Preparation and Stability Study of an Injectable Hydrogel for Artificial Intraocular Lenses

Currently available intraocular lenses (IOLs) on the market often differ significantly in elastic modulus compared to the natural human lens, which impairs their ability to respond effectively to the tension of the ciliary muscles for focal adjustment after implantation. In this study, we synthesized a polyacrylamide-sodium acrylate hydrogel (PAH) through the cross-linking polymerization of acrylamide and sodium acrylate. This hydrogel possesses excellent biocompatibility and exhibits several favorable properties. Notably, the hydrogel demonstrates high transparency (94%) and a refractive index (1.41 ± 0.07) that closely matches that of the human lens (1.42). Additionally, it shows strong compressive strength (14.00 kPa), good extensibility (1400%), and an appropriate swelling ratio (50 ± 2.5%). Crucially, the tensile modulus of the hydrogel is 2.07 kPa, which closely aligns with the elastic modulus of the human lens (1.70-2.10 kPa), enabling continuous focal adjustment under the tension exerted by the ciliary muscles.

Effect of chain structures of monomer on hydroxyethyl cellulose-based superabsorbent properties and improvement of chickpeas plant growth of water deficit-stressed

The aim of this research was evaluation of the influence of distance between zwitterionic monomer ions on the performance of superabsorbents. For this purpose, two zwitterionic monomers 4-(3-aminopropyl) amino-4-oxo-2-butenoic acid (APOB) and 4-(6-aminohexyl) amino-4-oxo-2-butenoic acid (AHOB) were prepared and applied for synthesis of two new superabsorbents through graft copolymerization onto hydroxyethyl cellulose (HEC) in the presence of acrylic acid (AA). In synthesis of superabsorbents factors such as the highest water absorbency capacity, absorbency rate, gel strength, and environmental problems should be resolved or improved. The results demonstrated that the water absorbency capacity and rate parameters (τ) of HEC-g-p(AA-co-APOB) and HEC-g-p(AA-co-AHOB) in distilled water were 986.62, 664.38 g/g, and 98.04, 140.84 min, respectively. The biodegradability of HEC-g-p(AA-co-APOB) was approximately 4 times more than HEC-g-p(AA-co-AHOB). However, based on the rheological analyses (G'/G″) HEC-g-p(AA-co-AHOB) was stronger than the other. Additionally, studies of water retention on soil containing HEC-g-p(AA-co-AHOB) superabsorbent (soil with 0.25 wt% material) showed that the after 30 days has ≤5 % water while soil in the absence of superabsorbent after 10 days completely dried. Studies of the growth of plants in soil demonstrated in the presence of HEC-g-p(AA-co-AHOB) the average length of shoots was 36 cm while without superabsorbent were 25 cm.

Comparison of Structural, Water-Retaining and Sorption Properties of Acrylamide-Based Hydrogels Cross-Linked by Physical and Chemical Methods

Two series of hydrogels based on acrylamide and its copolymers with acrylonitrile and acrylic acid were synthesized by two cross-linking methods - chemical (using N,N'-methylene bis-acrylamide) and physical (using montmorillonite (MMT)) ones. The structure of the gels was characterized by Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The swelling and sorption properties were analyzed as a function of both the monomer composition and the cross-linking method. The shift of the band corresponding to Si-O (995-1030 cm-1 ) confirmed the formation of intercalation structures for MMT-cross-linked gels. Moreover, physically cross-linked gels demonstrated a non-monotonic dependence of the swelling degree on the MMT concentration, and acrylamide-acrylic acid copolymer MMT-cross-linked gels showed pH sensitivity and the highest swelling degree of 150 g/g. The highest sorption capacity towards cadmium(II) ions was demonstrated by acrylamide-acrylic acid copolymer gels, both covalently cross-linked (30 mg/g) and MMT-cross-linked (8.9 mg/g).

Functional Hydrogels for Agricultural Application

Ten different hydrogels were prepared and analyzed from the point of view of their use in soil. FT-IR spectra, morphology, swelling ability, and rheological properties were determined for their characterization and appraisal of their stability. The aim was to characterize prepared materials containing different amounts of NPK as mineral fertilizer, lignohumate as a source of organic carbon, and its combination. This study of stability was focused on utility properties in their application in soil-repeated drying/re-swelling cycles and possible freezing in winter. Lignohumate supported the water absorbency, while the addition of NPK caused a negative effect. Pore sizes decreased with NPK addition. Lignohumate incorporated into polymers resulted in a much miscellaneous structure, rich in different pores and voids of with a wide range of sizes. NPK fertilizer supported the elastic character of prepared materials, while the addition of lignohumate shifted their rheological behavior to more liquid. Both dynamic moduli decreased in time. The most stable samples appeared to contain only one fertilizer constituent (NPK or lignohumate). Repeated re-swelling resulted in an increase in elastic character, which was connected with the gradual release of fertilizers. A similar effect was observed with samples that were frozen and defrosted, except samples containing a higher amount of NPK without lignohumate. A positive effect of acrylamide on superabsorbent properties was not confirmed.

