Modification of microstructure and selected physicochemical properties of bacterial cellulose produced by bacterial isolate using hydrocolloid-fortified Hestrin-Schramm medium.

Bacterial cellulose (BC) is a biopolymer with applications in numerous industries such as food and pharmaceutical sectors. In this study, various hydrocolloids including modified starches (oxidized starch-1404 and hydroxypropyl starch-1440), locust bean gum, xanthan gum (XG), guar gum, and carboxymethyl cellulose were added to the Hestrin-Schramm medium to improve the production performance and microstructure of BC by Gluconacetobacter entanii isolated from coconut water. After 14-day fermentation, medium supplemented with 0.1% carboxymethyl cellulose and 0.1% XG resulted in the highest BC yield with dry BC content of 9.82 and 6.06 g/L, respectively. In addition, scanning electron microscopy showed that all modified films have the characteristic three-dimensional network of cellulose nanofibers with dense structure and low porosity as well as larger fiber size compared to control. X-ray diffraction indicated that BC fortified with carboxymethyl cellulose exhibited lower crystallinity while Fourier infrared spectroscopy showed characteristic peaks of both control and modified BC films.

Strong Bacterial Cellulose-Based Films with Natural Laminar Alignment for Highly Sensitive Humidity Sensors.

Humidity sensors have been widely used for humidity monitoring in industry and agriculture fields. However, the rigid structure, nondegradability, and large dimension of traditional humidity sensors significantly restrict their applications in wearable fields. In this study, a flexible, strong, and eco-friendly bacterial cellulose-based humidity sensor (BPS) was fabricated using a two-step method, involving solvent evaporation-induced self-assembly and electrolyte permeation. Rapid evaporation of organic solvent induces the formation of nanopores of the bacterial cellulose (BC) surface and promotes structural densification. Furthermore, the successful embedding of potassium hydroxide into the sophisticated network of BC effectively enhanced the sensing performance of BPS. The BPS exhibits an excellent humidity sensing response of more than 103 within the relative humidity ranging from 36.4 to 93% and strong (66.4 MPa) and high flexibility properties owing to the ultrafine fiber network and abundant hydrophilic functional groups of BC. Besides being strong and thin, BPS is also highly flexible, biodegradable, and humidity-sensitive, making it a potential candidate in wearable electronics, human health monitoring, and noncontact switching.

Physical and antibacterial properties of bacterial cellulose films supplemented with cell-free supernatant enterocin-producing Enterococcus faecium TJUQ1.

In this study, a composite film was prepared with bacterial cellulose (BC) of Gluconacetobacter xylinus and cell-free supernatant (CFS) of Enterococcus faecium TJUQ1, which was named BC-E. The optimum conditions for the preparation of the composite film with a minimal antibacterial activity were the soak of BC in 80 AU/mL CFS for 6 h. By scanning electron microscope observation, the surface network structure of BC-E was denser than that of BC. The tensile strength of BC and BC-E was 4.65 ± 0.88 MPa and 16.30 ± 0.92 MPa, the elongation at break of BC and BC-E was 3.33 ± 0.89% and 31.60 ± 1.15%, respectively, indicating the mechanical properties of BC-E were significantly higher than that of BC (P < 0.05). The swelling ratio of BC-E (456.67 ± 7.20%) was lower than that of BC (1377.78 ± 9.07%), demonstrating BC-E films presented better water resistance. BC-E films were soaked with 320 AU/mL CFS, and then used to pack the ground meat with 6.55 log10 CFU/g of Listeria monocytogenes. After 8 days of storage, the number of bacteria decreased by 3.16 log10 CFU/g. Similarly, total mesophilic bacterial levels in the ground meat decreased by 2.41 log10 CFU/g compared to control groups.

Bacterial cellulose-based re-swellable hydrogel: Facile preparation and its potential application as colorimetric sensor of sweat pH and glucose.

Direct deposition of the negatively charged polyelectrolyte, carboxymethyl cellulose (CMC), into a bacterial cellulose (BC) matrix was used as a simple route to fabricate a re-swellable and biocompatible cellulose-based hydrogel. As a result of this non-destructive approach, the physical and mechanical property of the original BC were well-preserved within the resulting BC/CMC hydrogel. As a BC/CMC-based colorimetric pH sensor, it exhibited a rapid response with an easy color differentiation between each pH by the naked eye, and wide linear range of pH 4.0-9.0 with good linearity. For the detection of glucose in sweat, the BC/CMC-based colorimetric glucose sensor provided a low limit of detection (25 µM) with a wide linear detection range (0.0-0.5 mM) and high accuracy. These BC/CMC based sensors could potentially be applied as non-invasive semi-quantitative sensors for on-skin health monitoring.

