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A striking issue is the scarcity of imaging probes for the early diagnosis of Alzheimer's disease. For the development of Aβ biomarkers, a mitochondria targeting, de novo designed, aggregation-induced emission (AIE) probe Cou-AIE-TPP+ is constructed by engineering the aromatic coumarin framework into the bridge of electron donor–acceptor–donor tethered with a lipophilic cationic triphenylphosphonium (TPP+) group. The synthesized Cou-AIE-TPP+ probe exhibits biocompatibility, noncytotoxicity, and a huge Stokes shift (124 nm in PBS). Cou-AIE-TPP+ has respectable fluorescence augmentation inside the aggregated Aβ40 in comparison with monomeric Aβ40 with a high binding affinity (Kd = 83 nM) to Aβ40 aggregates, is capable of detecting the kinetics of amyloid aggregation, and is superior to the gold standard probe thioflavin T. Fluorescence lifetime and brightness are also augmented when the probe Cou-AIE-TPP+ binds with Aβ aggregates in PBS. Cou-AIE-TPP+ (λem 604 nm) selectively targets and images neuronal cell mitochondria, is useful to monitor mitochondrial morphology alteration and damage during Aβ40-induced neurotoxicity, recognizes neurotoxic Aβ fibrils, and is highly colocalized with thioflavin T, showing a decent Pearson correlation coefficient of 0.91 in the human neuroblastoma SH-SY5Y cell line. These findings indicate that the mitochondria targeting, de novo designed, functional AIE-based solvatofluorochromic Cou-AIE-TPP+ probe is a promising switch on biomarkers for fluorescence imaging of Aβ aggregates and to monitor mitochondrial morphology change and dysfunction during Aβ-induced neurotoxicity, which may offer imperative direction for the advancement of compelling AIE biomarkers for targeted early stage Aβ diagnosis in the future. [ABSTRACT FROM AUTHOR]

We have synthesized an acidic pH‐activatable dual targeting ratiometric fluorescent probe‐peptide conjugate using the SPPS protocol on Rink amide AM resin. Living carcinoma cell specific active targeting, successive cell penetration, and selective staining of lysosomes are accomplished. Real‐time monitoring of lysosomes, 3D, and multicolor cancer cell imaging are also attained. The de novo design consists of the integration of multifunctionality into a single molecular scaffold, e. g., RGDS peptide residue to target cancer cell surface overexpressed receptor αVβ3 integrin, live‐cell penetrating organic unsymmetrical rhodamine‐hemicyanine chromophore comprising a lysosome targeting morpholine group, and an acidic pH openable spiro‐lactam ring for a visible‐to‐NIR switchable ratiometric response. Water‐soluble fluorescent probe‐peptide conjugate exhibits intramolecular spirolactamization at basic pH through Arg amide N. The visible spirolactam state predominantly exists at physiological and basic pH and can be switched to the highly conjugated NIR open amide state (λem=735 nm) through spiro‐lactam ring opening triggered by acidic pH with a huge bathochromic shift (Δλabs=336 nm, ΔλFL=265 nm). Moreover, pH‐sensitive ratiometric optical switching is achieved. This in situ acidic cancer cell lysosome activatable multifunctional fluorophore‐peptide conjugate shows augmented molar absorptivity, enhanced quantum yield, and improved fluorescence lifetime at acidic lysosomal pH; negligible cytotoxicity; and dual targeted ratiometric imaging capability of living cancer cell selective lysosomes with a pKa value of 5.1. [ABSTRACT FROM AUTHOR]

A donor-acceptor substituted aromatic system (E)-3-(4-Methylamino-phenyl)-acrylic acid methyl ester (MAPAME) was synthesized, and its photophysical behavior obtained spectroscopically was compared with the theoretical results. The dual fluorescence observed from MAPAME is attributed to emission from locally excited and twisted intramolecular charge transfer states.

Photoinduced intramolecular charge-transfer reactions in 4-amino-3-methyl benzoic acid methyl ester (AMBME) have been investigated spectroscopically. AMBME, with its weak charge donor primary amino group, shows dual emission in polar solvents. Absorption and emission measurements in the condensed phase support the premise that the short wavelength emission band corresponds to local emission and the long wavelength emission band to the charge transfer emission. Laser-induced fluorescence excitation spectra show the presence of two low-energy conformers in jet-cooled molecular beams. Theoretical calculations using density functional theory help to determine structure, vibrational modes, potential energy surface, transition energy and oscillator strength for correlating experimental findings with theoretical results. [ABSTRACT FROM AUTHOR]

Integrating an NIR fluorescent probe with a magnetic resonance imaging (MRI) agent to harvest complementary imaging information is challenging. Here, we have designed water-soluble, biocompatible, noncytotoxic, bright-NIR-emitting, sugar-functionalized, mechanically interlocked molecules (MIMs)-capped superparamagnetic ultrasmall Fe 3 O 4 NPs for targeted multimodal imaging. Dual-functional stoppers containing an unsymmetrical NIR squaraine dye interlocked within a macrocycle to construct multifunctional MIMs are developed with enhanced NIR fluorescence efficiency and durability. One of the stoppers of the axle is composed of a lipophilic cationic TPP + functionality to target mitochondria, and the other stopper comprises a dopamine-containing catechol group to anchor at the surface of the synthesized Fe 3 O 4 NPs. Fe 3 O 4 NPs surface-coated with targeted NIR rotaxanes help to deliver ultrasmall magnetic NPs specifically inside the mitochondria. Two carbohydrate moieties are conjugated with the macrocycle of the rotaxane via click chemistry to improve the water solubility of MitoSQRot-(Carb-OH) 2 -DOPA-Fe 3 O 4 NPs. Water-soluble, rotaxane-capped Fe 3 O 4 NPs are used for live-cell mitochondria-targeted NIR fluorescence confocal imaging, 3D and multicolor imaging in combination with T 2 -weighted MRI on a 9.4 T MR scanner with a high relaxation rate ( r 2 ) of 180.7 mM -1 s -1 . Biocompatible, noncytotoxic, ultrabright NIR rotaxane-capped superparamagnetic ultrasmall monodisperse Fe 3 O 4 NPs could be a promising agent for targeted multimodal imaging applications.