Effect of molecular weight and degree of chitosan deacetylation on the preparation and characteristics of chitosan thermosensitive hydrogel as a delivery system

Polysaccharide-based hydrogels for cartilage regeneration

Cartilage defect is one of the common tissue defect clinical diseases and may finally lead to osteoarthritis (OA) which threat patients' physical and psychological health. Polysaccharide is the main component of extracellular matrix (ECM) in cartilage tissue. In the past decades, polysaccharide-based hydrogels have shown great potential for cartilage regeneration considering unique qualities such as biocompatibility, enhanced cell proliferation, drug delivery, low toxicity, and many others. Structures such as chain length and chain branching make polysaccharides have different physical and chemical properties. In this review, cartilage diseases and current treatment options of polysaccharide-based hydrogels for cartilage defection repair were illustrated. We focus on how components and structures of recently developed materials affect the performance. The challenges and perspectives for polysaccharide-based hydrogels in cartilage repair and regeneration were also discussed in depth.

A comprehensive review of chitosan-based functional materials: From history to specific applications

Chitosan (CTS), a natural biopolymer derived from chitin, has garnered significant attention owing to its potential chemical, biological, and physical properties, such as biocompatibility, bioactivity, and biosafety. This comprehensive review traces the historical development of CTS-based materials and delves into their specific applications across various fields. The study highlights the evolution of CTS from its initial discovery to its current state, emphasizing key milestones and technological advancements that have expanded its utility. Despite the extensive research, the synthesis and functionalization of CTS to achieve desired properties for targeted applications remain a challenge. This review addresses current problems such as the scalability of production, consistency in quality, and the environmental impact of extraction and modification processes. Additionally, it explores the novel applications of CTS-based materials in biomedicine, agriculture, environmental protection, and food industry, showcasing innovative solutions and future potentials. By providing a detailed analysis of the current state of CTS research and identifying gaps in knowledge, this review offers a valuable resource for researchers and industry professionals. The novelty of this work lies in its holistic approach, combining historical context with a forward-looking perspective on emerging trends and potential breakthroughs in the field of CTS-based functional materials. Therefore, this review will be helpful for readers by summarizing recent advances and discussing prospects in CTS-based functional materials.

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.

Hydrogels: An overview of its classifications, properties, and applications

The review paper starts with the introduction to hydrogels along with broad literature survey covering different modes of synthesis including high energy radiation methods. After that, paper covered broad classification of the hydrogels depending upon the basis of their source of origin, method of synthesis, type of cross-linking present and ionic charges on bound groups. Another advanced category response triggered hydrogels, which includes pH, temperature, electro, and light and substrate responsive hydrogels was also studied. Presented paper summarises chemical structure, properties, and synthesis of different kinds of hydrogels. Main focus was given to the preparation super absorbents such as: Semi-interpenetrating networks (semi-IPNs), Interpenetrating networks (IPNs) and cross-linked binary graft copolymers (BGCPs). The weak mechanical properties and easy degradation limit the uses of bio-based -hydrogels in biomedical field. Their properties can be improved through different chemical and physical methods. These methods were also discussed in the current research paper. Also, it includes development of hydrogels as controlled drug delivery devices, as implants and biomaterials to replace malfunctioned body parts along with their use in several other applications listed in the literature. Literature survey on the application of hydrogels in different fields like biomedical, nano-biotechnology, tissue engineering, drug delivery and agriculture was also carried out.

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.

Chitosan-Based Thermogelling System for Nose-to-Brain Donepezil Delivery: Optimising Formulation Properties and Nasal Deposition Profile

Donepezil nasal delivery strategies are being continuously investigated for advancing therapy in Alzheimer's disease. The aim of this study was to develop a chitosan-based, donepezil-loaded thermogelling formulation tailored to meet all the requirements for efficient nose-to-brain delivery. A statistical design of the experiments was implemented for the optimisation of the formulation and/or administration parameters, with regard to formulation viscosity, gelling and spray properties, as well as its targeted nasal deposition within the 3D-printed nasal cavity model. The optimised formulation was further characterised in terms of stability, in vitro release, in vitro biocompatibility and permeability (using Calu-3 cells), ex vivo mucoadhesion (using porcine nasal mucosa), and in vivo irritability (using slug mucosal irritation assay). The applied research design resulted in the development of a sprayable donepezil delivery platform characterised by instant gelation at 34 °C and olfactory deposition reaching a remarkably high 71.8% of the applied dose. The optimised formulation showed prolonged drug release (t_1/2 about 90 min), mucoadhesive behaviour, and reversible permeation enhancement, with a 20-fold increase in adhesion and a 1.5-fold increase in the apparent permeability coefficient in relation to the corresponding donepezil solution. The slug mucosal irritation assay demonstrated an acceptable irritability profile, indicating its potential for safe nasal delivery. It can be concluded that the developed thermogelling formulation showed great promise as an efficient donepezil brain-targeted delivery system. Furthermore, the formulation is worth investigating in vivo for final feasibility confirmation.

