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Optimized vascular network by stereolithography for tissue engineered skin

Figure 17. Cell vitality within a 1 x 1 cm hydrogel supported via (A) a stainless steel moulded central tube; (B,C) a branched BLI with
Irgacure 184 tube containing pores; (D) single central SLA-formed BLI with Irgacure 184 tube containing pores.
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branched vessel is the lowest (27%) compared with the 5. Conclusion and Future Work
pure hydrogel (35%) and hydrogel with a single tube
(55%). In this paper, an optimised vascular network was
The pure hydrogel used as a scaffold in this work has developed using a set of comprehensive design rules.
proven to be non-toxic and has a good biocompatibility. These design rules considered the physiological
This can also be seen in Figure 18 that the pure hydrogel requirements in both macro- and micro-scales. The
scaffold has less than 50% percent cell death rate optimised vascular network has several advantages:
after seven days. The curable resin made of BLI with 1) this design provides the maximum nutrient supply
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Irgacure 184 was proven to be biocompatible and with minimal complexity; 2) this design minimises the
cytocompatible among other photopolymers used in recirculation areas and 3) this design allows the WSS
the previous testing in section. However, when a single on the vessel in a healthy range. Suitable photo-curable
tube was embedded in the scaffold, the cell death rate resin with photoinitiators was then selected based on the
increased after seven days compared with the pure WST-1 assays and live/dead assays. The results show
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hydrogel scaffold. This may be a reason for sub-optimal that BLI with Irgacure 184 has the lowest cytotoxicity
nutrient supply. The cell death rate was decreased among three and it is the best candidate used in SLA for
significantly by embedding an optimised branched printing the design. Preliminary in vitro studies were
vascular vessel network into the scaffold. It shows a carried out by integrating the artificial vascular vessels
sharp drop (from 55% to 27%) of the cell death rate. into an adipose tissue scaffold. The in vitro study only
This testing indicates that using the optimised vascular has two tested time steps, and the results show that
network, cells viability may be improved by having a branched resin made vascular network has the lowest
better oxygen and nutrient supply from the bioreactor. cell death rate compared with the pure hydrogel scaffold
Further investigations are needed to determine the long- and the hydrogel scaffold embedded with a single
term cell survival and the further behaviour of the cells tube. The design and manufacturing route for vascular
in the bioreactor system. vessels developed in this paper proven to be feasible

14 International Journal of Bioprinting (2018)–Volume 4, Issue 2