Toward biomanufacturing of next-generation bacterial nanocellulose (BNC)-based materials with tailored properties: A review on genetic engineering approaches

Bacterial nanocellulose (BNC) is a biopolymer that is drawing significant attention for a wide range of applications thanks to its unique structure and excellent properties, such as high purity, mechanical strength, high water holding capacity and biocompatibility. Nevertheless, the biomanufacturing of BNC is hindered due to its low yield, the instability of microbial strains and cost limitations that prevent it from being mass-produced on a large scale. Various approaches have been developed to address these problems by genetically modifying strains and to produce BNC-based biomaterials with added value. These works are summarized and discussed in the present article, which include the overexpression and knockout of genes related and not related with the nanocellulose biosynthetic operon, the application of synthetic biology approaches and CRISPR/Cas techniques to modulate BNC biosynthesis. Further discussion is provided on functionalized BNC-based biomaterials with tailored properties that are incorporated in-vivo during its biosynthesis using genetically modified strains either in single or co-culture systems (in-vivo manufacturing). This novel strategy holds potential to open the road toward cost-effective production processes and to find novel applications in a variety of technology and industrial fields.

CSMed® wound dressing for prophylaxis and management of radiation dermatitis in breast and head-neck cancer patients: a single hospital prospective clinical trial

PURPOSE

CSMed® wound dressing, a dressing with various herb extracts, was tested for its therapeutic effect in radiation dermatitis of breast and head-and-neck cancer patients.

METHODS

This study included 20 breast cancer patients and 10 head-and-neck cancer patients. Half of the irradiated area was covered with CSMed® and the other half was under routine treatment. The severity of radiation dermatitis was evaluated with radiation therapy oncology group (RTOG) grade throughout the treatment and the follow-up period. The RTOG grade between the dressed and undressed area were compared to illustrate the therapeutic effect of CSMed® dressing.

RESULTS

The results showed that CSMed® dressed area had significant lower RTOG score at 3-7 weeks and final record during the treatment, and 1-3 weeks during follow-up than undressed area.

CONCLUSIONS

This indicated that CSMed® can delay the onset, reduce the severity, and enhance healing of radiation dermatitis. CSMed® can be used for prophylaxis and management of radiation dermatitis.

Recent advances in bacterial cellulose-based antibacterial composites for infected wound therapy

Wound infection arising from pathogenic bacteria brought serious trouble to the patient and medical system. Among various wound dressings that are effective in killing pathogenic bacteria, antimicrobial composites based on bacterial cellulose (BC) are becoming the most popular materials due to their success in eliminating pathogenic bacteria, preventing wound infection, and promoting wound healing. However, as an extracellular natural polymer, BC is not inherently antimicrobial, which means that it must be combined with other antimicrobials to be effective against pathogens. BC has many advantages over other polymers, including nano-structure, significant moisture retention, non-adhesion to the wound surface, which has made it superior to other biopolymers. This review introduces the recent advances in BC-based composites for the treatment of wound infection, including the classification and preparation methods of composites, the mechanism of wound treatment, and commercial application. Moreover, their wound therapy applications include hydrogel dressing, surgical sutures, wound healing bandages, and patches are summarized in detail. Finally, the challenges and future prospects of BC-based antibacterial composites for the treatment of infected wounds are discussed.

Effect of natural polymer materials on skin healing based on internal wound microenvironment: a review

The concept of wound microenvironment has been discussed for a long time. However, the mechanism of the internal microenvironment is relatively little studied. Here, we present a systematic discussion on the mechanism of natural polymer materials such as chitosan, cellulose, collagen and hyaluronic acid through their effects on the internal wound microenvironment and regulation of wound healing, in order to more comprehensively explain the concept of wound microenvironment and provide a reference for further innovative clinical for the preparation and application of wound healing agents.

Astragalus polysaccharides driven stretchable nanofibrous membrane wound dressing for joint wound healing

Joint wound dressings are currently significantly limited in their clinical applications due to their inferior mechanical properties and single therapeutic effect. Therefore, it is imperative to develop a versatile joint wound dressing that integrates adequate stretchability, desirable biocompatibility, and multiple biological effects into one system. We implemented the electrospinning technique in this study to fabricate a novel nanofibrous membrane (NFM) composed of gelatin (GEL) and astragalus polysaccharides (APS), termed GEL/APS NFM. The selection of GEL and APS confers excellent biocompatibility to GEL/APS NFM. Furthermore, the optimally proportioned GEL/APS NFM exhibits satisfactory stretchability and desirable wound healing efficiency. Furthermore, released APS can exert anti-inflammatory, procollagen deposition, and proangiogenic effects to accelerate epithelial tissue, enhancing joint wound healing. In summary, GEL/APS NFM offers a convenient and effective approach to promoting rapid joint wound healing, providing a novel approach to joint wound care.

