Reverse Reconstruction and Bioprinting of Bacterial Cellulose-Based Functional Total Intervertebral Disc for Therapeutic Implantation

Bacterial cellulose: Is it really a promising biomedical material?

Bacterial cellulose (BC) is currently considered a promising biomaterial due to its specific structure and properties. However, despite extensive research, questions about its fundamental properties, especially biocompatibility, remain. Thus, the purpose of this review is to analyze the results of in vivo trials from different areas of biomedicine, including wound healing, tissue engineering, drug delivery, and biomedical implants. The primary question guiding our review was "Why is bacterial cellulose still not used in clinical practice?" Analysis of the literature has shown that the results of in vivo studies often contradict each other. For example, BC caused and did not cause an immune response in an equal number of reviewed articles. Its efficacy in pure form generally does not differ significantly from that of materials already on the market. Conversely, BC may prove to be a valuable material in the long term, not because of its efficacy, but rather because of its affordability and ease of use. Additionally, challenges associated with immune reactions, long-term biocompatibility, and the necessity for standardized experimental protocols must be addressed. We expect that this review will encourage a more thoughtful investigation of BC to bring it into practical medicine.

Biomimetic Microchannel Integrated Silk Fibroin Scaffold for Regeneration of Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is the primary cause of low back pain, and patients with severe degeneration usually require lumbar fusion or total disc arthroplasty. Lumbar fusion carries the risk of accelerated degeneration of the adjacent intervertebral disc (IVD), and total disc arthroplasty could reduce the risk. However, the clinical application of artificial IVD whose nondegradable properties make it difficult to restore the biological function of the IVD. Therefore, we intend to fabricate a novel biomimetic microchannel integrated silk fibroin scaffold (BMI-SF scaffold) containing annulus fibrosus with oriented cross-microchannels and nucleus pulposus with interconnected porous structure. The BMI-SF scaffold exhibits controllable microchannels as well as excellent biocompatibility and biodegradability. In vitro and in vivo studies have demonstrated that microchannels can direct cells into the BMI-SF scaffold and enhance neovascularization, supplying adequate nutritional support for tissue regeneration. The IVD replacement model showed that the BMI-SF scaffold has superior regenerative effects, such as restoring IVD height and providing motion segments with dynamic mechanical properties akin to the natural IVD. In this study, the BMI-SF scaffold developed using controlled microchannels provides a new strategy for patients with severe IVDD and has broad clinical application prospects.

Suspension bioprinted whole intervertebral disc analogues enable regional stiffness- and hypoxia-regulated matrix secretion by primary human nucleus pulposus and annulus fibrosus cells

Intervertebral disc (IVD) degeneration is a leading cause of back pain, and while studies have revealed the roles resident nucleus pulposus (NP) and annulus fibrosus (AF) cells play in degeneration, tissue-engineered IVD models are needed to better investigate the mechanisms underpinning these cell-driven changes. This study therefore integrated suspension baths with bioprinting to create four multi-material, whole IVD analogues and investigated the combined effect of reduced oxygen tension and increased regional matrix stiffness on disc cell phenotype since these factors correlate with IVD degeneration. Primary NP and AF cells were seeded into alginate-collagen hydrogels and bioprinted into biphasic IVD structures. The nascent area, intensity, and integrated density of pro-collagen type I, collagen type VI, aggrecan, and hyaluronic acid were quantified using immunofluorescence staining in each region. Stiffness-mediated collagen and glycosaminoglycan production was observed in the AF, and increased stiffness downregulated collagen type VI in the AF but upregulated it in NP. Oxygen tension impacted proteoglycan production, with hypoxia increasing aggrecan and hyaluronic acid in both regions. This work represents a step towards the automated biofabrication of whole IVD analogues and expands the state-of-the-art in suspension bioprinting using regionally specific matrix cues. The findings provide important insights into two key microenvironmental factors driving IVD degeneration. STATEMENT OF SIGNIFICANCE: This manuscript outlines an original application of suspended layer additive manufacturing to biofabricate novel, biphasic intervertebral disc analogues containing patient-derived primary human cells. Significantly, the bioprinted models demonstrated biological function and were used to assess the effect of stiffness and oxygen concentration on regional matrix production using a range of internationally-recognized phenotypic intervertebral disc cell markers. The study therefore furthers the state-of-the-art in suspended bioprinting using regionally specific matrix cues and paves the way for future bioprinted disc models that can serve as biosimulators capable of generating insights into key mechanisms governing tissue development, homeostasis, and degeneration.

Water Transport-Modulated Highly Compressive Hydrogel for Total Biomimetic Sensing Intervertebral Disc

Degenerative disc disease (DDD) affects millions globally, with artificial total disc replacement (A-TDR) emerging as a key surgical intervention to restore spinal function and mobility. Current implantable prostheses incorporating multi-component architectures to replicate the functional heterogeneity of natural intervertebral discs (IVD) face challenges in achieving mechanical and physiological compatibility. Inspired by the natural IVD's structure, where a soft nucleus pulposus (NP) is encased by a tough annulus fibrosus (AF), a water transport-modulated directional annealing casting (DAC) approach has been developed to construct bulk hydrogels with tunable mechanical properties (up to ≈36.69 MPa compressive strength with ≈5.35 MPa modulus). This strategy enables the fabrication of an integrated hydrogel-based IVD (H-IVD) with biomechanically gradient structures, featuring a high-strength AF region (compressive modulus ≈2.77 MPa) seamlessly transitioning to a compliant NP core (modulus ≈0.26 MPa) while maintaining physiological water content throughout. The H-IVD exhibits excellent biocompatibility and load-bearing capacity, with inherent stress-sensing capabilities enabling dynamic functional assessment of spinal biomechanics. Furthermore, this integrated design strategy demonstrates broad applicability for engineering various dimensionally-controlled biomimetic tissues, from simple 1D structures to complex 3D organs requiring precise spatial control of material properties.

