Inkjet monitoring technique with quartz crystal microbalance (QCM) sensor for highly reproducible antibody immobilization

•This paper enables simple evaluation of inkjet microdeposition at room temperature.•Using only readily available devices, we succeeded both in minimizing the background noise from external sources and in continuously monitoring shot ejection and deposition of a concentrated (1mg/ml) antibody solution into 3D patterns.•The technique described in this paper simplifies the experimental evaluation of inkjet bioprinting in terms of the sensitive determination (at the pg level) of shot ejections.•The accurate determination of c-reactive protein by a printed sandwich enzyme-linked immunosorbant assay (ELISA) is demonstrated. We demonstrate that a calibrated amount of a biomolecule can be microdeposited using a commercially available quartz crystal microbalance (QCM) and a piezoelectric inkjet head with a flattened surface surrounding the ejection hole. Covering the QCM with a stainless-steel cover perforated with a precisely-machined hole both significantly decreased background noise due to external sources such as air flow and temperature fluctuations and allowed accurate droplet ejection at a constant temperature. Anti-c reactive protein antibody solution (anti-CRP; 1.0mg/ml) was continuously ejected onto a microchannel target using a piezoelectric injector; its microdeposition was monitored shot-by-shot using a 30MHz QCM. The dispersion of the QCM frequency change per shot decreased from 7.87 to 1.01Hz when a perforated stainless-steel cover was installed. The primary antibody was precisely deposited on the target with high reproducibility. The variation in luminescence measured by enzyme-linked immunosorbant assay (ELISA) decreased from 9.67% to 1.16% when calibrating the amount of primary antibody deposition with this developed technique.