Impregnation of silver sulfadiazine into bacterial cellulose for antimicrobial and biocompatible wound dressing

Synthesis, functionalization, and commercial application of cellulose-based nanomaterials

In recent times, cellulose, an abundant and renewable biopolymer, has attracted considerable interest due to its potential applications in nanotechnology. This review explores the latest developments in cellulose-based nanomaterial synthesis, functionalization, and commercial applications. Beginning with an overview of the diverse sources of cellulose and the methods employed for its isolation and purification, the review delves into the various techniques used for the synthesis of cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), highlighting their unique properties and potential applications. Furthermore, the functionalization strategies employed to enhance the properties and tailor the functionalities of cellulose-based nanomaterials were discussed. The review also provides insights into the emerging commercial applications of cellulose-based nanomaterials across diverse sectors, including packaging, biomedical engineering, textiles, and environmental remediation. Finally, challenges and prospects for the widespread adoption of cellulose-based nanomaterials are outlined, emphasizing the need for further research and development to unlock their full potential in sustainable and innovative applications.

Preparation and antibacterial evaluation of silver-doped zirconia for enhanced dental restoration performance

Because of its superior strength, esthetic properties, and excellent biocompatibility, zirconia is preferred for dental prosthetic such as crowns and bridges. However, zirconia crowns and bridges are susceptible to secondary caries owing to margin leakage. Silver is a well-known antibacterial agent, making it a desirable additive to zirconia crowns and bridges for secondary caries prevention. This study focuses on imparting zirconia composite with antibacterial properties to enhance its protective capacity in dental restorations. We used the sol-gel method to dope Ag into zirconia. Silver-doped zirconia powders were prepared at Zr:Ag molar ratios of 100:0,100:0.1, 100:0.5, 100:1, 100:3, and 100:5 (respective samples denoted as Ag-0, Ag-0.1, Ag-0.5, Ag-1, Ag-3, and Ag-5) and were subjected to firing at various temperatures (400 °C-1000 °C). We performed x-ray diffraction to investigate the crystal phase of these powders and x-ray fluorescence and field emission scanning electron microscopy to analyze their elemental composition and surface morphology, respectively. Moreover, we performed spectrophotometry to determine theL*a*b* color values, conducted dissolution tests, and quantified the Ag content through inductively coupled plasma optical emission spectroscopy. In addition, we studied the antibacterial activity of the samples. Analyses of the samples fired at ⩽600 °C revealed a predominantly white to grayish-white coloration and a tetragonal crystal phase. Firing at ⩾700 °C resulted in gray or dark gray coloration and a monoclinic crystal phase. The Ag content decreased after firing at 900 °C or 1000 °C. Ag-0.5 and above exhibited antibacterial activity against bothEscherichia coliandStaphylococcus aureus. Therefore, the minimum effective silver-doped zirconia sample was found to be Ag-0.5. This study allows the exploration of the antimicrobial potential of silver-doped zirconia materials in dental applications such as prosthdontical lining materials, promoting the development of innovative restorations with protective capacity against secondary caries.

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.

An introductory review on advanced multifunctional materials

This review summarizes the applications of some of the advanced materials. It included the synthesis of several nanoparticles such as metal oxide nanoparticles (e.g., Fe₃O₄, ZnO, ZrOSO₄, MoO_3-x, CuO, AgFeO₂, Co₃O₄, CeO₂, SiO₂, and CuFeO₂); metal hydroxide nanosheets (e.g., Zn₅(OH)₈(NO₃)₂·2H₂O, Zn(OH)(NO₃)·H₂O, and Zn₅(OH)₈(NO₃)₂); metallic nanoparticles (Ag, Au, Pd, and Pt); carbon-based nanomaterials (graphene, graphene oxide (GO), graphitic carbon nitride (g-C₃N₄), and carbon dots (CDs)); biopolymers (cellulose, nanocellulose, TEMPO-oxidized cellulose nanofibers (TOCNFs), and chitosan); organic polymers (e.g. covalent-organic frameworks (COFs)); and hybrid materials (e.g. metal-organic frameworks (MOFs)). Most of these materials were applied in several fields such as environmental-based technologies (e.g., water remediation, air purification, gas storage), energy (production of hydrogen, dimethyl ether, solar cells, and supercapacitors), and biomedical sectors (sensing, biosensing, cancer therapy, and drug delivery). They can be used as efficient adsorbents and catalysts to remove emerging contaminants e.g., inorganic (i.e., heavy metals) and organic (e.g., dyes, antibiotics, pesticides, and oils in water via adsorption. They can be also used as catalysts for catalytic degradation reactions such as redox reactions of pollutants. They can be used as filters for air purification by capturing carbon dioxide (CO₂) and volatile organic compounds (VOCs). They can be used for hydrogen production via water splitting, alcohol oxidation, and hydrolysis of NaBH₄. Nanomedicine for some of these materials was also included being an effective agent as an antibacterial, nanocarrier for drug delivery, and probe for biosensing.

