Sensing of phage-triggered ion cascades (SEPTIC)
Encyclopedia
Sensing of phage-triggered ion cascades (SEPTIC) is a bacterium identification method based on fluctuation-enhanced sensing
in fluid medium. The advantages of SEPTIC are the specificity and speed (needs only a few minutes) offered by the characteristics of phage infection, the sensitivity due to fluctuation-enhanced sensing
, and durability originating from the robustness of phages. An idealistic SEPTIC device may be as small as a pen and maybe able to identify a library of different bacteria within a few minutes measurement window.
s as indicators to trigger an ionic response by the bacteria during phage infection. Microscopic metal electrodes detect the random fluctuations of the electrochemical potential due to the stochastic fluctuations of the ionic concentration gradient caused by the phage infection of bacteria. The electrode pair in the electrolyte with different local ion concentrations at the vicinity of electrodes form an electrochemical cell
that produces a voltage depending on the instantaneous ratio of local concentrations. While the concentrations are fluctuating, an alternating random voltage difference will appear between the electrodes. According to the experimental studies, whenever there is an ongoing phage infection, the power density spectrum of the measured electronic noise
will have a noise spectrum
while, without phage infection, it is a 1/f noise spectrum. In order to have a high sensitivity, a DC electrical field attracts the infected bacteria (which are charged due to ion imbalance) to the electrode with the relevant polarization.
, and durability originating from the robustness of phages. An idealistic SEPTIC device may be as small as a pen and maybe able to identify a library of different bacteria within a few minutes measurement window.
and Maria Dobozi-King in 2004, and developed and demonstrated at the Electrical and Computer Engineering department of Texas A&M University
in collaboration with Mosong Cheng, Ry Young, Sergey M. Bezrukov
(NIH), and Bob Biard. A new, related scheme, BIPIF, that has recently been conceived and analyzed by Laszlo B. Kish
and Gabor Schmera (SPAWAR, United States Navy
) utilizes the AC impedance fluctuations at related arrangements, and it promises higher sensitivity and less dependence on the electrodes.
Fluctuation-Enhanced Sensing
Fluctuation-enhanced sensing is a specific type of chemical or biological sensing where the stochastic component, noise, of the sensor signal is analyzed...
in fluid medium. The advantages of SEPTIC are the specificity and speed (needs only a few minutes) offered by the characteristics of phage infection, the sensitivity due to fluctuation-enhanced sensing
Fluctuation-Enhanced Sensing
Fluctuation-enhanced sensing is a specific type of chemical or biological sensing where the stochastic component, noise, of the sensor signal is analyzed...
, and durability originating from the robustness of phages. An idealistic SEPTIC device may be as small as a pen and maybe able to identify a library of different bacteria within a few minutes measurement window.
The mechanism
SEPTIC utilizes bacteriophageBacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria. They do this by injecting genetic material, which they carry enclosed in an outer protein capsid...
s as indicators to trigger an ionic response by the bacteria during phage infection. Microscopic metal electrodes detect the random fluctuations of the electrochemical potential due to the stochastic fluctuations of the ionic concentration gradient caused by the phage infection of bacteria. The electrode pair in the electrolyte with different local ion concentrations at the vicinity of electrodes form an electrochemical cell
Electrochemical cell
An electrochemical cell is a device capable of either deriving electrical energy from chemical reactions, or facilitating chemical reactions through the introduction of electrical energy. A common example of an electrochemical cell is a standard 1.5-volt "battery"...
that produces a voltage depending on the instantaneous ratio of local concentrations. While the concentrations are fluctuating, an alternating random voltage difference will appear between the electrodes. According to the experimental studies, whenever there is an ongoing phage infection, the power density spectrum of the measured electronic noise
Noise (electronics)
Electronic noise is a random fluctuation in an electrical signal, a characteristic of all electronic circuits. Noise generated by electronic devices varies greatly, as it can be produced by several different effects...
will have a noise spectrum
Spectral density
In statistical signal processing and physics, the spectral density, power spectral density , or energy spectral density , is a positive real function of a frequency variable associated with a stationary stochastic process, or a deterministic function of time, which has dimensions of power per hertz...
while, without phage infection, it is a 1/f noise spectrum. In order to have a high sensitivity, a DC electrical field attracts the infected bacteria (which are charged due to ion imbalance) to the electrode with the relevant polarization.
Advantages
The advantages of SEPTIC are the specificity and speed (needs only a few minutes) offered by the characteristics of phage infection, the sensitivity due to fluctuation-enhanced sensingFluctuation-Enhanced Sensing
Fluctuation-enhanced sensing is a specific type of chemical or biological sensing where the stochastic component, noise, of the sensor signal is analyzed...
, and durability originating from the robustness of phages. An idealistic SEPTIC device may be as small as a pen and maybe able to identify a library of different bacteria within a few minutes measurement window.
History
The SEPTIC concept was first conceived by Laszlo B. KishLaszlo B. Kish
László Bela Kish is a physicist and professor of Electrical and Computer Engineering at Texas A&M University. His activities include a wide range of issues surrounding the physics and technical applications of stochastic fluctuations in physical, biological and technological systems, including...
and Maria Dobozi-King in 2004, and developed and demonstrated at the Electrical and Computer Engineering department of Texas A&M University
Texas A&M University
Texas A&M University is a coeducational public research university located in College Station, Texas . It is the flagship institution of the Texas A&M University System. The sixth-largest university in the United States, A&M's enrollment for Fall 2011 was over 50,000 for the first time in school...
in collaboration with Mosong Cheng, Ry Young, Sergey M. Bezrukov
Sergey M. Bezrukov
Sergey M. Bezrukov is a biophysicist notable for his work on ion channels and stochastic resonance.-Education:He received his MS in Electronics and Theoretical Physics fromSaint Petersburg Polytechnical University, 1973; and he obtained his PhD under...
(NIH), and Bob Biard. A new, related scheme, BIPIF, that has recently been conceived and analyzed by Laszlo B. Kish
Laszlo B. Kish
László Bela Kish is a physicist and professor of Electrical and Computer Engineering at Texas A&M University. His activities include a wide range of issues surrounding the physics and technical applications of stochastic fluctuations in physical, biological and technological systems, including...
and Gabor Schmera (SPAWAR, United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
) utilizes the AC impedance fluctuations at related arrangements, and it promises higher sensitivity and less dependence on the electrodes.