Visualization and measurement of the local absorption coefficients of single bilayer phospholipid membranes using scanning near-field optical microscopy

Abstract

Here we report the results of shear-mode thicknesses and absorption coefficient measurements made on neat membranes using scanning near-field optical microscopy (SNOM). Biomimic neat membranes composed of two different types of phoshpholipid molecules: 1,2dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were found to exhibit different absorption coefficients under the SNOM. The localization of the lipids could be identified and correlated to the morphology of the membrane domains indicating that SNOM can be an effective and accurate approach for the label-free characterization of the structure-function relationships in cell membranes.

Dielectric dispersion characteristics of the phospholipid bilayer with subnanometer resolution from terahertz to mid-infrared

“…Hielscher et al measured the absorbance spectra of six different types of phospholipids in the far-infrared region from 600 to 50 cm −1 using Fourier transform infrared spectroscopy ( Hielscher and Hellwig, 2012 ). Siddiquee et al imaged dioleoylphosphatidylcholine (DOPC) and DPPC membranes based on the local absorption coefficients measured by a scanning near-field optical microscopy system with 640 nm laser beam ( Siddiquee et al, 2019 ). In summary, although previous studies have made great contributions to the frequency-dependent optical/dielectric constants of the phospholipid bilayer, however, the dispersion profiles obtained by both theoretical and experiment methods are almost narrowband spectra.…”

Imaging and spectroscopy of domains of the cellular membrane by photothermal-induced resonance

“…The technique was first demonstrated using visible light 8 and later extended to the mid-IR region. 9 SNOM allows measuring samples as thin as single phospholipid bilayers with nanoscale resolution, 10 but the need to operate in a transmission configuration limits application to thicker samples, such as eukaryotic cells. The constrains of transmission measurements are circumvented by using a scattering SNOM configuration (s-SNOM), which allows nanoscale IR spectroscopy by using the light scattered at the interface between a nanoscale metallic tip and the sample.…”

Nanoscale Probing of Cholesterol-Rich Domains in Single Bilayer Dimyristoyl-Phosphocholine Membranes Using Near-Field Spectroscopic Imaging

“…In our previous work, we demonstrated the use of scanning near-field optical microscopy (SNOM) to visualize and characterize the molecular organization of single bilayer membranes at the nanoscale. 44 Similar to AFM, apertureless SNOM which is also known as scattering-type SNOM (s-SNOM) is a tapping-mode scanning force microscope 45,46 that provides morphological information of the samples surface; however, it also simultaneously generates an optical image at high spatial resolution which makes it ideal for imaging the coexisting membrane microdomains in lipid−cholesterol mixtures. Furthermore, by incorporating a Fourier transform spectrometer, s-SNOM can also be used to perform nano-FTIR measurements.…”