Bacterial cellulose in biomedical applications: A review

Repair of dural defects with electrospun bacterial cellulose membranes in a rabbit experimental model

To evaluate the advantages and mechanisms involved in repairing rabbit dural defect with a novel electrospun bacterial cellulose (EBC) membrane, a series of experiments were carried out in vitro and in vivo. Compared with common bacterial cellulose (BC) membrane, a more dispersed and regular fiber structure and a better porosity and water holding capacity were found in the EBC membrane, which also had superior degradability. However, the biomechanical properties were slightly decreased. The results demonstrated that BC and EBC membranes had little effect on proliferation and apoptosis of mouse fibroblast cells. There were no complications such as infection, cerebrospinal fluid leakage, epilepsy and brain swelling after BC and EBC membrane repairs in rabbit models. Using real-time quantitative polymerase chain reaction (RT-qPCR) and western blot, the early inflammatory reactions in the EBC group were shown to be lower than in the BC group, and were close to the autologous dura mater group. Histological observations and western blot revealed more collagen fibers evenly distributed on the outer side of EBC membranes than in the BC and unpatched groups, and fewer brain tissue adhesions and epidural scars were found in the EBC group. Compared with common BC membrane, the EBC membrane had better biophysical properties and biocompatibility. It is expected to be a suitable alternative material for the repair of damaged dura mater.

Fabrication and In-Vivo Study of Micro-Colloidal Zanthoxylum acanthopodium-Loaded Bacterial Cellulose as a Burn Wound Dressing

Bacterial cellulose (BC) is a biopolymer commonly used for wound dressing due to its high biocompatible properties either in-vitro or in-vivo. The three-dimensional fiber structure of BC becomes an advantage because it provides a template for the impregnation of materials in order to improve BC's properties as a wound dressing, since BC has not displayed any bioactivity properties. In this study, micro-colloidal Zanthoxylum acanthopodium (MZA) fruit was loaded into BC fibers via an in-situ method. Z. acanthopodium is known to have anti-inflammatory, antioxidant and antimicrobial activities that can support BC to accelerate the wound healing process. The FTIR, XRD and SEM analysis results showed that the loading process of MZA and the composite fabrication were successfully carried out. The TGA test also showed that the presence of MZA in BC fibers decreased Tmax composite from BC, from 357.8 to 334.5 °C for BC-MZA3. Other aspects, i.e., water content, porosity, hemocompatibility and histology studies, also showed that the composite could potentially be used as a wound dressing.

Khattab T. Recent Advances in Cellulose-Based Biosensors for Medical Diagnosis

Cellulose has attracted much interest, particularly in medical applications such as advanced biosensing devices. Cellulose could provide biosensors with enhanced biocompatibility, biodegradability and non-toxicity, which could be useful for biosensors. Thus, they play a significant role in environmental monitoring, medical diagnostic tools, forensic science, and foodstuff processing safety applications. This review summarizes the recent developments in cellulose-based biosensors targeting the molecular design principles toward medical detection purposes. The recognition/detection mechanisms of cellulose-based biosensors demonstrate two major classes of measurable signal generation, including optical and electrochemical cellulosic biosensors. As a result of their simplicity, high sensitivity, and low cost, cellulose-based optical biosensors are particularly of great interest for including label-free and label-driven (fluorescent and colorimetric) biosensors. There have been numerous types of cellulose substrates employed in biosensors, including several cellulose derivatives, nano-cellulose, bacterial cellulose, paper, gauzes, and hydrogels. These kinds of cellulose-based biosensors were discussed according to their preparation procedures and detection principle. Cellulose and its derivatives with their distinctive chemical structure have demonstrated to be versatile materials, affording a high-quality platform for accomplishing the immobilization process of biologically active molecules into biosensors. Cellulose-based biosensors exhibit a variety of desirable characteristics, such as sensitivity, accuracy, convenience, quick response, and low-cost. For instance, cellulose paper-based biosensors are characterized as being low-cost and easy to operate, while nano-cellulose biosensors are characterized as having a good dispersion, high absorbance capacity, and large surface area. Cellulose and its derivatives have been promising materials in biosensors which could be employed to monitor various bio-molecules, such as urea, glucose, cell, amino acid, protein, lactate, hydroquinone, gene, and cholesterol. The future interest will focus on the design and construction of multifunctional, miniaturized, low-cost, environmentally friendly, and integrated biosensors. Thus, the production of cellulose-based biosensors is very important.

