Biopolymer Hydrogels Research Articles

Remote magnetically stimulated xanthan-biochar-Fe3O4-molecularly imprinted biopolymer hydrogel toward electrochemical enantioselection of l-tryptophan

Monitoring the levels of L-Tryptophan (L-Trp) in body fluids is crucial due to its significant role in metabolism and protein synthesis, which ultimately affects neurological health. Herein, we have developed a novel magneto-responsive electrochemical enantioselective sensor for the recognition of L-Trp based on oriented biochar derived from Loofah, Fe3O4 nanoparticles, and molecularly imprinted polydopamine (MIPDA) in xanthan hydrogel. The successful synthesis of these materials has been confirmed through physicochemical and electrochemical characterization. Various operational factors such as pH, response time, loading sample volume, and loading of active materials were optimized. As a result, the sensor exhibited an affordable linear range of 1.0–60.0 μM, with a desirable limit of detection of 0.44 μM. Furthermore, the proposed electrochemical sensor demonstrated good reproducibility and desirable selectivity for the determination of L-Trp, making it suitable for analyzing L-Trp levels in human plasma and serum samples. The development presented offers an appealing, easily accessible, and efficient strategy. It utilizes xanthan hydrogel to improve mass transfer and adhesion, biochar-stabilized Fe3O4 to facilitate magnetic orientation and accelerate mass transfer and sensitivity, and polydopamine MIP to enhance selectivity. This approach enables on-site evaluation of L-Trp levels, which holds significant value for healthcare monitoring and early detection of related conditions.

Crosslinked hydrogel-derived carbons activated by trace amounts of aqueous potassium carbonate for carbon dioxide adsorption

A new method for green synthesis of activated carbon using chitosan-based hydrogel precursors is reported. Chitosan-based hydrogel materials are designed to absorb trace amounts of non-toxic and non-corrosive activating agent K2CO3 from dilute aqueous solution. The K2CO3 impregnated hydrogels are further freeze-dried and converted to activated carbons with tuneable pore structure by a single-step pyrolysis. Activated carbon with highest pore volume of 0.76 cm3/g and surface area of 2026 m2/g is obtained by using K2CO3 as low as 0.23 g per gram of chitosan hydrogel. It can adsorb maximum CO2 of 4.2 mmol/g at 25 °C and 1 bar. This study demonstrates that biopolymer hydrogels impregnated with trace amounts of K2CO3 are excellent precursor materials to design high surface area carbons for CO2 capture.

Synthesis, utilization, and recycling of graphene oxide-based nanohybrid biopolymeric hydrogels for purification of dye wastewater

ABSTRACT Wastewater from industries contributes significantly to pollution. Adsorption of acidic dye using nanohybrid biopolymeric hydrogels has evolved as one of the viable techniques. Graphene oxide (GO)/chitosan (CS)–polyvinyl alcohol (PVA), GO/starch–PVA, and GO/agar–PVA hydrogels were synthesized. The results revealed that the following are the ideal values: GO/CS–PVA: 3 pH (8.251 mg g−1), 0.05 g/50mL dosage (8.251 mg g−1), 90 min (8.251 mg g−1), 12 ppm dye concentration (8.251 mg g−1), and 30 °C (8.251 mg g−1); for GO/starch–PVA: 2 pH (7.437 mg g−1), 0.05 g/50 mL dosage (7.437 mg g−1), 90 min (7.437 mg g−1), 12 ppm dye concentration (7.437 mg g−1), and 30 °C (7.437 mg g−1); and for GO/agar–PVA; 3 pH (6.142 mg g−1), 0.05 g/50 mL dosage (6.142 mg g−1), 90 min (6.142 mg g−1), 12 ppm dye concentration (6.142 mg g−1), 30 °C (6.142 mg g−1). GO/CS–PVA outperformed the other hydrogels. The Langmuir model suited GO/CS–PVA data, while GO/starch–PVA and GO/agar–PVA hydrogels followed Freundlich isotherm models. The adsorption capacity data followed a pseudo-second-order model. Negative value of Gibbs free energy and enthalpy showed that the reactions were spontaneous and exothermic in nature. The presence of heavy metals, electrolytes, and detergents/surfactants affected the dye adsorption. Entropy changes positive values implied randomness at the solid/solution contact. The desorption (60, 55, and 58%) of GO/CS–PVA, GO/starch–PVA, and GO/agar–PVA hydrogels was obtained using 0.5 N NaOH. Scanning electron microscope, X-ray diffraction, and Fourier transform infrared (FT-IR) were used for characterization.

