Anisotropic Synthetic Allomelanin Materials via Solid‐State Polymerization of Self‐Assembled 1,8‐Dihydroxynaphthalene Dimers

Abstract

Melanosomes in nature have diverse morphologies, including spheres,r ods,a nd platelets.B yc ontrast, shapes of synthetic melanins have been almost entirely limited to spherical nanoparticles with few exceptions produced by complex templated synthetic methods.H ere,w er eport an ontemplated method to access synthetic melanins with avariety of architectures including spheres,sheets,and platelets.Three 1,8dihydroxynaphthalene dimers (4-4',2-4' and 2-2')were used as self-assembling synthons.T hese dimers packt of orm welldefined structures of varying morphologies depending on the isomer.S pecifically,d istinctive ellipsoidal platelets can be obtained using 4-4' dimers.S olid-state polymerization of the preorganized dimers generates polymeric synthetic melanins while maintaining the initial particle morphologies.This work provides an ew route to anisotropic synthetic melanins,w here the building blocks are preorganized into specific shapes, followed by solid-state polymerization.

Nanomodulators Capable of Timely Scavenging ROS for Inflammation and Prognosis Control Following Photothermal Tumor Therapy

“…Notably, the 1H NMR spectrum of DNA‐pDHN displayed a characteristic peak at δ = 11.7 ppm (Figure 1g), which should be assigned to self‐assembled material of 4‐4′ DHN dimers. [ 14 ] The preferential generation of 4‐4′ DHN dimers instead of 2–4′ DHN dimers and 2‐2′ DHN dimers may stem from the lower flexibility of the aromatic rings, [ 20 ] which makes it easier to accommodate between the DNA base planes. The red shift of two characteristic peaks (stretching and deformation of aromatic rings) in the Raman spectra (Figure S3, Supporting Information) revealed altered π–π stacking interactions inside the materials.…”

“…[ 12 ] In recent years, allomelanin generated by oxidative polymerization of 1,8‐dihydroxynaphthalene (1,8‐DHN) has received tremendous attention due to its superior antioxidant activity, which has even been used for radiation protection. [ 13 ] Compared with other synthetic melanin, the self‐assembly process of structural units (dimers/oligomers) of allomelanin is driven by aromatic stacking of the naphthalene rings and hydrogen bonding between the hydroxyl groups and co‐crystallized water molecules, [ 14 ] which may be more easily regulated to form a relatively ordered arrangement conducive to the proximity and reaction of external substances. However, previously developed nanostructures are mainly spherical, and a large number of phenolic groups inside are still inaccessible.…”