Core–shell
particles made of calcium carbonate and coated with biocompatible
polymers using the Layer-by-Layer technique can be considered as a
unique drug-delivery platform that enables us to load different therapeutic
compounds, exhibits a high biocompatibility, and can integrate several
stimuli-responsive mechanisms for drug release. However, before implementation
for diagnostic or therapeutic purposes, such core–shell particles
require a comprehensive in vivo evaluation in terms
of physicochemical and pharmacokinetic properties. Positron emission
tomography (PET) is an advanced imaging technique for the evaluation
of in vivo biodistribution of drug carriers; nevertheless,
an incorporation of positron emitters in these carriers is needed.
Here, for the first time, we demonstrate the radiolabeling approaches
of calcium carbonate core–shell particles with different sizes
(CaCO3 micron-sized core–shell particles (MicCSPs)
and CaCO3 submicron-sized core–shell particles (SubCSPs))
to precisely determine their in vivo biodistribution
after intravenous administration in rats. For this, several methods
of radiolabeling have been developed, where the positron emitter (68Ga) was incorporated into the particle’s core (co-precipitation
approach) or onto the surface of the shell (either layer coating or
adsorption approaches). According to the obtained data, radiochemical
bounding and stability of 68Ga strongly depend on the used
radiolabeling approach, and the co-precipitation method has shown
the best radiochemical stability in human serum (96–98.5% for
both types of core–shell particles). Finally, we demonstrate
the size-dependent effect of core–shell particles’ distribution
on the specific organ uptake, using a combination of imaging techniques,
PET, and computerized tomography (CT), as well as radiometry of separate
organs. Thus, our findings open up new perspectives of CaCO3-radiolabeled core–shell particles for their further implementation
into clinical practice.
Nowadays chemistry of 68Ga‐labelled radiopharmaceuticals is one of the drivers for Positron Emission Tomography (PET). Buffers solutions for radiolabelling play one of the important roles here. Despite HEPES buffer providing high radiochemical conversions, its use is undesirable due to high toxicity. In this article we report a simple procedure involving usage of aqueous triethanolammonium (TEA) and tris(hydroxymethyl)methyl‐ammonium (TRIS) salts of biologically active carboxylic acids in a process of gallium‐68 complexation with PSMA‐HBED‐CC. These salts provide not only high radiochemical conversions but also are already widely used in biochemistry, molecular biology, agriculture and medicine as drugs of a wide spectrum of action and growth stimulating drugs (Trekrezan™, Chlorokrezacin™).
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