Synthesis and antimicrobial activity of some novel cross-linked chitosan hydrogels

Chitosan-strigolactone mimics with synergistic effect: A new concept for plant biostimulants

The paper reports new multifunctional plant biostimulant formulations obtained via in situ hydrogelation of chitosan with salicylaldehyde in the presence of a mimetic naphthalimide-based strigolactone, in specific conditions. Various analytical techniques (FTIR, 1H NMR, SEM, POM, TGA, WRXD) were employed to understand the particularities of the hydrogelation mechanism and its consequences on the formulations' properties. Further, in order to evaluate their potential for the targeted application, the swelling in media of pH characteristic for different soils, water holding capacity, soil biodegradability, in vitro release of the strigolactone mimic and impact on tomatoes plant growth in laboratory conditions were investigated and discussed. It was found that the strigolactone mimic has the ability to bond to the chitosan matrix via physical forces, favoring a prolonged release. Moreover, the combination of chitosan with the strigolactone mimic in an optimal mass ratio triggered a synergistic effect on the plant growth, up to 4 times higher compared to the neat control soil.

Development of hybrid polyvinylpyrrolidone/carboxymethyl cellulose/collagen incorporated oregano scaffolds via direct ink write printing for potential wound healing applications

Additive manufacturing can develop regenerative scaffolds for wound healing. 3D printing offers meticulous porosity, mechanical integrity, cell adhesion and cost-effectiveness. Herein, we prepared ink composed of carboxymethyl cellulose (CMC), polyvinylpyrrolidone (PVP), collagen, and oregano extract for the fabrication of tissue constructs. The blend was optimized to form a homogeneous ink and rheological characterization demonstrated shear thinning behavior. The scaffolds were printed using Direct Ink Write (DIW) at a flow speed of 4 mm3/s and a layer height of 0.18 mm. The fabricated scaffolds demonstrated an ultimate tensile strength (UTS) and toughness of 730 KPa and 2.72 MJ/m3, respectively. Scanning Electron Microscopy (SEM) revealed an average pore size of 300 ± 30 μm. Fourier transform infrared spectroscopy (FTIR) analysis confirmed that all materials were present. The contact angle of the composite scaffold was 68° ± 1°. Moreover, the scaffolds presented 82 % mass loss (degradation) in phosphate buffer saline (PBS) over 14 days. The composite scaffold exhibited inhibition zones of 9 mm and 12 mm against Staphylococcus aureus and Escherichia coli, respectively. The PVP/CMC/collagen/oregano 3D printed scaffolds exhibited excellent biocompatibility with the mesenchymal stem cells and humman dermal fibroblast cells, confirmed by water-soluble tetrazolium - 8 (WST-8) assay (test conducted for 7 days). The enhanced angiogenic potential of said scaffold was assesed by release of vascular endothelial growth factor followed by further validation through in-vivo CAM assay. Thus, confirming suitability for the potential wound healing application.

Advances in Hydrogel Polymers for Microbial Control in Water Systems

Every year, contaminated water is responsible for over one million deaths globally. Microbiology leads other fields in the development of solutions to water contamination to reduce these deaths while advancing the achievement of SDG 6, which aims to ensure universal access to water and sanitation. This article explores hydrogel polymers as a solution to water contamination through microbial control. Using a systematic approach, this study collects, reviews, analyzes, and synthesizes the findings of studies on the structure, properties, and mechanisms used by hydrogel polymers in pathogen control in water systems, emphasizing recent advances in microbiology that have improved the antimicrobial properties of hydrogel polymers, enhanced their synthetic properties, and improved their overall ability to control the spread of pathogens in water. Other additional notable findings, including the applications of hydrogel polymers in water systems, the environmental implications of using the method to decontaminate and purify water for various purposes, and the regulatory standards needed to reinforce the viability and effectiveness of the adaptation of hydrogel polymers for the control of harmful or unwanted microorganisms in water systems, inform the presented inferences on the future of hydrogel technologies and new opportunities for the expansion of their commercial use.

Synthesis of carboxymethyl chitosan-guar gum-poly(vinylpyrrolidone) ternary blended hydrogels with antibacterial/anticancer efficacy and drug delivery applications

Biopolymers have the utmost significance in biomedical applications and blending synthetic polymers has shown favorable characteristics versus individual counterparts. The utilization of the blends can be restricted through the use of toxic chemical agents such as initiators or crosslinkers. In this regard, a chemical agent-free ionizing irradiation is a beneficial alternative for preparing the hydrogels for biomedical applications. In this study, carboxymethyl chitosan (CM-CS), guar gum (GG), and poly(vinylpyrrolidone) (PVP) based ternary blends (TB) were crosslinked using various doses of ionizing irradiation to fabricate hydrogels. The prepared hydrogels were characterized for physicochemical properties, swelling analysis, biological assays, and drug delivery applications. Swelling analysis in distilled water revealed that the hydrogels exhibit excellent swelling characteristics. An in vitro cytocompatibility assay showed that the hydrogels have greater than 90% cell viability for the human epithelial cell line and a decreasing cell viability trend for the human alveolar adenocarcinoma cell line. In addition, the prepared hydrogels possessed excellent antibacterial characteristics against gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli). Finally, the release studies of anti-inflammatory Quercus acutissima (QA) loaded hydrogels exhibited more than 80% release in phosphate-buffered saline (pH = 7.4). These findings suggest that TB hydrogels can be used as suitable carrier media for different release systems and biomedical applications.

