Production and Characterization of a New Bacterial Cellulose/Poly(Vinyl Alcohol) Nanocomposite

Bionanocellulose/Poly(Vinyl Alcohol) Composites Produced by In-Situ Method and Ex-Situ/Impregnation or Sterilization Methods

The purpose of the work was to obtain composites based on bionanocellulose (BNC) and poly(vinyl alcohol) (PVA) for specific biomedical and cosmetic applications and to determine how the method and conditions of their preparation affect their utility properties. Three different ways of manufacturing these composites (in-situ method and ex-situ methods combined with sterilization or impregnation) were presented. The structure and morphology of BNC/PVA composites were studied by ATR-FTIR spectroscopy and scanning microscopy (SEM, AFM). Surface properties were tested by contact angle measurements. The degree of crystallinity of the BNC fibrils was determined by means of the XRD method. The mechanical properties of the BNC/PVA films were examined using tensile tests and via the determination of their bursting strength. The water uptake of the obtained materials was determined through the gravimetric method. The results showed that PVA added to the nutrient medium caused an increase in biosynthesis yield. Moreover, an increase in base weight was observed in composites of all types due to the presence of PVA. The ex-situ composites revealed excellent water absorption capacity. The in-situ composites appeared to be the most durable and elastic materials.

Thermal, Mechanical and Chemical Analysis of Poly(vinyl alcohol) Multifilament and Braided Yarns

Poly(vinyl alcohol) (PVA) in multifilament and braided yarns (BY) forms presents great potential for the design of numerous applications. However, such solutions fail to accomplish their requirements if the chemical and thermomechanical behaviour is not sufficiently known. Hence, a comprehensive characterisation of PVA multifilament and three BY architectures (6, 8, and 10 yarns) was performed involving the application of several techniques to evaluate the morphological, chemical, thermal, and mechanical features of those structures. Scanning electron microscopy (SEM) was used to reveal structural and morphological information. Differential thermal analysis (DTA) pointed out the glass transition temperature of PVA at 76 °C and the corresponding crystalline melting point at 210 °C. PVA BY exhibited higher tensile strength under monotonic quasi-static loading in comparison to their multifilament forms. Creep tests demonstrated that 6BY structures present the most deformable behaviour, while 8BY structures are the least deformable. Relaxation tests showed that 8BY architecture presents a more expressive variation of tensile stress, while 10BY offered the least. Dynamic mechanical analysis (DMA) revealed storage and loss moduli curves with similar transition peaks for the tested structures, except for the 10BY. Storage modulus is always four to six times higher than the loss modulus.

Bacterial cellulose and its potential for biomedical applications

Bacterial cellulose (BC) is an important polysaccharide synthesized by some bacterial species under specific culture conditions, which presents several remarkable features such as microporosity, high water holding capacity, good mechanical properties and good biocompatibility, making it a potential biomaterial for medical applications. Since its discovery, BC has been used for wound dressing, drug delivery, artificial blood vessels, bone tissue engineering, and so forth. Additionally, BC can be simply manipulated to form its derivatives or composites with enhanced physicochemical and functional properties. Several polymers, carbon-based nanomaterials, and metal nanoparticles (NPs) have been introduced into BC by ex situ and in situ methods to design hybrid materials with enhanced functional properties. This review provides comprehensive knowledge and highlights recent advances in BC production strategies, its structural features, various in situ and ex situ modification techniques, and its potential for biomedical applications.

Lignocellulosic Biomass for the Synthesis of Nanocellulose and Its Eco-Friendly Advanced Applications

Nanocellulose is a unique and natural compound extracted from native cellulose using different extraction techniques. Nanocellulose is currently attracting attention due to its excellent properties such as special surface chemistry, exceptional physical and chemical strength, and rich hydroxyl groups for modification. In addition, its significant biological properties, like biodegradability, biocompatibility, and non-toxicity, accompanied by being environmentally friendly, are added advantages. The current review is focused on the lignocellulosic biomass processing methods for nanocellulose production and their usage for eco-friendly and environmental sustainability. We have also described insights into different techniques by which cellulosic materials can be changed into cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs). Lastly, we further discussed how nano-cellulosic materials are being used in a variety of industries such as the food sector, biomedical hygiene products, health care, water purification, and sensors. In the review, the unique uses of nanocelluloses in the production of nanocomposite materials, like flexible supercapacitor and polymer matrix, toward minimizing the utilization of global fossil energy and environmental pollution are envisaged. Finally, the significant application of nanomaterials in the areas of packaging industries, health and hygienic sector, cosmetics, and other important sectors are discussed. In the aspect of techno-economically feasibility, nano-cellulose-based materials may prove to be outstanding, environment friendly, and mitigate effluent load.

