Laser Goes Tubing for Faster Body-Fluid Tests
April 2, 2007University of Rochester researchers announce in the current issue of Applied Optics a technique that in 60 seconds or less measures multiple chemicals in body fluids, using a laser, white light, and a reflective tube. The technique tests urine and blood serum for common chemicals important to monitoring and treatment of diabetes and cardiovascular, kidney, urinary and other diseases, and lends itself to the development of fast batch testing in hospitals and other clinical settings.
Co-researchers Andrew J. Berger, associate professor of optics, and Dahu Qi, doctoral candidate, used low-refractive-index tubes instead of cuvettes or other bulky containers for holding biological specimens. And, to get more information from the fluids, they used white light—like that from an ordinary light bulb—along with the laser. The tubes and light bulbs made all the difference.
In the laser technique called Raman spectroscopy, scientists shine laser light onto molecules and the light scatters off, gaining or losing energy. A spectrograph translates the changed energies into spectra. Each chemical presents a Raman spectrum that scientists recognize. The Raman approach is a favorite for finding chemicals that overlap and mix in fluid, much like musical instruments in an orchestra. But Raman spectroscopy comes with a problem.
Raman signal is notoriously weak. Using it to test biofluids, with their lighter chemical concentrations than in many fluids, is not a natural choice. Berger and Qi injected fluid samples into a thin transparent tube specially made to contain the light, and the tube's long path length of interaction let the scientists collect more Raman scattering. "The tubes have a refractive index lower than water, so the light bounces along inside the liquid core, just as in solid optical fibers for telecommunications," said Berger. "Other groups had used these fibers to strengthen their Raman signals, so we wanted to see if we could translate that advantage to use with biofluids."
They did get the stronger signal they were looking for, but the increase threw off measurements when samples of urine or blood serum varied in color.
In previous experiments, Berger and his team had explored how a concentration of each chemical relates to the strength of Raman signal. It turned out the relationship is not a simple linear one. They were able to use that information for dealing with differences in sample color.
"We can't neglect that body fluid samples absorb light," said Berger. "We'd have two different samples with the same amount of protein and not get the same strength of signal. If we had two samples of blood serum, maybe one sample would be a little pinker due to a few ruptured red blood cells. Then we wouldn't get the same signal strength."
The solution flashed like a light bulb. The scientists sent a beam of white light through each sample to see how much light was absorbed at various wavelengths, and then they calculated corrections. It was easy enough to inject the light by using the end of the tube opposite the laser. The resulting corrections made chemical predictions significantly more accurate.
The team measured 11 chemicals in blood serum, including total protein, cholesterol, LDL and HDL levels, glucose, triglyceride, albumin, bilirubin, blood urea nitrogen, globulin, and CO2. In urine, they identified urea nitrogen and creatinine. The technique does not measure ions such as calcium or sodium, or other chemicals present at concentrations below about 0.01 mg/mL.
Spectral tests use no chemical reagents and therefore offer the advantage of being nondestructive to fluid samples, unlike many lab tests. After analysis, practitioners could use undamaged samples for other kinds of tests.
"We squeeze a small amount of fluid into the tube," said Berger. "In 10 or 20 seconds, we have a chemical breakdown, and we can see the presence of a lot of chemicals all at once. There's no chemistry performed, and there's no touching of the fluid."
The tubing doesn't just help with the signal strength; it also makes it easy to move biofluids around. "We pump a sample into the tube, pass some light through it, and send it along its way—and then we're all set to pump in the next one," said Berger.
