Synthesis and characterization of antimicrobial colloidal polyanilines

The potential application of colloidal polyaniline (PANI) as an antimicrobial is limited by challenges related to solubility in common organic solvents, scalability, and antimicrobial potency. To address these limitations, we introduced a functionalized PANI (fPANI) with carboxyl groups through the polymerisation of aniline and 3-aminobenzoic acid in a 1:1 molar ratio. fPANI is more soluble than PANI which was determined using a qualitative study. We further enhanced the solubility and antimicrobial activity of fPANI by incorporating Ag nanoparticles onto the synthesized fPANI colloid via direct addition of 10 mM AgNO3. The improved solubility can be attributed to an approximately 3-fold reduction in size of particles. Mean particle sizes are measured at 1322 nm for fPANI colloid and 473 nm for fPANI-Ag colloid, showing a high dispersion and deagglomeration effect from Ag nanoparticles. Antimicrobial tests demonstrated that fPANI-Ag colloids exhibited superior potency against Gram-positive Staphylococcus aureus, Gram-negative Escherichia coli, and Bacteriophage PhiX 174 when compared to fPANI alone. The minimum bactericidal concentration (MBC) and minimum virucidal concentration (MVC) values were halved for fPANI-Ag compared to fPANI colloid and attributed to the combination of Ag nanoparticles with the fPANI polymer. The antimicrobial fPANI-Ag colloid presented in this study shows promising results, and further exploration into scale-up can be pursued for potential biomedical applications.

Conductive hydrogels based on tragacanth and silk fibroin containing dopamine functionalized carboxyl-capped aniline pentamer: Merging hemostasis, antibacterial, and anti-oxidant properties into a multifunctional hydrogel for burn wound healing

Hydrogels possessing both conductive characteristics and notable antibacterial and antioxidant properties hold considerable significance within the realm of wound healing and recovery. The object of current study is the development of conductive hydrogels with antibacterial and antioxidant properties, emphasizing their potential for effective wound healing, especially in treating third-degree burns. For this purpose, various conductive hydrogels are developed based on tragacanth and silk fibroin, with variable dopamine functionalized carboxyl-capped aniline pentamer (CAP@DA). The FTIR analysis confirms that the CAP powder was successfully synthesized and modified with DA. The results show that the incorporation of CAP@DA into hydrogels can increase the porosity and swellability of the hydrogels. Additionally, the mechanical and viscoelastic properties of the hydrogels are also improved. The release of vancomycin from the hydrogels is sustained over time, and the hydrogels are effective in inhibiting the growth of Methicillin-resistant Staphylococcus aureus (MRSA). In vitro cell studies of the hydrogels show that all hydrogels are biocompatible and support cell attachment. The hydrogels' tissue adhesiveness yielded a satisfactory hemostatic outcome in a rat-liver injury model. The third-degree burn was created on the dorsal back paravertebral region of the rats and then grafted with hydrogels. The burn was monitored for 3, 7, and 14 days to evaluate the efficacy of the hydrogel in promoting wound healing. The hydrogels revealed treatment effect, resulting in enhancements in wound closure, dermal collagen matrix production, new blood formation, and anti-inflammatory properties. Better results were obtained for hydrogel with increasing CAP@DA. In summary, the multifunctional conducive hydrogel, featuring potent antibacterial properties, markedly facilitated the wound regeneration process.

Development of Novel Multifunctional Electroactive, Self-Healing, and Tissue Adhesive Scaffold To Accelerate Cutaneous Wound Healing and Hemostatic Materials

