A simple approach for synthesis, characterization and bioactivity of bovine bones to fabricate the polyurethane nanofiber containing hydroxyapatite nanoparticles.

In the present study, we had introduced polyurethane (PU) nanofibers that contain hydroxyapatite (HAp) nanoparticles (NPs) as a result of an electrospinning process. A simple method that does not depend on additional foreign chemicals had been employed to synthesize HAp NPs through the calcination of bovine bones. Typically, a colloidal gel consisting of HAp/PU had been electrospun to form nanofibers. In this communication, physiochemical aspects of prepared nanofibers were characterized by FE-SEM, TEM and TEM-EDS, which confirmed that nanofibers were well-oriented and good dispersion of HAp NPs, over the prepared nanofibers. Parameters, affecting the utilization of the prepared nanofibers in various nano-biotechnological fields have been studied; for instance, the bioactivity of the produced nanofiber mats was investigated while incubating in simulated body fluid (SBF). The results from incubation of nanofibers, indicated that incorporation of HAp strongly activates the precipitation of the apatite-like particles, because of the HAp NPs act as seed, that accelerate crystallization of the biological HAp from the utilized SBF.

Chiral separations using dipeptide polymerized surfactants: effect of amino acid order.

Chiral separations using various polymerized dipeptide surfactants in electrokinetic capillary chromatography (EKC) are investigated. The two main dipeptide surfactants used in this study were sodium N-undecylenyl-L-valine-L-leucine (L-SUVL), and sodium N-undecylenyl-L-leucine-L-valine (L-SULV). These studies were performed in order to determine if the order of amino acids in dipeptide surfactants is important in terms of chiral recognition and separations. Both the monomer and the polymer of these two surfactants were compared for the separation of two model atropisomers, (+/-)-1,1-bi-2-naphtol (BOH) and (+/-)-1,1'-bi-2-naphthyl-2,2'-diyl hydrogen phosphate (BNP). Some advantages and disadvantages of the polymer relative to the monomer are discussed. Four other surfactants, the polymers of sodium N-undecylenyl-L-leucine-L-leucine (L-SULL), sodium N-undecylenyl-L-valine-L-valine (L-SUVV), sodium N-undecylenyl-L-valine (L-SUV), and sodium N-undecylenyl-L-leucine (L-SUL), were also used in this study, and their performance was compared to that of poly(L-SULV). These data show conclusively that the order of amino acids in dipeptide surfactants has a dramatic effect on chiral recognition. Our investigations indicate that poly-(L-SULV) provides the best enantioselectivity among the four dipeptide and two single amino acid surfactants for the separation of BNP and BOH. The advantages of poly-(L-SULV) are demonstrated via the ultrafast separation of the enantiomers of BNP and BOH in less than 1 min.

Improved chiral separations using a polymerized dipeptide anionic chiral surfactant in electrokinetic chromatography: separations of basic, acidic, and neutral racemates.

Two polymeric chiral anionic surfactants [poly(sodium N-undecylenyl-L-valine) (poly-L-SUV) and poly(sodium N-undecylenyl-L-valine-valine) (poly-L-SUVV)] are compared as pseudostationary phases for chiral separations of basic, acidic, and neutral enantiomers. Parameters such as pH, concentration and type of background electrolyte, concentration of polymerized chiral surfactants, and injection size were studied to investigate the migration behavior and optimize the chiral resolution of several racemic analytes. At equivalent monomer concentrations, the migration factors for cationic enantiomers were larger with poly-L-SUV than with poly-L-SUVV. In contrast, the reverse was true for anionic enantiomers. However, in both cases, chiral recognition was significantly enhanced with poly-L-SUVV as compared to that with poly-L-SUV. It is interesting to note that the separation selectivity and resolution of a neutral racemate were slightly better with the latter, but only at the expense of longer analysis time and lower efficiencies.