Polyvinyl Alcohol-sodium Alginate Research Articles

Dispersion of halloysite nanotube/lipase nanohybrids as nanofillers into polyvinyl alcohol-sodium alginate cryogel: Characterization and bio-catalytic activity analysis

The purpose of this study is to formulate and characterize the cryogels containing halloysite nanotube (HNT)/lipase nanohybrid (NH-cryogel) in comparison to pure cryogels as well as cryogels containing lipase (lipase-cryogel). The cryogels were synthesized using polyvinyl alcohol (PVA) and sodium alginate (SA). The products are tested to explore the influence of the HNT/lipase nanohybride (NH) as nanofillers on the cryogel properties using methods such as swelling degree, water uptake measurement, TGA, XRD, FESEM and FTIR. Additionally, the effects of cryogels on the stability and biocatalytic activities of lipase and NH, were studied and compared to the free lipase to evaluate their potential applications as enzyme carriers. The addition of nanofillers into the cryogel improved is thermal stability. The results implied that NH-cryogel had better enzyme activity than lipase-cryogel and free lipase at different temperatures and pH values. The NH-cryogel residual activity was 85.5 % after ten cycles of reuse while lipase-cryogel showed lower residual activity (60.3 %). Furthermore, the NH-cryogel retained 81.1 % of its residual activity while this was 51.0 % for lipase-cryogel after thirty days of storage. Therefore, the presented results in this study provide a pathway to show that produced nano-composite cryogels could be useful substances for food and pharmaceutical industries applications.

Binary solvent-reinforced poly (vinyl alcohol)/sodium alginate double network hydrogel as a highly ion-conducting, resilient, and self-healing gel polymer electrolyte for flexible supercapacitors

We present a reliable approach for producing high-performance ion-conducting gel polymer electrolytes (GPEs) based on the sodium chloride (NaCl)-integrated dual network hydrogel of poly (vinyl alcohol)/sodium alginate (PVA/SA) using a binary solvent system of ethylene glycol (EG) and water, providing exceptional ionic conductivity, mechanical strength, and self-healing properties. Different GPEs were produced via the freezing-thawing method using different v/v% of EG and water (named PVA/SA/EG). The best PVA/SA/EG GPE provided a maximum ionic conductivity of 25 mS cm−1, astonishing mechanical strength of 0.42 MPa, exceptional stretchability of 462 %, and remarkable self-healing properties. The binary solvent system- and water-based GPEs were utilized in the construction of symmetric supercapacitors (SSCs) using carbon cloth electrodes and their electrochemical performance were compared. At a current density of 0.5 mA cm−2, the SSC prepared using the best PVA/SA/EG GPE demonstrated a high specific capacity of 577.21 mF cm−2, maintained 94.5 % capacitance after 5000 cycles at 1 mA cm−2, and provided an energy density of 80.14 mWh cm−2 while operating at a power density of 293.3 mW cm−2. The flexible SSC prepared based on this GPE demonstrated outstanding flexibility, while no significant decline in capacitive performance and ionic conductivity was detected when it was bent.

Preparation of a colorimetric hydrogel indicator reinforced with modified aramid nanofiber employing natural anthocyanin to monitor shrimp freshness.

The pH-responsive hydrogels have potential applications in food visualization detection, but their fragile mechanical properties limit their applicability. The excellent mechanical properties and thermal stability of aramid nanofibers (ANFs) can improve the structural stability of hydrogels. In this study, the surface properties of ANFs were enhanced through modification to improve their surface activity. The modified ANFs, designated as ANF-SN, were produced following treatment with a mixture of sulfuric acid (H2SO4) and nitric acid (HNO3), which led to increased reactivity and dispersibility of the ANFs due to the proliferation of active groups on their nanofiber surface. The preferred anthocyanin extract from purple sweet potatoes (purple sweet potato extract [PSPE]) had significant color responses to pH (2-12) and ammonia vapor. A stable dual-network colorimetric hydrogel was fabricated by combining ANF-SN, polyvinyl alcohol/sodium alginate (PVA/SA), and PSPE through a two-step method (freeze-thawing and staining). Characterization analysis showed that the strong acid modification of ANFs effectively improved their chemical reactivity. ANF-SN was better than ANF in promoting the formation of hydrogen bond networks, enhancing hydrogel network structures, and improving the viscoelasticity of hydrogels. The optimal hydrogel indicator PVA/SA/ANF-SN/PSPE had good color responsiveness and sensitivity to ammonia. It can also be used to further determine shrimp freshness value using a smartphone and RGB color-picking software.

