David Kovář

Nanoparticle-Based Immunochemical Biosensors and Assays: Recent Advances and Challenges

We review the progress achieved during the recent five years in immunochemical biosensors (immunosensors) combined with nanoparticles for enhanced sensitivity. The initial part introduces antibodies as classic recognition elements. The optical sensing part describes fluorescent, luminescent, and surface plasmon resonance systems. Amperometry, voltammetry, and impedance spectroscopy represent electrochemical transducer methods; electrochemiluminescence with photoelectric conversion constitutes a widely utilized combined method. The transducing options function together with suitable nanoparticles: metallic and metal oxides, including magnetic ones, carbon-based nanotubes, graphene variants, luminescent carbon dots, nanocrystals as quantum dots, and photon up-converting particles. These sources merged together provide extreme variability of existing nanoimmunosensing options. Finally, applications in clinical analysis (markers, tumor cells, and pharmaceuticals) and in the detection of pathogenic microorganisms, toxic agents, and pesticides in the environmental field and food products are summarized.

Rapid Detection of Microorganisms Based on Active and Passive Modes of QCM

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.

Detection of Aerosolized Biological Agents Using the Piezoelectric Immunosensor

Airborne microorganisms are a major cause of respiratory diseases. Detection of pathogenic bacteria in the form of bioaerosols is required not only in peacetime but also in the threat of biological attacks. The label-free and direct detection of aerosolized biological agents is presented here. A desktop bioaerosol chamber for safe work with aerosolized microbial cells was constructed, and its functionality was tested. The model organisms (Escherichia coli) were disseminated using an aerosol generator in the chamber filled with either common laboratory indoor air or sterile air. The particles from the generated aerosol were collected using the cyclone SASS 2300, suspended in buffer and then analyzed using the piezoelectric immunosensor modified with specific capture antibodies. The frequency shifts indicated presence of the model biological agent with limit of detection of 1.45 × 10(4) CFU·L(-1) of air. The total time from sample collection to detection was 16 min. The system was fully automated and controlled remotely through a local network.