Modeling and experiments in microchannels for the separation and detection of bacteria using antibody -coated filter and quantum dots

Narendra Sharma, University of Rhode Island


Capture and detection of biomarkers for organisms is an important aspect in the design of a Lab-on-a-Chip (LOC). In this research, modeling and experiments were conducted to separate, capture and detect E. coli K12 bacteria from water samples using microchannels. Microchannels were fabricated using the soft lithography technique. The bacteria were separated from the sample and captured at a polyester filter whose surface was modified by attaching functional groups that had affinity for antibodies specific to E. coli K12. The bacteria bound to the functionalized filter were then tagged with quantum dots conjugated with E. coli K12-specific antibodies for detection purposes.^ Three different optical methods were tested for bacteria quantification. It was determined that the optical scanner provided the best method for determining the signal intensity of the whole filter, compared with the epifluorescence microscope and the spectrofluorometer. All three methods showed that both filtration and antibodies attached to the functionalized filter contributed to the overall capture rates of the E. coli K12. The presence of K12-specific antibodies not only provided specificity to the capture mechanism, but also increased the capture rates by 106% compared to filtration alone. It was also found that a nonfunctionalized filter did not capture any bacteria, but that on a functionalized filter without any antibodies present, the signal intensity of the quantum dots increased by 177% above background levels, indicating that the process of functionalization caused both a decrease in porosity of the filter so that more bacteria were captured by filtration and an increase in the capture of quantum dots in the fibers/matrix of the filter. Thus, the functionalization of the filters not only enhanced bacteria capture due to the presence of antibodies, but also increased capture rate by filtration. The limit of detection for the system was determined to be 6 x 103 CFU/mL. ^

Subject Area

Engineering, Biomedical|Engineering, Mechanical

Recommended Citation

Narendra Sharma, "Modeling and experiments in microchannels for the separation and detection of bacteria using antibody -coated filter and quantum dots" (2009). Dissertations and Master's Theses (Campus Access). Paper AAI3346856.