Bacterial Cellulose as a Versatile Platform for Research and Development of Biomedical Materials

The unique pool of features found in intracellular and extracellular bacterial biopolymers attracts a lot of research, with bacterial cellulose (BC) being one of the most versatile and common. BC is an exopolysaccharide consisting solely of cellulose, and the variation in the production process can vary its shape or even its composition when compounding is applied in situ. Together with ex situ modification pathways, including specialised polymers, particles or exclusively functional groups, BC provides a robust platform that yields complex multifunctional compounds that go far beyond ultra-high purity, intrinsic hydrophilicity, mechanical strength and biocompatibility to introduce bioactive, (pH, thermal, electro) responsive, conductive and ‘smart’ properties. This review summarises the research outcomes in BC-medical applications, focusing mainly on data from the past decade (i.e., 2010–2020), with special emphasis on BC nanocomposites as materials and devices applicable in medicine. The high purity and unique structural/mechanical features, in addition to its capacity to closely adhere to irregular skin surfaces, skin tolerance, and demonstrated efficacy in wound healing, all stand as valuable attributes advantageous in topical drug delivery. Numerous studies prove BC compatibility with various human cells, with modifications even improving cell affinity and viability. Even BC represents a physical barrier that can reduce the penetration of bacteria into the tissue, but in its native form does not exhibit antimicrobial properties, therefore carious modifications have been made or specific compounds added to confer antimicrobial or anti-inflammatory properties. Progress in the use of BC-compounds as wound dressings, vascular grafts, and scaffolds for the treatment of cartilage, bone and osteochondral defects, the role as a basement membrane in blood-brain barrier models and many more are discussed to particular extent, emphasising the need for BC compounding to meet specific requirements.

Glycogen as a Building Block for Advanced Biological Materials

Biological nanoparticles found in living systems possess distinct molecular architectures and diverse functions. Glycogen is a unique biological polysaccharide nanoparticle fabricated by nature through a bottom-up approach. The biocatalytic synthesis of glycogen has evolved over time to form a nanometer-sized dendrimer-like structure (20-150 nm) with a highly branched surface and a dense core. This makes glycogen markedly different from other natural linear or branched polysaccharides and particularly attractive as a platform for biomedical applications. Glycogen is inherently biodegradable, nontoxic, and can be functionalized with diverse surface and internal motifs for enhanced biofunctional properties. Recently, there has been growing interest in glycogen as a natural alternative to synthetic polymers and nanoparticles in a range of applications. Herein, the recent literature on glycogen in the material-based sciences, including its use as a constituent in biodegradable hydrogels and fibers, drug delivery vectors, tumor targeting and penetrating nanoparticles, immunomodulators, vaccine adjuvants, and contrast agents, is reviewed. The various methods of chemical functionalization and physical assembly of glycogen nanoparticles into multicomponent nanodevices, which advance glycogen toward a functional therapeutic nanoparticle from nature and back again, are discussed in detail.

Crystal and Supramolecular Structure of Bacterial Cellulose Hydrolyzed by Cellobiohydrolase from Scytalidium Candidum 3C: A Basis for Development of Biodegradable Wound Dressings

The crystal and supramolecular structure of the bacterial cellulose (BC) has been studied at different stages of cellobiohydrolase hydrolysis using various physical and microscopic methods. Enzymatic hydrolysis significantly affected the crystal and supramolecular structure of native BC, in which the 3D polymer network consisted of nanoribbons with a thickness T ≈ 8 nm and a width W ≈ 50 nm, and with a developed specific surface S_BET ≈ 260 m²·g⁻¹. Biodegradation for 24 h led to a ten percent decrease in the mean crystal size D_hkl of BC, to two-fold increase in the sizes of nanoribbons, and in the specific surface area S_BET up to ≈ 100 m²·g⁻¹. Atomic force and scanning electron microscopy images showed BC microstructure “loosening“after enzymatic treatment, as well as the formation and accumulation of submicron particles in the cells of the 3D polymer network. Experiments in vitro and in vivo did not reveal cytotoxic effect by the enzyme addition to BC dressings and showed a generally positive influence on the treatment of extensive III-degree burns, significantly accelerating wound healing in rats. Thus, in our opinion, the results obtained can serve as a basis for further development of effective biodegradable dressings for wound healing.

