Label-free high-resolution infrared spectroscopy for spatiotemporal analysis of complex living systems

Abstract

Label-free chemical and structural imaging of complex living tissue and biological systems is the holy grail of biomedical research and clinical diagnostics. The current analysis techniques are time-consuming and/or require extensive sample preparation, often due to the presence of interfering molecules such as water, making them unsuitable for the analysis of such systems. Here, we demonstrate a proof-of-principle study using label-free optical photothermal mid-infrared microspectroscopy (O-PTIR) for fast, direct spatiotemporal chemical analysis of complex living biological systems at submicron resolution. While other analytical methods can provide only static snapshots of molecular structures, our O-PTIR approach enables time-resolved and in situ investigation of chemical and structural changes of diverse biomolecules in their native conditions. This comprises a technological breakthrough in infrared spectroscopy to analyze biomolecules under native conditions over time: in fresh unprocessed biopsies, living brain tissue, and vertebrates without compromising their viability.One-Sentence SummaryProof-of-principle application of non-destructive O-PTIR for high-resolution spatiotemporal chemical and structural analysis of unprocessed biopsies, living brain tissue, and vertebrates.

Protein-structure-sensitive mid-infrared optoacoustic microscopy enables label-free assessment of drug therapy in myeloma cells

“…[32][33][34] However, due to the low thermo-optic coefficients of water and protein (dn/dT: ~9 x 10 -5 and ~1.4 x 10 -4 , respectively), OPTIR applies high-intensity tightly-focused probe-beam irradiation for detection, which could induce thermal stress and photo-oxidative damage of cells over long exposure. 35,36 Unlike conventional optical microscopy, Mid-infraRed Optoacoustic Microscopy (MiROM) is a positive-contrast modality that allows label-free spectral imaging of biomolecules in living cells by detecting optically-generated ultrasound waves that increase in intensity as optical absorption increases. 37 We have previously demonstrated that MiROM affords higher sensitivity than Raman microscopy in the fingerprint spectral region (1800 -900 cm -1 ) but, until now, proteins have been detected mainly by using the amide II band (1600 -1500 cm −1 ) mainly associated with C-N stretching and N-H bending vibrations.…”