Fluorescence is a widely used transduction mechanism in bio-imaging, sensing or physical chemistry characterization applications. The ability to selectively excite desired molecules without generating considerable bulk background from nearby molecules is very important for all these applications. A near field excitation using an exponentially decaying evanescent field is often used to reduce the bulk background by selectively exciting molecules near to the surface. We propose an on-chip platform to improve the surface and bulk fluorescence separation by combining near-field excitation and near-field collection. We used the exponentially decaying evanescent tail of a Silicon Nitride rib waveguide to excite molecules and coupled the subsequent emission back via the same waveguide. We observe from the finite difference time domain simulation that both the excitation and coupling efficiency depend exponentially on the surface-molecule distance. Thus, combination of near field excitation and collection improves surface-bulk separation. A reduction by half in effective 1/e decay length was found experimentally for this combined near-field excitation and collection technique compare to the conventional only near-field excitation based technique . An analytical model is derived to find the optimum device efficiency for bio-sensing applications and established a general condition for sensor length to maximize the device efficiency and validated by experimental data. Finally, we used this platform for Fluorescence Correlation Spectroscopy and steady-state fluorescence anisotropy measurement. In this talk, I will present the fabrication, characterization and experimental results obtained using this proposed waveguide based platform.

Light reflectance and transmission from soft tissue has been utilized in noninvasive clinical measurement devices such as the photoplethysmograph (PPG) and reflectance pulse oximeter. Most methods of near infrared (NIR) spectroscopy focus on the volume reflectance from a semi-infinite sample, while very few measure transmission. We have previously shown that examining the full scattering profile (FSP), which is the angular distribution of exiting photons, provides more comprehensive information when measuring from a cylindrical tissue, such as earlobe, fingertip and pinched tissue. Our hypothesis is that the change in blood vessel diameter is more significant than the change in optical properties. The findings of this work demonstrate a realistic model for optical tissue measurements such as NIR spectroscopy, PPG and pulse oximetery.

Using resistive losses induced by optically excited surface plasmons has shown promise as a CMOS-compatible plasmonic light detector. Increased electron scattering introduced by surface plasmons in an applied current results in a measurable decrease in electrical conductance of a grating, allowing a purely electronic readout of surface plasmon excitation. Accordingly, because of its plasmonic nature, such a detector is dependent on both the wavelength and polarization of incident light with a response time limited by the surface plasmon lifetime. Our ultrafast measurements with electronic read-out indicate that the response time of this detector is on the order of 1ps. Thus such a detector would enable time-resolved biomedical applications such as real-time monitoring of protein structural dynamics for pharmacological applications and research.

Ion selective optical nanosensors allow accurate ion measurements in biological systems, without the physical limitations and invasiveness of ion selective electrodes. Optically based nanosensors (Photonic Explorers for Bioanalysis with Biologically Localized Embedding, PEBBLEs), have been optimized for fluorescence microscopy imaging, and have been applied for imaging various biochemical analytes. In here, we report the first example of a potassium selective nanosensor optimized for photoacoustic (PA) imaging. Notably, PA imaging overcomes the severe light penetration depth problem faced by fluorescence imaging in vivo. The new potassium selective nanosensor shows excellent response in the biological range, from 0 to 200 mM, as confirmed by both UV-Vis Spectroscopy and PA Spectroscopy. Furthermore, the K⁺ PEBBLE showed a 2 orders of magnitude, or higher, selectivity to K⁺ , relative to any other biological cations, such as Li⁺, Na⁺, Ca²⁺, and Mg²⁺.

The surface plasmon erupted by bare metallic film has limitation of localizing high intensity field. Thus, nanostructures on the metallic film (such as nanowire, nanopost) have been used to enhance the Plasmon field by antenna effect. In the case of nanowire, field is highly localized at the sharpened edge of the nanowire. If there is an additional enhancing factor such as a gap between the edges of the nanostructures, area of highly localized field is formed. By adopting reversed trapezoidal structure, we expected to control area and intensity of highly localized plasmon field from both the nano-antenna effect and the gap plasmonic effect. So, we simulated trapezoidal nanowire structure changing the ratio of bottom length and top length of nanostructure. Then we can observe the variation of Plasmon field and intensity. In addition, we can obtain unusual result that the intensity of Plasmon field is highly reduced at specific ratio of bottom length and top length.

