Cheaper and better
Silicon nanoparticles coped with the "highlighting" of the body better than gold
An international team of scientists with the participation of researchers from ITMO University has shown that spherical silicon nanoparticles coated with fluorescent (luminous) dye molecules can be successfully used to visualize internal organs, tissues and individual cells in the study of the human body. It was also found that silicon nanoparticles with a dye placed directly on the surface are more effective than similar particles made of gold. Such nanoobjects can be used both for biological imaging – obtaining images of what is happening inside the cell, and for delivering drugs or genetic material there. The corresponding article was published in Scientific Reports (Zyuzin et al., Photoluminescence quenching of dye molecules near a resonant silicon nanoparticle).
Fluorescent dyes are widely used in biological and medical research around the world. For example, they cover nanoparticles that are used to highlight intracellular processes or as a means of drug delivery. Due to luminescence, it is possible to trace the path of a nanoparticle loaded with drugs in the intracellular space. At the same time, it is important that the glow of the dye is strong enough.
To do this, it is necessary to take into account the material of the particle and the distance between the dye and its surface. Usually a special separator is used between the nanoparticle material and the fluorescent dye molecules. But there is also an alternative approach – to apply a dye to spherical nanoparticles with sufficiently good light scattering parameters. Scientists from ITMO University together with colleagues from Germany and Sweden studied in detail three configurations of different nanoparticles of this type.
The control sample was nonresonant nanoparticles of yttrium vanadate YVO 4. They do not affect the intensity of the dye's light signal in any way – they have neither a resonance that enhances the dye's glow, nor a noticeable parasitic absorption. In addition, spherical nanoparticles made of gold and silicon were used. The last two types of particles had the same proper sizes.
Both simulations and experiments have shown that the luminescent signal of a dye on a silicon particle can be amplified three times compared to their gold-based counterparts.
The reason for such a noticeable superiority of silicon over a noble metal is the so–called Mie scattering. Light scattering by a spherical particle can occur in different ways. If the diameter of a particle has a certain ratio with the wavelength of the radiation incident on it, an Mi resonance may occur, in which such radiation is reflected from the particle noticeably amplified. Due to the high refractive index of silicon, the resonance of its spherical particles with a size of one hundred nanometers falls into the visible region of the spectrum. Thus, resonant silicon particles can enhance spontaneous visible radiation from nanoparticles with dyes and improve the optical signal from the surface under study.
Interestingly, the luminescent signal fades on the surface of the gold particle, so the dye must be placed at some distance from the gold – using a special separator. To create it, you have to use chemical methods, which can be complex and costly. These additional steps can be avoided by using silicon nanoparticles that enhance the luminescent signal even if the dye is directly on their surface.
In addition, the work showed that silicon particles coated with luminescent molecules can be absorbed by cancer cells.
Portal "Eternal youth" http://vechnayamolodost.ru