Stephen M. Lane

Cell-Phone-Based Platform for Biomedical Device Development and Education Applications

In this paper we report the development of two attachments to a commercial cell phone that transform the phones integrated lens and image sensor into a 350× microscope and visible-light spectrometer. The microscope is capable of transmission and polarized microscopy modes and is shown to have 1.5 micron resolution and a usable field-of-view of 150×150 with no image processing, and approximately 350×350 when post-processing is applied. The spectrometer has a 300 nm bandwidth with a limiting spectral resolution of close to 5 nm. We show applications of the devices to medically relevant problems. In the case of the microscope, we image both stained and unstained blood-smears showing the ability to acquire images of similar quality to commercial microscope platforms, thus allowing diagnosis of clinical pathologies. With the spectrometer we demonstrate acquisition of a white-light transmission spectrum through diffuse tissue as well as the acquisition of a fluorescence spectrum. We also envision the devices to have immediate relevance in the educational field.

HYADES—A plasma hydrodynamics code for dense plasma studies

Abstract The one-dimensional radiation hydrodynamics code HYADES was originally developed to simulate laboratory experiments on dense plasmas driven by intense sources of energy. The code was constructed with the objectives of providing a tool that is (1) “easy to use” by an experimentalist, (2) formulated using simple yet accurate numerical approximations to the physics models, (3) easy to modify and extend with new models, and (4) run on a variety of computers including PCs and Macs. Improvements have been made to several of the physics packages, especially the atomic physics and opacity models. Recent additions and modifications have been made to allow more realistic simulations of materials at temperatures below a few eV. These include models for materials with strength, yield, and linear heat conduction. Examples of simulations of two recent laboratory experiments demonstrates the utility of the code.

Nondestructive Identification of Individual Leukemia Cells by Laser Trapping Raman Spectroscopy

Currently, a combination of technologies is typically required to assess the malignancy of cancer cells. These methods often lack the specificity and sensitivity necessary for early, accurate diagnosis. Here we demonstrate using clinical samples the application of laser trapping Raman spectroscopy as a novel approach that provides intrinsic biochemical markers for the noninvasive detection of individual cancer cells. The Raman spectra of live, hematopoietic cells provide reliable molecular fingerprints that reflect their biochemical composition and biology. Populations of normal T and B lymphocytes from four healthy individuals and cells from three leukemia patients were analyzed, and multiple intrinsic Raman markers associated with DNA and protein vibrational modes have been identified that exhibit excellent discriminating power for cancer cell identification. A combination of two multivariate statistical methods, principal component analysis (PCA) and linear discriminant analysis (LDA), was used to confirm the significance of these markers for identifying cancer cells and classifying the data. The results indicate that, on average, 95% of the normal cells and 90% of the patient cells were accurately classified into their respective cell types. We also provide evidence that these markers are unique to cancer cells and not purely a function of differences in their cellular activation.

Spectroscopic diagnostic for ablative compression experiments

A spectroscopic diagnostic which will be useful for laser-driven thick-shelled ablative compression targets is demonstrated. The diagnostic which uses spectral line emission from lithium-like bromine provides information from several allowed lines in a small spectral range and can be used to estimate ground state number density as well as electron density in the compressed core.

Controlled non-classical photon emission from single conjugated polymer molecules

Photon pair-correlation spectroscopy was used to study the photoluminescence of single, isolated chains of the conjugated polymer MEH-PPV (poly[2-methoxy,5-(2-ethyl-hexyloxy)-p-phenylene-vinylene]). The chain conformation of these multichromophoric molecules was controlled by varying solvent polarity to result in either tightly folded collapsed chain or extended chain structures. We demonstrate, that the polymer conformation has strong influence on the quantum optical nature of the single chain photon emission. Polymers in the collapsed-chain conformation exhibit the non-classical phenomenon of photon antibunching in contrast to extended-chain structures. Analysis of the second-order correlation function provides a quantitative measure of the number of active emitter sites.

