Application of Hierarchically Porous Chitosan Monolith for Enzyme Immobilization.

Enzyme immobilization is a crucial technique for improving the stability of enzymes. Compared with free enzymes, immobilized enzymes offer several advantages in industrial applications. Efficient enzyme immobilization requires a technique that integrates the advantages of physical absorption and covalent binding while addressing the limitations of conventional support materials. This study offers a practical approach for immobilizing α-amylase on a hierarchically porous chitosan (CS) monolith. An optimized CS monolith was fabricated using chemically modified chitin by thermally induced phase separation. By combining physical adsorption and covalent bonding, this technique leverages the amino and hydroxy groups present in CS to facilitate effective enzyme binding and stability. α-Amylase immobilized on the CS monolith demonstrated excellent stability, reusability, and increased activity compared to its soluble counterpart across various pH levels and temperatures. In addition, the CS monolith exhibited a significant potential to immobilize other enzymes, namely, lipase and catalase. Immobilized lipase and catalase exhibited higher loading capacities and enhanced activities than their soluble forms. This versatility highlights the broad applicability of CS monoliths as support materials for various enzymatic processes. This study provides guidelines for fabricating hierarchical porous monolith structures that can provide efficient enzyme utilization in flow systems and potentially enhance the cost-effectiveness of enzymes in industrial applications.

Cefixime loaded bare and functionalized halloysite nanocarriers and their biomedical applications.

Effective drug delivery for is the foremost requirement for the complete recovery of the disease. Nanomedicine and nanoengineering has provided so many spaces and ideas for the drug delivery design, whether controlled, targeted, or sustained. Different types of nanocarriers or nanoparticles are aggressively designed for the drug delivery applications. Clay minerals are identified as a one of the potential nanocarrier for the drug delivery. Owing to their biocompatibility and very low cytotoxicity, clay minerals showing effective therapeutic applications. In the present investigation, clay mineral, i.e., Halloysite nano tubes are utilized as a nanocarrier for the delivery of antibiotic cefixime (CFX), a third-generation cephalosporin. The HNT was first functionalized with the sulfuric acid and then further treated with the 3-(aminopropyl)triethoxysilane (APTES). The drug is loaded on three different classifications of HNTs, i.e., Bare-CFX-HNT, Acid-CFX-HNT, and APTES-CFX-HNT and their comparative analysis is established. Different characterization techniques such as X-ray diffractometry (XRD), Fourier transform infra-red (FT-IR), Transmission electron microscopy TEM), Brunauer-Emmett-Teller (BET), adsorption studies, and Thermogravimetric analysis (TGA) were performed to evaluate their chemical, structural, morphological, and thermal properties. TGA confirmed the encapsulation efficiency of Bare-CFX-HNT, Acid-CFX-HNT, and APTES-CFX-HNT as 42.65, 52.19, and 53.43%, respectively. Disk diffusion and MTT assay confirmed that the drug loaded HNTs have potential antibacterial activities and less cytotoxicity. The adsorption capacity of CFX with different HNTs are evaluated and Different adsorption and kinetic models have been discussed. Drug release studies shows that APTES-CFX-HNT showing sustained release of cefixime as compared to Bare-CFX-HNT and Acid-CFX-HNT.

Augmentin loaded functionalized halloysite nanotubes: A sustainable emerging nanocarriers for biomedical applications.

