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Hybrid polycaprolactone/hydrogel scaffold fabrication and in-process plasma treatment using PABS
rare cell adhesion in the core region of scaffolds, is
often caused by the tortuosity of the constructs.
• Moreover, the synthetic biopolymers, most commonly
used, are hydrophobic, and the cell colonization.
Different strategies have been explored to solve the
above problems. Multi-material has been developed
and utilized to produce multiple-material scaffolds [16,26] .
However, most of these systems can only form one type
of biomaterials, either soft hydrogels containing cells or
bio-signals in the scale of KPa or rigid biopolymers and
composites in the scale of MPa, which fails in the mimicry
of natural tissues. In addition, low-temperature plasma
modification is capable of improving the hydrophilicity
of biopolymers by inducing certain functional groups
on the surface to change the chemistry, wettability, and
energy without altering the bulk properties [27,28] . However,
Figure 1. Scaffold-based approach for tissue engineering. most plasma treatment can be conducted after scaffolds
printed and the penetration depth is limited, which results
scaffolds from biodegradable polymers. Biodegradable in non-uniform cell distribution along the scaffold.
polymers are attractive candidates for scaffolding A novel plasma-assisted bioprinting system (PABS)
materials because they degrade as the new tissues are has been developed in the University of Manchester,
formed, eventually leaving nothing foreign to the body. allowing processing soft hard biomaterial integration
The major challenges in scaffold manufacturing lie in and plasma surface modification layer by layer during
the design and fabrication of customizable biodegradable the fabrication process in the same chamber. This paper
constructs with properties that promote cell adhesion and utilized the plasma-assisted bio-extrusion system (PABS)
cell porosity, along with sufficient mechanical properties to produce PCL/Hydrogel hybrid scaffolds and plasma
that match the host tissue, with predictable degradation fully treated scaffolds. The hydrogel is assessed with
rate and biocompatibility [9,10] . the preparation process, functionalization process, and
For the fabrication methods, AM techniques have rheology properties, while the PCL fully treated scaffolds
been commonly applied in scaffold fabrication due to are both morphologically and biologically assessed.
the superior ability in controlling pore size, pore shape,
and pore distribution, and thus creating interconnected 2. Materials and Methods
porous structures [3,11] . When combined with clinical
imaging data, these fabrication techniques can be used 2.1. PCL
to produce constructs that are customized to the shape PCL (CAPATM6500, Mw = 50,000 g/mol), purchased
of the defect or injury . In terms of tissue and organ from Perstorp (Cheshire, UK) in the form of 3 mm
[12]
manufacturing, the additive nature ensures minimal pellets, was used to produce the scaffolds. PCL is an
waste of scarce and expensive building material, namely easy-to-process semi-crystalline polymer with a density
cells, growth factors, and biomaterials [13-15] . Among the of 1.1 g/cm , a melting temperature between 58 and 60°C,
3
AM techniques, material extrusion has been mostly and a glass transition temperature of -60°C.
applied in the bioengineering field due to the flexibility
in material selection based on the use of pneumatic [16,17] , 2.2. Hybrid Hydrogel Methacrylate Anhydride
piston , and screw-assisted [19-21] extrusion systems (Alg-Gel) Ma Preparation
[18]
enabling a wider range of materials to be applied. Some
processes operate at room temperature, thus allowing for Hybrid hydrogel system platform was considered in this
cell encapsulation and biomolecule incorporation without paper, which was made of mixing alginate methacrylate
significantly affecting viability. However, cell-seeding and gelation methacrylate at 50:50% v/v.
and proliferation efficiency is currently a big challenge Functionalization process for both polymers (alginate
due to the following limitations [22-25] : and gelatin) is necessary to introduce the carbon-carbon
• Most AM techniques are limited to single-material double bond into the polymer chains that eventually
fabrication, which is difficult to provide an appropriate convert the polymer into the photopolymerized
environment for cells due to the inadequate chemical, polymer. According to published protocols , alginate
[29]
physical, and biological cues provided during AM was functionalized with methacrylate groups with
processes. minor modifications to be photopolymerized. The 2%
• In addition, non-uniform cell distribution, especially wt. powder-type alginate (Sigma-Aldrich, UK) was

2 International Journal of Bioprinting (2019)–Volume 5, Issue 1