Evaluation of Cytotoxicity of Hyaluronic Acid/Chitosan/Bacterial Cellulose-Based Membrane

Novel wound dressing materials are required to non-cytotoxic with a viable cell ratio of above 92%. Herein, the cytotoxicity of hyaluronic acid/chitosan/bacterial cellulose-based (BC(CS/HA)) membranes are evaluated and compared to that of alginate/chitosan/bacterial cellulose-based (BC(CS/Alg)) membranes was investigated. Multilayer membranes with up to ten CS/HA or CS/Alg layers were prepared using the layer-by-layer (LBL) method. Scanning electron microscopy showed that the diameters of the fibers in the BC(CS/Alg) and BC(CS/HA) membranes were larger than those in a BC membrane. The cytotoxicity was analyzed using BALB-3T3 clone A31 cells (mouse fibroblasts, 1 × 10⁴ cells/well). The BC(CS/HA)₅ and BC(CS/HA)₁₀ membranes exhibited high biocompatibility, with the cell viabilities of 94% and 87% at 5 d, respectively, compared to just 82% for the BC(CS/Alg)₅ and BC(CS/Alg)₁₀ membranes with same numbers of layers. These results suggested that BC(CS/HA)₅ is a promising material for wound dressings.

Role of medicinal herbs and phytochemicals in post burn management

Burn management is a natural and distinctly programmed process involving overlapping phases of hemostasis, inflammation, proliferation and remodeling. Burn wound healing involves initiation of inflammation, re-epithelialization, granulation, neovascularization and wound contraction. Despite the availability of multiple preparations for management of burn wound, there is dire need for efficacious alternative agents. Current approaches for burn wound management include pharmaceutical agents and antibiotics. However, high cost of synthetic drugs and accelerated resistance to antibiotics is challenging for both developed and developing nations. Among alternative options, medicinal plants have been a biocompatible, safe and affordable source of preventive/curative approaches. Due to cultural acceptance and patient compliance, there has been a focus on the use of botanical drugs and phytochemicals for burn wound healing. Keeping in consideration of medicinal herbs and phytochemicals as suitable therapeutic/adjuvant agents for burn wound management, this review highlights therapeutic potential of 35 medicinal herbs and 10 phytochemicals. Among these, Elaeis guineensis, Ephedra ciliate and Terminalia avicennioides showed better burn wound healing potential with varied mechanisms such as modulation of TNF-alpha, inflammatory cytokines, nitric oxide, eicosanoids, ROS and leukocyte response. Phytochemicals (oleanolic acid, ursolic acid, kirenol) also showed promising role in burn wound management though various pathways involving such as down regulation of TNF-alpha, IL-6 and inflammatory mediators including plasma proteases and arachidonic acid metabolites. This review provides a pavement for therapeutic/adjuvant use of potential botanical drugs and novel druggable phyto-compounds to target skin burn injury with diverse mechanisms, affordability and safety profile.

Evolution of Bacterial Cellulose in Cosmetic Applications: An Updated Systematic Review

In recent decades, there has been an increase in environmental problems caused by cosmetic products derived from toxic substances. Based on this issue, researchers and developers of new beauty cosmetics are looking for new natural alternatives that work well for the consumer and have biodegradable characteristics. This systematic review highlights the major publications of bacterial cellulose used strictly for cosmetics in the last 10 years. Bacterial cellulose is a natural product with great cosmetic properties and low cost that has shown excellent results. This study aimed at collecting rigorous information on bacterial cellulose in the cosmetic field in the last decade to produce a systematized review. A comprehensive search was conducted with selected descriptors involving the topic of "bacterial cellulose", "cosmetics", "clean beauty", and "skin mask". Seventy studies were found, which went through exclusion criteria that selected only those related to the topic that was searched. In the 12 remaining studies that met the criteria, bacterial cellulose showed conditions for use as a mask-forming product for facial care. The increase in the number of publications concerning bacterial cellulose in cosmetics in the last ten years is a strong indicator that this is a growing area for both research and the industry.

Controlled release of vascular endothelial growth factor (VEGF) in alginate and hyaluronic acid (ALG–HA) bead system to promote wound healing in punch-induced wound rat model

For wound healing, angiogenesis is one of the main therapeutic factors for recovering the injured tissue. To address this issue, a combination of two different polymers, alginate (ALG) and hyaluronic acid (HA) in an 80:20 ratio composition is used to optimize the bead system along with the 5 IU heparin (Hep) by crosslinking into calcium chloride (CaCl₂). Encapsulation of Vascular endothelial growth factor (VEGF) in the bead system shows delayed cumulative release in phosphate buffer saline (PBS). For in vitro studies, calf pulmonary artery endothelial (CPAE) cells showed biocompatibility. ALG-HA/VEGF150 improves endothelial Vascular cell adhesion protein 1 (VCAM1) and endothelial nitric oxide synthase (eNOS) expression markers in CPAE cells. In vivo evaluation of the bead system shows around 68% of wound closure 2 weeks post-implantation in 8 mm punch wound models. The treatment group shows decreased epithelial gap between the ends of the wound and neo-epidermal regeneration. ALG-HA/VEGF150 induced significant vascularization, collagen type-1 (Col-1) and fibronectin (FN) development in the in vivo models after 2 weeks of the implantation. Hence, ALG-HA/VEGF150 beads can be used to promote wound healing.

