Crosslinking Time Research Articles

Laccase immobilized on amino modified magnetic biochar as a recyclable biocatalyst for efficient degradation of trichloroethylene

Bioremediation of trichloroethylene (TCE) contaminated groundwater has recently attracted considerable attention. In this study, laccase was immobilized on amino modified magnetic pine biochar (MBC-NH2) by adsorption-crosslinking-covalent binding method, and its application in the degradation of TCE was evaluated. MBC-NH2 was obtained from pine sawdust by calcination, magnetic modification and amino modification. MBC-NH2 had high specific surface area (71.3 m2/g), rich surface functional groups and good magnetism. Under the conditions of 25 °C, pH = 4, glutaraldehyde (GA) concentration of 7 %, crosslinking time of 1 h, laccase concentration of 0.75 mg/mL, and immobilization time of 7 h, the loading capacity of laccase on MBC-NH2 carrier was as high as 782 mg/g. Compared with free laccase, immobilized laccase showed higher pH stability and thermal stability, and its activity remained 48.5 % after being reused for 10 times, and 80.8 % after being stored at 4 °C for 30 days. The immobilized laccase exhibited a good degradation effect on TCE. At 25 °C, pH = 4, immobilized laccase concentration of 0.35 g/L, and initial TCE concentration of 10 mg/L, the degradation efficiency of TCE by immobilized laccase was as high as 92.1 % within 48 h. In addition, the degradation products of TCE were analyzed, and the results showed that immobilized laccase could degrade TCE into non-toxic products through epoxidation, hydroxylation, and dechlorination. The immobilized laccase biocatalyst prepared in this study can achieve efficient degradation of TCE, which provides a feasible solution for chlorinated pollution of water resources. These research results are of great significance for the synthesis of biocatalysts for the efficient degradation of chlorinated hydrocarbons.

Renewable Photo-Cross-Linkable Polyester-Based Biomaterials: Synthesis, Characterization, and Cytocompatibility Assessment.

The present work consist of the synthesis of photo-cross-linkable materials, based on unsaturated polyesters (UPs), synthesized from biobased monomers from renewable sources such as itaconic acid and 1,4-butanediol. The UPs were characterized to assess the influence of polycondensation reaction temperature and cross-linking time on their final properties. For this purpose, different UV irradiation exposure periods were tested. Homogeneous, uniform, and transparent films were obtained after 1, 3, and 5 min of UV exposure. These cross-linked films were then characterized. All materials presented high gel content, which was dependent on the reaction's temperature. The thermal behaviors of the UPs were shown to be similar. In vitro hydrolytic degradation tests showed that the materials can undergo degradation in phosphate-buffered saline (PBS) at pH 7.4 and 37 °C, ensuring their biodegradability over time. Finally, to assess the applicability of the polyesters as biomaterials, their cytocompatibility was determined by using human dermal fibroblasts.

Cross-Linker Architectures Impact Viscoelasticity in Dynamic Covalent Hydrogels.

Dynamic covalent cross-linked (DCC) hydrogels represent a significant advance in biomaterials for regenerative medicine and mechanobiology, offering viscoelasticity, and self-healing properties that more closely mimic in vivo tissue mechanics than traditional, predominantly elastic, covalent hydrogels. However, the effects of varying cross-linker architecture on DCC hydrogel viscoelasticity have not been thoroughly investigated. This study introduces hydrazone-based alginate hydrogels to explore how cross-linker architectures impact stiffness and viscoelasticity. In hydrogels with side-chain cross-linker (SCX), higher cross-linker concentrations enhance stiffness and decelerate stress relaxation, while an off-stoichiometric hydrazine-to-aldehyde ratio reduces stiffness and shortens relaxation time. In hydrogels with telechelic cross-linking, maximal stiffness and relaxation time occurs at intermediate cross-linker mixing ratio for both linear cross-linker (LX) and star cross-linker (SX), with higher cross-linker valency further enhancing these properties. Further, the ranges of stiffness and viscoelasticity accessible with the different cross-linker architectures are found to be distinct, with SCX hydrogels leading to slower stress relaxation relative to the other architectures, and SX hydrogels providing increased stiffness and slower stress relaxation versus LX hydrogels. This research underscores the pivotal role of cross-linker architecture in defining hydrogel stiffness and viscoelasticity, providing insights for designing DCC hydrogels with tailored mechanical properties for specific biomedical applications.