High-Strength Superstretchable Helical Bacterial Cellulose Fibers with a "Self-Fiber-Reinforced Structure".

As a hydrogel membrane grown on the gas-liquid interface by bacterial culture that can be industrialized, bacterial cellulose (BC) cannot give full play to the advantages of its natural nanofibers. Conversion to the properties of nanofibers from high-performance to macrofibers represents a difficult material engineering challenge. Herein, we construct high-strength BC macrofibers with a "self-fiber-reinforced structure" using a dry-wet spinning method by adjusting the BC dissolution and concentration. The macrofiber with a tensile strength of 649 MPa and a strain of 17.2% can be obtained, which is one of the strongest and toughest cellulose fibers. In addition, the macrofiber can be fabricated to a superstretchable helical fiber without adding other elastomers or auxiliary materials. When the helical diameter is 1.6 mm, the ultimate stretch reaches 1240%. Meanwhile, cyclic tests show that the mechanical properties and morphology of the fiber remained stable after 100 times of 100% cyclic stretching. It is exciting that the helical fiber also owns outstanding knittability, washability, scalability, and dyeability. Furthermore, superstretchable functional helical BC fibers can be fabricated by embedding functional materials (carbon materials, conductive polymers, etc.) on BC or in the spinning dope, which can be made to wearable devices such as fiber solid-state supercapacitors. This work provides a scalable way for high-strength superstretchable and multifunctional fibers applied in wearable devices.

Bacterial Nanocellulose/MoS2 Hybrid Aerogels as Bifunctional Adsorbent/Photocatalyst Membranes for in-Flow Water Decontamination.

To address the problems associated with the use of unsupported nanomaterials, in general, and molybdenum disulfide (MoS2), in particular, we report the preparation of self-supported hybrid aerogel membranes that combine the mechanical stability and excellent textural properties of bacterial nanocellulose (BC)-based organic macro/mesoporous scaffolds with the excellent adsorption-cum-photocatalytic properties and high contaminant removal performance of MoS2 nanostructures. A controlled hydrothermal growth and precise tuning of the synthetic parameters allowed us to obtain BC/MoS2-based porous, self-supported, and stable hybrid aerogels with a unique morphology resulting from a molecular precision in the coating of quantum-confined photocatalytic MoS2 nanostructures (2-4 nm crystallite size) on BC nanofibrils. These BC/MoS2 samples exhibit high surface area (97-137 m2·g-1) and pore volume (0.28-0.36 cm3·g-1) and controlled interlayer distances (0.62-1.05 nm) in the MoS2 nanostructures. Modification of BC with nanostructured MoS2 led to an enhanced pollutants removal efficiency of the hybrid aerogels both by adsorptive and photocatalytic mechanisms, as indicated by a detailed study using a specifically designed membrane photoreactor containing the developed photoactive/adsorptive BC/MoS2 hybrid membranes. Most importantly, the prepared BC/MoS2 aerogel membranes showed high performance in the photoassisted in-flow removal of both organic dye (methylene blue (MB)) molecules (96% removal within 120 min, Kobs = 0.0267 min-1) and heavy metal ions (88% Cr(VI) removal within 120 min, Kobs = 0.0012 min-1), separately and/or simultaneously, under UV-visible light illumination as well as excellent recyclability and photostability. Samples with interlayer expanded MoS2 nanostructures were particularly more efficient in the removal of smaller species (CrO42-) as compared to larger (MB) dye molecules. The prepared hybrid aerogel membranes show promising behavior for application in in-flow water purification, representing a significant advancement in the use of self-supported aerogel membranes for photocatalytic applications in liquid media.

Bacterial cellulose matrix with in situ impregnation of silver nanoparticles via catecholic redox chemistry for third degree burn wound healing.

