Ultrasensitive Electrochemical Sensors for PSA Detection: Related Surface Functionalization Strategies.

Prostate cancer is the most common male cancer in the world. The diagnosis, staging, prognosis and monitoring are usually done with Prostate Specific Antigen (PSA). Biosensors are emerging as a novel analytical technology for PSA detection. They provide several advantages for clinical applications and will benefit clinicians, patients and forensic workers in the future. Among them, electrochemical immunosensors have gained growing interests. Hence, their sensitivity is often improved by modifying them with nanoparticles especially iron oxide (IONP). Functionalized IONP attracted much attention in the fabrication of biosensing systems, due to their multiple properties, such as biocompatibility and signal amplification, and their ability to bind covalently to antibodies via their functional groups. In the present study, two electrochemical immunosensors were investigated for PSA detection. The first one was functionalized with 3- glycidoxypropyltrimethoxysilane self-assembled monolayer, while the second one was based on iron oxide nanoparticles functionalized with 3-aminopropyltriethoxysilane. Square wave voltammetry (SWV) has been investigated to follow-up the PSA detection in a phosphate buffer solution, in an artificial serum and in a human serum. The limit of detection (LOD) of both immunosensors was found of order of 10 fg/ml. When estimated in human serum this value increases up to 50 pg/ml.

AFM, CLSM and EIS characterization of the immobilization of antibodies on indium-tin oxide electrode and their capture of Legionella pneumophila.

The microscopic surface molecular structures and properties of monoclonal anti-Legionella pneumophila antibodies on an indium-tin oxide (ITO) electrode surface were studied to elaborate an electrochemical immunosensor for Legionella pneumophila detection. A monoclonal anti-Legionella pneumophila antibody (MAb) has been immobilized onto an ITO electrode via covalent chemical bonds between antibodies amino-group and the ring of (3-Glycidoxypropyl) trimethoxysilane (GPTMS). The functionalization of the immunosensor was characterized by atomic force microscopy (AFM), water contact angle measurement, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in the presence of [Fe(CN)6](3-/4-) as a redox probe. Specific binding of Legionella pneumophila sgp 1 cells onto the antibody-modified ITO electrode was shown by confocal laser scanning microscopy (CLSM) imaging and EIS. AFM images evidenced the dense and relatively homogeneous morphology on the ITO surface. The formation of the complex epoxysilane-antibodies acting as barriers for the electron transfer between the electrode surface and the redox species in the solution induced a significant increase in the charge transfer resistance (Rct) compared to all the electric elements. A linear relationship between the change in charge transfer resistance (ΔRct=Rct after immunoreactions - Rct control) and the logarithmic concentration value of L. pneumophila was observed in the range of 5 × 10(1)-5 × 10(4) CFU mL(-1) with a limit of detection 5 × 10(1)CFU mL(-1). The present study has demonstrated the successful deposition of an anti-L. pneumophila antibodies on an indium-tin oxide surface, opening its subsequent use as immuno-captor for the specific detection of L. pneumophila in environmental samples.