Interactions between polymeric surfactants and bile salts: new … · 2015-11-17 · Interactions...

Interactions between polymeric

surfactants and bile salts:

new routes for controlling lipid

digestion of oil-in-water emulsions

Amelia Torcello Gómez1

Julia Maldonado Valderrama2

Ana B. Jódar Reyes2

Timothy J. Foster1

1 2

Outline

Introduction and Aims

Experimental Section

Results and Discussion:

Interactions in aqueous phase

Interactions at the oil-water interface

Interactions in Pluronic-stabilised emulsions

Conclusions

Acknowledgements

2

Introduction

Controlling lipid digestion profiles would facilitate the development

of remodeled lipids with tailored properties:

Control of satiety

Delivery of bioactive components to specific locations

Lipids are present as O/W emulsions

3

Introduction Bile salts (BS) replace original emulsifier from the surface of

lipid droplets preparing the interface for lipolysis

lipid substrate

BS

lipase colipase

1. Adsorption of colipase in the presence of BS

hydrolysed lipids

2. Lipase coupling and lipolysis 3. Solubilisation of

hydrolysed lipids

mixed micelle

4

Stomach

Undispersed oil

Gastric lipase

Oil droplets

Pancreas

Small

intestine

Liver

Gall bladder

Bile salts (BS) replace original emulsifier from the surface of

lipid droplets preparing the interface for lipolysis

Lipolysis is an interfacial reaction that can be affected

by the presence of emulsifiers onto the oil-water interface:

either more surface active than BS

and/or resistant to displacement by BS

by events taking place in the bulk that may have an impact on the

interfacial properties

Introduction 5

Background Pluronics are promising surfactants opening up new horizons in the

control of lipid digestion (approved for oral intake by U.S. FDA)

Delay lipid digestion as compared with model emulsifiers (lecithin

or proteins)

Adsorbed layers provide a steric barrier which protects the o-w

interface from the action of BS and lipase

Oil droplets covered by larger Pluronics (F127) are digested at lower

rate and extent than those covered by smaller Pluronics (F68)

A. Torcello-Gómez, J. Maldonado-Valderrama, A. Martín-Rodríguez, D.J. McClements, Soft Matter 7 (2011) 6167.

M. Wulff-Pérez, J. de Vicente, A. Martín-Rodríguez, M.J. Gálvez-Ruiz, Int. J. Pharm. 423 (2012) 161.

PPO

PEO PEO

a a

b b = 65

a = 100

F127

b = 29

a = 75

F68

6

M. Wulff-Pérez, M.J. Gálvez-Ruiz, J. de Vicente, A. Martín-Rodríguez, Food Res. Int. 43 (2010) 1629.

Aims Analyse the bulk interactions between Pluronics (F127 or

F68) and a bile salt (NaTDC) in Pluronic-stabilised emulsions

Evaluate the impact of these interactions on the o-w interface in emulsions

Study in aqueous phase

Study at oil-water interface

Effect of the molecular differences of both Pluronics

Deepen the understanding of the mechanisms underlying lipid digestion of Pluronic-stabilised emulsions

7

Experimental Section: Materials

Pluronics: non-ionic triblock copolymers

F68: MW=8400 g/mol, 16% PPO

F127: MW=12600 g/mol, 25% PPO

Bile salt: NaTDC, MW=521.7 g/mol

Aqueous phase: 1.13 mM phosphate buffer, pH 7

Oil phase: highly refined and purified Olive Oil

γ0 = 29.5 mN/m, T = 20 °C

(density: 0.91 g/cm3, mean MW 800 g/mol)

Emulsion preparation: ULTRA-TURRAX® homogenizer (IKA® T18 basic)

10 wt% oil phase

90 wt% F68 or F127 aqueous phase at 1 wt%

PPO PEO PEO

8

Experimental Section: Micro-DSC

Micro-Differential Scanning Calorimetry: DSC III Setaram

Sample weight: 800 mg

Scanning rate: 1 ºC/min

Heating/cooling cycles: 10-90 ºC

Interactions between Pluronic and NaTDC in aqueous phase and in

Pluronic-stabilised emulsions

9

Experimental Section: The Octopus

Pendant Drop Surface Film Balance equipped with subphase multi-

exchange device

Cabrerizo-Vílchez et al. Patent submitted (P201001588)

Octopus Software-Dinaten© Dr. Juan Antonio Holgado-Terriza

10

Operation

Double capillary Normal capillary is substituted by an

arrangement of two coaxial capillaries

Connected to both syringes by channels

of the 8 port-valve micro-injectors

Both syringes operate independently

Automatic, non-invasive and complete

exchange of the subphase of the drop with

different solutions

Pendant drop volume and interfacial area

are preserved during the subphase

exchange

Cabrerizo-Vilchez et al. Spanish Patent, registration number: P9801626.

