1. The International Istanbul Textile Congress 2013
May 30th to June 1th 2013, Istanbul, Turkey
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MICRO-WEAVING OF HONEYCOMB NANOFIBROUS MEMBRANES:
APPLICATION TO BONE REGENERATION
S. NEDJARI1
, S. EAP2
, A. HEBRAUD1
, N. BENKIRANE-JESSEL2
, G. SCHLATTER1
1
ICPEES Institut de Chimie et Procédés pour l’Energie, l’Environnement et la Santé UMR 7515,
CNRS, Université de Strasbourg, 25 Rue Becquerel, 67087 Strasbourg Cedex, France
2
INSERM Nanomédecine Régénérative Ostéoarticulaire et Dentaire UMR 1109, Université de
Strasbourg, 11 Rue Humann, F-67085 Strasbourg Cedex, France
salima.nedjari@etu.unistra.fr
Abstract: Controlling the deposition of the nanofibres is crucial issue in novel strategies for tissue
engineering because electrospun structured scaffolds can mimic the complex structures of the body.
Electrostatic forces can be controlled at the vicinity of the collector by using structured collectors with
different shapes and dielectric properties [1]. By using this strategy, honeycomb electrospun nanofibrous
scaffolds with pattern diameters of 40 to 360 microns were obtained. Fibres structuration and osteoblastic
cell growth on electrospun scaffolds of two FDA approved polymers, poly(ε-caprolactone) and poly(D, L-
lactic acid), were studied : optimum structuration was achieved by playing on processing parameters
(solution conductivity, distance, voltage). The fibre morphologies, the scaffold roughness and the honeycomb
patterns size of the membrane were perfectly controlled.
Keywords: honeycomb electrospun scaffolds; bone regeneration; micro-weaving; organised nanofibres;
1. Introduction
Nerves, heart, bones are among the most complex structured tissues of the body. Researchers are
developing techniques to create new biomaterials that can enhance the tissue reconstruction.
Electrospinning is one of the most promising ways to generate scaffolds for tissue engineering: nanofibres
provide a good substrate for cells adhesion and proliferation because they can mimic the extra cellular
matrix. Moreover, as electrospinning is a very versatile method, many natural polymers (gelatin, silk fibroin
chitosan, collagen) and synthetic (PCL, PLA, PGA) can be electrospun and a large variety of nanofibrous
scaffolds can be achieved [2].
Although, electrospun nanofibres are generally obtained in random way, organised nanofibres (aligned
nanofibres, nanofibres meshes) [3] can be generated by changing the nature of the collector and therefore
the electrostatic forces applied on the jet. Indeed, at the vicinity of the collector, the electrostatic forces are
driven by the local structuration and dielectric properties of the collector [1]. By controlling the organisation of
the fibres, the scaffold’s performances are improved and the regeneration is enhanced: as an example, for
nerve regeneration application, when neurites are cultured on a parallel array of aligned nanofibres, they
preferentially extend along the long axis of the fibres [4].
Following this strategy, different honeycomb collectors were made by lithographic processes in order to
create honeycomb membranes for bone reconstruction. The range of the honeycomb pattern size is from 40
µm to 360 µm. Using this honeycomb micro-patterned collectors, PCL and PLA honeycomb nanofibres
membranes are successfully obtained (Figure1). By playing on the processing parameters, control of the
structuration can be achieved. Morphology of the scaffolds (fibre diameter, alignment degree, shrinkage) is
analysed and the differences of behaviour between PCL and PLA are shown. Finally, the influence of the
structuration on osteoblasts cells proliferation and cells morphology will be studied.

2. The International Istanbul Textile Congress 2013
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Figure 1: Electrospinning setup using a honeycomb collector.
2. Materials and Methods
Honeycomb micro-patterns were obtained thanks to photolithography process on silicon wafers. Photoresist
SU-8 2050 was used to obtain patterns with H = 60 µm in height. A conductive layer (Al-120 nm and Au-30
nm) was deposited on the wafers to make them conductive. Internal diameters of the honeycomb are DHC =
40 µm; 80 µm; 160 µm and 360 µm. The width of the honeycomb wall is fixed to 20 µm.
