Bacterial Nanocellulose: Methods, Properties, and Biomedical Applications

Abstract

Unlike plant and wood-origin cellulose, bacterial nanocellulose (BNC) produced by bacteria exhibits the highest purity and natural nanofiber morphology, attracting increasing interest from many researchers and industrial sectors. It has numerous unique features including the biomimetic nanoscale three-dimensional (3D) network, high water holding capacity, and moldability in different shapes, accepted wet strength, outstanding gas permeability, and good biocompatibility, which makes the BNC show great potential in a wide variety of biomedical applications. Extensive research has verified the feasibility of application in wound dressing, bone/cartilage tissue regeneration, vascular tissue engineering, and so on. This chapter focuses on the production and properties of BNC, the fabrication of BNC-based biomaterials, and the biomedical applications of BNC.

1. Introduction

Bacterial nanocellulose (BNC) as a type of extracellular polysaccharide polymer synthesized by bacteria has unique physical and chemical properties, including high purity (free from lignin and hemicellulose) and crystallinity (84–89%), high degree of polymerization, good mechanical properties, high water retention, and three-dimensional (3D) nanofibrous structure [1, 2]. All these features make BNC attractive for material scientists and engineers.

Importantly, BNC is environment-friendly due to its nontoxic, nonimmunogenic, biocompatible, biodegradable, and renewable nature [3]. The nanofibrillar network of BNC is similar to the structure of collagen in the native extracellular matrix (ECM), and the 3D uniform and interconnected pores facilitate cell infiltration and nutrient and waste exchange [4, 5]. As a promising natural biomaterial, BC has been extensively utilized in various biomedical fields for wound healing, bone, cartilage, and blood vessel engineering [6, 7].

During the past two decades, many studies have been dedicated to developing various BC-based biomaterials. The 3D porous structure and easily modified surface (abundant OH groups) of BNC are beneficial for introducing into BC varieties of reinforcement substances including biomolecules, nanoparticles, and polymers to acquire new materials with highly desirable properties, which can lead to the formation of BC-based functional materials for biomedical applications [3]. Moreover, BC-based scaffolds have been specifically designed to mimic the 3D structures of native tissues to support and provide the microenvironments required for cell adhesion, proliferation, migration, and differentiation [8]. These extensive efforts have accelerated the development of BNC-based biomaterial.

In this chapter, we briefly introduced the biosynthesis and properties of BNC. Furthermore, the strategies for fabricating the BNC biomaterial and applications in various biomedical fields were summarized.

2. Biosynthesis and properties of BNC

2.1 Biosynthesis and production of BNC

The bacterial synthesis of cellulose was first reported by Brown as early as 1886 [9]. Brown found that a white gel-like thin layer was formed on the surface of the culture medium after incubating Bacterium xylinum’ in a static state. Chemical analysis determined that the main component of the white gel is cellulose and does not contain hemicellulose and lignin, and further research found that the diameter of this cellulose is at the nanoscale.

Gluconacetobacter genus, as one of the most efficient BNC producers, is widely used in the biosynthesis of BNC [10, 11]. The general process to produce BNC is schematically described in Figure 1A. The biosynthesis process of BNC is mainly divided into four steps (Figure 1B): (1) glucose is converted into glucose-6-phosphate, (2) glucose-6-phosphate is converted into glucose-1-phosphate by phosphoglucomutase, (3) uridine diphosphate glucose (UDP-glucose) pyrophosphorylase converts glucose-1-phosphate to UDP-glucose, (4) the UDP-glucose is converted to cellulose by the action of cellulose synthase (Figure 1C) [13, 14]. The self-assembly and crystallization of BNC nanofibrils are regulated by the cell itself [15]. The synthesized chains are sequentially gathered in the culture medium at a rate of up to 200,000 glucose molecules per second and form protofibrils or sub-elementary fibrils, which are 2–4 nm in diameter. Each sub-elementary protofibril is composed of 12–16 glucan chains, where the glucan chains are aligned and stacked into ordered nanostructures called the microfibrils. The micro- and macrofibrils and loose bundles finally form 30–100 nm ribbon-like structures. The ribbons are highly porous and have 3D fibrous network.