Designing a multifunctional conducting hydrogel wound dressing of suitable mechanical properties, adhesiveness, self-healing, autolytic debridement, antibacterial properties, and radical scavenging ability, as well as retaining an appropriate level of moisture around the wound is highly desirable in clinical application for treating cutaneous wounds healing. Here, we designed a novel class of electroactive hydrogel based on thiol-functionalized silver-graphene oxide nanoparticles (GO/Ag/TGA) core polyaniline (PANI) shell GO/Ag/TGA/PANI nanocomposites. Thus, a series of physically cross-linked hydrogel based on GO/Ag/TGA/PANI and poly(vinyl alcohol) (PVA) was prepared by freeze-thawing method. The hydrogel was characterized by XRD, UV, FTIR, TGA, TEM, SEM, Raman spectroscopy, cyclic voltammetry (CV), and four probes test. The hydrogel showed favorable properties such as excellent tensile strength, suitable gelation time (30-56 s), tunable rheological properties (G' ∼ 1 kPa), adhesiveness, and interconnected porous structure (freeze-dried). Besides this, the hydrogel also exhibits excellent exudate uptake capacity (10.4-0.2 g/g), high swelling ratio (72.4 to 93.5%), long-term antibacterial activity against multidrug-resistant (MDR) bacterial isolates, promising antioxidant (radical scavenging) efficiency, keeping the wound moisturized, prominent hemostatic efficiency, and fast self-healing ability to bear deformation. Interestingly, in vivo experiments indicated that electroactive hydrogels can significantly promote the healing rate of artificial wounds in rats, and histological analysis by H&E reveals higher granulation tissue thickness, collagen deposition, hair follicles, dermal papillary, keratinocytes, and marked increase (P < 0.05) in hydroxyproline at the wound site during 15 days of healing of impaired wounds. On the basis of vivo and vitro assay results, it is concluded that electroactive-hydrogel-attributed multifunctional properties may serve as suitable scaffold for treating chronic wound healing and skin regeneration.

Fabrication and desired properties of conductive hydrogel dressings for wound healing

Conductive hydrogels are platforms recognized as constituting promising materials for tissue engineering applications. This is because such conductive hydrogels are characterized by the inherent conductivity properties while retaining favorable biocompatibility and mechanical properties. These conductive hydrogels can be particularly useful in enhancing wound healing since their favorable conductivity can promote the transport of essential ions for wound healing via the imposition of a so-called transepithelial potential. Other valuable properties of these conductive hydrogels, such as wound monitoring, stimuli-response etc., are also discussed in this study. Crucially, the properties of conductive hydrogels, such as 3D printability and monitoring properties, suggest the possibility of its use as an alternative wound dressing to traditional dressings such as bandages. This review, therefore, seeks to comprehensively explore the functionality of conductive hydrogels in wound healing, types of conductive hydrogels and their preparation strategies and crucial properties of hydrogels. This review will also assess the limitations of conductive hydrogels and future perspectives, with an emphasis on the development trend for conductive hydrogel uses in wound dressing fabrication for subsequent clinical applications.

Conductive Biomaterials as Bioactive Wound Dressing for Wound Healing and Skin Tissue Engineering

Conductive biomaterials based on conductive polymers, carbon nanomaterials, or conductive inorganic nanomaterials demonstrate great potential in wound healing and skin tissue engineering, owing to the similar conductivity to human skin, good antioxidant and antibacterial activities, electrically controlled drug delivery, and photothermal effect. However, a review highlights the design and application of conductive biomaterials for wound healing and skin tissue engineering is lacking. In this review, the design and fabrication methods of conductive biomaterials with various structural forms including film, nanofiber, membrane, hydrogel, sponge, foam, and acellular dermal matrix for applications in wound healing and skin tissue engineering and the corresponding mechanism in promoting the healing process were summarized. The approaches that conductive biomaterials realize their great value in healing wounds via three main strategies (electrotherapy, wound dressing, and wound assessment) were reviewed. The application of conductive biomaterials as wound dressing when facing different wounds including acute wound and chronic wound (infected wound and diabetic wound) and for wound monitoring is discussed in detail. The challenges and perspectives in designing and developing multifunctional conductive biomaterials are proposed as well.

Revealing Electrical and Mechanical Performances of Highly Oriented Electrospun Conductive Nanofibers of Biopolymers with Tunable Diameter

The present study outlines a reliable approach to determining the electrical conductivity and elasticity of highly oriented electrospun conductive nanofibers of biopolymers. The highly oriented conductive fibers are fabricated by blending a high molar mass polyethylene oxide (PEO), polycaprolactone (PCL), and polylactic acid (PLA) with polyaniline (PANi) filler. The filler-matrix interaction and molar mass (M) of host polymer are among governing factors for variable fiber diameter. The conductivity as a function of filler fraction (φ) is shown and described using a McLachlan equation to reveal the electrical percolation thresholds (φ_c) of the nanofibers. The molar mass of biopolymer, storage time, and annealing temperature are significant factors for φ_c. The Young’s modulus (E) of conductive fibers is dependent on filler fraction, molar mass, and post-annealing process. The combination of high orientation, tunable diameter, tunable conductivity, tunable elasticity, and biodegradability makes the presented nanofibers superior to the fibers described in previous literature and highly desirable for various biomedical and technical applications.

