Chitosan Research Articles

A Biocompatible, Highly Sensitive, and Non-Enzymatic Glucose Electrochemical Sensor Based on a Copper-Cysteamine (Cu-Cy)/Chitosan-Modified Electrode.

A biocompatible, highly sensitive, and enzyme-free glucose electrochemical sensor was developed based on a copper-cysteamine (Cu-Cy)-modified electrode. The catalytically active biocompatible material Cu-Cy was immobilized on the electrode surface by the natural polymer chitosan (CTS). The electrochemical characterization and glucose response of the Cu-Cy/CTS/glassy carbon electrode (GCE) were investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and constant potential amperometry. The significant electrocatalytic activity of Cu-Cy to the oxidation of glucose in an alkaline environment was revealed. Several crucial parameters, including the number of scanning cycles for electrode activation, applied potential, and the contents of Cu-Cy and chitosan, were investigated to understand their impact on the sensor's response. The proposed sensing platform exhibited linear ranges of 2.7 μM to 1.3 mM and 1.3 mM to 7.7 mM for glucose detection, coupled with high sensitivity (588.28 and 124.42 μA·mM-1·cm-2), and commendable selectivity and stability. Moreover, a Cu-Cy/CTS-modified screen-printed electrode (SPE) was further developed for portable direct detection of glucose in real samples.

Development and characterization of polyvinyl alcohol/chitosan crosslinked malic acid composite films with curcumin encapsulated in β-cyclodextrin for food packaging application

Considering that fruits are vulnerable to damage and waste during stockpiling, transport and marketing. Given this, an innovative curcumin inclusion compound (Cur@β-CD) was devised in this study to introduce oil-soluble curcumin (Cur) into water-soluble polyvinyl alcohol (PVA) materials, thereby fabricating food packaging films endowed with excellent properties. DPPH test manifested that the oxidation resistance for PCOMC-Cur@β-CD film was 95 % above PVA material. It was ascribed to the fact that the Cur@β-CD elevated the water solubility of Cur while the increase of water solubility heightened the antioxidant effect for Cur in the film. Additionally, the chitosan (CS) was crosslinked with malic acid (MA), which elevated the barrier property of the film, reduced the amount of oxygen transmission and further retarded the oxidation reaction of the fruits for packaging. The antibacterial test demonstrated that the antibacterial rates of PCOMC-Cur@β-CD film against E. coli and S. aureus reached 92 % and 95 %, respectively, which was attributed to the slow release of Cur when Cur@β-CD was dissolved in PVA material and the Schiff base reaction between Cur and amino groups on CS. These findings indicate that the PCOMC-Cur@β-CD film developed in this work can provide certain insights into the field of food packaging.

Chitosan mitigated the adverse effect of Cd by regulating antioxidant activities, hormones, and organic acids contents in pepper (Capsicum annum L.)

Chitosan (CTS) is one of the natural healers’ alternatives to chemical products within the scope of good agricultural practices. It can be used in the improvement of agriculture (prevention of toxic metal uptake by plants) due to its chelating feature of metal ions. This study aims to investigate the effectiveness of chitosan in eliminating the negative effects of cadmium (Cd) stress on pepper (Capsicum annum L.). The results showed that Cd stress significantly decreased plant growth, chlorophyll content, and leaf water relative content, followed by an increase in proline, antioxidant enzyme activities, and abscisic acid (ABA) content. According to the results, Cd treatment (200 mg kg-1) significantly increased the aspartate, glutamate, asparagine, histidine, and phenylalanine content, while it significantly decreased the content of endogenous hormones such as gibberellic acid (GA), indole-3-acetic acid (IAA), and salicylic acid (SA). However, CTS application decreased the uptake of Cd and caused a decrease in hydrogen peroxide (H2O2), abscisic acid (ABA), and melondialdehyde (MDA) content, as well as an increase in plant performance, and GA, IAA, and SA content in the plants grown under Cd pollution compared to the ones treated with Cd and without CTS. This study suggests that CTS application helps pepper seedlings tolerate Cd stress through a decrease in Cd uptake, and an increase in amino acids and hormone content.

