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Issue 33, 2017
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pH-Responsive unimolecular micelles based on amphiphilic star-like copolymers with high drug loading for effective drug delivery and cellular imaging

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Abstract

Herein, we report pH-responsive star-like polymers (denoted as CPO) with amphiphilic diblock copolymers poly(2-(diisopropylamino) ethylmethacrylate)-b-poly[(ethylene glycol) methyl ether methacrylate] (PDPA-b-POEGMA) grafted from β-cyclodextrin (β-CD) for efficient antitumor drug delivery. A series of amphiphilic CPO polymers were synthesized via two-step atom transfer radical polymerization (ATRP) utilizing β-CD-21Br as an initiator. Transmission electron microscopy and dynamic light scattering results demonstrated that these amphiphilic star-like polymers formed unimolecular micelles (UMs) in aqueous media and showed favorable robust micellar stability. The PDPA blocks are hydrophobic at pH = 7.4, which enabled these UMs to carry hydrophobic drugs such as doxorubicin (DOX) in their inner layer with a high drug loading content. Under an acidic environment, the hydrophobility–hydrophilicity transition of PDPA blocks induced the rapid pH-triggered release of drugs for cancer therapy. To endow these UMs with diagnostic functions, near-infrared fluorescent dye cyanine 5 (Cy5) was incorporated by post-decoration on the amine-functionalized precursor where their inner layer was replaced with copolymerized blocks of P(DPA-co-AMA). The UMs of the obtained Cy5 containing polymers (denoted as CPO-Cy5) exhibited switchable fluorescence in response to different pH conditions, where the fluorescence intensity could be enhanced by 7-fold with the change of pH from 9 to 4. The cytotoxicity experiments demonstrated that the DOX-loaded CPO or CPO-Cy5 micelles presented high cytotoxicity against HeLa and MCF-7 cancer cells but low cytotoxicity against normal L929 cells, likely implying their potential tumor-specific targeting ability. The integration of NIR imaging and effective therapeutic functions made DOX-loaded CPO-Cy5 a promising nanomedicine, providing new insights into the design of theranostic nanoplatforms.

Graphical abstract: pH-Responsive unimolecular micelles based on amphiphilic star-like copolymers with high drug loading for effective drug delivery and cellular imaging

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Publication details

The article was received on 01 Jun 2017, accepted on 18 Jul 2017 and first published on 18 Jul 2017


Article type: Paper
DOI: 10.1039/C7TB01477E
Citation: J. Mater. Chem. B, 2017,5, 6847-6859
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    pH-Responsive unimolecular micelles based on amphiphilic star-like copolymers with high drug loading for effective drug delivery and cellular imaging

    X. Shi, X. Ma, M. Hou, Y. Gao, S. Bai, B. Xiao, P. Xue, Y. Kang, Z. Xu and C. M. Li, J. Mater. Chem. B, 2017, 5, 6847
    DOI: 10.1039/C7TB01477E

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