Highly Sensitive Protein Detection By Asymmetric Mach-Zehnder Interferometry For Biosensing Applications

The sensitivity and performance of an asymmetric Mach-Zehnder interferometer (aMZI) were compared to those of quartz crystal microbalance with dissipation (QCM-D). The binding of streptavidin to sensor chips coated with poly-L-lysine (PLL), modified with biotin and oligoethyleneglycol (OEG) (PLLbiotin), was used to compare the binding signals obtained from both technologies. PLL-biotin proved to be an efficient method to add bioreceptors to both the QCM-D and aMZI chips. The final, saturated value of streptavidin binding was compared with those from aMZI (253 ng cm(-2)) and QCM-D (460 ng cm(-2)). These values were then used to evaluate that 45% of the measured streptavidin mass in the QCM-D came from hydrodynamically coupled water. Importantly, the signal-to-noise ratio of the aMZI was found to be 200 times higher than that of the QCM-D. These results indicate the potential of the aMZI platform for highly sensitive and accurate biosensing applications.