Citric Acid Cross-Linked Gelatin-Based Composites with Improved Microhardness.

The aim of this study is to investigate the influence of cross-linking and reinforcements in gelatin on the physico-mechanical properties of obtained composites. The gelatin-based composites cross-linked with citric acid (CA) were prepared: gelatin type B (GB) and ß-tricalcium phosphate (ß-TCP) and novel hybrid composite GB with ß-TCP and hydroxyapatite (HAp) particles, and their structure, thermal, and mechanical properties were compared with pure gelatin B samples. FTIR analysis revealed that no chemical interaction between the reinforcements and gelatin matrix was established during the processing of hybrid composites by the solution casting method, proving the particles had no influence on GB cross-linking. The morphological investigation of hybrid composites revealed that cross-linking with CA improved the dispersion of particles, which further led to an increase in mechanical performance. The microindentation test showed that the hardness value was increased by up to 449%, which shows the high potential of ß-TCP and HAp particle reinforcement combined with CA as a cross-linking agent. Furthermore, the reduced modulus of elasticity was increased by up to 288%. Results of the MTT assay on L929 cells have revealed that the hybrid composite GB-TCP-HA-CA was not cytotoxic. These results showed that GB cross-linked with CA and reinforced with different calcium phosphates presents a valuable novel material with potential applications in dentistry.

Electrospun polycaprolactone nanofibers functionalized with Achillea millefolium extract yield biomaterial with antibacterial, antioxidant and improved mechanical properties.

In this study, polycaprolactone (PCL), as a biocompatible polymer was functionalized by addition of medicinal plant extract- Achillea millefolium L. (yarrow). Nanofiber mats were fabricated from PCL solutions containing dry yarrow extract in four concentrations (5%, 10%, 15%, and 20% relative to the weight of the polymer) by using blend electrospinning method. The nanofibers were characterized for their biological, mechanical and drug release behavior. In vitro release of yarrow polyphenols from the electrospun PCL nanofibers over a period of 5 days showed the release of up to 98% of the total loaded polyphenols. The released polyphenols retained its antioxidant activity, which was determined by DPPH assay. Electrospun PCL/yarrow nanofiber mats exhibited the antibacterial effect against Staphylococcus aureus, but had no effect on the growth of Pseudomonas aeruginosa. All PCL/yarrow nanofiber mats had improved mechanical properties compared to the neat PCL nanofibers, as evident by an increase in Young's modulus of elasticity (up to 5.7 times), the tensile strength (up to 5.5 times), and the strain at break (up to 1.45 times). Based on our results, yarrow-loaded PCL nanofiber mats appeared to be multi-functional biomaterials suitable for the production of catheter-coating materials, patches, or gauzes with antibacterial and antioxidant properties.

Tetragonal CoMn2O4 nanocrystals on electrospun carbon fibers as high-performance battery-type supercapacitor electrode materials.

We herein report a simple two-step procedure for fabricating tetragonal CoMn2O4 spinel nanocrystals on carbon fibers. The battery-type behavior of these composite fibers arises from the redox activity of CoMn2O4 in an alkaline aqueous solution, which, in combination with the carbon fibers, endows good electrochemical performance and long-term stability. The C@CoMn2O4 electrode exhibited high specific capacity, up to 62 mA h g-1 at 1 A g-1 with a capacity retention of around 90% after 4000 cycles. A symmetrical coin-cell device assembled with the composite electrodes delivered a high energy density of 7.3 W h kg-1 at a power density of 0.1 kW kg-1, which is around 13 times higher than that of bare carbon electrodes. The coin cell was cycled for 5000 cycles with 96.3% capacitance retention, at a voltage of up to 0.8 V, demonstrating excellent cycling stability.

Preparation and modeling of three-layered PCL/PLGA/PCL fibrous scaffolds for prolonged drug release.

