In Situ Monitoring of Layer-by-Layer Assembly Surface Modification of Nanophotonic-Microfluidic Sensor

Abstract

An elaboration of the photonic based sensors is the most promising direction in modern analytical chemistry from the point of view of real clinical applications. The highest sensitivity is demonstrated by sensors based on photonic integrated circuits (PICs). This type of sensor has been recently successfully combined with microfluidics, which decreased the analyte volume for analysis down to microliter units. The most significant disadvantage regarding these photonic sensors is low specificity. One of the methods that could be useful for such type of problem is the layer by layer (LBL) assembly. The peculiarity of a PIC based sensor is the ability to precisely control surface modification by using measurements of a minimum resonance position shift. The bovine serum albumin (BSA) and tannic acid (TA) molecules were selected for LBL assembly because on one side they form a stable LBL assembly film based on hydrogen bonds, while the other side of both TA and BSA molecules can be used for conjugation with target molecules. A microring resonator (MRR) and a Mach–Zehnder interferometer (MZI) based on a silicon nitride platform combined with a microfluidic system were elaborated and used for monitoring the LBL film assembly. Obtained results have a good correlation with measurements carried out by atom force microscopy. Thus, the ability of using PIC based sensors for in situ control of surface modification was demonstrated and can be considered in point-of-care (POC) devices that have a very good perspective for both early pathological state diagnosis and evaluation of treatment efficiency.

Ultrasensitive Nanophotonic Random Spectrometer with Microfluidic Channels as a Sensor for Biological Applications

“…The advantages of this combination are, on one hand, provided by planar and CMOS compatible fabrication technology, high sensitivity, and low limit of detection (LOD), and on the other hand, by the possibility of pumping analytes and modifying the surface of sensitive areas of PICs for increasing specificity to determined analytes by using microfluidic channels. A lot of work related to these advantages has already been presented [ 10 , 11 ], among which devices can be distinguished by the chosen sensitive component, the microring resonators (MRRs), and Mach–Zehnder interferometers (MZIs). The operation principle of these devices is based on detection by the PICs due to a change in the refractive index of the medium above the sensitive area of the sensor.…”