In vitro assessment of Momordica charantia/Hypericum perforatum oils loaded PCL/Collagen fibers: Novel scaffold for tissue engineering

The research on tissue engineering applications has been progressing to manufacture ideal tissue scaffold biomaterials. In this study, a double-layered electrospun biofiber scaffold biomaterial including Polycaprolactone (PCL)/Collagen (COL) fibrous inner layer and PCL/ Momordica charantia (MC) and Hypericum perforatum (HP) oils fibrous outer layer was developed to manufacture a functional, novel tissue scaffold with the advantageous mechanical and biological properties. The main approach was to combine the natural perspective using medicinal oils with an engineering point of view to fabricate a potential functional scaffold for tissue engineering. Medicinal plants MC and HP are rich in functional oils and incorporation of them in a tissue scaffold will unveil their potential to augment both new tissue formation and wound healing. In this study, a novel double-layered scaffold prototype was fabricated using electrospinning technique with two PCL fiber layers, first is composed of collagen, and second is composed of oils extracted from medicinal plants. Initially, the composition of plant oils was analyzed. Thereafter the biofiber scaffold layers were fabricated and were evaluated in terms of morphology, physicochemistry, thermal and mechanical features, wettability, in vitro bio-degradability. Double-layered scaffold prototype was further analyzed in terms of in vitro biocompatibility and antibacterial effect. The medicinal oils blend provided antioxidant and antibacterial properties to the novel PCL/Oils layer. The results signify that inner PCL/COL layer exhibited advanced biodegradability of 8.5% compared to PCL and enhanced wettability with 11.7° contact angle. Strength of scaffold prototype was 5.98 N/mm2 thanks to the elastic PCL fibrous matrix. The double-layered functional biofiber scaffold enabled 92% viability after 72 h contact with fibroblast cells and furthermore provided feasible attachment sites for the cells. The functional scaffold prototype's noteworthy mechanical, chemical, and biological features enable it to be suggested as a different novel biomaterial with the potential to be utilized in tissue engineering applications.

The possible roles of residues 79 and 80 of the Trp repressor from Escherichia coli K-12 in trp operator recognition

We constructed mutants of the Trp repressor from Escherichia coli K-12 with all possible single amino acid exchanges at positions 79 and 80 (residues 1 and 2 of the recognition helix). We tested these mutants in vivo by measuring the repression of synthesis of beta-galactosidase with symmetric variants of alpha- and beta-centered trp operators, which replace the lac operator in a synthetic lac system. The Trp repressor carrying a substitution of isoleucine 79 by lysine, showed a marked specificity change with respect to base pair 7 of the alpha-centered trp operator. Gel retardation experiments confirmed this result. Trp repressor mutant IR79 specifically recognizes a trp operator variant with substitutions in positions 7 and 8. Another mutant, with glycine in position 79, exhibited loss of contact at base pair 7. We speculate that the side chain of Ile79 interacts with the AT base pairs 7 and 8 of the alpha-centered trp operator, possibly with the methyl groups of thymines. Replacement of thymine in position 7 or 8 by uracil confirms the involvement of the methyl group of thymine 8 in repressor binding. Several Trp repressor mutants in position 80 (i.e. A180, AL80, AM80 and AP80) broaden the specificity of the Trp repressor for alpha-centered trp operator variants with exchanges in positions 3, 4 and 5.