April 9 - 5. Nieves_ICMAB.pdf - icmab csic

Nanostructured Electroactive Materials
For Electrodes in the CNS stimulation and
repair
Prof. Nieves Casañ-Pastor, Ph.D.
Institut of Materials Science of Barcelona, CSIC
Spain

In collaboration with
Hospital Nacional de Paraplejicos in Toledo
Inst. Biomedical Sciences CSIC, Barcelona
And Univ. Aberdeen School of Medical Sciences
Finnancing CICYT (SPAIN)
EU STREP
CSIC

Nervous system and
Electroactive Materials
Prostheses/scaffolds
Electrostimulation in the nervous system
Inert Pt, Au RADICALS!!!!!!!!
Which material
-Electroactive
-Biocompatible
-Flexible

Deep Brain
Electrostimulation
Pt vs IrOx, pedot electrodes
http://my.clevelandclinic.org/neurological_institute/
Parkinson’s disease (PD),
such as tremor, rigidity, stiffness, slowed movement, and walking problems.
http://www.ninds.nih.gov/disorders/deep_brain_stimulation/deep_brain_stimulation.htm
2007

Neuroblastoma and dendrite growth
Growth cone directing
REPAIR

Migration towards cathode in embryo cells (XENOPUS)
http://www.abdn.ac.uk/ims/staff/details.phpid=c.mccaig
Epithelial Cells migrate towards cathode
WHAT IF CELLS ARE ON THE MATERIAL

WHICH MATERIALS

Most described materials in this field have a static property
BUT THE MATERIAL MAY BE SEEN
AS SOMETHING DYNAMIC
ITS PROPERTIES MODULATED:
ELECTROACTIVE
ELECTROCHEMISTRY IS INTERFACE
ALWAYS NANO !!!!!!

ELECTROACTIVE MATERIALS :
C, Oxides, Conducting polymers…
Active electrochemically
Electrodes
Mixed conduction
Intercalation (Li+, O- , Na+, …)
Redox Modulation of surface potential
Applications: Bateries, FC, supercapacitors : Energy storage
Sensors
Electrostimulation
Electronics
Photovoltaics
Electrochromism, electromechanics
Artificial muscles……

An example : Li + ion batteries
LiCoO 2 ↔ Li 1-x CoO 2 + xLi + + xe -
Cathode
All reactions occur at the interface
Whatever this is : flat or pores…..
C + xLi + + xe - ↔ Li x C
Anode
Ion diffusion : Interfaces
Particle size and NANO

Li+ in lithium batteries
Not only porosity or final nanosized

Electrochromism and conductivity switching
by redox intercalation
O
O
O
O
S
S
S
S
S
O
O
O
O
O
O
O O
A - O O
+
A -
S
S
+
S
S
S
O O
O O
O O
The electrochromic behavior is due to an electron transfer reaction taking place
during the electrochemical oxidation and reduction of the polymer.

New Anodes
NANO -----
Sn alloys –Li- C

NOW! Li not only in PC
Anode : TiOx NANO
Fastest exchange More power
Autonomy 150 Km
Rechargable in 30 min
(news 2009)

Intercalation in electrochemical systems :
Not only small ions like Li+
Not only positive ions
Halides, (F - , Br - ), O -x

1991 Casañ et al ICMAB
Oxygen intercalation and mobility at room
temperature also
Electrochemical cell
Semi to superconductor (Cu)
Magnetic changes 300% (Mn)
Oxygen enters in
interstitial positions
La 2 CuO 4 + d/n O -n La 2 CuO 4+d
Ln 2 MnO 4 + d/n O -n Ln 2 MnO 4+d

Same process
NEW PHASES by SOFT CHEMISTRY
1999: First Ag-Cu oxide Ag 2 Cu 2 O 3
(1)
In the search of new superconductors:
Replacing Ag by Hg
New oxide Ag 2 Cu 2 O 4
(3)
by oxygen doping of Ag 2 Cu 2 O 3 !!!!
(1) P. Gómez-Romero et al., Angew. Chem. 111, 1999, 544-6, Gómez-Romero, Casañ-Pastor et al, Inorg. Chem. 41, 2002,
6604. (2) Gómez-Romero, et. al., J. Solid State Chem. 163, 2002, 151, (3) Casañ-Pastor et al. Electrochem. Comm. 4,
(2002) , 684-689

Electrochemical Oxidation
in NaOH (aq): nanoparticles in suspension
Ag 2 Cu 2 O 3 Ag 2 Cu 2 O 4
d = 7.01 g/cc
-e - + O -2
d = 7.16 g/cc

Ag 2 Cu 2 O 4 structure
• 1 O atom “intercalated” per unit formula;
• Pass from a 3D structure to a 2D one at r.t. !!!!;
• Significant structure transformation and
electronic delocalization Ag octahedral
Ag 2 Cu 2 O 3 ; 3D
Ag 2 Cu 2 O 4 ; 2D