Sodium alginate/polyvinyl alcohol for the recovery of rare earth elements from mining wastewater: Mechanism and properties

With the demand for rare earth elements (REEs) increasing in the high-tech sector, the recovery of REEs from secondary sources is becoming very critical. In this study, sodium alginate/polyvinyl alcohol (SA/PVA) beads obtained by cross-linking alginate with polyvinyl alcohol were used to recover REEs from real rare-earth wastewaters. The results showed that SA/PVA beads are less affected by temperature and exhibited adsorption selectivity for REEs. The efficiency of adsorbing REEs ranged from 27.6% to 52.6%, but was significantly higher than that of 9.2% Mn. Meanwhile, among the observed REEs, SA/PVA beads revealed a preference for light REEs (44.3% − 52.6%). The adsorption process was investigated utilizing advanced characterization methods, namely Scanning Electron Microscope, Fourier Transform Infrared Spectrometer, and X-ray Diffraction Spectra. Combined with the results of Pearson correlation analysis, we proposed that the adsorption process involves the combined effects of ion exchange, complexation, electrostatic interaction and pore filling. As well, a desorption efficiency of more than 76.9% can be achieved with sodium citrate, which makes possible the effective recovery of REEs. In summary, this study provides a promising green, environmentally friendly and sustainable material for the enrichment and recovery of REEs from mining wastewater.

Designable polypyrrole pattern in hydrogel achieved by photo‐controllable concentration of Fe3+ initiator

AbstractConductive polymer hydrogels (CPHs) are promising in cutting‐edge applications including bioelectronics and tissue engineering. However, the precise regulation of the spatial distribution of the conductive polymer (CP) in the hydrogel network is still an issue for designing a smart material. Herein, we propose a facile method for preparing CPH‐based smart materials by controlling the distribution of Fe3+ initiator with UV light irradiation. Thus, designable polypyrrole (PPy) conductive patterns in the polyvinyl alcohol/sodium alginate (PVA/SA) semi‐interpenetrating hydrogel network are demonstrated by controlling the concentration of Fe3+ ions coordinated with carboxylate groups. Depending on the irradiation time, the reduction of Fe3+ to Fe2+ occurs in different extents. As a result, the controllable polymerization of pyrrole only initiated by Fe3+ is achieved to form desirable CPH patterns, which are confirmed by the characterization results of Fourier transform infrared spectrometry, X‐ray photoelectron spectroscopy, and scanning electron microscopy. Moreover, the developed hydrogel with PPy patterns is illustrated for the application in smart conductive circuit and information encryption. The simple procedure and the controllable conductive patterning of the proposed method make it a promising route in developing smart hydrogel materials, which can be extended to other Fe3+ initiated CP patterns.

Enhanced removal of 2,4-dichlorophenol by a novel biotic-abiotic hybrid system based on zeolitic imidazolate framework-8

Biotic-abiotic hybrid systems have recently emerged as a potential technique for stable and efficient removal of persistent contaminants due to coupling of microbial catabolic with abiotic adsorption/redox processes. In this study, Burkholderia vietnamensis C09V (B.V.C09V) was successfully integrated with a Zeolitic Imidazolate Framework-8 (ZIF-8) to construct a state-of-art biotic-abiotic system using polyvinyl alcohol/ sodium alginate (PVA/SA) as media. The biotic-abiotic system (PVA/SA-ZIF-8 @B.V.C09V) was able to remove 99.0 % of 2,4-DCP within 168 h, which was much higher than either PVA/SA, PVA/SA-ZIF-8 or PVA/SA@B.V.C09V (53.8 %, 72.6 % and 67.2 %, respectively). Electrochemical techniques demonstrated that the carrier effect of PVA/SA and the driving effect of ZIF-8 collectively accelerated electron transfer processes associated with enzymatic reactions. In addition, quantitative-PCR (Q-PCR) revealed that ZIF-8 stimulated B.V.C09V to up-regulate expression of tfdB, tfdC, catA, and catC genes (2.40-, 1.68-, 1.58-, and 1.23-fold, respectively), which encoded the metabolism of related enzymes. Furthermore, the effect of key physical, chemical, and biological properties of PVA/SA-ZIF-8 @B.V.C09V on 2,4-DCP removal were statistically investigated by Spearman correlation analysis to identify the key factors that promoted synergistic removal of 2,4-DCP. Overall, this study has created an innovative new strategy for the sustainable remediation of 2,4-DCP in aquatic environments.

