DANIELA F. COUTINHO* Supervisors: Nuno M. Neves, Manuela E. Gomes * [email protected]
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Transcript of DANIELA F. COUTINHO* Supervisors: Nuno M. Neves, Manuela E. Gomes * [email protected]
University of Minho
School of Engineering
3B’s Research Group
Uma Escola a Reinventar o Futuro – Semana da Escola de Engenharia – 24 a 27 de Outubro de 2011
DANIELA F. COUTINHO*
Supervisors: Nuno M. Neves, Manuela E. Gomes
PROCESSING A POLYELECTROLYTE COMPLEX HYDROGEL AT THE MICRO-SCALE
ACKNOWLEDGEMENTS
DFC acknowledges FCT and the MIT-Portugal Program for personal grant SFRH/BD/37156/2007.
CONCLUSIONS
We successfully fabricated a stable photocrosslinkable PEC hydrogel
using cationic CHT and photocrosslinkable anionic MeGG. This
biomaterial system is potentially useful for a variety of biomedical
applications simply by adjusting the microfabrication tools used.
INTRODUCTION
Natural tissues are structured at the micro-scale. Thus, a lot of effort
has been devoted to develop biomaterial systems enabling replicating
those natural structures in vitro. Microfabrication techniques have been
applied in the development of these biomaterials structures with tailored
architectural details. Hydrogels have been selected for the development
of engineered tissues, mainly due to their similarity with the extracellular
matrix (ECM) of tissues. Several mechanisms for the development of
hydrogels have been reported, namely the use of two oppositely
charged polyelectrolytes that complex when mixed together, forming a
physical hydrogel. This hydrogel is held together by molecular
entanglements that are reversible and can be disrupted by changes in
physical conditions (ionic strength, pH or temperature). Another key
feature of hydrogels is their ability to be micro-processed, allowing to
obtain biomaterials that replicate the micro-architecture of tissues.
MAIN GOAL
To develop a stable polyelectrolyte-complex hydrogel amenable to
microfabrication.
MATERIALS AND METHODS
Photolithography Microfluidics
Figure 5. Schematics of the microfabrication techniques used and Live/dead images of encapsulated rat cardiac fibroblasts
Chitosan - 1% (w/v) in acetic acid solution
Methacrylated Gellan Gum - 1% (w/v) in dionized water
Figure 4. TEM of the cross-section of the PEC hydrogel and confocal microscopy of the distribution of FITC-labeled CHT within a cross-section of the hydrogel.
Figure 3. FTIR and XPS analysis of the PEC hydrogel and the plain materials.
FTIR XPS
Figure 2. SEM of a cross-section of the PEC hydrogel (MeGG-CHT) and of the plain materials.
Figure 1. Schematics of the PEC hydrogel formation and representation of the electrostatic interactions between the polymers.
1st - Hydrogel formed through electrostatic interactions2nd - Hydrogel stabilized by UV
RESULTS AND DISCUSSION
Scanning electron microscopy (SEM) (Figure 2) showed a porous
structure with the presence of fibrous structures over the pores of the
PEC hydrogel that might be a result of the interaction between the
polymer chains of MeGG and CHT.
MeGG-CHT PEC hydrogel
The chemical structure of the PEC hydrogel (Figure 3) revealed the
presence of the absorption peaks characteristic of both raw polymers.
Analysis of the bulk of the hydrogel revealed that upon hydrogel
formation, the mixing of both polymers proceeded slowly. X-ray
photoelectron spectroscopy (XPS) (Figure 3) showed the presence of
protonated amines in the section of MeGG-CHT hydrogel, indicating the
migration of CHT to the interior of the apparent MeGG hydrogel.
MeGG-CHT MeGG-CHT sectionCHT
Transmission electron microscopy
(TEM) and confocal microscopy of
FITC-labeled CHT (Figure 4)
visually confirmed the presence of
CHT in the interior of the hydrogel.
The photocrosslinkable feature of MeGG enabled the formation of a
number of micro-scaled units. Encapsulated rat cardiac fibroblasts
showed to remain viable after the being exposed to the processing
methodologies used. Micro-building blocks with different shapes and
sizes were fabricated simply by changing a photomask (Figure 5).
These micro-units could potentially be used for replicating the micro-
environment features of tissues. On the other hand, the microfluidic
channel used to direct the formation of the PEC hydrogel resulted on
the engineering of a fibrous hydrogel that replicates at a micro-scale the
architecture of fiber bundles found in a variety of tissues (Figure 5).
Development of a MeGG-CHT PEC hydrogel (Figure 1). Morphological
and chemical characterization of PEC hydrogel. Rat cardiac fibroblasts
were isolated and encapasulated in MeGG before microfabrication. TEM Confocal