Novel biosensing device for point-of-care applications with plastic antibodies grown on Au-screen printed electrodes Felismina T.C. Moreira , Rosa A.F. Dutra , João P.C. Noronha , João C.S. Fernandes , M. Goreti F. Sales ABSTRACT A gold screen printed electrode (Au-SPE) was modified by merging Molecular Imprinting and Self- Assembly Monolayer techniques for fast screening cardiac biomarkers in point-of-care (POC). For this purpose, Myoglobin (Myo) was selected as target analyte and its plastic antibody imprinted over a glutaraldehyde (Glu)/cysteamine (Cys) layer on the gold-surface. The imprinting effect was produced by growing a reticulated polymer of acrylamide (AAM) and N,N ∗ -methylenebisacrylamide (NNMBA) around the Myo template, covalently attached to the biosensing surface. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) studies were carried out in all chemical modification steps to confirm the surface changes in the Au-SPE. The analytical features of the resulting biosensor were studied by different electrochemical techniques, including EIS, square wave voltammetry (SWV) and potentiometry. The limits of detection ranged from 0.13 to 8 µg/mL. Only potentiometry assays showed limits of detection including the cut-off Myo levels. Quantitative information was also produced for Myo concentrations ≥0.2 µg/mL. The linear response of the biosensing device showed an anionic slope of ∼70 mV per decade molar concentration up to 0.3 µg/mL.The interference of coexisting species was tested and good selectivity was observed. The biosensor was successfully applied to biological fluids. Keywords: Surface molecular imprint, Self-assembled monolayer, Screen-printed electrodes, Cardiac biomarker, Myoglobin, Biosensor 1. Introduction Acute myocardial infarction (AMI) leads to myocardium necro- sis and to an increasing number of specific biomolecules flowing in the blood and being excrete through urine, such as Myo [1]. Myo is the first biomolecule increasing after AMI [2–4], offering a high sensitive way to detect or exclude AMI conditions within 1–5 h of symptom onset [1]. Subsequent Myoglobinuria is also observed within 4–50 h [4]. Any intended protocol to determine Myo in POC must produce low turnaround times to detect such rapid biochemical alterations and be sufficiently cheap to be used routinely. Analytical data must be produced for normal/abnormal Myo ranges without requiring complex sample pre-treating steps. Myo cut-off levels range from 100–200 ng/mL [5–7]. The higher levels of Myo vary a lot, with previous studies showing 420–2000 ng/mL in serum [8] and 450 ng/mL in urine [9]. Several methods based on enzymatic and immunoassay was described in the literature [10]. The first methods for Myo determi- nation in blood were all supported by immunoreactions, including radioimmunoassay [8,11,12], counterimmunoelectrophoresis [13] enzyme-immunoassay [8] chemiluminescent immunoassay [14] and latex agglutination immunoassay [15–17], later coupled to tur- bidimetric [18] or nephelometric [19,20] readings and to other solid support materials, such as polystyrene [20]. In subsequent years many attempts have been made to create suitable devices for POC applications [21,22]. They employ various transducer principles but keep the immunochemical background. Immunoassays have the main advantage of offering a selectivity/specificity that cannot be matched by the chemical methods, but they lack the stability and the low price of these. A successful route to replace the immunoassays is the synthe- sis of plastic antibodies [23–25]. These materials are prepared by growing a solid polymer structure around a target compound, cre- ating sites that are expected to be complementary in size and electrostatic environment to the imprinted molecule. These sites