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Optical Nanoprobes for Diagnosis
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
R. G. Aswathy, D. Sakthi Kumar
These unique properties lead to QDs of different-size emitting lights of different wavelengths from ultraviolet to infrared spectrum. For example, the bulk bandgap of semiconductor cadmium selenide (CdSe) is 1.7 eV corresponding to 730 nm light emission. By changing the nanocrystal diameter of CdSe from 2 nm to 7 nm, it can be tuned to emit light with wavelength between 450 nm and 650 nm. The material composition can also be used as another factor for the modification of band gap of the semiconductor. By changing the composition of the alloy CdSexTe1–x of 5 nm size can be tuned to emit light in 610–800 nm. The size and shape of semiconductor QDs can be specifically controlled by factors such as experimental duration, temperature, and concentration of precursor molecules in the synthesis.
Nanomedicine(s) under the Microscope *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Like carbon nanotubes and silicon nanoparticles, the semiconductor nanocrystals known as QDs (1–100 nm) are among the most widely investigated new biomedical nanomaterials. They provide novel imaging labels (many excellent reviews e.g., Refs [359, 360]) for tumor imaging [361, 362] and for use in theranostics. Typically they are made from cadmium selenide (CdSe) with a surface coating of ZnS or CdS to protect against photo-oxidation and improve the fluorescence quantum yield (Fig. 13.6e) (for full review of the chemistry, see Ref. [360]). A variety of additional surface coatings (e.g., with hydrophobic or electrostatic interaction and/or PEGylation) have been used to minimize aggregation, to introduce targeting ligands, and to improve biodistribution/elimination. Coatings also stabilize against loss of signal in acid pH and salt solutions. Appealing properties of QDs include the ability to fine-tune the fluorescence emission color by varying composition, size, shape, solvent, and stability against photobleaching. However, on-off fluorescence (“blinking”) can be a disadvantage for detection.
Other Toxic Effects
Published in Lars Friberg, Tord Kjellström, Carl-Gustaf Elinder, Gunnar F. Nordberg, Cadmium and Health: A Toxicological and Epidemiological Appraisal, 2019
As rodents do not usually regurgitate stomach contents, exposure to higher doses is possible. The acute oral LD50 for soluble compounds, such as cadmium acetate, cadmium chloride, and cadmium sulfate, is in the order of 50 to 400 mg/kg body weight. Insoluble compounds, such as cadmium selenide and cadmium sulfide, have been reported to have oral LD50 values exceeding 5 g/kg body weight.44
The use of Drosophila melanogaster as a model organism to study immune-nanotoxicity
Published in Nanotoxicology, 2019
Cheng Teng Ng, Liya E Yu, Choon Nam Ong, Boon Huat Bay, Gyeong Hun Baeg
Metal-based NMs are also known to exert their toxicity through the release of ions. For example, CuO NPs found to be distributed inside the midgut cells were observed to translocate to the hemolymph which was followed by a reduced larval growth and decreased fly viability. This is accompanied by the dysregulation of antioxidant genes and injury on the intestinal barrier (Alaraby et al., 2016). However, the effect of CuO NPs on the hemolymph was not discussed. In another study, elevated ROS induction and DNA damage were detected in larval hemocytes exposed to cadmium selenide (CdSe) QDs, primarily due to the presence of free Cd2+ ion (Galeone et al., 2012). This may suggest that larval ingestion of NPs results in an increased ROS production in hemocytes which then leads to DNA damage, an aberrant proliferation and/or differentiation, as well as apoptosis in the cells (Figure 8). On the other hand, AgNPs at larval stage are reported to significantly alter metabolic activity, as evidenced by changes in lipid, carbohydrate and protein levels, in adult flies (Raj et al. 2017). The authors also observed an increased ROS production in larval tissues which suggests that this phenomenon could be attributed to the disruption of the mitochondrial respiratory chain, thereby giving rise to an oxidative stress. Although no direct observation of disturbance on the immune system was reported in this study, alteration in metabolic activity is believed to exert certain effects on the immune system.
Nanocarriers in advanced drug targeting: setting novel paradigm in cancer therapeutics
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Md. Habban Akhter, Md. Rizwanullah, Javed Ahmad, Mohamed Jawed Ahsan, Md. Ali Mujtaba, Saima Amin
Quantum dot: Tezpur University from India in collaboration with National University of Science and Technology MISIS (NUST MISIS) take a step towards innovation and development of cancer growth by taking their sharp image. Alphaneurotoxins, a toxin from cobra venom in combination with the so-called quantum dots, made to a hybrid compound. The quantum dot was composed of cadmium selenide which is fundamentally a fluorescent nanoparticle. The cadmium selenide nanoparticle has a film of short peptide chain which is biocompatible and nullifies the toxic effect of quantum dots. The incorporated new substances helped in tracing the boundaries of cancer growth and, therefore, a potential marker. Mechanistically, the toxin from snake venom conjugated with certain part of cancer cells and quantum dot emits light upon excitation. This neurotoxin quantum dot conjugate arrives at the target site through systemic circulation and boundaries of neoplasm highlighted by fluorescent nanoparticles that fluoresces upon UV irradiation. The collaborative research played a significant role in generating novel hybrid composite and tested in various types of cells in deciphering their toxicity [64] (http://economictimes.indiatimes.com).
Recent advances in intraocular and novel drug delivery systems for the treatment of diabetic retinopathy
Published in Expert Opinion on Drug Delivery, 2021
Deep Shikha Sharma, Sheetu Wadhwa, Monica Gulati, Arya Kadukkattil Ramanunny, Ankit Awasthi, Sachin Kumar Singh, Rubiya Khursheed, Leander Corrie, Nitin Chitranshi, Vivek Kumar Gupta, Sukriti Vishwas
Quantum dots (QDs) are semiconductor nanocrystals with a size between 2 and 6 nm [157]. They are made up of heavy metals such as cadmium selenide along with zinc sulfide. They are mainly used as imaging agents for labeling glia, neurons [158], and endothelial cells in retinal capillaries [159]. In one of the studies, silicon-based QDs were prepared and delivered via intravitreal route for delivering electrical stimulation to retinal cells in a model of retinal photoreceptor as a neuroprotective agent. These systems have been used for drug targeting into the posterior part of the eye for the treatment of ocular diseases [160].