In the present study, bacterial cellulose (BC) based nanocomposite dressing material was developed for third burn wound management by polydopamine (PD) coated BC with in situ reduction of silver nanoparticles (BC-PDAg). BC-PDAg nanocomposite was characterized to understand the morphological, physical and chemical properties. Antimicrobial activity of BC-PDAg against burn wound specific pathogens were significant. The in vitro cytotoxicity and proliferation studies revealed that BC-PDAg nanocomposite is biocompatible and it supports cell proliferation. Further, in vivo experiments on female albino Wistar rats confirmed that BC-PDAg was effective in wound healing by promoting re-epithelization, and collagen deposition as evidenced by histopathological analysis. Moreover, molecular gene expression study has revealed that BC-PDAg promotes healing process by regulating the expression of inflammatory, angiogenesis and growth factor genes. The overall performance of BC-PDAg nanocomposite suggests that it could be used as promising skin regenerative tool in modern medicine.

Synthesis and SERS application of gold and iron oxide functionalized bacterial cellulose nanocrystals (Au@Fe3O4@BCNCs).

Bacterial cellulose nanocrystals (BCNCs) are biocompatible cellulose nanomaterials that can host guest nanoparticles to form hybrid nanocomposites with a wide range of applications. Herein, we report the synthesis of a hybrid nanocomposite that consists of plasmonic gold nanoparticles (AuNPs) and superparamagnetic iron oxide (Fe3O4) nanoparticles supported on BCNCs. As a proof of concept, the hybrid nanocomposites were employed to isolate and detect malachite green isothiocyanate (MGITC) via magnetic separation and surface-enhanced Raman scattering (SERS). Different initial gold precursor (Au3+) concentrations altered the size and morphology of the AuNPs formed on the nanocomposites. The use of 5 and 10 mM Au3+ led to a heterogenous mix of spherical and nanoplate AuNPs with increased SERS enhancements, as compared to the more uniform AuNPs formed using 1 mM Au3+. Rapid and sensitive detection of MGITC at concentrations as low as 10-10 M was achieved. The SERS intensity of the normalized Raman peak at 1175 cm-1 exhibited a log-linear relationship for MGITC concentrations between 2 × 10-10 and 2 × 10-5 M for Au@Fe3O4@BCNCs. These results suggest the potential of these hybrid nanocomposites for application in a broad range of analyte detection strategies.

Physicochemical Properties and In Vitro Biocompatibility of Three Bacterial Nanocellulose Conduits for Blood Vessel Applications.

A novel design of bioreactor G-BNC, in combination with two previously reported designs of bioreactor were used to fabricate three small caliber bacterial nanocellulose (BNC) conduits (G-BNC, S-BNC and D-BNC). They were compared systematically with a clinically-used ePTFE graft. S-BNC possessed a laminated structure, the lowest BNC content, roughest luminal surface and weakest mechanical properties, and so might not be sufficiently strong for use as an artificial blood vessel alone. The D-BNC conduit possessed an unstratified structure with a fiber network that was more dense and the greatest BNC content, providing the strongest mechanical properties. G-BNC possessed a looser network with the smoothest luminal surface and greater hemocompatibility. Following comprehensive evaluation of mechanical properties and performance, we judge that D-BNC and G-BNC should possess greater potential in application as small caliber vascular grafts, however the patency of the three BNC conduits need be further verified in animal studies in vivo.

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.

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 Iα/Iß ratio (1.10). Therefore, 25 °C convection-dried BNC followed by soaking in water can be considered as a material suitable for cardiovascular implants.

Antibacterial properties of a bacterial cellulose CQD-TiO2 nanocomposite.

Antibacterial dressing can prevent the occurrence of many infections of wounds. Bacterial cellulose (BC) has the ability to carry and transfer the medicine to achieve a wound healing bandage. In this study, Carbon Quantum Dots-Titanium dioxide (CQD-TiO2) nanoparticles (NP) were added to BC as antibacterial agents. FTIR Spectroscopy illuminated that NPs were well-bonded to BC. Interestingly, MIC test proved that BC/CQD-TiO2 nanostructure (NS) has anti-bacterial properties against Staphylococcus aureus. The findings indicated that, CQD-TiO2 NPs have stronger antibacterial properties with better tensile strength compared to CQD NPs, in a concentration-dependent manner. Toxicity of CQD-TiO2 NPs on human L929 fibroblast cells was also evaluated. Most importantly, the results of the scratch test indicated that the NS was effective in wound healing in L929 cells. The approach in this study may provide an alternative to make an antibacterial wound dressing to achieve an effective drug-based bandage.

Glioblastoma cell adhesion properties through bacterial cellulose nanocrystals in polycaprolactone/gelatin electrospun nanofibers.

