A Photolabile Curcumin-Diazirine Analogue Enables Phototherapy with Physically and Molecularly Produced Light for Alzheimer's Disease Treatment

The development of Alzheimer's disease (AD) drugs has recently witnessed substantial achievement. To further enhance the pool of drug candidates, it is crucial to explore non-traditional therapeutic avenues. In this study, we present the use of a photolabile curcumin-diazirine analogue, CRANAD-147, to induce changes in properties, structures (sequences), and neurotoxicity of amyloid beta (Aβ) species both in cells and in vivo. This manipulation was achieved through irradiation with LED light or molecularly generated light, dubbed as "molecular light", emitted by the chemiluminescence probe ADLumin-4. Next, aided by molecular chemiluminescence imaging, we demonstrated that the combination of CRANAD-147/LED or CRANAD-147/ADLumin-4 (molecular light) could effectively slow down the accumulation of Aβs in transgenic 5xFAD mice in vivo. Leveraging the remarkable tissue penetration capacity of molecular light, phototherapy employing the synergistic effect of a photolabile Aβ ligand and molecular light emerges as a promising alternative to conventional AD treatment interventions.

Biocompatible zeolite-dye composites with anti-amyloidogenic properties

One of the most attractive approaches in biomedicine and pharmacy is the application of multifunctional materials. The mesoporous structure of clinoptilolite (CZ) absorbs various types of substances and can be used as a model for studying the carriers for targeted drug delivery with controlled release. CZ-dye composites are fabricated by incorporation into clinoptilolite pores commonly used dyes, aluminum phthalocyanine, zinc porphine, and hypericin. We examined and compared the effect of pure dyes and CZ-dye composites on insulin amyloidogenesis. The formation of insulin amyloid fibrils and the disassembly of preformed fibrils is significantly affected by any of the three compounds, however, the strongest effect is observed for aluminum phthalocyanine indicating a structurally-dependent anti-amyloidogenic activity of the dyes. The incorporation of dyes into CZ particles resulted in enhanced anti-amyloidogenic activity in comparison to pure CZ particles. The cell metabolic activity, biocompatibility and fluorescence biodistribution of the dyes entrapped in the composites were tested in vitro (U87 MG cells) and in vivo in the quail chorioallantoic membrane model. Considering the photoactive properties of the dyes used, we assume their applicability in photodiagnostics and photodynamic therapy. It can also be expected that their anti-amyloidogenic potential can be enhanced by photodynamic effect.

Protein redox by a piezoelectric acousto-nanodevice

Protein redox is responsible for many crucial biological processes; thus, the ability to modulate the redox proteins through external stimuli presents a unique opportunity to tune the system. In this work, we present an acousto-nanodevice that is capable of oxidizing redox protein under ultrasonic irradiation via surface-engineered barium titanate (BTO) nanoparticles with a gold half-coating. Using cytochrome c as the model protein, we demonstrate nanodevice-mediated protein oxidation. BINased on our experimental observations, we reveal that the electron transfer occurs in one direction due to the alternating electrical polarization of BTO under ultrasound. Such unique unidirectional electron transfer is enabled by modulating the work function of the gold surface with respect to the redox center. The new class of ultrasonically powered nano-sized protein redox agents could be a modulator for biological processes with high selectivity and deeper treatment sites.

Photooxidative inhibition and decomposition of β-amyloid in Alzheimer's by nano-assemblies of transferrin and indocyanine green

Photoinduced modulation of Aβ₄₂ aggregation has emerged as a therapeutic option for treating Alzheimer's disease (AD) due to its high spatiotemporal controllability, noninvasive nature, and low systemic toxicity. However, existing photo-oxidants have the poor affinity for Aβ₄₂, low depolymerization efficiency, and difficulty in crossing the blood-brain barrier (BBB), hindering their application in the treatment of AD. Here, through hydrophobic interactions and hydrogen bonding, we integrated the near-infrared (NIR) photosensitizer indocyanine green with transferrin (denoted as TF-ICG), a protein with a high affinity for Aβ₄₂, and demonstrated its anti-amyloid activity in vitro. TF-ICG was shown to bind to Aβ₄₂ residues via hydrophobic interaction, impeding π-π stacking of Aβ₄₂ peptide monomers and disassembling mature Aβ₄₂ protofibrils in a concentration-dependent manner. More importantly, under NIR (808 nm, 0.6w/cm²) irradiation, TF-ICG completely inhibited the fibrillation process of Aβ₄₂ to generate amorphous aggregates, with an inhibition rate of 96 % at only 65 nM. Meanwhile, TF-ICG could photo-oxidize rigid Aβ₄₂ aggregates and break them down into small amorphous structures. Tyrosine fluorescence assay further demonstrated the intrinsic affinity and targeting of TF-ICG to Aβ₄₂ fibrils. In vitro studies validated the anti-amyloid activity of TF-ICG, which provided a theoretical basis for further in vivo application as a BBB-penetrating nanotherapeutic platform.

Partial Destabilization of Amyloid-β Protofibril by Methionine Photo-Oxidation: A Molecular Dynamic Simulation Study

Selective photosensitized oxidation of amyloid protein aggregates is being investigated as a possible therapeutic strategy for treating Alzheimer's disease (AD). Photo-oxidation has been shown to degrade amyloid-β (Aβ) aggregates and ameliorate aggregate toxicity in vitro and reduce aggregate levels in the brains of AD animal models. To shed light on the mechanism by which photo-oxidation induces fibril destabilization, we carried out an all-atom molecular dynamics (MD) simulation to examine the effect of methionine (Met35) oxidation on the conformation and stability of a β-sheet-rich Aβ9-40 protofibril. Analyses of up to 1 μs simulations showed that the oxidation of the Met35 residues, which resulted in the addition of hydrophilic oxygens in the fibril core, reduced the overall conformational stability of the protofibril. Specifically, Met35 disrupted the hydrophobic interface that stabilizes the stacking of the two hexamers that comprise the protofibril. The oxidized protofibril is more solvent exposed and exhibits more backbone flexibility. However, the protofibril retained the underlying U-shaped architecture of each peptide upon oxidation, and although some loss of β-sheets occurred, a significant portion remained. Our simulation results are thus consistent with our experimental observation that photo-oxidation of Aβ40 fibril resulted in the dis-agglomeration and fragmentation of Aβ fibrils but did not cause complete disruption of the fibrillar morphology or β-sheet structures. The partial destabilization of Aβ aggregates supports the further development of photosensitized platforms for the targeting and clearing of Aβ aggregates as a therapeutic strategy for treating AD.

