pH-Sensitive Hydrogel from Polyethylene Oxide and Acrylic acid by Gamma Radiation

Synthesis of poly(ionic liquid-OH) mediated deacetylated chitin and its hydrogels: A study on their applications in controlled release of paracetamol and urea

Due to the biodegradable and biocompatible nature of chitin and chitosan, they are extensively used in the synthesis of hydrogels for various applications. In this work, deacetylation of chitin is carried out with alkaline poly(dimethyldiallylammonium-hydroxide) that gave a higher amount of water-soluble chitin (with 84 % of the degree of deacetylation = chitosan0.84) compared to deacetylation using NaOH. The water-soluble chitosan0.84 is used as intercalating chains for the preparation of acrylic acid and vinylimidazole-based hydrogels. The quaternization of imidazole groups is done with 1,ω-dibromoalkanes, which sets off the crosslinking in the above polymer network. A set of three chitosan0.84 intercalated hydrogels, namely Cs-C4-hydrogel, Cs-C5-hydrogel, and Cs-C10-hydrogel are prepared bearing butyl, pentyl, and decyl chains as respective crosslinkers. The swell ratios of these intercalated hydrogels are compared with those of non-intercalated hydrogels (C4-hydrogel, C5-hydrogel, and C10-hydrogel). Chitosan0.84 intercalated Cs-C10-hydrogel has excellent swelling properties (2330 % swelling ratio) among six synthesized hydrogels. SEM analysis reveals that decyl crosslinker-bearing hydrogels are highly porous. The multi-functionality of Cs-C10-hydrogel and C10-hydrogel is explored towards -the controlled release of paracetamol/urea, and methyleneblue dye absorption. These studies disclose that chitosan0.84 intercalated hydrogels are showing superior-swelling behavior, high paracetamol/urea loading capacities and better dye entrapment than their non-intercalated counterparts.

Graphene oxide-alginate hydrogel-based indicator displacement assay integrated with diaper for non-invasive Alzheimer's disease screening

Pyrocatechol violet/copper ion-graphene oxide/alginate (PV/Cu2+-GO/Alg) hydrogel was fabricated and applied as a colorimetric sensor for monitoring urinary cysteine via an indicator-displacement assay (IDA) and Cu2+-cysteine affinity pair. The hydrogel-based sensor was formed by Ca2+ cations cross-linked PV/Cu2+-GO/Alg. The morphologies of hydrogel were characterized by field-emission scanning electron microscopy with energy-dispersive X-ray spectroscopy and Fourier-transform Raman spectroscopy. Incorporating GO into the hydrogel improved its uniformity of porosity, large surface area, and compressive strength, leading to amplified colorimetric signals of the hydrogel sensor. Under optimal conditions, this sensor offered a linear range of 0.0-0.5 g/L with a detection limit of 0.05 g/L for cysteine without interfering effects in urine. Furthermore, this hydrogel-based sensor was applied for urinary cysteine detection and validated with laser desorption ionization mass spectrometry. This platform could be used to determine cysteine at its cutoff (0.25 g/L) in human urine, which was distinguishable between normal and abnormal individuals, to evaluate an early stage of Alzheimer's disease. Eventually, this system was integrated with diapers for a wearable cysteine sensor.

Rice straw derived cellulose-based hydrogels synthesis and applications as water reservoir system

This study synthesized new cellulose-based hydrogels, namely cellulose and cellulose/poly acrylic acid, using cellulose extracted from rice straw via alkaline and acidic pulping processes. The research demonstrated alkaline treatment with sodium hydroxide to be more effective for cellulose extraction compared to acidic treatment. Hydrogel synthesis used graft polymerization and chemical crosslinking with potassium persulfate as initiator and epichlorohydrin as a crosslinker. Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TG), and scanning electron microscopy (SEM) characterized the prepared hydrogels. Important factors determining hydrogel competence are swelling ratio and water retention rate. The cellulose hydrogel exhibited the highest swelling ratio in tap water (9811%) with 76.25 wt% water retention and in artificial hard water (3121.43%) with 64.58 wt% retention after 4 days outdoors at 298 K. Finally, hydrogels were investigated extensively for agricultural applications. Fenugreek seeds germinated and grew well (67% germination after 7 days) in normal soil mixed with 10% cellulose hydrogel. Biodegradability testing exhibited 6% degradation after 40 days and 10% after 120 days in an open-air lab at room temperature and 60% humidity.

