Free-standing three-dimensional hollow bacterial cellulose structures with controlled geometry via patterned superhydrophobic-hydrophilic surfaces

3D printing of bacterial cellulose for potential wound healing applications: Current trends and prospects

Several advances in skin tissue engineering have been made to restore skin damage, facilitating wound healing. Bacterial cellulose (BC), a naturally occurring polymer, has gained attention as a potential material in wound healing due to its unique physical and biological properties. In recent years, with the advent of 3D bio-printing technology, new avenues have opened for fabricating customized wound dressings and scaffolds for tissue engineering purposes. The existing literature in this field mainly focuses on the ways of modifications of bacterial cellulose to make it printable. Still, the applicability of 3D printed scaffolds for wound healing needs to be explored more. This review article focuses on the current research on using 3D-printed BC for skin regeneration, including its production methods and physical and biological properties, making it a better choice than traditional dressings. Furthermore, it also highlights the limitations and future directions for using BC in wound healing and tissue engineering applications. This review provides a comprehensive and up-to-date exploration of the applications of 3D-printed BC in wound healing, drawing insights from pre-existing studies and emphasizing patient compliance, clinical outcomes, and economic viability.

Biofabrication with microbial cellulose: from bioadaptive designs to living materials

Nanocellulose is not only a renewable material but also brings functions that are opening new technological opportunities. Here we discuss a special subset of this material, in its fibrillated form, which is produced by aerobic microorganisms, namely, bacterial nanocellulose (BNC). BNC offers distinct advantages over plant-derived counterparts, including high purity and high degree of polymerization as well as crystallinity, strength, and water-holding capacity, among others. More remarkably, beyond classical fermentative protocols, it is possible to grow BNC on non-planar interfaces, opening new possibilities in the assembly of advanced bottom-up structures. In this review, we discuss the recent advances in the area of BNC-based biofabrication of three-dimensional (3D) designs by following solid- and soft-material templating. These methods are shown as suitable platforms to achieve bioadaptive constructs comprising highly interlocked biofilms that can be tailored with precise control over nanoscale morphological features. BNC-based biofabrication opens applications that are not possible by using traditional manufacturing routes, including direct ink writing of hydrogels. This review emphasizes the critical contributions of microbiology, colloid and surface science, as well as additive manufacturing in achieving bioadaptive designs from living matter. The future impact of BNC biofabrication is expected to take advantage of material and energy integration, residue utilization, circularity and social latitudes. Leveraging existing infrastructure, the scaleup of biofabrication routes will contribute to a new generation of advanced materials rooted in exciting synergies that combine biology, chemistry, engineering and material sciences.

Bacterial Cellulose: A Sustainable Source for Hydrogels and 3D-Printed Scaffolds for Tissue Engineering

Bacterial cellulose is a biocompatible biomaterial with a unique macromolecular structure. Unlike plant-derived cellulose, bacterial cellulose is produced by certain bacteria, resulting in a sustainable material consisting of self-assembled nanostructured fibers with high crystallinity. Due to its purity, bacterial cellulose is appealing for biomedical applications and has raised increasing interest, particularly in the context of 3D printing for tissue engineering and regenerative medicine applications. Bacterial cellulose can serve as an excellent bioink in 3D printing, due to its biocompatibility, biodegradability, and ability to mimic the collagen fibrils from the extracellular matrix (ECM) of connective tissues. Its nanofibrillar structure provides a suitable scaffold for cell attachment, proliferation, and differentiation, crucial for tissue regeneration. Moreover, its mechanical strength and flexibility allow for the precise printing of complex tissue structures. Bacterial cellulose itself has no antimicrobial activity, but due to its ideal structure, it serves as matrix for other bioactive molecules, resulting in a hybrid product with antimicrobial properties, particularly advantageous in the management of chronic wounds healing process. Overall, this unique combination of properties makes bacterial cellulose a promising material for manufacturing hydrogels and 3D-printed scaffolds, advancing the field of tissue engineering and regenerative medicine.