Exploring the nanobiohybrids of nanodiamonds-functionalized MoAlB@MBene and microalgae synergistic potential for sustainable pharmaceutical removal

Nanobiohybrid systems combine nanomaterials and biological components, creating synergistic platforms for diverse applications. We successfully developed MoAlB@MBene core-shell structure using HCl/H2O2 mixture, transforming the densely packed nanolaminar MoAlB MAB phase into an expanded multilayered MBene’ structure, featuring open slit-shaped pores. EDS and XRF analysis suggested that the voids between the Mo-B layers were due to the removal of approximately one aluminum layer. The etching of the MAB phase also caused a transition in the zeta potential from 1.11 to −3.35. Such characteristics suggest a potential for MBene’ surface functionalization. SEM and EDS confirmed that functionalization with 1.0 wt% fluorescent nanodiamonds (FND) was optimal, and guaranteed uniform distribution of the FND. Functionalization with FND ensured favorable optical properties, including fluorescence in the orange/red region and reduced direct band gap value (from 1.32 eV to 0.54 eV). The presence of FND mitigated the ecotoxicological properties of MoAlB@MBene. We observed sustained proliferation even at a concentration of 500 mg L−1 of the nanocomposite, with toxicity plateauing after 48 h of incubation. Optimization of encapsulation with sodium alginate suggested the best concentration (1.5 wt%) and cross-linking time (10 min), allowing for structural integrity, sphericality, and rapid microalgae growth. The fluorescent nanocomposite within encapsulated microalgae improved the decomposition rate of tetracycline (18 vs 45%) and doxycycline (14 vs 48%), achieving almost threefold enhancement within 24 h. Furthermore, it positively influenced microalgae growth, counteracting pharmaceuticals toxic effects. Altogether, these findings provide insights into developing and maintaining nanobiohybrid systems, incorporating fluorescent nanocomposite and microalgae, combining the knowledge from environmental protection and materials science.

Influence of copper ion cross-linked CMC-PVA film on cell viability and cell proliferation study

In this study, films composed of carboxymethyl cellulose and polyvinyl alcohol were fabricated using the solution casting method. Citric acid (4 %) was employed as a cross-linking agent, while glycerol (3 %) as a plasticizer. Cupric chloride (CuCl2·2H2O) was used for cross-linking at concentrations 0.5 %, 1 %, and 3 % over different times. The cross-linking with copper ions led to a noticeable reduction in elasticity, with the breaking strain ranging from 17.9 %–52.9 %. The ion hydration phenomenon increased the contact angle and swelling ratio. Fourier-transform infrared (FTIR) spectroscopy confirmed esterification reactions and copper ion cross-linking with sodium carboxymethyl cellulose (Na-CMC). The films showed antibacterial activity against Staphylococcus aureus and Escherichia coli. The ion-released mechanism followed was the non-Fickian super case-II type. The concentration and duration of cross-linking significantly influenced cell viability and proliferation. FE-SEM analysis revealed that effective concentrations of CuCl2.2H2O were 0.5 % and 1 %, and cross-linking times were 5–15 min, facilitating cell attachment and proliferation. Films are non-adhesive with water vapor permeation 800–900 g/m2/day. These results indicate the potential use of the films in treating second-degree burn wounds with low to medium exudate levels. This study provides valuable insights into the development of copper-infused materials for advanced wound healing applications.

Study on the preparation of a novel acrylic modified magnetic chitosan adsorbent and the adsorption behavior on Ga (III)