De novo strategy with engineering a multifunctional bacterial cellulose-based dressing for rapid healing of infected wounds

The treatment and healing of infected skin lesions is one of the major challenges in surgery. To solve this problem, collagen I (Col-I) and the antibacterial agent hydroxypropyltrimethyl ammonium chloride chitosan (HACC) were composited into the bacterial cellulose (BC) three-dimensional network structure by a novel membrane–liquid interface (MLI) culture, and a Col-I/HACC/BC (CHBC) multifunctional dressing was designed. The water absorption rate and water vapor transmission rate of the obtained CHBC dressing were 35.78 ± 2.45 g/g and 3084 ± 56 g m⁻²·day⁻¹, respectively. The water retention of the CHBC dressing was significantly improved compared with the BC caused by the introduced Col-I and HACC. In vitro results indicated that the combined advantages of HACC and Col-I confer on CHBC dressings not only have outstanding antibacterial properties against Staphylococcus aureus (S. aureus) compared with BC and CBC, but also exhibit better cytocompatibility than BC and HBC to promote the proliferation and spread of NIH3T3 cells and HUVECs. Most importantly, the results of in vivo animal tests demonstrated that the CHBC dressings fully promoted wound healing for 8 days and exhibited shorter healing times, especially in the case of wound infection. Excellent skin regeneration effects and higher expression levels of collagen during infection were also shown in the CHBC group. We believe that CHBC composites with favorable multifunctionality have potential applications as wound dressings to treat infected wounds.

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The antibacterial agent HACC and collagen I were introduced into BC structure by a novel membrane–liquid interface culture.

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CHBC dressing has favorable thermostability, water absorption, water retention rate and WVTRs.

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CHBC dressing has outstanding antibacterial properties against S. aureus.

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CHBC dressing promoted the proliferation and spread of NIH3T3 cells and HUVECs.

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CHBC dressing prevented wound infection caused by S. aureus and accelerated wound healing.

Direct Synthesis of Photosensitizable Bacterial Cellulose as Engineered Living Material for Skin Wound Repair

Living materials based on bacterial cellulose (BC) represent a natural and promising candidate for wound dressing. Both physical adsorption and chemical methods have been applied to BC for realizing antibacterial function. However, effective and long-lasting incorporation of bactericidal moieties to BC remains challenging. Herein, a Komagataeibacter sucrofermentans-based direct synthetic method to fabricate photosensitizer-grafted BC through in situ bacterial metabolism in the presence of TPEPy-modified glucose is explored. The results verify that the direct biosynthesis method is efficient and convenient to endow BC with outstanding fluorescence and light-triggered photodynamic bactericidal activity for skin wound repair. This work presents a new approach to fabricate eco-friendly and active wound dressing with light-controlled bactericidal activity by microbial metabolism. The successful modification of the glucose carbon source of microorganisms also offers insights for biosyntheses of other living materials through microbial metabolism.

Antimicrobial Properties of Bacterial Cellulose Films Enriched with Bioactive Herbal Extracts Obtained by Microwave-Assisted Extraction

The use of bacterial cellulose (BC) as scaffold for active biofilms is one of the most interesting applications, especially for the biomedical and food industries. However, there are currently few studies evaluating the potential of incorporating herbal extracts into various biomaterials, including BC. Thus, the aim of this study is to report a screening of the total phenolic content and antioxidant and antimicrobial activity of ethanolic extracts of oregano, rosemary, parsley, and lovage. At the same time, the bioactive potential of BC enriched with the four ethanolic extracts is described. Microwave-assisted extraction was used to extract bioactive compounds from the four selected herbs. The physical, mechanical, structural, and chemical properties of BC were also assessed. Next, BC was enriched with the extracts, and their effect against Escherichia coli, Staphylococcus aureus, and Candida albicans was evaluated. The results showed that the bioactivity of the herbs varied significantly, with rosemary extract being the most bioactive. The BC films possessed good mechanical properties, and a three-dimensional network fibrillar structure appropriate for ethanolic-extract incorporation. The BC samples enriched with rosemary extracts had the highest antibacterial activity against S. aureus, while E. coli. and C. albicans seemed to be resistant to all extracts, regardless of herbs.

The 3D Bioprinted Scaffolds for Wound Healing

Skin tissue engineering and regeneration aim at repairing defective skin injuries and progress in wound healing. Until now, even though several developments are made in this field, it is still challenging to face the complexity of the tissue with current methods of fabrication. In this review, short, state-of-the-art on developments made in skin tissue engineering using 3D bioprinting as a new tool are described. The current bioprinting methods and a summary of bioink formulations, parameters, and properties are discussed. Finally, a representative number of examples and advances made in the field together with limitations and future needs are provided.

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.

Recent Advances on Bacterial Cellulose-Based Wound Management: Promises and Challenges

Wound healing is a therapeutic challenge due to the complexity of the wound. Various wounds could cause severe physiological trauma and bring social and economic burdens to the patient. The conventional wound healing treatments using bandages and gauze are limited particularly due to their susceptibility to infection. Different types of wound dressing have developed in different physical forms such as sponges, hydrocolloids, films, membranes, and hydrogels. Each of these formulations possesses distinct characteristics making them appropriate for the treatment of a specific wound. In this review, the pathology and microbiology of wounds are introduced. Then, the most recent progress on bacterial cellulose- (BC-) based wound dressing discussed and highlighted their antibacterial and reepithelization properties in vitro and in vivo wound closure. Finally, the challenges and future perspectives on the development of BC-based wound dressing biomaterials are outlined.

Surface Modification of Bacterial Cellulose for Biomedical Applications

Bacterial cellulose is a naturally occurring polysaccharide with numerous biomedical applications that range from drug delivery platforms to tissue engineering strategies. BC possesses remarkable biocompatibility, microstructure, and mechanical properties that resemble native human tissues, making it suitable for the replacement of damaged or injured tissues. In this review, we will discuss the structure and mechanical properties of the BC and summarize the techniques used to characterize these properties. We will also discuss the functionalization of BC to yield nanocomposites and the surface modification of BC by plasma and irradiation-based methods to fabricate materials with improved functionalities such as bactericidal capabilities.

