The thiolated chitosan: Synthesis, gelling and antibacterial capability

Harnessing the immunomodulatory potential of chitosan and its derivatives for advanced biomedical applications

The success of biomaterial applications in medicine, particularly in tissue engineering, relies on achieving a balance between promoting tissue regeneration and controlling the immune response. Due to its natural origin, high biocompatibility, and versatility, chitosan has emerged as a promising biomaterial especially for immunomodulation purposes. Immunomodulation, refers to the deliberate alteration of the immune system's activity to achieve a desired therapeutic effect either by enhancing or suppressing the function of specific immune cells, signaling pathways, or cytokine production. This modulation opens up the unlimited possibilities for the use of biomaterials, especially about the use of natural polymers such as chitosan. Although numerous chitosan-based immunoregulatory strategies have been demonstrated over the past two decades, the lack of in-depth exploration hinders the full potential of strategies that include chitosan and its derivatives in biomedical applications. Thus, in this review, the possible immunomodulatory effects of chitosan, chitosan derivatives and their potential combined with various agents and therapies are investigated in detail. Moreover, this report includes agents for localized immune response control, chitosan-based strategies with complementary immunomodulatory properties to create synergistic effects that will influence the success of cell therapies for enhanced tissue acceptance and regeneration. Finally, the challenges and outlook of chitosan-based therapies as a powerful tool for improving immunomodulatory applications are discussed for paving the way for further studies.

Research Progress on Chitosan Microneedle Arrays in Transdermal Drug Delivery

As a type of transdermal drug delivery system (TDDS), Microneedles (MNs) have garnered significant attention from researchers due to their ability to penetrate the stratum corneum (SC) of the skin, enhance drug permeability and bioavailability, avoid first-pass metabolism, and cause minimal damage to the skin. This makes them particularly suitable for localized transdermal drug delivery. Dissolvable microneedles (DMNs) can encapsulate sensitive particles, provide high drug-loading capacity, and possess biodegradability and biocompatibility, attracting extensive research interest. Chitosan (CS) has been selected as the matrix for manufacturing DMNs due to its excellent properties, including not eliciting an immune response in vivo and having active functional groups such as hydroxyl and amino groups that allow for modifications to impart appropriate mechanical strength and functionality to DMNs for specific applications. This paper provides a comprehensive review of the research status of various chitosan-based microneedles (CSMNs), explores the mechanisms of their dissolution in vivo, and discusses their applications in promoting wound healing, delivering macromolecular drugs, vaccine delivery, and anti-tumor therapies.

Hydrogel loaded with thiolated chitosan modified taxifolin liposome promotes osteoblast proliferation and regulates Wnt signaling pathway to repair rat skull defects

To alleviate skull defects and enhance the biological activity of taxifolin, this study utilized the thin-film dispersion method to prepare paclitaxel liposomes (TL). Thiolated chitosan (CSSH)-modified TL (CTL) was synthesized through charge interactions. Injectable hydrogels (BLG) were then prepared as hydrogel scaffolds loaded with TAX (TG), TL (TLG), and CTL (CTLG) using a Schiff base reaction involving oxidized dextran and carboxymethyl chitosan. The study investigated the bone reparative properties of CTLG through molecular docking, western blot techniques, and transcriptome analysis. The particle sizes of CTL were measured at 248.90 ± 14.03 nm, respectively, with zeta potentials of +36.68 ± 5.43 mV, respectively. CTLG showed excellent antioxidant capacity in vitro. It also has a good inhibitory effect on Escherichia coli and Staphylococcus aureus, with inhibition rates of 93.88 ± 1.59 % and 88.56 ± 2.83 % respectively. The results of 5-ethynyl-2 '-deoxyuridine staining, alkaline phosphatase staining and alizarin red staining showed that CTLG also had the potential to promote the proliferation and differentiation of mouse embryonic osteoblasts (MC3T3-E1). The study revealed that CTLG enhances the expression of osteogenic proteins by regulating the Wnt signaling pathway, shedding light on the potential application of TAX and bone regeneration mechanisms.

