Hydroxyapatite-hybridized chitosan/chitin whisker bionanocomposite fibers for bone tissue engineering applications

Progress in chitin/chitosan and their derivatives for biomedical applications: Where we stand

Chitin and its deacetylated form, chitosan, have demonstrated remarkable versatility in the realm of biomaterials. Their exceptional biocompatibility, antibacterial properties, pro- and anticoagulant characteristics, robust antioxidant capacity, and anti-inflammatory potential make them highly sought-after in various applications. This review delves into the mechanisms underlying chitin/chitosan's biological activity and provides a comprehensive overview of their derivatives in fields such as tissue engineering, hemostasis, wound healing, drug delivery, and hemoperfusion. However, despite the wealth of studies on chitin/chitosan, there exists a notable trend of homogeneity in research, which could hinder the comprehensive development of these biomaterials. This review, taking a clinician's perspective, identifies current research gaps and medical challenges yet to be addressed, aiming to pave the way for a more sustainable future in chitin/chitosan research and application.

Integrating molecular-caged nano-hydroxyapatite into post-crosslinked PVA nanofibers for artificial periosteum

Artificial periosteum is deemed a novel strategy for inducing endogenous bone regeneration, but ideal periosteum substitutes achieved by orchestrating a biomimetic microenvironment for bone regeneration remain a significant challenge. Here, we design and fabricate a hybridized nanofiber-based artificial periosteum with boosted osteoinduction properties. Via a "molecular cage" biomineralization strategy, nano-hydroxyapatite (nano-HAp) with a controllable size (∼22 nm) and excellent dispersion serves as unique nano-additives for water-soluble polyvinyl-alcohol (PVA)-based artificial periosteum. The PVA/HAp composite is electrospun into nanofibers to replicate the extracellular-matrix-inspired nanostructure for inducing cell adhesion, proliferation, and fate manipulation. A simple post-crosslinking treatment is subsequently applied to further booster its mechanical strength (6.6 MPa) and swelling stability. The optimized sample of C-PVA/HAp (10 wt% nano-HAp) artificial periosteum features excellent biocompatibility and remarkable in vitro mineralization. Cell experiments demonstrate that its effectively boasted cell modulation for enhanced osteogenesis without the aid of growth factors, showing a possible activation of the ERK/MAPK signaling pathway. This work provides an effective strategy for designing novel HAp nano-additives and expands the possibility of biomimetic fabrication for more advanced nanofiber-based artificial periosteum.

Present status and application prospects of green chitin nanowhiskers: A comprehensive review

Petrochemical resources are non-renewable, which has impeded the development of synthetic polymers. The poor degradability of synthetic polymers poses substantial environmental pressure. Additionally, the high cost of synthetic biopolymers with excellent degradation performance limits their widespread application. Thus, it is crucial to seek green, sustainable, low-cost polymers as alternatives to petrochemical-based synthetic polymers and synthetic biopolymers. Chitin is a natural and renewable biopolymer discovered in crustacean shells, insect exoskeletons, and fungal cell walls. Chitin chains consist of crystalline and amorphous regions. Note that various treatments can be employed to remove the amorphous region, enhancing the crystallinity of chitin. Chitin nanowhiskers are a high crystallinity nanoscale chitin product with a high aspect ratio, a large surface area, adjustable surface morphology, and biocompatibility. They discover widespread applications in biomedicine, environmental treatment, food packaging, and biomaterials. Various methods can be utilized for preparing chitin nanowhiskers, including chemical, ionic liquids, deacetylation, and mechanical methods. However, developing an environmentally friendly preparation process remains a big challenge for expanding their applications in different materials and large-scale production. This article comprehensively analyzes chitin nanowhiskers' preparation strategies and their drawbacks. It also highlights the extensive application in different materials and various fields, besides the potential for commercial application.

Novel PVA-Hyaluronan-Siloxane Hybrid Nanofiber Mats for Bone Tissue Engineering

Hyaluronan (HA) is a natural biodegradable biopolymer; its biological functions include cell adhesion, cell proliferation, and differentiation as well as decreasing inflammation, angiogenesis, and regeneration of damaged tissue. This makes it a suitable candidate for fabricating nanomaterials with potential use in tissue engineering. However, HA nanofiber production is restricted due to the high viscosity, low evaporation rate, and high surface tension of HA solutions. Here, hybrids in the form of continuous and randomly aligned polyvinyl alcohol (PVA)-(HA)-siloxane nanofibers were obtained using an electrospinning process. PVA-HA fibers were crosslinked by a 3D siloxane organic-inorganic matrix via sol-gel that restricts natural hydrophilicity and stiffens the structure. The hybrid nanofiber mats were characterized by FT-IR, micro-Raman spectroscopy, SEM, and biological properties. The PVA/HA ratio influenced the morphology of the hybrid nanofibers. Nanofibers with high PVA content (10PVA-8 and 10PVA-10) form mats with few beaded nanofibers, while those with high HA content (5PVA-8 and 5PVA-10) exhibit mats with mound patterns formed by "ribbon-like" nanofibers. The hybrid nanofibers were used as mats to support osteoblast growth, and they showed outstanding biological properties supporting cell adhesion, cell proliferation, and cell differentiation. Importantly, the 5PVA-8 mats show 3D spherical osteoblast morphology; this suggests the formation of tissue growth. These novel HA-based nanomaterials represent a relevant advance in designing nanofibers with unique properties for potential tissue regeneration.

