Preparation and biocompatibility evaluation of pectin and chitosan cryogels for biomedical application

Preparation and assessment of agar/TEMPO-oxidized bacterial cellulose cryogels for hemostatic applications

In this work, we have demonstrated agar and oxidized bacterial cellulose cryogels as a potential hemostatic dressing material. TEMPO-oxidized bacterial cellulose (OBC) was incorporated into the agar matrix, improving its mechanical and hemostatic properties. The oxidation of bacterial cellulose (BC) was evidenced by chemical characterization studies, confirming the presence of carboxyl groups. The in vitro blood clotting test conducted on agar/OBC composite cryogels demonstrated complete blood clotting within 90 seconds, indicating their excellent hemostatic efficacy. The cryogels exhibited superabsorbent properties with a swelling degree of 4200%, enabling them to absorb large amounts of blood. Moreover, the compressive strength of the composite cryogels was appreciably improved compared to pure agar, resulting in a more stable physical structure. The platelet adhesion test proved the significant ability of the composite cryogels to adhere to and aggregate platelets. Hemocompatibility and cytocompatibility tests have verified the safety of these cryogels for hemostatic applications. Finally, the material exhibited remarkable in vivo hemostatic performance, achieving clotting times of 64 seconds and 35 seconds when tested in the rat tail amputation model and the liver puncture model, respectively. The experiment results were compared with those of commercial hemostat, Axiostat, and Surgispon, affirming the potential of agar/OBC composite cryogel as a hemostatic dressing material.

Gelatin-Chitosan Hydrogel Biological, Antimicrobial and Mechanical Properties for Dental Applications

Chitosan, a natural polysaccharide sourced from crustaceans and insects, is often used with hydrogels in wound care. Evaluating its cytotoxicity and antimicrobial properties is crucial for its potential use in dentistry.

OBJECTIVE

To investigate the mechanical properties of gelatin hydrogels based on decaethylated chitosan and antimicrobial activity against Streptococcus mutans and their biological effects with stem cells from apical papilla (SCAPs).

MATERIAL AND METHODS

Gelatin-chitosan hydrogels were synthesized at concentrations of 0%, 0.2% and 0.5%. Enzymatic and hydrolytic degradation, along with swelling capacity, was assessed. Fourier transform infrared spectroscopy (FTIR) analysis was employed to characterize the hydrogels. The interaction between hydrogels and SCAPs was examined through initial adhesion and cell proliferation at 24 and 48 h, using the Thiazolyl Blue Tetrazolium Bromide (MTT assay). The antimicrobial effect was evaluated using agar diffusion and a microdilution test against S. mutans. Uniaxial tensile strength (UTS) was also measured to assess the mechanical properties of the hydrogels.

RESULTS

The hydrogels underwent hydrolytic and enzymatic degradation at 30, 220, 300 min and 15, 25, 30 min, respectively. Significantly, (p < 0.01) swelling capacity occurred at 20, 40, 30 min, respectively. Gelatin-chitosan hydrogels' functional groups were confirmed using vibrational pattern analysis. SCAPs proliferation corresponded to 24 h = 73 ± 2%, 82 ± 2%, 61 ± 6% and 48 h = 83 ± 11%, 86 ± 2%, 44 ± 2%, respectively. The bacterial survival of hydrogel interaction was found to be 96 ± 1%, 17 ± 1.5% (p < 0.01) and 1 ± 0.5% (p < 0.01), respectively. UTS showed enhanced (p < 0.05) mechanical properties with chitosan presence.

CONCLUSION

Gelatin-chitosan hydrogels displayed favorable degradation, swelling capacity, mild dose-dependent cytotoxicity, significant proliferation with stem cells from apical papilla (SCAPs), substantial antimicrobial effects against S. mutans and enhanced mechanical properties. These findings highlight their potential applications as postoperative care dressings.