Multifunctional thiolated chitosan/puerarin composite hydrogels with pH/glutathione dual responsiveness for potential drug carriers

Puerarin (PUE), a natural and biologically active isoflavone extracted from Chinese medicine Pueraria lobata, can self-assemble to form a hydrogel without other chemical modifications. However, although PUE hydrogel has pH responsivity, but it is difficult to adapt to the changeable pathological environment. Therefore, thiolated chitosan (TCS) is synthesized and hybridized with PUE hydrogel to prepare TCS10/PUE composite hydrogel. The results of rheological measurement showed that the resultant composite hydrogels inherited the low loss performance of TCS hydrogel, which means that they have stronger elasticity. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images displayed that TCS10/PUE composite hydrogel has a fibrous-network structure. X-Ray Diffractometer (XRD) and Fourier transform infrared spectroscopy (FT-IR) proved the existence of hydrogen bonds and disulfide bonds in the formation of composite hydrogel. Degradation experiment showed that TCS10/PUE composite hydrogels have pH and glutathione (pH/GSH) dual sensitivity. Furthermore, TCS10/PUE composite hydrogels exhibited multi-functionality including thixotropy, cytocompatibility, antibacterial and anti-inflammatory properties. Berberine chloride hydrate (BCH) was further used as a model drug for in vitro release study. BCH and PUE could be released cooperatively under pH/GSH dual responsivity. These results indicated that the resultant composite hydrogel has eminent pH/GSH dual responsivity and could act as a potential new intelligent drug carrier.

Chitosan as excellent bio-macromolecule with myriad of anti-activities in biomedical applications - A review

The aim of the study is to explore the myriad of anti-activities of chitosan - deacylated derivative of chitin in biomedical applications. Chitosan consists of reactive residual amino groups, which can be modified chemically to obtain wide range of derivatives. These derivatives exhibit the controlled physicochemical characteristics, which in turn improve its functional properties. Such derivatives find numerous applications in the field of biomedical science, agriculture, tissue engineering, bone regeneration and environmental science. This study presents a comprehensive overview of the multifarious anti-activities of chitosan and its derivatives in the field of biomedical science including anti-microbial, antioxidant, anti-tumor, anti-HIV, anti-fungal, anti- inflammatory, anti-Alzheimer's, anti-hypertensive and anti-diabetic activity. It briefly details these anti-activities with respect to its mode of action, pharmacological effects and potential applications. It also presents the overview of current research exploring novel derivatives of chitosan and its anti- activities in the recent past. Finally, the review projects the prospective potential of chitosan and its derivatives and expects to encourage the readers to develop new drug delivery systems based on such chitosan derivatives and explore its applications in biomedical science for benefit of mankind.

Chitosan-based promising scaffolds for the construction of tailored nanosystems against osteoporosis: Current status and future prospects

Despite advancements in therapeutic techniques, restoring bone tissue after damage remains a challenging task. Tissue engineering or targeted drug delivery solutions aim to meet the pressing clinical demand for treatment alternatives by creating substitute materials that imitate the structural and biological characteristics of healthy tissue. Polymers derived from natural sources typically exhibit enhanced biological compatibility and bioactivity when compared to manufactured polymers. Chitosan is a unique polysaccharide derived from chitin through deacetylation, offering biodegradability, biocompatibility, and antibacterial activity. Its cationic charge sets it apart from other polymers, making it a valuable resource for various applications. Modifications such as thiolation, alkylation, acetylation, or hydrophilic group incorporation can enhance chitosan's swelling behavior, cross-linking, adhesion, permeation, controllable drug release, enzyme inhibition, and antioxidative properties. Chitosan scaffolds possess considerable potential for utilization in several biological applications. An intriguing application is its use in the areas of drug distribution and bone tissue engineering. Due to their excellent biocompatibility and lack of toxicity, they are an optimal material for this particular usage. This article provides a comprehensive analysis of osteoporosis, including its pathophysiology, current treatment options, the utilization of natural polymers in disease management, and the potential use of chitosan scaffolds for drug delivery systems aimed at treating the condition.

Review on chitosan-based antibacterial hydrogels: Preparation, mechanisms, and applications

Chitosan (CS) is known for its remarkable properties, such as good biocompatibility, biodegradability, and renewability, in addition to its antibacterial and biological activities. However, as CS is insoluble in water, it displays limited antibacterial performance under neutral and physiological conditions. A viable solution to this problem is grafting chemically modified groups onto the CS framework, thereby increasing its solubility and enhancing its antibacterial effect. Herein, the antibacterial action mechanism of CS and its derivatives is reviewed, confirming the prevalent use of composite materials comprising CS and its derivatives as an antibacterial agent. Generally, the antimicrobial ability of CS-based biomaterials can be enhanced by incorporating supplementary polymers and antimicrobial agents. Research on CS-based composite biomaterials is ongoing and numerous types of biomaterials have been reported, including inorganic nanoparticles, antibacterial agents, and CS derivatives. The development of these composite materials has considerably expanded the application of CS-based antibacterial materials. This study reviews the latest progress in research regarding CS-based composite hydrogels for wound repair, tissue engineering, drug release, water purification, and three-dimensional printing applications. Finally, the summary and future outlook of CS-based antibacterial hydrogels are presented in anticipation of a broader range of applications of CS-based antibacterial hydrogels.

