Enhanced sensitivity of gold elliptic nanohole array biosensor with the surface plasmon polaritons coupling

Abstract

Surface plasmon resonance (SPR) spectroscopy of the metal nanostructure (MN) is widely used in chemical and biological sensing. The biosensor characteristics of the MN are affected by the size, shapes, substrate, and so on. Especially, some studies about the mode of the MN show that the surface plasmon polaritons (SPPs) coupled mode excitation has a significant impact on the sensitivity of the MN biosensor. To reach the aim of obtaining the high sensitivity MN biosensor, the coupled mode of the gold elliptic nanohole array (GENA) was simulated and analyzed. It shows that the coupled mode was influenced by the refractive indexes of medium and substrate. The coupled mode resonance peak shows a higher sensitivity than that of other SPPs mode peaks. The GENA biosensor chips were fabricated and integrated with polydimethylsiloxane (PDMS) microfluidics. The sensitivity of the GENA is characterized by transmission spectra of GENA in deionized water and aqueous NaCl solution. The coupled mode peak sensitivity of the biosensor reaches 549 nm/RIU. An antigen-antibody interaction experiment was also adopted to verify the sensitivity of the surface binding reaction. The sensitivity of detected concentration of the AFP (α-fetoprotein) in our experiment has been reached 25 ng/ml closed to the clinic concentration. The GENA biosensor chip has potential application in label-free chemical and biomedical fields, especially, cancer biomarker testing.