EMERGING AND NANOTECHNOLOGIES
Penicillin-Coated Polymer Staves Off Staph Infections
Scientists at the University of Southern Mississippi (USM; Hattiesburg, MS; www.usm.edu) have modified expanded polytetrafluoroethylene (ePTFE) to facilitate adhesion of penicillin to its surface. The resulting penicillin-coated polymer could impede bacterial colonization of gram-positive Staphylococcus aureus on implantable devices.
Known for its biocompatibility, resistance to chemicals and abrasion, and ability to withstand extreme temperatures, ePTFE is an inert material commonly used in implants. In its normal state, ePTFE is not capable of inhibiting growth of S. aureus bacteria. However, by modifying the polymer through a series of reactions, it can host penicillin on its surface.
“Any time you have an inert material, it is hard to modify,” says Marek Urban, professor and director, USM School of Polymers and High Performance Materials and the Materials Research Science and Engineering Center. “If you anchor a penicillin molecule close to the surface, it is not going to be active. You need to have a spongy surface so when [a bacterium] lands on the surface and tries to make itself comfortable, it is disrupted and does not form microbial films.”
Employing microwave plasma radiation, the researchers bonded maleic anhydrine to the surface of ePTFE, which, via hydrolysis reactions, was converted to carboxylic acid groups. Polyethylene glycol spacers with different molecular lengths then reacted to surface carboxylic acid groups, followed by reactions by penicillin to the hydroxyl end groups of the spacers.
Funded by the National Science Foundation Materials Research Science and Engineering Center program, the study is the first to demonstrate the efficacy of penicillin-coated ePTFE against the S. aureus bacteria. Potential applications for the penicillin-coated polymer include surgical devices, as well as catheters and other implantable items.
Hindrance of this common bacterium is regarded as a priority in the medical industry owing to mounting instances of hospital-acquired infections. The rising rates of infection are often attributed to the emergence of antimicrobial-resistant strains of bacteria. Infections can lead to extended hospital stays, increased expenses for both patients and hospitals, and even death.
Acknowledging the rise of antimicrobial-resistant bacteria, Urban notes that his team used penicillin, as well as previous research with amoxicillin, as a jumping-off point. He stresses that the long-term goal of this and other modifications of ePTFE is to incorporate antibacterial agents to which no bacteria have yet developed any immunity.
Yet Urban also points out that, when it comes to infection, something is better than nothing. He suggests that the presence of penicillin at the onset of an infection could help curb its spread.
“Everybody knows that penicillin is a shotgun approach to any infection. But sometimes that shotgun approach is helpful because [the infection site] may be a very small area, but it can grow out of control,” says Urban. “Without an antibiotic, that infection is going to grow unless the immune system is strong enough. But if you have initial disruption of the bacteria, then the chances are that this [presence of penicillin] will be successful.” Results of the USM-conducted study appeared in the January 11, 2007 issue of the American Chemical Society journal, Biomacromolecules.