Biodegradable chitosan nanogels crosslinked with genipin

Chitosan-based hydrogels: Influence of crosslinking strategy on rheological properties

The effect of two crosslink strategies on the preparation of chitosan-based covalent hydrogels was investigated employing the widely used thiol-ene reaction. This versatile "click" chemistry can be activated either photochemically or thermochemically. Initially, well-purified chitosan (CS, DA ∼4 %, Mw ∼580 kg mol-1) was separately functionalized with vinyl (CS-ene) or thiol (CS-SH) groups in aqueous media. Subsequently, two strategies were compared where thiol-ene reaction occurs respectively between: (S1) modified chitosans CS-ene and CS-SH, in a polymer - polymer strategy, and (S2) CS-ene and di(ethylene glycol) dithiol (dEG-(SH)2), in a polymer - molecule strategy. Both crosslinking strategies were evaluated through rheological measurements, starting with entangled chitosan solutions. The difference in diffusion of functional groups, whether attached to polymer chains or to free molecules, leads to faster gelation kinetics with S2. Consequently, stronger gels were obtained with S2, where the modulus was connected with the degree of functionalization, while S1 produced weaker gels closer to the percolation point, where crosslinked density was associated with the entanglement number derived from the initial concentration. Nevertheless, networks formed by both strategies were homogenous with minimal dissipative contributions to their rheological properties, indicating that structural defects are negligible.

An Investigation into the Effects of Processing Factors on the Properties and Scaling-Up Potential of Propranolol-Loaded Chitosan Nanogels

Chitosan-triphosphate (TPP) nanogels are widely studied drug delivery carrier systems, typically prepared via a simple mixing process. However, the effects of the processing factors on nanogel production have not been extensively explored, despite the importance of understanding and standardising such factors to allow upscaling and commercial usage. This study aims to systematically evaluate the effects of various fabrication and processing factors on the properties of nanogels using a Design of Experiment approach. Hydrodynamic size, polydispersity index (PDI), zeta potential, and encapsulation efficiency were determined as the dependent factors. The temperature, stirring rate, chitosan grade, crosslinker choice, and the interaction term between temperature and chitosan grade were found to have a significant effect on the particle size, whereas the effect of temperature and the addition rate of crosslinker on the PDI was also noteworthy. Moreover, the addition rate of the crosslinker and the volume of the reaction vessel were found to impact the encapsulation efficiency. The zeta potential of the nanogels was found to be governed by the chitosan grade. The optimal fabrication conditions for the development of medium molecular weight chitosan and TPP nanogels included the following: the addition rate for TPP solution was set at 2 mL/min, while the solution was then stirred at a temperature of 50 °C and a stirring speed of 600 rpm. The volume of the glass vial used was 28 mL, while the stirrer size was 20 mm. The second aim of the study was to evaluate the potential for scaling up the nanogels. Size and PDI were found to increase from 128 nm to 151 nm and from 0.232 to 0.267, respectively, when the volume of the reaction mixture was increased from 4 to 20 mL and other processing factors were kept unchanged. These results indicate that caution is required when scaling up as the nanogel properties may be significantly altered with an increasing production scale.

Recent developments in chitosan based microgels and their hybrids

Chitosan based microgels have gained great attention because of their chemical stability, biocompatibility, easy functionalization and potential uses in numerous fields. Production, properties, characterization and applications of chitosan based microgels have been systematically reviewed in this article. Some of these systems exhibit responsive behavior towards external stimuli like pH, light, temperature, glucose, etc. in terms of swelling/deswelling in an aqueous medium depending upon the functionalities present in the network which makes them a potential candidate for various applications in the fields of biomedicine, agriculture, catalysis, sensing and nanotechnology. Current research development and critical overview in this field accompanying by future possibilities is presented. The discussion is concluded with recommended possible future works for further progress in this field.

