PGS/HAp Microporous Composite Scaffold Obtained in the TIPS-TCL-SL Method: An Innovation for Bone Tissue Engineering

In this research, we synthesize and characterize poly(glycerol sebacate) pre-polymer (pPGS) (¹H NMR, FTiR, GPC, and TGA). Nano-hydroxyapatite (HAp) is synthesized using the wet precipitation method. Next, the materials are used to prepare a PGS-based composite with a 25 wt.% addition of HAp. Microporous composites are formed by means of thermally induced phase separation (TIPS) followed by thermal cross-linking (TCL) and salt leaching (SL). The manufactured microporous materials (PGS and PGS/HAp) are then subjected to imaging by means of SEM and µCT for the porous structure characterization. DSC, TGA, and water contact angle measurements are used for further evaluation of the materials. To assess the cytocompatibility and biological potential of PGS-based composites, preosteoblasts and differentiated hFOB 1.19 osteoblasts are employed as in vitro models. Apart from the cytocompatibility, the scaffolds supported cell adhesion and were readily populated by the hFOB1.19 preosteoblasts. HAp-facilitated scaffolds displayed osteoconductive properties, supporting the terminal differentiation of osteoblasts as indicated by the production of alkaline phosphatase, osteocalcin and osteopontin. Notably, the PGS/HAp scaffolds induced the production of significant amounts of osteoclastogenic cytokines: IL-1β, IL-6 and TNF-α, which induced scaffold remodeling and promoted the reconstruction of bone tissue. Initial biocompatibility tests showed no signs of adverse effects of PGS-based scaffolds toward adult BALB/c mice.     

Mechanism for the Role of Silicon on the Transition from Graphite to Cementite Eutectic in Cast Iron

In this work, an analytical solution is proposed to explain the influence of silicon on the transition from graphite to cementite eutectic in cast iron. It is found that this transition can be related to (1) the graphite nucleation potential (directly characterized by the cell count N and indirectly by the nucleation coefficients N _s and b), (2) the growth rate coefficient of graphite eutectic cells ??, (3) the temperature range ??T _sc?=?T _s ?C T _c (where T _s and T _c are the equilibrium temperature for graphite eutectic and the formation temperature for cementite eutectic, respectively), and (4) the liquid volume fraction f _l after preeutectic austenite solidification. Analytical equations were derived that describe the absolute and the relative chilling tendencies (CT and CT_r, respectively) as well as the critical cooling rate Q _cr and, hence, the chill w of the cast iron. Theoretical arguments are experimentally verified for castings with various silicon contents. This work also describes the methods used in the determination of N _s, b, and ?? values. It is found that the main role of silicon on the transition from graphite to cementite eutectic is to raise the density of the graphite nuclei N and temperature range ??T _sc. In addition, it is shown that increasing the silicon content of cast iron leads to an increasing value of Q _cr and decreasing values of CT and CT_r, and of the chill width w. In particular, this work shows that the chilling tendency indexes and, hence, the chill all can be estimated from a simple thermal analysis using reference castings.     

Multifunctional porous membranes with antibacterial properties

Abstract

The paper describes the results of research on obtaining porous membranes produced from polylactide fibers (PLA) by electrospinning, additionally modified with gentamicin antibiotic (GM) at the stage of preparing a spinning solution to provide bactericidal properties. Both solid (1^oPNF) and porous (2^oPNF 3^oPNF) polymer fibers were obtained, and the control of fiber porosity was achieved using various solvent systems: dichloromethane (DCM), dimethylformamide (DMF), chloroform (CHL) and dimethyl sulfoxide (DMSO). Three types of fibers differing in morphology (fiber diameter) and mean pore size were obtained. Physicochemical properties of porous and solid drug-containing fibers were examined, determining their surface free energy (SFE) and wetting angle (CA), and the effectiveness of modification with the drug was confirmed in spectroscopic studies (FTIR-ATR). Antibacterial activity of the prepared drug-modified nonwovens was confirmed by the disk diffusion method against Gram-negative Escherichia coli bacteria strain. The results of tests have shown that depending on the type of solvents used at the electrospinning stage, porous fibers can be obtained from polylactide. The addition of gentamicin affected antibacterial properties, and the pore size determined the rate of drug release monitored by the ion coupled plasma method (ICP).     

Determination of Metals and Metalloids in Wine Using Inductively Coupled Plasma Optical Emission Spectrometry and Mini-torch

In the present study, an inductively coupled plasma optical emission spectrometer ICPE-9820 with the mini-torch technology that significantly reduces the consumption of plasma gas to 7.0 L min^?1 was applied for the multielemental analysis of wine samples. Three sample preparation procedures (microwave digestion in closed vessels, acid digestion in open vessels in a water bath, both with HNO₃, and 1:10 dilution with deionized water) were compared for the determination of 15 elements in wines. In all wines analyzed, the lowest concentration was obtained for Li (0.06–0.09 mg L^?1) and the highest for K (475–995 mg L^?1). The concentration >1 mg L^?1 of B, Fe, and Na was determined in all wines analyzed by the three sample preparation procedures. The average concentrations found for the acid extracts for Al (1.31 mg L^?1) and Fe (3.40 mg L^?1) were higher in comparison to results of sample dilution (0.73 and 1.56 mg L^?1 respectively). The recoveries were between 88.2 and 110 %, 65.9 and 106 %, and 62.8 and 109 %, whereas the relative standard deviations (RSDs) varied between 0.04 and 4.62 %, 0.74 and 5.57 %, and 0.70 and 5.80 %, respectively, for the procedure of sample dilution, microwave digestion, and water bath digestion.     

Synthesis,Characterization and in Vitro Evaluation of New Composite Bisphosphonate Delivery Systems

In this study, new composite bisphosphonate delivery systems were obtained from polyurethanes (PUs) and nanocrystalline hydroxyapatite (HA). The biodegradable PUs were first synthesized from poly(ε-caprolactone) diols (PCL diols), poly(ethylene adipate) diol, 1,6-hexamethylene diisocyanate, 1,4-butanediol and HA. Moreover, the PCL diols were synthesized by the ring-opening polymerization catalysed by the lipase from Candida antarctica. Next, composite drug delivery systems for clodronate were prepared. The mechanical properties of the obtained biomaterials were determined. The cytotoxicity of the synthesized polymers was tested. The preliminary results show that the obtained composites are perspective biomaterials and they can be potentially applied in the technology of implantation drug delivery systems.