Glioblastoma (GBM), the most common and extremely lethal type of brain tumor, is resistant to treatment and shows high recurrence rates. In the last decades, it is indicated that standard two-dimensional (2D) cell culture is inadequate to improve new therapeutic strategies and drug development. Hence, well-mimicked three-dimensional (3D) tumor platforms are needed to bridge the gap between in vitro and in vivo cancer models. In this study, bacterial cellulose nano-crystal (BCNC) containing polycaprolactone (PCL) /gelatin (Gel) nanofibrous composite scaffolds were successfully fabricated by electrospinning for mimicking the extracellular matrix of GBM tumor. The fiber diameters in the nanofibrous matrix were increased with an increased concentration of BCNC. Moreover, fiber morphology changed from the smooth formation to the beaded formation by increasing the concentration of the BCNC suspension. In-vitro biocompatibilities of nanofibrous scaffolds were tested with U251 MG glioblastoma cells and improved cell adhesion and proliferation was compared with PCL/Gel. PCL/Gel/BCNC were found suitable for enhancing axon growth and elongation supporting communication between tumor cells and the microenvironment, triggering the process of tumor recurrence. Based on these results, PCL/Gel/BCNC composite scaffolds are a good candidate for biomimetic GBM tumor platform.

Robust All-Cellulose Nanofiber Composite from Stack-Up Bacterial Cellulose Hydrogels via Self-Aggregation Forces.

All-cellulose composites are usually prepared by removing impurities and using a surface-selective dissolution approach, which detract significantly from their environment-friendly properties. In this paper, we report an environment-friendly approach to fabricate all-cellulose nanofiber composites from stack-up bacterial cellulose (BC) hydrogels via self-aggregation forces of the hydrogen bond by water-based processing. Structural and mechanical properties of BC-laminated composites have been investigated. The results indicated that BC composites possess the structure of all nanofibers, a tensile strength of 116 MPa, and a storage modulus of 25 GPa. Additionally, the interfacial shear strength and tensile strength of piece-hot-press BC demonstrate the strong self-aggregation forces of BC nanofibers. Thus, BC-laminated composites will be attractive in structural material.

Intelligent optofluidic analysis for ultrafast single bacterium profiling of cellulose production and morphology.

Bacterial cellulose (BC), a renewable type of cellulose, has been used in the manufacture of foods, cosmetics, and biomedical products. To produce BC, a high-throughput single-bacterium measurement is necessary to identify the functional bacteria that can produce BC with sufficient amount and desirable morphology. In this study, a continuous-flow intelligent optofluidic device was developed to enable high-throughput single-bacterium profiling of BC. Single bacteria were incubated in agarose hydrogel particles to produce BC with varied densities and structures. An intelligent convolutional neural network (CNN) computational method was developed to analyze the scattering patterns of BC. The BC production and morphology were determined with a throughput of ∼35 bacteria per second. A total of ∼105 single-bacterium BC samples were characterized within 3 hours. The high flexibility of this approach facilitates high-throughput comprehensive single-cell production analysis for a range of applications in engineering biology.

In situ structural modification of bacterial cellulose by sodium fluoride.

Bacterial cellulose could be produced in any shape due to its high moldability during fermentation process, but structural modification often requires the inclusion of templates or other polymeric materials. In this work, sodium fluoride was introduced in bacterial cultivation process to modify the microstructure. Under static conditions, the final pH, BC yield, morphology, structure and properties of the obtained BC were investigated. Because of the stronger hydrogen bonding formed between fluoride and hydroxyl groups, majority of cellulose chains were no longer restricted and could not aggregate into wider cellulose ribbons. After the removal of fluoride, the cellulose chains undergo random rearrangement into bulky ribbon due to inter-fibril hydrogen bonding of hydroxyl groups, of which the crystallinity can remain as high as ∼60 % in dry state. The treatment of sodium fluoride led to different mechanical properties. The modification of BC structure can be easily achieved in situ by controlling NaF concentrations.

Synergistic effect of bacterial cellulose reinforcement and succinic acid crosslinking on the properties of agar.