Pectin Hydrogels: Gel-Forming Behaviors, Mechanisms, and Food Applications

Pectin hydrogels have garnered significant attention in the food industry due to their remarkable versatility and promising properties. As a naturally occurring polysaccharide, pectin forms three-dimensional (3D) hydrophilic polymer networks, endowing these hydrogels with softness, flexibility, and biocompatibility. Their exceptional attributes surpass those of other biopolymer gels, exhibiting rapid gelation, higher melting points, and efficient carrier capabilities for flavoring and fat barriers. This review provides an overview of the current state of pectin gelling mechanisms and the classification of hydrogels, as well as their crosslinking types, as investigated through diverse research endeavors worldwide. The preparation of pectin hydrogels is categorized into specific gel types, including hydrogels, cryogels, aerogels, xerogels, and oleogels. Each preparation process is thoroughly discussed, shedding light on how it impacts the properties of pectin gels. Furthermore, the review delves into the various crosslinking methods used to form hydrogels, with a focus on physical, chemical, and interpenetrating polymer network (IPN) approaches. Understanding these crosslinking mechanisms is crucial to harnessing the full potential of pectin hydrogels for food-related applications. The review aims to provide valuable insights into the diverse applications of pectin hydrogels in the food industry, motivating further exploration to cater to consumer demands and advance food technology. By exploiting the unique properties of pectin hydrogels, food formulations can be enhanced with encapsulated bioactive substances, improved stability, and controlled release. Additionally, the exploration of different crosslinking methods expands the horizons of potential applications.

Role of Chitosan Hydrogels in Clinical Dentistry

Biopolymers are organic polymers that can be treated into intricate designs with porous characteristics that mimic essential biologic components. Due to their superior biosafety, biodegradability, biocompatibility, etc., they have been utilized immensely in biomedical engineering, regeneration, and drug delivery. To obtain the greatest number of results, a literature search was undertaken in scientific search engines utilizing keywords. Chitosan is used in a variety of medical sectors, with the goal of emphasizing its applications and benefits in the clinical dental industry. Chitosan can be dissolved in liquid form and combined with other substances to create a variety of products, including fibers, hydrogels, membranes, microspheres, resins, sponges, pastes, tablets, and micro granules. Chitosan has been studied in a variety of dental applications. Chitosan is used in the prevention of caries and wear, in pulpotomy to accelerate osteogenesis in guided tissue regeneration due to its hemostatic property, and primarily to benefit from its antimicrobial activity by adding it to materials, such as glass ionomer cement, calcium hydroxide, and adhesive systems. With its antibacterial activity and biocompatibility, chitosan is leading the pack as a promising ingredient in the production of dental materials. The current review provides an update on the background, fundamentals, and wide range of uses of chitosan and its gels in dental science.

Preparation and Characterization of Hydrogel Films and Nanoparticles Based on Low-Esterified Pectin for Anticancer Applications

Prospective adjuvant anticancer therapy development includes the establishing of drug delivery systems based on biocompatible and biodegradable carriers. We have designed films and nanoparticles (NPs) based on low-esterified pectin hydrogel using the ionic gelation method. We investigated morphology, nanomechanical properties, biocompatibility and anticancer activity. Hydrogel films are characterized by tunable viscoelastic properties and surface nanoarchitectonics through pectin concentration and esterification degree (DE), expressed in variable pore frequency and diameter. An in vitro study showed a significant reduction in metabolic activity and the proliferation of the U87MG human glioblastoma cell line, probably affected via the adhesion mechanism. Glioma cells formed neurosphere-like conglomerates with a small number of neurites when cultured on fully de-esterified pectin films and they did not produce neurites on the films prepared on 50% esterified pectin. Pectin NPs were examined in terms of size distribution and nanomechanical properties. The NPs' shapes were proved spherical with a mean diameter varying in the range of 90-115 nm, and a negative zeta potential from -8.30 to -7.86 mV, which indicated their stability. The NPs did not demonstrate toxic effect on cells or metabolism inhibition, indicating good biocompatibility. Nanostructured biomaterials prepared on low-esterified pectins could be of interest for biomedical applications in adjuvant anticancer therapy and for designing drug delivery systems.