Double-Modified Bacterial Cellulose/Soy Protein Isolate Composites by Laser Hole Forming and Selective Oxidation Used for Urethral Repair

In this study, a double-modified bacterial cellulose/soybean protein isolate (DMBC/SPI), a new type of urethral tissue engineering scaffold with good biocompatibility, biodegradability, and cell-oriented growth, was prepared. Bacterial cellulose (BC) was physically and chemically modified by laser hole forming and selective oxidation to obtain the double-modified bacterial cellulose (DMBC). The soybean protein isolate (SPI) was compounded on DMBC to obtain DMBC/SPI with better biocompatibility. DMBC/SPI was used to repair the damaged urethra in rabbits. The results showed that DMBC/SPI was beneficial to heal the damaged urethra and did not cause a milder inflammatory response. The repaired urethra was smooth and continuous. DMBC/SPI has a good urethral repair effect and is expected to be used as a new urethral reconstruction material in clinical applications. In addition, FT-IR spectroscopy, SEM, static contact angle measurements, mechanical property investigation, and cell experiments were also performed to characterize the properties of DMBC/SPI composites.

Biofabrication of a Hyaluronan/Bacterial Cellulose Composite Nanofibril by Secretion from Engineered Gluconacetobacter

Naturally occurring polysaccharides, such as cellulose, hemicellulose, and chitin, have roles in plant skeletons and/or related properties in living organisms. Their hierarchically regulated production systems show potential for designing nanocomposite fabrication using engineered microorganisms. This study has demonstrated that genetically engineered Gluconacetobacter hansenii (G. hansenii) individual cells can fabricate naturally composited nanofibrils by simultaneous production of hyaluronan (HA) and bacterial cellulose (BC). The cells were manipulated to contain hyaluronan synthase and UDP-glucose dehydrogenase genes, which are essential for HA biosynthesis. Fluorescence microscopic observations indicated the production of composited nanofibrils and suggested that HA secretion was associated with the cellulose secretory pathway in G. hansenii. The gel-like nanocomposite materials produced by the engineered G. hansenii exhibited superior properties compared with conventional in situ nanocomposites. This genetic engineering approach facilitates the use of G. hansenii for designing integrated cellulose-based nanomaterials.

Bacterial Cellulose: Functional Modification and Wound Healing Applications

Significance: Wound dressings are frequently used for wound covering and healing. Ideal wound dressings should provide a moist environment for wounds and actively promote wound healing and skin recovery. The materials used as ideal wound dressings should possess specific properties, thus accelerating skin tissue regeneration process. Recent Advances: Bacterial cellulose (BC) is a natural polymer synthesized by some bacteria. As a kind of natural biopolymer, BC shows good biological activity, biodegradability, and biological adaptability. It has many unique physical, chemical, and biological properties, such as ultrafine nanofiber network, high crystallinity, high water absorption and retention capacity, and high tensile strength and elastic modulus. These excellent properties of BC have laid the foundation for its application as dressing in wound healing. Critical Issues: To optimize the biocompatibility and antimicrobial activity of BC, different methods including microbial fermentation, physical modification, chemical modification, and compound modification have been adopted to modify BC to ensure a better application in wound healing. BC-based wound dressings have been applied in infected wounds, acute traumatic injuries, burns, and diabetic wounds, showing remarkable therapeutic effects on promoting wound healing. Furthermore, there have been some commercial BC-based dressings and they have been utilized in clinical practice. Future Directions: Because of its excellent physicochemical characteristics and biological properties, BC shows high clinical value to be used as a wound dressing for skin tissue regeneration.

Recent advancements in cellulose-based biomaterials for management of infected wounds

INTRODUCTION

Chronic wounds are a substantial burden on the healthcare system. Their treatment requires advanced dressings, which can provide a moist wound environment, prevent bacterial infiltration, and act as a drug carrier. Cellulose is biocompatible, biodegradable, and can be functionalized according to specific requirements, which makes it a highly versatile biomaterial. Antimicrobial cellulose dressings are proving to be highly effective against infected wounds.

AREAS COVERED

This review briefly addresses the mechanism of wound healing and its pathophysiology. It also discusses wound infections, biofilm formation, and progressive emergence of drug-resistant bacteria in chronic wounds and the treatment strategies for such types of infected wounds. It also summarizes the general properties, method of production, and types of cellulose wound dressings. It explores recent studies and advancements regarding the use of cellulose and its derivatives in wound management.

EXPERT OPINION

Cellulose and its various functionalized derivatives represent a promising choice of wound dressing material. Cellulose-based dressings loaded with antimicrobials are very useful in controlling infection in a chronic wound. Recent studies showing its efficacy against drug-resistant bacteria make it a favorable choice for chronic wound infections. Further research and large-scale clinical trials are required for better clinical evidence of its efficiency.

Skin wound healing promoted by novel curcumin-loaded micelle hydrogel

Background

The development of biomaterials with the ability to promote skin wound healing is an important topic in the field of biomedical science. In this study, a topical curcumin (Cur) gel [Cur/hyaluronic acid (HA)] was prepared by combining curcumin-loaded PCL-b-PEG-b-PCL (PECE) nanomicelles (PCEC/Cur) and HA to effectively promote skin wound healing. Continuous drug release from PCEC/Cur can provide long-term protection and treatment of skin wounds.

