Supporting Information. Monodisperse Uni- and Multicompartment Liposomes

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1 Supporting Information Monodisperse Uni- and Multicompartment Liposomes Nan-Nan Deng, Maaruthy Yelleswarapu and Wilhelm T. S. Huck* Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands *Corresponding Author: Wilhelm T.S. Huck List of contents Part I. Supplementary Figures S1-S20. Part II. Supplementary Experimental Details & Tables S1-5 & Figures S21-S25 1. Interfacial tension of the monolayer forming bilayer between W1 and W2 2. Selection of surfactants 3. Characterization of monodispersity of resultant liposomes 4. Yields of resultant liposomes 5. Proportion of F-68 to lipid in liposomes 6. Detection of residual oil in liposomes Part III. Supplementary Movies S1-S6. Part IV. Supplementary References S1

2 Part I. Supplementary Figures S1-S20 Figure S1. Time-serial images of the dewetting of double emulsions. Figure S2. Optical image of as-formed double emulsions without adding F-68 in outer water phase. No dewetting occurs when no surfactant is used in outer phase. S2

3 Figure S3. Oil removal from liposome samples by exploring density differences of fluids. Figure S4. Optical image of mixtures of liposomes and residual oil drops when 5 wt.% F-68 was used in outer phase. S3

4 Figure S5. Optical image of liposomes prepared by respectively using (a) DOPC, (b) DMPC, (c) DPhPC, (d) E. coli lipids as well as mixtures of egg PC and cholesterol (3:1, w/w) in the middle oil phase at a concentration of 5 mg ml -1. S4

5 Figure S6. Confocal and optical image of labeled liposomes (green) and precursor oil drops (black) is used to calculate the yields of liposomes from double emulsion drops. Note thatt black spots with bright and transparent edges (A,B,C,D and E) are bubbles; The rest black spots are residual oil droplets. In Figure a, number of liposomes is 167 and that of oil drops is 178. To show the one-to-one relationship of oil droplets and relevant liposomes, optical image was captured before complete dewetting. S5

6 Figure S7. Effect of solvent quality on dewetting processs of W/O/WW emulsion drops. The freshly prepared emulsions weree collected in a semi-enclosed covered with a glass coverslide for silicone isolation chamber (diameter 9 mm, height 0.12mm), and observation. (a) 50 vol.% chloroform: dewetting occurs from the edge to the middle of container due to the gradient of chloroform created by evaporation. (b) 40 vol.% chloroform: the same phenomenon as that at 50 vol.% chloroform, but the boundaries between the three areas are not that clear because smaller chloroform concentration difference. (c) 30 vol.% chloroform. Dewetting is almost synchronous. These phenomena agree well with the analysis of interfacial energies as shown in Table S1. Figure S8. Confocal image of Rh-PE and lipid reservoirs. Yellow drops are residual oil labeled liposomes showing homogeneous membranes without oil pockets containing extra lipids. S6

7 Figure S9. Gas chromatography graphs of liposome sample in 100 mm sucrose solution (oil removed) (a) and pure oil phase without lipids. Figure S10. egfp (a.u.) x egfp+chloroform/hexane egfp no plasmid Time ( h) Effect of chloroform and hexanee (4 vol.% of gene expression solution) on the kinetics of the egfp expression. S7

8 Figure S11. Number of dye-released liposomes over time as shown in Figure 4c. Figure S12. Schematics and confocal image series show insertion of α-hemolysin into liposomess to selectively transport fluorescent molecules. S8

9 Figure S13. High-speed snapshot of the preparation of W/O/W double emulsions with two (b), three (c), four (d) and five (e) inner drops. Figure S14. Confocal images of dewetting process of double emulsions with two distinct cores and enlarged image showing dewetting water-oil interfaces. S9

10 Figure S15. Optical microscopy images of liposomes with two (a), three (b), four (c) and five (d) compartments prepared from multi-core double emulsions. Figure S16. Optical microscopy images of double emulsion drops (a) and resultant liposomes (b) with more than 30 compartments. S10

11 Figure S17. Schematics (a) and optical image (b and c) of the microfluidic device and dual-cored double emulsion formation. S11

12 Figure S18. Confocal image of labeled liposome dimers and precursor oil drops (black) is used to calculate the yields of liposomes containing two distinct compartments. S12

13 Figure S19. Confocal images showing part of possible configurati ions of liposomes containing 2:22 distinct compartments. Figure S20. Confocal image of a Rh-PE labeled dewetting liposome (a) and magnifications of the dashed areas in a (b) as well as fluorescence intensity-distance profiles along the lines in b (c). S13