Influence of chitosan and hydroxyethyl cellulose modifications towards the design of cross-linked double networks hydrogel for diabetic wound healing

The wound dressings' lack of antioxidant and antibacterial properties, and delayed wound healing limit their use in wound treatment and management. Recent advances in dressing materials are aimed at improving the limitations discussed above. Therefore, the aim of this study includes the preparation and characterization of oxidized hydroxyethyl cellulose (OHEC) and ferulic acid-grafted chitosan (CS-FA) hydrogel loaded with green synthesized selenium nanoparticles (Se NPs) (OHEC-CS-FA-Se NPs named as nanohydrogel) for diabetic wound healing. The structure and properties of the hydrogel was characterized by FTIR, FE-SEM, HR-TEM, EDAX, UV-Vis spectrophotometry, XRD, DLS, zeta potential and rheological studies. The findings of these experiments demonstrate that nanohydrogel possesses a variety of outstanding qualities, including an optimal gel time, good swelling characteristics, a fair water retention rate, a good degradation rate, and strong mechanical stability. Nanohydrogel has been shown to have a synergistic impact by significantly increasing antioxidant activity by scavenging ABTS and DPPH radicals. The nanohydrogel's strong biocompatibility was confirmed by cytocompatibility testing using L929 mouse fibroblast cells. In addition, the wound healing potential of nanohydrogel was tested on L929 cells by an in vitro scratch assay and the nanohydrogel showed a wound closure rate of 100 % after 12 h. In addition to this study, nanohydrogel has demonstrated significant antimicrobial properties against human and wound infection causing pathogens such as Bacillus subtilis, methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa. In the animal model, almost complete diabetic wound healing was achieved on day 14 after application of the nanohydrogel. The results obtained indicate that the multifunctional bioactive nature of OHEC-CS-FA-Se NPs showed exceptional antioxidant and antibacterial potential for the treatment of infected and chronic wounds.

Agar and Chitosan Hydrogels' Design for Metal-Uptaking Treatments

In the field of cultural heritage, the use of natural gels is rising for the application of active agents. Here, two natural polymers are assessed: agar, a pioneer hydrogel for conservation treatments, and chitosan, a rather novel and metal-binding gel. For chitosan, a state-of-the-art based formulation (CS-ItA-LCys) is evaluated as it was reported for silver-complexing properties. It is evaluated whether these polymers can withstand the addition of the chelating compound deferoxamine, which is a bacterial siderophore. This allows for the obtainment of completely bio-sourced gel systems. A Fourier-transformed (FT) infrared spectroscopy characterization is performed, completed with rheological measurements and Cryo-Scanning Electron Microscopy (cryo-SEM) to investigate the physico-chemical properties of the gels, as well as their interaction with deferoxamine. Both polymers are also tested for their inherent complexing ability on silver ions using FT-Raman spectroscopy. A multi-analytical comparison shows different microstructures, in particular, the presence of a thick membrane for chitosan and different mechanical behaviors, with agar being more brittle. Neither hydrogel seems affected by the addition of deferoxamine; this is shown by similar rheological behavior and molecular structures in the presence or absence of the chelator. The intrinsic abilities of the chitosan formulation to make silver complex are demonstrated with the observation of two peaks characteristic of Ag-S and Ag-O bonds. Agar and chitosan are both proven to be reliable gels to act as carriers for bio-based active agents. This paper confirms the potential asset of the chitosan formulation CS-ItA-LCys as a promising gel for the complexation of soluble silver.

Graphene oxide reinforced biopolymeric (chitosan) hydrogels for controlled cephradine release

In the current study, chitosan, poly (N-vinyl-2-pyrolidone) and polyamidoamine based hydrogels were prepared by Solution Casting Method using different quantity of graphene oxide (GO) for controlled cephradine (CPD) release. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, thermal analysis, scanning electron microscope and atomic force microscopy. FTIR results endorsed the presence of particular functionalities and developed interfaces in hydrogels. The thermal stability was directly proportional to the amount of GO. Antibacterial activity was investigated against gram-negative bacteria resultantly; CAD-2 exhibited maximum bactericidal activity against Escherichia coli and Psuedomonas aeruginosa. In addition, in-vitro biodegradation was examined in phosphate buffer saline solution and proteinase K for 21 and 07 days respectively. The maximum swelling was exhibited by CAD-133777 % in distilled water that was governed by quasi-Fickian diffusion. The swelling volumes were inversely proportional to the amount of GO. In the same way, pH sensitive CPD release was detected by UV visible spectrophotometer that followed zero order and Higuchi models. However, in 4 h, 89.4 % and 83.7 % of CPD was released in PBS and SIF solution correspondingly. Therefore, the chitosan-based biocompatible and biodegradable hydrogel platforms offered substantial potential for the controlled CPD release in medico-biological applications.

