Pickering emulsions stabilized by polysaccharide
nanocrystals for controlled release applications
D. Saidane*, M. Costard‡, G. Ongmayeb‡ and I. Capron*
*INRA, UR1268 Biopolymères, Interactions et Assemblages, 44300 Nantes, France
‡Capsulæ, Rue de la Géraudière, 44322 Nantes, France
INTRODUCTION
Increasing environmental awareness is prompting researchers and industrialists to develop strategies for environmental sustainability by using processes and materials with low cost, energy consumption
and toxicity. As an example, emulsions, used in large application domains such as cosmetics, pharmaceuticals… usually use surfactants issued from the petro-chemical industry.
In this framework, it is now well established that surfactant free can be stabilized by dispersed solid particles to form the so-called Pickering emulsions for which colloidal-sized particles may be irreversibly
anchored at the oil/water interface revealing a very high emulsion stability. Yet, it was demonstrated in our team that direct oil-in-water (O/W) Pickering emulsions can be stabilized only by negatively
charged Cellulose Nanocrystals (CNC) or positively charged Chitin Nanocrystals (ChNC).
In this study, two series of O/W emulsions stabilized by the two different types of solid nanoparticules (cellulose and chitin nanocrystals) were prepared.
A dye (paprika) was dissolved in the oil phase. The control of the dye release has been monitored by modification of the droplets surface making the wall of the droplets thicker.
NATURAL POLYSACCHARIDES
CHITIN
CELLULOSE
Chitin is a characteristic component of the cell walls of fungi, the exoskeletons of
arthropods such as crustaceans (crabs, lobsters and shrimps) and insects.
Cellulose is an important structural component of the primary cell wall of
green plants
● Abundance
● High-scale production
● Low toxicity
● Biodegradability
Linear chain of linked Nacetyl D-glucosamine
● Biocompatibility
Linear chain of linked D-glucose units
PREPARATION OF NANOCRYSTALS
POLYSACCHARIDES
PREPARATION
NANOCRYSTALS
PREPARATION
OFOF
THE
SURFACTANTPOLYSACCHARIDES
FREE PICKERING
EMULSIONS
Interfacial nanoparticles
Sulfated Cellulose
nanocrystals
Hexadecane
- - - - - - -- - - --- - - - - - - -
Hydrolyzed by 64 % H2SO4
70 °C / 40 min
Emulsification
Room T°
Nanocrystals in
Native cellulose from
L :150-200 nm
l :10-20 nm
cotton
10 m
Oil-in-water Pickering
emulsions
Chitin
Cellulose
suspension + NaCl
• time (> 1 year)
High stability
• temperature 4°C, 40°C or 2h à 80°C
• pH 1 to 12
Aminated Chitin
nanocrystals
RELEASE EXPERIMENTS
+
+
+ +
+
++ + + + +
++ +
+
+ + + +
Hydrolyzed by 3 N HCl
T°boiling / 90 min
Chitin powder from
shrimp shell
Two series of O/W emulsions stabilized by the two different types of solid nanoparticules (cellulose and chitin nanocrystals) were prepared
using a concentration of 5g/L in order to have a resistant shell. A dye (paprika) was dissolved in the oil phase and its delivery was studied.
Emulsion with NCC
(negatively charged) or
ChiNC (positively
charged) alone
L :150-200 nm
l :10-20 nm
Fast delivery of Paprika for NCC and
ChiNC (100% in less than 15 minutes)
Open structure: need to add a
EMULSION VS CONCENTRATION
Diameter
protection
Surface coverage
84% recouvrement
84% coverage
60
D(3,2) (µm)
50
40
Emulsion of NCC or ChiNC
coated with an alginate
(negatively charged) or
a chitosan (positively
charged) layer
The coating of alginate on chitin
reduces the releasing time
30
The releasing kinetic depends on
denser organization
20
alginate concentration
10
Not enough: Need to thicken more
0
0
2
4
6
8
10
CN concentration (g/L)
conc (g/L)
Stable drops were obtained (4 to 10 μm). The surface is not completely covered ;
Emulsion of CNC
coated with
multilayered
Chitosan / CNC
The coating of chitosan on cellulose
Porous drops
reduces the releasing time
Before centrifugation
The release is relatively slower
Drops highly stable at high
with chitosan-Cellulose multilayer
concentrations
Need to put more layer?
0.1 0.2 0.3 0.5 0.8
1
1.2 1.5
2
3
4
Crosslinking of the wall?
5 (g/L)
After centrifugation
CONCLUSION
Natural polysaccharides with their ecological properties can be viewed as new biobased materials with low environmental impact promoting
innovative functionality. We showed that it was possible to obtain highly stable oil-in-water Pickering emulsions stabilized only by unmodified
CNC or ChNC . The amazing properties of these systems in terms of stability and mechanical behavior for encapsulation of any oil, are due to
both of their anisotropic shape and the irreversible nature of such particles adsorption.
The structural properties of nanocrystals are combined to a layer-by-layer (LBL) approach for the fabrication of multilayer microcapsules using
nanocrystalline cellulose or chitin as one of the components of the assemby in order to delay the release time. The applicability of the
nanoassemblies as active component delivery carriers has been explored loading paprika.
REFERENCES

Kalashnikova, I.; Bizot, H.; Cathala, B.; Capron, I. Langmuir, 27, 7471–7479 (2011)

Perrin et al. Biomacromolecules, 15, 3766−3771 (2014)

Patent N° WO 10 55 836, Cathala, Capron et al. 2010

Bailly A., Quilliet C., Heux L., 247 th ACS National Meeting, Dallas (2012)