Poly(N-isopropylacrylamide) based pH- and temperature-sensitive ampholytic hydrogels with tunable mechanical, swelling and drug release properties

Abstract

pH-/temperature-sensitive ampholytic poly(N-isopropylacrylamide) (PNIPAAm) hydrogels containing N-[3-(dimethylamino)propyl]methacrylamide-itaconic acid (DMAPMAAm-IA) and DMAPMAAm-AMPS (2-acrylamido-2-methylpropane sulfonic acid) comonomer pairs have been designed and then synthesized. The results showed that (i) disk diameters and transparencies in the range of pH 2–12 increased only with increasing content of AMPS in the ampholytic NIPAAm/DMAPMAAm/AMPS hydrogels containing 10.0 mol % of DMAPMAAm + AMPS mixtures; (ii) maximum compressive strengths of NIPAAm/IA (62.5 ± 10.0 kPa) was higher than NIPAAm/AMPS (26.9 ± 1.1 kPa) hydrogels in DDW at 37 °C. (iii) In case of DFNa release, the decreasing values of n (≈0.30–0.50) indicated that ampholytic PNIPAAm hydrogels served as diffusion barrier.

Graphical Abstract

Abbreviations: NIPAAm/DMAPMAAm: copolymer of NIPAAm with DMAPMAAm; NIPAAm/AMPS: copolymer of NIPAAm with AMPS; NIPAAm/IA: copolymer of NIPAAm with IA; NIPAAm/DMAPMAAm/AMPS: terpolymer of NIPAAm containing DMAPMAAm and AMPS; NIPAAm/DMAPMAAm/IA: terpolymer of NIPAAm containing DMAPMAAm and IA.

Keywords:

• 2-acrylamido-2-methylpropane sulfonic acid
• ampholytic poly(N-isopropylacrylamide) hydrogels
• compression modulus
• diclofenac sodium release
• dynamic swelling
• N-[3-(dimethylamino)propyl] methacrylamideItaconic acid

Acknowledgements

We thank Dr. Gökhan Göksu for guidance on MATLAB^TM calculations.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Scientific Research Project Coordination Center of Istanbul Technical University (ITU) (Scientific Research Project Fund with the Project number 38387).