Infrared nanoimaging of neuronal ultrastructure and nanoparticle interaction with cells

• Published in: Nanoscale Vol. 16; no. 12; pp. 619 - 6198
• Main Authors: Greaves, George E, Allison, Leanne, Machado, Pedro, Morfill, Corinne, Fleck, Roland A, Porter, Alexandra E, Phillips, Chris C
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 21.03.2024; The Royal Society of Chemistry
• Subjects: Biomolecules; Chemistry; Functional groups; Infrared lasers; Labels; Light; Microscopy; Microscopy - methods; Nanomaterials; Nanoparticles; Nanospheres; Nanostructures - chemistry; Nanotechnology - methods; Optical microscopy; Organelles; Vibration mode
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/d3nr04948e

Here we introduce scattering-type scanning near-field optical microscopy (s-SNOM) as a novel tool for nanoscale chemical-imaging of sub-cellular organelles, nanomaterials and of the interactions between them. Our setup uses a tuneable mid-infrared laser and a sharp scanning probe to image at a resolution substantially surpassing the diffraction limit. The laser can be tuned to excite vibrational modes of functional groups in biomolecules, ( e.g. amide moieties), in a way that enables direct chemical mapping without the need for labelling. We, for the first time, chemically image neuronal ultrastructure, identify neuronal organelles and sub-organelle structures as small as 10 nm and validate our findings using transmission electron microscopy (TEM). We produce chemical and morphological maps of neurons treated with gold nanospheres and characterize nanoparticle size and intracellular location, and their interaction with the plasma membrane. Our results show that the label-free nature of s-SNOM means it has a 'true' chemical resolution of up to 20 nm which can be further improved. We argue that it offers significant potential in nanomedicine for nanoscale chemical imaging of cell ultrastructure and the subcellular distribution of nanomaterials within tissues. We use infrared nanoscopy to image subcellular components of hippocampal neurons in a chemistry specific way and to study their interaction with therapeutic nanoparticles.