Rational design of photoactivatable metal complexes to target and modulate amyloid-β peptides

The accumulation of amyloid-β (Aβ) aggregates is found in the brains of Alzheimer's disease patients. Thus, numerous efforts have been made to develop chemical reagents capable of targeting Aβ peptides and controlling their aggregation. In particular, tunable coordination and photophysical properties of transition metal complexes, with variable oxidation and spin states on the metal centers, can be utilized to probe Aβ aggregates and alter their aggregation profiles. In this review, we illustrate some rational strategies for designing photoactivatable metal complexes as chemical sensors for Aβ peptides or modulators against their aggregation pathways, with some examples.

Transcranial deep-tissue phototherapy for Alzheimer's disease using low-dose X-ray-activated long-afterglow scintillators

Non-invasive phototherapy has been emerging as an ambitious tactic for suppression of amyloid-β (Aβ) self-assembly against Alzheimer's disease (AD). However, it remains a daunting challenge to develop efficient photosensitizers for Aβ oxygenation that are activatable in a deep brain tissue through the scalp and skull, while reducing side effects on normal tissues. Here, we report an Aβ targeted, low-dose X-ray-excitable long-afterglow scintillator (ScNPs@RB/Ab) for efficient deep-brain phototherapy. We demonstrate that the as-synthesized ScNPs@RB/Ab is capable of converting X-rays into visible light to activate the photosensitizers of rose bengal (RB) for Aβ oxygenation through the scalp and skull. We show that the ScNPs@RB/Ab persistently emitting visible luminescence can substantially minimize the risk of excessive X-ray exposure dosage. Importantly, peptide KLVFFAED-functionalized ScNPs@RB/Ab shows a blood-brain barrier permeability. In vivo experimental results validated that ScNPs@RB/Ab alleviated Aβ burden and slowed cognitive decline in triple-transgenic AD model mice at extremely low X-ray doses without side effects. Our study paves a new pathway to develop high-efficiency transcranial AD phototherapy. STATEMENT OF SIGNIFICANCE: Non-invasive phototherapy has been emerging as an ambitious tactic for suppression of amyloid-β (Aβ) self-assembly against Alzheimer's disease (AD). However, it remains a daunting challenge to develop efficient photosensitizers for Aβ oxygenation that are activatable in a deep brain tissue through the scalp and skull, while reducing side effects on normal tissues. Herein, we report an Aβ targeted, low-dose X-ray-excitable long-afterglow scintillators (ScNPs@RB/Ab) for efficient deep-brain phototherapy. In vivo experimental results validated that ScNPs@RB/Ab alleviated Aβ burden and slowed cognitive decline in triple-transgenic AD model mice at extremely low X-ray doses without side effects.

Near-Infrared Photothermally Enhanced Photo-Oxygenation for Inhibition of Amyloid-β Aggregation Based on RVG-Conjugated Porphyrinic Metal-Organic Framework and Indocyanine Green Nanoplatform

Amyloid aggregation is associated with many neurodegenerative diseases such as Alzheimer's disease (AD). The current technologies using phototherapy for amyloid inhibition are usually photodynamic approaches based on evidence that reactive oxygen species can inhibit Aβ aggregation. Herein, we report a novel combinational photothermally assisted photo-oxygenation treatment based on a nano-platform of the brain-targeting peptide RVG conjugated with the 2D porphyrinic PCN-222 metal-organic framework and indocyanine green (PCN-222@ICG@RVG) with enhanced photo-inhibition in Alzheimer's Aβ aggregation. A photothermally assisted photo-oxygenation treatment based on PCN@ICG could largely enhance the photo-inhibition effect on Aβ₄₂ aggregation and lead to much lower neurotoxicity upon near-infrared (NIR) irradiation at 808 nm compared with a single modality of photo-treatment in both cell-free and in vitro experiments. Generally, local photothermal heat increases the instability of Aβ aggregates and keeps Aβ in the status of monomers, which facilitates the photo-oxygenation process of generating oxidized Aβ monomers with low aggregation capability. In addition, combined with the brain-targeting peptide RVG, the PCN-222@ICG@RVG nanoprobe shows high permeability of the human blood-brain barrier (BBB) on a human brain-on-a-chip platform. The ex vivo study also demonstrates that NIR-activated PCN-222@ICG@RVG could efficiently dissemble Aβ plaques. Our work suggests that the combination of photothermal treatment with photo-oxygenation can synergistically enhance the inhibition of Aβ aggregation, which may boost NIR-based combinational phototherapy of AD in the future.

Degradation of amyloid peptide aggregates by targeted singlet oxygen delivery from a benzothiazole functionalized naphthalene endoperoxide

Aggregate structures formed by amyloid-β (Aβ) are correlated with the progression of pathogenesis in Alzheimer's disease. Previous works have shown that photodynamic photosensitizers were effective in oxidatively degrading amyloid-β aggregates and thus decreasing their cytotoxicity under various conditions. In this work, we designed and synthesized a benzothiazole-naphthalene conjugate, with high level of structural analogy to Thioflavin T which is known to have high affinities for the amyloid peptide aggregates. The endoperoxide form (BZTN-O2) of this compound, which releases singlet oxygen with a half-life of 77 minutes at 37 °C, successfully inhibited and/or reversed amyloid aggregation. The endoperoxide is capable of singlet oxygen release without any need for light, and its charge-neutral form could allow blood-brain barrier (BBB) permeability. The therapeutic potential of such endoperoxide compounds with amyloid binding affinity is exciting.

