Manipulating the ordered nanostructure of self-assembled monoolein

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Manipulating the ordered nanostructure of self-assembled monoolein and phytantriol nanoparticles with unsaturated fatty acids Nhiem Tran, Xavier Mulet, Adrian M. Hawley, Celesta Fong, Jiali Zhai, Tu C Le, Julian Ratcliffe, and Calum J. Drummond Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b03541 • Publication Date (Web): 30 Jan 2018 Downloaded from http://pubs.acs.org on January 31, 2018

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Manipulating the ordered nanostructure of self-assembled monoolein and phytantriol nanoparticles with unsaturated fatty acids Nhiem Tran1, 2, *, Xavier Mulet2, *, Adrian Hawley3, Celesta Fong1,2, Jiali Zhai1, Tu C, Le4, Julian Ratcliffe2, Calum J Drummond1, * 1

School of Science, RMIT University, Melbourne, VIC 3001, Australia

2

CSIRO Manufacturing, Clayton, VIC 3149, Australia

3

Australian Synchrotron, ANSTO, Clayton, VIC 3149, Australia

4

School of Engineering, RMIT University, Melbourne, VIC 3001, Australia

*Corresponding authors: Dr Nhiem Tran School of Science, RMIT University GPO Box 2476, Melbourne, Vic 3000 Ph: +61 3 9925 2131 Email:[email protected]

Professor Calum Drummond Email: [email protected]

Dr Xavier Mulet Email: [email protected]

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Abstract Mesophase structures of self-assembled lyotropic liquid crystalline nanoparticles are important factors that directly influence their ability to encapsulate and release drugs, and their biological activities. However, it is difficult to predict and precisely control the mesophase behaviour of these materials, especially in complex systems with several components. In this study, we report the controlled manipulation of mesophase structures of monoolein and phytantriol nanoparticles by adding unsaturated fatty acids. By using high throughput formulation and small angle X-ray scattering (SAXS) characterization methods, the effects of fatty acids chain-length, cis-trans isomerism, double bond location, and level of chain unsaturation on self-assembled systems are determined. Additionally, the influence of temperature on phase behaviour of these nanoparticles is analysed. We found that in general, the addition of unsaturated fatty acids to monoolein and phytantriol induces the formation of mesophases with higher Gaussian surface curvatures. As a result, a rich variety of lipid polymorphs is found corresponding with the increasing amounts of fatty acids. These phases include inverse bicontinuous cubic, inverse hexagonal, and discrete micellar cubic phases and microemulsion. However, there are substantial differences between the phase behaviour of nanoparticles with trans fatty acid, cis fatty acids with one double bond, and cis fatty acids with multiple double bonds. Therefore, the material library produced in this study will assist the selection and development of nanoparticle based drug delivery systems with desired mesophase.

Keywords: cubosomes, hexosomes, monoolein, phytantriol, self-assembly, phase behaviour.


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Introduction Self-assembled lyotropic liquid crystalline nanoparticles have great potential as drug delivery systems due to their customisable internal nanostructures and functionalisable surfaces. Their mesoporous internal structures have allowed for the encapsulation of a wide range of hydrophobic and hydrophilic compounds, including chemotherapeutic drugs, antimicrobial agents, proteins, peptides, and nucleic acids.1, 2, 3 Previous studies have demonstrated that the nanostructures directly influence the release rate of drugs and biomolecules. 4, 5, 6, 7, 8, 9, 10, 11 For example, the release rate of hydrophilic compounds was found to be much faster in cubic phase than in hexagonal phase, micellar cubic phase, microemulsion.12 Additionally, it has been shown that the internal nanostructures also affect cellular response such as cell uptake of nanoparticles, haemolysis, and cytotoxicity. 13, 14, 15, 16, 17

More importantly, the in vivo behaviour of nanoparticles such as biodistribution appears to

be regulated by their nanostructures.18 Consequently, the phase behaviour of self-assembled lipid nanoparticles and the ability to tune it has been the subject of intense research interest to achieve drug delivery systems with desirable physical and biomedical properties. Among the studied lipids, monoolein (MO) and phytantriol (PHYT) have received high level attention due to their biocompatibility and the propensity to form non-lamellar phases in water. 19, 20, 21, 22 Depending on the environmental conditions and presence of additives, these lipids adopt various polymorphs including fluid lamellar phase (Lα), inverse bicontinuous cubic phase of diamond (QIID) and primitive (QIIP) symmetry, inverse hexagonal (H2) phase, micellar cubic phase (I2), and microemulsions (L2). 23, 24 One simple factor that provides a strong indication of the mesophase structure is the critical packing parameter (cpp). 25 For an amphiphile, the cpp is defined as ܿ‫= ݌݌‬

ܸ ݈ܽ


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in which V is the effective volume of the hydrophobic part of the amphiphile, a is the effective cross-section area of the headgroup, and l is the effective length of the hydrocarbon chain. As a result, inverse phases with negative Gaussian curvatures are usually formed when cpp > 1 while lamellar phase with a flat bilayer structure has a cpp = 1.25, 26 The addition of foreign molecules to an amphiphile system may change the effective cpp of the system and directs the transition into different mesophases.27 Additives such as fatty acids (FAs), oils, cholesterol, vitamin E acetate, and phospholipids have been added to MO and PHYT in both bulk and dispersion forms to modify the nanostructures. 28, 29, 30, 31, 32, 33 For instance, the addition of a FA to MO nanoparticles at low pH appeared to increases the effective cpp of the system, resulting in mesophases with higher negative curvatures. 34, 35, 36 It was evident from the phase sequence of MO nanoparticles in the presence of increasing amount of fatty acids from QIIP to QIID, to H2, and L2. In contrary, doping phospholipids such as DLPC and DSPC with large headgroups to MO nanoparticles reduced effective cpp, which was apparent from a phase sequence of H2 QIID QIIP Lα. 37, 38 Previously, we have used high throughput screening techniques to examine the influence of twelve saturated FAs on the mesophases of MO, PHYT and monopalmitolein (MP) nanoparticles.39 The data showed that increasing FA concentration in nanoparticles resulted in phase sequences that preferred mesophases with higher negative curvatures, suggesting elevated effective cpps. It appeared that the FA chainlength had a similar effect on nanoparticle mesophases with longer chain FAs encouraging the formation of more negatively curved interfaces. To further investigate the influence of FAs on lipid nanoparticles, herein, we report the phase behaviour of MO and PHYT nanoparticles doped with twenty different unsaturated FAs (Table 1). These FAs, which are typically Generally Regarded As Safe (GRAS), differed in chainlength, cis-trans isomerism, double bond


