Acta Physico-Chimica Sinica ›› 2019, Vol. 35 ›› Issue (8): 876-884.

• ARTICLE •

Design and Synthesis of Multi-Responsive Copolymers for Drug Carrier

Yizhou WANG1,2,Yehong LIU1,2,Shouhong XU1,2,*(),Honglai LIU1,2

1. 1 Key Laboratory for Advanced Materials, East China University of Science and Technology, Shanghai 200237, P. R. China
2 School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, P. R. China
• Received:2019-01-07 Accepted:2019-02-21 Published:2019-02-28
• Contact: Shouhong XU E-mail:xushouhong@ecust.edu.cn
• Supported by:
the National Natural Science Foundation of China(21776071);the National Natural Science Foundation of China(51621002)

Abstract:

A copolymer P(MEO2MAm-co-OEGMAn)-b-PDPAp (poly[di(ethylene glycol) methyl ether methacrylate-co-oligo(ethylene glycol) methacrylate]-b-poly[2-(diisopropylamino) ethyl methacrylate]) had been designed to have good stimuli-response for developing temperature/pH dual-responsive drug delivery systems. In this study, the copolymer was synthesized in two steps: atom transfer radical polymerization (ATRP) method, followed by the continuous ATRP method for P(MEO2MAm-co-OEGMAn) and P(MEO2MAm-co-OEGMAn)-b-PDPAp, respectively. The data of proton nuclear magnetic resonance spectroscopy (1H NMR) and gel permeation chromatography (GPC) showed that the chemical compositions of the two copolymers could be precisely controlled. The aqueous solution properties of the copolymers were investigated using a UV-visible spectrophotometer. Results showed that the former random copolymers had reversible temperature response, while the end product exhibited temperature/pH dual-responsive behaviors. Their lower critical solution temperatures (LCSTs) were found to be dependent on the ratios of the monomers. Firstly, the relationship between the monomer ratio and the low critical solution temperature (LCST) of P(MEO2MAm-co-OEGMAn) was investigated. It was found that within the range of the experimental study (m + n = 100, 0 < n < 30), the LCST of the copolymer showed a linear relationship with the number of OEGMA units in each polymer chain. Then, the proportion of the two monomers (MEO2MAm and OEGMA) was fixed (m = 90, n = 10) and the random terpolymer P(MEO2MAm-co-OEGMAn)-b-PDPAp was synthesized. The LCSTs of P(MEO2MAm-co-OEGMAn)-b-PDPAp were found to be highly dependent on the DPA unit numbers in the range of 15 < p < 30 while their pH trigger points were not related to the chemical composition of the P(MEO2MAm-co-OEGMAn)-b-PDPAp. Finally, the copolymer P(MEO2MA90-co-OEGMA10)-b-PDPA22 with a LCST of 43 ℃ and a pH trigger point of 6.5 was carefully selected for preparing micelles, as a nanocarrier of doxorubicin (DOX) for an in vitro release study. The in vitro release kinetics of copolymer micelles were studied under different conditions. At pH 7.4, which mimics the normal physiological condition, the total release amount of DOX at 37 ℃ was about 25%, which was much higher than that at a higher temperature of 45 ℃ (approximately 5%). However, at pH 5.0, which mimics the intracellular environment, the cumulative release of the DOX quickly reached 95% at 37 ℃, while the cumulative release of the drug at 45 ℃ was only about 65% in the same period of time. For the latter, a slow and sustained release was observed and the cumulative drug release amount reached about 85% in 30 h. These results showed that the environmental stimuli response of the copolymer determined the drug release behavior of the micelles. This copolymer-based drug carrier could be expected to undergo bursting and sustained drug release in response to different conditions. Therefore, the results show potential for applications in the design and preparation of controllable drug transportation systems.