(510j) Astrocytic Growth on Silicone Catheters with Different Hydrophobicities in a Model of Pulsatile Cerebrospinal Fluid Flow

While silicone catheters have vastly improved a wide array of medical treatments, reactions at the tissue-substrate interface often diminish their functionality. In the treatment of hydrocephalus, implanting a silicone catheter in the cerebral ventricles allows cerebrospinal fluid to be drained from the cranial cavity to an alternative absorption site, usually the abdominal cavity. While this ?shunt? controls intracranial pressure and improves neurological outcome, the catheter system is highly susceptible to blockage because the silicone interface is attractive to cells, primarily astroglia. Our previous in vitro experiments have shown that increases in hydrophobicity, caused by polymer immobilization on silicone, can inhibit cell adhesion. In the present study, the hydrophobicity of silicone catheters was further investigated in an ex vivo model of cerebrospinal fluid flow through a catheter. Using a pulsatile flow apparatus at 0.3 mL/min, 3 x 106 astrocytes (46,153 astrocytes/mL) were exposed for 20 hours to the lumen of native (contact angle measurement of 107.4°) and oxidated silicone (contact angle measurement of 0°), OD 2.5 mm and ID 1.3 mm. Catheter samples were analyzed by 2-photon confocal microscopy and cytospin methods. The observed trend in this fluidic culture study was an increase in astrocyte adhesion on native silicone when samples were held horizontally. Likewise, an increase in astrocyte adhesion occurred on oxidated silicone but only when samples were held vertically. Furthermore, a significant difference (p<0.05) between native and oxidated silicone was observed in the bottom half of the horizontal tubing, a region prone to astrocytic settling. When compared to standard cell culture preparations of astrocytes on silicone, these results were noticeably dissimilar. The results of this study provide a better understanding of the effects of pulsatile flow on astrocytic growth and should lead to the identification of novel surface modification strategies to improve long-term implantation of silicone catheters.