Figure 1.

(A) A schematic illustration of BNC production. (B) Schematic illustration of biochemistry of cellulose synthesis in a bacterial cell and the extracellular transport of cellulose chains and the formation of highly ordered structures. (C) Chemical structure of BNC. (D) Schematic illustration of the aerosol-assisted biosynthesis of BNC [12].

For many years, many researches have been focused on BNC production. Various culture methods have been used by controlling the fermentation conditions to increase the yield of BNC or obtain BNC with different characteristics [16]. Under static culture conditions, bacteria need to float on the surface of the medium to obtain enough oxygen, and cellulose microfibrils are extruded from the bacteria and synthesize a tight BNC pellicle. The BNC formed under static conditions usually has high crystallinity and tensile strength. In contrast, a fluffy, spherical, or irregular lump BNC was obtained via the agitating culture method. Although the agitating culture has faster cell growth rate than static conditions because of more oxygen filling in the culture medium, the production of BNC decreased, which perhaps due to the uniform aeration of cultures induced cells to grow intensively instead of the polymer synthesis. Based on this, the bioreactors have been developed that can produce BNC pellicles at higher yields under static conditions (Figure 1D) [12].

2.2 Properties of BNC

Compared to vegetal cellulose, its unique chemical composition and physical structure endows BNC with numerous unparalleled physical, chemical, and biological properties (Figure 2). BCN is an attractive candidate for widespread applications in various fields, especially in applications related to biomedical.

Figure 2.

A schematic representation of properties of BNC.

2.2.1 Physical properties

BNC has natural 3D porous network structure, which is composed of nanofibers and exhibits enormous mechanical properties. The Young’s modulus of BNC sheets up to 15 GPa, which is much greater than plant cellulose and several synthetic fibers [17]. The excellent mechanical properties make BNC to be used for blood vessels and bone tissue engineering. The water holding capacity of BNC is about 100 times its dry weight, which is attributed to the high surface area and pore volume of BNC that can intercept more water [18]. In addition, the average diameter of BNC nanofibers is 1.5 nm, showing higher surface area and flexibility. These fascinating physical properties make BNC become desirable wound dressing material.

2.2.2 Chemical properties

BNC is composed of linear homopolysaccharides conjugated by β-D-glucose units linked by 1,4-β-glycosidic linkages and has considerably higher crystallinity (80–90%) and degree of polymerization (up to 8000), which means that pure BNC can be obtained with simple processing. The abundant hydroxyl groups and high-level hydrogen bonds on the surface of BNC nanofibers allow for manipulation in their loading of functional molecules. Although BNC exhibits significant intrinsic characteristics, it is still necessary to develop more modified properties of BNC to meet the requirements of the required biomedical applications.

2.2.3 Biological properties

BNC has wide applications in biomedical engineering because of its excellent biological properties. Héctor and coworkers confirmed the nontoxicity and extremely low bacterial endotoxin of BNC nanofibers by using in vitro and in vivo tests [19]. In addition, the good biocompatibility of BNC is due to its peculiar 3D nanofibrous network structure that supports cell penetration and proliferation. Helenius et al. subcutaneously implanted the BNC in rats to systematically evaluate the biocompatibility of BNC [20]. The results showed no inflammation around the implants and the fibroblasts infiltrated BNC, which indicates the good biocompatibility of BNC and has the potential to be used as a scaffold in tissue engineering.

3. Fabrication of BNC biomaterials

Although the above excellent inherent characteristics make BNC have broad application prospects in the field of biomedical, pure BC possesses certain restrictions that limit its application due to the lack of unique biological functions. In recent years, several approaches have been developed to improve the physicochemical properties and function of BNC, including producing BNC composites, surface medication, and changes in porosity. These efforts have significantly improved the surface properties and biological functions of BNC and tremendously expanded its application in various tissue engineering fields.

