Electrochemical Immunosensor for the Quantification of S100B at Clinically Relevant Levels Using a Cysteamine Modified Surface.

Neuronal damage secondary to traumatic brain injury (TBI) is a rapidly evolving condition, which requires therapeutic decisions based on the timely identification of clinical deterioration. Changes in S100B biomarker levels are associated with TBI severity and patient outcome. The S100B quantification is often difficult since standard immunoassays are time-consuming, costly, and require extensive expertise. A zero-length cross-linking approach on a cysteamine self-assembled monolayer (SAM) was performed to immobilize anti-S100B monoclonal antibodies onto both planar (AuEs) and interdigitated (AuIDEs) gold electrodes via carbonyl-bond. Surface characterization was performed by atomic force microscopy (AFM) and specular-reflectance FTIR for each functionalization step. Biosensor response was studied using the change in charge-transfer resistance (Rct) from electrochemical impedance spectroscopy (EIS) in potassium ferrocyanide, with [S100B] ranging 10-1000 pg/mL. A single-frequency analysis for capacitances was also performed in AuIDEs. Full factorial designs were applied to assess biosensor sensitivity, specificity, and limit-of-detection (LOD). Higher Rct values were found with increased S100B concentration in both platforms. LODs were 18 pg/mL(AuES) and 6 pg/mL(AuIDEs). AuIDEs provide a simpler manufacturing protocol, with reduced fabrication time and possibly costs, simpler electrochemical response analysis, and could be used for single-frequency analysis for monitoring capacitance changes related to S100B levels.

Cinética de la transesterificación de la oleína de palma africana con etanol / Kinetics of african palm olein transesterification with ethanol

Se estudió la cinética de la reacción de transesterificación de la oleína de palma africana con etanol y las variables que afectan las condiciones del proceso. Se determinó que el mecanismo de reacción que corresponde a este proceso consta de tres etapas reversibles por medio de las cuales se parte de triglicéridos y alcohol hasta obtener éster y glicerina, teniendo como productos intermedios la formación de monoglicéridos y diglicéridos de los distintos ácidos grasos presentes en el aceite. Se determino cual es la influencia de la temperatura sobre las constantes de velocidad, encontrando que el modelo que mejor se ajusta es el de segundo orden y que ésta afecta principalmente la dinámica de formación de mono y diglicéridos, de tal modo que a mayor temperatura se generan menores concentraciones finales de estos productos intermedios.