A Microfluidic Chip Based on Localized Surface Plasmon Resonance for Real-Time Monitoring of Antigen–Antibody Reactions

Significant attention has been given to study of the biochips based on localized surface plasmon resonance (LSPR) phenomenon associated with noble metal nanoparticles in aspect of analytical chemistry and biological sensing.1)Theoretically, LSPR is excited, when the frequencies of incident photon match the collective oscillations of the conductive electrons of metal nanoparticles, resulting in peaks in the extinction spectrum at wavelengths determined by the types of materials, size and shape of nanoparticles.2,3)In the LSPR based biochips, a change in interfacial refractive index (RI) upon biomolecular binding events induces a change in peak position4)or peak magnitude,5)thus providing an efficiently detectable optical signal. At present, LSPR based biochip using gold nanoparticles have exploited thoroughly for analyzing the molecular interactions in many applications such as antibodyantigen reaction, DNA–DNA hybridization, receptor–ligand, ligand–membrane, etc.6)With the current advances in biochip technology, micrototal analysis systems (mTAS)7)also termed labonachip, have received a great attractions for highly efficient,simultaneously analysis of a number of important biomolecules from proteomics to genomics. To create the overall analytical systems, several microchips which have various functions such as sample preparation, injection, separation,mixing, detection, etc are integrated into a singe device.8)If the LPSR based chip, a surface detection tool for biomolecular interactions, is applied into the mTAS, this system has become more flexibly and widely in considerably analytical applications. Until now, a microfluidic flow cell for SPR spectroscopy was fabricated by soft lithography technique using poly(dimethylsiloxane) (PDMS).9)This microdevice was successful to monitor the sequential layers of protein binding in real-time with rapid detection and reagent economy. However, due to the requirement Kretschmann configuration in total internal reflection mode, the planar SPR system has been faced with some drawbacks for lab-on-a-chip incorporation. In current LSPR studies, a simple collinear optical system operated in transmission geometry (without using Kretschmann configuration) has been reported.10)Exploiting this advantage for mTAS, a microfluidic chip based on LSPR spectroscopy was proposed in this study.Previously, our group archived the label-free detection of antigen–antibody reactions, DNA–DNA hybridizations using LSPR based nanochip.11,12)On the basis of the characteristics of our previous chip, in this study, we have fabricated a PDMS microfluidic LSPR chip using soft-lithography technique. For evaluating of the chip, antibody–antigen reaction was performed to detection insulin, one of the most important indicators for diabetes diagnosis.13)Afterimmobilizing antibody on the chip surface, real-time monitoring of insulin and anti-insulin antibody immunoreactions was studied. The LSPR responds caused by the biomolecular bindings, the dynamic range as well as the sensitivity of the chip were reported in this research. Our chip brings several advantages such as real-time detection at low experimental cost with less reagent consumption,kinetic constant determination of antigen–antibody interaction, reduction of the total analysis time, and opening the high potential for mTAS integration.

The note is here