Dual-network hydrogels based on chemically and physically crosslinked chitosan/chondroitin sulfate

Poly[poly(ethylene glycol) methacrylate]-modified starch-based solid and gel polymer electrolytes for high performance Li-ion batteries

The idea of replacing liquid electrolytes with polymer electrolytes has been successful and the development of these electrolytes has provided acceptable results. With the start of using natural polymers in the polymer industry, as well as starch, these materials can be one of the most important candidates for the polymer matrix in electrolytes. In this study, starch has been investigated as a polymer electrolyte, poly[poly(ethylene glycol) methacrylate] (PEGMA) is grafted to the starch by radical polymerization, and synthesized copolymers are used as solid polymer electrolytes (SPEs). Furthermore, by adding N,N'-methylenebisacrylamide (MBA) as a cross-linking agent, gel polymer electrolytes (GPEs) are produced after swelling in the liquid electrolyte. After characterization, the synthesized polymer electrolytes are investigated in terms of electrochemical properties. The best ionic conductivity of 3.8 × 10-5 S cm-1 is obtained for SPEs whereas it is obtained 4.3 × 10-3 S cm-1 for GPEs at room temperature. The ion transfer number in the range of 0.47-0.91 confirms the compatibility between the electrolytes and electrode. Also, the prepared polymer electrolytes present excellent electrochemical properties, including, a wide electrochemical stability window above 4.7 V, good specific capacities in the range of 170-200 mAh g-1 with a storage capacity of more than 92 %, and Coulombic efficiency of about 98 % after 100 cycles at 0.2 C.

Synergistic Interaction between Polysaccharide-Based Extracellular Matrix and Mineralized Osteoblast-Derived EVs Promotes Bone Regeneration via miRNA-mRNA Regulatory Axis

Extracellular vesicles (EVs) derived from bone progenitor cells are advantageous as cell-free and non-immunogenic cargo delivery vehicles. In this study, EVs are isolated from MC3T3-E1 cells before (GM-EVs) and after mineralization for 7 and 14 days (DM-EVs). It was observed that DM-EVs accelerate the process of differentiation in recipient cells more prominently. The small RNA sequencing of EVs revealed that miR-204-5p, miR-221-3p, and miR-148a-3p are among the highly upregulated miRNAs that have an inhibitory effect on the function of mRNAs, Sox11, Timp3, and Ccna2 in host cells, which is probably responsible for enhancing the activity of osteoblastic genes. To enhance the bioavailability of EVs, they are encapsulated in a chitosan-collagen composite hydrogel that serves as a bioresorbable extracellular matrix (ECM). The EVs-integrated scaffold (DM-EVs + Scaffold) enhances bone regeneration in critical-sized calvarial bone defects in rats within 8 weeks of implantation by providing the ECM cues. The shelf life of DM-EVs + Scaffold indicates that the bioactivity of EVs and their cargo in the polymer matrix remains intact for up to 30 days. Integrating mineralized cell-derived EVs into an ECM represents a bioresorbable matrix with a cell-free method for promoting new bone formation through the miRNA-mRNA regulatory axis.

Nitric oxide-releasing photocrosslinked chitosan cryogels

The highly porous morphology of chitosan cryogels, with submicrometric-sized pore cell walls, provides a large surface area which leads to fast water absorption and elevated swelling degrees. These characteristics are crucial for the applications of nitric oxide (NO) releasing biomaterials, in which the release of NO is triggered by the hydration of the material. In the present study, we report the development of chitosan cryogels (CS) with a porous structure of interconnected cells, with wall thicknesses in the range of 340-881 nm, capable of releasing NO triggered by the rapid hydration process. This property was obtained using an innovative strategy based on the functionalization of CS with two previously synthesized S-nitrosothiols: S-nitrosothioglycolic acid (TGA(SNO)) and S-nitrosomercaptosuccinic acid (MSA(SNO)). For this purpose, CS was previously methacrylated with glycidyl methacrylate and subsequently submitted to photocrosslinking and freeze-drying processes. The photocrosslinked hydrogels thus obtained were then functionalized with TGA(SNO) and MSA(SNO) in reactions mediated by carbodiimide. After functionalization, the hydrogels were frozen and freeze-dried to obtain porous S-nitrosated chitosan cryogels with high swelling capacities. Through chemiluminescence measurements, we demonstrated that CS-TGA(SNO) and CS-MSA(SNO) cryogels spontaneously release NO upon water absorption at rates of 3.34 × 10-2 nmol mg-1 min-1 and 1.27 × 10-1 nmol mg-1 min-1, respectively, opening new perspectives for the use of CS as a platform for localized NO delivery in biomedical applications.

