Preparation and properties of temperature-sensitive soy protein/poly(N -isopropylacrylamide) interpenetrating polymer network hydrogels

The Hofmeister series: Anion effect on microbial transglutaminase cross-linked soybean protein isolate hydrogels

In this paper, the possibility of the kosmotropic anion (CO32-, Citrate3-, SO42-, H2PO4-, CH3COO- and Cl-) to improve the gel properties of microbial transglutaminase (MTG)-crosslinked soybean isolate protein (SPI)-based hydrogels was explored using a soaking strategy. The results of this experiment demonstrated that the hardness of the hydrogel undergoes different degrees of enhancement after different salt treatments in the following order: H2PO4- > CH3COO- > SO42- > Citrate3- > Cl- > CO32-. Rheological results showed that salt treatment led to enhancement of the energy storage modulus of the hydrogels. Further experiments indicated that the water-binding capacity of different salts depended on the salting out effect. Based on the Hofmeister effect, hardness-enhanced SPI-based hydrogels were successfully prepared. The Hofmeister effect offers a simple, an effective and a novel method for the preparation of functional SPI hydrogels.

Biomedical applications of stimuli-responsive "smart" interpenetrating polymer network hydrogels

In recent years, owing to the ongoing advancements in polymer materials, hydrogels have found increasing applications in the biomedical domain, notably in the realm of stimuli-responsive "smart" hydrogels. Nonetheless, conventional single-network stimuli-responsive "smart" hydrogels frequently exhibit deficiencies, including low mechanical strength, limited biocompatibility, and extended response times. In response, researchers have addressed these challenges by introducing a second network to create stimuli-responsive "smart" Interpenetrating Polymer Network (IPN) hydrogels. The mechanical strength of the material can be significantly improved due to the topological entanglement and physical interactions within the interpenetrating structure. Simultaneously, combining different network structures enhances the biocompatibility and stimulus responsiveness of the gel, endowing it with unique properties such as cell adhesion, conductivity, hemostasis/antioxidation, and color-changing capabilities. This article primarily aims to elucidate the stimulus-inducing factors in stimuli-responsive "smart" IPN hydrogels, the impact of the gels on cell behaviors and their biomedical application range. Additionally, we also offer an in-depth exposition of their categorization, mechanisms, performance characteristics, and related aspects. This review furnishes a comprehensive assessment and outlook for the advancement of stimuli-responsive "smart" IPN hydrogels within the biomedical arena. We believe that, as the biomedical field increasingly demands novel materials featuring improved mechanical properties, robust biocompatibility, and heightened stimulus responsiveness, stimuli-responsive "smart" IPN hydrogels will hold substantial promise for wide-ranging applications in this domain.

Phase transition and potential biomedical applications of thermoresponsive compositions based on polysaccharides, proteins and DNA: A review

Smart thermoresponsive polymers have long attracted attention as materials of a great potential for biomedical applications, mainly for drug delivery, tissue engineering and wound dressing, with a special interest to injectable hydrogels. Poly-N-isopropylacrylamide (PNIPAM) is the most important synthetic thermoresponsive polymer due to its physiologically relevant transition temperature. However, the use of unmodified PNIPAM encounters such problems as low biodegradability, low drug loading capacity, slow response to thermal stimuli, and insufficient mechanical robustness. The use of natural polysaccharides and proteins in combinations with PNIPAM, in the form of grafted copolymers, IPNs, microgels and physical mixtures, is aimed at overcoming these drawbacks and creating dual-functional materials with both synthetic and natural polymers' properties. When developing such compositions, special attention should be paid to preserving their key property, thermoresponsiveness. Addition of hydrophobic and hydrophilic fragments to PNIPAM is known to affect its transition temperature. This review covers various classes of natural polymers - polysaccharides, fibrous and non-fibrous proteins, DNA - used in combination with PNIPAM for the prospective biomedical purposes, with a focus on their phase transition temperatures and its relation to the natural polymer's structure.

