title: Rapid detection of microorganisms based on active and passive modes of QCM.
abstract: Label-free immunosensors are well suited for detection of microorganisms because of their fast response and reasonable sensitivity comparable to infection doses of common pathogens. Active (lever oscillator and frequency counter) and passive (impedance analyzer) modes of quartz crystal microbalance (QCM) were used and compared for rapid detection of three strains of E. coli. Different approaches for antibody immobilization were compared, the immobilization of reduced antibody using Sulfo-SMCC was most effective achieving the limit of detection (LOD) 8 × 104 CFU·mL-1 in 10 min. For the passive mode, software evaluating impedance characteristics in real-time was developed and used. Almost the same results were achieved using both active and passive modes confirming that the sensor properties are not limited by the frequency evaluation method but mainly by affinity of the antibody. Furthermore, reference measurements were done using surface plasmon resonance. Effect of condition of cells on signal was observed showing that cells ruptured by ultrasonication provided slightly higher signal changes than intact microbes.
authors.affiliation: CEITEC MU, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic. farka@mail.muni.cz.
authors.forename: Zdeněk
authors.initials: Z
authors.lastname: Farka
authors.affiliation: CEITEC MU, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic. kovar@nanobio.cz.
authors.forename: David
authors.initials: D
authors.lastname: Kovář
authors.affiliation: CEITEC MU, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic. skladal@chemi.muni.cz.
authors.forename: Petr
authors.initials: P
authors.lastname: Skládal
mesh_terms: D000906:Antibodies / Q000378:metabolism; D002138:Calibration; D017097:Electric Impedance; D004926:Escherichia coli / Q000302:isolation & purification*; D055767:Immobilized Proteins / Q000378:metabolism; D007118:Immunoassay; D018625:Microscopy, Atomic Force; D058525:Quartz Crystal Microbalance Techniques / Q000379:methods*; D020349:Surface Plasmon Resonance
chemical_list: D000906:Antibodies; D055767:Immobilized Proteins