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

Leveraging the Attributes of Mucor hiemalis-Derived Silver Nanoparticles for a Synergistic Broad-Spectrum Antimicrobial Platform

Driven by the need to engineer robust surface coatings for medical devices to prevent infection and sepsis, incorporation of nanoparticles has surfaced as a promising avenue to enhance non-fouling efficacy. Microbial synthesis of such nanoscale metallic structures is of substantive interest as this can offer an eco-friendly, cost-effective, and sustainable route for further development. Here we present a Mucor hiemalis-derived fungal route for synthesis of silver nanoparticles, which display significant antimicrobial properties when tested against six pathological bacterial strains (Klebsiella pneumoniae, Pseudomonas brassicacearum, Aeromonas hydrophila, Escherichia coli, Bacillus cereus, and Staphylococcus aureus) and three pathological fungal strains (Candida albicans, Fusarium oxysporum, and Aspergillus flavus). These antimicrobial attributes were comparable to those of established antibiotics (streptomycin, tetracycline, kanamycin, and rifampicin) and fungicides (amphotericin B, fluconazole, and ketoconazole), respectively. Importantly, these nanoparticles show significant synergistic characteristics when combined with the antibiotics and fungicides to offer substantially greater resistance to microbial growth. The blend of antibacterial and antifungal properties, coupled with their intrinsic “green” and facile synthesis, makes these biogenic nanoparticles particularly attractive for future applications in nanomedicine ranging from topical ointments and bandages for wound healing to coated stents.

In situ and ex situ modifications of bacterial cellulose for applications in tissue engineering

Bacterial cellulose (BC) is secreted by a few strains of bacteria and consists of a cellulose nanofiber network with unique characteristics. Because of its excellent mechanical properties, outstanding biocompatibilities, and abilities to form porous structures, BC has been studied for a variety of applications in different fields, including the use as a biomaterial for scaffolds in tissue engineering. To extend its applications in tissue engineering, native BC is normally modified to enhance its properties. Generally, BC modifications can be made by either in situ modification during cell culture or ex situ modification of existing BC microfibers. In this review we will first provide a brief introduction of BC and its attributes; this will set the stage for in-depth and up-to-date discussions on modified BC. Finally, the review will focus on in situ and ex situ modifications of BC and its applications in tissue engineering, particularly in bone regeneration and wound dressing.

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.

Novel Cu@SiO2/bacterial cellulose nanofibers: Preparation and excellent performance in antibacterial activity

The antibacterial composite based on bacterial cellulose (BC) was successfully prepared by in-situ synthesis of SiO2 coated Cu nanoparticles (Cu@SiO2/BC) and its properties were characterized. Its chemical structures and morphologies were evaluated by Fourier transformation infrared spectrum (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the SiO2 coated Cu particles were well homogeneously precipitated on the surface of BC. The Cu@SiO2/BC was more resistant to oxidation than the Cu nanoparticles impregnated into BC (Cu/BC) and then Cu@SiO2/BC could prolong the antimicrobial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli).

Antimicrobial activity of bone cements embedded with organic nanoparticles

Infections after orthopedic surgery are a very unwelcome outcome; despite the widespread use of antibiotics, their incidence can be as high as 10%. This risk is likely to increase as antibiotics are gradually losing efficacy as a result of bacterial resistance; therefore, novel antimicrobial approaches are required. Parabens are a class of compounds whose antimicrobial activity is employed in many cosmetic and pharmaceutical products. We developed propylparaben nanoparticles that are hydrophilic, thus expanding the applicability of parabens to aqueous systems. In this paper we assess the possibility of employing paraben nanoparticles as antimicrobial compound in bone cements. The nanoparticles were embedded in various types of bone cement (poly(methyl methacrylate) [PMMA], hydroxyapatite, and brushite) and the antimicrobial activity was determined against common causes of postorthopedic surgery infections such as: Staphylococcus aureus, methicillin-resistant S. aureus, Staphylococcus epidermidis, and Acinetobacter baumannii. Nanoparticles at concentrations as low as 1% w/w in brushite bone cement were capable of preventing pathogens growth, 5% w/w was needed for hydroxyapatite bone cement, while 7% w/w was required for PMMA bone cement. No detrimental effect was determined by the addition of paraben nanoparticles on bone cement compression strength and cytocompatibility. Our results demonstrate that paraben nanoparticles can be encapsulated in bone cement, providing concentration-dependent antimicrobial activity; furthermore, lower concentrations are needed in calcium phosphate (brushite and hydroxyapatite) than in acrylic (PMMA) bone cements. These nanoparticles are effective against a wide spectrum of bacteria, including those already resistant to the antibiotics routinely employed in orthopedic applications, such as gentamicin.