Rapid fabricated in-situ polymerized lignin hydrogel sensor with highly adjustable mechanical properties

Conductive hydrogels have been widely used as sensors owing to their tissue-like properties. However, the synthesis of conductive hydrogels with highly adjustable mechanical properties and multiple functions remains difficult to achieve yet highly needed. In this study, lignin hydrogel characterized by frost resistance, UV resistance, high conductivity, and highly adjustable mechanical properties without forming by-products was prepared through a rapid in-situ polymerization of acrylic acid/zinc chloride (AA/ZnCl2) aqueous solution containing lignin extract induced by the reversible quinone-catechol redox of the ZnCl2-lignin system at room temperature. Results revealed that the PAA/ZnCl2/lignin hydrogel exhibited mechanical properties with tensile stress (ranging from 0.08 to 3.28 MPa), adhesion to multiple surfaces (up to 62.05 J m-2), excellent frost resistance (-70-20 °C), UV resistance, and conductivity (0.967 S m-1), which further endow the hydrogel as potential strain and temperature sensor with wide monitor range (0-300 %), fatigue resistance, and quick response (70 ms for 150 % strain). This study proposed and developed a green, simple, economical, and efficient processing method for a hydrogel sensor in flexible wearable devices and man-machine interaction fields.

Construction of a dual-component hydrogel matrix for 3D biomimetic skin based on photo-crosslinked chondroitin sulfate/collagen

The main challenge in the field of 3D biomimetic skin is to search for a suitable hydrogel matrix with good biocompatibility, appropriate mechanical property and inner porosity that can support the adhesion and proliferation of skin cells. In this study, photocurable chondroitin sulfate methacrylate (CSMA) and collagen methacrylate (CoLMA) synthesized from chondroitin sulfate (CS) and type I collagen I (CoL) in the dermal matrix were used to construct a photo-crosslinked dual-component CSMA-CoLMA hydrogel matrix. Due to the toughening effect of the dual-component, the CSMA-CoLMA hydrogel improved the intrinsic brittleness of the single-component CSMA hydrogel, presented good mechanical tunability. The average storage and elasticity modulus could reach 3.3 KPa and 30.3 KPa, respectively, which were close to those of natural skin. The CSMA-CoLMA hydrogel with a ratio of 8/6 showed suitable porous structure and good biocompatibility, supporting the adhesion and proliferation of skin cells. Furthermore, the expression of characteristic marker proteins was detected in the epidermal and dermal bi-layered models constructed with the hydrogel containing keratinocytes and fibroblasts. These results suggest that the dual-component CSMA-CoLMA hydrogel has promising potential as a matrix to construct 3D biomimetic skin.

Aptamer-modified chitosan-capped mesoporous silica nanoparticles for co-delivery of cytarabine and daunorubicin in leukemia

In this study, surface modified mesoporous silica nanoparticles (MSNs) were prepared for the targeted delivery of the anticancer agents, daunorubicin (DNR) and cytarabine (CTR), against K562 leukemia cancer cell lines. The MSNs were surface-modified with pH-sensitive chitosan (CS) to prevent the burst release of anticancer agents at the physiological pH of 7.4 and to enable a higher drug release at lower pH and higher concentration of glutathione. Finally, the MSNs were surface modified with KK1B10 aptamer (Apt) to enhance their uptake by K562 cells through ligand-receptor interactions. The MSNs were characterized using different methods and both in vitro and in vivo experiments were utilized to demonstrate their suitability as targeted anticancer agents. The resultant MSNs exhibited an average particle size of 295 nm, a surface area of 39.06 m2/g, and a cumulative pore volume of 0.09 cm3/g. Surface modification of MSNs with chitosan (CS) resulted in a more regulated and acceptable continuous release rate of DNR. The drug release rate was significantly higher at pH 5 media enriched with glutathione, compared to pH 7.4. Furthermore, MSNs coated with CS and conjugated with aptamer (MSN-DNR + CTR@CS-Apt) exhibited a lower IC50 value of 2.34 µg/ml, compared to MSNs without aptamer conjugation, which displayed an IC50 value of 12.27 µg/ml. The results of the cell cycle analysis indicated that the administration of MSN-DNR + CTR@CS-Apt led to a significant increase in the population of apoptotic cells in the sub-G1 phase. Additionally, the treatment arrested the remaining cells in various other phases of the cell cycle. Furthermore, the interactions between Apt-receptors were found to enhance the uptake of MSNs by cancer cells. The results of in vivo studies demonstrated that the administration of MSN-DNR + CTR@CS-Apt led to a significant reduction in the expression levels of CD71 and CD235a markers, as compared to MSN-DNR + CTR@CS (p < 0.001). In conclusion, the surface modified MSNs prepared in this study showed lower IC50 against cancer cell lines and higher anticancer activity in animal models.