Conformal Bacterial Cellulose Coatings as Lubricious Surfaces

We report a versatile method to form bacterial cellulose coatings through simple dip-coating of 3D objects in suspensions of cellulose-producing bacteria. The adhesion of cellulose-secreting bacteria on objects was promoted through surface roughness and chemistry. Immobilized bacteria secreted highly porous hydrogels with high water content directly from the surface of a variety of materials. The out-of-plane orientation of cellulose fibers present in this coating leads to high mechanical stability and energy dissipation with minimal cellulose concentration. The conformal, biocompatible, and lubricious nature of the in situ grown cellulose surfaces makes the coated 3D objects attractive for biomedical applications.

Bacterial cellulose micro-nano fibres for wound healing applications

Bacterial cellulose (BC) is cellulose produced by a few limited species of bacteria in given conditions. BC has many remarkable properties such as its attractive mechanical properties, water uptake ability and biocompatibility which makes it a very desirable material to be used for wound healing. Inherently due to these important properties, the material is very resistant to easy processing and thus difficult to produce into useful entities. Additionally, being rate limited by the dependency on bacterial production, high yield is difficult to obtain and thus secondary material processing is sought after. In this review, BC is explained in terms of synthesis, structure and properties. These beneficial properties are directly related to the material's great potential in wound healing where it has also been trialled commercially but ultimately failed due to processing issues. However, more recently there has been increased frequency in scientific work relating to BC processing into hybrid polymeric fibres using common laboratory fibre forming techniques such as electrospinning and pressurised gyration. This paper summarises current progress in BC fibre manufacturing, its downfalls and also gives a future perspective on how the landscape should change to allow BC to be utilised in wound care in the current environment.

Bacterial Cellulose-Modified Polyhydroxyalkanoates Scaffolds Promotes Bone Formation in Critical Size Calvarial Defects in Mice

Bone regeneration is a claim challenge in addressing bone defects with large tissue deficits, that involves bone grafts to support the activity. In vitro biocompatibility of the bacterial cellulose-modified polyhydroxyalkanoates (PHB/BC) scaffolds and its osteogenic potential in critical-size mouse calvaria defects had been investigated. Bone promotion and mineralization were analyzed by biochemistry, histology/histomorphometry, X-ray analysis and immunofluorescence for highlighting osteogenesis markers. In summary, our results showed that PHB/BC scaffolds are able to support 3T3-L1 preadipocytes proliferation and had a positive effect on in vivo osteoblast differentiation, consequently inducing new bone formation after 20 weeks post-implantation. Thus, the newly developed PHB/BC scaffolds could turn out to be suitable biomaterials for the bone tissue engineering purpose.

Design Considerations for Hydrogel Wound Dressings: Strategic and Molecular Advances

