Controlled Release of Phosphorus from Superabsorbent Phosphate-Bound Alginate-Graft-Polyacrylamide: Resistance to Soil Cations and Release Mechanism

Biodegradable Dextrin-Based Microgels for Slow Release of Dual Fertilizers for Sustainable Agriculture

In this research, we report dextrin-based biodegradable microgels (PDXE MGs) having phosphate-based cross-linking units for slow release of urea and a potential P source to improve fertilization. PDXE MGs (∼200 nm) are synthesized by cross-linking the lauroyl-functionalized dextrin chains with sodium tripolyphosphate. The developed PDXE MGs exhibit high loading (∼10%) and encapsulation efficiency (∼88%) for urea. It is observed that functionalization of PDXE MGs with lauroyl chains slows down the release of urea (90% in ∼24 days) as compared to nonfunctionalized microgels (PDX MGs) (99% in ∼17 days) in water. Further studies of the developed formulation display that Urea@PDXE MGs significantly boost maize seed germination and overall plant growth as compared to pure urea fertilizer. Moreover, analysis of maize leaves obtained from plants treated with Urea@PDXE MGs reveals 3.5 ± 0.3% nitrogen content and 90 ± 0.7 mg/g chlorophyll content. These values are significantly higher than 1.4 ± 0.6% nitrogen content and 48 ± 0.05 mg/g chlorophyll content obtained by using bare urea. Further, acid phosphatase activity in roots is reduced upon treatment with PDXE MGs and Urea@PDXE MGs, suggesting the availability of P upon degradation of PDXE MGs by the amylase enzyme in soil. These experimental results present the developed microgel-based biodegradable formulation with a slow release feature as a potential candidate to move toward sustainable agriculture practices.

Preparation and characterization of slow-release fertilizers loaded guar gum-g-poly methylmethacrylate-cl-polylactic acid (Gg-g-PMMA-cl-PLA) hydrogel and its effect on wheat growth

In order to reduce the harmful effects of synthetic non-biodegradable hydrogel, biopolymers have attracted attention, particularly for use in slow-release fertilizers. The current attempt intends to develop a hydrogel from biopolymers for sustainable release of water and nutrients in soil. Here, guar gum is used as a polysaccharide, MMA as a monomer, KPS as an initiator, and Polylactic acid as a cross-linker. Further investigation is done to study synthesized hydrogel in the development of wheat crop. Biodegradation study shows that it's environmentally favorable and degradable, contributing nutrients to the soil as it decomposes. Fertilizer release studies in soil and water show that the timing of the nutrient release is delayed, improving soil water holding capacity and retention studies. The agronomic parameters show that fertilizers-loaded hydrogel has a positive effect on physiological, morphological characteristics like shoot length, root length, number of shoots and roots, shoot weight and root weight, chlorophyll content, and most notably, fruiting efficiency is enhanced as compared with commercially available hydrogel. ATR-FTIR, SEM-EDX, TGA-DTA, and XRD analysis used to confirm successful loading of fertilizers and biodegradation of hydrogel. The encouraging findings suggested that this hydrogel could be used as a multifunctional, fertilizers-loaded hydrogel in crop production.

Significance of biopolymer-based hydrogels and their applications in agriculture: a review in perspective of synthesis and their degree of swelling for water holding

Hydrogels are three-dimensional polymer networks that are hydrophilic and capable of retaining a large amount of water. Hydrogels also can act as vehicles for the controlled delivery of active compounds. Bio-polymers are polymers that are derived from natural sources. Hydrogels prepared from biopolymers are considered non-toxic, biocompatible, biodegradable, and cost-effective. Therefore, bio-polymeric hydrogels are being extensively synthesized and used all over the world. Hydrogels based on biopolymers finds important applications in the agricultural field where they are used as soil conditioning agents as they can increase the water retention ability of soil and can act as a carrier of nutrients and other agrochemicals. Hydrogels are also used for the controlled delivery of fertilizer to plants. In this review, bio-polymeric hydrogels based on starch, chitosan, guar gum, gelatin, lignin, and alginate polymer have been discussed in terms of their synthesis method, swelling behavior, and possible agricultural application. The urgency to address water scarcity and the need for sustainable water management in agriculture necessitate the exploration and implementation of innovative solutions. By understanding the synthesis techniques and factors influencing the swelling behavior of these hydrogels, we can unlock their full potential in fostering sustainable agriculture and mitigating the challenges posed by an ever-changing environment.

Composite hydrogel based on alginate-g-poly(acrylamide)/carbon nanotubes for solid phase extraction of metals from corn cereal samples

Composite hydrogels containing nanofillers are extensively applied in the sorption of different compounds from aqueous solutions; however, this ability is poorly exploited in the extraction and pre-concentration of analytes from complex matrices. As a contribution to this field, this study reports the synthesis of a composite hydrogel of alginate-g-poly(acrylamide) matrix filled with functionalized multi-walled carbon nanotubes (ALG-g-PAAM/MWCNT-f). This composite served as a solid-phase extractor (SPE) for the separation of Pb²⁺ and Cd²⁺ ions from a digested corn cereal sample before their analytical determination. After composite characterization, a series of experiments using low dosages of ALG-g-PAAM/MWCNT-f demonstrated that the composite has a higher sorption capacity for Pb²⁺ (5.1 mg/g) and Cd²⁺ (3.9 mg/g) under favorable experimental conditions. As demonstrated, the presence of the MWCNT-f benefited the SPE performance of the composite. The sorption of both cations followed the pseudo-first order kinetics, while the experimental data were well-fitted by the Freundlich isotherm. Also, ALG-g-PAAM/MWCNT-f showed selectivity for Pb²⁺, and it is reusable up to 10 times without losing sorption performance. After sorption and extraction, both metals were completely recovered, facilitating their quantification by the MIP OES technique. In short, ALG-g-PAAM/MWCNT-f was an effective SPE for the separation and extraction of Pb²⁺ and Cd²⁺, which can be beneficial for food control and safety.