In the current study, a novel acrylic modified magnetic chitosan adsorbent (M- AA −CTS) was prepared, and then characterized using SEM, FTIR, and XPS. The preparation conditions, adsorption conditions, adsorption kinetics and thermodynamics were also studied. FTIR results indicate that acrylic acid is grafted onto the amino groups of chitosan in the form of poly acrylic acid and the amino groups are also crosslinked with glutaraldehyde. For the preparation process, the removal efficiency of Ga (III) ions is higher when the amount of acrylic acid is 3 mL, the reaction temperature is 308 K, the crosslinking time is 80 min, and the amount of glutaraldehyde is 0.6 mL. During the adsorption process, the higher adsorption capacity of Ga (III) ions can be achieved under the condition of the initial concentration of Ga (III) ions 50 mg/L, the adsorbent dose 0.05 g, the oscillation temperature 308 K and pH 3. The study on the adsorption kinetic indicates that the adsorption follows the pseudo-second-order kinetic model. The study on isotherm adsorption and thermodynamic indicates that the adsorption isotherm fits the Langmuir isotherm model better and the saturated adsorption capacity of Ga (III) ions on M−CTS−AA can reach 183.09 mg/g. Study on desorption and regeneration shows that after four cycles of desorption and reuse, the regeneration rate decreased from the initial 91.47 % to 73.3 %.

Investigating the impact of manufacturing conditions on crack growth rate in nitrile butadiene rubber for enhanced service life – Part 02: Crosslink density via multi-stage swelling analysis

The importance of the state of cure of elastomer components with regard to fatigue behavior and thus also durability was already discussed in more detail in Part 01 of the paper. It was shown that crosslinking time and temperature have an enormous influence on the crack growth behavior in nitrile butadiene rubber (NBR). In the course of this, a fourfold deceleration in crack growth was observed with a 20 K increase in manufacturing temperature. To confirm this trend, test specimens were produced at 180 °C. Crack growth was found to be 40 times slower, especially in high tearing energy ranges, compared to 150 °C. To analyze the observed behavior in more detail, cylindrical samples were taken from the plain strain test specimens (used for the crack growth measurements), and multi-stage swelling was performed with them. This allowed a detailed analysis of the degree of cure and the sulfur chain composition. It was found that the crosslink density decreases with increasing manufacturing temperature due to decomposition and the proportion of polysulfidic crosslinks decreases with increasing heating time due to desulfurization. Furthermore, a correlation between the results found by means of the rubber process analyzer (RPA) and the swelling results could be established looking at the maximum transmitted torque during the isothermal crosslinking phase.

Structure, Properties and Degradation of Self-Assembled Fibrinogen Nanofiber Scaffolds.

Self-assembled fibrinogen nanofibers are promising candidates for skin tissue engineering due to their biocompatibility and ability to mimic the native blood clot architecture. Here, we studied the structure-property relationship and degradation of rehydrated fibrinogen nanofibers prepared by salt-induced self-assembly, focusing on the effect of scaffold layering, cross-linking time and freeze-drying. Optimal fiber stability was achieved with cross-linking by formaldehyde (FA) vapor, while treatment with liquid aldehydes, genipin, EDC, and transglutaminase failed to preserve the nanofibrous architecture upon rehydration. Scaffold layering did not significantly influence the mechanical properties but changed the scaffold architecture, with bulk fiber scaffolds being more compact than layered scaffolds. Freeze-drying maintained the mechanical properties and interconnected pore network with average pore diameters around 20 μm, which will enhance the storage stability of self-assembled fibrinogen scaffolds. Varying cross-linking times altered the scaffold mechanics without affecting the swelling behavior, indicating that scaffold hydration can be controlled independently of the mechanical characteristics. Cross-linking times of 240 min increased scaffold stiffness and decreased elongation, while 30 min resulted in mechanical properties similar to native skin. Cross-linking for 120 min was found to reduce scaffold degradation by various enzymes in comparison to 60 min. Overall, after 35 days of incubation, plasmin and a combination of urokinase and plasminogen exhibited the strongest degradative effect, with nanofibers being more susceptible to enzymatic degradation than planar fibrinogen due to their higher specific surface area. Based on these results, self-assembled fibrinogen fiber scaffolds show great potential for future applications in soft tissue engineering that require controlled structure-function relationships and degradation characteristics.

Immobilization of Lipase from Thermomyces Lanuginosus and Its Glycerolysis Ability in Diacylglycerol Preparation.