Methods

The study was completed in two stages. The first stage (in vitro): PCEC/Cur were prepared by thin film hydration method. The second stage (in vivo): 36 anesthetized rats were used to prepare a round full-thickness skin defect wound with a diameter of 23 mm on the dorsal side of the spine, and the rats were randomly divided into 4 groups with 9 rats in each group.

Results

The results showed that wounds in the Cur/HA group were restored to normal after 14 days after operation, representing 96%±3% wound healing. Hematoxylin and eosin (HE) staining showed that hair follicles in the Cur/HA group were visible and that the re-epithelialization time was earlier. Masson staining showed that Cur/HA promoted the formation of collagen fibers. Immunohistochemical observation showed that angiogenesis and subsequent healing of the wound surface was enhanced in the Cur/HA group.

Conclusions

The injectable hyaluronic acid gel complex Cur/HA is a promising candidate material for a wound dressing to promote healing.

Recent Advances in Cellulose-Based Structures as the Wound-Healing Biomaterials: A Clinically Oriented Review

Application of wound-healing/dressing biomaterials is amongst the most promising approaches for wound repair through protection from pathogen invasion/contamination, maintaining moisture, absorbing exudates, modulating inflammation, and facilitating the healing process. A wide range of materials are used to fabricate wound-healing/dressing biomaterials. Active wound-healing/dressings are next-generation alternatives for passive biomaterials, which provide a physical barrier and induce different biological activities, such as antibacterial, antioxidant, and proliferative effects. Cellulose-based biomaterials are particularly promising due to their tunable physical, chemical, mechanical, and biological properties, accessibility, low cost, and biocompatibility. A thorough description and analysis of wound-healing/dressing structures fabricated from cellulose-based biomaterials is discussed in this review. We emphasize and highlight the fabrication methods, applied bioactive molecules, and discuss the obtained results from in vitro and in vivo models of cellulose-based wound-healing biomaterials. This review paper revealed that cellulose-based biomaterials have promising potential as the wound-dressing/healing materials and can be integrated with various bioactive agents. Overall, cellulose-based biomaterials are shown to be effective and sophisticated structures for delivery applications, safe and multi-customizable dressings, or grafts for wound-healing applications.

Optimization of Moist and Oven-Dried Bacterial Cellulose Production for Functional Properties

Bacterial cellulose (BC) is a natural polymer with properties suitable for tissue engineering and possible applications in scaffold production. However, current procedures have limitations in obtaining BC pellicles with the desired structural, physical, and mechanical properties. Thus, this study analyzed the optimal culture conditions of BC membranes and two types of processing: draining and oven-drying. The aim was to obtain BC membranes with properties suitable for a wound dressing material. Two studies were carried out. In the preliminary study, the medium (100 mL) was inoculated with varying volumes (1, 2, 3, 4, and 5 mL) and incubated statically for different periods (3, 6, 9, 12, and 18 days), using a full factorial experimental design. Thickness, uniformity, weight, and yield were evaluated. In the optimization study, a Box–Behnken design was used. Two independent variables were used: inoculum volume (X₁: 1, 3, and 5 mL) and fermentation period (X₂: 6, 12, and 18 d) to determine the target response variables: thickness, swelling ratio, drug release, fiber diameter, tensile strength, and Young’s modulus for both dry and moist BC membranes. The mathematical modelling of the effect of the two independent variables was performed by response surface methodology (RSM). The obtained models were validated with new experimental values and confirmed for all tested properties, except Young’s modulus of oven-dried BC. Thus, the optimal properties in terms of a scaffold material of the moist BC were obtained with an inoculum volume of 5% (v/v) and 16 d of fermentation. While, for the oven-dried membranes, optimal properties were obtained with a 4% (v/v) and 14 d of fermentation.

Homogeneous and efficient production of a bacterial nanocellulose-lactoferrin-collagen composite under an electric field as a matrix to promote wound healing

BNC was functionalized with collagen (COL) and lactoferrin (LF) to form three different composites: BNC/COL, BNC/LF and BNC/LF/COL using a novel electrophoresis-based technology. The technology is less time-consuming than traditional immersion-adsorption methods and offers the additional advantages of greater protein loading, better homogeneity and a lower requirement for processing solution. Significantly, it has general applicability and great potential for fabricating other similar composites. The water-holding capability and water vapor transmission rate (WVTR) of BNC composites were significantly improved, particularly in the case of BNC/LF/COL, with a WVTR of 2600 g m-2 d-1, indicating that the composite maintains a moderately moist environment over the wound bed, which would enhance epithelial cell migration during the healing process. Compared with BNC and BNC/COL, the LF-impregnated composites mediated a reduction in bacterial viability of at least 77%. Impregnation with COL significantly improved the cytocompatibility of BNC composites to promote the adhesion and proliferation of fibroblast cells. Furthermore, a greater therapeutic effect of BNC/LF/COL was observed in a rat model of wound healing, with a new epithelium formed within 9 days and without any significant adverse reactions. These results suggest that BNC/LF/COL obtained using the electrophoresis method represents a promising wound dressing for use in practical applications.