Preparation and modeling of electrospun polyhydroxybutyrate/polyaniline composite scaffold modified by plasma and printed by an inkjet method and its cellular study

The reconstruction of the nerve tissue engineering scaffold is always of particular interest due to the inability to recover and repair neural tissues after being damaged by diseases or physical injuries. The primary purpose of this study was obtaining a model used to predict the diameter of the fibers of electrospun polyhydroxybutyrate (PHB) scaffolds. Accordingly, the range of operating parameters, namely the applied voltage, the distance between the nozzle to the collector, and solution concentration, was designed for the electrospinning process at three different levels, giving seventeen experiments. These data were modeled utilizing response surface methodology and artificial neural network method using Design Expert and Matlab software.The effect of process parameters on the diameter, as well as their interactions were investigated in detail, and the corresponding models were suggested. Both the RSM and ANN models showed an excellent agreement between the experimental and predicted response values. In the second phase of the study, PHB natural polymer was electrospun into scaffolds with high biocompatibility, resulting in a 224-360 nm diameter range .To further modify the scaffold in order to improve the compatibility of PHB, the fibrous surface of scaffolds was exposed to oxygenated plasma gas radiation under controlled conditions. Next, polyaniline (PANI) nanoparticles were then synthesized and printed on the surface of scaffolds as parallel lines. Then samples were exposed to the electric field. Fourier-transform infrared spectroscopy, water contact angle, optical and electron microscopy, tensile test, and cell viability analysis were performed to study properties of resulting scaffolds. The results indicated the fact that modification of the scaffolds by oxygen plasma and printing PANI nanoparticles in particular patterns had a favorable impact on cell adhesion and direction of cell growth, showing the potential of resulting scaffolds for nerve tissue engineering applications.

Effect of structural factors on the physicochemical properties of functionalized polyanilines

This review discusses the physical and physicochemical properties of polyaniline (PANI) derivatives. The most important methods for the preparation of functionalized polyanilines are presented. The presence of various substituents in its structure changes the polymer characteristics significantly due to steric and electronic effects of the functional groups. This review describes the relationship between the properties of functionalized polyanilines depending on the nature, number and position of the substituents at the aromatic ring.

3D Printing of Polycaprolactone-Polyaniline Electroactive Scaffolds for Bone Tissue Engineering

Electrostimulation and electroactive scaffolds can positively influence and guide cellular behaviour and thus has been garnering interest as a key tissue engineering strategy. The development of conducting polymers such as polyaniline enables the fabrication of conductive polymeric composite scaffolds. In this study, we report on the initial development of a polycaprolactone scaffold incorporating different weight loadings of a polyaniline microparticle filler. The scaffolds are fabricated using screw-assisted extrusion-based 3D printing and are characterised for their morphological, mechanical, conductivity, and preliminary biological properties. The conductivity of the polycaprolactone scaffolds increases with the inclusion of polyaniline. The in vitro cytocompatibility of the scaffolds was assessed using human adipose-derived stem cells to determine cell viability and proliferation up to 21 days. A cytotoxicity threshold was reached at 1% wt. polyaniline loading. Scaffolds with 0.1% wt. polyaniline showed suitable compressive strength (6.45 ± 0.16 MPa) and conductivity (2.46 ± 0.65 × 10⁻⁴ S/cm) for bone tissue engineering applications and demonstrated the highest cell viability at day 1 (88%) with cytocompatibility for up to 21 days in cell culture.

