On the Cyto‐Toxicity Caused by Quantum Dots

Abstract

Quantum dots (QDs) such as CdSe QDs are nano-sized metal clusters. QDs have specific characteristics such as the quantum effect, which is a special photo quality caused by the widening of the band gap when the spatial dimension is reduced. Kubo et al. predicted the specific character of the quantum dot theoretically in 1962 (14-16). Since then, research concerning the applications of QDs has gained a great amount of interest. For example, in the field of Information Technology and optical-engineering (3, 10, 21, 29, 30), QDs have been proposed for use as a new material for memory, and as miniature laser-beam emitting devices. Furthermore , the biological applications of QDs conjugated with antibody have started to attract much attention, especially in immunostaining, separating cells, and diagnostics, because of their advantages such as longer lifetime and higher fluorescence over conventional organic fluorophores (1, 2, 8, 27). The first synthesized QDs are insoluble in biological solvents because non-polar groups of organic molecules are exposed on the surface of QDs. However the water-soluble QDs covered with mercapto-undecanoic acid (MUA) have been reported (2). In addition, the MUA-QD covered with sheep serum albumin (SSA) is well dispersed in water (2, 9). The advantages of MUA-QDs described above make it possible to consider the application of MUA-QDs to drug delivery systems (6, 20, 25, 28) as a drug-carrier and cell delivery system. Quantum dots have a longer lifetime compared to conventional organic fluo-rophores and thus make it easier to trace the drug delivered in living organisms. To make sure the application is feasible, an in-depth evaluation using MUA-QD in living organisms is needed. In fact cadmium (13) and selenium (24) are known to be toxic. Though the use of MUA-QDs for organisms has been known and some other studies about the actual injections into organisms have been conducted, the toxicity of MUA-QDs has not been reported in detail yet. Published works regarding Abstract: Quantum dots (QDs) such as CdSe QDs have been introduced as new fluorophores. The QDs conjugated with antibody are starting to be widely used for immunostaining. However there is still not sufficient analysis of the toxicity of QDs in the literature. Therefore we evaluated the cell damage caused by the quantum dots for biological applications. We performed cell viability assay to determine the difference in cell damage depending on the sizes and colors of mercapto-undecanoic acid (MUA) QDs and the cell types. The results showed that the cell viability decreased with increasing concentration of MUA-QDs. But in the case of Vero cell (African green monkey's kidney cell) with red fluorescence QD (QD640), the cell damage was less than for the others. Furthermore through the flow cytometry assay we found that this cell damage caused by MUA-QD turned out to be cell death after 4-6-hr incubation. From the two assays described above, we found that there is a range of concentration of MUA-QDs where the cell viability decreased wi...

In vivo quantum dot labeling of mammalian stem and progenitor cells

“…The majority of in vitro studies to date have not found any adverse effects of QDs on cell viability, morphology, or function (Ballou et al, 2004;Kim et al, 2004) provided the QDs were capped by both ZnS and hydrophilic shells. However, it has been shown that surface modifications can modulate the biocompatibility of QDs used in certain applications (Shiohara et al, 2004;Kirchner et al, 2005). We used lactic acid dehydrogenase (LDH) release and reactive oxygen cytotoxicity assays to investigate whether cells loaded with carboxy-functionalized QD could survive and function normally.…”

Nonendosomal cellular uptake of ligand‐free, positively charged gold nanoparticles

“…This is especially important concerning long-term and in vivo studies, for which they are particularly suitable due to their resistance to photobleaching and their very high photon efficiency and therefore low excitation power. Although the potential of quantum dots to be harmful has been rather controversially discussed (12,13), the effect of metal nanoparticles differs greatly depending on the metal used for their generation. In case of gold, evidence for toxicity is so far comparatively low (14).…”

Assessment of Cytotoxicity of Quantum Dots and Gold Nanoparticles Using Cell-Based Impedance Spectroscopy

“…CdSe/ZnS-MUA (mercapto undecanoic acid) QDs are cytotoxic at 100 µg/mL with respect to HeLa cells. 18 CdSe/ZnS-SSA (sheep serum albumin) QDs were reported to be cytotoxic, since the cell viability (EL-4 cells plated at 10 6 cells/mL) decreased with increasing time (3-24 h) as the QD concentration increased (100-400 µg/mL). 19 Almost all the cells were dead at 400 µg/mL after 6 h of incubation.…”

“…22 Similarly, CdSeZnS-MUA or CdSe/ZnS-SSA QDs at 400 µg/mL were reported to have no affect on the viability of Vero cells after 2 h. 23 In contrast, QD-induced cytotoxicity tends to be longer in nature, with exposure times up to 24 h required as previously mentioned. [17][18][19] In brief, we have described an online and continuous technique based on electric cell-substrate impedance sensing for measuring the concentration and time response function of fibroblastic V79 cells exposed to various nanoparticles including quantum dots and fluorescent gold nanoparticles. The half-inhibition concentration, the required concentration to achieve 50% inhibition, can be estimated from the response function to ascertain cytotoxicity during the course of the assay.…”