Nanotexaphyrin: One-pot synthesis of a manganese texaphyrin-phospholipid nanoparticle for magnetic resonance imaging

The discovery and synthesis of novel multifunctional organic building blocks for nanoparticles is challenging. Texaphyrin macrocycles are capable and multifunctional chelators. However, they remain elusive as building blocks for nanoparticles because of the difficulty associated with synthesis of texaphyrin constructs capable of self-assembly. A novel manganese (Mn)-texaphyrin-phospholipid building block is described, along with its one-pot synthesis and self-assembly into a Mn-nanotexaphyrin. This nanoparticle possesses strong resilience to manganese dissociation, structural stability, in vivo bio-safety, and structure-dependent T₁ and T₂ relaxivities. Magnetic resonance imaging (MRI) contrast enhanced visualization of lymphatic drainage is demonstrated with respect to proximal lymph nodes on the head and neck VX-2 tumors of a rabbit. Synthesis of 17 additional metallo-texaphyrin building blocks suggests that this novel one-pot synthetic procedure for nanotexaphyrins may lead to a wide range of applications in the field of nanomedicines. Contrast and compare: A one-pot synthesis and self-assembly method is described for preparation of Mn-texaphyrin-phospholipids, allowing facile self-assembly of Mn-nanotexaphyrins. Each Mn-nanotexaphyrin constitutes a stable 1:1 porphyrin:metal chelation, equating to 8×10⁴ Mn^II ions. The newly prepared contrast agent was applied to magnetic resonance imaging (MRI) of lymphatic metastasis drainage, revealing drainage from the tumor site to the adjacent metastatic lymph node.