Characterization of Polyethersulfone (PES) and Polyvinylidene Difluoride (PVDF) Resistive Membranes under In Vitro Staphylococcus aureus Challenge

Abstract

Bacterial colonization of a medical device has been seen to precede clinical infection as well as adversely affect function of the indwelling device. This is a major cause of implant failure with the most common bacterial infections being due to Staphylococcus aureus. This strain has been known to be anti-biotic resistant, therefore it is very important to test and find biomaterials with low bacterial adhesion properties to avoid device-associated infections when implanted into the body. In the present study, three specific aims were preformed to characterize the performance of Polyethersulfone (PES) and polyvinylidene difluoride (PVDF) membranes. These polymeric membranes are commonly used in nanofiltration applications in the water and waste water market; therefore they are of high interest for use in the medical device market. PES and PVDF hydrophilic filter disks of 25mm diameter were purchased from Millipore with pore sizes of 0.22 µm. Bacterial migration (N=4), bacterial adhesion (N=4) and outflow resistance (N=4) studies were tested for each filter. Bacteria cultured to a concentration of 1 McFarland (3x108 cells/mL) were used for migration and adhesion studies. Migration was tested by pumping bacterial broth through the membranes and collecting the perfusate to quantify the bacterial migration. Adhesion studies were quantified by incubating filters in bacterial broth for 24hrs and plating attached bacteria after detachment by sonication. SEM images were taken for visual analysis of bacteria and filters. Lastly, outflow resistance was measured by pumping deionized water while recording pressure readings throughout 5 minutes. Results of the studies demonstrated that bacteria did not migrate through both PES and PVDF filters, thus properly filtering S. aureus cells. PES membranes were found to have more bacterial adherence to the surface and a lower outflow resistance than PVDF. Both filters could be considered to be used as a part of biomedical devices depending on the specific applications and resistance requirement. However, further studies are needed to inhibit bacterial adherence such as antibacterial coatings or incorporating antimicrobial compounds within polymeric biomaterials. The use of selenium as an antibacterial agent in biomedical devices has sparked a great interest in recent years this, incorporating this in PES and PVDF membranes are the next goal for these studies.