Research finds engineered exosomes enhance blood-brain barrier penetration and improve Alzheimer's disease through multiple pathways

The pathogenesis of Alzheimer's disease (AD) is complex, involving excessive β-amyloid (Aβ) deposition, microglial dysfunction, and neuroinflammation. Consequently, single-target therapies are insufficient to address the multifaceted pathology of AD. Moreover, the low permeability of the blood-brain barrier (BBB) and the lack of site-specific targeting in AD further limit the efficacy of current AD therapeutics.

2025, 5 9,BiomaterialsPublish online as "Multi-targeted engineered hybrid exosomes as Aβ nanoscavengers and inflammatory modulators for multi-pathway intervention in Alzheimer's diseaseresearch paper on.

This study hybridized the membranes of brain microvascular endothelial cell-derived exosomes and macrophage-derived exosomes, then integrated polydopamine nanoparticles, resveratrol, and an Aβ-targeting aptamer to engineer a multifunctional exosome (RPDA@Rb-A) for enhancing Aβ clearance and modulating microglial dysfunction.

Leveraging the homing capability of brain microvascular endothelial cell-derived exosomes and the innate inflammatory targeting ability of macrophage-derived exosomes, RPDA@Rb-A captures Aβ aggregates and efficiently crosses the blood-brain barrier to accumulate at sites of neuroinflammation. RPDA@Rb-A effectively intervenes in Alzheimer's disease (AD) through multiple mechanisms: near-infrared laser-induced local heating degrades toxic Aβ aggregates and reduces neurotoxicity; Aβ capture promotes microglial clearance; and efficient delivery of small-molecule drugs modulates microglia-driven neuroinflammation.

In the AD mouse model, RPDA@Rb-A treatment significantly reduced amyloid plaque deposition, neuroinflammation, and cognitive impairment.Engineered exosomes based on membrane hybridization overcome the limitations of poor blood-brain barrier penetration and insufficient targeting in traditional drug carriers, offering a promising platform for multi-pathway intervention in Alzheimer's disease.

As the global population grows, the incidence of Alzheimer's disease (AD) is rising annually, causing severe physical suffering and financial burden for patients.Studies show that excessive deposition of β-amyloid (Aβ) is a key factor in AD pathology. Therefore, targeting Aβ clearance is an important therapeutic strategy for AD. While multiple Aβ-targeted drugs have entered clinical trials, their success rates remain low, and the therapeutic value of targeting Aβ continues to be debated.

Growing pathological evidence indicates that the key issue is not whether Aβ is a suitable therapeutic target, but rather the disruptive effects of various Aβ-related pathological pathways. For instance, amyloid plaques and neuronal degeneration often occur alongside oxidative stress and neuroinflammation. In the early stages of AD, microglia can recognize Aβ deposits and clear harmful factors via phagocytosis to maintain brain homeostasis.

However, persistent microglial formation of Aβ and excessive Aβ clearance lead to reduced phagocytosis and the production of proinflammatory mediators. Conversely, these proinflammatory mediators further promote Aβ formation and accumulation. Alzheimer's disease progression results from the interplay of multiple pathological mechanisms that together create a complex vicious cycle, making single-target drugs insufficient to meet therapeutic needs for AD.

Additionally, most AD drugs face significant hurdles in crossing the blood-brain barrier (BBB) and targeting AD lesions, which limits their therapeutic efficacy in clinical settings.Therefore, an ideal AD therapy should effectively cross the BBB, actively target AD lesions, and address multiple pathological hallmarks of AD.

Leveraging the low thermal stability of Aβ aggregates, photothermal therapy (PTT) uses photothermal agents to disassemble toxic Aβ aggregates, offering a non-invasive intervention strategy for Alzheimer's disease.

Photothermal agents can induce localized heat under near-infrared (NIR) irradiation to disrupt the β-sheet ordered assembly of Aβ aggregates. Photothermal materials such as carbon quantum dots, gold nanorods, Prussian blue nanoparticles, and MoS2 quantum dots have been used to disassemble Aβ aggregates.

Reports indicate that NIR irradiation can temporarily open the BBB, thereby enhancing drug delivery efficiency and enabling spatiotemporal control and rapid release of drugs within drug delivery systems. Polydopamine nanoparticles (PDA), formed by polymerizing the neurotransmitter dopamine in the human body, exhibit excellent biocompatibility, biodegradability, and photothermal conversion performance. They serve as an ideal photothermal carrier with dual functionality for Aβ depolymerization and drug delivery.