Fumed nano-silica modified PVA-chitosan composite hydrogel with Janus structure for solar-driven interfacial evaporation

Solar-driven interfacial evaporation (SIE) receives much attention nowadays. At present, efficient thermal management and salt resistance during operation are still the difficulties of SIE technology. In this work, a new composite hydrogel for SIE has been reported. This composite hydrogel uses polyvinyl acetate (PVA) and chitosan (CS) as the framework, carbon nanoparticles (CB) as the photothermal material, modified with hydrophilic/hydrophobic fumed nano-silica. The addition of fumed nano-silica reduces the thermal conductivity and effectively immobilizes heat energy on the evaporator’s top surface, which reduces heat loss and improves the evaporation rate. The CSPC (CB/Nano-silica PVA-CS) evaporator modified with hydrophobic nano-silica exhibits Janus structure with transition from a hydrophobic top to a hydrophilic bottom. The Janus-structured CSPC evaporator has the characteristics of excellent salt resistance, simple preparation process, low heat loss with self-floating property. The CSPC evaporator containing 0.5 g hydrophobic fumed nano-silica has a maximum evaporation rate of 1.58 kg/(m2·h), about 1.6 times higher than the evaporator without fumed nano-silica, which proves that the introduction of fumed nano-silica can effectively improve the evaporation performance of hydrogel. The overall efficiency of CSPC evaporator in simulated seawater is 88.63 %. The evaporation rate of CSPC evaporator has reached a high level in the evaporators using carbon black as photothermal material which was prepared by simple and low-cost method. It should be a promising category of material to be employed for solar desalination.

Study on Preparation and Performance of Acid pH-Responsive Intelligent Self-Healing Coating.

In this paper, microcapsules with acidic pH stimulus responsiveness were prepared through a one-step in situ polymerization method and a layer-by-layer assembly method. The effects of factors such as chitosan (CS) concentration, polymerization time, polymerization process temperature, and the number of polymerization layers on the performance of microcapsules were explored, and microcapsules with optimal performance were prepared and added to the epoxy coating. The morphology and structure of the microcapsules were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and zeta potential testing. The thermal stability and sustained release properties of the microcapsules were studied through thermogravimetric analysis and sustained release curve testing. Through scratch experiments, immersion experiments, salt spray experiments, and electrochemical impedance spectroscopy tests, the impact of the added amount of microcapsules on the self-healing performance and anti-corrosion performance of the coating in complex environments was explored. The results show that the optimal preparation process of acidic pH-responsive microcapsules requires that the concentration of chitosan is 2 mg/mL, the polymerization time of the polyelectrolyte layer is 8 h, the heating temperature during the polymerization process is 75 °C, and the number of polyelectrolyte layers is three. The prepared acidic pH-responsive microcapsules have good morphology, pH sensitivity, and thermal stability. The average particle size is approximately 203 μm, the drug loading rate reaches 59.74%, and the encapsulation rate reaches 63.99%. The optimal added amount of the acidic pH-responsive microcapsule coating is 15 wt%. The coating has a dual-trigger mechanism underlying it stimulus response capability and has an obvious stimulus response to acidic pH. It can inhibit corrosion in non-scratch areas, and its anti-corrosion ability is significantly stronger than that of epoxy coatings and ordinary self-healing coatings. The coating has a stronger repair effect and anti-corrosion ability when the environmental pH becomes acidic.

Eco-Friendly Design of Chitosan-Based Films with Biodegradable Properties as an Alternative to Low-Density Polyethylene Packaging.