Cofactors-like peptide self-assembly exhibiting the enhanced catalytic activity in the peptide-metal nanocatalysts

The peptide self-assembly would be expected to be as the assistance of metallic nanocatalysts to promote the catalytic reaction, attracting limited attention, but being highly anticipated. Herein, we proposed and verified an alternative strategy for enhancing the catalytic activity of the 4-nitrophenol reduction as a model reaction, by optimizing and constructing "cofactors" inspired amyloid peptide self-assembly applied in the peptide-metal nanocatalysts as the template due to the potential superiority of substrate binding. Amyloid peptide self-assembled membrane exhibited better enhanced catalytic activity, compared to peptide nanofibers as the template in the peptide-gold nanocatalysts. The optimized amyloid peptide was designated by molecular dynamic simulation to display the relative strongest interaction with specific substrate and the relative good template effect on the enhanced catalytic activity was also proved accordingly. This work may shed light on the future design and construction of novel enzyme mimics with dramatic enhanced catalytic activity by peptide assembly-metal nanocatalysts.

Prion Strains Differ in Susceptibility to Photodynamic Oxidation

Prion disorders, or transmissible spongiform encephalophaties (TSE), are fatal neurodegenerative diseases affecting mammals. Prion-infectious particles comprise of misfolded pathological prion proteins (PrP^TSE). Different TSEs are associated with distinct PrP^TSE folds called prion strains. The high resistance of prions to conventional sterilization increases the risk of prion transmission in medical, veterinary and food industry practices. Recently, we have demonstrated the ability of disulfonated hydroxyaluminum phthalocyanine to photodynamically inactivate mouse RML prions by generated singlet oxygen. Herein, we studied the efficiency of three phthalocyanine derivatives in photodynamic treatment of seven mouse adapted prion strains originating from sheep, human, and cow species. We report the different susceptibilities of the strains to photodynamic oxidative elimination of PrP^TSE epitopes: RML, A139, Fu-1 > mBSE, mvCJD > ME7, 22L. The efficiency of the phthalocyanine derivatives in the epitope elimination also differed (AlPcOH(SO₃)₂ > ZnPc(SO₃)_1-3 > SiPc(OH)₂(SO₃)_1-3) and was not correlated to the yields of generated singlet oxygen. Our data suggest that the structural properties of both the phthalocyanine and the PrP^TSE strain may affect the effectiveness of the photodynamic prion inactivation. Our finding provides a new option for the discrimination of prion strains and highlights the necessity of utilizing range of prion strains when validating the photodynamic prion decontamination procedures.

Light-Stimulated Carbon Dot Hydrogel: Targeting and Clearing Infectious Bacteria In Vivo

Infectious bacteria evolve fast into resistance to conventional antimicrobial agents, whereas treatments for drug resistance bacteria progress more slowly. Here, we report a universally applicable photoactivated antimicrobial modality through light-responsive carbon dot-embedding soft hyaluronic acid hydrogel (CDgel). Because of the innate nature of the infectious bacteria that produce hyaluronidase, applied hyaluronic acid-based CDgel breaks down via bacteria and releases carbon dots (CDs) into the infectious sites. The released CDs possess photodynamic capabilities under light irradiation, inducing ¹O₂ generation and growth inhibition of the infectious bacteria, S. aureus and E. coli (∼99% and ∼97%, respectively), in vitro. In particular, these photodynamic effects of CDs from CDgel have been shown to accelerate the healing of infected wounds in vivo, showing a higher wound regeneration rate as compared to that of untreated wounds. Our work demonstrates that the biocompatible and shape-controllable CDgel possesses therapeutic potential as a treatment modality for the light-driven control of drug-resistant bacterial infections.

Structure and mechanism behind the inhibitory effect of water soluble metalloporphyrins on Aβ1-42 aggregation

Although the exact molecular mechanism of the pathogenesis of Alzheimer’s disease (AD) is still unclear, compounds that can inhibit the aggregation of amyloid-β peptide (Aβ1-42) or scavenge the highly toxic...

A Ratiometric Fluorescent Conjugated Oligomer for Amyloid β Recognition, Aggregation Inhibition, and Detoxification

The sensitive recognition and effective inhibition of toxic amyloid β protein (Aβ) aggregates play a critical role in early diagnosis and treatment of neurodegenerative diseases. In this work, a new conjugated oligo(fluorene-co-phenylene) (OFP) modified with 1,8-naphthalimide (NA) derivative OFP-NA-NO₂ is designed and synthesized as a ratiometric fluorescence probe for sensing Aβ, inhibiting the assembly of Aβ, and detoxicating the cytotoxicity of Aβ aggregates. In the presence of Aβ, the active ester group on the side chain of OFP-NA-NO₂ can covalently react with the amino group on Aβ, effectively inhibiting the formation of Aβ aggregates and degrading the preformed fibrils. In this case, the fluorescence intensity ratio of NA to OFP (I_NA /I_OFP ) increases greatly. The detection limit is calculated to be 89.9 nM, presenting the most sensitive ratiometric recognition of Aβ. Interestingly, OFP-NA-NO₂ can dramatically recover the cell viability of PC-12 and restore the Aβ-clearing ability of microglia. Therefore, this ratiometric probe exhibits the targeted recognition of Aβ, effective inhibition of Aβ aggregates, and detox effect, which is potential for early diagnosis and treatment of neurodegenerative diseases.

Hydroxy-Porphyrin as an Effective, Endogenous Molecular Clamp during Early Stages of Amyloid Fibrillization

Amyloid fibril formation of proteins is of great concern in neurodegenerative disease and can be detrimental to the storage and stability of biologics. Recent evidence suggests that insulin fibril formation reduces the efficacy of type II diabetes management and may lead to several complications. To develop anti-amyloidogenic compounds of endogenous origin, we have utilized the hydrogen bond anchoring, π stacking ability of porphyrin, and investigated its role on the inhibition of insulin amyloid formation. We report that hydroxylation and metal removal from the heme moiety yields an excellent inhibitor of insulin fibril formation. Thioflavin T, tyrosine fluorescence, Circular Dichorism (CD) spectroscopy, Field emission scanning electron microscopy (FESEM) and molecular dynamics (MD) simulation studies suggest that hematoporphyrin (HP) having hydrogen bonding ability on both sides is a superior inhibitor compared to hemin and protoporphyrin (PP). Experiments with hen egg white lysozyme (HEWL) amyloid fibril formation also validated the efficacy of endogenous porphyrin based small molecules. Our results will help to decipher a general therapeutic strategy to counter amyloidogenesis.

