Perspectives

SERS has long been considered as a potential biosensing technology due to its inherently high sensitivity and its ability to provide unique spectroscopic fingerprints of the target analyte. Our recent studies show that, with the appropriate substrate, SERS offers a potent biosensing platform with many advantages over current biosensing or detection applications.

Despite the potential power of SERS as a biosensing tool, there remain critical and practical issues that need to be addressed before the technique can be routinely applied. One consideration is the need to produce inexpensive and reliable SERS substrates having uniformly high enhancements. Another important consideration is the reproducibility of the spectral response from the target biomolecule, which ultimately relates to the statistical reliability of the method. A practical SERS substrate fabrication method would produce an inexpensive, uniform, reproducible, and reusable SERS-active substrate. Since SERS enhancements critically depend on substrate nanomorphology, a practical fabrication method should have the ability to produce nanostructured arrays with specific size, shape, alignment, and architecture within very tight tolerances. Thus, the challenges for a practical SERS nanostructure fabrication method are the ability to:

(i) control the size, aspect ratio, and shape of nanostructures;

(ii) grow the desired nanostructure at low temperature and onto a particular substrate geometry, e.g. flat, cylindrical, or tapered;

(iii) fabricate metallic and dielectric nanostructures in a multilayered fashion; and

(iv) integrate the fabrication process with other conventional microfabrication techniques.

When considering ultrasensitive SERS detection, e.g. low viral or bacterial loads in a clinical sample, the issue of statistical sampling arises. In such cases, it is possible that when the amount of SERS analyte presents a severe limitation, surface coverage relative to the laser spot size may become an issue in detection. However, this situation may be overcome by employing analyte capture methods, e.g. using antibodies, or by concentrating the limited analyte to be detected. Solutions for these critical issues are addressable and are being investigated so that the door may be opened to a new era of biodetection.