Antifungal edible coatings for fruits based on zein and chitosan nanowhiskers

Fresh produce have a more limited shelf life than processed ones. Their sensory attributes such as appearance and surface texture are important features in consumer perception and liking. The decomposition of fresh produce, which is caused by enzymes, chemical reactions, and microbial infections, often caused by Colletotrichum species, is inevitable. However, it can be slowed down. Several materials have been developed for this purpose, with an emphasis on active coatings using nanomaterials. In this study, the protective effects of a zein coating containing chitosan nanowhiskers (CSW) for the maintenance of fruit quality were investigated using guava (Psidium guajava L.) as a model fruit. CSW were previously characterized, and their antifungal effects against distinct Colletotrichum species (Colletotrichum asianum, Colletotrichum tropicale, Colletotrichum gloeosporioides, and Colletotrichum brevisporum) were proven. Coatings were characterized by thermogravimetric analysis, optical profilometry, and mechanical properties. Total soluble solids, pH, mass loss, and visual inspection of uncoated and coated guava fruits were also verified during 9 days. Results show that CSW length and aspect ratio decreased for longer extraction times. A similar behavior was found for x-ray diffraction in which peak intensity decreases under the same conditions. CSW degradation (ca. 250-400°C) also depends on extraction time in which more crystalline whiskers are the most thermally stable ones. The addition of CSW did not significantly (p < 0.05) modify the homogeneity and continuity of coating but prevented microbial growth assuring fruit quality during storage. In summary, coatings protected guava fruits from post-harvest spoilage while preserving quality and extending shelf life. PRACTICAL APPLICATION: Fresh foods such as fruits and vegetables have a more limited shelf life than processed ones.

A Review of Chitosan and Chitosan Nanofiber: Preparation, Characterization, and Its Potential Applications

Chitosan is produced by deacetylating the abundant natural chitin polymer. It has been employed in a variety of applications due to its unique solubility as well as its chemical and biological properties. In addition to being biodegradable and biocompatible, it also possesses a lot of reactive amino side groups that allow for chemical modification and the creation of a wide range of useful derivatives. The physical and chemical characteristics of chitosan, as well as how it is used in the food, environmental, and medical industries, have all been covered in a number of academic publications. Chitosan offers a wide range of possibilities in environmentally friendly textile processes because of its superior absorption and biological characteristics. Chitosan has the ability to give textile fibers and fabrics antibacterial, antiviral, anti-odor, and other biological functions. One of the most well-known and frequently used methods to create nanofibers is electrospinning. This technique is adaptable and effective for creating continuous nanofibers. In the field of biomaterials, new materials include nanofibers made of chitosan. Numerous medications, including antibiotics, chemotherapeutic agents, proteins, and analgesics for inflammatory pain, have been successfully loaded onto electro-spun nanofibers, according to recent investigations. Chitosan nanofibers have several exceptional qualities that make them ideal for use in important pharmaceutical applications, such as tissue engineering, drug delivery systems, wound dressing, and enzyme immobilization. The preparation of chitosan nanofibers, followed by a discussion of the biocompatibility and degradation of chitosan nanofibers, followed by a description of how to load the drug into the nanofibers, are the first issues highlighted by this review of chitosan nanofibers in drug delivery applications. The main uses of chitosan nanofibers in drug delivery systems will be discussed last.

Resorbable Biomaterials Used for 3D Scaffolds in Tissue Engineering: A Review

This article provides a thorough overview of the available resorbable biomaterials appropriate for producing replacements for damaged tissues. In addition, their various properties and application possibilities are discussed as well. Biomaterials are fundamental components in tissue engineering (TE) of scaffolds and play a critical role. They need to exhibit biocompatibility, bioactivity, biodegradability, and non-toxicity, to ensure their ability to function effectively with an appropriate host response. With ongoing research and advancements in biomaterials for medical implants, the objective of this review is to explore recently developed implantable scaffold materials for various tissues. The categorization of biomaterials in this paper includes fossil-based materials (e.g., PCL, PVA, PU, PEG, and PPF), natural or bio-based materials (e.g., HA, PLA, PHB, PHBV, chitosan, fibrin, collagen, starch, and hydrogels), and hybrid biomaterials (e.g., PCL/PLA, PCL/PEG, PLA/PEG, PLA/PHB PCL/collagen, PCL/chitosan, PCL/starch, and PLA/bioceramics). The application of these biomaterials in both hard and soft TE is considered, with a particular focus on their physicochemical, mechanical, and biological properties. Furthermore, the interactions between scaffolds and the host immune system in the context of scaffold-driven tissue regeneration are discussed. Additionally, the article briefly mentions the concept of in situ TE, which leverages the self-renewal capacities of affected tissues and highlights the crucial role played by biopolymer-based scaffolds in this strategy.

