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Diagnostics and Therapy
Proposed model for optical pulse-driven adsorption of fluorescent proteins on gold nanoparticles.

Nano-manipulations of macro-molecules

Currently under study The unique optical properties of gold nanoparticles make them attractive for a wide range of applications which require optical detection and manipulation techniques. Here, we experimentally demonstrate the use of single femtosecond pulses at resonance wavelength for a controlled conjugation of gold nanoparticles and fluorescent proteins. This optically driven reaction is rigorously studied and analyzed using a variety of experimental techniques, and a detailed model is proposed which describes the adsorption of the proteins onto the nanoparticles’ surface, as well as their subsequent desorption by a reducing agent. Potential applications of the resulting nanoparticle-protein conjugates include controlled delivery of fluorescent markers and local sensing of biochemical processes. Fig. 1. (a) Fluorescence images of the nanoparticle-protein solutions following resonant illumination by a single pulse. The (false) colors correspond to the fluorescence emission wavelength of each protein. The field of view of each frame is 2.5 mm × 1.87
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Nanoparticle-pulse interaction

Nanoparticle-pulse interaction

Gold nanoparticles find a wide range of applications in optics and photonics; however, their detailed interaction with intense laser light is only partially understood. Previous works have studied the effect of intense pulse trains on gold nanoparticles at a wide range of illumination parameters, and observed diverse optical and morphological changes. In this work we study, for the first time, the interaction between single femtosecond pulses and gold nanoparticles. Using transmission electron microcopy and optical spectroscopy, we have found that nanoparticles illuminated by 50 fs pulses with fluence of less than 0.15 J/cm2 per pulse (3 TW/cm2) undergo morphological changes which affect their extinction spectra. Experimentation with particles of different diameters show similar qualitative effects, which are more pronounced for larger particles. Pulses at different excitation wavelengths were found to induce different effects for resonance and off-resonance conditions. The presented results provide valuable experimental data on the complex pulse-particle interaction
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Nano-manipulations of cells

Nano-manipulations of cells

Specifically targeting and manipulating living cells is a key challenge in biomedicine and in cancer research in particular. Several studies have shown that nanoparticles irradiated by intense lasers are capable of conveying damage to nearby cells for various therapeutic and biological applications. In this work we utilize ultrashort laser pulses and gold nanospheres for the generation of localized, nanometric disruptions on the membranes of specifically targeted cells. The high structural stability of the nanospheres and the resonance pulse irradiation allow effective means for controlling the induced nanometric effects. The technique is demonstrated by inducing desired death mechanisms in epidermoid carcinoma and Burkitt lymphoma cells, and initiating efficient cell fusion between various cell types. Main advantages of the presented approach include low toxicity, high specificity and high flexibility in the regulation of cell damage and cell fusion, which would allow it to play an important role in various future clinical and
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The attachment between two different cells

Specific cell fusion

The attachment between two different cells via a bispecific nanoparticle is illustrated in Figure 1a. Following the addition of the nanoparticles to the growth medium of an equally (1:1) mixed BJAB (green labeled) and human monocyte-derived dendritic (blue labeled) cell population (Figure 1b), approximately 30% of the cells formed pairs or small clusters of physically attached cells (Figure 1c). Significantly lower cell attachment levels of 7, 6.5, and 4.5% were observed when incubating similar cell mixtures with only single antibody (anti-CD20) nanoparticles, nonspecific antiepidermal growth factor receptor (EGFR)-coated nanoparticles, and in the absence of nanoparticles, respectively. A closer view of a fi xated BJAB–DC pair is shown in the false-color scanning electron microscopy (SEM) image ( Figure 2a), revealing the light-toned BJAB cell (green) attached to the larger and feature-rich DC (blue). A magnified view (Figure 2b) of the region marked by a rectangle in Figure 2a, overlaid by an
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Our benchtop spectrally encoded imaging system

