The techniques will enable surgery on structures within cells themselves at sizes as small as a thousandth of a millimeter. The science will come into its own where ordinary scalpels are simply too large and cumbersome to perform delicate operations.

The Atomic Force Microscopy technique has already enabled scientists to manipulate single atoms in labs.

This and other techniques have become basic tools used in much research today, in fields such as nano technology.

But even this science is too imprecise to carry out microsurgery and certain biological experiments.

Techniques are now needed to manipulate objects in tiny spaces without deforming them, and the technique of carrying out surgery on organelles - structures within cells themselves - has almost been perfected.

Beams can now be focused onto organelles to hold them in place, acting as "tweezers," while a second beam serves as a scalpel to conduct delicate surgery on the tiny structures.

The technology has been designed and worked on by scientists from around the world, including the Chinese.

Now cell biologists can use "laser tweezers" and "laser scissors" to perform minimally invasive manipulations on living cells and their organelles.

The devices they are working on in labs will soon have practical uses.

A research team from the Science and Technology University of China recently made a major high-tech industry breakthrough with their Optical Micro Manipulation System.

The system is a combination of what scientists call optical tweezers and scissors, using laser beams.

With it, scientists can precisely manipulate micron-sized objects - objects one millionth of a meter in size - such as cells and molecules.

"The Optical Micro Manipulation System is the ideal device for manipulating and processing objects of this size," the experts panel which reviewed the system said in its conclusion. "It has bright prospects in a broad range of scientific researches and practical uses."

The system has already demonstrated stunning precision and steadiness in displays by the team, led by Professor Li Yinmei.

In one display, the optical tweezers penetrate the membrane of a wheat cell and effortlessly move an organelle from one end to the other within the narrow cell, about 100 micrometers long and 10 micrometers in diameter. One micrometer is a thousandth of a millimeter.

In another more sophisticated display, a set of optical tweezers and scissors work together to fuse two living cells together in 40 seconds without damaging their activity.

All manipulations are controlled by computer programs developed by the team, and the process can be viewed using traditional microscopic technology.

At the heart of the system are the optical tweezers and scissors that have laser characteristics such as precision and steadiness.

Optical tweezers use a focused laser beam to trap and manipulate microscopic particles sized between 100 nanometers (one nanometer is a thousandth of a micrometer) and 100 micrometers.

The science uses light to hold and move objects, creating enough force to influence biological processes at sub-cellular level, where targets are infinitesimal.

Objects small enough to be transparent to laser beams of particular frequencies can refract the beams and bend the light.

The refraction creates a momentum which is transferred from the light to the target.

When the geometry of the arrangement of light beams and the target is precise enough, the momentum created pulls the target in the direction of the incident laser beam, which can then hold the target in place.

A single beam can grasp a cell or organelle, but that object may still be able to move slightly; a second beam locks the target in place.

Moving the laser beams enables the laser operator to pull the target from place to place.

"The creation of perfect optical tweezers largely depends on the arrangement of laser beams of varied wavelengths and their refracting angles," said Zhou Hui, a member of the research team. "The approach used in the process can make a great difference."

According to the research team, using lasers to manipulate organelles effectively prevents damage to the cell membrane and areas surrounding the organelle. "Laser is light - which means no physical contact between the laser tweezers and the object," Zhou explained.

"Lasers have varied wavelengths. By choosing the proper wavelength of the laser beams that penetrate the cell membrane, we can position its focal point precisely onto a part within the cell so it doesn't damage the surrounding areas and the cell membrane."

These characteristics could have great significance in the study of biological molecules, he said.

Optical scissors use similar basic principles, but significantly differ from tweezers in the duration and intensity of the laser beams.

Where the tweezers use continuous, low-irradiance beams, the scissors employ short pulses of high irradiance.

Experiments suggest that optical scissors can effortlessly cut open micron-sized holes in living cells that seal within a fraction of second.

If accurately used, it can perform precise cutting in chromosomes and even DNA fragments.

Researchers from the University of California, in the United States, have discovered it is possible to insert foreign genes into living cells that can be "expressed."

This means that the foreign gene is activated within the cell and its properties can be demonstrated by the whole cell.

It is possible that in the near future, genetic diseases will be cured in this way.

The Californian researchers have cooperated with the State Gene Research Center under the Chinese Academy of Sciences to apply the Optical Micro Manipulation System in the study of rice.

So far they have successfully isolated a single rice chromosome, and the system has turned out to be much more efficient and precise than the traditional approach, using enzymes.

According to Zhou, the researchers have been developing the Optical Micro Manipulation System since the early 1990s, making its prototype in 1996.

Although claiming the system is suitable for practical use in particular areas, Zhou admitted it is in need of improvement.

One problem is in the power source, the laser beamer itself.

The Optical Micro Manipulation System is currently equipped with laser beamers made by domestic companies, which can only yield a relatively low output of energy.

"This low energy output significantly affects the dexterity of the optical tweezers and the limits of their ability to move objects," Zhou said.

Another defect is that the system is more agile and precise in moving micro-objects horizontally than vertically, a design fault, said Zhou.

Groups from other Chinese universities are also engaged in this area, and Zhou said they were considering cooperating with major manufacturers in China to produce the system in Shanghai.

If signed and sealed, the project would give a good boost to further research in the area, he added.

(China Daily 02/02/2001)