Revolutionizing targeting precision: microfluidics-enabled smart microcapsules for tailored delivery and controlled release

As promising delivery systems, smart microcapsules have garnered significant attention owing to their targeted delivery loaded with diverse active materials. By precisely manipulating fluids on the micrometer scale, microfluidic has emerged as a powerful tool for tailoring delivery systems based on potential applications. The desirable characteristics of smart microcapsules are associated with encapsulation capacity, targeted delivery capability, and controlled release of encapsulants. In this review, we briefly describe the principles of droplet-based microfluidics for smart microcapsules. Subsequently, we summarize smart microcapsules as delivery systems for efficient encapsulation and focus on target delivery patterns, including passive targets, active targets, and microfluidics-assisted targets. Additionally, based on release mechanisms, we review controlled release modes adjusted by smart membranes and on/off gates. Finally, we discuss existing challenges and potential implications associated with smart microcapsules.

Cellulose-Based Ionic Conductor: An Emerging Material toward Sustainable Devices

Ionic conductors (ICs) find widespread applications across different fields, such as smart electronic, ionotronic, sensor, biomedical, and energy harvesting/storage devices, and largely determine the function and performance of these devices. In the pursuit of developing ICs required for better performing and sustainable devices, cellulose appears as an attractive and promising building block due to its high abundance, renewability, striking mechanical strength, and other functional features. In this review, we provide a comprehensive summary regarding ICs fabricated from cellulose and cellulose-derived materials in terms of fundamental structural features of cellulose, the materials design and fabrication techniques for engineering, main properties and characterization, and diverse applications. Next, the potential of cellulose-based ICs to relieve the increasing concern about electronic waste within the frame of circularity and environmental sustainability and the future directions to be explored for advancing this field are discussed. Overall, we hope this review can provide a comprehensive summary and unique perspectives on the design and application of advanced cellulose-based ICs and thereby encourage the utilization of cellulosic materials toward sustainable devices.

Living materials made by 3D printing cellulose-producing bacteria in granular gels

Bacterial cellulose is an attractive resource for the manufacturing of sustainable materials, but it is usually challenging to shape it into elaborate three-dimensional structures. Here, we report a manufacturing platform for the creation of complex-shaped cellulose objects by printing inks loaded with bacteria into a silicone-based granular gel. The gel provides the viscoelastic behavior necessary to shape the bacteria-laden ink in three dimensions and the gas permeability required to sustain cellular growth and cellulose formation after the printing process. Using Gluconacetobacter xylinus as model cellulose-producing bacteria, we study the growth and the mechanical properties of cellulose fiber networks obtained upon incubation of the printed inks. Diffusion processes within the ink were found to control the growth of the cellulose structures, which display mechanical properties within the range expected for conventional hydrogels. By keeping the bacteria alive in the printed object, we produce living materials in complex geometries that are able to self-regenerate their cellulose fiber network after damage. Such living hydrogels represent an enticing development towards functional materials with autonomous self-healing and self-regenerating capabilities.

Melanoma growth in non-chemically modified translucid bacterial nanocellulose hollow and compartimentalized spheres

BACKGROUND

Bacterial nanocellulose (BNC) has been used as cell support in numerous tissue engineering studies. Its use can be explained based on the fact its structure allows the creation of a required microenvironment for an ideal material, which supports 3D cell culture. Its structure and interconnected pores lead to animal cells adhesion and proliferation, also allowing oxygen and nutrients transportation.

METHODS

We developed a new methodology to produce spherical platforms synthesized by Komagataebacter hansenii (ATCC 23769) under dynamic culture conditions in minimal medium. The chemical composition and physical properties of the platforms were evaluated. Then, human melanoma cells (SK-MEL-28) were encapsulated into the platforms and evaluated by metabolic activity, morphology and their ability on adhering to the Hollow Translucid BNC Spheres (BNC-TS-H) and Compartmentalized Translucid BNC Spheres (BNC-TS-C) up to 3 days.

RESULTS

BNC-TS-H and BNC-TS-C platforms were produced as translucid spheroid platforms with distinct microenvironment under dynamic fermentation. The chemical and physical characterizations confirmed the platforms composition as BNC. The produced internal microenvironments in spherical platforms are relevant to determine tumor cell fate. In the first 12 h of culture, cells were could adhere to nanocellulose microfibers assuming their typical tumorous phenotype in 72 h of culture.