The biological processes during wound healing

Numerous individuals suffer from impaired wound healing, such as chronic ulcers, severe burns and immune disorders, resulting in both public health and economic burdens. Skin is the first line of defense and the largest organ of the human body, however, an incomplete understanding of underlying cellular and molecular mechanisms of dermal repair leads to a lack of effective therapy for healing impaired wounds. There are strong clinical and social needs for improved therapeutic approaches to enhance endogenous tissue repair and regenerative capacity. The purpose of this review is to illuminate the cellular and molecular aspects of the healing process and highlight potential therapeutic strategies to accelerate translational research and the development of clinical therapies in dermal wounds.

A review of functionalised bacterial cellulose for targeted biomedical fields

Bacterial cellulose (BC), which can be produced by microorganisms, is an ideal biomaterial especially for tissue engineering and drug delivery systems thanks to its properties of high purity, biocompatibility, high mechanical strength, high crystallinity, 3 D nanofiber structure, porosity and high-water holding capacity. Therefore, wide ranges of researches have been done on the BC production process and its structural and physical modifications to make it more suitable for certain targeted biomedical applications thoroughly. BC's properties such as mechanical strength, pore diameter and porosity can be tuned in situ or ex situ processes by using various polymer and compounds. Besides, different organic or inorganic compounds that support cell attachment, proliferation and differentiation or provide functions such as antimicrobial effectiveness can be gained to its structure for targeted application. These processes not only increase the usage options of BC but also provide success for mimicking the natural tissue microenvironment, especially in tissue engineering applications. In this review article, the studies on optimisation of BC production in the last decade and the BC modification and functionalisation studies conducted for the three main perspectives as tissue engineering, drug delivery and wound dressing with diverse approaches are summarized.

Homogeneous and efficient production of a bacterial nanocellulose-lactoferrin-collagen composite under an electric field as a matrix to promote wound healing

A novel BNC/LF/COL membrane fabricated using an electrophoresis-based technology showed superior advantages in water-holding capability and antibacterial activity, with higher cytocompatibility as well as greater therapeutic effect in wound healing.

3D Bioprinting of Lignocellulosic Biomaterials

The interest in bioprinting of sustainable biomaterials is rapidly growing, and lignocellulosic biomaterials have a unique role in this development. Lignocellulosic materials are biocompatible and possess tunable mechanical properties, and therefore promising for use in the field of 3D-printed biomaterials. This review aims to spotlight the recent progress on the application of different lignocellulosic materials (cellulose, hemicellulose, and lignin) from various sources (wood, bacteria, and fungi) in different forms (including nanocrystals and nanofibers in 3D bioprinting). Their crystallinity, leading to water insolubility and the presence of suspended nanostructures, makes these polymers stand out among hydrogel-forming biomaterials. These unique structures give rise to favorable properties such as high ink viscosity and strength and toughness of the final hydrogel, even when used at low concentrations. In this review, the application of lignocellulosic polymers with other components in inks is reported for 3D bioprinting and identified supercritical CO₂ as a potential sterilization method for 3D-printed cellulosic materials. This review also focuses on the areas of potential development by highlighting the opportunities and unmet challenges such as the need for standardization of the production, biocompatibility, and biodegradability of the cellulosic materials that underscore the direction of future research into the 3D biofabrication of cellulose-based biomaterials.

Bacterial Envelope Damage Inflicted by Bioinspired Nanostructures Grown in a Hydrogel

Surface-associated bacterial communities, known as biofilms, are responsible for a broad spectrum of infections in humans. Recent studies have indicated that surfaces containing nanoscale protrusions, like those in dragonfly wings, create a hostile niche for bacterial colonization and biofilm growth. This functionality has been mimicked on metals and semiconductors by creating nanopillars and other high aspect ratio nanostructures at the interface of these materials. However, bactericidal topographies have not been reported on clinically relevant hydrogels and highly compliant polymers, mostly because of the complexity of fabricating nanopatterns in hydrogels with precise control of the size that can also resist aqueous immersion. Here, we report the fabrication of bioinspired bactericidal nanostructures in bacterial cellulose (BC) hydrogels using low-energy ion beam irradiation. By challenging the currently accepted view, we show that the nanostructures grown in BC affect preferentially stiff membranes like those of the Gram-positive bacteria Bacillus subtilis in a time-dependent manner and, to a lesser extent, the more deformable and softer membrane of Escherichia coli. Moreover, the nanostructures in BC did not affect the viability of murine preosteoblasts. Using single-cell analysis, we demonstrate that indeed B. subtilis requires less force than E. coli to be penetrated by nanoprobes with dimensions comparable to those of the nanostructured BC, providing the first direct experimental evidence validating a mechanical model of membrane rupture via a tension-induced mechanism within the activation energy theory. Our findings bridge the gap between mechano-bactericidal surfaces and low-dimensional materials, including single-walled carbon nanotubes and graphene nanosheets, in which a higher bactericidal activity toward Gram-positive bacteria has been extensively reported. Our results also demonstrate the ability to confer bactericidal properties to a hydrogel by only altering its topography at the nanoscale and contribute to a better understanding of the bacterial mechanobiology, which is fundamental for the rational design bactericidal topographies.