Locust bean gum provides excellent mechanical and release attributes to soy protein-based natural hydrogels

The current study concentrated on designing soy protein (SP)-based natural hydrogels in the presence of locust bean gum (LBG). For this, the gums were recovered from the kernel of the relevant plant and incorporated into SP gel models. Three more hydrogels were fabricated using commercial carbohydrates (gum Arabic (GA), maltodextrin (MD), and pectin (PC)) to decipher exactly the ability of LBG in these models. The chemical and morphological structures of the samples were elaborated by FTIR and SEM analyses. The coexistence of protein and carbohydrates led to an enhancement in functional (water holding capacity (WHC), swelling ratio, protein leachability, volumetric gel index (VGI)) and mechanical (textural and rheological behavior) features of natural gels compared to SP alone (control) but the quality of hydrogels was impressed by the carbohydrate type. Hydrogels designed with LBG came to the fore in terms of these attributes. Additionally, these gel models created awareness for phenolic delivery.

Mechanical properties of PNIPAM based hydrogels: A review

Materials which adjust their properties in response to environmental factors such as temperature, pH and ionic strength are rapidly evolving and known as smart materials. Hydrogels formed by smart polymers have various applications. Among the smart polymers, thermoresponsive polymer poly(N-isopropylacrylamide)(PNIPAM) is very important because of its well defined structure and property specially its temperature response is closed to human body and can be finetuned as well. Mechanical properties are critical for the performance of stimuli responsive hydrogels in diverse applications. However, native PNIPAM hydrogels are very fragile and hardly useful for any practical purpose. Intense researches have been done in recent decade to enhance the mechanical features of PNIPAM hydrogel. In this review, several strategies including interpenetrating polymer network (IPN), double network (DN), nanocomposite (NC) and slide ring (SR) hydrogels are discussed in the context of PNIPAM hydrogel.

Investigation of soy protein hydrogels for biomedical applications: Materials characterization, drug release, and biocompatibility

Soy protein is emerging as a novel material for biomedical applications due to its abundance in nature, ease of isolation and processing, and inherent properties for mediating cell adhesion and growth. In this study, mechanically robust soy protein hydrogels were fabricated with varying weight percentages in water (15, 18, and 20 wt.%) without the use of chemical modifiers or crosslinkers. This fabrication method is beneficial because it allows for the direct injection of these soy hydrogels in vivo. The material properties, drug releasing capability, and biocompatibility in vitro and in vivo were assessed. The different concentrations of soy protein varied the rheological, swelling, and mechanical properties and affected the release of the model drug fluorescein from the hydrogels in vitro. Higher weight percent of soy increased the robustness of the hydrogels and released a lower amount of fluorescein over one week. Viability and growth of seeded L929 mouse fibroblasts demonstrated that the hydrogels were biocompatible in vitro for one week. Soy hydrogels were injectable in vivo into the subcutaneous pocket of mice, and histological staining showed minimal fibrous capsule formation for up to 20 days. The ease of fabrication and tailorable properties of soy hydrogels render it a promising biomaterial for tissue engineering and drug delivery applications, particularly for wound healing.

Mechanical, thermal and surface properties of polyacrylamide/dextran semi-interpenetrating network hydrogels tuned by the synthesis temperature

The mechanical, rheological, thermal, and surface behaviors of three polyacrylamide/dextran (PAAm/Dx) semi-interpenetrating polymer network (semi-IPN) hydrogels, prepared at 22°C, 5°C and −18°C, were investigated. The results were compared with those obtained on cross-linked PAAm without Dx synthesized under the same conditions. Hydrogels prepared at the lowest temperature were the most mechanically stable. The thermal stability of the semi-IPN hydrogels is slightly lower than the corresponding PAAm gels, irrespective of preparation temperature. The water vapor sorption capacity depended on the presence of Dx as well as preparation temperature, which determines the network morphology.