1,720,968 research outputs found
Quantum dot nanoparticles: Properties, surface functionalization, and their applications in biosensoring and imaging
No full textColloidal semiconductor nanocrystals, also known as Quantum Dots (QDs), posses unique properties due to their nanometric size. They have broad absorption spectra and narrow emission bands that are related to the materials used and to their size. QDs represent a new class of fluorescent probes that are gradually substituting traditional organic dyes since they present many advantages compared to them, first of all improved photostability. Furthermore, since QDs have broad absorption spectra, it is possible to excite many QDs using just one wavelength.
Much progress has been made in the last years in the synthesis of QDs, which now can yield highly homogeneous and highly crystalline QDs. Many strategies are also available nowadays to make QDs water soluble and biocompatible, the most common being the ligand exchange and polymer coating. The surface passivation of the QDs to make them water soluble also allows for further functionalization. As an example, if biological ligands are attached to the outer shell of the nanocrystals, they can selectively recognize specific targets. This approach can be exploited for numerous applications, among them biosensoring and imaging. Biosensors are a class of probes developed for biomarkers detection on a real-time or continuous basis in a complex mixture. This easy to use and low cost technique perfectly combines with the optical properties of QD. For example, the high photostability of QDs can allow for continuous monitoring of a signal over time. Furthermore, simultaneous detection of several specific receptors can be also achieved if many QDs with different emission colors are combined into a single structure, effectively behaving as an optical barcode. Optical imaging, in particular fluorescence imaging, is an area where QDs are gaining increasing popularity. Near-infrared wavelengths are of key importance for biological analysis since in this region biological tissues absorb only weakly. Few traditional organic dyes are available for such spectral window and in addition they suffer from photobleaching. On the other hand, QDs can be tuned to the desired emission wavelength by adjusting their composition and size. QDs have been already extensively used for cell imaging in vitro; however, the full potential of QDs can be appreciated only when they are employed in in vivo imaging. The preparation of multicolor probes which are highly stable in biological buffers and can be followed over long periods of time can be achieved by exploiting
the QDs properties. Although just in its infancy, biosensoring and imaging by means of QDs has already proved to be of paramount importance in biomedicine and future developments in QDs synthesis and functionalization will probably yield nano-tools of priceless value for medical application, e.g. for the early detection of diseases, such as in cancer diagnosis. In this chapter, we will try to give to the reader a general overview on the many aspects of QDs, mainly of their physical properties that are relevant for biological applications and on the strategies followed to make them biocompatible. Then the main biological applications of QDs will be reviewed, their implementation in biosensoring and imaging, both in vitro and in vivo, including their exploitation in photodynamic therapy. Finally, we will give an overview on the toxicity issues and on the upcoming new generations of QDs that should solve those issues
Cytomechanical and topological investigation of MCF-7 cells by Scanning Force Microscopy
No full textDespite enormous advances in breast cancer biology, there is an increased demand for new technologies/methods that are able to provide supplementary information to genomics and proteomics. Here, we exploit scanning force microscopy (SFM) in combination with confocal microscopy, to investigate the morphological and mechanical properties of two neoplastic cell lines: (i)MCF-7 (human breast cancer) and (ii)HeLa (human cervical carcinoma). Living and fixed cells either in phosphate buffer solution (PBS) or in air have been studied, and the viscoelastic properties (including the Young's modulus) of cells grown onto standard and modified (e.g.by fibronectin, one of the cellular matrix components) substrates have been measured. We observed different Young's modulus values, influenced by the adhesion and growth behaviour onto specific substrate surfaces
Transition from nonresonant to resonant random lasers by the geometrical confinement of disorder
No full textWe report on a transition in random lasers that is induced by the geometrical confinement of the emitting material. Different dye doped paper devices with controlled geometry are fabricated by soft lithography and show two distinguished behaviors in the stimulated emission: in the absence of boundary constraints, the energy threshold decreases for larger laser volumes showing the typical trend of diffusive nonresonant random lasers, while when the same material is lithographed into channels, the walls act as cavity and the resonant behavior typical of standard lasers is observed. The experimental results are consistent with the general theories of random and standard lasers and a clear phase diagram of the transition is reported. (C) 2013 Optical Society of Americ
Free-standing micropatternable nanocomposites as efficient colour converting filters for light emitting devices
No full textOne step preparation of quantum dot-embedded lipid nanovesicles by a microfluidic device
No full textSynthetic carriers that mimic "natural lipid-based vesicles" (such as micro/nanovesicles, exosomes) have found broad applications in biomedicine for the delivery of biomolecules and drugs. Remarkable advantages of using synthetic carriers include control over the lipid composition, structure and size, together with the possibility to add tracer molecules to monitor their in situ distribution via fluorescence microscopy. Over the past few years, new methods of vesicles production have been developed and optimized, such as those based on microfluidic techniques. These innovative approaches allow us to overcome the limitations faced in conventional methods of liposome preparation, such as size distribution and polydispersity. Herein, a Microfluidic Hydrodynamic Focusing (MHF) device has been used for the production of lipid-based vesicles with different lipid combinations that resemble natural exosomes, such as phosphatidylcholines (PC), cholesterol (Chol), dicetyl phosphate (DCP) and ceramide (Cer). Thanks to a fine control on fluid manipulation, the MHF device allows preparation of vesicles with controlled size, a relevant feature in the emerging field of carrier-assisted cell-delivery. Interestingly, PC/Chol/Cer vesicles exhibit low polydispersity and high stability up to 45 days. Later, quantum dots (QDs) were successfully embedded in these vesicles through the same preparation process. The development of QD-embedded lipid nanovesicles by MHF devices has never been described previously
Fast and safe microwave-assisted glass channel-shaped microstructure fabrication
No full textGlass micromachining is a basic technology to achieve microfluidic networks for lab-on-a-chip applications. Among several methods to microstructure glass, the simplest and most widely applied is wet chemical etching (WE). However, accurate control of the reaction conditions to perform reproducible, fast and safe glass etching is not straightforward. Herein, microwave-assisted WE is demonstrated to intensify the glass etching action under safe working and finely monitored operative conditions and to produce smooth deep channels in short processing times with reduced underetching effects
Lipid-Based Nanovesicles for Simultaneous Intracellular Delivery of Hydrophobic, Hydrophilic, and Amphiphilic Species
Full text linkRandom laser emission from a paper-based device
No full textRandom laser emission is obtained from a fluidic paper-based device realized by conventional soft-lithography techniques on common, flexible, renewable and biocompatible commercial paper. The device is realized exclusively on paper by creating microfluidic porous channels on the cellulose fibres, in which a laser dye (Rhodamine B) can flow by capillarity. The modulation of the random lasing characteristics, in terms of threshold and spectral position, can be tailored by acting on the confinement induced by the lithographic process as well as on the shape and functionalization at the interface of the emitting regions
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