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Page 12 of 16 Wang et al. Microstructures 2023;3:2023042 https://dx.doi.org/10.20517/microstructures.2023.46

Figure 7. Anticancer effect of gelatin/Fe O porous scaffolds. Live/dead staining of MDA-MB-231-Luc cells cultured with gelatin/Fe O
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scaffold discs via sitting (A), transwell (C), and adhesion (E) modes before and after AMF irradiation (live cells: green fluorescence,
dead cells: red fluorescence). Quantified cell viability after culture with gelatin/Fe O scaffold discs via sitting (B), transwell (D), and
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adhesion (F) modes before and after AMF irradiation. Cell viability was normalized to that cultured with gelatin porous scaffold without
free Fe O NPs before AMF irradiation. Data are the mean ± SD (n = 3). Significant difference: *P < 0.05, **P < 0.01, ***P < 0.001. N.S. :
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no significant difference.
NPs in agarose hydrogels and porous scaffolds was decreased to 51.5%-59.5% and 20.1%-23.8% of that of
free Fe O NPs, respectively. The results of Fe O NPs embedded in hydrogels were the same as the
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previously reported influence on their magnetic thermal property. Embedding in porous scaffolds further
decreased the magnetic-thermal conversion capacity of Fe O NPs.
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The matrix influence should be due to the variation of Brownian relaxation of Fe O NPs in the matrices.
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The heat generation mechanism of MNPs exposed to AMF includes Néel relaxation and Brownian
[62]
relaxation . Néel relaxation refers to the heating due to the energy loss produced by the rotation of
individual magnetic moments within the MNPs under AMF irradiation, and Brownian relaxation refers to
the rotation of entire MNPs to produce heat [63,64] . The Néel relaxation of Fe O NPs in the hydrogels and
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porous scaffolds might not change. However, the matrices should affect the Brownian relaxation of Fe O
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NPs. The Brownian relaxation of Fe O NPs under AMF irradiation should be partially suppressed in the
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agarose hydrogel, leading to a decreased heating effect of Fe O NPs. When the Fe O NPs were embedded
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in gelatin porous scaffolds, the Fe O NPs were tightly constrained in the gelatin fibers, and the Brownian
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relaxation of Fe O NPs should be heavily inhibited. Therefore, the Fe O NPs in the gelatin porous scaffolds
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generated heat predominantly through Néel relaxation.
Due to the influence of matrices on the magnetic thermal property of Fe O NPs, the anticancer effect of
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Fe O NPs was also dependent on the matrices. The breast cancer cells cultured with free Fe O NPs were
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most efficiently killed by AMF irradiation. Embedding in agarose hydrogels and gelatin porous scaffolds