Recent Advancements in Electrospun Chitin and Chitosan Nanofibers for Bone Tissue Engineering Applications

Treatment of large segmental bone loss caused by fractures, osteomyelitis, and non-union results in expenses of around USD 300,000 per case. Moreover, the worst-case scenario results in amputation in 10% to 14.5% of cases. Biomaterials, cells, and regulatory elements are employed in bone tissue engineering (BTE) to create biosynthetic bone grafts with effective functionalization that can aid in the restoration of such fractured bones, preventing amputation and alleviating expenses. Chitin (CT) and chitosan (CS) are two of the most prevalent natural biopolymers utilized in the fields of biomaterials and BTE. To offer the structural and biochemical cues for augmenting bone formation, CT and CS can be employed alone or in combination with other biomaterials in the form of nanofibers (NFs). When compared with several fabrication methods available to produce scaffolds, electrospinning is regarded as superior since it enables the development of nanostructured scaffolds utilizing biopolymers. Electrospun nanofibers (ENFs) offer unique characteristics, including morphological resemblance to the extracellular matrix, high surface-area-to-volume ratio, permeability, porosity, and stability. This review elaborates on the recent strategies employed utilizing CT and CS ENFs and their biocomposites in BTE. We also summarize their implementation in supporting and delivering an osteogenic response to treat critical bone defects and their perspectives on rejuvenation. The CT- and CS-based ENF composite biomaterials show promise as potential constructions for bone tissue creation.

Chitin whiskers enhanced methacrylated hydroxybutyl chitosan hydrogels as anti-deformation scaffold for 3D cell culture

Hydrogel, as three-dimensional (3D) cell culture scaffold, is an effective strategy for tissue and organ regeneration due to their good biocompatibility, biodegradability and resemblance to body microenvironments in vivo. However, the inherent weak mechanical properties and strong shrinkage of hydrogels during cell culture hinder its application in clinical. In this study, a two-component thermo/photo dual-sensitive hydrogel (M/C) was prepared from methacrylated hydroxybutyl chitosan (MHBC) and chitin whisker (CHW) via physical and chemical cross-linking methods. M/C hydrogel showed a special internal structure with lamellar arrangement. The rheological properties of the hydrogels could be regulated with the change of M/C ratio. It is worth emphasizing that the mechanical properties, shrinkage resistance and cellular capacitances of the M/C hydrogel were improved with the addition of CHW. Moreover, the M/C hydrogel not only exhibited excellent degradability and antibacterial properties, but also significantly promoted the adhesion and proliferation of MC3T3-E1 cells in vitro. Therefore, the M/C hydrogel showed a wide application potential in tissue regeneration as a 3D cell culture scaffold.

Synthesis and characterization of gentamicin loaded ZSM-5 scaffold: Cytocompatibility and antibacterial activity

Porous structure, biocompatibility and biodegradability, large surface area, and drug-loading ability are some remarkable properties of zeolite structure, making it a great possible option for bone tissue engineering. Herein, we evaluated the potential application of the ZSM-5 scaffold encapsulated GEN with high porosity structure and significant antibacterial properties. The space holder process has been employed as a new fabrication method with interconnected pores and suitable mechanical properties. In this study, for the first time, ZSM-5 scaffolds with GEN drug-loading were fabricated with the space holder method. The results showed excellent open porosity in the range of 70-78% for different GEN concentrations and appropriate mechanical properties. Apatite formation on the scaffold surface was determined with Simulation body fluid (SBF), and a new bone-like apatite layer shaping on all samples confirmed the in vitro bioactivity of ZSM-5-GEN scaffolds. Also, antibacterial properties were investigated against both gram-positive and gram-negative bacteria. The incorporation of various amounts of GEN increased the inhibition zone from 24 to 28 (for E. coli) and 26 to 37 (for S. aureus). In the culture with MG63 cells, great cell viability and high cell proliferation after 7 days of culture were determined.

Nigella/honey/garlic/olive oil co-loaded PVA electrospun nanofibers for potential biomedical applications

The current work focuses on the formation of nanofibrous mats without the use of toxic solvents and metallic nanoparticles utilizing polyvinyl alcohol (PVA) and a blend of nigella, honey, garlic, and olive oil. Using deionized water (DI) water as a solvent, nanofibrous mats composed of PVA/nigella/honey (PNH) and PVA/garlic/honey/olive oil (PGHO) were developed. Methanol extraction was utilized to extract the therapeutic components of nigella sativa. Antibacterial and moisture management tests (MMT) were employed to examine the antibacterial and absorbance characteristics of the PNH and PGHO nanofibrous. Scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) tests were employed to analyze the morphological and chemical characteristics. PGHO showed thermal stability up to 245 °C, and PNH withstands until 225 °C. PNH and PGHO both exhibited antibacterial activity against Staphylococcus aureus (S. aureus), with inhibition zones of 36 mm and 35 mm, respectively. The synthesized materials exhibited excellent absorbance properties, thermal stability, cytotoxicity, and the production of thin nanofibers with an average diameter between 150 and 170 nm. The samples were characterized using FTIR spectra, which confirmed the presence of all components in the developed samples. To date, extensive research on electrospinning for biomedical applications has been undertaken using a variety of hazardous solvents and metallic nanoparticles. Briefly, our objective is to develop nanofibrous materials from plant extracts through a process called "green electrospinning" to observe the synergistic effect of multiple biocomponents incorporated nanofibers avoiding toxic solvents and metallic compounds for potential biomedical applications.