Ag 2 Cu 2 O 4 vs its precursor 200 nm size part.
• SEM
Solid State Nano-transformations : Oxygen diffusion induced electrochemically
Ag 2 Cu 2 O 3 Ag 2 Cu 2 O 4
• HRTEM

I / A
After been prepared, it has electrochemical transformations
also in solid state .
•CV Ag 2 Cu 2 O 3 pellet ; NaOH(1M); 0.35 mV/s
Cathodic run
0.06
reduction
A
Ag + Ag 0
0.04
B
C
Cu 2+ Cu +
0.02
OCV
0.00
Cu + Cu 0 5
-0.02
Single oxides
A’
B’
C’
1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5
E / V vs. Au

INTENSITY (Arbitrary Units)
Hydrothermal oxidation
eff
( B
)
1/ mol
/ mol/emu
Ag + Cu +2 with MnO4 - :
Ag 2 CuMnO 4
5
4.5
4
3.5
180
3
160
140
2.5
2
120
100
80
60
1.5
40
20
0 50 100 150 200 250 300 350
T (K)
1
0 50 100 150 200 250 300 350
T (K)
10 19 28 37 46 55 64 73 82 91 100
2Theta (Degrees)
Ferro and Antiferrom
Coupling in layered
phase
N. Casañ-Pastor et al. ,
J. Solid State Chem. , 179, 2006, 3883

When „Nano“ was not named Nano
Technology can precede science
Mayan BLUE
Now we know: heat can embed aniline, a bright indigo
chemical from the plant Indigofera suffruticosa, into
the natural clay palygorskite, which provides a
protective lattice.
Really : HYBRID NANOCOMPOSITE Organic-
Inorganic
(Mg,Al) 2 Si 4 O 10 (OH)·4(H 2 O) clay mineral

Materials- Polymers
• Polypyrrole and PEDOT
Poly (3,4-ethylenedioxythiophene)
electrochemically synthesized on Pt substrates
With counterions as
• Anionic surfactants (potentiostatic deposition)
-PSS: poly (sodium 4-styrenesulfonate)
• Aminoacids (dynamic deposition):
-Glutamate
-Glutamine
-Glycine
-Glutamine
-Lysine
Oxidation state modulation of Polymer coatings

Atomic Force Microscopy- Topography
Current sensing AFM
PPy-aminoacid films
Polymer films < 1 m thick
Coatings on transparent Pt (Ti) 12 + 5 nm
Sample
PSS As
prepared
Roughness
RMS (nm)
Peak to valley
Maximum (nm)
15.5 86.3
Glutamate 30.9 176.3
Glutamine 16.9 107.2
Glycine 26.9 165.2
Glutamic
acid
73.3 610.0
1 μm
Glutamate
1 μm
Glutamine
Polypyrrole-PSS < 1 m thick
Institut de Ciència de Materials de
Barcelona
0 200 400 600 800 1000 nm
0
100
200
300
400
500
600
700
800
900
1000
nm
nm
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
1 μm
Glycine
1 μm
Glutamic acid
Current sensing measurements show how samples are much more
conductive at the top of the grains for all cases

Cell cultures on polymers
Ppy-PSS 4DIV
Ppy-Glutamina 4DIV
Ppy-Lisina 4DIV
Ppy-Lisina pH 12 , 4DIV
Aminoacid insertion improves material 500%

Steel/ppy/ electrolyte /ppy/steel
electrochemical cell
T.Otero, Chem. Comm. 1997

Materials: Electroactive oxides …
Iridium Oxide IrOx
Mixed Valence Ir (III) – Ir (IV)
IV
III IV
Intercalation redox process
Ir O2 xe xH H
xIrx
Ir O2
Charge transference without
injurious reactions or thermal
Low effects impedance !!!
Biocompatibility + good electrochemical properties

I(mA)
Synthesis
• Constant current
35 A/cm 2 (* Petit et al. 1998)
• Cyclyc Voltametry
Voc – 0.55 V, 10mV/s 50 and 100 cycles
Substrates:
soda lime glass coated with Pt 12 nm
(5nm Ti adhesion layer)
Oxalic acid + K 2
CO 3
+ IrCl 3
(CV, 0.55V, 10mV/s 1 cycle)
0.8
0.6
0.4
0.2
0.0
≈ 130 nm thick
-0.2
-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6
E (V) Vs Pt
* PETIT, M.A; PICHON, V. Anodic electrodeposition of iridium oxide films. J. Electroanal. Chem. v. 444, p. 247-252, 1998

EQCM SÍNTHESIS of IrOx…
Pulsed deposition
m
Q
13.2 µg
depositada
oxidación
Q/m : 6 to 4 e-/ Ir
4.2 e - /Ir
Aditional process: Oxalate oxidation to CO2
Carga superior a la esperada …
21