Potential applications of bacterial cellulose and its composites for cancer treatment

Bacterial cellulose (BC) has received immense interest in medical, pharmaceutical, and other related fields owing to its intrinsic physical, mechanical, and biological features. Its structural features offer an ideal environment for developing composites, thereby further extending its areas of applications. BC was initially used in wound dressing, artificial blood vessels, organ development, and tissue regeneration; however, the recent focus has switched to 3D printing techniques. BC can serve as suitable material for treating different cancers due to unique liquid absorbing and drug loading properties. BC-based scaffolds have been synthesized and tested for in vitro culturing of cancer cells to simulate tumor microenvironments. These scaffolds support normal growth of cancer cells, particularly breast and ovarian cancer cells, showing significant adhesion, proliferation, ingrowth, and differentiation. This review describes the different approaches of manipulating BC for use in medicine, with particular focus on the applications of BC composites in cancer treatment. A detailed discussion about various formulations of BC in multiple cancer therapeutics is summarized.

Permeability is the Critical Factor Governing the Life Cycle Environmental Performance of Drinking Water Treatment Using Living Filtration Membranes

Living Filtration Membranes (LFMs) are a water filtration technology that was recently developed in the lab (Technology Readiness Level 4). LFMs have shown filtration performance comparable with that of ultrafiltration, far better fouling resistance than conventional polymer membranes, and good healing capabilities. These properties give LFMs promise to address two significant issues in conventional membrane filtration: fouling and membrane damage. To integrate environmental considerations into future technology development (i.e., Ecodesign), this study assesses the life cycle environmental performance of drinking water treatment using LFMs under likely design and operation conditions. It also quantitatively ranks the engineering design and operation factors governing the further optimization of LFM environmental performance using a global sensitivity analysis. The results suggest that LFMs' superior fouling resistance will reduce the life cycle environmental impacts of ultrafiltration by 25% compared to those of a conventional polymer membrane in most impact categories (e.g., acidification, global warming potential, and carcinogenics). The only exception is the eutrophication impact, where the need for growth medium and membrane regeneration offsets the benefits of LFMs' fouling resistance. Permeability is the most important factor that should be prioritized in future R&D to further improve the life cycle environmental performance of LFMs. A 1% improvement in the permeability will lead to a ∼0.7% improvement in LFMs' environmental performance in all the impact categories, whereas the same change in the other parameters investigated (e.g., LFM lifespan and regeneration frequency) typically only leads to a <0.2% improvement.

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.

Effect of Atomized Delivery of Nutrients on the Growth Characteristics and Microstructure Morphology of Bacterial Cellulose

This work demonstrates a general strategy for introducing remarkable changes in matrix organization and, consequently, functional properties of bacterial cellulose (BC). BC-producing cells were induced, using a well-defined atomized droplet nutrient delivery (ADND) system, to form pellicles with a regular layered morphology that persists throughout the mat depth. In contrast, the morphology of mats formed by conventional static medium nutrient delivery (SMND) is irregular with no distinguishable pattern. ADND also resulted in larger meso-scale average pore sizes but did not alter the fibril diameter (∼70 nm) and crystallinity index (92-95%). The specific modulus and specific tensile strength of ADND mats are higher than those of SMND mats. This is due to the regularity of dense layers that are present in ADND mats that are able to sustain tensile loads, when applied parallel to these layers. The density of BC films prepared by ADND is 1.63-fold lower than that of the SMND BC film. Consequently, the water contents (g/g) of ADND- and SMND-prepared BC mats are 263 ± 8.85 and 99.6 ± 2.04, respectively. A model that rationalizes differences in mat morphology resulting from these nutrient delivery methods based on nutrient and oxygen concentration gradients is proposed. This work raises questions as to the extent that ADND can be used to fine-tune the matrix morphology and how the resulting lower density mats will alter the diffusion of actives from the films to wound sites and increase the ability of cells to infiltrate the matrix during tissue engineering.

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.

Inhalation of Bacterial Cellulose Nanofibrils Triggers an Inflammatory Response and Changes Lung Tissue Morphology of Mice

