Fabrication of multifunctional Guar gum-silver nanocomposite hydrogels for biomedical and environmental applications.

Poly(acrylamide-co-acrylamidoglycolic acid)/guar gum@ Ag-nanocomposite (AgNC@PAAG) hydrogels has been fabricated by a green protocol utilizing rhubarb stem-extract as bioreductant. The prepared nanocomposites (NCs) are formulated by varying guar gum (GG) polymer and cross-linker content, and used remarkably to study the release of an anticancer drug, 5-fluorouracil (FU). The AgNC@PAAG has demonstrated its potential in bacterial inactivation and p-nitrophenol (PNP) reduction. The AgNC@PAAG hydrogels showed extended FU release time, which was up to 23 h in pH 7.4. The higher zone of inhibition was documented for AgNC@PAAG against B. subtilis and E. coli. It was noticed that, the inhibition activity of AgNC@PAAG, was directly proportional to cross-linker content than the GG polymer. The efficiency of AgNC@PAAG as a nanocatalyst was evaluated for a model reduction reaction of p-nitrophenol (PNP) reduction by aqueous sodium borohydride (NaBH4), with an apparent rate constant of 121.8 × 10-3 min-1 at ambient temperature. The proposed nanocatalysts are reliable and recyclable, demonstrated its catalytic recycle efficacy of 85% after the third successive run. These NCs robust its biological and catalytic activity after embedding silver nanoparticles (AgNPs) by the bioreduction process; these optimized nanocatalysts can be remarkably used in biomedical healthcare sectors and industrial catalysis.

Palem RR ，Shimoga G ，Kang TJ ，Lee SH ... -  《-》

Self-healable and dual-functional guar gum-grafted-polyacrylamidoglycolic acid-based hydrogels with nano-silver for wound dressings.

Dual-functional carbohydrate polymer-based silver nanocomposite (AgNC) hydrogels with self-healing, injectable, and bacterial inactivation properties have attracted particular attention in the wound dressing field. In this study, a rapid formation of AgNC hydrogels were prepared via in situ addition of guar gum-grafted-polyacrylamidoglycolic acid (GG-g-PAGA) polymer and silver nitrate (AgNO3) and sodium borohydride (NaBH4). The GG-g-PAGA polymer and its AgNC hydrogels were analyzed by FTIR, 1H and 13C NMR, UV-vis spectra, FE-SEM, EDX, and FE-TEM. The GG-g-PAGA@AgNC hydrogels exhibited self-healing ability, injectability, stretchability, flowability, high swelling, porosity, upright mechanical behavior, and biodegradability. Moreover, their bacterial inactivation and cytotoxicity were tested against wound pathogens and skin fibroblast cells, respectively. Therefore, incorporating GG-g-PAGA@AgNC hydrogels could be a versatile strategy to speed up wound healing processes, but a clinical trial is still required for its medical applications.

Palem RR ，Madhusudana Rao K ，Kang TJ 《-》

In situ generation of silver nanoparticles within crosslinked 3D guar gum networks for catalytic reduction.

The direct use of guar gum (GG) as a green reducing agent for the facile production of highly stable silver nanoparticles (Ag NPs) within this biopolymer and subsequent crosslinking with borax to form crosslinked Ag@GG beads with a 3D-structured network are presented here. These crosslinked Ag@GG beads were characterized using UV-vis absorption spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy, and then tested as a solid-phase heterogenerous catalyst for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of excess borohydride. The results indicate that these crosslinked Ag@GG beads show excellent catalytic performance for the reduction of 4-NP within 20 min and can be readily used for 10 successive cycles.

Zheng Y ，Zhu Y ，Tian G ，Wang A ... -  《-》

Highly stable silver nanoparticles containing guar gum modified dual network hydrogel for catalytic and biomedical applications.

Although many preparation methods have been reported till date, it is still a great challenge to prepare silver nanoparticles (AgNPs) that simultaneously possess high stability and enhanced applicability. We report a rapid and efficient synthesis of AgNPs containing polyvinyl alcohol (PVA)-guar gum (GG) smart hydrogel composite, which exhibited pH-dependent swelling and enhanced mechanical strength. The AgNPs were synthesized in situ in the PVA-GG hydrogel from various concentrations of the AgNO3 precursor solution in the presence of NaBH4. Stable AgNPs (90 days) of 10-20 nm uniformly dispersed in PVA-GG hydrogel was obtained. Simultaneously, at the optimum concentration of AgNO3 (0.01 M), the tensile strength and elongation at break were enhanced by 74 % and 11 %, and swelling capacity was increased by 18 % as compared to PVA-GG hydrogel (control). The PVA-GG-AgNPs hydrogel composite exhibited excellent catalytic activity and antibacterial property, which makes them a suitable candidate for industrial applications.

Deka R ，Sarma S ，Patar P ，Gogoi P ，Sarmah JK ... -  《-》

Electrically conducting silver/guar gum/poly(acrylic acid) nanocomposite.

This article describes the synthesis of an electrically conducting silver/guar gum/poly(acrylic acid) nanocomposite hydrogel. The synthesis process started with grafting acrylic acid monomers onto the natural polymer guar gum by the use of ammonium persulphate as a free radical initiator in acid medium. Guar gum/poly(acrylic acid) graft copolymer was separated from the polymerization medium, purified and subjected to crosslinking treatment, using alkaline epichlorohydrin as a crosslinking agent. Silver nitrate solution was added during the crosslinking treatment in varying concentrations, that the reaction conditions affect crosslinking of guar gum/poly(acrylic acid) graft copolymer to a hydrogel, as well as reduction of silver nitrate to silver nanoparticles, giving rise to the formation of silver/guar gum/poly(acrylic acid) nanocomposite. Factors affecting the grafting reaction as well as those affecting the crosslinking/reduction treatment were optimized. The so synthesized nanocomposite hydrogel samples were fully characterized, regarding their contents of silver nanoparticles and swelling ratio. The electrical conductivity of the nanocomposite hydrogel was studied and it was found to be affected by the swelling ratio of the hydrogel as well as its content of silver nanoparticles.

Abdel-Halim ES ，Al-Deyab SS 《-》