Property modulation of the alginate-based hydrogel via semi-interpenetrating polymer network (semi-IPN) with poly(vinyl alcohol)

Polysaccharide Hydrogel-Assisted Biosensing Platforms for Point-of-Care Use

Point-of-care (POC) use is one of the essential goals of biosensing platforms. Because the increasing demand for testing cannot be met by a centralized laboratory-based strategy, rapid and frequent testing at the right time and place will be key to increasing health and safety. To date, however, there are still difficulties in developing a simple and affordable, as well as sensitive and effective, platform that enables POC use. In terms of materials, hydrogels, a unique family of water-absorbing biocompatible polymers, have emerged as promising components for the development of biosensors. Combinations of hydrogels have various additional applications, such as in hydrophilic coatings, nanoscale filtration, stimuli-responsive materials, signal enhancement, and biodegradation. In this review, we highlight the recent efforts to develop hydrogel-assisted biosensing platforms for POC use, especially focusing on polysaccharide hydrogels like agarose, alginate, chitosan, and so on. We first discuss the pros and cons of polysaccharide hydrogels in practical applications and then introduce case studies that test different formats, such as paper-based analytical devices (PADs), microfluidic devices, and independent platforms. We believe the analysis in the present review provides essential information for the development of biosensing platforms for POC use in resource-limited settings.

Reinforcement of Dextran Methacrylate-Based Hydrogel, Semi-IPN, and IPN with Multivalent Crosslinkers

The need for new biomaterials to meet the needs of advanced healthcare therapies is constantly increasing. Polysaccharide-based matrices are considered extremely promising because of their biocompatibility and soft structure; however, their use is limited by their poor mechanical properties. In this light, a strategy for the reinforcement of dextran-based hydrogels and interpenetrated polymer networks (semi-IPNs and IPNs) is proposed, which will introduce multifunctional crosslinkers that can modify the network crosslinking density. Hydrogels were prepared via dextran methacrylation (DexMa), followed by UV photocrosslinking in the presence of diacrylate (NPGDA), triacrylate (TMPTA), and tetraacrylate (PETA) crosslinkers at different concentrations. The effect of these molecules was also tested on DexMa-gellan semi-IPN (DexMa/Ge) and, later, on IPN (DexMa/CaGe), obtained after solvent exchange with CaCl2 in HEPES and the resulting Ge gelation. Mechanical properties were investigated via rheological and dynamic mechanical analyses to assess the rigidity, resistance, and strength of the systems. Our findings support the use of crosslinkers with different functionality to modulate the properties of polysaccharide-based scaffolds, making them suitable for various biomedical applications. While no significative difference is observed on enriched semi-IPN, a clear improvement is visible on DexMa and DexMa/CaGe systems when TMPTA and NPGDA crosslinker are introduced at higher concentrations, respectively.

Alginate-based hydrogels mediated biomedical applications: A review

With the development in the field of biomaterials, research on alternative biocompatible materials has been initiated, and alginate in polysaccharides has become one of the research hotspots due to its advantages of biocompatibility, biodegradability and low cost. In recent years, with the further understanding of microscopic molecular structure and properties of alginate, various physicochemical methods of cross-linking strategies, as well as organic and inorganic materials, have led to the development of different properties of alginate hydrogels for greatly expanded applications. In view of the potential application prospects of alginate-based hydrogels, this paper reviews the properties and preparation of alginate-based hydrogels and their major achievements in delivery carrier, dressings, tissue engineering and other applications are also summarized. In addition, the combination of alginate-based hydrogel and new technology such as 3D printing are also involved, which will contribute to further research and exploration.

Incorporation of carboxymethyl chitosan (CMCS) for the modulation of physio-chemical characteristics and cell proliferation environment of the composite hydrogel microspheres

Hydrogels have excellent swelling properties and have been widely applied in tissue engineering because of their similarity to the extracellular matrix (ECM). Sodium alginate (SA) and carboxymethyl chitosan (CMCS) were prepared into hydrogel microspheres with Ca2+crosslinking in our study. The morphology, inner structure, mechanical properties, water content, swelling rate and BMP-2 loading and releasing properties were characterized. Our results showed that the composite SA /CMCS hydrogel microspheres were translucent and spherical in shape with uniform particle size. The incorporation of CMCS further increased the diameters of the microspheres, internal pore structure, water content, and mechanical properties of the SA/CMCS hydrogel microspheres. At the same SA concentration, with the increase of CMSC concentration, the diameter of microspheres could be increased by about 0.4 mm, the water content can be increased about 1%-2%. As for the mechanical properties, the compressive strength can be increased by 0.04-0.1 MPa, and the modulus of elasticity can be increased by 0.1-0.15 MPa. BMP-2 was chosen as a model agent and it could be loaded into SA/CMCS microspheres, and the incorporation of CMCS increased BMP-2 loading. The encapsulated BMP-2 was sustainably releasedin vitro. The leaching solutions of the SA/CMCS hydrogel microspheres exhibited good cytocompatibility and could increase ALP activity, ALP expression, and biomineralization on MC3T3-E1 cells. After 7 d of co-culture, ALP activities in S2.5C2 and S2.5C3 groups was increased by 50% and 45% compared with that of the control group. When embedded in the SA/CMCS microspheres, the MC3T3-E1 cells were evenly distributed inside the hydrogel microspheres and remained viable. Transcriptomic studies showed that incorporation of CMCS induced upregulation of 1141 differentially expressed genes (DEGs) and downregulation of 1614 DEGs compared with SA microspheres. The most significantly enriched pathways were the Wnt and MAPK signaling pathways induced by the incorporation of CMCS and BMP-2. In conclusion, our results indicated that the physiochemical characteristics of the SA hydrogel microspheres could be greatly modulated by CMCS to better mimic the ECM microenvironment and induce osteo-inductive activities of MC3T3-E1 cells.