Chitosan/copper sulfide nanoparticles (CS/CuSNPs) hybrid fibers with improved mechanical and photo-thermal conversion properties via tuning CuSNPs' morphological structures

Conventional textiles are inadequate for maintaining warmth in extremely cold conditions. Therefore, the development of photo-thermal fibers for personal thermal management textiles has emerged as an urgent need. Herein, novel chitosan/copper sulfide nanoparticles (CS/CuSNPs) hybrid fibers with photo-thermal function were fabricated successfully. Significantly, our study demonstrated that the tensile and photo-thermal conversation properties of the CS/CuSNPs hybrid fibers could be effectively regulated by altering the CuSNPs` morphological structures. Compared with other CuSNPs (tube-like, sphere-like, and flower-like), the plate-like CuSNPs with smooth surfaces and uniform nanometer size played a significant role by scattering incident light in the fibers as a secondary light source for CuSNPs absorbance. Thus, under IR light irradiation at a power density of 1.0 W/cm2, the surface temperature of CS/0.1 wt% plate-like CuSNPs hybrid fibers sharply increased by 27.6 °C, which was more than 4 times of the pure CS fibers. And the breaking strength and initial modulus of CS/0.1 wt% plate-like CuSNPs hybrid fibers increased by more than 18.37 and 6.88 % compared with the nascent CS fibers. This study develops a novel and effective strategy to tune the photo-thermal and tensile properties of CS hybrid fibers without incorporating more content or additives.

Optimized DOX Drug Deliveries via Chitosan-Mediated Nanoparticles and Stimuli Responses in Cancer Chemotherapy: A Review

Chitosan nanoparticles (NPs) serve as useful multidrug delivery carriers in cancer chemotherapy. Chitosan has considerable potential in drug delivery systems (DDSs) for targeting tumor cells. Doxorubicin (DOX) has limited application due to its resistance and lack of specificity. Chitosan NPs have been used for DOX delivery because of their biocompatibility, biodegradability, drug encapsulation efficiency, and target specificity. In this review, various types of chitosan derivatives are discussed in DDSs to enhance the effectiveness of cancer treatments. Modified chitosan-DOX NP drug deliveries with other compounds also increase the penetration and efficiency of DOX against tumor cells. We also highlight the endogenous stimuli (pH, redox, enzyme) and exogenous stimuli (light, magnetic, ultrasound), and their positive effect on DOX drug delivery via chitosan NPs. Our study sheds light on the importance of chitosan NPs for DOX drug delivery in cancer treatment and may inspire the development of more effective approaches for cancer chemotherapy.

Recent advances in chitosan-based materials; The synthesis, modifications and biomedical applications

The attention to polymer-based biomaterials, for instance, chitosan and its derivatives, as well as the techniques for using them in numerous scientific domains, is continuously rising. Chitosan is a decomposable naturally occurring polymeric material that is mostly obtained from seafood waste. Because of its special ecofriendly, biocompatible, non- toxic nature as well as antimicrobial properties, chitosan-based materials have received a lot of interest in the field of biomedical applications. The reactivity of chitosan is mainly because of the amino and hydroxyl groups in its composition, which makes it further fascinating for various uses, including biosensing, textile finishing, antimicrobial wound dressing, tissue engineering, bioimaging, gene, DNA and drug delivery and as a coating material for medical implants. This study is an overview of the different types of chitosan-based materials which now a days have been fabricated by applying different techniques and modifications that include etherification, esterification, crosslinking, graft copolymerization and o-acetylation etc. for hydroxyl groups' processes and acetylation, quaternization, Schiff's base reaction, and grafting for amino groups' reactions. Furthermore, this overview summarizes the literature from recent years related to the important applications of chitosan-based materials (i.e., thin films, nanocomposites or nanoparticles, sponges and hydrogels) in different biomedical applications.

