Nanobiotechnology for health-care
Piezo-mechanical impedance of electrode with nanosized CdS crystals immersed in  bio-electrolyte 
 
Nesterenko E.O.1, Bogoslovskaya A.B. 2 , Doroshenko T.P. 2, Grynko D.O.1,2
1  Institute of Molecular Biology and Genetics of NAS of Ukraine ,                     150, Zabolotnogo Str., 03143 Kyiv,  Ukraine. 
2 V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
41, prospect Nauky, 03680 Kyiv, Ukraine, 		E-mail: dgrynko@gmail.com 

The aim of the presented project is to develop of a new high informative technique for weighting of molecular shell on piezoelectric CdS nano-crystals [1] in the order of femto- grams and its application for DNA bio-sensors.   The series of resonances in the range 1-10 MHz detected in the impedance spectra of conductive micro-wire electrode with nano-sized CdS crystals on its surface, which have been immersed into bio-electrolyte. The constructive and technological realization of a measuring flow cell is offered for experimental investigation. The cell is designed for single use, has a plastic body. The flow channel has a volume of up to 200 μl at a constant temperature in the range from 35 C to 85 C with a reproducibility of thermal stabilization of the electrolyte 0.1 C. The cell is equipped with two measuring electrodes, one of which is nanostructured and may be biofunctionalized  with oligonucleotide. We demonstrated measuring procedure for surface density of molecular shell as well at the process of immobilization of modPh on surface of CdS nano-crystals, as hybridization of oligonucleotide P1, which is complementary to Ph. Range of oligonucleotides surface density was 0.15 - 10 nm-2 at experimentally tested P1 concentrations from 0.001 nM to 100 nM in SSC buffer solutions. This device responds to changes in the attached mass and viscous layer at the boundary crystal-electrolyte. The mass of nano-crystals is in the range of nano-grams, so the added mass of the order of pico-grams or less registered. The selectivity of the device is ensured at the biochemical level - when using, for example, hybridization of single-stranded DNA. If a monomolecular layer is covalently bound to the surface of nanocrystals, the added mass increased in the process of hybridization with complementary single-stranded DNA in the electrolyte and the resonance frequencies of the crystals were changed. 
1. A.B. Bogoslovskaya, O.M. Khalimovskyy, D.O. Grynko  Piezo-mechanical impedance of nanosized CdS single crystal  //Semiconductor physics, quantum electronics and optoelectronics, 22 (4), P. 479-485 (2019).