Biopsies are conventionally performed in two dimensions. Histological slices in general present some micrometers in thickness, allowing that some molecular domains stay out of the resulting image. Thus the histopathological assay potentially is based on an incomplete set of information. The use of quantum dots as fluorescente probes allows the investigation of labelling pattern and biomarkers expression, along the three-dimensions of fresh histological slices, leading to more precise results. Present work show and discuss pattern and fluorescence intensity emission at the visible region obtained as a function of tissue thickness in histological (thickness(z)=7.6μm) breast cancer samples labeled with compact (7-10 nm) water soluble quantum dots. Series of 154 three-dimensional (3D) images were recorded from each tissue sample by laser scanning confocal microscopy, using 488 nm excitation.. In order to compare the results obtained, all the acquisition parameters were maintained constant. Results point to the possibility of more accurate histological diagnostics, once they clearly show distinct labeling patterns across sample thickness.

Cardiovascular diseases are the leading cause of death worldwide. Atherosclerosis is closely related to the majority of these diseases, as a process of thickening and stiffening of the arterial walls through accumulation of lipids, which is a consequence of aging and life style. Atherosclerosis affects all people in some extent, but not all arterial plaques will necessarily lead to the complications, such as thrombosis, stroke and heart attack. One of the greatest challenges in the risk assessment of atherosclerotic depositions is the detection and recognition of plaques which are unstable and prone to rupture. These vulnerable plaques usually consist of a lipid core that attracts macrophages, a type of white blood cells that are responsible for the degradation of lipids. It has been hypothesized that the amount of macrophages relates to the overall plaque stability. As phagocytes, macrophages also act as recipients for nanoscale particles or structures. Administered gold nanoparticles are usually rabidly taken up by macrophages residing within arterial walls and can therefore be indirectly detected. A very sensitive strategy for probing gold nanoparticles is by utilizing surface enhanced Raman scattering (SERS). By modifying the surface of these particles with SERS active labels it is possible to generate highly specific signals that exhibit sensitivity comparable to fluorescence. SERS labeled gold nanoparticles have been synthesized and the uptake dynamics and efficiency on macrophages in cell cultures was investigated using Raman microscopic imaging. The results clearly show that nanoparticles are taken up by macrophages and support the potential of SERS spectroscopy for the detection of vulnerable plaques. Acknowledgements: Financial support from the Carl Zeiss Foundation is highly acknowledged. The project “Jenaer Biochip Initiative 2.0” (03IPT513Y) within the framework “InnoProfile Transfer – Unternehmen Region“ is supported by the Federal Ministry of Education and Research, Germany (BMBF).

Continuous noninvasive measurement of vital bio-signs, such as cardiopulmonary parameters, is an important tool in evaluation of the patient’s physiological condition and health monitoring. On the demand of new enabling technologies, some works have been done in continuous monitoring of blood pressure and pulse wave velocity. In this paper, we introduce two techniques for non-contact sensing of vital bio signs. In the first approach the optical sensor is based on single mode in-fibers Mach-Zehnder interferometer (MZI) to detect heartbeat, respiration and pulse wave velocity (PWV). The introduced interferometer is based on a new implanted scheme. It replaces the conventional MZI realized by inserting of discontinuities in the fiber to break the total internal reflection and scatter/collect light. The proposed fiber sensor was successfully incorporated into shirt to produce smart clothing. The measurements obtained from the smart clothing could be obtained in comfortable manner and there is no need to have an initial calibration or a direct contact between the sensor and the skin of the tested individual. In the second concept we show a remote noncontact blood pulse wave velocity and pressure measurement based on tracking the temporal changes of reflected secondary speckle patterns produced in human skin when illuminated by a laser beams. In both concept experimental validation of the proposed schemes is shown and analyzed.

In this paper, we describe the fiber optic low-coherence sensors using thin film. We investigated their metrological parameters. Presented sensors were made with the use of standard telecommunication single mode optical fiber (SMF- 28). Different materials were applied to obtain thick layers, such as boron doped diamond, silver and gold. The thickness of layers used in the experiments ranged from 100 nm to 300 nm. Measurements were performed with broadband source operating at central wavelength 1300 nm. The measurement signal was acquired by an optical spectrum analyzer. Measured signal was analyzed in the spectrum domain. Any change of the phase difference between interfering beams reflected from the sensor head depends on measurand occurred in the spectrum of the measurement signal. We obtain the visibility value of the measured signal equal to 0.97.

