br The amphiphilic molecules HA NB
The amphiphilic molecules HA-NB-SC can self-assemble into hy-drophobic cored nanomicelles stabilized with SC 560 HA coronae in aqueous solution, and its self-assembly behavior of HA-NB-SC con-jugate in aqueous solution was characterized in detail by means of fluorescence spectroscopy, DLS and TEM. To make sure the micelle formation and calculate the CMC of amphiphilic molecule, NR, a hy-drophobic fluorescence probe, was used to be loaded into the nano-micelles (Hu et al., 2015; Zhang, Zhang et al., 2013). As shown in Fig. 2A, the emission fluorescence intensity gradually increased fol-lowing a non-linear trend with increasing amphiphile concentrations, suggesting a micro-environmental change in solution and spontaneous self-assembly of nanomicelles. And as shown in Fig. 2B, the intersection of extrapolated straight line segments yielded the CMC value of 0.0151 mg/mL for HA-NB-SC conjugate in water at room temperature. The low CMC value suggested that nanomicelles formed from HA-NB-SC conjugate are thermo-dynamically stable in aqueous solution (Hu et al., 2015).
DLS and TEM gave the information about the size and morphology of the self-assembled nanomicelles. TEM picture (Fig. 2C inset) revealed HA-NB-SC self-assembled into spherical nanomicelles in aqueous solu-tion with an average size of 99 nm. However, in DLS experiment, results demonstrated the nanomicelles have a number-average hydrodynamic diameter of 139 nm and a polydispersity (PDI) of 0.636, suggesting the nanomicelles had a narrow distribution. The bigger diameter of the nanomicelles determined by DLS than that by TEM was possibly owing to the diﬀerence in physical states of the sample. DLS was used for the liquid sample, but TEM was used for the dry solid one. Zeta potential of HA-NB-SC nanomicelles was −41.20 mV.
3.2. Drug loading and photo-responsive behaviors of nanomicelles
amphiphilic polymers by physical interaction (Thombre & Sarwade, 2005; Tomida, Nakato, Matsunami, & Kakuchi, 1997; Uhrich, Cannizzaro, Langer, & Shakesheﬀ, 1999; Yang et al., 2011; Zhan et al., 2011). Thus, we designed HA-NB-SC nanomicelles as a carrier for DOX to enhance its aqueous solubility. DOX was physically packaged into HA-NB-SC nanomicelles using a nanoprecipitation method at room temperature (showed in Scheme 1). The size and morphology of DOX-loaded HA-NB-SC nanomicelles were determined by DLS and TEM analysis. As shown in Fig. 2D, the particle size increased to 202 nm when DOX was incorporated. HA-NB-SC remained nearly spherical
shape with increased particle size after DOX loading (Fig. 2D inset). Such small sizes of restriction fragment length polymorphism (RFLP) DOX-loaded HA-NB-SC nanomicelles were regarded appropriate for passive delivery of DOX to targeted tumors through the EPR eﬀect (Maeda, Wu, Sawa, Matsumura, & Hori, 2000). The DLC, the DOX content in the HA-NB-SC micelles, and EE, the DOX encapsulation eﬃciency was determined as 2.91, 23.28 wt% from the UV absorbance measurement at 484 nm, respectively.
In vitro drug release analysis was conducted on NR-loaded HA-NB-SC nanomicelles upon diﬀerent irradiation time by monitoring the variation of NR fluorescence intensities (Fig. 3A). This small molecule
Fig. 2. Characterizations of the nanomicelles: emission spectra of NR (λex = 550 nm) in HA-NB-SC nanomicelles solutions (A), plot emis-sion intensity at 630 nm versus the log of mi-celle concentration of HA-NB-SC (B); size dis-tribution profile of HA-NB-SC (C) with TEM image (inset, scale bar, 100 nm) and DOX loaded HA-NB-SC (D) with TEM image (inset, scale bar, 100 nm).
Fig. 3. Emission spectra of NR (λex = 550 nm) in HA-NB-SC nanomicelles solutions upon UV light irradiation for diﬀerent time (A), plot emission intensity at 630 nm versus the time of irradiation time (B); UV–vis spectra of HA-NB-SC solution (1 mg/mL) irradiated for diﬀerent time (C); The fluorescence intensities of NR en-capsulated by HA-NB-SC nanomicelles after placing at 4 °C or 37 °C up to seven days (D).