5 and 441.9 nm, with a PDI of 0.172 and 0.189, and a zeta potential of −24.3 and −42.0 mV, respectively. Smaller particle size favored EPR targeting; lower PDI indicated good dispersibility, a prerequisite of good stability. Higher zeta potential supported that the NPs did not aggregate much in aqueous state in general and in physiologically this website relevant media in particular. Knowledge on these characteristics of a NP system can help predict the fate and biodistribution of NPs at the cellular or animal level in vivo after administration [1, 6]. As clearly seen from Figure  3A, the hydrodynamic particle size of PTX-MPEG-PLA NPs was much less than that of PTX-PLA NPs; the particle size is compatible

in EPR targeting attributed to the leaky nature of tumor vessels. Therefore, PTX-MPEG-PLA NPs were chosen as an effective model drug carrier as their particle size distribution and zeta potential distribution were narrow. Figure 3 Particle

size and zeta potential. Particle size determined by DLS (A) and zeta potential determined by ELS (B) of PTX-MPEG-PLA NPs and PTX-PLA NPs. Additionally, TEM images revealed that PTX-MPEG-PLA NPs were regularly spherical in shape and have a generally smooth Cell Cycle inhibitor surface with an approximate average size of around 100 nm, and the core particles contain a lighter outer MGCD0103 chemical structure region (see Figure  4). The average size of these NPs determined by DLS was 179.5 nm, not well consistent with the size determined by TEM. These factors were possibly responsible for the following differences. First, in the case of the TEM method, TEM depicted the size in the dried state of the sample, whereas DLS determined the size in the hydrated state of the sample. Second, the polymer shell of the particle surface tended to expand in aqueous environment which inevitably increased the hydrodynamic size of NPs because of solvent effect. Third, some NPs may be likely aggregated in the aqueous environment. Figure 4 TEM images of PTX-PLA NPs (A, B)

and PTX-MPEG-PLA NPs (C, D). Dialysis 17-DMAG (Alvespimycin) HCl offered an easy and effective method for the preparation of small and well-distributed NPs. At present, the mechanism of NP formation by dialysis method is not fully understood. It was thought that it may be based on a mechanism similar to that of nanoprecipitation. It was based on the utilization of a physical barrier that allowed the passive transport of organic solvents to slow down the mixing of MPEG-PLA with water; the organic solvent played a role in the morphology and particle size distribution of the NPs [20]. The presence of hydrophilic PEG chain, small particle size, high zeta potential, sharp curve of the particle size, and zeta potential distribution indicated that the spherical NPs as effective nano drug delivery systems were expected to be relatively stable in physiologic media for intravenous delivery.