Swelling Monitorization of Poly[(N-isopropylacrylamide)-co-(methacrylic acid)] Copolymers by Magnetic Resonance Imaging

Abstract

The dynamic swelling behavior in phosphate buffer solution (PBS) (pH 7) of poly[(Nisopropylacrylamide)-co-(methacrylic acid)] P[(N-iPAAm)-co-(MAA)] hydrogels has been studied by using magnetic resonance imaging (MRI), which provides information at a local level. To determine the water uptake at a global level, a gravimetric technique was also employed. Photographs were taken providing valuable information on the hydrogel morphology at different stages of swelling. By combining the data from these three methods, the pattern of water uptake may be clearly elucidated. The gravimetric swelling curves and photographs were in agreement with the information obtained from MRI images acquired on central slices of the hydrogels. In contrast to the homopolymers, when the corresponding copolymers hydrogels were soaked under acidic conditions (pH 2), they exhibited characteristic sigmoidal swelling curves at pH 7. Furthermore, the hydrogel slabs adopt a peculiar morphology as it was photographically observed. In the MRI images two processes were distinguished, corresponding to a highly swollen external region in contrast to a rigid core which starts to swell after a lag time depending on sample composition.

Tuning the non-equilibrium state of a drug-encapsulated poly(ethylene glycol) hydrogel for stem and progenitor cell mobilization

“…[16] It has been demonstrated that “bound water” presents much stronger signal intensity than “free water”. [16] Following imaging of the hydrogels, the resonance intensities in the MRI was converted to the color density map as shown in the scale bar (Fig. 3).…”

“…[16–18] The maximum strength of the magnetic field gradient was 90 G cm −1 . Each hydrogel disk (10 mm in diameter, 1 mm in thickness) was incubated in deionized water.…”

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

“…1 H MRI experiments were carried out using a Bruker Avance 400 spectrometer/imager (Bruker Analytik GmbH, Karlsruhe, Germany) equipped with a Bruker UltraShield 9.4T ( 1 H resonance frequency of 400.14 MHz). The experimental conditions were similar to those previously employed 34…”

Synthesis and Characterization of a Novel Thermo‐Sensitive Copolymer of N‐Isopropylacrylamide and Dibenzo‐18‐crown‐6‐diacrylamide

“…[15,16] A great deal of attention has been placed on the thermo-responsive properties and applications of various copolymers of PNIPAM with acrylic acid, methacrylic acid, hydroxyethyl methacrylate, acrylamide, maleic anhydride, polyethyleneglycol derivatives, vinyl laurate, dodecyl groups, as well as other functional comonomers. [17][18][19][20][21][22][23][24][25][26] Recently, hydrophobically modified water-soluble polymers have received a great deal of experimental and theoretical interests. [27] Hydrophobically modified PNIPAM has been studied and used in designing materials for various applications such as drug controlled-release systems, bioseparations, and surface modification.…”