Cytotoxicity of quantum dots: Use of quasiSMILES in development of reliable models with index of ideality of correlation and the consensus modelling

The assessment of cytotoxicity of quantum dots is very essential for environmental and health risk analysis. In the present work we have modelled HeLa cell cytotoxicity of sixty one CdSe quantum dots with ZnS shell as a function of its experimental conditions and molecular construction using quasiSMILES representations. The index of ideality of correlation helps in the building of ten statistically significant models having good fitting ability with value of R² ranging from 0.8414 to 0.9609 for the training set. The split 5 model is rated as the best model with values of R², Q²_F1, Q²_F2 and Q²_F3 as 0.8964, 0.8267, 0.8264 and 0.8777 respectively for the calibration set. The extraction of features causing increase and decrease of cytotoxicity of quantum dots indicates importance of neutral surface charge, surface modified with protein, 72 h exposure time, combination of MTT assay with surface protein in decreasing the cytotoxicity. Amphiphilic polymer, polyol ligand with neutral charge, 0.5 - 0.6 nm quantum dot diameter with lipid ligand and unmodified positively charged surface are grouped in toxicity enhancer features. Further, consensus modelling using split 5 and 8 patterns enhances the prediction quality by increasing the R²_val to 0.9361 and 0.9656 respectively.

The delivery of doxorubicin of multifunctional β-cyclodextrin-modified CdSe/ZnS quantum dots for bioactivity and nano-probing

The modified quantum dots (QDs) have been used in intracellular probing and drug delivery because of their special chemical and physical properties. In this paper, two β-cyclodextrin (β-CD)-modified CdSe/ZnS QDs with strong optical emission properties were synthesized as drug carriers to induce apoptosis. The positively charged l-Arginine (l-Arg) and neutral l-Tryptophan (l-Trp) were selected as ligands to compare the effect of charge on bioactivity of QDs nanoparticles. The in vitro assays revealed that these modified QDs showed good Dox carrier ability and significantly high inhibition rate to cancer cells. Especially, the more positively charged β-CD-l-Arg-polyamine-coated CdSe/ZnS QDs could effectively deliver the doxorubicin (Dox) into cells and exhibit excellent cell selectivity in cancer versus normal cells. The Dox-loaded QDs could enter intracellular, which showed that the Dox can efficiently go through the membranes at the existence of β-CD. Several lines of evidence suggest that the Dox-loaded QDs can efficiently induce apoptosis likely related to the production of ROS. We expect that the modified QDs can enhance the amount of hydrophobic antitumor drugs in cells and can also be used as fluorescent imaging agents.

Meta-analysis of cellular toxicity for cadmium-containing quantum dots

Understanding the relationships between the physicochemical properties of engineered nanomaterials and their toxicity is critical for environmental and health risk analysis. However, this task is confounded by material diversity, heterogeneity of published data and limited sampling within individual studies. Here, we present an approach for analysing and extracting pertinent knowledge from published studies focusing on the cellular toxicity of cadmium-containing semiconductor quantum dots. From 307 publications, we obtain 1,741 cell viability-related data samples, each with 24 qualitative and quantitative attributes describing the material properties and experimental conditions. Using random forest regression models to analyse the data, we show that toxicity is closely correlated with quantum dot surface properties (including shell, ligand and surface modifications), diameter, assay type and exposure time. Our approach of integrating quantitative and categorical data provides a roadmap for interrogating the wide-ranging toxicity data in the literature and suggests that meta-analysis can help develop methods for predicting the toxicity of engineered nanomaterials.

Aptamer-capped multifunctional mesoporous strontium hydroxyapatite nanovehicle for cancer-cell-responsive drug delivery and imaging

A novel cancer-cells-triggered controlled-release gadolinium-doped luminescent and mesoporous strontium hydroxyapatite nanorods (designated as Gd:SrHap nanorods) system using cell-type-specific aptamers as caps has been constructed. Aptamers behave as a dual-functional molecule that acts as not only a lid but also a targeted molecular that can be used in an effective way for therapeutically special cancer cells. After incubated with cancer cells, for example, MCF-7 cells, the doxorubicin-loaded and aptamer-capped Gd:SrHap nanorods (designated as Gd:SrHap-Dox-aptamer) can be internalized into MCF-7 cells, resulting in the pore opening and drug releasing. Furthermore, the high biocompatibility and biodegradability Gd:SrHap nanorods with blue autofluorescence and paramagnetism could serve as a good contrast agent of targeting fluorescence and magnetic resonance imaging. We envision that this Gd:SrHap system could play a significant role in developing new generations of site-selective, controlled-release delivery and interactive sensory nanodevices.

Delivery of custom-purposed colloidal nanocrystals to cancer cells

Colloidal inorganic nanocrystals are abound with magnetic, luminescent and plasmonic properties that are attractive for medical diagnostics and therapy. Our group, among others, have been interested in conferring nanocrystals, by design, with new capabilities that are not possible with conventional materials approaches. Two areas where the fruits of these efforts are paying dividends are in their implementation as in vivo imaging probes and as biosensors that dynamically respond to the local chemical or physical environment in cells and tissues. For applications in medical imaging, nanocrystal probes with unusual shapes are showing exceptional promise over existing technologies, while for environment-responsive probes, a hybrid approach involving tailored organic coatings is being implemented alongside the nanocrystals for the realization of dynamic, information-rich optical outputs.