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location, and level of chain unsaturation. The material library created here will be valuable for the design of advanced lipid systems for drug delivery. Materials and Methods Materials Monoolein (MO) and 20 unsaturated fatty acids (FA) listed in Table 1 were obtained from Nuchek-Prep, Inc (Elysian, MN, USA). Phytantriol (PHYT) is from TCI (Tokyo, Japan). The purity of MO and FAs is greater than 99% except arachidonic acid, whose purity is over 90%. The purity of Phytantriol is at least 95%. Pluronic F127 and ethanol were also purchased from Sigma-Aldrich. Fatty acids selection and categorisation Among twenty selected unsaturated FAs, six of them contain only trans isomers, thirteen contain only cis isomers, and one contain both cis and trans isomers. Their chemical structures are provided in Figure 1. Nine FAs have more than one double bond with DHA having the highest number of double bonds (6 double bonds). It is generally expected that the behaviour of trans FAs more closely resembles saturated chain FAs compared to cis FAs.40, 41 It is therefore sensible to assume that the cpps of trans FAs are smaller than those of cis FAs. Among trans FAs with similar degree of unsaturation, it is expected that the longer the hydrocarbon chain, the higher the cpp. This assumption is derived from our previous study suggesting that longer chain saturated FAs triggered phase transition in MO nanoparticles at lower FA concentration than that of shorter chain saturated FAs.39 Among cis FAs, it is also reasonable to assume that FAs with more double bonds will have higher cpp. Considering these assumptions, the FAs are categorised as in Table 1. FAs 1 to 6 contain trans isomers. FAs 7 – 13 contain cis isomers with single double bond and increasing molecular weight. An exception is 8 with a cis and a trans isomer making it likely to behave similarly to 9 and 10


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(vaccenic acid and oleic acid). FAs 14 - 20 contain more than one all-cis double bonds with increasing molecular weight and degree of unsaturation. By arranging the FAs in this order, it is easier to compare the influence of these FAs on MO and PHYT nanoparticle mesophases. Table 1. Twenty unsaturated fatty acids that were added to MO and PHYT nanoparticles to study their phase behaviour. Sample number

Fatty acid

M.W.

Common name

Structure*

1

trans-9-hexadecenoic acid

254

Palmitelaidic acid

trans-16:1, n-7

2

trans-9-Octadecenoic acid

282

Elaidic acid

trans -18:1, n-9

3

trans-11-octadecenoic acid

282

trans Vaccenic acid

trans -18:1, n-7

4

trans-11-eicosenoic acid

311

trans Gondoic acid

trans -20:1, n-9

5

trans-13-docosenoic acid

339

Brassidic acid

trans -22:1, n-9

6

trans-9,12-octadecadienoic acid

280

Linoelaidic acid

trans -18:2, n-6

7

cis-9-hexadecenoic acid

254

Palmitoleic acid

cis-16:1, n-7

8

cis-9-trans-11-octadecadienoic acid

280

Rumenic acid

cis, trans-18:2, n-7

9

cis-11-octadecenoic acid

282

Vaccenic acid

cis -18:1, n-7

10

cis-9-Octadecenoic acid

282

Oleic acid

cis -18:1, n-9

11

cis-11-eicosenoic acid

311

Gondoic acid

cis -20:1, n-9

12

cis-13-Docosenoic acid

339

Erucic acid

cis -22:1, n-9

13

cis-15-Tetracosenoic acid

367

Nervonic acid

cis -24:1, n-9

14

cis-9,12- Octadecadienoic acid

280

Linoleic acid

cis -18:2, n-6

15

cis-9,12,15-Octadecatrienoic acid

278

α-Linolenic acid

cis -18:3, n-3

16

cis-6,9,12-octadecatrienoic acid

278

γ-Linolenic acid

cis -18:3, n-6

17

cis-11,14,17-Eicosatrienoic acid

307

ETA

cis -20:3, n-3

18

cis-5,8,11,14-Eicosatetraenoic acid

305

Arachidonic acid

cis -20:4, n-6

19

cis-5,8,11,14,17-Eicosapentaenoic acid

302

EPA

cis -20:5, n-3

20

cis-4,7,10,13,16,19 Docosahexaenoic acid

329

DHA

cis -22:6, n-3

*Note: the FA structure is described as “cis/trans-a:b, n-c”, where a is the number of carbon in the FA molecule, b is the number of double bonds, and c is the location of the first unsaturated carbon.


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Figure 1. Chemical structures of the selected unsaturated FAs listed in Table 1. These structures were generated by Chem3D software. 7 ACS Paragon Plus Environment

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Preparation of Nanoparticles A materials library consisting of 442 unique nanoparticle samples was formulated by using high throughput methods. Briefly, MO, PHYT, and FAs were dissolved in absolute ethanol separately. Lipids and FAs solutions were combined in a well of a 2mL 96-well master block (Greiner Bio-One, Interpath Inc., VIC Australia). MO and PHYT weights were fixed at 10 mg per well, while FAs weights varied. Ratios rMO and rPHYT are defined as molar ratios of FA to MO and PHYT in the mixture, respectively. The specific compositions of the studied MO and PHYT nanoparticles are provided in Supporting Information Table S1 and S2, respectively. Ethanol was then evaporated overnight using a centrifugal evaporator (GeneVac, NSW, Australia). 500 µL of Pluronic F127 in Milli-Q water was added to the dried mixtures at 10 % to MO or PHYT weight. Nanoparticles were produced by sonicating the mixtures for 3 minutes at instrument amplitude of 30 using a high throughput 24-tip sonicator (Q700, QSonica, CT, USA). After sonication, the plate was sealed and the nanoparticles were kept at room temperature for further characterization. The presence of homogeneous opaque dispersions without sedimentation confirmed the effectiveness of the F127 steric stabilizer. Small angle X-ray scattering (SAXS) SAXS experiments were performed at the SAXS/WAXS beamline at the Australian Synchrotron (Clayton, VIC, Australia). The instrument used an X-ray of wavelength of λ = 1.128 Å (11.0 keV) with a typical flux of approximately 1013 photons/s. The sample to detector distance (camera length) was chosen as 0.9 m which covers a q-range of 0.01- 0.6 Å-1 (scattering vector q = 4π sin(θ)/λ where θ is the scattering angle and λ is the wavelength). Two dimensional X-ray diffraction images were recorded on a Decris-Pilatus 1-M detector using in-house IDL-based ScatterBrain software. The scattering images were integrated into one dimensional plots of intensity versus q for phase identification. A silver behenate 8 ACS Paragon Plus Environment

