나노입자, 멀리서도 DNA 손상
나노미터 수준의 미세한 금속 입자가 세포막을 통과하지 않고서도 세포의 DNA를 변화시키거나 파손시킬 수 있다는 사실이 밝혀졌다고 BBC 뉴스가 최신 연구를 인용 보도했다. 영국 브리스톨 이식연구센터 과학자들은 네이처 나노테크놀로지 저널 최신호에 이런 연구 결과를 발표하면서 나노 입자에 의존하는 의학 치료가 늘어나는 현실에서 이는 나노물질의 메커니즘이 약이 될 수도, 독이 될 수도 있음을 의미하는 것이라고 지적했다.
나노입자는 최근 MRI 영상의 화질을 높이거나 암치료 약물을 직접 전달하는 운반용으로 고려되고 있다.
연구진은 나노미터(10억분의1m), 또는 마이크로미터(100만분의1m)급 입자들이 이전에 관찰된 적이 없는 세포의 신호 과정을 통해 DNA의 파손 정도를 증가시키는 것으로 나타났다고 밝혔다.
이들은 실험실의 비교적 단순한 모델을 이용해 30나노미터, 또는 4마이크로미터 크기의 코발트와 크롬 입자의 효과가 어떻게 나타나는지 관찰했다. 이 두 종류의 금속은 인공 고관절이나 인공 무릎관절 등의 이식에 사용되는 물질이다.
연구진은 사람의 세포를 이용해 가느다란 인공막을 배양한 뒤 그 위에 나노 입체들을 얹었으며 밑에는 연결조직을 형성하는 데 중요한 역할을 하는 섬유아(芽)세포들을 배치했다.
그 결과 금속 나노입자들이 막을 통과하지 않았는데도 세포막 밑의 섬유아세포들은 나노입자가 없는 경우보다 10배나 많은 DNA 손상이 일어난 것으로 나타났다.
연구진은 그러나 `갭 결합’과 `헤미채널’ 등 세포 간 연락 구조를 차단하는 다양한 화학물질을 사용해 본 결과 이런 손상이 완전히 예방되는 것으로 밝혀졌다면서 따라서 인체 이식물질이 신호체계를 통해 위험을 야기한다고 볼만한 이유는 없다고 지적했다.
이들은 그러나 DNA 손상을 일으키는 것으로 보이는 메커니즘이 이들 물질에 국한되는 것인지, 아니면 같은 크기의 다른 물질이 있을 때도 일어나는지는 더 연구해야 할 과제라고 말했다.
youngnim@yna.co.kr
(서울=연합뉴스)
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PARIS — Scientists reported Thursday that nano-particles used in medical applications can indirectly damage DNA inside cells by transmitting signals through a protective barrier of human tissue.
The stunning discovery adds to a growing body of research highlighting proven and potential health hazards from the rapidly expanding universe of engineered objects measured in billionths of a metre.
Nano-scale products already widely in use range from cosmetics to household cleaning products to sporting goods.
But the new findings, reported in the British journal Nature Nanotechnology, could also point to new ways in which nano-therapies might zero in on disease-causing tumours, the researchers said.
They could even shed light on how poorly understood pathogens penetrate into human organs.
In laboratory experiments, scientists led by Charles Case of Southmead Hospital in Bristol, Britain, grew a multi-layer “barrier” of human cells to mimic specialised protective tissues found in the body.
One such barrier, for example, separates blood from the brain.
Underneath this layer three-to-four cells thick, they placed human fibroblast cells, which play a key role in the formation of connective and scar tissue.
And on top they put nano-scale particles of cobalt-chromium, an alloy that has long been used in the making of hip- and knee-replacement joints, and more recently in drug-delivery mechanisms used inside arteries.
Earlier studies had shown that direct exposure to large quantities of the alloy could severely damage DNA is some cells, and the researchers wanted to find out how well the lab-grown barrier would protect the fibroblast cells below.
“We never imagined that it wouldn’t,” Case told journalists by phone.
“But to our great surprise, not only did we see damage on the other side of the barrier, we saw as much damage as if we had not had a barrier at all,” he said.
At first, the researchers speculated that the tiny particles — barely 30 billionth of a meter in diameter — had slipped through microscopic cracks in the cellular blockade.
But there was no sign of the alloy on the other side, and when the experiment was repeated with far larger particles, the result was essentially the same.
“We could only conclude that the DNA damage occurred after indirect exposure depending on a process of signalling between cells rather than the passage of metal through the barrier,” said Gevdeep Bhabra, a surgeon at Southmead and a co-author of the study.
For Jim Thomson of the Canada-based technology watchdog ETC Group, the findings “expand significantly the hurdles that any theoretical nano-safety assessment would need to clear.”
His views were echoed by the researchers themselves and experts not involved in the study.
“What it tells me is that the precaution with which some scientists and regulators say we should proceed is the right way to go,” said Vyvyan Howard, a pathologist at the University of Ulster who founded the Journal of Nanotoxicology.
But the newly uncovered mechanism holds promise too, these and others experts said.
“The first exciting question is, can we deliver novel therapies across barriers without having to cross them?”, said Ashley Blom, an orthopaedic surgeon and professor at the University of Bristol.
“There are also implications as to how nano-particles that we all have in our bodies might act across membranes — small particles like prions and viruses may use some of these mechanisms.
“This opens up a whole new field of research,” he added.
Prion diseases occur when a mutated form of the prion protein runs amok, destroying brain cells.
When considering the safety of nano-particles, one must distinguish between medical and broader industrial applications, said Howard.
New drugs are carefully tested, reducing the chances of widespread harm. And even if nano-delivery and imaging systems turn out not to be risk-free, that does not necessarily mean they shouldn’t be used.
“Depending on the kind of disease you have, you will accept some very nasty therapies,” such as a chemotherapy for cancer, he said.
“But there is a world of difference between accepting a therapy under informed consent, and involuntary exposure,” he added, pointing out most industrial uses are not regulated at all.
