Adding carbonyl groups into the hydrogel matrix improves the stability and biocompatibility of the hydrogels, making them suitable for different biomedical applications. In this review article, we will discuss the use of hydrogels based on polysaccharides modified by oxidation, with particular attention paid to the introduction of carbonyl groups. These hydrogels have been developed for several applications in tissue engineering, drug delivery, and wound healing. The review article discusses the mechanism by which oxidized polysaccharides can introduce carbonyl groups, leading to the development of hydrogels through cross-linking with proteins. These hydrogels have tunable mechanical properties and improved biocompatibility. Hydrogels have dynamic properties that make them promising biomaterials for various biomedical applications. This paper comprehensively analyzes hydrogels based on cross-linked proteins with carbonyl groups derived from oxidized polysaccharides, including microparticles, nanoparticles, and films. The applications of these hydrogels in tissue engineering, drug delivery, and wound healing are also discussed.

The main goal of this research was to create biocompatible hydrogels using gelatin and a double cross-linking technique involving both covalent and ionic bonds to immobilize propolis. The covalent bonds were formed through Schiff base cross-links between protein-free amino groups (NH₂) from the lysine residue and aldehyde groups (CHO) produced by oxidizing sodium alginate with NaIO₄, while the ionic bonds were achieved using Mg²⁺ ions. Hydrogel films were obtained by varying the molar ratios of –CHO/–NH₂ under different pH conditions (3.5 and 5.5). The presence of aldehyde groups in the oxidized sodium alginate (OSA) was confirmed using FTIR and NMR spectroscopy. The oxidation degree was monitored over 48 h, and the influence of temperature was examined. Results showed that higher –CHO/–NH₂ molar ratios led to increased conversion index values of NH₂ groups, and a decrease in swelling degree values was observed in mediums with pH values of 5.5 and 7.4. The encapsulation and release efficiency of propolis decreased with an increase in the hydrogel cross-linking degree. UV irradiation enhanced the antioxidant activity of both free and encapsulated propolis. These findings offer valuable insights for the biomedical and pharmaceutical fields into designing biocompatible hydrogels for propolis immobilization, with potential for controlled release.

The main goal of this research is to create biocompatible hydrogels using gelatin and a double cross-linking technique involving both covalent and ionic bonds to immobilize propolis. Covalent bonds are formed through Schiff base cross-links between protein-free amino groups (NH2) from the lysine residue and aldehyde groups (CHO) produced by oxidizing sodium alginate with NaIO4, while the ionic bonds are achieved using Mg2+ ions. Hydrogel films were obtained by varying the molar ratios -CHO/NH2 under different pH conditions (3.5 and 5.5). The presence of aldehyde groups in the oxidized sodium alginate (OSA) was confirmed using FTIR and NMR spectroscopy. The oxidation degree was monitored over 48 hours, and the influence of temperature was examined. Results showed that higher -CHO/-NH2 molar ratios led to increased conversion index values of NH2 groups, and a decrease in swelling degree values was observed in mediums with pH of 5.5 and 7.4. The encapsulation and release efficiency of propolis decreased with the increase of the hydrogel cross-linking degree. UV irradiation enhanced the antioxidant activity of both free and encapsulated propolis. These findings offer valuable insights into designing biocompatible hydrogels for propolis immobilization, with potential for controlled release in biomedical and pharmaceutical fields.

Currently, in Chlef (Algeria), Municipal solid wastes (MSWs) are treated by landfill. This work proposes the incineration of MSWs, with the bottom ash (BA) generated being used in cement manufacturing. This treatment is a promising way to achieve a circular economy and reduce the environmental impact of MSWs in Chlef and Algeria. This research focused on two major goals. First, it studied the influence of the raw composition of MSWs incinerated on the characteristics of BAs generated. Second, it investigated the recycling of BAs as supplementary cementitious material (SCM). To achieve the above objectives, one tonne of MSWs and 500 kg of organic MSWs generated in the City of Chlef (Algeria) were incinerated in a rotary kiln, and a part of the ordinary Portland cement (OPC) was replaced by 0 wt%, 5 wt%, 10 wt%, and 20 wt% of the two types of the generated BAs. The results show that the oxides and heavy metal contents were not similar in both BAs. The incorporation of both BAs into cement results in an increase in water demand for normal consistency. The results indicate that the soundness values of all the cement pastes are less than 10 mm. From the results, it is important to mention that there was a delay in the initial setting time for cement prepared with BA from the incineration of one tonne of MSW. Both BAs adversely affected strength at a replacement level of 20 wt%. However, the results also show that both BAs are beneficial when used as SCMs at replacement levels of 5 wt% and 10 wt%, as the physical and mechanical properties of the blended types of cement remain comparable to those of OPC.