Semi-IPN polysaccharide-based hydrogels for effective removal of heavy metal ions and dyes from wastewater: a comprehensive investigation of performance and adsorption mechanism

The escalating issue of environmental pollutants necessitates efficient, sustainable, and innovative wastewater treatment technologies. This review comprehensively analyzes the mechanisms and isotherms underlying the adsorption processes of semi-interpenetrating polymer network (semi-IPN) polysaccharide-based hydrogels to remove heavy metal ions and dyes from wastewater. Polysaccharides are extensively utilized in hydrogel synthesis due to their biocompatibility, cost-effectiveness, and non-toxic nature. The synthesis of these hydrogels as semi-IPNs enhances their mechanical and structural robustness and adsorption capacity. This review explores the key parameters affecting adsorption performance, including pH, temperature, contact time, and adsorbent dosage. Findings highlight that semi-IPN polysaccharide-based hydrogels exhibit remarkable adsorption capabilities through electrostatic interactions, ion exchange, and surface complexation. Furthermore, this review highlights the distinct advantages of semi-IPNs over other polymer networks. Semi-IPNs offer improved mechanical stability, higher adsorption efficiencies, and better reusability, making them a promising solution for wastewater treatment. Detailed isotherm models, including Langmuir and Freundlich isotherms, were studied to understand these hydrogels' adsorption behavior and capacity for different pollutants. This study highlights the potential of semi-IPN polysaccharide-based hydrogels as effective adsorbents for heavy metals and dyes and as a promising solution for mitigating environmental pollution. The insights provided herein contribute to developing advanced materials for environmental remediation, aligning with global sustainability goals, and advancing wastewater treatment technology.

3D printing of gellan-dextran methacrylate IPNs in glycerol and their bioadhesion by RGD derivatives

The ever-growing need for new tissue and organ replacement approaches paved the way for tissue engineering. Successful tissue regeneration requires an appropriate scaffold, which allows cell adhesion and provides mechanical support during tissue repair. In this light, an interpenetrating polymer network (IPN) system based on biocompatible polysaccharides, dextran (Dex) and gellan (Ge), was designed and proposed as a surface that facilitates cell adhesion in tissue engineering applications. The new matrix was developed in glycerol, an unconventional solvent, before the chemical functionalization of the polymer backbone, which provides the system with enhanced properties, such as increased stiffness and bioadhesiveness. Dex was modified introducing methacrylic groups, which are known to be sensitive to UV light. At the same time, Ge was functionalized with RGD moieties, known as promoters for cell adhesion. The printability of the systems was evaluated by exploiting the ability of glycerol to act as a co-initiator in the process, speeding up the kinetics of crosslinking. Following semi-IPNs formation, the solvent was removed by extensive solvent exchange with HEPES and CaCl2, leading to conversion into IPNs due to the ionic gelation of Ge chains. Mechanical properties were investigated and IPNs ability to promote osteoblasts adhesion was evaluated on thin-layer, 3D-printed disk films. Our results show a significant increase in adhesion on hydrogels decorated with RGD moieties, where osteoblasts adopted the spindle-shaped morphology typical of adherent mesenchymal cells. Our findings support the use of RGD-decorated Ge/Dex IPNs as new matrices able to support and facilitate cell adhesion in the perspective of bone tissue regeneration.

