3 research outputs found
Strontium Ion-Functionalized Nano-Hydroxyapatite/Chitosan Composite Microspheres Promote Osteogenesis and Angiogenesis for Bone Regeneration
Critical-size bone defects are an important problem in
clinical practice, which usually occurs in severe trauma, or tumor
resection, and cannot heal completely and autonomously. Implantation
of grafts is often required to promote the regeneration of critical-size
bone defects. Metal ions play an important role in human health, as
they affect the body’s metabolism and the tissue function.
Strontium ions (Sr2+) can promote osteogenesis and angiogenesis.
Herein, we prepared nano-hydroxyapatite (nHA)/chitosan (CS) composite
microspheres with a uniform particle size distribution and an extracellular
matrix-like nanofiber structure using microfluidic technology and
direct alkali-induced gelation. Strontium ions were stably added into
the microspheres by using polydopamine (PDA) to chelate metal ions
forming a bone repair material (nHA/CS@PDA-Sr) with good bioactivity.
The coordination reaction of PDA can effectively control the release
of strontium ions and avoid the negative effects caused by the high
strontium concentration. Our in vitro experiments showed that the
composite microspheres had good biocompatibility and that the PDA
coating promotes cell adhesion. The slow release of strontium ions
can effectively promote mesenchymal stem cells osteogenic differentiation
and the vascularization of endothelial cells. In addition, we injected
composite microspheres into cranial defects of rats to evaluate osseointegration
in vivo. The results showed that nHA/CS@PDA-Sr could effectively promote
bone regeneration in the defect area. This study demonstrates that
composite microspheres stimulate bone repair providing a promising
way for bone-defect regeneration
Polydopamine-Functionalized Strontium Alginate/Hydroxyapatite Composite Microhydrogel Loaded with Vascular Endothelial Growth Factor Promotes Bone Formation and Angiogenesis
Critical-size
bone defects are a common and intractable clinical
problem that typically requires filling in with surgical implants
to facilitate bone regeneration. Considering the limitations of autologous
bone and allogeneic bone in clinical applications, such as secondary
damage or immunogenicity, injectable microhydrogels with osteogenic
and angiogenic effects have received considerable attention. Herein,
polydopamine (PDA)-functionalized strontium alginate/nanohydroxyapatite
(Sr-Alg/nHA) composite microhydrogels loaded with vascular endothelial
growth factor (VEGF) were prepared using microfluidic technology.
This composite microhydrogel released strontium ions stably for at
least 42 days to promote bone formation. The PDA coating can release
VEGF in a controlled manner, effectively promote angiogenesis around
bone defects, and provide nutritional support for new bone formation.
In in vitro experiments, the composite microhydrogels had good biocompatibility.
The PDA coating greatly improves cell adhesion on the composite microhydrogel
and provides good controlled release of VEGF. Therefore, this composite
microhydrogel effectively promotes osteogenic differentiation and
vascularization. In in vivo experiments, composite microhydrogels
were injected into critical-size bone defects in the skull of rats,
and they were shown by microcomputed tomography and tissue sections
to be effective in promoting bone regeneration. These findings demonstrated
that this novel microhydrogel effectively promotes bone formation
and angiogenesis at the site of bone defects
A pH-Responsive Yolk-Like Nanoplatform for Tumor Targeted Dual-Mode Magnetic Resonance Imaging and Chemotherapy
Incorporation
of T<sub>1</sub> and T<sub>2</sub> contrast material
in one nanosystem performing their respective MR contrast role and
simultaneously serving as an efficient drug delivery system (DDS)
has a significant potential application for clinical diagnosis and
chemotherapy of cancer. However, inappropriate incorporation always
encountered many issues, such as low contact area of T<sub>1</sub> contrast material with water-proton, inappropriate distance between
T<sub>2</sub> contrast material and water molecule, and undesirable
disturbance of T<sub>2</sub> contrast material for T<sub>1</sub> imaging.
Those issues seriously limited the T<sub>1</sub> or T<sub>2</sub> contrast
effect. In this work, we developed a yolk-like Fe<sub>3</sub>O<sub>4</sub>@Gd<sub>2</sub>O<sub>3</sub> nanoplatform functionalized by
polyethylene glycol and folic acid (FA), which could efficiently exert
their tumor targeted T<sub>1</sub>–T<sub>2</sub> dual-mode
MR imaging and drug delivery role. First, this nanoplatform possessed
a high longitudinal relaxation rate (<i>r</i><sub>1</sub>) (7.91 mM<sup>–1</sup> s<sup>–1</sup>) and a stronger
transverse relaxation rate (<i>r</i><sub>2</sub>) (386.5
mM<sup>–1</sup> s<sup>–1</sup>) than that of original
Fe<sub>3</sub>O<sub>4</sub> (268.1 mM<sup>–1</sup> s<sup>–1</sup>). Second, cisplatin could be efficiently loaded into this nanoplatform
(112 mg/g) and showed pH-responsive release behavior. Third, this
nanoplatform could be effectively internalized by HeLa cells with
time and dosage dependence. Fourth, the FA receptor-mediated nanoplatform
displayed excellent T<sub>1</sub>–T<sub>2</sub> dual mode MR
contrast enhancement and anticancer activity both <i>in vitro</i> and <i>in vivo</i>. Fifth, no apparent toxicity for vital
organs was observed with systemic delivery of the nanoplatform <i>in vivo</i>. Thus, this nanoplatform could be a potential nanotheranostic
for tumor targeted T<sub>1</sub>–T<sub>2</sub> dual-mode MR
imaging and chemotherapy