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Investigation of process parameters of electrohydrodynamic jetting for 3D printed PCL fibrous scaffolds with complex geometries

to be successful in engineering a tissue [1–2] , namely (i) technology. E-jetting has the same working principle
scaffold should biomimic the native tissue environ- as Electrospinning technique which is widely
ment as close as possible, (ii) material selection, used to fabricate controlled porous scaffolds for tissue
should be biocompatible and biodegradable, (iii) ap- engineering applications [21–26] . Various studies were
propriate surface chemistry to promote cell attachment, made on the effect of Electrospinning parameters on
proliferation and differentiation, (iv) adequate me- the electrospun fibres [27–28] . Subsequently, the most
chanical properties, and (v) fabrication flexibility to important parameters that have been identified were
have a variety of shapes and sizes. The utmost cha- namely, the volumetric charge density, distance from
llenge with the current tissue engineering techniques nozzle to collector, initial jet/orifice radius, relaxation
is imitation of the native tissue environment. Tradi- time, and viscosity [29] . Numerous novel and hybrid
tional tissue engineering methods use 2D materials or techniques of Electrospinning were developed in or-
scaffolds for cell culture and tissue construction. The der to overcome the limitation of non-orientated ran-
main drawback of 2D substrate is that it fails to pro- dom fibres from the Electrospinning process. Bu et
vide the cell with its native architecture. Most impor- al. [30] developed a mechano-electrospinning technique
tantly, native tissue micro-architecture is highly for fabricating oriented nanofibres and the controlled
complex and highly oriented due to its 3D environ- parameter was the moving speed of the substrate.
ment. Obviously, when a 3D environment is provided Chanthakulchan et al. [31] developed an Electrospin-
rather than 2D or 2.5D, the cells grow, proliferate and ning-based rapid prototyping method for fabrication
differentiate closer to the native tissue [3–5] . There are of patterned scaffolds but only achieved a certain level,
several techniques to create a3D environment, such as due to the challenges of controlling the vibration. Au-
[32]
solvent-casting particulate-leeching, gas foaming, ph- yson et al. studied the effect of various parameters
ase separation, melt moulding, solution casting, freeze of the hybrid Electrospinning / Fused Depositio Mod-
drying and emulsion freeze drying, however, they suf- elling (FDM) on the fabricated scaffold and concluded
fer from the drawback of producing only a foam that two most important parameters to get a conti-
structure, and not a highly controlled porous 3D mi- nuous jet are the voltage applied and the standoff dist-
cro-architecture, which leads to several other prob- ance between the nozzle and the substrate. On the other
[6]
lems . Though microscale fabrication technologies hand, a low voltage near-field Electrospinning method
[33]
like soft lithography were able to create a microscale reported by Bisht et al. was able to pattern nanofi-
resolution scaffold [7–8] , they also suffer from several bres continuously on both 2D and 3D substrates, re-
limitations associated with inflexibility in fabricating spectively. Besides that, other vital parameters were
[34]
complex geometries and the optimization of scaffold namely, the viscosity and elasticity of the polymer ink .
In this study, an E-jetting setup was built in-house
[9]
architecture . Electrospinning is looked at as an al- in order to fabricate 3D scaffolds out of PCL material.
ternate technology to fabricate nanofibrous scaffolds PCL material is widely used as a biomaterial for scaf-
for tissue engineering applications [10–14] and shows a folds which possess extremely good mechanical pro-
considerable progress with several reports portraying perties. The structure of the printed scaffold depends
its successfulness. Nonetheless, electrospinning tech- on two important elements namely, the fibre diameter
nology suffers from the limitation of randomly ori- and the pore size. The parameters of the E-jetting system,
ented fibres and inability to fabricate a controlled i.e. the supply voltage, solution concentration, nozzle-
uniformly porous scaffolds. 3D printing is currently to-substrate distance, stage (printing) speed and solu-
seen as the potential solution to fabricate layer by layer, tion dispensing feed rate greatly influences the fibre
controlled 3D porous scaffolds [6,15–19] . A new term diameter of the printed structure. Briefly, the relation
known as 3D bioprinting has emerged recently and between these parameters and the fibre diameter were
researchers are working towards the realization of discussed in this work. Parameters were optimized and
printing functional human organs with this novel scaffolds of complex geometries i.e. semi-lunar and
technology. An et al. [20] reviewed vastly on various spiral shapes have been successfully printed.
state-of-the-art 3D printing technologies for tissue
engineering applications, limitations of the current 2. Experimental Section
technologies and the possible future improvements.
Electrohydrodynamic Jetting, which is also known as 2.1 Materials
EHD-Jetting or E-jetting is one type of bioprinting Acetate (Aladdin A116171, electronic grade, >99.7%)

64 International Journal of Bioprinting (2016)–Volume 2, Issue 1