Wound dressings are traditionally used to protect a wound and to facilitate healing. Currently, their function is expanding. There is an urgent need for new smart products that not only act as a protective barrier but also actively support the wound healing process. Hydrogel dressings are an example of such innovative products and typically facilitate wound healing by providing a hospitable and moist environment in which cells can thrive, while the wound can still breathe and exudate can be drained. These dressings also tend to be less painful or have a soothing effect and allow for additional drug delivery. In this review, various strategic and molecular design considerations are discussed that are relevant for developing a hydrogel into a wound dressing product. These considerations vary from material choice to ease of use and determine the dressing's final properties, application potential, and benefits for the patient. The focus of this review lies on identifying and explaining key aspects of hydrogel wound dressings and their relevance in the different phases of wound repair. Molecular targets of wound healing are discussed that are relevant when tailoring hydrogels toward specific wound healing scenarios. In addition, the potential of hydrogels is reviewed as medicine advances from a repair-based wound healing approach toward a regenerative-based one. Hydrogels can play a key role in the transition toward personal wound care and facilitating regenerative medicine strategies by acting as a scaffold for (stem) cells and carrier/source of bioactive molecules and/or drugs. Impact statement Improved wound healing will lead to a better quality of life around the globe. It can be expected that this coincides with a reduction in health care spending, as the duration of treatment decreases. To achieve this, new and modern wound care products are desired that both facilitate healing and improve comfort and outcome for the patient. It is proposed that hydrogel wound dressings can play a pivotal role in improving wound care, and to that end, this review aims to summarize the various design considerations that can be made to optimize hydrogels for the purpose of a wound dressing.

The effect of dehydration/rehydration of bacterial nanocellulose on its tensile strength and physicochemical properties

Bacterial nanocellulose (BNC) is a natural biomaterial with a wide range of biomedical applications. BNC contains 99 % of water which makes it too thick to be used as a bioimplant material. The aim of the work was to determine the effect of the BNC dehydration followed by rehydration on its mechanical and physicochemical properties, in the context of the use of BNC as bio-prostheses in the cardiovascular system. Dehydration involved the convection-drying at 25 and 105 °C, and the freeze-drying, while rehydration - the soaking in water. All modified BNC samples had reduced thickness, and results obtained from FT-IR, XRD, and SEM analysis revealed that 25 °C BNC convection-dried after soaking in water was characterized by the highest: tensile strength (17.4 MPa), thermal stability (253 °C), dry mass content (4.34 %) and I_α/I_β ratio (1.10). Therefore, 25 °C convection-dried BNC followed by soaking in water can be considered as a material suitable for cardiovascular implants.

Composite scaffolds based on calcium phosphates and barium titanate obtained through bacterial cellulose templated synthesis

Taking into account the potential of barium titanate to deliver electrical stimulation to the physiological microenvironment and offer beneficial conditions for the cellular metabolism, this mineral phase was selected for the development of new composites. In this context, calcium phosphates and barium titanate were deposited on bacterial cellulose membranes under ultrasonic irradiation, the resulting system being subjected to a thermal treatment in optimized conditions in order to remove the polymeric template and achieve 3D porous architectures. The complex characterization performed on the intermediate and final samples demonstrated the suitability of such materials for hard tissue engineering applications.

Applications of bacterial-synthesized cellulose in veterinary medicine – a review

Tissue engineering promotes tissue regeneration through biomaterials that have excellent properties and have the potential to replace tissues. Many studies show that bacterial cellulose (BC) might ensure tissue regeneration and substitution, being used for the bioengineering of hard, cartilaginous and soft tissues. Bacterial cellulose is extensively used as wound dressing material and results show that BC is a promising tissue scaffold (bone, cardiovascular, urinary tissue). It can be combined with polymeric and non-polymeric compounds to acquire antimicrobial, cell-adhesion and proliferation properties. To ensure proper tissue regeneration, the material has to be: biocompatible, with minimum tissue reaction and biodegradability; bio-absorbable, to promote tissue development, cellular interaction and grow; resistant to support the weight of the newly formed tissue. Its versatile structure, physical and biochemical properties can be adjusted by adapting the bacteria culturing conditions. The main biomedical applications seem to be as hard (bone, dental), fibrocartilaginous (meniscal) and soft tissue (skin, cardiovascular, urinary) substituents. This paper reviews the current state of knowledge, challenges and future applications of BC and its biomedical potential in veterinary medicine. It was focused on the main uses in regeneration and scaffold tissue replacement and, although BC showed promising results, there is a lack of successful results of BC use in clinical practice. Most studies were performed only at experimental level and further research is needed for BC to enter clinical veterinary practice.