Enhanced arsenic removal using biochar immobilized bacteria encapsulated in polyvinyl alcohol-sodium alginate beads: Fabrication, optimization and performance evaluation

Arsenic ranks first on the Substance Priority List of the Agency for Toxic Substances and Disease Registry and causes a wide range of health problems, including cancer and even death. The present work was focused on the removal of arsenic using bacteria, Proteus alimentorum strain TY6 and Pseudomonas aeruginosa strain K7Pb, immobilized on peanut shell biochar [0.05 % (w/v)] and encapsulated in polyvinyl alcohol (PVA) – sodium alginate (SA) beads crosslinked with calcium chloride (CaCl2). The maximum removal efficiency obtained was 92.29 ± 0.51 % and 93.63 ± 0.09 % for As(V), using beads of K7Pb and K7Pb + TY6 respectively, whereas for As(III), it was 91.71 ± 0.51 % with TY6 and 93.35 ± 0.05 % for KP7b + TY6, at pH 7 at 30 °C. Surface morphology was characterized by scanning electron microscopy and energy-dispersive x-ray analysis. This study revealed that the encapsulated bacteria immobilized on biochar were more effective than the free-cell and bacteria immobilized on biochar. It was also found that the beads could be reused effectively for five cycles (for K7Pb and TY6) and eight cycles (for K7Pb + TY6) before their removal efficiency reduced to below 80 %.

Degradable, biocompatible, and flexible capacitive pressure sensor for intelligent gait recognition and rehabilitation training

Gait recognition and rehabilitation training based on pressure sensing technology have an important role in the field of rehabilitation medicine. However, existing pressure sensors that are used in this process are often fabricated from non-degradable or non-biocompatible source materials, which limits their application in long-term sustainable use. In this study, we propose a high-performance, degradable, biocompatible and flexible capacitive pressure sensor. Its dielectric layer is prepared using a polyvinyl alcohol/sodium alginate (PVA/SA) electrospun nanofiber membrane (ENM), while its upper and lower electrodes are fabricated from PVA@graphene screen-printed ENMs. Experimental results demonstrate the sensor's exceptional pressure sensing performance, characterized by its high sensitivity (0.54 kPa−1 at 0–10 kPa), low detection limit (∼2.2 Pa), rapid response time (26.6/29.9 ms), and excellent stability (5000 cycles). Furthermore, it exhibits outstanding biocompatibility, achieving a cell viability assay survival rate exceeding 97%, and remarkable degradability, completely degrading within one hour. A gait recognition and rehabilitation training system has been developed by integrating the sensors with a deep learning algorithm and wireless transmission technology. The system can effectively monitor and record dynamic parameters of lower limb swing during walking, exhibiting an impressive gait recognition accuracy of 98% over five normal and abnormal gaits. Moreover, it can guide patients in performing diverse rehabilitation actions as well as monitor their progress through action count recording. This innovative solution offers a sustainable approach to gait recognition and rehabilitation training within the field of rehabilitation medicine, thereby opening up new avenues for patient recovery.

Preparation and Characterization of Amoxicillin-Loaded Polyvinyl Alcohol/Sodium Alginate Nanofibrous Mat: Drug Release Properties, Antibacterial Activity, and Cytotoxicity

