A Magnetic Resonance Study of Temperature Responsive Volume Phase Transition in a Hydrogel and Its Concurrent Release of Drug Carrier Molecules

Hydrogels can be combined with molecular carriers to achieve controlled delivery of hydrophobic drugs. The purpose of this study was to use an experimental protocol consisting of spatially localized magnetic resonance (MR) techniques to investigate the changes in a poly(N-isopropylacrylamide) P(NIPAM) hydrogel incorporating <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> -cyclodextrins ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> CD) undergoing a volume phase transition (VPT). The MR protocol presented in this study allows to follow the shrinking of the hydrogel and the release of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> CD, with subsequent determination of the self-diffusion coefficients of both water and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> CD in the hydrogel. The obtained data enable a detailed correlation of the change in hydrogel structure and spatial variation in gel volume and the corresponding time-dependent spatial variation in the concentration of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> CD.