Thiolated chitosan hydrogel-embedded niosomes: A promising crocin delivery system toward the management of aphthous stomatitis

Aphthous stomatitis is a common inflammatory oral disease with challenging management. Crocin is a natural carotenoid that has shown great anti-inflammatory properties. The aim of this study was to develop thiolated chitosan (TCS)-based hydrogels containing niosomes to serve as a mucoadhesive crocin delivery system for aphthous stomatitis. Crocin-loaded niosomes were prepared and the impact of surfactant type, cholesterol content, and lipid to drug ratio on the characteristics of niosomes was evaluated. TCS was synthesized and the success of thiolation was investigated. The optimum niosomal formulation was loaded into the hydrogel and the hybrid system was characterized regarding the morphology, mucoadhesive properties, viscosity, chemical structure, in vitro drug release, and in vivo efficacy. The optimized niosome formulation showed 77% crocin entrapment, a particle diameter of 59 nm, and a zeta potential of -18 mV. The niosome-containing hydrogel exhibited pseudoplastic rheological behavior, mucoadhesive properties, suitable swelling, and sustained release of crocin. In vivo study revealed that the niosome-containing hydrogel improved ulcer healing and decreased the expression of tumor necrosis factor-alpha (TNF-α) and p53 while increasing the expression of vascular endothelial growth factor (VEGF) and alpha-smooth muscle actin (α-SMA). Collectively, TCS hydrogel-embedded crocin-loaded niosomes is a promising therapeutic option for aphthous stomatitis. CHEMICAL COMPOUNDS STUDIED IN THIS ARTICLE: Crocin (PubChem CID: 5281233) Chitosan (PubChem CID: 71853) Thioglycolic acid (PubChem CID: 1133) 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (PubChem CID: 2723939) 5,5'-dithiobis (2-nitrobenzoic acid) (PubChem CID: 6254) Cholesterol (PubChem CID: 5997).

Polysaccharide hydrogel platforms as suitable carriers of liposomes and extracellular vesicles for dermal applications

Lipid-based nanocarriers have been extensively investigated for their application in drug delivery. Particularly, liposomes are now clinically established for treating various diseases such as fungal infections. In contrast, extracellular vesicles (EVs) - small cell-derived nanoparticles involved in cellular communication - have just recently sparked interest as drug carriers but their development is still at the preclinical level. To drive this development further, the methods and technologies exploited in the context of liposome research should be applied in the domain of EVs to facilitate and accelerate their clinical translation. One of the crucial steps for EV-based therapeutics is designing them as proper dosage forms for specific applications. This review offers a comprehensive overview of state-of-the-art polysaccharide-based hydrogel platforms designed for artificial and natural vesicles with application in drug delivery to the skin. We discuss their various physicochemical and biological properties and try to create a sound basis for the optimization of EV-embedded hydrogels as versatile therapeutic avenues.

Mucoadhesive drug delivery systems: a promising non-invasive approach to bioavailability enhancement. Part I: biophysical considerations

INTRODUCTION

Mucoadhesive drug delivery systems (MDDS) are specifically designed to interact and bind to the mucosal layer for localized, prolonged, and/or targeted drug delivery. Over the past 4 decades, different sites have been explored for mucoadhesion including the nasal, oral, and vaginal cavities, the gastrointestinal tract and ocular tissues.

AREAS COVERED

The present review aims to provide a comprehensive understanding of different aspects of MDDS development. Part I focuses on the anatomical and biological aspects of mucoadhesion, which include a detailed elucidation of the structure and anatomy of the mucosa, the properties of mucin, the different theories of mucoadhesion and evaluation techniques.

EXPERT OPINION

The mucosal layer presents a unique opportunity for effective localization as well as systemic drug delivery via MDDS. Formulation of MDDS requires a thorough understanding of the anatomy of mucus tissue, the rate of mucus secretion and turnover, and the physicochemical properties of mucus. Further, the moisture content and the hydration of polymers are crucial for interaction with mucus. A confluence of different theories used to explain the mechanism of mucoadhesion is useful for understanding the mucoadhesion of different MDDS and their evaluation is subject to factors, such as the site of administration, type of dosage form, and duration of action. [Figure: see text].

The Progress of Chitosan-Based Nanoparticles for Intravesical Bladder Cancer Treatment

Bladder cancer (BC) is the most frequently occurring cancer of the urinary system, with non-muscle-invasive bladder cancer (NMIBC) accounting for 75-85% of all the bladder cancers. Patients with NMIBC have a good survival rate but are at high risk for tumor recurrence and disease progression. Intravesical instillation of antitumor agents is the standard treatment for NMIBC following transurethral resection of bladder tumors. Chemotherapeutic drugs are broadly employed for bladder cancer treatment, but have limited efficacy due to chemo-resistance and systemic toxicity. Additionally, the periodic voiding of bladder and low permeability of the bladder urothelium impair the retention of drugs, resulting in a weak antitumoral response. Chitosan is a non-toxic and biocompatible polymer which enables better penetration of specific drugs to the deeper cell layers of the bladder as a consequence of temporarily abolishing the barrier function of urothelium, thus offering multifaceted biomedical applications in urinary bladder epithelial. Nowadays, the rapid development of nanoparticles significantly improves the tumor therapy with enhanced drug transport. This review presents an overview on the state of chitosan-based nanoparticles in the field of intravesical bladder cancer treatment.

