It used to be the scourge of New York. Graffiti - the anarchistic street painting used to scar subway trains and walls.

But now graffiti art is taking hold in a big way and advertisers are sitting up and taking notice.

Sento, a graffiti artist, is spraying his message and his tag line across a wall.

His canvas is no longer an inner city ghetto. These days, he is putting together his first exhibition of his work for an art gallery in fashionable downtown Chelsea.

The move upmarket

Graffiti has come a long way in New York, the city known as the Mecca of street art. It is now a fixture in New York's galleries and museums.

Sento is following in the tradition of graffiti legends like Keith Haring and Jean Michel Basquiat.

"You can do just about anything with a spray can that you can with any other medium.

"It should be an art form that is respected for what it is and not for what the media portray it as.

"Hopefully, I can inspire the kids in a positive way - to do something with yourselves. If you follow your dream, you can get somewhere," he says

The Martinez Gallery has been at the forefront of efforts to get graffiti acknowledged as art.

Owner Hugo Martinez says: "A lot of it comes from being bombarded by logos, trademarks and superheroes."

It is a far cry from the days when every subway train in New York was scarred with graffiti.

New York City cleans up

Due to aggressive clean up efforts over the last few years, trains cannot enter stations if they have been hit with a spray can.

Teams of cleaners work round the clock to keep the subways clear of street art.

New York City's mayor, Rudolph Giuliani, ordered the transformation. His 'graffiti czar', Augostino Camgeni, has been supervising the clean-up.

"People feel better living here. It allows business owners to feel proud of the property and they want to stay and continue to stay. It reduces their business costs," says Mr Camgeni.

Graffiti arrests continue

Graffiti is still a dirty word in New York. More than 1200 people have been arrested so far this year for wielding spray cans.

However, the commercial world is increasingly being won over by its charms.

Artists who used to spray walls to make a statement against advertising are now finding that the companies they used to disdain are supporting them in their work.

Today graffiti artists like the Tats Cru group from the Bronx are working for one of America's biggest plumbing companies.

They are borrowing from the advertising style of the 1950s to convey their message.

They also help to promote multinational soft drink and sports shoe manufacturers.

No 'sell-out'

These graffiti artists refute suggestions by purists that they are selling out.

"They can't tell us we're selling out because we've been part of this movement for over 20 years.

"We've done it all: the subways, the street bombing, the whole deal.

"What we're doing is a natural progression. We've done all of that other stuff. We took it to the next level.

"What we do now, as opposed to going out and bombing, we collaborate with these artists from throughout the world and put together these huge murals," says Bio, a Tats Cru artist.

Rebellious youngsters in New York have used graffiti to make themselves heard for decades.

There may still be a debate over whether it is a pest or an art form. But no one disputes that it will continue to mark the streets of the city for many decades more.