Cryogels: Advancing Biomaterials for Transformative Biomedical Applications

Cryogels, composed of synthetic and natural materials, have emerged as versatile biomaterials with applications in tissue engineering, controlled drug delivery, regenerative medicine, and therapeutics. However, optimizing cryogel properties, such as mechanical strength and release profiles, remains challenging. To advance the field, researchers are exploring advanced manufacturing techniques, biomimetic design, and addressing long-term stability. Combination therapies and drug delivery systems using cryogels show promise. In vivo evaluation and clinical trials are crucial for safety and efficacy. Overcoming practical challenges, including scalability, structural integrity, mass transfer constraints, biocompatibility, seamless integration, and cost-effectiveness, is essential. By addressing these challenges, cryogels can transform biomedical applications with innovative biomaterials.

Chitosan and Pectin Hydrogels for Tissue Engineering and In Vitro Modeling

Hydrogels are fascinating biomaterials that can act as a support for cells, i.e., a scaffold, in which they can organize themselves spatially in a similar way to what occurs in vivo. Hydrogel use is therefore essential for the development of 3D systems and allows to recreate the cellular microenvironment in physiological and pathological conditions. This makes them ideal candidates for biological tissue analogues for application in the field of both tissue engineering and 3D in vitro models, as they have the ability to closely mimic the extracellular matrix (ECM) of a specific organ or tissue. Polysaccharide-based hydrogels, because of their remarkable biocompatibility related to their polymeric constituents, have the ability to interact beneficially with the cellular components. Although the growing interest in the use of polysaccharide-based hydrogels in the biomedical field is evidenced by a conspicuous number of reviews on the topic, none of them have focused on the combined use of two important polysaccharides, chitosan and pectin. Therefore, the present review will discuss the biomedical applications of polysaccharide-based hydrogels containing the two aforementioned natural polymers, chitosan and pectin, in the fields of tissue engineering and 3D in vitro modeling.

Polysaccharide-based porous biopolymers for enhanced bioaccessibility and bioavailability of bioactive food compounds: Challenges, advances, and opportunities

Bioactive food compounds, such as lycopene, curcumin, phytosterols, and resveratrol, have received great attention due to their potential health benefits. However, these bioactive compounds (BCs) have poor chemical stability during processing and low bioavailability after consumption. Several delivery systems have been proposed for enhancing their stability and bioavailability. Among these methods, porous biopolymers have emerged as alternative encapsulation materials, as they have superior properties like high surface area, porosity, and tunable surface chemistry to entrap BCs. This reduces the crystallinity (especially for the lipophilic ones) and particle size, and in turn, increases solubilization and bioavailability. Also, loading BCs into the porous matrix can protect them against environmental stresses such as light, heat, oxygen, and pH. This review introduces polysaccharide-based porous biopolymers for improving the bioaccessibility/bioavailability of bioactive food compounds and discusses their recent applications in the food industry. First, bioaccessibility and bioavailability are described with a special emphasis on the factors affecting them. Then, porous biopolymer fabrication methods, including supercritical carbon dioxide (SC-CO₂ ) drying, freeze-drying, and electrospinning and electrospraying, are thoroughly discussed. Finally, common polysaccharide-based biopolymers (i.e., starch, nanocellulose, alginate, and pectin) used for generating porous materials are reviewed, and their current and potential future food applications are critically discussed.

Chitosan versus Carboxymethyl Chitosan Cryogels: Bacterial Colonization, Human Embryonic Kidney 293T Cell Culturing and Co-Culturing

The potential of chitosan and carboxymethyl chitosan (CMC) cryogels cross-linked with diglycidyl ether of 1,4-butandiol (BDDGE) and poly(ethylene glycol) (PEGDGE) have been compared in terms of 3D culturing HEK-293T cell line and preventing the bacterial colonization of the scaffolds. The first attempts to apply cryogels for the 3D co-culturing of bacteria and human cells have been undertaken toward the development of new models of host-pathogen interactions and bioimplant-associated infections. Using a combination of scanning electron microscopy, confocal laser scanning microscopy, and flow cytometry, we have demonstrated that CMC cryogels provided microenvironment stimulating cell-cell interactions and the growth of tightly packed multicellular spheroids, while cell-substrate interactions dominated in both chitosan cryogels, despite a significant difference in swelling capacities and Young's modulus of BDDGE- and PEGDGE-cross-linked scaffolds. Chitosan cryogels demonstrated only mild antimicrobial properties against Pseudomonas fluorescence, and could not prevent the formation of Staphylococcus aureus biofilm in DMEM media. CMC cryogels were more efficient in preventing the adhesion and colonization of both P. fluorescence and S. aureus on the surface, demonstrating antifouling properties rather than the ability to kill bacteria. The application of CMC cryogels to 3D co-culture HEK-293T spheroids with P. fluorescence revealed a higher resistance of human cells to bacterial toxins than in the 2D co-culture.