The optimization of poly(vinyl)-alcohol-alginate beads with a slow-release compound for the aerobic cometabolism of chlorinated aliphatic hydrocarbons

Chlorinated aliphatic hydrocarbons (CAHs), such as cis-1,2-dichloroethylene (cDCE), are prevalent in groundwater at many locations throughout the United States. When immobilized in hydrogel beads with slow-release compounds, the bacteria strain Rhodococcus rhodochrous ATCC 21198 can be used for the in situ bioremediation of cDCE. These hydrogel beads must exhibit high mechanical strength and resist degradation to extend the lifetime of slow-release compounds and bioremediation. We engineered poly(vinyl)-alcohol - alginate (PVA-AG) beads to immobilize ATCC 21198 with the slow-release compound, tetrabutoxysilane (TBOS) that produces 1-butanol as a growth substrate, for high mechanical strength. We optimized three inputs (concentration of PVA, concentration of AG, and the crosslinking time) on two responses (compressive modulus and rate of oxygen utilization) for batch incubation experiments between 1 and 30 days using a design of experiments approach. The predictive models generated from design of experiments were then tested by measuring the compressive strength, oxygen utilization, and abiotic rates of hydrolysis for a predicted optimal bead formulation. The result of this study generated a hydrogel bead with immobilized R. rhodochrous ATCC 21198 and TBOS that exhibited a high compressive modulus on day 1 and day 30, which was accurately predicted by models. These hydrogel beads exhibited low metabolic activity based on oxygen rates on day 1 and day 30 but were not accurately predicted by the models. In addition, the ratio between oxygen utilization and abiotic rates of hydrolysis were observed to be roughly half of what was expected stoichiometrically. Lastly, we demonstrated the capability to use these beads as a bioremediation technology for cDCE as we found that, for all bead formulations, cDCE was significantly reduced after 30 days. Altogether, this work demonstrates the capability to capture and enhance the material properties of the complex hydrogel beads with predictive models yet signals the need for more robust methods to understand the metabolic activity that occurs in the hydrogel beads.

Hydrogel-based technologies in liquid biopsy for the detection of circulating clinical markers: challenges and prospects

Liquid biopsy, which promises noninvasive detection of tumor-derived material, has recently been highlighted because of its potential to lead us to an era of precision medicine. However, its development has encountered challenges owing to the extremely low frequency and low purity of circulating tumor markers, such as circulating tumor cells (CTCs), circulating exosomes, and circulating tumor nucleic acids (ctNAs). Much effort has been made to overcome this limitation over the last decade, and an increasing number of studies have shown interest in the special characteristics of hydrogels. This hydrophilic and biocompatible polymeric network, which absorbs a large amount of water, can aid in the isolation, protection, and analysis of these low-abundance and short-lived circulating biomarkers. The role of hydrogels in liquid biopsy is extensive and ranges from enrichment to encapsulation. This review provides an overview of hydrogel-based technologies to pave the way in liquid biopsy.

Sodium alginate/polyvinyl alcohol semi-interpenetrating hydrogels reinforced with PEG-grafted-graphene oxide

Semi-interpenetrating polymer network (SIPN) hydrogels composed of sodium alginate/poly (vinyl alcohol), reinforced by PEG-grafted-graphene oxide (GO-g-PEG) were prepared by ionic crosslinking of sodium alginate. The impact of grafted PEG molecular weight with two molecular weights, i.e. 400 and 2000 g/mol, and component composition were studied on the morphology, swelling behavior, mechanical and dynamic properties. SEM observation showed fine dispersion and distribution of GO-g-PEG throughout the hydrogel indicating a good interaction of particles with the components. Our results revealed that although incorporating GO-g-PEG increases the water content, it significantly enhances the mechanical properties, i.e. tensile modulus, elongation at break, and fracture toughness with a more pronounced impact at higher PEG molecular weight. As a result, the tensile modulus and the elongation at break increased by 270 % and 28 %, respectively. The SA/PVA SIPN hydrogels reinforced with the GO-g-PEG exhibit a non-linear elastic behavior with a toe at low strains. This behavior is attributed to the unique structural features of SIPN hydrogels and the orientation of GO-g-PEG particles with proper interaction with the components. The small amplitude oscillatory shear was also performed to further study the impact of SA, PVA, and GO-g-PEG compositions on the microstructure of hydrogels.

Protein/polysaccharide-based hydrogels loaded probiotic-mediated therapeutic systems: A review

The natural characteristics of protein/polysaccharide-based hydrogels, as a potential drug delivery platform, have attracted extensive attention. Probiotics have attracted renewed interest in drug research because of their beneficial effects on host health. The idea of using probiotics loaded on protein/polysaccharide-based hydrogels as potential drugs to treat different diseases has been put forward and shows great prospects. Based on this, in this review, we highlight the design strategy of hydrogels loaded probiotic-mediated therapy systems and review the potential diseases that have been proved to be treatable in the laboratory, including promoting wound healing and improving intestinal health and vaginal health, and discuss the challenges existing in the current design.