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standard (d = 58.38 Å) was used for calibration of the camera length. The exposure time for each sample was 1 s. 100 µL of prepared nanoparticles were loaded into a clear 96-well half-area polystyrene plate (Greiner Bio-One, Interpath Inc., VIC, Australia). The plate was placed in a holder perpendicularly to the X-Ray beam. The sample holder was moved by motors that were controlled by ScatterBrain software for automatic SAXS screening. The sample temperature was controlled by a circulating water bath. SAXS data analysis Phase identification of self-assembled lipid nanoparticles was based on the relative distance of the Bragg peaks in the scattering profile, which corresponds to diffraction planes defined by their (hkl) Miller indices. For this, the one dimensional SAXS profiles were analysed by an in-house developed RapidPhaseIdent software and an IDL-based AXcess software package.42 These programs identify lyotropic liquid crystalline phases and calculate the lattice parameter of each lyotropic liquid crystalline phase. Lattice parameter (LP) a was calculated using the equation a = d(h2+k2+l2)1/2 for cubic phase or a = d(h2+k2+hk)1/2 for hexagonal phase where d is the spacing between the diffraction planes, defined by Bragg’s law d = 2π/q. Cryogenic Transmission Electron Microscopy Cryo-TEM was used to visualize the formulated nanoparticles. Copper grids (200-mesh) coated with perforated carbon film (Lacey carbon film, ProSci Tech, Australia) were glow discharged in nitrogen to render them hydrophilic and placed in a laboratory-built humiditycontrolled vitrification system. Aliquots of samples were applied onto the grids and after 30 s adsorption time, grids were blotted manually by filter paper for approximately 3 s. Grids were then plunged into liquid ethane cooled by liquid nitrogen. The samples were examined using


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a Gatan 626 cryoholder (Gatan, Pleasanton, CA, USA) and Tecnai 12 Transmission Electron Microscope (FEI, Eindhoven, The Netherlands) at an operating voltage of 120 kV. At all times low dose procedures were followed, using an electron dose of 8–10 electrons Å−2 for all imaging. Images were recorded using a FEI Eagle 4k × 4k CCD camera at magnifications ranging from 15000× to 50000×. Cryo-TEM images were analyzed using ImageJ software (NIH).

Results and Discussions In this study, unsaturated fatty acids (FAs) were mixed with either MO or PHYT to study their influence on the mesophase structure lipid nanoparticles. The list of twenty unsaturated FAs is given in Table 1. All solutions contain nanoparticles appeared to be milky white without visible precipitation. This method of preparation has been shown to be successful in creating lipid nanoparticles with a hydrodynamic diameter around 200 nm.16, 39 Representative hydrodynamic diameters and polydispersity index (PdI) of MO-linoelaidic acid nanoparticles at various acid concentrations were measured and provided in Figure S1. The mean diameters for these nanoparticles were around 220 nm and gradually increased with the fatty acid content to around 300 nm in the microemulsion sample with highest linoelaidic acid concentration. Representative cryo-TEM images of cubosomes, hexosomes, and microemulsion of MOlinoelaidic acid nanoparticles at different acid concentrations are presented in Figure 2. The cubosomes show a typical cubic symmetry when analysed by Fast Fourier Transformation (FFT) (Figure 2A), while the hexosome exhibits sharp edges and a hexagonal symmetry (Figure 2B). Some other hexosomes are also found with “finger-print” patterns, which are commonly observed in these nanoparticles. The microemulsion show no ordered internal structure (Figure 2C).


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Figure 2. Representative cryo-TEM images of cubosomes (A), hexosomes (B), and microemulsion (C) of MO-linoelaidic acid nanoparticles at different acid concentrations. Phase behaviour of MO-FA nanoparticles The phase diagram for FA/MO nanoparticles at 25oC is obtained directly from SAXS data and is presented in Figure 3. Representative SAXS scattering profiles of MO-linoelaidic acid nanoparticles are provided in Supporting Information Figure S2. The FA content in the mixture is represented by rMO, which is defined as the molar ratio of FA to MO. As expected, the addition of unsaturated FAs to MO nanoparticles greatly altered their mesophase structure. It should be noted that the original phase of MO nanoparticles stabilised with Pluronic F127 is primitive cubic phase QIIP. An overall trend observed here is the formation of nanostructures with higher negative curvatures with increasing amount of FAs in nanoparticles. This result indicates that the addition of unsaturated FAs increases the effective cpp of the system (Figure 4).


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Figure 3. Partial phase diagram for MO nanoparticles with increasing amounts of unsaturated FAs at 25oC. The list of twenty unsaturated FAs is provided in Table 1. The FA content in the mixture is represented by rMO, which is defined as the molar ratio of FA to MO. Specifically, for nanoparticles with increasing amounts of trans FAs, there is an appearance of the QIID phase, replacing the QIIP phase of MO. This is followed by a transition into an inverse hexagonal phase H2. For FAs 1 and 4 (palmitoelaidic and trans brassidic acid), a lamellar crystalline phase Lc is found at the highest concentration of FAs. The Lc phase is evident by the spotty lamellar X-ray scattering pattern.39 The phase behaviour observed here for trans-FA-MO nanoparticles is similar to that of saturated FA-MO


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systems.39 However, due to the presence of the double bond, there is a permanent kink in the hydrocarbon chain, which enlarges and alters the geometry of the effective tail volume. Consequently, the trans FAs here were incorporated into MO bilayers much easier and at higher amounts compared to saturated FAs of similar chain length. For example, the Lc phase was found in all MO nanoparticles added with palmitic acid (16:0) at a rMO higher than 0.2.39 However, in the case of palmitelaidic acid (trans-16:1), Lc phase is only found at rMO = 1.4. For MO nanoparticles doped with FA 6, a trans FA with two double bonds, at the highest tested FA concentration, the microemulsion (L2 phase) with a single broad scattering peak is observed. The forming of L2 instead of Lc at this concentration is likely due to the presence of two double bonds, which enlarges the effective tail volume and lowers the melting point of 6, and makes it easier to be incorporated into the MO bilayer. A molecular modelling of the chemical structure of 6 in vacuum, which shows the bent hydrocarbon chain due to the two double bonds, is provided in Figure S3. The appearance of QIID phase at lower FA concentration in 4, 5, 6 compared to 1, 2, 3 suggests that 4, 5, 6 have higher cpp and thus affects the original QIIP phase of MO more strongly than 1, 2, 3. The phase behaviour of MO nanoparticles added with 7 (cis-16:1) and 8 (cis, trans-18:2) is similar to that of 6 and short chain saturated FAs (C8-C12). A phase transition sequence from QIIP QIID H2 L2 is observed with increasing FA concentration. It is counterintuitive that 6, a trans FA with two double bonds, can induce phase transition from QIIP to QIID at lower concentration than 7, a cis FA. This result indicates that the kink in the molecular structure of trans FA 6 may have a significant effect on increasing its effective tail volume and cpp compared to its saturated FA counterpart or cis FA 7. Further molecular modelling to calculate the exact values of the cpp of these FAs may elucidate this observation.


