Effects of Montmorillonite and Gentamicin Addition on the Properties of Electrospun Polycaprolactone Fibers.

Electrospinning was used to obtain multifunctional fibrous composite materials with a matrix of poly-ɛ-caprolactone (PCL) and 2 wt.% addition of a nanofiller: montmorillonite (MMT), montmorillonite intercalated with gentamicin sulphate (MMTG) or gentamicin sulphate (G). In the first stage, the aluminosilicate gallery was modified by introducing gentamicin sulfate into it, and the effectiveness of the intercalation process was confirmed on the basis of changes in the clay particle size from 0.5 µm (for MMT) to 0.8 µm (for MMTG), an increase in the interplanar distance d001 from 12.3 Å (for MMT) to 13.9 Å (for MMTG) and altered clay grain morphology. In the second part of the experiment, the electrospinning process was carried out in which the polymer nonwovens with and without the modifier were prepared directly from dichloromethane (DCM) and N,N-dimethylformamide (DMF). The nanocomposite fibrous membranes containing montmorillonite were prepared from the same polymer solution but after homogenization with the modifier (13 wt.%). The degree of dispersion of the modifier was evaluated by average microarray analysis from observed area (EDS), which was also used to determine the intercalation of montmorillonite with gentamicin sulfate. An increase in the size of the fibers was found for the materials with the presence of the modifier, with the largest diameters measured for PCL_MMT (625 nm), and the smaller ones for PCL_MMTG (578 nm) and PCL_G (512 nm). The dispersion of MMT and MMTG in the PCL fibers was also confirmed by indirect studies such as change in mechanical properties of the nonwovens membrane, where the neat PCL nonwoven was used as a reference material. The addition of the modifier reduced the contact angle of PCL nonwovens (from 120° for PCL to 96° for PCL_G and 98° for PCL_MMTG). An approximately 10% increase in tensile strength of the nonwoven fabric with the addition of MMT compared to the neat PCL nonwoven fabric was also observed. The results of microbiological tests showed antibacterial activity of all obtained materials; however, the inhibition zones were the highest for the materials containing gentamicin sulphate, and the release time of the active substance was significantly extended for the materials with the addition of montmorillonite containing the antibiotic. The results clearly show that the electrospinning technique can be effectively used to obtain nanobiocomposite fibers with the addition of nonintercalated and intercalated montmorillonite with improved strength and increased stiffness compared to materials made only of the polymer fibers, provided that a high filler dispersion in the spinning solution is obtained.

Chemical Modification as a Method of Improving Biocompatibility of Carbon Nonwovens.

It was shown that carbon nonwoven fabrics obtained from polyacrylonitrile fibers (PAN) by thermal conversion may be modified on the surface in order to improve their biological compatibility and cellular response, which is particularly important in the regeneration of bone or cartilage tissue. Surface functionalization of carbon nonwovens containing C-C double bonds was carried out using in situ generated diazonium salts derived from aromatic amines containing both electron-acceptor and electron-donor substituents. It was shown that the modification method characteristic for materials containing aromatic structures may be successfully applied to the functionalization of carbon materials. The effectiveness of the surface modification of carbon nonwoven fabrics was confirmed by the FTIR method using an ATR device. The proposed approach allows the incorporation of various functional groups on the nonwovens' surface, which affects the morphology of fibers as well as their physicochemical properties (wettability). The introduction of a carboxyl group on the surface of nonwoven fabrics, in a reaction with 4-aminobenzoic acid, became a starting point for further modifications necessary for the attachment of RGD-type peptides facilitating cell adhesion to the surface of materials. The surface modification reduced the wettability (θ) of the carbon nonwoven by about 50%. The surface free energy (SFE) in the chemically modified and reference nonwovens remained similar, with the surface modification causing an increase in the polar component (ɣp). The modification of the fiber surface was heterogeneous in nature; however, it provided an attractive site of cell-materials interaction by contacting them to the fiber surface, which supports the adhesion process.

