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Jing, et al.
Traditional scaffolding methods such as freeze- to their wide availability, consistent quality, and structural
drying, gas-forming, and solvent-casting particulate diversity . As alcohol-soluble plant proteins, zein protein
[17]
leaching can produce sponge structure scaffolds for cell contains different subunits including α-zein (75 – 85 wt%
culture, but they are not capable of controlling scaffolds’ of zein), β-zein, γ-zein, and δ-zein with different molecular
microstructure, which is critical for cell-scaffold weight and composition. Similarly, gliadin also consists of
interactions . Recent advances in 3D printing, also various fractions. Both zein and gliadin can be fabricated
[7]
known as additive manufacturing, bring new chances to into various structures such as thin films, nanoparticles,
fabricate scaffolds with customizable microstructures in fibers, and porous scaffold. The poor mechanical strength of
reproducible features . For instance, extrusion-based natural polymers can be improved by mixing with synthetic
[8]
3D printing such as fused deposition modeling has been polymers. As a class of prolamin protein found in corn, zein
widely used to fabricate polymer-based fibrous scaffolds resists to microbial attacks and has been applied as coating
for biomedical devices . Droplet-based bioprinting material for encapsulated nutrition and drugs . Zein has
[18]
[9]
enables precise control on deposition of microdroplets been regarded as a potential biopolymer candidate with
containing biological substances, such as growth its hydrophobicity, cytoaffinity, and biodegradability .
[19]
factors, cells, modified genes, small molecule drugs, and Porous zein scaffold can support rat mesenchymal stem
biomaterials, in a fast and high-resolution manner. Vat cells to grow and differentiate into osteoblasts in vitro .
[16]
polymerization-based bioprinting allows direct fabrication Because of the amphiphilic and biodegradable nature of
of high-resolution cell-laden tissue constructs . zein, researchers mixed zein with synthetic polymers and
[10]
Among these 3D printing methods, produced PCL/zein fibers by coaxial electrospinning to
electrohydrodynamic printing (EHDP) has drawn great release metronidazole in a controlled manner . Thus,
[20]
interest for its capability of producing ultrafine fibers with blending PCL with zein to prepare composite biomaterial
high resolution and reproducibility . Like the working inks may be an effective way to improve scaffolds’ cell
[11]
principle of near-field electrospinning, EHDP employs a affinity and biodegradability.
high electric field to induce fiber ejection from viscous Gliadin, one of the major gluten storage proteins
biopolymer solution, ranging from a few hundreds of of wheat, has been investigated for its carrier role for
nanometers to micrometers, from viscous biopolymer controlled release of lipophilic and cationic drugs due
solution. . However, very limited polymer materials are to its unique physicochemical properties . It can also
[12]
[21]
available for this technique due to the harsh requirement deliver sensitive enzymes and avoid their breakdown
on biomaterial ink properties. by stomach acids. Nevertheless, further developments
The scaffold materials should provide temporary of gliadin are hindered by its low water stability and
support for cells to attach, proliferate, and deliver immunogenic toxicity in patients with celiac disease .
[22]
bioactive components. In general, synthetic biopolymers An alternative plan is to blend a small amount of gliadin
such as polyethylene glycol, poly(vinyl alcohol), with PCL in the preparation of composite biomaterial inks
poly(lactide-co-glycolide), and poly-ε-caprolactone for scaffold fabrication, with the purpose of improving
(PCL) are usually used as scaffold materials due to their cell affinity and suppressing gliadin’s side effect. In
excellent printability, favorable biodegradability, and short, both zein and gliadin are abundant and structurally
biocompatibility . They can be applied to common diverse, which may overcome the current limitations
[13]
scaffold fabrication methods to produce porous scaffolds of components extracted from animals in terms of their
with varied pore size, shape, interconnectivity, and supply and quality. These plant proteins are also easy to
porosity . Especially, PCL, a biodegradable polyester blend with other synthetic biopolymers because of their
[14]
with a low melting point, has received extensive attention specific solubility and film-forming properties.
on accounts of its ideal rheological and viscoelastic In this study, we introduce plant-derived proteins
properties, excellent solubility, and biocompatibility . to develop composite biomaterial inks to improve the
[15]
However, the in vivo degradation period of PCL is biocompatibility and mechanical strength of scaffold
up to few years due to its hydrophobicity and semi- materials. These proposed composite biomaterial inks
crystallinity . A simple way to overcome this bottleneck are fed into EHDP system for high-precision scaffold
[16]
is to prepare composite materials by mixing PCL with fabrication. Two types of composite scaffolds are
hydrophilic polymers extracted from animals such as developed, namely, PCL/zein and PCL/gliadin. With the
collagen and alginate. The properties of these natural help of a developed monitoring and identification system,
derived components may vary from batch to batch and EHDP process parameters and environmental parameters
bring in safety concern like transmission of zoonotic are optimized to fabricate such composite scaffolds. To
diseases. analyze the scaffolds’ performance, mouse embryonic
Compared with animal-derived components, plant fibroblasts (NIH/3T3) cells were cultured to examine the
proteins, such as zein and gliadin, are favorable choices due cellular responses on PCL/zein, PCL/gliadin, and pure

International Journal of Bioprinting (2021)–Volume 7, Issue 1 67