Traditional AD drugs (e.g., donepezil and galantamine) primarily alleviate cognitive impairment by inhibiting acetylcholinesterase but do not directly target core pathologies such as Aβ deposition or disease progression driven by neuroinflammation.

Resveratrol is a natural polyphenol that modulates microglial dysfunction in Alzheimer's disease (AD) through anti-inflammatory and antioxidant mechanisms, enhancing microglial phagocytosis and degradation of Aβ aggregates. When combined with PTT therapy, it effectively reduces Aβ burden in the AD brain.

However, resveratrol's poor bioavailability—due to BBB-limited solubility, chemical instability, and insufficient permeability—significantly restricts its further application in AD intervention.

Exosomes are endogenous extracellular vesicles with a natural vesicular structure, making them effective drug delivery carriers.Compared with other synthetic nanoparticle drug carriers, such as gold nanomaterials, 2D nanomaterials, and polymers, exosomes exhibit lower immunogenicity and cytotoxicity, and possess the ability to actively cross the blood-brain barrier to reach deep brain tissues.

Furthermore, the natural "homing effect" of exosomes facilitates their uptake by autologous cells. Some exosomes are specifically recognized and internalized by target cells via their intrinsic membrane receptors or extracellular matrix-binding proteins, making them an effective carrier for brain drug delivery.

Currently, research on AD has leveraged exosomes as drug delivery vehicles to enhance the bioavailability of small molecules (e.g., donepezil, curcumin, quercetin, silymarin), nucleic acids, and proteins, thereby improving the efficacy of AD interventions.However, after systemic administration, exosomes primarily accumulate non-specifically in the spleen and liver, resulting in relatively low accumulation in the brain and unintended toxicity in non-target organs.

To overcome the above limitations, drug-loaded exosomes were surface-modified with rabies virus glycoprotein (RVG) peptide, Ang2 peptide-2, mannose, and Fe65 protein. These modifications enhanced the targeting of exosomes to lesion sites, thereby improving therapeutic efficacy for Alzheimer's disease (AD). However, most current studies are limited to single-stage targeting strategies, which are insufficient given the complexity of the AD brain microenvironment, including targets such as inflammation and Aβ.

To enable more effective AD intervention, engineered exosomes must possess superior targeting capabilities. Beyond crossing the BBB, they need to simultaneously target multiple brain sites. Therefore, developing engineered exosomes capable of multi-target and multi-pathway intervention is a key focus for future research.

This study fused brain microvascular endothelial cell-derived exosomes with natural brain-homing properties (bEnd.3Exo) and RAW264.7 macrophage-derived exosomes with innate inflammatory tropism using membrane fusion technology. The resulting hybrid exosomes were surface-modified with Aβ40-targeting aptamers (chol-Apt40) and loaded with PDA and Res to generate the engineered exosome RPDA@Rb-A.

RPDA@Rb-A leverages the distinct targeting capabilities of different exosomes to simultaneously target the BBB, inflammatory microglia, and Aβ aggregates. This approach avoids density and steric hindrance issues associated with modifying exosomes with two or more ligands, while enabling multi-pathway intervention in AD.Leveraging the natural homing of exosomes derived from brain microvascular endothelial cells, RPDA@Rb-A can easily cross the BBB and effectively intervene in AD through multiple pathways:

(1) PDA endows RPDA@Rb-A with excellent photothermal properties, enabling drug release under near-infrared laser irradiation and photothermal depolymerization of Aβ aggregates to alleviate the metabolic burden on microglia.

(2) The binding of Apt40 to Aβ enables the targeted, continuous accumulation of RPDA@Rb-A at Aβ plaques. Leveraging the inflammatory tropism of macrophage-derived exosomes, RPDA@Rb-A delivers Aβ into activated microglia, enhancing their phagocytic uptake and degradation of Aβ.

(3) Resveratrol (Res) is a natural polyphenol that downregulates the expression of inflammation-related factors and normalizes microglial function, thereby enhancing microglia-mediated Aβ clearance.

Overall, RPDA@Rb-A exhibits strong BBB permeability, lesion-targeting capability, and the ability to intervene in AD through multiple pathways, providing a reference for developing new drugs to treat AD and other neurodegenerative diseases.