A hyaluronic acid hydrogel as a mild photothermal antibacterial, antioxidant, and nitric oxide release platform for diabetic wound healing

Hyaluronic acid (HA)-based biopolymer hydrogels are promising therapeutic dressings for various wounds but still underperform in treating diabetic wounds. These wounds are extremely difficult to heal and undergo a prolonged and severe inflammatory process due to bacterial infection, overexpression of reactive oxygen species (ROS), and insufficient synthesis of NO. In this study, a dynamic crosslinked hyaluronic acid (HA) hydrogel dressing (Gel-HAB) loaded with allomelanin (AMNP)-N, N′-dis-sec-butyl-N, N′-dinitroso-1, 4-phenylenediamine (BNN6) nanoparticles (AMNP-BNN6) was developed for healing diabetic wounds. The dynamic acylhydrazone bond formed between hydrazide-modified HA (HA-ADH) and oxidized HA (OHA) makes the hydrogel injectable, self-healing, and biocompatible. The hydrogel, loaded with AMNP-BNN6 nanoparticles, exhibits promising ROS scavenging ability and on-demand release of nitric oxide (NO) under near-infrared (NIR) laser irradiation to achieve mild photothermal antibacterial therapy (PTAT) (∼ 48 °C). Notably, the Gel-HAB hydrogel effectively reduced the oxidative stress level, controlled infections, accelerated vascular regeneration, and promoted angiogenesis, thereby achieving rapid healing of diabetic wounds. The injectable self-healing nanocomposite hydrogel could serve as a mild photothermal-enhanced antibacterial, antioxidant, and nitric oxide release platform for the treatment of diabetic wounds.

Fluorescent biopolymer hydrogels crosslinked with carbon quantum dots for selective detection of heavy iron (III) ions

In this study, carbon quantum dots (CQDs) were synthesized using glycerol and citric acid under microwave radiation, achieving an 83 % quantum yield (QY) and 1.59 nm particle size. These CQDs were employed as softeners and crosslinkers for the production of fluorescent granular and film hydrogels, in combination with biopolymers such as starch, chitosan (Ch), and gelatin (Ge). The resulting biopolymer-CQD composites were evaluated for their ability to selectively detect heavy metal ions, such as iron (III), as well as for their water vapor permeability (WVP), water solubility (WS), and swelling properties. Various analyses confirmed the formation of fluorescence bio-nanocomposites and improvements in their properties. Notably, a hydrogel film containing 50% wt CQDs exhibited the highest mechanical strength, with a tensile strength of 6.28 MPa and an elongation at fracture of 91.2%. Additionally, a strongly crosslinked fluorescent granular hydrogel with a ratio of Ge 25%: Ch 75% and a fixed amount of CQDs was able to absorb 136 times its own weight in water and exhibited increased water vapor permeability with higher CQD content. Overall, the fabricated materials show potential for the detection of iron (II), iron (III), and mercury (II) in aqueous media.