In the glycerolysis process for diacylglycerol (DAG) preparation, free lipases suffer from poor stability and the inability to be reused. To address this, a cost-effective immobilized lipase preparation was developed by cross-linking macroporous resin with poly (ethylene glycol) diglycidyl ether (PEGDGE) followed by lipase adsorption. The selected immobilization conditions were identified as pH 7.0, 35 °C, cross-linking agent concentration 2.0%, cross-linking time 4 h, lipase amount 5 mg/g of support, and adsorption time 4 h. Enzymatic properties of the immobilized lipase were analyzed, revealing enhanced pH stability, thermal stability, storage stability, and operational stability post-immobilization. The conditions for immobilized enzyme-catalyzed glycerolysis to produce DAG were selected, demonstrating the broad applicability of the immobilized lipase. The immobilized lipase catalyzed glycerolysis reactions using various oils as substrates, with DAG content in the products ranging between 35 and 45%, demonstrating broad applicability. Additionally, the changes during the repeated use of the immobilized lipase were characterized, showing that mechanical damage, lipase leakage, and alterations in the secondary structure of the lipase protein contributed to the decline in catalytic activity over time. These findings provide valuable insights for the industrial application of lipase.

Enzymatic Insitu Crosslinking Can Improve Hydrogel Stability While Maintaining Matrix Stiffness

AbstractNext to the choice of a material, the crosslinking characteristics play an important role in the development of hydrogels for applications in the biomedical field. By decreasing crosslinking time or concentration one can reduce the density of the network and hence the stiffness of the hydrogel. However, at the same time in many cases the stability of the matrix is significantly reduced, leading to a rapidly degrading hydrogel structure. In this study, we evaluate and compare two different crosslinking methods while maintaining the material chemistry. The hydrogel system evaluated consisted of oxidized hyaluronic acid and gelatin, and it was crosslinked with microbial transglutaminase. We found that by in situ crosslinking (CL) instead of post CL we can significantly increase the stability of the hydrogel while maintaining the matrix stiffness. Encapsulated embryonic mouse fibroblasts showed an increased viability in in situ crosslinked samples. These findings indicate that it is possible to change hydrogel parameters independently, even if they are otherwise interrelated.

PH and Temperature-Responsive Silk Sericin/N-Isopropyl Acrylamide Interpenetrating Network Gel and Viscose Non-Woven Cross-Linked Composite Dressing

A gel (SNA-Ag) loaded with nanoscale silver particles and a pH-responsive agent was prepared using N-isopropyl acrylamide (NIPAAm) as the first network structure, silk sericin (SS) as the second network structure and reducing agent, alizarin as the pH indicator and co-reducing agent, N, N-methylene bisacrylamide (BIS) as the crosslinking agent, ammonium persulfate (APS) as the initiator and N, N, N, N-tetramethylethylenediamine (TEMED) as co-initiator. To improve the breaking strength of the gel, the temperature and pH-responsive antibacterial (V/SNA-Ag) composite dressing was prepared by crosslinking the SNA-Ag gel with viscose non-woven fabric using glutaraldehyde as the crosslinking agent. Fourier transform infrared spectrometer (FTIR) and scanning electron microscopy (SEM) showed that the SNA-Ag hydrogel was successfully crosslinked with the viscose non-woven fabric. Meanwhile, a gel coating was formed on the fabric, and the coating thickness increased when the crosslinking time was extended. Differential Scanning Calorimetry (DSC) and pH response tests confirmed that the dressing was temperature sensitive, and the Lower Critical Solution Temperature (LCST) of the dressing was about 35 °C. When the pH of the dressing was changed from acidic to alkaline, its color was changed from yellow to purple, indicating that its color presented pH response characteristics. The dressing not only had excellent swelling performance but also had outstanding antibacterial activity; the antibacterial degree for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was up to 99%. A cytotoxicity test suggested that the survival degree of mouse cells after incubation for 96 h was more than 75%, proving that it was safe and nontoxic. In addition, compared with viscose non-woven fabric, the breaking strength of composite dressing was increased, and the air permeability was decreased. In conclusion, we suggest that V/SNA-Ag composite dressings have great potential for monitoring and treating wounds.

