Structure of novel interpenetrating polymer network medical devices

Danish company Biomodics is working with the University of Copenhagen to understand how their novel interpenetrating polymer networks (IPN) are structured in silicone medical devices.

The risk of infection is a very serious problem for patients admitted to hospital, and one of the most impactful types of infection is for patients requiring urinary catheters. Biomodics have developed a novel method to process silicone medical devices, including the urinary catheters used for patients with bladder problems, that introduces a hydrophilic, water-swelling gel called a hydrogel into the otherwise hydrophobic silicone. The introduction of the hydrogel results in a device that reduces formation of the biofilms that often lead to infection. Not only that, but the hydrogel also can act as a channel to controllably release drugs to a patient.

Biomodics introduce the hydrogel polymer into the silicone by swelling it in supercritical carbon dioxide, at elevated temperature and pressure, and then synthesizing the hydrogel within the swollen medical device. Once the carbon dioxide is released, the silicone collapses with the hydrogel located throughout the material. This forms an interpenetrating polymer network (IPN), which is a fully mixed network of two immiscible polymers that cannot be separated. The existence of the IPN could be inferred from the performance of the medical devices, but Biomodics had been unable to directly observe it.

Read the interesting one pager about this project: Interpenetrating polymer networks for drug delivery.

Techniques and Methods

With the goal of characterizing the structure of their IPN material, Biomodics has worked with the LINX team at the University of Copenhagen to perform small-angle scattering measurements. They performed a wide range of small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) measurements to elucidate the IPN structure. SAXS could only detect the presence of inorganic filler particles, but by using SANS on IPNs that were hydrated with heavy water (D2O), it was possible to highlight the structure of the hydrogel itself. Not only was it possible to determine that the hydrogel does indeed form a network throughout the silicone, but the relevant and important length scales could be determined. This information is useful for Biomodics as a confirmation of the structure of their material as well as providing a way to relate the distribution of the hydrogel to the function of their medical devices in the clinical setting.

Project Information

Participants: Biomodics, University of Copenhagen.
Start date, end date:
 May 2016 – August 2018.
Characterization of Interpenetrating Polymer Networks (IPNs) (FP04.002, Colloid materials).