Characterization and Biocompatibility Properties In Vitro of Gel Beads Based on the Pectin and κ-Carrageenan

This study aimed to investigate the influence of kappa (κ)-carrageenan on the initial stages of the foreign body response against pectin gel. Pectin-carrageenan (P-Car) gel beads were prepared from the apple pectin and κ-carrageenan using gelling with calcium ions. The inclusion of 0.5% κ-carrageenan (Car0.5) in the 1.5 (P1.5) and 2% pectin (P2) gel formulations decreased the gel strength by 2.5 times. Car0.5 was found to increase the swelling of P2 gel beads in the cell culture medium. P2 gel beads adsorbed 30–42 mg/g of bovine serum albumin (BSA) depending on pH. P2-Car0.2, P2-Car0.5, and P1.5-Car0.5 beads reduced BSA adsorption by 3.1, 5.2, and 4.0 times compared to P2 beads, respectively, at pH 7. The P1.5-Car0.5 beads activated complement and induced the haemolysis less than gel beads of pure pectin. Moreover, P1.5-Car0.5 gel beads allowed less adhesion of mouse peritoneal macrophages, TNF-α production, and NF-κB activation than the pure pectin gel beads. There were no differences in TLR4 and ICAM-1 levels in macrophages treated with P and P-Car gel beads. P2-Car0.5 hydrogel demonstrated lower adhesion to serous membrane than P2 hydrogel. Thus, the data obtained indicate that the inclusion of κ-carrageenan in the apple pectin gel improves its biocompatibility.

A hybrid hydrogel composed of chitin and β-glucan for effectively management of wound healing and scarring

Non-functional scar commonly forms after the skin injury. At present, most of the clinical treatments for scar eradication are typically with long treatment courses, low curative effects and expensive. In...

Distribution of Biominerals and Mineral-Organic Composites in Plant Trichomes

Biomineralization is a common phenomenon in plants and has been shown to be chemically, functionally and topologically diverse. Silica and calcium carbonate have long been known as structural plant biominerals and calcium phosphate (apatite)–long known from animals–has recently been reported. Strikingly, up to three different biominerals may occur in a single trichome in, e.g., Urticaceae and Loasaceae, and in combination with organic compounds, can form organic/inorganic composite materials. This article presents an extension of previous studies on the distribution of these biominerals in Loasaceae trichomes with a focus on their spatial (three-dimensional) distribution and co-localization with organic substances. Light microscopy and scanning electron microscopy with high-resolution EDX element analyses of sample surfaces and sections illustrate the differential distribution and composition of the different biomineral phases across cell surfaces and cell walls. Raman spectroscopy additionally permits the identification of organic and inorganic compounds side by side. All three biominerals may be found in a nearly pure inorganic phase, e.g., on the plant surfaces and in the barbs of the glochidiate trichomes, or in combination with a larger proportion of organic compounds (cellulose, pectin). The cell lumen may be additionally filled with amorphous mineral deposits. Water-solubility of the mineral fractions differs considerably. Plant trichomes provide an exciting model system for biomineralization and enable the in-vivo study of the formation of complex composite materials with different biomineral and organic compounds involved.