Preparation of aminoalkyl-grafted bacterial cellulose membranes with improved antimicrobial properties for biomedical applications

Bacterial cellulose (BC) membranes display special properties and structures, thus attracting much attention in application in the biomedical areas, for example, as implants for bone or cartilage tissue engineering, as substitutes for skin repairing, and as supports for controlled drug delivery. However, native BC lacks the activity to inhibit bacteria growth on its surface, which limits its applications in biomedical fields. There have been reports on chemical modification of BC membranes to endow them with antimicrobial properties needed for some special biomedical applications. In the present study, aminoalkyl-grafted BC membranes were prepared by alkoxysilane polycondensation using 3-aminopropyltriethoxysilane (APTES). The characterization for morphology and chemical composition showed that BC membranes were successfully grafted with aminoalkylsilane groups through covalent bonding. The surface morphology and roughness of the membranes changed after chemical grafting. Furthermore, after grafting with APTES, the membranes got less hydrophilic than native BC. The aminoalkyl-grafted BC membranes showed strong antibacterial properties against Staphylococcus aureus and Escherichia coli and moreover, they were nontoxic to normal human dermal fibroblasts. These results indicate that aminoalkyl-grafted BC membranes are potential to be used for biomedical applications.

Preparation of Polyvinyl Alcohol/Bacterial-Cellulose-Coated Biochar–Nanosilver Antibacterial Composite Membranes

Pathogenic bacteria and microorganisms in drinking water can cause various diseases, and new types of antibacterial material for water treatment and filtration are urgently needed. In this work, polyvinyl alcohol/bacterial cellulose/biochar–nanosilver (PVA/BC/C-Ag) antibacterial composite membrane materials were prepared by uniformly dispersing C-Ag particles in a PVA/BC mixed gel. Fourier-transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), scanning electron microscopy (SEM), and thermogravimetric differential scanning calorimetry (TG-DSC) were used to characterize the composite membranes. Results indicated that the BC was uniformly mixed into the PVA gel and that the C-Ag particles were uniformly immobilized in the PVA/BC hybrid membrane. The PVA/BC/C-Ag composite membranes exhibited excellent antibacterial activity against Escherichia coli when assayed using a plate-counting technique. When used to treat actual contaminated water, the composite membranes demonstrated sustained antibacterial activity and good reusability. PVA/BC/C-Ag composite membranes have great potential for the development of drinking water treatment applications.

Bioactive bacterial cellulose membrane with prolonged release of chlorhexidine for dental medical application

Bioabsorbable barrier membrane is desired in dental medicine for treatment of periodontal diseases caused by different types of bacteria. Bioactive and bioabsorbable bacterial cellulose (BC) is a promising material for such application. However, a key challenge to implement this approach is produce BC membranes selectively oxidized and loaded with a bactericide, in order to modulate bioabsortion time and bactericide effect, respectively. In the present study, the drug model chlorhexidine (CHX) was chosen and NaIO₄ was used as oxidizing agent. To modulate CHX release and efficacy, inclusion complexes of CHX with β-cyclodextrin (CHX:βCD) were synthesized. A linear dependence between degree of oxidation (DO) and oxidant concentration was found (DO = 2.07 + 45 [NaIO₄]). CHX has strong chemical interaction with cellulose structure, contributing for its significant retention. The association of membrane oxidation and formation of the inclusion complex with βCD causes a 10-fold increase in CHX release rate compared to unmodified cellulose. Thus, validating the concept that CHX release can be modulated using these two strategies. All membranes loaded with CHX inhibited S. aureus, E. coli and C. albicans growth, but DABC+CHX:βCD showed greater inhibition zone (p < 0.05). That, associated with other results, indicates potential application as bioactive and bioabsorbable membrane.

A Comprehensive Review on Bio-Nanomaterials for Medical Implants and Feasibility Studies on Fabrication of Such Implants by Additive Manufacturing Technique

Nanomaterials have allowed significant breakthroughs in bio-engineering and medical fields. In the present paper a holistic assessment on diverse biocompatible nanocomposites are studied. Their compatibility with advanced fabrication methods such as additive manufacturing for the design of functional medical implants is also critically reviewed. The significance of nanocomposites and processing techniques is also envisaged comprehensively in regard with the needs and futures of implantable medical device industries.

