This interaction

could lead to formation of NChitosan-DMNPs dispersed in aqueous phase with high colloidal stability. NChitosan-DMNPs were loaded with 27.5 wt.% MNCs and exhibited superparamagnetic behavior with a magnetization saturation value of 40.4 emu/gFe + Mn at 1.2 T (Figure 5). In addition, iron (Fe) and manganese (Mn) were not detected by X-ray photoelectron spectroscopy (XPS) analysis, which indicates that MNCs were safely encapsulated inside the NChitosan-DMNPs (Figure 5). The availability of NChitosan-DMNPs as MRI contrast agents was evaluated by measuring spin-spin relaxation times (T2) of water protons in the aqueous solutions buy PD-0332991 using 1.5-T MR images. As the selleck products concentration of MNCs (Fe + Mn) in NChitosan-DMNPs increased, the MR image was proportionally darkened with an R2 coefficient of 254.6/mMs, demonstrating that NChitosan-DMNPs have sufficient ability as MRI contrast agents (Figure 6). Figure 5 Characterizations of N Chitosan-DMNPs. (a) Thermogravimetric analysis (TGA), (b) magnetic hysteresis loops, and (c) XPS patterns of N-naphtyl-O-dimethymaleoyl chitosan-based drug-loaded magnetic nanoparticles (NChitosan-DMNPs). Figure 6 Assessment of the ability of N Chitosan-DMNPs as MRI contrast agents. (a) T2-weighted MR images of NChitosan-DMNPs in aqueous solution and (b) relaxation rate (R2) versus NChitosan-DMNPs

concentration. pH-sensitive drug release properties To investigate the pH-dependent behavior of NChitosan-DMNPs, they were dispersed in different pH solutions (pH 5.5, 7.4, and 9.8) and their sizes were analyzed using laser scattering. NChitosan-DMNPs KU55933 cost in a pH 9.8 solution showed stable particle size around 100 nm (100.3 ± 4.9 nm), but their sizes increased slightly with increased buffer solution acidity (pH 5.5, 185.3 ± 13.5 nm and pH 7.4, 158.8 ± 10.6 nm) (Figure 7a) [17, 20, 30, 83, 84]. This is because the solubility

of N-nap-O-MalCS of NChitosan-DMNPs was weakened by acid hydrolysis of maleoyl groups, as mentioned above. This pH-dependent behavior was expected to Ribose-5-phosphate isomerase induce pH-sensitive drug release profiles. DOX was abruptly released from NChitosan-DMNPs under acidic conditions (pH 5.5) with about 90% of drug release within 24 h (Figure 7b), whereas only 20% of DOX was released at higher pH conditions (pH 7.4 and 9.8) during the same time period and both release profiles showed sustained release patterns for 8 days. This result implies that drugs could be released more from NChitosan-DMNPs in acidic tumor sites than in normal tissues with decreased drug loss during blood circulation. After NChitosan-DMNPs internalization by endocytosis, drug release could be further accelerated inside the acidic endosomes of tumor cells. Figure 7 Particle size of N Chitosan-DMNPs in different pH conditions (a) and pH-sensitive drug release profiles (b). Red pH 5.5, blue pH 7.4, and green pH 9.8. Cellular uptake and cytotoxicity NIH3T6.