3.1 Surface modifications

3.1.1 Physical modifications

The BNC nanofibers were physical modifications by using bioactive materials, which not only preserves the unique properties but also enhances the biological functions to meet the requirements of biomedical applications. To improve the biocompatibility of BNC, Luo et al. selected a new type of coating, chondroitin sulfate (CS) modified with gelatin (Gel), to modify BNC scaffold [21]. The coating on the surface of the BNC nanofibers is linked by hydrogen bonding. The results of in vitro cell studies indicated that the CS/Gel coatings significantly promote cell proliferation, adhesion, differentiation, and ingrowth into scaffolds. Nanomaterials can also be used for surface modification of BNC. He et al. developed a Cu²⁺ loaded phase-transited lysozyme (PTL) nanocoating for surface modification of BNC. The coating endowed the BNC with inhibiting bacterial growth and inflammation and simultaneously induced vascularization, collagen deposition, and reepithelialization of wounds promising dressings for healing infected wound, which was considered a promising dressing for treating infected wounds. In addition, polymer composite nanoparticles are also used for surface modification of fibers. Ma et al. developed a homogeneous AgNP-loaded polydopamine (PDA)/polyethyleneimine (PEI) coating on the surface of BNC nanofibers, which exhibited excellent antibacterial activities and cytocompatibility [22].

3.1.2 Chemical modifications

The only surface functional group on the surface of BNC nanofibers is the hydroxyl group, which is not suitable for cell proliferation [23]. Nevertheless, the hydroxyl groups on the surface of BNC nanofibers are beneficial for surface chemical modifications; they can be treated with various chemical reagents tomodify their chemical structure and incorporate additional functionalities. Therefore, the surface chemical modifications of BNC are required for biomedical applications. Oxidation is an important reaction for adding new functional groups to BNC, which creates infinite possibilities for the functionalization of BNC nanofibers. TEMPO (2,2,6,6-Tetramethylpiperidinyloxy or 2,2,6,6-Tetramethylpiperidine-1-oxyl radical)-mediated oxidization is a simple and effective chemical reaction, in which C₆ of a hydroglucose units selectively gain an anionic carboxyl group [24]. A new bone repair composite scaffold (CS/OBC/nHAP) was constructed by evenly dispersing the in situ crystalline nano-hydroxyapatite (nHAP) in oxidized bacterial cellulose (OBC) and chitosan (CS) scaffolds [7]. Shahriari-Khalaji et al. achieved high carboxylate content by optimizing the TEMPO-mediated oxidation of BNC and then covalently bonded the ε-poly-L-lysine (PLL) with oxidized BNC to develop an O-BNC-based functional wound dressing [25]. Furthermore, Xie et al. prepared biofunctional group-modified bacterial cellulose (DCBC) by carboxymethylation and selective oxidation to achieve the perfect compound of cellulose and chitosan [26]. The obtained BNC-based dressing can effectively inhibit bacterial proliferation in wounds and kill the bacteria.