Clay minerals such as Halloysite nanotubes (HNTs), abundantly available green nanomaterial, exhibit a significant advantage in biomedical applications such as drug delivery, antibacterial and antimicrobials, tissue engineering or regeneration, etc. Because of the mesoporous structure and high absorbability, HNTs exhibit great potential as a nanocarrier in drug delivery applications. The sulfuric acid treatment enhances the surface area of the HNTs and thereby improves their drug-loading capacity by enlarging their lumen space/inner diameter. In the present investigation, based on the literature that supports the efficacy of drug loading after acid treatment, a dual treatment was performed to functionalize the HNTs surface. First, the HNTs were etched and functionalized using sulfuric acid. The acid-functionalized HNTs underwent another treatment using (3-aminopropyl) triethoxysilane (APTES) to better interact the drug molecules with the HNTs surfaces for efficient drug loading. Augmentin, a potential drug molecule of the penicillin group, was used for HNTs loading, and their antibacterial properties, cytotoxicity, and cumulative drug release (%) were evaluated. Different characterization techniques, such as X-ray diffractometer (XRD) and Fourier Transform Infra-Red (FT-IR), confirm the loading of Augmentin to the APTES@Acid HNTs. TEM images confirm the effective loading of the drug molecule with the HNTs. The drug encapsulation efficiency shows 40.89%, as confirmed by the Thermogravimetric Analysis (TGA). Also, the Augmentin-loaded APTES@Acid HNTs exhibited good antibacterial properties against E. coli and S. aureus and low cytotoxicity, as confirmed by the MTT assay. The drug release studies confirmed the sustainable release of Augmentin from the APTES@Acid HNTs. Hence, the treated HNTs can be considered as a potential nanocarrier for effectively delivering Augmentin and promoting enhanced therapeutic benefits.

Zn salts incorporated polyurethane/polyacrylonitrile electrospinning fiber membrane for high porosity polymer electrolyte in Zn ion battery.

So far, a large variety of polymer molecule architectures have been explored in the electrolyte field. Polymer electrolytes have gathered research efforts as an interesting alternative to conventional liquid electrolytes due to their advantages of low probability of leakage and low volatility of liquid solvent, lightweight, flexibility, inertness, high durability, and thermal stability. In this work, a polymer electrolyte developed from a polyurethane/polyacrylonitrile (PU/PAN) electrospinning fiber membrane was added with different zinc (Zn) salts, namely, Zn(CH3CO2)2, ZnSO4, and Zn(OTf)2. The samples with the Zn salt presented many different properties; especially, the high Zn(OTf)2 sample showed gradually bundle morphology in its structure. Characterization revealed improved properties in contact angle, water uptake, and thermal resistance. Namely, the 15 wt% Zn(OTf)2) sample exhibited an outstandingly high ionic conductivity of 3.671 mS cm-1, which is 10 times higher than that of the neat PU/PAN membrane.

Optimization of rapid self-healing and self-adhesive gluten/guar gum crosslinked gel for strain sensors and electronic devices.

In this study, a smart strain sensor based on gluten/guar gum (GG) copolymer containing a combination of additives was developed. The mix proportions of strain sensors were designed using Taguchi method coupled with Grey relational analysis. L16 orthogonal array with three factors, viz. tannic acid (TA), glycerol and sodium chloride (NaCl) at four-levels each was optimized. The addition of TA substantially enhanced tensile strength, self-adhesion ability and conductivity. The self-adhesion ability could also be improved by adding NaCl in range of 0-5 wt%. The presence of glycerol in strain sensors could reduce the self-healing time which was found in the range of 28.75-150 s. In addition, the incorporation of glycerol into gel also improved stretchability of strain sensors. The best mix proportion of strain sensor was found to be 3.75 wt% TA, 30 vol% glycerol and 5 wt% NaCl. The best mixture of stain sensor showed the highest gauge factor (GF) of 0.61 % at a stretchability of 665 % and rapid self-healing at 70 s. This strain sensor could be applied to monitor human limb movements in a wide temperature range from -20 °C to 50 °C. Furthermore, the obtained gel was successfully used as electronic devices and self-powered sensors.

Waste plastics derived nickel-palladium alloy filled carbon nanotubes for hydrogen evolution reaction.

Carbon nanotubes (CNTs) composed of bimetallic nickel-palladium (NiPd) nanoparticles encapsulated in graphitic carbon shells (NdPd@CNT) are prepared by the chemical vapour deposition method using waste polyethylene terephthalate (PET) plastic carbon sources and NiPd-decorated carbon sheets (NiPd@C) catalyst. The characterization results reveal that the face-centered cubic crystalline (fcc)-structured NiPd bimetallic alloy nanoparticles are encased by thin carbon nanotubes. The bimetallic synergism of NiPd nanoparticles actuates the outer CNT layers and accelerates the electrical conductivity, stimulating the electrochemical activity toward an effective hydrogen evolution reaction (HER). By virtue of the collective individualities of highly conductive aligned carbon walls and bimetallic active sites, the NiPd@CNT-equipped HER delivers a minimum overpotential of 87 mV and a Tafel slope value of 95 mV dec-1. The existing intact contact between NiPd and CNT facilitates continuous electron and ion transportation and firm stability toward long-term hydrogen production in HER. Notably, the NiPd@CNT reported here produces excellent electrochemical activity with minimal charge transference resistance, substantiating the efficacy of NiPd@CNT for futuristic green hydrogen production.