Reaction kinetics of chitosan nanogels crosslinked by genipin

Crosslinking of chitosan chains in dilute solution by natural crosslinker genipin leads to biocompatible nanogels. Here we investigated the reaction kinetics between chitosan and genipin in a 200 mM acetate buffer at 37 °C, and the structural and conformational evolutions of the nanogels during the crosslinking reaction by multi detection asymmetric flow field-flow fractionation (AF4). Upon crosslinking by genipin, the z-average hydrodynamic radius Rhz of the chitosan chains increased from 26 nm to 130 nm, while the weight average molar mass Mw increased from 2.0 × 105 g/mol to 1.8 × 107 g/mol. The crosslinking reaction appeared to be first-order and size-dependent. In particular, the intrachain crosslinking reaction was preferentially for nanogels having the larger size, leading to formation of branched chains/nanogels having a wide range of molar masses between 106 and 108 g/mol but a similar radius of gyration Rg ∼ 40 nm. For the largest nanogel fractions with M > 2.0 × 108 g/mol, both Rg and Rh showed a scaling relation with exponent 1/3 and a structure parameter Rg/Rh = 0.74, as expected for the hard sphere particle. The reaction was accompanied by a reduction of charge density and an increase in hydrophobicity of chitosan nanogels, which plays a key role in the formation of uniform size nanogels with chain density ρ(Rh) up to 0.45 g/cm3.

Double network structure via ionic bond and covalent bond of carboxymethyl chitosan and poly(ethylene glycol): Factors affecting hydrogel formation

The factors were studied that affect the formation of DN hydrogel, which was prepared using a water-based, environmental-friendly system. The DN hydrogel was designed and prepared based on a cross-linked, polysaccharide-based, polymer carboxymethyl chitosan (CMCS) via an ionic crosslinking reaction for the first network structure. UV irradiation created a radical crosslinking reaction of poly(ethylene glycol) from a double bond at the chain end for the second network structure. It was found that the optimum hydrogel was produced using 9.5 %v/v of 1000PEGGMA, CMCS 5%w/v, and CaCl₂ 3%w/v. The results showed the highest percentage of the gel fraction was 87.84 % and the hydrogel was stable based on its rheological properties. Factors affecting the hydrogel formation were the concentration and molecular weight of PEGGMA and the concentrations of CMCS and calcium chloride (CaCl₂). The DN hydrogel had bioactivity due to its octacalcium phosphate (OCP) hydroxyapatite crystal form. In addition, the composite DN scaffold with a conductive polymer of chitosan-grafted-polyaniline (CS-g-PANI) had conduction of 2.33 × 10^-5 S/cm when the concentration of CS-g-PANI was 3 mg/ml, confirming the semi-conductive nature of the material. All the results indicated that DN hydrogel could be a candidate to apply in tissue-engineering applications.

Chitosan-Based Self-Healing Hydrogel: From Fabrication to Biomedical Application

Biocompatible self-healing hydrogels are new-generation smart soft materials that hold great promise in biomedical fields. Chitosan-based self-healing hydrogels, mainly prepared via dynamic imine bonds, have attracted broad attention due to their mild preparation conditions, excellent biocompatibility, and self-recovery ability under a physiological environment. In this review, we present a comprehensive overview of the design and fabrication of chitosan-based self-healing hydrogels, and summarize their biomedical applications in tissue regeneration, customized drug delivery, smart biosensors, and three/four dimensional (3D/4D) printing. Finally, we will discuss the challenges and future perspectives for the development of chitosan-based self-healing hydrogels in the biomedical field.

Interfacial biosilica coating of chitosan gel using fusion silicatein to fabricate robust hybrid material for biomolecular applications

An enzyme-encapsulated silica-based hybrid material was developed using a chitosan gel. Fusion silicatein (InaKC-ChBD-Sil), silicatein fused with a soluble tag and chitin-binding domain, was employed as an interfacial catalyst to form silica on a chitosan gel matrix under physiological conditions, and horseradish peroxidase was immobilised on the hybrid material. Silica formation on the gel was verified via fluorescence microscopy using a designed fusion protein called TBP-mCherry, a fluorescent protein fused with a silica-binding peptide. We report a chitosan gel-silica hybrid material capable of encapsulating enzymes for biomedical and environmental applications.

