A new method for immunosensor preparation: Atmospheric plasma torch

This paper describes a new method for the modification of piezoelectric quartz crystals for immunosensor preparation. The surfaces of the piezoelectric quartz crystals were modified employing Atmospheric Pressure Plasma System using different monomers such as Ethylene diamine (EDA), 1,4-Diaminobutane (DAB) and n-Butylamine (BA). The atmospheric pressure plasma system was adjusted to use the temperature sensitive and volatile monomers. A tunnel from stainless steel was constructed and combined with the plasma torch to introduce the monomers into the plasma jet and preventing the mixing of atmospheric air with the plasma jet. Plasma parameters were; power: 1 kW, pressure: 1 atm, speed of plasma particles: 219 m/s, and exposure time 10 min for EDA and BA monomers, 15 min for DAB monomer. Crystals were characterized by frequency shift measurements, Atomic Force Microscopy (AFM) imaging, contact angle measurements and Infrared (IR) spectra. Frequency shifts for EDA, DAB and BA modified crystals after plasma modification were 56 ± 10, 143 ± 3 and 904 ± 3 Hz respectively. AFM images showed the presence of a film on the surfaces for all monomers. N–H, C–N, C–H and CO group bands were determined in the IR spectra of the crystals. Decrease in the contact angle values of the modified crystals indicated the increase in hydrophilicity. Those results showed that amine containing films on the crystal surfaces were successfully deposited using atmospheric pressure plasma torch. The chemical groups on quartz surface were further activated with gluteraldehyde (GA) and protein immobilisation properties were checked with test antibody (anti-aflatoxin B1) in liquid phase quartz crystal microbalance system. The dip coating method was chosen for immobilisation procedure. After the immobilisation step, chemical structure of surfaces was analyzed by X-ray Photoelectron Spectroscopy.