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FAs 9-13 each possesses one cis double bond. The increasing addition of these FAs to MO nanoparticles also induces a phase transition from QIIP to QIID and to H2. However, at the highest FA concentration tested, a micellar cubic phase (I2) of space group Fd3m is found. Previous studies have shown the existence of an I2 phase in MO-Oleic acid bulk and dispersion systems.28, 35, 43 It is likely that due to the structural similarity of these FAs with Oleic acid and MO, they were able to form an I2 phase. The rarity of the I2 phase reported in the literature makes this composition worth highlighting. Furthermore, in MO nanoparticles with 12 (Erucic acid, cis-22:1) at a rMO of 0.13, the co-existence of QIIP, QIID, and H2 is detected using SAXS. Recently, observations of stable Janus lipid nanoparticles with coexisting QIID/QIIP phases or QIID/H2 phases were reported.36 This raised a question regarding the existence of a nanoparticle with three coexisting phases. Consequently, we have surveyed these nanoparticles using cryo-TEM, however, no such nanoparticles were found. 14-20 are cis FAs with more than one double bond. Among these FAs, only the phase behaviour of MO nanoparticles added with 14 (Linoleic acid, cis-18:2) is similar to that of FAs with one double bond. As the concentration of 14 increased, the nanoparticles went through a phase sequence from QIIP QIID H2 L2. For cis FAs 15-20, the phase transition from QIIP to QIID occurred at low FA concentration and the window in which the two phases coexist is wider than that for other FAs (1-14) with lower degree of unsaturation. For example, in MO nanoparticles added with 18 (Arachidonic acid, cis-20:4), the QIID/QIIP coexistence was observed up to a rMO = 0.22 whereas this value for FAs 1-14 was less than 0.144. Curiously, the nanoparticles added with 15-20 did not transform into a hexagonal phase as the FA concentration increased. Instead, the SAXS profiles of these nanoparticles showed a single strong peak at concentrations higher than rMO = 0.271 on top of a broad peak (Figure S4a). The broad peak is typical of a L2 phase, which has no long range order. However, phase identification from the single strong peak is difficult due to no visible 14 ACS Paragon Plus Environment

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secondary peaks. Upon further investigation using cryo-TEM, it is apparent that the solution consists of sponge phase nanoparticles (L3) and multilamellar vesicles (Lα) in addition to microemulsions (L2) (Figure S4b). When the FA concentration was further increased, L2 phase was found in MO nanoparticles added with 15-18. The sponge phase nanoparticles (L3) are usually regarded as swollen cubic phase, which represent the isotropic liquid phase between Lα and cubic phase. 44, 45 However, there have been reports showing L3 sponge phase as an intermediate of the transition between H2 and L2 phase.46 The “missing” H2 phase here could be explained when considering the packing frustration. The concept of packing frustration is based on the idea of the optimized tiling (packing) of elements of uniform geometry, for example, cylinders into hexagonally close packed symmetries (hcp).24 Such arrangement results in “void” space that has to be filled by amphiphile alkyl chains that must extend beyond their preferred conformation. Previous studies have shown that by adding oil into the “void” volume, relief of the packing frustration of the chains could be achieved.47, 48 For cis FAs with a high level of unsaturation (15-20), the kinks in their structure may have resulted in (1) bent molecules with shorter effective chain length and higher cpp and (2) a hydrocarbon chain that is unable to fully stretch to fill the “void” space, hence, no H2 phase is formed. nanoparticles.


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Figure 4. Schematic representation of the effect of increasing concentration of fatty acid on molecular packing, surface curvature, and the phase behaviour of MO and PHYT Similarly to the addition of oil, temperature is known to have a strong effect on the formation of mesophases in these types of systems. When temperature rises, the fluidity of the hydrocarbon chain increases, leading to a larger effective tail volume and a higher cpp. Consequently, increasing temperature is often associated with the formation of phases with higher negative surface curvature.49 The partial phase diagrams of MO-FA nanoparticles at 37oC and 60oC are provided in Figure S5 and Figure S6, respectively. It is evident that the phase diagram is shifted through a phase sequence from QIIP QIID H2 L2. At this 60oC, the presence of Lc phase is no longer detected. This is likely because 60oC is higher than the melting points of all studied FAs. Similarly, the I2 phase is replaced by L2 in MO nanoparticles added with FAs 9-13. Lattice parameter of MO-FA nanoparticles The lattice parameter (LP) for each mesophase was calculated from the SAXS data. LP is plotted against rMO and presented in Figure 5. It has been shown before that MO nanoparticles stabilised with Pluronic F127 in water exhibit a QIIP phase with lattice parameter around 145Å.39 As the concentration of FA increases, the LP of the nanoparticle 16 ACS Paragon Plus Environment

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gradually decreases until a second phase appears. This is a general trend with all FAs studied here, with the exception of a few FAs with a high degree of unsaturation such as 16 and 19. In any case, the LP of QIIP, QIID, and H2 range from around 120 Å -145 Å, 80 Å – 110 Å, and 50 Å - 65 Å, respectively. These values cluster around the expected LPs for cubic and hexagonal phases of MO. 27 Previously, several theoretical models were developed to determine the water channel size from the LP data. For example, water channel radius of a cubic structure can be calculated based on minimal surface theory, which gives: ‫ݎ‬௪ = ቀ−

ఙ

ଵ/ଶ

ቁ ଶగఞ

ܽ − ݈ , where χ is

Euler-Poincaré characteristic and σ is the ratio of the minimal surface in a unit cell to the value (unit cell volume)2/3; a and l are lattice parameter of the cubic phase and the monolayer thickness respectively.20, 50 Using this approach, the water channel radii of QIIP and QIID phase are rw = (0.306)a – l and rw = (0.391)a – l, respectively. If we assume that l is a constant in excess water condition, the decrease of LP due to increasing FA content in nanoparticles leads to smaller water channel size in cubic phase. This observation has several implications to the applicability of these lipid nanoparticles. Indeed, the relative size of a compound to the water channel will determine whether it can reside in the water channel or not. For example, Pluronic F127 induced phase change in MO from QIID to QIIP but not in Phytantriol. This was shown to be due to the larger water channel size of MO compared to that of Phytantriol, which led to the distribution of F127 inside MO water channels, reducing interfacial curvature and induce phase transition.51 This size-dependent encapsulation is also applied for small molecular drugs, proteins, peptides, DNA and siRNA. The relative size of the encapsulated compounds to the water channel size also has significant influence on the release of the compounds.4 For soluble compounds whose release rate is controlled by diffusion, the smaller the compound the faster the release rate. Similarly, it is expected that retardation in diffusion occurs more readily in matrices with smaller water channel size. 17 ACS Paragon Plus Environment