Recent Advances in Modeling Tissues Using 3D Bioprinted Nanocellulose Bioinks

Bioprinting creates 3D tissue models by depositing cells encapsulated in biocompatible materials. These 3D printed models can better emulate physiological conditions in comparison with traditional 2D cell cultures or animal models. Such models can be produced from human cells, possessing human genetics and replicating the 3D microenvironment found in vivo. Many different types of biocompatible materials serve as bioinks, including gelatin methacryloyl (GelMA), alginate, fibrin, and gelatin. Nanocellulose has emerged as a promising addition to these materials. Nanocellulose─composed of cellulose chain bundles with lateral dimensions ranging from a few to several tens of nanometers─possesses key properties for 3D bioprinting applications. It can form biocompatible hydrogels, which have excellent physical properties, and its structure resembles collagen, making it useful for modeling tissues with high collagen content such as bone, cartilage, sink, and muscle. Here we review some of the recent advances in the use of nanocellulose in bioinks for the creation of bone, cartilage, skin, and muscle tissue specific models and identify areas for future progress.

Hyaluronan composite bioink preserves nucleus pulposus cell phenotype in a stiffness-dependent manner

Intervertebral disc degeneration is a major cause of neck and back pain, representing a significant global socioeconomic burden. The polysaccharide hyaluronan is key to maintaining disc physiology and mediating disc disease through its structural and biological roles in the nucleus pulposus, a component of the intervertebral disc highly susceptible to degeneration. In this study, we introduce a novel composite bioink designed for extrusion bioprinting of structures resembling the nucleus pulposus. Our bioink combines levels of hyaluronic acid and collagen that approach physiological concentrations and effectively mimics the disc's hydrated and mechanically resilient environment. We modulated the composite's mechanical properties through the tyramination of hyaluronic acid and subsequent photocrosslinking, influencing morphology and gene expression of embedded bovine nucleus pulposus cells. This allows us to replicate a range of properties from healthy to degenerated human nucleus pulposus, which would be challenging to achieve with traditional cell culture and in vivo models. Our results show that modulating hyaluronan physico-chemical properties influenced embedded cell phenotype. The outcomes of this study inform the future design of biomaterials for the modelling of disc disease and regeneration, and present a versatile platform that can be readily integrated with other biofabricated components to form engineered intervertebral disc-like structures.

Polysaccharide-based biomaterials for regenerative therapy in intervertebral disc degeneration

Intervertebral disc (IVD) degeneration represents a significant cause of chronic back pain and disability, with a substantial impact on the quality of life. Conventional therapeutic modalities frequently address the symptoms rather than the underlying etiology, underscoring the necessity for regenerative therapies that restore disc function. Polysaccharide-based materials, such as hyaluronic acid, alginate, chitosan, and chondroitin sulfate, have emerged as promising candidates for intervertebral disc degeneration (IVDD) therapy due to their biocompatibility, biodegradability, and ability to mimic the native extracellular matrix (ECM) of the nucleus pulposus (NP). These materials have demonstrated the capacity to support cell viability, facilitate matrix production, and alleviate inflammation in vitro and in vivo, thus supporting tissue regeneration and restoring disc function in comparison to conventional treatment. Furthermore, polysaccharide-based hydrogels have demonstrated the potential to deliver bioactive molecules, including growth factors, cytokines and anti-inflammatory drugs, directly to the degenerated disc environment, thereby enhancing therapeutic outcomes. Therefore, polysaccharide-based materials provide structural support and facilitate the regeneration of native tissue, representing a versatile and effective approach for the treatment of IVDD. Despite their promise, challenges such as limited long-term stability, potential immunogenicity, and the difficulty in scaling up production for clinical use remain. This review delineates the potential of various polysaccharides during the fabrication of hydrogels and scaffolds for disc regeneration, guiding and inspiring future research to focus on optimizing these materials for clinical translation for IVDD repair and regeneration.

Electric stimulation: a versatile manipulation technique mediated microbial applications

Electric stimulation (ES) is a versatile technique that uses an electric field to manipulate microorganisms individually. Over the past several decades, the capabilities of ES have expanded from bioremediation to the precise motion control of cells and microorganisms. However, there is limited information on the underlying mechanisms, latest advancement and broader microbial applications of ES in various fields, such as the production of extracellular polymers with upgraded properties. This review article summarizes recent advancements in ES and discusses it as a unique external manipulation technique for microorganisms with wide applications in bioremediation, industry, biofilm deactivation, disinfection, and controlled biosynthesis. One specific application of ES discussed in this review is the extracellular biosynthesis, regulation, and organization of extracellular polymers, such as bacterial cellulose nanofibrils, curdlan, and microbial nanowires. Overall, this review aims to provide a platform for microbial biotechnologists and synthetic biologists to leverage the manipulation of microorganisms using ES for bio-based applications, including the production of extracellular polymers with enhanced properties. Researchers can engineer, manipulate, and control microorganisms for various applications by harnessing the potential of electric fields.

Polyphenol-modified biomimetic bioadhesives for the therapy of annulus fibrosus defect and nucleus pulposus degeneration after discectomy

