Materials Science

Beating Fluorescent Background

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Science  13 Sep 2013:
Vol. 341, Issue 6151, pp. 1153
DOI: 10.1126/science.341.6151.1153-b

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A challenge for fluorescent imaging of biological samples is that compounds in cells and tissues, such as flavins, autofluoresce. One way to overcome this autofluorescent background is to work in the near-infrared spectral region (wavelengths of 650 to 900 nm). However, even in this region, some background signal is present, so it is desirable to use markers that have longer lifetimes than those of the naturally present molecules (typically tens of nanoseconds). Gu et al. describe the use of photoluminescent porous silicon nanoparticles for imaging. The nanoparticles were synthesized by electrochemical etching of the surface of a single-crystal silicon in hydrofluoric acid. This layer was then removed and fractured with ultrasound, and the size-filtered nanoparticles were coated with polyethylene glycol. The luminescent lifetime of the nanoparticles (5 to 13 µs) allowed for time-gated imaging of samples. This approach achieved a greater than 50-fold reduction in background signal in vitro and greater than 20-fold in vivo. The authors used this method to image human ovarian cancer xenografts in a mouse model.

Nat. Comm. 4, 2326 (2013).

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