Disgraced cloning scientist Hwang Woo-suk's controversial NT-1 "embryonic stem cell line" officially received a United States patent on Tuesday in a development that could reignite debate surrounding his research.

The U.S. Patent and Trademark Office's (USPTO) public notification site confirmed the "human embryonic stem cell line prepared by nuclear transfer of a human somatic cell into an enucleated human oocyte" has been patented and subject to legal protection.

The office added that a patent has also been granted for the process of making the stem cell line.

The patent, given registration number 8,647,872, listed 15 inventors including Hwang; Roh Sung-il, the head of MizMedi Hospital; Lee Byeong-chun, a veterinary professor at Seoul National University (SNU); and former research assistant Kang Sung-keun.

The NT-1, first announced in 2004, is the only cell line that actually exists, as others that Hwang and his team claimed to have created were later proven to have been fabricated.

There are still contesting views on whether the sole remaining cell line actually consists of human embryonic stem cells as claimed by Hwang. There has even been speculation that it may be ova that went through a parthenogenesis process and started dividing up on their own. This view was advocated by the SNU team that carried out research on Hwang's work in 2006.

Related to the patent, experts said that while the patent provides legal protection, it does not mean that the cells and production process have been proven scientifically.

Besides the NT-1, there has never been a repeat of anyone creating a human embryonic stem cell. Although they have never been created, pluripotent human stem cells theoretically have considerable therapeutic potential for paraplegics and could open a new page in regenerative medicine because such cells can be turned into any organ in the body.

South Korean observers said that because no one has actually made stem cells, it will be difficult for Hwang to make money with the patent. They pointed out that U.S. patents can be received for ideas, even if they have never been tested.

On the other hand, Hwang may use the patent to ask Seoul to lift the ban on research that has been turned down twice since he was barred from continuing the work more than seven years ago.

"The patent is important because it officially confirms that the NT-1 is a human embryonic stem," argued Hyun Sang-hwan, a professor of animal science at Chungbuk National University. The professor who acts as the unofficial spokesperson for Hwang, however, did not say what actions will be taken in the future.

In 2011, Hwang, a former professor at Seoul National University, was convicted of embezzling research funds and illegally buying human eggs for research in violation of the country's ethics code, though he was cleared of fraud and never went to jail. Hwang had admitted early on that his team had created false data, yet insisted he was unaware of such actions until the accusations were raised.

Despite such setbacks, Hwang currently leads the Sooam Biotech Research Foundation that is engaged in bio-engineering work, including an ongoing effort to clone a mammoth.

He is credited with being the first person to clone a dog in 2005. (Yonhap)