Discectomy is the surgical standard of care to relieve low back pain caused by intervertebral disc (IVD) herniation. However, there remains annulus fibrosus (AF) defect and nucleus pulposus (NP) degeneration, which often result in recurrent herniation (re-herniation). Herein, we develop a polyphenol-modified waterborne polyurethane bioadhesives (PPU-glues) to promote therapy prognosis after discectomy. Being composed of tannic acid (TA) mixed cationic waterborne polyurethane nanodispersions (TA/WPU+) and curcumin (Cur) embedded anionic waterborne polyurethane nanodispersions (Cur-WPU-), PPU-glue gels rapidly (<10 s) and exhibits low swelling ratios, tunable degradation rates and good biocompatibility. Due to the application of an adhesion strategy combing English ivy mechanism and particle packing theory, PPU-glue also shows considerable lap shear strength against wet porcine skin (≈58 kPa) and burst pressure (≈26 kPa). The mismatched particle sizes and the opposite charges of TA/WPU+ and Cur-WPU- in PPU-glue bring electrostatic interaction and enhance particle packing density. PPU-glue possesses superior reactive oxygen species (ROS)-scavenging capacity derived from polyphenols. PPU-glue can regulate extracellular matrix (ECM) metabolism in degenerated NP cells, and it can promote therapy biologically and mechanically in degenerated rat caudal discs. In summary, this study highlights the therapeutic approach that combines AF seal and NP augmentation, and PPU-glue holds great application potentials for post discectomy therapy. STATEMENT OF SIGNIFICANCE: Currently, there is no established method for the therapy of annulus fibrosus (AF) defect and nucleus pulposus (NP) degeneration after discectomy. Herein, we developed a polyphenol-modified biomimetic polyurethane bioadhesive (PPU-glue) with strong adhesive strength and superior bioactive property. The adhesion strategy that combined a particle packing theory and an English ivy mechanism was firstly applied to the intervertebral disc repair field, which benefited AF seal. The modified method of incorporating polyphenols was utilized to confer with ROS-scavenging capacity, ECM metabolism regulation ability and anti-inflammatory property, which promoted NP augmentation. Thus, PPU-glue attained the synergy effect for post discectomy therapy, and the design principle could be universally expanded to the bioadhesives for other surgical uses.

Cutting-Edge Biomaterials in Intervertebral Disc Degeneration Tissue Engineering

Intervertebral disc degeneration (IVDD) stands as the foremost contributor to low back pain (LBP), imposing a substantial weight on the world economy. Traditional treatment modalities encompass both conservative approaches and surgical interventions; however, the former falls short in halting IVDD progression, while the latter carries inherent risks. Hence, the quest for an efficacious method to reverse IVDD onset is paramount. Biomaterial delivery systems, exemplified by hydrogels, microspheres, and microneedles, renowned for their exceptional biocompatibility, biodegradability, biological efficacy, and mechanical attributes, have found widespread application in bone, cartilage, and various tissue engineering endeavors. Consequently, IVD tissue engineering has emerged as a burgeoning field of interest. This paper succinctly introduces the intervertebral disc (IVD) structure and the pathophysiology of IVDD, meticulously classifies biomaterials for IVD repair, and reviews recent advances in the field. Particularly, the strengths and weaknesses of biomaterials in IVD tissue engineering are emphasized, and potential avenues for future research are suggested.

From Nature-Sourced Polysaccharide Particles to Advanced Functional Materials

Polysaccharides constitute over 90% of the carbohydrate mass in nature, which makes them a promising feedstock for manufacturing sustainable materials. Polysaccharide particles (PSPs) are used as effective scavengers, carriers of chemical and biological cargos, and building blocks for the fabrication of macroscopic materials. The biocompatibility and degradability of PSPs are advantageous for their uses as biomaterials with more environmental friendliness. This review highlights the progresses in PSP applications as advanced functional materials, by describing PSP extraction, preparation, and surface functionalization with a variety of functional groups, polymers, nanoparticles, and biologically active species. This review also outlines the fabrication of PSP-derived macroscopic materials, as well as their applications in soft robotics, sensing, scavenging, water harvesting, drug delivery, and bioengineering. The paper is concluded with an outlook providing perspectives in the development and applications of PSP-derived materials.

Technologies for the fabrication of crosslinked polysaccharide-based hydrogels and its role in microbial three-dimensional bioprinting - A review

Three-Dimensional bioprinting has recently gained more attraction among researchers for its wide variety of applicability. This technology involving in developing structures that mimic the natural anatomy, and also aims in developing novel biomaterials, bioinks which have a better printable ability. Different hydrogels (cross-linked polysaccharides) can be used and optimized for good adhesion and cell proliferation. Manufacturing hydrogels with adjustable characteristics allows for fine-tuning of the cellular microenvironment. Different printing technologies can be used to create hydrogels on a micro-scale which will allow regular, patterned integration of cells into hydrogels. Controlling tissue constructions' structural architecture is the important key to ensuring its function as it is designed. The designed tiny hydrogels will be useful in investigating the cellular behaviour within the environments. Three-Dimensional designs can be constructed by modifying their shape and behaviour analogous concerning pressure, heat, electricity, ultraviolet radiation or other environmental elements. Yet, its application in in vitro infection models needs more research and practical study. Microbial bioprinting has become an advancing field with promising potential to develop various biomedical as well as environmental applications. This review elucidates the properties and usage of different hydrogels for Three-Dimensional bioprinting.

Production of Bacterial Exopolysaccharides: Xanthan and Bacterial Cellulose

Recently, degradable biopolymers have become increasingly important as potential environmentally friendly biomaterials, providing a wide range of applications in various fields. Bacterial exopolysaccharides (EPSs) are biomacromolecules, which due to their unique properties have found applications in biomedicine, foodstuff, textiles, cosmetics, petroleum, pharmaceuticals, nanoelectronics, and environmental remediation. One of the important commercial polysaccharides produced on an industrial scale is xanthan. In recent years, the range of its application has expanded significantly. Bacterial cellulose (BC) is another unique EPS with a rapidly increasing range of applications. Due to the great prospects for their practical application, the development of their highly efficient production remains an important task. The present review summarizes the strategies for the cost-effective production of such important biomacromolecules as xanthan and BC and demonstrates for the first time common approaches to their efficient production and to obtaining new functional materials for a wide range of applications, including wound healing, drug delivery, tissue engineering, environmental remediation, nanoelectronics, and 3D bioprinting. In the end, we discuss present limitations of xanthan and BC production and the line of future research.