AbstractThis study aimed to prepare a polyvinyl alcohol/sodium alginate (PVSA) nanofibrous mat as an amoxicillin (AMOX) delivery system. AMOX was loaded to the PVSA nanofibers during electrospinning, and the AMOX-loaded PVSA (PVSA/AMOX) nanofibrous mat was cross-linked by glutaraldehyde (GA). The PVSA/AMOX nanofibrous mat was characterized by Fourier Transform infrared spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller, and mercury porosimetry analyses. The thickness, air permeability, and water vapor transmission rate of the PVSA/AMOX nanofibrous mat were 0.43 ± 0.08 mm, 17.2 ± 4.91 L/m2/s, and 1485 ± 13.6 g/m2/d, respectively, which were suitable for wound dressing applications. The tensile strength was 6.73 ± 0.48 MPa and elongation at a maximum load was 81.9 ± 17.0%, within the ranges of human skin’s values. The total porosity was 59.4%, enabling cell adhesion, migration, and proliferation. The PVSA/AMOX nanofibrous mat has high swelling (319 ± 4.2%) and low degradation (2.2 ± 0.1% in 10 days) ratios. The nanofibrous mat cross-linked with 0.25% GA solution for 20 min had a 73.07% cumulative release for 90 min. The drug release kinetics were obeyed to the Korsmeyer-Peppas model. The nanofibrous mat presented antibacterial activity on S. aureus ATCC 29213 and E. coli ATCC 25922, and there was no cytotoxic effect on the human normal keratinocyte cells, demonstrating the potential for use in wound dressing applications.

A new strategy for accelerating recovery of anaerobic granular sludge after low-temperature shock: In situ regulation of quorum sensing microorganisms embedded in polyvinyl alcohol sodium alginate

Low-temperature could inhibit the performance of anaerobic granular sludge (AnGS). Quorum sensing (QS), as a communication mode between microorganisms, can effectively regulate AnGS. In this study, a kind of embedded particles (PVA/SA@Serratia) based on signal molecule secreting bacteria was prepared by microbial immobilization technology based on polyvinyl alcohol and sodium alginate to accelerate the recovery of AnGS system after low temperature. Low-temperature shock experiment verified the positive effect of PVA/SA@Serratia on restoring the COD removal rate and methanogenesis capacity of AnGS. Further analysis by metagenomics analysis showed that PVA/SA@Serratia stimulated higher QS activity and promoted the secretion of extracellular polymeric substance (EPS) in AnGS. The rapid construction of EPS protective layer effectively accelerated the establishment of a robust microbial community structure. PVA/SA@Serratia also enhanced multiple methanogenic pathways, including direct interspecies electron transfer. In conclusion, this study demonstrated that PVA/SA@Serratia could effectively strengthen AnGS after low-temperature shock.

Hesperidin - loaded PVA/alginate hydrogel: targeting NFκB/iNOS/COX-2/TNF-α inflammatory signaling pathway.

Skin injuries represent a prevalent form of physical trauma, necessitating effective therapeutic strategies to expedite the wound healing process. Hesperidin, a bioflavonoid naturally occurring in citrus fruits, exhibits a range of pharmacological attributes, including antimicrobial, antioxidant, anti-inflammatory, anticoagulant, and analgesic properties. The main objective of the study was to formulate a hydrogel with the intention of addressing skin conditions, particularly wound healing. This research introduces a methodology for the fabrication of a membrane composed of a Polyvinyl alcohol - Sodium Alginate (PVA/A) blend, along with the inclusion of an anti-inflammatory agent, Hesperidin (H), which exhibits promising wound healing capabilities. A uniform layer of a homogeneous solution comprising PVA/A was cast. The process of crosslinking and the enhancement of hydrogel characteristics were achieved through the application of gamma irradiation at a dosage of 30 kGy. The membrane was immersed in a Hesperidin (H) solution, facilitating the permeation and absorption of the drug. The resultant system is designed to deliver H in a controlled and sustained manner, which is crucial for promoting efficient wound healing. The obtained PVA/AH hydrogel was evaluated for cytotoxicity, antioxidant and free radical scavenging activities, anti-inflammatory and membrane stability effect. In addition, its action on oxidative stress, and inflammatory markers was evaluated on BJ-1 human normal skin cell line. We determined the effect of radical scavenging activity PVA/A (49 %) and PVA/AH (87%), the inhibition of Human red blood cell membrane hemolysis by PVA/AH (81.97 and 84.34 %), hypotonicity (83.68 and 76.48 %) and protein denaturation (83.17 and 85.8 %) as compared to 250 μg/ml diclofenac (Dic.) and aspirin (Asp.), respectively. Furthermore, gene expression analysis revealed an increased expression of genes associated with anti-oxidant and anti-inflammatory properties and downregulated TNFα, NFκB, iNOS, and COX2 by 67, 52, 58 and 60%, respectively, by PVA/AH hydrogel compared to LPS-stimulated BJ-1 cells. The advantages associated with Hesperidin can be ascribed to its antioxidant and anti-inflammatory attributes. The incorporation of Hesperidin into hydrogels offers promise for the development of a novel, secure, and efficient strategy for wound healing. This innovative approach holds potential as a solution for wound healing, capitalizing on the collaborative qualities of PVA/AH and gamma irradiation, which can be combined to establish a drug delivery platform for Hesperidin.

