Imaging gap junctions with silica-coated upconversion nanoparticles

Abstract

Upconversion nanoparticles (UCN) that are excited in the near infrared (NIR) region were synthesized and modified to enable their application to biological systems for imaging. The UCN obtained are oleic acid capped and hence hydrophobic in nature. Since the particles were to be used for imaging cells, a surface modification to make them hydrophilic and biocompatible was performed. Silica coating was chosen for the modification due to the possibility to further functionalize the surface and conjugate biomolecules. Cardiac cells which are capable of forming gap junctions were selected to be labeled. Gap junction specific antibodies were conjugated to the silica-coated UCN. The fluorescence emission spectrum of the particles was obtained with a continuous wave 980 nm laser and size of the particles before and after coating was determined to be 30 and 50 nm, respectively, by TEM. A covalent coupling method was used to bind the gap junction specific antibody to the nanoparticles. The fluorescence imaging experiments were carried out on cardiomyoblast cells and co-culture of bone marrow stem cells/cardiomyoblast cells after incubation with the antibody-modified UCN. Images of the particles after incubation with cardiac cells obtained over days demonstrated the potentials of the UCN for fluorescence imaging.

Time-gated luminescence bioimaging with new luminescent nanocolloids based on [Mo6I8(C2F5COO)6]2−metal atom clusters

“…13,14 They are usually achieved through the encapsulation of superparamagnetic nanocrystals such as ferrites 15 or photonic nanocrystals such as metal nanoparticles 16,17 or luminescent nanophosphors such as organic dyes, 18,19 semi-conductor quantum dots, [20][21][22][23][24][25][26][27] organometallic complexes, 28,29 metal atom cluster (MC) [30][31][32][33][34] or doped nanocrystals. [35][36][37] Thus, since 2006, some of us developed a simple, versatile, highly reproducible and efficient method based on microemulsion process to prepare large amount of silica nanoparticles incorporating luminescent nanosized inorganic Mo6 or Re6 metal atom clusters based on octahedra. [30][31][32][33][34] These MC salts are generally synthesized by a solid state chemistry route at high 8 I 8X ] 2-nano-sized cluster units (M = Mo, W or Re) wherein the M6 cluster is face-capped by eight inner ligands (X i ) and additionally bonded to six apical ligands (X a ).…”

Small Upconverting Fluorescent Nanoparticles for Biosensing and Bioimaging

“…[ 153 ] Other works have imaged cancer cell with UCNPs conjugated with folic acid, which target folate receptors overexpressed on various types of cancer cells. [ 155 ] Another representative study from Zhang's group [ 156 ] utilizes the sandwich structure of UCNPs to produce three spectrally distinct UCNPs, which when individually conjugated to different antibodies, enables the multiplexed imaging of three subcellular targets with a single NIR excitation wavelength ( Figure 5 ). [ 155 ] Another representative study from Zhang's group [ 156 ] utilizes the sandwich structure of UCNPs to produce three spectrally distinct UCNPs, which when individually conjugated to different antibodies, enables the multiplexed imaging of three subcellular targets with a single NIR excitation wavelength ( Figure 5 ).…”

Lanthanide-Based Upconversion Nanoparticles for Connexin-Targeted Imaging in Co-cultures

“…The primary advantage is excitation in the near-infrared wavelength and emission in the visible region (e.g., ytterbium (Yb 3+ ), erbium (Er 3+ ) doping) or nearinfrared region (e.g., ytterbium (Yb 3+ ), thulium (Tm 3+ )). The NIR excitation and emission would allow noninvasive in-depth imaging as the longer wavelengths are absorbed/scattered less by biological tissue (9)(10)(11)(12). These particles also do not show blinking and have negligible photobleaching when compared to organic fluorophores (13,14).…”

“…Thus it was of interest to use cardiac cells and bone marrow stem cell co-culture as a model and target UCNs conjugated to the connexin 43-specific antibody. Since the nanoparticles do not photobleach over time it would be possible to image the cells over different time points or days (9). Here we discuss the synthesis and modification of the surface of the nanoparticles using silica to obtain core/shell structure and further using a covalent coupling method to conjugate the antibody to the surface of the nanoparticles.…”