Nanoscale Observation of Dehydration Process in PHEMA Hydrogel Structure

Abstract

One of the most important field of interest in respect to hydrogel materials is their capability to water storage. The problem mentioned above plays an important role regarding to diffusion of fluid media containing nanoparticles, what is very useful in biomedical applications, such as artificial polymeric implants, drug delivery systems or tissue engineering.In presented work, dehydration process in hydrogels used in ophthalmology as intraocular lenses was observed. Before measurements studied materials were immersed in deionized water and saline solution to obtain equilibrium swelling state. Studies of the dehydration process were carried out by use of gravimetric analysis, Fourier-Transform Infrared and Positron Annihilation Lifetime Spectroscopy. Obtained results revealed changes in hydrogen bonding structure and free volume holes induced by saline solution ingredients.

2‐Hydroxyethyl Methacrylate Hydrogels for Local Drug Delivery: Study of Topotecan and Vincristine Sorption/Desorption Kinetics and Polymer‐Drug Interaction by ATR‐FTIR Spectroscopy

“…Hydrophilic groups of two distinct chains can be bridged by the water molecules, and the strength of the interaction between water molecules and hydrophilic groups depends on the proton–acceptor character of such groups and on the amount of water absorbed by the hydrogel. Following many investigations and using several experimental techniques, [ 39–44 ] a three‐state model for water in the hydrogel has been proposed [ 41 ] : i) nonfreezing water – tightly bound water that does not crystallize below 0 °C due to a strong interaction with a polymer chain, ii) intermediate water – loosely bound water that interacts with polymer chains in an intermediate way, that is, stronger than free water but weaker than tightly bound water; it does not freeze at 0 °C but exhibits melting/crystallization peaks at temperatures below 0 °C, and iii) freezing water – free water that crystallizes at ≈0 °C (as in the case of neat water) and hardly interacts with the polymer chain, but is trapped in the polymer matrix.…”

“…Furthermore, the case of hydrogen bonds formed in hydrophilic structures is more complex due to inter and intramolecular bonding. [ 43 ]…”

“…[ 46 ] This is in agreement with recently published results of experiments with a change of water content during the dehydration process, in which the band in the range of 3630–3670 cm −1 with the lowest intensity indicates nonhydrogen bonded OH groups in the pHEMA hydrogel, and the maximum at about 3540 cm −1 is assigned to the dimer OH…HO or intramolecular OH…OC bonded stretching vibrations, whereas the two other bands at frequencies at about 3370 and 3235 cm −1 in the pHEMA equilibrated hydrogel are connected with the intermolecular OH and OH…OH…OH aggregates with different degrees of bonding. [ 43 ]…”

Positronium Physics and Biomedical Applications

“…However, he focused his attention on the order and arrangement of tissue water and not on muscle structure. Further studies on complex biological systems like biological membranes or proteins moved positronium research towards structural biology and showed that this approach was efficient in the study of biological reactions (such as electron transfer (Jean and Ache, 1977)), phase transition of lipids (Chow et al, 1981;Jean and Hancock, 1982;Stinson et al, 1980) macromolecule structure (Handel et al, 1976), hydratation (Akiyama et al, 2007Gregory et al, 1992;Handel et al, 1980) and porosity (Chamerski et al, 2017;Pamula et al, 2006) of biological samples. Nowadays, after many years of focused research, PALS appears to be a promising technique in the investigation of the structure of macromolecules (Chen et al, 2012) and clinical samples (Avachat et al, 2022;Moskal et al, 2021a,b;Zgardzinska et al, 2020).…”

Replica-mold nanopatterned PHEMA hydrogel surfaces for ophthalmic applications

“…We determined characteristic methylene, carbonyl, and hydroxyl groups commonly presented in PHEMA hydrogels 33 . The spectra comprised -OH stretching vibration bands at 3590 cm -1 with a lower intensity and a slight band shift toward the higher frequencies caused by PHEMA dehydration before the measurement 34 . Stretching vibrations of C-H appeared around 3975 and 2890 cm −1 ; the stretching of C=O was observed at 1740 cm −1 , and the absorption band of C-O characteristic for PHEMA was observed with peaks at 1290 cm −1 , 1197 cm −1 , and 1094 cm -1 .…”