Development and Evaluation of Nanobiosensors for the detection of contaminants in food
Allergic reactions to food have evolved into one of the most widespread forms of non-communicable chronic diseases, world-wide. Their interaction with the human body is specific to significant factors such as exposure time, intake levels, mechanism of action, immunological reaction to the allergen and overall metabolism. Small molecule contaminants in food can be broadly classified as toxic and non-toxic substances, based on their origin. Food allergens are protein compounds that stimulate an immunological reaction on ingestion. Mycotoxins, on the other hand (both aquatic and land-based), are secondary metabolites of fungal origin. Addressing the challenge of accidental exposure via food and feed, governing bodies like the World Health Organization (WHO), the US Food and Drug Administration (FDA) and the European Commission have devised regulatory threshold limits and imposed proper labelling measures. Therefore, to maintain food standards, there remains a pressing need for the development and validation of a reliable, sensitive and accurate detection technique for such contaminants. This study involves the development of various bioanalytical platforms for the rapid and sensitive detection of 4 small molecule contaminants: Okadaic Acid (OA), Brevetoxin (BTX), Gliadin and Gentamicin. While OA and BTX are marine biotoxin, Gliadin is one of the major food allergens and Gentamicin is an antibiotic. Affinity biosensors exploring the concepts of electrochemistry, surface plasmon resonance (SPR- optical technique) and quartz crystal mass balance techniques were fabricated and analyzed. While the transduction elements were varied through the study, the bio-recognition element was chosen to be a highly specific, single-stranded DNA called ‘aptamer’. The chapters in this thesis explore an electrochemical approach to determine the extent of Okadaic Acid and Gliadin in food samples. An optical biosensing route using gold nanoparticles was adapted for the detection of Gentamicin in milk, performed on a paper sensor. Further, a piezoelectric mass balance technique was chosen to determine the extent of BTX in shellfish samples. Each of the biosensing platforms discussed in this thesis was optimized to performance and studied for their sensitivity, selectivity, repeatability and stability.