Alzheimer's disease (AD) is pathologically characterized by the accumulation of β-amyloid (Aβ) deposits in the parenchymal and cortical brain. In this work, we designed, synthesized, and evaluated a series of near-infrared (NIR) probes with electron donor-acceptor end groups interacting through a π-conjugated system for the detection of Aβ deposits in the brain. Among these probes, 3b and 3c had excellent fluorescent properties (emission maxima > 650 nm and high quantum yields) and displayed high sensitivity and high affinities to Aβ aggregates (3b, Kd = 8.8 nM; 3c, Kd = 1.9 nM). Both 3b and 3c could readily penetrate the blood-brain barrier with high initial brain uptake and fast to moderate washout from the brain. In vivo NIR imaging revealed that 3b and 3c could efficiently differentiate transgenic and wild-type mice. In summary, our research provides new hints for developing smarter and more activatable NIR probes targeting Aβ.

Background Previous studies presumed that the disturbed neurovascular coupling to be a critical risk factor of cognitive impairments in type 2 diabetes mellitus (T2DM), but distinct clinical manifestations were lacked. Consequently, we decided to investigate the neurovascular coupling in T2DM patients by exploring the MRI relationship between neuronal activity and the corresponding cerebral blood perfusion. Methods Degree centrality (DC) map and amplitude of low-frequency fluctuation (ALFF) map were used to represent neuronal activity. Cerebral blood flow (CBF) map was used to represent cerebral blood perfusion. Correlation coefficients were calculated to reflect the relationship between neuronal activity and cerebral blood perfusion. Results At the whole gray matter level, the manifestation of neurovascular coupling was investigated by using 4 neurovascular biomarkers. We compared these biomarkers and found no significant changes. However, at the brain region level, neurovascular biomarkers in T2DM patients were significantly decreased in 10 brain regions. ALFF-CBF in left hippocampus and fractional ALFF-CBF in left amygdala were positively associated with the executive function, while ALFF-CBF in right fusiform gyrus was negatively related to the executive function. The disease severity was negatively related to the memory and executive function. The longer duration of T2DM was related to the milder depression, which suggests T2DM-related depression may not be a physiological condition but be a psychological condition. Conclusion Correlations between neuronal activity and cerebral perfusion maps may be a method for detecting neurovascular coupling abnormalities, which could be used for diagnosis in the future. Trial registry number: This study has been registered in ClinicalTrials.gov ( NCT02420470 ) on April 2, 2015 and published on July 29, 2015.

To expand the scope of D-π-A based near-infrared (NIR) probes for detecting β-amyloid (Aβ) plaques and to systematically explore the relationship among their structural characteristics, optical properties, and biological properties, three series of smart NIR probes with different aromatic rings and up to seven trans double bonds were synthesized and evaluated. Marked correlations between the conjugated π system and properties of these probes, such as optical data, binding ability, and brain uptake, were observed. One probe, PHC-4, displayed improved properties as a NIR probe for the in vivo detection of Aβ plaques.

Novel D-π-A-π-D probes were investigated for the detection of Aβ plaques and NFTs. The probes displayed remarkable optical properties, and DADNIR-2 possessed high affinity towards Tau and Aβ aggregates (Kd = 0.41 nM and 1.04 nM, respectively) with certain selectivity. DADNIR-2 could penetrate the BBB and label Aβ plaques in vivo.

The early noninvasive diagnosis of Alzheimer’s disease targeted β-amyloid (Aβ) plaques or Tau tangles is a major challenge because of the coshared β-sheet structure of the target. In contrast to tailoring probes to specific amyloids, here, we showed that near-infrared (NIR) environment-sensitive probe 18 could fluorescently discriminate Aβ and Tau from artificial aggregates to pathological change in the brain tissue. The biological evaluation demonstrated that the substantial fluorescence enhancement, large blueshift in the emission upon interactions with the aggregates, and the high binding affinity significantly contributed to the fluorescent discrimination. A simplified Ooshika–Lippert–Mataga equation provided an effective means of correlating 18 with the static relative permittivity (ε0) of proteins, elucidating the origin of the distinction capabilities, and quantitatively estimating the dielectric properties of proteins. Moreover, 18 possessed high bioavailability, including sufficient blood–brain barrier penetration, in vivo NIR imaging, and ex vivo histology in living mice.