Silver Nanocolloids Disrupt
Medaka Embryogenesis through
Vital Gene Expressions
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Abstract
Silver nanomaterials are the major components of healthcare
products
largely because of their antimicrobial effects. However, their unintended
toxicity to biological organisms and its mechanism are not well understood.
Using medaka fish embryo model, the toxic effects and corresponding
mechanisms of silver nanocolloids (SNC, particle size 3.8 ± 1.0-diameter
nm) were investigated. SNC caused morphological changes in embryos
including cardiovascular malformations, ischemia, underdeveloped central
nervous system and eyes, and kyphosis at exposures of 0.5 mg/L. Interestingly,
SNC were observed inside the eggs at a level of 786.1 ± 32.5
pg/mg egg weight, and TEM analysis showed that SNC adhered to the
surface and inside of the chorion. Meanwhile, medaka oligo DNA microarray
and qRT-PCR were used for gene expression analysis in the embryos
exposed to 0.05 mg/L SNC for 48 h. As a result, expressions of six
of the oxidative stress-, embryogenesis- and morphogenesis-related
genes, <i>ctsL</i>, <i>tpm1</i>, <i>rbp</i>, <i>mt</i>, <i>atp2a1</i>, and <i>hox6b6</i>, were affected by the SNC exposure, and these genes’ involvement
in those malformations was implied. Thus, SNC could potentially cause
malformations in the cardiovascular and central nervous systems in
developing medaka embryo through SNC-induced differential expression
of the genes related to oxidative stress, embryonic cellular proliferation,
and morphological development