Therapeutic potential of two formulated novel chitosan derivatives with prominent antimicrobial activities against virulent microorganisms and safe profiles toward fibroblast cells

The development of new antimicrobial agents has been drawing considerable attention due to the extreme escalation of multi-drug resistant microorganisms. We thus sought to ameliorate the antimicrobial activities of the chitosan (Cs) biopolymer by coupling chitosan with cyclohexanone and 2-N-methyl pyrrolidone, synthesizing two novel Schiff bases (CsSB1 and CsSB2), respectively. FT-IR, TGA, DSC, SEM, and potentiometric titration were employed to characterize the formulated chitosan derivatives. The findings exposed that the degrees of deacetylation were 88.12% and 89.98% for CsSB1 and CsSB2, respectively. The antimicrobial capacities of CsSB1 and CsSB2 were substantially enhanced compared with prime chitosan. Furthermore, the CsSB1 and CsSB2 demonstrated minimum inhibitory concentrations (MIC) of 50 µg/ml in relation to all studied microorganisms, whereas chitosan revealed MIC value of 50 µg/ml only for E. coli. Furthermore, CsSB1 with a concentration of 250 µg/ml manifested the highest antibacterial activity against Gram-positive bacteria. Correspondingly, CsSB2 revealed a comparable trend of microbial hindrance with lower activities. Besides, the two derivatives could thwart the growth of Candida albicans (C. albicans). The cytotoxicity assay of the biomaterials accentuated their biocompatibility with fibroblasts. Collectively, the two formulated chitosan derivatives could competently rival the native chitosan, particularly for future applications in wound healing.

Preparation and characterization of functionalized chitosan/polyvinyl alcohol composite films incorporated with cinnamon essential oil as an active packaging material

In this study, amphiphilic chitosan (NPCS-CA) was synthesized by grafting quaternary phosphonium salt and cholic acid onto the chain of chitosan, aiming to develop an active edible film based on NPCS-CA and polyvinyl alcohol (PVA) incorporated with cinnamon essential oil (CEO) by the casting method. The chemical structure of the chitosan derivative was characterized by FT-IR, ¹H NMR and XRD. Through the characterization of FT-IR, TGA, mechanical and barrier properties of the composite films, the optimal proportion of NPCS-CA/PVA was determined as 5/5. And, the tensile strength and elongation at break of the NPCS-CA/PVA (5/5) film with 0.4 % CEO were 20.32 MPa and 65.73 %, respectively. The results revealed that the NPCS-CA/PVA-CEO composite films exhibited an excellent ultraviolet barrier property at 200-300 nm and significantly reduced oxygen permeability, carbon dioxide permeability and water vapor permeability. Furthermore, the antibacterial property of film-forming solutions against E. coli, S. aureus, and C. lagenarium was distinctly improved with the increase of NPCS-CA/PVA proportion. And, the multifunctional films effectively extended the shelf-life of mangoes at 25 °C based on the characterization of surface changes and quality indexes. The NPCS-CA/PVA-CEO films could be developed as biocomposite food packaging material.

Antibacterial composite: polymeric mesoporous silica nanoparticles and combination of imipenem/meropenem

Using nanomaterials is a novel strategy to eliminate drug resistance against bacteria. Nanoparticles with metal sites show antimicrobial activities that counteract or obstruct antibiotic-resistant mechanisms expressed by the pathogens. Here, a nanocomposite based on mesoporous silica nanoparticles with active sites of silver, and a combination of imipenem and meropenem as antibiotic drugs, was synthesized and characterized using different physicochemical methods. The antibacterial assessments exhibited sensitivity by Staphylococcus aureus (S. aureus), Klebsiella pneumoniae (K. pneumoniae) and Escherichia coli (E. coli) toward the synthesized composite, which showed a suitable safety profile in human cells. This composite has an excellent synergic mechanism based on reactive oxygen species (ROS) to kill bacteria due to penetrating the microbial membrane. In addition, this composite is resistant to hydrolysis by plasmids and chromosomally mediated β-lactamases. This nanocomposite showed extraordinary antiseptic power against Gram-positive and Gram-negative microbes.

Preparation, Characterization, and Bio Evaluation of Fatty N- Hexadecanyl Chitosan Derivatives for Biomedical Applications

The objective of this study was to improve the antibacterial activities of chitosan via N-alkyl substitution using 1-bromohexadecane. Mono and di substitution (Mono-NHD-Ch and Di-NHD-Ch) were prepared and characterized using FT-IR, HNMR, TGA, DSC, and SEM. Elemental analysis shows an increase in the C/N ratio from 5.45 for chitosan to 8.63 for Mono-NHD-Ch and 10.46 for Di-NHD-Ch. The antibacterial properties were evaluated against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus cereus. In the examined microorganisms, the antibacterial properties of the novel alkyl derivatives increased substantially higher than chitosan. The minimum inhibitory concentration (MIC) of Mono-NHD-Ch and Di-NHD-Ch was perceived at 50 μg/mL against tested microorganisms, except for B. cereus. The MTT test was used to determine the cytotoxicity of the produced materials, which proved their safety to fibroblast cells. The findings suggest that the new N-Alkyl chitosan derivatives might be used as antibacterial alternatives to pure chitosan in wound infection treatments.