Electrically Conductive Materials: Opportunities and Challenges in Tissue Engineering

Tissue engineering endeavors to regenerate tissues and organs through appropriate cellular and molecular interactions at biological interfaces. To this aim, bio-mimicking scaffolds have been designed and practiced to regenerate and repair dysfunctional tissues by modifying cellular activity. Cellular activity and intracellular signaling are performances given to a tissue as a result of the function of elaborated electrically conductive materials. In some cases, conductive materials have exhibited antibacterial properties; moreover, such materials can be utilized for on-demand drug release. Various types of materials ranging from polymers to ceramics and metals have been utilized as parts of conductive tissue engineering scaffolds, having conductivity assortments from a range of semi-conductive to conductive. The cellular and molecular activity can also be affected by the microstructure; therefore, the fabrication methods should be evaluated along with an appropriate selection of conductive materials. This review aims to address the research progress toward the use of electrically conductive materials for the modulation of cellular response at the material-tissue interface for tissue engineering applications.

Scaffolding polymeric biomaterials: Are naturally occurring biological macromolecules more appropriate for tissue engineering?

Nowadays, tissue and organ failures resulted from injury, aging accounts, diseases or other type of damages is one of the most important health problems with an increasing incidence worldwide. Current treatments have limitations including, low graft efficiency, shortage of donor organs, as well as immunological problems. In this context, tissue engineering (TE) was introduced as a novel and versatile approach for restoring tissue/organ function using living cells, scaffold and bioactive (macro-)molecules. Among these, scaffold as a three-dimensional (3D) support material, provide physical and chemical cues for seeding cells and has an essential role in cell missions. Among the wide verity of scaffolding materials, natural or synthetic biopolymers are the most commonly biomaterials mainly due to their unique physicochemical and biological features. In this context, naturally occurring biological macromolecules are particular of interest owing to their low immunogenicity, excellent biocompatibility and cytocompatibility, as well as antigenicity that qualified them as popular choices for scaffolding applications. In this review, we highlighted the potentials of natural and synthetic polymers as scaffolding materials. The properties, advantages, and disadvantages of both polymer types as well as the current status, challenges, and recent progresses regarding the application of them as scaffolding biomaterials are also discussed.

The antimicrobial action of polyaniline involves production of oxidative stress while functionalisation of polyaniline introduces additional mechanisms

Polyaniline (PANI) and functionalised polyanilines (fPANI) are novel antimicrobial agents whose mechanism of action was investigated. Escherichia coli single gene deletion mutants revealed that the antimicrobial mechanism of PANI likely involves production of hydrogen peroxide while homopolymer poly(3-aminobenzoic acid), P3ABA, used as an example of a fPANI, disrupts metabolic and respiratory machinery, by targeting ATP synthase and causes acid stress. PANI was more active against E. coli in aerobic, compared to anaerobic, conditions, while this was apparent for P3ABA only in rich media. Greater activity in aerobic conditions suggests involvement of reactive oxygen species. P3ABA treatment causes an increase in intracellular free iron, which is linked to perturbation of metabolic enzymes and could promote reactive oxygen species production. Addition of exogenous catalase protected E. coli from PANI antimicrobial action; however, this was not apparent for P3ABA treated cells. The results presented suggest that PANI induces production of hydrogen peroxide, which can promote formation of hydroxyl radicals causing biomolecule damage and potentially cell death. P3ABA is thought to act as an uncoupler by targeting ATP synthase resulting in a futile cycle, which precipitates dysregulation of iron homeostasis, oxidative stress, acid stress, and potentially the fatal loss of proton motive force.

Biocompatibility Assessment of Conducting PANI/Chitosan Nanofibers for Wound Healing Applications

As electroactive polymers have recently presented potential in applications in the tissue engineering and biomedical field, this study is aiming at the fabrication of composite nanofibrous membranes containing conducting polyaniline and at the evaluation of their biocompatibility. For that purpose, conducting polyaniline–chitosan (PANI/CS) defect free nanofibres of different ratios (1:3; 3:5 and 1:1) were produced with the electrospinning method. They were characterized as for their morphology, hydrophilicity and electrical conductivity. The membranes were then evaluated for their cellular biocompatibility in terms of cell attachment, morphology and cell proliferation. The effect of the PANI content on the membrane properties is discussed. Increase in PANI content resulted in membranes with higher hydrophobicity and higher electrical conductivity. It was found that none of the membranes showed any toxic effects on osteoblasts and fibroblasts, and that they all supported cell attachment and growth, even to a greater extent than tissue culture plastic. The membrane with the PANI/CS ratio 1:3 supports better cell attachment and proliferation for both cell lines due to a synergistic effect of hydrophilicity retention due to the high chitosan content and the conductivity that PANI introduced to the membrane.