In situ forming dialdehyde xanthan gum-gelatin Schiff-base hydrogels as potent controlled release fertilizers

Controlled release fertilizer (CRF) hydrogels have blossomed into promising materials in agriculture owing to the sustained release of the fertilizer and also as soil conditioner. Apart from the traditional CRF hydrogels; Schiff-base hydrogels have garnered significant thrust that release nitrogen slowly in addition to reducing the environmental pollution. Herein, we have fabricated Schiff-base CRF hydrogels composed of dialdehyde xanthan gum (DAXG) and gelatin. The formation of the hydrogels was accomplished via the simplistic in situ crosslinking reaction between the aldehyde groups of DAXG and the amino groups of gelatin. The hydrogels acquired a compact network upon increasing the DAXG content in the matrix. The phytotoxic assay on different plants indicated the hydrogels to be nontoxic. The hydrogels demonstrated good water-retention behaviour in soil, along with reusability even after 5 cycles. A controlled release profile for urea was evident from the hydrogels wherein macromolecular relaxation played a crucial role in the release mechanism. Growth assays on Abelmoschus esculentus (Okra) plant presented an intuitive evaluation on the growth and water-holding capacity of the CRF hydrogel. The present work demonstrated a facile preparation of CRF hydrogels to enhance the utilization of urea and retain soil humidity as fertilizer carriers.

Graphene Oxide-Carbamoylated Chitosan Hydrogels with Tunable Mechanical Properties for Biological Applications

Chitosan (CH)-based hydrogels have been extensively researched in numerous biological applications, including drug delivery, biosensing, wound healing, and tissue engineering, to name a few. Previously, modified CH hydrogels by carbamoylation, using potassium cyanate (KCNO) as the cross-linker, have shown improvement in viscoelastic properties and biocompatibility. In this study, graphene oxide (GO) nanofillers are added to carbamoylated CH to form a nanocomposite hydrogel and study the influence of CH molecular weight (M_w) and GO loading concentrations on hydrogel properties. The physical properties (swelling, degradation, and porous structure) of the hydrogels can be tuned as required for cell attachment and spreading by varying both the GO concentration and the M_w of CH. Rheological characterization showed an improvement in the mechanical properties (storage modulus, yield stress, and viscosity) of the synthesized CH-GO hydrogels with an increase in the M_w of CH and the GO concentration. Human retinal pigmented epithelial-1 (RPE-1) cells seeded onto the prepared hydrogel scaffolds showed good cell viability, adhesion, and cell spreading, confirming their cytocompatibility, with dependence on both M_w of CH and GO loading.

One-step preparation of hydrogel based on different molecular weights of chitosan with citric acid

BACKGROUND

Chitosan-based hydrogels have been prepared previously by a two-step protocol in which chitosan was first dissolved in dilute acetic acid and then crosslinked by glutaraldehyde or genipin. This was a time-consuming method, which had the disadvantages of high costs and biological safety problems.

RESULTS

Scanning electron microscopy (SEM) results verified the successful preparation of hydrogels based on high, medium, and low molecular-weight chitosan (HCS, MCS, and LCS), respectively. The hydrogels prepared with HCS, MCS, and LCS were formed through the accumulation of different-sized crystals. The framework density of the hydrogel was enhanced by an increase in the chitosan molecular weight and exhibited a crack pore pattern composed of flake particles. Medium molecular-weight chitosan-based hydrogel exhibited the highest specific surface area and total pore volume, with values of 3.81 m² g^-1 and 0.0109 cm³ g^-1 , respectively. The water absorption rate of the chitosan based hydrogels was influenced by its molecular weights at the sequence of LCS > HCS > MCS, while the maximum compression stress was affected at the sequence of HCS > MCS > LCS. The network structure was enhanced with an increase in the chitosan molecular weight and reached maximum stress levels of 4.50, 1.50 and 0.75 MPa for HCS-, MCS-, and LCS-based hydrogels, respectively.

CONCLUSION

Citric acid was shown to be an effective dissolving and crosslinking agent in the preparation of MCS- and HCS-based hydrogels. The physiochemical properties of the hydrogels were enhanced as the molecular weight of the chitosan increased. © 2021 Society of Chemical Industry.

Preparation of a "Branch-Fruit" structure chitosan nanofiber physical hydrogels with high mechanical strength and pH-responsive controlled drug release properties

The poor mechanical properties of chitosan physical hydrogels seriously hinder their application in the biomedical field. Inspired by the structure of cell tissues, a novel chitosan nanofiber (CSNF)/Hyaluronic acid (HA)/β-glycerophosphate disodium (β-GP) drug-loaded hydrogel was prepared by micro-dissolution and physical crosslinking. The hydrogel has a “Branch-Fruit” structure and exhibits excellent mechanical properties, good biocompatibility and cell-adhesion properties. Human cancer cells (HeLa) can adhere to the hydrogel surface, which might facilitate tumor site-specific administration of drugs. This material also exhibits high pH sensitivity, with which drug release can be triggered under acidic conditions at pH 4.00. The mechanical strength and drug release behavior of this hydrogel can be easily adjusted by varying the CSNF content.

Representation of the gelation mechanism of CSNF/HA/β-GP precursor solution.

Evaluating Non-Conventional Chitosan Sources for Controlled Release of Risperidone

In this work, two chitosan samples from cuttlebone and squid pen are produced and characterized. We studied the formation of thermoresponsive hydrogels with β-glycerol phosphate and found proper formulations that form the hydrogels at 37 °C. Gel formation depended on the chitosan source being possible to produce the thermoresponsive hydrogels at chitosan concentration of 1% with cuttlebone chitosan but 1.5% was needed for squid pen. For the first time, these non-commercial chitosan sources have been used in combination with β-glycerol phosphate to prepare risperidone formulations for controlled drug delivery. Three types of formulations for risperidone-controlled release have been developed, in-situ gelling formulations, hydrogels and xerogels. The release profiles show that in-situ gelling formulations and particularly hydrogels allow an extended control release of risperidone while xerogels are not appropriate formulations for this end since risperidone was completely released in 48 h.