pH-responsive in situ gelling properties of thiolated citrus high-methoxyl pectin and its potential gel mechanism

pH-responsive in situ gelling properties of thiolated citrus high-methoxyl pectin (TCHMP) were investigated in this study. The gelation capacity results revealed that the in situ gelation behavior of TCHMP only occurred when the pH value was higher than 6.25. The gel strength increased from 26.63 g to 42.77 g as the pH value increased from 7.4 to 8.9. Rheological measurements confirmed that the apparent viscosity and viscoelasticity of TCHMP were highly dependent on pH value and dialysis time. Compared with the control group, the apparent viscosity of TCHMP dialyzed in phosphate-buffered saline (PBS) of pH 8.9 for 180 min increased 695-fold. During the dialysis process of TCHMP at different pH values (7.4-8.9), the final thiol groups content decreased and the final disulfide bonds content increased with the increase in pH value. This illustrates that the mechanism of in situ gelation is mainly the oxidation of thiol-thiol groups to form disulfide bonds. These results can put forward new insights into the pH-responsive in situ gelling properties of TCHMP and provide a theoretical basis for the application of TCHMP in neutral and alkaline gel systems.

Corrigendum: Applications of chitosan and its derivatives in skin and soft tissue diseases

[This corrects the article DOI: 10.3389/fbioe.2022.894667.].

Preparation and detailed characterization of the thiomer chitosan-cysteine as a suitable mucoadhesive excipient for nasal powders

The therapeutic application of nasal powders requires the development of novel mucoadhesive excipients. Thiolated polymers exhibit significant potential for this purpose based on their increased mucoadhesion attributable to the formation of disulfide bonds between the polymer and mucus surface. A chitosan-cysteine (chit-cyst) conjugate was synthesized using 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide in aqueous solution. The synthetic yield and synthesis conditions were optimized, and the efficiency of the reaction was evaluated. Rheological measurements revealed that the polymer derivative exhibited increased mucoadhesive properties in comparison to chitosan powder. To characterize the polymer, a novel purity investigation method was developed and verified to investigate the residual l-cysteine content. The results revealed that l-cysteine was not detectable in the resultant polymer matrix. Based on the cytotoxicity studies, chit-cyst was found to be safe for nasal application. Thereafter, nasal powder formulations were prepared using the polymer and the antiparkinsonian drug levodopa methyl ester hydrochloride by freeze-drying to investigate their nasal applicability. Based on the in vitro studies, these powders might be suitable for reducing the off periods of Parkinson's disease because of their expected higher in vivo mucoadhesion.

In-situ forming hydrogel based on thiolated chitosan/carboxymethyl cellulose (CMC) containing borate bioactive glass for wound healing

Suitable wound dressings for accelerating wound healing are actively being designed and synthesised. In this study, thiolated chitosan (tCh)/oxidized carboxymethyl cellulose (OCMC) hydrogel containing Cu-doped borate bioglass (BG) was developed as a wound dressing to improve wound healing in a full-thickness skin defect of mouse animal model. Thiolation was used to incorporate thiol groups into chitosan (Ch) to enhance its water solubility and mucoadhesion characteristics. Here, the in situ forming hydrogel was successfully developed using the Schiff-based reaction, and its physio-chemical and antibacterial characteristics were examined. Borate BG was also incorporated in the generated hydrogel to promote angiogenesis and tissue regeneration at the wound site. Investigations of in vitro cytotoxicity assays demonstrated that the synthesised hydrogels showed good biocompatibility and promoted cell growth. These results inspired us to investigate the effectiveness of skin wound healing in a mouse model. On the backs of animals, two full-thickness wounds were created and treated utilising two different treatment conditions: (1) OCMC/tCh hydrogel, (2) OCMC/tCh/borate BG, and (3) control defect. The wound closure ratio, collagen deposition, and angiogenesis activity were measured after 14 days to determine the healing efficacy of the in situ hydrogels used as wound dressings. Overall, the hydrogel containing borate BG was maintained in the defect site, healing efficiency was replicable, and wound healing was apparent. In conclusion, we found consistent angiogenesis, remodelling, and accelerated wound healing, which we propose may have beneficial effects on the repair of skin defects.

