Hierarchical melanin-like nanoparticles as bioinspired multimodal theragnostic agents

In this study, hierarchical melanin-like nanoparticles with mimosa-like shape (HMNs) are produced by initiating dopamine polymerization on the surface of wrinkled silica nanoparticles (WSNs), followed by the removal of the ceramic template in acidic environment. The nanostructures are further functionalized with (poly)ethylene glycol (PEG) and decorated with either Fe(III) or Ag(I) cations. The engineered nanoparticles exhibit significant nanozyme activities, mimicking the catalytic functions of catalase (CAT), superoxide dismutase (SOD) and peroxidase endogenous enzymes. The Fe(III)-loaded nanoparticles demonstrate notable photothermal performance, achieving an increase of 20 °C upon continuous near infrared (NIR) laser irradiation. Furthermore, Fe(III) chelation results in a transverse relaxation effect (R2 = 10.6 s−1mM−1) making them effective T2-weighted magnetic resonance imaging (MRI) contrast agents. The incorporation of Ag(I) cations leads to the formation of nanometric silver clusters at the nanoparticle surface, enhancing the photoacoustic signal through the localized surface plasmon resonance (SPR) effect under pulsed near NIR laser excitation. They result biocompatible in Human Umbilical Vein Endothelial Cells (HUVEC) cells and able to load with good efficiency a peptidomimetic of suppressor of cytokine signaling (SOCS1) endowed with anti-inflammatory effects. These engineered nanostructures candidate to be safe and versatile theragnostic platforms for drug delivery, photoacoustic imaging, photothermal therapy and MRI.