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Figure 5. Lattice parameter (LP) of MO nanoparticulate dispersion added with increasing amount of unsaturated fatty acids. Lattice parameters of several mesophases including primitive cubic (QIIP of Im3m space group,

), diamond cubic (QIID of Pn3m space group,

), hexagonal (H2, ), micellar cubic (I2 of Fd3m space group, lamellar crystal (Lc,

), microemulsion (L2,

), and

) was determined by SAXS. A nanoparticle solution ( ) with mixed 18 ACS Paragon Plus Environment

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phases of L2, sponge phase (L3) and fluid lamellar phase (Lα) was also detected. Since the microemulsion phase (L2) lacks long range order, the correlation distances were calculated instead of lattice parameter. The coexistence of two cubic phases QIIP and QIID is an intriguing aspect that needs to be emphasised. Theoretically, the P-type and D-type minimal surfaces are related through the so-called Bonnet transformation,52, 53 which indicates that minimal surfaces can be isometrically bent without stretching into one another while preserving the Gaussian curvature at all points. According to the minimal surface theory, the LP ratio of Bonnet related P-type and D-type surfaces should be 1.28. 25 In MO nanoparticles with coexisting QIIP and QIID, we found that the LP of each phase varied with the FA content, however, the LP ratio remained relatively unchanged. The average LP ratios of QIIP/QIID (γP-D) for samples where coexisting cubic phases were detected were calculated and presented in Table 2. The LP ratios γP-D for MO nanoparticles spread from 1.29 to 1.35, slightly larger than the theoretical value of 1.28. Our finding here supports several previous studies in which γP-D is found to be around 1.33. 33, 39, 54, 55, 56, 57 The results presented here are consistent with the existence of periodic minimal surfaces within the formulated nanoparticles. Five occurrence of a micellar cubic phase I2 (space group Fd3m) was recorded in MO nanoparticles added with FAs 9-15. The LP of these I2 phases appeared to be dependent of chain length. As the chain length increased from C18 to C24, the LP of the I2 phase also gradually increased from 142 Å in system with FA 10 (Oleic acid) to a maximum of 166 Å in system with FA 13 (Nervonic acid).


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Table 2. Average lattice parameter ratios for coexisting QIIP/QIID (γP-D) Fatty acid 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Name Palmitelaidic acid Elaidic acid trans Vaccenic acid trans Gondoic acid Brassidic acid Linoelaidic acid Palmitoleic acid Rumenic acid Vaccenic acid Oleic acid Gondoic acid Erucic acid Nervonic acid Linoleic acid α-Linolenic acid γ-Linolenic acid ETA Arachidonic acid EPA DHA

Structure

γP-D

trans-16:1, n-7 trans -18:1, n-9 trans -18:1, n-7 trans -20:1, n-9 trans -22:1, n-9 trans -18:2, n-6 cis-16:1, n-7 cis, trans-18:2, n-7 cis -18:1, n-7 cis -18:1, n-9 cis -20:1, n-9 cis -22:1, n-9 cis -24:1, n-9 cis -18:2, n-6 cis -18:3, n-3 cis -18:3, n-6 cis -20:3, n-3 cis -20:4, n-6 cis -20:5, n-3 cis -22:6, n-3

1.35 1.31 1.34 1.32 ± 0.03 1.32 ± 0.01 1.30 1.34 1.34 1.30 ± 0.03 1.33 ± 0.03 1.33 ± 0.06 1.30 ± 0.01 1.30 ± 0.01 1.33 ± 0.02 1.33 ± 0.01 1.33 ± 0.02 1.32 ± 0.02 1.32 ± 0.01 1.29 ± 0.06

Phase behaviour of PHYT-FA nanoparticles Unlike MO, PHYT’s isoprenoid type chain contains no double bond. However, due to the branching in the hydrocarbon backbone, PHYT molecule can be described as “banana shaped” with a strong tendency to form non-lamellar mesophase structures. 22, 58 Bulk PHYT in excess water showed an inverse bicontinuous cubic symmetry of diamond type (QIID). This QIID structure is preserved when PHYT is dispersed and stabilised with Pluronic F127 up to 10% weight of PHYT. 32 This behaviour is different from that of MO, which changes from Pn3m (QIID) symmetry in bulk to Im3m (QIIP) symmetry in dispersion in the presence of 10% w/w F127.51 The partial phase diagram of PHYT nanoparticles added with unsaturated FAs at 25oC is presented in Figure 6. Overall, no obvious phase separation was detected. It is clear that within the studied compositional space, the phase behaviour of PHYT is much less complex with fewer lyotropic liquid crystalline polymorphic states compared to that of MO


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nanoparticles. At low FA concentration, all nanoparticles exhibit a QIID phase, the same as the PHYT nanoparticles without FA. Similar to the case of MO nanoparticles, the addition of unsaturated FAs increases the Gaussian curvature of PHYT membrane surfaces. This is evident from the phase sequence from QIID to H2 and eventually L2 with increasing FA content. Notably, the phase diagram of PHYT nanoparticles is dominated by H2 phase, which is present in all samples, spanning a large concentration window from rPHYT around 0.32 to 0.64. The H2 phase window is much larger in nanoparticles with trans FAs (1-6). Lamellar crystal phase (Lc) is observed in PHYT nanoparticles with 2, 3, and 5 trans FAs. This phase behaviour again resembles that of PHYT nanoparticles with saturated FAs with chainlength longer than C12.39 Compared to the trans FAs, the cis FAs are readily induce a phase transition in PHYT nanoparticles from H2 to the fluid isotropic phase L2. This reaffirms the notion that effective cpp of cis FAs is generally larger than that of trans FAs. An increase in temperature is also expected to have an influence on PHYT nanoparticle phase behaviour. The partial phase diagrams of PHYT nanoparticles with unsaturated FAs at 37oC and 60oC are provided in Figure S7 and Figure S8, respectively. As expected, the higher temperature drives the system toward mesophases with higher negative interfacial curvatures. This is clear from the replacement of QIID phases by H2 phases and associated higher effective cpp. Additionally, Lc phase is no longer detected in nanoparticles with 2, 3, and 5 trans FAs, most likely because 60oC is higher than the melting point of all studied FAs.