Hybrid Silver-Containing Materials Based on Various Forms of Bacterial Cellulose: Synthesis, Structure, and Biological Activity

Sustained interest in the use of renewable resources for the production of medical materials has stimulated research on bacterial cellulose (BC) and nanocomposites based on it. New Ag-containing nanocomposites were obtained by modifying various forms of BC with Ag nanoparticles prepared by metal-vapor synthesis (MVS). Bacterial cellulose was obtained in the form of films (BCF) and spherical BC beads (SBCB) by the Gluconacetobacter hansenii GH-1/2008 strain under static and dynamic conditions. The Ag nanoparticles synthesized in 2-propanol were incorporated into the polymer matrix using metal-containing organosol. MVS is based on the interaction of extremely reactive atomic metals formed by evaporation in vacuum at a pressure of 10^-2 Pa with organic substances during their co-condensation on the cooled walls of a reaction vessel. The composition, structure, and electronic state of the metal in the materials were characterized by transmission and scanning electron microscopy (TEM, SEM), powder X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and X-ray photoelectron spectroscopy (XPS). Since antimicrobial activity is largely determined by the surface composition, much attention was paid to studying its properties by XPS, a surface-sensitive method, at a sampling depth about 10 nm. C 1s and O 1s spectra were analyzed self-consistently. XPS C 1s spectra of the original and Ag-containing celluloses showed an increase in the intensity of the C-C/C-H groups in the latter, which are associated with carbon shell surrounding metal in Ag nanoparticles (Ag NPs). The size effect observed in Ag 3d spectra evidenced on a large proportion of silver nanoparticles with a size of less than 3 nm in the near-surface region. Ag NPs in the BC films and spherical beads were mainly in the zerovalent state. BC-based nanocomposites with Ag nanoparticles exhibited antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli bacteria and Candida albicans and Aspergillus niger fungi. It was found that AgNPs/SBCB nanocomposites are more active than Ag NPs/BCF samples, especially against Candida albicans and Aspergillus niger fungi. These results increase the possibility of their medical application.

Opportunities for bacterial nanocellulose in biomedical applications: Review on biosynthesis, modification and challenges

Bacterial nanocellulose (BNC) is a natural polysaccharide produced as extracellular material by bacterial strains and has favorable intrinsic properties for primary use in biomedical applications. In this review, an update on state-of-the art and challenges in BNC production, surface modification and biomedical application is given. Recent insights in biosynthesis allowed for better understanding of governing parameters improving production efficiency. In particular, introduction of different carbon/nitrogen sources from alternative feedstock and industrial upscaling of various production methods is challenging. It is important to have control on the morphology, porosity and forms of BNC depending on biosynthesis conditions, depending on selection of bacterial strains, reactor design, additives and culture conditions. The BNC is intrinsically characterized by high water absorption capacity, good thermal and mechanical stability, biocompatibility and biodegradability to certain extent. However, additional chemical and/or physical surface modifications are required to improve cell compatibility, protein interaction and antimicrobial properties. The novel trends in synthesis include the in-situ culturing of hybrid BNC nanocomposites in combination with organic material, inorganic material or extracellular components. In parallel with toxicity studies, the applications of BNC in wound care, tissue engineering, medical implants, drug delivery systems or carriers for bioactive compounds, and platforms for biosensors are highlighted.

Bacterial Cellulose-Based Materials as Dressings for Wound Healing

Bacterial cellulose (BC) is produced by several microorganisms as extracellular structures and can be modified by various physicochemical and biological strategies to produce different cellulosic formats. The main advantages of BC for biomedical applications can be summarized thus: easy moldability, purification, and scalability; high biocompatibility; and straightforward tailoring. The presence of a high amount of free hydroxyl residues, linked with water and nanoporous morphology, makes BC polymer an ideal candidate for wound healing. In this frame, acute and chronic wounds, associated with prevalent pathologies, were addressed to find adequate therapeutic strategies. Hence, the main characteristics of different BC structures-such as membranes and films, fibrous and spheroidal, nanocrystals and nanofibers, and different BC blends, as well as recent advances in BC composites with alginate, collagen, chitosan, silk sericin, and some miscellaneous blends-are reported in detail. Moreover, the development of novel antimicrobial BC and drug delivery systems are discussed.

Extraction of high-quality grade cellulose and cellulose nanocrystals from different lignocellulosic agri-food wastes

Introduction

Prompted by the increasing need for an intensified valorization of agri-food waste, in this work a three-step chemical procedure was used to extract high-purity cellulose from garlic stalk, corncob, and giant cane cut-up by a sequential removal of hemicellulose, lignin, ash, and organic compounds. Cellulose nanocrystals of potential interest for nanocomposite applications were then obtained through acid hydrolysis.