Facile Multifunction Biopolymer Hydrogels for the Potential Treatment of Historical Paper

Facile Multifunction Biopolymer Hydrogels for the Potential Treatment of Historical Paper

Polymeric Hydrogels for Energy Devices

Innovative energy storage devices, viz., supercapacitors and rechargeable batteries are of great awareness owing to their comprehensive claims in flexible electronics and implantations. In simple electronic devices, frequently facing problems like bending, collision, steeping, piercing, and even encountering shearing, fire, water, etc. Hence, a high mandate is needed for the constructive and consistency of energy storage devices. Hydrogels are hydrophilic three-dimensional polymers filled with water which are highly noticeable electrolyte materials due to their high-water permeability and smoothness, which enable them to fulfil the vital necessities for flexible energy storage devices. Hydrogels with intriguing physicochemical assets for justifiable energy storing for water production. The proposal of novel hydrogel electrolytes for supercapacitors and batteries with electrochemical performances for imminent growth. The biopolymeric hydrogel electrolytes can be chosen as substitute materials for supercapacitors due to their decent ionic conductivity, no fluid seepage, and no toxicity. Focus of the review aims to highlight the hydrogels materials combined into batteries and deliver thrilling tailorable architectures for multifunctionalities with amicable applications.

In Vitro Characterization of Poly(Ethylene Glycol) Dimethacrylate-Nanofibrillated Cellulose as an Injectable Biomaterial for Herniated Nucleus Pulposus Substitute

Highlights:1. Novel synthetic biopolymer hydrogels were successfully prepared from pristine poly(ethylene glycol) dimethacrylate (PEGDMA) and nanofibrillated cellulose (NFC) using the photopolymerization method.2. PEGDMA-NFC biocomposite hydrogel can be developed as an affordable biomaterial for herniated nucleus pulposus substitute, with the potential to meet clinical application standards. Abstract Herniated nucleus pulposus develops when the intervertebral disc portudes through the annulus fibrosus due to the rupture of the annulus fibrosus or a decrease in proteoglycans. Hydrogel implant material can be injected into the disc space to restore disc thickness caused by disc degeneration with minimal invasiveness. This study aimed to characterize poly(ethylene glycol) dimethacrylate-nanofibrillated cellulose (PEGDMA-NFC) in vitro as a potential biomaterial for herniated nucleus pulposus substitute. This study utilized PEGDMA-NFC to treat first-degree herniated nucleus pulposus using the photopolymerization method. PEGDMA was selected because of its hydrophilic ability to produce hydrogel. The addition of NFC to the PEGDMA precursor was expected to show mechanical properties as a hydrogel bio composite candidate. The characterization of PEGDMA-NFC was conducted using three tests: Fourier-transform infrared spectroscopy (FTIR), viscosity assessment, and an in vitro injection testing model. The normal distribution of the data was analyzed using the Kolmogorov-Smirnov test, while the homogeneity was assessed using Levene's test. Homogenous and normally distributed data were analyzed using a one-way analysis of variance (ANOVA) with a p-value of <0.05. The explored concentrations of PEGDMA-NFC included a ratio of 1:0 for the control samples and ratios of 1:0.5 (K1), 1:0.75 (K2), and 1:1 (K3) for the experimental samples. The FTIR analysis revealed the presence of various functional groups in PEGDMA-NFC, indicating its potential classification as a hydrogel biomaterial. The characterization data showed that the K3 sample yielded the most favourable outcome with a viscosity value of 74.67 dPa·s. From the in vitro injection testing result, the addition of NFC demonstrated that the hydrogel would not rupture when released from the mold. The hydrogel could be injected with an 18 gauge needle. The statistical analysis results showed a significant difference among the samples (p<0.05). This study concludes that the PEGDMA-NFC hydrogel biocomposite can be effectively applied in herniated nucleus pulposus cases.

Modulation of the biocompatibility of collagen/polyelectrolyte semi-IPN hydrogels with Zn-bioMOFs.