A critical review on the prospect of polyaniline-grafted biodegradable nanocomposite

Among the various electrically conducting polymers, polyaniline (PANI) has gained attentions due to its unique properties and doping chemistry. A number of electrically conducting biodegradable polymers has been synthesized by incorporating a biodegradable content of cellulose, chitin, chitosan, etc. in the matrix of PANI. The hybrid materials are also employed as photocatalysts, antibacterial agents, sensors, fuel cells and as materials in biomedical applications. Furthermore, these biodegradable and biocompatible conducting polymers are employed in tissue engineering, dental implants and targeted drug delivery. This review presents state of the art of PANI based biodegradable polymers along with their synthesis routes and unique applications in diverse fields. In future, the synthesis of PANI-grafted biodegradable nanocomposite material is expected to open innovative ways for their outstanding applications.

Conductive and biodegradable scaffolds based on a five-arm and functionalized star-like polyaniline–polycaprolactone copolymer with a d-glucose core

The scaffolds demonstrated a porous structure with a large surface area and electrical conductivity, imitating the ECM to regulate cell attachment, proliferation, and differentiation.

The tuberculocidal activity of polyaniline and functionalised polyanilines

Tuberculosis is considered a leading cause of death worldwide. More than 95% of cases and deaths occur in low- and middle-income countries. In resource-limited countries, hospitals often lack adequate facilities to manage and isolate patients with infectious tuberculosis (TB), relying instead on personal protective equipment, such as facemasks, to reduce nosocomial transmission of the disease. Facemasks impregnated with an antimicrobial agent may be a cost-effective way of adding an extra level of protection against the spread of TB by reducing the risk of disease transmission. Conducting polymers, such as polyaniline (PANI), and their functionalised derivatives are a novel class of antimicrobial agents with potential as non-leaching additives to provide contamination resistant surfaces. We have investigated the antimicrobial action of PANI and a functionalised derivative, poly-3-aminobenzoic acid (P3ABA), against mycobacteria and have determined the optimal treatment time and concentration to achieve significant knockdown of Mycobacterium smegmatis and Mycobacterium tuberculosis on an agar surface. Results indicated that P3ABA is a potential candidate for use as an anti-tuberculoid agent in facemasks to reduce TB transmission.

Fabrication of silver nanoparticles embedded into polyvinyl alcohol (Ag/PVA) composite nanofibrous films through electrospinning for antibacterial and surface-enhanced Raman scattering (SERS) activities

Silver nanoparticle-embedded polyvinyl alcohol (PVA) nanofibers were prepared through electrospinning technique, using as antimicrobial agents and surface-enhanced Raman scattering (SERS) substrates. Ag nanoparticles (NPs) were synthesized in liquid phase, followed by evenly dispersing in PVA solution. After electrospinning of the mixed solution at room temperature, the PVA embedded with Ag NPs (Ag/PVA) composite nanofibers were obtained. The morphologies and structures of the as-synthesized Ag nanoparticles and Ag/PVA fibers were characterized by the techniques of transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Ag NPs have an average diameter of 13.8nm, were found to be uniformly dispersed in PVA nanofibers. The Ag/PVA nanofibers provided robust antibacterial activities against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) microorganisms. It's also found that Ag/PVA nanofibers make a significant contribution to the high sensitivity of SERS to 4-mercaptophenol (4-MPh) molecules.

Cellulose-based spreadable new thixo gels: synthesis and their characterization

Carboxymethyl cellulose (CMC) based new thixotropic gels were synthesized by a facile microwave-induced reaction of aminobenzoic acids (ABAs) e.g. para- and meta-aminobenzoic acids.

Electrically conductive nanofibrous scaffolds based on poly(ethylene glycol)s-modified polyaniline and poly(ε-caprolactone) for tissue engineering applications

The objective of this study was to design and development of electrically conductive nanofibrous scaffolds composed of PEGs-b-(PANI)₄ and PCL for tissue engineering applications.

