title: Near-field penetrating optical microscopy: a live cell nanoscale refractive index measurement technique for quantification of internal macromolecular density.
abstract: Quantification of intracellular nanoscale macromolecular density distribution is a fundamental aspect to understanding cellular processes. We report a near-field penetrating optical microscopy (NPOM) technique to directly probe the internal nanoscale macromolecular density of biological cells through quantification of intracellular refractive index (RI). NPOM inserts a tapered optical fiber probe to successive depths into an illuminated sample. A 50 nm diameter probe tip collects signal that exhibits a linear relationship with the sample RI at a spatial resolution of approximately 50 nm for biologically relevant measurements, one order of magnitude finer than the Abbe diffraction limit. Live and fixed cell data illustrate the mechanical ability of a 50 nm probe to penetrate biological samples.
authors.affiliation: Biomedical Engineering Department, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Samantha Dale
authors.initials: SD
authors.lastname: Strasser
authors.forename: Gajendra
authors.initials: G
authors.lastname: Shekhawat
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Rogers
authors.forename: Vinayak P
authors.initials: VP
authors.lastname: Dravid
authors.forename: Allen
authors.initials: A
authors.lastname: Taflove
authors.forename: Vadim
authors.initials: V
authors.lastname: Backman
mesh_terms: D002477:Cells / Q000648:ultrastructure*; D002610:Cheek; D006801:Humans; D046911:Macromolecular Substances / Q000648:ultrastructure; D008853:Microscopy / Q000379:methods*; D020527:Microscopy, Scanning Probe / Q000379:methods; D055100:Optical Fibers; D012031:Refractometry / Q000379:methods
chemical_list: D046911:Macromolecular Substances