Highly Sensitive SPR Biosensor Based on Nanoimprinting Technology

Abstract

Detection of biomolecular interactions is becoming more important as a technique to achieve rapid diagnoses of incipient diseases and preventive medical care. Among various detection techniques currently available (e.g., fluorometry, quartz crystal microbalance, etc.), surface plasmon resonance (SPR)-based biosensing has received much attention since it does not require any labelling of the analytes and enables high-throughput real-time sensing. The SPR technique allows very fast measurements of the order of several minutes, whereas conventional enzyme-linked immunosorbent assay (ELISA) methods are often lengthy processes. Recently, SPR-based biosensors have been extensively applied to analyses in biomedical (Vaisocherova et al., 2006), environmental (Dostalek et al., 2006), and food sciences (Ladd et al., 2006). In conventional SPR, the evanescent field penetrates into the metal surface by as much as ~300 nm (Stenberg et al., 1991, Homola, 2003). When the target analyte binds to the metal surface, changes in the local refractive index occur, which in turn causes the SPR angle to shift. However, the sensing of target molecules suffers due to unwanted noise factors such as the instability of the temperature and the change in the refractive index of the mobile phase. Thus, the “sensing depth” of conventional SPR is significantly larger than the range required for practical use such as in clinical diagnoses. In this paper, we demonstrate that the sensing depth of SPR can be controlled by producing a pattern of periodic metal nanogrooves on the sensor surface.