Superabsorbent Polymer Sponge for Saliva Absorption Pad

Aim:

Saliva is a significant hindrance to most dental procedures (e.g., root canal treatment) as the flow of saliva increases in patients undergoing dental treatment due to anxiety. Saliva absorption pads based on superabsorbent polymers can provide a dry oral environment to ease the dental treatment procedure and reduce the swallowing reflexes common during cotton use. This study focused on developing an indigenous saliva absorption pad using biodegradable superabsorbent polymer (BSAP) sponges.

Materials and Methods:

BSAP sponges were synthesized using carboxymethyl cellulose (CMC) as the base matrix. Different crosslinking mechanisms were implemented to prepare BSAP sponges, such as ionic crosslinking using aluminum ammonium sulfate (AlAS) and chemical crosslinking using methylene bisacrylamide. Three different BSAP sponges (Sap-2, SAP-PAA-1, and SAP-PAA-2) were characterized for their free swell capacity and thermal degradation kinetics along with other characterization techniques to optimize the composition for saliva absorption pad. One-way ANOVA was used for statistical evaluation.

Results:

SAP-2, synthesized using 10 wt.% AlAS showed the highest free swell capacity in water and saline (83.21 ± 3.8 g/g and 40.7 ± 3.4 g/g, respectively). However, the moisture content of the particular BSAP sponge was higher (~13%) compared to the standard limit (ISO 17190-4:2001(E)). It was observed that as the crosslinking density increases free swell capacity increases to a threshold point and decreases thereafter. As reported earlier, percentage swelling was controlled by multiple factors including crosslinking that opposes swelling and polymer/water interaction and Donnan pressure that promotes swelling.

Conclusion:

BSAP sponge based on crosslinked CMC matrix is highly advantageous in developing saliva absorption pad. Hydrophobic surface modification is recommended to reduce the moisture content to improve the storage stability of BSAP sponges.

Maleic acid as an important monomer in synthesis of stimuli-responsive poly(acrylic acid-co-acrylamide-co-maleic acid) superabsorbent polymer

Poly(acrylic acid-co-acrylamide-co-maleic acid) (p(AA-co-AM-co-MA)) superabsorbent polymer was synthesized from acrylic acid (AA), acrylamide (AM), and maleic acid (MA) via free radical copolymerization. Results showed the presence of maleic acid in structure of superabsorbent has the key and superior role in creating a smart superabsorbent. The structure, morphology, and strength of the superabsorbent were characterized using FT-IR, TGA, SEM, and rheology analysis. The effect of different factors was investigated to determine the ability of water absorbency of the superabsorbent. According to optimized conditions, the water absorbency capacity of the superabsorbent in distilled water (DW) was 1348 g/g and in a solution containing 1.0 wt.% NaCl (SCS) was 106 g/g. The water retention ability of the superabsorbent was also investigated. The kinetic swelling of superabsorbent was identified by Fickian diffusion and Schott's pseudo-second-order model. Furthermore, the reusability of superabsorbent was studied in distilled water and saline solution. The ability of superabsorbent was investigated in simulated urea and glucose solutions, and very good results were obtained. The response ability of the superabsorbent was confirmed by swelling and shrinking behavior against changes of temperature, pH, and ionic strength.

Synthesis of pH-sensitive crosslinked guar gum-g-poly(acrylic acid-co-acrylonitrile) for the delivery of thymoquinone against inflammation

The present work aims to synthesize the pH-sensitive crosslinked guar gum-g-poly(acrylic acid-co-acrylonitrile) [guar-g-(AA-co-ACN)] via microwave-assisted technique for the sustained release of thymoquinone. The synthesized material [guar-g-(AA-co-ACN)] was optimized by varying synthetic parameters viz. monomer concentration, reaction time, and microwave power to obtain the maximum yield of the crosslinked guar gum grafted product as well as maximum encapsulation of thymoquinone. The synthesized material [guar-g-poly(AA-co-ACN)] was characterized by FT-IR, SEM, XRD, NMR, zeta potential, and thermal techniques. This synthesized material was used to encapsulate thymoquinone (TQ) for effective nanotherapeutic delivery. In-vitro thymoquinone release behavior of guar-g-poly(AA-co-ACN) based nanoparticles (NpTGG) was investigated. The maximum thymoquinone release (78%) was achieved at pH 7.4 and time (6 h). The NpTGG also exhibited better antioxidant activity and hemocompatibility as compared to thymoquinone. Cytotoxicity of uar-g-(AA-co-ACN) and NpTGG was also evaluated against the human kidney VERO cell line and found to be nontoxic. Current research provides a cost-effective and green approach for the synthesis of guar-g-(AA-co-ACN) and NpTGG for sustained release of thymoquinone.