Projects

Ultra-Sensitive Detection of Breast Cancer Biomarkers Using Time-Resolved FRET and Quantum Dots

Breast cancer is defined as a malignant neoplasm that occurs at or around the breast issue area. This disease affected 25,000 women last year in Canada and claimed the lives of 5,000 women. These numbers represent 26% and 14% of all new breast cancer and deaths, respectively, for Canadian women in 2015. These numbers do not tell us the amount of lives that were affected due to the disease, which can go into the hundred thousands. Here we develop a multiplexed microfluidics chip that accurately detects miR-195 and let-7a in human serum samples. MicroRNAs (miRNA) are small non-coding messenger RNA that are derived from messenger RNA. These small robust RNAs are looked at as precursors to many different diseases including breast cancer. Both miR-195 and let-7a have been shown to increases in concentration in human serum samples during cancer and decrease in concentration within tumor cells during cancer. To effectively measure miRNA concentration in blood with minimally invasive techniques, the developed microfluidics chip detects the miRNA levels from human blood using time resolved-förster resonance energy transfer. The detection mechanism uses a DNA zipper that binds the miRNA with an 8 base pair (bp) DNA supporter sequence and a complementary DNA sequence. When the supporter, complementary and miRNA sequences bind together a terbium-cryptate molecule excites a quantum-dot (710 nm for let-7a and 655 nm for miR-195) and the fluorescence is measured. Detection limits of the miRNAs are 10 picomolar, with a dynamic range of 10 nM to 0.1 nM when measured with microfluidics chips.

Rapid Detection of Food Allergens by Microfluidics ELISA Based Optical Biosensor

The risks associated with the presence of hidden allergens in food have increased the need for rapid, sensitive, and reliable methods for tracing food allergens in commodities. Conventional enzyme immunosorbent assay (ELISA) has usually been performed in a centralized lab, requiring considerable time and sample/reagent consumption and expensive detection instruments. In this study, a microfluidic ELISA platform combined with a custom-designed optical sensor was developed for the quantitative analysis of the proteins wheat gluten and Ara h 1. The developed microfluidic ELISA biosensor reduced the total assay time from hours (up to 3.5 h) to 15–20 min and decreased sample/reagent consumption to 5–10 μL, compared to a few hundred microliters in commercial ELISA kits, with superior sensitivity. The quantitative capability of the presented biosensor is a distinctive advantage over the commercially available rapid methods such as lateral flow devices (LFD) and dipstick tests. The developed microfluidic biosensor demonstrates the potential for sensitive and less-expensive on-site determination for rapidly detecting food allergens in a complex sample system.

Development of Bulk Acoustic Wave Sensors for Detection of Melamine in Milk and Infant Formula

Melamine, a synthetically produced compound, is considered as an illegal adulteration and also a contamination in dairy products. Food contaminated with the trace amount of melamine can result in the urinary calculi and the kidney failure. Health Canada has set a maximum tolerable limit of 0.5 ppm in infant formula and 2.5 ppm in other food products. Different techniques have been employed. However, they need expensive laboratory facilities, which is not applicable for the field test application. Therefore, there is a need for a real-time detection of melamine.

In this project, a Bulk acoustic wave (BAW) sensor was employed to detect trace amounts of melamine in the milk. Using thiolation chemistry, the gold electrode surface was modified to provide selective sensing. A change in mass loading on the crystal, results a shift in resonant frequency. By monitoring the resonant frequency versus the change in the melamine concentration, sensor specification is obtained. The preliminary results show that there is a decreasing trend of the resonant frequency with increase in the concentration of melamine. Bulk wave acoustic sensor has the potential to detect food adulterants such as melamine with higher specificity and sensitivity. The sensor will significantly aid the management of dairy products to preserve quality and thus quality of processed foods made from milk.

Previously described methods to study the motility of Helicobacter pylori (H. pylori) in response to chemical gradients (chemotaxis) are subject to limitations such as false positives, long assay times, and low sensitivity. While automated tracking of individual cells within the well-defined environments produced in microfluidic devices has been successfully applied to study other bacteria, the combination has not previously been reported for H. pylori. Steeper concentration gradients established in our microfluidic device help overcomes some difficulties in fitting the model given in, which explains how a given chemoeffector biases the random walk. Results collected for E. coli help validate performance of the microfluidics, data analysis, since chemotaxis in E. coli is well understood.

Main results include application of the above microfluidic and computer model to study H. pylori response to the known attractant urea, and the known repellent bile acid deoxycholic acid. While it has been found that H. pylori growth is inhibited by capsaicin, it was previously unknown whether capsaicin is an attractant, repellent or otherwise impacts behaviour.

Results help to address an apparent conflict between previous in vitro tests, which suggest that capsaicin inhibits H. pylori growth, and epidemiological studies which link higher capsaicin consumption with morbidity. Analysis of the fitted model suggests whether or not the H. pylori chemotactic response adapts to a background concentration. Evidence for adaptation lends support to the hypothesis that CheV are responsible for this behaviour in H. pylori.

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Contact Us

Bionanotechnology Laboratory
Suresh Neethirajan

School of Engineering
University of Guelph
Guelph, Ontario
Canada N1G 2W1

Office:
Room 3513 - Richards Building
50 Stone Road East

Lab: THRN 2133 BioNano Lab

Phone: (519) 824-4120 Ext 53922
Fax: (519) 836-0227

E-mail: sneethir@uoguelph.ca

 
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