Chemical catalyst-promoted photooxygenation of amyloid proteins

Misfolded proteins produce aberrant fibrillar aggregates, called amyloids, which contain cross-β-sheet higher order structures. The species generated in the aggregation process (i.e., oligomers, protofibrils, and fibrils) are cytotoxic and can cause various diseases. Interfering with the amyloid formation of proteins could be a drug development target for treating diseases caused by aberrant protein aggregation. In this review, we introduce a variety of chemical catalysts that oxygenate amyloid proteins under light irradiation using molecular oxygen as the oxygen atom donor (i.e., photooxygenation catalysts). Catalytic photooxygenation strongly inhibits the aggregation of amyloid proteins due to covalent installation of hydrophilic oxygen atoms and attenuates the neurotoxicity of the amyloid proteins. Recent in vivo studies in disease model animals using photooxygenation catalysts showed promising therapeutic effects, such as memory improvement and lifespan extension. Moreover, photooxygenation catalysts with new modes of action, including interference with the propagation of amyloid core seeds and enhancement in the metabolic clearance of amyloids in the brain, have begun to be identified. Manipulation of catalytic photooxygenation with secured amyloid selectivity is indispensable for minimizing the side effects in clinical application. Here we describe several strategies for designing catalysts that selectively photooxygenate amyloids without reacting with other non-amyloid biomolecules.

Nanoparticle-Guided Brain Drug Delivery: Expanding the Therapeutic Approach to Neurodegenerative Diseases

Neurodegenerative diseases (NDs) represent a heterogeneous group of aging-related disorders featured by progressive impairment of motor and/or cognitive functions, often accompanied by psychiatric disorders. NDs are denoted as 'protein misfolding' diseases or proteinopathies, and are classified according to their known genetic mechanisms and/or the main protein involved in disease onset and progression. Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD) are included under this nosographic umbrella, sharing histopathologically salient features, including deposition of insoluble proteins, activation of glial cells, loss of neuronal cells and synaptic connectivity. To date, there are no effective cures or disease-modifying therapies for these NDs. Several compounds have not shown efficacy in clinical trials, since they generally fail to cross the blood-brain barrier (BBB), a tightly packed layer of endothelial cells that greatly limits the brain internalization of endogenous substances. By engineering materials of a size usually within 1-100 nm, nanotechnology offers an alternative approach for promising and innovative therapeutic solutions in NDs. Nanoparticles can cross the BBB and release active molecules at target sites in the brain, minimizing side effects. This review focuses on the state-of-the-art of nanoengineered delivery systems for brain targeting in the treatment of AD, PD and HD.

NIR-II Hydrogen-Bonded Organic Frameworks (HOFs) Used for Target-Specific Amyloid-β Photooxygenation in an Alzheimer's Disease Model

Phototherapy has emerged as a powerful approach for interrupting β-amyloid (Aβ) self-assembly. However, deeper tissue penetration and safer photosensitizers are urgent to be exploited for avoiding damaging nearby normal tissues and improving therapeutic effectiveness. A hydrogen-bonded organic framework (HOF)-based NIR-II photooxygenation catalyst is presented here to settle the abovementioned challenges. By encapsulating the pyridinium hemicyanine dye DSM with a large two-photon absorption (TPA) cross-section in NIR-II window into the porphyrin-based HOF, the resultant DSM@n-HOF-6 exhibits significant two-photon NIR-II-excited Fluorescence Resonance Energy Transfer (FRET) to generate singlet oxygen (¹ O₂ ) for Aβ oxidation. Further, the target peptides of KLVFFAED (KD8) are covalently grafted on DSM@n-HOF-6 to enhance the blood-brain barrier (BBB) permeability and Aβ selectivity. The HOF-based photooxygenation catalyst shows an outstanding inhibitory effect of Aβ aggregation upon the NIR-II irradiation. Further in vivo studies demonstrate the obvious decrease of craniocerebral Aβ plaques and recovery of memory deficits in triple-transgenic AD (3×Tg-AD) model mice.

Photothermal and Photodynamic Therapies via NIR-Activated Nanoagents in Combating Alzheimer's Disease

It is well established that the polymerization of amyloid-β peptides into fibrils/plaques is a critical step during the development of Alzheimer's disease (AD). Phototherapy, which includes photodynamic therapy and photothermal therapy, is a highly attractive strategy in AD treatment due to its merits of operational flexibility, noninvasiveness, and high spatiotemporal resolution. Distinct from traditional chemotherapies or immunotherapies, phototherapies capitalize on the interaction between photosensitizers or photothermal transduction agents and light to trigger photochemical reactions to generate either reactive oxygen species or heat effects to modulate Aβ aggregation, ultimately restoring nerve damage and ameliorating memory deficits. In this Review, we provide an overview of the recent advances in the development of near-infrared-activated nanoagents for AD phototherapies and discuss the potential challenges of and perspectives on this emerging field with a special focus on how to improve the efficiency and utility of such treatment. We hope that this Review will spur preclinical research and the clinical translation of AD treatment through phototherapy.

Nanomaterials for Modulating the Aggregation of β-Amyloid Peptides

The aberrant aggregation of amyloid-β (Aβ) peptides in the brain has been recognized as the major hallmark of Alzheimer's disease (AD). Thus, the inhibition and dissociation of Aβ aggregation are believed to be effective therapeutic strategiesforthe prevention and treatment of AD. When integrated with traditional agents and biomolecules, nanomaterials can overcome their intrinsic shortcomings and boost their efficiency via synergistic effects. This article provides an overview of recent efforts to utilize nanomaterials with superior properties to propose effective platforms for AD treatment. The underlying mechanismsthat are involved in modulating Aβ aggregation are discussed. The summary of nanomaterials-based modulation of Aβ aggregation may help researchers to understand the critical roles in therapeutic agents and provide new insight into the exploration of more promising anti-amyloid agents and tactics in AD theranostics.