Biopolymer-based films are a promising alternative for the food packaging industry, in which petrochemical-based polymers like low-density polyethylene (LDPE) are commanding attention because of their high pollution levels. In this research, a biopolymer-based film made of chitosan (CS), gelatin (GEL), and glycerol (GLY) was designed. A Response Surface Methodology (RSM) analysis was performed to determine the chitosan, gelatin, and glycerol content that improved the mechanical properties selected as response variables (thickness, tensile strength (TS), and elongation at break (EAB). The content of CS (1.1% w/v), GEL (1.1% w/v), and GLY (0.4% w/v) in the film-forming solution guarantees an optimized film (OPT-F) with a 0.046 ± 0.003 mm thickness, 11.48 ± 1.42 mPa TS, and 2.6 ± 0.3% EAB. The OPT-F was characterized in terms of thermal, optical, and biodegradability properties compared to LDPE films. Thermogravimetric analysis (TGA) revealed that the OPT-F was thermally stable at temperatures below 300 °C, which is relevant to thermal processes in the food industry of packaging. The reduced water solubility (WS) (24.34 ± 2.47%) and the improved biodegradability properties (7.1%) compared with LDPE suggests that the biopolymer-based film obtained has potential applications in the food industry as a novel packaging material and can serve as a basis for the design of bioactive packaging.

Injectable nanogels to improve triamcinolone acetonide delivery and toxicity on the treatment of eye diseases.

Triamcinolone acetonide (TA) is a corticosteroid, and widely used in the treatment of eye diseases such as macular edema, proliferative vitreoretinopathy, and chronic uveitis. It's also used in diseases such as osteoarthritis and rheumatoid arthritis. Despite the width of its usage, it has toxicity in the eye. Nanogels are advantageous in applying toxic and low bioavailability drugs thanks to their swelling ability and stability. In the presented study, to minimize the disadvantages of TA, and to reach the drug into the back segment of the eye, TA-loaded chitosan (CS) nanogel (CS-TA Nanogel) has been prepared, and in vitro characterized. CS-TA nanogels were prepared by ionic gelation and characterized by SEM, FTIR, and TGA. Drug release profile, and in vitro cytotoxicity was determined to evaluate the efficacy of nanogels for intravitreal eye applications. DNA damage, and oxidative stress caused by nanogels in eye endothelial cells were investigated. CS and CS-TA nanogels were synthesized in the sizes range 200-300nm with an overall positive charge surface. The loading efficiency of TA on nanogels was determined as 50%. Cells exposed to 250µg/ml free TA showed 74% viability, while this rate was 90% in cells exposed to CS-TA nanogels. 8-OHdG levels were determined as 54.93 ± 1.118ng/mL in control cells and 92.47 ± 0.852ng/mL in cells exposed to 250µg/ml TA. TA both induces oxidative stress and causes DNA damage in HRMEC cells. However, administration of TA with carrier increased cell viability, total antioxidant capacity, and reduced oxidative DNA damage.

Enhanced hemocompatibility and antioxidant efficacy of chitosan-PCL nanofibrous mats with olive oil and honey nika cream for wound healing applications

This study introduces an innovative approach utilizing electrospun scaffold matrices comprising polycaprolactone (PCL) and chitosan (CS), enriched with active ingredients of olive and Honey Nika cream (NC). These matrices were assessed for their potential as advanced wound dressings. The microstructures shown uniformly smooth nanofibers with diameters ranging from 200 to 250 nm across various formulations. XRD results demonstrated that incorporating NC and CS simultaneously, increased the crystallinity of PCL. The thermal analysis illustrated that although the addition of NC and CS declined the thermal stability of PCL fibers, but had no significant influence on the microstructure of the PCL fibers, and scaffolds have suitable chemical stability. FTIR analysis revealed the presence of olive oil, honey, and propolis components in the scaffolds. The developed nanofibers demonstrated advantageous properties such as prolonged NC release due to the incorporation of chitosan, enhanced cell adhesion, optimal swelling and degradation rates, minimal hemolytic activity (less than 0.44 %), and suitable antioxidant capabilities (approximately 50.97 for PNC mat). Further corroborated by in vitro cytocompatibility assessments via MTT assays were shown biocompatibility of the prepared nanofibrous mats. This research highlights the promise of PCL/CS electrospun nanofbrous scaffold for wound healing applications.

