By
treating catheter surfaces with a polymer coating, life-threatening microbial
infections may soon become a problem of the past.
Antibacterial
and antifouling polymer coatings could soon relegate catheter-associated
infections in the blood to history
Catheters play a crucial role in hospital
care, particularly in the transport of intravenous fluids and medication.
Typically, they are made of flexible low-toxicity silicon rubber that is,
unfortunately, prone to colonization by bacteria or other microbes. Once
settled, the microbes form a biofilm that provides resistance to antimicrobial
agents and the body’s immune response. These biofilms are the leading cause of
potentially lethal healthcare-related infections. To prevent this build-up, or
fouling, a team led by Yi-Yan Yang from the A*STAR Institute of Bioengineering
and Nanotechnology (IBN) has developed a simple and effective method to modify
the rubber surface of catheter tubing1.
Existing approaches against microbial
adhesion use antibiotics or silver to coat the catheter surface.
However, overuse of antibiotics can lead to
bacterial resistance and the silver coating can be toxic to blood, limiting the
clinical implementation of these methods. “Moreover, the ‘burst release’ of
these antibiotics and silver affects their efficacy,” says Yang.
Yang and her co-workers therefore adopted an
alternative approach: they altered the silicon rubber using antimicrobial and
antifouling copolymers consisting of a polyethylene glycol (PEG) polymer linked
to a strand of polycarbonate polymer. The polycarbonate strand was composed of
positively charged hydrophilic and hydrophobic units, or monomers. Adopting a
cleverly low-effort strategy, the team modified the rubber surface with a
reactive substance known as dopamine, and then simply dipped the pre-coated
surface in a solution containing the polymer precursors to anchor the copolymer
chains.
The researchers determined the antibacterial
and antifouling performance of the coatings by incubating the
multidrug-resistant Staphylococcus aureus Gram-positive bacteria with the
treated rubber. All coatings exhibited antifouling properties thanks to their
flexible and bulky PEG portions, which prevented microbial cells from
approaching the rubber surface. Furthermore, only coatings that contained
hydrophobic monomers in the positively charged polycarbonate killed bacteria in
solution. This highlights the importance of these monomers, which may insert
into bacterial membranes and thereby enhance the interaction between polymer
and bacteria.
Noting that very few red blood cells ruptured
upon contact with the coatings, Yang says that there was no blood protein
adsorption or platelet adhesion on the treated surface — proof of the excellent
blood compatibility of the polymers.
Yang and her team recently optimized the
polymer compositions to also fight Gram-negative bacteria. “We plan to expand
these technologies to other coating applications, such as to contact lenses and
to implant coatings, to prevent biofilm formation,” she adds.
The A*STAR-affiliated researchers
contributing to this research are from the Institute of Bioengineering and
Nanotechnology
References
- Ding, X., Yang, C., Lim, T. P., Hsu, L. Y.,
Engler, A. C. et al. Antibacterial and antifouling catheter
coatings using surface grafted PEG-b-cationic polycarbonate diblock
copolymers. Biomaterials 33, 6593–6603
(2012). | article
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