Safranin T- SDS- GO ternary system: A fluorescent pH sensor

Graphene oxide (GO), one of the popular materials in recent years, has been synthesized according to the modified Hummers' method. Stable dispersions of different amounts of negatively charged GO were prepared in aqueous media. The GO/dye composites were prepared in deionized water by a simple method with the positively charged Safranin T compound (SfT), which is known to have strong fluorescence properties. By changing the GO/dye ratio, it was obtained stable composites in aqueous media. It was investigated the interaction of SfT with GO in an aqueous solution under the critical micelle concentration (CMC), at the CMC and above the CMC by adding sodium dodecyl sulfate (SDS). It was clarified the formation of GO-SfT composites by using spectroscopic techniques. In these composites, the effect of GO layers on the SfT's photophysical properties was examined by absorption and fluorescence spectroscopy techniques. The change in the quenching effect of GO was monitored both adding a stabilizing electrolyte (NaCl) to the media and changing the pH of the medium. The evaluation was on the probability of the GO-SfT-SDS ternary system being a pH sensing biological sensor material. As a result of this study, it was thought that the GO-SfT-SDS system could be functionalized as a fluorescent pH sensor by taking advantage of GO's sensitivity to pH.

Sustained delivery of growth factors with high loading efficiency in a layer by layer assembly

Layer by layer (LBL) assembly has garnered considerable interest due to its ability to generate multifunctional films with high tunability and versatility in terms of substrates and polyelectrolytes, allowing the option to use complex devices and drugs. Polyelectrolytes, such as growth factors (GFs), are essential, but costly, delicate, biological molecules that have been used in various tissue regeneration applications. For this reason, the controlled drug delivery of efficiently loaded GFs via LBL assembly (GF-LBL) can contribute to the establishment of cost-effective biologically triggered biomedical applications. We have developed an LBL method to load GFs (specifically, transforming growth factor beta 1, platelet-derived growth factor ββ, and insulin growth factor 1), with up to 90% efficiency approximately, by gas plasma surface activation and tuning the pH to increase the ionic strength of polyelectrolytes. Poly(styrenesulfonate) (PSS) and poly(ethyleneimine) (PEI) have been used to provide the initial necessary charge for multilayer build-up. Heparin and dextran sulphate have been investigated as counter polyelectrolytes to enhance the activity of GFs by protecting their ligands, where heparin resulted in the highest achievable loading efficiency for all GFs. Oxygen gas plasma and acidic pH levels also resulted in a significant increase in GF loading efficiency. The three GFs were released by diffusion and erosion in a controlled manner over lengthy time scales and the bioactivity was maintained for up to 14 days. When tested as implants in vitro, GF-LBL constructs increased fibroblast proliferation, influenced cell morphology and migration, and enhanced myofibroblast differentiation, indicating that the biological functionalities of the GFs were preserved. In conclusion, this developed LBL assembly method can provide a simple drug delivery system, which may yield more effective applications for tissue regeneration as well as biomedical sciences at large.