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Download fileNonresonant CARS Imaging of Porous and Solid Silicon Nanoparticles in Human Cells
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posted on 2021-09-23, 13:35 authored by Maxim B. Gongalsky, Daniela A. Muftieva, Jukka K.S. Saarinen, Antti Isomaki, Nikolay V. Pervushin, Gelina S. Kopeina, Leena J. Peltonen, Clare J. Strachan, Boris Zhivotovsky, Hélder
A. Santos, Liubov A. OsminkinaCoherent
anti-Stokes Raman scattering (CARS), a nonlinear optical
method for rapid visualization of biological objects, represents a
progressive tool in biology and medicine to explore cells and tissue
structures in living systems and biopsies. In this study, we report
efficient nonresonant CARS imaging of silicon nanoparticles (SiNPs)
in human cells as a proof of concept. As both bulk and porous silicon
exhibit a high third-order nonlinear susceptibility, χ(3), which is responsible for the CARS intensity, it is possible to
visualize the SiNPs without specific labels. Porous and solid SiNPs
were obtained from layers of porous and nonporous silicon nanowires
and mesoporous silicon. Electron microscopy and Raman spectroscopy
showed that porous SiNPs consisted of ∼3 nm silicon nanocrystals
(nc-Si) and pores, whereas solid nanoparticles comprised ∼30
nm nc-Si. All types of SiNPs were nontoxic at concentrations up to
500 μg/mL after 24 h of incubation with cells. We demonstrated
that although nc-Si possesses a distinguished narrow Raman band of
about 520 cm–1, it is possible to detect a high
CARS signal from SiNPs in the epi-direction even in a nonresonant
regime. 3D CARS images showed that all types of studied SiNPs were
visualized as bright spots inside the cytoplasm of cells after 3–6
h of incubation because of the contrast provided by the high third-order
nonlinear susceptibility of SiNPs, which is 1 × 104 to 1 × 105 times higher than that of water and typical
biological media. Overall, CARS microscopy can provide localization
of SiNPs within biological structures at the cellular level and can
be a powerful tool for in vitro monitoring of silicon-based drug delivery
systems or use SiNPs as labels to monitor various bioprocesses inside
living cells.
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stokes raman scatteringraman spectroscopy showedorder nonlinear susceptibilitynonlinear optical methodbright spots inside1 × 10typical biological medianonporous silicon nanowires5 sup4 supnonresonant cars imaginghigh cars signalporous silicon exhibitsolid silicon nanoparticlesporous sinps consistedsilicon nanoparticlessolid sinpsnonresonant regimehigh thirdbiological objectscars microscopycars intensitycars ),mesoporous siliconvitro monitoringuse sinpstissue structurestimes higherstudied sinpsrapid visualizationprovide localizationprogressive toolpowerful toolliving systemselectron microscopydirection evencontrast providedcellular level520 cm500 μg24 h