Progress in Utilizing Chitosan-Based Nanoparticles for Pulmonary Drug Administration

The escalating prevalence of respiratory ailments poses a significant global public health challenge, ranking among the primary causes of mortality worldwide. Notably, diseases such as asthma, chronic obstructive pulmonary disease, pneumonia, cystic fibrosis, and lung cancer, alongside the emergence of respiratory diseases, notably those induced by the coronavirus family, have contributed substantially to global fatalities in the past two decades. Consequently, numerous studies have been undertaken to enhance the effectiveness of therapeutic interventions against these diseases, with a particular emphasis on nanomedicine-driven pulmonary drug delivery. As a result, the development of nanocarriers has emerged as a promising avenue to surmount the constraints associated with traditional therapies, aiming to elevate drug bioavailability at the intended site while minimizing undesired side effects. Within this domain, nanoparticles fashioned from chitosan (CS) exhibit distinct advantages over alternative nanocarriers owing to the inherent biological properties of chitosan, including its anti-inflammatory, antimicrobial, and mucoadhesive attributes. Furthermore, CS nanoparticles have demonstrated the potential to augment drug stability, extend the duration of action, refine drug targeting, regulate drug release kinetics, optimize the dissolution of poorly soluble drugs, and enhance the cell membrane permeability of hydrophobic drugs. These unique properties position CS nanoparticles as a promising candidate for optimizing drug performance following pulmonary administration. Consequently, this review endeavors to elucidate the potential of chitosan nanoparticles in the realm of pulmonary drug delivery, shedding light on how their intrinsic biological characteristics can ameliorate the treatment landscape of pulmonary diseases. Emphasis is placed on delineating the synergistic interplay between chitosan nanoparticles and the encapsulated drug, thereby offering insights into the prospective advancements in treating respiratory ailments.

Development of ROS-sensitive capofungin hydrogel by crosslinking chitosan with four-arm polyethylene glycol derivative for treatment of vulvovaginal candidiasis

Both exogenous and endogenous reactive oxygen species (ROS) in vulvovaginal candidiasis (VVC) play pivotal roles in promoting the hyphal formation of Candida albicans (CA), which suggests that clearing ROS could inhibit CA hyphae formation. A ROS-sensitive hydrogel (CAS@4Arm-PB/CS) was formulated by using a novel four-arm polyethylene glycol (4Arm-PEG) derivative (4Arm-PB) as a crosslinking agent, chitosan (CS) as the hydrogel matrix, and caspofungin (CAS) as the antifungal drug against CA. The ROS-sensitivity, disintegration mechanism, crosslinking action, swelling degree, microstructure, modulus, and rheological properties of 4Arm-PB were characterized. According to the results, 5.0 % 4Arm-PB could quickly and efficiently cross-link 0.5 mg/mL of CS. The ROS-sensitivity of 4Arm-PB was 10–50 μM, indicating a strong ROS sensitivity. The in vitro and in vivo anti-CA results indicated that CAS@4Arm-PB/CS not only cleared endogenous and exogenous ROS and inhibited the formation of CA hyphae and biofilm but also contributed beneficially to the treatment of VVC mice caused by CA infection, implying a certain safety aspect and an in vivo applicability. This research introduces a novel functional crosslinking agent for CS hydrogel formulation, presenting a new avenue for hydrogel-based drug delivery systems and therapeutic strategies for VVC treatment.

Efficient removal of organophosphate insecticide employing magnetic chitosan-derivatives

Herein, this work reports an efficient acephate adsorption using chitosan (CS) incorporating varying amounts of magnetite. A co-precipitation methodology was employed for the functionalization of chitosan with iron nanoparticles, using Fe2+ as the sole iron source and with a low energy requirement. The adsorbents were characterized by FTIR, XRD, VSM, and nitrogen porosimetry techniques. The CS∙Fe3O4 1:1 NPs showed the highest acephate removal percentage (74.96 %) at pH 9 and ambient temperatures. The adsorption process exhibited high dependencies on pH, adsorbent dosage, initial concentration of adsorbate, and ionic strength. Sips and pseudo-second-order kinetics models best adjusted the experimental data, suggesting that the process occurs on a heterogeneous surface. Thermodynamic evaluation showed that the adsorption was exothermic, favorable, and predominately through chemical interactions. Finally, the CS∙Fe3O4 showed no significant decrease after several cycles of adsorption/desorption, avoiding centrifugation-filtration steps.

