Ultrasensitive microfluidic immunosensor based on electrodeposited nanoporous gold for cancer biomarker detection

DANIEL MATIAS GASTON REGIART; MAILEN G. NEIRA; ALBA MARINA GIMENEZ; MARCELO N.P. CARREÑO; MAURO BERTOTTI

Congreso; 43 Reunião Anual Virtual da Sociedade Brasileira de Química (SBQ); 2020

Sociedade Brasileira de Química (SBQ)

SOX-2, a protein also known as SRY-box 2 (Sex determining Region Y-box 2), is a transcription factor whose function is essential in the regulation of embryonic development, the induction of mother cell pluripotentiality, and the determination of cell differentiation [1]. Several mutations in this gene have been associated with a severe malformation in the eye structure called anophthalmia. It has also been determined that the ectopic expression of SOX-2 could be related to abnormal differentiation of colorectal cancer cells, as well as to overexpression in breast, ovarian, lung, esophageal, prostate, pancreatic, testicular, and cutaneous, neck and head squamous cell carcinoma, among others [2]. We developed an ultrasensitive and portable microfluidic electrochemical immunosensor for SOX-2 determination in human serum samples. The selectivity and sensitivity of the sensor were improved by using a hybrid PDMS-glass microfluidic channels modification based on a physical-chemical treatment to obtain a hydrophilicity functional platform, with an increased surface to volume/ratio, where the anti-SOX-2 antibodies can be covalently immobilized. The characterization of the modified channel surface was carried out by Infrared Spectroscopy. Moreover, the gold electrode surface was modified by using a dynamic hydrogen bubble template, and a gold nanoporous structure (NPAu) was obtained. Such platform has outstanding properties, like high specific surface area, large pore volume, uniform nanostructure, good conductivity, and excellent electrochemical activity [3]. NPAu was characterized by scanning electron microscopy, energy dispersive spectrometry, cyclic voltammetry, and X-ray diffraction. SOX-2 present in the samples binds to the anti-SOX-2 immobilized and was then quantified by using a second antibody labeled with horseradish peroxidase (HRP- anti-SOX-2). Finally, a H2O2 + 4-tert-butyl catechol solution was added, and the enzymatic product (quinone) was reduced on the NPAu electrode at +100 mV (vs. Ag). The current obtained is directly proportional to the SOX-2 concentration in the sample. The detection limit was found to be 30 pg mL-1, and the coefficient of variation was less than 3.75 %. As it can be seen, the microfluidic electrochemical immunosensor is a suitable clinical device for in situ SOX-2 determination in real samples.