3.2 BNC-based composites

3.2.1 BNC nanocomposites

To improve the mechanical and biological properties of BNC biomaterials, various BNC-based nanocomposites were prepared by incorporating different kinds of nanomaterials, including carbon-based nanoparticles (NPs) [27], metal/metal oxide NPs [28], and other inorganic NPs [29]. The simplest and most convenient method for fabricated BNC nanocomposites is the mechanical mixing method. Yang et al. prepared the BNC/Ti3C2Tx nanocomposites using mechanical mixing. Although this strategy allows for sufficient mixing of nanomaterials with BNC nanofibers, it damages the intrinsically continuous 3D structure of BNC. To maintain the intrinsically continuous 3D structure of BC, Luo et al. developed a cost-effective, scalable, and efficient approach, membrane-liquid interface (MLI) culture, to prepare BNC-based nanocomposite [30]. The MLI culture technology is schematically illustrated in Figure 3A [31]. First, a layer of BNC film (around 3 mm in thickness) was grown as a substrate using a conventional static culture method. Then, a nanomaterials-dispersed medium was sprayed onto the BNC substrate followed by the culturing of BNC on the substrate–medium interface. After the sprayed medium was completely consumed off by the BNC growth, another layer of the medium was sprayed. This process was repeated until the designed thickness was achieved. It is noted that the thickness of nanocomposites prepared using the MLI method can be accurately controlled by the spray cycles of the medium. In addition, the sample shape and dimension can be facially designed by the geometry of the containers used for the preparation. This method has been widely used to prepare various nanocomposites (Figure 3B) [12].

Figure 3.

(A) Schematic illustration of the preparation of BNC nanocomposites by using membrane-liquid interface culture technology [31]. (B) SEM and photographs of BC-based nanocomposites were prepared by using membrane-liquid interface culture technology [12].

3.2.2 BNC-based biocomposites

Compared with other natural biopolymers, pristine BNC lacks cytocompatibility and important biological functions. The abundant ∙OH groups on the surface of BNC provide binding stable sites for biopolymers in biocomposites. Therefore, various techniques including in situ addition, solution impregnation, and chemical cross-linking were used to combine various bioactive substances to obtain the BNC-based biocomposites with enhanced physicomechanical, antimicrobial, and biocompatible properties. In order to enhance the antibacterial properties and cytocompatibility of BNC, Zhou et al. composited the collagen I (Col-I) and the antibacterial agent hydroxypropyltrimethyl ammonium chloride chitosan (HACC) into the BNC 3D network structure by a novel membrane-liquid interface (MLI) culture (Figure 4A and B) [32]. The introduction of HACC and Col-I makes BNC have outstanding antibacterial properties and improved cytocompatibility to promote NIH3T3 cell and HUVEC proliferation and spread (Figure 4C). The BNC-(polypyrrole) Ppy composites were prepared to mimic the natural myocardial microenvironment by in situ polymerization [33]. The composites were flexible and still maintained 3D network structure and displayed electrical conductivities in the range of native cardiac tissue. Wan et al. reported extracellular matrix (ECM)-mimetic scaffolds by conjugating electrospun cellulose acetate (CA) submicrofibers with BNC nanofibers via a facile and scalable dispersion freeze-drying process [34]. It is found that the composites have a 3D porous network structure and improved cell behavior.

Figure 4.

(A) Schematic illustration of the preparation of BNC-based biocomposites. (B) SEM images of BNC-based biocomposites. (C) The characteristice of BNC-based biocomposites [32].

3.3 3D porous BNC scaffold

As a promising biomaterial, BNC has some intrinsic disadvantages when applied in tissue engineering; its dense nanofibrous network (the pore sizes of pristine BNC are only approximately 0.02–10 μm) markedly limits cell migration and 3D tissue regeneration. To date, different methods have been reported for the fabrication of 3D porous BNC scaffolds. The paraffin microparticles, potato starch, agarose microparticles, and gelatin microspheres as porogens have also been used to fabricate 3D porous BNC scaffolds by using the in situ porogen technique [35, 36, 37, 38]. Cui et al. described the utilization of gelatin microspheres in BNC production for porosity enhancement, and the observed porosity depended on the diameter of microspheres (Figure 5A) [36]. However, a nonuniform pore structure would be formed due to the bacteria moving to the air/medium interface during the culture process of the in situ porogen impregnation technique.

Figure 5.

Different 3D porous BNC scaffolds were fabricated by using in situ porogen [34], laser patterning [39], freeze-drying and cross-linking [40], and 3D bioprinting [41].