Advances in preparation and application of antibacterial hydrogels

Bacterial infections, especially those caused by drug-resistant bacteria, have seriously threatened human life and health. There is urgent to develop new antibacterial agents to reduce the problem of antibiotics. Biomedical materials with good antimicrobial properties have been widely used in antibacterial applications. Among them, hydrogels have become the focus of research in the field of biomedical materials due to their unique three-dimensional network structure, high hydrophilicity, and good biocompatibility. In this review, the latest research progresses about hydrogels in recent years were summarized, mainly including the preparation methods of hydrogels and their antibacterial applications. According to their different antibacterial mechanisms, several representative antibacterial hydrogels were introduced, such as antibiotics loaded hydrogels, antibiotic-free hydrogels including metal-based hydrogels, antibacterial peptide and antibacterial polymers, stimuli-responsive smart hydrogels, and light-mediated hydrogels. In addition, we also discussed the applications and challenges of antibacterial hydrogels in biomedicine, which are expected to provide new directions and ideas for the application of hydrogels in clinical antibacterial therapy.

Composite hydrogel based on alginate-g-poly(acrylamide)/carbon nanotubes for solid phase extraction of metals from corn cereal samples

Composite hydrogels containing nanofillers are extensively applied in the sorption of different compounds from aqueous solutions; however, this ability is poorly exploited in the extraction and pre-concentration of analytes from complex matrices. As a contribution to this field, this study reports the synthesis of a composite hydrogel of alginate-g-poly(acrylamide) matrix filled with functionalized multi-walled carbon nanotubes (ALG-g-PAAM/MWCNT-f). This composite served as a solid-phase extractor (SPE) for the separation of Pb²⁺ and Cd²⁺ ions from a digested corn cereal sample before their analytical determination. After composite characterization, a series of experiments using low dosages of ALG-g-PAAM/MWCNT-f demonstrated that the composite has a higher sorption capacity for Pb²⁺ (5.1 mg/g) and Cd²⁺ (3.9 mg/g) under favorable experimental conditions. As demonstrated, the presence of the MWCNT-f benefited the SPE performance of the composite. The sorption of both cations followed the pseudo-first order kinetics, while the experimental data were well-fitted by the Freundlich isotherm. Also, ALG-g-PAAM/MWCNT-f showed selectivity for Pb²⁺, and it is reusable up to 10 times without losing sorption performance. After sorption and extraction, both metals were completely recovered, facilitating their quantification by the MIP OES technique. In short, ALG-g-PAAM/MWCNT-f was an effective SPE for the separation and extraction of Pb²⁺ and Cd²⁺, which can be beneficial for food control and safety.

Introducing photo-crosslinked bio-nanocomposites based on polyvinylidene fluoride/poly(glycerol azelaic acid)-g-glycidyl methacrylate for bone tissue engineering

As a glycerol-based polyester, poly(glycerol azelaic acid) (PGAz) has shown great potential for biomedical applications, such as tissue engineering. However, it tends to show low mechanical strength and a relatively fast biodegradation rate, limiting its capability of mimicking and supporting a broad range of hard tissues such as bone. Moreover, the typical thermal curing process of poly(glycerol-co-diacids) is one of their drawbacks. To overcome these limitations, glycidyl methacrylate (GMA) moieties were first grafted on the backbone of PGAz herein to achieve a UV-curable PGAz-g-GMA (PGAG) resin. Then polyvinylidene fluoride (PVDF), nano-hydroxyapatite, and Cloisite Na⁺ nanoclay were used to fabricate photo-crosslinked PGAG/PVDF nanocomposites with efficient properties to mimic various hard tissues. Our results demonstrated that all nanocomposites possessed a semi-crystalline structure with noticeable PVDF β-phase fraction. The scaffolds yielded Young's modulus, ultimate tensile strength, and elongation at break of 15-24 MPa, 13-15 MPa, and 50-65%, respectively that could meet the requirements for supporting cancellous bone tissue. The presence of nanofillers improved the hydrophilicity and slightly accelerated the biodegradation rate of the scaffolds. Additionally, it was illustrated that the scaffolds had no noticeable in vitro cytotoxicity, and mouse fibroblast L929 cells and osteoblast MG-63 cells attached to and proliferated on their surface desirably. Our findings indicate that the PGAG/PVDF blend and its nanocomposites could be high-potential candidates for a range of hard tissues, specifically cancellous bones.