Preparation of Poly(Acrylic Acid-co-acrylamide)-Grafted Deproteinized Natural Rubber and Its Effect on the Properties of Natural Rubber/Silica Composites

This work aims to enhance the polarity of natural rubber by grafting copolymers onto deproteinized natural rubber (DPNR) to improve its compatibility with silica. Poly(acrylic acid-co-acrylamide)-grafted DPNR ((PAA-co-PAM)-DPNR) was successfully prepared by graft copolymerization with acrylic acid and acrylamide in the latex stage, as confirmed by FTIR. The optimum conditions to obtain the highest conversion, grafting efficiency, and grafting percentage were a reaction time of 360 min, a reaction temperature of 50 °C, and an initiator concentration of 1.0 phr. The monomer conversion, grafting efficiency, and grafting percentage were 91.9–94.1, 20.8–38.9, and 2.1–9.9%, respectively, depending on the monomer content. It was shown that the polarity of the natural rubber increased after grafting. The (PAA-co-PAM)-DPNR was then mixed with silica to prepare DPNR/silica composites. The presence of the (PAA-co-PAM)-DPNR and silica in the composites was found to improve the mechanical properties of the DPNR. The incorporation of 10 phr of silica into the (PAA-co-PAM)-DPNR with 10 phr monomer increased its tensile strength by 1.55 times when compared to 10 phr of silica loaded into the DPNR. The silica-filled (PAA-co-PAM)-DPNR provided s higher storage modulus, higher Tg, and a lower tan δ peak, indicating stronger modified DPNR/silica interactions and greater thermal stability when compared to silica-filled DPNR.

3D Bioprinted Alginate-Silk-Based Smart Cell-Instructive Scaffolds for Dual Differentiation of Human Mesenchymal Stem Cells

Designing smart bioinks, which can provide multifunctionality and instructive cues to cells, is a current need of the tissue engineering field. Addressing these parameters, this work aims at developing a smart dual 3D bioprinted scaffold that is capable of differentiating human mesenchymal stem cells into two different lineages within the same construct without providing any exogenous cues. Here, biocompatible alginate- and silk-based bioinks were developed to print self-standing structures with the ability of spatially controlled differentiation of the encapsulated hMSCs. We present this proof of concept and have demonstrated a smart design where the incorporation of phosphate groups enhanced the osteogenic differentiation, whereas the addition of silk promoted the chondrogenic differentiation. Altogether, the present work suggests the potential of the developed bioinks for use in creating clinically viable osteochondral grafts.

Biosynthesis and Characterization of Silver Nanoparticles Produced by Phormidium ambiguum and Desertifilum tharense Cyanobacteria

The world faces a challenge with the pervasion of multidrug-resistant bacteria that encourages scientists to develop and discover alternative, ecofriendly, and easy-to-produce new antibacterial agents. Our work is part of the greater effort of scientists around the world to achieve this goal by the biological synthesis of silver nanoparticles using cyanobacterial extracellular and intracellular components as nonchemical reducing agents. Two Egyptian cyanobacteria were isolated and identified according to 16S rRNA gene sequencing as Phormidium ambiguum and a novel species Desertifilum tharense. The sequences were deposited with accession numbers MW762709 and MW762710 for Desertifilum tharense and Phormidium ambiguum, respectively, in the GenBank. The results of UV-Vis analysis showed promising extracellular Ag-NPs synthesis by Desertifilum tharense and Phormidium ambiguum under light conditions. Therefore, these Ag-NPs were characterized and evaluated for antibacterial and antioxidant activity. TEM and SEM analyses revealed the spherical crystals with face-centered cubic structures and size range of 6.24-11.4 nm and 6.46-12.2 nm for Ag-NPs of Desertifilum tharense and Phormidium ambiguum, respectively. XRD and EDX results confirmed the successful synthesis of Ag-NPs in their oxide form or chloride form. The FTIR spectrum data confirmed the presence of hydroxyl and amide groups. Desertifilum tharense Ag-NPs displayed the largest inhibition zone that ranged from 9 mm against Micrococcus luteus ATCC 10240 to 25 mm against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300. For Phormidium ambiguum Ag-NPs, the inhibition zone diameter was in the range of 9 mm to 18 mm. The biosynthesized Ag-NPs significantly inhibited the growth of medically important resistance-pathogenic Gram-positive and Gram-negative bacteria. The Ag-NPs of Phormidium ambiguum exhibited the highest scavenging activity of 48.7% when compared with that of Desertifilum tharense, which displayed 43.753%.