Dipalmitoyl sn glycero 3 phosphocholine dppc

Perfluorobutane (C₄H₁₀, PFB)-filled MBs with a phospholipid shell containing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) (Avanti Polar Lipids), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-(polyethylene glycol)-2000 (DSPE-PEG2k) (NanoCS), and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N[maleimide(polyethylene glycol)-2000 (DSPE-PEG2k-Mal) (NanoCS) in a 90:5:5 molar ratio were formulated. Briefly, lipid films were solvated in a mixture of PBS 1X/propylene glycol/glycerol (8:1:1 v/v/v, 10 mL), heated in a heating block until the solution reached 65 °C, and then bath sonicated at 70 °C until the solution was clear. PFB gas was then introduced into the headspace, and the lipid solution was sonicated for 5 s with a tip sonicator (Branson). The vial was then cooled down in an ice bath for 5 min. Foam was removed via syringe transfer, and the MBs were washed by slow centrifugation (300 g, 3 min, 3 times) with PBS 1X, pH 6.5, and 1 mM EDTA (4 mL) to yield PEGylated MBs with maleimide functionality. The MBs were then sized and counted using a Beckman Multisizer 4.

N-(carbonyl-methoxypolyethylene-glycol-2000)-1, 2-distearoyl-sn-glycero-3-phospho-ethanolamine (DSPE-PEG₂₀₀₀), dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol were obtained from Avanti Polar Lipids (Alabaster, AL). PTX was a gift of Samyang Biopharm (Seoul, Korea). Gemcitabine HCl was purchased from Biotang Inc. (Lexington, MA). All other materials, including solvents, were purchased from Sigma Aldrich (St. Louis, MO).