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: Hydrogels are natural or synthetic polymeric networks, insoluble in water, or sometimes found as colloidal gel where the dispersion medium is water. Hydrogels can absorb approximately 90% water and are regarded as superabsorbent materials hence resembles the natural living tissue, more than any other biological-based materials. Because of its ability to absorb water, they are used to investigate the properties of swollen polymer networks and have wide applications in different fields such as contact lenses, drug delivery systems for proteins, and many others. To make biodegradable, labile chemical bonds are introduced in the main backbone through crosslinking. These unstable bonds can then be broken down by various agents via chemically, physically, or enzymatically, generally by hydrolysis or through some controlled parameters. Hydrogels are frequently used in the medical field. For instance, pH and temperaturesensitive hydrogels may be used in the targeted drug delivery which will be explained in detail in the current review. The other applications of hydrogels will be explained in personal health care products, biomedical, bio-separation, wound healing, tissue engineering, and drug delivery, etc. which make them promising materials in pharmaceutics. They are also used in agriculture and environmental remediation. The purpose of this review is to expose their silent features and biomedical applications.

The development of a solid substrate for the support and stabilization of zero-valent metal nanoparticles (NPs) is the heart of the catalyst system. In the current embodiment, we have prepared solid support comprise of alginate-coated cellulose filter paper (Alg/FP) for the synthesis and stabilization of Co nanoparticles (NPs) named as Alg/FP@Co NPs. Furthermore, Alginate polymer was blended with 1 and 2 weight percent of CoNi NPs to make Alg-CoNi1/FP and Alg-CoNi2/FP, respectively. All these stabilizing matrixes were used as dip-catalyst for the degradation of azo dyes and reduction of 4-nitrophenol (4NP). The effect of initial dye concentration, amount of NaBH4, and catalyst dosage was assessed for the degradation of Congo red (CR) dye by using Alg-CoNi2/FP@Co NPs. Results indicated that the highest kapp value (3.63 × 10−1 min−1) was exhibited by Alg-CoNi2/FP@Co NPs and lowest by Alg/FP@Co NPs against the discoloration of CR dye. Furthermore, it was concluded that Alg-CoNi2/FP@Co NPs exhibited strong catalyst activity against CR, and methyl orange dye (MO) degradation as well as 4NP reduction. Antibacterial activity of the prepared composites was also investigated and the highest l activity was shown by Alg-CoNi2/FP@Co NPs, which inhibit 2.5 cm zone of bacteria compared to other catalysts.

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