Inexpensive and Reliable Monitoring of the Microdeposition of Biomolecules

Abstract

Anti-C-reactive protein antibody is used to quantify C-reactive protein in diagnostic tests for assessing inflammation levels. In order to develop a practical chip for diagnostic tests, anti-C-reactive protein antibody was continuously ejected using a piezoelectric injector and microdeposition was monitored on a shot-by-shot basis using a 30 MHz quartz crystal microbalance. Background noise due to external sources such as air flow and temperature fluctuations were largely eliminated by covering the quartz crystal microbalance with a stainless-steel cover and maintaining a fixed distance between the optical microscope lamp and the piezoelectric injector. Each shot of a 1 mg ml−1 solution of anti-C-reactive protein antibody solution delivered approximately 30 pl to the quartz crystal microbalance. The frequency change per shot was 2.21 ± 0.97 Hz and the injected mass was estimated to be 44.2 pg using the Sauerbrey equation. This approach simplifies the experimental evaluation of inkjet bioprinting by allowing the sensitive determination of shot ejection mass and volume, and realizes label-free detection, continuous monitoring, and simple temperature control. Measurements can be performed at atmospheric pressure and at room temperature. Furthermore, the system uses only commercially available devices.