Preparation and characterization of chitosan derivatives modified with quaternary ammonium salt and quaternary phosphate salt and its effect on tropical fruit preservation

In this paper, HACC modified with (5-Carboxypentyl) (triphenyl) phosphonium bromide (HA-CS-NP) was synthesized. Then, a multifunctional food packaging composite film with good thermal stability and antibacterial functions was fabricated by HA-CS-NP and poly (vinyl alcohol) (PVA). The tensile strength and elongation at break of HA-CS-NP/PVA composite film at the weight ratio of 3/7 were 20.32 ± 1.02 MPa and 65.73 ± 3.29%, respectively. And, the inhibition rates of HA-CS-NP (0.5%) on Mango C. lagenarium and Papaya C. gloeosporioides on day 6 were up to 80.92 ± 4.12%. Compared with CK group, the weight loss of experimental groups were 23.96 ± 2.46 g/206 ± 7.25 g (mangoes) and 59.45 ± 3.06 g/496 ± 6.37 g (papaya), reduced by 35.76 ± 1.15%. Moreover, the final hardness value of the fruits coated with composite films was 4.94 ± 0.23 kg/cm³ and increased by 20.79 ± 1.04%, and the rot index was reduced by 71.43 ± 3.24%. The multifunctional HA-CS-NP/PVA coating has broad prospects in the application of food packaging.

Functionally graded membrane deposited with PDLLA nanofibers encapsulating doxycycline and enamel matrix derivatives-loaded chitosan nanospheres for alveolar ridge regeneration

Functionally graded membranes (FGM) with regenerative signals and nanofibrous topography mimicking the native extracellular matrix have been shown to improve the outcome of alveolar ridge regeneration (ARR). This study developed a novel FGM with doxycycline-enamel matrix derivative (EMD) nanofibrous composites deposition to coordinate anti-inflammation and differentiation signals, thus facilitating ARR. Doxycycline-loaded PDLLA nanofibers (PD), EMD-loaded chitosan nanospheres (CE), and CE-embedded PD (CE-PD) were fabricated by electrospinning, deposited on the surfaces of barrier membrane to develop a FGM, and the efficacy was validated by delivering the FGM to regenerate experimental alveolar ridge defects in rats. Results revealed that PD had potent antibacterial capability, and CE-PD allowed sustained release of EMD to promote osteogenesis in vitro. In the alveolar ridge defects, FGM with PD on the outer surface downregulated MMP-8, and wound dehiscence was further reduced with Cbfa1 upregulation in those treated by FGM with CE-PD on the inner surface at 1 week. FGM with CE-PD revealed significantly greater new bone formation and defect fill at 4 weeks. In conclusion, FGM with PD reduced early tissue breakdown and with CE-PD nanofibrous composites accelerated wound healing and facilitated osteogenesis, and thus could be an advantageous strategy for ARR.

Evaluation of the properties and antibacterial activity of microchitosan film impregnated with Shirazi thyme (Zataria multiflora) and garlic (Allium sativum) essential oils

Background

Recent research has shown that chitosan has good moisture-absorbing properties at the micro and nanoscale, and seems to be a good candidate for the production of biodegradable moisture-absorbing films.

Aims

The aim of this study was to evaluate the properties and antibacterial activity of starch-based microchitosan (MCH) films impregnated with two essential oils (EOs).

Methods

MCH films with varying thicknesses were made from cornstarch (6%), microchitosan (1%), glycerol (2.25%), and/or EOs (2%), and their characteristics, including swelling degree (SD), tensile strength (TS), and elongation at break (EB%), were examined. The film structures were confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). To determine the antibacterial activity against Escherichia coli and Staphylococcus aureus, two EOs of Shirazi thyme, garlic, and a mixture of them were used in the experimentation.

Results

The EB% and TS had a linear relationship with the thickness of samples and improved by increasing the thickness of films. The XRD pattern showed that the MCH films had an amorphous structure. SEM of the films showed a homogeneous dispersion of MCH in the starch matrix without any porosity. The AFM images showed a simultaneous increase in the thickness of the MCH films and surface roughness. The film was able to absorb water up to 15.78 times its weight in 48 h. The inhibition zone of films containing 2% thyme EO was 42.0 mm for S. aureus and 12.3 mm for E. coli (P<0.05).

Conclusion

MCH film containing Shirazi thyme can be described as a moisture-absorbing antibacterial pad and is a new idea for active food packaging to increase the shelf life of foods with fully degradable properties.

Zinc Oxide and Copper Chitosan Composite Films with Antimicrobial Activity

The role of the oral microbiome and its effect on dental diseases is gaining interest. Therefore, it has been sought to decrease the bacterial load to fight oral cavity diseases. In this study, composite materials based on chitosan, chitosan crosslinked with glutaraldehyde, chitosan with zinc oxide particles, and chitosan with copper nanoparticles were prepared in the form of thin films, to evaluate a new alternative with a more significant impact on the oral cavity bacteria. The chemical structures and physical properties of the films were characterized using by Fourier transform infrared spectroscopy (FTIR,) Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle measurements. Subsequently, the antimicrobial activity of each material was evaluated by agar diffusion tests. No differences were found in the hydrophilicity of the films with the incorporation of ZnO or copper particles. Antimicrobial activity was found against S. aureus in the chitosan film crosslinked with glutaraldehyde, but not in the other compositions. In contrast antimicrobial activity against S. typhimurium was found in all films. Based on the data of present investigation, chitosan composite films could be an option for the control of microorganisms with potential applications in various fields, such as medical and food industry.

Antimicrobial and antiviral activities with molecular docking study of chitosan/carrageenan@clove oil beads

BACKGROUND

Biopolymers are promising candidates that can be fabricated into hydrophilic matrices and used for many applications due to their distinctive properties such as non-toxic, biodegradable, biocompatibility, and low cost. A promising composite of chitosan and carrageenan with self-crosslinking has been prepared.