In view of the growing industrial use of Bacterial cellulose (BC), and taking into account that it might become airborne and be inhaled after industrial processing, assessing its potential pulmonary toxic effects assumes high relevance. In this work, the murine model was used to assess the effects of exposure to respirable BC nanofibrils (nBC), obtained by disintegration of BC produced by Komagataeibacter hansenii. Murine bone marrow-derived macrophages (BMMΦ) were treated with different doses of nBC (0.02 and 0.2 mg/mL, respectively 1 and 10 μg of fibrils) in absence or presence of 0.2% Carboxymethyl Cellulose (nBCMC). Furthermore, mice were instilled intratracheally with nBC or nBCMC at different concentrations and at different time-points and analyzed up to 6 months after treatments. Microcrystaline Avicel-plus® CM 2159, a plant-derived cellulose, was used for comparison. Markers of cellular damage (lactate dehydrogenase release and total protein) and oxidative stress (hydrogen peroxidase, reduced glutathione, lipid peroxidation and glutathione peroxidase activity) as well presence of inflammatory cells were evaluated in brochoalveolar lavage (BAL) fluids. Histological analysis of lungs, heart and liver tissues was also performed. BAL analysis showed that exposure to nBCMC or CMC did not induce major alterations in the assessed markers of cell damage, oxidative stress or inflammatory cell numbers in BAL fluid over time, even following cumulative treatments. Avicel-plus® CM 2159 significantly increased LDH release, detected 3 months after 4 weekly administrations. However, histological results revealed a chronic inflammatory response and tissue alterations, being hypertrophy of pulmonary arteries (observed 3 months after nBCMC treatment) of particular concern. These histological alterations remained after 6 months in animals treated with nBC, possibly due to foreign body reaction and the organism's inability to remove the fibers. Overall, despite being a safe and biocompatible biomaterial, BC-derived nanofibrils inhalation may lead to lung pathology and pose significant health risks.

Bacterial cellulose-assisted de-lignified wheat straw-PVA based bio-composites with novel characteristics

In the present study, in-house extracted ligninolytic consortium was used as a green catalyst to modify the pristine wheat straw through de-lignification. The ligninolytic consortium showed an enhanced level of de-lignification with a maximal cellulose exposure from 24% to 76.54% cellulose. The de-lignified wheat straw was further strengthened using bacterial cellulose integration. Subsequently, a well-known compression molding technique was used to develop bio-composites from a de-lignified and bacterially modified wheat straw in the presence of polyvinyl alcohol (PVA) and glycerol as a plasticizer. The newly developed bio-composites were characterized using a variety of analytical and imaging techniques including Fourier Transform Infra-Red Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM). Evidently, the characterization profile revealed a considerable improvement in the morphology, mechanical and water uptake features of the newly developed bio-composites. In summary, the improved characteristics of bacterial cellulose-assisted de-lignified wheat straw-PVA based bio-composites suggest a high potential of enzymatic treatment for biotechnological exploitability.

Advances in biomedical and pharmaceutical applications of functional bacterial cellulose-based nanocomposites

Bacterial cellulose (BC) synthesized by certain species of bacteria, is a fascinating biopolymer with unique physical and mechanical properties. BC's applications range from traditional dessert, gelling, stabilizing and thickening agent in the food industry to advanced high-tech applications, such as immobilization of enzymes, bacteria and fungi, tissue engineering, heart valve prosthesis, artificial blood vessels, bone, cartilage, cornea and skin, and dental root treatment. Various BC-composites have been designed and investigated in order to enhance its biological applicability. This review focuses on the application of BC-based composites for microbial control, wound dressing, cardiovascular, ophthalmic, skeletal, and endodontics systems. Moreover, applications in controlled drug delivery, biosensors/bioanalysis, immobilization of enzymes and cells, stem cell therapy and skin tissue repair are also highlighted. This review will provide new insights for academia and industry to further assess the BC-based composites in terms of practical applications and future commercialization for biomedical and pharmaceutical purposes.

Potential of PVA-doped bacterial nano-cellulose tubular composites for artificial blood vessels

Introduction of PVA can improve the compliance of bacterial nano-cellulose hydrogel, which has been suggested as a promising biomaterial for artificial blood vessels especially for small-caliber vessels.

Effect of water state and polymer chain motion on the mechanical properties of a bacterial cellulose and polyvinyl alcohol (BC/PVA) hydrogel

The effects of water state and polymer chain motion on the mechanical property of bacterial cellulose and a polyvinyl alcohol hydrogel.

Electrophoretic deposition of cellulose nanocrystals (CNs) and CNs/alginate nanocomposite coatings and free standing membranes

This study presents the electrophoretic deposition (EPD) of cellulose nanocrystals (CNs) and CNs-based alginate composite coatings for biomedical applications. The mechanism of anodic deposition of CNs and co-deposition of CNs/alginate composites was analyzed based on the results of zeta-potential, Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) analyses. The capability of the EPD technique for manipulating the orientation of CNs and for the preparation of multilayer CNs coatings was demonstrated. The nanotopographic surface roughness and hydrophilicity of the deposited coatings were measured and discussed. Electrochemical testing demonstrated that a significant degree of corrosion protection of stainless steel could be achieved when CNs-containing coatings were present. Additionally, the one-step EPD-based processing of free-standing CNs/alginate membranes was demonstrated confirming the versatility of EPD to fabricate free-standing membrane structures compared to a layer-by-layer deposition technique. CNs and CNs/alginate nanocomposite coatings produced by EPD are potential candidates for biomedical, cell technology and drug delivery applications.