A natural toolbox for brain delivery: Optimizing magnesium phosphate nanoparticles with "orifice-opening" compounds

The blood-brain barrier (BBB) imposes a severe constraint on the delivery of therapeutic agents for the treatment of brain disorders. In traditional Chinese medicine (TCM), "orifice-opening" compounds, including muscone (Mu), borneol (Bo), α-asarone (αA), and β-asarone (βA), are proposed to enhance the penetration of drugs into the brain. However, a systematic comparison of classic "orifice-opening" TCM agents and their underlying mechanisms remains unexplored. Herein, magnesium phosphate nanoparticles were employed to systematically compare the brain-targeting efficiency of these four "orifice-opening" compounds across both in vitro and in vivo experimental models. Our findings reveal a critical structure-activity dichotomy: free forms of Mu, Bo, and αA significantly enhanced brain targeting at optimal concentrations, primarily by regulating VEGF to disrupt BBB tight junctions. In contrast, βA was effective only when chemically conjugated to the nanoparticles. Mechanistic investigations uncovered that this conjugated βA promotes cellular uptake via multiple endocytic pathways (caveolin- and clathrin-mediated endocytosis, and macropinocytosis). Furthermore, it downregulated tight junction protein genes while upregulated cytoskeleton and endocytosis-related pathways. These results highlight the influence of the application methods of the "orifice-opening" compounds on the brain-targeting effect of the nanoparticles. This strategy bridges ancient pharmacological concepts "orifice-opening" of TCM with modern nanotechnology, offering a promising platform for brain-targeted therapeutics.