Effects of Process Parameters on Structure and Properties of Melt-Blown Poly(Lactic Acid) Nonwovens for Skin Regeneration.

Skin regeneration requires a three-dimensional (3D) scaffold for cell adhesion, growth and proliferation. A type of the scaffold offering a 3D structure is a nonwoven material produced via a melt-blown technique. Process parameters of this technique can be adapted to improve the cellular response. Polylactic acid (PLA) was used to produce a nonwoven scaffold by a melt-blown technique. The key process parameters, i.e., the head and air temperature, were changed in the range from 180-270 °C to obtain eight different materials (MB1-MB8). The relationships between the process parameters, morphology, porosity, thermal properties and the cellular response were explored in this study. The mean fiber diameters ranged from 3 to 120 µm. The average material roughness values were between 47 and 160 µm, whereas the pore diameters ranged from 5 to 400 µm. The calorimetry thermograms revealed a correlation between the temperature parameters and crystallization. The response of keratinocytes and macrophages exhibited a higher cell viability on thicker fibers. The cell-scaffold interaction was observed via SEM after 7 days. This result proved that the features of melt-blown nonwoven scaffolds depended on the processing parameters, such as head temperature and air temperature. Thanks to examinations, the most suitable scaffolds for skin tissue regeneration were selected.

How Surface Properties of Silica Nanoparticles Influence Structural, Microstructural and Biological Properties of Polymer Nanocomposites.

The aim of this work was to study effect of the type of silica nanoparticles on the properties of nanocomposites for application in the guided bone regeneration (GBR). Two types of nanometric silica particles with different size, morphology and specific surface area (SSA) i.e., high specific surface silica (hss-SiO2) and low specific surface silica (lss-SiO2), were used as nano-fillers for a resorbable polymer matrix: poly(L-lactide-co-D,L-lactide), called PLDLA. It was shown that higher surface specific area and morphology (including pore size distribution) recorded for hss-SiO2 influences chemical activity of the nanoparticle; in addition, hydroxyl groups appeared on the surface. The nanoparticle with 10 times lower specific surface area (lss-SiO2) characterized lower chemical action. In addition, a lack of hydroxyl groups on the surface obstructed apatite nucleation (reduced zeta potential in comparison to hss-SiO2), where an apatite layer appeared already after 48 h of incubation in the simulated body fluid (SBF), and no significant changes in crystallinity of PLDLA/lss-SiO2 nanocomposite material in comparison to neat PLDLA foil were observed. The presence and type of inorganic particles in the PLDLA matrix influenced various physicochemical properties such as the wettability, and the roughness parameter note for PLDLA/lss-SiO2 increased. The results of biological investigation show that the bioactive nanocomposites with hss-SiO2 may stimulate osteoblast and fibroblast cells'proliferation and secretion of collagen type I. Additionally, both nanocomposites with the nanometric silica inducted differentiation of mesenchymal cells into osteoblasts at a proliferation stage in in vitro conditions. A higher concentration of alkaline phosphatase (ALP) was observed on the material modified with hss-SiO2 silica.

Multifunctional biodegradable polymer/clay nanocomposites with antibacterial properties in drug delivery systems.

PURPOSE: The aim of this study was to investigate the possibility of intercalation of gentamicin and neomycin in montmorillonite (MMT) nanofillers, as well as to study the in vitro antimicrobial properties of nanocomposite films containing a small amount of thus obtained nanofillers. METHODS: The polylactide matrix (PLA) nanocomposite films with drug-intercalated montmorillonite fillers were obtained by casting after intercalation of drugs in aqueous solutions. The efficiency of intercalation has been confirmed by X-ray diffraction (XRD) and Zeta potential measurements. The materials were studied for surface wettability, roughness and mechanical properties during 6 weeks of incubation in phosphate buffer saline, and their bactericidal activity was tested against Escherichia coli bacteria before and after 6 weeks of incubation in distilled water at 37 °C. The presence of antibiotics during the incubation was monitored by conductivity and pH measurements. RESULTS: The results indicate that nanocomposite polylactide films with montmorillonite filler intercalated with gentamicin and neomycin tend to degrade faster that their counterparts with non-intercalated fillers, which affects their mechanical properties. However, drug intercalation provided an antibacterial activity, which was confirmed by the presence of zones inhibiting the growth of Gram-negative bacteria for both antibiotics. It was also confirmed that the interaction of antibiotics with clay and polymer matrix did not adversely affect this bactericidal effect. CONCLUSIONS: Montmorillonite can be successfully intercalated with both gentamicin and neomycin, and then used as active filler for polylactide films having very good antibacterial properties, therefore their use in biomedical applications can be significantly expanded.

