An embedded portable biosensor system for bacterial concentration detection

Abstract

Microbial screening is a primary concern for many products. Traditional techniques based on standard plate counts (SPC) are accurate, but time consuming. Furthermore, they require a laboratory environment and qualified personnel. The Impedance Technique (IT) looking for changes in the electrical characteristics of the Sample Under Test (SUT) induced by bacterial metabolism represents an interesting alternative to SPC since it is faster (3-12 hours vs 24-72 hours for SPC) and can be easily implemented in automatic form. With this approach, the essential parameter is the time for bacteria concentration to reach a critical threshold value (about 10 7 cfu•mL -1 ) capable of inducing significant variations in the SUT impedance, measured by applying a 100 mV peak to peak 200 Hz sinusoidal test signal at time intervals of 5 minutes. The results of this work show good correlation between data obtained with the SPC approach and with impedance measurements lasting only 3 hours, in the case of highly contaminated samples (10 6 cfu•mL -1 ).Furthermore, this work introduces a portable system for impedance measurements composed of an incubation chamber containing the SUT, a thermoregulation board to control the target temperature and an impedance measurement board. The mix of cheap electronics and fast detection time provides a useful tool for microbial screening in industrial and commercial environments.

Electrical impedance spectroscopy (EIS) for biological analysis and food characterization: a review

“…Grossi et al (2010Grossi et al ( , 2013a) designed a portable biosensor to measure bacterial concentration in liquid and semiliquid media that includes an incubation chamber (featuring stainless steel electrodes, heating resistances and a temperature sensor for thermoregulation) and two electronic boards, connected to a PC via RS-232 for data analysis and filing. A Telit GT 863-PY module integrated into the system allows wireless data transmission to remote hosts.…”

Evaporation-induced stimulation of bacterial osmoregulation for electrical assessment of cell viability

“…These techniques can be broadly divided into growth-based vs. nongrowth-based assays. Growth-based techniques [such as colony counting (14), impedance microbiology (16)(17)(18)(19), monitoring the resonance frequency (32), etc.] rely on cell division to reach a threshold level so that the signal becomes detectable.…”

“…Under a microscope, bacteria cells are amazingly alive and perform a whole host of physiological functions, namely, multiplication through cell division, searching for resources by chemotaxis (5-9), controlling water pressure by exchange of ions (through the osmoregulatory system) (10)(11)(12), etc. However, since the introduction of the plate counting method almost 130 y ago, traditional viability assays, such as impedance microbiology, rely on cell multiplication to differentiate between dead and live cells (13)(14)(15)(16)(17)(18)(19). Cell division time can vary from hours to weeks depending on the bacteria type (e.g., 10-20 min for Escherichia coli vs. 15-16 h for Mycobacterium tuberculosis), which makes fast, real time detection of cells challenging, especially at low concentration.…”

Development of a sensor for the detection of Escherichia coli in brackish waters

“…Impedentiometric methods offer another strategy for bacterial pathogen detection [11,12]. A portable sensor implemented as an electronic embedded system featuring disposable measurement cells already described by Grossi et al was used with the aim of evaluating the suitability and the sensitivity of this device in the detection of E. coli contamination in transitional waters [11,12].…”