Polymeric Hydrogels for Controlled Drug Delivery to Treat Arthritis

Rheumatoid arthritis (RA) and osteoarthritis (OA) are disabling musculoskeletal disorders that affect joints and cartilage and may lead to bone degeneration. Conventional delivery of anti-arthritic agents is limited due to short intra-articular half-life and toxicities. Innovations in polymer chemistry have led to advancements in hydrogel technology, offering a versatile drug delivery platform exhibiting tissue-like properties with tunable drug loading and high residence time properties This review discusses the advantages and drawbacks of polymeric materials along with their modifications as well as their applications for fabricating hydrogels loaded with therapeutic agents (small molecule drugs, immunotherapeutic agents, and cells). Emphasis is given to the biological potentialities of hydrogel hybrid systems/micro-and nanotechnology-integrated hydrogels as promising tools. Applications for facile tuning of therapeutic drug loading, maintaining long-term release, and consequently improving therapeutic outcome and patient compliance in arthritis are detailed. This review also suggests the advantages, challenges, and future perspectives of hydrogels loaded with anti-arthritic agents with high therapeutic potential that may alter the landscape of currently available arthritis treatment modalities.

Stability and surface properties of selenium nanoparticles coated with chitosan and sodium carboxymethyl cellulose

The effect of polysaccharide coatings on the stability and release characteristics of selenium nanoparticles (SeNPs) was evaluated by comparing the characteristics of chitosan-coated SeNPs (CS-SeNPs) and sodium carboxymethyl cellulose-coated SeNPs (CMC-SeNPs). The release characteristics of SeNPs were investigated in storage conditions, gastrointestinal conditions, and free radical systems. CMC-SeNPs formed dimers or trimers, whereas CS-SeNPs were monodispersed but formed large aggregates in a pH range of 7.4-8.25. Upon 50 days of storage at 30 °C, both CMC-SeNPs and CS-SeNPs were converted to Se⁴⁺. SeNPs exhibited a lower release rate in simulated gastrointestinal conditions than in free radical systems. SeNPs release in ABTS and superoxide anion free radical systems followed the first-order and Korsmeyer-Peppas models, respectively, indicating that SeNP release is mainly governed by dissolution mechanisms. Additional studies are needed to examine the potential environmental effects and biological activity of the Se⁴⁺ released from SeNPs.

Design and evaluation of chitosan-amino acid thermosensitive hydrogel

Chitosan/glycerophosphate thermosensitive hydrogel crosslinked physically was a potential drug delivery carrier; however, long gelation time limits its application. Here, chitosan-amino acid (AA) thermosensitive hydrogels were prepared from chitosan (CS), αβ-glycerophosphate (GP), and l-lysine (Lys) or l-glutamic acid (Glu). The prepared CS-Lys/GP and CS-Glu/GP hydrogel showed good thermosensitivity and could form gels in a short time. The optimal parameters of CS-Lys/GP hydrogel were that the concentration of CS-Lys was 2.5%, the ratio of CS/Lys was 3.5/1.0, the ratio of CS-Lys/GP was 4.5/1.0. The optimal parameters of CS-Glu/GP hydrogel were that the concentration of CS-Glu was 3.0%, the ratio of CS/Glu was 2.0/1.0, and the ratio of CS-Glu/GP was 4.0/1.5. Chitosan-amino acid (CS-AA) thermosensitive hydrogel had a three-dimensional network structure. The addition of model drug tinidazole (TNZ) had no obvious effect on the structure of hydrogel. The results of infrared spectroscopy showed that there were hydrogen bonds between amino acids and chitosan. In vitro release results showed that CS-Lys/GP and CS-Glu/GP thermosensitive hydrogels had sustained release effects. Thus, the chitosan-amino acid thermosensitive hydrogels hold great potential as a sustained release drug delivery system.

Dexamethasone-Loaded Injectable In-situ Thermal Crosslinking Magnetic Responsive Hydrogel for the Physiochemical Stimulation of Acupoint to Suppress Pain in Sciatica Rats

The physicochemical stimulation of acupoints is a widespread treatment strategy for different diseases, such as sciatica. Its efficacy is mainly based on the temporal and spatial modulation of the physicochemical properties of the acupoints. The existing therapies based on the stimulation of acupoints have certain disadvantages. Therefore, in this study, injectable dexamethasone (DXM)- and magnetic Fe₃O₄ nanoparticles-loaded chitosan/β-glycerophosphate (CS/GP) thermal crosslinking hydrogels were prepared, thereby improving the performance of embedding materials. The sciatica rat models were established to compare the therapeutic effects of hydrogels and catgut. The DXM or Fe₃O₄-loaded CS/GP hydrogels were compared in terms of their gelation kinetics, release kinetics, magnetic responsiveness in-vitro, and biocompatibility as well as their analgesic effects on the chronic constriction injury of the sciatic nerve (CCI) rats in-vivo. The CS/GP/Fe₃O₄/DXM hydrogel showed comparable gelation kinetics and good magnetic responsiveness in-vitro. This hydrogel could relieve sciatica by reducing the expression levels of inflammatory factors in serum, inhibiting the p38MAPK (p38, mitogen-activated protein kinase) phosphorylation, and decreasing the expression level of the P2X4 receptor (P2X4R) in the spinal dorsal horn. In conclusion, the DXM or Fe₃O₄-loaded CS/GP hydrogels can be considered as a treatment option for the physiochemical stimulation therapy of acupoints to improve sciatica.