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Figure 6. Partial phase diagram PHYT nanoparticles with increasing amount of unsaturated FAs at 25oC. The list of twenty unsaturated FAs is provided in Table 1. The FA content in the mixture is represented by rPHYT, which is defined as the molar ratio of FA to PHYT. The lattice parameters (LPs) of PHYT nanoparticles with unsaturated FAs at 25oC are presented in Figure 7. The PHYT nanoparticles without FAs showed a QIID phase with a LP of around 66Å, similar to what has been reported. 32, 59 This QIID LP is smaller than that of MO QIID nanoparticles observed above, which ranged from 82 Å to 111 Å depending on the FA concentration and FA molecular structure. When the FA content increases, the LP of PHYT nanoparticles decreases to around 63 Å, at which a phase transition from QIID to H2 22 ACS Paragon Plus Environment

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occurred. At the transition point, the LP of the H2 phase is around 48-49 Å. These LP values for QIID and H2 phases are very close to those reported in PHYT-saturated FAs nanoparticle systems at the same temperature.39 These results suggest that the LP of PHYT nanoparticles at the phase transition point is independent of the FAs molecular structure or the degree of unsaturation. As the concentration of FA further increases, the LP of H2 phase also decreases and eventually the nanoparticles lose their long range order and transition into L2 phase. For all PHYT nanoparticles, at the transition point from H2 to L2 phase, the LP of H2 phase is around 43 Å.


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Figure 7. Lattice parameter (LP) of PHYT nanoparticulate dispersions with increasing amount of unsaturated fatty acids. Lattice parameters of several mesophases including diamond cubic (QIID of Pn3m space group, ), hexagonal (H2, ), microemulsion (L2,

),

and lamellar crystal (Lc, ) is determined by SAXS. Since the microemulsion (L2) lacks long range order, the correlation distances were calculated instead of lattice parameter.


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Conclusion In summary, we have formulated and studied the phase behaviour of self-assembled internally ordered lipid nanoparticles consisting of either MO or PHYT and unsaturated FAs. The study exemplified the benefit of high throughput methodologies, which allow us to both formulate and then characterize a large number of samples. The results illustrate that temperature, FA concentration, and FA molecular structure all have direct influence on the mesophase and lattice parameter of the nanoparticles. In the presence of increasing amounts of FAs, the effective cpps of both MO/FA and PHYT/FA systems increase, which leads to a phase transition process toward mesophases with higher Gaussian negative surface curvatures. In the studied FA concentration range MO nanoparticles transformed from QIIP QIID H2 L2. Micellar cubic phase I2 is found in several MO nanoparticle formulations in between H2 and L2 phase. For PHYT the phase sequence was QIID H2 L2. The phase diagrams and the calculated lattice parameters (LP) suggest gradual transitions with coexistence of mixed phases as the FA concentration increases. Notably, mixed SAXS signals of QIIP/QIID/H2 were detected in MO nanoparticles with FA 13 (erucic acid). However, no nanoparticles with three coexisting phases were found in cryo-TEM. Additionally, the LP ratios of the two cubic phases (γP−D) were calculated to be between 1.29 – 1.35. These γP−D values are consistent with the transformation between QIIP and QIID following the theoretical Bonnet transition. This study also emphasizes the complex phase behaviour of self-assembled lipid systems with multiple components. As the requirement for multiple functionalities in drug delivery systems increases, a move beyond the binary compositional spaces is inevitable.27 In such scenario, the material library, the characterisation methods, and insights described herein may be valuable.


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Supporting Information Representative hydrodynamic diameter, polydispersity index, and SAXS patterns of MO-FA nanoparticles. SAXS profile and cryo-TEM images of MO nanoparticles with FA 18 (Arachidonic acid, cis-20:4) showing the presence of nanoparticles with sponge phase (L3) and multilamellar phase (Lα). Partial phase diagrams of MO-FA and PHYT-FA at temperatures from 37oC and 60oC. Tables with detailed compositions of MO-FA and PHYTFA nanoparticles. This material is available free of charge via the Internet. Acknowledgements N.T. is currently a RMIT University Vice-Chancellor’s Research Fellow and was supported by the Science and Industry Endowment Fund (SIEF) postdoctoral fellowship. This research includes work undertaken on the SAXS/WAXS beamline at the Australian Synchrotron, ANSTO, Victoria, Australia. Conflict of interest The authors declare no conflict of interest.


