1. Presented By : Laleh Mehryar (871101007) Dear Professor : Dr. Rezazadeh Department of Food Science, Urmia University Seminar 1

2. Father of the Biosensor Professor Leland C Clark Jnr 1918–2005

3. Review

4. What is a Biosensor? in : Biosensor (www.google.com) International Union of Pure and Applied Chemistry (IUPAC) defines biosensor as a “device that uses specific biochemical reactions mediated by isolated enzymes, immunosystems, tissues, organelles or whole cells to detect chemical compounds usually by electrical, thermal or optical signals”.

6. Block Diagram of a Biosensor Sample (Analyte or Substrate) Biorecognition Element Transducer Signal Processing Device Olfactory Membrane Olfactory Nerve Cell Introduction to Biophotonics – Prasad - John Wiley & Sons © 2003 odor Brain

10. 1 2 3 4 5 6 7 8 9 analyte BM Signal transducer Affinity reaction How it works ???

11. The ability to determine the occurrence of food contamination due to foodborne pathogens at every stage of food production , processing , and distribution is crucial to improving the safety of our food supply. There are more than 250 known food borne diseases caused by bacterial and viral infections in the United States. Annually, these foodborne diseases result in an estimated 76 million illnesses, 325,000 hospitalizations, 5,000 deaths, and 6 billions dollars in unneeded expenditure. Bacterial contamination accounts for 91% of total foodborne diseases. Salmonella sp., Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, Campylobacter jejuni, Campylobacter coli and Bacillus cereus were found to be main source of bacterial contaminations in our food supply.

35. Biosnsors for detection of: L. monocytogenes

40. Magnetoelastic biosensor for the detection of Salmonella typhimurium in food products

42. Fig. Schematic drawing illustrating the wireless nature of the magnetoelastic biosensors and the basic principle for detecting bacterial cells. The fundamental resonant frequency of the biosensor is f 0 without antigen binding, which shifts (decreases) to f analyte due to the increased mass of antigen binding to antibody immobilized on the sensor surface(2). Salmonella

46. Sensor surface bacterial densities of 0.105, 0.075 and 0.105 cells/µm 2 were observed on the samples which were exposed to S. typhimurium suspensions in water, fat-free milk, and apple juice respectively at the highest bacterial concentrations(2).

47. The Escherichia coli O157:H7 DNA detection on a gold nanoparticle-enhanced piezoelectric biosensor E. Coli (2)

50. Nanoparticles are a new class of materials, which has been adopted for improving the detection limit and sensitivity of the DNA biosensors. In order to form a more effective and sensitive system , we adopted the gold nanoparticles in the construction of E. coli O157: H7 DNA biosensor for the goal of signal amplification, because (i) colloidal Au has a good biocompatibility ; (ii) gold nanoparticle has a larger surface area , and helps to immobilize more biofunctional molecules onto the surface of the sensor; (iii) avidin-conjugated Au nanoparticle could be used as “mass enhancer” to amplify the frequency change depending on its relatively large mass compared to DNA target.

51. The whole detection course of this QCM DNA sensor mainly included two parts: sensor fabrication and detection . During the process of sensor fabrication, how to immobilize more ssDNA probes was pivotal for the following bacteria DNA detection, so two important routes for DNA probes immobilization were introduced to this part, which were: • Self-assembled monolayers (SAMs). • Au-thiol binding . A stepwise decrease of Δ f was observed in each fabrication step(6).

55. E. coli

61. Any Questions???

62. The End Thanks