Methods

The purity of the cellulose was determined employing Nuclear Magnetic Resonance and infrared spectroscopy, whereas dynamic light scattering, optical, atomic force microscopy, and transmission electron microscopy were used for morphological characterization. The high purity and crystallinity of cellulose was confirmed by comparison with the ultra-pure bacterial cellulose originating from K. sucrofermentans, irrespective of the waste used.

Results and discussion

At the end of the extraction procedure, cellulose yields of 35.73, 37.15, and 39.10%, for garlic stalk, corncob, and giant cane cut-up, respectively, were achieved. Dynamic light scattering and atomic force microscopy analyses showed that the length of the whisker-like nanocrystals depended on the raw material (from ~100 nm up to > 2μm), while the final yield was ~40–50% for all three wastes. The versatility and effectiveness of the method here proposed can be profitably used for a wide range of agro-waste feedstocks.

Enhanced Antimicrobial Activity of Silver Sulfadiazine Cosmetotherapeutic Nanolotion for Burn Infections

Burns are highly traumatizing injuries that can be complicated by various microbial infections, leading to morbidity and mortality. The ultimate goal of burn therapy is to prevent any microbial infection and rapid wound healing with epithelization. The current study aimed to develop and investigate the potential of nanoemulsion-based cosmetotherapeutic lotion of silver sulfadiazine (SSD) for increased antimicrobial activity to treat burn injuries. Silver sulfadiazine is the standard topical treatment for burn patients, but is allied with major limitations of poor solubility, low bioavailability, and other hematologic effects, hindering its pharmaceutical applications. The nanoformulation was fabricated through the ultrasonication technique and optimized by selecting various parameters and concentrations for the formation of water-in-oil (w/o) emulsion. The optimized formulation depicts a smaller particle size of 213 nm with an encapsulation efficiency of approx. 80%. Further, nanoemulsion-based SSD lotion by utilizing argan oil as a cosmetotherapeutic agent was prepared for scar massaging with improved permeation properties. The designed cosmeceutical formulation was characterized in terms of physical appearance, refractive index, particle size, encapsulation efficiency, and biocompatibility. The compatibility of the formulation ingredients were determined through FTIR (Fourier Transform Infrared Spectroscopy). The formulated nanolotion containing SSD demonstrated superior antimicrobial activities against different bacterial strains in comparison to commercialized burn creams.

Dual photothermal nanocomposites for drug-resistant infectious wound management

Management of antibiotic-resistant bacteria-induced skin infections for rapid healing remains a critical clinical challenge. Photothermal therapy, which uses mediated hyperthermia to combat such problems, has recently been recognised as a promising approach to take. In this study, bacterial cellulose-based photothermal membranes were designed and developed to combat bacterial infections and promote rapid wound healing. Polydopamine was incorporated into gold nanoparticles to produce superior dual-photothermal behaviour. The in vitro antibacterial efficacy of the prepared composite membranes against S. aureus, E. coli and methicillin-resistant Staphylococcus aureus (MRSA) could reach 99% under near-infrared (NIR) irradiation. In addition, the synthesised nanocomposite exhibited good biocompatibility in vitro as demonstrated by a cell survival ratio of >85%. The effectiveness of the composite membranes on wound healing was further investigated in a murine model of MRSA-infected wounds, focusing on the effect of photothermal temperature. According to the detailed therapeutic mechanism study undertaken, the composite membranes cause bacterial killing initially and promote the transition from the inflammatory phase to proliferation by suppressing pro-inflammatory cytokine production, promoting collagen deposition, and stimulating angiogenesis. Considering their remarkable effectiveness and facile fabrication process, it is expected that these novel materials could serve as competitive multifunctional dressings in the management of infectious wounds and accelerate the regeneration of damaged tissues related to abnormal immune responses.

Biosynthetic cellulose compared to porcine xenograft in the treatment of partial-thickness burns: A randomised clinical trial

AIM

The aim was to compare two dressing treatments for partial-thickness burns: biosynthetic cellulose dressing (BsC) (Epiprotect® S2Medical AB, Linköping, Sweden) and porcine xenograft (EZ Derm®, Mölnlycke Health Care, Gothenburg, Sweden).

METHODS

Twenty-four adults with partial-thickness burns were included in this randomized clinical trial conducted at The Burn Centers in Linköping and Uppsala, Sweden between June 2016 and November 2018. Time to healing was the primary outcome. Secondary outcomes were wound infection, pain, impact on everyday life, length of hospital stay, cost, and burn scar outcome (evaluated with POSAS).

RESULTS

We found no significant differences between the two dressing groups regarding time to healing, wound infection, pain, impact on everyday life, duration of hospital stay, cost, or burn scar outcome at the first follow up. Burn scar outcome at the 12-month follow up showed that the porcine xenograft group patients scored their scars higher on the POSAS items thickness (p = 0.048) and relief (p = 0.050). This difference was, however, not confirmed by the observer.

CONCLUSIONS

The results showed the dressings performed similarly when used in adults with burns evaluated as partial thickness.