Exploration of Chitinous Scaffold-Based Interfaces for Glucose Sensing Assemblies

: The nanomaterial-integrated chitinous polymers have promoted the technological advancements in personal health care apparatus, particularly for enzyme-based devices like the glucometer. Chitin and chitosan, being natural biopolymers, have attracted great attention in the field of biocatalysts engineering. Their remarkable tunable properties have been explored for enhancing enzyme performance and biosensor advancements. Currently, incorporation of nanomaterials in chitin and chitosan-based biosensors are also widely exploited for enzyme stability and interference-free detection. Therefore, in this review, we focus on various innovative multi-faceted strategies used for the fabrication of biological assemblies using chitinous biomaterial interface. We aim to summarize the current development on chitin/chitosan and their nano-architecture scaffolds for interdisciplinary biosensor research, especially for analytes like glucose. This review article will be useful for understanding the overall multifunctional aspects and progress of chitin and chitosan-based polysaccharides in the food, biomedical, pharmaceutical, environmental, and other diverse applications.

Biocompatible Polymers and their Potential Biomedical Applications: A Review

Background:

Biocompatible polymers are gaining great interest in the field of biomedical applications. The term biocompatibility refers to the suitability of a polymer to body and body fluids exposure. Biocompatible polymers are both synthetic (man-made) and natural and aid in the close vicinity of a living system or work in intimacy with living cells. These are used to gauge, treat, boost, or substitute any tissue, organ or function of the body. A biocompatible polymer improves body functions without altering its normal functioning and triggering allergies or other side effects. It encompasses advances in tissue culture, tissue scaffolds, implantation, artificial grafts, wound fabrication, controlled drug delivery, bone filler material, etc.

Objectives:

This review provides an insight into the remarkable contribution made by some well-known biopolymers such as polylactic-co-glycolic acid, poly(ε-caprolactone) (PCL), polyLactic Acid, poly(3- hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), Chitosan and Cellulose in the therapeutic measure for many biomedical applications.

Methods: :

Various techniques and methods have made biopolymers more significant in the biomedical fields such as augmentation (replaced petroleum based polymers), film processing, injection modeling, blow molding techniques, controlled / implantable drug delivery devices, biological grafting, nano technology, tissue engineering etc.

Results:

The fore mentioned techniques and other advanced techniques have resulted in improved biocompatibility, nontoxicity, renewability, mild processing conditions, health condition, reduced immunological reactions and minimized side effects that would occur if synthetic polymers are used in a host cell.

Conclusion:

Biopolymers have brought effective and attainable targets in pharmaceutics and therapeutics. There are huge numbers of biopolymers reported in the literature that has been used effectively and extensively.

Kombucha from alternative raw materials - The review

Nowadays, people's awareness about the role of diet in maintaining well-being and good health has increased. Consumers expect that the products not only provide them with essential nutrients but will also be a source of biologically active substances, which are beneficial to their health. One of the "healthy trends," which has appeared among the consumers worldwide is kombucha, a tea drink with high antioxidant potential, obtained through the activity of a consortium of acetic acid bacteria and osmophilic yeast, which is also called "tea fungus." Kombucha obtained from tea is characterized by its health-promoting properties. Promising results in in vitro and in vivo studies have prompted research groups from around the world to search for alternative raw materials for tea fungus fermentation. Attempts are made to obtain functional beverages from leaves, herb infusions, vegetable pulp, fruit juices, or milk. This review focuses on describing the progress in obtaining a fermented beverage and bacterial cellulose using tea fungus on alternative raw materials.