METHODS AND RESULTS

In this study, a rigorous approach for an inexpensive and non-toxic combination of different amounts of clove oil with two polyelectrolytes including chitosan and carrageenan in the form of beads have been prepared. The structure and the surface morphology of the beads were investigated using FTIR, XRD, and SEM. Moreover, antimicrobial, antiviral activity, and molecular docking were evaluated. Antibacterial results revealed that chitosan/carrageenan@clove oil beads have antimicrobial activity as well as chitosan/carrageenan without clove oil against Escherichia colia ATCC25922, Pseudomonas aeruginosa aATCC27853, Staphylococcus aureus ATCC25923, Bacillus subtilisaATCC6051 and Candida albicanssATCC90028. Furthermore, maximum non-toxic concentration (MNTC) of chitosan/carrageenan@clove oil beads was (31.25 μg/mL) which exhibited promising antiviral activity against Herpes simplex virus-1 (HSV-1), and was significantly higher than chitosan/carrageenan without clove oil, where antiviral activity was 82.94 and 57.64% respectively. Eventually, docking study and computational calculation have been used to show the reactivity of the molecules.

CONCLUSIONS

The developed chitosan/carrageenan@clove oil beads have shown promising properties to be used as carriers of drug delivery, tissue engineering, and regenerative medicine. This article is protected by copyright. All rights reserved.

Development and Evaluation of Thermosensitive Hydrogels with Binary Mixture of Scutellariae baicalensis radix Extract and Chitosan for Periodontal Diseases Treatment

Scutellaria baicalensis root displays anti-inflammatory and antibacterial properties due to the presence of flavonoids, particularly baicalin, baicalein, and wogonin. Our work aimed at developing thermosensitive hydrogels containing a binary mixture of S. baicalensis radix lyophilized extract and chitosan as a novel approach for periodontal diseases treatment. Two types of chitosan were employed in preliminary studies on binary mixtures with S. baicalensis radix lyophilized extract standardized for baicalin, baicalein, and wogonin. Thermosensitive hydrogels were prepared of poloxamer 407, alginate sodium, and cellulose derivatives and evaluated in terms of rheological and mucoadhesive behavior. The presence of chitosan altered the release profile of active compounds but did not affect their in vitro permeation behavior in PAMPA assay. The synergistic effects of S. baicalensis radix lyophilized extract and chitosan toward ferrous ion-chelating activity, inhibition of hyaluronidase, and pathogen growth were observed. The thermosensitive gelling system showed shear-thinning properties, gelation temperature between 25 and 27 °C, and favorable mucoadhesiveness in contact with porcine buccal mucosa, which was enhanced in the presence of binary mixture of S. baicalensis radix extract and chitosan. The release tests showed that baicalin and baicalein were liberated in a prolonged manner with a fast onset from hydrogel formulations.

Development of Antibacterial, Degradable and pH-Responsive Chitosan/Guar Gum/Polyvinyl Alcohol Blended Hydrogels for Wound Dressing

The present research is based on the fabrication preparation of CS/PVA/GG blended hydrogel with nontoxic tetra orthosilicate (TEOS) for sustained paracetamol release. Different TEOS percentages were used because of their nontoxic behavior to study newly designed hydrogels' crosslinking and physicochemical properties. These hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and wetting to determine the functional, surface morphology, hydrophilic, or hydrophobic properties. The swelling analysis in different media, degradation in PBS, and drug release kinetics were conducted to observe their response against corresponding media. The FTIR analysis confirmed the components added and crosslinking between them, and surface morphology confirmed different surface and wetting behavior due to different crosslinking. In various solvents, including water, buffer, and electrolyte solutions, the swelling behaviour of hydrogel was investigated and observed that TEOS amount caused less hydrogel swelling. In acidic pH, hydrogels swell the most, while they swell the least at pH 7 or higher. These hydrogels are pH-sensitive and appropriate for controlled drug release. These hydrogels demonstrated that, as the ionic concentration was increased, swelling decreased due to decreased osmotic pressure in various electrolyte solutions. The antimicrobial analysis revealed that these hydrogels are highly antibacterial against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The drug release mechanism was 98% in phosphate buffer saline (PBS) media at pH 7.4 in 140 min. To analyze drug release behaviour, the drug release kinetics was assessed against different mathematical models (such as zero and first order, Higuchi, Baker-Lonsdale, Hixson, and Peppas). It was found that hydrogel (CPG2) follows the Peppas model with the highest value of regression (R2 = 0.98509). Hence, from the results, these hydrogels could be a potential biomaterial for wound dressing in biomedical applications.

Design of Chitosan Sterilization Agents by a Structure Combination Strategy and Their Potential Application in Crop Protection

Chitosan is the only cationic polysaccharide in nature. It is a type of renewable resource and is abundant. It has good biocompatibility, biodegradability and biological activity. The amino and hydroxyl groups in its molecules can be modified, which enables chitosan to contain a variety of functional groups, giving it a variety of properties. In recent years, researchers have used different strategies to synthesize a variety of chitosan derivatives with novel structure and unique activity. Structure combination is one of the main strategies. Therefore, we will evaluate the synthesis and agricultural antimicrobial applications of the active chitosan derivatives structure combinations, which have not been well-summarized. In addition, the advantages, challenges and developmental prospects of agricultural antimicrobial chitosan derivatives will be discussed.

