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Investigation into Polyurethane at Varying Dose Rates of Ionizing Radiation for Clinical Application 时间:2018-10-02 22:52   来源:未知   作者:admin   点击: 次   Abstract:Polyurethanes (PUs) are commonly used materials for medical devices. These devices are exposed repeatedly to radiation when patients undergo radiotherapy treatments. It has been found that peripherally inserted central catheters (PICCs) and central venous catheters (CVCs) fail at an increased rate (14.7% and 8.8%, respectively) when radiated. Currently, little research is available on increased failure seen in conjunction with radiation, but complex in vivo environments within a human patient make it difficult to isolate effects of individual variables. This research investigated effects of radiation in an aqueous environment to determine whether radiation combined with a mimicked in vivo environment is sufficient to change PU devices. The following dose rates were used in this study: 3.2 Gy·min−1, 4.5 Gy·min−1, 44 Gy·min−1, and 833 Gy·min−1. Samples were characterized in four main ways: cellular response, physical changes, chemical changes, and mechanical changes. Results reveal normal cellular response at all dose rates, indicating dose rate does not alter cellular adhesion or proliferation, and biocompatibility of the material is not being altered. Results from physical, chemical, and mechanical effects confirm that varying dose rates alone do not initiate material changes, which negates the hypothesis that varying dose rates of radiation contribute to the complications in PICC and CVCs.
1. Introduction
   Polyurethane biomaterials are often studied for use in fabricating 3D tissue scaffolds, catheters, blood contact materials (heart valves and artificial veins), hospital bedding, injection molded implants, and other short-term implants [1–3]. Polyurethane catheters, specifically PICCs and CVCs, have been shown to fail at higher rates when exposed to radiotherapy in cancer patient [4, 5], 14.7% and 8.8%, respectively [4]. Postinsertion complication rate of nonirradiated PICC lines is 30.4% [4–7]. Previous investigations in our lab (data not shown) have indicated that varying total therapeutic radiation doses at a constant dose rate does not alter PU enough to cause instability in an aqueous environment. However, altering radiotherapy dose rate is commonly used in treating different types of cancer or targeting specific tumor locations on the body [8] and may be a contributing factor to material stability in vivo [6]. Some researchers and clinicians have suggested that radiation should be applied prior to PICC line insertion to reduce complications believed to occur through radiation exposure (thrombosis, infection, mechanical occlusion/puncture, catheter movement, and extravasation), and this study aims to investigate whether radiation may be the cause of any complications [6,9–11].
  The leading causes of PU catheter complications are infection and thrombosis (blood clotting). Radiation may play a role leading up to these biological responses and will be investigated using cell proliferation and adhesion studies on PU films [7]. Occlusion and puncture are mainly affected by the placement of the catheter in the body and may arise due to improper placement causing pinching of the catheter from arm movement or pinching between rib and clavicle, rupture due to pressure from liquid moving through catheter and the body’s natural immune reaction to foreign materials causing catheter-associated thrombosis [9–12]. This study investigated these complications using biocompatibility tests combined with mechanical or chemical to provide indication of strength or chemical structure changes in the material which can aid in the movement of catheters contributing to complications [12]. Our current investigation does not focus on how material properties of catheters change only on whether or not they need to be removed.