The authors present the preparation procedure and a computational model of a three-layered fibrous scaffold for prolonged drug release. The scaffold, produced by emulsion/sequential electrospinning, consists of a poly(D,L-lactic-co-glycolic acid) (PLGA) fiber layer sandwiched between two poly(ε-caprolactone) (PCL) layers. Experimental results of drug release rates from the scaffold are compared with the results of the recently introduced computational finite element (FE) models for diffusive drug release from nanofibers to the three-dimensional (3D) surrounding medium. Two different FE models are used: (1) a 3D discretized continuum and fibers represented by a simple radial one-dimensional (1D) finite elements, and (2) a 3D continuum discretized by composite smeared finite elements (CSFEs) containing the fiber smeared and surrounding domains. Both models include the effects of polymer degradation and hydrophobicity (as partitioning) of the drug at the fiber/surrounding interface. The CSFE model includes a volumetric fraction of fibers and diameter distribution, and is additionally enhanced by using correction function to improve the accuracy of the model. The computational results are validated on Rhodamine B (fluorescent drug l) and other hydrophilic drugs. Agreement with experimental results proves that numerical models can serve as efficient tools for drug release to the surrounding porous medium or biological tissue. It is demonstrated that the introduced three-layered scaffold delays the drug release process and can be used for the time-controlled release of drugs in postoperative therapy.

Cefazolin-loaded polycaprolactone fibers produced via different electrospinning methods: Characterization, drug release and antibacterial effect.

Antibiotic containing polycaprolactone (PCL) fibers were produced by using three electrospinning methods: blend, emulsion and co-axial electrospinning (labeled as S1, S2 and S3, respectively). The profiles of drug release from three different systems were studied and antimicrobial properties of produced materials were evaluated. Morphology of the produced fibers was characterized and revealed that cefazolin-loaded PCL fibers had smaller diameter compared to neat PCL fibers, while the chemical interaction between the antibiotic and PCL showed that cefazolin neither had reacted with PCL phase, nor had degraded during the electrospinning process. The crystallinity and thermal characterization of fabricated fibers showed that the addition of cefazolin decreased the crystallinity of PCL. The results of the drug release behavior of the blend and co-axial electrospun fibers was on a higher level (~68% and ~43%, respectively) compared to the emulsion electrospun fibers (~5%), after a period of 30 days. The obtained data had the best fitting with the first order model and the Higuchi model, while the Korsmeyer-Peppas model showed a Pseudo-Fickian diffusion of the drug. Antibacterial evaluations showed that cefazolin-loaded PCL fibers had better effects on Staphylococcus aureus compared to Escherichia coli during the treatment period and that the effect of the emulsion fibers was notably weaker than the other two studied systems. The aim of the study was to test different systems for control drug release of different dynamics, which will be applied for prevent bacterial accumulation when indwelling urinary catheters, applied for different periods of time.

Application of cellulose acetate for controlled release of thymol.

Cellulose acetate (CA) was investigated as a carrier towards development of material with controlled release of thymol as a natural substance with strong antibacterial properties using high pressure techniques. Effect of thymol content on CA was confirmed by SEM, FTIR and DSC methods. Kinetic of thymol release from CA was tested using simulated gastric and intestinal fluids (hydrochloric acid and phosphate buffer saline). Results were correlated with Korsmeyer-Peppas and Weibull model. Depending on the thymol content and chemical nature of the release medium, the time of thymol release varied from one to three days indicating CA as a promising carrier of thymol with potential uses from medicine to agriculture. The impregnated CA showed antibacterial activity against 23 tested bacterial strains including methicillin-resistant Staphylococcus aureus (MRSA) which is particularly important bearing in mind that this strain causes fatal infections in humans and animals.

QSAR modeling of the antimicrobial activity of peptides as a mathematical function of a sequence of amino acids.

Antimicrobial peptides have emerged as new therapeutic agents for fighting multi-drug-resistant bacteria. However, the process of optimizing peptide antimicrobial activity and specificity using large peptide libraries is both tedious and expensive. Therefore, computational techniques had to be applied for process optimization. In this work, the representation of the molecular structure of peptides (mastoparan analogs) by a sequence of amino acids has been used to establish quantitative structure-activity relationships (QSARs) for their antibacterial activity. The data for the studied peptides were split three times into the training, calibration and test sets. The Monte Carlo method was used as a computational technique for QSAR models calculation. The statistical quality of QSAR for the antibacterial activity of peptides for the external validation set was: n=7, r(2)=0.8067, s=0.248 (split 1); n=6, r(2)=0.8319, s=0.169 (split 2); and n=6, r(2)=0.6996, s=0.297 (split 3). The stated statistical parameters favor the presented QSAR models in comparison to 2D and 3D descriptor based ones. The Monte Carlo method gave a reasonably good prediction for the antibacterial activity of peptides. The statistical quality of the prediction is different for three random splits. However, the predictive potential is reasonably well for all cases. The presented QSAR modeling approach can be an attractive alternative of 3D QSAR at least for the described peptides.