08▒cm length). The volume ratio of dispersing phase to diffusing phase was 1:40. Polymer nanoprecipitation was immediately visible upon injection of the protein suspensions. The PLGA nanoparticles formed were immediately centrifuged for 10▒min at 8000▒rpm, the supernatant discarded, and the pellet re-suspended in distilled water. This washing step was thrice repeated and the samples subsequently freeze-dried by first rapidly freezing them in liquid nitrogen followed by lyophilization at a condenser temperature of ⁻45▒°C and a pressure of <60▒µm

of Hg [26]. Cyt-c encapsulation was performed using the same optimum conditions established by learn more us for lysozyme since it has a similar size and net charge. After protein nanoprecipitation, the resulting protein suspension was centrifuged at 5000▒rpm for 10▒min. The supernatant was discarded and the pellet vacuum dried for 30▒min. Protein concentration and protein aggregates in the pellet were determined

as described by us in detail [[26], [27], [28] and [29]]. In brief, the protein pellet was suspended in 2▒ml of potassium phosphate buffer for 2▒h to dissolve the buffer-soluble fraction. The samples were then subjected to centrifugation at 5000▒rpm for 5▒min and the supernatant used to determine the concentration of soluble protein. Next, 1▒ml of 6▒M urea was added to the pellet to dissolve the buffer-insoluble protein fraction and used to determine (-)-p-Bromotetramisole Oxalate the concentration of aggregated click here protein by measuring the UV absorbance at 280▒nm. The precipitation yield was calculated from the actual and theoretical quantity of protein recovered after nanoprecipitation and rehydration. The experiments were performed in triplicate, the results averaged, and the standard deviations calculated. The size of protein nanoparticles and PLGA nanospheres was determined by dynamic light scattering using a DynaPro Titan with MicroSampler from Wyatt Technology Corporation

(Santa Barbara, CA) as described by us in detail [20]. Protein particles were measured as a suspension in acetonitrile and the PLGA nanospheres as a suspension in water at 100% power intensity. Data analysis was performed using the Dynamic 6.7.6 software supplied with the instrument. The instrument was periodically calibrated using BSA as a standard. In the past, we found that scanning electron microscopy images and size data from dynamic light scattering were consistent [20]. The actual protein loading of nanospheres was determined following a methodology developed in our laboratory [27]. In brief, 20▒mg of PLGA nanospheres were dissolved in 2▒ml of ethyl acetate and stirred for 2▒h followed by centrifugation at 9000▒rpm for 10▒min. The supernatant was discarded and the pellet vacuum dried for 30▒min.