Ferri, Kotsmar and Miller. From surfactant adsorption kinetics to asymmetric nanomembrane mechanics: Pendant drop

experiments with subphase exchange. Adv. Colloid Interface Sci., 2010.

11


Operation

Interfacial dilatational rheology

Small-amplitude < 10 % (Viscoelastic Linear Regime)

f = 0.1 Hz

9,6

10

10,4

10,8

3670 3720 3770

γ (

mN

/m)

t (s)

36

37

38

39

40

3670 3720 3770

A (

mm

2)

t (s)

ln

dE

d A

E* = E’ + iE’’ = + i2πf

12


Interactions at the o-w interface:

Sequential adsorption of Pluronics and NaTDC

Competitive adsorption of Pluronics and NaTDC

Record in-situ the interfacial tension during the whole process of

adsorption

Measure the dilatational elastic modulus at the end of each step of

adsorption

13


Micro-DSC

10 20 30 40 50-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

Heat F

low

(m

W)

Temperature (ºC)

1 wt% F127

heating

cooling

endo

40 50 60 70 80-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

Temperature (ºC)

1 wt% F68

heating

cooling

endo

Results: Interactions in aqueous phase

E. Hecht, H. Hoffmann, Langmuir, 10 (1994) 86.

P. Alexandridis, T. Nivaggioli, T.A. Hatton, Langmuir, 11 (1995) 1468.

A. Cabana, A. Aït-Kadi, J. Juhász, J. Colloid Interface Sci., 190 (1997) 307.

A.A. Barba et al., J. Applied Polymer Sci., 114 (2009) 688.

I. Boucenna et al., Langmuir, 26 (2010) 14430.

ΔH = 350 kJ/mol ΔH = 80 kJ/mol

14

Micro-DSC

10 20 30 40 50-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

Heat F

low

(m

W)

Temperature (ºC)

1 wt% F127

+ 5 mM NaTDC

heating

cooling

endo

40 50 60 70 80-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

Temperature (ºC)

1 wt% F68

+ 5 mM NaTDC

heating

cooling

endo

14


Micro-DSC

Lower NaTDC concentration seems to suppress micellization of Pluronic F68

10 20 30 40 50-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

Heat F

low

(m

W)

Temperature (ºC)

1 wt% F127

+ 5 mM NaTDC

+ 10 mM NaTDC

heating

cooling

endo

40 50 60 70 80-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

Temperature (ºC)

1 wt% F68

+ 5 mM NaTDC

+ 10 mM NaTDC

heating

cooling

endo

14


Micro-DSC

Lower NaTDC concentration seems to suppress micellization of Pluronic F68

F127 interacts with larger amount of NaTDC molecules

0,1 1 10 100

0

50

100

150

200

250

300

350

400 1 % F127

1 % F68

H(

kJ/m

ol)

[NaTDC] (mM)

15


Micro-DSC

Lower NaTDC concentration seems to suppress micellization of F68

F127 interacts with larger amount of NaTDC molecules

NaCl allows more compact arrangement of BS within mixed complexes

0,1 1 10 100

0

50

100

150

200

250

300

350

400 1 % F127

+ 0.15 M NaCl

1 % F68

+ 0.15 M NaCl

H(

kJ/m

ol)

[NaTDC] (mM)

15


Sequential adsorption of NaTDC and desorption

0 1000 2000 3000 4000 5000 60000

5

10

15

20

25

F127-covered interface


oil-water interface

(mN

/m)

t (s)

Pluronic

adsorption

subphase exchange by

NaTDCdesorption

Results: Interactions at the o-w interface

16

Sequential adsorption of NaTDC and desorption

STEPS 1 wt% Pluronic adsorption 10 mM NaTDC adsorption Desorption

Pluronic γ (mN/m) E (mN/m) γ (mN/m) E (mN/m) γ (mN/m) E (mN/m)