Multicomponent biodegradable hydrogels based on natural biopolymers as environmentally coating membrane for slow-release fertilizers: Effect of crosslinker type

This work aims to explore the suitable crosslinker type for synthesizing multicomponent biodegradable hydrogels of cassava starch (CSt) grafted with acrylic acid (AA) semi-interpenetrated by natural rubber (NR)/polyvinyl alcohol (PVA) blend (CSt-g-PAA/NR/PVA, CSB semi-IPN hydrogel) as coating membranes for slow-release urea fertilizers. Three crosslinker types (ethylene glycol dimethacrylate (EGDMA), glutaraldehyde (GA) and N,N'- methylene-bis-acrylamide (MBA)) were employed to investigate their influences on the properties of CSB semi-IPN hydrogels. The results revealed that the different crosslinkers clearly exhibited different water-retention capacity, biodegradation, slow release and plant growth performance of the CSB semi-IPN hydrogels. The CSB-G2 hydrogel (crosslinked with GA at 2 wt%) remained higher water-retention at 30 days (20.2 %), greater rate of degradation (1.37 %/day) and better biosafety (OD600 = 2.26) compared to CSB-M2 and CSB-E2 hydrogels. After urea pellets were coated by CSB hydrogels and wax layers (UCSBw formulation), the urea release rates from the UCSBw-M2, UCSBw-E2 and UCSBw-G2 formulations in 30 days were 67.7 %, 68.7 % and 78.3 %, respectively, corresponding well with swelling ratio and pore size. Besides, the UCSBw-G2 formulation yielded the greater plant growth performance (height, leaf length and product weight) than other two formulations and commercial fertilizer. In conclusion, GA is the suitable crosslinker for synthesizing the CSB-g-PAA/NR/PVA hydrogels with high water-retention, excellent biodegradation, less negative impact on environments, acceptable slow-release rate, good biosafety and reasonable price for slow-release fertilizers.

Effects of polycationic drug carriers on the electromechanical and swelling properties of cartilage

Cationic nanocarriers offer a promising solution to challenges in delivering drugs to negatively charged connective tissues, such as to articular cartilage for the treatment of osteoarthritis (OA). However, little is known about the effects that cationic macromolecules may have on the mechanical properties of cartilage at high interstitial concentrations. We utilized arginine-rich cationic peptide carriers (CPCs) with varying net charge (from +8 to +20) to investigate the biophysical mechanisms of nanocarrier-induced alterations to cartilage biomechanical properties. We observed that CPCs increased the compressive modulus of healthy bovine cartilage explants by up to 70% and decreased the stiffness of glycosaminoglycan-depleted tissues (modeling OA) by 69%; in both cases, the magnitude of the change in stiffness correlated with the uptake of CPC charge variants. Next, we directly measured CPC-induced osmotic deswelling in cartilage tissue due to shielding of charge repulsions between anionic extracellular matrix constituents, with magnitudes of reductions between 36 and 64 kPa. We then demonstrated that electrostatic interactions were required for CPC-induced stiffening to occur, evidenced by no observed increase in tissue stiffness when measured in hypertonic bathing salinity. We applied a non-ideal Donnan osmotic model (under triphasic theory) to separate bulk modulus measurements into Donnan and non-Donnan components, which further demonstrated the conflicting charge-shielding and matrix-stiffening effects of CPCs. These results show that cationic drug carriers can alter tissue mechanical properties via multiple mechanisms, including the expected charge shielding as well as a novel stiffening phenomenon mediated by physical linkages. We introduce a model for how the magnitudes of these mechanical changes depend on tunable physical properties of the drug carrier, including net charge, size, and spatial charge distribution. We envision that the results and theory presented herein will inform the design of future cationic drug-delivery systems intended to treat diseases in a wide range of connective tissues.

