Furthermore, it was also observed that PDC shows time-dependent cytotoxicity against U87MG cells, as at 12 h drug treatment. PDC shows a slightly lower inhibitory effect on cell survival (EC50 = 25.82 ± 0.31 nM) than PTX alone (EC50 = 12.25 ± 0.13 nM), and CPP-SA alone shows higher EC50 = 54.37 ± 0.24 in U87MG cells. Besides this, it was previously observed that CPP-treated healthy VERO cells showed 88.05 ± 0.86% viable cells even using 10 uM concentration, indicating the specificity of CPP for glioblastoma cells. However, at 24 h incubation period, our PDC shows a significantly enhanced cell survival inhibitory effect with EC50 = 8.32 ± 0.09 nM, suggesting the delayed effect of PDC because of the time required for the intracellular pH to cause maximal cleavage of PTX from the PDC. Moreover, it also shows that CPP-SA has a lower cytotoxicity effect on glioblastoma cells compared with PTX alone and PDC, indicating its specificity as a carrier and selectivity for integrin receptors overexpressed on the cell surface. Additionally, we have also studied the potential of our novel-designed PDC to internalize into PTX-resistant glioblastoma (U87MG-PR) cells to show cytotoxic activity upon intracellular cleavage of PTX from CPP. The data presented in Figure 3b reveal approximately 15% viability increases in U87MG-PR cells compared with parent U87MG cells. It can be seen in the inset in Figure 3b that PTX alone (EC50 = 41.3 ± 1.5 nM) showed significantly 2-fold reduced cytotoxic activity in U87MG-PR cells in comparison with our novel-designed PDC having EC50 = 20.55 ± 1.02 nM. It was also observed in Figure 3b that at lower concentrations (0-10 nM) the viable cell count was ˜75%; however, it significantly decreased to ˜20% viability with an increase in concentration (40 nM) of the test samples, highlighting the dose-dependent cytotoxicity behavior of PDC in a 24 h incubation period.

Furthermore, it was also observed that PDC shows time-dependent cytotoxicity against U87MG cells, as at 12 h drug treatment. PDC shows a slightly lower inhibitory effect on cell survival (EC50 = 25.82 ± 0.31 nM) than PTX alone (EC50 = 12.25 ± 0.13 nM), and CPP-SA alone shows higher EC50 = 54.37 ± 0.24 in U87MG cells. Besides this, it was previously observed that CPP-treated healthy VERO cells showed 88.05 ± 0.86% viable cells even using 10 uM concentration, indicating the specificity of CPP for glioblastoma cells. However, at 24 h incubation period, our PDC shows a significantly enhanced cell survival inhibitory effect with EC50 = 8.32 ± 0.09 nM, suggesting the delayed effect of PDC because of the time required for the intracellular pH to cause maximal cleavage of PTX from the PDC. Moreover, it also shows that CPP-SA has a lower cytotoxicity effect on glioblastoma cells compared with PTX alone and PDC, indicating its specificity as a carrier and selectivity for integrin receptors overexpressed on the cell surface. Additionally, we have also studied the potential of our novel-designed PDC to internalize into PTX-resistant glioblastoma (U87MG-PR) cells to show cytotoxic activity upon intracellular cleavage of PTX from CPP. The data presented in Figure 3b reveal approximately 15% viability increases in U87MG-PR cells compared with parent U87MG cells. It can be seen in the inset in Figure 3b that PTX alone (EC50 = 41.3 ± 1.5 nM) showed significantly 2-fold reduced cytotoxic activity in U87MG-PR cells in comparison with our novel-designed PDC having EC50 = 20.55 ± 1.02 nM. It was also observed in Figure 3b that at lower concentrations (0-10 nM) the viable cell count was ˜75%; however, it significantly decreased to ˜20% viability with an increase in concentration (40 nM) of the test samples, highlighting the dose-dependent cytotoxicity behavior of PDC in a 24 h incubation period.