Cellulose-Based Nanomaterials Advance Biomedicine: A Review

There are various biomaterials, but none fulfills all requirements. Cellulose biopolymers have advanced biomedicine to satisfy high market demand and circumvent many ecological concerns. This review aims to present an overview of cellulose knowledge and technical biomedical applications such as antibacterial agents, antifouling, wound healing, drug delivery, tissue engineering, and bone regeneration. It includes an extensive bibliography of recent research findings from fundamental and applied investigations. Cellulose-based materials are tailorable to obtain suitable chemical, mechanical, and physical properties required for biomedical applications. The chemical structure of cellulose allows modifications and simple conjugation with several materials, including nanoparticles, without tedious efforts. They render the applications cheap, biocompatible, biodegradable, and easy to shape and process.

Synthesis of Poly(ε-caprolactone) Diacrylate for Micelle-Cross-Linked Sodium AMPS Hydrogel for Use as Controlled Drug Delivery Wound Dressing

This study focuses on the synthesis of poly(ε-caprolactone) diacrylate (PCLDA) for the fabrication of micelle-cross-linked sodium AMPS wound dressing hydrogels. The novel synthetic approach of PCLDA is functionalizing a PCL diol with acrylic acid. The influences of varying the PCL diol/AA molar ratio and temperature on the suitable conditions for the synthesis of PCLDA are discussed. The hydrogel was synthesized through micellar copolymerization of sodium 2-acrylamido-2-methylpropane sulfonate (Na-AMPS) as a basic monomer and PCLDA as a hydrophobic association monomer. In this study, an attempt was made to develop new hydrogel wound dressings meant for the release of antibacterial drugs (ciprofloxacin and silver sulfadiazine). The chemical structures, morphology, porosity, and water interaction of the hydrogels were characterized. The hydrogels' swelling ratio and water vapor transmission rate (WVTR) showed a high swelling capacity (4688-10753%) and good WVTR (approximately 2000 g·m^-2·day^-1), which can be controlled through variation of the PCLDA concentration. The mechanical property results confirmed that PCLDA improved the mechanical properties of the hydrogel; the stress increased from 37 to 68 kPa, and the strain increased from 198 to 360% with increasing PCLDA (0-30% wt of Na-AMPS). These hydrogels presented no cytotoxicity based on over 70% cell viability responses (L929 fibroblasts) using an in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, the drug release mechanism, kinetic models, and antibacterial activity were determined. The results demonstrated that antibiotics were released from the hydrogel with a Fickian diffusion mechanism and antibacterial activity against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus). Based on the results obtained, and bearing in mind that further progress still needs to be made, the fabricated hydrogels show considerable potential for meeting the stringent property requirements of hydrogel wound dressings.

Applications of Bacterial Cellulose as a Natural Polymer in Tissue Engineering

Choosing the material with the best regeneration potential and properties closest to that of the extracellular matrix is one of the main challenges in tissue engineering and regenerative medicine. Natural polymers, such as collagen, elastin, and cellulose, are widely used for this purpose in tissue engineering. Cellulose derived from bacteria has excellent mechanical properties, high hydrophilicity, crystallinity, and a high degree of polymerization and, therefore, can be used as scaffold/membrane for tissue engineering. In the current study, we reviewed the latest trends in the application of bacterial cellulose (BC) polymers as a scaffold in different types of tissue, including bone, vascular, skin, and cartilage. Also, we mentioned the biological and mechanical advantages and disadvantages of BC polymers. Given the data presented in this study, BC polymer could be suggested as a favorable natural polymer in the design of tissue scaffolds. Implementing novel composites that combine this polymer with other materials through modern or rapid prototyping methods can open up a great prospect in the future of tissue engineering and regenerative medicine.

Follow-up of pressure ulcer treatment with photodynamic therapy, low level laser therapy and cellulose membrane

OBJECTIVE

A pressure ulcer (PU) is an area of tissue trauma caused by continuous and prolonged pressure, often associated with hospitalised patients immobilised due to neurological problems, negatively affecting their quality of life, and burdening the public budget. The aim of this study was to report the follow-up, for 45 weeks, of three patients with neurological lesions due to trauma who subsequently developed PUs, and who were treated with a combination of photodynamic therapy (PDT), low level laser therapy (LLLT) and cellulose membrane (CM).

METHOD

PDT was mediated by the photosensitiser curcumin on a 1.5% emulsion base. Blue LED light at 450 nm was delivered continuously for 12 minutes at an irradiance of 30mW/cm² and total energy delivered to the tissue was 22J/cm². LLLT was performed with 660 nm laser, punctuated and continuous, twice a week with parameters: spot size 0.04cm², power of 40mW, 10 seconds per point, fluence of 10J/cm² and irradiance of 1000mW/cm².

RESULTS

All PUs had a significant reduction (range: 95.2-100%) of their area after 45 weeks of follow-up and two PUs had complete healing at 20 weeks and 30 weeks. All of the PUs showed a reduction in contamination with the PDT treatments in different proportions.