Fabrication of Chitosan-Based Network Polysaccharide Nanogels

In this study, we developed a method to fabricate chitosan-based network polysaccharides via the condensation between amino groups in water-soluble chitosan (WSCS) and a carboxylate-terminated maltooligosaccharide crosslinker. We previously reported on the fabrication of network-polysaccharide-based macroscopic hydrogels via the chemical crosslinking of water-soluble chitin (WSCh) with the crosslinker. Because the molecular weight of the WSCS was much smaller than that of the WSCh, in the present investigation, the chemical crosslinking of the WSCS with the crosslinker was observed at the nanoscale upon the condensation between amino and carboxylate groups in the presence of a condensing agent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide, affording nano-sized chitosan-based network polysaccharides. The occurrence of the crosslinking via the formation of amido linkages was supported by the IR analysis and ¹H NMR measurements after the dissolution via acid hydrolysis in DCl/D₂O. The products formed nanogels, whose sizes depended on the amino/carboxylate feed ratio. The nanoscale morphology and size of the products were evaluated via scanning electron microscopy, dynamic light scattering analyses, and transition electron microscopy. In the present study, we successfully developed the method to fabricate nanogel materials based on network polysaccharide structures, which can practically be applied as new polysaccharide-based 3D bionanomaterials.

Simultaneous loading of (-)-epigallocatechin gallate and ferulic acid in chitosan-based nanoparticles as effective antioxidant and potential skin-whitening agents

Chitosan (CS) based nanoparticles simultaneously loaded with (-)-epigallocatechin gallate (EGCG) and ferulic acid (FA) were fabricated via ionic gelation method modified by sodium tripolyphosphate and genipin (G-CS-EGCG-FA NPs). The particle size, morphology, entrapment efficiency, rheological properties, antioxidant and tyrosinase inhibitory activity of NPs were investigated. The G-CS-EGCG-FA NPs exhibited irregular ellipsoidal shape with average diameter of 412.3 nm and high DPPH and ABTS·⁺ scavenging ability. The entrapment efficiency of EGCG and FA in NPs was 46.0 ± 1.3 % and 46.8 ± 1.6 %, respectively. CS-based NPs show no toxic effects on NIH 3 T3 cells and B16-F10 melanoma cells with concentration <200 μg/mL and 25 μg/mL, respectively and the cell viability ranged from 100 % to 118 %. Meanwhile, the oxidative repaired capacity of G-CS-EGCG-FA NPs (200 μg/mL) in H₂O₂-induced cells was over 100 %, higher than that of the same dose of free EGCG or FA. Moreover, the tyrosinase inhibition activity of G-CS-EGCG-FA NPs (25 μg/mL) (84.6 %) was more potent than that of free EGCG (55.3 %), free FA (47.1 %) and kojic acid, indicating the good skin repairing and whitening ability of G-CS-EGCG-FA NPs. Given these results, this research provides new insights for designing novel particles loaded with dual bioactive agents that possess synergistic benefits.

Cross-linked enzyme aggregates immobilization: preparation, characterization, and applications

Enzymes are commonly used as biocatalysts for various biological and chemical processes. However, some major drawbacks of free enzymes (e.g. poor reusability and instability) significantly restrict their industrial practices. How to overcome these weaknesses remain considerable challenges. Enzyme immobilization is one of the most effective ways to improve the reusability and stability of enzymes. Cross-linked enzyme aggregates (CLEAs) has been known as a novel and versatile carrier-free immobilization method. CLEAs is attractive due to its simplicity and robustness, without purification. It generally shows: high catalytic specificity and selectivity, good operational and storage stabilities, and good reusability. Moreover, co-immobilization of different kinds of enzymes can be acquired. These CLEAs advantages provide opportunities for further industrial applications. Herein, the preparation parameters of CLEAs were first summarized. Next, characterization of structural and catalytic properties, stability and reusability are also proposed. Finally, some important applications of this technique in: environmental protection, industrial chemistry, food industry, and pharmaceutical synthesis and delivery are introduced. Potential challenges and future research directions, such as improving cross-linking efficiency and internal mass transfer efficiency, are also presented. This implies that CLEAs provide an efficient and feasible technique to improve the properties of enzymes for use in the industry.