Analysis of Single Bacterial Spores by Micro-Raman Spectroscopy

The spectroscopic analysis of individual living cells in their native state provides a powerful tool for the investigation of complex biological systems. Micro-Raman spectroscopy, in which confocal microscopy is combined with Raman spectroscopy, offers a promising route to achieving this, because it provides a means to study individual cells and cellular components.1–9 Here we describe the analysis of individual bacterial endospores from four species in the genus Bacillus by micro-Raman spectroscopy. Previous Raman studies on Bacillus spores resulted in spectra with strong scattering from calcium dipicolinate (CaDPA), which is the calcium chelate of dipicolinic acid (2,6-pyridinedicarboxylic acid, DPA); however, these earlier studies were conducted on concentrated samples of spores.10–14 By using micro-Raman spectroscopy, we demonstrate the ability to obtain similar information from individual spores. The Raman spectra for most spores studied were dominated by scattering from CaDPA, although Raman scattering assignable to protein bands and to phenylalanine was also observed. Approximately 4% of the spores analyzed did not exhibit Raman intensity from CaDPA, possibly due to incomplete sporulation. The results presented indicate that micro-Raman spectroscopy is a promising technique for in-

Effect of Cefazolin Treatment on the Nonresonant Raman Signatures of the Metabolic State of Individual Escherichia coli Cells

Laser tweezers Raman spectroscopy (LTRS) was used to characterize the Raman fingerprints of the metabolic states of Escherichia coli (E. coli) cells and to determine the spectral changes associated with cellular response to the antibiotic Cefazolin. The Raman spectra of E. coli cells sampled at different time points in the bacterial growth curve exhibited several spectral features that enabled direct identification of the growth phase of the bacteria. Four groups of Raman peaks were identified based on similarities in the time-dependent behavior of their intensities over the course of the growth curve. These groupings were also consistent with the different biochemical species represented by the Raman peaks. Raman peaks associated with DNA and RNA displayed a decrease in intensity over time, while protein-specific Raman vibrations increased at different rates. The adenine ring-breathing mode at 729 and the 1245 cm(-1) vibration peaked in intensity within the first 10 h and decreased afterward. Application of principal component analysis (PCA) to the Raman spectra enabled accurate identification of the different metabolic states of the bacterial cells. The Raman spectra of cells exposed to Cefazolin at the end of log phase exhibited a different behavior. The 729 and 1245 cm(-1) Raman peaks showed a slight decrease in intensity from 4 to 10 h after inoculation. Moreover, a shift in the spectral position of the adenine ring-breathing mode from 724 to 729 cm(-1), which was observed during normal bacterial growth, was inhibited during antibiotic drug treatment. These results suggest that potential Raman markers exist that can be used to identify E. coli cell response to antibiotic drug treatment.

Femtosecond X-ray diffraction from two-dimensional protein crystals

Bragg diffraction achieved from two-dimensional protein crystals using femtosecond X-ray laser snapshots is presented.

Evaluation of Escherichia coli Cell Response to Antibiotic Treatment by Use of Raman Spectroscopy with Laser Tweezers

ABSTRACT Laser tweezers Raman spectroscopy was used to detect the cellular response of Escherichia coli cells to penicillin G-streptomycin and cefazolin. Time-dependent intensity changes of several Raman peaks at 729, 1,245, and 1,660 cm−1 enabled untreated cells and cells treated with the different antibiotic drugs to be distinguished.

Optical coherence tomography and Raman spectroscopy of the ex-vivo retina

Imaging the structure and correlating it with the biochemical content of the retina holds promise for fundamental research and for clinical applications. Optical coherence tomography (OCT) is commonly used to image the 3D structure of the retina and while the added functionality of biochemical analysis afforded by Raman scattering could provide critical molecular signatures for clinicians and researchers, there are many technical challenges to combine these imaging modalities. We describe an OCT microscope for ex-vivo imaging combined with Raman spectroscopy capable of collecting morphological and molecular information about a sample simultaneously. We present our first results and discuss the challenges to further development of this dual-mode instrument and limitations for future in-vivo retinal imaging.