In this work, the modification of agar is presented with the synergistic effect of bacterial cellulose reinforcement and succinic acid crosslinked agar. The effect of crosslinking agar with succinic acid on tensile strength and water absorption were studied. Crosslinking was confirmed with Fourier infrared spectroscopy. The tensile strength of agar was increased by 70% by succinic acid crosslinking (from55 ± 9.97 MPa to 93.40 ± 9.97 MPa) and the crosslinked agar absorbed only 18.66% water compared to uncrosslinked agar. The tensile strength of agar was increased by 56% by bacterial cellulose reinforcement (55 ± 9.97 MPa to 86.30 ± 14.70 MPa). The strength of agar was improved by 101% by the synergistic effect of bacterial cellulose reinforcement and succinic acid crosslinking (55 ± 9.97 MPa to 111 ± 12.30 MPa). Cytocompatibility studies of the developed films suggested that the crosslinked samples can also have potential applications in biomedical engineering apart from packaging applications.

In vivo evaluation of the effectiveness of biocellulose facial masks as active delivery systems to skin.

BACKGROUND: In recent years, bacterial cellulose (BC), or biocellulose, a natural polymer synthesized by certain bacteria, has attracted great interest in dermatology and cosmetic applications. Several bioactive ingredients are currently loaded into BC masks. However, only a few studies have reported the effectiveness of such delivery systems. AIM: The aim of this study was to evaluate the effect on skin parameters of three biocellulose masks formulated to have different cosmetic effects (anti-aging, lifting, and cell renewal). In particular, skin moisturizing, skin color, skin viscoelastic properties, skin surface smoothness, wrinkle reduction, dermal homogeneity, and stratum corneum renewal were evaluated. MATERIALS AND METHODS: The study involved 69 healthy Caucasian female volunteers between 25 and 64 years, who were divided into three different studies. Biocellulose facial masks were applied using the split-face method three times a week for 4-8 weeks depending on the study. RESULTS: The results obtained from this work highlight that biocellulose masks are very well tolerated. A significant decrease in skin roughness and wrinkle breadth, and an improvement in dermal homogeneity and firmness, was observed after 2 months of treatment with "anti-aging" masks. A significant improvement in skin firmness and elasticity was observed after 1 month of treatment with "lifting" masks. Furthermore, a 1-month treatment with "cell renewal" masks promoted the production of new skin cells through a mild exfoliating action. CONCLUSIONS: This study highlights that biocellulose masks are effective delivery systems to successfully release into the skin several types of active compounds exerting many beneficial effects.

Development and antibacterial activities of bacterial cellulose/graphene oxide-CuO nanocomposite films.

The absence of antibacterial activity of bacterial cellulose (BC) restricts its applications in the biomedical field. To introduce antimicrobial properties into BC, we studied the synthesis, structure, and antimicrobial properties of a novel nanocomposite film comprising BC, graphene oxide (GO), and copper-oxide (CuO) nanosheets. The nanocomposite film was synthesized by incorporating GO-CuO nanohybrids into BC matrix through homogenized blending. The CuO nanosheets, with a length range of 50 nm-200 nm and width range of 20 nm-50 nm, which were uniformly grown on the GO along with even distribution of GO-CuO nanohybrids on the surface of the cellulose fibers. The nanocomposites displayed better antibacterial activity against gram-positive than gram-negative bacteria. BC/GO-CuO nanocomposites showed higher antibacterial activity than BC/CuO. We also elucidated the mechanism of antibacterial activity of the nanocomposites. Further, the nanocomposites exhibited biocompatibility towards mice fibroblast cells. The nanocomposites might serve as an excellent source for development of antibacterial materials.

Soft Bacterial Cellulose Microcapsules with Adaptable Shapes.

Microcapsules with controlled stability and permeability are in high demand for applications in separation and encapsulation. We have developed a biointerfacial process to fabricate strong, but flexible, porous microcapsules from bacterial cellulose at an oil-water emulsion interface. A broad range of microcapsule sizes has been successfully produced, from 100 µm to 5 cm in diameter. The three-dimensional capsule microstructure was imaged using confocal microscopy, showing a cellulose membrane thickness of around 30 µm that is highly porous, with some pores larger than 0.5 µm that are permeable to most macromolecules by free diffusion but can exclude larger structures like bacteria. The mechanical deformation of cellulose microcapsules reveals their flexibility, enabling them to pass through constrictions with a much smaller diameter than their initial size by bending and folding. Our work provides a new approach for producing soft, permeable, and biocompatible microcapsules for substance encapsulation and protection. The capsules may offer a replacement for suspended polymer beads in commercial applications and could potentially act as a framework for artificial cells.