Perfluorooctyl silane

Positive masters and pillar array casting were described previously (Poole et al., 2014 (link)). Briefly, positive silicon masters were silanised using vapour phase Trichloro(1H,1H,2H,2H-perfluorooctyl) silane (Sigma-Alrich) for 16 hr. Negative masters were cast from this substrate in polydimethylsiloxane (PDMS) (Sylgard 184, Dow Corning), mixed at a ratio of 1:10 and cured at 110°C for 15 min. Negative masters were silanised as above and used to cast pillar arrays. Arrays were coated with degassed PDMS (1:10) and left for 30 min. A thickness two coverslip activated with oxygen plasma generated using a low pressure Zepto plasma system (Diener, Germany) was placed over the still liquid PDMS. Pillar arrays were cured for 1 hr at 110°C. Pillar arrays were activated using the oxygen plasma system and either cells were directly seeded onto this activated surface or arrays were first functionalised by coating with 10 μg/ml LM-511 (BioLamina, Sweden) for one hour at 37°C. Cells were seeded at a concentration of 2 × 10⁴ cells/mL in complete media and incubated overnight.

The designs for the poly(dimethyl)siloxane (PDMS) chip devices were prepared using Autocad CAD software and designs are shown in Supplementary Fig. 4. The corresponding CAD files can be downloaded from http://openwetware.org/wiki/DropBase (a database of microfluidic device designs). The devices were fabricated with standard soft lithographic procedures59 (link). The photoresist material SU-8 2015 was used to obtain a 15 μm channel height. PDMS monomer and curing agent were mixed at a ratio 10:1 and then poured onto the lithographic plate before degassing. After PDMS solidification (65 °C, 4 h), PDMS was activated by exposure to an oxygen plasma and devices were sealed onto a microscope glass slide (or cover slip (thickness: 0.13 mm) for the sorting chip). Hydrophobic modification of the channels surface was achieved by injecting a solution of 1% (v/v) trichloro(1H,1H,2H,2H-perfluorooctyl)silane (Sigma) in HFE-7500 oil into the channels. Electrodes for the sorting devices were prepared using low melting point indium composite solder (51 In/32.5 Bi/16.5 Sn, Indium Corporation).

Highly pure phosphatidylcholine (PC) 90% from soybean was purchased from Phospolipon 90G Lipoid, Germany; cholesterol 97% from Fluka, Germany; and dimethyldioactdecyl-ammoniumbromide (DDAB) from Sigma-Aldrich, UK. 1,2-dimyristoyl-sn-slycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (ammonium salt) (14:0 PEG2000 PE) were purchased from Avanti Polar Lipids; polydimethylsiloxane (PDMS) monomer Sylgard^® 184 and curing agent were purchased from Dow Corning (USA); SU-8 photoresist was obtained from Chestech (UK); trichloro (1 H,1 H,2 H,2 H)-perfluorooctylsilane, hydrofluoric acid, ammonium fluoride, ivermectin, and suramin sodium salt were purchased from Sigma-Aldrich (UK). All the other regents and solvents not included in this section were also purchased from Sigma-Aldrich (UK).