UBE4B, a microRNA-9 target gene, promotes autophagy-mediated Tau degradation

The formation of hyperphosphorylated intracellular Tau tangles in the brain is a hallmark of Alzheimer's disease (AD). Tau hyperphosphorylation destabilizes microtubules, promoting neurodegeneration in AD patients. To identify suppressors of tau-mediated AD, we perform a screen using a microRNA (miR) library in Drosophila and identify the miR-9 family as suppressors of human tau overexpression phenotypes. CG11070, a miR-9a target gene, and its mammalian orthologue UBE4B, an E3/E4 ubiquitin ligase, alleviate eye neurodegeneration, synaptic bouton defects, and crawling phenotypes in Drosophila human tau overexpression models. Total and phosphorylated Tau levels also decrease upon CG11070 or UBE4B overexpression. In mammalian neuroblastoma cells, overexpression of UBE4B and STUB1, which encodes the E3 ligase CHIP, increases the ubiquitination and degradation of Tau. In the Tau-BiFC mouse model, UBE4B and STUB1 overexpression also increase oligomeric Tau degradation. Inhibitor assays of the autophagy and proteasome systems reveal that the autophagy-lysosome system is the major pathway for Tau degradation in this context. These results demonstrate that UBE4B, a miR-9 target gene, promotes autophagy-mediated Tau degradation together with STUB1, and is thus an innovative therapeutic approach for AD.

Current Strategies for Modulating Aβ Aggregation with Multifunctional Agents

Alzheimer's disease (AD), as the primary cause of dementia, has seriously affected millions of people worldwide and brought a very heavy financial and social burden. With the growth of population and aging, the situation will worsen unless efficacious drugs are found to reverse, stop, or even slow down disease progression. More and more evidence has demonstrated that amyloid-β (Aβ) aggregation is an upstream causative factor in AD pathogenesis and then triggers a slew of pathological events. Furthermore, the concentrated redox metal ions in the AD brain, especially Cu(II), can significantly exacerbate Aβ aggregation and contribute to the formation of neurotoxic reactive oxygen species (ROS). Therefore, the inhibition of Aβ aggregation and relief of amyloidosis-initiated neurotoxicity play a critical role in AD treatment. Until now, several methods have been proposed to modulate Aβ aggregation, such as developing aggregation inhibitors to interfere with Aβ assembly via noncovalent interactions, copper chelators to cut off metal-accelerated Aβ aggregation and concomitant cytotoxicity, photooxidation to reduce the hydrophobicity and aggregation tendency of Aβ, thermal dissociation to disrupt amyloid aggregates susceptible to temperature, degradation with artificial protease to fracture the Aβ peptide into small fragments, and the clearance of peripheral Aβ to bypass the obstruction of the BBB and reduce the Aβ burden.In this Account, we focus on our contributions to the development of Aβ-targeted multifunctional molecules and nanoparticles, emphasizing the diversified strategies and synergistic therapeutic effects. These therapeutic agents possess the following multifunctionalities: (1) compared with frequently used aggregation inhibitors restricted by intrinsically feeble and sensitive noncovalent interactions, multifunctional agents can efficiently block Aβ aggregation by exploiting two or more Aβ-specific inhibition strategies simultaneously; (2) apart from regulating Aβ aggregation, multipronged agents can also target and modulate other pathological factors in AD pathogenesis, such as increased oxidative stress, abnormal copper accumulation, and irreversible neuron loss; (3) multifunctional platforms with both diagnostic and therapeutic modalities through integrating in situ imaging, real-time diagnostics, a multitarget direction, stimuli-responsive drug release, and the blood-brain barrier (BBB) translocation features are instrumental in improving drug levels at trouble sites, diminishing off-target adverse reactions, evaluating therapeutic effects, and averting overtreatment.Given the fact that amyloid aggregation, local inflammation, and metal dyshomeostasis are universal biomarkers shared by various neurodegenerative disorders, this Account provides a perspective for the evolution of customized therapeutic agents with multiple reactivities for other neurodegenerative diseases. In addition, recent studies have indicated that Aβ aggregates can enter the nucleus and induce DNA damage and anomalous conformational transition. We also explore the influences of DNA on the biological effects of Aβ aggregates.

Photoresponsive materials for intensified modulation of Alzheimer's amyloid-β protein aggregation: A review

The abnormal self-assembly of amyloid-β protein (Aβ) into toxic aggregates is a major pathological hallmark of Alzheimer's disease (AD). Modulation of Aβ fibrillization with pharmacological modalities has become an active field of research, which aims to mitigate Aβ-induced neurotoxicity and ameliorate impaired recognition. Among the various strategies for AD treatment, phototherapy, including photothermal therapy (PTT), photodynamic therapy (PDT), and photoresponsive release systems have attracted increased attention because of the spatiotemporal controllability. Under the irradiation of light, the heat or reactive oxygen species generated by photothermal or photodynamic processes significantly enhances the efficacy of the inhibitor or modulator, and the "caged" drug can be accurately released at the intended site, thus avoiding adverse effects. This review, from a viewpoint of materials, focuses on the recent advances in modulating Aβ aggregation by light that irradiates on the materials that function on modulating Aβ aggregation. Representative examples of PTT, PDT, and photoresponsive drug release systems are discussed in terms of inhibitory mechanism, the unique properties of materials, and the design of modulators. The major challenges of phototherapy against AD are addressed and the promising prospects are proposed. It is concluded that the noninvasive light-assisted approaches will become a promising strategy for intensifying the modulation of Aβ aggregation and thus facilitating AD treatment. STATEMENT OF SIGNIFICANCE: Alzheimer's disease (AD) with the hallmark of amyloid-β protein (Aβ) deposition is affecting more than 50 million people globally. It is urgent to explore intelligent materials to modulate Aβ aggregation. This review summarizes the intensified modulation of Aβ aggregation by a variety of photoresponsive materials including photothermal, photosensitizing and photoresponsive release materials, focusing on their characteristics and functionalities. We believe this review would arouse more interest in the research field of stimuli-responsive materials and promote their clinical applications in AD therapy.