In this study, we examined the impact of Zn-bioMOF structures on the physical and chemical characteristics as well as the in vitro biocompatibility of a matrix composed of semi-interpenetrating polymeric networks (semi-IPN) made from collagen and L-tyrosine-based polyelectrolytes. We hydrothermally synthesized L-1, ZIF-8H Zn-bioMOFs, and the Zn-(L-His)2 complex, utilizing L-histidine, a bioactive amino acid, as a ligand. These metal-organic compounds primarily enhance the mechanical properties of the novel composite hydrogels through physical interactions such as hydrogen bonds and dipolar interactions. They also accelerate the gelation process. Composites containing Zn-bioMOFs exhibited greater biocompatibility than the collagen/polyelectrolyte matrix alone, as evidenced by cytotoxicity assays conducted with porcine fibroblasts, human monocytes, and RAW 264.7 cells. Furthermore, the evaluated materials did not exhibit hemolysis. We investigated the influence of Zn-bioMOFs on cell signaling by measuring the levels of crucial cytokines involved in the healing process, such as MCP-1, TGF-β, IL-10, and TNF-α secreted by human monocytes. The composite with Zn(L-His)2 promoted the secretion of MCP-1, TGF-β, and IL-10, while a decrease in TNF-α secretion was observed with the composite containing ZIF-8H. Zn-bioMOFs enhanced certain aspects of the biomedical and physicochemical properties of the composite hydrogels. Although the overall performance of the tested materials did not differ significantly, it is worth noting that the presence of Zn-bioMOFs in biopolymeric hydrogels modulated the metabolic activity of cells important for healing and their cytokine signaling, leading to improved biomedical performance.

Biocompatibility of intraperitoneally implanted TEMPO-oxidized cellulose nanofiber hydrogels for antigen delivery in Atlantic salmon (Salmo salar L.) vaccines

Disease outbreaks are a major impediment to aquaculture production, and vaccines are integral for disease management. Vaccines can be expensive, vary in effectiveness, and come with adjuvant-induced adverse effects, causing fish welfare issues and negative economic impacts. Three-dimensional biopolymer hydrogels are an appealing new technology for vaccine delivery in aquaculture, with the potential for controlled release of multiple immunomodulators and antigens simultaneously, action as local depots, and tunable surface properties. This research examined the intraperitoneal implantation of a cross-linked TEMPO cellulose nanofiber (TOCNF) hydrogel formulated with a Vibrio anguillarum bacterin in Atlantic salmon with macroscopic and microscopic monitoring to 600-degree days post-implantation. Results demonstrated a modified passive integrated transponder tagging (PITT) device allowed for implantation of the hydrogel. However, the Atlantic salmon implanted with TOCNF hydrogels exhibited a significant foreign body response (FBR) compared to sham-injected negative controls. The FBR was characterized by gross and microscopic external and visceral proliferative lesions, granulomas, adhesions, and fibrosis surrounding the hydrogel using Speilberg scoring of the peritoneum and histopathology of the body wall and coelom. Acutely, gross monitoring displayed rapid coagulation of blood in response to the implantation wound with development of fibrinous adhesions surrounding the hydrogel by 72 h post-implantation consistent with early stage FBR. While these results were undesirable for aquaculture vaccines, this work informs on the innate immune response to an implanted biopolymer hydrogel in Atlantic salmon and directs future research using cellulose nanomaterial formulations in Atlantic salmon for a new generation of aquaculture vaccine technology.

Injectable ultrasound-powered bone-adhesive nanocomposite hydrogel for electrically accelerated irregular bone defect healing

The treatment of critical-size bone defects with irregular shapes remains a major challenge in the field of orthopedics. Bone implants with adaptability to complex morphological bone defects, bone-adhesive properties, and potent osteogenic capacity are necessary. Here, a shape-adaptive, highly bone-adhesive, and ultrasound-powered injectable nanocomposite hydrogel is developed via dynamic covalent crosslinking of amine-modified piezoelectric nanoparticles and biopolymer hydrogel networks for electrically accelerated bone healing. Depending on the inorganic-organic interaction between the amino-modified piezoelectric nanoparticles and the bio-adhesive hydrogel network, the bone adhesive strength of the prepared hydrogel exhibited an approximately 3-fold increase. In response to ultrasound radiation, the nanocomposite hydrogel could generate a controllable electrical output (-41.16 to 61.82 mV) to enhance the osteogenic effect in vitro and in vivo significantly. Rat critical-size calvarial defect repair validates accelerated bone healing. In addition, bioinformatics analysis reveals that the ultrasound-responsive nanocomposite hydrogel enhanced the osteogenic differentiation of bone mesenchymal stem cells by increasing calcium ion influx and up-regulating the PI3K/AKT and MEK/ERK signaling pathways. Overall, the present work reveals a novel wireless ultrasound-powered bone-adhesive nanocomposite hydrogel that broadens the therapeutic horizons for irregular bone defects.

