7 research outputs found
Carbonated Nano Hydroxyapatite Crystal Growth Modulated by Poly(ethylene glycol) with Different Molecular Weights
The effects of poly(ethylene glycol) (PEG) molecular
weights on nano hydroxyapatite (n-HA) crystal growth were studied,
and a possible mechanism was proposed. n-HA crystals were synthesized
in the presence of PEG with different molecular weights via hydrothermal
method. Transmission electron microscopy (TEM) analysis showed that
the presence of PEG increased the size of n-HA crystals; PEG with
larger molecular weights produced larger n-HA crystals. High-resolution
TEM observation indicated that all of the n-HA crystals tended to
grow along the ⟨002⟩ axis. X-ray diffraction patterns
showed that all of the samples consisted of only the HA phase. Besides,
PEG increased the crystallinity of n-HA crystals, and this effect
was more significant for PEGs with larger molecular weights. Fourier
transform infrared results further revealed that all of the crystals
were carbonated HA. Thermogravimetry/differential scanning calorimetry
analysis detected PEG residues on n-HA particles. To thoroughly study
the modulating mechanism of PEGs on n-HA crystal growth, n-HA samples
heat-treated for various times were prepared in the presence of PEG20000,
and a possible mechanism in which PEG modulated the growth of n-HA
crystals was discussed
NIR-to-Red Upconversion Nanoparticles with Minimized Heating Effect for Synchronous Multidrug Resistance Tumor Imaging and Therapy
Lanthanide-doped
upconversion nanoparticles (UCNPs), especially the 808 nm activated
UCNPs, are promising imaging agents for biological applications because
of their minimal tissue overheating effects and low autofluorescence
background. Optimizing the emission peaks located in the “biological
window (600–1100 nm)” is of vital importance to obtain
the maximum penetration depth and intense deep tissue imaging. On
the other hand, because of the widely existing multidrug resistance
(MDR) of tumor cells, traditional tumor chemotherapy often fails to
achieve the desired effect. Herein, a new type of 808 nm excited pure
red luminescence core–shell Nd<sup>3+</sup>-sensitized NaY(Mn)F<sub>4</sub>:Yb/Er@NaYbF<sub>4</sub>:Nd UCNPs (CSUCNPs) was designed and
synthesized for deep tissue imaging and MDR tumor diagnosis with a
minimized heating effect. In the meanwhile, d-α-tocopherol
polyethylene glycol 1000 succinate (TPGS) coating was introduced to
endow CSUCNPs with capabilities of drug loading and overcoming MDR.
The in vitro cytotoxicity test revealed that CSUCNPs-TPGS-doxorubicin
(D-CSUCT) had excellent MDR cancer cell killing efficacy. The in vivo
test showed that D-CSUCT can target the tumor site by enhanced retention
effect, and the intense luminescent signals from the tumor site in
the deep tissue were detected. Generally, this work shows D-CSUCT
can overcome the MDR effect, diagnose the tumor, inhibit tumor growth,
and induce tumor cells necrosis and apoptosis, without causing damage
to major organs and other side effects. Overall, the study demonstrates
the conjugation of red-emitted UCNPs with a minimized heating effect
and that the anti-MDR carrier is highly promising for developing multifunctional
theranostic system with effective simultaneous diagnosis and for multidrug-resistant
tumor treatment
Two-Step Nucleation of CdS Magic-Size Nanocluster MSC–311
Nucleation has been generally acknowledged
as a rapid but uncontrollable
process that is difficult to decouple from the subsequent growth phase.
Here, we report our finding that nucleation of semiconductor magic-size
clusters (MSCs) can be well-regulated, without a subsequent evolution
in size. Colloidal semiconductor CdS MSCs were synthesized by a two-step
approach intentionally designed, without the simultaneous formation
of nanocrystals of other sizes. The nuclei MSCs exhibit a sharp optical
absorption peaking at 311 nm and are thus denoted by MSC–311.
We prepared the immediate precursor for MSC–311 denoted by
IP311 which is liquid-like, through a reaction which was normally
performed to grow CdS conventional quantum dots (QDs), but at a different
temperature (180 °C) prior to the nucleation and growth of CdS
QDs. We demonstrate that the nucleation of MSC–311 from IP311
followed first order kinetics remarkably well, and the presence of
a small amount of methanol accelerated this process effectively. Moreover,
the liquid-like prenucleation cluster IP311 and the nuclei MSC–311
have similar masses. Accordingly, we propose that the intramolecular
reorganization of IP311 results in the nuclei MSC–311, the
formation of which features a two-step nucleation pathway. The present
study introduces methodology via absorption spectroscopy to monitor
the nucleation kinetics of semiconductor MSCs from their immediate
precursors. The repeatable, predictable, and controllable nucleation
process investigated here brings a deeper insight into nucleation
of other semiconductor nanocrystals and contributes to the foundation
for the future development of advanced theoretical models for crystal
nucleation
Colloidal CdSe 0‑Dimension Nanocrystals and Their Self-Assembled 2‑Dimension Structures
We
report on a particular type of CdSe nanocrystals (NCs) that
exhibit a single optical absorption doublet. The two peaks in the
doublet are relatively sharp with a full width half-maximum as narrow
as 10 nm. The peak positions vary with passivation ligands (at ∼426
and ∼453 nm for amine ligand passivation and at ∼432
and ∼460 nm for carboxylate ligand passivation). To date, it
has been generally concluded that these NCs have a two-dimension (2D)
morphology with 1D quantum confinement. Here, we report that zero-dimension
(0D) NCs with 3D quantum confinement can exhibit a very similar static
optical feature consisting of a sharp absorption doublet. We show
that our as-prepared CdSe NCs (without further purification) were
mainly 0D NCs, as observed when they were deposited on transmission
electron microscopy (TEM) grids directly from toluene or hexane dispersions.
