1. A Facile Way to Fabricate Polyester Microcapsules
Xi Yu, Jintao Zhu* School of Chemistry and Chemical Engineering , Huazhong University of Science & Technology, Wuhan,
Introduction
Controlled Release Profile
Polymer microcapsules possess a large hollow space and could protect trapped species from the external environment and release them under specified conditions thus playing an important role in the fields of medicine, pesticide, food, and cosmetics, etc.
We introduce a facile way to fabricate biodegradable polyester microcapsules and explored the functionalization of the capsules
Is it possible to adjust the controlled process through regulating the morphology of the microcapsules?
(I)
(II)
(III)
(IV)
Fig 7. wall thickness/diameter relationship : PMMA (I, II); PDLLA (III); PLGA(IV)
Wall thicknesses of the capsules increase from dozens of to hundreds of nanometers as the average sizes of the capsules decrease.
Microcapsules(MCs)
(a)
(b)
(a)
(b)
Fig 1.PMMA( Mw=20k)
Fig 2. PLGA( Mw=400k)
(a)
(b)
(a)
(b)
Fig 3. PDLLA( Mw=500k)
Fig 4. Nanoscale PDLLA(a),PLGA(b) MCs
Fig 8. Controlled release of Cango Red from PDLLA capsules with different sizes.
MCs size in sevaral to dozens of micros are formed,with uniform wall thicknesses range from dozens to hundreds of nanometers.
Nanoscale MCs prepared from a mini-extruder device.
MCs are dyed with Nile Red.
MCs Functionalization
Proposed Formation Mechanism
(a)
(b)
Different kinds of nanoparticles could be co-incorporated into shell of the MCs.
Quantum dots and nanoparticles are chemically modified to seperate in oil phase
Fig 9. Quantum dots incorporated capsules
(b)
(c)
Fig 4. Sketch of proper formation progress and corresponding optical images
Polymers were dissolved in chloroform and then emulsified(Fig 1a)
Water molecules diffuse into the resulting emulsion droplets(Fig 1b)
Double emulsions formed(Fig 1d).
MCs obtained after organic solvent removal(Fig 1e).
Fig 10. Quantum dots and Fe3O4 nanoparticles co-incorporated capsules
Summary
This self-emulsification method could be applied to a range of biodegradable materials.
The wall thickness is tunable just by changing the size of the emulsions and microcapsules of different sizes generate diverse controlled release rates.
Small molucules(like nile red) or functional nanoparticles(like CdSe quantum dots and Fe3O4 nanoparticles) could be incorporated into the shell of the microcapsules.
Effect of AOT and Polymer Concentration
AOT 0.5 mg/mL
50μm
AOT 5 mg/mL
50μm
AOT 15 mg/mL
50μm
MCs formed within a range of polymer and AOT concentration (several to dozens of mg/mL).
Optimal concentrations of AOT and polymers lie in 5-10 mg/mL.
Fig 5. Microcapsules of different AOT concentration,PMMA10 mg/mL
References
PMMA 10mg/mL
50μm
PMMA 30mg/mL
50μm
PMMA 50mg/mL
50μm
[1] H.N. Yow, A.F. Routh, Soft Matter 2(11) (2006)
[2] J.T Zhu, R.C. Hayward, Angew. Chem., Int. Ed. 47(11) (2008)
[3] Yang, C. H,Huang, K. S, etc. Lab on a Chip 9(7) (2009)
Acknowledgment: We are grateful for the financial support provided by the Program of New Century Excellent Talents in University (NCET ) and Initiatory Financial Support from HUST ( )
Fig 6. Microcapsules of different polymer concentration,AOT10 mg/mL