Polyelectrolyte gelatin-chitosan hydrogel optimized for 3D bioprinting in skin tissue engineering

Bioprinting is a promising automated platform that enables the simultaneous deposition of multiple types of cells and biomaterials to fabricate complex three-dimensional (3D) tissue constructs. Collagen-based biomaterial used in most of the previous works on skin bioprinting has poor printability and long crosslinking time. This posed an immense challenge to create 3D constructs with pre-determined shape and configuration at high throughput. Recently, the use of chitosan for wound healing applications has attracted huge attention due to its attractive traits such as its antimicrobial properties and ability to trigger hemostasis. In this paper, we optimized polyelectrolyte gelatin-chitosan hydrogel for 3D bioprinting. Modification to the chitosan was carried out via the oppositely charged functional groups from chitosan and gelatin at a specific pH of ~pH 6.5 to form polyelectrolyte complexes. The polyelectrolyte hydrogels were evaluated in terms of physical interactions within polymer blend, rheological properties (viscosities, storage and loss modulus), printing resolution at varying pressures and feed rates and biocompatibility. The polyelectrolyte gelatin-chitosan hydrogels formulated in this work was optimized for 3D bioprinting at room temperature to achieve high shape fidelity of the printed 3D constructs and good biocompatibility with fibroblast skin cells.

Environmental-Friendly, Long-Lastingly Moist Phase Change Gel with Tunable Cross-Linking Time for Effective Borehole Sealing.

Flexible environmental phase change gel (EPCG) is a promising and attractive material for borehole sealing due to its relatively lower usage, tunable cross-linking time, and potential degradable properties. However, conventional borehole sealing materials lack a lower manufacturing cost, lower reaction temperature, remarkable antimold function, and admirable hole sealing performance for long-term high-performance borehole sealing. Hence, it remains a critical challenge to realize a flexible phase-change gel featuring tunable cross-linking time, antimold ability and degradability, and long-lasting moist performance for high-performance borehole sealing. Herein, we illustrate a facile approach to fabricate the borehole sealing materials based on environmentally friendly, antimold, long-lasting moist composite phase-change gel fabricated from a modified cellulose gel polymer network. The prepared phase change gel presents adjustable cross-linking time with the initial setting time of 30-60 min, which could be used to seal holes with different drilling parameters. Furthermore, the fabricated gel illustrates reliable water retentiveness performance and antimold ability, assuring the long-period borehole sealing effect. Furthermore, EPCG has been applied for borehole sealing and shows great sealing ability and gas extraction performance. Therefore, this work paves the way to fabricate a flexible phase-change gel featuring tunable cross-linking time, antimold ability, and long-lasting moist performance for high performance borehole sealing.

Cellulase entrapment into alginate-PEG beads cross-linked with glutaraldehyde: Optimization of the immobilization conditions and kinetic characterization of the immobilized enzyme

Immobilization methods for cellulase entrapped into alginate beads with glutaraldehyde (GA) cross-linking were investigated. Cellulase entrapped into alginate-polyethylene glycol beads with glutaraldehyde cross-linking (SA-PEG-E) showed more superiority both in terms of catalytic performance and reusability than other methods. Several conditions during SA-PEG-E immobilization such as cellulase concentration, GA amount, pH of immobilization, cross-linking time and hardening temperature were evaluated to study their effect on immobilized enzyme activity, immobilization yield and immobilization efficiency. Based on the results, GA amount, pH of immobilization and hardening temperature were selected for process optimization of SA-PEG-E using the Box-Behnken design of response surface methodology. The results showed that the optimum immobilized conditions were obtained with a GA amount of 0.8 mL, pH of immobilization 4.7, and hardening temperature of 47.5 °C when the cellulase concentration was 7.5 mg/mL and cross-linking time was 2 h. Then, the characterization of SA-PEG-E was studied. The optimum pH of SA-PEG-E was observed to be 4, 1 unit lower than that of the free enzyme (pH 5). The optimum temperature was the same for both free and immobilized cellulase at 50 °C. In addition, the SA-PEG-E exhibited broad pH and temperature adaptability.

Magnetic ligand fishing protocol combined with HPLC-FT-ICR-MS for screening potential α-Glucosidase inhibitors from UCG and in silico analysis