Chitosan-G-Glycidyl Methacrylate/Au Nanocomposites Promote Accelerated Skin Wound Healing

Herein, we report the synthesis of Au nanoparticles (AuNPs) in chitosan (CTS) solution by chemically reducing HAuCl₄. CTS was further functionalized with glycidyl methacrylate (chitosan-g-glycidyl methacrylate/AuNP, CTS-g-GMA/AuNP) to improve the mechanical properties for cellular regeneration requirements of CTS-g-GMA/AuNP. Our nanocomposites promote excellent cellular viability and have a positive effect on cytokine regulation in the inflammatory and anti-inflammatory response of skin cells. After 40 days of nanocomposite exposure to a skin wound, we showed that our films have a greater skin wound healing capacity than a commercial film (TheraForm^®), and the presence of the collagen allows better cosmetic ave aspects in skin regeneration in comparison with a nanocomposite with an absence of this protein. Electrical percolation phenomena in such nanocomposites were used as guiding tools for the best nanocomposite performance. Our results suggest that chitosan-based Au nanocomposites show great potential for skin wound repair.

Progress in Antibacterial Hydrogel Dressing

Antibacterial hydrogel has excellent antibacterial property and good biocompatibility, water absorption and water retention, swelling, high oxygen permeability, etc.; therefore, it widely applied in biomedicine, intelligent textiles, cosmetics, and other fields, especially for medical dressing. As a wound dressing, the antibacterial hydrogel has the characteristics of absorbing wound liquid, controlling drug release, being non-toxic, being without side effects, and not causing secondary injury to the wound. Its preparation method is simple, and can crosslink via covalent or non-covalent bond, such as γ-radiation croFsslinking, free radical polymerization, graft copolymerization, etc. The raw materials are easy to obtain; usually these include chondroitin sulfate, sodium alginate, polyvinyl alcohol, etc., with different raw materials being used for different antibacterial modes. According to the hydrogel matrix and antibacterial mode, the preparation method, performance, antibacterial mechanism, and classification of antibacterial hydrogels are summarized in this paper, and the future development direction of the antibacterial hydrogel as wound dressing is proposed.

UV-Cured Chitosan and Gelatin Hydrogels for the Removal of As(V) and Pb(II) from Water

In this study, new photocurable biobased hydrogels deriving from chitosan and gelatin are designed and tested as sorbents for As(V) and Pb(II) removal from water. Those renewable materials were modified by a simple methacrylation reaction in order to make them light processable. The success of the reaction was evaluated by both 1H-NMR and FTIR spectroscopy. The reactivity of those formulations was subsequently investigated by a real-time photorheology test. The obtained hydrogels showed high swelling capability reaching up to 1200% in the case of methacrylated gelatin (GelMA). Subsequently, the Z-potential of the methacrylated chitosan (MCH) and GelMA was measured to correlate their electrostatic surface characteristics with their adsorption properties for As(V) and Pb(II). The pH of the solutions proved to have a huge influence on the As(V) and Pb(II) adsorption capacity of the obtained hydrogels. Furthermore, the effect of As(V) and Pb(II) initial concentration and contact time on the adsorption capability of MCH and GelMA were investigated and discussed. The MCH and GelMA hydrogels demonstrated to be promising sorbents for the removal of heavy metals from polluted waters.

Physical and Bioactive Properties of Glycosaminoglycan Hydrogels Modulated by Polymer Design Parameters and Polymer Ratio

Glycosaminoglycans (GAGs), such as hyaluronic acid (HA) and chondroitin sulfate (CS), have seen widespread adoption as components of tissue engineering scaffolds because of their potent bioactive properties and ease of chemical modification. However, modification of the biopolymers will impair biological recognition of the GAG and reduce the bioactive properties of the material. In this work, we studied how the degree of thiolation of HA and CS, along with other key hydrogel design parameters, affected the physical and bioactive properties of the bulk hydrogel. Although properties, such as the HA molecular weight, did not have a major effect, increasing the degree of thiolation of both HA and CS decreased their biorecognition in experimental analogues for cell/matrix remodeling and binding. Furthermore, combining HA and CS into dual polymer network hydrogels also modulated the physical and bioactive properties, as seen with differences in gel stiffness, degradation rate, and encapsulated cell viability.

Development of novel biopolymer-based nanoparticles loaded cream for potential treatment of topical fungal infections

OBJECTIVE

Biodegradable polymers are extensively used due to their efficient safety profiles. The aim of the current study was to fabricate, evaluate, and characterize biodegradable, biocompatible fluconazole (FLZ) loaded chitosan (CHS) chondroitin sulfate (CS) nanoparticles (NPs) for topical delivery. Polymers utilized in the formulation not only served as a carrier system but also aided in fighting with complex etiology of the disease due to their innate antifungal activities.

METHODS

NPs were prepared by the complex coacervation method, then were optimized for various parameters and subsequently loaded into a cream.

