Avidin from egg white

Tetrachloroauric(III) acid trihydrate (HAuCl₄.3H₂O, 99.5%), trisodium citrate (C₆H₅Na₃O₇, 99.0%), avidin from egg white, and biotin-4-fluorescein were purchased from Sigma-Aldrich (Germany). Lacto-N-fucopentaose I-biotin (H-1-biotin) was purchased from Dextra Laboratories (United Kingdom). Streptococcus pyogenes M1 (ATCC^® 700294), Streptococcus pyogenes M6 (ATCC^® BAA-946), Streptococcus pyogenes M12 (ATCC^® BAA-1315), and E. coli O157:H7 (ATCC35150) were purchased from ATCC (United States). UV–Vis absorption spectrophotometer (CE7500, United States), Transmission Electron Microscope (Zeiss EM 900, Germany), Dynamic Light Scattering (Scatteroscope I, South Korea), and fluorescence spectrometer (PerkinElmer, United States) were used.

Phosphate-buffered saline (PBS) powder, ethanol, 30% hydrogen peroxide, 1 N (0.5 mol/L) sulfuric acid, 3-aminopropyltriethoxysilane (APTES) 99%, trimethylamine ≥ 99% and avidin from egg white ≥ 98% were purchased from Sigma-Aldrich (Madrid, Spain). The N-Hydroxysuccinimid (NHS)-polyethylenglycol (PEG27) biotin linkers were purchased from JKU Linz [30 (link)].

All buffer solutions were prepared with purified Milli-Q water (18.2 MΩ). Poly(allylamine hydrochloride), (PAA MW~50,000), poly(sodium 4-styrenesulfonate) (PSS, MW~70,000), tetraethyl orthosilicate (TEOS), acridine orange (AO), and avidin from egg white were purchased from Sigma-Aldrich (St. Louis, MO, USA). Sodium chloride, methylene blue (MB), 2-propanol, 25% ammonium solution, 28–30% ammonium hydroxide, acetone, and 95% ethanol were purchased from Merck (Darmstadt, Germany). Dynabeads^TM MyOne^TM Streptavidin T1 was purchased from Thermo Fisher Scientific (Waltham, MA, USA). AccuPower 2× Greenstar qPCR Master Mix was purchased from Bioneer (Daejeon, Korea), 2× PCR Master Mix Solution (i-StarTaq) was purchased from iNtRON Biotechnology (Seongnam, Korea).
For electrochemical measurements, screen-printed carbon electrodes (SPCE) were obtained from Quasense (Bangkok, Thailand) and the PalmSens4 potentiostat with PSTrace software version 5.8 was obtained from Palmsens (Houten, The Netherlands).

Human cardiac troponin I (hcTnI) was purchased from Life Diagnostics Inc. (West Chester, PA, USA), aliquoted and stored at −80 °C until being used. Human skeletal troponin I (hsTnI) was kindly provided by Dr. Tamas Mészáros from Semmelweiss University (Budapest, Hungary), aliquoted and stored at −80 °C until used. Streptavidin-Horseradish Peroxidase bioconjugate (Sigma-Aldrich, St. Louis, MO, USA) was dissolved in 10 mM of phosphate saline buffer (PBS) solution at pH 7.5 at a final concentration of 1 mg mL⁻¹, aliquoted and stored at −20 °C until used. EZ Link sulfo-NHS-LC-LC-Biotin reagent was purchased from Pierce Biotechnology (Rockford, IL, USA). N-ethyl-N-dimethylaminopropyl-carbodiimide (EDC), N-hydroxysulfo-succinimide (NHS), bovine serum albumin (BSA), avidin from egg white, casein from bovine milk and 2-(4-Hydroxyphenylazo) benzoic acid (HABA) were purchased to Sigma-Aldrich. Methyl-(octaethyleneglycol) amine (mPEG-Amine) was acquired from Laysan Bio, Inc. (Arab, AL, USA). Other chemicals and biochemicals used were purchased to Sigma Chemical Co. (St. Louis, MO, USA) and all salts were provided by Merck (Darmstadt, Germany). SiMAG-Carboxyl magnetic beads (SiMAG-Carboxyl, 1 µm Ø, Prod. No. 1402) were purchased from Chemicell GmbH (Berlin, Germany). Qdot^TM 585 Streptavidin Conjugate (Qdot-SAv) was purchased from Molecular probes® (Eugine, OR, USA).