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References 1. Mulet, X.; Boyd, B. J.; Drummond, C. J. Advances in drug delivery and medical imaging using colloidal lyotropic liquid crystalline dispersions. Journal of colloid and interface science 2013, 393, 1-20. 2. Angelov, B.; Angelova, A.; Filippov, S. K.; Drechsler, M.; Štěpánek, P.; Lesieur, S. Multicompartment Lipid Cubic Nanoparticles with High Protein Upload: Millisecond Dynamics of Formation. ACS nano 2014, 8 (5), 5216-5226. 3. Angelova, A.; Angelov, B.; Mutafchieva, R.; Lesieur, S.; Couvreur, P. Self-assembled multicompartment liquid crystalline lipid carriers for protein, peptide, and nucleic acid drug delivery. Accounts of chemical research 2010, 44 (2), 147-156. 4. Clogston, J.; Caffrey, M. Controlling release from the lipidic cubic phase. Amino acids, peptides, proteins and nucleic acids. Journal of controlled release 2005, 107 (1), 97-111. 5. Nguyen, T.-H.; Hanley, T.; Porter, C. J.; Boyd, B. J. Nanostructured liquid crystalline particles provide long duration sustained-release effect for a poorly water soluble drug after oral administration. Journal of controlled release 2011, 153 (2), 180-186. 6. Tarahovsky, Y. S.; Koynova, R.; MacDonald, R. C. DNA release from lipoplexes by anionic lipids: correlation with lipid mesomorphism, interfacial curvature, and membrane fusion. Biophysical journal 2004, 87 (2), 1054-1064. 7. Koltover, I.; Salditt, T.; Rädler, J. O.; Safinya, C. R. An inverted hexagonal phase of cationic liposome-DNA complexes related to DNA release and delivery. Science 1998, 281 (5373), 78-81. 8. Fong, C.; Le, T.; Drummond, C. J. Lyotropic liquid crystal engineering–ordered nanostructured small molecule amphiphile self-assembly materials by design. Chemical Society Reviews 2012, 41 (3), 1297-1322. 9. Fong, W.-K.; Hanley, T.; Boyd, B. J. Stimuli responsive liquid crystals provide ‘ondemand’drug delivery in vitro and in vivo. Journal of Controlled Release 2009, 135 (3), 218-226. 10. Fong, W.-K.; Negrini, R.; Vallooran, J. J.; Mezzenga, R.; Boyd, B. J. Responsive selfassembled nanostructured lipid systems for drug delivery and diagnostics. Journal of Colloid and Interface Science 2016, In Press. 11. Meikle, T. G.; Yao, S.; Zabara, A.; Conn, C. E.; Drummond, C. J.; Separovic, F. Predicting the release profile of small molecules from within the ordered nanostructured lipidic bicontinuous cubic phase using translational diffusion coefficients determined by PFG-NMR. Nanoscale 2017, 9 (7), 2471-2478. 12. Phan, S.; Fong, W.-K.; Kirby, N.; Hanley, T.; Boyd, B. J. Evaluating the link between selfassembled mesophase structure and drug release. International journal of pharmaceutics 2011, 421 (1), 176-182. 13. Falchi, A. M.; Rosa, A.; Atzeri, A.; Incani, A.; Lampis, S.; Meli, V.; Caltagirone, C.; Murgia, S. Effects of monoolein-based cubosome formulations on lipid droplets and mitochondria of HeLa cells. Toxicology Research 2015, 4, 1025-1036. 14. Murgia, S.; Falchi, A. M.; Mano, M.; Lampis, S.; Angius, R.; Carnerup, A. M.; Schmidt, J.; Diaz, G.; Giacca, M.; Talmon, Y. Nanoparticles from lipid-based liquid crystals: emulsifier influence on morphology and cytotoxicity. The Journal of Physical Chemistry B 2010, 114 (10), 3518-3525. 15. Shen, H.-H.; Crowston, J. G.; Huber, F.; Saubern, S.; McLean, K. M.; Hartley, P. G. The influence of dipalmitoyl phosphatidylserine on phase behaviour of and cellular response to lyotropic liquid crystalline dispersions. Biomaterials 2010, 31 (36), 9473-9481. 16. Tran, N.; Mulet, X.; Hawley, A. M.; Hinton, T. M.; Mudie, S. T.; Muir, B. W.; Giakoumatos, E. C.; Waddington, L. J.; Kirby, N. M.; Drummond, C. J. Nanostructure and Cytotoxicity of SelfAssembled Monoolein-Capric Acid Lyotropic Liquid Crystalline Nanoparticles. RSC Advances 2015, 5 (34), 26785-26795. 17. Zhai, J.; Suryadinata, R.; Luan, B.; Tran, N.; Hinton, T.; Ratcliffe, J.; Hao, X.; Drummond, C. J. Amphiphilic brush polymers produced by the RAFT polymerisation method stabilise and reduce the cell cytotoxicity of lipid lyotropic liquid crystalline nanoparticles. Faraday Discussions 2016, 191, 545-563. 18. Tran, N.; Bye, N.; Moffat, B. A.; Wright, D. K.; Cuddihy, A.; Hinton, T. M.; Hawley, A. M.; Reynolds, N. P.; Waddington, L. J.; Mulet, X. Dual-modality NIRF-MRI cubosomes and hexosomes: 27 ACS Paragon Plus Environment

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High throughput formulation and in vivo biodistribution. Materials Science and Engineering: C 2016, 71, 584-593. 19. Briggs, J.; Chung, H.; Caffrey, M. The temperature-composition phase diagram and mesophase structure characterization of the monoolein/water system. Journal de Physique II 1996, 6 (5), 723-751. 20. Kulkarni, C. V.; Wachter, W.; Iglesias-Salto, G.; Engelskirchen, S.; Ahualli, S. Monoolein: a magic lipid? Physical Chemistry Chemical Physics 2011, 13 (8), 3004-3021. 21. Hato, M.; Yamashita, J.; Shiono, M. Aqueous phase behavior of lipids with isoprenoid type hydrophobic chains. The Journal of Physical Chemistry B 2009, 113 (30), 10196-10209. 22. Barauskas, J.; Landh, T. Phase behavior of the phytantriol/water system. Langmuir 2003, 19 (23), 9562-9565. 23. Luzzati, V.; Spegt, P. Polymorphism of lipids. Nature 1967, 215, 701-704. 24. Seddon, J.; Templer, R. Polymorphism of lipid-water systems. Handbook of biological physics 1995, 1, 97-160. 25. Hyde, S. T. Identification of lyotropic liquid crystalline mesophases. Handbook of applied surface and colloid chemistry 2001, 2, 299-332. 26. Shearman, G.; Ces, O.; Templer, R.; Seddon, J. Inverse lyotropic phases of lipids and membrane curvature. Journal of Physics: Condensed Matter 2006, 18 (28), S1105. 27. van‘t Hag, L.; Gras, S. L.; Conn, C. E.; Drummond, C. J. Lyotropic liquid crystal engineering moving beyond binary compositional space–ordered nanostructured amphiphile self-assembly materials by design. Chemical Society Reviews 2017, 46 (10), 2705-2731. 28. Borné, J.; Nylander, T.; Khan, A. Phase behavior and aggregate formation for the aqueous monoolein system mixed with sodium oleate and oleic acid. Langmuir 2001, 17 (25), 7742-7751. 29. Caboi, F.; Amico, G. S.; Pitzalis, P.; Monduzzi, M.; Nylander, T.; Larsson, K. Addition of hydrophilic and lipophilic compounds of biological relevance to the monoolein/water system. I. Phase behavior. Chemistry and physics of lipids 2001, 109 (1), 47-62. 30. Angelov, B.; Angelova, A.; Ollivon, M.; Bourgaux, C.; Campitelli, A. Diamond-type lipid cubic phase with large water channels. Journal of the American Chemical Society 2003, 125 (24), 7188-7189. 31. Negrini, R.; Mezzenga, R. Diffusion, molecular separation, and drug delivery from lipid mesophases with tunable water channels. Langmuir 2012, 28 (47), 16455-16462. 32. Dong, Y.-D.; Larson, I.; Hanley, T.; Boyd, B. J. Bulk and dispersed aqueous phase behavior of phytantriol: effect of vitamin E acetate and F127 polymer on liquid crystal nanostructure. Langmuir 2006, 22 (23), 9512-9518. 33. Yaghmur, A.; Sartori, B.; Rappolt, M. Self-assembled nanostructures of fully hydrated monoelaidin–elaidic acid and monoelaidin–oleic acid systems. Langmuir 2012, 28 (26), 10105-10119. 34. Aota-Nakano, Y.; Li, S. J.; Yamazaki, M. Effects of electrostatic interaction on the phase stability and structures of cubic phases of monoolein/oleic acid mixture membranes. Biochimica et Biophysica Acta (BBA)-Biomembranes 1999, 1461 (1), 96-102. 35. Salentinig, S.; Sagalowicz, L.; Glatter, O. Self-Assembled Structures and p K a Value of Oleic Acid in Systems of Biological Relevance. Langmuir 2010, 26 (14), 11670-11679. 36. Tran, N.; Mulet, X.; Hawley, A.; Conn, C. E.; Zhai, J.; Waddington, L. J.; Drummond, C. J. First Direct Observation of Stable Internally Ordered Janus Nanoparticles Created by Lipid SelfAssembly. Nano letters 2015, 15 (6), 4229-4233. 37. Zhai, J.; Tran, N.; Sarkar, S.; Fong, C.; Mulet, X.; Drummond, C. J. Self-assembled Lyotropic Liquid Crystalline Phase Behavior of Monoolein–Capric Acid–Phospholipid Nanoparticulate Systems. Langmuir 2017, 33 (10), 2571-2580. 38. Razumas, V.; Talaikytedot, Z.; Barauskasa, J.; Larsson, K.; Miezis, Y.; Nylander, T. Effects of distearoylphosphatidylglycerol and lysozyme on the structure of the monoolein-water cubic phase: X-ray diffraction and Raman scattering studies. Chemistry and physics of lipids 1996, 84 (2), 123138. 39. Tran, N.; Hawley, A.; Zhai, J.; Muir, B. W.; Fong, C.; Drummond, C. J.; Mulet, X. Highthroughput screening of saturated fatty acid influence on nanostructure of lyotropic liquid crystalline lipid nanoparticles. Langmuir 2016, 32 (18), 4509-4520.


