Nano Technology Electronic Biosensors for Food Safety

Gary K. Maki, Nirankar Mishra, Shiva Rastogi, Paul Winterrowd, Eric Cameron and Wusi C. Maki

Center for Advanced Microelectronics Biomolecular Research, University of Idaho, Post Falls, ID 83854, USA

E-mail: gmaki@cambr.uidaho.edu

ABSTRACT

Nanosensor-based device creation must be approached as a system design as opposed of an assembly of technologies combined into a product. The work described here is an example system design that produced an electronic biosensor targeted for agrifood biosafety. The system expertise required for such a device component includes nano technology (in this case, nanotransistor design), surface chemistry, organic chemistry, molecular biology and electronics. A proper system design cannot be achieved without such integrated expertise. This paper describes an electronic nanotransistor-based sensor with excellent sensitivity with demonstrated results in the detection of Staphylococcus aureus.

Electronic nanotransistor design

Most nanotechnology currently targets basic science, which is the logical place to begin a new national technology program. System level design targeting practical nano devices is not well addressed at this point in time. Most attempts at nano system design involve experts from one or two disciplines, not the required four or five. In the system proposed here, each discipline area of nanotechnology, surface chemistry, organic chemistry, molecular biology and electronics play critical roles; deletion of any one area will deeply affect the final system performance.

The preliminary work reported herein presents an integrated electronic molecular sensor for the detection of Staph. aureus, which is a versatile and dangerous pathogen in humans. The frequencies of both community-acquired and hospital-acquired staphylococcal infections have increased steadily, with little change in overall mortality. This microorganism causes also severe animal diseases, such as suppurative disease, mastitis, arthritis, and urinary tract infection, which associate with numerous virulence factors, such as the production of extracellular toxins and enzymes. Staph. aureus is a major pathogen in bovine intramammary infections of subclinical and chronic nature. Some strains of Staph. aureus may induce a relatively mild response in mammary glands of cows in mid lactation, and that the concomitant development of such chronic Staph. aureus infections in two quarters may not be detected by changes in the EC of composite milk and in the yield of the cow. From May 2001 to April 2003, various types of specimens from major food animals, including cattle, pigs, and chickens, were collected and examined for the presence of Staph. aureus in South Korea. The results showed that 421 contained Staph. aureus among 1,913 specimens collected from the animals. More seriously, methicillin-resistant Staph. aureus was reported breaking out in a veterinary teaching hospital, suggesting a potential human-to-animal transmission, raising health risk to both animals/human handlers. The first line of defense is early and accurate detection in infected animals.

Current detection methods for Staph. aureus infection heavily depend on the microbial culture process. Protein A, a surface protein of this microorganism, non-specific binding to various antibodies cause problems in immuno-detection. The techniques used for Staphylococcus aureus identification include Gram staining, colony morphology, tests for coagulase and urease activities, and an API Staph Ident system. These conventional methods are time consuming. Therefore, new technology to improve detection of Staphylococcus aureus will have a great impact in animal health and food safety.

The proposed work seeks to build upon the excellent basis established by CAMBR (Maki et al. 2007a,b, Mishra et al. 2007, Rastogi et al. 2007). A promising new nano technology sensor has been demonstrated in the last 6 months based on nano electronic detectors which promise high sensitivity, low-cost, and portable diagnostics. CAMBR has a working relationship with the Cornell NanoScale Facility (CNF) where specific nano scale transistors are fabricated. At this writing, nano detection devices have been demonstrated in the laboratory and show excellent potential (Mishra et al. 2007, Maki et al. 2007a).

Shown in Figure 1 is a system level view of the final electronic biosensor device (Maki et al. 2007a,b). The system consists of the detector composed of both micro and nano electronic devices. Staph. aureus 16S rRNA and Toxin B are used as target molecules in the nucleic acid and protein detection models. A unique signal transduction system is used in the target capturing process and generation of signal molecules which are captured and detected on the sensing surface. The presence of signal molecules on the sensing surface will change electronic properties of nano-transistor and generate a detectable electronic signal. The nano-electronic interface with micro-electronics translates low level analog signals to digital signals which are input to an on-chip microprocessor. The microprocessor provides the embedded intelligence for the final user and provides communication ports with numerous devices including cell phones, the Internet, satellites or other computers. Such a system, being portable, has attractive features for animal point of contact health care.

Shown in Figure 3 are experimental results from the nanotransistor system which demonstrate detection at 10^-18 moles for Staph. aureus Toxin B.

Figure 1: Overview of electronic nano biosensor

Figure 2: Nano Transistor

Figure 3: Detection of Staphylococcus aureus Toxin B

References

Mishra, N, Winterrowd, P, Nelson R, Rastogi, S, Maki, W and Maki, G. 2007. Fabrication and characterization of nano-field effect transistor for bio-safety, Nano Science and Technology Institute, NanoTech 2007, www.nsti.org , ISBN 1420061836 Vol. 2, pp 453-456.

Maki, G, Mishra, N, Rastogi, S, Filanoski, B, Nelson, R, Cameron, E, Winterrowd, P and Maki, W. 2007 (accepted) Electronic non-semiconductor biomolecular pathogen detector. Nanotechnology Applications in Agriculture and Food Systems, American Chemical Society.

Maki, W, Mishra, N, Cameron, E, Winterrowd, P, Rastogi, S and Maki, G. 2007. A universal signal transduction nano transistor based system for biomolecular detection. Nanoelectronic Devices for Defense & Security Conference, June, 2007.

Rastogi, S, Mishra, N, Winterrowd, P, Nelson, R, Maki, W and Maki, G. 2007. Peptide nucleic acids modified nano-biosensor for early cancer diagnosis. Nano Science and Technology Institute, NanoTech 2007, www.nsti.org, ISBN 1420061836, Vol. 2, pp 443-446.