Applications of Chitosan and its Derivatives in Skin and Soft Tissue Diseases

Chitosan and its derivatives are bioactive molecules that have recently been used in various fields, especially in the medical field. The antibacterial, antitumor, and immunomodulatory properties of chitosan have been extensively studied. Chitosan can be used as a drug-delivery carrier in the form of hydrogels, sponges, microspheres, nanoparticles, and thin films to treat diseases, especially those of the skin and soft tissue such as injuries and lesions of the skin, muscles, blood vessels, and nerves. Chitosan can prevent and also treat soft tissue diseases by exerting diverse biological effects such as antibacterial, antitumor, antioxidant, and tissue regeneration effects. Owing to its antitumor properties, chitosan can be used as a targeted therapy to treat soft tissue tumors. Moreover, owing to its antibacterial and antioxidant properties, chitosan can be used in the prevention and treatment of soft tissue infections. Chitosan can stop the bleeding of open wounds by promoting platelet agglutination. It can also promote the regeneration of soft tissues such as the skin, muscles, and nerves. Drug-delivery carriers containing chitosan can be used as wound dressings to promote wound healing. This review summarizes the structure and biological characteristics of chitosan and its derivatives. The recent breakthroughs and future trends of chitosan and its derivatives in therapeutic effects and drug delivery functions including anti-infection, promotion of wound healing, tissue regeneration and anticancer on soft tissue diseases are elaborated.

Peripheral nerve regeneration by thiolated chitosan hydrogel containing Taurine: In vitro and in vivo study

About 2.8% of trauma sick persons hurt from peripheral nerve damages, thus, numerous approaches are using to improve peripheral nerve regeneration. In the current study, the efficacy of several dosages of Taurine for peripheral nerve regeneration was evaluated. About 0.1%, 1%, and 10% (w/w) of Taurine were added into thiolated chitosan hydrogel and its features including morphology, swelling properties, weight loss, hemo-, and cytocompatibility were assessed. Hydrogels’ functionality was evaluated by injecting them into the crushed sciatic nerve of rats by using walking-foot-print analysis, Hot plate latency test, gastrocnemius muscle wet weight loss, and histopathological evaluation. Results demonstrated that the average pore size is in the area of 30–40 μm with interconnected pores and their weight loss was around 70% after 7 days. Results of blood compatibility and the MTT tests confirmed the biocompatibility of hydrogels. In vivo study illustrate thiolated Chitosan/Taurine hydrogels especially hydrogel includes 1% of Taurine enhanced sciatic nerve regeneration. In conclusion, Taurine can be used as a feasible treatment for peripheral nerve regeneration.

Application of Chitosan and Its Derivative Polymers in Clinical Medicine and Agriculture

Chitosan is a biodegradable natural polymer derived from the exoskeleton of crustaceans. Because of its biocompatibility and non-biotoxicity, chitosan is widely used in the fields of medicine and agriculture. With the latest technology and technological progress, different active functional groups can be connected by modification, surface modification, or other configurations with various physical, chemical, and biological properties. These changes can significantly expand the application range and efficacy of chitosan polymers. This paper reviews the different uses of chitosan, such as catheter bridging to repair nerve broken ends, making wound auxiliaries, as tissue engineering repair materials for bone or cartilage, or as carriers for a variety of drugs to expand the volume or slow-release and even show potential in the fight against COVID-19. In addition, it is also discussed that chitosan in agriculture can improve the growth of crops and can be used as an antioxidant coating because its natural antibacterial properties are used alone or in conjunction with a variety of endophytic bacteria and metal ions. Generally speaking, chitosan is a kind of polymer material with excellent development prospects in medicine and agriculture.

Thiolated Chitosan Microneedle Patch of Levosulpiride from Fabrication, Characterization to Bioavailability Enhancement Approach