CONCLUSION

The dynamic fermentation in minimal medium produced distinct microstructured platforms of BNC-TS-H and BNC-TS-C. The platforms microstructure resulted in microenvironments that enabled distinct cell-cell and cell-matrix interactions. This behavior suggests several applications on tissue engineering.

GENERAL SIGNIFICANCE

The method produced translucid BNC sphere platforms with distinct microenvironments for 3D cell culture.

A pilot and open trial to evaluate topical Bacterial Cellulose bio-curatives in the treatment of cutaneous leishmaniasis caused by L. braziliensis

The treatment of cutaneous leishmaniasis (CL) in Brazil using pentavalent antimony (Sb^v) is associated with a high failure rate and long time to heal. Moreover, standard Sb^v treatment cures only 50-60% of the cases. In this pilot clinical trial, we evaluated the topical use of bacterial cellulose (BC) bio-curatives + Sb^v in the treatment of CL caused by L. braziliensis, in Bahia, Brazil. A total of 20 patients were randomized in two groups assigned to receive either parenteral Sb^v alone or parenteral Sb^v plus topically applied BC bio-curatives. CL patients treated with Sb^v + topical BC bio-curatives had a significantly higher cure rate at 60 days post initiation of treatment compared to CL patients treated with Sb^v alone (P=0.01). At day 90 post initiation of treatment, cure rate was similar in the two groups as was overall healing time. Adverse effects or local reactions to topical BC application were not observed. This pilot trial shows that the potential use of a combined therapy consisting of topical BC bio-curatives and parenteral Sb^v in favoring healing of CL lesions caused by L. braziliensis, at an early time point.

Bacterial Cellulose: Production, Characterization, and Application as Antimicrobial Agent

Bacterial cellulose (BC) is recognized as a multifaceted, versatile biomaterial with abundant applications. Groups of microorganisms such as bacteria are accountable for BC synthesis through static or agitated fermentation processes in the presence of competent media. In comparison to static cultivation, agitated cultivation provides the maximum yield of the BC. A pure cellulose BC can positively interact with hydrophilic or hydrophobic biopolymers while being used in the biomedical domain. From the last two decades, the reinforcement of biopolymer-based biocomposites and its applicability with BC have increased in the research field. The harmony of hydrophobic biopolymers can be reduced due to the high moisture content of BC in comparison to hydrophilic biopolymers. Mechanical properties are the important parameters not only in producing green composite but also in dealing with tissue engineering, medical implants, and biofilm. The wide requisition of BC in medical as well as industrial fields has warranted the scaling up of the production of BC with added economy. This review provides a detailed overview of the production and properties of BC and several parameters affecting the production of BC and its biocomposites, elucidating their antimicrobial and antibiofilm efficacy with an insight to highlight their therapeutic potential.

One-Step Biosynthesis of Soft Magnetic Bacterial Cellulose Spheres with Localized Nanoparticle Functionalization

Actuated structures are becoming relevant in medical fields; however, they call for flexible/soft-base materials that comply with biological tissues and can be synthesized in simple fabrication steps. In this work, we extend the palette of techniques to afford soft, actuable spherical structures taking advantage of the biosynthesis process of bacterial cellulose. Bacterial cellulose spheres (BCS) with localized magnetic nanoparticles (NPs) have been biosynthesized using two different one-pot processes: in agitation and on hydrophobic surface-supported static culture, achieving core-shell or hollow spheres, respectively. Magnetic actuability is conferred by superparamagnetic iron oxide NPs (SPIONs), and their location within the structure was finely tuned with high precision. The size, structure, flexibility and magnetic response of the spheres have been characterized. In addition, the versatility of the methodology allows us to produce actuated spherical structures adding other NPs (Au and Pt) in specific locations, creating Janus structures. The combination of Pt NPs and SPIONs provides moving composite structures driven both by a magnetic field and a H₂O₂ oxidation reaction. Janus Pt/SPIONs increased by five times the directionality and movement of these structures in comparison to the controls.