CONCLUSION

From the results obtained, we conclude that the combination of PDT, LLLT and CM is a promising treatment for PU healing.

Bacterial Cellulose Membrane Containing Epilobium angustifolium L. Extract as a Promising Material for the Topical Delivery of Antioxidants to the Skin

Bacterial cellulose membranes (BCs) are becoming useful as a drug delivery system to the skin. However, there are very few reports on their application of plant substances to the skin. Komagataeibacter xylinus was used for the production of bacterial cellulose (BC). The BC containing 5% and 10% ethanolic extract of Epilobium angustifolium (FEE) (BC-5%FEE and BC-10%FEE, respectively) were prepared. Their mechanical, structural, and antioxidant properties, as well as phenolic acid content, were evaluated. The bioavailability of BC-FESs using mouse L929 fibroblasts as model cells was tested. Moreover, In Vitro penetration through the pigskin of the selected phenolic acids contained in FEE and their accumulation in the skin after topical application of BC-FEEs was examined. The BC-FEEs were characterized by antioxidant activity. The BC-5% FEE showed relatively low toxicity to healthy mouse fibroblasts. Gallic acid (GA), chlorogenic acid (ChA), 3,4-dihydroxybenzoic acid (3,4-DHB), 4-hydroxybenzoic acid (4-HB), 3-hydroxybenzoic acid (3-HB), and caffeic acid (CA) found in FEE were also identified in the membranes. After topical application of the membranes to the pigskin penetration of some phenolic acid and other antioxidants through the skin as well as their accumulation in the skin was observed. The bacterial cellulose membrane loaded by plant extract may be an interesting solution for topical antioxidant delivery to the skin.

Transdermal Delivery Systems for Ibuprofen and Ibuprofen Modified with Amino Acids Alkyl Esters Based on Bacterial Cellulose

The potential of bacterial cellulose as a carrier for the transport of ibuprofen (a typical example of non-steroidal anti-inflammatory drugs) through the skin was investigated. Ibuprofen and its amino acid ester salts-loaded BC membranes were prepared through a simple methodology and characterized in terms of structure and morphology. Two salts of amino acid isopropyl esters were used in the research, namely L-valine isopropyl ester ibuprofenate ([ValOiPr][IBU]) and L-leucine isopropyl ester ibuprofenate ([LeuOiPr][IBU]). [LeuOiPr][IBU] is a new compound; therefore, it has been fully characterized and its identity confirmed. For all membranes obtained the surface morphology, tensile mechanical properties, active compound dissolution assays, and permeation and skin accumulation studies of API (active pharmaceutical ingredient) were determined. The obtained membranes were very homogeneous. In vitro diffusion studies with Franz cells were conducted using pig epidermal membranes, and showed that the incorporation of ibuprofen in BC membranes provided lower permeation rates to those obtained with amino acids ester salts of ibuprofen. This release profile together with the ease of application and the simple preparation and assembly of the drug-loaded membranes indicates the enormous potentialities of using BC membranes for transdermal application of ibuprofen in the form of amino acid ester salts.

A review of functionalised bacterial cellulose for targeted biomedical fields

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

Permeation of Silver Sulfadiazine Into TEMPO-Oxidized Bacterial Cellulose as an Antibacterial Agent

Surface oxidation of bacterial cellulose (BC) was done with the TEMPO-mediated oxidation mechanism system. After that, TEMPO-oxidized bacterial cellulose (TOBC) was impregnated with silver sulfadiazine (AgSD) to prepare nanocomposite membranes. Fourier transform infrared spectroscopy (FTIR) was carried out to determine the existence of aldehyde groups on BC nanofibers and X-ray diffraction (XRD) demonstrated the degree of crystallinity. FESEM analysis revealed the impregnation of AgSD nanoparticles at TOBC nanocomposites with the average diameter size ranging from 11 nm to 17.5 nm. The sample OBCS3 showed higher antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli by the disc diffusion method. The results showed AgSD content, dependent antibacterial activity against all tested bacteria, and degree of crystallinity increases with TOBC and AgSD. The main advantage of the applications of TEMPO-mediated oxidation to BC nanofibers is that the crystallinity of BC nanofibers is unchanged and increased after the oxidation. Also enhanced the reactivity of BC as it is one of the most promising method for cellulose fabrication and functionalization. We believe that the novel composite membrane could be a potential candidate for biomedical applications like wound dressing, BC scaffold, and tissue engineering.

Nanocellulose in Drug Delivery and Antimicrobially Active Materials

In recent years, nanocellulose (NC) has also attracted a great deal of attention in drug delivery systems due to its unique physical properties, specific surface area, low risk of cytotoxicity, and excellent biological properties. This review is focused on nanocellulose based systems acting as carriers to be used in drug or antimicrobial delivery by providing different but controlled and sustained release of drugs or antimicrobial agents, respectively, thus showing potential for different routes of applications and administration. Microorganisms are increasingly resistant to antibiotics, and because, generally, the used metal or metal oxide nanoparticles at some concentration have toxic effects, more research has focused on finding biocompatible antimicrobial agents that have been obtained from natural sources. Our review contains the latest research from the last five years that tested nanocellulose-based materials in the field of drug delivery and antimicrobial activity.