Electrospun Nanofibrous Membranes for Tissue Engineering and Cell Growth

In biotechnology, the field of cell cultivation is highly relevant. Cultivated cells can be used, for example, for the development of biopharmaceuticals and in tissue engineering. Commonly, mammalian cells are grown in bioreactors, T-flasks, well plates, etc., without a specific substrate. Nanofibrous mats, however, have been reported to promote cell growth, adhesion, and proliferation. Here, we give an overview of the different attempts at cultivating mammalian cells on electrospun nanofiber mats for biotechnological and biomedical purposes. Starting with a brief overview of the different electrospinning methods, resulting in random or defined fiber orientations in the nanofiber mats, we describe the typical materials used in cell growth applications in biotechnology and tissue engineering. The influence of using different surface morphologies and polymers or polymer blends on the possible application of such nanofiber mats for tissue engineering and other biotechnological applications is discussed. Polymer blends, in particular, can often be used to reach the required combination of mechanical and biological properties, making such nanofiber mats highly suitable for tissue engineering and other biotechnological or biomedical cell growth applications.

Chitosan based antibacterial composite materials for leather industry: a review

Abstract

Chitosan is an amorphous translucent substance with a structural unit similar to the polysaccharide structure of the extracellular matrix, It has good antibacterial, biocompatible, and degradable properties. It has important application value in leather, water treatment, medicine, food and other fields, so chitosan and its modified products have received widespread attention. This article reviewed the preparation methods of chitosan-based antibacterial composites in recent years, including chitosan/collagen, chitosan/graphene, chitosan/tannic acid, and chitosan/polyethylene glycol composite materials, elaborates their modification methods and antibacterial mechanism were reviewed in detail, and its applications in the leather industry as antibacterial auxiliaries and water treatment antibacterial adsorption materials were discussed. Finally, the future development and challenges of chitosan-based composite materials in the leather industry were forecasted.

Graphical abstract

Hydroxyapatite Based Materials for Bone Tissue Engineering: A Brief and Comprehensive Introduction

Hydroxyapatite (HA) is widely used in bone tissue engineering for its bioactivity and biocompatibility, and a growing number of researchers are exploring ways to improve the physical properties and biological functions of hydroxyapatite. Up to now, HA has been used as inorganic building blocks for tissue engineering or as nanofillers to blend with polymers, furthermore, various methods such as ion doping or surface modification have been also reported to prepare functionalized HA. In this review, we try to give a brief and comprehensive introduction about HA-based materials, including ion-doped HA, HA/polymer composites and surface modified HA and their applications in bone tissue engineering. In addition, the prospective of HA is also discussed. This review may be helpful for researchers to get a general understanding about the development of hydroxyapatite based materials.

Engineered biomaterial strategies for controlling growth factors in tissue engineering

Growth factors are multi-functional signaling molecules that coordinate multi-stage process of wound healing. During wound healing, growth factors are transmitted to wound environment in a positive and physiologically related way, therefore, there is a broad prospect for studying the mediated healing process through growth factors. However, growth factors (GFs) themselves have disadvantages of instability, short life, rapid inactivation of physiological conditions, low safety and easy degradation, which hinder the clinical use of GFs. Rapid development of delivery strategies for GFs has been trying to solve the instability and insecurity of GFs. Particularly, in recent years, GFs delivered by scaffolds based on biomaterials have become a hotspot in this filed. This review introduces various delivery strategies for growth factors based on new biodegradable materials, especially polysaccharides, which could provide guidance for the development of the delivery strategies for growth factors in clinic.

Regulation of the Morphological and Physical Properties of a Soft Tissue Scaffold by Manipulating DD and DS of O-Carboxymethyl Chitin

To improve the biocompatibility/biodegradability as well as to lower the cost of the popular glycosaminoglycan/collagen scaffold, a monocomponent's polysaccharide scaffold based on biomimetic chemical modification of chitin from lower organisms was developed creatively. O-Carboxymethyl chitin (O-CMCH) was prepared by chloroacetic acid substitution of alkalized chitin. The cross-linked O-CMCH soft tissue scaffold was constructed by a sol-gel freeze-drying method. The key parameters of the O-CMCH molecular structure, the degree of deacetylation (DD), and the degree of substitution (DS) were used to regulate the morphology and physical properties of the scaffold. The optimized scaffolds were implanted subcutaneously in mice, and the inflammation reaction of surrounding tissues, dermal tissue growth, and scaffold degradation were observed dynamically by light microscopy and scanning electron microscopy. The results showed that the micropores of the scaffold constructed by O-CMCH with DD = 0.53 and DS = 0.61 were uniformly distributed and in communication with each other, and the pore size was 100-150 μm, with high porosity (93.52 ± 4.68%), high swelling ratio (1402 ± 70%), and high skeleton cross-linking degree (93.4 ± 4.6%). Its tensile strength reached 0.183 ± 0.009 MPa, and its elongation at break was 18.7 ± 0.9%. Furthermore, it could be degraded to less than 10% after 16 days in phosphate buffer solution (pH = 7.4) with 0.2 mg/mL lysozymes (≥ 20 000 U/mg). The early inflammation after implanting the optimized scaffolds in mice showed no difference compared with the control. The scaffold material induced dermal tissues to grow over it and was degraded gradually in vivo. The optimized scaffold regulated by DD and DS of O-CMCH possessed suitable morphology and physical properties for soft tissue engineering technology and exhibited a high applicable value.

