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338 Cell-Penetrating Peptides: Processes and Applications
Counts
0 40 80 120 160 200
10 0
Before labeling After CLIO-tat labeling
40 hrs later
M2
10 1
LX1.002 LX1-CLIO-TAT.003 LX1-CLIO-TAT.003
10 2
FL1-Height
10 3
10 4
Counts
0 40 80 120 160 200
10 0
FIGURE 15.6 CLIO–Tat (containing an FITC label) appears to be distributed in roughly
equal amounts to daughter cells after cell division.
To answer the second question we labeled actively dividing human LX1 tumor
cells (doubling time of 20 h) with CLIO–Tat and performed FACS analysis before
labeling, immediately after labeling, and 40 h (2 division cycles) after labeling
(Figure 15.6). Data from these studies support the hypothesis that CLIO–Tat is
equally distributed to progeny cells, similar to the case for many cellular fluorescent
stains.
15.3.1.3 CLIO–Tat Is not Toxic to Cells at Concentrations Used
for Magnetic Labeling
10 1
In order to determine the dose at which Tat labeled particles become toxic to cells,
a trypan blue exclusion assay was initially performed. For these studies, mouse
lymphocytes were incubated with Tat-labeled particles ranging from 7 to 700 nmol
peptide per 10 6 cells for 3 h followed by trypan blue staining. Tat-labeled particles
were nontoxic to cells at incubation concentrations