14 Part II. Supplementary Experimental Details. 1. Interfacial tension of the monolayer forming bilayer between W1 and W2 Since there is no direct method to measure the interfacial tension of bilayer membrane, we employ adhesion experiments of two water drops and then calculate the interfacial tension between them according to force balance. For a balanced doublet of two lipid (or surfactant) stabilized water drops (W1 and W2) dispersed in continuous oil phase (O) as shown in Figure S21a, the three interfacial tensions are fitted with the Neumann triangle described as 1 cos 1 cos 2, 1, 2 2, (S1) where is the interfacial tension of a monolayer composing the bilayer; and are respectively the interfacial tensions between water 1 and oil phases and that between water 2 and oil phases saturated with phospholipids. The adhesion energy of this drop system can be described as 2 (S2) We first use the pendant drop method to the interfacial tensions between O-W1 phases ( ) and that between O-W2 phases ( ), then calculate the in terms of equation (S1). However, when two droplets cannot adhere to each other (Figure S21b) or the form a spherical shape (Figure S21c), we make assumptions of the two boundary conditions as following. S14

15 Figure S21. Analyzing interfacial energies of doublets formed by two lipid stabilized water drops: (a) 1, 2 2,, (b) 1 2 and (c) Figure S22. Drop adhesion experiments: (a) W/O emulsion drops without F-68 showing no adhesion between drops; (b) W/O emulsion drops containing 0. 5 wt.% F-68 were adhered together: (b1) four drops and (b2) two drops. Case 1 S15

16 When 1 2, as shown in Figure S21b and Figure S22a, the two drops cannot adhere when they contact each other. According to equation (S1) and (S2), we can conclude that, and 0. That is to say, there is no adhesion force between the two water drops. However, ( 0) is also possible. Consequently, in this case we consider the interfacial tension of the two monolayer forming bilayer between the two drops is described as. Case 2 When 1 2 2, as shown in Figure S21c and S22b, the doublet exhibits a spherical shape. According to equation (S1) and (S2), we can get that and 0, 0. In this case, the interfacial tension of the monolayer forming bilayer is 0. Therefore, liposomes composing of this bilayer approach a zero interfacial tension. S16

17 2. Selection of surfactants Pluronic block copolymers, also known as poloxamers are composed of hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly(propylene oxide) (PPO) blocks arranged in A-B-A tri-block structure: PEO-PPO-PEO (Figure S23). With different numbers of hydrophilic ethylene oxide and hydrophobic propylene oxide units, these block copolymers are characterized by different hydrophilic-lipophilic balance (HLB). Because of their amphiphilic character these copolymers display surfactant properties including ability to interact with hydrophobic surfaces and biological membranes. Besides, these commercial surfactants are nonionic and compatible with biological research. To find a proper surfactant that is able to adjusting interfacial energies in W/O/W emulsion system to fit with the criterion for complete dewetting, i.e., 0, Pluronic copolymers with diverse molecule weights and different HLB values such as Pluronic F-127, F-108, F-68, P-123 and L-35 (Table S5) were used at a concentration of 1 wt.%, 2 wt.% and 5 wt.% in outer phase to prepare double emulsions that were observed to check dewetting processes. Meanwhile, the interfacial tensions in these systems were also measured. Results show that only F68 can assist the dewetting process, while F-127, F-108, P-123 and L-35 cannot. Double emulsion drops stabilized by F-127, F-108, P-123 or L-35 are stable and can maintain the core-shell structure for several hours (Figure S24), which is in line with the analysis of interfacial energies (Table S4). S17

18 Figure S23. A-B-A tri-block structure of Pluronic block copolymers Figure S24. No dewetting occurs when P-123 (a), L-35 (b), F-108 (c) or F-127 (d) is used as surfactant in outer water phase. As-formed W/O/W double emulsion drops can keep their core-shell structures for more than 5 hours. S18

19 Table S1. Interfacial tensions, and in W1/O/W2 emulsion system. W1: 8 wt.% PEG + 2 wt.% PVA; O: chloroform + hexane + 5 mg ml -1 egg PC; W2: 10 wt.% PVA wt.% F-68. Fraction of chloroform (vol.%) (mn m -1 ) (mn m -1 ) (mn m -1 ) a 0.05 a In this case, two adhesion drops exhibit an almost spherical shape, so 0 and Table S2. Interfacial tensions, and in W1/O/W2 emulsion. W1: 8 wt.% PEG + 2 wt.% PVA; O: chloroform + hexane + 5 mg ml -1 egg PC; W2: 10 wt.% PVA. a Fraction of chloroform (vol.%) (mn m -1 ) (mn m -1 ) (mn m -1 ) a In all case, 0 S19