Glycosaminoglycan-Based Cryogels as Scaffolds for Cell Cultivation and Tissue Regeneration

Cryogels are a class of macroporous, interconnective hydrogels polymerized at sub-zero temperatures forming mechanically robust, elastic networks. In this review, latest advances of cryogels containing mainly glycosaminoglycans (GAGs) or composites of GAGs and other natural or synthetic polymers are presented. Cryogels produced in this way correspond to the native extracellular matrix (ECM) in terms of both composition and molecular structure. Due to their specific structural feature and in addition to an excellent biocompatibility, GAG-based cryogels have several advantages over traditional GAG-hydrogels. This includes macroporous, interconnective pore structure, robust, elastic, and shape-memory-like mechanical behavior, as well as injectability for many GAG-based cryogels. After addressing the cryogelation process, the fabrication of GAG-based cryogels and known principles of GAG monomer crosslinking are discussed. Finally, an overview of specific GAG-based cryogels in biomedicine, mainly as polymeric scaffold material in tissue regeneration and tissue engineering-related controlled release of bioactive molecules and cells, is provided.

Graphene oxide-reinforced pectin/chitosan polyelectrolyte complex scaffolds

Three-dimensional (3D) porous scaffolds based on graphene oxide (GO) incorporated pectin/chitosan polyelectrolyte complex (PCGO) were prepared by the freeze-drying technique. The chemical composition and microstructure of the prepared PCGO scaffolds were studied by FTIR and XRD analysis. The presence of GO and its uniform distribution within the polymer matrix was confirmed by Raman spectroscopy and confocal Raman mapping analysis, respectively. TGA analysis revealed that the addition of GO improves the thermal stability of the pectin/chitosan complex. SEM analysis confirmed the uniform pore distribution of PCGO scaffolds. Moreover, it showed that the pore size of the scaffolds was decreased with the increase in GO content. Among the developed PCGO scaffolds, the scaffolds with 1 wt.% of GO presented the improved hydrophilicity by exhibiting the water swelling degree of 2004%, water retention capacity of 1101% and water contact angle (WCA) of 21°. In addition, these scaffolds presented better compressive strength (∼283 kPa) and resistance towards lysozyme-mediated degradation. The PCGO scaffolds presented an acceptable level of bio-and hemocompatibility and GO concentration-dependent cell attachment ability. These results demonstrate the suitability of PCGO scaffolds for tissue engineering.

Design and Assessment of Biodegradable Macroporous Cryogels as Advanced Tissue Engineering and Drug Carrying Materials

Cryogels obtained by the cryotropic gelation process are macroporous hydrogels with a well-developed system of interconnected pores and shape memory. There have been significant recent advancements in our understanding of the cryotropic gelation process, and in the relationship between components, their structure and the application of the cryogels obtained. As cryogels are one of the most promising hydrogel-based biomaterials, and this field has been advancing rapidly, this review focuses on the design of biodegradable cryogels as advanced biomaterials for drug delivery and tissue engineering. The selection of a biodegradable polymer is key to the development of modern biomaterials that mimic the biological environment and the properties of artificial tissue, and are at the same time capable of being safely degraded/metabolized without any side effects. The range of biodegradable polymers utilized for cryogel formation is overviewed, including biopolymers, synthetic polymers, polymer blends, and composites. The paper discusses a cryotropic gelation method as a tool for synthesis of hydrogel materials with large, interconnected pores and mechanical, physical, chemical and biological properties, adapted for targeted biomedical applications. The effect of the composition, cross-linker, freezing conditions, and the nature of the polymer on the morphology, mechanical properties and biodegradation of cryogels is discussed. The biodegradation of cryogels and its dependence on their production and composition is overviewed. Selected representative biomedical applications demonstrate how cryogel-based materials have been used in drug delivery, tissue engineering, regenerative medicine, cancer research, and sensing.

Injectable Cryogels in Biomedicine

Cryogels are interconnected macroporous materials that are synthesized from a monomer solution at sub-zero temperatures. Cryogels, which are used in various applications in many research areas, are frequently used in biomedicine applications due to their excellent properties, such as biocompatibility, physical resistance and sensitivity. Cryogels can also be prepared in powder, column, bead, sphere, membrane, monolithic, and injectable forms. In this review, various examples of recent developments in biomedical applications of injectable cryogels, which are currently scarce in the literature, made from synthetic and natural polymers are discussed. In the present review, several biomedical applications of injectable cryogels, such as tissue engineering, drug delivery, therapeutic, therapy, cell transplantation, and immunotherapy, are emphasized. Moreover, it aims to provide a different perspective on the studies to be conducted on injectable cryogels, which are newly emerging trend.