Chitosan/β-glycerophosphate in situ forming thermo-sensitive hydrogel for improved ocular delivery of moxifloxacin hydrochloride

The aim of the current work is to develop a thermo-sensitive hydrogel system of moxifloxacin hydrochloride (MOX) for improved ocular delivery. Fifteen formulations were prepared at different concentrations of β-glycerophosphate disodium salt (β-GP) 12-20% (w/v) and chitosan (CS) 1.7-1.9% (w/v). The optimized MOX loaded thermo-sensitive hydrogel system (F8), consisting of CS (1.8%, w/v) and β-GP (16%, w/v), showed optimum gelation temperature (35 °C) and gelation time (2 min), thus was selected for further investigations. It showed a significant decrease (p < 0.05) in the zeta potential value compared to CS solution with a favorable pH value (7.1) and confirmed thermoreversible behavior. MOX loaded F8 displayed a porous structure under scanning electron microscopy. Rheological investigation of MOX loaded F8 revealed the presence of a strong hydrogel network with high elasticity along with a small loss factor of 0.08 indicating a great ease of gel formation. The release of MOX from F8 was found to be governed by a combined mechanism of diffusion and relaxation. Biological assessment of two concentrations of MOX loaded F8 (0.25 and 0.5%) was conducted using healthy and infected male albino New Zealand rabbits, where an improved and prolonged antibacterial activity against Staphylococcus aureus compared to plain MOX (0.5%), marketed MOX eye drops (0.5%), was shown. Moreover, histopathological examination of ocular tissues confirmed the antibacterial efficacy of the optimized formulation eight days post topical therapy. Consequently, the developed CS/β-GP thermo-sensitive hydrogel system (F8) reveals a promising potential for enhancing the ocular delivery of MOX for treatment of bacterial infections.

Rapid self-healing and self-adhesive chitosan-based hydrogels by host-guest interaction and dynamic covalent bond as flexible sensor

A sensor used to monitor tissue deformation requires good flexibility, stretchability, self-adhesion, cyto-compatibility, and antibacterial property. Here, we prepared hydrogel sensor based on O-carboxymethyl chitosan (O-CMCS) and poly(vinyl alcohol) (PVA) for monitoring human and organ motions. Based on the host-guest complexing of poly(β-cyclodextrin) with diamantane, a cross-linker containing multiple aldehyde groups was prepared for cross-linking with O-CMCS through Schiff base linkages. Borax was used as the second cross-linker to cross-link PVA through dynamic borate ester bonds. Carbon nanotubes (CNTs) were added into the hydrogels to improve their electrical conductivity and mechanical properties. The obtained hydrogel exhibited rapid self-healing ability with healing efficiency as high as 97%-103% (in 15 s), good adhesion to human skin and wet organ, good antibacterial property, cyto-compatibility, and stretchability. Furthermore, the hydrogel sensor can monitor the respiratory movement of porcine lungs and the beating of rat hearts.

Chitosan Functionalization: Covalent and Non-Covalent Interactions and Their Characterization

Chitosan (CS) is a natural biopolymer that has gained great interest in many research fields due to its promising biocompatibility, biodegradability, and favorable mechanical properties. The versatility of this low-cost polymer allows for a variety of chemical modifications via covalent conjugation and non-covalent interactions, which are designed to further improve the properties of interest. This review aims at presenting the broad range of functionalization strategies reported over the last five years to reflect the state-of-the art of CS derivatization. We start by describing covalent modifications performed on the CS backbone, followed by non-covalent CS modifications involving small molecules, proteins, and metal adjuvants. An overview of CS-based systems involving both covalent and electrostatic modification patterns is then presented. Finally, a special focus will be given on the characterization techniques commonly used to qualify the composition and physical properties of CS derivatives.

Design and optimization of process parameters of polyvinyl alcohol-graft-lactic acid films for transdermal drug delivery

The objective was to apply a simplex lattice design to determine the properties of polyvinyl alcohol-graft-lactic acid (PVA-g-LA) with different values for two independent variables: curing time (X1) and LA ratio (X2). Each independent variable was varied among three levels: -1, 0, and +1. Three coded levels were 120 min, 150 min, and 180 min for X1 and 2.5 g, 5 g, and 7.5 g for X2. Dependent variables of swelling behavior in various swelling media and thermal analysis parameters were monitored. The optimal formulation was selected based on the desirability value. The prediction was accurate, showing a low value of percent error. The morphology of the selected formulation with the highest desirability value showed a compact and dense film. Propranolol hydrochloride used as a model drug, was loaded into PVA-g-LA film. The propranolol hydrochloride content was 4.19 ± 1.05 mg/cm2. The cumulative release and permeation of drug were 61.94 ± 8.03% and 59.96 ± 6.61%, respectively. Thus, response surface methodology can be used as a tool to predict or optimize the process parameters for PVA-g-LA transdermal films in an accurate manner. PVA-g-LA could control the release and permeation of drug from the film layer.

Recent Applications of Dual-Stimuli Responsive Chitosan Hydrogel Nanocomposites as Drug Delivery Tools

Polysaccharides are a versatile class of macromolecules that are involved in many biological interactions critical to life. They can be further modified for added functionality. Once derivatized, these polymers can exhibit new chemical properties that can be further optimized for applications in drug delivery, wound healing, sensor development and others. Chitosan, derived from the N-deacetylation of chitin, is one example of a polysaccharide that has been functionalized and used as a major component of polysaccharide biomaterials. In this brief review, we focus on one aspect of chitosan's utility, namely we discuss recent advances in dual-responsive chitosan hydrogel nanomaterials.

