Langmuir-Blodgett films of fluorescently labeled phospholipid for nano-biosensors characterized by laser-induced fluorescence

Abstract We studied the structural and optical properties of organic single monolayers from the phospholipid Dipalmitoyl Phosphatidyl Ethanolamine head-labeled with the fluorescent chromophore Nitrobenzoxadiazole (DPPE-NBD). Nano-thin (∼ 3.1 nm) Langmuir-Blodgett (LB) films were deposited on different solid substrates. The structure of the produced single monolayers was characterized using fluorescence spectroscopy, subnanosecond laser excited Fluorescence Lifetime Imaging Microscopy (FLIM) and Atomic Force Microscopy (AFM). The obtained structural properties of the DPPE-NBD LB single monolayers were used for optimizing their density and the technology of their deposition targeted at chemical sensing applications. At specialized deposition conditions, stable 3D aggregates in the monolayer were formed, thus yielding a high surface-to-volume ratio, which gives high sensitivity and fast response time. The chemical sensitivity was tested towards non-polar and polar Volatile Organic Compounds (VOCs). In this case, the LB deposition was carried on a two-port 434 MHz Surface Acoustic Wave (SAW) resonator. A combination of gravimetry and Electrical Impedance Spectroscopy (EIS) was used for the transduction. Combining two transduction methods on a single device provides additional information for differentiating between compounds with similar responses to one of the methods.