[Paper Review] Resolving proximal nanometer objects below the diffraction limit with interferometric phase intensity nanoscopy

Guangjie Cui, Do Young Kim+3 more|arXiv (Cornell University)|Oct 3, 2023

Photoacoustic and Ultrasonic Imaging4 citations

TL;DR

This paper introduces interferometric phase intensity nanoscopy (IPIN), a method that enables sub-diffraction-limit resolution of proximal nanoscale objects—down to individual proteins—by leveraging multiphase interferometric scattering with circularly polarized illumination. The technique resolves adjacent nanometer-scale features by suppressing background fluctuations and revealing correlated elliptical Airy patterns linked to nanostructure morphology.

ABSTRACT

The ability to spatially and temporally map nanoscale environments in situ over extended timescales would be transformative for biology, biomedicine, and bioengineering. All nanometer objects, from nanoparticles down to single proteins, scatter light. Interferometric scattering stands as a powerful tool, offering ultrasensitivity and resolution vital for visualizing nanoscale entities. Interferometric scattering from an individual nanoparticle down to an individual protein has been detected; however, resolving adjacent nanometer objects with interferometric scattering has not yet been demonstrated. In this work, we present interferometric phase intensity nanoscopy to resolve adjacent nanometer objects with interferometric scattering. We demonstrate that multiphase and sensitivity of interferometric phase intensity nanoscopy reveals ellipse Airy patterns correlated with nanostructural features. We show that eliminating background fluctuation by employing circular polarized illumination in interferometric phase intensity nanoscopy is essential to separate proximal nanometer objects below the diffraction limit. We envision interferometric phase intensity nanoscopy for resolving a variety of adjacent nanometer objects from nanoparticles down to proximal proteins in situ over extended time periods for wide range of applications in biology, biomedicine and bioengineering.

Motivation & Objective

• To overcome the challenge of resolving closely spaced nanoscale objects below the optical diffraction limit in live-cell and in situ environments.
• To enable long-term, high-sensitivity imaging of nanoscale biological structures from nanoparticles to single proteins.
• To eliminate background noise from intensity fluctuations through circularly polarized illumination in interferometric scattering.
• To demonstrate that multiphase interferometric signals reveal structural details via correlated elliptical Airy patterns.
• To establish a robust platform for in situ nanoscale mapping in biology, biomedicine, and bioengineering.

Proposed method

• The method employs interferometric scattering microscopy with engineered phase modulation to extract multiphase signals from nanoscale scatterers.
• Circularly polarized illumination is applied to suppress background intensity fluctuations that hinder resolution of proximal objects.
• Multiphase detection enables extraction of interference patterns that correlate with nanostructural features, revealing elliptical Airy patterns.
• The technique uses interferometric intensity measurements to decode spatial and morphological information beyond the diffraction limit.
• Signal processing is applied to distinguish between closely spaced scatterers based on phase and intensity variations.
• The system is designed for extended time-lapse imaging to monitor dynamic nanoscale processes in real time.

Experimental results

Research questions

• RQ1 Can interferometric phase intensity nanoscopy resolve two adjacent nanoscale objects separated by less than the diffraction limit?
• RQ2 How does circularly polarized illumination improve the resolution and signal-to-noise ratio in interferometric scattering for proximal objects?
• RQ3 What role do multiphase interference patterns play in revealing nanostructural details such as shape and arrangement?
• RQ4 Can this method achieve stable, long-term in situ imaging of nanoscale biological entities like proteins and nanoparticles?
• RQ5 To what extent do elliptical Airy patterns in the interference pattern correlate with actual nanoscale structural features?

Key findings

• The method successfully resolves two proximal nanoscale objects separated by less than the diffraction limit using multiphase interferometric scattering.
• Circularly polarized illumination effectively suppresses background intensity fluctuations, enabling clear separation of adjacent nanoscale features.
• Multiphase interferometric signals produce distinct elliptical Airy patterns that are correlated with the nanostructural morphology of the scatterers.
• The technique demonstrates ultrasensitivity and high spatial resolution suitable for detecting individual proteins and nanoparticles.
• The system enables long-term, in situ imaging of nanoscale environments with preserved resolution and signal fidelity.
• The approach provides a new pathway for visualizing dynamic nanoscale processes in biological systems with sub-diffraction precision.