Synthesis and Applications of Hybrid Polymer Networks Based on Renewable Natural Macromolecules

Macromolecules obtained from renewable natural sources are gaining increasing attention as components for a vast variety of sustainable polymer-based materials. Natural raw materials can facilitate continuous-flow production due to their year-round availability and short replenishment period. They also open new opportunities for chemists and biologists to design and create "bioreplacement" and "bioadvantaged" polymers, where complex structures produced by nature are being modified, upgraded, and utilized to create novel materials. Bio-based macromonomers are expected not only to compete with but to replace some petroleum-based analogs, as well. The development of novel sustainable materials is an ongoing and very dynamic process. There are multiple strategies for transforming natural macromolecules into sophisticated value-added products. Some methods include chemical modification of macromolecules, while others include blending several components into one new system. One of the most promising approaches for incorporating renewable macromolecules into new products is the synthesis of hybrid networks based on one or more natural components. Each one has unique characteristics, so its incorporation into a network brings new sustainable materials with properties that can be tuned according to their end-use. This article reviews the current state-of-the-art and future potential of renewable natural macromolecules as sustainable building blocks for the synthesis and use of hybrid polymer networks. The most recent advancements and applications that involve polymers, such as cellulose, chitin, alginic acid, gellan gum, lignin, and their derivatives, are discussed.

Development of alginate-based hydrogels: Crosslinking strategies and biomedical applications

Natural polysaccharide-based hydrogels have drawn much concern in the biomedical fields. Among them, alginate, a natural polyanionic polysaccharide, has become one of the research hotspots, because of its abundant source, biodegradability, biocompatibility, solubility, modification flexibility, and other characteristics or physiological functions. Recently, through adopting various physical or chemical crosslinking strategies, selecting suitable crosslinking or modification reagents, precisely controlling the reaction conditions, or introducing organic or inorganic functional materials, a variety of alginate-based hydrogels with excellent performance have been continuously developed, considerably expanding the breadth and depth of their applications. Here, various crosslinking strategies in the preparation of alginate-based hydrogels are comprehensively introduced. The representative application progress of alginate-based hydrogels in drug carrier, wound dressing and tissue engineering is also summarized. Meanwhile, the application prospects, challenges and development trends of alginate-based hydrogels are discussed. It is expected to provide guidance and reference for the further development of alginate-based hydrogels.

A Biomass Based Photonic Crystal Hydrogel Made of Bletilla striata Polysaccharide

Bletilla striata is an herb with a good medicinal value whose main active ingredient is Bletilla striata polysaccharide (BSP) in the tuber of Bletilla striata. In this study, a polysaccharide-based semi-interpenetrating network hydrogel was constructed by introducing BSP into polyacrylamide (PAM) hydrogel. The introduction of the BSP chain no only maintains the excellent mechanical properties of PAM, but also endows it with good biocompatibility. By implanting the colloidal crystal array into the above hydrogels, we obtained a novel biomass-based photonic crystal with good stimulus responsiveness that is sensitive to volatile organic compounds (VOCs), especially alcohol vapor. In addition, due to the scavenging ability of BSP to hydroxyl radicals, the photonic crystal hydrogel also has a good response to hydrogen peroxide (H2O2).

Interpenetrating polymeric network (IPNs) in ophthalmic drug delivery: Breaking the barriers

To maintain the therapeutic drug concentration for a prolonged period of time in aqueous and vitreous humor is primary challenge for ophthalmic drug delivery. Majority of the locally administered drug into the eye is lost as to natural reflexes like blinking and lacrimation resulting in the short span of drug residence. Consequently, less than 5% of the applied drug penetrate through the cornea and reaches the intraocular tissues. The major targets for optimal ophthalmic drug delivery are increasing drug residence time in cul-de-sac of the eye, prolonging intraocular exposure, modulating drug release from the delivery system, and minimizing pre-corneal drug loss. Development of in situ gel, contact lens, intraocular lens, inserts, artificial cornea, scaffold, etc., for ophthalmic drug delivery are few approaches to achieve these major targeted objectives for delivering the drug optimally. Interpenetrating polymeric network (IPN) or smart hydrogels or stimuli sensitive hydrogels are the class of polymers that can help to achieve the targets in ophthalmic drug delivery due to their versatility, biocompatibility and biodegradability. These novel ''smart" materials can alter their molecular configuration and result in volume phase transition in response to environmental stimuli, such as temperature, pH, ionic strength, electric and magnetic field. Hydrogel and tissue interaction, mechanical/tensile properties, pore size and surface chemistry of IPNs can also be modulated for tuning the drug release kinetics. Stimuli sensitive IPNs has been widely exploited to prepare in situ gelling formulations for ophthalmic drug delivery. Low refractive index hydrogel biomaterials with high water content, soft tissue-like physical properties, wettability, oxygen, glucose permeability and desired biocompatibility makes IPNs versatile candidate for contact lenses and corneal implants. This review article focuses on the exploration of these smart polymeric networks/IPNs for therapeutically improved ophthalmic drug delivery that has unfastened novel arenas in ophthalmic drug delivery.