It is shown in Figure 4a that the fluorescent intensity of the sample gradually increases from about 0 to 900 with ranging the SBC concentration from 10-4 to 1 mg/mL. The absorption band of the sample with a SBC concentration of 10-4 mg/mL has shifted from 335.6 to 339.4 nm when the SBC concentration reaches 1 mg/mL. As is shown in Figure 5a, the fluorescent intensity of characteristic peaks at about 376 and 386 nm also gradually enhance from around (0, 0)
to (700, 900) with increasing the SBC concentration from 10-4 to 1 mg/mL. The above see more phenomena indicate that insoluble pyrene molecules have been gradually transferred from water to the inside of the SBC micelles with increasing the SBC concentration in aqueous Selleckchem ITF2357 solution [30–32]. Figure 4 Excitation spectra of different SBC micelles (a); influence of SBC concentration on ratio of I 339.4 /I 335.6 (b). Figure 5 Emission spectra of different SBC micelles
(a); influence of SBC concentration on ratio of I 386 /I 376 (b). Critical micelle concentration (CMC) is an important parameter to characterize the thermodynamic stability of micellar system upon dilution in nanomicelles in vivo. The ratio of I339.4/I335.6 in the excitation spectra is usually used to determine the CMC of amphiphilic molecules . The influence of the SBC concentration in aqueous solution on the ratio Caspase activity assay of I339.4/I335.6 is shown in Figure 4b. The ratio of I339.4/I335.6 is found to dramatically increase from 0.8 to 1.38 with the enhancement of the SBC concentration from 1 × 10-4 to 4.9 × 10-2 mg/mL. It is almost unchanged with further increasing the SBC concentration from 4.9 × 10-2 to 1 mg/mL. Consequently, a CMC value of 4.57 × 10-4 mg/mL can be obtained from the intersection of the two tangent lines shown in Figure 4b. Similarly, a typical ratio of I3/I1 (about I383/I373) of pyrene probe in emission spectra is also usually used to determine the CMC value C1GALT1 of micelles. It is shown in Figure 5b, the ratio of I3/I1 rapidly decreases from 1.67 to 1.21 when the SBC concentration increases from 1 × 10-4 to 1 × 10-3 mg/mL. It only fluctuates near 1.18 with further increasing the
SBC concentration from 1 × 10-3 to 1 mg/mL, revealing the un-sensitivity of the I3/I1 ratio at high SBC concentrations. A CMC value of 1.23 × 10-4 mg/mL (CMC2) can be also obtained from Figure 5b, which is slightly lower than the CMC1 observed from the excitation spectra. Consequently, the CMC value of the prepared SBC micelles is ranged from 1.23 × 10-4 to 4.57 × 10-4 mg/mL. The detected CMC value is much lower than those reported for well-known linear and nonlinear block copolymers, such as 4.1 × 10-2, 6.46 × 10-2, and 1.2 × 10-3 for conventional biodegradable thermogelling poly(ethylene glycol)/poly(ϵ-caprolactone) (PEG/PCL) diblock , branched PCL/PEG copolymers , and PCL/PEG/PCL triblock , respectively.