Cytocompatibility of Bilayer Scaffolds Electrospun from Chitosan/Alginate-Chitin Nanowhiskers

In this work, a bilayer chitosan/sodium alginate scaffold was prepared via a needleless electrospinning technique. The layer of sodium alginate was electrospun over the layer of chitosan. The introduction of partially deacetylated chitin nanowhiskers (CNW) stabilized the electrospinning and increased the spinnability of the sodium alginate solution. A CNW concentration of 7.5% provided optimal solution viscosity and structurization due to electrostatic interactions and the formation of a polyelectrolyte complex. This allowed electrospinning of defectless alginate nanofibers with an average diameter of 200-300 nm. The overall porosity of the bilayer scaffold was slightly lower than that of a chitosan monolayer, while the average pore size of up to 2 μm was larger for the bilayer scaffold. This high porosity promoted mesenchymal stem cell proliferation. The cells formed spherical colonies on the chitosan nanofibers, but formed flatter colonies and monolayers on alginate nanofibers. The fabricated chitosan/sodium alginate bilayer material was deemed promising for tissue engineering applications.

Chitin and its derivatives: Structural properties and biomedical applications

Chitin, a polysaccharide that occurs abundantly in nature after cellulose, has attracted the interest of the scientific community due to its plenty of availability and low cost. Mostly, it is derived from the exoskeleton of insects and marine crustaceans. Often, it is insoluble in common solvents that limit its applications but its deacetylated product, named chitosan is found to be soluble in protonated aqueous medium and used widely in various biomedical fields. Indeed, the existence of the primary amino group on the backbone of chitosan provides it an important feature to modify it chemically into other derivatives easily. In the present review, we present the structural properties of chitin, and its derivatives and highlighted their biomedical implications including, tissue engineering, drug delivery, diagnosis, molecular imaging, antimicrobial activity, and wound healing. We further discussed the limitations and prospects of this versatile natural polysaccharide.

Chitin and Chitinases: Biomedical And Environmental Applications of Chitin and its Derivatives

Disposal of chitin wastes from crustacean shell can cause environmental and health hazards. Chitin is a well known abundant natural polymer extracted after deproteinization and demineralization of the shell wastes of shrimp, crab, lobster, and krill. Extraction of chitin and its derivatives from waste material is one of the alternative ways to turn the waste into useful products. Chitinases are enzymes that degrade chitin. Chitinases contribute to the generation of carbon and nitrogen in the ecosystem. Chitin and chitinolytic enzymes are gaining importance for their biotechnological applications. The presence of surface charge and multiple functional groups make chitin as a beneficial natural polymer. Due to the reactive functional groups chitin can be used for the preparation of a spectrum of chitin derivatives such as chitosan, alkyl chitin, sulfated chitin, dibutyryl chitin and carboxymethyl chitin for specific applications in different areas. The present review is aimed to summarize the efficacy of the chitinases on the chitin and its derivatives and their diverse applications in biomedical and environmental field. Further this review also discusses the synthesis of various chitin derivatives in detail and brings out the importance of chitin and its derivatives in biomedical and environmental applications.

Adipose-Derived Mesenchymal Stem Cell Chondrospheroids Cultured in Hypoxia and a 3D Porous Chitosan/Chitin Nanocrystal Scaffold as a Platform for Cartilage Tissue Engineering

Articular cartilage degeneration is one of the most common causes of pain and disability in middle-aged and older people. Tissue engineering (TE) has shown great therapeutic promise for this condition. The design of cartilage regeneration constructs must take into account the specific characteristics of the cartilaginous matrix, as well as the avascular nature of cartilage and its cells' peculiar arrangement in isogenic groups. Keeping these factors in mind, we have designed a 3D porous scaffold based on genipin-crosslinked chitosan/chitin nanocrystals for spheroid chondral differentiation of human adipose tissue-derived mesenchymal stem cells (hASCs) induced in hypoxic conditions. First, we demonstrated that, under low oxygen conditions, the chondrospheroids obtained express cartilage-specific markers including collagen type II (COL2A1) and aggrecan, lacking expression of osteogenic differentiation marker collagen type I (COL1A2). These results were associated with an increased expression of hypoxia-inducible factor 1α, which positively directs COL2A1 and aggrecan expression. Finally, we determined the most suitable chondrogenic differentiation pattern when hASC spheroids were seeded in the 3D porous scaffold under hypoxia and obtained a chondral extracellular matrix with a high sulphated glycosaminoglycan content, which is characteristic of articular cartilage. These findings highlight the potential use of such templates in cartilage tissue engineering.

