Biosensors and Biodetection

Volume 1571 of the series Methods in Molecular Biology pp 287-299


Rapid Detection of Microbial Contamination Using a Microfluidic Device

  • Mustafa Al-AdhamiAffiliated withUniversity of Maryland Baltimore County
  • , Dagmawi TilahunAffiliated withUniversity of Maryland Baltimore County
  • , Govind RaoAffiliated withUniversity of Maryland Baltimore County
  • , Chandrasekhar GurramkondaAffiliated withUniversity of Maryland Baltimore County
  • , Yordan KostovAffiliated withUniversity of Maryland Baltimore County Email author 

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A portable kinetics fluorometer is developed to detect viable cells which may be contaminating various samples. The portable device acts as a single-excitation, single-emission photometer that continuously measures fluorescence intensity of an indicator dye and plots it. The slope of the plot depends on the number of colony forming units per milliliter. The device uses resazurin as the indicator dye. Viable cells reduce resazurin to resorufin, which is more fluorescent. Photodiode is used to detect fluorescence change. The photodiode generated current proportional to the intensity of the light that reached it, and an op-amp is used in a transimpedance differential configuration to ensure amplification of the photodiode’s signal. A microfluidic chip is designed specifically for the device. It acts as a fully enclosed cuvette, which enhances the resazurin reduction rate. In tests, the E. coli-containing media are injected into the microfluidic chip and the device is able to detect the presence of E. coli in LB media based on the fluorescence change that occurred in the indicator dye. The device provides fast, accurate, and inexpensive means to optical detection of the presence of viable cells and could be used in the field in place of more complex methods, i.e., loop-meditated isothermal amplification of DNA (LAMP) to detect bacteria in pharmaceutical samples (Jimenez et al., J Microbiol Methods 41(3):259–265, 2000) or measuring the intrinsic fluorescence of the bacterial or yeast chromophores (Estes et al., Biosens Bioelectron 18(5):511–519, 2003).

Key words

Contamination detection device Resazurin Resorufin E. coli detection Microfluidic device Thermal bonding of PMMA