In this study, a first attempt has been made to deliver levosulpiride transdermally through a thiolated chitosan microneedle patch (TC-MNP). Levosulpiride is slowly and weakly absorbed from the gastrointestinal tract with an oral bioavailability of less than 25% and short half-life of about 6 h. In order to enhance its bioavailability, levosulpiride-loaded thiolated chitosan microneedle patches (LS-TC-MNPs) were fabricated. Firstly, thiolated chitosan was synthesized and characterized by nuclear magnetic resonance (1HNMR) spectroscopy, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Thiolated chitosan has been used in different drug delivery systems; herein, thiolated chitosan has been used for the transdermal delivery of LS. LS-TC-MNPs were fabricated from different concentrations of thiolated chitosan solution. Furthermore, the levosulpiride-loaded thiolated chitosan microneedle patch (LS-TC-MNP) was characterized by FTIR spectroscopic analysis, scanning electron microscopy (SEM) study, penetration ability, tensile strength, moisture content, patch thickness, and elongation test. LS-TC-MNP fabricated with 3% thiolated chitosan solution was found to have the best tensile strength, moisture content, patch thickness, elongation, drug-loading efficiency, and drug content. Thiolated chitosan is biodegradable, nontoxic and has good absorption and swelling in the skin. LS-TC-MNP-3 consists of 100 needles in 10 rows each with 10 needles. The length of each microneedle was 575 μm; they were pyramidal in shape, with sharp pointed ends and a base diameter of 200 µm. The microneedle patch (LS-TC-MNP-3) resulted in-vitro drug release of 65% up to 48 h, ex vivo permeation of 63.6%, with good skin biocompatibility and enhanced in-vivo pharmacokinetics (AUC = 986 µg/mL·h, Cmax = 24.5 µg/mL) as compared to oral LS dispersion (AUC = 3.2 µg/mL·h, Cmax = 0.5 µg/mL). Based on the above results, LS-TC-MNP-3 seems to be a promising strategy for enhancing the bioavailability of levosulpiride.

Synthesis and Characterization of Thiolated Gum Ghatti as a Novel Excipient: Development of Compression-Coated Mucoadhesive Tablets of Domperidone

Mucoadhesive polymers represent a major part of site-specific and localized retention strategies in oral drug delivery. The present research was designed to synthesize and characterize a novel mucoadhesive carbohydrate polymer (thiolated gum ghatti; TGG), which was employed to formulate mucoadhesive tablets of domperidone using an industrially viable compression coating technique. Thiolation of gum ghatti was achieved by the ester formation (esterification) between the hydroxyl group and the carboxyl group of gum ghatti and thioglycolic acid. TGG was characterized by various physicochemical techniques such as FTIR, XRD, SEM, and DSC. In rheological studies, the observed viscosities of pure gum mucin were 45.45 and 71.75 mPa·s and those of the thiolated gum were 78.7 and 112.58 mPa·s, respectively, in water and simulated gastric fluid. A significant increase in viscosity for thiolated gum may be attributed to increased macromolecular interactions responsible for enhanced mucoadhesive potential of thiolated gum. In silico studies corroborate the role of mucin gum interaction and energetic stabilization for enhanced mucoadhesion properties of thiolated gum. Ex vivo mucoadhesion strength of gum ghatti- and TGG-coated tablets was found to be ranging between 45.77 ± 1.49 and 88.16 ± 1.75 and 115.32 ± 2.36 and 184.65 ± 2.07 mN, respectively. In an acute oral toxicity study, TGG did not show any toxicity on the vital organs of the Wistar rat and proved to be a safe polymer. TGG may be regarded as a promising polymer for developing different mucoadhesive drug delivery systems.

Thiolated-Polymer-Based Nanoparticles as an Avant-Garde Approach for Anticancer Therapies-Reviewing Thiomers from Chitosan and Hyaluronic Acid

Thiomers (or thiolated polymers) have broken through as avant-garde approaches in anticancer therapy. Their distinguished reactivity and properties, closely linked to their final applications, justify the extensive research conducted on their preparation and use as smart drug-delivery systems (DDSs). Multiple studies have demonstrated that thiomer-rich nanoformulations can overcome major drawbacks found when administering diverse active pharmaceutical ingredients (APIs), especially in cancer therapy. This work focuses on providing a complete and concise review of the synthetic tools available to thiolate cationic and anionic polymers, in particular chitosan (CTS) and hyaluronic acid (HA), respectively, drawing attention to the most successful procedures. Their chemical reactivity and most relevant properties regarding their use in anticancer formulations are also discussed. In addition, a variety of NP formation procedures are outlined, as well as their use in cancer therapy, particularly for taxanes and siRNA. It is expected that the current work could clarify the main synthetic strategies available, with their scope and drawbacks, as well as provide some insight into thiomer chemistry. Therefore, this review can inspire new research strategies in the development of efficient formulations for the treatment of cancer.

Preparation and evaluation of an innovative antibacterial bi-layered composite dressing for skin wound healing

AIM OF THE STUDY

The aim of the current study was to develop collagen-based bi-layered composite dressings with antibacterial property and evaluate the efficiency for wound healing.

