Spectroscopic biosensors for pathogen detection
Abstract
The advancements in miniaturized instrumentation have accelerated the development of biosensors capable of integrating biorecognition and spectroscopy tools with specifications capable of supporting pathogen detection to address safety concerns in the food supply chain. The ideal method for pathogen detection would require minimal sample preparation, rapid and automated analysis, non-invasive and quantitative inexpensive assessment. Among the available techniques, FTIR and Raman spectroscopies are particularly attractive as they possess inherent molecular selectivity, and can perform both qualitative and quantitative analysis of various chemical and biological species. When integrated with effective sample processing modules, they can be developed into highly sensitive and accurate biosensor technologies. Two simple yet innovative pathogen detection tools were developed for rapid and precise detection. One method involves pathogen capture from complex food matrices such as 2% milk and spinach extracts using magnetic nanoparticles to realize the detection using a portable mid-IR spectrometer. The second method demonstrates Raman spectroscopy based multiplex detection with a cross-platform module using aptamers and antibodies. Magnetic nanoparticles functionalized with anti-E. coli O157:H7 or anti-S. typhimurium antibodies that can specifically bind to their target organisms were used to isolate E. coli O157:H7 and S. typhimurium separately from a cocktail of bacteria and from food matrices. Highly selective detection was achieved in less than 30 minutes at both species and strain levels with a limit of detection (LOD) of 104 - 10 5 CFU/ml. In a second method, Gold (Au), Silver (Ag), and Ag-Au Core-shell nanoparticles were functionalized with anti-S. typhimurium aptamers, anti-S. aureus and anti-E. coli O157:H7 antibodies respectively and labeled with unique Raman reporters (or Raman labels). A microfiltration driven platform was developed to complete the detection in less than 45 minutes at both species and strain levels with a LOD of 2*10 2 – 6*102 CFU/ml. Usage of three types of nanoparticles for pathogen detection using UV-Visible and Raman spectroscopies with multiplexing up to 3 simultaneous targets, all using a single standard laser line, was demonstrated. Development of smart and robust sample preparation methods can lead to effective incorporation of similar strategies over a wide array of currently available Mid-IR technologies that can be used in field at sites-of contamination as portable sensors.
Degree
M.S.E.
Advisors
Irudayaraj, Purdue University.
Subject Area
Agricultural engineering|Biomedical engineering
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