2.3. Biological application of TPEARG at the cellular level
Afterward, due to the outstanding detection performances of TPEARG
toward arginase, its biological applications were investigated in living
cells in detail. Research works reported that arginase was high
expressed in the M2 macrophages[6a, 6b]. Thus, the
RAW 264.7 cells were stimulated into M1 or M2 type using IFN-γ/LPS or
IL-4, respectively. The RAW 264.7 cells treated with PBS (pH=7.2) and
BEC (An arginase inhibitor) were set as the control groups. Then, the
cells were incubated with 1 μM TPEARG and imaged under laser scanning
confocal microscope. Compared to the undifferentiated RAW 264.7 and M1
macrophage, the M2 macrophage displayed over 20-fold fluorescence
intensity enhancement (Figure 3A and B). In addition, when the arginase
was inhibited by BEC, the cellular fluorescence intensity decreased
significantly. These results suggest that TPEARG possess splendid
potential in the detection of cellular arginase. To further explore the
dynamic detection capability of TPEARG, we applied the TPEARG in M2
macrophages with sequential levels of arginase. M2 macrophages were
pretreated with BEC for incremental time to obtain reduced expressions
of arginase (Figure S5). Then, the TPEARG was used to observe the
variation of cellular arginase. As displayed in Figure 3C and D, with
the incubation time increased, the cellular fluorescence intensity
decreased gradually. These results confirm that our established imaging
method hold great potential in the dynamic detection of cellular
arginase.