A lock-in amplifier biosensor for dairy applications

Abstract

Antibiotic exposure can cause the development of antibiotic resistant bacteria and can induce allergic reactions in humans. A source of high antibiotic exposure is contaminated dairy milk. To prevent contaminated dairy milk, development of antibiotic biosensors for on-site detection is required. This is particularly important for dairy farmers as fines and suspension of license are consequences of shipping contaminated milk to processing plants, where antibiotic tests are currently performed. There are also environmental and economic consequences when whole dairy tanks are contaminated and go to waste. Our work addresses this problem by developing an antibiotic biosensor for farmers to test their milk onsite for ciprofloxacin prior to sending to processing plants. Ciprofloxacin is frequently used to treat common bacterial infections in cattle. Our work provides the following contributions. We introduce an antibiotic biosensor that integrates fluorescence spectroscopy, microfluidic processing, and lock-in amplification to improve the limit-of-detection of ciprofloxacin below the regulatory limit for milk. We also perform traditional fluorescence detection for comparison. Our antibiotic biosensor has a signal-flow starting with an ultraviolet light emitting diode for illumination of ciprofloxacin, and moving through a microfluidic platform, a photodiode for detection of the fluorescent wavelength, and a lock-in amplifier. Our antibiotic biosensor is well-suited for fast on-site analyses and is designed for ease-of-use. Overall, our work shows promise for the integration of real-time on-site antibiotic detection of antibiotics in dairy.