Nanoparticles labeled with radiometals enable whole-body nuclear imaging and therapy. Though chelating agents are commonly used to radiolabel biomolecules, nanoparticles offer the advantage of attaching a radiometal directly to the nanoparticle itself without the need of such agents. We previously demonstrated that direct radiolabeling of silica nanoparticles with hard, oxophilic ions, such as the positron emitters zirconium-89 and gallium-68, is remarkably efficient. However, softer radiometals, such as the widely employed copper-64, do not stably bind to the silica matrix and quickly dissociate under physiological conditions. Here, we overcome this limitation through the use of silica nanoparticles functionalized with a soft electron-donating thiol group to allow stable attachment of copper-64. This approach significantly improves the stability of copper-64 labeled thiol-functionalized silica nanoparticles relative to native silica nanoparticles, thereby enabling in vivo PET imaging, and may be translated to other softer radiometals with affinity for sulfur. The presented approach expands the application of silica nanoparticles as a platform for facile radiolabeling with both hard and soft radiometal ions.
The control and enhancement of resonance
energy transfer is highly
desirable for a variety of applications ranging from solar cells to
spectroscopic rulers. However, the process of direct resonance energy
transfer is distance dependent and limited to ∼10 nm for typical
donor–acceptor pairs. Here we demonstrate long-range (∼160
nm) direct energy transfer between donor quantum dots and acceptor
dye molecules through the use of an optical topological transition
(OTT) in a metamaterial. The OTT in a metamaterial, modifies the density
of states between the donor and acceptor, resulting in the long-range
energy transfer with transfer efficiency of ∼32%. Theoretical
calculation based on master-equation formalism is used to model the
system and is found to be in good agreement with the experimental
observation. The use of OTTs in metamaterials to enhance and control
energy transfer process can have wide array of potential applications
ranging from organic solar cells to quantum entanglement.
A physical organic chemistry experiment
is described for second-year
college students. Students performed nucleophilic aromatic substitution
(NAS) reactions on 5,10,15,20-tetrakis(2,3,4,5,6-pentafluorophenyl)porphyrin
(TPPF20) using three different nucleophiles. Substitution
occurs preferentially at the 4-position (para) because
it is thermodynamically favored, and the 2- and 6- (ortho) positions are kinetically disfavored because of steric interactions
with the porphyrin ring. The activation energy depends heavily on
the nucleophile. Open-source software (ImageJ from NIH) was used to
quantify relative intensities of spots on a TLC plate obtained from
different times and varying temperatures. These data were used to
generate Arrhenius plots allowing students to determine relative activation
energies for three different primary nucleophiles. The experiment
was developed by 5 undergraduates and evaluated by 40 organic chemistry
II students and 8 students in a physical chemistry laboratory. Students
gained a deeper understanding of the relationships between the NAS
mechanism, Arrhenius plots, and activation energy.
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