Semiconductor quantum dots (QDs) could significantly impact the performance of biomedical near-infrared (NIR) imaging by providing fluorescent probes that are brighter and more photostable than conventional organic dyes. However, the toxicity of the components of NIR emitting II-VI and IV-VI QDs that have been made so far (Cd, Hg, Te, Pb, etc.) has remained a major obstacle to the clinical use of QDs. Here, we present the synthesis of CuInS(2)/ZnS core/shell QDs emitting in the NIR ( approximately 800 nm) with good quantum yield and stability even after transfer into water. We demonstrate the potential of these QDs by imaging two regional lymph nodes (LNs) in vivo in mice. We then compare the inflammatory response of the axillary LN induced by different doses of CuInS(2)/ZnS and CdTeSe/CdZnS QDs and show a clear difference in acute local toxicity, the onset of inflammation only occurring at a 10 times more concentrated dose for CuInS(2)/ZnS QDs than for their Cd-containing counterparts.
Near-infrared (NIR) semiconductor quantum dots (QDs) represent promising fluorescent probes for biological and biomedical imaging. CuInSe2 is a good candidate for these applications due to its bandgap in the near-infrared and the reduced toxicity of its components compared to other NIR QD materials (CdTe, CdHgTe, PbS, etc.). Here we present a simple one-pot synthetic route without injection to make fluorescent sphalerite Cu−In−Se core and Cu−In−Se/ZnS core/shell QDs. We show that the photoluminescence (PL) of the resulting core QDs can be tuned from ∼700 nm to ∼1 μm depending on the QD size (from ∼2 to ∼5 nm in diameter). The optical and structural properties of these QDs are consistent with charge recombination via donor−acceptor levels instead of direct excitonic recombination. Finally, we show that the growth of a ZnS shell around these QDs increases their PL quantum yield substantially (up to 40−50% at 800 nm) and allows preservation of their PL properties after solubilization into water and in vivo, as demonstrated by detection of the regional lymph node in a mouse.
Immunohistochemistry to active caspase-3, recently recommended for apoptosis detection, is inappropriate to detect apoptosis involving caspase-7. Cleavage of poly-ADP-ribose polymerase 1 (PARP-1), a major substrate of both caspases, is a valuable marker of apoptosis. Apoptosis evaluation induced in vitro either by paclitaxel or by photodynamic treatment (PDT) with Foscan in HT29 or KB monolayer cells and HT29 spheroids yielded a close percentage of labeled cells whatever the antibody used, whereas in control specimens, cleaved PARP (c-PARP) immunostaining failed to detect apoptosis as efficiently as active caspase-3 or −7 immunostaining. Studies in MDA-MB231 monolayer cells and HT29 xenografts either subjected or not subjected to Foscan-PDT resulted in a significant higher number of active caspase-3–labeled cells, although immunofluorescence analysis showed c-PARP and active caspase-3 perfectly colocalized in tumors. A restricted expression of c-PARP was obvious in the greater part of caspase-3 expressing cells from control tumor, whereas photosensitized tumors showed a higher number of cells expressing large fluorescent spots from both active caspase-3 and c-PARP. These results support the assumption that c-PARP expression was dependent on treatment-induced apoptosis. The absence of caspase-7 activation in some caspase-3–expressing cells undergoing Foscan-PDT shows the relevance of using antibodies that can discriminate caspase-dependent apoptotic pathways.
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