Biomedical Engineering Reference
In-Depth Information
Fig. 7
Plasma TACA concentrations in pigs (
n
) (5 per time point) following suprachoroidal deliv-
ery of a 1.5-mg dose of TACA, measured using the ultrasensitive approach developed in this study
(Reproduced with permission from American Chemical Society)
in vitro or preclinical experiments suggest that paclitaxel and other drugs can exert
antivascular or antiangiogenic effects and some of these effects are observed at
ultralow concentrations. In vivo
,
low-dose paclitaxel regimens employing more fre-
quent administration have shown activity in cancer patients without significant side
effects such as myelosuppression or acquired drug resistance. Interestingly, recent
studies have shown that paclitaxel can exert antiangiogenic effects in the range of
0.1-100 pM, which is approximately 5,000-fold lower than concentrations required
for antimitotic effects. In order to study the antiangiogenic mechanisms or pharma-
cokinetics (PK) of low-dose paclitaxel, highly sensitive methods are necessary to
enable quantification of low pg/mL concentrations of drugs in complex biological
matrices. The lower limits of quantification (LOQ) of paclitaxel using HPLC-UV
are reported as 5-20 ng/mL [
10
], and for conventional LC-MS/MS are in the range
of 0.1-0.25 ng/mL biological matrices. Recent preliminary work suggests the feasi-
bility of quantification of paclitaxel in cell lysates at concentrations as low as 20 pg/
mL. However, no published method provides sufficient sensitivity and operational
robustness to quantify paclitaxel routinely in the low pg/mL range.
3.2
Experimental
In this study, A121a human ovarian cancer cells were incubated with low dose
paclitaxel in four levels: 0.2, 0.8, 2, and 5 ng/mL respectively at 37 °C. Cells were
harvested at five time points of 10, 30, 60, 180, and 360 min. The cells were lysated