TGF-β1-supplemented decellularized annulus fibrosus matrix hydrogels promote annulus fibrosus repair

Annulus fibrosus (AF) repair remains a challenge because of its limited self-healing ability. Endogenous repair strategies combining scaffolds and growth factors show great promise in AF repair. Although the unique and beneficial characteristics of decellularized extracellular matrix (ECM) in tissue repair have been demonstrated, the poor mechanical property of ECM hydrogels largely hinders their applications in tissue regeneration. In the present study, we combined polyethylene glycol diacrylate (PEGDA) and decellularized annulus fibrosus matrix (DAFM) to develop an injectable, photocurable hydrogel for AF repair. We found that the addition of PEGDA markedly improved the mechanical strength of DAFM hydrogels while maintaining their porous structure. Transforming growth factor-β1 (TGF-β1) was further incorporated into PEGDA/DAFM hydrogels, and it could be continuously released from the hydrogel. The in vitro experiments showed that TGF-β1 facilitated the migration of AF cells. Furthermore, PEGDA/DAFM/TGF-β1 hydrogels supported the adhesion, proliferation, and increased ECM production of AF cells. In vivo repair performance of the hydrogels was assessed using a rat AF defect model. The results showed that the implantation of PEGDA/DAFM/TGF-β1 hydrogels effectively sealed the AF defect, prevented nucleus pulposus atrophy, retained disc height, and partially restored the biomechanical properties of disc. In addition, the implanted hydrogel was infiltrated by cells resembling AF cells and well integrated with adjacent AF tissue. In summary, findings from this study indicate that TGF-β1-supplemented DAFM hydrogels hold promise for AF repair.

Intervertebral Disc Tissue Engineering Using Additive Manufacturing

Intervertebral disc (IVD) degeneration is one of the major causes of lower back pain, a common health condition that greatly affects the quality of life. With an increasing elderly population and changes in lifestyle, there exists a high demand for novel treatment strategies for damaged IVDs. Researchers have investigated IVD tissue engineering (TE) as a way to restore biological and mechanical functions by regenerating or replacing damaged discs using scaffolds with suitable cells. These scaffolds can be constructed using material extrusion additive manufacturing (AM), a technique used to build three-dimensional (3D), custom discs utilising computer-aided design (CAD). Structural geometry can be controlled via the manipulation of printing parameters, material selection, temperature, and various other processing parameters. To date, there are no clinically relevant TE-IVDs available. In this review, advances in AM-based approaches for IVD TE are briefly discussed in order to achieve a better understanding of the requirements needed to obtain more effective, and ultimately clinically relevant, IVD TE constructs.

Emerging polymeric material strategies for cartilage repair

Cartilage is found throughout the body, serving an array of essential functions. Owing to the limited healing capacity of cartilage, damage or degeneration is often permanent and so requires clinical intervention. Established surgical techniques generally rely on biological grafting. However, recent advances in polymeric materials provide an encouraging alternative to overcome limits of auto- and allografts. For regenerative engineering of cartilage, a polymeric scaffold ideally supports and instructs tissue regeneration while also providing mechanical integrity. Scaffolds direct regeneration via chemical and mechanical cues, as well as delivery and support of exogenous cells and bioactive factors. Advanced polymeric scaffolds aim to direct regeneration locally, replicating the heterogeneities of native tissues. Alternatively, new cartilage-mimetic hydrogels have potential to serve as synthetic cartilage replacements. Prepared as multi-network or composite hydrogels, the most promising candidates have simultaneously realized the hydration, mechanical, and tribological properties of native cartilage. Collectively, the recent rise in polymers for cartilage regeneration and replacement proposes a changing paradigm, with a new generation of materials paving the way for improved clinical outcomes.

Bacterial Cellulose-Based Polymer Nanocomposites: A Review

Bacterial cellulose (BC) is currently one of the most popular environmentally friendly materials with unique structural and physicochemical properties for obtaining various functional materials for a wide range of applications. In this regard, the literature reporting on bacterial nanocellulose has increased exponentially in the past decade. Currently, extensive investigations aim at promoting the manufacturing of BC-based nanocomposites with other components such as nanoparticles, polymers, and biomolecules, and that will enable to develop of a wide range of materials with advanced and novel functionalities. However, the commercial production of such materials is limited by the high cost and low yield of BC, and the lack of highly efficient industrial production technologies as well. Therefore, the present review aimed at studying the current literature data in the field of highly efficient BC production for the purpose of its further usage to obtain polymer nanocomposites. The review highlights the progress in synthesizing BC-based nanocomposites and their applications in biomedical fields, such as wound healing, drug delivery, tissue engineering. Bacterial nanocellulose-based biosensors and adsorbents were introduced herein.

Multifunctional Nanofibrous Scaffolds with Angle-Ply Microstructure and Co-Delivery Capacity Promote Partial Repair and Total Replacement of Intervertebral Disc

There is an urgent clinical need for the treatment of annulus fibrosus (AF) impairment caused by intervertebral disc (IVD) degeneration or surgical injury. Although repairing injured AF through tissue engineering is promising, the approach is limited by the complicated angle-ply microstructure, inflammatory microenvironment, poor self-repairing ability of AF cells and deficient matrix production. In this study, electrospinning technology is used to construct aligned core-shell nanofibrous scaffolds loaded with transforming growth factor-β3 (TGFβ3) and ibuprofen (IBU), respectively. The results confirm that the rapid IBU release improves the inflammatory microenvironment, while sustained TGFβ3 release enhances nascent extracellular matrix (ECM) formation. Biomaterials for clinical applications must repair local AF defects during herniectomy and enable AF regeneration during disc replacement, so a box defect model and total IVD replacement model in rat tail are constructed. The dual-drug delivering electrospun scaffolds are assembled into angle-ply structure to form a highly biomimetic AF that is implanted into the box defect or used to replace the disc. In two animal models, it is found that biomimetic scaffolds with good anti-inflammatory ability enhance ECM formation and maintain the mechanical properties of IVD. Findings from this study demonstrate that the multifunctional nanofibrous scaffolds provide inspirations for IVD repair.

