It is the dream of biomedical scientists to be able to classify cells according to different requirements in millions and tens of millions of cell mixtures, find out a few strange mutant cells, or count the number of cells of a particular type, so that this kind of work, which is tantamount to finding a needle in a haystack, can be carried out automatically.
Scientists, physiologists and engineers from Livermore Laboratory in San Francisco and University of California Medical College invented a laser computer counting device called "Cell Classification Optical Machine", which can quickly and accurately detect a cancer cell or other mutant cells from 65438+ 1 100 million normal cells, judge fetal defects through chromosome detection, and distinguish two pairs of sex chromosomes of sperm.
The device consists of a small atmospheric ion laser and a helium ion laser with a power of only 1 watt, as well as two sets of line flow nozzles, an optical system and a computer. The sensor converts the cell flash in the laser beam into a digital signal and sends it to the computer for processing. The computer immediately sorts the cells, and then applies an appropriate voltage to the deflection plate, so that the droplets directly fall into one of the three collectors. The repetition frequency of this process is 2000 times per second.
The first step of the operation is to dye the normal cell mixture taken from the patient with special fluorescent dyes. The requirement of dye is that it has affinity for deoxyribonucleic acid (DNA) in the nucleus and can match the excitation wavelength of argon ion laser. Take distinguishing cancer cells as an example: because cancer cells are usually much larger than normal cells, they can absorb more dyes. Put the dyed cell suspension into a small reservoir with two sets of nozzles, which is very similar to a thin-bottomed straw for drinking soda. Pressurized physiological saline is injected into the jacket of the nozzle, and its function is to eject the cell fluid from the nozzle and disperse the cell fluid into small droplets to form a linear jet, which passes through the laser beam. When laser irradiates the cells adsorbed with dye, the cells will produce fluorescent flash, and the detected fluorescent signal will be converted into digital signal by condensing optical system and sent to computer for data processing. The bigger the cell, the more DNA in the nucleus, the more dyes adsorbed and the stronger the fluorescence signal. This is the basis for distinguishing cancer cells from normal cells. In turn, the signal intensity will give information about the shape and size of cancer cells. This is why the detection rate of cancer cells is one in ten million.
The operation of detecting chromosomes is a bit troublesome. It requires breaking the cells first, leaving only chromosomes and discarding the rest. The rest of the operation is the same as detecting cancer cells. The difference is that argon ion laser and krypton ion laser need to work at the same time. The two laser beams are very close, up and down like two bullets from a double-barrel shotgun, passing through the liquid jet. When a small droplet passes through two beams, it will produce two fluorescent flashes. The interference pattern is generated on the detector through the optical system, and the signal is sent to the computer for processing. Each chromosome has a different interference pattern, and the computer can give a high-resolution outline. Defective chromosomes have unique interference patterns, which can be seen on the computer screen.
The optical machine has novel design concept, simple operation and high cell classification efficiency, which provides a brand-new means for biomedical research and strongly promotes the development of cytotaxonomy.