Catalytic photooxygenation degrades brain Aβ in vivo

Protein degradation induced by small molecules by recruiting endogenous protein degradation systems, such as ubiquitin-proteasome systems, to disease-related proteins is an emerging concept to inhibit the function of undruggable proteins. Protein targets without reliable ligands and/or existing outside the cells where ubiquitin-proteasome systems do not exist, however, are beyond the scope of currently available protein degradation strategies. Here, we disclose photooxygenation catalyst 7 that permeates the blood-brain barrier and selectively and directly degrades an extracellular Alzheimer's disease-related undruggable protein, amyloid-β protein (Aβ). Key was the identification of a compact but orange color visible light-activatable chemical catalyst whose activity can be switched on/off according to its molecular mobility, thereby ensuring high selectivity for aggregated Aβ. Chemical catalyst-promoted protein degradation can be applied universally for attenuating extracellular amyloids and various pathogenic proteins and is thus a new entry to induced protein degradation strategies.

Non-Oncologic Applications of Nanomedicine-Based Phototherapy

Phototherapy is widely applied to various human diseases. Nanomedicine-based phototherapy can be classified into photodynamic therapy (PDT) and photothermal therapy (PTT). Activated photosensitizer kills the target cells by generating radicals or reactive oxygen species in PDT while generating heat in PTT. Both PDT and PTT have been employed for treating various diseases, from preclinical to randomized controlled clinical trials. However, there are still hurdles to overcome before entering clinical practice. This review provides an overview of nanomedicine-based phototherapy, especially in non-oncologic diseases. Multiple clinical trials were undertaken to prove the therapeutic efficacy of PDT in dermatologic, ophthalmologic, cardiovascular, and dental diseases. Preclinical studies showed the feasibility of PDT in neurologic, gastrointestinal, respiratory, and musculoskeletal diseases. A few clinical studies of PTT were tried in atherosclerosis and dry eye syndrome. Although most studies have shown promising results, there have been limitations in specificity, targeting efficiency, and tissue penetration using phototherapy. Recently, nanomaterials have shown promising results to overcome these limitations. With advanced technology, nanomedicine-based phototherapy holds great potential for broader clinical practice.

Photomodulating Carbon Dots for Spatiotemporal Suppression of Alzheimer's β-Amyloid Aggregation

Extracellular deposition of β-amyloid (Aβ) peptide aggregates is a major characteristic of Alzheimer's disease (AD) brain. Because Aβ peptide aggregates aggravate neuropathy and cognitive impairment for AD patients, numerous efforts have been devoted to suppressing Aβ self-assembly as a prospective AD treatment option. Here, we report Aβ-targeting, red-light-responsive carbon dots (CDs), and their therapeutic functions as a light-powered nanomodulator to spatiotemporally suppress toxic Aβ aggregation both in vitro and in vivo. Our aptamer-functionalized carbon dots (Apta@CDs) showed strong targeting ability toward Aβ₄₂ species. Moreover, red LED irradiation induced Apta@CDs to irreversibly denature Aβ peptides, impeding the formation of β-sheet-rich Aβ aggregates and attenuating Aβ-associated cytotoxicity. Consequently, Apta@CDs-mediated photomodualtion modality achieved effective suppression of Aβ aggregation in vivo, which significantly reduced the Aβ burden at the targeted sites in the brain of 5xFAD mice by ∼40% and ∼25% according to imaging and ELISA analyses, respectively. Our work demonstrates the therapeutic potential of photomodulating CDs for light-driven suppression against Aβ self-assembly and related neurotoxicity.

Engineering of fluorescent or photoactive Trojan probes for detection and eradication of β-Amyloids

Trojan horse technology institutes a potentially promising strategy to bring together a diagnostic or cell-based drug design and a delivery platform. It provides the opportunity to re-engineer a novel multimodal, neurovascular detection probe, or medicine to fuse with blood-brain barrier (BBB) molecular Trojan horse. In Alzheimer's disease (AD) this could allow the targeted delivery of detection or therapeutic probes across the BBB to the sites of plaques and tangles development to image or decrease amyloid load, enhance perivascular Aβ clearance, and improve cerebral blood flow, owing principally to the significantly improved cerebral permeation. A Trojan horse can also be equipped with photosensitizers, nanoparticles, quantum dots, or fluorescent molecules to function as multiple targeting theranostic compounds that could be activated following changes in disease-specific processes of the diseased tissue such as pH and protease activity, or exogenous stimuli such as, light. This concept review theorizes the use of receptor-mediated transport-based platforms to transform such novel ideas to engineer systemic and smart Trojan detection or therapeutic probes to advance the neurodegenerative field.

Use of Biodegradable, Chitosan-Based Nanoparticles in the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects more than 24 million people worldwide and represents an immense medical, social and economic burden. While a vast array of active pharmaceutical ingredients (API) is available for the prevention and possibly treatment of AD, applicability is limited by the selective nature of the blood-brain barrier (BBB) as well as by their severe peripheral side effects. A promising solution to these problems is the incorporation of anti-Alzheimer drugs in polymeric nanoparticles (NPs). However, while several polymeric NPs are nontoxic and biocompatible, many of them are not biodegradable and thus not appropriate for CNS-targeting. Among polymeric nanocarriers, chitosan-based NPs emerge as biodegradable yet stable vehicles for the delivery of CNS medications. Furthermore, due to their mucoadhesive character and intrinsic bioactivity, chitosan NPs can not only promote brain penetration of drugs via the olfactory route, but also act as anti-Alzheimer therapeutics themselves. Here we review how chitosan-based NPs could be used to address current challenges in the treatment of AD; with a specific focus on the enhancement of blood-brain barrier penetration of anti-Alzheimer drugs and on the reduction of their peripheral side effects.