Applications of chitin and chitosan nanofibers in bone regenerative engineering

Promoting bone regeneration and repairing defects are urgent and critical challenges in orthopedic clinical practice. Research on bone substitute biomaterials is essential for improving the treatment strategies for bone regeneration. Chitin and its derivative, chitosan, are among the most abundant natural biomaterials and widely found in the shells of crustaceans. Chitin and chitosan are non-toxic, antibacterial, biocompatible, degradable, and have attracted significant attention in bone substitute biomaterials. Chitin/chitosan nanofibers and nanostructured scaffolds have large surface area to volume ratios and high porosities. These scaffolds can be fabricated by electrospinning, thermally induced phase separation and self-assembly, and are widely used in biomedical applications such as biological scaffolds, drug delivery, bacterial inhibition, and wound dressing. Recently, some chitin/chitosan-based nanofibrous scaffolds have been found structurally similar to bone's extracellular matrix and can assist in bone regeneration. This review outlines the biomedical applications and biological properties of chitin/chitosan-based nanofibrous scaffolds in bone tissue engineering.

An overview of advanced biocompatible and biomimetic materials for creation of replacement structures in the musculoskeletal systems: focusing on cartilage tissue engineering

Tissue engineering, as an interdisciplinary approach, is seeking to create tissues with optimal performance for clinical applications. Various factors, including cells, biomaterials, cell or tissue culture conditions and signaling molecules such as growth factors, play a vital role in the engineering of tissues. In vivo microenvironment of cells imposes complex and specific stimuli on the cells, and has a direct effect on cellular behavior, including proliferation, differentiation and extracellular matrix (ECM) assembly. Therefore, to create appropriate tissues, the conditions of the natural environment around the cells should be well imitated. Therefore, researchers are trying to develop biomimetic scaffolds that can produce appropriate cellular responses. To achieve this, we need to know enough about biomimetic materials. Scaffolds made of biomaterials in musculoskeletal tissue engineering should also be multifunctional in order to be able to function better in mechanical properties, cell signaling and cell adhesion. Multiple combinations of different biomaterials are used to improve above-mentioned properties of various biomaterials and to better imitate the natural features of musculoskeletal tissue in the culture medium. These improvements ultimately lead to the creation of replacement structures in the musculoskeletal system, which are closer to natural tissues in terms of appearance and function. The present review article is focused on biocompatible and biomimetic materials, which are used in musculoskeletal tissue engineering, in particular, cartilage tissue engineering.

Preparation and Performances of Warp-Knitted Hernia Repair Mesh Fabricated with Chitosan Fiber

In this paper, warp-knitted knitted fabrics with chitosan fibers for ventral hernia repair were fabricated with three kinds of structures. The properties of chitosan fiber, yarns, and fabrics were tested. The results demonstrated that the properties of a mesh fabricated with 1-0/1-2/2-3/2-1// structure were slightly better than those of other fabrics. The mechanical properties of the three produced fabrics were weak. However, the results demonstrated that chitosan meshes have many advantages, such as excellent hygroscopicity, and thermal and antimicrobial properties, which makes them one of the best materials for ventral hernia repair. The findings have theoretical and practical significance for the industrial uses of chitosan in ventral hernia repair.

Release Behavior of Folic Acid Grafted Hollow Hydroxyapatite as Drug Carrier

Based on the formation of carbodiimide compounds between carboxyl and primary amines, hollow microspheres arising from the folic acid (folate-FA) grafted onto the surface of the modified hydroxyapatite were successfully prepared. The hollow morphology and composition of the FA-grafted hydroxyapatite microspheres were confirmed by scanning electron microscopy (SEM) and other characterizations. Brunauer-Emmett-Teller (BET) assay revealed the specific surface area and average pore size of the microspheres were 34.58m2/g and 17.80 nm, respectively. As a drug carrier, the kinetic investigation of doxorubicin (DOX) loaded shows that the adsorbed behavior of drug on the adsorbent is more suitable to be described with pseudo-first-order model. Furthermore, the release rate can reach 83% at pH 5.7, which is greater than the release of 39% at pH 7.4, indicating an excellent performance of controlled drug release for response pH. The release mechanism of DOX coincides with Fickian diffusion as a result of Korsmeyer-Peppas model analysis and the release phenomena can be well explained by Fickian diffusion second law.

Biomedical applications of chitosan electrospun nanofibers as a green polymer - Review

This review outlines new developments in the biomedical applications of environmentally friendly ('green') chitosan and chitosan-blend electrospun nanofibers. In recent years, research in functionalized nanofibers has contributed to the development of new drug delivery systems and improved scaffolds for regenerative medicine, which is currently one of the most rapidly growing fields in all of the life sciences. Chitosan is a biopolymer with non-toxic, antibacterial, biodegradable and biocompatible properties. Due to these properties, they are widely applied for biomedical applications such as drug delivery, tissue engineering scaffolds, wound dressings, and antibacterial coatings. Electrospinning is a novel technique for chitosan nanofiber fabrication. These nanofibers can be used in unique applications in biomedical fields due to their high surface area and porosity. The present work reviews recent reports on the biomedical applications of chitosan-based nanofibers in detail.

