Clinical validation of fiberoptic immunobiosensor for point-of-care analysis of plasma nerve growth factor

Background: Upregulation of plasma nerve growth factor (NGF) is indicative of cardiac nerve sprouting that is underlying the mechanisms for cardiac arrhythmias. A conventional assay method (e.g., enzyme-linked immunosorbent assay [ELISA]) is usually time consuming and technically complicated for NGF analysis for potential arrhythmia prognosis. Objective: This study is to develop a rapid and and reliable assay method for point-of-care (POC) testing of plasma NGF. Methods: We recently developed a fiberoptic immunobiosensor for point-of-care testing of human plasma NGF. Physiological concentrations of NGF (1 to 200 ng/ml) could be quantified in both buffer and human blood plasma samples (100 μl) within 5 min. The intra-assay coefficient of variation was 5%, and the interassay coefficient of variation was 8%. The clinical utility of the NGF biosensor was evaluated using clinical blood samples from atrial fibrillation patients (n = 21). Peripheral venous blood was sampled before and immediately after radiofrequency ablation and again at postoperative day 1. Results: The NGF level did not change significantly between before (15.73 ± 16.67 ng/ml) and immediately after radiofrequency ablation (13.58 ± 11.45 ng/ml, P = NS); however, there was a significant elevation to 28.41 ± 19.52 ng/ml in postoperative day 1 (P <.01). In a follow-up study (11 ± 1 months), the increased magnitude in patients with atrial fibrillation recurrence (4.1-fold ± 1.96-fold) was significantly higher than those without (1.72-fold ± 0.53-fold; P <.001). The results were highly comparable to those of the ELISA analysis. Conclusion: Because of the comparable data accuracy and much faster assay time as compared with ELISA, the fiberoptic biosensor is promising as a clinical POC assay method for plasma NGF analysis at patient bedsides for potential cardiac disease diagnosis and prognosis.