Rho pe

A zwitterionic lipid, PC (Avanti Polar Lipids, Alabaster, AL, USA), and a nonionic surfactant, sorbitan monooleate (Span80, Tokyo Chemical Industry Co., Tokyo, Japan), were dissolved in hexadecane (purity > 98%; Tokyo Chemical Industry Co., Tokyo, Japan) and used as the continuous oil phase. Milli-Q water (H20MB0124, Merck KGaA) was used as the aqueous phase. To visualize a lipid membrane covering a droplet, a fluorescent-labeled lipid, 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) (ammonium salt; Rho-PE, Avanti Polar Lipids) was used. Calcein (Sigma-AldrichSt. Louis, MO, USA), a water-soluble fluorescein, was used to analyze the function of α-hemolysin isolated from Staphylococcus aureus (Sigma-Aldrich) reconstituted in a DIB. The microfluidic device was developed using a photoresist (SU-8 3025, MicroChem Corp., Westborough, MA, USA) and a polydimethylsiloxane (PDMS) package (Sylgard 184, Dow Corning Toray Corp., Tokyo, Japan).

Dipalmitoyl phosphatidyl choline (DPPC), poly(ethylene glycol) (PEG-2000) covalently linked to distearoyl phosphatidyl ethanolamine (DSPE-PEG), rhodamine covalently linked to phosphatidyl ethanolamine (Rho-PE) and the functionalized DSPE-PEG phospholipids with folate (DSPE-PEG-FA) were purchased from Avanti Polar Lipids (Alabaster, AL, USA). Cholesterol (Chol), and phosphate buffered saline (PBS) were obtained from Sigma-Aldrich (St. Louis, MO, USA). Pan was purchased from Selleckchem (Houston, TX USA, Cat # S1030). All other reagents were of analytical grade.