Source: University of Rochester
-
Scientists get first detailed look at nitrogen doping in single-layer graphene
Sep 21, 2011 |
5 / 5 (3) |
1
-
Reverse engineering materials with a rapid, non-destructive laser-based technique can aid the fight against counterfeits
Sep 19, 2011 |
not rated yet |
0
-
New laser could treat acne with telecom technology
Aug 31, 2011 |
5 / 5 (4) |
0
-
Authenticating ancient artifacts
Aug 09, 2011 |
not rated yet |
1
-
Discovery of parathyroid glow promises to reduce endocrine surgery risk
Jun 20, 2011 |
5 / 5 (2) |
1
-
Engineers build first sub-10-nm carbon nanotube transistor
Feb 01, 2012 |
4.9 / 5 (31) |
30
-
Something old, something new: Evolution and the structural divergence of duplicate genes
Jan 31, 2012 |
4.6 / 5 (7) |
1
-
The hidden nanoworld of ice crystals: Revealing the dynamic behavior of quasi-liquid layers
Jan 30, 2012 |
5 / 5 (3) |
1
-
Stock market network reveals investor clustering
Jan 27, 2012 |
3.9 / 5 (23) |
8
-
Of microchemistry and molecules: Electronic microfluidic device synthesizes biocompatible probes
Jan 26, 2012 |
5 / 5 (1) |
0
-
Is Everyday Technology Killing Us?
Feb 08, 2012
-
Exercise and weight loss
Feb 08, 2012
-
Why do we have head aches? Our brains can't feel anything.
Feb 07, 2012
-
"The end of diseases" by David Agus, interview from Daily Show with Jon Stewart
Feb 04, 2012
-
Oncolytic adenovirus
Feb 04, 2012
-
Nutrition label stuffs and diets
Feb 02, 2012
- More from Physics Forums - Medical Sciences
More news stories
Study finds that anti-diabetic medication can prevent the long-term effects of maternal obesity
In a study to be presented today at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Dallas, Texas, researchers will report findings that show that short therapy with the anti-diabetic medication ...
12 hours ago |
5 / 5 (1) |
1
Steroid injections prove effective in treatment of lumbar disc herniations
The use of epidural steroid injections may be a more efficient treatment option for lumbar disc herniations, according to research presented today at the American Orthopaedic Society for Sports Medicine's Specialty Day in ...
12 hours ago |
not rated yet |
0
Amateur football players not always keen on returning to play after ACL injuries
Despite the known success rates of reconstructive Anterior Cruciate Ligament (ACL) surgery, the number of high school and collegiate football players returning to play may not be as high as anticipated, say researchers presenting ...
12 hours ago |
not rated yet |
0
Study finds elevated levels of cell-free DNA in first trimester do not predict preeclampsia
In a study to be presented today at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Dallas, Texas, researchers will report findings that indicate that elevated levels of cell-free DNA in ...
12 hours ago |
not rated yet |
0
PRP treatment aids healing of elbow injuries say researchers
As elbow injuries continue to rise, especially in pitchers, procedures to help treat and get players back in the game quickly have been difficult to come by. However, a newer treatment called platelet rich plasma (PRP) may ...
12 hours ago |
5 / 5 (1) |
0
Walney offshore wind farm is world's biggest (for now)
(PhysOrg.com) -- The Walney wind farm on the Irish Sea--characterized by high tides, waves and windy weather--officially opened this week. The farm is treated in the press as a very big deal as the Walney ...
GPS court ruling leaves US phone tracking unclear
A US Supreme Court decision requiring a warrant to place a GPS device on the car of a criminal suspect leaves unresolved the bigger issue of police tracking using mobile phones, legal experts say.
Europeans protest controversial Internet pact
Tens of thousands of people marched in protests in more than a dozen European cities Saturday against a controversial anti-online piracy pact that critics say could curtail Internet freedom.
Europe stakes billion-dollar bet on new rocket
A pencil-slim rocket is scheduled to lift into space from South America on Monday, carrying a billion-dollar bet that Europe can grab a juicy slice of the market to place satellites in low orbit.
Netflix settlement trims 14 pct off 4Q earnings
(AP) -- Netflix pressed the rewind button on its fourth-quarter earnings after settling allegations that the video subscription service violated a consumer-privacy law.
Elbow position not a predictor of injury
Elbow position alone appeared to not affect injury rates and performance in college-level, male pitchers say researchers presenting at the American Orthopaedic Society for Sports Medicine's Specialty Day in San Francisco, ...