Bacterial cellulose spheroids as building blocks for 3D and patterned living materials and for regeneration

Engineered living materials (ELMs) based on bacterial cellulose (BC) offer a promising avenue for cheap-to-produce materials that can be programmed with genetically encoded functionalities. Here we explore how ELMs can be fabricated in a modular fashion from millimetre-scale biofilm spheroids grown from shaking cultures of Komagataeibacter rhaeticus. Here we define a reproducible protocol to produce BC spheroids with the high yield bacterial cellulose producer K. rhaeticus and demonstrate for the first time their potential for their use as building blocks to grow ELMs in 3D shapes. Using genetically engineered K. rhaeticus, we produce functionalized BC spheroids and use these to make and grow patterned BC-based ELMs that signal within a material and can sense and report on chemical inputs. We also investigate the use of BC spheroids as a method to regenerate damaged BC materials and as a way to fuse together smaller material sections of cellulose and synthetic materials into a larger piece. This work improves our understanding of BC spheroid formation and showcases their great potential for fabricating, patterning and repairing ELMs based on the promising biomaterial of bacterial cellulose.

Bacterial cellulose is a promising cheap-to-produce programmable engineered living material. Here the authors present a method for production of spheroids for use as engineerable building blocks able to sense and respond to chemical inputs.

Bioinspired wettable-nonwettable micropatterns for emerging applications

Superhydrophilic and superhydrophobic surfaces are prevalent in nature and have received tremendous attention due to their importance in both fundamental research and practical applications. With the high interdisciplinary research and great development of microfabrication techniques, artificial wettable-nonwettable micropatterns inspired by the water-collection behavior of desert beetles have been successfully fabricated. A combination of the two extreme states of superhydrophilicity and superhydrophobicity on the same surface precisely, wettable-nonwettable micropatterns possess unique functionalities, such as controllable superwetting, anisotropic wetting, oriented adhesion, and other properties. In this review, we briefly describe the methods for fabricating wettable-nonwettable patterns, including self-assembly, electrodeposition, inkjet printing, and photolithography. We also highlight some of the emerging applications such as water collection, controllable bioadhesion, cell arrays, microreactors, printing techniques, and biosensors combined with various detection methods. Finally, the current challenges and prospects of this renascent and rapidly developing field are proposed and discussed.

Limbal Stem Cells on Bacterial Nanocellulose Carriers for Ocular Surface Regeneration

Limbal stem cells (LSCs) are already used in cell-based treatments for ocular surface disorders. Clinical translation of LSCs-based therapies critically depends on the successful delivery, survival, and retention of these therapeutic cells to the desired region. Such a major bottleneck could be overcome by using an appropriate carrier to provide anchoring sites and structural support to LSC culture and transplantation. Bacterial nanocellulose (BNC) is an appealing, yet unexplored, candidate for this application because of its biocompatibility, animal-free origin and mechanical stability. Here, BNC as a vehicle for human embryonic stem cells-derived LSC (hESC-LSC) are investigated. To enhance cell-biomaterial interactions, a plasma activation followed by a Collagen IV and Laminin coating of the BNC substrates is implemented. This surface functionalization with human extracellular matrix proteins greatly improved the attachment and survival of hESC-LSC without compromising the flexible, robust and semi-transparent nature of the BNC. The surface characteristics of the BNC substrates are described and a preliminary ex vivo test in simulated transplantation scenarios is provided. Importantly, it is shown that hESC-LSC retain their self-renewal and stemness characteristics up to 21 days on BNC substrates. These results open the door for future research on hESC-LSC/BNC constructs to treat severe ocular surface pathologies.

Modified Bacterial Cellulose Dressings to Treat Inflammatory Wounds

Natural products suited for prophylaxis and therapy of inflammatory diseases have gained increasing importance. These compounds could be beneficially integrated into bacterial cellulose (BC), which is a natural hydropolymer applicable as a wound dressing and drug delivery system alike. This study presents experimental outcomes for a natural anti-inflammatory product concept of boswellic acids from frankincense formulated in BC. Using esterification respectively (resp.) oxidation and subsequent coupling with phenylalanine and tryptophan, post-modification of BC was tested to facilitate lipophilic active pharmaceutical ingredient (API) incorporation. Diclofenac sodium and indomethacin were used as anti-inflammatory model drugs before the findings were transferred to boswellic acids. By acetylation of BC fibers, the loading efficiency for the more lipophilic API indomethacin and the release was increased by up to 65.6% and 25%, respectively, while no significant differences in loading could be found for the API diclofenac sodium. Post-modifications could be made while preserving biocompatibility, essential wound dressing properties and anti-inflammatory efficacy. Eventually, in vitro wound closure experiments and evaluations of the effect of secondary dressings completed the study.