The Osteogenetic Potential of Chitosan Coated Implant: An In Vitro Study

Objective: Chitosan is a promising polymer that has been used for coating dental implants. However, research concerning coatings with implant surfaces other than commercially pure titanium is limited. Therefore, this study aims to clarify the chitosan material's effect with two degrees of deacetylation (DDA) as coatings for laser surface microtopographic implants. Methods: Sixty-three Laser-Lok (LL) implant discs were divided into three groups (21 in each group), and two groups were coated with either 80 or 95 DDA chitosan. The groups were categorized as LL 95, LL 80, or LL control. Then, hMSC-TERT 20 cells were used to evaluate the cell morphology, viability, and osteogenic capacity of the chitosan material 7 and 14 days after culture. Two-way ANOVA followed by one-way analysis of variance (ANOVA) and Tukey's post hoc test were used. Results: All samples were biocompatible and allowed cell attachment. However, cell spreading and attachment were noticeably increased in the LL 95 group. There was a significant increase in the expression of osteogenic markers in chitosan-coated samples compared to the control group. The 95 DDA-coated group exhibited higher ALP, Runx2, osteocalcin, and osteonectin expression compared to the 80 DDA and control groups on days 7 and 14. Conclusion: A high DDA of chitosan promotes biomineralization and osteoblast formation. Therefore, this combination of laser surface and chitosan can enhance future dental implant healing processes and osseointegration.

Chitosan coated catheters alleviates mixed species biofilms of Staphylococcus epidermidis and Candida albicans

Microorganisms which adhere to the surfaces of indwelling medical implants develop into a sessile microbial community to form monomicrobial or polymicrobial biofilms. Staphylococcus epidermidis and Candida albicans are the most common pathogens co-isolated from device mediated infections. Hence development of catheters coated with anti-fouling substances is of great interest. In this current study, chitosan, extracted from the shells of marine crab Portunus sanguinolentus was coated over the surface of the urinary catheters and checked for its efficacy to inhibit the adherence of both mono and mixed species biofilms. The Extracted Chitosan (EC) coated catheters showed profound activity in reducing the preformed biofilms and the other virulence factors of the pathogens like slime production in S. epidermidis and yeast to hyphal swtich in C. albicans. Furthermore, qPCR analysis showed that EC could downregulate the virulence genes in both the pathogens when grown as monospecies and mixed species biofilms.

Multifunctional Tissue-Adhesive Cryogel Wound Dressing for Rapid Nonpressing Surface Hemorrhage and Wound Repair

Cryogels with tissue adhesion have great potential as wound dressings for rapid hemostasis for uncontrollable nonpressing surface hemorrhage and wound healing, but their use has not been reported previously. Herein, we designed a series of antibacterial and antioxidant tissue-adhesive cryogels based on quaternized chitosan (QCS) and polydopamine (PDA). These cryogels had good blood cell and platelet adhesion, enrichment, and activation properties for rapid nonpressing surface hemostasis and wound healing. The cryogels exhibited outstanding mechanical strength and easy removability, antioxidant activity, and NIR photothermal-enhanced antibacterial performance. The cryogels showed much better hemostasis than gauze and gelatin sponge in a standardized strip rat liver injury model, a standardized circular rabbit liver section model, and a pig skin laceration model. Furthermore, the excellent hemostatic performance of the QCS/PDA2.0 cryogel (containing 20 mg/mL QCS and 2.0 mg/mL PDA) for coagulopathic hemorrhages was confirmed in a standardized coagulation disorder rabbit circular liver section model. In addition, the QCS/PDA2.0 cryogel promoted rapid hemostasis in a deep noncompressible wound and a much better wound healing effect than a chitosan sponge and Tegaderm film in a full-thickness skin defect model. Overall, these multifunctional tissue-adhesive cryogels with excellent hemostatic performance and enhanced wound healing properties are suitable candidates for tissue-adhesive hemostat and wound healing dressings.