Laser patterning as an efficient method is used to prepare 3D porous BNC scaffold. Laser treatment has universality, and the obtained scaffolds do not contain pollutants and chemical cross-linking agents, thereby having better biocompatibility. The pore structure prepared by laser is parallel microchannels. Yang et al. fabricated the nano-submicrofibrous cellulose scaffolds with microchannels by laser-aided punching (Figure 5B) [39]. The cell study found that the presence of microchannels favors cell proliferation and migration at an optimum microchannel size. However, laser-aided punching prepared microchannels can lead to cell leakage from the scaffold, making it difficult to achieve 3D culture.

Freeze-drying is the most common technique for preparing a 3D porous BNC scaffold, which can obtain the BNC sponges with higher porosity and specific surface. However, the pore size of freeze-dried BNC sheets is unable to precisely regulate, and the pore structure is instability. Therefore, improvements need to be made to address these issues. Xun et al. first reported an improved strategy to fabricating 3D macroporous BNC scaffolds with controllable pore size by freeze-drying and cross-linking the mechanically disintegrating shortcut BNC nanofiber suspensions (Figure 5C) [40]. The pore sizes of the MP-BNC scaffolds were controlled by adjusting the concentration of BNC in the suspensions. The fabrication process was facile, scalable, and effective in controlling the pore structure. The cross-linked BNC scaffolds exhibited excellent compression properties and shape recovery ability compared to the original BNC. Moreover, the results of in vitro and in vivo studies demonstrated that the scaffolds had excellent biocompatibility and were effective in regenerating cartilage tissue.

Additive manufacturing or 3D printing is an emerging technology to prepare 3D porous scaffolds through rapid prototyping. In recent years, it has been widely used in personalized customization of tissue engineering scaffolds. Li et al. used the gelatin methacrylate (GelMA)/BNC bioink formulations to develop heterogeneous tissue-engineered skin (HTS) containing layers of fibroblast networks with larger pores, basal layers with smaller pores, and multilayered keratinocytes (Figure 5D) [41]. The results revealed that the 10%GelMA/0.3%BNC bioink was better to bioprint dermis due to its high printability and cell-friendly sparse microenvironment. The approaches developed in the above-described studies and their findings suggest that BNC has great potential to be printed into 3D microstructures for the development of scaffolds and medical devices for various biomedical applications.

4. Biomedical applications of BNC

In the past two decades, BNC has aroused great attention to fundamental and scientific research for biomedical applications due to its unique properties [42]. Functionalized BNC and its composites have been applied in several medical applications, such as wound dressing, bone and cartilage tissue regeneration, and the development of artificial organs and blood vessels’ substitutes (Figure 6) [23, 43]. This section focuses on the research progress of the main biomedical applications of BNC in recent years.

Figure 6.

A schematic representation of the potential biomedical applications of BNC biomaterials.

4.1 Wound healing

The skin is the main protective barrier of the human body and has many functions, such as controlling body temperature and maintaining a balance of electrolytes and water [44]. However, large-scale skin damage caused by trauma, ulcers, and burns is difficult to heal on its own and requires human intervention to promote wound healing [45, 46]. Wound dressings have been developed to prevent infection and dehydration of wound, reduce inflammatory responses, and promote wound healing. BNC is one of the most promising wound dressings due to its ultrafine 3D network structure, excellent gas permeability, high water absorbency, and favorable biocompatibility [47]. Furthermore, BNC-based dressings can also prevent bacterial invasion, absorb excess exudates, and retain moisture in wounds to promote the growth of granulation.

