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Quantam dots:

Quantam dots Presented by K.VIJAY BHASKAR REDDY, Saastra college of pharmaceutical education & research, Nellore, andhrapradesh. UNDER THE ESTEEMED GUIDENCE OF Ms.p.mahalakshmi , m.pharm .


NANOCARRIERS Nanocarriers work by bringing drugs directly to diseased areas of the body, thereby minimizing the exposure of healthy tissues while increasing the accumulation of the drug in the tumour area. This reduces both the dose necessary for treatment and the damage that can be caused to healthy tissue by powerful medicine. 2 SAASTRA COLLEGE OF PHARMACY


QUANTUM DOTS Quantum dots are semiconducting nanocrystals, which range in size from 2 nm to 10 nm. They can be used for both diagnosis and drug delivery, especially for cancer treatments. By coating the quantum dot with a protective layer that is laced with a cancer-fighting drug, bio-compatibility molecules, and antibodies that stick only to a specific type of cancer, the QD is made ready for injection. The QD enters the bloodstream and attaches itself to a cancer cell using the antibodies. The cancer cell takes in the QD, and the location is radiated with infrared light. This causes the QD to emit photons, allowing the site of the tumor to be located, and release the anti-cancer drug directly into the cancer cell.


Quantum dots are made from tiny bits of metal about thousand times smaller than width of a hair. They can be molded into different shapes and coated with a variety of biomaterials. QUANTUM DOTS


Just as in an atom, the energy levels are quantized due to the confinement of electrons. The 3D spatial confinement is observed in the quantum dots. In some quantum dots even if one electron leaves the structure there is a significant change in the properties. Unlike atoms however, quantum dots can be easily connected to electrodes and are therefore excellent tools to study atomic-like properties… A quantum dot can have anything from a single electron to a collection of several thousands… QUANTUM DOTS

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QDS COMPOSITION QDs are nanocrystals composed of a semiconductor core including group II-VI or group III-V elements encased within a shell comprised of a second semiconductor material. A typical QD has a diameter ranging from 2 to 10 nm containing roughly 200 to 10,000 atoms, with size comparable to a large protein. In comparison with organic dyes and fluorescent proteins, QDs have unique optical properties. QD cores are usually composed of elements from groups II and VI, e.g., CdSe (most common) or groups III and V, e.g., InP, while the shell is typically a high band gap material such as ZnS ..

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Composite with A Novel Structure for Active Sensing in Living cells Silica ZnS CdSe Co ① Cobalt core : active manipulation diameter : ~10 nm superparamagnetic NPs → manipulated or positioned by an external field without aggregation in the absence of an external field ② CdSe shell : imaging with fluorescence thickness : 3-5 nm visible fluorescence (~450 – 700 nm) ability to tune the band gap → by controlling the thickness, able to tune the emission wavelength, i.e., emission color ④ Silica shell : bio-compatibility & functionalization with specific targeting group thickness : ~10 nm bio-compatible, & non-toxic to live cell functions stable in aqueous environment ability to functionalize its surface with specific targeting group ③ ZnS shell : electrical passivation thickness : 1-2 nm having wider band gap (3.83 eV ) than CdSe (1.91 eV ) enhancement of QY → CdSe (5-10%)  CdSe / ZnS (~50%)


properties Electronic properties such as size and composition-tunable light emission, improved signal brightness, resistance to photo bleaching and simultaneous excitation of multiple fluorescence colors. In addition, different colors of QDs can be simultaneously excited with a single light source, with minimal spectral overlapping, which provides significant advantages for multiplexed detection of target molecules. However, as QDs are hydrophobic by nature, it is necessary to solubilize QDs before application by surface modification with biofunctional molecules because QDs have large surface areas for the attachment of such molecules. When conjugated with diagnostic (e.g. optical) and therapeutic (e.g., anticancer) agents, QDs can be used for cancer diagnosis and therapy with high specificity.


QUANTUM DOTS QD in Tissues QD in Rat


history In the 1970s the first low dimensional structures QW (Quantum Wells) were developed. 1D (quantum wires) and 0D (quantum dots) were subsequently developed. They were initially prepared in 1982 for use as a probes for investigation of surface kinetics, where it was found that the quantum yield of the nanocrystals was sensitive to the concentration of surface adsorbed species that can undergo reduction .


history In a different approach to creating white light several researchers at the Department of Energy's (DOE) Sandia National Laboratories have developed the first solid state white light-emitting device using quantum dots.

Glossary of terms related to quantum dots :

Glossary of terms related to quantum dots Spectral band gap - The separation between electronic energy levels of a material. Bohr Radius - The natural separation distance between the positive and negative charges in the excited state of a material Quantum yield - The ratio of photons absorbed to photons emitted by a fluorophore . Blinking - The property of a fluorophore where it switches between fluorescent and non-fluorescent states. In the case of QDs, this occurs when they switch between the ionized and neutral states. Fluorescence resonance energy transfer (FRET) - A process in which energy is transferred from an excited donor molecule to an acceptor molecule through near-field dipole–dipole interaction. The process is very sensitive to the distance between the donor and acceptor molecules. Stoke's shift - The energy (and thus wavelength) difference between absorption and emission spectra.

Biomedical applications of quantum dots:

Biomedical applications of quantum dots Microscopy and multiplexed histology Flow-cytometry Drug delivery Photodynamic therapy In vivo whole animal and clinical imaging (e.g., angiography) Tissue mapping and demarcation (e.g., sentinel lymph node) Real time detection of intracellular events, signalling, and bio- sensing Tracking cell migration (e.g., stem cells) Low cost but sensitive point-of-care detection (e.g., lateral flow) Environment and bio-defence Color Coded Quantum Dots For Fast DNA Testing 3-D Imaging Inside Living Organism, Using Quantum Dots

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