Fucoidan-loaded nanofibrous scaffolds promote annulus fibrosus repair by ameliorating the inflammatory and oxidative microenvironments in degenerative intervertebral discs

Tissue engineering holds potential in the treatment of intervertebral disc degeneration (IDD). However, implantation of tissue engineered constructs may cause foreign body reaction and aggravate the inflammatory and oxidative microenvironment of the degenerative intervertebral disc (IVD). In order to ameliorate the adverse microenvironment of IDD, in this study, we prepared a biocompatible poly (ether carbonate urethane) urea (PECUU) nanofibrous scaffold loaded with fucoidan, a natural marine bioactive polysaccharide which has great anti-inflammatory and antioxidative functions. Compared with pure PECUU scaffold, the fucoidan-loaded PECUU nanofibrous scaffold (F-PECUU) decreased the gene and protein expression related to inflammation and the oxidative stress in the lipopolysaccharide (LPS) induced annulus fibrosus cells (AFCs) significantly (p<0.05). Especially, gene expression of Ill 6 and Ptgs2 was decreased by more than 50% in F-PECUU with 3.0 wt% fucoidan (HF-PECUU). Moreover, the gene and protein expression related to the degradation of extracellular matrix (ECM) were reduced in a fucoidan concentration-dependent manner significantly, with increased almost 3 times gene expression of Col1a2 and Acan in HF-PECUU. Further, in a 'box' defect model, HF-PECUU decreased the expression of COX-2 and deposited more ECM between scaffold layers when compared with pure PECUU. The disc height and nucleus pulposus hydration of repaired IVD reached up to 75% and 85% of those in the sham group. In addition, F-PECUU helped to maintain an integrate tissue structure with a similar compression modulus to that in sham group. Taken together, the F-PECUU nanofibrous scaffolds showed promising potential to promote AF repair in IDD treatment by ameliorating the harsh degenerative microenvironment. STATEMENT OF SIGNIFICANCE: Annulus fibrosus (AF) tissue engineering holds potential in the treatment of intervertebral disc degeneration (IDD), but is restricted by the inflammatory and oxidative microenvironment of degenerative disc. This study developed a biocompatible polyurethane scaffold (F-PECUU) loaded with fucoidan, a marine bioactive polysaccharide, for ameliorating IDD microenvironment and promoting disc regeneration. F-PECUU alleviated the inflammation and oxidative stress caused by lipopolysaccharide and prevented extracellular matrix (ECM) degradation in AF cells. In vivo, it promoted ECM deposition to maintain the height, water content and mechanical property of disc. This work has shown the potential of marine polysaccharides-containing functional scaffolds in IDD treatment by ameliorating the harsh microenvironment accompanied with disc degeneration.

Bacterial Cellulose and Its Applications

The sharp increase in the use of cellulose seems to be in increasing demand in wood; much more research related to sustainable or alternative materials is necessary as a lot of the arable land and natural resources use is unsustainable. In accordance, attention has focused on bacterial cellulose as a new functional material. It possesses a three-dimensional, gelatinous structure consisting of cellulose with mechanical and thermal properties. Moreover, while a plant-originated cellulose is composed of cellulose, hemi-cellulose, and lignin, bacterial cellulose attributable to the composition of a pure cellulose nanofiber mesh spun is not necessary in the elimination of other components. Moreover, due to its hydrophilic nature caused by binding water, consequently being a hydrogel as well as biocompatibility, it has only not only used in medical fields including artificial skin, cartilage, vessel, and wound dressing, but also in delivery; some products have even been commercialized. In addition, it is widely used in various technologies including food, paper, textile, electronic and electrical applications, and is being considered as a highly versatile green material with tremendous potential. However, many efforts have been conducted for the evolution of novel and sophisticated materials with environmental affinity, which accompany the empowerment and enhancement of specific properties. In this review article, we summarized only industry and research status regarding BC and contemplated its potential in the use of BC.

Bacterial cellulose-based biomaterials: From fabrication to application

Driven by its excellent physical and chemical properties, BC (bacterial cellulose) has achieved significant progress in the last decade, rendering with many novel applications. Due to its resemblance to the structure of extracellular matrix, BC-based biomaterials have been widely explored for biomedical applications such as tissue engineering and drug delivery. The recent advances in nanotechnology endow further modifications on BC and generate BC-based composites for different applications. This article presents a review on the research advancement on BC-based biomaterials from fabrication methods to biomedical applications, including wound dressing, artificial skin, vascular tissue engineering, bone tissue regeneration, drug delivery, and other applications. The preparation of these materials and their potential applications are reviewed and summarized. Important factors for the applications of BC in biomedical applications including degradation and pore structure characteristic are discussed in detail. Finally, the challenges in future development and potential advances of these materials are also discussed.

Bacterial Cellulose Properties Fulfilling Requirements for a Biomaterial of Choice in Reconstructive Surgery and Wound Healing

Although new therapeutic approaches for surgery and wound healing have recently made a great progress, there is still need for application of better and use novel methods to enhance biocompatibility as well as recovery and healing process. Bacterial Cellulose (BC) is natural cellulose in the form of nanostructure which has the advantages of being used in human body. The medical application of BC in reconstructive, cardiac and vascular surgery as well as wound healing is still under development, but without proved success of repetitive results. A review of studies on Bacterial Cellulose (BC) since 2016 was performed, taking into account the latest reports on the clinical use of BC. In addition, data on the physicochemical properties of BC were used. In all the works, satisfactory results of using Bacterial Cellulose were obtained. In all presented studies various BC implants demonstrated their best performance. Additionally, the works show that BC has the capacity to reach physiological as well as mechanical properties of relevance for various tissue replacement and can be produced in surgeons as well as patient specific expectations such as ear frames, vascular tubes or heart valves as well as wound healing dressings. Results of those experiments conform to those of previous reports utilizing ADM (acellular dermal matrix) and demonstrate that the use of BC has no adverse effects such as ulceration or extrusion and possesses expected properties. Based on preliminary animal as well as the few clinical data BC fittings are promising implants for various reconstructive applications since they are biocompatible with properties allowing blood flow, attach easily to wound bed and remain in place until donor site is healed properly. Additionally, this review shows that BC can be fabricated into patient specific shapes and size, with capability to reach mechanical properties of relevance for heart valve, ear, and muscle replacement. Bacterial cellulose appears, as shown in the above review, to be one of the materials that allow extensive application in the reconstruction after soft tissue defects. Review was created to show the needs of surgeons and the possibilities of using BC through the eyes and knowledge of biotechnologists.