Alendronate crosslinked chitosan/polycaprolactone scaffold for bone defects repairing

Here, we evaluated osteogenic differentiation in vitro and new bone formation in vivo using an alendronate-loaded chitosan/polycaprolactone scaffold (CS/PCL) in rats with a critical-sized calvarial defect. Through the action of genipin, which has a crosslinking function, alendronate (AL) was anchored throughout the CS/PCL composite scaffold (CS/PCL@AL) to form an AL sustained release system. We demonstrated that CS/PCL@AL scaffolds significantly enhanced the osteogenic differentiation of ectomesenchymal stem cells (EMSCs) in vitro. Additionally, we explored the possible molecular mechanism of CS/PCL@AL scaffolds in the osteogenic differentiation of EMSCs. This composite scaffold exerted two positive effects on EMSC osteogenic differentiation: 1) the CS/PCL@AL scaffold enhanced EMSC osteogenic differentiation by upregulating bone morphogenetic protein 2, interleukin 10 and laminin expression; and 2) the CS/PCL@AL scaffold promoted the osteogenic differentiation of EMSCs by activating the yes-associated protein (YAP) signaling pathway. YAP and its downstream target transglutaminase are crucial mediators in the osteogenic differentiation of EMSCs. Finally, micro-computed tomography analyses and histology results suggested that the CS/PCL@AL scaffold exhibited a superior capacity to accelerate new and mature bone formation in skull bone defects in Sprague-Dawley rats. This simple and low-cost technology may represent a promising strategy to construct an efficient delivery system to repair bone defects.

Application of chitosan nanoparticles in skin wound healing

The rising prevalence of impaired wound healing and the consequential healthcare burdens have gained increased attention over recent years. This has prompted research into the development of novel wound dressings with augmented wound healing functions. Nanoparticle (NP)-based delivery systems have become attractive candidates in constructing such wound dressings due to their various favourable attributes. The non-toxicity, biocompatibility and bioactivity of chitosan (CS)-based NPs make them ideal candidates for wound applications. This review focusses on the application of CS-based NP systems for use in wound treatment. An overview of the wound healing process was presented, followed by discussion on the properties and suitability of CS and its NPs in wound healing. The wound healing mechanisms exerted by CS-based NPs were then critically analysed and discussed in sections, namely haemostasis, infection prevention, inflammatory response, oxidative stress, angiogenesis, collagen deposition, and wound closure time. The results of the studies were thoroughly reviewed, and contradicting findings were identified and discussed. Based on the literature, the gap in research and future prospects in this research area were identified and highlighted. Current evidence shows that CS-based NPs possess superior wound healing effects either used on their own, or as drug delivery vehicles to encapsulate wound healing agents. It is concluded that great opportunities and potentials exist surrounding the use of CSNPs in wound healing.

Multifunctional Polymeric Nanogels for Biomedical Applications

Currently, research in nanoparticles as a drug delivery system has broadened to include their use as a delivery system for bioactive substances and a diagnostic or theranostic system. Nanogels, nanoparticles containing a high amount of water, have gained attention due to their advantages of colloidal stability, core-shell structure, and adjustable structural components. These advantages provide the potential to design and fabricate multifunctional nanosystems for various biomedical applications. Modified or functionalized polymers and some metals are components that markedly enhance the features of the nanogels, such as tunable amphiphilicity, biocompatibility, stimuli-responsiveness, or sensing moieties, leading to specificity, stability, and tracking abilities. Here, we review the diverse designs of core-shell structure nanogels along with studies on the fabrication and demonstration of the responsiveness of nanogels to different stimuli, temperature, pH, reductive environment, or radiation. Furthermore, additional biomedical applications are presented to illustrate the versatility of the nanogels.

Chemical synthesis of polysaccharide-protein and polysaccharide-peptide conjugates: A review

Polysaccharides are abundant natural polymers, which in nature are at times covalently modified with peptides and proteins. Polysaccharide-protein or polysaccharide-peptide conjugates, natural or otherwise, may have increased solubility, improved emulsion properties, prolonged circulation time, reduced immunogenicity, and enhanced selectivity for targeting specific tissues compared to native peptides and proteins. In this paper, we will review recent advances in synthetic methods for producing polysaccharide-protein conjugates and discuss their advantages with a focus on drug targeting.