Biomimetic Aspects of Restorative Dentistry Biomaterials

Biomimetic has emerged as a multi-disciplinary science in several biomedical subjects in recent decades, including biomaterials and dentistry. In restorative dentistry, biomimetic approaches have been applied for a range of applications, such as restoring tooth defects using bioinspired peptides to achieve remineralization, bioactive and biomimetic biomaterials, and tissue engineering for regeneration. Advancements in the modern adhesive restorative materials, understanding of biomaterial–tissue interaction at the nano and microscale further enhanced the restorative materials’ properties (such as color, morphology, and strength) to mimic natural teeth. In addition, the tissue-engineering approaches resulted in regeneration of lost or damaged dental tissues mimicking their natural counterpart. The aim of the present article is to review various biomimetic approaches used to replace lost or damaged dental tissues using restorative biomaterials and tissue-engineering techniques. In addition, tooth structure, and various biomimetic properties of dental restorative materials and tissue-engineering scaffold materials, are discussed.

Chitin/chitosan derivatives and their interactions with microorganisms: a comprehensive review and future perspectives

Chitosan, obtained as a result of the deacetylation of chitin, one of the most important naturally occurring polymers, has antimicrobial properties against fungi, and bacteria. It is also useful in other fields, including: food, biomedicine, biotechnology, agriculture, and the pharmaceutical industries. A literature survey shows that its antimicrobial activity depends upon several factors such as: the pH, temperature, molecular weight, ability to chelate metals, degree of deacetylation, source of chitosan, and the type of microorganism involved. This review will focus on the in vitro and in vivo antimicrobial properties of chitosan and its derivatives, along with a discussion on its mechanism of action during the treatment of infectious animal diseases, as well as its importance in food safety. We conclude with a summary of the challenges associated with the uses of chitosan and its derivatives.

A novel cell encapsulatable cryogel (CECG) with macro-porous structures and high permeability: a three-dimensional cell culture scaffold for enhanced cell adhesion and proliferation

Hydrogel scaffold is a popular cell delivery vehicle in tissue engineering and regenerative medicine due to its capability to encapsulate cells as well as its modifiable properties. However, the inherent submicron- or nano-sized polymer networks of conventional hydrogel will produce spatial constraints on cellular activities of encapsulated cells. In this study, we endeavor to develop an innovative cell encapsulatable cryogel (CECG) platform with interconnected macro-pores, by combining cell cryopreservation technique with cryogel preparation process. The hyaluronan (HA) CECG constructs are fabricated under the freezing conditions via UV photo-crosslinking of the HA methacrylate (HA-MA) that are dissolved in the 'freezing solvent', namely the phosphate buffered saline supplemented with dimethyl sulphoxide and fetal bovine serum. Two model cell types, chondrocytes and human mesenchymal stem cells (hMSCs), can be uniformly three-dimensionally encapsulated into HA CECG constructs with high cell viability, respectively. The macro-porous structures, generated from phase separation under freezing, endow HA CECG constructs with higher permeability and more living space for cell growth. The chondrocytes encapsulated in HA CECG possess enhanced proliferation and extracellular matrix secretion than those in conventional HA hydrogels. In addition, the HA-Gel CECG constructs, fabricated with HA-MA and gelatin methacrylate precursors, provide cell-adhesive interfaces to facilitate hMSCs attachment and proliferation. The results of this work may lay the foundation for us to explore the applications of the CECG-based scaffolds in the field of tissue engineering and regenerative medicine.

Supermacroporous Composite Cryogels in Biomedical Applications

Supermacroporous gels, called cryogels, are unique scaffolds that can be prepared by polymerization of monomer solution under sub-zero temperatures. They are widely used in many applications and have significant potential biomaterials, especially for biomedical applications due to their inherent interconnected supermacroporous structures and easy formation of composite polymers in comparison to other porous polymer synthesis techniques. This review highlights the fundamentals of supermacroporous cryogels and composite cryogels, and then comprehensively summarizes recent studies in preparation, functionalization, and utilization with mechanical, biological and physicochemical features, according to the biomedical applications. Furthermore, conclusions and outlooks are discussed for the use of these promising and durable supermacroporous composite cryogels.