Arabinoxylan/graphene-oxide/nHAp-NPs/PVA bionano composite scaffolds for fractured bone healing

The importance of bone scaffolds has increased many folds in the last few years; however, during bone implantation, bacterial infections compromise the implantation and tissue regeneration. This work is focused on this issue while not compromising on the properties of a scaffold for bone regeneration. Biocomposite scaffolds (BS) were fabricated via the freeze-drying technique. The samples were characterized for structural changes, surface morphology, porosity, and mechanical properties through spectroscopic (Fourier transform-infrared [FT-IR]), microscopic (scanning electron microscope [SEM]), X-ray (powder X-ray diffraction and energy-dispersive X-ray), and other analytical (Brunauer-Emmett-Teller, universal testing machine Instron) techniques. Antibacterial, cellular, and hemocompatibility assays were performed using standard protocols. FT-IR confirmed the interactions of all the components. SEM illustrated porous and interconnected porous morphology. The percentage porosity was in the range of 49.75%-67.28%, and the pore size was 215.65-470.87 µm. The pore size was perfect for cellular penetration. Thus, cells showed significant proliferation onto these scaffolds. X-ray studies confirmed the presence of nanohydroxyapatite and graphene oxide (GO). The cell viability was 85%-98% (BS1-BS3), which shows no significant toxicity of the biocomposite. Furthermore, the biocomposites exhibited better antibacterial activity, no effect on the blood clotting (normal in vitro blood clotting), and less than 5% hemolysis. The ultimate compression strength for the biocomposites increased from 4.05 to 7.94 with an increase in the GO content. These exciting results revealed that this material has the potential for possible application in bone tissue engineering.

Effect of Varying Amount of Polyethylene Glycol (PEG-600) and 3-Aminopropyltriethoxysilane on the Properties of Chitosan based Reverse Osmosis Membranes

Chitosan and polyethylene glycol (PEG-600) membranes were synthesized and crosslinked with 3-aminopropyltriethoxysilane (APTES). The main purpose of this research work is to synthesize RO membranes which can be used to provide desalinated water for drinking, industrial and agricultural purposes. Hydrogen bonding between chitosan and PEG was confirmed by displacement of the hydroxyl absorption peak at 3237 cm-1 in pure chitosan to lower values in crosslinked membranes by using FTIR. Dynamic mechanical analysis revealed that PEG lowers Tg of the modified membranes vs. pure chitosan from 128.5 °C in control to 120 °C in CS-PEG5. SEM results highlighted porous and anisotropic structure of crosslinked membranes. As the amount of PEG was increased, hydrophilicity of membranes was increased and water absorption increased up to a maximum of 67.34%. Permeation data showed that flux and salt rejection value of the modified membranes was increased up to a maximum of 80% and 40.4%, respectively. Modified films have antibacterial properties against Escherichia coli as compared to control membranes.

Injectable Hydrogels: From Laboratory to Industrialization

The transfer of some innovative technologies from the laboratory to industrial scale is many times not taken into account in the design and development of some functional materials such as hydrogels to be applied in the biomedical field. There is a lack of knowledge in the scientific field where many aspects of scaling to an industrial process are ignored, and products cannot reach the market. Injectable hydrogels are a good example that we have used in our research to show the different steps needed to follow to get a product in the market based on them. From synthesis and process validation to characterization techniques used and assays performed to ensure the safety and efficacy of the product, following regulation, several well-defined protocols must be adopted. Therefore, this paper summarized all these aspects due to the lack of knowledge that exists about the industrialization of injectable products with the great importance that it entails, and it is intended to serve as a guide on this area to non-initiated scientists. More concretely, in this work, the characteristics and requirements for the development of injectable hydrogels from the laboratory to industrial scale is presented in terms of (i) synthesis techniques employed to obtain injectable hydrogels with tunable desired properties, (ii) the most common characterization techniques to characterize hydrogels, and (iii) the necessary safety and efficacy assays and protocols to industrialize and commercialize injectable hydrogels from the regulatory point of view. Finally, this review also mentioned and explained a real example of the development of a natural hyaluronic acid hydrogel that reached the market as an injectable product.

Antibacterial Behavior of Chitosan-Sodium Hyaluronate-PEGDE Crosslinked Films

Chitosan is a natural polymer that can sustain not only osteoblast adhesion and proliferation for bone regeneration purposes, but it is also claimed to exhibit antibacterial properties towards several Gram-positive and Gram-negative bacteria. In this study, chitosan was modified with sodium hyaluronate, crosslinked with polyethylene glycol diglycidyl ether (PEGDE) and both osteoblast cytotoxicity and antibacterial behavior studied. The presence of sodium hyaluronate and PEGDE on chitosan was detected by FTIR, XRD, and XPS. Chitosan (CHT) films with sodium hyaluronate crosslinked with PEGDE showed a better thermal stability than pristine hyaluronate. In addition, osteoblast cytocompatibility improved in films containing sodium hyaluronate. However, none of the films exhibit antimicrobial activity against Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus while exhibiting low to mild activity against Salmonella typhimurion.

Antibacterial Activity of a Novel Biocomposite Chitosan/Graphite Based on Zinc-Grafted Mesoporous Silica Nanoparticles

INTRODUCTION

A novel biocomposite chitosan/graphite based on zinc-grafted mesoporous silica nanoparticles (CGZM-bio) was synthesized and the antibacterial activities of this compound along with that of Zn-MSN nanoparticles were investigated.