Encapsulation of Natural Bioactive Compounds by Electrospinning-Applications in Food Storage and Safety

Packaging is used to protect foods from environmental influences and microbial contamination to maintain the quality and safety of commercial food products, to avoid their spoilage and to extend their shelf life. In this respect, bioactive packaging is developing to additionally provides antibacterial and antioxidant activity with the same goals i.e., extending the shelf life while ensuring safety of the food products. New solutions are designed using natural antimicrobial and antioxidant agents such as essential oils, some polysaccharides, natural inorganic nanoparticles (nanoclays, oxides, metals as silver) incorporated/encapsulated into appropriate carriers in order to be used in food packaging. Electrospinning/electrospraying are receiving attention as encapsulation methods due to their cost-effectiveness, versatility and scalability. The electrospun nanofibers and electro-sprayed nanoparticles can preserve the functionality and protect the encapsulated bioactive compounds (BC). In this review are summarized recent results regarding applications of nanostructured suitable materials containing essential oils for food safety.

Nanogels: A novel approach in antimicrobial delivery systems and antimicrobial coatings

The implementation of nanotechnology to develop efficient antimicrobial systems has a significant impact on the prospects of the biomedical field. Nanogels are soft polymeric particles with an internally cross-linked structure, which behave as hydrogels and can be reversibly hydrated/dehydrated (swollen/shrunken) by the dispersing solvent and external stimuli. Their excellent properties, such as biocompatibility, colloidal stability, high water content, desirable mechanical properties, tunable chemical functionalities, and interior gel-like network for the incorporation of biomolecules, make them fascinating in the field of biological/biomedical applications. In this review, various approaches will be discussed and compared to the newly developed nanogel technology in terms of efficiency and applicability for determining their potential role in combating infections in the biomedical area including implant-associated infections.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

The hollow core-shell ferric oxide entrapped chitosan microcapsules as phosphate binders for phosphorus removal in vitro

Patients in hyperphosphatemia are orally prescribed with phosphate binders to excrete the non-metabolic phosphorus. Aiming for the bio-compatibility and binding efficacy, the Fe-based phosphate binders of low toxicity have been explored and improved. Herein, the hollow core-shell microcapsules as Fe@CH (nano ferric oxide entrapped in the polymerized chitosan) were constructed via emulsion interface polymerization, to enhance the phosphate binding from -NH₂ group and iron complex, and limit iron leakage significantly. Via the double emulsion polymerization based on the primary Pickering emulsion stabilized by oleic acid-modified ferric oxide, Fe@CH performed as the rough polymerized-chitosan microcapsules entrapping well-distributed ferric oxide for the phosphate adsorption in vitro. At pH 3 and pH 5, Fe@CH bound phosphorus efficiently, with the capacity of 55 mg/g and 65 mg/g respectively, along with the excellent shell isolation from iron leakage and remarkable safety. Prospectively, the Fe@CH micro-sorbent is the proper candidate as the phosphate binder for hyperphosphatemia.

Genipin-cross-linked hydrogels based on biomaterials for drug delivery: a review

Genipin is a naturally occurring nontoxic cross-linker, which has been widely used for drug delivery due to its excellent biocompatibility, admirable biodegradability and stable cross-linked attributes. These advantages led to its extensive application in the fabrication of hydrogels for drug delivery. This review describes the physicochemical characteristics and pharmacological activities of genipin and attempts to elucidate the detailed mechanisms of the cross-linking reaction between genipin and biomaterials. The current article entails a general review of the different biomaterials cross-linked by genipin: chitosan and its derivatives, collagen, gelatin, etc. The genipin-cross-linked hydrogels for various pharmaceutical applications, including ocular drug delivery, buccal drug delivery, oral drug delivery, anti-inflammatory drug delivery, and antibiotic and antifungal drug delivery, are reported. Finally, the future research directions and challenges of genipin-cross-linked hydrogels for pharmaceutical applications are also discussed in this review.