20 Table S3. Interfacial tensions, and in W1/O/W2 emulsion system. W1: 8 wt.% PEG + 2 wt.% PVA; O: chloroform + hexane + 5 mg ml -1 egg PC; W2: 10 wt.% PVA + 2 wt.% F-68. Fraction of chloroform (vol.%) (mn m -1 ) (mn m -1 ) (mn m -1 ) a 0.15 a In this case, two adhesion drops exhibit an almost spherical shape, so 0 and Table S4. Interfacial tensions, in W1/O/W2 emulsion. W1: 8 wt.% PEG + 2 wt.% PVA; O: chloroform + hexane + 5 mg ml -1 egg PC, W2: 10 wt.% PVA wt.% L-35; W2 : 10 wt.% PVA wt.% F-108; W2 : 10 wt.% PVA wt.% F-127. a Fraction of chloroform (vol.%) (mn m -1 ) (mn m -1 ) L-35 (mn m -1 ) F-108 " (mn m -1 ) F a In all cases, drops cannot adhere to each other in adhesion experiments, so, leading to 0 and 0. S20

21 Table S5. Physicochemical characteristics of Pluronic block copolymers. a Copolymer Molecule Average number Average number HLB weight of EO units (2x) of PO units (y) F >24 F F >24 P L a Data provided by BASF ( pluronic) S21

22 3. Characterization of monodispersity of resultant liposomes To characterize the monodispersity of the resultant liposomes, we use an index called coefficient of variation (CV) value which is define as the as the ratio of the standard deviation of size distribution to its arithmetic mean, and calculated with an equation n 2 d i d ( n 1) 100% CV, (S3) d i 1 in which d is the diameter of the ith liposome, d is the arithmetic average diameter, i and n is the number of liposomes measured. d was measured by ImageJ and i n 100 in statistics. S22

23 4. Characterization of yields of resultant liposomes To characterize the yields of liposomes generated from double emulsions, we used a simple method based on the statistics of as-formed liposomes and residual oil droplets, which benefits from mondispersity and stability of both the liposomes and the oil droplets (Figures S5 and S18). Briefly, we first collected the freshly prepared double emulsions in a semi-enclosed silicone isolation chamber (diameter 9 mm, height 0.12mm, SecureSeal TM ) covered with a glass coverslide, then observed the sample by using a confical microscope or an inverted microscope. Images were captured when double emulsions were complete dewetted. Note that no coalescence of oil drops was observed in our experiments, because they are stabilized by excess lipids. Lastly, numbers of liposomes (N) and residual oil droplets (M) were counted to calculate the yields (Y). N Y 100% (S4) M S23

24 5. Proportion of F-68 to lipid in liposomes We used F-68 in outer water phase to control the whole dewetting process of double emulsion drops, so the F-68 may display in the outer bilayer leaflet. The interaction between PEO-PPO-PEO triblock copolymers including F-68 and lipid bilayers has been extensitively studied before The surfactant F-68 has 27 PO units (hydrophobic part, see Figure S23 and Table S5) that cannot achieve a membrane spanning configuration, because a spanning configuration requires at least 40 PO units. 8 The use of F-68 to adjust interfacial energies is the key to successful preparation of liposomes in our method. To minimize the contamination to the membrane, we only use the F-68 in outer water phase, therefore, the F-68 only displays in the outer bilayer leaflet, and no surfactant exists inside the liposome or adheres to the inner bilayer leaflet. Moreover, because the liposomes are composed of closely packed lipids; the presence of F-68 at the interface acts to force lipid molecules to pack more tightly, and the amount of F-68 incorporated into the lipid film is likely to be controlled by the surface free energy. As reported previously, 4 when the surface pressure of lipid monolayer is low, F-68 adsorbs to the oil-water interface and physically occupies a portion of the available area, but when the surface pressure is increased to a threshold, F-68 cannot pentrate into the membrane any more, and the concentration of membrane-bound surfactant will be constant. The following are several mothod to define the amount of F-68 absorbed in liposomes: 1. The proportion of F-68 to lipid in a liposome can be measured by isothermal titration S24

25 calorimetry (ITC) and also can be calculated from the partition coefficient K of surfactant into lipid membranes defined in terms of mole fractions: 5,10 K b (S5) P L P P b P W t b where W= 55.5 M is the molarity of water, L is the lipid concentration, and P t and P b are the concentrations of total surfactant and the surfactant in the bilayers, respectively. The partition coefficient is a constant, as reported, 5,10 the partition coefficients of Pluronic surfactants into lipid membranes are about 1~ For example, assuming that K in our case, and when L= 5 mg ml -1, P t = 0.2 wt.% (2 mg ml -1 ), we can get the surfactant concentration in the bilayers from Equation (S5) P b mm. Assuming that half of the lipids formed the liposomes, that is 3.25 mm. Therefore the proportion of F-68 to lipid in a liposome is approximately 0.236:3.25=1: It has been reported that when the concentration of Pluronic surfactant in the bilayer increase to a threshold, the hydrophilic chains start to interact laterally to form polymer mushrooms because of neglecting interactions. 7 In this context it allows calculating the concentration needed in the bilayer of F-68 to enter the so-called brush regime. The random coil chain length of F-68 can be calculated by the following equation. 7,9 3 5 R f an (S7) S25

