The use of bone marrow stromal cells (BMSCs) for bone
defect repair
has shown great promise due to their differentiation potential. However,
isolating the BMSCs from various cell types within the bone marrow
remains challenging. To tackle this issue, we utilized semiconducting
polymer dots (Pdots) as markers to select the BMSCs within a specific
time frame. The therapeutic efficacy of the obtained Pdot-labeled
BMSCs was assessed in a bone defect model. Initially, we evaluated
the binding capacity of the Pdots with four different types of cells
present in the bone marrow including BMSCs, osteoblasts, macrophages,
and vascular endothelial cells, in vitro. Notably, BMSCs showed the
most rapid uptake of the Pdots, being labeled within only one h of
coculture, while other cells took four h to become labeled. Moreover,
by colocalizing the Pdots with Prrx1, Sca-1, OSX, F480, and CD105
in the bone marrow cells of monocortical tibial defect (MTD) mice
in vivo, we determined the proportions of BMSCs, macrophages, and
vascular endothelial cells among all labeled cells from 1 to 8 h after
the Pdots injection. It was found that BMSCs have the highest proportion
(92%) among all labeled cells extracted after 1 h of Pdots injection.
The therapeutic efficacy of the obtained Pdots-labeled BMSCs (1 h)
was assessed in a bone defect model. Results showed that the new bone
accrual was significantly increased in the treatment of Pdots-labeled
BMSCs compared to the bone marrow cell-treated group. Our study revealed
that BMSCs screened by the Pdots could improve bone defect repair,
suggesting a promising application of the Pdots in bone healing.