Sustainable functionalized chitosan based nano-composites for wound dressings applications: A review.

Functionalized chitosan nanocomposites have been studied for wound dressing applications due to their excellent antibacterial and anti-fungal properties. Polysaccharides show excellent antibacterial and drug-release properties and can be utilized for wound healing. In this article, we comprise distinct approaches for chitosan functionalization, such as photosensitizers, dendrimers, graft copolymerization, quaternization, acylation, carboxyalkylation, phosphorylation, sulfation, and thiolation. The current review article has also discussed brief insights on chitosan nanoparticle processing for biomedical applications, including wound dressings. The chitosan nanoparticle preparation technologies have been discussed, focusing on wound dressings owing to their targeted and controlled drug release behavior. The future directions of chitosan research include; a) finding an effective solution for chronic wounds, which are unable to heal completely; b) providing effective wound healing solutions for diabetic wounds and venous leg ulcers; c) to better understanding the wound healing mechanism with such materials which can help provide the optimum solution for wound dressing; d) to provide an improved treatment option for wound healing.

Microinjection Molded Biopolymeric Airway Stent with Antibacterial and Anti-Hyperplastic Properties.

Central airway stenosis is a condition that the diameter of the trachea or main bronchus shrinkage is caused by external compression or internal tissue hyperplasia, which can cause difficulty breathing, asphyxia, and even death. Airway stenting is an easy way to restore the patency of the central airway, but airway stents commonly used in clinical practice can lead to complications such as mucus plugging, bacterial infection, and granulation tissue hyperplasia. Moreover, the non-degradable characteristic makes it requires a second operation to remove, which has the potential to cause tissue damage. In this study, a biodegradable airway stent is fabricated by microinjection molding using the bioelastomer of poly (L-lactide-co-ε-caprolactone) as the matrix material. The airway stent has excellent mechanical properties and an appropriate degradation rate. The hydrophilic surface of the airway stent can inhibit mucus plugging. The loading of silver nanoparticles and cisplatin endows the stent with antibacterial and anti-hyperplastic functions. In vitro and in vivo experiments demonstrate that this study provides an antibacterial and anti-hyperplastic biodegradable airway stent with elastic properties to avoid secondary removal operation and reduce complications associated with mucus plugging, bacterial infection, and granulation tissue hyperplasia.

Cellulose Nanocrystal-Based Gradient Hydrogel Actuators with Controllable Bending Properties.

Stimuli-responsive hydrogel actuators are being increasingly used in microtechnology, but typical bilayer hydrogel actuators have significant drawbacks due to weak adhesive interface between the two layers. In this study, thermoresponsive single-layer hydrogel actuators are produced by generating a gradient distribution of cellulose nanocrystals (CNCs) in a poly(N-isopropylacrylamide) (PNIPAAm) hydrogel network by electrophoresis. Tunable bending properties of the composite hydrogels, such as the thermoresponsive bending speed and angle, are realized by varying the electrophoresis time, applied voltage, and CNC concentration. By varying these conditions, the gradient distribution of the CNCs can be optimized, leading to fast bending and large bending angles of the hydrogels. Bending properties are attributed to the gradient distribution of CNCs causing different deswelling rates across the hydrogel network owing to reinforcing effects. Bending ability is also influenced by differences in the CNC dimensions based on the sources of cellulose, which determine the rigidity of the CNC-rich layer of the polymer composite. It is thus shown that thermoresponsive single-layer gradient hydrogels with tunable bending properties can be realized.

Bio-Inspired Homogeneous Conductive Hydrogel with Flexibility and Adhesiveness for Information Transmission and Sign Language Recognition.

