Ultrathin and smooth poly(methyl methacrylate) (PMMA) films for label-free biomolecule detection with total internal reflection ellipsometry (TIRE)

Abstract

Ultrathin poly(methyl methacrylate) PMMA films were prepared on gold substrates by spin coating PMMA dissolved in toluene. By varying the concentration of PMMA, spin coating speed and curing condition, we obtained very smooth and ultrathin PMMA films. The PMMA films were transformed into highly reactive film containing carboxylic functionalities using UV/O(3) irradiation. These films were shown to remain stable and reactive for at least one week. We then demonstrated the application of the UV/O(3) treated PMMA films for the detection of microRNAs using a label-free detection method called total internal reflection ellipsometry (TIRE). A limit of detection of 10 pM was established. The technique proposed here is a simple and quick method for generating carboxylic functional films for label-free bioanalytical detection techniques.