26 where a is the monomer chain length (a = 0.35 nm for (CH2CHO)), N is the number of EO monomer unit. For F-68, N= 80, we can get R f = 4.85 nm. As Figure S25 shows, when the distance between the grafting points (d) is equal to or less than the random coil chain length, the transition from the mushroom regime to the brush regime occurs. The number of PEO chains per unit area (M) is approximately calculated by 7 2 M 1 d (S8) For d= 4.85 nm, we obtained M= chains/nm 2. Because an average area per egg PC molecule is about 0.64 nm 2, 11 the ratio of F-68 to egg PC is : For other pluronic surfactants such as F-127 (N= 101) and F-87 (N= 61), the transition from the mushroom regime to the brush regime may take place at the concentration of 2 mol % and 4 mol%, respectively. 7 Here we estimate the concentration of F-68 is approximately 3 mol% (to lipid), which is equivalent to 0.2 wt% f-68 in outer water phase when 5 mg ml -1 egg PC is used in oil phase. S26

27 Figure S25. Schematics showing the random coil chain length R f of the surfactant and the distance between the insertionn points d Kostarelos et al. have reported the amount of the adsorbed F-68 molecules to liposomes is about 1.7 mg m -2 and total liposome surface area is about 280 m 2 g -1. Thus the ratio of adsorbed F-68 to lipid is about 1/23 (mol/mol). In conclusion, when 0.2 wt.% F-68 and 5 mg ml -1 egg PC are used in outer and middle phase, the proportion of F-68 to lipid in as-formed liposomess is approximately 1:17 (mol/mol). S27

28 6. Detection of residual oil in liposomes Freshly-prepared liposome samples were collected in a vial containing 5 ml sucrose solution (100 mm) to remove the residual oil droplets formed form dewetting of double emulsions (see Figure S3 for details). Sucrose used here is to balance the osmotic pressure between interior and exterior of liposomes. Then we carefully updated the sucrose solution in the vial five times to remove the solvents dissolved in the collection fluids. Finally, 0.4 µl liposome sample was injected into the gas chromatography to detect the residual oil in liposomes. As a control, pure solvents (chloroform and hexane, 30:70, v/v) were also detected. S28

29 Part III. Supplementary Movies S1-S6 Movie S1. One-step preparation of W/O/W emulsions. Movie S2. Controlled dewetting of W/O/W emulsion drops to assemble liposomes. Movie S3. Insertion of melittin into liposome bilayers to transport fluorescent molecules. Movie S4. Two-step preparation of W/O/W emulsions with three inner drops. Movie S5. Drop pairing in microchannels. Movie S6. Controllable preparation of W/O/W emulsions with diverse inner drops. S29

30 Part IV. Supplementary References (1) Torza, S.; Mason, S. G. Science 1969, 163, (2) Thiam, A. R.; Bremond, N.; Bibette, J. Phys. Rev. Lett. 2011, 107, (3) Deng, N.-N.; Mou, C.-L.; Wang, W.; Ju, X.-J.; Xie, R.; Chu, L.-Y. Microfluid. Nanofluidics 2014, 17, (4) Wu, G.; Majewski, J.; Ege, C.; Kjaer, K.; Weygand, M. J.; Lee, K. Y. Biophys. J. 2005, 89, (5) Heerklotz, H. H.; Binder, H.; Epand, R. M. Biophys. J. 1999, 76, (6) Kostarelos, K.; Tadros, T. F.; Luckham, P. F. Langmuir 1999, 15, (7) Johnsson, M.; Silvander, M.; Karlsson, G.; Edwards, K. Langmuir 1999, 15, (8) Firestone, M. A.; Wolf, A. C.; Seifert, S. Biomacromolecules 2003, 4, (9) Liang, X.; Mao, G.; Ng, K. Y. S. J. Colloid Interface Sci. 2005, 285, (10) Wu, G.; Khant, H. A.; Chiu, W.; Lee, K. Y. C. Soft Matter 2009, 5, (11) McIntosh, T. J.; Magid, A. D.; Simon, S. A. Biochemistry 1989, 28, S30