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In this paper, an electrochemical magneto-immunosensor for the detection of human growth hormone (hGH) is described for the first time. The immunosensor involves the use of tosyl-activated magnetic microparticles (TsMBs) to covalently immobilize a monoclonal mAbhHG antibody. A sandwich-type immunoassay with a secondary pAbhGH antibody and anti-IgG labelled with alkaline phosphatase (anti-IgG-AP) was employed. TsMBs–mAbhGH–hGH–pAbhGH–anti-IgG-AP conjugates were deposited onto the surface of a screen-printed gold electrode using a small neodymium magnet, and electrochemical detection was performed by square-wave voltammetry upon the addition of 4-aminophenyl phosphate as the AP substrate. All the variables involved in the preparation of immunoconjugates and in the immunoassay protocol were optimized. A calibration curve for hGH was constructed with a linear range between 0.01 and 100 ng/mL (r = 0.998) and a limit of detection of 0.005 ng/mL. This value is nearly three orders of magnitude lower than that obtained using surface plasmon resonance (Treviño et al., Talanta 78:1011-1016, 2009). Furthermore, good repeatability, with RSD = 3% (n = 10) at the 1-ng/mL hGH level, was obtained. Cross-reactivity studies with other hormones demonstrated good selectivity. The magneto-immunosensor was applied to the analysis of human serum spiked with hGH at the 4- and 0.1-ng/mL levels. Mean recoveries of 96 ± 6% and 99 ± 2%, respectively, were obtained.

A sensitive and rapid method for the determination of the clinically relevant biomarker receptor tyrosine kinase AXL in serum involving amperometric disposable immunosensors is reported. The target protein was sandwiched between a specific capture antibody covalently immobilized on screen-printed carbon electrodes modified with electropolymerized poly(pyrrolepropionic acid) and a biotinylated detector antibody labeled with a streptavidin-horseradish peroxidase conjugate. The amperometric responses were measured at −0.20 V vs the Ag pseudo-reference electrode of the SPCE upon the addition of H 2 O 2 in the presence of hydroquinone (HQ) as mediator. This integrated immunosensing platform showed a low limit of detection (337 pg mL −1 ), a good selectivity against other non-target serum proteins, and provided results statistically in agreement with those obtained by using a commercial ELISA kit. These attractive features together with the simplicity and easy automation and miniaturization of the required instrumentation make the developed methodology a promising alternative in the development of devices for on-site clinical analysis. [ABSTRACT FROM AUTHOR]

Abstract: A novel electrochemical platform for the preparation of disposable enzyme biosensors is reported in this work. This platform is constructed by electrodeposition of poly(3,4-ethylenedioxythiophene) (PEDOT) using the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) as the electropolymerization solvent onto gold nanoparticles-modified screen-printed carbon electrodes (SPCE). The enzymes alcohol dehydrogenase (ADH) or Tyrosinase were entrapped onto the electrode surface during the electropolymerization step. The potentiostatic electropolymerization process of PEDOT on gold nanoparticles-modified SPCE was optimized and the resulting modified electrodes characterized voltammetrically and by electrochemical impedance spectroscopy (EIS). The NADH amperometric detection at PEDOT/nAu/SPCE was also optimized and compared with that produced at a PEDOT/SPCE. ADH/PEDOT/nAu/SPCEs were constructed. The measured current for ethanol was 30% larger than that obtained using ADH/PEDOT/SPCEs. At a detection potential of +300mV, a calibration graph for ethanol with a linear range between 5 and 100μM was obtained with a detection limit of 2μM. The PEDOT/nAu/SPCEs electrodes were also tested for the preparation of Tyrosinase biosensors. Using a detection potential of −150mV, a linear calibration graph for phenol was constructed over the 0.1–50μM concentration range, with a limit of detection of 0.02μM. [Copyright &y& Elsevier]