Thread-based microfluidic devices have become attractive platforms for rapid detection due to the low cost, small sample volume and easy use. However, the relatively poor sensitivity has limited their wide applications. Polysiloxanes are inorganic polymers that can resist to breaching by liquids and surfactants with low surface energy. Despite its ability to create hydrophobic zones and channels in the microfluidic devices, the possibility of tuning its hydrophobicity in the microfluidic assays has remained unexplored yet. In this study, we demonstrated a new approach of incorporating polysiloxanes with tunable hydrophobicity into the thread-based microfluidic devices to manipulate the fluidic flow for the enhancement of detection sensitivity. A mixture of methanol and isopropanol was used as a diluent for siloxane precursor, which was included into the thread to enable rapid curing of polysiloxanes for fluidic control. Twelve-fold diluted polysiloxanes achieved desirable fluidic delay and optimum interaction between the targeted antigen and detection antibody-gold nanoparticles (dAb-AuNPs) in the thread-based immunoassay, generating more antigen-dAb-AuNP complexes that bound to the capture antibody at the test zone and achieved ∼10-fold signal enhancement over the unmodified device. The phenomenon of fluidic delay was evaluated by mathematical simulation, through which the fluidic movement on the polysiloxanes-coated region was observed and the simulation mathematical data was agreed with the experimental data. Salmonella enterica serotype Enteritidis was used as a model bacterium and detected by this polysiloxanes-modified device in phosphate buffered saline, spiked whole milk, juice and lettuce with the detection limit of 500, 1000, 1000 and 5000 CFU/mL, respectively. The result was comparable to or even more sensitive than the existing immunoassays. This work expands the application of polysiloxanes in the microfluidic devices for the environmental monitoring, biomedical diagnosis, and food safety surveillance.

Polysiloxanes modified thread-based microfluidic device for the development of an innovative immunoassay to detect Salmonella in food products

2019 Spring National Meeting

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