Near-Field Scanning Optical Microscopy for High-Resolution Membrane Studies

Abstract

The desire to directly probe biological structures on the length scales that they exist has driven the steady development of various high-resolution microscopy techniques. Among these, optical microscopy and, in particular, fluorescence-based approaches continue to occupy dominant roles in biological studies given their favorable attributes. Fluorescence microscopy is both sensitive and specific, is generally noninvasive toward biological samples, has excellent temporal resolution for dynamic studies, and is relatively inexpensive. Light-based microscopies can also exploit a myriad of contrast mechanisms based on spectroscopic signatures, energy transfer, polarization, and lifetimes to further enhance the specificity or information content of a measurement. Historically, however, spatial resolution has been limited to approximately half the wavelength due to the diffraction of light. Near-field scanning optical microscopy (NSOM) is one of several optical approaches currently being developed that combines the favorable attributes of fluorescence microscopy with superior spatial resolution. NSOM is particularly well suited for studies of both model and biological membranes and application to these systems is discussed.

3D nano surface profilometry by combining the photonic nanojet with interferometry

“…By decreasing the wavelength and increasing the NA, at best the lateral resolution can be improved to a value of 200 nm [3]. Near field techniques have clearly overcome the lateral resolution problem, but remain limited by the need for point scanning [4].…”

Ga-GaP nanowire hybrid optical system for enhanced coupling, focusing and steering of light

“…In figure 8(c), the field pattern of NW-droplet configuration, when excited by a plane wave of magnitude 1 V m −1 from the end of NW opposite to the droplet, resembles apertureless NSOM tip with field enhancement up to ten times at the metallic surface for the studied material system. The basic idea of NSOM is to confine the light to nano dimensions to break the diffraction limit that cannot be achieved by traditional farfield optical microscope [26]. In practical applications, NSOM metal tips are sharp and provide enhancement of the orders of magnitude for very small area whereas in our case intensity is enhanced 100 times for wider area as illustrated in figure 8(c).…”

Quantifying Polymer Chain Orientation in Strong and Tough Nanofibers with Low Crystallinity: Toward Next Generation Nanostructured Superfibers

“…200 As a result, these artifacts can severely limit the application of a-NSOM. 201 Despite the above limitations, a-NSOM version of techniques such as fluorescence spectroscopy, 202 polarization modulation (PM) optical microscopy, 203,204 as well as measurements of birefringence 205 are theoretically possible. Application of these techniques for macromolecular orientation quantification is similar in theory to their far-field counterparts (see Section 3.2), but with better spatial resolution.…”