Heather Clark Copyright (c) 2012 All rights reserved. http://works.bepress.com/hclark Recent documents in Heather Clark en-us Sat, 24 Nov 2012 09:28:24 PST 3600 Novel optical biosensors using a gold colloid monolayer substrate http://works.bepress.com/hclark/4 http://works.bepress.com/hclark/4 Thu, 04 Nov 2010 13:32:57 PDT A novel optical biosensor matrix has been developed to exploit the native fluorescence of certain proteins. This matrix uses a gold colloid monolayer attached to an end of a fiber as a substrate for protein attachment. The effect of the gold monolayer size has been investigated through the techniques of fluorescence, scanning electron microscopy, and transmission electron microscopy. It has been shown that the size ofthe gold colloid does produce a marked difference in the fluorescence intesity measured. It is surmised through the use of microscopy techniques that the intensity changes seen in the fluorescence emission are not a result of surface coverage, or availability of sites for protein adsorption, but instead of quenching or enhancement by the gold itself.

]]> Heather A. Clark et al. Optochemical nanosensors for intracellular chemical measurement http://works.bepress.com/hclark/5 http://works.bepress.com/hclark/5 Thu, 04 Nov 2010 13:32:57 PDT The development of a submicron optical fiber "supertip" has provided advantages over previously produced submicron tips, such as facilitating insertion of these sensors into cells while minimizing damage to the cell membrane. Fiber optic ion correlation-based nanosensors for sodium, potassium and chloride employing these "supertips" have been applied to the monitoring of ion concentrations in single mouse oocytes. These sensors have also been used to monitor the effect of an ion channel-blocking agent. In order to address the challenge associated with single-cell simultaneous measurement of multiple analytes, the use of submicron optical fiber multiprobes has been explored.

]]> Raoul Kopelman et al. Second-harmonic imaging microscopy of living cells http://works.bepress.com/hclark/3 http://works.bepress.com/hclark/3 Thu, 04 Nov 2010 13:32:56 PDT Second harmonic generation (SHG) has been developed in our laboratories as a high-resolution nonlinear optical imaging microscopy for cellular membranes and intact tissues. SHG shares many of the advantageous features for microscopy of another more established nonlinear optical technique: two-photon excited fluorescence (TPEF). Both are capable of optical sectioning to produce threedimensional images of thick specimens and both result in less photodamage to living tissue than confocal microscopy. SHG is complementary to TPEF in that it uses a different contrast mechanism and is most easily detected in the transmitted light optical path. It can be used to image membrane probes with high membrane specificity and displays extraordinary sensitivity in reporting membrane potential; it also has the ability to image highly ordered structural proteins without any exogenous labels.

]]> Paul J. Campagnola et al. Sub-wavelength plasmonic readout for direct linear analysis of optically tagged DNA http://works.bepress.com/hclark/2 http://works.bepress.com/hclark/2 Thu, 04 Nov 2010 13:32:55 PDT This work describes the development and fabrication of a novel nanofluidic flow-through sensing chip that utilizes a plasmonic resonator to excite fluorescent tags with sub-wavelength resolution. We cover the design of the microfluidic chip and simulation of the plasmonic resonator using Finite Difference Time Domain (FDTD) software. The fabrication methods are presented, with testing procedures and preliminary results.

This research is aimed at improving the resolution limits of the Direct Linear Analysis (DLA) technique developed by US Genomics. In DLA, intercalating dyes which tag a specific 8 base-pair sequence are inserted in a DNA sample. This sample is pumped though a nano-fluidic channel, where it is stretched into a linear geometry and interrogated with light which excites the fluorescent tags. The resulting sequence of optical pulses produces a characteristic "fingerprint" of the sample which uniquely identifies any sample of DNA. Plasmonic confinement of light to a 100 nm wide metallic nano-stripe enables resolution of a higher tag density compared to free space optics. Prototype devices have been fabricated and are being tested with fluorophore solutions and tagged DNA. Preliminary results show evanescent coupling to the plasmonic resonator is occurring with 0.1 micron resolution, however light scattering limits the S/N of the detector. Two methods to reduce scattered light are presented: index matching and curved waveguides.

]]> Jonathan Varsanik et al. A comparative study of optical fluorescent nanosensors (PEBBLEs) and fiber optic microsensors for oxygen sensing http://works.bepress.com/hclark/1 http://works.bepress.com/hclark/1 Thu, 04 Nov 2010 13:32:54 PDT In this paper we report the use of phase sensitive fluorometry to obtain preliminary results from opto-chemical fluorescent oxygen nanosensors. PEBBLE (Probe Encapsulated By Biologically Localized Embedding) sensors were fabricated by immobilizing tris(4,7-diphenyl—1, 10-phenanthroline)Ru(II) chloride and tris(1,10-phenanthroline)Ru(II) chloride within a polyacrylamide matrix. PEBBLEs have diameters of 20-200 nm and exhibit excellent performance for dissolved oxygen detection. Their performance is compared with micrometer-sized (10-20 μm) optical fiber sensors and free dye in solution. Oxygen sensing ability of PEBBLEs was tested in the presence of other quenchers and compared with free dyes in solution. While PEBBLEs have been developed for minimally invasive intracellular chemical analysis, they show additional advantages, such as increased dynamic range, compared to microsensors, and an absence of interference (quenching) by heavy ions, in contrast to free dye solutions.

]]> Z. Chen-Esterlit et al.