A Highly Sensitive Chitosan-Based SERS Sensor for the Trace Detection of a Model Cationic Dye.

The rapid detection of contaminants in water resources is vital for safeguarding the environment, where the use of eco-friendly materials for water monitoring technologies has become increasingly prioritized. In this context, the role of biocomposites in the development of a SERS sensor is reported in this study. Grafted chitosan was employed as a matrix support for Ag nanoparticles (NPs) for the surface-enhanced Raman spectroscopy (SERS). Chitosan (CS) was decorated with thiol and carboxylic acid groups by incorporating S-acetyl mercaptosuccinic anhydride (SAMSA) to yield CS-SAMSA. Then, Ag NPs were immobilized onto the CS-SAMSA (Ag@CS-SAMSA) and characterized by spectral methods (IR, Raman, NIR, solid state 13C NMR with CP-MAS, XPS, and TEM). Ag@CS-SAMSA was evaluated as a substrate for SERS, where methylene blue (MB) was used as a model dye adsorbate. The Ag@CS-SAMSA sensor demonstrated a high sensitivity (with an enhancement factor ca. 108) and reusability over three cycles, with acceptable reproducibility and storage stability. The Raman imaging revealed a large SERS effect, whereas the MB detection varied from 1-100 μM. The limits of detection (LOD) and quantitation (LOQ) of the biocomposite sensor were characterized, revealing properties that rival current state-of-the-art systems. The dye adsorption profiles were studied via SERS by fitting the isotherm results with the Hill model to yield the ΔG°ads for the adsorption process. This research demonstrates a sustainable dual-function biocomposite with tailored adsorption and sensing properties suitable for potential utility in advanced water treatment technology and environmental monitoring applications.

Development of biomass aerogels with aligned channels: For continuous treatment of oily wastewater and solar-powered oil evaporation

A biomass CS/CNTs@MTMS (MCCS) aerogel with both aligned channel network, superhydrophobicity, and photothermal conversion ability was prepared by a green and facile strategy of directed freeze-drying and chemical vapor deposition using chitosan (CS), carbon nanotubes (CNTs), and methyltrimethoxysilane (MTMS) as the building materials. Capacity to adsorb a large variety of oils and organic solvents, with an adsorption capacity of up to 34–83 g/g. After 10 cycles, the adsorption capacity of MCCS remained at 94 % of the initial capacity, providing excellent reusability. In addition, due to its unique network of aligned channels, the MCCS can continuously separate oil and water, making it a sustainable oil–water separator. More interestingly, the MCCS aerogel has excellent photothermal conversion capabilities, and it was utilized to evaporate oil collected during the oil–water separation process using solar energy. This work provides an opportunity to design novel self-cleaning photothermally driven oil–water separation biomass materials with superhydrophobicity-strong lipophilicity.

Fabrication and characterization of multifunctional, asymmetric bilayer films based on chitosan/gelatin/mesoporous bioactive glass nanoparticles for guided bone regeneration

AbstractTwo-faced GBR membranes were fabricated by electrophoretic deposition (EPD) using a combination of biopolymers and mesoporous bioactive glass nanoparticles (MBGNs). The membrane design was aimed at leveraging the advantageous properties of both biopolymers and MBGNs. The dense composite layer consisted of chitosan (CS) incorporating MBGNs and it was functionalized with a phytotherapeutic drug, naringin (Nar). The porous layer consisted of CS-gelatin (Gel)- MBGNs as well as copper chelated chitosan (Cu(II)-CS)-Gel-MBGNs composites. EPD was conducted in direct current mode. The antibacterial activity of the membranes as a result of the presence of Cu(II) and Nar was confirmed. The films were cytocompatible when tested with MC3T3-E1 (pre-osteoblastic) and MG-63 (osteoblast like) cell lines. However, a slight cytotoxic effect of the releasing Cu(II) ions was determined. In contrast, Nar-loaded films revealed improved cell viability. The results indicate the high potential of EPD to fabricate bilayer structures for GBR applications. Graphical abstract

