Solubility and kinetics of soybean oil and fatty acids in supercritical CO2

Supercritical CO₂ extraction of soybean oil was investigated. The fatty acid composition was determined using GC. The solubility and kinetic experiments were performed in the pressure range of 100–300 bar and in the temperature range of 313–323 K. The solubility data were correlated using empirical equation proposed by Gordillo et al. Mass transfer model described by Martinez et al. was used to describe the kinetic curves of soybean oil. The main fatty acids of soybean oil were linoleic, oleic, palmitic, stearic and linolenic acid. The improved Gordillo et al. equation was proposed to correct the effect of temperature on the solubility. The new equation was successfully applied for calculating the solubility of fatty acids and soybean oil in supercritical CO₂.     

Impedimetric Measurements for Monitoring Avidin-Biotin Interaction on Self-Assembled Monolayer

Avidin-biotin has been controllable immobilized on the surface of gold electrodes using mercaptopropionic acid as self-assembled monolayer. Electrochemical impedance spectroscopy (EIS) was employed to investigate the changes that appear at the electrode surface in the presence of a redox mediator, K₃[Fe(CN)₆]. An electrical model more complex than that in other studies was used to interpret the EIS measurements (Randles circuit). This model is very useful because it takes into consideration both the transfer of electrons at the electrode/electrolyte interface and the diffusion of redox species through the double layer. The model allowed us to determine some important parameters like solution resistance R_sol, charge-transfer resistance R_ct, double-layer capacitance C_dl, Warburg resistance R_W, and the diffusion time constant τ. The EIS results proved that immobilization of avidin-biotin increased the charge-transfer resistance R_ct, due to the insulating character of these molecules.     

Single-Step Synthesis of Gold Nanowires Using Biomolecules as Capping Agent/Template: Applications for Tissue Engineering

Gold nanochains/nanowires were prepared by simultaneously reducing the gold salt in the presence of stabilizing biomolecules —L-aspartate and L-lysine, Collagen—that acts as capping agent and as a template in the formation of two-dimensional gold nanostructures. L-aspartate and L-lysine were used in order to form nanochains due to their ability to cap gold nanoparticles through an oriented attachment mechanism that leads to the formation of one-dimensional nanostructures. The formation of the nanowires was controlled by reducing the gold salt onto the surface of the collagen template. Transmission electron microscopy (TEM) and x-ray powder diffraction were employed in order to demonstrate the morphological and structural properties of the nanowires. In order to provide evidence of the possible applications of gold nanostructures as biocompatible substrates for tissue engineering, mesenchymal stem cells were cultured in their presence. MTT proliferation assays, as well as immunohistochemistry assays, were performed. The experiments demonstrated that each nanostructure stimulates cell proliferation, but better results were obtained in the case of collagen. Moreover, we noticed that the nanostructures are tracked inside of the cells, most likely in the perinuclear region of the stem cells.