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.
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ABSTRACT: Upconversion nanoparticles (UCNs) are nanoparticles that are excited in the near infrared (NIR) region with emission in the visible or NIR regions. This makes these particles attractive for use in biological imaging as the NIR light can penetrate the tissue better with minimal absorption/scattering. This paper discusses the study of the depth to which cells can be imaged using these nanoparticles. UCNs with NaYF(4) nanocrystals doped with Yb(3+), Er(3+) (visible emission)/Yb(3+), Tm(3+) (NIR emission) were synthesized and modified with silica enabling their dispersion in water and conjugation of biomolecules to their surface. The size of the sample was characterized using transmission electron microscopy and the fluorescence measured using a fluorescence spectrometer at an excitation of 980 nm. Tissue phantoms were prepared by reported methods to mimic skin/muscle tissue and it was observed that the cells could be imaged up to a depth of 3 mm using the NIR emitting UCNs. Further, the depth of detection was evaluated for UCNs targeted to gap junctions formed between cardiac cells.Nanotechnology 09/2011; 22(39):395101. · 3.98 Impact Factor