@article{0bc1714492de42ed91a321dc8c8a9b97,
title = "Near-infrared and pH responsive molecular machine for controlled encapsulation and release of drugs",
abstract = "It is difficult to form nanoparticles by traditional polymerization methods, using the azobenzene monomer with large hindrance. In this work, distillation precipitation polymerization (DPP) with lowering the monomer content at the beginning and distilling the solvent at a constant speed. Monofunctional 6-(4-methoxy-4′-oxygen-azobenzene) hexyl methacrylate (Azo) as a photo-responsive monomer and methacrylic acid (MAA) as a pH responsive monomer, were used to synthesize UCNPs@SiO2@PAzo/MAA nanoparticles. After the SiO2 was etched, UCNPs@PAzo/MAA nanocapsules (NCs) were formed. The trans isomer in the PAzo shell is converted into cis under 980 nm near-infrared (NIR) irradiation, leading to a variation of size and hydrophilicity of the nanocapsules. Controlled drug loading (∼17.5%) could be performed using UV irradiation, in which the pendant Azo groups have an cis “open” state and larger hydrophilicity. Under weak acid and NIR irradiation, the pendant Azo group with constant isomerization is like a “molecular impeller” agitator and the cumulative release rate of the doxorubicin (DOX) reaches 67.88%. Furthermore, UCNPs@PAzo/MAA nanocapsules were applied to the intracellular environment, and the cytotoxicity was studied. The cell images and cytotoxicity studies showed that the drug could be efficiently delivered to the nucleus by the UCNPs@PAzo/MAA nanocapsules in a controlled manner.",
keywords = "Azobenzene, Controlled release, Dual-responsive, Photoisomerization, Upconversion",
author = "Xiaotao Wang and Zhuofan Chen and Yebin Yang and Huiling Guo and Yingkui Yang and Tang, {Chak Yin} and Xuefeng Li and Law, {Wing Cheung}",
note = "Funding Information: Another method to determine the cis content is in the supporting information, in which the result is consistent with the above. The Azo continuously absorbs 470 nm visible light and 365 nm UV light, generated by the UCNPs, to support the continuous isomerization of Azo group between its trans and cis forming a “rotator” effect, which constantly converts light energy to mechanical energy to facilitate the release of drugs in the targeted sites.On the basis of exploring the cell survival rate of UCNPs@PAzo/MAA NCs with different concentrations under dark conditions, the cell survival rate of DOX-UCNPs@PAzo/MAA loaded particles under different light conditions was further explored [38]. Fig. 9(a) shows the effect of different concentrations of UCNPs@PAzo/MAA NCs on MCF-7 cell survival under irradiation with and without NIR, which indicates that low power (0.5 W) 980 nm NIR light results in no damage to the cells. UCNPs@PAzo/MAA NCs did not have toxic side effects on cells under NIR irradiation, providing experimental support that DOX-UCNPs@PAzo/MAA NCs can be used to study the intracellular drug release process of DOX-UCNPs@PAzo/MAA NCs with NIR as the excitation light-stimulus. Fig. 9(b) shows the cell survival rate of MCF-7 cells with DOX-UCNPs@PAzo/MAA NCs and DOX-UCNPs@PAzo/MAA drug-loaded NCs under NIR light. Negligible toxicity was obtained for all concentrations of NCs (6.25 μg/mL to 100 μg/mL). Even at a high concentration of 100 μg/mL, the cell survival rate was still 86.86%. When DOX-UCNPs@PAzo/MAA NCs were introduced to MCF-7 cells and irradiated with NIR light, an obvious apoptosis occurred in the tumor cells and the cell survival rate dropped from 79.93% (6.25 μg/mL) to 43.70% (50 μg/mL) and 21.82% (100 μg/mL) respectively, indicating that the cell survival ratio was concentration-dependent of the NCs. Compared with the non-irradiated group, the cell survival ratio was significantly reduced under NIR light irradiation. Continuous cis-trans and trans-cis isomerism of Azo acted like a stirrer to facilitate the release of the drug up to 67.88%, resulting in high cytotoxicity of DOX-UCNPs@PAzo/MAA NCs. In our work, Azo moieties acted as the molecular impeller machine, that could continuously transform the light energy to mechanical energy which can be further applied to the therapeutic purposes [39].This work was supported by the National Natural Science Foundation of China (51303049 and 31871442). Funding Information: This work was supported by the National Natural Science Foundation of China ( 51303049 and 31871442 ). Publisher Copyright: {\textcopyright} 2022 The Authors",
year = "2022",
month = aug,
doi = "10.1016/j.polymertesting.2022.107631",
language = "English",
volume = "112",
journal = "Polymer Testing",
issn = "0142-9418",
publisher = "Elsevier Ltd",
}