Target-driven supramolecular self-assembly for selective amyloid-β photooxygenation against Alzheimer's disease

Photo-oxygenation of β-amyloid (Aβ) has been considered an efficient way to inhibit Aβ aggregation in Alzheimer's disease (AD). However, current photosensitizers cannot simultaneously achieve enhanced blood-brain barrier (BBB) permeability and selective photooxygenation of Aβ, leading to poor therapeutic efficacy, severe off-target toxicity, and substandard bioavailability. Herein, an Aβ target-driven supramolecular self-assembly (PKNPs) with enhanced BBB penetrability and switchable photoactivity is designed and demonstrated to be effective in preventing Aβ aggregation in vivo. PKNPs are prepared by the self-assembly of the Aβ-targeting peptide KLVFF and an FDA-approved porphyrin derivative (5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin). Due to the photothermal effect of PKNPs, the BBB permeability of PKNPs under irradiation is 8.5-fold higher than that of porphyrin alone. Moreover, upon selective interaction with Aβ, PKNPs undergo morphological change from the spherical to the amorphous form, resulting in a smart transformation from photothermal activity to photodynamic activity. Consequently, the disassembled PKNPs can selectively oxygenate Aβ without affecting off-target proteins (insulin, bovine serum albumin, and human serum albumin). The well-designed PKNPs exhibit not only improved BBB permeability but also highly selective Aβ photooxygenation. Furthermore, in vivo experiments demonstrate that PKNPs can alleviate Aβ-induced neurotoxicity and prolong the life span of the commonly used AD transgenic Caenorhabditis elegans CL2006. Our work may open a new path for using supramolecular self-assemblies as switchable phototheranostics for the selective and effective prevention of Aβ aggregation and related neurotoxicity in AD.

A Biocompatible Second Near-Infrared Nanozyme for Spatiotemporal and Non-Invasive Attenuation of Amyloid Deposition through Scalp and Skull

Phototherapy, such as photodynamic therapy and photothermal therapy, holds great potential for modulation of Alzheimer's β-amyloid (Aβ) self-assembly. Unfortunately, current works for phototherapy of Alzheimer's disease (AD) are just employing either visible or first near-infrared (NIR-I) light with limited tissue penetration, which can not avoid damaging nearby normal tissues of AD patients through the dense skull and scalp. To overcome the shortcomings of AD phototherapy, herein we report an amyloid targeting, N-doped three-dimensional mesoporous carbon nanosphere (KD8@N-MCNs) as a second near-infrared (NIR-II) PTT agent. This makes it possible for photothermal dissociation of Aβ aggregates through the scalp and skull in a NIR-II window without hurting nearby normal tissues. Besides, KD8@N-MCNs have both superoxide dismutase and catalase activities, which can scavenge intracellular superfluous reactive oxygen species and alleviate neuroinflammation in vivo. Furthermore, KD8@N-MCNs efficiently cross the blood-brain barrier owing to the covalently grafted target peptides of KLVFFAED on the nanosphere surface. In vivo studies demonstrate that KD8@N-MCNs decrease Aβ deposits, ameliorate memory deficits, and alleviate neuroinflammation in the 3xTg-AD mouse model. Our work provides a biocompatible and non-invasive way to attenuate AD-associated pathology.

Alzheimer's Therapeutic Strategy: Photoactive Platforms for Suppressing the Aggregation of Amyloid β Protein

Neurodegenerative diseases such as Alzheimer's disease (AD) have become a public health problem. Progressive cerebral accumulation of amyloid protein (Aβ) was widely considered as the cause of AD. One promising strategy for AD preclinical study is to degrade and clear the deposited amyloid aggregates with β-sheet-rich secondary structure in the brain. Based on the requirement, photo-active materials with the specific excitation and the standardization of the photosensitizer preparation and application in clinics, have attracted increased attention in the study and treatment of neurodegenerative disease as a novel method termed as photodynamic therapy (PDT). This review will focus on the new photosensitizing materials and discuss the trend of PDT techniques for the possible application in the treatment strategy of amyloid-related diseases.

Photonic Carbon Dots as an Emerging Nanoagent for Biomedical and Healthcare Applications

As a class of carbon-based nanomaterials, carbon dots (CDs) have attracted enormous attention because of their tunable optical and physicochemical properties, such as absorptivity and photoluminescence from ultraviolet to near-infrared, high photostability, biocompatibility, and aqueous dispersity. These characteristics make CDs a promising alternative photonic nanoagent to conventional fluorophores in disease diagnosis, treatment, and healthcare managements. This review describes the fundamental photophysical properties of CDs and highlights their recent applications to bioimaging, photomedicine (e.g., photodynamic/photothermal therapies), biosensors, and healthcare devices. We discuss current challenges and future prospects of photonic CDs to give an insight into developing vibrant fields of CD-based biomedicine and healthcare.

Efficient suppression of amyloid-β peptide aggregation and cytotoxicity with photosensitive polymer nanodots

The deposition of amyloid plaques resulting from the aggregation of amyloid-β (Aβ) peptides is closely related to Alzheimer's disease (AD). With the development of various therapeutic methods, the oxidative modification of Aβ has emerged as a fascinating noninvasive photo-therapeutic intervention for treating AD by altering the Aβ aggregation tendency. Herein, we report the photo-triggered inhibition of Aβ aggregation and cytotoxicity by utilizing polymer nanodots (Pdots) modified with rose bengal (RB), methylene blue (MB), and riboflavin (RF). Experimental results demonstrate that these functionalized Pdots manifest a superior suppression effect on Aβ aggregation under irradiation. This can be attributed to the formation of reactive oxygen species (ROS) (i.e., singlet oxygen (¹O₂)), resulting in the oxygenation of Aβ and the change of Aβ aggregation tendency. Especially, RB-Pdots manifest better biocompatibility and higher ¹O₂ productivity. In a word, this hybridized nanostructure will provide a promising platform for the noninvasive photo-therapeutic treatment of AD in the future.

