Improving
the stability of porous materials for practical applications
is highly challenging. Aluminosilicate zeolites are utilized for adsorptive
and catalytic applications, wherein they are sometimes exposed to
high-temperature steaming conditions (∼1000 °C). As the
degradation of high-silica zeolites originates from the defect sites
in their frameworks, feasible defect-healing methods are highly demanded.
Herein, we propose a method for healing defects to create extremely
stable high-silica zeolites. High-silica (SiO2/Al2O3 > 240) zeolites with *BEA-, MFI-, and MOR-type topologies
could be stabilized by significantly reducing the number of defect
sites via a liquid-mediated treatment without using additional silylating
agents. Upon exposure to extremely high temperature (900–1150
°C) steam, the stabilized zeolites retain their crystallinity
and micropore volume, whereas the parent commercial zeolites degrade
completely. The proposed self-defect-healing method provides new insights
into the migration of species through porous bodies and significantly
advances the practical applicability of zeolites in severe environments.
Although PET amyloid-β imaging agents are available, they cannot be used with SPECT scanners. Maya
et al
. report that a novel SPECT imaging agent, 123I-ABC577, has a high affinity for amyloid-β, and differentiates Alzheimer's disease patients from healthy controls, with low non-specific retention in the white matter.
In this study, we synthesized of a series of 2-phenyl- and 2-pyridyl-imidazo[1,2- a]pyridine derivatives and examine their suitability as novel probes for single-photon emission computed tomography (SPECT)-based imaging of β-amyloid (Aβ). Among the 11 evaluated compounds, 10 showed moderate affinity to Aβ(1-42) aggregates, exhibiting half-maximal inhibitory concentrations (IC) of 14.7 ± 6.07-87.6 ± 39.8 nM. In vitro autoradiography indicated that I-labeled triazole-substituted derivatives displayed highly selective binding to Aβ plaques in the hippocampal region of Alzheimer's disease (AD)-affected brain. Moreover, biodistribution studies performed on normal rats demonstrated that allI-labeled probes featured high initial uptake into the brain followed by a rapid washout and were thus well suited for imaging Aβ plaques, with the highest selectivity observed for a 1 H-1,2,3-triazole-substituted 2-pyridyl-imidazopyridine derivative, [I]ABC577. This compound showed good kinetics in rat brain as well as moderate in vivo stability in rats and is thus a promising SPECT imaging probe for AD in clinical settings.
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