Excited-State Intramolecular Hydrogen Transfer of Compact Molecules Controls Amyloid Aggregation Profiles

Rational Design, Synthesis, and Evaluation of Rofecoxib-Based Photosensitizers for the NIR Imaging and Photo-Oxidization of Aβ Aggregates

The photo-oxidation of amyloid-β (Aβ) protein catalyzed by Aβ-targeting photosensitizers shows high potential in treating Alzheimer's disease (AD). Herein, we report the first example of photosensitizers based on the rofecoxib scaffold, in which rational introduction of the electron-absorbing pyridinium/quinolinium moiety to the skeleton of rofecoxib could not only extend the absorption and emission wavelengths but also increase the efficiency of singlet oxygen (1O2) production. The emission wavelengths of R-S-MP, R-S-MC, and R-S-MQ are red-shifted to 860 nm, which might benefit the NIR imaging of Aβ aggregates with low photoscattering and autofluorescence. In addition, R-S-MP can identify Aβ plaques in brain sections of AD mice and detect abnormal viscosity environments, facilitating the pathological study of Alzheimer's disease. Most importantly, upon complexation with Aβ plaques, R-S-MP and R-S-MC could produce high singlet oxygen (1O2) under light irradiation, which can achieve the specific photo-oxidation of Aβ protein. Our optimized photosensitizers could change the conformation of β-rich Aβ protein and enhance its clearance through the lysosomal pathway, leading to the reduction of the Aβ-mediated neurotoxicity. All these excellent characteristics of our dual-functional photosensitizers for simultaneous imaging and photo-oxidation of Aβ aggregates suggest their promising prospects in pathological research in AD.

Fighting fire with fire: remodeling Aβ aggregation with H-aggregates of a europium(III) complex

We herein report a "Fight Aggregation with Aggregation" (FAA) approach for redirection of amyloid-β peptide (Aβ) aggregation using a europium(III) complex (EuL3) that can undergo H-aggregation in aqueous solution under physiological conditions. The H-aggregates of EuL3 may serve as scaffolds that can facilitate the accumulation of Aβ to form non-fibrillar co-assemblies. As a result, the Aβ aggregation-induced cytotoxicity was inhibited.

Straightforward computational determination of energy-transfer kinetics through the application of the Marcus theory

Energy transfer (EnT) photocatalysis holds the potential to revolutionize synthetic chemistry, unlocking the excited-state reactivity of non-chromophoric compounds via indirect sensitization. This strategy gives access to synthetic routes to valuable molecular scaffolds that are otherwise inaccessible through ground-state pathways. Despite the promising nature of this chemistry, it still represents a largely uncharted area for computational chemistry, hindering the development of structure-activity relationships and design rules to rationally exploit the potential of EnT photocatalysis. Here, we examined the application of the classical Marcus theory in combination with DFT calculations as a convenient strategy to estimate the kinetics of EnT processes, focusing on the indirect sensitization of alkenes recently reported by Gilmour, Kerzig and co-workers for subsequent isomerization [Zähringer et al., J. Am. Chem. Soc., 2023, 145, 21576]. Our results demonstrate a remarkable capability of this approach to estimate free-energy barriers for EnT processes with high accuracy, yielding precise qualitative assessments and quantitative predictions with typical discrepancies of less than 2 kcal mol-1 compared to experimental values and a small mean average error (MAE) of 1.2 kcal mol-1.

Unimolecular Chemiexcited Oxygenation of Pathogenic Amyloids

Pathogenic protein aggregates, called amyloids, are etiologically relevant to various diseases, including neurodegenerative Alzheimer disease. Catalytic photooxygenation of amyloids, such as amyloid-β (Aβ), reduces their toxicity; however, the requirement for light irradiation may limit its utility in large animals, including humans, due to the low tissue permeability of light. Here, we report that Cypridina luciferin analogs, dmCLA-Cl and dmCLA-Br, promoted selective oxygenation of amyloids through chemiexcitation without external light irradiation. Further structural optimization of dmCLA-Cl led to the identification of a derivative with a polar carboxylate functional group and low cellular toxicity: dmCLA-Cl-acid. dmCLA-Cl-acid promoted oxygenation of Aβ amyloid and reduced its cellular toxicity without photoirradiation. The chemiexcited oxygenation developed in this study may be an effective approach to neutralizing the toxicity of amyloids, which can accumulate deep inside the body, and treating amyloidosis.

Antimicrobial photodynamic inactivation pH-responsive films based on gelatin/chitosan incorporated with aloe-emodin

Using novel active food packaging has gradually become a daily necessity in terms of impeding microbial contamination. Here, an antimicrobial photodynamic inactivation (PDI) pH-responsive film is developed by incorporating aloe-emodin (AE) into a vehicle of gelatin/chitosan (GC). Besides enhancement in hydrophobicity, the well-dispersed crystals of AE in the GC matrix by hydrogen bonding can upgrade the film's mechanical strength and barrier. The matrix is capable of regulating the release of AE in response to acidic stimuli by a combination mechanism of diffusion and polymer relaxation. Being benefitted from the inherent bioactivity of AE and the PDI activity under visible light irradiation (i.e., 456 nm), the target film of GC-AE2 has excellent antibacterial effect towards Staphylococcus aureus and Escherichia coli, showing bacterial viability of 9.93 ± 1.33 % and 14.85 ± 1.16 %, respectively. Furthermore, the film can effectively thwart Botrytis cinerea infection in cherry tomatoes, demonstrating its potential in preventing the microbial spoilage of postharvest fruits.

Targeting misfolding and aggregation of the amyloid-β peptide and mutant p53 protein using multifunctional molecules

Biomolecule misfolding and aggregation play a major role in human disease, spanning from neurodegeneration to cancer. Inhibition of these processes is of considerable interest, and due to the multifactorial nature of these diseases, the development of drugs that act on multiple pathways simultaneously is a promising approach. This Feature Article focuses on the development of multifunctional molecules designed to inhibit the misfolding and aggregation of the amyloid-β (Aβ) peptide in Alzheimer's disease (AD), and the mutant p53 protein in cancer. While for the former, the goal is to accelerate the removal of the Aβ peptide and associated aggregates, for the latter, the goal is reactivation via stabilization of the active folded form of mutant p53 protein and/or aggregation inhibition. Due to the similar aggregation pathway of the Aβ peptide and mutant p53 protein, a common therapeutic approach may be applicable.

In Vivo Near-Infrared Fluorescence Imaging Selective for Soluble Amyloid β Aggregates Using y-Shaped BODIPY Derivative

Soluble amyloid β (Aβ) aggregates, suggested to be the most toxic forms of Aβ, draw attention as therapeutic targets and biomarkers of Alzheimer's disease (AD). As soluble Aβ aggregates are transient and diverse, imaging their diverse forms in vivo is expected to have a marked impact on research and diagnosis of AD. Herein, we report a near-infrared fluorescent (NIRF) probe, BAOP-16, targeting diverse soluble Aβ aggregates. BAOP-16, whose molecular shape resembles "y", showed a marked selective increase in fluorescence intensity upon binding to soluble Aβ aggregates in the near-infrared region and a high binding affinity for them. Additionally, BAOP-16 could detect Aβ oligomers in the brains of Aβ-inoculated model mice. In an in vivo fluorescence imaging study of BAOP-16, brains of AD model mice displayed significantly higher fluorescence signals than those of wild-type mice. These results indicate that BAOP-16 could be useful for the in vivo NIRF imaging of diverse soluble Aβ aggregates.