In between each injection, regeneration of the BSA sensor was performed using a low-pH buffer [48]. Selectivity of the developed BSA-imprinted electrode was tested together with other proteins (HSA, IgG) and selectivity as a result of imprinting efficiency was indicated with the comparison of the results obtained from NIP (non-imprinted) electrode. Bovine serum albumin (BSA), tyramine (99%, HOC6H4CH2CH2NH2) and human serum albumin (HSA) were obtained from Sigma (Steinheim, Germany). Acryloyl chloride

and 1-dodecanethiol were obtained from Aldrich (Deisenhofen, Germany). Glutaraldehyde 50% (w/v), triethylamine, 3-amino-propyl-triethoxysilane (APTES) and α-α’-azoisobutyronitrile (AIBN) were purchased from Fluka (Buchs, Switzerland). Human gamma globulin (human IgG) was purchased from Octapharma AB (Stockholm, Sweden). Glass microscope Cytoskeletal Signaling inhibitor cover slips (24 × 40 mm) (Menzel-Glaser) were selleck chemicals llc used as the base for protein stamp in microcontact imprinting. All other chemicals used were of analytical grade. All buffers were prepared with water processed using a reverse osmosis step with a Milli-Q system from Millipore (Bedford, MA, USA). Prior to use, all buffers were filtered through a Millipore filter (pore size 0.22 μm) and degassed for 1 h. The microcontact-BSA imprinted capacitive electrodes were prepared in three steps:

(a) Preparation of the glass cover slips (protein stamps): Glass cover slips (24 × 40 mm) were used for the preparation of protein stamps in this procedure. In the first step, cover slips were cleaned in 10 mL of 1 M HCl, de-ionized water, 1 M NaOH, de-ionized water and ethanol, respectively in ultrasonic cleaner for 10 min in each step. After cleaning, the cover slips were dried with nitrogen gas. The cleaned cover slips were immersed in 10% (v/v) APTES (3-amino-propyl-triethoxysilane) in ethanol

at room temperature for 1 h to introduce amino groups on the surface. Subsequently, the electrodes were rinsed with ethanol to remove any unbound APTES molecules. For the activation of the amino groups on the APTES modified cover slip surface, they were immersed in 5% (v/v) glutaraldehyde (GA) solution in 10 mM phosphate buffer (pH 7.4) at room temperature for 2 h. Then, the cover slips were rinsed with phosphate buffer to remove excess GA and dried with nitrogen triclocarban gas. In the last step, the cover slips were immersed in 0.1 mg/mL BSA solution (in phosphate buffer, 10 mM, pH 7.4) at 4 °C for 24 h for the immobilization of BSA onto the surface. Finally, the cover slips were washed with phosphate buffer and then, dried with nitrogen gas. They were kept at 4 °C in a closed Petri dish until use. (b) Preparation of the capacitive gold electrodes: In the first step, gold electrodes were washed with ethanol, de-ionized water, acetone, de-ionized water and piranha solution (3:1, H2SO4:H2O2, v/v), respectively for 10 min in each step in ultrasonic cleaner.