Advancements in the fabrication of upconversion nanoparticles (UCNPs) for synthetic control can enable a broad range of applications in biomedical systems. Herein, we experimentally verified the role of the hydrothermal reaction (HR) time in the synthesis of NaYF4:20%Yb3+/3%Er3+ UCNPs on their morphological evolution and phase transformation at different temperatures. Characterizations of the as-prepared UCNPs were conducted using X-ray diffraction (XRD), electron microscopy and spectroscopy, and thermogravimetric and upconversion (UC) luminescence analysis. We demonstrated that determining the optimal HR time, also referred to here as the threshold time, can produce particles with good homogeneity, hexagonal phase, and UC luminescence efficiency. Subsequently, the polymer coated UCNPs maintained their original particle size distribution and luminescence properties, and showed improved dispersibility in a variety of solvents, cellular nontoxicity, in vitro bioimaging, and biocompatibility as compared to the bare UCNP. Besides this, polyacrylic acid conjugated UCNPs (UCNP@PAA) also revealed the strong anticancer effect by conjugating with doxorubicin (DOX) as compared to the free DOX. Based on these findings, we suggest that these particles will be useful in drug-delivery systems and as in vivo bioimaging agents synchronously.
A library of peptoid-based antimicrobial photodynamic therapy (aPDT) agents was prepared, and the structural requirement for efficient aPDT was disclosed.
Natural
light-harvesting complexes (LHCs) absorb a broad spectrum
of sunlight using a collection of photosynthetic pigments whose spatial
arrangement is controlled by a protein matrix and exhibit efficient
energy transfer. We constructed a novel light-harvesting protein mimic,
which absorbs light in the UV to visible region (280–700 nm)
by displaying flavone and porphyrin on a peptoid helix. First, an
efficient synthesis of 4′-derivatized 7-methoxyflavone (7-MF, 3 and 4) was developed. The flavone–porphyrin–peptoid
conjugate (FPPC) was then prepared via Miyaura borylation on a resin-bound
peptoid followed by Suzuki coupling between the peptoid and pigment.
Circular dichroism spectroscopy indicated that the FPPC underwent
helix-to-loop conversion of the peptoid scaffold upon changing the
solvent conditions. A distinct intramolecular energy transfer was
observed from 7-MF to porphyrin with greater efficiency in the helix
than that in the loop conformation of the peptoid, whereas no clear
evidence of energy transfer was obtained for unstructured FPPC. We
thus demonstrate the value of the helical peptoid, which provided
a controlled orientation for 7-MF and porphyrin and modulated the
energy transfer efficiency via conformational switching. Our work
provides a way to construct a sophisticated LHC mimic with enhanced
coverage of the solar spectrum and controllable energy transfer efficiency.
Herein, we report
a siloxane-encapsulated upconversion nanoparticle
hybrid composite (SE-UCNP), which exhibits excellent photoluminescence
(PL) stability for over 40 days even at an elevated temperature, in
high humidity, and in harsh chemicals. The SE-UCNP is synthesized
through UV-induced free-radical polymerization of a sol–gel-derived
UCNP-containing oligosiloxane resin (UCNP-oligosiloxane). The siloxane
matrix with a random network structure by Si–O–Si bonds
successfully encapsulates the UCNPs with chemical linkages between
the siloxane matrix and organic ligands on UCNPs. This encapsulation
results in surface passivation retaining the intrinsic fluorescent
properties of UCNPs under severe conditions (e.g., 85 °C/85%
relative humidity) and a wide range of pH (from 1 to 14). As an application
example, we fabricate a two-color binary microbarcode based on SE-UCNP
via a low-cost transfer printing process. Under near-infrared irradiation,
the binary sequences in our barcode are readable enough to identify
objects using a mobile phone camera. The hybridization of UCNPs with
a siloxane matrix provides the capacity for highly stable UCNP-based
applications in real environments.
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