Bioinspired Environmentally Friendly Amorphous CaCO3-Based Transparent Composites Comprising Cellulose Nanofibers

Amorphous calcium carbonate (ACC) stabilized by acidic macromolecules is a useful material for the development of environmentally friendly composites. In this study, we synthesized transparent and mechanically tough ACC-based composite materials by the incorporation of water-dispersible cellulose derivatives, namely, carboxymethyl cellulose (CMC) and surface-modified crystalline cellulose nanofibers (CNFs). A solution mixing method used in the present work proved to be a powerful and efficient method for the production of mechanically tough and environmentally friendly materials. Molecular-scale interactions between carboxyl groups and Ca2+ ions induce homogeneous dispersion of CNFs in the composites, and this gives composite films with high transparency and high mechanical properties. The composite films of CMC, CNFs, and ACC at the mixture ratios of 40, 40, and 20 wt %, showed high mechanical properties of 15.8 ± 0.93 GPa for the Young's modulus and 268 ± 20 MPa for the tensile strength. These designed materials that are based on ACC may open up new opportunities in many fields in applications that require the use of environmentally friendly, biodegradable, mechanically tough, and transparent composite materials.

Nanoscale and Macroscale Scaffolds with Controlled-Release Polymeric Systems for Dental Craniomaxillofacial Tissue Engineering

Tremendous progress in stem cell biology has resulted in a major current focus on effective modalities to promote directed cellular behavior for clinical therapy. The fundamental principles of tissue engineering are aimed at providing soluble and insoluble biological cues to promote these directed biological responses. Better understanding of extracellular matrix functions is ensuring optimal adhesive substrates to promote cell mobility and a suitable physical niche to direct stem cell responses. Further, appreciation of the roles of matrix constituents as morphogen cues, termed matrikines or matricryptins, are also now being directly exploited in biomaterial design. These insoluble topological cues can be presented at both micro- and nanoscales with specific fabrication techniques. Progress in development and molecular biology has described key roles for a range of biological molecules, such as proteins, lipids, and nucleic acids, to serve as morphogens promoting directed behavior in stem cells. Controlled-release systems involving encapsulation of bioactive agents within polymeric carriers are enabling utilization of soluble cues. Using our efforts at dental craniofacial tissue engineering, this narrative review focuses on outlining specific biomaterial fabrication techniques, such as electrospinning, gas foaming, and 3D printing used in combination with polymeric nano- or microspheres. These avenues are providing unprecedented therapeutic opportunities for precision bioengineering for regenerative applications.

Chitin Nanoforms Provide Mechanical and Topological Cues to Support Growth of Human Adipose Stem Cells in Chitosan Matrices

The precise role and value of incorporating nanoforms in biologically active matrices for medical applications is not known. In our current work, we incorporate two chitin nanoforms (i.e., nanocrystals or nanofibers) into Genipin-chitosan crosslinked matrices. These materials were studied as 2D films and 3D porous scaffolds to assess their potential as primary support and guidance for stem cells in tissue engineering and regenerative medicine applications. The incorporation of either nanoforms in these 2D and 3D materials reveals significantly better swelling properties and robust mechanical performance in contrast to nanoform-free chitosan matrices. Furthermore, our data shows that these materials, in particular, incorporation of low concentration chitin nanoforms provide specific topological cues to guide the survival, adhesion, and proliferation of human adipose-derived stem cells. These findings demonstrate the potential of Genipin-chitosan crosslinked matrices impregnated with chitin nanoforms as value added materials for stem cell-based biomedical applications.

Comparison of nanocrystals and nanofibers produced from shrimp shell α-chitin: From energy production to material cytotoxicity and Pickering emulsion properties

Chitin nanocrystals (ChNCs) and chitin nanofibers (ChNFs) are nanomaterials with great innovative potential for sustainable applications in academic and industrial fields. The research related to their isolation and production, characterization, and utilization is still new. The aim of this study is to investigate the effects of the production process on the morphology and properties of ChNFs and ChNCs produced from the same source of chitin. ChNCs were prepared by acid hydrolysis of commercial shrimp shell α-chitin, and ChNFs were prepared by mechanical defibrillation using closed loop supermass colloidal grinding. Differences in their shape, size, and crystallinity were observed. ChNFs were observed to have higher aspect ratio, higher viscosity, and better thermal stability than ChNCs. Although the ChNC casting film had a higher degree of transparency, it had lower mechanical properties than ChNF film. In addition, the capacities of each nanomaterial for producing Pickering emulsions were comparatively investigated. ChNFs showed better oil-in-water emulsion stabilization ability than ChNCs at the same concentrations. In vitro cytotoxicity assays using two epithelial-like cell lines and two fibroblast-like cell lines demonstrated that both nanomaterials were non-toxic. Finally, we evaluated the economics of production using process engineering simulation to assess the energy and chemical consumption for each process of production of these nanomaterials.