Recent advances of emerging green chitosan-based biomaterials with potential biomedical applications: A review

Chitosan is the most abundant natural biopolymer, after cellulose. It is mainly derived from the fungi, shrimp's shells, and exoskeleton of crustaceans, through the deacetylation of chitin. The ecological sustainability associated with its exercise and the flexibility of chitosan owing to its active functional hydroxyl and amino groups makes it a promising candidate for a wide range of applications through a variety of modifications. The biodegradability and biocompatibility of chitosan and its derivatives along with their various chemical functionalities make them promising carriers for pharmaceutical, nutritional, medicinal, environmental, agriculture, drug delivery, and biotechnology applications. The present work aims to provide a detailed and organized description of modified chitosan and its derivatives-based nanomaterials for biomedical applications. We addressed the biological and physicochemical benefits of nanocomposite materials made up of chitosan and its derivatives in various formulations, including improved physicochemical stability and cells/tissue interaction, controlled drug release, and increased bioavailability and efficacy in clinical practice. Moreover, several modification techniques and their effective utilization are also reviewed and collected in this review.

Graphene-Based Materials Immobilized within Chitosan: Applications as Adsorbents for the Removal of Aquatic Pollutants

Graphene and its derivatives, especially graphene oxide (GO), are attracting considerable interest in the fabrication of new adsorbents that have the potential to remove various pollutants that have escaped into the aquatic environment. Herein, the development of GO/chitosan (GO/CS) composites as adsorbent materials is described and reviewed. This combination is interesting as the addition of graphene to chitosan enhances its mechanical properties, while the chitosan hydrogel serves as an immobilization matrix for graphene. Following a brief description of both graphene and chitosan as independent adsorbent materials, the emerging GO/CS composites are introduced. The additional materials that have been added to the GO/CS composites, including magnetic iron oxides, chelating agents, cyclodextrins, additional adsorbents and polymeric blends, are then described and discussed. The performance of these materials in the removal of heavy metal ions, dyes and other organic molecules are discussed followed by the introduction of strategies employed in the regeneration of the GO/CS adsorbents. It is clear that, while some challenges exist, including cost, regeneration and selectivity in the adsorption process, the GO/CS composites are emerging as promising adsorbent materials.

Review of Applications and Future Prospects of Stimuli-Responsive Hydrogel Based on Thermo-Responsive Biopolymers in Drug Delivery Systems

Some of thermo-responsive polysaccharides, namely, cellulose, xyloglucan, and chitosan, and protein-like gelatin or elastin-like polypeptides can exhibit temperature dependent sol–gel transitions. Due to their biodegradability, biocompatibility, and non-toxicity, such biomaterials are becoming popular for drug delivery and tissue engineering applications. This paper aims to review the properties of sol–gel transition, mechanical strength, drug release (bioavailability of drugs), and cytotoxicity of stimuli-responsive hydrogel made of thermo-responsive biopolymers in drug delivery systems. One of the major applications of such thermos-responsive biopolymers is on textile-based transdermal therapy where the formulation, mechanical, and drug release properties and the cytotoxicity of thermo-responsive hydrogel in drug delivery systems of traditional Chinese medicine have been fully reviewed. Textile-based transdermal therapy, a non-invasive method to treat skin-related disease, can overcome the poor bioavailability of drugs from conventional non-invasive administration. This study also discusses the future prospects of stimuli-responsive hydrogels made of thermo-responsive biopolymers for non-invasive treatment of skin-related disease via textile-based transdermal therapy.

Recent Advances in 3D Printing for Parenteral Applications

3D printing has emerged as an advanced manufacturing technology in the field of pharmaceutical sciences. Despite much focus on enteral applications, there has been a lack of research focused on potential benefits of 3D printing for parenteral applications such as wound dressings, biomedical devices, and regenerative medicines. 3D printing technologies, including fused deposition modeling, vat polymerization, and powder bed printing, allow for rapid prototyping of personalized medications, capable of producing dosage forms with flexible dimensions based on patient anatomy as well as dosage form properties such as porosity. Considerations such as printing properties and material selection play a key role in determining overall printability of the constructs. These parameters also impact drug release kinetics, and mechanical properties of final printed constructs, which play a role in modulating immune response upon insertion in the body. Despite challenges in sterilization of printed constructs, additional post-printing processing procedures, and lack of regulatory guidance, 3D printing will continue to evolve to meet the needs of developing effective, personalized medicines for parenteral applications.

Injectable chitosan hydrogel embedding modified halloysite nanotubes for bone tissue engineering

Low mechanical strength and untargeted osteoinduction of chitosan hydrogel limit its application for bone regeneration. This study aimed to develop an injectable chitosan hydrogel with enhanced mechanical strength and improved osteoinductivity for bone tissue engineering. For this purpose, chitosan-modified halloysite nanotubes (mHNTs) were synthesized first. Then, icariin as a bone inducer was loaded into mHNTs (IC@mHNTs), resulting in a sustained drug release system. Further, nanocomposite chitosan/mHNTs hydrogels were prepared by the sol-gel transition, leading to decreased gelation time and temperature and enhanced mechanical strength of the resulting scaffolds. The mesenchymal stem cells were encapsulated into the hydrogels, and in vitro viability assays showed scaffold biocompatibility. Moreover, embedded mHNTs or IC@mHNTs in the scaffold resulted in enhanced proliferation and bone differentiation of encapsulated cells. It was collectively demonstrated that the injectable in situ forming nanocomposite chitosan hydrogel loaded with IC@mHNTs is a promising candidate for bone regeneration.

