Objective       To investigate the effect of superparamagnetic iron oxid (SPIO) coated with amphiphilic polyethylenimine (PEI) on the proliferation and type Ⅱ collagen secretion of labeled articular chondrocytes

and to determine the optimal labeling concentration and incubation time of PEI-SPIO.       Methods       Chondrocytes from knee joints of Bama mini-pigs (1-3 months old) were harvested and cultured. Cells in passage two that were labeled with PEI-SPIO at the concentrations of 2

4

6

8

10

12 and 14 μg/mL were enrolled as experiment groups

and the unlabeled cells served as control. All the cells were incubated in 37 ℃ for 6

12

18

24 and 30 h

respectively. Prussian blue staining

transmission electron microscopy

intracellular iron content test

WST-1 test and semi-quantitative RT-PCR were applied to evaluate the effect of PEI-SPIO on articular chondrocytes for screening the optimal labeling concentration and incubation time.       Results       Prussian blue staining showed that more than 90% of chondrocytes were labeled in 6

8

10

12 and 14 μg/mL of PEI-SPIO. Intracellular iron content increased slowly and became steady after 24 h. There was no statistically significant difference in cell viability and proliferation between the labeled and unlabeled cells (P0.05). Type Ⅱ collagen expression in the 8 μg/mL group was significantly lower than that in the control group [(13.04±0.60)% vs (18.89±1.26)%

P0.05]

while the difference of type Ⅱ collagen expression was not significant between the 6 μg/mL group and the group [(27.32±1.02)% vs (28.56±1.15)%

P0.05].       Conclusion        PEI-SPIO can effectively and safely label articular chondrocytes. In this study

the optimal labeling concentration and incubation time of PEI-SPIO are determined as 6 μg/mL and 24 h

which do not affect the viability

proliferation and type Ⅱ collagen secretion of articular chondrocytes.