Developments in conducting polymer fibres: from established spinning methods toward advanced applications

This review provides a comprehensive picture of the history and latest developments in the field of conducting polymer fibres as well as their current/future applications.

Stimulation of Wound Healing by Electroactive, Antibacterial, and Antioxidant Polyurethane/Siloxane Dressing Membranes: In Vitro and in Vivo Evaluations

A series of novel polyurethane/siloxane-based wound dressing membranes was prepared through sol-gel reaction of methoxysilane end-functionalized urethane prepolymers composed of castor oil and ricinoleic methyl ester as well as methoxysilane functional aniline tetramer (AT) moieties. The samples were fully characterized and their physicochemical, mechanical, electrical, and biological properties were assayed. The biological activity of these dressings against fibroblast cells and couple of microbes was also studied. It was revealed that samples that displayed electroactivity by introduction of AT moieties showed a broad range of antimicrobial activity toward different microorganisms, promising antioxidant (radical scavenging) efficiency and significant activity for stimulation of fibroblast cell growth and proliferation. Meanwhile, these samples showed appropriate tensile strength and ability for maintaining a moist environment over a wound by controlled equilibrium water absorption and water vapor transmission rate. The selected electroactive dressing was subjected to an in vivo assay using a rat animal model and the wound healing process was monitored and compared with analogous dressing without AT moieties. The recorded results showed that the electroactive dressings induced an increase in the rate of wound contraction, promoted collagen deposition, and encouraged vascularization in the wounded area. On the basis of the results of in vitro and in vivo assays, the positive influence of designed dressings for accelerated healing of a wound model was confirmed.

Electrical Stimulation of Human Mesenchymal Stem Cells on Conductive Nanofibers Enhances their Differentiation toward Osteogenic Outcomes

Tissue scaffolds allowing the behavior of the cells that reside within them to be controlled are of particular interest for tissue engineering. Herein, the preparation of conductive fiber-based bone tissue scaffolds (nonwoven mats of electrospun polycaprolactone with an interpenetrating network of polypyrrole and polystyrenesulfonate) is described that enable the electrical stimulation of human mesenchymal stem cells to enhance their differentiation toward osteogenic outcomes.

Electrospun rubber fibre mats with electrochemically controllable pore sizes

Electroactive, elastomeric, microfiber mats that show controllable pore size variation upon electrochemical stimulation are produced from semi-interpenetrating polymer networks (s-IPNs).

Conductive polymers: towards a smart biomaterial for tissue engineering

Developing stimulus-responsive biomaterials with easy-to-tailor properties is a highly desired goal of the tissue engineering community. A novel type of electroactive biomaterial, the conductive polymer, promises to become one such material. Conductive polymers are already used in fuel cells, computer displays and microsurgical tools, and are now finding applications in the field of biomaterials. These versatile polymers can be synthesised alone, as hydrogels, combined into composites or electrospun into microfibres. They can be created to be biocompatible and biodegradable. Their physical properties can easily be optimized for a specific application through binding biologically important molecules into the polymer using one of the many available methods for their functionalization. Their conductive nature allows cells or tissue cultured upon them to be stimulated, the polymers' own physical properties to be influenced post-synthesis and the drugs bound in them released, through the application of an electrical signal. It is thus little wonder that these polymers are becoming very important materials for biosensors, neural implants, drug delivery devices and tissue engineering scaffolds. Focusing mainly on polypyrrole, polyaniline and poly(3,4-ethylenedioxythiophene), we review conductive polymers from the perspective of tissue engineering. The basic properties of conductive polymers, their chemical and electrochemical synthesis, the phenomena underlying their conductivity and the ways to tailor their properties (functionalization, composites, etc.) are discussed.

Cell attachment on poly(3-hydroxybutyrate)-poly(ethylene glycol) copolymer produced by Azotobacter chroococcum 7B

BACKGROUND

The improvement of biomedical properties, e.g. biocompatibility, of poly(3-hydroxyalkanoates) (PHAs) by copolymerization is a promising trend in bioengineering. We used strain Azotobacter chroococcum 7B, an effective producer of PHAs, for biosynthesis of not only poly(3-hydroxybutyrate) (PHB) and its main copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-HV), but also alternative copolymer, poly(3-hydroxybutyrate)-poly(ethylene glycol) (PHB-PEG).

