Doxorubicin-loaded aromatic imine-contained amphiphilic branched star polymer micelles: synthesis, self-assembly, and drug delivery

Abstract

Redox-and pH-sensitive branched star polymers (BSPs), BP(DMAEMA-co-MAEBA-co-DTDMA)(PMAIGP)_ns, have been successively prepared by two steps of reversible addition–fragmentation chain transfer (RAFT) polymerization. The first step is RAFT polymerization of 2-(N,N-dimethylaminoethyl)methacrylate (DMAEMA) and p-(methacryloxyethoxy) benzaldehyde (MAEBA) in the presence of divinyl monomer, 2,2′-dithiodiethoxyl dimethacrylate (DTDMA). The resultant branched polymers were used as a macro-RAFT agent in the subsequent RAFT polymerization. After hydrolysis of the BSPs to form BP(DMAEMA-co-MAEBA-co-DTDMA)(PMAGP)_ns (BSP-H), the anticancer drug doxorubicin (DOX) was covalently linked to branched polymer chains by reaction of primary amine of DOX and aldehyde groups in the polymer chains. Their compositions, structures, molecular weights, and molecular weight distributions were respectively characterized by nuclear magnetic resonance spectra and gel permeation chromatography measurements. The DOX-loaded micelles were fabricated by self-assembly of DOX-containing BSPs in water, which were characterized by transmission electron microscopy and dynamic light scattering. Aromatic imine linkage is stable in neutral water, but is acid-labile; controlled release of DOX from the BSP-H-DOX micelles was realized at pH values of 5 and 6, and at higher acidic solution, fast release of DOX was observed. In vitro cytotoxicity experiment results revealed low cytotoxicity of the BSPs and release of DOX from micelles in HepG2 and HeLa cells. Confocal laser fluorescence microscopy observations showed that DOX-loaded micelles have specific interaction with HepG2 cells. Thus, this type of BSP micelle is an efficient drug delivery system.

Keywords:

• RAFT polymerization
• controlled release
• doxorubicin
• branched star polymer
• pH-sensitive

Supplementary materials

Figure S1 GPC curves of the branched polymers, BP(DMAEMA-MAEBA-DTDMA)-1 (BP-1), BP(DMAEMA-MAEBA-DTDMA)-2 (BP-2), and BP(DMAEMA-MAEBA-DTDMA)-3 (BP-3) prepared by RAFT copolymerization at 70°C for 24 hours with feed molar ratios of [DMAEMA]:[MAEBA]:[DTDMA]:[CPDA]:[AIB N] =36:4:1.5:1:0.25, 32:8:1.5:1:0.25, and 16:24:1.5:1:0.25, respectively.

Abbreviations: GPC, gel permeation chromatography; BP, branched polymer; DTDMA, 2,2′-dithiodiethyoxly dimethacrylate; DMAEMA, 2-(N,N-dimethylamin-oethyl)methacrylate; MAEBA, p-(methacryloxyethoxy)benzaldehyde; RAFT, rev er-sible addition–fragmentation chain transfer; CPDB, cyanoisopropyl dithio benzoate; AIBN, Azobis (isobutyronitrile).

Figure S2 GPC curves of the branched star polymers (BSPs), BP(DMAEMA-MAEBA-DTDMA)1(PMAIGP)_n (BSP-1), BP(DMAEMA-MAEBA-DTDMA)2(PMAIGP)_n (BSP-2), and BP(DMAEMA-MAEBA-DTDMA)3(PMAIGP)_n (BSP-3) prepared by RAFT polymerization of MAlGP at 70°C for 24 hours with the feed molar ratios of [MAlGP]:[BP-1 or BP-2 or BP-3] =100:1.

Abbreviations: GPC, gel permeation chromatography; BP, branched polymer; DTDMA, 2,2′-dithiodiethyoxly dimethacrylate; DMAEMA, 2-(N,N-dimethy-laminoethyl)methacrylate; MAEBA, p-(methacryloxyethoxy)benzaldehyde; RAFT, reversible addition–fragmentation chain transfer; CPDB, cyanoisopropyl dithiobe-nzoate; AIBN, Azobis(isobutyronitrile); MAlGP, poly(6-O-methacryloyl-1,2; 3,4-di-O-isopropylidene-D-galactopyranose.

Figure S3 TEM images of the micelles prepared respectively from BSP-H1 to BSP-H3.

Abbreviations: TEM, transmission electron microscopy; BSP, branched star polymer.

Figure S4 TEM images of BSP-H-DOX pro-drug.

Abbreviations: TEM, transmission electron microscopy; BSP, branched star polymer; DOX, doxorubicin.

Acknowledgments

This work was supported by National Natural Science Foundation of China under contract numbers 21090354 and 21374107, and was also supported by the Fundamental Research Funds for the Central Universities (grant number WK 2060200012).

Disclosure

The authors report no conflicts of interest in this work.