The wearable electronic technique is increasingly becoming an effective approach to overcoming the communication obstacles between signers and non-signers. However, the efficacy of conducting hydrogels currently proposed as flexible sensor devices is hindered by their poor processability and matrix mismatch, which frequently results in adhesion failure at the combined interfaces and deterioration of mechanical and electrochemical performance. Herein, we propose a hydrogel composed of a rigid matrix in which the hydrophobic and aggregated polyaniline was homogeneously embedded, while quaternate-functionalized nucleobase moieties endowed the flexible network with adhesiveness. Accordingly, the resulting hydrogel with chitosan-graft-polyaniline (chi-g-PANI) copolymers exhibited a promising conductivity (4.8 S·m-1) because of the uniformly dispersed polyaniline components and a high strain strength (0.84 MPa) because of the chain entanglement of chitosan after soaking. In addition, the modified adenine molecules not only realized synchronization in improving the stretchability (up to 1303%) and exhibiting a skin-like elastic modulus (≈184 kPa), but also provided a durable interfacial contact with various materials. The hydrogel was further fabricated into a strain-monitoring sensor for information encryption and sign language transmission based on its sensing stability and strain sensitivity of up to 2.77. The developed wearable sign language interpreting system provides an innovative strategy to assist auditory or speech-impaired people in communicating with non-signers using visual-gestural patterns including body movements and facial expressions.

Surface modification of cellulose with succinic anhydride in dimethyl sulfoxide using potassium carbonate as a catalyst.

Cellulose succinates (CSs) having degrees of substitution (DSs) ranging from 0.78 to 2.77 were successfully obtained by reacting cellulose with succinic anhydride (SA) in dimethyl sulfoxide at room temperature using a small amount of inexpensive solid potassium carbonate as a catalyst. Interestingly, CSs with higher DS values were obtained with a much smaller amount of catalyst than previously reported. Moreover, it is possible to control the DS by tailoring the reaction time and mass ratio of cellulose/SA. The hydroxyl groups at the C-6, C-2, and C-3 positions were the main esterification positions. In this process, most of the raw materials are either incorporated into the product or are recoverable. The E-factor, which reflects the sustainability of a given process, was demonstrated to be reduced by 93% by recovering the raw materials.

Design of biomass-based N, S co-doped porous carbon via a straightforward post-treatment strategy for enhanced CO2 capture performance.

Biomass-based adsorbents are considered to have great potential for CO2 capture due to their low cost, high efficiency and exceptional sustainability. The aim of this work is to design a simple method for preparing biomass-based adsorbents with abundant active sites and large numbers of narrow micropores, so as to enhance CO2 capture performance. Herein, N, S co-doped porous carbon (NSPC) was created utilizing walnut shell-based microporous carbon (WSMC) as the main framework and thiourea as N/S dopant through physical grinding and post-treatment process at a moderate temperature without any other reagents and steps. By altering the post-treatment parameters, a series of porous carbons with varying physico-chemical properties were prepared to discuss the roles of microporosity and N/S functional groups in CO2 adsorption. NSPC with narrow micropore volume of 0.74 cm3 g-1, N content of 4.89 % and S contents of 0.71 % demonstrated the highest CO2 adsorption capacity of 7.26 (0 °C) and 5.51 mmol g-1 (25 °C) at 1 bar. Meanwhile, a good selectivity of binary gas mixture CO2/N2 (15/85) of 29.72 and outstanding recyclability after ten cycles of almost 100 % adsorption capacity retention were achieved. The proposed post-treatment method was beneficial in maintaining the narrow micropores and forming N/S active sites, which together improve the CO2 adsorption performance of NSPC. The novel NSPC displays amazing CO2 adsorption characteristics, and the practical, affordable synthetic approach exhibits significant potential to produce highly effective CO2 adsorbents on a broad scale.

A starch-based, crosslinked blend film with seawater-specific dissolution characteristics.

Existing biodegradable plastics may not be ideal replacements of petroleum-based single-use plastics owing to their slow biodegradation in seawater. To address this issue, a starch-based blend film with different disintegration/dissolution speeds in freshwater and seawater was prepared. Poly(acrylic acid) segments were grafted onto starch; a clear and homogenous film was prepared by blending the grafted starch with poly(vinyl pyrrolidone) (PVP) by solution casting. After drying, the grafted starch was crosslinked with PVP by hydrogen bonds, owing to which the water stability of the film is higher than that of unmodified starch films in fresh water. In seawater, the film dissolves quickly as a result of disruption of the hydrogen bond crosslinks. This technique balances degradability in marine environment and water resistance in everyday environment, provides an alternative route to mitigate marine plastic pollution and could be potentially useful for single-use applications in different fields such as packaging, healthcare, and agriculture.