RESULTS

Scanning electron microscopic (SEM) analysis showed spherical morphology of the NPs. Prepared NPs showed an average particle size in the range of 350-450 nm and an encapsulation efficiency (EE) of 86%. The polydispersity index (PDI) was found to be 0.148 that showed a uniform distribution of NPs. Fourier transform infrared (FTIR) spectroscopy confirmed the absence of any electrostatic interaction between ingredients. In vitro drug release analyses exhibited a sustained release of the drug and higher antifungal activity than free FLZ. Ex vivo permeability and drug distribution in different skin layers ensured a site-specific delivery of the FLZ-NPs. As compared with free FLZ and other control groups, the prepared NPs also exhibited significantly higher antifungal activity against Candida albicans (p < .01).

CONCLUSION

It was concluded from the results that the FLZ-NPs laden cream could be a potential candidate for topical and site-specific delivery of the drug cargo for the potential treatment of fungal infections.

Superabsorbent Hydrogels Based to Polyacrylamide/Cashew Tree Gum for the Controlled Release of Water and Plant Nutrients

Agricultural production is influenced by the water content in the soil and availability of fertilizers. Thus, superabsorbent hydrogels, based on polyacrylamide, natural cashew tree gum (CG) and potassium hydrogen phosphate (PHP), as fertilizer and water releaser were developed. The structure, morphology, thermal stability and chemical composition of samples of polyacrylamide and cashew tree gum hydrogels with the presence of fertilizer (HCGP) and without fertilizer (HCG) were investigated, using X-ray diffractometry (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA/DTG) and Energy Dispersive Spectroscopy (EDS). Swelling/reswelling tests, textural analysis, effect of pH, release of nutrients and kinetics were determined; the ecotoxicity of the hydrogels was investigated by the Artemia salina test. The results showed that PHP incorporation in the hydrogel favored the crosslinking of chains. This increased the thermal stability in HCGP but decreased the hardness and adhesion properties. The HCGP demonstrated good swelling capacity (~15,000 times) and an excellent potential for reuse after fifty-five consecutive cycles. The swelling was favored in an alkaline pH due to the ionization of hydrophilic groups. The sustained release of phosphorus in HCGP was described by the Korsmeyer-Peppas model, and Fickian diffusion is the main fertilizer release mechanism. Finally, the hydrogels do not demonstrate toxicity, and HCGP has potential for application in agriculture.

Manufacturing micro/nano chitosan/chondroitin sulfate curcumin-loaded hydrogel in ionic liquid: A new biomaterial effective against cancer cells

Chitosan/chondroitin sulfate (CHT/CS) curcumin-charged hydrogels were prepared through polyelectrolytic complexation (PEC) following two methodologies (PEC-CUR and PEC-T-CUR) and were applied on apoptosis of HeLa, HT29 and PC3 cancer cells. PEC-T-CUR (ionic liquid (IL) mixed using ultraturrax homogenizer) results show to be far better than for PEC-CUR (IL mixed using magnetic stirring), with IC₅₀ being improved 5.13 times to HeLa cancer cells (from 1675.2 to 326.7 μg mL^-1). PECs produced by this methodology presented favorable characteristics, such as particle size, hydrophobicity, pH swelling. Beyond this, the IL was quantitatively recovered in both cases. CUR entrapment levels were hugely loaded into PEC at around 100%. Swelling, dissolution/degradation, and pH_pzc assays showed that PECs may positively act in several environments, releasing the CUR, the CHT and CS as well. Characterization through FTIR, SEM, TEM, TGA, DSC, and WAXS confirmed CUR presence in both types of PECs, and cytotoxic studies showed the significant anticancer effects of CUR-containing PECs.

Tissue Adhesives: From Research to Clinical Translation

Sutures, staples, clips and skin closure strips are used as the gold standard to close wounds after an injury. In spite of being the present standard of care, the utilization of these conventional methods is precarious amid complicated and sensitive surgeries such as vascular anastomosis, ocular surgeries, nerve repair, or due to the high-risk components included. Tissue adhesives function as an interface to connect the surfaces of wound edges and prevent them from separation. They are fluid or semi-fluid mixtures that can be easily used to seal any wound of any morphology - uniform or irregular. As such, they provide alternatives to new and novel platforms for wound closure methods. In this review, we offer a background on the improvement of distinctive tissue adhesives focusing on the chemistry of some of these products that have been a commercial success from the clinical application perspective. This review is aimed to provide a guide toward innovation of tissue bioadhesive materials and their associated biomedical applications.