Near-Infrared-Active Copper Bismuth Oxide Electrodes for Targeted Dissociation of Alzheimer's β-Amyloid Aggregates

The abnormal accumulation of β-amyloid (Aβ) aggregates in the brain is a major pathological hallmark of Alzheimer's disease. We report a near-infrared (NIR)-active CuBi₂O₄-based photocathodic platform that can target intact Aβ aggregates and dissociate them into nontoxic species. Because of its relatively narrow band gap, CuBi₂O₄ exhibits strong absorption of NIR light, which allows for deeper tissue penetration and causes less photodamage to tissues compared to visible light. Furthermore, its high stability in aqueous media, biocompatibility, and robustness against photocorrosion make CuBi₂O₄ an ideal material for medical applications. For the targeted clearance of Aβ aggregates, we have conjugated the KLVFF peptide which specifically recognizes and captures Aβ aggregates on the surface of silver-doped CuBi₂O₄ (Ag:CuBi₂O₄). Upon illumination of NIR light under a cathodic bias, the KLVFF-immobilized Ag:CuBi₂O₄ (KLVFF-Ag:CuBi₂O₄) effectively dissociated β-sheet-rich, long, and entangled Aβ fibrillary aggregates into small fragmented, soluble species through photo-oxygenation. We also verified that the KLVFF-Ag:CuBi₂O₄ photocathode is biocompatible and effective in reducing Aβ aggregate-induced neurotoxicity. Our work demonstrates the potential of the KLVFF-Ag:CuBi₂O₄ platform for the targeted disassembly of cytotoxic, robust Aβ aggregates with the aid of NIR energy and cathodic bias.

Genetic Dissection of Alzheimer's Disease Using Drosophila Models

Alzheimer’s disease (AD), a main cause of dementia, is the most common neurodegenerative disease that is related to abnormal accumulation of the amyloid β (Aβ) protein. Despite decades of intensive research, the mechanisms underlying AD remain elusive, and the only available treatment remains symptomatic. Molecular understanding of the pathogenesis and progression of AD is necessary to develop disease-modifying treatment. Drosophila, as the most advanced genetic model, has been used to explore the molecular mechanisms of AD in the last few decades. Here, we introduce Drosophila AD models based on human Aβ and summarize the results of their genetic dissection. We also discuss the utility of functional genomics using the Drosophila system in the search for AD-associated molecular mechanisms in the post-genomic era.

Multifunctional nano-enabled delivery systems in Alzheimer's disease management

This review discusses the recent advances in multifunctional nano-enabled delivery systems (NDS) for Alzheimer's disease management, including multitherapeutics, multimodal imaging-guided diagnostics, and theranostics.

Photodegradation of porphyrin-bound hIAPP(1–37) fibrils

Amyloid deposits in pancreatic islets of type 2 diabetes mellitus (T2DM) are mainly comprised of human islet amyloid polypeptide (hIAPP), the degradation of hIAPP fibrils by photoactive porphyrin could be a preventive strategy against T2DM.

Self-triggered click reaction in an Alzheimer's disease model: in situ bifunctional drug synthesis catalyzed by neurotoxic copper accumulated in amyloid-β plaques

Cu is one of the essential elements for life. Its dyshomeostasis has been demonstrated to be closely related to neurodegenerative disorders, such as Alzheimer's disease (AD), which is characterized by amyloid-β (Aβ) aggregation and Cu accumulation. It is a great challenge as to how to take advantage of neurotoxic Cu to fight disease and make it helpful. Herein, we report that the accumulated Cu in Aβ plaques can effectively catalyze an azide-alkyne bioorthogonal cycloaddition reaction for fluorophore activation and drug synthesis in living cells, a transgenic AD model of Caenorhabditis elegans CL2006, and brain slices of triple transgenic AD mice. More importantly, the in situ synthesized bifunctional drug 6 can disassemble Aβ-Cu aggregates by extracting Cu and photo-oxygenating Aβ synergistically, suppressing Aβ-mediated paralysis and diminishing the locomotion defects of the AD model CL2006 strain. Our results demonstrate that taking the accumulated Cu ions in the Aβ plaque for an in situ click reaction can achieve both a self-triggered and self-regulated drug synthesis for AD therapy. To the best of our knowledge, a click reaction catalyzed by local Cu in a physiological environment has not been reported. This work may open up a new avenue for in situ multifunctional drug synthesis by using endogenous neurotoxic metal ions for the treatment of neurodegenerative diseases.

Nanocatalytic Medicine

Catalysis and medicine are often considered as two independent research fields with their own respective scientific phenomena. Promoted by recent advances in nanochemistry, large numbers of nanocatalysts, such as nanozymes, photocatalysts, and electrocatalysts, have been applied in vivo to initiate catalytic reactions and modulate biological microenvironments for generating therapeutic effects. The rapid growth of research in biomedical applications of nanocatalysts has led to the concept of "nanocatalytic medicine," which is expected to promote the further advance of such a subdiscipline in nanomedicine. The high efficiency and selectivity of catalysis that chemists strived to achieve in the past century can be ingeniously translated into high efficacy and mitigated side effects in theranostics by using "nanocatalytic medicine" to steer catalytic reactions for optimized therapeutic outcomes. Here, the rationale behind the construction of nanocatalytic medicine is eludicated based on the essential reaction factors of catalytic reactions (catalysts, energy input, and reactant). Recent advances in this burgeoning field are then comprehensively presented and the mechanisms by which catalytic nanosystems are conferred with theranostic functions are discussed in detail. It is believed that such an emerging catalytic therapeutic modality will play a more important role in the field of nanomedicine.

Characterizing the inhibition of α-synuclein oligomerization by a pharmacological chaperone that prevents prion formation by the protein PrP

Aggregation of the disordered protein α-synuclein into amyloid fibrils is a central feature of synucleinopathies, neurodegenerative disorders that include Parkinson's disease. Small, pre-fibrillar oligomers of misfolded α-synuclein are thought to be the key toxic entities, and α-synuclein misfolding can propagate in a prion-like way. We explored whether a compound with anti-prion activity that can bind to unfolded parts of the protein PrP, the cyclic tetrapyrrole Fe-TMPyP, was also active against α-synuclein aggregation. Observing the initial stages of aggregation via fluorescence cross-correlation spectroscopy, we found that Fe-TMPyP inhibited small oligomer formation in a dose-dependent manner. Fe-TMPyP also inhibited the formation of mature amyloid fibrils in vitro, as detected by thioflavin T fluorescence. Isothermal titration calorimetry indicated Fe-TMPyP bound to monomeric α-synuclein with a stoichiometry of 2, and two-dimensional heteronuclear single quantum coherence NMR spectra revealed significant interactions between Fe-TMPyP and the C-terminus of the protein. These results suggest commonalities among aggregation mechanisms for α-synuclein and the prion protein may exist that can be exploited as therapeutic targets.