Karol Waszczuk

Application of quartz tuning forks for detection of endotoxins and Gram-negative bacterial cells by monitoring of Limulus Amebocyte Lysate coagulation.

Endotoxins, pyrogens of bacterial origin, are a significant threat in many areas of life. Currently, the test most commonly used for endotoxin level determination is LAL (Limulus Amebocyte Lysate) assay. This paper presents application of commercially available low-frequency piezoelectric tuning forks (QTFs) for endotoxin detection. Measurement of the decrease in the QTF oscillation amplitude provides information about the viscosity changes, occurring in the tested sample upon addition of LAL. That method was used to determine the concentrations of endotoxins and bacterial cells (E. coli O157:H19). The relevance of the obtained results was confirmed using a commercially available colorimetric LAL assay. The constructed system can detect bacterial endotoxins in the range of 0.001-5EU/ml and bacterial cells in the range of 10(2)-10(7)CFU/ml. The presented technique requires very simple sample preparation and the sensor response is obtained using compact, portable readout electronics. The single test cost is low compared to commercial endotoxin assays and other novel systems based on micromechanical sensors.

Modulation of excitation signal as a method for measurement of the mechanical properties of miniature piezoelectric resonant devices in a viscous and conductive environment

A novel approach to electric measurement of mechanical properties of piezoelectric resonators is presented. Modulation of the actuation signal and application of dedicated, in-house built readout electronics makes it possible to precisely analyse resonance response of low-frequency piezoelectric devices in conductive and viscous environment. The method presented is inexpensive and allows us to measure highly damped piezoelectric resonator properties without being influenced by the parasitic elements present in the resonator structure or due to the properties of the environment.