Bacterial cellulose-based composites for biomedical and cosmetic applications: Research progress and existing products

Bacterial cellulose (BC) is a promising unique material for various biomedical and cosmetic applications due to its morphology, mechanical strength, high purity, high water uptake, non-toxicity, chemical controllability, and biocompatibility. Today, extensive investigation is into the manufacturing of BC-based composites with other components such as nanoparticles, synthetic polymers, natural polymers, carbon materials, and biomolecules, which will allow the development of a wide range of biomedical and cosmetic products. Moreover, the addition of different reinforcement substances into BC and the organized arrangement of BC nano-fibers have proven a promising improvement in their properties for biomedical applications. This review paper highlights the progress in synthesizing BC-based composites and their applications in biomedical fields, such as wound healing, drug delivery, tissue engineering, and cancer treatment. It emphasizes high-performance BC-based materials and cosmetic applications. Furthermore, it presents challenges yet to be defeated and future possibilities for BC-based composites for biomedical and cosmetic applications.

The Food-Materials Nexus: Next Generation Bioplastics and Advanced Materials from Agri-Food Residues

The most recent strategies available for upcycling agri-food losses and waste (FLW) into functional bioplastics and advanced materials are reviewed and the valorization of food residuals are put in perspective, adding to the water-food-energy nexus. Low value or underutilized biomass, biocolloids, water-soluble biopolymers, polymerizable monomers, and nutrients are introduced as feasible building blocks for biotechnological conversion into bioplastics. The latter are demonstrated for their incorporation in multifunctional packaging, biomedical devices, sensors, actuators, and energy conversion and storage devices, contributing to the valorization efforts within the future circular bioeconomy. Strategies are introduced to effectively synthesize, deconstruct and reassemble or engineer FLW-derived monomeric, polymeric, and colloidal building blocks. Multifunctional bioplastics are introduced considering the structural, chemical, physical as well as the accessibility of FLW precursors. Processing techniques are analyzed within the fields of polymer chemistry and physics. The prospects of FLW streams and biomass surplus, considering their availability, interactions with water and thermal stability, are critically discussed in a near-future scenario that is expected to lead to next-generation bioplastics and advanced materials.

Tissue-Engineering of Human Intervertebral Disc: A Concise Review

Intervertebral disc (IVD) represents a structure of crucial structural and functional importance for human spine. Pathology of IVD institutes a frequently encountered condition in current clinical practice. Degenerative Disc Disease (DDD), the principal clinical representative of IVD pathology, constitutes an increasingly diagnosed spinal disorder associated with substantial morbidity and mortality in recent years. Despite the considerable incidence and socioeconomic burden of DDD, existing treatment modalities including conservative and surgical methods have been demonstrated to provide a limited therapeutic effect, being not capable of interrupting or reversing natural progress of underlying disease. These limitations underline the requirement for development of novel, innovative and more effective therapeutic strategies for DDD management. Within this literature framework, compromised IVD replacement with a viable IVD construct manufactured with Tissue-Engineering (TE) methods has been recommended as a promising therapeutic strategy for DDD. Existing preliminary preclinical data demonstrate that proper combination of cells from various sources, different scaffold materials and appropriate signaling molecules renders manufacturing of whole-IVD tissue-engineered constructs a technically feasible process. Aim of this narrative review is to critically summarize current published evidence regarding particular aspects of IVD-TE, primarily emphasizing in providing researchers in this field with practicable knowledge in order to enhance clinical translatability of their research and informing clinical practitioners about the features and capabilities of innovative TE science in the field of IVD-TE.

Plant Nanomaterials and Inspiration from Nature: Water Interactions and Hierarchically Structured Hydrogels

Recent developments in the area of plant-based hydrogels are introduced, especially those derived from wood as a widely available, multiscale, and hierarchical source of nanomaterials, as well as other cell wall elements. With water being fundamental in a hydrogel, water interactions, hydration, and swelling, all critically important in designing, processing, and achieving the desired properties of sustainable and functional hydrogels, are highlighted. A plant, by itself, is a form of a hydrogel, at least at given states of development, and for this reason phenomena such as fluid transport, diffusion, capillarity, and ionic effects are examined. These aspects are highly relevant not only to plants, especially lignified tissues, but also to the porous structures produced after removal of water (foams, sponges, cryogels, xerogels, and aerogels). Thus, a useful source of critical and comprehensive information is provided regarding the synthesis of hydrogels from plant materials (and especially wood nanostructures), and about the role of water, not only for processing but for developing hydrogel properties and uses.

Overall Structure Construction of an Intervertebral Disk Based on Highly Anisotropic Wood Hydrogel Composite Materials with Mechanical Matching and Buckling Buffering

Natural intervertebral disks (IVDs) exhibit distinctive anisotropic mechanical support and dissipation performances due to their well-developed special microstructures. As the intact IVD structure degrades, the absence of function will lead to severe backache. However, the complete simulation for the characteristic structure and function of native IVD is unattainable using current methods. In this work, by overall construction of the two-phase structure of native IVD (extraction of the naturally aligned cellulose framework and in situ polymerization of the nanocomposite hydrogel), a complete wood framework IVD (WF-IVD) is manufactured containing elastic nanocomposite hydrogel-based nucleus pulposus (NP) and anisotropic wood cellulose hydrogel-based annulus fibrosus (AF). In addition to the imitation and construction of the natural structure, WF-IVD also achieves favorable mechanical matching and good biocompatibility and possesses unique mechanical buckling buffer characteristics owing to the aligned fiber bundles. This study offers a promising strategy for the mimicking and construction of complex native tissues.

