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Objective: The aim of this work was to investigate the effect of iRGDpeptide on labeling pancreatic carcinoma cell with Superparamagnetic IronOxide（SPIO）and approach the best concentration match and suitableconcentration range of SPIO and iRGD peptide by using MR imaging.Material and Method: (1) The experiment object of this study wasHuman pancreatic carcinoma cells strain (PANC-1), and its’characteristic waspoor differentiation and good cell initiative. (2) Different concentration seriesof SPIO (8.4μg/ml, 12.6μg/ml, 14.7μg/ml, 16.8μg/ml, 21μg/ml) was used tolabel human pancreatic carcinoma cell. Within each series, SPIO-PLL andSPIO group as control, and the other five groups was caregorized by differentconcentration of iRGD peptide (0.25μg/ml, 0.5μg/ml, 0.75μg/ml, 1μg/ml,1.25μg/ml). Different concentration of SPIO was used to label pancreaticcarcinoma cell until cells reached logarithmic phase, combined with differentconcentration of iRGD peptide. All the aboved mentioned series wererepeated 3 times. Three holes were set aside with the same cell quantities asblank group, but no SPIO and iRGD peptide. Then the labled cells were madeinto samples performing MR (3.0T) scan, the scanning sequence includeT2WI-FRFSE, T2-WPROPELLER and T2*MAPPING. The signalattenuation values (△S) of each sample of different concentration of iRGDpeptide compared to SPIO control group within same SPIO series on differentsequences were analyzed and found out the best concentration match of SPIOand iRGD peptide. T2* and△T2* values were measured and analyzed on T2* MAPPING sequence. (3) The signal attenuation values (△S′) of eachsample of different concentration of iRGD peptide compared to PBS liquidcontrol group within same SPIO series on different sequences were analyzedand found out the appropriate concentration range of iRGD peptide withindifferent SPIO series. (4) Using the best concentration match labeledpancreatic carcinoma cell, and deal with as follows: 1, Prussian blue stainingobserved the iron and took photos, calculated the masccline rate of labeledcells; 2, the iron quantitation test with atomic absorption spectrum, and thencompared with SPIO control group. (5) The average signal changes onT2WI-FRFSE and T2-W PROPELLER sequence with appropriateconcentration range of SPIO and iRGD peptide were measured and analyzed.(6)△S were analyzed between each sample of different iRGD peptideconcentration and SPIO-PLL control group within the same SPIO series. (7)When the concentration of SPIO was 21μg/ml, the cells were incubatedaccording to different concentration of iRGD peptide, and then Trypan Bluewas tested to analized cell viability .Result: (1) Different concentration series of SPIO (8.4μg/ml, 12.6μg/ml,14.7μg/ml, 16.8μg/ml, 21μg/ml) labeled human pancreatic carcinoma cell. OnT2WI-FRFSE MR imaging, when the concentration of SPIO was 8.4μg/ml,with the increase of iRGD peptide concentration, the signal intensity ofsamples tended to decline, and△S changes of different concentration iRGDpeptide sample showed increase tendency; when the concentration of SPIOwas 12.6μg/ml, with the increase of iRGD peptide concentration, the signalintensity of samples tended to increase after an initial decline, and△Schanges of different concentration iRGD peptide sample showed decline afteran initial increase tendency; when the concentration of SPIO were 14.7μg/ml and 16.8μg/ml, with the increase of iRGD peptide concentration, the signalintensity of samples tended to increase, and△S changes of differentconcentration iRGD peptide sample showed decline tendency; when theconcentration of SPIO was 21μg/ml, with the increase of iRGD peptideconcentration, the signal intensity of samples had no regularity, and△Schanges of different concentration iRGD peptide sample showed wavilness(down-up-down)，all the△S were negative. When the SPIO and iRGDpeptide concentration were 12.6μg/ml and 1μg/ml respectively, the signalintensity was the lowest, and the△S is biggest(243.89±89.1). OnPROPELLER sequence, all the△S had no regularity with different iRGDpeptide on different SPIO series, while when the SPIO and iRGD peptideconcentration were 14.7μg/ml and 0.5μg/ml respectively, the signal intensitywas the lowest, and the△S is biggest (393.88±86.19). On T2* MAPPINGsequence, the change tendency of△T2* is consistent with△S change onT2WI-FRFSE sequence. When the SPIO and iRGD peptide concentrationwere 12.6μg/ml and 1μg/ml respectively, the△T2* value was 9.43±7.13, andat top of the curve. (2) When the concentration of SPIO was 8.4μg/ml,△S′ofall different concentration of iRGD peptide samples with comparison to SPIOcontrol group (604.79±58.64) had no statistical significance (P＞0.05); whenthe concentration of SPIO was 12.6μg/ml,△S′of all different concentrationof iRGD peptide samples were bigger than SPIO control group (313.03±56.9),it had statistical significance (P＜0.05); when the concentration of SPIO was14.7μg/ml, only 0.25μg/ml concentration of iRGD peptide△S′sample wasbigger than SPIO control group (510.5±73.47), it had statistical significance(P＜0.05); when the concentration of SPIO were 16.8μg/ml and 21μg/ml respectively,△S′of all different concentration of iRGD peptide samples weresmaller than SPIO control group on the same SPIO series, the former had nostatistical significance (P＞0.05), while the latter han statistical significance(P＜0.05). (3) Cells labeled with 12.6μg/ml concentration of SPIO combinedwith 1μg/ml concentration of iRGD peptide showed rhombus and oval-shapelike, majority of blue-stain particles was in cytoplasm，minority was innucleus, and The masccline rate of labeled cells was 82.9%; the iron quantitywas about 13.2pg per cell. While the control group rate of labeled cells was59.9%, and the iron quantity was about 9.4pg per cell. (4) The average signalchange percentage of suitable SPIO and iRGD peptide concentration rangegroup were 21.07%, 22.81%, 23.09%, 24.66%, 24.2% on T2WI-FRFSE and20.91%, 20.8%, 22.79%, 21.93%, 21.26% on T2-W PROPELLER, the datasuggested the former was better than the latter. (5) When the concentration ofSPIO were 8.4μg/ml, 12.6μg/ml, 14.7μg/ml, 16.8μg/ml respectively,comparison△S of each different concentration iRGD peptide samples withSPIO-PLL control group on the same SPIO series had no statisticalsignificance (P＞0.05). (6) The cell viability of 5 groups were 97.2%, 96.9%,96.3%, 96.5% and 95.8% respectively by Trypan Blue, and there were nosignificant changes between different groups.Conclusion: (1) iRGD peptide can enhance the pancreatic carcinomacell lable efficiency with SPIO; T2WI-FEFSE sequence is better for imaging;the best concentration match of SPIO and iRGD peptide was 12.6μg/ml and1μg/ml respectively. (2) The suitable concentration range of iRGD peptide onthe same concentration of SPIO: 12.6μg/ml concentration of SPIO, thesuitable concentration range of iRGD peptide was 0.25μg/ml-1.25μg/ml;14.7μg/ml concentration of SPIO, the suitable concentration of iRGD peptide was 0.25μg/ml.
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