In the healing process, it is important to prevent bacterial infection on the wound site. However, BNC does not have intrinsic bactericidal properties to eliminate the colonized bacteria. Therefore, the initial research focus was on antibacterial BNC-based dressings. Hence, various promising antibacterial agents are introduced into BNC, such as metals and their oxides, antimicrobial peptides, and biological and synthetic polymers (chitosan) [48]. Ao et al. fabricated the quaternized chitosan (HACC)/BNC antibacterial wound dressing by using in situ synthesis possessed, and the obtained dressing had favorable antibacterial properties [49]. To further improve the antibacterial properties of BNC dressings, silver nanoparticles (AgNPs) were introduced into the BNC structure [22]. The results of the standard plate count assay indicated that the antibacterial BNC dressing showed antibacterial rates of over 99.9% against Escherichia coli and Staphylococcus aureus. The in vivo assay demonstrated that the antibacterial BNC dressing could inhibit infection and inflammation and accelerate wound healing within 12 days compared with BNC. To reduce the cytotoxicity of sliver-based dressing and promote wound healing, a novel multifunctional sliver nanowires (AgNWs)/collagen I (Col I)/BNC dressing was constructed via compositing AgNWs into BNC and adsorbing Col I [50]. The antibacterial assay demonstrated that the multifunctional AgNWs/Col I/BNC dressing could kill S. ausreus and E. coli colonizing on the surface of material due to the silver ions released. Importantly, this dressing had lower cytotoxicity and promoted collagen deposition, hair follicle growth, neovascularization, and wound healing. A novel copper ion (Cu²⁺)-loaded BNC-based antibacterial wound dressing was prepared via codeposition of polydopamine (PDA) and Cu²⁺ [51]. The in vivo study revealed that the dressing can eliminate S. aureus infections and inflammatory response and promote collagen deposition, capillary angiogenesis, and wound healing.

In addition, BNC composites containing nanomaterials, biopolymers, antioxidants, antibiotics, and blood clotting agents have been fabricated to improve the wound healing of BNC-based dressings. Cai et al. fabricated a composite adhesive organo hydrogel by introducing BNC and platelet-rich plasma (PRP) into a poly-N-(tris[hydroxymethyl]methyl)acrylamide (THMA)/N-acryloyl aspartic acid (AASP) hybrid gel network infiltrated with glycerol/water binary solvent [52]. The PRP-loaded organo hydrogel has good tissue adhesion properties and releases a variety of growth factors to accelerate the wound healing process through collagen deposition and angiogenesis. Shen et al. developed an aggregation-induced emission (AIE) molecule BITT-composited BNC for wound healing [53]. The BNC-BITT composites retained the advantages of biocompatible of BNC and displayed photodynamic and photothermal synergistic antibacterial effects under irradiation of a 660 nm laser, which endowed the dressings with excellent wound healing performance in a mouse full-thickness skin wound model infected by multidrug-resistant bacteria. In response to hemostasis and repair of irregular and deep skin wounds, an injectable aldehyde BNC/polydopamine (DBNC/PDA) photothermal cryogel was prepared by oxidation polymerization method [6]. The PDA enhances the photothermal properties of DBNC/PDA cryogel to kill most bacteria and provides wound protection under near-infrared light. Otherwise, the DBNC/PDA low temperature gel has rapid hemostatic effect in the face of irregular and deep skin wounds. It is worth noting that the nanoenzyme with excellent peroxidase (POD) activity has been used to prepare BNC-based wound dressing. Zhang et al. introduced the metal-organic frameworks (MOF)-based nanocatalysts loaded with glucose oxidase (GOx) into the BNC-reinforced hydrogel for the treatment of diabetic foot ulcers [54]. The designed nanoenzyme could effectively catalyze the decomposition of glucose and in situ generate •OH for bacteria killing. In addition, this nanoenzyme-based hydrogel exhibited excellent hemostatic properties owing to the enhanced absorption capacity.