Advances in Tissue Engineering for Disc Repair

Intervertebral disc (IVD) degeneration is a leading cause of chronic low back pain (LBP) that results in serious disability and significant economic burden. IVD degeneration alters the disc structure and spine biomechanics, resulting in subsequent structural changes throughout the spine. Currently, treatments of chronic LBP due to IVD degeneration include conservative treatments, such as pain medication and physiotherapy, and surgical treatments, such as removal of herniated disc without or with spinal fusion. However, none of these treatments can completely restore a degenerated disc and its function. Thus, although the exact pathogenesis of disc degeneration remains unclear, there are studies examining the effectiveness of biological approaches, such as growth factor injection, gene therapy, and cell transplantation, in promoting IVD regeneration. Furthermore, tissue engineering using a combination of cell transplantation and biomaterials has emerged as a promising new approach for repair or restoration of degenerated discs. The main purpose of this review was to provide an overview of the current status of tissue engineering applications for IVD regenerative therapy by performing literature searches using PubMed. Significant advances in tissue engineering have opened the door to a new generation of regenerative therapies for the treatment of chronic discogenic LBP.

Electrospinning and 3D bioprinting for intervertebral disc tissue engineering

Intervertebral disc (IVD) degeneration is a major cause of low back pain and represents a massive socioeconomic burden. Current conservative and surgical treatments fail to restore native tissue architecture and functionality. Tissue engineering strategies, especially those based on 3D bioprinting and electrospinning, have emerged as possible alternatives by producing cell-seeded scaffolds that replicate the structure of the IVD extracellular matrix. In this review, we provide an overview of recent advancements and limitations of 3D bioprinting and electrospinning for the treatment of IVD degeneration, focusing on future areas of research that may contribute to their clinical translation.

Latest Advances on Bacterial Cellulose-Based Antibacterial Materials as Wound Dressings

At present, there are various wound dressings that can protect the wound from further injury or isolate the external environment in wound treatment. Whereas, infection and slow self-healing still exist in wound healing process. Therefore, it is urgent to develop an ideal wound dressing with good biocompatibility and strong antibacterial activity to promote wound healing. Bacterial cellulose is a kind of promising biopolymer because it can control wound exudate and provide a moist environment for wound healing. However, the lack of antibacterial activity limits its application. In this paper, the advantages of bacterial cellulose as wound dressings were introduced, and the preparation and research progress of bacterial cellulose-based antibacterial composites in recent years were reviewed, including adding antibiotics, combining with inorganic antibacterial agents or organic antibacterial agents. Finally, the existing problems and future development direction of bacterial cellulose-based antibacterial wound dressings were discussed.

Elastic fibers: The missing key to improve engineering concepts for reconstruction of the Nucleus Pulposus in the intervertebral disc

The increasing prevalence of low back pain has imposed a heavy economic burden on global healthcare systems. Intense research activities have been performed for the regeneration of the Nucleus Pulposus (NP) of the IVD; however, tissue-engineered scaffolds have failed to capture the multi-scale structural hierarchy of the native tissue. The current study revealed for the first time, that elastic fibers form a network across the NP consisting of straight and thick parallel fibers that were interconnected by wavy fine fibers and strands. Both straight fibers and twisted strands were regularly merged or branched to form a fine elastic network across the NP. As a key structural feature, ultrathin (53 ± 7 nm), thin (215 ± 20 nm), and thick (890 ± 12 nm) elastic fibers were observed in the NP. While our quantitative analysis for measurement of the thickness of elastic fibers revealed no significant differences (p < 0.633), the preferential orientation of fibers was found to be significantly different (p < 0.001) across the NP. The distribution of orientation for the elastic fibers in the NP represented one major organized angle of orientation except for the central NP. We found that the distribution of elastic fibers in the central NP was different from those located in the peripheral regions representing two symmetrically organized major peaks (±45⁰). No significant differences in the maximum fiber count at the major angles of orientation (±45⁰) were observed for both peripheral (p = 0.427) and central NP (p = 0.788). Based on these new findings a structural model for the elastic fibers in the NP was proposed. The geometrical presentation, along with the distribution of elastic fibers orientation, resulting from the present study identifies the ultrastructural organization of elastic fibers in the NP important towards understanding their mechanical role which is still under investigation. Given the results of this new geometrical analysis, more-accurate multiscale finite element models can now be developed, which will provide new insights into the mechanobiology of the IVD. In addition, the results of this study can potentially be used for the fabrication of bio-inspired tissue-engineered scaffolds and IVD models to truly capture the multi-scale structural hierarchy of IVDs. STATEMENT OF SIGNIFICANCE: Visualization of elastic fibers in the nucleus of the intervertebral disk under high magnification was not reported before. The present research utilized extracellular matrix partial digestion to address significant gaps in understanding of nucleus microstructure that can potentially be used for the fabrication of bio-inspired tissue-engineered scaffolds and disk models to truly capture the multi-scale structural hierarchy of discs.