F68 13.0 ± 0.5 12 ± 1 10.0 ± 0.5 5 ± 1 15.0 ± 0.5 14 ± 1

F127 10.0 ± 0.5 12 ± 1 11.0 ± 0.5 6 ± 1 13.0 ± 0.5 14 ± 1

0 1000 2000 3000 4000 5000 60000

5

10

15

20

25



oil-water interface

(mN

/m)

t (s)

Pluronic

adsorption

subphase exchange by

NaTDCdesorption

F68 is more

susceptible to be

displaced by NaTDC

16


Competitive adsorption with NaTDC (1h)

1E-5 1E-4 1E-3 0,01 0,15

10

15

20

25

30

0.5 wt% F127

0.5 wt% F68

(m

N/m

)

[NaTDC] (M)

1E-5 1E-4 1E-3 0,01 0,10

5

10

15

0.5 wt% F127

0.5 wt% F68

E (

mN

/m)

[NaTDC] (M)

17


Competitive adsorption with NaTDC (1h)

1E-5 1E-4 1E-3 0,01 0,15

10

15

20

25

30

0.5 wt% F127

0.5 wt% F68

NaTDC

(m

N/m

)

[NaTDC] (M)

1E-5 1E-4 1E-3 0,01 0,10

5

10

15

0.5 wt% F127

0.5 wt% F68

NaTDC

E (

mN

/m)

[NaTDC] (M)

Pluronics compete with bile salts for the oil-water interface

F127 better competes for the oil-water interface with NaTDC

17


35 40 45 50 55 60 65 70 75 80-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Heat

Flo

w (

mW

)

Temperature (ºC)

emulsion stabilised by 1 wt% F68

15 20 25 30 35 40 45 50 55-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Heat

Flo

w (

mW

)

Temperature (ºC)


Micro-DSC

Results: Interactions in Pluronic-stabilised

emulsions

18

35 40 45 50 55 60 65 70 75 80-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Heat

Flo

w (

mW

)

Temperature (ºC)


35 40 45 50 55 60 65 70 75 80-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Temperature (ºC)

washed emulsion

35 40 45 50 55 60 65 70 75 80-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Temperature (ºC)

subnatant of washed emulsion

15 20 25 30 35 40 45 50 55-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Heat

Flo

w (

mW

)

Temperature (ºC)


15 20 25 30 35 40 45 50 55-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Temperature (ºC)

washed emulsion

15 20 25 30 35 40 45 50 55-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Temperature (ºC)


Micro-DSC

18 Results: Interactions in Pluronic-stabilised

emulsions

35 40 45 50 55 60 65 70 75 80-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Heat

Flo

w (

mW

)

Temperature (ºC)


+ 10 mM NaTDC

35 40 45 50 55 60 65 70 75 80-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Temperature (ºC)

washed emulsion

+ 10 mM NaTDC

35 40 45 50 55 60 65 70 75 80-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Temperature (ºC)


+ 10 mM NaTDC

15 20 25 30 35 40 45 50 55-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Heat

Flo

w (

mW

)

Temperature (ºC)


+ 10 mM NaTDC

15 20 25 30 35 40 45 50 55-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

endo

Temperature (ºC)


+ 10 mM NaTDC

Micro-DSC


emulsions

Cryo-SEM

F68 F127 10 μm 5 μm

F127 F68 10 μm 5 μm

+ NaTDC


emulsions

Conclusions Pluronics seem to prevent BS from adsorbing onto the surface

of oil droplets in emulsions due to a combination of complexation and competitive adsorption

Pluronics are also resistant to displacement by BS from the oil-water interface

The more hydrophobic and larger Pluronic (F127) better competes for the oil-water interface and interacts with greater amount of BS molecules

These findings are relevant to the rational design in the control of lipid digestion

Identifying functionalities of other potential (bio)polymers

Further work

20

A. Torcello-Gómez, J. Maldonado-Valderrama, A.B. Jódar-Reyes, T.J. Foster, Langmuir 29 (2013) 2520.

Further details

Acknowledgements

European Community’s FP7-PEOPLE-2012-IEF

under Grant Agreement No. 326581

Thank you for your attention

Interactions between polymeric surfactants and bile salts: new … · 2015-11-17 · Interactions...

Documents

Transcript of Interactions between polymeric surfactants and bile salts: new … · 2015-11-17 · Interactions...