Antibacterial Properties of Dandelion Extract-Based PVA/CTS/DAN/CuNP Composite Gel

Dandelion extract is a reducing agent, and CuSO4∙5H2O was used as a carrier to create copper nanoparticles (CuNPs). A novel polyvinyl alcohol–chitosan–dandelion–CuNP (PVA/CTS/DAN/CuNP) gel was acquired by cross-linking Polyvinyl alcohol (PVA) and chitosan (CTS) solution. Its structure was analyzed using Fourier transform infrared spectroscopy, Scanning electron microscopy, and X-ray diffraction. The PVA/CTS/DAN/CuNP gels manifested good stability, recycling ability, swelling properties, and biocompatibility. Using the agar diffusion method, the diameters of the inhibition zone of the composite gel against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa could be over 21 mm. In conclusion, the PVA/CTS/DAN/CuNP composite gel had good antibacterial performance, which has a high potential for application in microbial contamination treatment and environmental protection.

Integrating L-cysteine coated polydopamine nanoparticles and deep eutectic solvents into chitosan matrix for multifunctional food packaging application

To reduce the deterioration of fruits and vegetables caused by food-borne microorganisms, this study proposed a bio-sustainable PCD-CS photothermal bactericidal nanocomposite film. This film integrated L-Cysteine (L-Cys) coated polydopamine nanoparticles (PDA@L-Cys NPs) and deep eutectic solvents (DES) into the chitosan (CS) matrix. The DES effectively improved the mechanical property of composite film, water vapor barrier property (WVP), transparency, and biodegradability. The inclusion of PDA@L-Cys NPs significantly increased the oxidation resistance, UV-shielding, and photothermal conversion capabilities. The oxidation resistance of composite film improved 3–7 times compared to the bare CS film. Under near-infrared irradiation (NIR) for just 10 min, the temperature of the film can rise to 55.8 °C, achieving a photothermal antibacterial rate reached 99.9% against Escherichia coli (E. coli, ATCC 8739) and Staphylococcus aureus (S. aureus, ATCC 6538). Under single short-time NIR trigger, the PCD-CS nanocomposite film effectively maintained good color, pH value, soluble solid content (TSS), and appearance of cherry tomato, and delayed the decrease of weight. The successful implementation of this work provides new insights and approaches for creating and advancing sustainable antibacterial food packaging.

Chitosan-based bilayer shell phase change nano-capsules with excellent anti-permeability for thermal regulation dressings

Nano-encapsulated phase change materials (NEPCMs) with appropriate phase change temperature range and excellent anti-permeability have significant application value in the field of thermal regulation dressings. In this study, NEPCMs were synthesized using the microemulsion polymerization method, with eutectic fatty acids (LA-SA) as the core material and poly(methyl methacrylate) (PMMA) as the shell material. Subsequently, using the electrostatic adsorption method, chitosan (CS) was successfully coated onto the outer surface of NEPCMs, resulting in the preparation of a novel bilayer shell nano-encapsulated phase change materials (BS-NEPCMs) for thermal regulation dressings. The impact of core/shell ratio, CS acid solution concentration and cross-linking agent content on capsule properties was investigated. It was found that BS-NEPCMs exhibited excellent cyclical stability and thermal stability. In particular, the CS shell layer provided excellent interfacial impermeability effects for the capsules, achieving an anti-permeability efficiency of 96.21 %. This not only helps address the problem of high leakage rates in single wall capsules, but also ensures that the capsules maintain high phase change enthalpies of 99.32 J/g and 96.38 J/g, respectively. The dressings based on BS-NEPCMs demonstrated good thermal regulation at 33–42 °C with maximum phase change enthalpies of 39.53 J/g and 34.08 J/g, respectively. Swelling and rheological analysis showed that the dressing exhibits a gel state, with a swelling ratio of 343 %, an elastic modulus of 15 kPa and a viscous modulus of 4 kPa. This study indicated that BS-NEPCMs hold significant promise for various applications in energy storage and body thermal regulation fields.