Guiding Bacterial Activity for Biofabrication of Complex Materials via Controlled Wetting of Superhydrophobic Surfaces

Superhydrophobic surfaces are promising for preventing fouling and the formation of biofilms, with important implications in the food chain, maritime transport, and health sciences, among others. In this work, we exploit the interplay between wetting principles of superhydrophobic surfaces and microbial fouling for advanced three-dimensional (3D) biofabrication of biofilms. We utilize hydrostatic and capillary pressures to finely control the air-water interface and the aerotaxis-driven biofabrication on superhydrophobic surfaces. Superhydrophobic 3D molds are produced by a simple surface modification that partially embeds hydrophobic particles in silicone rubber. Thereafter, the molds allow the templating of the air-water interface of the culture medium, where the aerobic nanocellulose-producing bacteria (Komagataeibacter medellinensis) are incubated. The biofabricated replicas are hollow and seamless nanofibrous objects with a controlled morphology. Gradients of thickness, topographical feature size, and fiber orientation on the biofilm are obtained by controlling wetting, incubation time, and nutrient availability. Furthermore, we demonstrate that capillary length limitations are overcome by using pressurized closed molds, whereby a persistent air plastron allows the formation of 3D microstructures, regardless of their morphological complexity. We also demonstrate that interfacial biofabrication is maintained for at least 12 days without observable fouling of the mold surface. In summary, we achieve controlled biofouling of the air-water interface as imposed by the experimental framework under controlled wetting. The latter is central to both microorganism-based biofabrication and fouling, which are major factors connecting nanoscience, synthetic biology, and microbiology.

Bacterial nanocellulose as a corneal bandage material: a comparison with amniotic membrane

Corneal trauma and ulcerations are leading causes of corneal blindness around the world. These lesions require attentive medical monitoring since improper healing or infection has serious consequences in vision and quality of life. Amniotic membrane grafts represent the common solution to treat severe corneal wounds. However, amniotic membrane's availability remains limited by the dependency on donor tissues, its high price and short shelf life. Consequently, there is an active quest for biomaterials to treat injured corneal tissues. Nanocellulose synthetized by bacteria (BNC) is an emergent biopolymer with vast clinical potential for skin tissue regeneration. BNC also exhibits appealing characteristics to act as an alternative corneal bandage such as; high liquid holding capacity, biocompatibility, flexibility, natural - but animal free-origin and a myriad of functionalization opportunities. Here, we present an initial study aiming at testing the suitability of BNC as corneal bandage regarding preclinical requirements and using amniotic membrane as a benchmark. Bacterial nanocellulose exhibits higher mechanical resistance to sutures and slightly longer stability under in vitro and ex vivo simulated physiological conditions than amniotic membrane. Additionally, bacterial nanocellulose offers good conformability to the shape of the eye globe and easy manipulation in medical settings. These excellent attributes accompanied by the facts that bacterial nanocellulose is stable at room temperature for long periods, can be heat-sterilized and is easy to produce, reinforce the potential of bacterial nanocellulose as a more accessible ocular surface bandage.

Bacterial cellulose/graphene oxide aerogels with enhanced dimensional and thermal stability

We present a novel method for processing bacterial cellulose/graphene oxide (BC/GO) aerogels with multifunctional properties. The addition of a small amount of dimethyl sulfoxide (DMSO) to the aqueous dispersion of the nanomaterials during the gelification process affected the water freezing temperature of the system and thereby affecting the porous structure of the aerogel obtained after liophilization. The possibility to obtain small and elongated pore with axial orientation allowed a significant improvement of the structural stability of the aerogels. Moreover, the aerogels reduction by thermal treatment with ammonia gas induced crosslinking between the different nanophases, thus given an incremental factor for the mechanical performance of the aerogels under harsh conditions. The resulting aerogels also showed significant improvements in terms of thermal stability and electrical conductivity. These multifunctional BC/GO aerogels present high potential as sustainable and ecological alternative materials for lightweight packaging, filters for atmosphere and water treatment, or energy applications.

