Friday, July 26, 2013

RET 2013: The IRIS

My research this year is on viral detection and viral sizing. I scan chips that have been spotted with various antibodies, then incubate these chips with virus and re-scan them afterwards. These scans are done on the IRIS, Interferometric Reflectance Imaging Sensor. I will go into how we capture the virus and what viruses I am looking at in more detail in another post (I need to find out what information is OK for public consumption!), but for now I want to talk about how the IRIS works.

Here is a photo of the machine. It is called the SP-IRIS. SP stands for single particle because our pictures are magnified enough to see single viral particles attached to antibodies on the surface of our chip. The drawings below explain what is going on. The first picture is a drawing of the device you see in the photograph above. See the green light in the photo above? In the pic below it is the green line going through two 'lenses.' See Jyothsna's hands in the photo (she has on blue gloves)? She is moving the stage around to place a chip in the correct spot under the objective. Find the objective in the photo below. The box labeled CCD is a camera. It is the white roundish box in the photo above.

The SP IRIS works by shining LED light at a Si/SiO2 chip. See the chip in the picture above? It is blue and grey with red lines coming off of it? Below is what it really looks like. The very small dots are antibody spots.

We put that under the objective and shine green LED light on it. The light reflects off of the different layers on the chip causing interference (look at part (b) below- the grey thing is the chip with light reflecting off of it. The red and green symbols are particles attached to the chip. They change how the light interferes with itself as it bounces off of the chip. When additional materials (for example antibodies and antigens) are adhered to the chip, the resulting height difference changes how the light interferes. The CCD camera images the difference in how the light interacts, thereby indicating how much biomass is adhered to the chip.

    By taking images of the light bouncing off the chip we can tell where the particles are. On our screen we see large light gray spots (see (c)) where we placed the antibodies and if we zoom (see below) in we see small white dots. The white dots are individual viral particles. 

We can count these viral particles to see how many adhered and we can determine how large these particles are by how the interference of the light changed. Most viruses I've looked at are around 70-120 nanometers in length. How big is a nanometer?!?!? The ruler below has centimeters graduated into millimeters, A nanometer is 1 millionth the size of that millimeter. It is SMALL!.

No comments:

Post a Comment