03 October 2012

Deep glow of nanoparticles

Nanoparticles shimmer through a thick layer of fabric

News of the innovation worldThe new biocompatible nanoparticles shine through 3 centimeters of biological tissue, demonstrating the potential of nanotechnology in biomedical scanning.

An international team of scientists has created unique photoluminescent nanoparticles that shine brightly and are visible even under a three-centimeter biological tissue, that is, at a depth that makes them a promising tool for optical tissue bio-scanning.

Although optical scanning is a convenient and inexpensive technology commonly used in the field of biomedicine, modern technologies do not study tissue deeply enough.

Thus, there is a need to develop new approaches that provide high-contrast optical bio-scanning with high resolution, which doctors and scientists can use to identify tumors and other anomalies deep under the skin.

The newly developed nanoparticles consist of a nanocrystalline core containing thulium, sodium, ytterbium and fluorine, each of which is enclosed in a square shell of fluorine and calcium.

Particles are special for a number of reasons. First, they absorb and emit near-infrared light with a much shorter wavelength than the absorbed light. This is different from how molecules in biological tissues absorb and emit light, and therefore scientists can use nanoparticles to produce deeper contrast images than traditional fluorescence-based methods.

Secondly, the material for shells – calcium fluoride – is a substance contained in the mineral of teeth and bones. It makes the particles biocompatible, reducing the risk of negative effects of nanoparticles on the body. The shell, as it turned out, significantly increases the efficiency of photoluminescence.

To emit light, nanoparticles use the NIR-to-NIR (near-infrared-to-near-infrared up-conversion) process or the conversion of near-infrared to near-infrared. During this process, the particles absorb pairs of photons and combine them into single high-energy photons, which are then emitted.

One of the reasons that this process is ideal for optical scanning is that the particles absorb and emit light in the near-infrared region of the electromagnetic spectrum, which helps to reduce the secondary interaction. This region of the spectrum is known as the optical transparency window for biological tissue, since biological tissues absorb and scatter light to a minimum extent in this range.

The scientists tested the particles in experiments on mice, and also obtained a visual representation of a capsule full of particles through a piece of pork more than 3 cm thick. In each case, the scientists were able to obtain bright high-contrast images of particles shining through the fabric.

The results of the study are published in ACS Nano: Dong et al., NIR-to-NIR Two-Photon Excited CaF2:Tm3+,Yb3+ Nanoparticles: Multifunctional Nanoprobes for Highly Penetrating Fluorescence Bio-Imaging.

Portal "Eternal youth" http://vechnayamolodost.ru03.10.2012

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