METHODS

The CGZM-bio biocomposite was synthesized using sol-gel and post-synthesis method under UV radiation. The characterizations of the samples were carried out using FTIR, XRD, SEM, and nitrogen adsorption and desorption. The antibacterial activity was carried out against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) after 18 h at 310 K.

RESULTS

The suspension samples of the Zn-MSN and CGZM-bio (2-100 µg.mL-1) presented antibacterial activities against S. aureus and E. coli. The minimum inhibitory concentration (MIC) values against E. coli for the Zn-MSN and CGZM-bio samples were 10 and 5 µg.mL-1, respectively, while the MIC against S. aureus for both nanomaterials was 10 µg.mL-1.

DISCUSSION

The antibacterial activities of these materials are due to the generation of radical oxygen species such as •OH, H2O2, and O2 2- during the UV radiation via the generation of the electron-hole pairs which in turn damage the bacteria cells. These nanomaterials may be used in biomedical devices as antibacterial agents.

Preparation of In Situ Cross-Linked N-Maleoyl Chitosan-Oxidized Sodium Alginate Hydrogels for Drug Delivery Applications

AIM

This study was aimed to prepare in situ cross-linked N-maleoyl chitosan - oxidised sodium alginate (MCS - OSA) hydrogel loaded with metronidazole (MTZ) for drug delivery applications.

METHODS

The hydrogel was prepared by in situ cross-linking via Schiff base reaction between amine (-NH2) groups from MCS and aldehyde (-CHO) groups from OSA at the different ratio, and the MTZ was loaded into the hydrogels along with the gelatin processes.

RESULTS

The highest drug entrapment efficiency (DEE) was exhibited by MTZ-H3 (5: 5) with DEE of 99.20% and a gel fraction of 97.52%. FTIR results revealed that Schiff base reaction was occurred by the absorption peak of -C = N- groups at 1628 cm-1 and indicated that there is insignificant alteration at different ratio of MCS and OSA. The best sustained of in vitro release profiles of MTZ was shown by MTZ-H3, which is 74.92% and 75.65% at pH 1.2 and 7.4 for 12 h of release, respectively.

CONCLUSION

The optimised ratio between MCS and OSA to prepare in situ cross-linked hydrogels were found to be 5:5 according to the results of DEE and in vitro drug release profiles of MTZ and the MTZ loaded MCS-OSA hydrogels have a great potential which can be applied in biomedical applications.

Starch/PVA hydrogels for oil/water separation

PVA polymers have been well-known as water-absorbing materials but their brittle nature hinders their applicability. In this study, we enhanced the strength of hydrogel and its water-absorbing capabilities by glutaraldehyde-assisted crosslinking of starch with PVA and blending BMIM-BF₄ to enhance the plasticity and generate porosity within the hydrogel multiplying the swelling capacity up to 300% and understand the kinetics and mechanism of water absorption based on the structure of the hydrogel. The ability of starch/PVA hydrogel to selectively adsorb water from oil-water emulsions was determined by establishing the underwater oleophobic nature (oil contact angle ~ 153.6°), subjecting the hydrogel to oil-water emulsion to determine the water absorbed. The hydrogels' biodegradable nature was tested by an efficient in-house biotic system and mechanisms for biodegradation have been discussed. The biodegradability (~ 90%) was determined for 50% starch in PVA sample in 28 days. These properties observed in the hydrogels will find applications in irrigating arid and semi-arid areas and also in developing superabsorbent hydrogels for hygiene-related product development etc. which can be biodegraded in an economic way. Graphical abstract.

In vitro study of chitosan-based multi-responsive hydrogels as drug release vehicles: a preclinical study

Systematic administration of painkillers and anti-inflammatory drugs is routinely employed to minimize pain and bodily disorders. Controlled drug delivery has the potential to improve the outcomes of disorders by providing sustained exposure to efficacious drug concentrations. Herein, we report the fabrication of multi-responsive hydrogels using reactive and functional polymers such as chitosan and polyvinyl pyrrolidone by varying the concentration of a cleavable crosslinker, tetraethyl orthosilicate. The swelling indices of the hydrogels were evaluated in distilled water, solutions with different pH values and different electrolytes. FTIR, WAXRD and TGA were conducted to investigate the structures, crystallinities and thermal stabilities of the prepared multi-responsive hydrogels, respectively. The ultimate tensile strength and elongations at break of the fabricated hydrogels were investigated to assess their mechanical stability. Optical microscopy, biodegradation, antimicrobial and cytotoxicity analyses were further carried out to verify the magnified crosslinked and porous structures, biodegradabilities, biocompatibilities and toxic behaviour of the as-prepared hydrogels, respectively. Drug release analysis was conducted to evaluate their release behaviour in PBS, SGF, SIF and electrolyte solutions. The overall results indicate the successful development of novel, non-toxic and sustained drug deliverable hydrogels, which can be considered as a paramount success towards the fabrication of controlled drug delivery systems.