4.2 Bone/cartilage tissue regeneration

Another area of potential exciting application for BNC biomaterial is bone/cartilage tissue engineering due to its biomimetic ECM properties, excellent mechanical properties, and highly porous structure [7, 55, 56]. Biosynthetic BNC has some intrinsic disadvantages (the dense nanofibrous network) that markedly limit its applications in tissue engineering. However, the in situ biosynthetic BNC could serve as a surface coating for Ti implants to improve their biological function [57, 58]. Liu et al. reported a metal ions-containing BNC coating for functional Ti implant by in situ biosynthesis on the surface of Ti with complex shapes [59]. The results of in vitro and in vivo experiments confirmed that the functional BNC coating on the Ti can integrate the operative crevices and promote osteogenesis. To optimize the pore structure of BNC to meet the requirements of bone and cartilage tissue, Xun et al. developed a 3D macroporous BNC scaffold by freeze-drying and cross-linking the BNC shortcut nanofibers [40]. After the 3D macroporous BNC scaffolds were implanted into nude mice subcutaneously for 8 weeks, the neocartilage tissue with native cartilage appearance and abundant cartilage-specific extracellular matrix deposition was successfully regenerated. To construct the BNC scaffolds with structurally and biochemically biomimetic cartilage tissue microenvironment, the 3D hierarchical porous BNC/decellularized cartilage extracellular matrix (DCECM) scaffold was fabricated by freeze-drying technique after EDC/NHS chemical crosslinking [60]. The in vitro and in vivo tests indicated that the BC/DCECM scaffolds achieved satisfactory neocartilage tissue regeneration with superior original shape fidelity, exterior natural cartilage-like appearance, and histologically cartilage-specific lacuna formation and ECM deposition. Ling et al. fabricated a hierarchically porous SF/BC/MXene (FSCM) scaffold with ~20.0 μm macropore and nanofibrillar wall, which has excellent bone defect repair ability [61]. In addition, the BNC can also be used for the osteochondral repair. Lou et al. designed a bilayer structure osteochondral scaffold with a dense γ-Polyglutamic acid/carboxymethyl chitosan/BNC (PGA/CMCS/BNC) hydrogel cartilage layer and a porous nano HA-containing PGA/CMCS/BNC hydrogel osteogenic layer [62]. The in vivo experiments indicated that the scaffold with bioactive ions had a much better effect on the repair of osteochondral defects.

4.3 Blood vessels

BNC is a possible material to use for artificial blood vessels for small- or large-sized vascular grafts due to its good mechanical strength (a burst pressure of up to 880 mmHg), blood biocompatibility, and moldability [63]. The bioreactor to produce tubular BNC was developed to prepared BNC-based vascular grafts with excellent cytocompatibility and hemocompatibility [64, 65]. A tubular BNC graft with greater mechanical strength and thinner walls was obtained by mercerization; this technology made fewer platelets adhere to the luminal surface and promoted the proliferation of endothelial cells [63]. Mimicking the morphological structure of native blood vessels is critical for the development of vascular grafts. Vascular grafts with BNC nanofibers and submicrofibrous cellulose acetate (CA) were fabricated to mimic the morphological structure of native blood vessels. Regulating the content of BNC can reduce the thrombosis potential of stents and enhance endothelialization.

4.4 Other biomedical application

In addition to the above biomedical applications, BNC has been applied in other biomedical fields, such as nerve repair [66, 67] and muscle [33], corneal [68, 69], urethral [70], and intervertebral disc [71]. These researches will be sure of certain theoretical value and practical significance to the biomedical application of BNC.

5. Conclusion

In this chapter, we provide an overview of the fabrication and biomedical application of BNC-based biomaterials. First, the biosynthesis of BNC in biology, chemistry, and physics is introduced, and the properties of BNC are summarized. Furthermore, we introduce and discuss the various techniques to fabricate BNC-based composites and 3D porous BNC scaffolds to enhance the mechanical and biological properties. Due to the rapid development of the abovementioned technologies, BNC has a broad range of applications in biomedicine, including wound dressing, bone/cartilage tissue regeneration, vascular tissue engineering, and so on.

Acknowledgments

This work was supported by National Natural Science Foundation of China (grant nos. 82160355), the Science and Technology Research Project of Jiangxi Education Department (grant nos. GJJ2200657), and Natural Science Foundation of Jiangxi Province (grant nos. 20212ACB214002).

Conflict of interest

The authors declare no conflict of interest.