Fabrication of a novel alginate-xanthan biopolymer hydrogel bead for cationic surfactant removal from aqueous medium

Fabrication of a novel alginate-xanthan biopolymer hydrogel bead for cationic surfactant removal from aqueous medium

DNA Crosslinked Mucin Hydrogels Allow for On-Demand Gel Disintegration and Triggered Particle Release.

Whereas hydrogels created from synthetic polymers offer a high level of control over their stability and mechanical properties, their biomedical activity is typically limited. In contrast, biopolymers have evolved over billions of years to integrate a broad range of functionalities into a single design. Thus, biopolymeric hydrogels can show remarkable capabilities such as regulatory behavior, selective barrier properties, or antimicrobial effects. Still, despite their widespread use in numerous biomedical applications, achieving a meticulous control over the physical properties of macroscopic biopolymeric networks remains a challenge. Here, a macroscopic, DNA-crosslinked mucin hydrogel with tunable viscoelastic properties that responds to two types of triggers: temperature alterations and DNA displacement strands, is presented. As confirmed with bulk rheology and single particle tracking, the hybridized base pairs governing the stability of the hydrogel can be opened, thus allowing for a precise control over the hydrogel stiffness and even enabling a full gel-to-sol transition. As those DNA-crosslinked mucin hydrogels possess tunable mechanical properties and can be disintegrated on demand, they can not only be considered for controlled cargo release but may also serve as a role model for the development of smart biomedical materials in applications such as tissue engineering and wound healing.

A Review of the Synthesis of Biopolymer Hydrogel Electrolytes for Improved Electrode–Electrolyte Interfaces in Zinc-Ion Batteries

The market for electric vehicles and portable and wearable electronics is expanding rapidly. Lithium-ion batteries currently dominate the market, but concerns persist regarding cost and safety. Consequently, alternative battery chemistries are investigated, with zinc-ion batteries (ZIBs) emerging as promising candidates due to their favorable characteristics, including safety, cost-effectiveness, theoretical volumetric capacity, energy density, and ease of manufacturing. Hydrogel electrolytes stand out as advantageous for ZIBs compared to aqueous electrolytes. This is attributed to their potential application in flexible batteries for wearables and their beneficial impact in suppressing water-induced side reactions, zinc dendrite formation, electrode dissolution, and the risk of water leakage. The novelty of this review lies in highlighting the advancements in the design and synthesis of biopolymer hydrogel electrolytes in ZIBs over the past six years. Notable biopolymers include cellulose, carboxymethyl cellulose, chitosan, alginate, gelatin, agar, and gum. Also, double-network and triple-network hydrogel electrolytes have been developed where biopolymers were combined with synthetic polymers, in particular, polyacrylamide. Research efforts have primarily focused on enhancing the mechanical properties and ionic conductivity of hydrogel electrolytes. Additionally, there is a concerted emphasis on improving the electrochemical performance of semi-solid-state ZIBs. Moreover, some studies have delved into self-healing and adhesive properties, anti-freezing characteristics, and the multifunctionality of hydrogels. This review paper concludes with perspectives on potential future research directions.

Piezo-enhanced near infrared photocatalytic nanoheterojunction integrated injectable biopolymer hydrogel for anti-osteosarcoma and osteogenesis combination therapy