Enhancing the oxygen reduction activity by constructing nanocluster-scaled Fe2O3/Cu interfaces.

Interface engineering is a promising strategy to enhance the catalytic performance of electrocatalysts for the oxygen reduction reaction (ORR). However, it is still a challenge to modulate the size into a suitable range (e.g., nanocluster-scale) to make the most of the interface. Moreover, the explicit mechanism of the interface for enhancing catalytic performance is still elusive. Herein, a model catalyst (FeCu@NC) loaded with nanocluster-scaled Fe2O3/Cu interfaces was prepared by modulating the metal components of the precursor to explore the enhancement of interface engineering for the ORR. Benefiting from the synergistic effect of the strong interfacial coupling effects of Fe2O3/Cu and optimized microstructure, FeCu@NC exhibited superior ORR activity and zinc-air battery performance. Experimental and theoretical calculations revealed that the presence of the Fe2O3/Cu interface breaks the traditional cognition to endow the Cu atoms (intrinsically inferior for the ORR) with a slight positive charge, which serves as the active sites for the ORR. This study provides a novel insight into the design of advanced electrocatalysts for the ORR by interface engineering.

High electrolyte uptake of MXene integrated membrane separators for Zn-ion batteries.

The recent development of separators with high flexibility, high electrolyte uptake, and ionic conductivity for batteries have gained considerable attention. However, studies on composite separators with the aforementioned properties for aqueous electrolytes in Zn-ion batteries are limited. In this research, a polyacrylonitrile (PAN)/bio-based polyurethane (PU)/Ti3C2Tx MXene composite membrane was fabricated using an electrospinning technique. Ti3C2 MXene was embedded in fibers and formed a spindle-like structure. With Ti3C2Tx MXene, the electrolyte uptake and ionic conductivity reached the superior values of 2214% and 3.35 × 10-3 S cm-1, respectively. The composite membrane presented an excellent charge-discharge stability when assembled in a Zn//Zn symmetrical battery. Moreover, the developed separator exhibited a high flexibility and no dimensional and structural changes after heat treatment, which resulted in the high-performance separator for the Zn-ion battery. Overall, the PAN/bio-based PU/Ti3C2Tx MXene composite membrane can be potentially used as a high-performance separator for Zn-ion batteries.

Gamma-Glutamylcysteine Production Using Phytochelatin Synthase-Like Enzyme Derived from Nostoc sp. Covalently Immobilized on a Cellulose Carrier.

Gamma-glutamylcysteine (γ-EC) is an intermediate generated in the de novo synthesis of glutathione (GSH). Recent studies have revealed that the administration of γ-EC shows neuroprotective effects against oxidative stress in age-related disorders and chronic diseases like Alzhiemer's disease in model animals, which is not expected function in GSH. A phytochelatin synthase-like enzyme derived from Nostoc sp. (NsPCS) mediates γ-EC synthesis from GSH. To achieve low-cost and stable commercial level supply, the availability of immobilized NsPCS for γ-EC production was investigated in this study. Among the tested immobilization techniques, covalent binding to the cellulose carrier was most effective, and could convert GSH completely to γ-EC without decreasing the yield. The stable conversion of γ-EC from 100 mM GSH was achieved by both batch repeated and continuous reactions using the immobilized NsPCS on cellulose sheet and column shape monolith, respectively. The immobilization of NsPCS on those carriers is promising alternative technique for high-yielding and cost-effective production of γ-EC on its commercial applications.

Exploring the structural dependence of metal-free carbon electrocatalysts on zinc-based metal-organic framework types.