RESULTS

In biosynthesis we used sucrose as the primary carbon source and valeric acid or poly(ethylene glycol) 300 (PEG 300) as additional carbon sources. The chemical structure of PHB-PEG and PHB-HV was confirmed by 1H nuclear-magnetic resonance (1H NMR) analysis. The physico-chemical properties (molecular weight, crystallinity, hydrophilicity, surface energy) and surface morphology of films from PHB copolymers were studied. To study copolymers biocompatibility in vitro the protein adsorption and COS-1 fibroblasts growth on biopolymer films by XTT assay were analyzed. Both copolymers had changed physico-chemical properties compared to PHB homopolymer: PHB-HV and PHB-PEG had less crystallinity than PHB; PHB-HV was more hydrophobic than PHB in contrast to PHB-PEG appeared to have greater hydrophilicity than PHB; whereas the morphology of polymer films did not differ significantly. The protein adsorption to PHB-PEG was greater and more uniform than to PHB and PHB-PEG copolymer promoted better growth of COS-1 fibroblasts compared with PHB homopolymer.

CONCLUSIONS

Thus, despite low EG-monomers content in bacterial origin PHB-PEG copolymer, this polymer demonstrated significant improvement in biocompatibility in contrast to PHB and PHB-HV copolymers, which may be coupled with increased protein adsorption and hydrophilicity of PEG-containing copolymer.

Electrically conductive nanofibers with highly oriented structures and their potential application in skeletal muscle tissue engineering

Recent trends in scaffold design have focused on materials that can provide appropriate guidance cues for particular cell types to modulate cell behavior. In this study highly aligned and electrically conductive nanofibers that can simultaneously provide topographical and electrical cues for cells were developed. Thereafter their potential to serve as functional scaffolds for skeletal muscle tissue engineering was investigated. Well-ordered nanofibers, composed of polyaniline (PANi) and poly(ε-caprolactone) (PCL), were electrospun by introducing an external magnetic field in the collector region. Incorporation of PANi into PCL fibers significantly increased the electrical conductivity from a non-detectable level for the pure PCL fibers to 63.6±6.6mS cm(-1) for the fibers containing 3wt.% PANi (PCL/PANi-3). To investigate the synergistic effects of topographical and electrical cues using the electrospun scaffolds on skeletal myoblast differentiation, mouse C2C12 myoblasts were cultured on random PCL (R-PCL), aligned PCL (A-PCL), random PCL/PANi-3 (R-PCL/PANi) and aligned PCL/PANi-3 (A-PCL/PANi) nanofibers. Our results showed that the aligned nanofibers (A-PCL and A-PCL/PANi) could guide myoblast orientation and promote myotube formation (i.e. approximately 40% and 80% increases in myotube numbers) compared with R-PCL scaffolds. In addition, electrically conductive A-PCL/PANi nanofibers further enhanced myotube maturation (i.e. approximately 30% and 23% or 15% and 18% increases in the fusion and maturation indices) compared with non-conductive A-PCL scaffolds or R-PCL/PANi. These results demonstrated that a combined effect of both guidance cues was more effective than an individual cue, suggesting a potential use of A-PCL/PANi nanofibers for skeletal muscle regeneration.

Nanofibrous poly(lactide-co-glycolide) membranes loaded with diamond nanoparticles as promising substrates for bone tissue engineering

BACKGROUND

Nanofibrous scaffolds loaded with bioactive nanoparticles are promising materials for bone tissue engineering.

METHODS

In this study, composite nanofibrous membranes containing a copolymer of L-lactide and glycolide (PLGA) and diamond nanoparticles were fabricated by an electrospinning technique. PLGA was dissolved in a mixture of methylene chloride and dimethyl formamide (2:3) at a concentration of 2.3 wt%, and nanodiamond (ND) powder was added at a concentration of 0.7 wt% (about 23 wt% in dry PLGA).

