Nitric oxide-enhanced blood–brain barrier penetration and mitochondria-targeted antioxidant carbon dots for Alzheimer's disease

Abstract

Alzheimer's disease (AD) involves a complex pathogenesis in which the β-amyloid (Aβ) cascade and oxidative stress hypotheses interact through mitochondrial dysfunction, forming a vicious cycle that underscores the need for multi-targeted therapeutic strategies. In this study, multifunctional carbon dots (EMA-CDs) were rationally designed and synthesised via a simple one-pot hydrothermal approach to integrate antioxidant activity, nitric oxide (NO) release capability, and mitochondrial targeting. EMA-CDs exhibited potent reactive oxygen species (ROS) scavenging abilities, efficiently eliminating hydroxyl radicals, superoxide anions, and DPPH radicals with rates exceeding 80%. Their mitochondrial specificity further alleviated intracellular oxidative stress and neuroinflammation. Notably, EMA-CDs at low concentrations (80 µg mL⁻¹) markedly inhibited Aβ₄₂ aggregation and promoted fibril disassembly, achieving inhibition and depolymerisation efficiencies of approximately 97.1% and 99.4%, respectively. In addition, EMA-CDs promoted NO production, which in turn modulated the expression of MMP-9 and ZO-1 proteins. This led to a reversible and transient opening of the blood–brain barrier (BBB), resulting in an enhanced penetration efficiency with a cumulative rate of 65.4% over 12 h. Furthermore, in the C. elegans CL2006 model, EMA-CDs significantly alleviated Aβ₄₂ plaque deposition and reduced intracellular ROS levels by approximately 55%. Moreover, EMA-CDs extended the mean lifespan of the worms by about 6 days and enhanced reproductive capacity to 1.25-fold of the control, demonstrating potent in vivo neuroprotective and antioxidative stress effects. Collectively, this study demonstrates that EMA-CDs function as a versatile therapeutic platform for AD treatment and provide a promising avenue for the development of multi-target nanotherapeutics and novel AD intervention strategies.