Metal-organic frameworks (MOFs) have been widely used as precursors to derive carbon-based electrocatalysts for the oxygen reduction reaction (ORR) due to their high porosity and tunable chemical composition/structure. However, the influence of MOF type on the structure and further ORR activity of derived metal-free carbon catalysts is still elusive. In the present work, a series of different Zn-based MOFs were employed as precursors to explore this issue. Meanwhile, prepare N-doped metal-free carbon catalysts were prepared for the ORR under the activation of sacrificial urea (which is effective to enhance the ORR activity of carbon-based catalysts). By analyzing the intermediates during pyrolysis, it is found that the decisive role of MOF types on the doped N and the morphology of derived carbon catalysts was played by the Zn coordination environment of MOFs and its reactivity with the decomposition intermediate of urea. Although the structure and porosity of derived carbon catalysts from different MOFs are very different, they all showed superior ORR activity and Zn-air battery performance up to 20 wt% Pt/C benchmark catalysts. From the above analyses, the combination of urea and compounded Zn is also a promising activation method for the preparation of highly-efficient metal-free carbon electrocatalysts.

Facile Fabrication of Hierarchically Porous Boronic Acid Group-Functionalized Monoliths With Optical Activity for Recognizing Glucose With Different Conformation.

At present, various materials based on helical polymers are nanoparticle or microsphere, which is not ease of use in practical application. Accordingly, facile preparation hierarchically porous monolith based on helical polymer needs to be developed. Herein, hierarchically porous boronic acid group-functionalized monoliths that exhibited optical activity were fabricated with a facile method based on crosslinking and polymerization-induced phase separation (CPIPS). Chiral substituted acetylene and achiral substituted acetylene with a boronic acid group were used as monomers. By regulating the composition of the pre-polymerization solution, the permeability and macropore size of the porous structure could be controlled. The hierarchically porous structure and large surface area were confirmed by scanning electron microscopy and nitrogen gas adsorption/desorption isotherms. In particular, the boronic acid functional group that can interact with a cis-diol group was successfully introduced on the skeleton surface of the monoliths. Further, the main chain of the copolymer that constituted the monoliths exhibited a high cis content and tacticity, and the monoliths showed good optical activity. Thus, the present study established a facile method to synthesize hierarchically porous boronic acid group-functionalized monoliths with optical activity via CPIPS, and the monoliths showed potential in recognition, separation, and adsorption of compound with chirality and cis-diol groups.

Porosity-Induced Improvement in KOH Activation of Chitin Nanofiber-Based Porous Carbon Leading to Ultrahigh Specific Capacitance.

The applicability of chitin-based carbon as a supercapacitor electrode material was investigated by adjusting its pore structure through polystyrene latex templating, without significant N doping. 2,2,6,6-tetramethylpiperidinyloxy (TEMPO)-oxidized chitin nanofibers were mixed with polystyrene latex, hydrothermally treated at 220 °C, carbonized, and activated using KOH at 800 °C, yielding activated hierarchical porous carbon. The variation of both polystyrene latex amount and carbonization temperature resulted in changes in the surface area and pore structure, which dictated the degree of pore uniformity and activation efficiency. The pore structure affected activation by allowing the selective removal of amorphous carbon, exposing the basal plane carbon, resulting in higher specific capacitance. By making activated hierarchical porous carbon more conducive to activation, specific capacitance of 567 F g-1 at 0.5 A g-1 was achieved, with no loss in performance after 10000 charge-discharge cycles.

Multi-Responsive Optimization of Novel pH-Sensitive Hydrogel Beads Based on Basil Seed Mucilage, Alginate, and Magnetic Particles.

Conventional drug delivery systems often cause side effects and gastric degradation. Novel drug delivery systems must be developed to decrease side effects and increase the efficacy of drug delivery. This research aimed to fabricate hydrogel beads for use as a drug delivery system based on basil seed mucilage (BSM), sodium alginate (SA), and magnetic particles (MPs). The Taguchi method and Grey relational analysis were used for the design and optimization of the hydrogel beads. Three factors, including BSM, SA, and MPs at four levels were designed by L-16 orthogonal arrays. BSM was the main factor influencing bead swelling, drug release rate at pH 7.4, and release of antioxidants at pH 1.2 and 7.4. In addition, SA and MPs mainly affected drug loading and drug release rate in acidic medium, respectively. Grey relational analysis indicated that the composition providing optimal overall properties was 0.2 vol% BSM, 0.8 vol% SA, and 2.25 vol% MPs. Based on the findings of this work, BSM/SA/MPs hydrogel beads have the potential to be used as a pH-sensitive alternative material for drug delivery in colon-specific systems.