Evaluations\nof the Chemical Stability and Cytotoxicity\nof CuInS₂ and CuInS₂/ZnS Core/Shell Quantum\nDots

Abstract

Recently, CuInS₂ quantum\ndots (CIS QDs) are extensively\napplied in biological applications because of their distinctive optical\nproperty. These novel ternary semiconductor CIS QDs can be developed\ninto good biomarkers or trackers because they do not contain cadmium,\nunlike CdTe and CdSe QDs with high risk for cytotoxicity. However,\nreports on toxicity and effective factors affecting CIS QDs are seldom\ndeveloped, and in vivo chemical stability has not been clearly investigated.\nIn this study, we focused on the fate, degradation, and exposure time\nof CIS QDs in Caenorhabditis elegans (C. elegans), which is used as a\nmodel organism in biology. Moreover, X-ray absorption near-edge structure\n(XANES) is used to identify the oxidation state of CIS and CIS/ZnS\nQDs in various exposure times. The purpose was to use different oxidation\nstates of copper and zinc ions of QDs to achieve chemical stability\nin C. elegans. CIS and CIS/ZnS QDs\nwere synthesized by hydrothermal method, and QDs were transferred\nto aqueous solution by coating with <i>O</i>-carboxymethylchitosan\n(OCMCS). Moreover, intracellular uptake and cell viability tests were\nestimated as preliminary experiments for in vitro cytotoxicity testing.\nOur results showed that the supported QD materials can be applied\nin biological systems. Consequently, we further considered the function\nof QD materials in C. elegans. The\nQD materials of coating OCMCS could be successfully delivered to the\ninterior of the C. elegans through\nthe alimentary system in a manner dependent on the exposure time.\nMost importantly, XANES results revealed that the oxidative state\nof CIS QDs did not change without an outer layer after treatment for\n96 h in C. elegans. Therefore, the\nextreme chemical stability of CIS QDs may explain the low cytotoxicity\nin the organism and thus has potential biomedical applications.