Poly-(ε-caprolactone) (PCL) (Mw = 80 kg/mol
-1
,Perstrop, commercial name: CAPA 6806) was dissolved into
dichloromethane (DCM )/N,N-dimethyl-formamide (DMF) (60/40 V/V) at a concentration of 15 % w/w. 5% of
formic acid was added to the solution to increase its conductivity . The flow rate was at 1.1 mL/h and the
tip to-collector distance was 13 cm. The voltage was 25 kV. After 10 minutes of electrospinning, the PCL
honeycomb scaffold was immerged into ethanol to peel the membrane from the collector.
Poly (D, L-lactic acid) (PLA), (Mw = 180 kg/mol
-1
, Natureworks, commercial name: 7000D) was dissolved into
(50/50 V/V) DCM/DMF, at a concentration of 8.2% w/w. The flow rate was also 1.1 mL/h and the distance
was 18 cm. Two power supplies were used: at the needle, the voltage was Vneedle = +12 kV and at the
collector, it was Vcollector = -5 kV. After 15 minutes of electrospinning, the membrane was peeled from the
collector in isopropanol.
The morphology of the honeycomb nanofibres scaffolds were observed with a scanning electron microscopy
(SEM) with an accelerating voltage of 5 kV (VEGA 3 LMV, TESCAN, Czech Republic).
3. Results
Figure 2: A) SEM image of a PCL honeycomb scaffold. B) SEM images of PLA honeycomb scaffold
Thanks to architectured collectors, electrospun PCL and PLA scaffolds present honeycomb electrospun
shape. However, the morphology of architectured PCL scaffolds is different from architectured PLA ones
(Figure 2A and 2B).
For PCL scaffolds, a bimodal distribution of fibre diameters is observed, with thin fibres of diameter around
250 nm and thicker fibres of diameters between 1 and 2 µm. The thicker fibres, probably still wet and more
charged are attracted by the conductive walls of the collector. Therefore, thicker fibres are preferentially
situated on the hillside of the wall, forming high walls, while thinner fibres are located both in the centre and
on the walls of the honeycomb patterns. Only fibres on the hillside align along the sides of the hexagon
shape.
B)A)

3. The International Istanbul Textile Congress 2013
May 30th to June 1th 2013, Istanbul, Turkey
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In contrary, for the PLA scaffolds, the fibre diameter distribution is monomodal and the average diameter is
around 500 nm. In this case, all the fibres located on the wall present high degree of alignment along the
sides of the hexagon shape.
Due to the differences in fibre diameter distribution and fibre deposition, the PCL scaffolds present a higher
roughness than PLA ones with higher honeycomb walls. Besides, the height H of the scaffold is also
increasing with the diameter of the honeycomb pattern.
Moreover, shrinkage happens during the peeling (in ethanol for the PCL and in isopropanol for the PLA
scaffolds) of the scaffolds from the patterned collector. Thus, and the honeycomb pattern size of the final
membrane is generally inferior to the collector one. This shrinkage is more important for PLA than for PCL.
Fibre diameter, alignment degree and the roughness are parameters that will influence osteoblasts
behaviour. In vitro studies on these architectured scaffolds will show the impact of the honeycomb
organisation the osteoblasts proliferation and morphology. The comparison between PCL and PLA will help
us in choosing the best biocompatible polymer for structured electrospun scaffold for bone regeneration.
4. Conclusion
The lithographic process is a good way to produce structured collectors with specific shapes. Coupled with
electrospinning, honeycomb electrospun scaffolds in PCL and PLA can be made with a good control of their
morphology. By using the same collector, differences are observed between the final structures of PCL and
PLA scaffolds. These differences will affect osteoblasts cell behaviour, known to be very sensitive to the
topography and the roughness of the substrate.
Acknowledgements
This study was supported by the Agence Nationale de la Recherche (NeoTissage), France. We also thank
the cleanroom STNANO of Strasbourg: Sabine Siegwald, Romain Bernard for their technical support. We
also thank Christophe Mélart, Christophe Sutter and Thierry Djekriff for their help in the electrospinning set
up.
References
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