Cocaine Biosensor

Aaron Rowe writes "The MIT Technology review reports that a lab at UC Santa Barbara has created a biosensor by attaching a special type of DNA called an aptamer to a gold electrode. When cocaine is present, the aptamer tightly hugs a cocaine molecule and leans over so that a metal tag can touch the gold surface. This causes a spike in a plot of current versus voltage when the electrode is attached to a machine called a cyclic voltmeter."

Re:Gold?

[rubycodez]

Gold being soft means less force is required to make a good low-resistance electrical contact. So gold is the king of conductors for contact applications. Add to that the fact that it doesn't corrode or oxidize under normal conditions, it beats the two better conductors (at room temperature), silver and copper.

Re:Gold?

[Anonymous Coward]

I actually came across this paper in JACS a few days ago and a tiny amount of gold is used in the electrode, primarily because it makes the chemistry of attaching the aptamer to the electrode easy. Basically, aside from being easy to tether stuff to, gold doesn't play an integral role in the analysis.

Re:Posession of a controlled substance

[Anonymous Coward]

You cannot buy cocaine in a drug store. It is not in many cold remedies.

Is slashdot getting supider, or is it just you.

Re:Gold?

[Anonymous Coward]

If you want more info, look up info on gold-thiol self assembled monolayers (SAMs). Basically, if you have a gold surface, thiols spontanteously sit down on it in an organized way. If you can attach a thol group to your molecule of interest it is easy to stick it on a gold-coated surface.

Re:Posession of a controlled substance

[MyNymWasTaken]

You are thinking of codeine which is a morphine, i.e. opium, derivative.

Currently, the medicinal use of cocaine is limited to topical anesthesia of the upper respiratory tract and eye because the vasoconstrictive properties of cocaine are desirable during procedures.
Ref [emedicine.com]

Re:Posession of a controlled substance

[fafalone]

Cocaine is a Schedule II controlled substance, it's illegal in ANY quantity with a license. Its uses are confined to a very limited number of surgeries since it's both a local anaesthetic and vasoconstrictor; that's it. It's not prescribed to patients for any reason. Your post would be true about 100 years ago, however.

Re:Posession of a controlled substance

[fafalone]

Researchers can obtain a license from the DEA to acquire (from a company possessing a DEA license to manufacture/distribute, which every major chemical company like Mallinkrodt or Sigma Aldrich has) and possess controlled substances. It's not easy to get, they obsessively track what you purchase and you have to file paperwork accouting for every last bit of it, but many such licenses exist. For more information on obtaining such licenses, see: http://www.deadiversion.usdoj.gov/drugreg/index.ht ml [usdoj.gov]

Re:Posession of a controlled substance

[eclectro]

How they get the coke for testing?

It's simple. Somebody whips out a twenty dollar bill out of their pocket, because ten out of eleven [tafkac.org] bills have cocaine on them.

Re:Gold?

[Anonymous Coward]

Gold leaf. Gold is capable of being made a lot thinner and smoother-faced than most other metals and its high conductivity generally makes an excellent substrate for these sorts of uses. SEE ALSO: scanning tunneling microscope and others.

Re:Posession of a controlled substance

[Anonymous Coward]

Morphine and opium are not synonymous. Opium is dried latex from the plant papaver somniferum. Morphine is one of many active ingredients in opium. Codeine is another. Morphine can be chemically processed to form diacetyl morphine, which is also known as heroin. Opium can also be processed to produce hydrocodone, oxycontin, methadone, and other, stronger drugs.

Fun fact: The drug "DXM", found in many cough syrups, is a stereoisomer to levomethorphan, an opioid.

Re:Gold?

[Cadallin]

Xanax isn't an antidepressant. It's a member of the benzodiazapine class of drugs (the most common one actually). Benzodiazapines are the "drug of the day" for Anti-anxiety and also for anaesthesia in high doses. It does the same thing as barbiturates (Qualudes) and Codeine/Morphine/Heroine did in their times respectively. Your employee was probably placed on Xanax temporarily as her medical provider put her on a regime of anti-depressants (Prozac, Paxil, or something else). The Xanax is there to serve essentially as a sedative. This is common practice, especially with patients considered a suicide risk by their Doctors (As sedated people generally don't kill themselves) alhough at the same time is something of risk itself, as it is possible to commit suicide through Benzodiazapine overdose, just as it is possible with Barbiturates, or Opiates. But the medical community has weighed this risk, and generally sedates mild suicide risk patients, while those considered at high risk are generally hospitalized.

Re:Posession of a controlled substance

[Anonymous Coward]

cocaine is not available OTC or otherwise. Several analogs are used by doctors and such though. Benzocaine is used in some throat lozenges same with Lidocaine. Xylocaine I think is used as a local anasthetic during dental and other types of surgery.

Re:Torn & Amused

[Mr2001]

It's one of the only stores that I know of that often has a few hundred lbs of moving merchandise on a moving forklift several feet above customers heads. So, I don't want someone who's just done a line at the wheel.

Problem is, the kind of drug testing employers do--analysis of urine to find the metabolites of illegal drugs--won't catch this at all. They can only detect past use, and for some drugs (e.g. marijuana) "past use" can go back several weeks.

There are other methods that can test whether someone is actually under the influence of a drug right now, but they're more expensive and obviously must be done at least every day when an employee arrives, so employers don't really use them.

Who cares?

[TallMatthew]

Returning instant results doesn't mean anything if the drug's not in your system.

Cocaine has a plasma half-life of 90 minutes. Current cocaine drug tests detect metabolites, not the drug itself, and even those only work within 24-48 hours after using.

Re:Gold?

[pimpimpim]

I'm currently doing a research project on biomaterial-surface interactions (which is a huge field, so I might miss out on some points).

There are several properties that make gold suitable for these medicinal applications. I'll give a few that I took from chem rev 2005, 105, 1103 [acs.org](*).:

• It can readily form a thiol-bond with sulfur-containing molecules, this allows for sticking lots of stuff to it, synthetic carbon chains, but also DNA and proteins, all by relatively simple techniques
• It is very easy to create gold layers of a known structure, there are several deposition techniques available.
• It is biocompatible: less noble metals like Nickel have Nickel atoms migrating into the system, which can kill cells. Furthermore there will be a lot of oxidation going on at those less noble metal surfaces.
• Gold can be combined with a lot of electrochemical analysis techniques, and others like SPR, MS, etc.

There are alternatives available, e.g. Palladium, Platinum, but gold is so versatile that it will be the mostly used metal for quite some time I would say.

(*) the article is mostly about self-assembled monolayers, so not very general and most of it will not be useful to you, but it contains a very good explanation of the reason why people choose gold in any of these applications.