Sustainable antimicrobial effect of silver sulfadiazine-loaded nanosheets on infection in a mouse model of partial-thickness burn injury

Partial-thickness burn injury has the potential for reepithelialization and heals within 3weeks. If the wound is infected by bacteria before reepithelization, however, the depth of disruption increases and the lesion easily progresses to the full-thickness dermal layers. In the treatment of partial-thickness burn injury, it is important to prevent the wound area from bacterial infection with an antimicrobial dressing. Here, we have tested the antimicrobial properties of polymeric ultra-thin films composed of poly(lactic acid) (termed "PLA nanosheets"), which have high flexibility, adhesive strength and transparency, and silver sulfadiazine (AgSD), which exhibits antimicrobial efficacy. The AgSD-loaded nanosheet released Ag(+) for more than 3days, and exerted antimicrobial efficacy against methicillin-resistant Staphylococcus aureus (MRSA) in an in vitro Kirby-Bauer test. By contrast, a cell viability assay indicated that the dose of AgSD used in the PLA nanosheets did not show significant cytotoxicity toward fibroblasts. In vivo evaluation using a mouse model of infection in a partial-thickness burn wound demonstrated that the nanosheet significantly reduced the number of MRSA bacteria on the lesion (more than 10(5)-fold) and suppressed the inflammatory reaction, thereby preventing a protracted wound healing process.

Immobilization of collagen peptide on dialdehyde bacterial cellulose nanofibers via covalent bonds for tissue engineering and regeneration

Bacterial cellulose (BC) is an alternative nanostructured biomaterial to be utilized for a wide range of biomedical applications. Because of its low bioactivity, which restricted its practical application, collagen and collagen hydrolysate were usually composited into BC. It is necessary to develop a new method to generate covalent bonds between collagen and cellulose to improve the immobilization of collagen on BC. This study describes a facile dialdehyde BC/collagen peptide nanocomposite. BC was oxidized into dialdehyde bacterial cellulose (DBC) by regioselective oxidation, and then composited with collagen peptide (Col-p) via covalent bonds to form Schiff’s base type compounds, which was demonstrated by the results of microstructures, contact angle, Col-p content, and peptide-binding ratio. The peptide-binding ratio was further affected by the degree of oxidation, pH value, and zeta potential. In vitro desorption measurement of Col-p suggested a controlled release mechanism of the nanocomposite. Cell tests indicated that the prepared DBC/Col-p composite was bioactive and suitable for cell adhesion and attachment. This work demonstrates that the DBC/Col-p composite is a promising material for tissue engineering and regeneration.

Do bacterial cellulose membranes have potential in drug-delivery systems?

INTRODUCTION

Bacterial cellulose (BC) is an extremely pure form of cellulose, which, due to its unique properties, such as high purity, water-holding capacity, three-dimensional nanofibrilar network, mechanical strength, biodegradability and biocompatibility, shows a high potential as nanomaterial in a wide range of high-tech domains including biomedical applications, and most notably in controlled drug-delivery systems.

AREAS COVERED

This appraisal is intended to cover the major characteristics of BC, followed by the key aspects of BC production both in static and agitated conditions, and a glance of the major applications of BC, giving some emphasis to biomedical applications. Finally, a detailed discussion of the different applications of BC in controlled drug-delivery systems will be put forward, with focus on topical and oral drug-delivery systems, using either native BC or composite materials thereof.

EXPERT OPINION

The limited number of studies carried out so far demonstrated that BC, or materials prepared from it, are interesting materials for drug-delivery systems. There is, however, a large field of systematic research ahead to develop new and more selectively responsive materials and eventually to conjugate them with other biomedical applications of BC under development.

Active wound dressings based on bacterial nanocellulose as drug delivery system for octenidine

Although bacterial nanocellulose (BNC) may serve as an ideal wound dressing, it exhibits no antibacterial properties by itself. Therefore, in the present study BNC was functionalized with the antiseptic drug octenidine. Drug loading and release, mechanical characteristics, biocompatibility, and antimicrobial efficacy were investigated. Octenidine release was based on diffusion and swelling according to the Ritger-Peppas equation and characterized by a time dependent biphasic release profile, with a rapid release in the first 8h, followed by a slower release rate up to 96 h. The comparison between lab-scale and up-scale BNC identified thickness, water content, and the surface area to volume ratio as parameters which have an impact on the control of the release characteristics. Compression and tensile strength remained unchanged upon incorporation of octenidine in BNC. In biological assays, drug-loaded BNC demonstrated high biocompatibility in human keratinocytes and antimicrobial activity against Staphylococcus aureus. In a long-term storage test, the octenidine loaded in BNC was found to be stable, releasable, and biologically active over a period of 6 months without changes. In conclusion, octenidine loaded BNC presents a ready-to-use wound dressing for the treatment of infected wounds that can be stored over 6 months without losing its antibacterial activity.