We further demonstrate that it was possible to alter this 0D morphology
by using dispersion additives and/or purification solvents to result
in the appearance of 2D NCs under TEM. Although the 0D and self-assembled
2D NCs displayed similar static optical features, the two morphologies
behaved quite differently in polarized emission. The 2D NCs exhibited
detection angle dependent polarized emission, whereas the 0D NCs do
not. Our findings indicate that a well-like morphology can be induced
by the presence of hexadecylamine (HDA) in the dispersion with sonication
for amine-passivated 0D NCs or by the use of ethanol during purification
with dispersion storage for carboxylate-passivated 0D NCs. In this
way, it is possible to manipulate the NC morphology for a targeted
application through the appropriate post-treatment. This study highlights
that more sophisticated theoretical studies are required to account
for the experimental observations in which both 0D NCs and their self-assembled
2D NC products display similar static optical features
Antitumor Effect by Hydroxyapatite Nanospheres: Activation of Mitochondria-Dependent Apoptosis and Negative Regulation of Phosphatidylinositol-3-Kinase/Protein Kinase B Pathway
Hydroxyapatite nanoparticles
(HA NPs) have been acknowledged for
their benign biocompatibility and proliferation inhibition effect
on tumor cells, attracting considerable attention for tumor therapeutics
without late effects. However, unnoticeable tumor cytotoxicity of
HA NPs limited the final clinical therapeutic efficacy. Herein, a
two-phase synthetic approach was developed to synthesize sphere-like
HA NPs by varying the conventional growth habit of HA precipitate.
We present our <i>in vitro</i> and <i>in vivo</i> experimental evidence that spherical HA NPs have surprisingly high
inhibitory activities against tumor cells. We demonstrate further,
based on our experimental data, that the underlying cause for the
death of the tumor cells is related to two concurrent pathways, the
mitochondria-dependent apoptosis pathway and negative regulation of
the phosphatidylinositol-3-kinase/protein kinase B (PIK3/AKT) pathway.
The present study indicated that HA nanospheres can be engineered
as nontoxic specific inhibitors for efficient tumor therapeutics with
nanobiomaterials
Vascularization in Engineered Tissue Construct by Assembly of Cellular Patterned Micromodules and Degradable Microspheres
Tissue engineering aims to generate
functional tissue constructs in which proper extracellular matrix
(ECM) for cell survival and establishment of a vascular network are
necessary. A modular approach via the assembly of modules mimicking
the complex tissues’ microarchitectural features and establishing
a vascular network represents a promising strategy for fabricating
larger and more complex tissue constructs. Herein, as a model for
this modular tissue engineering, engineered bone-like constructs were
developed by self-assembly of osteon-like modules and fast degradable
gelatin microspheres. The collagen microspheres acting as osteon-like
modules were developed by seeding human umbilical vein endothelial
cells (HUVECs) onto collagen microspheres laden with human osteoblast-like
cells (MG63) and collagenase. Both HUVECs and MG63 cells were well
spatially patterned in the modules, and collagen as ECM well supported
cell adhesion, spreading, and functional expression due to its native
RGD domains and enzymatic degradation activity. The patterned modules
facilitated both the cellular function expression of osteogenic MG63
cells and vasculogenic HUVECs; that is, the osteon-like units were
successfully achieved. The assembly of the osteon-like modules and
fast degradable gelatin microspheres promoted the vascularization,
thus facilitating the osteogenic function expression. The study provides
a highly efficient approach to engineering complex 3D tissues with
micropatterned cell types and interconnected channels
Photo-Cross-Linkable Methacrylated Gelatin and Hydroxyapatite Hybrid Hydrogel for Modularly Engineering Biomimetic Osteon
Modular tissue engineering holds
great potential in regenerating natural complex tissues by engineering
three-dimensional modular scaffolds with predefined geometry and biological
characters. In modular tissue-like construction, a scaffold with an
appropriate mechanical rigidity for assembling fabrication and high
biocompatibility for cell survival is the key to the successful bioconstruction.
In this work, a series of composite hydrogels (GH0, GH1, GH2, and
GH3) based on a combination of methacrylated gelatin (GelMA) and hydroxyapatite
(HA) was exploited to enhance hydrogel mechanical rigidity and promote
cell functional expression for osteon biofabrication. These composite
hydrogels presented a lower swelling ratio, higher mechanical moduli,
and better biocompatibility when compared to the pure GelMA hydrogel.
Furthermore, on the basis of the composite hydrogel and photolithograph
technology, we successfully constructed an osteon-like concentric
double-ring structure in which the inner ring encapsulating human
umbilical vascular endothelial cells (HUVECs) was designed to imitate
blood vessel tubule while the outer ring encapsulating human osteoblast-like
cells (MG63s) acts as part of bone. During the coculture period,
MG63s and HUVECs exhibited not only satisfying growth status but also
the enhanced genic expression of osteogenesis-related and angiogenesis-related
differentiations. These results demonstrate this GelMA–HA composite
hydrogel system is promising for modular tissue engineering