In Vivo Cartilage Regeneration with Cell-Seeded Natural Biomaterial Scaffold Implants: 15-Year Study

Articular cartilage can be easily damaged from human's daily activities, leading to inflammation and to osteoarthritis, a situation that can diminish the patients' quality of life. For larger cartilage defects, scaffolds are employed to provide cells the appropriate three-dimensional environment to proliferate and differentiate into healthy cartilage tissue. Natural biomaterials used as scaffolds, attract researchers' interest because of their relative nontoxic nature, their abundance as natural products, their easy combination with other materials, and the relative easiness to establish Marketing Authorization. The last 15 years were chosen to review, document, and elucidate the developments on cell-seeded natural biomaterials for articular cartilage treatment in vivo. The parameters of the experimental designs and their results were all documented and presented. Considerations about the newly formed cartilage and the treatment of cartilage defects were discussed, along with difficulties arising when applying natural materials, research limitations, and tissue engineering approaches for hyaline cartilage regeneration.

Recent Developments in Chitosan-Based Adsorbents for the Removal of Pollutants from Aqueous Environments

The quality of water is continuously under threat as increasing concentrations of pollutants escape into the aquatic environment. However, these issues can be alleviated by adsorbing pollutants onto adsorbents. Chitosan and its composites are attracting considerable interest as environmentally acceptable adsorbents and have the potential to remove many of these contaminants. In this review the development of chitosan-based adsorbents is described and discussed. Following a short introduction to the extraction of chitin from seafood wastes, followed by its conversion to chitosan, the properties of chitosan are described. Then, the emerging chitosan/carbon-based materials, including magnetic chitosan and chitosan combined with graphene oxide, carbon nanotubes, biochar, and activated carbon and also chitosan-silica composites are introduced. The applications of these materials in the removal of various heavy metal ions, including Cr(VI), Pb(II), Cd(II), Cu(II), and different cationic and anionic dyes, phenol and other organic molecules, such as antibiotics, are reviewed, compared and discussed. Adsorption isotherms and adsorption kinetics are then highlighted and followed by details on the mechanisms of adsorption and the role of the chitosan and the carbon or silica supports. Based on the reviewed papers, it is clear, that while some challenges remain, chitosan-based materials are emerging as promising adsorbents.

One-step fabrication of chitosan sponge and its potential for rapid hemostasis in deep trauma

In this paper, a facile and efficient preparation strategy for a porous and hydrophilic chitosan sponge is demonstrated, combining a surfactant and a pore-foaming agent. The resulting chitosan sponge possesses an interconnected pore structure and soft texture, exhibits fast water absorption rate and capacity, and the compressed sponge can achieve full shape recovery 5 s after absorbing water. Moreover, our process removes the residual acid commonly found in chitosan sponges prepared by the acid method. In addition, the results demonstrate the useful characteristics of our chitosan sponge, in terms of its contribution to improved blood coagulation, together with its compression strength and biocompatibility. It also demonstrates effective antibacterial properties in relation to both Escherichia coli and Staphylococcus aureus. Further testing via animal experimentation reveals that rapid hemostasis can be achieved within 50 s using our chitosan sponge.

Implementation and in vitro characterization of calcium-free in situ gelling oral reconstituted suspension for potential overweight treatment

In this work, oral granules that were easily dissolved in aqueous dispersion, were prepared. These oral suspensions were formulated with sodium alginate (AlgNa), chitosan (CHI) and sodium carboxymethylcellulose (CMC Na). The gels were formulated by pouring the suspensions into 150 ml of simulated gastric fluid (SGF) pH 1.2 at 37° C. The in-situ gelling mechanism was based on the ionization states of the three biopolymers as a function of the pH of the medium. Fourier transform infrared analysis of gels confirmed the interactions between alginate and chitosan. According to the scanning electron microscopy analysis, the gels were characterized by a firm and homogeneous structure. The obtained values of the elastic storage modulus, G', varied between 10 1   and 10 7 Pa. The eliminated volume of the unabsorbed liquid by the gels fluctuated between 25% and 55% of the total liquid volume. The quality of the gels was improved when a maximum concentration of alginate ( 4   g / 100   ml ) , a minimum concentration of chitosan ( 0.5   g / 100   ml ) and a maximum amount of carboxymethylcellulose ( 4   g / 100   ml ) were used. The value of their elastic modulus, G' was around 10 5 Pa and the residual unabsorbed volume of the liquid was 25% of the total liquid volume. According to the obtained results, the prepared gels could induce a feeling of fullness by stimulating the gastric distension and they could potentially be applied as anti-obesity medication.

Biodegradable thermoresponsive oligochitosan nanoparticles: Mechanisms of phase transition and drug binding-release

Oligochitosan, a low molecular weight derivative of the cationic biopolymer, chitosan, currently shows a great potential of application as a biodegradable non-toxic stimuli-sensitive drug carrier. This paper aimed to elucidate the thermoresponsive potential of oligochitosan and the temperature-controlled drug binding and release to shed light on oligochitosan potential in stimuli-responsive drug delivery. Mechanisms of thermoresponsive behavior of oligochitosan induced by β-glycerophosphate (GP) were investigated using ITC, DSC, and DLS. Upon heating, the aqueous oligochitosan solution underwent a cooperative transition of the microphase separation type resulting in the formation of stable nano-sized particles. Energetics of the GP-oligochitosan interaction (evaluated by ITC) revealed a positive enthalpy of the GP binding to oligochitosan, which pointed to a notable contribution of dehydration and the related rearrangement of the polysaccharide hydration shell. Energetics of the thermal phase transition of oligochitosan was investigated by DSC upon variation of the solvent dielectric constant and GP concentration. The dependences of the transition parameters on these variables were determined and used for the analysis of the oligochitosan thermoresponsivity mechanism. The binding of ibuprofen to the thermotropic oligochitosan nanogel particles and its release from them were evaluated under near-physiological conditions. Relevantly, the oligochitosan nanoparticles surpassed some reference macromolecular adsorbers by the affinity for the drug and by the delayed release kinetics.