Preparation of stretchable composite film and its application in skin burn repair

The poor elasticity of wound dressings often leads to wound healing failure due to rupture and fall off. In this study, the composite films of zein and hydrogel poly (acrylic acid) were developed in order to obtain stretchable wound dressing for skin burn repair. The mechanical test revealed that the maximum elongation of break of composite films could reach 349.76% when the mass ratio of zein to poly (acrylic acid) was 1.5. SEM and FTIR analysis demonstrated the good elasticity of composite films might be due to the formation of a dense structure and the strong interaction between zein and poly (acrylic acid). Interestingly, the composite films exhibited great adhesiveness to human finger skin and stretchable ability under strenuous joint exercise. CCK-8 assay and fluorescence staining showed that the composite films and their extract had good cytocompatibility on human foreskin fibroblasts (L929) cells. The in vivo experiment on rat's skin burning model indicated that the composite films could promote wound healing and collagen synthesis by comparison with commercial gauze. It could be concluded that the stretchable composite films of zein and hydrogel poly (acrylic acid) had the potential as the wound dressing.

Glycoside hydrolase (PelAh) immobilization prevents Pseudomonas aeruginosa biofilm formation on cellulose-based wound dressing

Bacterial cellulose (BC) is recognized as a wound dressing material well-suited for chronic wounds; however, it has no intrinsic antimicrobial activity. Further, the formation of biofilms can limit the effectiveness of the pre-saturation of BC with antimicrobial agents. Here, to hinder biofilm formation by P. aeruginosa, we immobilized the hydrolytic domain of PelA (a glycohydrolase involved in the synthesis of biofilm polysaccharide Pel) on the surface of BC. The immobilization of 32.35 ± 1.05 mg PelA_h per g BC membrane resulted in an eight-fold higher P. aeruginosa cell detachment from BC membrane, indicating reduced biofilm matrix stability. Further, 1D and 2D infrared spectroscopy analysis indicated systematic reduction of polysaccharide biofilm elements, confirming the specificity of immobilized PelA_h. Importantly, BC-PelA_h was not cytotoxic towards L929 fibroblast cells. Thus, we conclude that PelA_h can be used in BC wound dressings for safe and specific protection against biofilm formation by P. aeruginosa.

Novel bacterial cellulose membrane biosynthesized by a new and highly efficient producer Komagataeibacter rhaeticus TJPU03

Bacterial cellulose(BC) is a kind of extracellular polymer synthesized by bacteria and it has very wide applications in many fields. However, the application of BC in a large commercial scale can still not be fulfilled due to the low yield and demanding for BC membranes with very different properties. To this end, a new BC-producer Komagataeibacter rhaeticus TJPU03 was isolated from rotten orange peel, which produced 8.28 ± 0.27 g/L(dry weight) in standard HS medium at the 10th day. The membrane is easier to be purified by one-step alkaline treatment and the produced BC(K-BC) membranes possess homogeneous, looser and more porous three-dimensional network composed by thinner cellulose fibrils. However, the wet K-BC possesses stronger mechanical properties and exhibits lower toxicity and higher cytocompatibility to mammalian cell. Owing to the more porous and homogeneous network, K-BC possesses high loading capacity of cell and protein drugs. Also, it exhibits sustained-controlled release ability for proteinaceous drug. The high yield of this strain and the special characteristics of K-BC predict this strain to be a very promising BC-producer and broad applications of K-BC in the fields of wound healing, scaffolds of tissue engineering, tissue repair and regeneration.

One-component waterborne in vivo cross-linkable polysiloxane coatings for artificial skin

Polysiloxane-based artificial skins are able to emulate the mechanical and barrier performance of human skin. However, they are usually fabricated in vitro, restricting their diverse applications on human body. Herein, we presented one-component waterborne cross-linkable polysiloxane coatings prepared from emulsified vinyl dimethicone, emulsified hydrogen dimethicone, and Karstedt catalyst capsules that were first synthesized by solvent evaporation method. The coating had good storage stability and meanwhile could form an elastic film quickly through merging of silicone oil droplets and subsequent hydrosilylation reaction. It was found that the mass ratio of vinyl dimethicone emulsion/hydrogen dimethicone emulsion (V/H), and the dosage of Karstedt catalyst capsules (K/(V + H)) were critical to the curing time, morphology, and mechanical properties of the coatings. With appropriate values of V/H and K/(V + H), the polysiloxane film had the mechanical performance comparable to that from solvent-based one. The coating could be topically applied to human skin in vivo and in situ turned into an elastic, invisible thin film with good water resistance. In contrast to those reported polysiloxane materials, the one-component waterborne polysiloxane coating was nontoxic and convenient for in vivo application on human body, making it be a promising candidate as artificial skin in the fields of cosmetics, medical treatment, and E-skin.

Bioinspired multifunctional biomaterials with hierarchical microstructure for wound dressing

