Abstract:Commonly known as a skin pigment, melanin has a vital role in UV radiation protection, primarily acting as a radical scavenger. However, a lesser known natural property of melanin, observed in some melanized organisms, is its capacity to adsorb toxins, including metals and organic molecules. Inspired by this, we set out to generate a synthetic porous melanin that would pave the way to enhancing the natural adsorbent properties of melanin and melanin-like materials. Here, we developed a method for the synthesis… Show more
“…This is in agreement with the findings of Rahmani Eliato et al 20 who reported that the size of horsehair melanin pores is in the range of 3–5 nm. Such pore sizes and large specific surface area make date fruit melanin a suitable candidate for various applications such as a natural toxins absorber 21 . Figure 4 Date fruit melanin particle characteristics, ( a ) Scanning electron microscopic (SEM) Images of melanin particles at different magnification, ( b ) Sorption isotherm, ( c ) Relative Barret-Joyner Halender (BJH) pore size calculated from the sorption isotherm, ( d ) X-ray diffraction (XRD) profile showing the amorphous nature of the melanin.…”
Date palm fruits (Phoenix dactylifera L.) were found to contain high levels of allomelanin (1.2–5.1%). The melanin is localized in the tanniferous cells between the inner and outer mesocarp tissues of the fruit. The melanin, extracted with 2 M sodium hydroxide, consisted of amorphous graphene-like granular structures of irregular shape and variable size. The date fruit melanin mainly comprises carbon (64.6%) and oxygen (30.6) but no nitrogen, and was thermally stable. It has radical scavenging (63.6–75.1 IC50, µg/mL), antimicrobial (250–1000 µg/mL), hypoglycemic (51.8–58.2%), and angiotensin-converting-enzyme inhibitory (65.8%) effects. The high level of melanin in date fruits highlights the importance of investigating its dietary intake and its impact on nutrition. This study also suggests that date fruit melanin can be a functional ingredient in foods, food packages, pharmaceuticals, and cosmetics.
“…This is in agreement with the findings of Rahmani Eliato et al 20 who reported that the size of horsehair melanin pores is in the range of 3–5 nm. Such pore sizes and large specific surface area make date fruit melanin a suitable candidate for various applications such as a natural toxins absorber 21 . Figure 4 Date fruit melanin particle characteristics, ( a ) Scanning electron microscopic (SEM) Images of melanin particles at different magnification, ( b ) Sorption isotherm, ( c ) Relative Barret-Joyner Halender (BJH) pore size calculated from the sorption isotherm, ( d ) X-ray diffraction (XRD) profile showing the amorphous nature of the melanin.…”
Date palm fruits (Phoenix dactylifera L.) were found to contain high levels of allomelanin (1.2–5.1%). The melanin is localized in the tanniferous cells between the inner and outer mesocarp tissues of the fruit. The melanin, extracted with 2 M sodium hydroxide, consisted of amorphous graphene-like granular structures of irregular shape and variable size. The date fruit melanin mainly comprises carbon (64.6%) and oxygen (30.6) but no nitrogen, and was thermally stable. It has radical scavenging (63.6–75.1 IC50, µg/mL), antimicrobial (250–1000 µg/mL), hypoglycemic (51.8–58.2%), and angiotensin-converting-enzyme inhibitory (65.8%) effects. The high level of melanin in date fruits highlights the importance of investigating its dietary intake and its impact on nutrition. This study also suggests that date fruit melanin can be a functional ingredient in foods, food packages, pharmaceuticals, and cosmetics.
“…In contrast to these methods, we used polydopamine (PDA) to protect pristine GNR probe from the shape deformation. PDA coatings are robust, biocompatible, and surface functionalization [28,29]. We thus hypothesized that PDA is a pragmatic choice as a GNR shape-preserving coating for theranostic applications.…”
Gold nanorods (GNRs) have attracted great interest for photo-mediated biomedicines due to their tunable and high optical absorption, high photothermal conversion efficiency and facile surface modifiability. GNRs that have efficient absorption in second near-infrared (NIR-II) window hold further promise in bio-applications due to low background signal from tissue and deep tissue penetration. However, bare GNRs readily undergo shape deformation (termed as 'melting effect') during the laser illumination losing their unique localized surface plasmon resonance (LSPR) properties, which subsequently leads to PA signal attenuation and decreased photothermal efficiency. Polydopamine (PDA) is a robust synthetic melanin that has broad absorption and high photothermal conversion. Herein, we coated GNRs with PDA to prepare photothermally robust GNR@PDA hybrids for enhanced photo-mediated theranostic agents. Ultrasmall GNRs (SGNRs) and conventional large GNRs (LGNRs) that possess similar LSPR characteristics as well as GNR@PDA hybrids were compared side-by-side in terms of the size-dependent photoacoustic (PA) imaging, photothermal therapy (PTT), and structural stability. In vitro experiments further demonstrated that SGNR@PDA showed 95% ablation of SKOV3 ovarian cancer cells, which is significantly higher than that of LGNRs (66%) and SGNRs (74%). Collectively, our PDA coating strategy represents a rational design for enhanced PA imaging and efficient PTT via a nanoparticle, i.e., nanotheranostics.
“…While the PBDT nanoparticles are primarily stabilized by p-p interactions, the formation of PDA is dominated by robust covalent interactions. [43,44] Therefore, we hypothesized that the supramolecular PBDT nanoparticles would be removed during the solvent treatment to produce uniform PDA nanocapsules. [45] This is corroborated by incubating the core-shell nanoparticles in dimethyl sulfoxide (DMSO) for 15 min: SEM and atomic force microscopy (AFM) demonstrated the transformation of core-shell nanoparticles into crumpled nanocapsules via DMSO (Figure 3 b-e and S10,11).…”
Polymer nanocapsules have demonstrated significant value in materials science and biomedical technology, but require complicated and time-consuming synthetic steps. We report here the facile synthesis of monodisperse polymer nanocapsules via a redox-mediated kinetic strategy from two simple molecules: dopamine and benzene-1,4-dithiol (BDT). Specifically, BDT forms core templates and modulates the oxidation kinetics of dopamine into polydopamine (PDA) shells. These uniform nanoparticles can be tuned between % 70 and 200 nm because the core diameter directly depends on BDT while the shell thickness depends on dopamine. The supramolecular core can then rapidly disassemble in organic solvents to produce PDA nanocapsules. Such nanocapsules exhibit enhanced physicochemical performance (e.g., loading capacity, photothermal transduction, and anti-oxidation) versus their solid counterparts. Particularly, this method enables a straightforward encapsulation of functional nanoparticles providing opportunities for designing complex nanostructures such as yolk-shell nanoparticles.
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