Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

UCSD researchers develop flexible, biocompatible polymers with optical properties of hard crystalline sensors

28.03.2003


Researchers at the University of California, San Diego have discovered how to transfer the optical properties of silicon crystal sensors to plastic, an achievement that could lead to the development of flexible, implantable devices capable of monitoring the delivery of drugs within the body, the strains on a weak joint or even the healing of a suture.

The discovery is detailed in the March 28 issue of Science by a UCSD team that pioneered the development of a number of novel optical sensors from silicon wafers, the raw starting material for computer chips.

Led by Michael J. Sailor, a professor of chemistry at UCSD, the team recently developed sensors from dust-sized chips of “porous” silicon capable of detecting biological or chemical agents that might be present in a terrorist attack. It also developed a new kind of nerve gas detector based on a porous silicon chip optical sensor that changes color when it reacts to sarin and other nerve agents.



Now Sailor and his team have developed a way to transfer the optical properties of such silicon sensors, once thought to be the exclusive domain of “nanostructured” crystalline materials, such as porous silicon, to a variety of organic polymers.

“While silicon has many benefits, it has its downsides,” explains Sailor. “It’s not particularly biocompatible, it’s not flexible and it can corrode. You need something that possesses all three traits if you want to use it for medical applications. You also need something that’s corrosion resistant if you want to use it as an environmental sensor. This is a new way of making a nanostructured material with the unique optical properties of porous silicon combined with the reliability and durability of plastics.”

Besides Sailor, the researchers involved in the discovery included UCSD chemists Yang Yang Li, Frederique Cunin, Jamie Link, Ting Gao, Ronald E. Betts and Sarah Reiver; Sangeeta Bhatia, an associate professor of bioengineering at UCSD, and UCSD bioengineer Vicki Chin.

The method Sailor’s team uses to create the flexible, polymer-based sensors is something similar to the injection-molding process that manufacturers use in creating plastic toys. The scientists first start by treating a silicon wafer with an electrochemical etch to produce a porous silicon chip containing a precise array of tiny, nanometer-sized holes. This gives the chip the optical properties of a photonic crystal—a crystal with a periodic structure that can precisely control the transmission of light much as a semiconductor controls the transmission of electrons.

The scientists then cast a molten or dissolved plastic into the pores of the finished porous silicon photonic chip. The silicon chip mold is dissolved away, leaving behind a flexible, biocompatible “replica” of the porous silicon chip.

“It’s essentially a similar process to the one used in making a plastic toy from a mold,” explains Sailor. “But what’s left behind in our method is a flexible, biocompatible nanostructure with the properties of a photonic crystal.”

Those properties could allow a physician to directly see whether the biodegradable sutures used to sew up an incision have dissolved, how much strain is being placed on a newly implanted joint or how much of a drug implanted in a biodegradable polymer is being delivered to a patient.

This is possible because the properties of porous silicon allow Sailor’s team to “tune” their sensors to reflect over a wide range of wavelengths, some of which are not absorbed by human tissue. In this way, the scientists can fabricate polymers to respond to specific wavelengths that penetrate deep within the body.

A physician monitoring an implanted joint with this polymer would be able to see the changes in the reflection spectrum as the joint is stressed at different angles. A physician in need of information about the amount of a drug being delivered by an implanted device can obtain this by seeing how much the reflection spectrum of a biodegradable polymer diminishes as it and the drug dissolve into the body.

Such degradable polymers are used to deliver antiviral drugs, pain and chemotherapy medications and contraceptives.

“The drugs are released as the polymer carrier degrades, a process that can vary from patient to patient, depending on the site of implantation or the progression of a disease,” says Bhatia, who is a physician. “This approach offers a noninvasive way to monitor the degradation of the device, decide on when it needs to be replaced, and evaluate its function. This same approach would be useful for other implantable devices like evaluating the status of implantable glucose sensors diabetes or monitoring the process of tissue repair in tissue engineering.”

To demonstrate that this process would work in a medical drug delivery simulation, the researchers created a polymer sensor impregnated with caffeine. The sensor was made of polylactic acid, a polymer used in dissolvable sutures and a variety of medically implanted devices. The researchers watched as the polymer dissolved in a solution that mimicked body fluids and found that the absorption spectrum of the polymer decayed in step with the increase of caffeine in the solution.

“This confirms that the drug is released on a time scale comparable to polymer degradation,” the researchers report in the journal.

“The artificial color code embedded in the material can be read through human tissue and provides a noninvasive means of monitoring the status of the fixture,” adds Sailor. “Such polymers could be used as drug delivery materials, in which the color provides a surrogate measure of the amount of drug remaining.”

The study was supported by grants from the National Science Foundation, The David and Lucile Packard Foundation and the Air Force Office of Scientific Research.

Kim McDonald | University of California - San D
Further information:
http://ucsdnews.ucsd.edu/newsrel/science/mcpolymer.htm

More articles from Life Sciences:

nachricht What the world's tiniest 'monster truck' reveals
23.08.2017 | American Chemical Society

nachricht Treating arthritis with algae
23.08.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

What the world's tiniest 'monster truck' reveals

23.08.2017 | Life Sciences

Treating arthritis with algae

23.08.2017 | Life Sciences

Witnessing turbulent motion in the atmosphere of a distant star

23.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>