Enhancing nitrogen removal performance using immobilized aerobic denitrifying bacteria by modified polyvinyl alcohol/sodium alginate (PVA/SA)

Aerobic denitrification has emerged as a promising and efficient method for nitrogen removal from wastewater. However, the direct application of aerobic denitrifying bacteria has faced challenges such as low nitrogen removal efficiency, bacterial loss, and poor stability. To address these issues, this study developed a novel microbial particle carrier using NaHCO3-modified polyvinyl alcohol (PVA)/sodium alginate (SA) gel (NaHCO3-PVA/SA). This carrier exhibits several advantageous properties, including excellent mass transfer efficiency, favorable biocompatibility, convenient film formation, abundant biomass, and exceptional pollutant treatment capacity. The carrier was modified with 0.3% NaHCO3, 8.0% PVA, and 1.0% SA, resulting in a remarkable 3.4-fold increase in the average pore diameter and a 12.8% improvement in mass transfer efficiency. This carrier was utilized to immobilize the aerobic denitrifying bacterium Stutzerimonas stutzeri W-2 to enhance nitrogen removal (NaHCO3-PVA/SA@W-2), resulting in a NO3−-N removal efficiency of 99.06%, which was 21.39% higher than that without modification. Compared with the non-immobilized W-2, the degradation efficiency was improved by 43.70%. After five reuses, the NO3−-N and TN removal rates remained at 99% and 93.01%, respectively. These results provide a solid foundation for the industrial application of the modified carrier as an effective tool for nitrogen removal in large-scale wastewater treatment processes.

Enhanced treatment of acute organophosphorus pesticide poisoning using activated charcoal-embedded sodium alginate-polyvinyl alcohol hydrogel.

The adsorption of activated charcoal is currently a major clinical treatment for acute organophosphorus pesticide poisoning (AOPP). However, the adsorption duration and efficiency of this method is unstable. In this study, a hydrogel embedding activated charcoal was prepared and its alleviating effects on AOPP were investigated. A composite hydrogel using sodium alginate and polyvinyl alcohol (SA-PVA) hydrogel was prepared in this study. The structural properties of the SA-PVA hydrogel were characterized via multiple analysis including FTIR, TGA, XRD, SEM, tensile strength and expansion rate. Based on these, activated charcoal (AC) was embedded within the SA-PVA hydrogel (SA-PVA-AC) and it was used for the treatment of AOPP. Structural characterization indicated SA-PVA hydrogel possesses excellent mechanical properties and biocompatibility. The invivo study demonstrated that SA-PVA-AC significantly alleviated the inflammation and oxidative damage in the liver, as evidenced by reduced levels of IL-6, TNF-α, and, IL-1β, SOD, and MDA. Furthermore, SA-PVA-AC treatment effectively re-regulated the activities of serum AST and ALT, exhibiting an improved effect on liver function. The findings suggest that activated charcoal embedded within SA-PVA hydrogel has significant potential as a therapeutic agent in treating AOPP, and offering a novel approach to managing pesticide-induced toxicity.

Characterizations of Centrifugal Electrospun Polyvinyl Alcohol/Sodium Alginate/Tamanu Oil/Silver Nanoparticles Wound Dressing.

