Synthesis and optimization of organic sensing platforms for label-free DNA detection

Label-free DNA detection by silicon-based field effect devices has been widely studied in recent years. DNA recognition is based on the detection of changes in the electrical surface potential and thus requires reliable and selective immobilization of charged biomolecules on the device surface. Self-Assembled monolayers of phosphonic acids (SAMPs) can be used as an underlying platform to prepare well-defined organic interfaces with a high density of receptor binding sites close to the sensing surface. In this work, we report the functionalization and characterization of a silicon surfaces covered by a thin native oxide layer with different types of peptide nucleic acid (PNA), a synthetic analogue to DNA. To investigate the impact of receptor density and morphology on DNA hybridization, PNA molecules are covalently bound either in a multidentate or monodentate fashion to the underlying SAMPs. Multidentate binding of the receptor via attachment groups at the γ-points along the PNA backbone results in a rigid, lying configuration on the device surface, whereas a monodentate binding provides more flexible and more accessible receptor binding sites.