Preventing local tumor recurrence while promoting bone tissue regeneration is an urgent need for osteosarcoma treatment. However, the therapeutic efficacy of traditional photosensitizers is limited, and they lack the ability to regenerate bone. Here, a piezo-photo nanoheterostructure is developed based on ultrasmall bismuth/strontium titanate nanocubes (denoted as Bi/SrTiO3), which achieve piezoelectric field-driven fast charge separation coupling with surface plasmon resonance to efficiently generate reactive oxygen species. These hybrid nanotherapeutics are integrated into injectable biopolymer hydrogels, which exhibit outstanding anticancer effects under the combined irradiation of NIR and ultrasound. In vivo studies using patient-derived xenograft models and tibial osteosarcoma models demonstrate that the hydrogels achieve tumor suppression with efficacy rates of 98.6 % and 67.6 % in the respective models. Furthermore, the hydrogel had good filling and retention capabilities in the bone defect region, which exerted bone repair therapeutic efficacy by polarizing and conveying electrical stimuli to the cells under mild ultrasound radiation. This study provides a comprehensive and clinically feasible strategy for the overall treatment and tissue regeneration of osteosarcoma.

Modelling methacrylated chitosan hydrogel properties through an experimental design approach: from composition to material properties.

Hydrogels of biopolymers are gradually substituting synthetic hydrogels in tissue engineering applications due to their properties. However, biopolymeric hydrogels are difficult to standardize because of the intrinsic variability of the material and the reversibility of physical crosslinking processes. In this work, we synthesized a photocrosslinkable derivative of chitosan (Cs), namely methacrylated chitosan (CsMA), in which the added methacrylic groups allow the formation of hydrogels through radical polymerization triggered by UV exposure. We then performed a systematic study to link the physical properties of the materials to its preparation parameters to standardize its preparation according to specific applications. We studied the properties of CsMA solutions and the derived hydrogels using a statistical method, namely, response surface method, which allowed us to build empirical models describing material properties in terms of several selected processing factors. In particular, we studied the viscosity of CsMA solutions as a function of CsMA concentration, temperature, and shear rate, while hydrogel compression modulus, morphology, degradation and solubilization were investigated as a function of CsMA concentration, photoinitiator concentration and UV exposure. CsMA solutions resulted in shear thinning and were thus suitable for extrusion-based 3D printing. The CsMA hydrogel was found to be highly tunable, with a stiffness in the 12-64 kPa range, and was stable over a long timeframe (up to 60 days). Finally, the possibility to engineer hydrogel stiffness through an empirical model allowed us to hypothesize a number of possible applications based on the mechanical properties of several biological tissues reported in the literature.

Fabrication of silica/calcium alginate nanocomposite based on rice husk ash for efficient adsorption of phenol from water.

The current work discusses the synthesis of three different solid adsorbents: silica nanoparticles derived from rice husk (RS), calcium alginate beads (AG), and silica/alginate nanocomposite (RSG). The fabricated solid adsorbents were characterized by using different physicochemical techniques such as TGA, XRD, nitrogen adsorption/desorption analysis, ATR-FTIR, pHPZC, SEM, and TEM. The adsorption efficiencies of the prepared solid adsorbents were considered for the removal of phenol as a selected hazardous pollutant. Because of its improved adsorption capacity and environmentally friendly character, a composite made of biosilica nanoparticles and naturally occurring alginate biopolymer by click chemistry is significant in environmental treatment. Adding silica nanoparticles to the alginate biopolymer hydrogel has many advantages, including increased surface area, easier recovery of the solid adsorbent, and additional surface chemical functional groups. The silica/alginate nanocomposite showed surface heterogeneity with many chemical functional groups present, whereas silica nanoparticles had the highest surface area (893.1 m2 g-1). It has been found that the average TEM particle size of RS, AG, and RSG was between 18 and 82 nm. RSG displayed the maximum adsorption capacity of phenol (100.55 mg g-1) at pH 7 and 120 min as equilibrium adsorption time. Adsorption of phenol onto the solid adsorbents fit well with a nonlinear Langmuir isotherm with favorable adsorption. Kinetic and thermodynamic studies prove that the adsorption process follows a pseudo-second-order kinetic model, endothermic process, physical, and spontaneous adsorption. Sodium hydroxide is effective in desorbing 94% of the loaded phenols, according to desorption investigations. Solid reusability tests showed that, after seven cycles of phenol adsorption/desorption, RSG lost only 8.8% of its adsorption activity.

