<i>In vitro</i> and <i>in vivo</i> immunotoxicity of PEGylated Cd-free CuInS₂/ZnS quantum dots

Abstract

The annual increase in the production and the use of engineering quantum dots (QDs) have led to concern about exposure and safety of QDs. To resolve the risk of Cd release from QDs, a series of Cd-free QDs, represented by CuInS₂/ZnS QDs, has been developed in recent years. However, the toxicological profile of CuInS₂/ZnS QDs has not been fully elucidated, especially, their immunotoxicity. Here, we performed a detailed <i>in vitro</i> cytotoxicity study on PEGylated CuInS₂/ZnS QDs using the DC2.4 cell line and investigated their <i>in vivo</i> immunotoxicity using BALB/c mice. <i>In vitro</i> experiments showed that CuInS₂/ZnS QDs were taken up by cells, promoted cell viability, enhanced release of tumor necrosis factor-α, and decreased the level of interleukin (IL)-6 in response to lipopolysaccharide stimulation. More than 5000 genes at the transcriptome level were observed by high-throughput RNA sequencing after CuInS₂/ZnS QD exposure. <i>In vivo</i> study showed that CuInS₂/ZnS QDs increased the levels of IL-4 on day 1 and enhanced the levels of IL-10 and IL-13 on day 28 in mice. There was no obvious difference in the number of spleen-derived lymphocytes, organic index, hematology and immune organ histology on days 1 and 28 after treatment. These findings demonstrated that PEGylated CuInS₂/ZnS QDs disturbed the function of DC2.4 immune cells <i>in vitro</i>, but caused no obvious toxicity to immune system <i>in vivo</i>, suggesting that PEGylated CuInS₂/ZnS QDs are biocompatible and have potential for bioapplication in the future.