in this work we designed a pendant-functionalized, thermoresponsive, amphiphilic block copolymer.

METHODS

Methoxy poly(ethylene glycol) (MPEG)-b-[poly(ε-caprolactone)-ran-poly(ε-caprolactone-3-one)-ran-polylactic acid] (MCL) and (MPEG-b-[PCL-ran-POD-ran-PLA]) [MCL-(CO)] block copolymers were prepared by ring-opening polymerization of ε-caprolactone, OD and lactide monomers. The subsequent derivatization of MCL-(CO) provided MPEG-b-[PCL-ran-poly(ε-caprolactone-3-COOH)-ran-PLA] [MCL-(COOH)] with COOH pendant groups and MPEG-b-[PCL-ran-poly(ε-caprolactone-3-NH2)-ran-PLA] [MCL-(NH2)] with NH2 pendant groups.

RESULTS

The measured segment ratios of MCL-(CO), MCL-(COOH), and MCL-(NH2) agreed well with the target ratios. The abundances of the COOH and NH2 groups in the MCL-(COOH) and MCL-(NH2) copolymers were determined by 1H- and 13C-nuclear magnetic resonance spectroscopy, and agreed well with the target abundances. MCL-(CO), MCL-(COOH), and MCL-(NH2) formed homogeneous, white, opaque emulsions at room temperature. Rheological analysis of the block copolymer suspensions indicated a solution-to-hydrogel phase transition as a function of temperature. The solution-to-hydrogel phase transitions and the biodegradation of MCL-(CO), MCL-(COOH), and MCL-(NH2) were affected by varying the type (ketone, COOH, or NH2) and abundance of the pendant groups.

CONCLUSION

MCL-(CO), MCL-(COOH), and MCL-(NH2) with ketone, COOH, and NH2 pendant groups showed solution-to-hydrogel phase transitions and biodegradation behaviors that depended on both the type and number of pendant groups.