Fabrication and characterization of biodegradable KH560 crosslinked chitin hydrogels with high toughness and good biocompatibility

Chitin hydrogels have multiple advantages of nontoxicity, biocompatibility, biodegradability, and three-dimensional hydrophilic polymer network structure similar to the macromolecular biological tissue. However, the mechanical strength of chitin hydrogels is relatively weak. Construction of chitin hydrogels with high mechanical strength and good biocompatibility is essential for the successful applications in biomedical field. Herein, we developed double crosslinked chitin hydrogels by dissolving chitin in KOH/urea aqueous solution with freezing-thawing process, then using KH560 as cross-linking agent and coagulating in ethanol solution at low temperature. The obtained chitin/ KH560 (CK) hydrogels displayed good transparency and toughness with compressed nanofibrous network and porous structure woven with chitin nanofibers. Moreover, the optimal CK hydrogels exhibited excellent mechanical properties (σ_b = 1.92 ± 0.21 Mpa; ε_b = 71 ± 5 %), high swelling ratio, excellent blood compatibility, biocompatibility and biodegradability, which fulfill the requirements of biomedical materials and showing potential applications in biomedicine.

Chitosan hydrogel/silk fibroin/Mg(OH)2 nanobiocomposite as a novel scaffold with antimicrobial activity and improved mechanical properties

Herein, a novel nanobiocomposite scaffold based on modifying synthesized cross-linked terephthaloyl thiourea-chitosan hydrogel (CTT-CS hydrogel) substrate using the extracted silk fibroin (SF) biopolymer and prepared Mg(OH)2 nanoparticles was designed and synthesized. The biological capacity of this nanobiocomposite scaffold was evaluated by cell viability method, red blood cells hemolytic and anti-biofilm assays. According to the obtained results from 3 and 7 days, the cell viability of CTT-CS/SF/Mg(OH)2 nanobiocomposite scaffold was accompanied by a considerable increment from 62.5 to 89.6% respectively. Furthermore, its low hemolytic effect (4.5%), and as well, the high anti-biofilm activity and prevention of the P. aeruginosa biofilm formation confirmed its promising hemocompatibility and antibacterial activity. Apart from the cell viability, blood biocompatibility, and antibacterial activity of CTT-CS/SF/Mg(OH)2 nanobiocomposite scaffold, its structural features were characterized using spectral and analytical techniques (FT-IR, EDX, FE-SEM and TG). As well as, given the mechanical tests, it was indicated that the addition of SF and Mg(OH)2 nanoparticles to the CTT-CS hydrogel could improve its compressive strength from 65.42 to 649.56 kPa.

Immobilization of laccase via cross-linked enzyme aggregates prepared using genipin as a natural cross-linker

Genipin is a nontoxic natural cross-linker that was successfully used to prepare cross-linked enzyme aggregates (CLEAs) of Trametes versicolor laccase. The recovered activity of CLEAs was influenced by the co-solvent type, genipin concentration, cross-linking time, preparation pH, and bovine serum albumin (BSA; amino group feeder) concentration. The characteristics of CLEAs prepared using genipin under optimal conditions (genipin-BSA-CLEAs) were compared with those of typical CLEAs prepared using glutaraldehyde or dextran polyaldehyde. Genipin-BSA-CLEAs were nano-sized (average diameter, approximately 700 nm), had a ball-like shape, showed a narrow size distribution, and exhibited the highest substrate affinity among the prepared CLEAs. The thermal stability of genipin-BSA-CLEAs was 6.8-fold higher than that of free laccase, and their pH stability was also much higher than that of free laccase in the tested range. Additionally, genipin-BSA-CLEAs retained 85% of their initial activity after 10 cycles of reuse. Particularly, genipin-BSA-CLEAs showed higher thermal and pH stability than CLEAs that were cross-linked using glutaraldehyde. Therefore, genipin represents an alternative to toxic compounds such as glutaraldehyde during cross-linking to prepare CLEAs.