IrO x
Similar to palygorskite
≈ 130 nm thick
Corriente
aumenta
IrOx.nH 2 O Oxohydroxide amorphous/channels
Local structure
similar to IrO 2 rutile
Grazing angle XRay
XAS (ESRF)

IrO x
The microestructure depends of the
synthesis conditions and oxidation
state !!!
Synthesys Conditions
RMS
(nm)
35 A/cm 2 > 1000
0.55V/2mV/s/17cycles 5.6
0.55V/10mV/s/50cycles 20.7
0.55V/10mV/s/100cycles 84.5
Modulation of Ir oxidation state
Ir reduction at -0.23 V and simultaneous
H + (H2O) intercalation assumed MW 13

In general IrO 2 crystallizes in the rutile form but in this case …
GIXRD, XAS
XPS y ATG
XPS
Amophous phase with local
structure rutile
Wet phase. OH - y H 2 O in the structure
K ions in the structure, it is not residual.
Is this K localized in channels
Hollandite structure …
Rutile
Hollandite
Proton, K, H 2 O, OH -
Intercalation …
Electrochemical Window of -1 V to 0.7V
(no water redox processes)

Electrochemistry in AFM
Current (mA)
Iridium Oxide
Electrochemistry in AFM
CV scans_1st experiment
-0.04
-0.08
-0.12
-0.16
-0.20
0 1 2 3 4 5 µm
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
RMS= 25.7 nm
5
µm
0 1 2 3 4 5 µm
0
0.5
1
nm
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
nm
140
120
0.12 V
-0.06 V
-0.33 V
-0.24
1.5
2
2.5
100
80
-0.6 -0.4 -0.2 0.0 0.2
E (V) vs Pt
3
3.5
4
4.5
5
µm
RMS= 14.2 nm
60
40
20
0
-0.57 V

Electroactive materials, electrochemistry, field applications, interfaces and cultures
Hybrids
IrOx encapsulated on PPy
SEM
Ir shows brighter
Back-scattered Electrons
Institut de Ciència de Materials de
Barcelona NERBIOS Meeting, Aberdeen 21-22 otc 2009

IrOx-PEDOT
IrOx-PPy

IrOx encapsulation with polypyrrole

Intensity (counts)
Scaffold Hybrids IrOx
–nanotubes and IrOXnanotubes
-polys
1,0
0,8
0,6
IrOx + CNTs
IrOx + PEDOT + CNTs
IrOx AP
Ir 4s
O1s
Ir 4d
Ir 4d 5/2
3/2 Ir 4f
Ir 4p
C1s 5/2 Ir 4f7/2
3/2
K 2s
0,4
0,2
Cl 2s
Cl 2p
S 2s
S 2p
0,0
1000 800 600 400 200 0
Binding Energy (eV)

Intensity (cps)
j(mA/cm2)2)
INTERFACE MATERIAL - CELL
Polylysine: Evidence of polypeptide adhesion
• Both CV and XPS evidence the adhesion of P-L-Lysine to the PPy coating
Electrochemical effect
Not passivating
DBS 0,75V as prep. samples
1
0.5
0
-2 -1.5 -1 -0.5 0
-0.5
-1
-1.5
-2
phosphate
phosphate p-
lysine
medium
50000
40000
30000
20000
XPS N 1s
N 1s
PPY-PSS As prepared
PPY-PSS AP
with lysyne
PPY-PSS AP
with polilysyne
x 10
E(V) vs Pt
-2.5
XPS
O 1s
medium p-
lysine
10000
0
398 400 402 404
Binding Energy (eV)
Institut de Ciència de Materials de
Barcelona

Intensity (cps)
Oxides IrOx and polypyrrole with lysine and polylysine
XPS
18000
16000
14000
12000
10000
8000
6000
4000
2000
O 1s Comparison
*TiO O 1s
2
Ppy
IrOx AP with lysyne
IrOx AP with poliysyne
TiO2 350ºC, 3x with lysysne
TiO2 350ºC, 3x with polilysysne
PPY-PSS AP with lysysne
PPY-PSS AP with polilysysne
IrOx
528 530 532 534 536
Binding Energy (eV)

Contact angle (deg)
Contact angle (deg)
Contact angle (deg)
Surface Hydrophylicity: Contact Angle
with PLL
As prepared
PPY-PSS
PEDOT-PSS
IrOx
100
Ppy-pss
100
Pedot-pss
100
IrOx
90
80
As prepared
with PLL
90
80
As prepared
with PLL
90
80
70
70
70
60
50
40
water
medium
60
50
40
water
medium
60
50
40
As prepared
With PLL
water
medium
PLL decreases contact angle
increases wetability
θ
A
θ
B
Contact angle for IrOx samples without
(A) and with PLL (B) in water

mA
PLL Peptide adhesion 1 nm does not modify electroactivity
Voltammetry.
5
cv_red_medio_ IrOx
4
3
as prepared
con PLL
2
1
0
-1
-1,0 -0,5 0,0 0,5 1,0
Ewe/V vs SCE

