Biodegradable polymer coating for implants

December 15, 2016
The microscopic fluorescence image reveals structures printed onto the biodegradable coating for test purposes. Credit: KIT

Medical implants often carry surface substrates that release ac-tive substances or to which biomolecules or cells can adhere better. However, degradable gas-phase coatings for degradable implants, such as surgical suture materials or scaffolds for tis-sue culturing, have been lacking so far. In the journal An-gewandte Chemie, researchers of Karlsruhe Institute of Technol-ogy now present a polymer coating that is degraded in the body together with its carrier.

"Our new degradable might be applied for functionali-zation and coating of surfaces in biosciences, medicine, or food packaging," says Professor Joerg Lahann, Co-Director of the Insti-tute of Functional Interfaces of Karlsruhe Institute of Technology (KIT). Together with an international team, he produced films with functional groups as "anchor sites" for fluorescent dyes or biomolecules.

For the first time, the researchers present a CVD (chemical vapor deposition) method to produce biodegradable polymers. Via spe-cial side groups, biomolecules or active substances can be at-tached. This opens up new potentials for e.g. coating biodegrada-ble implants. Polymerization by is a sim-ple and widely used method to modify surfaces, by means of which also complex and irregular carrier substrates can be coated homo-geneously with polymers.

In CVD polymerization, the initial compounds are evaporated, acti-vated at high temperature, and deposited onto surfaces, where they polymerize. However, so far it has been possible to coat permanent implants only. Coating has been impossible for materials that are to be degraded after fulfilling their tasks, such as surgical suture mate-rials, systems for the controlled release of substances, stents re-leasing medical substances or scaffolds for culturing tissue. Bio-degradable coatings could not be produced by CVD.

Now, this gap is closed, as scientists of Karlsruhe Institute of Tech-nology, University of Michigan (Ann Arbor, USA), and Northwestern Polytechnical University (Xi'an, China) for the first time synthesized a CVD polymer with a degradable backbone. The team applied co-polymerization of two special monomer types: The para-cyclophanes usually used for this method were combined with cy-clic ketene acetals. While classical polymers on the basis of para-cyclophanes are linked by carbon-carbon bonds exclusively, ketene acetal is repositioned during polymerization, such that ester bonds (e.g. bonds between carbon and oxygen atoms) are formed in the polymer backbone. Ester bonds can be cleaved in aqueous medi-um.

"The degradation rate depends on the ratio of both monomer types and on the side groups of the monomers," Lahann explains. "Polar side groups make the polymer film less water-repellent and acceler-ate degradation, as water can enter more easily. In this way, the degradation rate can be adapted to application." Using cell cultures, the researchers already demonstrated that neither the polymer nor its degradation products are toxic.

Explore further: Biodegradable polymers made by chemical vapor deposition

More information: Fan Xie et al, Backbone-Degradable Polymers Prepared by Chemical Vapor Deposition, Angewandte Chemie (2016). DOI: 10.1002/ange.201609307

Related Stories

Biodegradable polymers made by chemical vapor deposition

December 1, 2016

Polymerization by chemical vapor deposition (CVD) is a simple method for modifying surfaces by which topologically challenging substrates can be evenly coated with polymers. In the journal Angewandte Chemie, researchers have ...

Researchers use light to design defined molecule chains

December 15, 2016

Chemists of Karlsruhe Institute of Technology (KIT) have succeeded in specifically controlling the setup of precision polymers by light-induced chemical reactions. The new method allows for the precise, planned arrangement ...

Researchers develop inexpensive hydrolysable polymer

December 2, 2014

Researchers at the University of Illinois at Urbana-Champaign have figured out how to reverse the characteristics of a key bonding material—polyurea—providing an inexpensive alternative for a broad number of applications, ...

'Swiss army knife' molecule

February 16, 2016

Scientists at ETH Zurich and an ETH spin-off have developed a novel polymer for coating materials, in order to prevent biofilms from forming on their surfaces. Thanks to the technological platform developed, it is now possible ...

Recommended for you

Life's building blocks observed in spacelike environment

December 12, 2017

Where do the molecules required for life originate? It may be that small organic molecules first appeared on earth and were later combined into larger molecules, such as proteins and carbohydrates. But a second possibility ...

Teaching antibiotics to be more effective killers

December 12, 2017

Research from the University of Illinois at Chicago suggests bond duration, not bond tightness, may be the most important differentiator between antibiotics that kill bacteria and antibiotics that only stop bacterial growth.

Hot vibrating gases under the electron spotlight

December 12, 2017

Natural gas is used in refineries as the basis for products like acetylene. The efficiency of gaseous reactions depends on the dynamics of the molecules—their rotation, vibration and translation (directional movement). ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.