In this study, pH, reduction and light triple-responsive nanocarriers based on hollow mesoporous silica nanoparticles (HMSNs) modified with poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) were developed via surface-initiated atom transfer radical polymerization. Both reduction-cleavable disulfide bond and light-cleavable o-nitrobenzyl ester were used as the linkages between HMSNs and pH-sensitive PDEAEMA polymer caps. A series of characterization techniques were applied to characterize and confirm the structures of the intermediates and final nanocarriers. Doxorubicin (DOX) was easily encapsulated into the nanocarriers with a high loading capacity, and quickly released in response to the stimuli of reducing agent, acid environment or UV light irradiation. In addition, flow cytometry analysis, confocal laser scanning microscopy observations and cytotoxicity studies indicated that the nanocarriers were efficiently internalized by HeLa cancer cells, exhibiting (i) enhanced release of DOX into the cytoplasm under external UV light irradiation, (ii) better cytotoxicity against HeLa cells, and (iii) superior control over drug delivery and release. Thus, the triple-responsive nanocarriers present highly promising potentials as a drug delivery platform for cancer therapy.

Combination therapy with high spatial and temporal resolution is highly promising for efficient medical treatment of cancer. In this study, doxorubicin (DOX) conjugated amphiphilic block copolymer with a terminal folic acid moiety was prepared, which could self-assemble into nanoparticles by encapsulating organic near-infrared (NIR) absorbing dye IR825 for combined photothermal-chemotherapy. The resulting PDOX/IR825 nanoparticles showed excellent colloidal stability and monodispersity in aqueous solution. Specifically, the conjugated DOX could be released quickly in weak acidic environment for chemotherapy due to the cleavage of acid-labile hydrazone bond. Meanwhile, the encapsulated dye could convert the NIR light energy into heat with high efficiency, which makes the self-assembled nanoparticles an effective platform for photothermal therapy. Confocal microscopy observations and flow cytometry analysis confirmed that the PDOX/IR825 nanoparticles could be efficiently endocytosed by HeLa cells and deliver DOX into the nuclei of cancer cells. The in vitro cell viability assays indicated that both DOX-sensitive HeLa cells and DOX-resistant A2780/DOX R cells were completely killed by the treatment of PDOX/IR825 under NIR light irradiation. Significant tumor regression was also observed in the zebrafish liver hyperplasia model upon combinational therapy provided from the PDOX/IR825 nanoparticles. Hence, the PDOX/IR825 nanoparticles exhibited a great potential in site-specific combined photothermal-chemotherapy of tumor.

The well-defined photoresponsive polymethacrylate containing azo chromophore, poly{1‘-octyloxy-4‘-(6-methacryloxy)hexyloxy-5‘-phenylmethaneone-(2-phenyl)azobenzene (AHMA)} (PAHMA), was prepared via reversible addition−fragmentation chain transfer (RAFT) polymerization in anisole solution using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the RAFT agent and 2,2‘-azobis(isobutyronitrile) (AIBN) as an initiator. The kinetic plots of polymerization were first-order and the molecular weights (M n(GPC)s) of the homopolymer (PAHMA) with relatively low polydispersity index values (PDIs ≤ 1.37) increased with monomer conversions throughout the polymerization processes. Furthermore, the kinetic plots of chain extension with both methyl methacrylate (MMA) and styrene (St) using the obtained PAHMA as a macro-RAFT agent were also first-order. The M n(GPC)s of the diblock copolymers, PAHMA-b-PMMA and PAHMA-b-PS, increased with the respective monomer conversions. These results indicated that most of the PAHMA chains were still “living”. The structure and properties of the polymers were characterized by 1H NMR, GPC, and UV−vis spectra. The photoisomerization of the polymer was examined. On irradiation with a linearly polarized Kr+ laser beam, the birefringence was induced in the polymer films to the level of 0.075. With illumination of linearly polarized Kr+ laser beam at modest intensities (120 mW/cm2), significant surface relief gratings (SRGs) formed on the polymer films were observed.

Multifunctional hollow mesoporous silica nanoparticles were constructed by firstly loading with doxorubicin and then capping with disulfide linked β-cyclodextrin followed by complexation with adamantane functionalized indocyanine dye, showing improved anticancer efficacy through combined photothermal-chemotherapy.

A three‐arm star azo side‐chain liquid crystalline (LC) homopolymer, poly[6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate] (PMMAZO), was synthesized by atom transfer radical polymerization (ATRP) method. The polymerization of 6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate proceeded in a controlled/“living” way. A series of three‐arm star LC block copolymers (PMMAZO‐b‐PMMA) were also synthesized. The polymers were characterized by 1H NMR, gel permeation chromatograph, and UV–vis spectra, respectively. The both polymers of PMMAZO and copolymers of PMMAZO‐b‐PMMA exhibited a smetic phase and a nematic phase. As concern to the PMMAZO, the glass‐transition temperature (Tg) and phase‐transition temperature from the smetic to nematic phase and from the nematic to isotropic phase increased with the increase of molecular weight (Mn(GPC)) of PMMAZO. The phase transition temperature of the block copolymers, PMMAZO‐b‐PMMA, with the same PMMA block was similar to that of PMMAZO. However, the Tg of the PMMAZO‐b‐PMMA decreased at low azo content and then increased with the increasing Mn(GPC) when azo content was above 61.3%. With illumination of linearly polarized Kr+ laser beam at modest intensities (35 mW/cm2), significant surface relief gratings formed on PMMAZO films with different molecular weights were observed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 777–789, 2008

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