Solid matrix-assisted printing for three-dimensional structuring of a viscoelastic medium surface

Gluconacetobacter xylinus (G. xylinus) metabolism is activated by oxygen, which makes the formation of an air-medium interface critical. Here we report solid matrix-assisted 3D printing (SMAP) of an incubation medium surface and the 3D fabrication of bacterial cellulose (BC) hydrogels by in situ biosynthesis of G. xylinus. A printing matrix of polytetrafluoroethylene (PTFE) microparticles and a hydrogel ink containing an incubation medium, bacteria, and cellulose nanofibers (CNFs) are used in the SMAP process. The hydrogel ink can be printed in the solid matrix with control over the topology and dimensional stability. Furthermore, bioactive bacteria produce BC hydrogels at the surface of the medium due to the permeability of oxygen through the PTFE microparticle layer. The flexibility of the design is verified by fabricating complex 3D structures that were not reported previously. The resulting tubular BC structures suggest future biomedical applications, such as artificial blood vessels and engineered vascular tissue scaffolding. The fabrication of a versatile free-form structure of BC has been challenged due to restricted oxygen supplies at the medium and the dimensional instability of hydrogel printing. SMAP is a solution to the problem of fabricating free-form biopolymer structures, providing both printability and design diversity.

Molecular insight into the wetting behavior and amphiphilic character of cellulose nanocrystals

The study of nanocellulose is a field of growing interest due to its many applications and its use in the development of biocompatible and eco-friendly materials. In spite of the vast number of studies in the field, many questions about the role of the molecular structure in the properties of cellulose are still subject of debate. One of these fundamental questions is the possible amphiphilic nature of cellulose and the relative role of hydrogen bonding and hydrophobic effect on the interactions of cellulose. In this work we present an extensive molecular dynamics simulation study of this question by analyzing the wetting of cellulose with water and organic solvent, its interaction with hydrophilic and hydrophobic ions and its interaction with a protein (human epidermal growth factor, hEGF). We consider two characteristic cellulose crystal planes of Iβ cellulose with very different roughness, different hydrogen bonding capability and different exposure of cellulose hydrophobic groups (the (010) plane which has exposed -OH groups and the (100) plane with buried -OH groups). Our results show that both surfaces are simultaneously hydrophilic and lipophilic, with both surfaces having very similar contact angles. In spite of the global similarity of wetting of both surfaces, the molecular details of wetting are very different and substantial local wetting heterogeneities (which strongly depend on the surface) appear for both solvents. We also observe a weak interaction of both surfaces with hydrophobic and hydrophilic solutes. These weak interactions are attributed to the simultaneous lipophilic and hydrophilic character of both (100) and (010) cellulose surfaces. Interestingly, we found a substantial interaction of both cellulose planes with polar and apolar residues of the hEGF protein.

Cellulose Biomaterials for Tissue Engineering

In this review, we highlight the importance of nanostructure of cellulose-based biomaterials to allow cellular adhesion, the contribution of nanostructure to macroscale mechanical properties, and several key applications of these materials for fundamental scientific research and biomedical engineering. Different features on the nanoscale can have macroscale impacts on tissue function. Cellulose is a diverse material with tunable properties and is a promising platform for biomaterial development and tissue engineering. Cellulose-based biomaterials offer some important advantages over conventional synthetic materials. Here we provide an up-to-date summary of the status of the field of cellulose-based biomaterials in the context of bottom-up approaches for tissue engineering. We anticipate that cellulose-based material research will continue to expand because of the diversity and versatility of biochemical and biophysical characteristics highlighted in this review.

