HONG KONG, April 8 (Reuters) - Scientists in Singapore have developed a strategy to "clean up" embryonic stem cells, which researchers hope can one day be used to replace damaged tissues and for other tailor-made personal treatments.

Embryonic stem cells are master cells that can grow, or "differentiate", into any type of cell or tissue, and are subsequently transplanted into the body.

But some studies have shown that residual stem cells that fail to differentiate can turn cancerous later on.

In the journal Stem Cells, scientists in Singapore said they generated antibodies that successfully killed off these residual stem cells in mice.

"Although human embryonic stems cells are a very powerful source to make differentiated cells, like heart cells, the problem is that you can have residual cells and there is a safety concern because they can form ... a mass of tumour cells," said Andre Choo, senior scientist at the Bioprocessing Technology Institute in Singapore.

"So if you give a product that is 95 percent heart cells, but 5 percent embryonic stem cells, it may be a problem later on," he said by telephone.

The researchers managed to generate antibodies in mice after injecting human embryonic stem cells into the animals.

The antibodies were then harvested and added to cultured embryonic stem cells that had been newly differentiated on laboratory dishes.

"It (the antibody) specifically eliminated undifferentiated cells within 30 minutes but left differentiated cells untouched," the researchers wrote.

The mixture was later injected into a batch of mice, while another batch of mice were given untreated stem cells.

After 6 to 8 weeks, the researchers detected tumours in the mice that received untreated stem cells, but those that received the mixture of stem cells and antibodies were free of tumours even after 20 weeks.

"We made antibodies that can kill them (undifferentiated stem cells) ... it acts as a clean up step for you to remove any of these rogue cells or potentially problematic cells," Choo said. (Reporting by Tan Ee Lyn; Editing by Alex Richardson)

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