Metal Enhanced Fluorescence Improved Highly Sensitive Capillary Electrophoresis by Localized Oblique Angle Deposition

The aim of this proposal is to improve the performance and sensitivity of capillary electrophoresis (CE), an important biomolecules separation technique, by reducing Joule heating in separation channel and enhancing the detection signal.

Biomolecules separation is an important step in biological analysis and medical diagnostics of single type biomolecules. In the separation system, the biomolecules are normally labeled with fluorophores so that the separation can be detected by fluorescence signal. A large cross section for the separation channel is helpful for signal detection but easy to cause Joule heating, which is not desirable for the separation efficiency and reproducibility. On the contrary, the reduced channel cross section can minimize Joule heating but is difficult for signal observation. To overcome this challenge, metal enhanced fluorescence (MEF) could be used to enhance the fluorescence signal to 10-100 times in the reduced CE microchannels. MEF refers to the improved fluorescence intensity when the fluorophores are in close proximity of metal nanostructures, especially Au or Ag nanostructures, owing to their unique plasmon resonance property.

To integrate MEF into CE microfluidic system, one challenge is how to incorporate metal nanostructures into microchannels. Here we propose to employ localized oblique angle deposition (LOAD) to fabricate metal nanostructures in the microchannels. LOAD can overcome a few difficulties the current fabrication methods are facing, such as the limit of channel dimension, difficulty in alignment, etc. In this project, preliminary research on MEF effects of metal nanostructures integrated into microchannel by LOAD will be investigated; and further experiments on DNA separation will be carried out.

There are currently more than 200 diagnostic centers in Hong Kong. Most of them mainly focus on bioanalytical and medical diagnostic applications. Our studies will lead to the development of simple, low-cost, and highly sensitive biomolecules separation technique by taking the advantages of metal enhanced fluorescence in microfluidic systems. We believe that the success of this proposal will lead to commercialization of lab-on-a-chip bio-analysis and bio-detection technique in the related industry.