Uremic Clearance Granule (UCG) is a traditional Chinese medicines (TCMs) that has been recognized as potentially effective treatment for diabetic nephropathy (DN). However, the chemical composition and the hypoglycemic ingredients of UCG remain unclear. In this experiment, a magnetic ligand fishing protocol combined with HPLC coupled Fourier transform ion cyclotron resonance mass spectrometry (HPLC-FT-ICR-MS) technology was developed to screen and identify α-Glucosidase inhibitors from UCG. First, constituents of UCG was identified by HPLC-FT-ICR-MS. Next, α-Glucosidase coated Fe3O4@SiO2@NH2 (Fe3O4@SiO2@NH2@α-Glucosidase) nano composites was synthesized. The essential parameters (concentration of Glutaraldehyde (GA), ratio of Fe3O4@SiO2@NH2 to enzyme, crosslinking time and immobilization time) were optimized to obtain maximum enzyme activity and the performance of immobilized enzyme was compared with that of free enzyme. The α-Glucosidase inhibitory activities were then evaluated using autodock and the 4-Nitrophenyl-α-D-glucopyranoside (pNPG) method. As a result, 142 compounds were identified were identified by comparing the retention time, molecular ions and fragmentation behaviors with the reference compounds or the in-house database. 20 possible α-Glucosidase activity inhibitory components were identified using HPLC-FT-ICR-MS. Molecular docking and inhibition studies showed that 4 compuunds including Limonexic acid, Sanggenol A, Glabrone, Matrine were more likely to stronger α-Glucosidase inhibitory activities than acarbose. In conclusion, the proposed approach, which combined highly specific screening with HPLC-FT-ICR-MS, provided a powerful platform for discovering bioactive components from multi-component and multi-target traditional Chinese medicines (TCMs).

Preparation and Screening of SRB Gel Particles Used for Deep Purification of Acid Mine Drainage.

The progressive decline of the coal industry necessitates the development of effective treatment solutions for acid mine drainage (AMD), which is characterized by high acidity and elevated concentrations of heavy metals. This study proposes an innovative approach leveraging sulfate-reducing bacteria (SRB) acclimated to contaminated anaerobic environments. The research focused on elucidating the physiological characteristics and optimal growth conditions of SRB, particularly in relation to the pH level and temperature. The experimental findings reveal that the SRB exhibited a sulfate removal rate of 88.86% at an optimal temperature of 30 °C. Additionally, SRB gel particles were formulated using sodium alginate (SA) and carboxymethyl cellulose (CMC), and their performance was assessed under specific conditions (pH = 6, C/S = 1.5, T = 30 °C, CMC = 4.5%, BSNa = 0.4 mol/L, and cross-linking time = 9 h). Under these conditions, the SRB gel particles demonstrated an enhanced sulfate removal efficiency of 91.6%. Thermal analysis via differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) provided further insights into the stability and properties of the SRB gel spheres. The findings underscore the potential of SRB-based bioremediation as a sustainable and efficient method for AMD treatment, offering a novel and environmentally friendly solution to mitigating the adverse effects of environmental contamination.

Triaxial mechanical characterization of ultrasoft 3D support bath-based bioprinted tubular GelMA constructs

Support bath-based extrusion bioprinting is an emerging additive manufacturing paradigm that allows for the creation of geometrically complex three-dimensional tissue-mimicking constructs. Although this approach enables arbitrary geometries to be printed, preserving shape and mechanical integrity after the construct is extracted from the support bath is one of the main challenges today. In the present study, we systematically tested the effect of critical printing parameters on construct integrity and stiffness. Specifically, we varied the concentration and temperature of the bioink and support bath material, hydrogel crosslinking time, and cell density of the bioink. While previous studies on hydrogel materials quantify construct properties based on a single loading mode-such as uniaxial testing or rheological experiments, for example—we used a multiaxial mechanical testing protocol to assess the printed construct’s response in tension, compression, and shear. For each sample, we determined a single set of material parameters by simultaneously fitting all three modes in our inverse finite element framework. In support of future modeling work, we analyzed three different constitutive models with respect to their ability to match the construct’s mechanical response. We observed that GelMA concentration, temperature, and cell density have a statistically significant effect on the construct stiffness; support bath temperature and UV crosslinking time have a weak effect on construct stiffness; and support bath concentration appears to have no direct effect on the measured construct properties. Our construct stiffness were found to vary between 0.07 and 2.2 kPa depending on printing conditions, and showed noticeable tension–compression asymmetry as well as pronounced nonlinear behavior when loaded under shear.