Stimuli responsive biopolymer (chitosan) based blend hydrogels for wound healing application

Stimuli responsive chitosan (CS) and poly (N-vinyl-2-pyrrolidone) (PVP) have attained hydrogel properties in the presence of 74% neutralized poly acrylic acid (PAA) which can be exploited for wound healing applications. The FTIR spectra confirmed the presence of all specific functional groups and the developed interactions in the hydrogels. The thermal analysis explained that the hydrogel samples are thermally more stable than individual chitosan and PVP. The antimicrobial analysis revealed that all the samples show antibacterial activity against E. coli and the biodegradation analysis is performed to confirm the hydrogels degradation. The hydrogels showed enhanced responsive swelling behavior against different media depending upon the amount of PVP. The %age swelling in water is decreased with the increase in the amount of PVP. The most considerable swelling behavior is observed against pH, as they manifested low swelling at acidic pH and high swelling at neutral pH while at pH 8, the prominent values are obtained. This distinctive behavior of hydrogels and their biocompatibility made them pertinent to drug delivery and their release profile is examined spectrophotometrically using silver sulfadiazine (antibiotic for burnt wounds) showed 91.2% of drug release for a period of 1 h in phosphate buffer saline (PBS) in a consistent and controlled manner.

Cellulose⁻Chitosan Antibacterial Composite Films Prepared from LiBr Solution

Cellulose and chitosan solutions were prepared in 60% LiBr and mixed with a different weight ratio. The washing and drying of the prepared cellulose–chitosan composite films were performed under identical conditions. The color of the liquefied mixtures and films was initially transparent but changed from colorless to brownish yellow depending on the ratio of chitosan in the solution. The cross section observed in the SEM results indicated that the film developed with a higher ratio of chitosan was more robust and possessed greater antibacterial properties. FT-IR analysis of the films showed that hydrogen bonds between cellulose and chitosan in composite films were successfully achieved and retained excellent mechanical properties. The proper ratio of chitosan in the cellulose solution can increase the tensile strength and improve the elongation of the films; however, the E-modulus property was consistently reduced. The antibacterial activity and mechanical properties of the films were greatly improved as the amount of chitosan in the film increased.

Preparation, physicochemical characterization and antimicrobial activities of novel two phenolic chitosan Schiff base derivatives

This study intends to develop novel two antimicrobial phenolic chitosan Schiff bases (I) and (II) via coupling of chitosan with Indole-3-carboxaldehyde and 4-dimethylaminobenzaldehyde, respectively, for boosting the antimicrobial activity of native chitosan. The alterations in the chemical structure and morphology of the Schiff bases were verified using FT-IR, electronic spectrum analysis, and SEM, whereas the thermal properties were investigated by TGA and DSC instruments. The results obtained from the potentiometric analysis referred that the degrees of substitution were 1.15 and 12.05% for Schiff bases (I) and (II), respectively. The antimicrobial activities of Schiff base (I) were significantly augmented more than Schiff base (II) and chitosan. Minimum inhibitory concentration (MIC) of Schiff base (I) was perceived at 50 µg/ml against tested microorganisms except for B. cereus and C. albicans. The highest concentration of Schiff base (I) could inhibit the growth of Gram-positive up to 99%. However, Schiff base (II) recorded the maximum inhibition rate versus Gram-positive approximately 82%. The cytotoxicity of the developed materials was estimated by MTT assay that substantiated their safety to fibroblast cells. The findings emphasized that the developed Schiff bases might be implemented as antimicrobial contenders to pure chitosan for treatments of wound infections.

An unexpected reactivity during periodate oxidation of chitosan and the affinity of its 2, 3-di-aldehyde toward sulfa drugs

In an attempt to determine the reactivity during the periodate oxidation of the vicinal amino sugar, chitosan was oxidized by KIO₄ in a neutral medium. The reactivity was unexpectedly found to be low. The formation of di-aldehyde chitosan (DACT) might cause the low reactivity of chitosan oxidation. Therefore, density functional theory (DFT) calculations were carried out, which revealed that the greater stability of the cyclic amino iodate intermediate might retard the ring opening to form DACT. Furthermore, the affinity of the formation of two novel Schiff bases from the interaction of delivered DACT with two sulfa drugs [sulfanilamide and sulfathiazole] was also investigated using aldehyde content estimation. DACT and Schiff's bases were characterized by FT-IR spectroscopy, X-ray diffraction, and DTA analysis. The X-ray diffraction plane (110) of DACT at the high angle side was expanded more by sulfathiazole than sulfanilamide, indicating that sulfathiazole reacted effectively with DACT. The lowest interaction of DACT with sulfa drugs could be ascribed to the lowest aldehyde content and the intramolecular hemiacetal formation that hinders the Schiff's base condensation.

Advances in the Fabrication of Antimicrobial Hydrogels for Biomedical Applications

This review describes, in an organized manner, the recent developments in the elaboration of hydrogels that possess antimicrobial activity. The fabrication of antibacterial hydrogels for biomedical applications that permits cell adhesion and proliferation still remains as an interesting challenge, in particular for tissue engineering applications. In this context, a large number of studies has been carried out in the design of hydrogels that serve as support for antimicrobial agents (nanoparticles, antibiotics, etc.). Another interesting approach is to use polymers with inherent antimicrobial activity provided by functional groups contained in their structures, such as quaternary ammonium salt or hydrogels fabricated from antimicrobial peptides (AMPs) or natural polymers, such as chitosan. A summary of the different alternatives employed for this purpose is described in this review, considering their advantages and disadvantages. Finally, more recent methodologies that lead to more sophisticated hydrogels that are able to react to external stimuli are equally depicted in this review.