Known for its water solubility, flexibility, strong adhesion, and eco-friendly nature, polyvinyl alcohol (PVA) is widely used in various industries. In the medical field, it is used for applications such as creating bandages and orthopaedic devices. Incorporating sodium alginate (SA) into PVA membranes enhances their structural integrity, breathability, and permeability, thereby minimising the risk of cellular damage in the wound zone. Moreover, the addition of tamanu oil (C alophyllum inophyllum L.) and silver nanoparticles, both of which are known for their antibacterial properties and benefits in traditional wound healing, further enhances the membranes' wound-healing effectiveness. Following production, the membranes undergo a series of tests designed to evaluate their physical properties as well as their antioxidant and antibacterial capabilities. Subsequently, in vitro testing is conducted using human skin cells; experiments on Wistar rats are then performed. Numerous experiments have consistently demonstrated that the performance of polyvinyl alcohol/sodium alginate/tamanu oil (PVA/SA/Oil) membrane is superior to that of polyvinyl alcohol/sodium alginate/tamanu oil/silver nanoparticles (PVA/SA/Oil/Ag NP) membrane. Specifically, the polyvinyl alcohol/sodium alginate (PVA/SA) combination exhibits an impressive wound-healing rate of 98.82% after 15 days, with cells maintaining a high viability of 92% in a nourishing environment. Moreover, these membranes exhibit exceptional resistance to the oxidation of free radicals, surpassing the 70% threshold, and they possess antibacterial activity against Staphylococcus aureus subsp. aureus in vitro. Based on the obtained results, the nanofiber membranes composed of polyvinyl alcohol/ alginate/ tamanu oil, with or without silver nanoparticles, have shown potential as wound dressings in the wound care discipline.

Invasive plant-derived biochar for sustainable bioremediation of pesticide contaminated soil

Managing invasive plant presents a significant challenge to both the environment and the economy. There is an opportunity to address this issue by utilizing invasive plants as a sustainable and cost-effective source of valuable functional materials for environmental remediation. In this study, a promising Mikania micrantha biochar (MB) was synthesized by pyrolyzing an invasive plant, which was utilized for bacterial immobilization and adsorption of contaminants. By embedding Proteus terrae ZQ02-MB within a polyvinyl alcohol-sodium alginate gel to create a biochar-modified bacterial microsphere (BBM), the superior degradation of pesticide contaminants was observed. Taking chlorothalonil (CHT) as an example, field experiments demonstrated that BBM achieved a removal efficiency of 59.8% by the third day. Additionally, BBM not only improved the richness and diversity of soil bacteria but also enhanced the microbial community structure by the seventh day. On this basis, the adsorption capacity of MB, biofilm growth promoting ability of BBM, and the CHT mineralization ability of strain ZQ02 were validated as a joint mechanism to promote efficient CHT removal. Overall, this study proposes a composite model of invasive plant-derived biochar loaded microorganisms, which has great potential in eliminating pollutant residues and paves new paths to develop strategies for reusing invasive species resources.

Evaluating the Volume Ratio Effect on Absorption Time of Polyvinyl Alcohol-Sodium Alginate Based Fiber Membranes as a Wound Dressing

This research was observed absorption of the membrane PVA/SA fiber as wound dressing. The electrospinning method is used to make fiber membranes. This method with a volume ratio composition of Polyvinyl Alcohol (PVA) - sodium alginate (SA) (PVA/ SA) of 9 :1 (v/v), 8:2 (v/v), and 7:3 (v/v). The PVA/SA membrane was characterized with absorption characterization-water absorption test, morphology and fiber diameter. Absorption characterization-water absorption test results that the fastest absorption time occurred on the PVA/SA fiber membrane with a ratio of 7:3 (v/v). From the SEM results, it is known that the morphology of the PVA/SA membrane shows a fiber size with a uniform diameter. The fiber diameter decreases as it increases SA volume fraction. Fibers with a small diameter will have a large surface area and absorb liquid more quickly. Keywords: electrospinning, wound dressing, absorption characterization-water absorption test, size fiber

Continuous monitoring of temperature and freshness in cold chain transport based on the dual-responsive fluorescent hydrogel

Comprehensive attention should be paid to the potential food spoilage in food transport. However, there is a problem of freshness destruction by repeated freezing and thawing during the cold chain transport. Herein, a fluorescent hydrogel with N-doped green-emitting carbon dots (N-GCDs), bovine serum albumin-gold nanoclusters (BSA-AuNCs) as fluorescent probes and polyvinyl alcohol-sodium alginate hydrogel as carrier matrix was developed to continuously detect temperature and freshness. Due to the solvatochromic effect of N-GCDs, when the temperature surpassed the threshold, the mixture of water and dimethyl sulfoxide underwent a phase transition and melted into the gel, changing the fluorescence color to realize the temperature monitoring. Then, due to the pH effect of BSA-AuNCs, the gel could respond to pH changes in food deterioration to monitor the food freshness. Thus, the changes of both fluorescence color and intensity of the hydrogel provides a new method for visual and portable authenticity of food freshness.