MATERIALS AND METHODS

A bi-layered composite wound dressing was fabricated using two marine biomacromolecules (collagen and chitosan or carboxymethyl chitosan). Non-crosslinked and N-Ethyl-N'-(3-dimethylaminopropyl) carbodiimide/N-Hydroxy succinimide (EDC/NHS) cross-linked collagen sponges fabricated by vacuum freeze-drying technology was used as the inner layer. The medical spun-laced nonwoven coated with chitosan and carboxymethyl chitosan was used as the outer layer. The antibacterial activities against E. coli and S. aureus were evaluated by the inhibition zone assay. Deep second-degree scald model was performed to evaluate the efficiency of bi-layered composite dressings for wound healing.

RESULTS

In view of comprehensive evaluation of appearance and in vitro antibacterial activity, medical spun-laced nonwoven coated with 3% of chitosan solution was chosen to be used as the optimized preparation conditions to produce the outer layer of composite dressing, which acted as a barrier against microorganisms and provided mechanical support. Furthermore, the results of wound closure and histopathological analysis indicated that EDC/NHS cross-linked collagen-based bi-layered composite dressing was superior to non-crosslinked and commercial products, which stimulated the wound healing process and accomplished deep second-degree scalded skin healing within a time span of 28 days.

CONCLUSION

The EDC/NHS cross-linked collagen-based bi-layered composite dressing had immense potential to be applied for an ideal wound dressing for more efficient and faster wound healing. Therefore, the findings provided the essential theoretical basis for great potential of collagen-based composite dressing used in wound healing applications.

Self-Assembled Nanocarriers Based on Modified Chitosan for Biomedical Applications: Preparation and Characterization

Protein-polysaccharide systems are of increasing interest as their combined attributes allow for fulfilling a broad range of applications in biomedical and pharmaceutical fields. In this study, the preparation of nanogels based on maleic anhydride chitosan derivatives (MAC) and bovine serum albumin (BSA) was achieved through a self-assembly process performed in aqueous phase. A series of experiments performed by varying the concentrations of MAC and BSA were conducted to find an appropriate mixing ratio for the polymer solutions leading to thermodynamically stable nanogels with the ability to encapsulate active compounds. The influence of temperature on the formation of nanogels was also studied. The consequent conformational changes were monitored using ultraviolet-visible (UV-VIS) spectrophotometry. The spectrophotometric investigations combined with diffraction light scattering (DLS) technique and zeta potential measurement results were correlated to determine the interaction mechanism and assess the self-assembling processes during nanogel formation. It was found that the hydrodynamic diameter (D_h) of the nanoparticles increased slightly at acidic pH, and the protonation of ionizable amino groups with the pH was confirmed by the zeta potential measurements. MAC/BSA nanogels also exhibited antimicrobial properties after being loaded with amoxicillin (Amox), which is an antibiotic used for the treatment of various infections. The experimental data resulting from this study provide theoretical guidance for the design and development of attractive nanocarriers for a large variety of biomedical applications.

Thiolated Chitosans: A Multi-talented Class of Polymers for Various Applications

Various properties of chitosan can be customized by thiolation for very specific needs in a wide range of application areas. Since the discovery of thiolated chitosans, many studies have proven their advantageous characteristics, such as adhesion to biological surfaces, adjustable cross-linking and swelling behavior, controllable drug release, permeation as well as cellular uptake enhancement, inhibition of efflux pumps and enzymes, complexation of metal ions, antioxidative properties, and radical scavenging activity. Simultaneously, these polymers remain biodegradable without increased toxicity. Within this Review, an overview about the different possibilities to covalently attach sulfhydryl ligands to the polymeric backbone of chitosan is given, and the resulting versatile physiochemical properties are discussed in detail. Furthermore, the broad spectrum of applications for thiolated chitosans in science and industry, ranging from their most advanced use in pharmaceutical and medical science over wastewater treatment to the impregnation of textiles, is addressed.

Chitosan Derivatives and Their Application in Biomedicine

Chitosan is a product of the deacetylation of chitin, which is widely found in nature. Chitosan is insoluble in water and most organic solvents, which seriously limits both its application scope and applicable fields. However, chitosan contains active functional groups that are liable to chemical reactions; thus, chitosan derivatives can be obtained through the chemical modification of chitosan. The modification of chitosan has been an important aspect of chitosan research, showing a better solubility, pH-sensitive targeting, an increased number of delivery systems, etc. This review summarizes the modification of chitosan by acylation, carboxylation, alkylation, and quaternization in order to improve the water solubility, pH sensitivity, and the targeting of chitosan derivatives. The applications of chitosan derivatives in the antibacterial, sustained slowly release, targeting, and delivery system fields are also described. Chitosan derivatives will have a large impact and show potential in biomedicine for the development of drugs in future.