Synthesis, Structural, and Adsorption Properties and Thermal Stability of Nanohydroxyapatite/Polysaccharide Composites

A series of composites based on nanohydroxyapatite (nHAp) and natural polysaccharides (PS) (nHAp/agar, nHAp/chitosan, nHAp/pectin FB300, nHAp/pectin APA103, nHAp/sodium alginate) was synthesized by liquid-phase two-step method and characterized using nitrogen adsorption-desorption, DSC, TG, FTIR spectroscopy, and SEM. The analysis of nitrogen adsorption-desorption data shows that composites with a nHAp: PS ratio of 4:1 exhibit a sufficiently high specific surface area from 49 to 82 m²/g. The incremental pore size distributions indicate mainly mesoporosity. The composites with the component ratio 1:1 preferably form a film-like structure, and the value of S _BET varies from 0.3 to 43 m²/g depending on the nature of a polysaccharide. Adsorption of Sr(II) on the composites from the aqueous solutions has been studied. The thermal properties of polysaccharides alone and in nHAp/PS show the influence of nHAp, since there is a shift of characteristic DSC and DTG peaks. FTIR spectroscopy data confirm the presence of functional groups typical for nHAp as well as polysaccharides in composites. Structure and morphological characteristics of the composites are strongly dependent on the ratio of components, since nHAp/PS at 4:1 have relatively large S _BET values and a good ability to adsorb metal ions. The comparison of the adsorption capacity with respect to Sr(II) of nHAp, polysaccharides, and composites shows that it of the latter is higher than that of nHAp (per 1 m² of surface).

Fabrication and Characterization of Polyphosphazene/Calcium Phosphate Scaffolds Containing Chitosan Microspheres for Sustained Release of Bone Morphogenetic Protein 2 in Bone Tissue Engineering

Bone morphogenetic protein 2 has a major role in promoting bone regeneration in tissue engineering scaffolds. Growth factor release rate is a remaining crucial problem in these systems. The aim of this study was to fabricate and characterize a novel calcium phosphate/polyphosphazenes porous scaffold for the sustained release of bone morphogenetic protein 2 in bone tissue engineering. Polyphosphazenes were substituted with 2-dimethylaminoethanol and evaluated by GPC, NMR, and in vitro degradation. Calcium phosphate porous samples were prepared from hydroxyapatite nanoparticles and naphthalene using the sintering method at 1250 °C before being composited with poly(dimethylaminoethanol)phosphazenes containing chitosan microspheres loaded with bone morphogenetic protein 2. The characteristics and biodegradability of the product were evaluated by SEM, XRD, and in vitro degradation. Moreover, the release rate and mechanical properties of the scaffolds were investigated. The release behavior was found to be sustained since the scaffolds had been fabricated from polyphosphazenes with a low degradation rate. The release rates of the scaffolds were observed to increase with increasing chitosan microspheres content from 10 to 30%. The bioactivity of the scaffolds depended on the release rate of growth factor while bone morphogenetic protein 2 was able to induce an osteoblast proliferation. The results of cell adhesion and cell viability tests showed that scaffolds displayed a non-toxic behavior and western blot analyses confirmed that the scaffolds loaded with growth factor increased the osteogenic differentiation potential of cells when compared with scaffolds alone. These results demonstrate that these scaffolds can be successfully utilized in bone tissue engineering.

Nano-hydroxyapatite/β-CD/chitosan nanocomposite for potential applications in bone tissue engineering

Herein, we report the synthesis of a novel tri-component nanocomposite system incorporating β-cyclodextrin (β-CD) with nano-hydroxyapatite (n-HA) and chitosan (CS), (n-HA/β-CD/CS) at three different temperatures via co-precipitation method. The chemical interactions and surface morphology have been evaluated by TEM, SEM and AFM techniques revealing the agglomerated nanoparticles in CS/n-HA-HA binary system whereas the ternary systems produced needle shaped nanoparticles dispersed homogeneously at low temperature with more porous and rougher surface. The addition of β-CD in CS/n-HA at low temperature decreased the particle size and raised the thermal stability as compared to CS/n-HA. The comparative hemolytic, protein adsorption and platelet adhesion studies confirmed the better hemocompatibility of n-HA/β-CD/CS-(RT,HT,LT) nanocomposites relative to CS/n-HA. The cell viability has been evaluated in vitro using MG-63 cell line which revealed superior non toxicity of n-HA/β-CD/CS-LT nanocomposite in comparison to n-HA/β-CD/CS-(RT,HT) and CS/n-HA nanocomposites. Thus it may be concluded that the orchestrated organic/inorganic n-HA/β-CD/CS-(RT,HT,LT) nanocomposites exhibited relatively higher cell viability of human osteoblast cells, stimulated greater osteogenesis, controlled biodegradation, enhanced antibacterial activity with excellent in-vitro biomineralization and remarkable mechanical parameters as compared to CS/n-HA nanocomposite and thus may provide opportunities for potential use as an alternative biomaterial for Bone tissue engineering applications.