Modeling of Smart Bio-Medical Active Polymeric Hydrogel Transdermal Materials

In this article, effective 3D printing modeling technology of smart bio-medical polymeric hydrogel transdermal materials based on gelatin and sodium alginate, modified by humic acids, was researched. Such smart biologically active polymeric hydrogel materials showed interesting applicability in tissue engineering fields due to their intrinsic biological compatibility, adaptability, and capacity to replicate the extracellular matrix environment. A literature review was carried out and proved that 3D printing modeling technology is a perspective for the functional effect on the smart bio-medical polymer hydrogel transdermal properties. Smart biomedical polymeric transdermal hydrogel patches were produced using a micromolding technique. A stereolithography (SLA) 3D printer was used to print the master mold. The three-stage technology of lignite humic acids modification of smart biologically active polymeric hydrogel transdermal microneedles patches based on gelatin, hydroxypropyl methylcellulose, and sodium alginate was designed. It was shown that modification of gelatin-sodium alginate and hydroxypropyl methylcellulose-sodium alginate biopolymer hydrogels by humic acids makes it possible to obtain smart biologically active polymeric hydrogel transdermal materials with an increased swelling degree and ability to improve the skin moisture-lipid balance (from the initial moisture 34–36 % and fatness 8–10, they increase to 58–66 % and 52–60 %). Finally, the developed 3D printing modeling technology of smart bio-medical polymeric hydrogel transdermal materials hydrogel based on gelatin sodium alginate, modified by humic acids, is a transdermal material with required properties.

Mechanical characterization of soft biomaterials: which time and spatial scale to choose?

The mechanical properties of soft gels hold significant relevance in biomedicine and biomaterial design, including the development of tissue engineering constructs and bioequivalents. It is important to adequately characterize the gel's mechanical properties since they play a role both in the overall structural properties of the construct and the physiological responses of cells. The question remains which approach for the mechanical characterization is most suitable for specific biomaterials. Our investigation is centered on the comparison of three types of gels and four distinct mechanical testing techniques: shear rheology, compression, microindentation, and nanoindentation by atomic force microscopy. While analyzing an elastic homogeneous synthetic hydrogel (a polyacrylamide gel), we observed close mechanical results across the different testing techniques. However, our findings revealed more distinct outcomes when assessing a highly viscoelastic gel (Ecoflex) and a heterogeneous biopolymer hydrogel (enzymatically crosslinked gelatin). To ensure precise data interpretation, we introduced correction factors to account for the boundary conditions inherent in many of the testing methods. The results of this study underscore the critical significance of considering both the temporal and spatial scales in mechanical measurements of biomaterials. Furthermore, they encourage the employment of a combination of diverse testing techniques, particularly in the characterization of heterogeneous viscoelastic materials such as biological samples. The obtained results will contribute to the refinement of mechanical testing protocols and advance the development of soft gels for tissue engineering.

Renewable whey-based hydrogel with polysaccharides and polyvinyl alcohol as a soil amendment for sustainable agricultural application

This work describes the preparation of a novel biopolymer hydrogel based on acid whey, cellulose derivatives and polyvinyl alcohol (PVA). The hydrogel was prepared and characterized with the aim of producing an environmentally-friendly soil amendment to increase water retention capacity of the soil. The findings showed considerable swelling properties of the hydrogels depending on the PVA content and crosslinking density. The samples with PVA in a concentration 2.5 % and 5 % were more rigid, the gel fraction increased with a subsequently decrease in their swelling capacity. The hydrogels crosslinked with 15 % of citric acid demonstrated a constant swelling ratio (SR) of around 500 % within 10 swelling/drying cycles. The hydrogels crosslinked with 10 % citric acid and supplemented with 1 % of PVA showed SR of 1000–1400 % caused by less crosslinked polymer network and increased pore volume for water uptake. It was found that hydrogel with a higher gel fraction had a stable structure. Supplementing PVA at 5 % extended the period of decomposition of the hydrogel material by almost 60 % in the soil environment and soil humidity was maintained for longer. Applying 2 % of the hydrogel 5PVA to soil increased the water retention capacity by 19 %.