Characterization of DSPA films onto solid substrates using optical and electrochemical techniques

ALEXIS PECCI GENARO; TOMÁS E. BENAVIDEZ; CANDELARIA I. CAMARA

Campinas

Congreso; 47th Annual Meeting of the Bazilian Biophysical Society; 2023

Brazilian Biophysical Society

With the intention to obtain biologically active substrates, different techniques have been employed to modify solid surfaces (conductive materials, polymers, etc.) for being applied in biosensors. For this purpose, physical and chemical immobilization methods have been developed since the last decades of the 20th century. Particularly, Langmuir-Blodgett deposition has the advantage to obtain controlled accurate lipidic films stabilized by film-substrate physical interactions. In this work, distearoylphosphatidic acid (DSPA) was used to modify different solid substrates such as ITO (Indium Tin-Oxide) and silicon wafer (SW) by Langmuir-Blodgett technique. DSPA films were deposited at 40 mN.m-1 with a resulting transfer rate of 0.97 onto the solid substrates. Then, DSPA layers were characterized using contact angle, ellipsometric spectroscopy, AFM, and different electrochemical methods (Ciclyc Voltammetry, CV and Electrochemical Impedance Spectroscopy, EIS). The electrochemical experiments were carried out in a 50 mmol.L-1 phosphate buffer solution containing 5 mmol.L-1 K3Fe(CN)6/K4Fe(CN)6 at pH = 7.6.The electrochemical data demonstrated that homogeneous compact Langmuir-Blodgett (LB) films were obtained with DSPA onto ITO electrodes. Accordingly, an increased resistance to the charge transfer process and a decreasing interfacial capacitive behavior were observed by EIS. In addition, CV experiments also showed that the electrochemical response of ITO displayed a much more quasi-reversible behavior when the DSPA film blocked the electrode surface. The surface modification was also evaluated by contact angle. In this case, a hydrophobic response was developed on the hydrophilic substrate surface (55°) upon DSPA film deposition (79°).The experimental results demonstrated that DSPA was able to acquire stable LB films onto hydrophilic substrates. Also, the electrochemical techniques were a helpful tool to study DSPA layers adsorbed onto conducting materials. In this regard, DSPA films are able to be considered as a stable platform to immobilize biological molecules like proteins (enzymes, SpA, antibodies) for being applied in the development of biosensors.