Electrophoretic Characterization and Purification of Silica-Coated Photon-Upconverting Nanoparticles and Their Bioconjugates

Abstract

Photon-upconverting nanoparticles (UCNPs) have attracted much interest as a new class of luminescent label for the background-free detection in bioanalytical applications. UCNPs and other nanoparticles are commonly coated with a silica shell to improve their dispersibility and chemical stability in aqueous buffer and to incorporate functional groups for subsequent bioconjugation steps. The process of silica coating, however, is difficult to control without suitable analytical and preparative methods. Here, we have introduced agarose gel electrophoresis for the analysis and purification of silica-coated UCNPs. The silica shell can be doped with a fluorescent dye for direct detection in the gel without influencing the structure or electrophoretic mobility of the nanoparticles. The preparation of a bare silica shell by reverse microemulsion resulted in individual nanoparticles but also distinct aggregates that could be separated and isolated from the agarose gel. In contrast, the preparation of an ultrathin carboxylated silica shell yielded non-aggregated UCNPs only that could be directly used for protein conjugation. Agarose gel electrophoresis has also facilitated an efficient separation of protein-UCNP conjugates from excess reagents.

Encapsulation of Dual Emitting Giant Quantum Dots in Silica Nanoparticles for Optical Ratiometric Temperature Nanosensors

“…Here, we performed a systematic control of the synthetic conditions, such as control of the ligand composition at the GQD surface by post synthesis ligand exchange reaction and of GQDs/TEOS molar ratio, to prevent the formation of multicore GQD silica shell structures, and, at the same time, to limit the formation of empty silica NPs that would reduce the yield of photoactive structures, tightly aggregated NPs and inhomogeneous silica shells [47,55]. Figure 2B-D displays the TEM micrographs of the silica nanostructures prepared from pristine ( Figure 2B) and OLA-treated ( Figure 2C,D) GQDs, at increasing GQD concentration and fixed surfactant (350 µL) and TEOS volume (50 µL).…”

Microfluidic Technology for Cell Manipulation

“…EP has been mainly utilized for particle purification [87][88][89][90] and separation [83,[91][92][93][94][95][96]. It has advantages of ease of particle manipulation and simplicity [24,27].…”

Surface Functionalisation of Upconversion Nanoparticles with Different Moieties for Biomedical Applications

“…The use of agarose gel electrophoresis for the detection, separation and purification of various UCNPs based on their surface charge was reviewed by Hlaváček, A. et al (2014) [69] . Various UCNPs (NaGdF4 and NaYF4: Yb 3+ , Er 3+ ) were coated with dSiO2 and subsequently functionalised with either APTES or CEST (as displayed in Figure 9).…”

“…In parallel approaches, fluorescein (green) was added to the (d) bare or (e) carboxylated silica shell. Reprinted with permission from ref [69]. .…”