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 How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>