Kinetics and controlled release of lidocaine from novel carrageenan and alginate-based blend hydrogels

The controlled release of drug from drug carrier has been a point of concern for the researchers to ensure the bioavailability of drug with reduced side effects. The formulation in this study is based upon biopolymers; carrageenan (CG), sodium alginate (SA) and various molecular weights of polyethylene glycol (PEG), cross-linked with (3-Aminopropyl)triethoxysilane, APTES for the sustained release of model drug (lidocaine). The physicochemical properties of the formulated hydrogel blends include bonding pattern (using Fourier Transform Infra-Red Spectroscopy (FTIR), Thermogravimetric analysis (TGA), X-ray diffraction (XRD), swelling study, antimicrobial activity and morphology of hydrogel films was analyzed by scanning electron microscopy (SEM). The as-prepared hydrogels show an improved cell compatibility against 3T3 cell line as well as cell proliferation and kinetics of drug release showed that these hydrogels are potential for controlled release of lidocaine, a numbing agent. GAP 60 exhibited maximum swelling percent (910%) and was employed to load the drug. By using in vitro model, the drug release was studied in PBS solution. Non-Fickian and other kinetic models (Zero order, Higuchi, Hixson, Korsmeyer Peppas and Baker-Lonsdale) for diffusion were followed in results. The improved properties showed that the formulated hydrogels can easily be used for the sustain drug release studies.

Green electrochemical synthesis of silver sulfadiazine microcrystals

Electrochemical synthesis of silver sulfadiazine (AgSD) microcrystals was carried out galvanostatically in a special two-electrode cell equipped with a sacrificial silver rod anode and a stainless steel plate cathode. The cell used in this work consists of a small cylindrical chamber containing aqueous sulfadiazine/sodium nitrate as the anode compartment inside a larger cylindrical chamber containing nitric acid solution as the cathode compartment. The ionic connection of two chambers is carried out through a solvent surface layer. In this study, the effect of the experimental parameters such as applied current density and sodium nitrate concentration as well as nitric acid concentration on the yield and energy consumption of AgSD is discussed. The proposed method is fast and green and has unique features including synthesis in a single step, and no need for a metal salt.

Green synthesis of bacterial cellulose/bioactive glass nanocomposites: Effect of glass nanoparticles on cellulose yield, biocompatibility and antimicrobial activity

Despite the advantages of bacterial cellulose (BC) over traditional cellulose, its low yield and little bioactivity makes a limitation to be used in an industrial scale. This paper was mainly dual aimed to increase the BC yield using a nanobioactive glass (NBG), and in situ synthesize BC/NBG bioactive nanocomposites by a novel and simple green method. Accordingly, the composites were prepared via in situ fermentation approach by incorporation of NBG particles into BC producing culture medium. The effect of NBG addition on the production process of cellulose, biocompatibility, bioactivity and antimicrobial activity were investigated. The results showed that NBG was enhanced and increased the BC yield and this has been achieved by maintaining these NBG on the pH value of the culture medium during the fermentation period. Moreover, it was effectively improved biocompatibility and antimicrobial properties of BC. This study evidenced that BC/NBG composite can be expected to be widely applied in biomedical industries such as bone regeneration and wound healing with the unique of being not harmful to humans.

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.

A Study of the Physical and Mechanical Properties of Aerogels Obtained from Bacterial Cellulose

Aerogels with a density of 4.2-22.8 kg/m³ were obtained from bacterial cellulose synthesized under static and dynamic cultivation conditions on a molasses medium. The strength properties and porous structure of the aerogels strongly depended on their density. With an aerogel density of 22.8 kg/m³, the modulus of elasticity at 80% compression of the sample was 0.1 MPa. The decrease in the density of aerogels led to an increase in the pore sizes ranging from 20 to 1000 μm and a decrease in the modulus of elasticity. These characteristics were more pronounced in aerogels obtained from bacterial cellulose under static cultivation conditions. The aerogels had a low coefficient of thermal conductivity (0.0257 W m^-1 °C^-1), which is comparable to the thermal conductivity of air, and moderate thermal stability because the degradation processes of the aerogels began at 237 °C. The aerogels obtained from bacterial cellulose had high sound absorption coefficients in the frequency range of 200-5000 Hz, which makes it possible to use the aerogels as heat- and sound-insulating materials.

Three Years' Experience of a Novel Biosynthetic Cellulose Dressing in Burns

Objective: The use of porcine xenograft (PX) is widely spread in burn care. However, it may cause immunologic responses and other ethical and cultural considerations in different cultures. Therefore, there is a need for alternatives. The aim of this work is to test a novel biosynthetic cellulose dressing (Epiprotect^®) on burn patients.

