Water Transport Properties of pH‐Responsive Hydrogels Based on Poly(methacrylic acid) with Polyether Side Chains by Magnetic Resonance Imaging

Abstract

Three pH‐responsive hydrogel families have been synthesized through the photopolymerization of methacrylic acid (MAA) with: i) a poly(ethylene glycol) macromonomer, P(MAA‐co‐PEGMEMA), ii) a poly(propylene glycol) macromonomer, P(MAA‐co‐PPGMEMA), and iii) the two above‐mentioned macromonomers, to give a terpolymer P(MAA‐co‐PEGMEMA‐co‐PPGMEMA). Their swelling properties at pH 7 have been investigated by magnetic resonance imaging (MRI). Equimolecular compositions of both P(MAA‐co‐PEGMEMA) and P(MAA‐co‐PPGMEMA) hydrogels showed the lowest swelling kinetics rates. For P(MAA‐co‐PEGMEMA‐co‐PPGMEMA) hydrogels, the different structure of the side chains established an antagonist effect on the swelling. In addition, from the MRI intensity profiles and taking into account the first stage of the swelling, water diffusion coefficients (D) have been estimated.

Thermo‐ and pH‐sensitive hydrogels based on 2‐(2‐methoxyethoxy)ethyl methacrylate and methacrylic acid

“…During swelling, two main regions can be distinguished in the samples, a highly swollen outer region, and a core which remains unswollen during a first stage and starts to swell after some period of time. This is the usual behaviour found for hydrogels that form hydrogen bond bridge interactions between their comonomeric units 34, 41, 44…”

“…It is important to mention that these hydrogels were previously soaked in PBS at pH = 2. This pre‐treatment allows the full protonation of the acid groups and should promote hydrogen bond arrangements between both comonomeric units, as has been observed for similar systems 25, 26, 29, 33, 40, 41…”

“…This pre-treatment allows the full protonation of the acid groups and should promote hydrogen bond arrangements between both comonomeric units, as has been observed for similar systems. 25,26,29,33,40,41 To establish a relationship between the swelling kinetics and copolymer composition, the normalized swelling curves were obtained, as shown in Fig. 4(b).…”

pH‐ and Temperature‐Sensitive Chitosan Hydrogels: Swelling and MRI Studies

“…Hydrogels have been studied by using this technique with different purposes such as study of drug release from hydrogels [20] study of fixation of hydrogel scaffolds into a defect site for tissue engineering, [21] water transport properties, [22] dynamic swelling. [23,24] Pulsed-field gradient magnetic resonance techniques using strong field gradients (either in NMR or MRI) has proven, in previous studies, to be a very powerful tool in the study of slow diffusion processes in polysaccharide gels, including alginate, dextran, gellan and agarose. [25][26][27][28] To the best of our knowledge, this is the first study that accounts for the use of MRI techniques to characterize the physicochemical properties of chitosan hydrogels, in particular, their diffusion and relaxation behavior and relate these to their swelling properties at varying pH.…”

Swelling control in thermo-responsive hydrogels based on 2-(2-methoxyethoxy)ethyl methacrylate by crosslinking and copolymerization with N-isopropylacrylamide

“…Thus, such stimuli-sensitive hydrogels have been intensively studied with respect to drug delivery 9,10 and other biomedical applications. [11][12][13][14][15][16][17] Recently, hydrogels based on oligo(ethylene glycol) side chains methacrylic monomers, [18][19][20][21][22] such as 2-(2-methoxyethoxy)ethyl methacrylate (MEO 2 MA), were highlighted as a successful alternative to poly(N-iPAAm)-based hydrogels because of the advantages of a controllable lower critical solution temperature, 23,24 high biocompatibility/ low cytotoxicity 25,26 and facile polymerization by both the free radical and the anionic polymerization mechanisms. 27 The previous investigations on MEO 2 MA-based hydrogels were mainly focused on controlling the thermo-responsive behavior for biomedical applications.…”