Page 28 of 31

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Langmuir

40. Funari, S. S.; Barceló, F.; Escribá, P. V. Effects of oleic acid and its congeners, elaidic and stearic acids, on the structural properties of phosphatidylethanolamine membranes. Journal of lipid research 2003, 44 (3), 567-575. 41. Roach, C.; Feller, S. E.; Ward, J. A.; Shaikh, S. R.; Zerouga, M.; Stillwell, W. Comparison of cis and trans fatty acid containing phosphatidylcholines on membrane properties. Biochemistry 2004, 43 (20), 6344-6351. 42. Seddon, J. M.; Squires, A. M.; Conn, C. E.; Ces, O.; Heron, A. J.; Mulet, X.; Shearman, G. C.; Templer, R. H. Pressure-jump X-ray studies of liquid crystal transitions in lipids. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 2006, 364 (1847), 2635-2655. 43. Nakano, M.; Teshigawara, T.; Sugita, A.; Leesajakul, W.; Taniguchi, A.; Kamo, T.; Matsuoka, H.; Handa, T. Dispersions of liquid crystalline phases of the monoolein/oleic acid/Pluronic F127 system. Langmuir 2002, 18 (24), 9283-9288. 44. Ridell, A.; Ekelund, K.; Evertsson, H.; Engström, S. On the water content of the solvent/monoolein/water sponge (L 3) phase. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2003, 228 (1), 17-24. 45. Cherezov, V.; Clogston, J.; Papiz, M. Z.; Caffrey, M. Room to move: crystallizing membrane proteins in swollen lipidic mesophases. Journal of molecular biology 2006, 357 (5), 1605-1618. 46. Angelov, B.; Angelova, A.; Mutafchieva, R.; Lesieur, S.; Vainio, U.; Garamus, V. M.; Jensen, G. V.; Pedersen, J. S. SAXS investigation of a cubic to a sponge (L 3) phase transition in selfassembled lipid nanocarriers. Physical Chemistry Chemical Physics 2011, 13 (8), 3073-3081. 47. Duesing, P.; Templer, R.; Seddon, J. Quantifying packing frustration energy in inverse lyotropic mesophases. Langmuir 1997, 13 (2), 351-359. 48. Shearman, G. C.; Khoo, B. J.; Motherwell, M.-L.; Brakke, K. A.; Ces, O.; Conn, C. E.; Seddon, J. M.; Templer, R. H. Calculations of and evidence for chain packing stress in inverse lyotropic bicontinuous cubic phases. Langmuir 2007, 23 (13), 7276-7285. 49. Qiu, H.; Caffrey, M. The phase diagram of the monoolein/water system: metastability and equilibrium aspects. Biomaterials 2000, 21 (3), 223-234. 50. Anderson, D. M.; Gruner, S. M.; Leibler, S. Geometrical aspects of the frustration in the cubic phases of lyotropic liquid crystals. Proceedings of the National Academy of Sciences 1988, 85 (15), 5364-5368. 51. Tilley, A. J.; Drummond, C. J.; Boyd, B. J. Disposition and association of the steric stabilizer Pluronic® F127 in lyotropic liquid crystalline nanostructured particle dispersions. Journal of colloid and interface science 2013, 392, 288-296. 52. Hyde, S. T. Bicontinuous structures in lyotropic liquid crystals and crystalline hyperbolic surfaces. Current Opinion in Solid State and Materials Science 1996, 1 (5), 653-662. 53. Larsson, K.; Tiberg, F. Periodic minimal surface structures in bicontinuous lipid–water phases and nanoparticles. Current opinion in colloid & interface science 2005, 9 (6), 365-369. 54. Larsson, K. Two cubic phases in monoolein–water system. Nature 1983, 304 (5927), 664664. 55. Gustafsson, J.; Ljusberg-Wahren, H.; Almgren, M.; Larsson, K. Submicron particles of reversed lipid phases in water stabilized by a nonionic amphiphilic polymer. Langmuir 1997, 13 (26), 6964-6971. 56. Abraham, T.; Hato, M.; Hirai, M. Polymer‐Dispersed Bicontinuous Cubic Glycolipid Nanoparticles. Biotechnology progress 2005, 21 (1), 255-262. 57. Yaghmur, A.; De Campo, L.; Sagalowicz, L.; Leser, M. E.; Glatter, O. Control of the internal structure of MLO-based isasomes by the addition of diglycerol monooleate and soybean phosphatidylcholine. Langmuir 2006, 22 (24), 9919-9927. 58. Rizwan, S.; Dong, Y.-D.; Boyd, B.; Rades, T.; Hook, S. Characterisation of bicontinuous cubic liquid crystalline systems of phytantriol and water using cryo field emission scanning electron microscopy (cryo FESEM). Micron 2007, 38 (5), 478-485. 59. Rizwan, S.; Assmus, D.; Boehnke, A.; Hanley, T.; Boyd, B.; Rades, T.; Hook, S. Preparation of phytantriol cubosomes by solvent precursor dilution for the delivery of protein vaccines. European Journal of Pharmaceutics and Biopharmaceutics 2011, 79 (1), 15-22.


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Table of Content Graphic


Manipulating the ordered nanostructure of self-assembled monoolein

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