RESULTS

In the composite scaffolds, the ND particles were either arranged like beads in the central part of the fibers or formed clusters protruding from the fibers. In the PLGA-ND membranes, the fibers were thicker (diameter 270 ± 9 nm) than in pure PLGA meshes (diameter 218 ± 4 nm), but the areas of pores among these fibers were smaller than in pure PLGA samples (0.46 ± 0.02 μm(2) versus 1.28 ± 0.09 μm(2) in pure PLGA samples). The PLGA-ND membranes showed higher mechanical resistance, as demonstrated by rupture tests of load and deflection of rupture probe at failure. Both types of membranes enabled the attachment, spreading, and subsequent proliferation of human osteoblast-like MG-63 cells to a similar extent, although these values were usually lower than on polystyrene dishes. Nevertheless, the cells on both types of membranes were polygonal or spindle-like in shape, and were distributed homogeneously on the samples. From days 1-7 after seeding, their number rose continuously, and at the end of the experiment, these cells were able to create a confluent layer. At the same time, the cell viability, evaluated by a LIVE/DEAD viability/cytotoxicity kit, ranged from 92% to 97% on both types of membranes. In addition, on PLGA-ND membranes, the cells formed well developed talin-containing focal adhesion plaques. As estimated by the determination of tumor necrosis factor-alpha levels in the culture medium and concentration of intercellular adhesion molecule-1, MG-63 cells, and RAW 264.7 macrophages on these membranes did not show considerable inflammatory activity.

CONCLUSION

This study shows that nanofibrous PLGA membranes loaded with diamond nanoparticles have interesting potential for use in bone tissue engineering.

The effect of poly(3-hydroxybutyrate) modification by poly(ethylene glycol) on the viability of cells grown on the polymer films

A biodegradable polymer of bacterial origin, poly(3-hydroxybutyrate) (PHB), is intensively studied as biomaterial for tissue engineering. However, factors determining its biocompatibility still require better understanding. To analyze the PHB films biocompatibility, the polymer material was modified by hydrophilic polymer, poly(ethylene glycol) 300 (PEG). The blends PHB/PEG with different PEG content (10, 20, 30 and 50%) were produced by subsequent incubation in water resulted in removal of 95% PEG. The surface roughness and hydrophilicity were studied by atomic force microscopy (AFM) and contact angle "water-polymer" measurement, respectively. The film biocompatibility on cell culture of COS-1 fibroblasts was studied in vitro. It was shown that both roughness and hydrophobicity are directly proportional to initial PEG content in the PHB/PEG blends. The growth rate of COS-1 fibroblasts on polymer films is determined by combination of two basic physicochemical properties of the polymer surface: the roughness and hydrophilicity. The optimal roughness requred for COS-1 cells growth is the average roughness more than 25 nm, whereas the limit values of the contact angle "water-polymer" that was responsible for relatively high cell viability were not found. These data indicate that the film surface roughness had the greatest effect on the cell growth, whereas the increase in the polymer surface hydrophilicity caused the additional positive effect on viability of attached cells. Thus, the modification of PHB polymer material by PEG resulted in the improved viability of cells cultivated on the polymer films in vitro. The obtained data can be used for development of such medical devices as surgeon patches and periodontal membranes.

Electroactive porous tubular scaffolds with degradability and non-cytotoxicity for neural tissue regeneration

Electroactive degradable porous tubular scaffolds were fabricated from the blends of polycaprolactone and a hyperbranched degradable conducting copolymer at different feed ratios by a solution-casting/salt-leaching method. Scaning electron microscopy (SEM) and microcomputed tomography tests indicated that these scaffolds had homogeneously distributed interconnected pores on the cross-section and surface. The electrical conductivity of films with the same composition as the scaffolds was between 3.4×10(-6) and 3.1×10(-7) S cm(-1), depending on the ratio of hyperbranched degradable conducting copolymer to polycaprolactone. A hydrophilic surface with a contact angle of water about 30° was achieved by doping the films with (±)-10-camphorsulfonic acid. The mechanical properties of the films were investigated by tensile tests, and the morphology of the films was studied by SEM. The scaffolds were subjected to the WST test (a cell proliferation and cytotoxicity assay using water-soluble tetrazolium salts) with HaCaT keratinocyte cells, and the results show that these scaffolds are non-cytotoxic. These degradable electroactive tubular scaffolds are good candidates for neural tissue engineering application.