Background: Photodynamic therapy is a safe, noninvasive modality for cancer therapy, in which the photosensitizer (PS) is a crucial component. Hypericin (Hy) is a promising PS; however, its clinical application is significantly limited by its poor hydrophilicity. 
Materials and methods: To overcome the clinical application limitation of Hy, a novel strategy is developed here by entrapping Hy into polydopamine (PDA) film formed on the surface of magnetic iron oxide nanoparticles (MNPs) through the self-polymerization of dopamine under alkaline condition. The amount of Hy in the Hy-entrapped PDA–MNP composite nanoparticles (denoted as PHMs) was measured by spectrophotometry. Furthermore, lactose, as the targeting ligand to asialoglycoprotein receptors, was conjugated to the surface of the PHMs by taking advantage of the spontaneous reaction of PDA with amino groups. 
Results: Spectrophotometry analysis revealed that the amount of Hy in the PHMs was 72 µmol g^-1 PHMs. The fabricated Hy-entrapped glyconanoparticle (Lac-PHM) exhibited excellent water dispersibility, stability, and selectivity for asialoglycoprotein receptors overexpressing HepG2 cells. Atomic absorption spectroscopy analysis showed that the amount of the Lac-PHMs taken in HepG2 cells was 2.1-fold higher than that of the triethylene glycol-modified PHMs. The results of intracellular reactive oxygen species generation detection, cytotoxicity study, and apoptosis detection indicated that the Lac-PHMs had a satisfying photodynamic effect to HepG2 cells.
Conclusion: The strategy developed in this work offers great potential for delivery of a variety of hydrophobic PSs.
Keywords: hypericin, photodynamic therapy, glyconanoparticles, targeted drug delivery