Silver nanoparticle/bacterial cellulose gel membranes for antibacterial wound dressing: investigation in vitro and in vivo

Bacterial cellulose (BC) has attracted increasing attention as a novel wound dressing material, but its antimicrobial activity, which is one of the critical skin-barrier functions in wound healing, is not sufficient for use in practical applications. To overcome such a deficiency, silver nanoparticles were generated and self-assembled on the surface of BC nanofibers, forming a stable and evenly distributed Ag nanoparticle coated BC nanofiber (AgNP-BC). The performance of AgNP-BC was systematically studied in terms of antibacterial activities, cytocompatibility and effects on wound healing. The results showed that AgNP-BC exhibited significant antibacterial activity against Staphylococcus aureus. Moreover, AgNP-BC allowed attachment, and growth of rat fibroblasts with low cytotoxicity emerged. Based on these advantages, AgNP-BC samples were applied in a second-degree rat wound model. Wound flora showed a significant reduction during the healing. The fresh epidermal and dermis thicknesses with AgNP-BC samples were 111 and 855 µm respectively, higher than 74 and 619 µm for BC groups and 57 and 473 µm for untreated control wounds. The results demonstrated that AgNP-BC could reduce inflammation and promote scald wound healing.

Topical application of zinc oxide nanoparticles reduces bacterial skin infection in mice and exhibits antibacterial activity by inducing oxidative stress response and cell membrane disintegration in macrophages

Here we studied immunological and antibacterial mechanisms of zinc oxide nanoparticles (ZnO-NPs) against human pathogens. ZnO-NPs showed more activity against Staphylococcus aureus and least against Mycobacterium bovis-BCG. However, BCG killing was significantly increased in synergy with antituberculous-drug rifampicin. Antibacterial mechanistic studies showed that ZnO-NPs disrupt bacterial cell membrane integrity, reduce cell surface hydrophobicity and down-regulate the transcription of oxidative stress-resistance genes in bacteria. ZnO-NP treatment also augmented the intracellular bacterial killing by inducing reactive oxygen species production and co-localization with Mycobacterium smegmatis-GFP in macrophages. Moreover, ZnO-NPs disrupted biofilm formation and inhibited hemolysis by hemolysin toxin producing S. aureus. Intradermal administration of ZnO-NPs significantly reduced the skin infection, bacterial load and inflammation in mice, and also improved infected skin architecture. We envision that this study offers novel insights into antimicrobial actions of ZnO-NPs and also demonstrates ZnO-NPs as a novel class of topical anti-infective agent for the treatment of skin infections.

FROM THE CLINICAL EDITOR

This in-depth study demonstrates properties of ZnO nanoparticles in infection prevention and treatment in several skin infection models, dissecting the potential mechanisms of action of these nanoparticles and paving the way to human applications.

Production of biocompatible and antimicrobial bacterial cellulose polymers functionalized by RGDC grafting groups and gentamicin

Bacterial cellulose (BC), a three-dimensional fibril, is a natural polymer that can be used for many applications. BC effectiveness may be improved by enhancing surface characteristics contributing to a better physiologic interaction with human and animal cells and to intrinsically present antimicrobial agents. In the present study, gentamicin-activated BC membranes were obtained by chemically grafting RGDC peptides (R: arginine; G: glycine; D: aspartic acid; C: cysteine) using coupling agent 3-aminopropyltriethoxysilane (APTES) followed by covalent attachment of gentamicin onto the surface of the BC membrane network. X-ray photoelectron spectroscopy (XPS) analyses showed that the BC-APTES contained 0.7% of silicon in terms of elemental composition, corresponding to a grafting ratio of 1:12. The presence of silicon and nitrogen in the BC-APTES confirmed the surface functionalization of the BC membrane. Fourier-transform infrared (FTIR) analyses show the formation of the secondary amide as supported by the valence bond C═O (ν(C═O)), a characteristic vibrational transition at 1650 cm(-1) which is particularly intense with the BC-RGDC-gentamicin membrane. Energy-dispersive X-ray (EDX) analyses showed a low level of carbon and nitrogen (C + N) in pure BC but a high level of (C + N) in BC-RGDC-gentamicin confirming the surface modification of the BC membrane by RGDC and gentamicin enrichment. Of great interest, the gentamicin-RGDC-grafted BC membranes are bactericidal against Streptococcus mutans but nontoxic to human dermal fibroblasts and thus may be useful for multiple applications such as improved wound healing and drug delivery systems.

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

Bacterial cellulose (BC) is characterized for its high water holding capacity, high crystallinity, an ultrafine fiber network and high tensile strength. This work demonstrates the production of a new interpenetrated polymer network nanocomposite obtained through the incorporation of poly(vinyl alcohol) (PVA) on the BC matrix and evaluates the effect of oven drying on the morphological, mechanical and mass transfer properties of the composite membranes. Both the addition of PVA and oven drying induce the appearance of larger pores (circa 1–3 µm in average diameter) in dried BC/PVA membranes. Both types of treatments also affect the permeability of the composite, as assessed by the diffusion coefficients of polyethylene glycol (PEG) molecules (900, 8,000, 35,000 and 100,000 Da) across the membranes. Finally, the Young’s modulus of dry pristine BC decreases following PVA incorporation, resulting in a change from 3.5 GPa to 1 GPa and a five-fold loss in tensile strength.