Effect of hydrogels on cell viability.
During the study of new drug formulations, polymeric scaffolds, or
devices for biomedical applications, safety profiles are essential
before their use in living cells and organisms (Rawal, 2019; Sudarsan,
2016). Using biocompatible materials is relevant for safe systems
design, but it does not guarantee the absence of toxicity. Factors such
as the presence of toxic reagents, even in small quantities, could
induce some level of cytotoxicity (Ali, 2018). That is why, an in
vitro viability assay is mandatory in this kind of studies.
HEp-2 cells viability in the presence of the four hydrogels was
evaluated by MTT (Figure 6 ). The viability of the control cells
(CC), incubated without hydrogels, was set as the 100% value.
Incubation with Triton X-100 (1% v/v), a non-ionic surfactant that
induces cell lysis, was used as cytotoxicity control (CT).
Starch hydrogel resulted the safest material; while starch-chitosan,
regardless of the method of synthesis, showed good viability percentages
(higher than 80%). In contrast, cells incubated with starch-PVA
hydrogel were the most affected, presenting significantly lower values
of cell viability. Considering that both polymers, starch and PVA, are
biocompatible per se (Mansur, 2009; Perez, 2018), other factors
related to hydrogel structure may be contributing to this result. The
rigid starch-PVA structure and the lower water absorption, may influence
the flow of substances through the hydrogel, originating areas of less
access to nutrients in the plate. Particularly, by having less swelling,
starch-PVA hydrogel remains drier and introduces a structural barrier to
cell growth, leading to smaller values of cell viability.
The formation of rigid networks in PVA hydrogels indicates the existence
of inter- and intra- polymer chain bonds; this decreases the number of
exposed hydrophilic groups and reduces the swelling (Mansur, 2009; Tang,
2011). Starch-PVA hydrogels have been studied before, showing increased
swelling with higher starch quantities (Hsie, 2013), and major
(negative) effect on cell viability when PVA is a primary component of
the hydrogel (Bernal-Ballen, 2019). According to these results, a
possible way to decrease the negative effect on cell viability and to
improve the swelling of our starch-PVA hydrogel could be an increase of
starch quantity and/or a reduction of PVA content.