BIOPOLYMER CONTROLLED RELEASE SYSTEMS BASED ON HYDROLYZED COLLAGEN: RELATIONSHIP OF CRYOFORMING CONDITIONS, STRUCTURE AND PROPERTIES

Biopolymer materials based on natural collagen (gelatin and hydrolyzed collagen) are widely used in the food, pharmaceutical and cosmetic industries due to their low toxicity, high biocompatibility, low antigenicity, and unique mechanical and technological properties. Hydrolyzed collagen, unlike gelatin, is formed by peptides with a lower molecular weight. It has higher bioavailability and biodegradability compared to gelatin. In this work, using low-temperature technologies, biopolymer matrices based on hydrolyzed collagen containing the antibacterial drug dioxidine were obtained. It has been shown that by varying such synthesis parameters such as the concentration of hydrolyzed collagen in the precursor solution (from 1 to 10%), matrix cross-linking time (0.1-24 hours), cryoforming temperature (-30 and -196 °C) it is possible to change the morphology and structure matrix, its degradation time and drug release time. The composition and structure of dioxidine/hydrolyzed collagen systems were characterized by SEM, IR and UV spectroscopy. The antibacterial activity of the resulting dioxidine/hydrolyzed collagen systems against E. coli and S. aureus was characterized by the disk diffusion method.

Poly(glycerol sebacate)-based soft-tissue-mimicked active layers for triboelectric nanogenerators

Herein poly(glycerol sebacate) (PGS) has been synthesized and characterized to identify it’s potential as an active triboelectric layer in implantable and biodegradable TENG devices. The implantable and biodegradable TENG devices require excellent triboelectric properties, as well as the ability to mimic the mechanical properties of the surrounding tissues and exhibiting low cytotoxicity and eventual degradation and removal by bio-absorption. Two-step synthesis of PGS was carried out by using polycondensation between glycerol and sebacic acid in 1:1 molar ratio, followed by film preparation by spray-coating of the prepolymer solution. Crosslinking conditions were elaborated to yield good triboelectric performance together with low cytotoxicity. Triboelectric surface charge density of up to 0.188 nC cm−2 was obtained, exceeding the values of common triboelectric materials such as PDMS and PTFE by 2.89 and 3.76 times, respectively, when tested under identical contact-separation parameters. The mechanical properties of PGS can be tuned by varying the crosslinking degree to mimic soft tissues. In this context, in vitro studies on human skin fibroblasts revealed cell viability up to 78%. Furthermore, the cell viability is found to be strongly related to the crosslinking time of the PGS. The results show significantly lower cytotoxicity as compared to, for example, poly(sorbitol sebacate) and poly(hexanediol-co-citric acid). The flexibility and the confirmed biocompatibility beside the unique mechanical and physio-chemical collective properties of the of the polymer demonstrates the potential use of PGS for the next generation of implantable TENG devices.Graphical abstract

Genipin crosslinked L-asparaginase CLEAs effectively mitigate acrylamide in deep-fried sweet potato chips

Crosslinked enzyme aggregates of L-asparaginase (A-CLEAs) were prepared using genipin, a non-toxic crosslinker. The process parameters for the preparation of A-CLEAs were optimized using a 3-level factorial design, which predicted the optimized conditions to be 60 mg/mL BSA, 2 mg/mL genipin and a crosslinking time of 4 h. The model which was validated experimentally, resulted in a recovery of 90% activity of L-asparaginase. While the optimum pH shifted to a slightly acidic range, the optimum temperature remained unchanged. A-CLEAs displayed the best pH stability at pH 9 (48%) after 24 h of incubation. At 50 °C, the deactivation rate constant (Kd) of A-CLEA decreased by 24%. A-CLEAs showed excellent reusability, retaining 79% of their initial activity after 10 cycles of use. The formation of a dark-blue coloured pigmented A-CLEA and the presence of the carboxymethyl group of genipin in FTIR spectrum confirmed the crosslinking reaction. The increase in the β-sheet content of A-CLEA, correlated with its improved stability. The improved thermostability with regards to structural integrity was well established by TGA-DSC analyses. Morphologically, A-CLEAs showed a highly clustered ball-like appearance. As a model example, the ability of genipin crosslinked A-CLEAs to reduce acrylamide in sweet potato chips was checked. The asparagine content of sweet potato was found to be 2906 ± 15.02 mg/kg as quantified by HPTLC. Analysis of acrylamide by GC-FID showed a 94% reduction in sweet potato chips on contact of sweet potato slices with A-CLEAs for 40 min.