Effect of chitooligosaccharide on the binding domain of the SARS-COV-2 receptor

The receptor-binding domain (RBD) is crucial for understanding how severe acute respiratory syndrome coronavirus (SARS-CoV-2) recognizes and infects host cells. Chitooligosaccharide (CS) exhibits diverse antiviral activities, with its derivatives showing remarkable efficacy in blocking SARS-CoV-2 infection. Thus, this study employed spectroscopy, virus-infected cell experiments, and molecular simulation to investigate the molecular interactions between CS and SARS-CoV-2 RBD, as well as their mechanisms. In spectroscopic experiments, all four CS variants with different molecular weights formed interactions with the RBD. These variants increased the resistance of HEK293ACE2 cells to SARS-CoV-2 invasion. Molecular docking revealed that the four CS variants could bind to the RBD through hydrogen bonding or salt-bridge interactions, forming stable complexes. Chitotetraose provided stronger protection to HEK293ACE2 cells compared to other CS variants and displayed higher molecular docking scores. Further investigation into the optimal docking conformation of chitotetraose was conducted through molecular dynamics simulation methods. This study lays a solid theoretical foundation and provides a scientific basis for the development of targeted RBD inhibitors, as well as drug screening and application against novel coronaviruses.

In situ forming hydrogels based on modified gellan gum/chitosan for ocular drug delivery of timolol maleate

In situ forming hydrogels are suitable candidates for increasing drug residence time in ocular drug delivery. In this study, gellan gum (GG) was oxidized to form aldehyde groups and in situ gelling hydrogels were synthesized based on a Schiff-base reaction between oxidized GG (OGG) and chitosan (CS) in the presence of β-glycerophosphate. The effect of OGG and CS concentration on the physical and chemical properties of the resulting hydrogels was investigated. The FT-IR spectroscopy confirmed the chemical modification of OGG as well as the functional groups of the prepared hydrogels. The scanning electron microscope (SEM) revealed the highly porous structure of hydrogels. The obtained hydrogels indicated a high swelling degree and degradability. Also, the rheological studies demonstrated self-healing behavior, shear thinning, thixotropy, and mucoadhesion properties for the developed hydrogels. The results of in vitro and ex vivo studies showed that the timolol-loaded hydrogel with a higher amount of OGG has a higher release rate. Moreover, the MTT cytotoxicity test on bone marrow mesenchymal stem cells (BMSCs) confirmed that developed hydrogels are not toxic. The obtained results revealed that the developed hydrogels can be a desirable choice for the ocular drug delivery of timolol in the treatment of glaucoma.

Functionality, physicochemical properties, and applications of chitosan/nano-hydroxyapatite–tea polyphenol films

An active chitosan (CS) film containing a nano-hydroxyapatite–tea polyphenol (HAP-TP) complex was designed and prepared. The effects of HAP-TP loading on the structural and physicochemical properties of the CS-based film were evaluated. The mechanical and thermal properties of the film were significantly improved by the resulting intermolecular interactions and formation of hydrogen bonds between HAP-TP and CS, which reduced the water vapor and oxygen permeabilities of the film by 29.78 and 35.59 %, respectively. The CS-HAP-TP film exhibited excellent slow-release behavior and antioxidant activity, with a cumulative release rate at 700 h 6.79 % lower than that of CS-TP films. The CS-HAP-TP film significantly inhibited the deterioration of semi-dried golden pompano, and thus helped to retain the taste of umami and sweet amino acids in fish samples, while reducing off-flavor generation. The film therefore shows considerable potential as an active packaging material for the preservation of semi-dried fish products.