Print-and-stick unibody microfluidics coupled surface plasmon resonance (SPR) chip for smartphone imaging SPR (Smart-iSRP)

The design of a smartphone imaging surface plasmon resonance (Smart-iSPR) system integrated with an affordable 3D-printed microfluidic SPR chip fabricated via a facile manufacturing approach could pave the way towards the development of miniaturized and integrated smartphone iSPR biosensors for emerging point-of-use applications. Conventional smartphone-based SPR systems using soft photolithography for the fabrication of microfluidics SPR chips are costly, labour-intensive and required a specially-equipped light-controlled environment, that is inadequate and mismatched with the consumer-based smartphone detection platform. Herein, we report the design, fabrication and testing of an innovative print-and-stick unibody microfluidics coupled SPR chip for smartphone iSPR. The 3D-printed microfluidics (∼€0.006) is assembled via an aptly-sized adhesive tape with the gold SPR sensing surface. Such a simple integrated microfluidic SPR chip with the print-and-stick configuration has a high resistance to fluid leakages at the channel-to-sensor interface with pressure up to 66.9 Pa and the tubing-to-inset interfaces with pressure up to 86.9 Pa. The smartphone iSPR platform weighs 138 g and with a dimension of around 70 × 60 × 40 mm3, and its performance was characterized using a standard Biacore® β2-microglobulin calibration kit. The sensorgrams obtained by the smartphone iSPR show all the typical characteristics for surface functionalization, association and dissociation events. The smartphone iSPR responds linearly to β2-microglobulin within the range of 10–200 nM (R2 = 0.986) with a limit-of-detection (LOD) of 1.5 nM. Given the miniaturized feature and simple camera-based imaging smartphone iSPR, the analytical performance is satisfactory when compared with the analytical dynamic range of 2–32 nM described in the Biacore® protocol.