A 3D-Bioprinted dual growth factor-releasing intervertebral disc scaffold induces nucleus pulposus and annulus fibrosus reconstruction

Regeneration of Intervertebral disc (IVD) is a scientific challenge because of the complex structure and composition of tissue, as well as the difficulty in achieving bionic function. Here, an anatomically correct IVD scaffold composed of biomaterials, cells, and growth factors were fabricated via three-dimensional (3D) bioprinting technology. Connective tissue growth factor (CTGF) and transforming growth factor-β3 (TGF-β3) were loaded onto polydopamine nanoparticles, which were mixed with bone marrow mesenchymal stem cells (BMSCs) for regenerating and simulating the structure and function of the nucleus pulposus and annular fibrosus. In vitro experiments confirmed that CTGF and TGF-β3 could be released from the IVD scaffold in a spatially controlled manner, and induced the corresponding BMSCs to differentiate into nucleus pulposus like cells and annulus fibrosus like cells. Next, the fabricated IVD scaffold was implanted into the dorsum subcutaneous of nude mice. The reconstructed IVD exhibited a zone-specific matrix that displayed the corresponding histological and immunological phenotypes: primarily type II collagen and glycosaminoglycan in the core zone, and type I collagen in the surrounding zone. The testing results demonstrated that it exhibited good biomechanical function of the reconstructed IVD. The results presented herein reveal the clinical application potential of the dual growth factors-releasing IVD scaffold fabricated via 3D bioprinting. However, the evaluation in large mammal animal models needs to be further studied.

Biomimetic angle-ply multi-lamellar scaffold for annulus fibrosus tissue engineering

Constructing a biomimetic scaffold that replicates the complex architecture of intervertebral disc annulus fibrosus (AF) remains a major goal in AF tissue engineering. In this study, a biomimetic angle-ply multi-lamellar polycaprolactone/silk fibroin (PCL/SF) AF scaffold was fabricated. Wet-spinning was used to obtain aligned PCL/SF microfiber sheets, and these were excised into strips with microfibers aligned at +30° or -30° relative to the strip long axis. This was followed by stacking two strips with opposing fiber alignment and wrapping them concentrically around a mandrel. Our results demonstrated that the scaffold possessed spatial structure and mechanical properties comparable to natural AF. The scaffold supported rabbit AF cells adhesion, proliferation, infiltration and guided oriented growth and extracellular matrix deposition. In conclusion, our angle-ply multi-lamellar scaffold offers a potential solution for AF replacement therapy and warrants further attention in future investigations.

Biomimetic intestinal barrier based on microfluidic encapsulated sucralfate microcapsules

Intestinal barriers play an important role in preventing intestinally derived diseases, and maintaining their function is a promising approach to prevent and treat those diseases. Here, inspired by the protection effect of intestinal barriers in live organisms and the mucosa adhesive property of sucralfate, we present a biomimetic intestinal barrier based on microfluidic encapsulated sucralfate microcapsules. Benefiting from the flexible selectivity and precise control of microfluidic electrospray flows, the generated microcapsules were imparted with stomach-tolerant dietary-fibre shells and controllable released sucralfate cores, both of which could contribute to forming a continuous biomimetic intestinal barrier on the intestine. Through in vitro adhesive study, in vivo computed tomography (CT) imaging and in vivo imaging system (IVIS) methods, we have demonstrated that the microcapsule-derived biomimetic intestinal barrier can effectively block food fermentation in the gut, reduce generation of fat, decrease disease risk indexes, and prevent obesity. These features make the microfluidic encapsulated sucralfate microcapsules and their resultant biomimetic intestinal barrier an approach for treating obesity and other intestinal diseases.

Latest Advances on Bacterial Cellulose-Based Materials for Wound Healing, Delivery Systems, and Tissue Engineering

Bacterial cellulose (BC) is a nanocellulose form produced by some nonpathogenic bacteria. BC presents unique physical, chemical, and biological properties that make it a very versatile material and has found application in several fields, namely in food industry, cosmetics, and biomedicine. This review overviews the latest state-of-the-art usage of BC on three important areas of the biomedical field, namely delivery systems, wound dressing and healing materials, and tissue engineering for regenerative medicine. BC will be reviewed as a promising biopolymer for the design and development of innovative materials for the mentioned applications. Overall, BC is shown to be an effective and versatile carrier for delivery systems, a safe and multicustomizable patch or graft for wound dressing and healing applications, and a material that can be further tuned to better adjust for each tissue engineering application, by using different methods.

Nanomaterials for the theranostics of obesity

As a chronic and lifelong disease, obesity not only significant impairs health but also dramatically shortens life span (at least 10 years). Obesity requires a life-long effort for the successful treatment because a number of abnormalities would appear in the development of obesity. Nanomaterials possess large specific surface area, strong absorptivity, and high bioavailability, especially the good targeting properties and adjustable release rate, which would benefit the diagnosis and treatment of obesity and obesity-related metabolic diseases. Herein, we discussed the therapy and diagnosis of obesity and obesity-related metabolic diseases by using nanomaterials. Therapies of obesity with nanomaterials include improving intestinal health and reducing energy intake, targeting and treating functional cell abnormalities, regulating redox homeostasis, and removing free lipoprotein in blood. Diagnosis of obesity-related metabolic diseases would benefit the therapy of these diseases. The development of nanomaterials will promote the diagnosis and therapy of obesity and obesity-related metabolic diseases.

Bacterial Cellulose as a Supersoft Neural Interfacing Substrate

Biocompatible neural interfaces hold great promise for treating neurological disorders and enhancing the mental and physical ability of human beings. Most of the currently available neural interfaces are made from rigid, dense inorganic materials that cause tissue damage. We present supersoft multichannel electrodes by depositing gold layers on thin bacterial cellulose (BC) (Au-BC electrodes). The Young's modulus of BC ( E_BC = 120 kPa) is between those of the brain tissue ( E_brain = 2.7-3.1 kPa) and the peripheral neural tissues ( E_{peripheral nerve} = 580-840 kPa). The bending stiffness of the Au-BC electrodes corresponds to 1/5200 of Au-polyimide electrodes with the same layout. Furthermore, the Au-BC electrodes are highly durable (conductivity >95% after 100 cycles of 180° bending). In vivo recording of brain electric activity demonstrates the great potential of the Au-BC electrodes for neural interfacing applications.