Hyaluronic acid and chondroitin sulfate (meth)acrylate-based hydrogels for tissue engineering: Synthesis, characteristics and pre-clinical evaluation

Hydrogels based on photocrosslinkable Hyaluronic Acid Methacrylate (HAMA) and Chondroitin Sulfate Methacrylate (CSMA) are presently under investigation for tissue engineering applications. HAMA and CSMA gels offer tunable characteristics such as tailorable mechanical properties, swelling characteristics, and enzymatic degradability. This review gives an overview of the scientific literature published regarding the pre-clinical development of covalently crosslinked hydrogels that (partially) are based on HAMA and/or CSMA. Throughout the review, recommendations for the next steps in clinical translation of hydrogels based on HAMA or CSMA are made and potential pitfalls are defined. Specifically, a myriad of different synthetic routes to obtain polymerizable hyaluronic acid and chondroitin sulfate derivatives are described. The effects of important parameters such as degree of (meth)acrylation and molecular weight of the synthesized polymers on the formed hydrogels are discussed and useful analytical techniques for their characterization are summarized. Furthermore, the characteristics of the formed hydrogels including their enzymatic degradability are discussed. Finally, a summary of several recent applications of these hydrogels in applied fields such as cartilage and cardiac regeneration and advanced tissue modelling is presented.

Chondroitin sulfate hydrogels based on electrostatic interactions with enhanced adhesive properties: exploring the bulk and interfacial contributions

Adhesive polysaccharide gels have highlighted their potential in biomedicine, tissue engineering, and wearable/implantable devices due to their tissue adhesive nature and excellent biocompatibility. However, the weak adhesive strength caused by the unclear relationship between the structure and the adhesive properties seriously hinders their further practical application. Here, a facile one-step synthesis method for adhesive and self-healing hydrogels with chondroitin sulfate (CS) and poly (methyl chloride quarternized N,N-dimethylamino ethylacrylate) (PDMAEA-Q) by ultraviolet light irradiation has been presented. We investigate the mechanism of the adhesion enhancement including improving the mechanical strength of gels (cohesion) and gel/substrate interfacial interactions (interfacial adhesion) by tailoring the compliance and cohesive energy density of the gel. The resultant soft and viscoelastic hydrogels displayed favorable adhesion ability on various substrates, and the adhesive strength to the iron substrate and porcine skin can reach 49.4 kPa and 15.4 kPa, respectively. Additionally, the gels also exhibited rapid self-healing properties and good cytocompatibility. We believe that the adhesive PDMAEA-Q/CS gel would be an ideal candidate for hydrogel glues for human-machine interfaces and biological tissues, and this design idea can open a new path for the preparation of adhesive polysaccharide hydrogels.

Allylated chitosan-poly(N-isopropylacrylamide) hydrogel based on a functionalized double network for controlled drug release

Smart hydrogels with dual network were presented since a new allylated chitosan was conceived. As a double network hydrogel, its first network consisted of poly(N-isopropylacrylamide) worked as the gel matrix, and its second network with Schiff base bond enabled itself function as a molecular switch through the formation and break of the bond. When only the intestinal fluid was used, the second network could provide efficient protection for the loaded drug, and the drug release mechanism conformed to the non-Fickian type diffusion. While pre-treated with simulated gastric fluid, the switch would be opened and the mechanism was the Fickian type, which increased the cumulative percentage of drug release by about 25% and the release time by about 300 min. Besides, the hydrogel was characterized by ¹H NMR, FT-IR and SEM. The effects of allylated chitosan, pH and crosslinker on the swelling ratio and morphology of hydrogel were also studied.

Influence of chitosan oligosaccharide on the gelling and wound healing properties of injectable hydrogels based on carboxymethyl chitosan/alginate polyelectrolyte complexes

In situ injectable hydrogels for wound healing based on carboxymethyl chitosan (CMCS) and alginate were developed in this work. The liquid mixture of CMCS and alginate solutions formed a gel by polyelectrolyte complexation after addition of d-glucono-δ-lactone (GDL), which slowly hydrolyzed and donated protons. When chitosan oligosaccharide (COS) was added into the mixture, a two-stage gelling process occurred. The primary gelling process was similar to that of the hydrogel without COS, while the secondary gelling process appeared about 20 min later, and much stronger hydrogels with storage modulus G' about 1 MPa, 10⁴ times higher, were obtained. COS also significantly influenced the microstructure of hydrogels as well as their biological activities. The hydrogels with 0.5% of COS significantly promoted proliferation of human umbilical cord mesenchymal stem cells (HUMSCs). These injectable hydrogels, especially when COS was added, remarkably accelerated the wound healing process in a mouse skin defect model. Microscopic wound analysis showed an increase of the thickness and integrity of epidermal tissue, increased formation of collagen fibers, and enhanced expression of vascular endothelial growth factor as compared to the control group.