Porous poly(lactic acid) based fibres as drug carriers in active dressings.

PURPOSE: The polymeric porous surface of fibres (PLA) may influence the kinetics of release of biologically active compounds (gentamicin, G and ethacridine lactate, R) affecting development of a bacterial biofilm. METHODS: The porous fibres with different morphology were manufactured by the electrospinning method from ternary systems composed of PLA and selected solvents. Fibres morphology was examined using a scanning electron microscopy (SEM), their structure was analyzed by FT-IR ATR spectroscopy and differential scanning calorimetry (DSC). Changes in the drug release profile were measured using ICP/UV-Vis methods and the resulting bactericidal or bacteriostatic properties were tested by two-layer disk diffusion test in relation to various drug incorporation methods. RESULTS: The porous fibres can be applied to produce drug-bearing membranes. The spectroscopic studies confirmed incorporation of gentamicin into the fibres and the presence of ethacridine lactate on their surface. Bimodal fibres distribution (P3) promoted faster release of gentamicin and ethacridine lactate from P3G and P3R materials. The electrospinning process coupled with the vapor induced phase separation influenced the glass transition temperature of the porous polymer fibres. The pre/post-electrospinning modification influenced the glass transition, maximum temperature of cold crystallization and melting point of the porous membrane, compared to the neat polymer. The polylactide fibres with gentamicin showed strong bactericidal effect on Gram-positive bacteria, while fibres with ethacridine lactate were bacteriostatic. CONCLUSIONS: The obtained fibres with complex surface morphology can be used as a membrane in active dressings as they make it possible to control the release profile of the active compounds.

The membrane with polylactide and hyaluronic fibers for skin substitute.

PURPOSE: Skin substitutes are heterogeneous group of scaffolds (natural or synthetic) and cells. We hypothesize that nanofibers with layer composition made of polylactide (PLA) and sodium hyaluronate (HA) obtained using electrospinning method are a good matrix for cell adhesion and proliferation. METHODS: Optimal conditions of electrospinning of PLA and HA nanofibers to create layered compositions (PLA membrane covered with HA nonwovens) were determined by modifying parameters such as the appropriate amount of solvents, polymer concentration, mixing temperature and electrospinning process conditions. By changing the parameters, it was possible to control the diameter and properties of both polymer fibers. The spinning solution were characterized by surface tension and rheology. A scanning electron microscope (SEM) was used to determine the morphology and fiber diameters: PLA and HA. Structure of the PLA/HA nonwoven was analyzed using spectroscopy (FTIR/ATR). Biocompatibility of the nonwoven with fibroblasts (ECM producers) was assessed in the in vitro conditions. RESULTS: The results showed that stable conditions for the formation of submicron PLA fibers were obtained using a 13% wt. solution of the polymer, dissolved in a 3:1 mixture of DCM:DMF at 45 °C. The hyaluronic fibers were prepared from a 12% wt. solution of the polymer dissolved in a 2:1 mixture of ammonia water and ethyl alcohol. All materials were biocompatible but to a different degree. CONCLUSIONS: The proposed laminate scaffold was characterized by a hydrophobic-hydrophilic domain surface with a maintained fiber size of both layers. The material positively underwent biocompatibility testing in contact with fibroblasts.