In vitro biological response of human osteoblasts in 3D chitosan sponges with controlled degree of deacetylation and molecular weight

We have studied the effect of chitosan sponges, produced from chitosan batches with distinct degree of deacetylation (DDA) and molecular weight (Mw), on the adhesion, growth and differentiation of primary human osteoblasts with an aim to offer a suitable tool for guided bone regeneration. All the chitosan sponges revealed similar microstructure, irrespective of the DDA (58, 73, 82, 88, and 91 %) and Mw (749, 547, 263, 215, and 170 kDa, respectively). Cell spreading was higher on sponges having a higher DDA. Higher DDA induced a more pronounced increase in alkaline phosphatase activity, osteopontin (OPN), vascular endothelial growth factor-A (VEGF), interleukin-6 (IL-6), and reduction in monocyte chemoattractant protein-1 (MCP-1), sclerostin (SOST) and dickkopf related protein-1 as compared to lower DDA. Lower DDA induced the increased secretion of osteoprotegerin and SOST as compared to higher DDA. The combination of higher DDA and Mw induced an increased secretion of VEGF and IL-6, however reduced the secretion of OPN as compared to chitosan with similar DDA but with lower Mw. In summary, the variations in cellular responses to the different chitosan sponges indicate a potential for individual tailoring of desired responses in guided bone regeneration.

Nanoscale Thermosensitive Hydrogel Scaffolds Promote the Chondrogenic Differentiation of Dental Pulp Stem and Progenitor Cells: A Minimally Invasive Approach for Cartilage Regeneration

Purpose

Several scaffolds and cell sources are being investigated for cartilage regeneration. The aim of the study was to prepare nanocellulose-based thermosensitive injectable hydrogel scaffolds and assess their potential as 3D scaffolds allowing the chondrogenic differentiation of embedded human dental pulp stem and progenitor cells (hDPSCs).

Materials and Methods

The hydrogel-forming solutions were prepared by adding β-glycerophosphate (GP) to chitosan (CS) at different ratios. Nanocellulose (NC) suspension was produced from hemp hurd then added dropwise to the CS/GP mixture. In vitro characterization of the prepared hydrogels involved optimizing gelation and degradation time, mass-swelling ratio, and rheological properties. The hydrogel with optimal characteristics, NC-CS/GP-21, was selected for further investigation including assessment of biocompatibility. The chondrogenesis ability of hDPSCs embedded in NC-CS/GP-21 hydrogel was investigated in vitro and compared to that of bone marrow-derived mesenchymal stem cells (BMSCs), then was confirmed in vivo in 12 adult Sprague Dawley rats.

Results

The selected hydrogel showed stability in culture media, had a gelation time of 2.8 minutes, showed a highly porous microstructure by scanning electron microscope, and was morphologically intact in vivo for 14 days after injection. Histological and immunohistochemical analyses and real-time PCR confirmed the chondrogenesis ability of hDPSCs embedded in NC-CS/GP-21 hydrogel.

Conclusion

Our results suggest that nanocellulose–chitosan thermosensitive hydrogel is a biocompatible, injectable, mechanically stable and slowly degradable scaffold. hDPSCs embedded in NC-CS/GP-21 hydrogel is a promising, minimally invasive, stem cell-based strategy for cartilage regeneration.

In-situ crosslinked hydrogel based on amidated pectin/oxidized chitosan as potential wound dressing for skin repairing

Hydrogel can provide a favorable moisture environment for skin wound healing. In this study, a novel in-situ crosslinked injectable hydrogel was prepared using the water-soluble amidated pectin (AP) and oxidized chitosan (OC) through Schiff-base reaction without any chemical crosslinker. The influence of AP content on the properties of the hydrogel was systemically investigated. It showed that gelation time, pore structure, swelling capability and degradability of the hydrogel can be tuned by varying the content of amine and aldehyde groups from AP and OC. All the porous hydrogels with various AP contents (65%, 70%, and 80%) presented desirable gelation time, swelling property, high hemocompatibility and biocompatibility. Particularly, AP-OC-65 hydrogel presented superior swelling capability and better hemo- and bio-compatibility, owing to more residual amine sites in the hydrogel. Therefore, the injectable AP-OC-65 hydrogel has a greater potential for application to wound dressing or skin substitute.

Rapid hemostatic chitosan/cellulose composite sponge by alkali/urea method for massive haemorrhage

Here, a simple and efficient strategy to produce porous and hydrophilic chitosan/cellulose sponge using surfactant and pore-forming agent is demonstrated. The preparation of composite sponge by LiOH/KOH/urea solvent system effectively solve the problems of uneven distribution of chitosan, poor softness and acid residue caused by soaking in chitosan acid solution. The obtained chitosan/cellulose sponges exhibit high water absorption capacity and rapid shape recoverability, as well as good mechanical properties. Effective inhibitory on Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa are particularly proved. Besides, the result of the dynamic whole blood clotting time indicated that the chitosan/cellulose composite sponge has better coagulation ability than those of traditional gauze and gelatin sponge. Animal experiment further showed that rapid hemostasis within 34 s can be reached with the composite sponge. Better biocompatibility of the composite sponge is proved by the results of hemocompatibility and cytotoxicity, indicating an excellent candidate for rapid hemostasis in massive haemorrhage.