Polyelectrolyte Complex Nanoparticles from Chitosan and Acylated Rapeseed Cruciferin Protein for Curcumin Delivery

Curcumin is a polyphenol that exhibits several biological activities, but its low aqueous solubility results in low bioavailability. To improve curcumin bioavailability, this study has focused on developing a polyelectrolyte complexation method to form layer-by-layer assembled nanoparticles, for curcumin delivery, with positively charged chitosan (CS) and negatively charged acylated cruciferin (ACRU), a rapeseed globulin. Nanoparticles (NPs) were prepared from ACRU and CS (2:1) at pH 5.7. Three samples with weight of 5%, 10%, and 15% of curcumin, respectively, in ACRU/CS carrier were prepared. To verify the stability of the NPs, encapsulation efficiency and size of the 5% Cur-ACRU/CS NPs were determined at intervals of 5 days in a one month period. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, and differential scanning calorimetry confirmed the electrostatic interaction and hydrogen bond formation between the carrier and core. The result showed that hollow ACRU/CS nanocapsules (ACRU/CS NPs) and curcumin-loaded ACRU/CS nanoparticles (Cur-ACRU/CS NPs) were homogenized spherical with average sizes of 200-450 nm and zeta potential of +15 mV. Encapsulation and loading efficiencies were 72% and 5.4%, respectively. In vitro release study using simulated gastro (SGF) and intestinal fluids (SIF) showed controlled release of curcumin in 6 h of exposure. Additionally, the Cur-ACRU/CS NPs are nontoxic to cultured Caco-2 cells, and the permeability assay indicated that Cur-ACRU/CS NPs had improved permeability efficiency of free curcumin through the Caco-2 cell monolayer. The findings suggest that ACRU/CS NPs can be used for encapsulation and delivery of curcumin in functional foods.

Advances in the Fabrication of Antimicrobial Hydrogels for Biomedical Applications

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

Dual crosslinked iminoboronate-chitosan hydrogels with strong antifungal activity against Candida planktonic yeasts and biofilms

Chitosan based hydrogels are a class of cross-linked materials intensely studied for their biomedical, industrial and environmental application, but their biomedical use is limited because of the toxicity of different organic crosslinkers. To overcome this disadvantage, a new strategy to produce supramolecular chitosan hydrogels using low molecular weight compounds able to form covalent linkages and H-bonds to give a dual crosslinking is proposed. For this purpose we used 2-formylphenylboronic acid, which brings the advantage of imine stabilization via iminoboronate formation and potential antifungal activity due to the presence of boric acid residue. FTIR and NMR spectroscopy indicated that the gelling process took place by chemo-physical crosslinking forming a dual iminoboronate-chitosan network. Further, X-ray diffraction demonstrated a three-dimensional nanostructuring of the iminoboronate network with consequences on the micrometer-scale morphology and on the improvement of mechanical properties, as demonstrated by SEM and rheological investigation. The hydrogels proved strong antifungal activity against Candida planktonic yeasts and biofilms, promising to be a friendly treatment of the recurrent vulvovaginitis infections.

Physico-chemical characterization and cytotoxicity evaluation of curcumin loaded in chitosan/chondroitin sulfate nanoparticles

In this study, chitosan (CTS)/chondroitin sulfate (CS) nanoparticles, both pure and curcumin-loaded, were synthesized by ionic gelation. This method is simple and efficient for obtaining nanoparticles with a low polydispersity index (0.151±0.03 to 0.563±0.07) and hydrodynamic diameter in the range of 175.7±2.5 to 710.2±8.9nm, for this study. Samples have a relatively high zeta potential value, a fact that indicates that the colloidal system has good physical and chemical stabilities. The efficiency of the curcumin encapsulation in nanoparticles, which ranged from 62.4±0.61% to 68.3±0.88%, depends on the pH of the chitosan solution. The release of curcumin from the nanoparticles was enabled by a diffusion mechanism, with fast release in a phosphate buffer solution at pH6.8. The assaying of cell viability by the MTT test showed that the presence of both free curcumin and curcumin in the nanoencapsulated form leads to a statistically significant reduction in the viability of A549 cells, by comparison with the control group. The most significant reductions in cell viability of 41.1% and 60.4% (p<0.0001) were observed after 72h, by using 40μmol∙L(-1) free curcumin and curcumin encapsulated in CTS/CS nanoparticles with the chitosan solution at pH6.0, respectively.