Opportunities of Bacterial Cellulose to Treat Epithelial Tissues

In this mini-review, we highlight the potential of the biopolymer bacterial cellulose to treat damaged epithelial tissues. Epithelial tissues are cell sheets that delimitate both the external body surfaces and the internal cavities and organs. Epithelia serve as physical protection to underlying organs, regulate the diffusion of molecules and ions, secrete substances and filtrate body fluids, among other vital functions. Because of their continuous exposure to environmental stressors, damage to epithelial tissues is highly prevalent. Here, we first compare the properties of bacterial cellulose to the current gold standard, collagen, and then we examine the use of bacterial cellulose patches to heal specific epithelial tissues; the outer skin, the ocular surface, the oral mucosa and other epithelial surfaces. Special emphasis is made on the dermis since, to date, this is the most widespread medical use of bacterial cellulose. It is important to note that some epithelial tissues represent only the outermost layer of more complex structures such as the skin or the cornea. In these situations, depending on the penetration of the lesion, bacterial cellulose might also be involved in the regeneration of, for instance, inner connective tissue.

Scaffolds for Chondrogenic Cells Cultivation Prepared from Bacterial Cellulose with Relaxed Fibers Structure Induced Genetically

Development of three-dimensional scaffolds mimicking in vivo cells' environment is an ongoing challenge for tissue engineering. Bacterial nano-cellulose (BNC) is a well-known biocompatible material with enormous water-holding capacity. However, a tight spatial organization of cellulose fibers limits cell ingrowth and restricts practical use of BNC-based scaffolds. The aim of this study was to address this issue avoiding any chemical treatment of natural nanomaterial. Genetic modifications of Komagataeibacter hansenii ATCC 23769 strain along with structural and mechanical properties characterization of obtained BNC membranes were conducted. Furthermore, the membranes were evaluated as scaffolds in in vitro assays to verify cells viability and glycosaminoglycan synthesis by chondrogenic ATDC5 cells line as well as RBL-2H3 mast cells degranulation. K. hansenii mutants with increased cell lengths and motility were shown to produce BNC membranes with increased pore sizes. Novel, BNC membranes with relaxed fiber structure revealed superior properties as scaffolds when compared to membranes produced by a wild-type strain. Obtained results confirm that a genetic modification of productive bacterial strain is a plausible way of adjustment of bacterial cellulose properties for tissue engineering applications without the employment of any chemical modifications.

3D bacterial cellulose biofilms formed by foam templating

Bacterial cellulose is a remarkable fibrous structural component of biofilms, as it forms a mechanically strong hydrogel with high water adsorption capabilities. Additionally, bacterial cellulose is biocompatible and therefore of potential interest for skin regeneration and wound healing applications. However, bacterial cellulose produced through conventional production processes at water–air interfaces lack macroporosity control, which is crucial for regenerative tissue applications. Here we demonstrate a straightforward and efficient approach to form a macroporous bacterial cellulose foam by foaming a mannitol-based media with a bacterial suspension of Gluconoacetobacter xylinus. The bacterial suspension foam is stabilized with Cremodan as a surfactant and viscosified with Xanthan preventing water drainage. Further foam stabilization occurs through cellulose formation across the foam network. As bacterial cellulose formation is influenced by the viscosity of the growth media, we fine-tuned the concentration of Xanthan to allow for bacterial cellulose formation while avoiding water drainage caused by gravity. With this simple approach, we were able to design 3D bacterial cellulose foams without any additional processing steps. We argue that this templating approach can further be used to design foamy biofilms for biotechnological approaches, increasing the surface area and therefore the yield by improving the exchange of nutrients and metabolic products.

A simple and efficient method to control the structure of bacterial cellulose foams could advance uses in tissue regeneration and other biotechnology applications. Bacterial cellulose is a natural fibrous component of biofilms. It forms a strong biocompatible “hydrogel” that can absorb large quantities of water and dissolved substances. Exploiting its medical and commercial potential has been limited by lack of control over a foam’s microporous structure. Patrick Rühs and colleagues at the Swiss Federal Institute of Technology in Zurich (ETH Zurich) devised a chemical procedure to control the pore formation and stability of cellulose foams derived from the bacterium Gluconoacetobacter xylinus. The fine control their generally applicable procedure achieves could greatly improve the chemical exchange properties of the foams. This could lead to materials for healing wounds and biotechnology applications such as bioremediation of pollutants.