Developing multifunctional wound dressing with desired mechanical strength is of great significance for the treatment of different types of skin wounds. Inspired by the close relationship between strength and hierarchical structure of nacre, hierarchical and porous graphene oxide-chitosan-calcium silicate (GO-CTS-CS) film biomaterials are fabricated by a combination of vacuum filtration-assisted assembly and freeze-drying methods. The bioinspired hierarchical materials emulate an orderly porous lamellar micron-scale structure and the "brick-and-mortar"-layered nanostructure. The hierarchical microstructure endows the GO-CTS-CS biomaterials with good tensile strength, compatible breathability, and water absorption. Furthermore, the hierarchical GO-CTS-CS biomaterials exhibit ideal photothermal performance, leading to significant photothermal antibacterial and antitumor efficacy. Further, the hierarchical GO-CTS-CS biomaterials show stimulatory effect on in vivo chronic wound healing. Therefore, such a high performance and multifunctional biomaterial is believed to offer a promising alternative to traditional wound dressing in future. STATEMENT OF SIGNIFICANCE: Although it is an effective strategy to prepare high-performance materials by mimicking the hierarchical microstructure of nacre, the preparation of nacre-inspired materials in tissue engineering fields still needs to be investigated. In this work, we prepared a nacre-inspired multifunctional graphene oxide-chitosan-calcium silicate (GO-CTS-CS) biomaterial with a hierarchical microstructure. The hierarchical microstructure endows the biomaterials with desired properties of strength, breathability, and water absorption. Further, the hierarchical GO-CTS-CS biomaterial showed good photothermal antibacterial/antitumor and wound healing effects. This work may provide an approach to combine the preparation of multifunctional biomaterials with bioinspired engineering by constructing a hierarchical microstructure, indicating that the assembling hierarchical microstructure in biomaterials is of great importance for tissue engineering and regenerative medicine.

Bacterial cellulose/hyaluronic acid nanocomposites production through co-culturing Gluconacetobacter hansenii and Lactococcus lactis in a two-vessel circulating system

Bacterial cellulose (BC) based composites have been widely studied in the biomedical field. In this study, the BC/HA (hyaluronic acid) nanocomposites in the pellicle form were directly produced through co-culturing Gluconacetobacter hansenii ATCC 23769 and Lactococcus lactis APJ3 in a novel two-vessel circulating system. The concentration of HA secreted by L. lactis was controlled through adjusting the constant feed rate of glucose. The dynamic growth of the strains revealed that L. lactis was mainly growing within 48 h while G. hansenii started to grow after 48 h. XRD analysis indicated the presence of HA would not affect the crystallinity of cellulose but increase the crystalline sizes. The FESEM images showed that more ribbons within the width of 20-40 nm and larger ribbons between 180 and 360 nm were observed in BC/HA. The strain at break and the water holding capacity of BC/HA increased with the concentration of HA.

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/phytochemical's extracts biocomposites for potential active wound dressings

The present study describes the impregnation of coffee extract (CE) into bacterial cellulose synthesized from kombucha tea fungus (KBC) of different cellulose content, incubated for different incubation periods (2, 4, and 10 days), to prepare biocomposites having the potential for wound healing applications. Total polyphenols in hydroalcoholic extracts from ground roasted coffee and its release from the prepared biocomposites were determined as gallic acid equivalent. The polyphenols content was found to be 13.66 mg/g and the minimum inhibitory concentration (MIC) of the CE was determined using colony-forming unit (CFU) method against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus where the growth inhibition was 86 and 97% respectively. Biocomposites (KBC/CE) with the lowest cellulose and CE content showed the highest wet tensile stress (3.35 MPa), absorption of pseudo extracellular fluid (154.32% ± 4.84), and water vapor transmission rate (3184.94 ± 198.07 g/m²/day), whereas it showed the lowest polyphenols' release (51.85% ± 2.94)when immersed in PBS buffer of pH 7.4. The impregnation of CE into KBC provided biocomposites that can enlarge the range of BC in the biomedical application.

From a Basic Microalga and an Acetic Acid Bacterium Cellulose Producer to a Living Symbiotic Biofilm

Bacterial cellulose (BC) has recently been the subject of a considerable amount of research, not only for its environmentally friendly biosynthesis, but also for its high potential in areas such as biomedicine or biomaterials. A symbiotic relationship between a photosynthetic microalga, Chlamydomonas debaryana, and a cellulose producer bacterium, Komagataeibacter saccharivorans, was established in order to obtain a viable and active biofilm. The effect of the growth media composition ratio on the produced living material was investigated, as well as the microalgae biomass quantity, temperature, and incubation time. The optimal temperature for higher symbiotic biofilm production was 30 °C with an incubation period of 14 days. The high microalgae presence, 0.75% w/v, and 60:40 HS:BG-11 medium (v/v) induced a biofilm microalgae incorporation rate of 85%. The obtained results report, for the first time, a successful symbiotic interaction developed in situ between an alkaline photosynthetic microalga and an acetic acid bacterium. These results are promising and open a new window to BC living biofilm applications in medical fields that have not yet been explored.

Bacterial cellulose: a versatile biopolymer for wound dressing applications

Although several therapeutic approaches are available for wound and burn treatment and much progress has been made in this area, room for improvement still exists, driven by the urgent need of better strategies to accelerate wound healing and recovery, mostly for cases of severe burned patients. Bacterial cellulose (BC) is a biopolymer produced by bacteria with several advantages over vegetal cellulose, such as purity, high porosity, permeability to liquid and gases, elevated water uptake capacity and mechanical robustness. Besides its biocompatibility, BC can be modified in order to acquire antibacterial response and possible local drug delivery features. Due to its intrinsic versatility, BC is the perfect example of a biotechnological response to a clinical problem. In this review, we assess the BC main features and emphasis is given to a specific biomedical application: wound dressings. The production process and the physical-chemical properties that entitle this material to be used as wound dressing namely for burn healing are highlighted. An overview of the most common BC composites and their enhanced properties, in particular physical and biological, is provided, including the different production processes. A particular focus is given to the biochemistry and genetic manipulation of BC. A summary of the current marketed BC-based wound dressing products is presented, and finally, future perspectives for the usage of BC as wound dressing are foreseen.