Intra-articular injection of anti-inflammatory peptide-loaded glycol chitosan/fucoidan nanogels to inhibit inflammation and attenuate osteoarthritis progression

Glycol chitosan/fucoidan nanogels loaded with anti-inflammatory peptide KAFAK (GC/Fu@KAFAK NGs) were fabricated based on the electrostatic interaction and genipin cross-linking methods. The prepared NGs had an average size of 286.3 ± 5.0 nm and positive surface charge of 14.0 ± 0.2 mV. The anti-inflammatory and chondro-protective effects of GC/Fu@KAFAK NGs were evaluated on interlecukin-1β (IL-1β)-stimulated rat chondrocytes. We found that GC/Fu@KAFAK NGs not only inhibited the expression of inflammatory factors interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), but also enhanced the expression of chondrogenic markers type II collagen, aggrecan, and Sox9. More importantly, in rat osteoarthritis (OA) model, the intra-articular (IA) injection of GC/Fu@KAFAK NGs reduced glycosaminoglycan loss and diminished inflammatory cytokine release. In addition, GC/Fu@KAFAK NGs showed good biocompatibility both in vitro and in vivo. In conclusion, IA inject-able GC/Fu@KAFAK NGs might have great potential in OA treatment.

Encapsulation of essential oils using cinnamic acid grafted chitosan nanogel: Preparation, characterization and antifungal activity

Chemical modifications in the chitosan structure may result in obtaining a new material with improved chemical properties, such as an ability to encapsulate lipophilic compounds. This study aimed to synthesize cinnamic acid grafted chitosan nanogel to encapsulate the essential oils of Syzygium aromaticum and Cinnamomum ssp., in order to develop a material to be applied in the control of dermatophytosis caused by the fungus Microsporum canis. The cinnamic acid graft in chitosan was verified by the Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Solid State Nuclear Magnetic Resonance of the ¹³C Nucleus (¹³C SSNMR) and Thermal analysis coupled to mass spectrometry (TG-MS) techniques. The nanogel obtained showed affinity for the essential oils of S. aromaticum and Cinnamomum, with encapsulation efficiencies equal to 74% and 89%, respectively. When in an aqueous medium the nanogel with the encapsulated essential oils was able to form stable nanoparticles with average sizes of 176.0 ± 54.3 nm and 263.0 ± 81.4 nm. The cinnamic acid grafted chitosan nanogel showed antifungal activity in vitro against M. canis, inhibiting up to 53.96% of its mycelial growth. Complete inhibition of mycelial growth was achieved by the nanogel with encapsulated essential oils. The results found in this work demonstrated the development of a material with potential application in the control of dermatophytosis caused by the fungus M. canis.

A review on techniques utilized for design of controlled release food active packaging

Active packaging (AP) is a new class of innovative food packaging, containing bioactive compounds, is able to maintain the quality of food and extend its shelf life by releasing active agent during storage. The main challenge in designing the AP system is slowing the release rate of active compounds for its prolonged activity. Controlled-release active packaging (CRP) is an innovative technology that provides control in the release of active compounds during storage. Various approaches have been proposed to design CRP. The purpose of this review was to gather and present the strategies utilized for release controlling of active compounds from food AP systems. The chemical modification of polymers, the preparation of multilayer films and the use of cross-linking agents are some methods tried in the last decades. Other approaches use molecular complexes and irradiation treatments. Micro- or nano-encapsulation of active compounds and using nano-structured materials in the AP film matrix are the newest techniques used for the preparation of CRP systems. The action mechanism for each technique was described and an effort was made to highlight representative published papers about each release controlling approach. This review will benefit future prospects of exploring other innovative release controlling methods in food CRP.

Development of chitosan nanocapsules containing essential oil of Matricaria chamomilla L. for the treatment of cutaneous leishmaniasis

Matricaria chamomilla L. has been used for centuries in many applications, including antiparasitic activity. Leishmaniasis is a parasitic disease, with limited treatments, due to high cost and toxicity. Thus, there is a need to develop new treatments, and in this context, natural products are targets of these researches. We report the development of chitosan nanocapsules containing essential oil of M. chamomilla (CEO) from oil-in-water emulsions using chitosan modified with tetradecyl chains as biocompatible shell material. The nanocapsules of CEO (NCEO) were analyzed by optical microscopy and dynamic light scattering, which revealed spherical shape and an average size of 800 nm. Successful encapsulation of CEO was further confirmed by fluorescence microscopy observations taking advantage of the autofluorescence properties of CEO. The encapsulation efficiency was around 90%. The entrapment of CEO reduced its cytotoxicity towards normal cells. On the other hand, the CEO was active against promastigotes and intracellular amastigotes, exhibiting IC₅₀ of 3.33 μg/mL and 14.56 μg/mL, respectively, while NCEO showed IC₅₀ for promastigotes of 7.18 μg/mL and for intracellular amastigotes of 14.29 μg/mL. These results demonstrate that encapsulation of CEO in nanocapsules using an alkylated chitosan biosurfactant as a "green" stabilizer is a promising therapeutic strategy to treat leishmaniasis.