Electroactive materials, electrochemistry, field applications, interfaces and cultures
Confocal Microscope (Fluorescence)
PEDOT-PSS 4 μg/cm 2 PEDOT-PSS 28 μg/cm 2 IrOx 4 μg/cm 2
Sample
Integrated intensity
(arbitrary units)
PEDOT-PSS 4 μg/cm 2 (5,04 ± 2,25)·10 5
PEDOT-PSS 28 μg/cm 2 (2,75 ± 0,96)·10 7
* Marker: FITC
IrOx 4 μg/cm 2 (1,50 ± 0,52)·10 6
Institut de Ciència de Materials de
Barcelona NERBIOS Meeting, Aberdeen 21-22 otc 2009

Atomic Force Microscopy (contact mode)
with poly-L-lysine
WEAR TESTS on Au and TiO 2 flat facet
TiO 2 rutile 1 nm thickness PLL
Au

Interdigital patterns by UV lithography
PPY on Pt patterns
Screen printing
electrodes
1. Substrate treatment
Humidity
2.- UV-Resin deposition
3.- UV- insulation
PPY-PSS
4.- Developing
5.- Platinum
deposition
6.- Lift-off
7.- Electrodeposition

Cultivos celulares (células primarias embrionarias) …
Rata Whistar Embrión E14/18 Córtex Siembra sobre el
material
Lamelopodia
Neuritas
Inmaduras
Formación
del Axón
Dendritas
múltiples
Formación de
las Dendritas
Maduración
Ramifica
ciones
Axón
8

Neural cortex Cell cultures on polymer
100 m
PPY-DBS (Surfactant) 100 4DIVm
Control 4 DIV (borosilicate glass) PPY-DBS (Surfactant) 4DIV
Cells grow better on aminoacid
containning polymers vs. those
with surfactants
Living cells statistics
(25000 neurons/cm 2 original seeding)
100 m
100 m
35000
30000
PEDOT-PPy Lysine 4DIV
PEDOT-PPy Glutamine 4DIV
25000
20000
15000
Neurons/cm 2
10000
5000
0
PPy DBS
PEDOT-PPy-
Glutamine
PEDOT-PPy-
Lysine
Control
Material

There is no inhibition in the dendrite
growth
Neural cortex Cell cultures on IrOx
Cerebral Cortex of embryos of Whistar E14 rats
Survival is statistically
equivalent to the control
Good cell survival, adhesion, proliferation up to 4 days…and more

NEURONS GROWTH from Cerebral Cortex of embryos of Whistar E14 rats
IrO x
(Ir-Ti)O x
There is no inibition in
the dendrite growth
4DIV
Survival is
statistically
equivalent to the
control
Cell survival improve when Ir
content increase

Surface potential may also be modified in situ !
Material in the media
Or
Material as substrate and electrode

http://www.abdn.ac.uk/ims/staff/details.phpid
=c.mccaig
Epithelial Cells migrate towards cathode

I/mA
Surface potential may also be modified in situ
IrOx
0 min
Cultures
Rat Cortical neurons
3 min
E-18
Neurobasal + B27
DC -0.2V
DC ON
-15 μA -0.1μA
Q = 0.84 mC
6 min
15% IrOx capacity
10 min
6,00E-01
5,00E-01
4,00E-01
3,00E-01
20x
2,00E-01
1,00E-01
0,00E+00
-1,00E-01
-2,00E-01
IrOx MC -
0 50 100 150 200
time / s
OFF
14 hours after

An example: STIMULATION
ON PEDOT-PSS HEPARIN CATHODE

Electric field modulation in nanoparticles or nanostructured coatings
-Control of doping state/redox potential may change the physical properties largely.
Applicable to surfaces acting as electrodes..
-Intercalation achieved yielding to solid state reactions and new phases
- Neural cells grow well in electroactive materials and survive in both
OXIDES and AMINOACID containning POLYMERS.
-Peptides absorb in both types of surfaces
-Electroactivity is preserved after peptide adhesion, and is not modified by it
- IrOx as an open structure with channels allows ion intercalation during redox changes,
-Polymers behave also as an open structure allowing the same type of behavior
-Modulation of the surface oxidation state and electrical potential is posible.
Minimal changes occur in topography, hydrophilicity, or structure in IrOx , max in polymer

People involved in this work
Dr. N. Casañ, Ph.D.
Dr. J. Fraxedas
Dr. P. Lozano
Nina Carretero
Dr. Ll. Abad
MSc. A. M. Cruz
Dr. C. de Haro
MSc. J. Moral