RESUMEN

There is an increasing need for rapid, low cost, reusable, reliable and sensitive detection systems for diagnosing infectious diseases, metabolic disorders, rapidly advancing cancers and detecting the presence of environmental pollutants. Most traditional methods are invasive, slow, expensive and laborious, requiring highly specialized instruments. Introduction of biosensors with nanomaterials as transducers of signals have helped in removing the disadvantages associated with traditional detectors. The properties of high mechanical strength, better electrical conductivity and ability to serve as efficient signal transducers make carbon nanotubes (CNTs) ideal material for biosensor applications among the gamut of nanomaterials. Further, CNTs with their high surface areas, easily functionalizable surfaces for receptor immobilization are gaining importance in the construction of biosensors. The expanding field of CNTs bridges the physical sciences with biology, as chemical methods are employed to develop novel tools and platforms for understanding biological systems, in disease diagnosis and treatment. This review presents recent advances in surface functionalization of CNTs necessary for immobilization of enzymes and antibodies for biosensor applications and the methodologies used for the detection of a number of chemical and biological species. The review ends with a speculation on future prospects for CNTs in biology and medicine.

Asunto(s)

RESUMEN

The surface immobilization of beta-cyclodextrins on the surface of multiwalled carbon nanotubes (MWNTs) in an aqueous medium was achieved by covalent-binding of diamino-functionalized beta-cyclodextrin with carboxylic acid-functionalized MWNTs via amide linkages using a water-soluble condensation agent at room temperature. The obtained product denoted as beta-cyclodextrin-modified MWNTs was highly dispersible in an aqueous medium. The covalent surface functionalization of MWNTs by beta-cyclodextrin was characterized by FTIR, TGA, EDS and TEM. The thermogravimetric analyses indicated that -70 wt% beta-cyclodextrin was attached on the surface of MWNTs. Furthermore, the fluorometric analysis for adsorption of rhodamine 6G dye suggested that the formation of beta-cyclodextrin-dye inclusion conjugate takes place prior to the adsorption of dyes on MWNTs and uniform dispersion of MWNTs after surface immobilization allows superior fluorescence quenching than the pristine and oxidized MWNTs.

RESUMEN

Solubilization of [60]fullerene in water by complexation with disaccharides in mixed homogeneous solvent system, is described for the first time. The complexation of extremely water-insoluble [60]fullerene dissolved in non-polar solvent toluene and extremely water-soluble disaccharides dissolved in polar solvent DMSO resulted in an unique self-assembled highly crystalline water-soluble [60]fullerene-disaccharide complex. The interaction between [60]fullerene and disaccharides was found to be non-covalent and were characterized by FTIR, UV-Vis, NMR, XRD, and thermogravimetric analysis. The particle size of the lactose-C(60) complex was found to be monodisperse ~60 nm from Transmission Electron Microscopy (TEM) and matched with the size obtained from Static Light Scattering (SLS). Preliminary studies of radical scavenging on the most stable free radical 2,2'-diphenyl-1-picrylhydrazyl (DDPH) suggested that complex has potential biological applications.

Asunto(s)

RESUMEN

Low-molecular weight amphiphilic diblock copolymers, polystyrene-block-poly (2-vinylpyridine) (PS-b-P2VP), and (P2VP-b-PS) with different block ratios were synthesized for the first time via organotellurium-mediated living radical polymerization (TERP). For both the homo- and block copolymerizations, good agreement between the theoretical, and experimental molecular weights was found with nearly 100% yield in every case. The molecular weight distribution for all the samples ranged between 1.10 and 1.24, which is well below the theoretical lower limit of 1.50 for a conventional free radical polymerization. Furthermore, a very simple approach to producing highly dense arrays of titania nanoparticles (TiO2 ) is presented using a site-selective reaction of titanium tetraisopropoxide within the P2VP domains of micellar film of P2VP-b-PS in toluene through the sol-gel method.

Asunto(s)

RESUMEN

[60] Fullerene has been nanoencapsulated by the formation of an inclusion complex with a beta-cyclodextrin-containing lactose copolymer. The cyclodextrin polymer was synthesized by reaction of beta-cyclodextrin chlorotriazine with beta-lactose, and the polymer was highly soluble in water. Encapsulation of the carbon allotrope was achieved by forming a stable inclusion complex between the water-soluble cyclodextrin and [60] fullerene by a new synthetic procedure. Preliminary studies indicate that this complex has potential for biomedical applications because of its radical scavenging properties.

Asunto(s)

RESUMEN

A novel encoding technique is proposed for the recognition of patterns using four different techniques for training artificial neural networks (ANNs) of the Kohonen type. Each template or model pattern is overlaid on a radial grid of appropriate size, and converted to a two-dimensional feature array which then acts as the training input to the ANN. The first technique employs Kohonen's self-organizing network, each neuron of which is assigned, after training, the label of the model pattern. It is found that a graphical plot of the labels of the neurons exhibits clusters (which means in effect that the feature array pertaining to distorted versions of the same pattern belongs to a specific cluster), thereby justifying the coding strategy used in this paper. When the new, unknown pattern is input to the network, it is classified to have the same label of the neuron whose corresponding model pattern is closest to the given pattern. In an attempt to reduce the computational time and the size of the network, and simultaneously improve accuracy in recognition, Kohonen's learning vector quantization (LVQ) algorithm is used to train the ANN. To further improve the network's performance and to realize a network of minimum size, two constructive learning algorithms, both based on LVQ, are proposed: (1) multi-step learning vector quantization (MLVQ), and (2) thermal multi-step learning vector quantization (TLVQ). When the proposed algorithms are applied to the classification of noiseless and noisy (and distorted) patterns, the results demonstrate that the pattern encoding strategy and the suggested training techniques for ANNs are efficient and robust. For lack of space, only the most essential results are presented here. For details, see Ganesh Murthy and Venkatesh (1996b).

RESUMEN

An accurate, rapid calculation of Cardiac Output is of great importance during the treatment of critically ill patients. This paper describes a complete, self-contained mini-computer system, based on a Data General NOVA 1220 which can accurately sample data and compute the results in about 30 sec. The system uses the thermodilution method with a Swan-Ganz catheter to collect data and a weighted least-squares technique to compute the results.

Asunto(s)