Chitosan based hydrogels and their use in medicine

Chitosan is a natural biopolymer, polysaccharide, a product of chitin deacetylation. Chitosan is a non-toxic, biocompatible and biodegradable polymer with high biological activity and stability in the environment. In addition, chitosan is obtained from natural renewable resources and is an inexpensive substance. Due to all these properties, chitosan is widely used in practical medicine, for example, in the form of hydrogel dosage forms in combination with natural and synthetic polymers. This review is focused on polymer hydrogel materials based on chitosan. Special attention is paid to the preparation and use of wound dressings for the treatment of wounds of various etiologies. The use of hydrogel wound dressings based on this polysaccharide allows to create a protective shell on the surface of various wounds, to prolong delivery of antibacterial agents, peptides and other active substances, which significantly increases the effectiveness of therapy. Bactericidal and sorption properties of chitosan-based hydrogels established in experimental and clinical studies are discussed.

Biopolymers for hydrogels in cosmetics: review

Hydrogels are cross-linked networks of macromolecular compounds characterized by high water absorption capacity. Such materials find a wide range of biomedical applications. Several polymeric hydrogels can also be used in cosmetics. Herein, the structure, properties and selected applications of hydrogels in cosmetics are discussed in general. Detailed examples from scientific literature are also shown. In this review paper, most common biopolymers used in cosmetics are presented in detail together with issues related to skin treatment and hair conditioning. Hydrogels based on collagen, chitosan, hyaluronic acid, and other polysaccharides have been characterized. New trends in the preparation of hydrogels based on biopolymer blends as well as bigels have been shown. Moreover, biopolymer hydrogels employment in encapsulation has been mentioned.

Chitosan nanoparticles loaded with clove essential oil: Characterization, antioxidant and antibacterial activities

One of the recent trends in the food industry is application of natural antioxidant/antimicrobial agents. In this study, essential oil of clove buds was extracted and encapsulated in chitosan nanoparticles using a two-step technique of emulsion-ionic gelation. A good retention rate (55.8-73.4 %) of clove essential oil (CEO) loaded in chitosan nanoparticles was confirmed. Also, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses revealed the success of CEO encapsulation. Scanning electron microscopy (SEM) images illustrated regular distribution and spherical shape of nanoparticles with a size range of 223-444 nm. The antioxidant activity of CEO-loaded chitosan nanoparticles was higher than free CEO. Similarly, CEO-loaded chitosan nanoparticles had a high antibacterial activity against L. monocytogenes and S. aureus (inhibition halo diameter of 4.80-4.78 cm). This technique could improve the efficiency of CEO in food products and a delivery system for novel applications such as active packaging.

Genipin as An Emergent Tool in the Design of Biocatalysts: Mechanism of Reaction and Applications

Genipin is a reagent isolated from the Gardenia jasminoides fruit extract, and whose low toxicity and good crosslinking properties have converted it into a reactive whose popularity is increasing by the day. These properties have made it widely used in many medical applications, mainly in the production of chitosan materials (crosslinked by this reactive), biological scaffolds for tissue engineering, and nanoparticles of chitosan and nanogels of proteins for controlled drug delivery, the genipin crosslinking being a key point to strengthen the stability of these materials. This review is focused on the mechanism of reaction of this reagent and its use in the design of biocatalysts, where genipin plays a double role, as a support activating agent and as inter- or intramolecular crosslinker. Its low toxicity makes this compound an ideal alterative to glutaraldehyde in these processes. Moreover, in some cases the features of the biocatalysts prepared using genipin surpassed those of the biocatalysts prepared using other standard crosslinkers, even disregarding toxicity. In this way, genipin is a very promising reagent in the design of biocatalysts.