Determination of live and dead Komagataeibacter xylinus cells and first attempt at precise control of inoculation in nanocellulose production

The timely enumeration of cells of nanocellulose-producing bacteria is challenging due to their unique growth properties. To better understand the metabolism of the bacteria and better control the concentration of living cells during cultivation, a prompt cell counting technology is crucial and urgently required. In this work, two fluorescent dyes, the asymmetrical anthocyanidin dye SYBR Green I (SG) and propidium iodide (PI), were first combined for Komagataeibacter xylinus species to determine live/dead bacterial cells quantitatively and promptly. The number of live and dead K. xylinus cells determined using an epifluorescence microscope corresponded well to the results obtained using a fluorescence microplate reader. The R² values were 0.9986 and 0.9920, respectively, and were similar to those obtained with the LIVE/DEAD^® BacLight^TM commercial kit. SG/PI double-staining showed proper efficiency in distinguishing live/dead cells for the K. xylinus strain (R²  = 0.9898). The technology was applied to standardize four different K. xylinus strains, and the initial cell concentration of the strains was precisely controlled (no significant difference among the strains, P> 0.05). The cellulose yield per live cell was calculated, and significant differences (P < 0.05) were found among the four strains in the following order: DHU-ATCC-1> DHU-ZCY-1> DHU-ZGD-1> ATCC 23770. The study shows (i) the application of the SG/PI staining to standardizing inocula for bacterial cellulose production so that a more accurate comparison can be made between different strains, and (ii) the lower cost of using SG rather than the SYTO 9 of the commercially available LIVE/DEAD^® BacLight^TM kit.

Production with a High Yield of Bacterial Cellulose Nanocrystals by Enzymatic Hydrolysis

Bacterial cellulose nanocrystals are highly crystalline structures with nanoscopic scale dimensions that have received increased attention in the nanocomposites area. Its properties, such as large surface area, low density, mechanical strength and ease of modification, are attractive to the preparation many kinds of nanomaterials applied multifunctional in various fields. Besides, the cellulose nanocrystals are from abundant and renewable sources that are biodegradable. An altemative method is to obtain bacterial cellulose nanocrystal by enzymatic hydrolysis because it is, less expensive, it does not use chemicals and it requires much less energy. In this sense, the primary objective of this study was to produce bacterial cellulose using glycerol as a carbon source and isolate nanocrystals from bacterial cellulose using the enzymatic hydrolysis. This study also investigated the yield of nanocrystals depending on the weight of the bacterial cellulose hydrogel, keeping constant some enzymes. The study shows us that the enzymatic method has the best performance when using cellulose hydrogel 2[Formula: see text]g to 40[Formula: see text][Formula: see text]L cellulase enzyme (endoglucanase) and 1[Formula: see text]mL of citrate buffer. Also, it was observed that the yield of nanocrystals decrease with increasing time required for the hydrolysis.

Bacterial Cellulose: Production, Modification and Perspectives in Biomedical Applications

Bacterial cellulose (BC) is ultrafine, nanofibrillar material with an exclusive combination of properties such as high crystallinity (84%-89%) and polymerization degree, high surface area (high aspect ratio of fibers with diameter 20-100 nm), high flexibility and tensile strength (Young modulus of 15-18 GPa), high water-holding capacity (over 100 times of its own weight), etc. Due to high purity, i.e., absence of lignin and hemicellulose, BC is considered as a non-cytotoxic, non-genotoxic and highly biocompatible material, attracting interest in diverse areas with hallmarks in medicine. The presented review summarizes the microbial aspects of BC production (bacterial strains, carbon sources and media) and versatile in situ and ex situ methods applied in BC modification, especially towards bionic design for applications in regenerative medicine, from wound healing and artificial skin, blood vessels, coverings in nerve surgery, dura mater prosthesis, arterial stent coating, cartilage and bone repair implants, etc. The paper concludes with challenges and perspectives in light of further translation in highly valuable medical products.

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.

Efficacy of Bacterial Cellulose as a Carrier of BMP-2 for Bone Regeneration in a Rabbit Frontal Sinus Model

