MCF-7 cells were grown in Dulbecco’s modified Eagle’s Medium (Invitrogen) supplemented with 10% (v/v) fetal bovine serum (FBS) and placed in an incubator with 5% CO2 at 37°C. The cells used in the experiments were obtained from passages

5-6. 2.3. Preparation of DOX-Loaded PEI-Enhanced HSA Nanoparticles PEI-coated HSA nanoparticles were prepared at room Inhibitors,research,lifescience,medical temperature using an ethanol desolvation technique [22, 27–29]. In brief, 20mg of HSA was added to 1mL of 10mM NaCl (aq) under MS-275 chemical structure constant stirring (800rpm) at room temperature. The solution was stirred for 10min. After total dissolution, the solution was titrated to pH 8.5 with 1N NaOH (aq) and stirred for 5min. This aqueous phase was desolvated by the dropwise addition of ethanol to aqueous HSA solution under constant stirring. Ethanol was added until the HSA solution became turbid (~1-2mL). Cross-linking agent, 8% glutaraldehyde, was added to form stable HSA particles. The obtained nanoparticles were centrifuged three times and washed with Inhibitors,research,lifescience,medical deionized water (dH20), followed by resuspension in an equal Inhibitors,research,lifescience,medical volume of PBS. PEI dissolved in dH20 was added to the nanoparticle

preparation to allow PEI to form an outer coating due to electrostatic binding. For the preparation of drug-loaded HSA nanoparticles, doxorubicin was added to 1mL HSA solution after pH adjustment and allowed Inhibitors,research,lifescience,medical to stir for 4hrs, followed by ethanol addition. To determine the drug encapsulation efficiency, an indirect method was employed

as shown by Sebak et al. [27]. The unloaded drug was quantified by measuring the free drug found in the supernatant of the prepared drug-loaded nanoparticles, using a UV spectrophotometer. Using the amount of unloaded drug, the drug-loaded quantity was determined (Total drug added (μg)—free drug). The encapsulation efficiency was then calculated using the amount of drug loaded into the nanoparticles: amount of drug loaded (μg)/theoretical maximum Inhibitors,research,lifescience,medical drug loading (μg) [8]. 2.4. Purification of PEI-Enhanced HSA Nanoparticles PEI-coated HSA nanoparticles were ultracentrifuged (16500g) for 12min and added to 10mM NaCl (aq) by vortexing and ultrasonication (Branson 2510). This method was repeated thrice to ensure complete removal of impurities. 2.5. Determining Particle Size and Surface Zeta Potential The particle size and nearly zeta potential were measured by electrophoretic laser Doppler anemometry, using a zeta potential analyzer (Brookhaven Instruments Corporation, USA). The nanoparticles were diluted 1:15 with distilled water prior to measurement [27]. 2.6. Surface Characterization of PEI-Enhanced HSA Nanoparticles The size and shape of the HSA nanoparticles were observed by transmission electron microscopy (TEM), using Philips CM200 200kV TEM (Markham, Canada).