A biologist specializing in skin research, he has been working to invent an artificial skin that may almost be considered as the real thing.

After more than 10 years of research and experimentation, Wu, a doctor and researcher in Southwest China's Chongqing Municipality, believes he is close to achieving that goal.

His research team at the Daping Hospital, affiliated with the No.3 University of Military Medicine in Chongqing, recently created a new type of artificial skin by using natural materials.

Tests show the skin is infection-resistant after it is grafted onto wounded areas.

It is reportedly the first such case in which anti-infection artificial skin has been developed.

The man-made product is of special significance to burns patients and people with other skin diseases where infection is a major challenge to regrowth.

More than 100,000 people suffer from severe burns each year in China. Most of them need new skin to heal wounds and regain confidence, Wu said.

Diabetes and cancer patients are other groups of sufferers in China who will benefit from the invention.

More than 1.2 million diabetes and cancer patients need urgent skin transplants each year, according to a survey by Ministry of Health of China.

"We are very much encouraged by the experimental results that fit our expectations," Wu said, "It has brought us a step forward on a long course."

Before Artificial Skin

For burns victims, the commonly used method is to take skin from other parts of their body and stretch it out before covering wounds.

Known as autografts, the method can be impracticable for patients who have been left with very little skin.

Wu said attempts had been made to use animal skin as a substitute in such extreme cases.

Wu said experiments were being carried out to graft frogs skin onto the human body as early as 1,500 years ago in Egypt, followed by trials with rabbits and dogs.

Bovine skin has been widely used in recent times because of its availability in large quantities.

There is a catch with bovine skin as it does not take to human skin well, due to an inability to obtain blood, and falls off.

Cadaver skin is another major source, but there was always the risk of rejection by the patient's body, Wu said.

Artificial skin, therefore, has aroused interest in medical researchers.

"The trend in the international medical community appears to have turned from autografts to artificial substitutes," Wu said.

He said artificial skin had to protect the body from water loss, infection and allow new skin to grow.

An ability to satisfy those criteria rested with the materials being used to make the skin.

New Substance

The new generation artificial skin comprises a collagen matrix in which normal human skin cells are cultured in two layers.

The double-layer structure resembles real skin, which is composed of epidermis and dermis that sits on a layer of fat-producing cells called the subcutaneous tissue.

The collagen matrix was created out of animal tendons and cartilage.

"All the materials used are natural," Wu said.

A shrimp, crab and insect extract called chitosan, which makes the skin immune to bacteria, is added to the collagen.

Chitosan, once used as a dietary supplement to reduce unwanted body fat, assists the collagen fibers to grow around the wound and eventually turns into skin.

Chitosan also makes the artificial skin more elastic and resilient, allowing for easier surgical use.

"You can close the wounds with any sizes or shapes with the substitute skin," Wu said.

"It has appeared to grow well with the surrounding skin."

A research team at the Nanyang Technological University in Singapore has reportedly taken a similar approach by growing skin cells around a scaffold of chitosan.

The scaffold is gradually absorbed by the human skin.

Wu's artificial skin also solved another long-standing problem in the field.

Artificial skin previously developed with collagen often contracted by up to 80 percent.

It means a big amount of skin is needed to treat severe burns.

Wu's team has completed successful tests on rats. The artificial and rat's skin meshed after three months and new blood vessels began to grow in the artificial skin.

Now Wu and his colleagues are planning to proceed to clinical trials, to test the artificial skin on humans.

Wu said they had applied to the relevant administrative authorities for heath approvals for the trials and he hoped to be undertaking the tests early next year.

The Singapore-based research team is yet to carry out animal testing and plans to be offering their product within five years.

So will such artificial skin be able to function as well as real skin?

Despite its qualities, Wu does not think so. He says it still lacks the ability to regulate heat and excrete sebum.

The team's next step is to develop artificial skin with hair follicles and sebaceousand sweat glands.

Structure and Function

The epidermis is the outermost layer of skin and consists of four layers.

Several kinds of cells are formed in the innermost layer (the basal cell layer or stratum germinativum) and they push their way to the outermost layer (the horny layer or stratum corneum).

In the process the live cells turn into dead, hard, flattened cells. Dead cells on the surface are constantly being shed or rubbed off, making way for newer cells from below.

The horny layer of the epidermis is the body's first layer of defence.

It consists primarily of flattened cells, called keratinocytes, which are joined together by skin lipids. The lipids are a combination of four fats.

The horny layer is similar to a brick wall with mortar.

It prevents most substances from passing into lower layers, only a few very light oils and skin identical substances can penetrate deeper.

Besides keratinocytes, the basal cell layer also produces melanocytes, a cell that produces a substance called melanin.

Melanocytes are stimulated to produce melanin by ultraviolet (UV) rays in sunlight.

Melanin is a dark pigment which blocks UV rays.

The greater the exposure to sunlight, the greater the production of melanin.

The dermis is the foundation of the skin.

It contains blood and lymphatic vessels, sweat glands, hair follicles, sebaceous glands and nerve endings.

They are held together by collagen and elastin fibers, which together give skin its strength and flexibility.

Blood and lymphatic vessels in the skin do more than just bring nutrients to skin cells and carry away waste.

They also act as heat regulators, similar to a car radiator.

These vessels dilate when hot and carry more fluid, radiating heat to the outside.

When you feel cold, they contract to reduce the flow of fluid to the body's surface and preserve body heat.

Sweat glands also help regulate temperature by producing sweat, which evaporates from the surface to lower skin temperatures.

Hair follicles produce hair. There are also sebum-producing sebaceous glands, which forms a majority of the lipids in hair and skin.

An excess of sebum makes skin look and feel oily.

The dermis stores a substance called sterol, which in itself is of no use to the body.

It is, however, converted into Vitamin D by UV rays, so a certain amount of sunlight is good for the body.

The subcutaneous (meaning below the skin) layer is a fatty region that is not always considered part of the skin.

Its health, however, has a direct bearing on the dermis and the epidermis.

(China Daily August 9, 2002)