γ-Irradiation crosslinking of graphene oxide/cellulose nanofiber/poly (acrylic acid) hydrogel as a urea sensing patch

Poly (acrylic acid) (PAA) nanocomposite hydrogel was fabricated as a sensing patch for non-invasive dual detection of urea in sweat. The hydrogel was prepared by γ-irradiation crosslinking of PAA solution incorporated with graphene oxide (GO) and cellulose nanofiber (CNF). With high water-sorption capacity and transparency, the hydrogel was suitable to accommodate coloring reagents and enzymes for colorimetric sensing of urea in sweat. The colorimetric sensor exhibited vivid color change towards the increase of urea concentration in a linear range of 40-80 mM covering a cut-off value (60 mM) for chronic kidney disease (CKD) indication. Furthermore, the hydrogel could be directly applied as a substrate for direct quantitation of urea in sweat by laser desorption ionization mass spectroscopy (LDI-MS). While CNF improved the mechanical properties of the hydrogel, GO played a key role in enhancing laser desorption ionization of urea in LDI-MS and increased the hydrogel functionalities. LDI-MS verified that GO/CNF/PAA hydrogel could act as a direct matrix for promoting urea ionization and these results corresponded well with the colorimetric sensor. Hence, this hydrogel patch might be a potential material to be applied in non-invasive and dual-detection of CKD in medical diagnosis.

Modification of Superabsorbent Hydrogels for Industrial Wastewater Treatment

A breakthrough in superabsorbent hydrogel (SAH) preparation was studied in the current issue by blending potato starch and acrylic acid for wastewater treatment. Gamma irradiation source (60Co irradiation) was used to irradiate SAH from 1 to 10 kGy dose at room temperature (~27°C). The swelling ratio, water absorption, equilibrium water content, and gel fraction properties of the hydrogel were investigated. The as-prepared hydrogel treated with KOH (THG) showed excellent absorption capacity but less mechanical stability compared to untreated hydrogel (UHG). The gel fraction of treated SAH was slightly lower in methanol, but the utmost in water at 5 kGy infers the proper grafting of SAH at this point. The prepared SAH was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) to investigate the surface morphology and molecular interaction, respectively. Moreover, this study’s focal point is to propose an alternative method to remove chromium and methylene blue by SAH from industrial wastewater. The Cr adsorption capacity of UHG was higher than that of THG because the proton’s replacement is easier than that of K by Cr. On the other hand, THG was found to be more efficient in removing methylene blue from industrial wastewater due to the presence of an easily ionized group (–COOK) in SAH. Therefore, the hydrogel can be proposed as a potential superabsorbent to remove heavy metals and organic dyes from industrial wastewater.

Alginate Hydrogels with Aloe vera: The Effects of Reaction Temperature on Morphology and Thermal Properties

In this study, we investigated the impact of reaction temperature on the physicochemical, structural, morphological, and thermal properties of sodium alginate/poly (vinyl alcohol)-based hydrogels, both in the pure form and with the addition of 20% (v/v) Aloe vera solution. The materials were prepared by chemical crosslinking at temperatures in the range of 65–75 °C. Poly (ethylene glycol) diacrylate was used as a crosslinking agent. The extent to which the crosslinking reaction proceeded was studied as a function of the reaction temperature, along with the thermal properties and morphology of the final materials. A measurement of gel fraction, in agreement with differential scanning calorimetry and Fourier transform infrared spectroscopy, showed that a higher temperature of reaction promoted the crosslinking reaction. On the basis of the aforementioned techniques, as well as by energy dispersive X-ray analysis under an electron microscope, it was also shown that the bioadditive Aloe vera promoted the crosslinking reaction.

Hydrogels as Potential Nano-, Micro- and Macro-Scale Systems for Controlled Drug Delivery

This review is an extensive evaluation and essential analysis of the design and formation of hydrogels (HGs) for drug delivery. We review the fundamental principles of HGs (their chemical structures, physicochemical properties, synthesis routes, different types, etc.) that influence their biological properties and medical and pharmaceutical applications. Strategies for fabricating HGs with different diameters (macro, micro, and nano) are also presented. The size of biocompatible HG materials determines their potential uses in medicine as drug carriers. Additionally, novel drug delivery methods for enhancing treatment are discussed. A critical review is performed based on the latest literature reports.