Electrically conductive hydrogel with positively charged surfaces for nerve tissue engineering
Xifeng Liu, Michael J. Yaszemski and Lichun Lu
Departments of Physiology and Biomedical Engineering, and Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA.
bearing cell percentage for PC12 cells growing on the
Statement of Purpose: Nerve cells relay on
rGOaCNTpega-OPF-MTAC hydrogel.
electrical potential to conduct signals (Fig. 1a). Polymeric
nerve conduit is a promising strategy to provide axon
growth guidance thus facilitates nerve regeneration.
Previous work in our lab has found that the substrate
conductivity and surface charges could stimulate nerve
cell responses [1,2]. In this study, we successfully
constructed an electrically conductive oligo(polyethylene
glycol) fumarate (OPF) hydrogel incorporating
functionalized graphene oxide acrylate (GOa) sheets and
carbon nanotubes functionalized with poly(ethylene
glycol) acrylate chain (CNTpega) for nerve regeneration.
To further enhance cellular function, 2-(methacryloyloxy)
ethyl)-trimethyl ammoniumchloride (MTAC) was also
incorporated to provide positive charges to the composite
hydrogel. After reduction of GOa sheets, the final
obtained
rGOa-CNTpega-OPF-MTAC
composite
hydrogel were evaluated for stimulation of nerve cell
growth and neurite development (Fig. 1b).
Methods: Components used for fabrication of hydrogels
were presented in Fig. 1c. The neutral OPF hydrogel,
positively charged OPF-MTAC hydrogel, conductive
rGOaCNTpega-OPF
hydrogel,
and
composite
rGOaCNTpega-OPF-MTAC hydrogel with electrical
conductivity and positively charged surface were
fabricated using chemical crosslinking methods similar to
our previous report [3]. Briefly, OPF polymer together
with required components were dissolved in deioinized
water followed by the addition of ammonium persulfate
(APS)
and
N,N,N′,N′-tetramethylethylenediamine
(TEMED) for chemical crosslinking for one hour at 60
°C.
To
make
GOa-CNTpega-OPF
and
GOa-CNTpega-OPF-MTAC hydrogels conductive, these
Figure 1. (a) Signal conduction in neuronal cells through
two types of hydrogels were soaked in L-ascorbic acid
polarization and depolarization in ionic channels. (b) The
solution for 2 days. PC12 cells cultured in Dulbecco’s
materials used for fabrication of composite hydrogels. (c)
Modified Eagle’s Medium (DMEM) supplemented with
The obtained four types of hydrogels. (d) PC12 cell
5% fetal bovine serum, 10% horse serum, 0.5%
growth on these hydrogels stained with rhodamine
streptomycin/penicillin and 50 ng mL-1 NGF were seeded
phalloidin (red) and DAPI (blue). (f) The cell spreading
on these hydrogels. The cellular proliferation, spreading
area and (g) neurite bearing cell percentage of PC12 cells
area, and neurite development ability were evaluated.
seeding on these hydrogels.
Results: Four types of hydrogels were successfully
Conclusions: Hydrogels with inherent electrical
fabricated. As shown in Fig. 1d, the neutral OPF hydrogel
conductivity and/or positively charged surface were
is transparent composed solely of the polymeric network.
successfully fabricated Enhanced proliferation, spreading
The OPF-MTAC is transparent with positive charges
and neurite development were demonstrated for PC12
originated from the pendant MTAC chains. After
cells growing on the composite hydrogel with both
incorporating crosslinkable GOa sheets and CNTpega
conductivity and positive charged surface. These results
tubes,
both
rGOaCNTpega-OPF
and
showed that rGOaCNTpega-OPF-MTAC hydrogels have
rGOaCNTpega-OPF-MTAC hydrogels showed an opaque
promising potential as conduits for nerve tissue
dark color resulted from the carbon content in the
engineering.
hydrogel. Cellular immunofluorescence images showed
References: 1. Runge MB. Biomacromolecules 2010, 11,
higher
density
of
PC12
cells
on
the
2845–2853.
rGOaCNTpega-OPF-MTAC hydrogel with both electrical
2. Dadsetan M. Biomaterials 2009, 30, 3874–3881.
conductivity and positive charged surface compared to
3. Liu X. J Mater Chem B, 2016, 4, 6930-6941.
other types of hydrogels (Fig. 1e). Quantitative analysis
Acknowledgments: This work was supported by the
demonstrated a larger spreading area and higher neurite
Mayo Foundation.