Silk degumming time controls horseradish peroxidase-catalyzed hydrogel properties

Hydrogels provide promising applications in tissue engineering and regenerative medicine, with silk fibroin (SF) offering biocompatibility, biodegradability and tunable mechanical properties. The molecular weight (MW) distribution of SF chains varies from ∼80 to 400 kDa depending on the extraction and purification process utilized to prepare the protein polymer. Here, we report a fundamental study on the effect of different silk degumming (extraction) time (DT) on biomaterial properties of enzymatically crosslinked hydrogels, including secondary structure, mechanical stiffness, in vitro degradation, swelling/contraction, optical transparency and cell behaviour. The results indicate that DT plays a crucial role in determining material properties of the hydrogel; decrease in DT increases β-sheet (crystal) formation and mechanical stiffness while decreasing degradation rate and optical transparency. The findings on the relationships between properties of silk hydrogels and DT should facilitate the more rational design of silk-based hydrogel biomaterials to match properties needed for diverse purpose in biomedical engineering.

Synthesis and Biological Evaluation of Three New Chitosan Schiff Base Derivatives

Recently, chemical modifications of chitosan (CS) have attracted the attention of scientific researchers due to its wide range of applications. In this research, chitin (CH) was extracted from the scales of Cyprinus carpio fish and converted to CS by three chemical steps: (i) demineralization, (ii) deprotonation, and (iii) deacetylation. The degree (measured as a percentage) of deacetylation (DD %) was calculated utilizing the acid-base titration method. The structure of CS was characterized by Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). Three new CS Schiff bases (CSSBs) (CS-P1, CS-P2, and CS-P3) were synthesized via coupling of CS with 2-chloroquinoline-3-carbaldehyde, quinazoline-6-carbaldehyde, and oxazole-4-carbaldehyde, respectively. The newly prepared derivatives were verified, structurally, by nuclear magnetic resonance (¹H and ¹³C NMR) and FT-IR spectroscopy. Antimicrobial activity was evaluated for the prepared compounds against both "Gram-negative" and "Gram-positive" bacteria, namely, Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, and Streptococcus mutans, in addition to two kinds of fungi, Candida albicans and Aspergillus fumigates. Cytotoxicity of the synthesized CSSBs was evaluated via a MTT screening test. The results indicated a critical activity increase of the synthesized compound rather than CS generally tested bacteria and fungi and the absence of cytotoxic activity. These findings suggested that these new CSSBs are novel biomaterial candidates with enhanced antibacterial and nontoxic characteristics for applications in areas of both biology and medicine.

Three-Dimensional Printing Constructs Based on the Chitosan for Tissue Regeneration: State of the Art, Developing Directions and Prospect Trends

Chitosan (CS) has gained particular attention in biomedical applications due to its biocompatibility, antibacterial feature, and biodegradability. Hence, many studies have focused on the manufacturing of CS films, scaffolds, particulate, and inks via different production methods. Nowadays, with the possibility of the precise adjustment of porosity size and shape, fiber size, suitable interconnectivity of pores, and creation of patient-specific constructs, 3D printing has overcome the limitations of many traditional manufacturing methods. Therefore, the fabrication of 3D printed CS scaffolds can lead to promising advances in tissue engineering and regenerative medicine. A review of additive manufacturing types, CS-based printed constructs, their usages as biomaterials, advantages, and drawbacks can open doors to optimize CS-based constructions for biomedical applications. The latest technological issues and upcoming capabilities of 3D printing with CS-based biopolymers for different applications are also discussed. This review article will act as a roadmap aiming to investigate chitosan as a new feedstock concerning various 3D printing approaches which may be employed in biomedical fields. In fact, the combination of 3D printing and CS-based biopolymers is extremely appealing particularly with regard to certain clinical purposes. Complications of 3D printing coupled with the challenges associated with materials should be recognized to help make this method feasible for wider clinical requirements. This strategy is currently gaining substantial attention in terms of several industrial biomedical products. In this review, the key 3D printing approaches along with revealing historical background are initially presented, and ultimately, the applications of different 3D printing techniques for fabricating chitosan constructs will be discussed. The recognition of essential complications and technical problems related to numerous 3D printing techniques and CS-based biopolymer choices according to clinical requirements is crucial. A comprehensive investigation will be required to encounter those challenges and to completely understand the possibilities of 3D printing in the foreseeable future.

In-situ forming chitosan implant-loaded with raloxifene hydrochloride and bioactive glass nanoparticles for treatment of bone injuries: Formulation and biological evaluation in animal model

In-situ forming implants receive great attention for repairing serious bone injuries. The aim of the present study was to prepare novel chitosan in-situ forming implants (CIFI) loaded with bioactive glass nanoparticles and/or raloxifene hydrochloride (RLX). Incorporating raloxifene hydrochloride (RLX) as a selective estrogen receptor modulator was essential to make use of its anti-resorptive properties. The prepared formulae were tested for their in-vitro gelation time, drug release, injectability, rheological properties, erosion rate and morphological properties. Results revealed that the formulation composed of 1% (w/v) chitosan with 2% (w/v) NaHCO₃ and 1% (w/v) bioactive glass nanoparticles (CIFI-BG) possessed the most sustained drug release profile which extended over four months with low burst release effect compared to the same formulation lacking bioactive glass nanoparticles (CIFI). Selected formulations were tested for their ability to enhance bone regeneration in induced puncture in rate tibia. Results declared that these formulations were able to enhance bone regeneration after 12 weeks in comparison to the untreated tibial punctures and that containing bioactive glass could be considered as novel approach for treatment of serious bone injuries which require long term treatment and internal mechanical bone support during healing.