Approach: Charts from 38 patients with superficial burns (SBs) (n = 18) or excised burns (n = 20) that got biosynthetic cellulose dressing instead of PX at a national burn center during 3 years were reviewed. Time to healing, length of stay, and wound infection were extracted from the medical records.

Results: SBs hospitalization time was 11 days comparable to PXs reported by others. In the excised group, median duration of hospital stay was 35 days. Time to healing was 28 days. Seven wound infections were confirmed in the superficial group (39%) and 11 infections in the excised group (61%). Patients with superficial wounds reported pain relief on application.

Innovation: A dressing (17 × 21 cm) consisting of biosynthetic cellulose replacing PX.

Conclusion: Outcome of treatment of SBs or temporary coverage of excised deep burns with biosynthetic cellulose is comparable to treatment with PX. However, biosynthetic cellulose has benefits such as providing pain relief on application and ethical or cultural issues with the material is nonexistent.

Versatile Application of Nanocellulose: From Industry to Skin Tissue Engineering and Wound Healing

Nanocellulose is cellulose in the form of nanostructures, i.e., features not exceeding 100 nm at least in one dimension. These nanostructures include nanofibrils, found in bacterial cellulose; nanofibers, present particularly in electrospun matrices; and nanowhiskers, nanocrystals, nanorods, and nanoballs. These structures can be further assembled into bigger two-dimensional (2D) and three-dimensional (3D) nano-, micro-, and macro-structures, such as nanoplatelets, membranes, films, microparticles, and porous macroscopic matrices. There are four main sources of nanocellulose: bacteria (Gluconacetobacter), plants (trees, shrubs, herbs), algae (Cladophora), and animals (Tunicata). Nanocellulose has emerged for a wide range of industrial, technology, and biomedical applications, namely for adsorption, ultrafiltration, packaging, conservation of historical artifacts, thermal insulation and fire retardation, energy extraction and storage, acoustics, sensorics, controlled drug delivery, and particularly for tissue engineering. Nanocellulose is promising for use in scaffolds for engineering of blood vessels, neural tissue, bone, cartilage, liver, adipose tissue, urethra and dura mater, for repairing connective tissue and congenital heart defects, and for constructing contact lenses and protective barriers. This review is focused on applications of nanocellulose in skin tissue engineering and wound healing as a scaffold for cell growth, for delivering cells into wounds, and as a material for advanced wound dressings coupled with drug delivery, transparency and sensorics. Potential cytotoxicity and immunogenicity of nanocellulose are also discussed.

Stimuli responsive biopolymer (chitosan) based blend hydrogels for wound healing application

Stimuli responsive chitosan (CS) and poly (N-vinyl-2-pyrrolidone) (PVP) have attained hydrogel properties in the presence of 74% neutralized poly acrylic acid (PAA) which can be exploited for wound healing applications. The FTIR spectra confirmed the presence of all specific functional groups and the developed interactions in the hydrogels. The thermal analysis explained that the hydrogel samples are thermally more stable than individual chitosan and PVP. The antimicrobial analysis revealed that all the samples show antibacterial activity against E. coli and the biodegradation analysis is performed to confirm the hydrogels degradation. The hydrogels showed enhanced responsive swelling behavior against different media depending upon the amount of PVP. The %age swelling in water is decreased with the increase in the amount of PVP. The most considerable swelling behavior is observed against pH, as they manifested low swelling at acidic pH and high swelling at neutral pH while at pH 8, the prominent values are obtained. This distinctive behavior of hydrogels and their biocompatibility made them pertinent to drug delivery and their release profile is examined spectrophotometrically using silver sulfadiazine (antibiotic for burnt wounds) showed 91.2% of drug release for a period of 1 h in phosphate buffer saline (PBS) in a consistent and controlled manner.

Nanocellulose-Based Antibacterial Materials

In recent years, nanocellulose-based antimicrobial materials have attracted a great deal of attention due to their unique and potentially useful features. In this review, several representative types of nanocellulose and modification methods for antimicrobial applications are mainly focused on. Recent literature related with the preparation and applications of nanocellulose-based antimicrobial materials is reviewed. The fabrication of nanocellulose-based antimicrobial materials for wound dressings, drug carriers, and packaging materials is the focus of the research. The most important additives employed in the preparation of nanocellulose-based antimicrobial materials are presented, such as antibiotics, metal, and metal oxide nanoparticles, as well as chitosan. These nanocellulose-based antimicrobial materials can benefit many applications including wound dressings, drug carriers, and packaging materials. Finally, the challenges of industrial production and potentials for development of nanocellulose-based antimicrobial materials are discussed.

