13 research outputs found
Carbonated Nano Hydroxyapatite Crystal Growth Modulated by Poly(ethylene glycol) with Different Molecular Weights
The effects of polyÂ(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
Surface Structure of Hydroxyapatite from Simulated Annealing Molecular Dynamics Simulations
The surface structure
of hydroxyapatite (HAP) is crucial for its
bioactivity. Using a molecular dynamics simulated annealing method,
we studied the structure and its variation with annealing temperature
of the HAP (100) surface. In contrast to the commonly used HAP surface
model, which is sliced from HAP crystal and then relaxed at 0 K with
first-principles or force-field calculations, a new surface structure
with gradual changes from ordered inside to disordered on the surface
was revealed. The disordering is dependent on the annealing temperature, <i>T</i><sub>max</sub>. When <i>T</i><sub>max</sub> increases
up to the melting point, which was usually adopted in experiments,
the disordering increases, as reflected by its radial distribution
functions, structural factors, and atomic coordination numbers. The
disordering of annealed structures does not show significant changes
when <i>T</i><sub>max</sub> is above the melting point.
The thickness of disordered layers is about 10 Ă…. The surface
energy of the annealed structures at high temperature is significantly
less than that of the crystal structure relaxed at room temperature.
A three-layer model of interior, middle, and surface was then proposed
to describe the surface structure of HAP. The interior layer retains
the atomic configurations in crystal. The middle layer has its atoms
moved and its groups rotated about their original locations. In the
surface layer, the atomic arrangements are totally different from
those in crystal. In particular for the hydroxyl groups, they move
outward and cover the Ca<sup>2+</sup> ions, leaving holes occupied
by the phosphate groups. Our study suggested a new model with disordered
surface structures for studying the interaction of HAP-based biomaterials
with other molecules
A summary of tissue response to the three types of ceramics in different animals.
<p>A summary of tissue response to the three types of ceramics in different animals.</p
SEM micrographs showing macrostructure (A–C) and surface microstructure (D–F) of BCP1100 (A,D), BCP1200 (B,E) and HA1200 (C,F).
<p>All ceramics were porous with similar macroporous structure (A–C). The surface of the BCP1100 (D) ceramic exhibited smaller grains and a larger number of micropores than the chemically identical BCP1200, that was sintered at 1200°C (E). Grain size and number of micropores in HA1200 were between those of BCP110 and BCP1200 (F), which is in accordance with specific weight measurements in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107044#pone-0107044-t001" target="_blank">Table 1</a>. Scale bar = 1 mm for A–C and 10 µm for D–F.</p
Histological evaluation of bone formation upon implantation of the three ceramics in dorsal muscles of dogs for 12 weeks.
<p>The highest amount of osteoid and ectopic bone were observed in BCP1100 (A), followed by BCP1200 (B) an HA1200 (C). In all cases, bone was trabecular in appearance, with laminar bone and osteocytes contained in the lacunae, and infiltrated by blood vessels. Decalcified sections, Masson’s trichrome staining, magnification = ×100, scale bar = 200 µm; V→Blood vessel, CT→Connective tissue, M→Material, O→Osteoid tissue, B→Bone.</p
XRD patterns of the three ceramics.
<p>The patterns of BCP1100 and BCP1200 demonstrated biphasic nature of the ceramics consisting of HA and β-TCP. No apparent differences were found as a result of difference in sintering temperature. The pattern of HA1200 was typical of phase-pure hydroxyapatite.</p
Histological evaluation of tissue formation in the three ceramics upon intramuscular implantation in rats, rabbits and dogs.
<p>Representative images showing tissue response to BCP1100 (A, D, G), BCP1200 (B, E, H) and HA1200 (C, F, I) upon implantation in the femoral muscle of rat, dorsal muscle of rabbit and dog for 6 weeks. Decalcified sections, HE Staining, magnification = ×100, scale bar = 200 µm; V→ Blood vessel, CT→Connective tissue, M→Material, O→Osteoid tissue, B→Bone.</p
Physico-chemical characterization of biphasic calcium phosphate sintered at 1100°C (BCP1100), of biphasic calcium phosphate sintered at 1200°C (BCP1200) and of phase-pure hydroxyapatite sintered at 1200°C (HA1200).
<p>Physico-chemical characterization of biphasic calcium phosphate sintered at 1100°C (BCP1100), of biphasic calcium phosphate sintered at 1200°C (BCP1200) and of phase-pure hydroxyapatite sintered at 1200°C (HA1200).</p
Reduction-Degradable Polymeric Micelles Decorated with PArg for Improving Anticancer Drug Delivery Efficacy
In this study, five kinds of reduction-degradable
polyamide amine-<i>g</i>-polyethylene glycol/polyarginine
(PAA-<i>g</i>-PEG/PArg) micelles with different proportions
of hydrophilic and
hydrophobic segments were synthesized as novel drug delivery vehicles.
Polyarginine not only acted as a hydrophilic segment but also possessed
a cell-penetrating function to carry out a rapid transduction into
target cells. Polyamide amine-<i>g</i>-polyethylene glycol
(PAA-<i>g</i>-PEG) was prepared for comparison. The characterization
and antitumor effect of the DOX-incorporated PAA-<i>g</i>-PEG/PArg cationic polymeric micelles were investigated <i>in
vitro</i> and <i>in vivo</i>. The cytotoxicity experiments
demonstrated that the PAA-<i>g</i>-PEG/PArg micelles have
good biocompatibility. Compared with DOX-incorporated PAA-<i>g</i>-PEG micelles, the DOX-incorporated PAA-<i>g</i>-PEG/PArg micelles were more efficiently internalized into human
hepatocellular carcinoma (HepG2) cells and more rapidly released DOX
into the cytoplasm to inhibit cell proliferation. In the 4T1-bearing
nude mouse tumor models, the DOX-incorporated PAA-<i>g</i>-PEG/PArg micelles could efficiently accumulate in the tumor site
and had a longer accumulation time and more significant aggregation
concentration than those of PAA-<i>g</i>-PEG micelles. Meanwhile,
it excellently inhibited the solid tumor growth and extended the survival
period of the tumor-bearing Balb/c mice. These results could be attributed
to their appropriate nanosize and the cell-penetrating peculiarity
of polyarginine as a surface layer. The PAA-<i>g</i>-PEG/PArg
polymeric micelles as a safe and high efficiency drug delivery system
were expected to be a promising delivery carrier that targeted hydrophobic
chemotherapy drugs to tumors and significantly enhanced antitumor
effects
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 NaYÂ(Mn)ÂF<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