Chondrogenic potential of macroporous biodegradable cryogels based on synthetic poly(α-amino acids)

In this study, the potential of highly porous hydrogels based on biodegradable synthetic poly(α-amino acids) to support proliferation and chondrogenesis of human dental pulp stem cells (hDPSCs) was investigated. Covalently crosslinked gels with permanent pores were formed under cryogenic conditions by free-radical copolymerization of poly[N⁵-(2-hydroxyethyl)-l-glutamine-stat-N⁵-(2-methacryloyl-oxy-ethyl)-l-glutamine] (PHEG-MA) with 2-hydroxyethyl methacrylate (HEMA) and N-propargyl methacrylamide (PrMAAm) as minor co-monomers. PrMAAm provided alkyne groups for modifying the gels with cell-supporting moieties (RGDS peptides) by the azide-alkyne "click"-reaction. Two types of gels with different compressive moduli were prepared. Each type was modified with two different concentrations of RGDS peptide. X-ray computed nanotomography (nanoCT) was used to visualize and analyze the 3D-structure of the cryogels. It was shown that modifying the PHEG-MA cryogels within the range of RGDS concentrations examined here had a positive effect on the proliferation of hDPSCs. Immunofluorescence staining for collagen type 2 and aggrecan proved that there was differentiation of hDPSCs into chondrocytes.

Mussel-Inspired Fabrication of Konjac Glucomannan/Poly (Lactic Acid) Cryogels with Enhanced Thermal and Mechanical Properties

Three-dimensional nanofibers cryogels (NFCs) with both thermally-tolerant and mechanically-robust properties have potential for wide application in biomedical or food areas; however, creating such NFCs has proven to be extremely challenging. In this study, konjac glucomannan (KGM)/poly (lactic acid) (PLA)-based novel NFCs were prepared by the incorporation of the mussel-inspired protein polydopamine (PDA) via a facile and environmentally-friendly electrospinning and freeze-shaping technique. The obtained KGM/PLA/PDA (KPP) NFCs were characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and compressive and tensile test. The results showed that the hierarchical cellular structure and physicochemical properties of KPP NFCs were dependent on the incorporation of PDA content. Moreover, the strong intermolecular hydrogen bond interactions among KGM, PLA and PDA also gave KPP NFCs high thermostability and mechanically-robust properties. Thus, this study developed a simple approach to fabricate multifunctional NFCs with significant potential for biomedical or food application.

Mechanical properties, structure, bioadhesion, and biocompatibility of pectin hydrogels

The surface structure, biocompatibility, textural, and adhesive properties of calcium hydrogels derived from 1, 2, and 4% solutions of apple pectin were examined in this study. An increase in the pectin concentration in hydrogels was shown to improve their stability toward elastic and plastic deformation. The elasticity of pectin hydrogels, measured as Young's modulus, ranged from 6 to 100 kPa. The mechanical properties of the pectin hydrogels were shown to correspond to those of soft tissues. The characterization of surface roughness in terms of the roughness profile (Ra) and the root-mean-square deviation of the roughness profile (Rq) indicated an increased roughness profile for hydrogels depending on their pectin concentration. The adhesion of AU2% and AU4% hydrogels to the serosa abdominal wall, liver, and colon was higher than that of the AU1% hydrogel. The adhesion of macrophages and the non-specific adsorption of blood plasma proteins were found to increase as the pectin concentration in the hydrogels increased. The rate of degradation of all hydrogels was higher in phosphate buffered saline (PBS) than that in DMEM and a fibroblast cell monolayer. The pectin hydrogel was also found to have a low cytotoxicity. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2572-2581, 2017.

Chitosan Biomaterials for Current and Potential Dental Applications

Chitosan (CHS) is a very versatile natural biomaterial that has been explored for a range of bio-dental applications. CHS has numerous favourable properties such as biocompatibility, hydrophilicity, biodegradability, and a broad antibacterial spectrum (covering gram-negative and gram-positive bacteria as well as fungi). In addition, the molecular structure boasts reactive functional groups that provide numerous reaction sites and opportunities for forging electrochemical relationships at the cellular and molecular levels. The unique properties of CHS have attracted materials scientists around the globe to explore it for bio-dental applications. This review aims to highlight and discuss the hype around the development of novel chitosan biomaterials. Utilizing chitosan as a critical additive for the modification and improvement of existing dental materials has also been discussed.