On the Importance of Controlling Film Architecture in Detecting Prostate Specific Antigen

Publication year: 2018
Authors: Graça J. S. a, Miyazaki C. M. a, Shimizu F. M. b, Volpati D. c, Mejía-Salazar J. R. b, Oliveira O.N. Jr. b, Ferreira M. a
Affiliations:

a - Federal University of São Carlos, Center for Sciences and Technology for Sustainability, 18055-720 Sorocaba, SP, Brazil
b - São Carlos Institute of Physics, University of São Paulo, P.O. Box 369, 13560-970 São Carlos, SP, Brazil
c - Department of Natural Sciences, Mid Sweden University, SE-851 70 Sundsvall, Sweden

Published in: Applied Surface Science, 2018, Vol. 434, p. 1175-1182
doi: 10.1016/j.apsusc.2017.10.122

Immunosensors made with nanostructured films are promising for detecting cancer biomarkers, even at early stages of the disease, but this requires control of film architecture to preserve the biological activity of immobilized antibodies. In this study, we used electrochemical impedance spectroscopy (EIS) to detect Prostate Specific Antigen (PSA) with immunosensors produced with layer-by-layer (LbL) films containing anti-PSA antibodies in two distinct film architectures. The antibodies were either adsorbed from solutions in which they were free, or from solutions where they were incorporated into liposomes of dipalmitoyl phosphatidyl glycerol (DPPG). Incorporation into DPPG liposomes was confirmed with surface plasmon resonance experiments, while the importance of electrostatic interactions on the electrical response was highlighted using the Finite Difference Time-Domain Method (FDTD). The sensitivity of both architectures was sufficient to detect the threshold value to diagnose prostate cancer (ca. 4 ng mL−1). In contrast to expectation, the sensor with the antibodies incorporated into DPPG liposomes had lower sensitivity, though the range of concentrations amenable to detection increased, according to the fitting of the EIS data using the Langmuir-Freundlich adsorption model. The performance of the two film architectures was compared qualitatively by plotting the data with a multidimensional projection technique, which constitutes a generic approach for optimizing immunosensors and other types of sensors.


MP-SPR keywords: antibodies incorporated into phospholipid liposomes, biosensor, cancer detection, computational simulation, detection of prostate specific antigen, immunosensor, LbL film growth