Molybdenum disulfide nanoflowers - doped sodium alginate/polyvinyl alcohol porous xerogel for methylene blue and copper ion adsorption

In order to improve the adsorption performance of MoS2, as well as to solve the problems of MoS2-powder in adsorption, which is prone to agglomeration and difficulty to be recycled, we prepared MoS2-nanoflowers(MoS2-NFs), and mixed them with sodium alginate/polyvinyl alcohol(SA/PVA) to prepare MoS2-NFs/SA/PVA xerogel(MSP) by freezing-lyophilization. Then two forms of xerogels - block-MSP(MSPB) and spherical-MSP(MSPS) were prepared, and they were used as methylene blue(MB) and Cu2+ adsorbent. It was found that MoS2-NFs were evenly dispersed inside the SA/PVA with no agglomeration, while the interior of MSPB/MSPS showed the structure of parallel-pores and radial-pores, respectively. The adsorption capacity of MSPB/MSPS on MB can reach 233 mg/g, which is five times higher than SA/PVA-gel, showing excellent synergistic-adsorption effect, and the adsorption capacity for Cu2+ reaches 271 mg/g. The adsorption mechanism indicated that the adsorption of MB by MSPB/MSPS conformed to pseudo-first-order model, with electrostatic force as the main force. And their adsorption of Cu2+ conformed to pseudo-second-order model and was dominated by Lewis acid/base soft-soft interactions. Notably, after long-term adsorption, MSPB/MSPS maintains its shape and more than 90 % of the adsorption capacity, ensuring the recovery and reuse of materials. So, MSPB/MSPS has great potential in adsorption, providing a new solution for sewage purification.

Investigation on polyvinyl alcohol and sodium alginate blend matrix with ammonium nitrate conducting electrolytes for electrochemical applications

Polyvinyl alcohol (PVA) Sodium alginate (NaAlg) polymer composites were synthesized by solution casting technique and doping with ammonium nitrate (NH4NO3). The functionalization structure of the produced electrolytes was investigated using XRD and AC impedance spectroscopy. XRD confirms amorphous nature. The ionic conductivity of the electrolytes is evaluated using ac impedance measurements at temperatures ranging from 303 to 353 K. PVA: NaAlg: NH4NO3 (60:40:15 wt%) blend polymer electrolyte was observed to have the highest conductivity of 1.05 × 10−6 S cm−1. The Arrhenius plot appears to be obeyed by the temperature dependent ionic conductivity and is of non-debye type. Activation energy for best conducting electrolyte was 0.2364 eV. The dielectric relaxation of the polymer electrolyte has been studied, and the results are described. Relaxation time estimated from loss tangent analysis also affirms that value is low for highest conducting sample. Results of CV and LSV studies gave a plausible approach for electrochemical application.

A Novel Method for γ-Aminobutyric Acid Biosynthesis Using Glutamate Decarboxylase Entrapped in Polyvinyl Alcohol-Sodium Alginate Capsules.

γ-aminobutyric acid (GABA) has essential physiological functions in the human body. A novel method using glutamate decarboxylase (GAD) entrapped in polyvinyl alcohol (PVA)-sodium alginate (SA) capsules provides a green biological strategy for GABA synthesis. In this investigation, the stability range of immobilized GAD was effectively broadened, and immobilized GAD could be repeatedly used as a batch and fixed-bed column catalyst. The immobilized enzymes were stable and retained 89% of their activity in a pH range of 4.0-5.6, while there was an approximately 50% decrease in free GAD activity in the pH range of 4.8 ± 0.4. The immobilized GAD affinity to the substrate improved, and this was evidenced by the apparent decrease in Km to 13.3 mmol/L from the 30.9 mmol/L for free GAD. The immobilized GAD retained >90.6% activity after eight cycles and a near-100% enzyme activity retention after 120 h of a continuous fixed-bed column catalyst operation. This study has thus presented an effective PVA-SA-GAD immobilization method that could be used to continuously scale-up GABA biosynthesis.