If the alveolar bone height of patients requiring dental implants in the maxillary molar region is inadequate, it is difficult to achieve satisfactory outcomes using existing bone graft materials. We previously reported the possible utility of bacterial cellulose (BC) as a new dental treatment material. BC has a high absorptive capacity, good mechanical strength, and good volume retention. BC loaded with bone morphogenetic protein-2 (BMP-2) might allow effective alveolar bone augmentation. We created critical frontal bone defect models in 12 male Japanese white rabbits and divided them into four groups: sham; BC (BC grafting only); BMP-2 (treated with BMP-2 solution only); and BC+BMP-2 (grafted with BC loaded with BMP-2). Newly formed bone volume was calculated via hematoxylin-eosin staining evaluation. The proliferating cell nuclear antigen and osteocalcin levels were determined by the immunohistochemical staining analysis. All measured indices of the BC+BMP-2 group were significantly superior to those of the other groups (all p < 0.05). BC maintained the graft space and released BMP-2 in a sustained manner, promoting optimal bone formation. The BC+BMP-2 combination enhanced bone regeneration and shows promise as a useful means of clinical pre-dental implant bone augmentation in the maxillary sinus.

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 nanocellulose: Present status, biomedical applications and future perspectives

Bacterial nanocellulose (BNC) has emerged as a natural biopolymer of significant importance in diverse technological areas due to its incredible physicochemical and biological characteristics. However, the high capital investments, production cost and lack of well-organized scale-up processes resulting in low BNC production are the major impediments need to be resolved. This review enfolds the three different and important portions of BNC. Firstly, advancement in production technologies of BNC like cell-free extract technology, static intermittent fed batch technology and novel cost-effective substrates that might surmount the barriers associated with BNC production at industrial level. Secondly, as BNC and its composites (with other polymers/nanoparticles) represents the utmost material of preference in current regenerative and diagnostic medicine, therefore recently reported biomedical applications of BNC and functionalized BNC in drug delivery, tissue engineering, antimicrobial wound healing and biosensing are widely been focused here. The third and the most important aspect of this review is an in-depth discussion of various pitfalls associated with BNC production. Recent trends in BNC research to overcome the existing snags that might pave a way for industrial scale production of BNC thereby facilitating its feasible application in various fields are highlighted.

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.

Structural changes of bacterial nanocellulose pellicles induced by genetic modification of Komagataeibacter hansenii ATCC 23769

Bacterial nanocellulose (BNC) synthesized by Komagataeibacter hansenii is a polymer that recently gained an attention of tissue engineers, since its features make it a suitable material for scaffolds production. Nevertheless, it is still necessary to modify BNC to improve its properties in order to make it more suitable for biomedical use. One approach to address this issue is to genetically engineer K. hansenii cells towards synthesis of BNC with modified features. One of possible ways to achieve that is to influence the bacterial movement or cell morphology. In this paper, we described for the first time, K. hansenii ATCC 23769 motA+ and motB+ overexpression mutants, which displayed elongated cell phenotype, increased motility, and productivity. Moreover, the mutant cells produced thicker ribbons of cellulose arranged in looser network when compared to the wild-type strain. In this paper, we present a novel development in obtaining BNC membranes with improved properties using genetic engineering tools.

Generation of Cost-Effective Paper-Based Tissue Models through Matrix-Assisted Sacrificial 3D Printing

Due to the combined advantages of cellulose and nanoscale (diameter 20-60 nm), bacterial cellulose possesses a series of attractive features including its natural origin, moderate biosynthesis process, good biocompatibility, and cost-effectiveness. Moreover, bacterial cellulose nanofibers can be conveniently processed into three-dimensional (3D) intertwined structures and form stable paper devices after simple drying. These advantages make it suitable as the material for construction of organ-on-a-chip devices using matrix-assisted sacrificial 3D printing. We successfully fabricated various microchannel structures embedded in the bulk bacterial cellulose hydrogels and retained their integrity after the drying process. Interestingly, these paper-based devices containing hollow microchannels could be rehydrated and populated with relevant cells to form vascularized tissue models. As a proof-of-concept demonstration, we seeded human umbilical vein endothelial cells (HUVECs) into the microchannels to obtain the vasculature and inoculated the MCF-7 cells onto the surrounding matrix of the paper device to build a 3D paper-based vascularized breast tumor model. The results showed that the microchannels were perfusable, and both HUVECs and MCF-7 cells exhibited favorable proliferation behaviors. This study may provide a new strategy for constructing simple and low-cost in vitro tissue models, which may find potential applications in drug screening and personalized medicine.