Bismuth Phosphinates in Bi-Nanocellulose Composites and their Efficacy towards Multi-Drug Resistant Bacteria

A series of poorly soluble phenyl bis-phosphinato bismuth(III) complexes [BiPh(OP(=O)R¹ R² )₂ ] (R¹ =R² =Ph; R¹ =R² =p-OMePh; R¹ =R² =m-NO₂ Ph; R¹ =Ph, R² =H; R¹ =R² =Me) have been synthesised and characterised, and shown to have effective antibacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). The bismuth complexes were incorporated into microfibrillated (nano-) cellulose generating a bismuth-cellulose composite as paper sheets. Antibacterial evaluation indicates that the Bi-cellulose materials have analogous or greater activity against Gram positive bacteria when compared with commercial silver based additives: silver sulfadiazine loaded at 0.43 wt % into nanocellulose produces a 10 mm zone of inhibition on the surface of agar plates containing S. aureus whereas [BiPh(OP(=O)Ph₂ )₂ ] loaded at 0.34 wt % produces an 18 mm zone of inhibition. These phenyl bis-phosphinato bismuth(III) complexes show potential to be applied in materials in healthcare facilities, to inhibit the growth of bacteria capable of causing serious disease.

Functionalization of cotton cellulose for improved wound healing

Wound dressing research has been determined by population aging, persistence of wound infection and the increase in chronic wound cases. Thus, besides mechanical protection, wound dressings must interact with the wound and improve the healing process. To achieve this demanding goal, wound dressing research has been focussing on the development of composite wound dressings that combine the best of two or more polymeric materials. Cellulosic materials are still the most used for wound management. Their importance is reflected in the number of publications on this subject in the textile engineering field. Textile wound dressing can cause maceration to the wound and pain during removal. However, the limitations of cellulosic wound dressings can be overcome by functionalization with hydrogels, which will maintain the moisture environment and improve the drug delivery ability of cotton. Therefore, the present review summarizes the composite materials research on the functionalization of cotton cellulose with hydrogels, to be applied as a wound dressing, and the methods and techniques used to synthesize those composites.

Nanocellulose as a sustainable biomass material: structure, properties, present status and future prospects in biomedical applications

Nanocellulose, extracted from the most abundant biomass material cellulose, has proved to be an environmentally friendly material with excellent mechanical performance owing to its unique nano-scaled structure, and has been used in a variety of applications as engineering and functional materials. The great biocompatibility and biodegradability, in particular, render nanocellulose promising in biomedical applications. In this review, the structure, treatment technology and properties of three different nanocellulose categories, i.e., nanofibrillated cellulose (NFC), nanocrystalline cellulose (NCC) and bacterial nanocellulose (BNC), are introduced and compared. The cytotoxicity, biocompatibility and frontier applications in biomedicine of the three nanocellulose categories were the focus and are detailed in each section. Future prospects concerning the cytotoxicity, applications and industrial production of nanocellulose are also discussed in the last section.

Production and Status of Bacterial Cellulose in Biomedical Engineering

Bacterial cellulose (BC) is a highly pure and crystalline material generated by aerobic bacteria, which has received significant interest due to its unique physiochemical characteristics in comparison with plant cellulose. BC, alone or in combination with different components (e.g., biopolymers and nanoparticles), can be used for a wide range of applications, such as medical products, electrical instruments, and food ingredients. In recent years, biomedical devices have gained important attention due to the increase in medical engineering products for wound care, regeneration of organs, diagnosis of diseases, and drug transportation. Bacterial cellulose has potential applications across several medical sectors and permits the development of innovative materials. This paper reviews the progress of related research, including overall information about bacterial cellulose, production by microorganisms, mechanisms as well as BC cultivation and its nanocomposites. The latest use of BC in the biomedical field is thoroughly discussed with its applications in both a pure and composite form. This paper concludes the further investigations of BC in the future that are required to make it marketable in vital biomaterials.

In vitro and in vivo studies of a novel bacterial cellulose-based acellular bilayer nanocomposite scaffold for the repair of osteochondral defects

Bacterial cellulose (BC) is a naturally occurring nanofibrous biomaterial which exhibits unique physical properties and is amenable to chemical modifications. To explore whether this versatile material can be used in the treatment of osteochondral defects (OCD), we developed and characterized novel BC-based nanocomposite scaffolds, for example, BC-hydroxyapatite (BC-HA) and BC-glycosaminoglycans (BC-GAG) that mimic bone and cartilage, respectively. In vitro biocompatibility of BC-HA and BC-GAG scaffolds was established using osteosarcoma cells, human articular chondrocytes, and human adipose-derived mesenchymal stem cells. On subcutaneous implantation, the scaffolds allowed tissue ingrowth and induced no adverse immunological reactions suggesting excellent in vivo biocompatibility. Implantation of acellular bilayered scaffolds in OCD created in rat knees induced progressive regeneration of cartilage tissue, deposition of extracellular matrix, and regeneration of subchondral bone by the host cells. The results of micro-CT revealed that bone mineral density and ratio of bone volume to tissue volume were significantly higher in animals receiving bilayered scaffold as compared to the control animals. To the best of our knowledge, this study proves for the first time, the functional performance of acellular BC-based bilayered scaffolds. Thus, this strategy has great potential for clinical translation and can be used in repair of OCD.