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Biosensing With A DNA-Diamond-Silicon Sandwich
Makarand writes "A
unique diamond film with DNA
attached to it coupled with sensitive microelectronics might be the
sensor needed to sniff out harmful biological agents.
If DNA is attached to diamond it is possible to electronically
detect the electrical response when biomolecules bind to the DNA-diamond surface.
A DNA-Diamond interface deposited on a silicon surface can act as a sensitive biosensor.
These inexpensive and compact sensors can make it possible to continuously scan
public places like airports and subways and send out
security alerts to agencies if required."
Did DeBeers finally go under?
Sweet.
Keep your packets off my GNU/Girlfriend!
Now let me see this technology put to use to make MY life better. I this syetm in place in my apartment so that whever a foul odor is present (Ie my gargantuan roommate take the Browns to the Suberbowl) this DNA diamond detects it and sends a text message to my cell phone. "DO NOT COME HOME FOR 4 HOURS."
This is the kind of stuff they said would happen in the future!
"Moderate drinking can help prevent amputated limbs" -- Abigail Zuger, NYTimes, 12/31/02
That article was extremely lacking in details, says nothing about how it works; especially how it should be able to tell the difference between a biological weapon and a natural virus/bacteria/fungus...
a DNA is forever...
this is not a sig.
DNA-Diamond-Silicon Sandwich....
can i get bacon on that?
.cig - what you do after winning a good flame war
Title sums it up. Is this thing set up with short stretches of DNA that recognize pathogen DNA stretches or just detect anything that can bind to and distort DNA? Just from reading the blurb the latter seems possible. The different bases A,T,C,G of DNA have a largish flat ring structure which are stacked if DNA's in a double helix. If something comes along and binds DNA by intercalating, or slipping between the stacked bases the DNA may have to bend to accomodate the foreign compound. Such a bend might be used for a detection system if there is a big enough mechanical signal. Not saying that's how this thing works, just kinda thinking...uh...outloud? Anybody got an better reference?
This press release is rather short on information (read: no information), but the Nature Materials article itself is a bit more helpful. Now, my university is shelling out a bunch of cash for a site license, and I'm sure neither they nor Nature would like me to post that article here, so I will not do that. The abstract is free though:
Diamond, because of its electrical and chemical properties, may be a suitable material for integrated sensing and signal processing. But methods to control chemical or biological modifications on diamond surfaces have not been established. Here, we show that nanocrystalline diamond thin-films covalently modified with DNA oligonucleotides provide an extremely stable, highly selective platform in subsequent surface hybridization processes. We used a photochemical modification scheme to chemically modify clean, H-terminated nanocrystalline diamond surfaces grown on silicon substrates, producing a homogeneous layer of amine groups that serve as sites for DNA attachment. After linking DNA to the amine groups, hybridization reactions with fluorescently tagged complementary and non-complementary oligonucleotides showed no detectable non-specific adsorption, with extremely good selectivity between matched and mismatched sequences. Comparison of DNA-modified ultra-nanocrystalline diamond films with other commonly used surfaces for biological modification, such as gold, silicon, glass and glassy carbon, showed that diamond is unique in its ability to achieve very high stability and sensitivity while also being compatible with microelectronics processing technologies. These results suggest that diamond thin-films may be a nearly ideal substrate for integration of microelectronics with biological modification and sensing.
The method of attachment of DNA to a diamond surface is particularly clever: they use photochemistry to attach a long chain primary amine to the surface of the diamond, and then use a rather curious and complicated sulfur-containing organic molecule called SSMCC to act as a bridge between the diamond/amine and the strand of DNA. Essentially, you get these strands of DNA that point out into the environment like sticky threads. The sensing aspect, presumably (they don't go too much into it in the article - as the press release notes, they plan on discussing that in a meeting of the ACS) takes place as foreign DNAs contact the sensor. As the abstract tells us, the specificity of the attached DNA strands is not compromised by the diamond bonding technique, so the DNA strands can identify a certain complementary DNA sequence present in the enviroment, say, from Bacillus anthracis. Presumably the change induced in the diamond-bonded DNA that occurs when the complement hydrogen bonds with it will then trigger some sort of physically detectable action- you could tag the DNA with a fluorescent dye, for example, and measure how the fluorescence levels change between bonded and unbounded forms. This sort of information can then be translated into an electronic signal. This has a long ways to go before being a practical outside-the-lab type of device, but the results are still pretty exciting.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
.. mmm, not bad, nice hot DNA, good Diamond, Silicon is a little dry... THE SILICON IS A LITTLE DRY!!!
Cool...sounds like it might be genechip version 2.0. But it also sounds like (I don't have access to Nature Materials and I'm not gonna pay $15 for the article) they PT Barnumed their article a bit. I don't study pathology, but I don't know how much DNA fragments anthrax will leave around. And sarin? Geeze...yeah you can make it from Castor beans but will your end product definitely won't have DNA remaining. But like the blurp said, it's preliminary.
Yeah, I don't know just how practical this setup would actually be out in the real world as far as biosensing. It's probably more suited to the next generation of laboratory gene chips, as you say. The Nature Materials paper of course says nothing about combating bioterror (it does mention the possible use of this technique in improved biosensors), so I think your "P.T. Barnum" comment may be right on target as far as the buzzword-laden but noninformative press release goes. Can't really blame the university from a public relations standpoint, as "Scientists create prototype for next-gen gene array" just doesn't have the same punch as "SCIENCE FIGHTS TERROR!" grandstanding.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
Hi.
/. . -Jenny
I think I can clarify some of these things. I'm the person that grows the diamond films for the research in question. Bob Hamers is the head of that group- I'm here at Argonne in the nanostructured thin films group. I'm also on the paper- if anyone really wants a copy I can send them a reprint.
We grow diamond with microwave plasma chemical vapor deposition. Basically: take can, pump out air in can, put in argon and a tad of methane, make a plasma with a microwave source (one could also use other types of sources to ignite the plasma), make C2 radicals, heat your substrate, and you have a very fine-grained diamond film. This is rather different than how other people do it- they use methane and hydrogen and grow larger grained films. They are still interesting and useful, but are rough, and can't be doped n-type the way way we can.
I should emphasize that it's cheap since we don't use single crystal diamond substrates.. unlike some other diamond film technologies.
What gets exciting is that this type of film is not only dirt cheap to make, but it has all sorts of exciting tribological properties (low friction, stiction, roughness- due to the very small grain size) which makes it perfect for MEMS- so you have a MEMS/biosensor. I'm specifically working on doping it- so we dope it with nitrogen (which doesn't work in other types of diamond films) and we get highly conducting n-type diamond films. So now you have electronics/MEMS/biosensors all on the same chip and made at the same time. It's rather nice. We're working on low temperature growth (coating artifical retinas- there's a bit of press out there on that) etc. This stuff is called UNCD- ultra nanocrystalline diamond- and it was in slashot a couple of years back.
I'd be happy to answer any more questions. I just love seeing anything I'm working on in