Label-free methods of multiparametric surface plasmon resonance and MPQ-cytometry for quantitative real-time measurements of targeted magnetic nanoparticles complexation with living cancer cells

Most of the methods used today for investigation of nanoparticle binding to living cells imply a quantitative or qualitative analysis and do not provide information on the binding dynamics. To meet the challenge, we show here for the first time that the interaction of metal nanoparticles with eukaryotic cells in the flow system in dynamics can be studied by the method of multiparametric surface plasmon resonance. To this aim, we obtained a spectrum of colloidally stable targeted magnetite nanoparticles modified by phytolectins (SBA, WGA, ConA) of different specificity to monosaccharides (GalNAc, GlcNAc, and Man, respectively), and studied the interaction of these conjugates with human epidermoid carcinoma A431 cells. We showed that multiparametric surface plasmon resonance can be effectively used as a label-free method to study the process of dynamic mass transfer in the nanoparticle*cell system in the fluid cell. We show that not only the commonly used parameter in such systems, the angle of the minimum peak, theta(SPR), at the full angular spectrum, but also the intensity, I, of this peak, can be used to study the binding of targeted nanoparticles with living cells in dynamics. This is due to the contribution of metal nanoparticles to resonant absorption of incident electromagnetic radiation by free electrons at the interface between media with different refractive indices. To get the most relevant quantitative data on nanoparticle binding to the cell surface, we combined this assay with our original MPQ-cytometry method (Magnetic Particle Quantification based cytometry) precisely quantifying the nanoparticles in the static cell sample. By the combination of label-free plasmonic and magnetometry-based MPQ-cytometry methods, we showed that nanoparticles modified with agglutinin from soybeans, SBA, most efficiently (up to 4.2 +/- 0.1 pg/ cell) bind to epidermoid carcinoma cells with achieving a saturation at 12 min.

Automated summary

The study shows that multiparametric surface plasmon resonance is an effective label-free method for investigating the dynamic binding process between nanoparticles and cells, where both the angle and intensity of the peak in the full angular spectrum can be utilized.