119 A Hook Effect-based Lateral Flow Immunoassay Sensor for Cerebrospinal Leak Detection

Abstract

INTRODUCTION: A rapid test for the presence of cerebrospinal fluid (CSF) would be ideal in the management of postoperative fluid collections after spinal surgery. In order to ascertain the nature of the fluid the gold standard has been to send the fluid for gel electrophoresis which is time consuming and expensive in order to determine the presence or absence of beta-2 transferrin. METHODS: A cassette containing a lateral flow strip was used with two conjugates: a gold nanoshell-anti-TF antibody conjugate (conjugate 1) and a gold nanoshell-lectin conjugate (conjugate 2).After a sample is applied, a chromatographic sandwhich forms in two detection zones to yield a detectable dark line: Test line 1 (T1) where anti-TF antibodies are embedded form a sandwich reaction with analyte (TF) and with conjugate 1 and test line 2 (T2) where embedded serum glycoproteins react with conjugate 2. A control line with anti-mouse IgG antibody is embedded to form a reaction with conjugate 1. We availed the well-known hook effect as both T1 and T2 detection zone development was inhibited by the saturation of binding sites of the conjugates and embedded material. RESULTS: 18 clinical samples of either CSF or postoperative drain fluid (serum) were tested using a third generation LFI. There were 7 CSF samples and 11 serum samples and one with buffer only. The hook effect-based LFI successfully discriminated positive clinical CSF samples from negative samples in all cases. CONCLUSIONS: This novel hook effect-based LFI sensor offers a fast, highly accurate and easy to use POC test for CSF leak.