Allomelanin is a type of nitrogen-free melanin most commonly found in fungi. Its existence enhances resistance of the organisms to environmental damage and helps fungi survive harsh radiation conditions such as those found on spacecraft and inside contaminated nuclear power plants. We report the preparation and characterization of artificial allomelanin nanoparticles (AMNPs) via oxidative oligomerization of 1,8-dihydroxynaphthalene (1,8-DHN). We describe the resulting morphological and size control of AMNPs and demonstrate that they are radical scavengers. Finally, we show that AMNPs are taken up by neonatal human epidermal keratinocytes and packaged into perinuclear caps where they quench reactive oxygen species generated following UV exposure.
Human hair is naturally
colored by melanin pigments, which afford
myriad colors from black, to brown, to red depending on the chemical
structures and specific blends. In recent decades, synthetic efforts
have centered on dopamine oxidation to polydopamine, an effective
eumelanin similar to the one found in humans. To date, only a few
attempts at polydopamine deposition on human hair have been reported,
and their translation to widespread usage and potential commercialization
is still hampered by the harsh conditions employed. We reasoned that
novel, mild, biocompatible approaches could be developed to establish
a metal-free route to tunable, nature-inspired, long-lasting coloration
of human hair. Herein, we describe synthetic and formulation routes
to achieving this goal and show efficacy on a variety of human hair
samples via multiple spectroscopic and imaging techniques. Owing to
the mild and inexpensive conditions employed, this novel approach
has the potential to replace classical harsh hair dyeing conditions
that have raised concerns for several decades due to their potential
toxicity.
Zr6-based
metal–organic frameworks (MOFs) with
tetratopic organic linkers have been extensively investigated owing
to their versatile structural tunability. While diverse topologies
and polymorphism in the resulting MOFs are often encountered with
tetratopic linkers and Zr6 nodes, reports on phase transitions
within these systems are rare. Thus, we have a limited understanding
of polymorph transformations, hindering the rational development of
pure phase materials. In this study, a phase transition from a microporous
MOF, scu-NU-906, to a mesoporous MOF, csq-NU-1008, was discovered
and monitored through in situ variable temperature
liquid-cell transmission electron microscopy (VT-LCTEM), high-resolution
transmission electron microscopy (HRTEM), and in situ variable temperature powder X-ray diffraction (VT-PXRD). It was
found that the microporous- to-mesoporous transformation in the presence
of formic acid occurs via a concomitant dissolution–reprecipitation
process.
Metal–organic
nanotubes (MONTs) are tunable porous 1D materials
that are envisioned to be complementary to carbon nanotubes for anisotropic
applications. To date, characterization of MONTs relies on single
crystal X-ray diffraction (SCXRD) to determine structure and composition.
This requires crystals on the micrometer regime, effectively rendering
bulk 3D materials. By tracking the growth of a MONT as a function
of time with liquid-cell transmission electron microscopy (LCTEM),
TEM, and SCXRD, it was possible to ascertain that the material in
the bulk phase matches the nanomaterial in terms of molecular structure.
This result allowed for the first measurements of finite bundles of
MONTs on the nanometer scale. By employing in situ LCTEM, a time course of the formation of small bundles of MONTs
could be acquired which provided mechanistic information on MONT formation
which is of utility in reaction optimization and applications development.
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