Adjusting field of view using dispersion

Utilizing Fourier-domain interferometry, spectrally encoded endoscopy (SEE) was shown capable of video-rate three-dimensional imaging, albeit at limited depth of field due to the limited spectral resolution of the detection spectrometer. We show that by using dispersion management at the reference arm of the interferometer, the tilt and curvature of the field of view could be adjusted without modifying the endoscopic probe itself. By controlling the group velocity dispersion, this technique is demonstrated useful for imaging specimen regions which reside outside the system’s depth of field. This approach could be used to improve usability, functionality and image quality of SEE without affecting probe size and flexibility. Our benchtop spectrally encoded imaging system (figure 1) consisted of a broadband titanium sapphire oscillator (Femtolasers Rainbow, 300 nm bandwidth, 800 nm center wavelength) coupled to a 50/50 single-mode optical fiber coupler within a Michelson interferometer arrangement. The sample arm consisted of a fiber collimator,
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A single cell crossing the spectral line produces a two-dimensional image with one axis encoded by wavelength and the other by time.

Imaging blood flow

Optical microscopy of blood cells in vivo provides a unique opportunity for clinicians and researchers to visualize the morphology and dynamics of circulating cells, but is usually limited by the imaging speed and by the need for exogenous labeling of the cells. Here we present a label-free approach for in vivo flow cytometry of blood using a compact imaging probe that could be adapted for bedside real-time imaging of patients in clinical settings, and demonstrate subcellular resolution imaging of red and white blood cells flowing in the oral mucosa of a human volunteer. By analyzing the large data sets obtained by the system, valuable blood parameters could be extracted and used for direct, reliable assessment of patient physiology. Fig. 1. Image acquisition in SEFC. (a) A single line within a blood vessel is imaged with multiple colors of light that encode lateral positions. (b) A single cell crossing the spectral
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An image of a USAF-1951 fluorescence resolution target

Multi-channel spectrally encoded endoscope

In its current mode of implementation, SEE has several limiting factors which need to be addressed before its clinical promise could be realized. First, the use of wavelength to encode space imposes some difficulties on wavelength-sensitive imaging modalities. For example, fluorescence spectrally encoded imaging required a sophisticated optical setup for frequency-encoding [19]. Additionally, the use of spatially coherent illumination through a single mode fiber causes pronounced speckle noise, small depth of field, and poor signal collection efficiency which often requires the use of lasers, supercontinuum generation sources, or high power super-luminescent diode arrays. One possible solution for addressing these issues includes the use of a double-clad fiber for spatially coherent sample illumination and incoherent signal collection. While double-clad SEE was demonstrated capable of speckle-free imaging with large depth of field, the endoscopic probe itself suffered from significant cross-talk between the illumination and the collection channels. Back reflections from the probe’s
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Miniature endoscope

Spectrally encoded endoscopy

Endoscopes help medical procedures to be less invasive, thereby reducing the risk of complications as well as costs and recovery times, but their application is limited in part by their size and inflexibility and by their inability to provide a three-dimensional perspective. We study a new type of endoscopy that enables video-rate, three-dimensional images to be transmitted from flexible probes that are comparable in diameter to a human hair. This technology opens up the possibility of moving operations to an outpatient setting, reducing requirements for anesthesia, and minimizing tissue damage. The first endoscope was invented almost 50 years ago and consisted of a bundle of optical fibers. Miniature endoscopes still use bundles of optical fibers to transmit a two-dimensional image, but larger endoscopes now employ solid-state, charge-coupled-device cameras for superior image quality. Fiber-bundle endoscopes with sub millimeter diameters have been used for a variety of clinical applications. However, they have
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Blood microscope

Imaging blood flow

Red blood cell imagingOptical microscopy of blood cells in vivo provides a unique opportunity for clinicians and researchers to visualize the morphology and dynamics of circulating cells, but is usually limited by the imaging speed and by the need for exogenous labeling of the cells. Here we present a label-free approach for in vivo flow cytometry of blood using a compact imaging probe….
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