Abstract
Bacteriophages are responsible for significant material and time losses in the dairy industry. This because these viruses infect the selected lactic starter cultures used for milk fermentation, i.e., the first stage toward cheese production. Standard detection techniques are time- and labor-consuming, causing huge costs related to production plant sanitation and product wasting. A new type of biosensor for early detection of bacteriophage contamination is highly demanded by the milk processing market, and inkjet-printed electrochemical sensors could be the answer. Inkjet printing is a well-known technology that has been revisited in recent years, using silver nanoparticle (AgNP) based inks for low-cost and easy fabrication of sensing and biosensing systems on flexible and eco-compatible substrates. In this research, we studied inkjet printing for the manufacturing of both interdigitated electrodes arrays (IDEAs), and a versatile system to monitor bacterial cultures by electrochemical impedance spectroscopy (EIS). In particular, we studied this biosensing system for the detection of bacteriophages by comparing its performance with standard microbiological methods. We performed electrical and morphological characterizations of the devices produced with a consumer-use inkjet printer with commercial AgNPs ink on flexible substrates, such as office paper, polyethylene (PET), and photo paper. We used light microscopy optical analysis, profilometry, atomic force microscopy (AFM), and scanning electron microscopy (SEM) imaging to define the objects resolution, their real dimensions, and thickness. We also investigated the devices’ conductivity and layout, by EIS measurements with a standard buffer solution, i.e., phosphate buffered saline (PBS). Finally, we tested our system by monitoring Lactococcus lactis cultures and bacteriophage infection. We compared the results to those obtained by two standard microbiological methods in terms of response time, proving that our technique requires less than half the time of other methods and no specialized personnel.
Highlights
IntroductionBacterial viruses (bacteriophages or phages) are naturally occurring parasites that have an antibiotic effect, i.e., they selectively infect only bacteria
Bacterial viruses are naturally occurring parasites that have an antibiotic effect, i.e., they selectively infect only bacteria
We propose a preliminary study on a novel system to detect bacteriophage contaminations by low-cost inkjet-printed biosensors made by an interdigitated electrodes array
Summary
Bacterial viruses (bacteriophages or phages) are naturally occurring parasites that have an antibiotic effect, i.e., they selectively infect only bacteria. Since the amount of milk used in the plants is in the order of tons, the losses could be massive; the strategies to control phages in dairy facilities (such as factory/equipment design, sanitation, and culture rotations), are expensive and time consuming [1]. The detection of dairy phages is typically performed by standard microbiological methods, such as plaque assays, spot tests, and turbidity tests [2]. Many producers prefer to avoid controls for phage presence in the dairy environment, and preventively perform sanitation protocols as often as possible. For industrial purposes, detection of phages by rapid, reliable, and user-friendly methods, such as biosensors, is highly advisable, so a timely intervention can be introduced to prevent fermentation failure
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