Utilizing the surface plasmon resonance (SPR) effect of gold nanoparticles (GNPs) enables their using as contrast agents in a variety of biomedical applications for diagnostics and treatment. These applications use both the very strong scattering and absorption properties of the GNPs due to their SPR effects. Most imaging methods use the light-scattering properties of the GNPs. However, the illumination source is in the same wavelength of the GNPs scattering wavelength, leading to background noise caused by light scattering from the tissue. In this paper we present a method to improve border detection of regions enriched with GNPs aiming for real time application of complete tumor resection by utilizing the absorption of specially targeted GNPs using photothermal imaging. Phantoms containing different concentrations of GNPs were irradiated with continuous-wave laser and measured with a thermal imaging camera which detected the temperature field of the irradiated phantoms. By modulating the laser illumination, and use of a simple post processing, the border location was identified in accuracy of better than 0.5 mm even when the surrounding area get heated. This work is in continuation to our previous research ¹.

Photonic crystal slabs (PCSs), which generally consist of two-dimensional arrays of nanoholes in the top layer of a dual layer dielectric film, have been demonstrated as a promising platform for optical biosensing. Both the Fano resonance in a perfect PCS and the Lorentzian resonance in a micro-cavity resulted from an introduced defect in PCS have been studied. While, the use of resonance peak shift for detecting molecules owing to the change of the refractive index is a nonspecific biosensing technique. Biorecognition molecules, such as antibodies that can specific bond to interesting molecules, are conjugated on the PCS to improve the detection specificity. It is a widely adopted assumption that the conjugated molecules form into a uniform nanofilm in the PCS based biosensors, which covers either the entire surface of the dielectric layer or the entire sidewalls of nanoholes. However, the actual device performance is much lower than that obtained based on this assumption, which suggests the over-simplicity of the hypothesis above. It is of keen interest to reveal the actual arrangement and distribution of molecules on PCS for designing high-performance PCS biosensors. Here, we propose models and analysis of the distribution of nanofilms on PCS. We employed Raman scattering technique to experimentally reveal the actual various configurations of nanofilms, which support our theoretical modeling. The results obtained in this research can be essential for designing high-performance PCS based nanobiosensors.

Surface Plasmon Resonance (SPR) has been widely studied for various application. Due to the highly sensitive optical property to the change of the refractive index of the surrounded medium, there have been lots of reports for biological sensing. Direct Plasmon-to-Electric conversion device using metal nanostructures and semiconductor does not require additional readout optics and the device size and sensing area could be much smaller (1/100 to 1/10 of size) than current technologies. In addition, our sensing platform designed to address the issue of using the colored medium (e.g. whole blood) for detection. The detection signal comes only from plasmonic absorption and is not affected by the absorption from the medium. We developed a plasmonic sensing platform using a metal-semiconductor-metal detector by incorporating gold nanostructures on top of the semiconducting layer. The gold nanostructures are functionalized using antibodies to detect Troponin I, which is very important molecule to prevent hart attacks. In this presentation, we report a successful demonstration of a point-of-care sensing platform to detect cardiac Troponin I using antibody functionalized plasmonic nanostructures. Because the sensors are integrated into a microfluidic channel, it requires only a few µl of sample volume. The limit of detection was 20 pg/ml in our preliminary results, and we successfully demonstrated sensor operation using whole blood. This plasmonic sensor has several advantages such as extremely small size for the point-of-care system, multiplexing capability, no need of complex optical geometry and real-time binding monitoring.

The highly used cancer imaging technique, [18F]FDG-PET, is based on the increased glucose metabolic activity in tumors. However, since there are other biological processes that exhibit increased metabolic activity, in particular inflammation, this methodology is prone to non-specificity for cancer. Herein we describe the development of a novel nanoparticle-based approach, utilizes Glucose-Functionalized Gold Nanoparticles (GF-GNPs) as a metabolically targeted CT contrast agent. Our method has demonstrated specific tumor targeting and has successfully differentiated between cancer and inflammation in a combined tumor-inflammation mouse model, due to dissimilarities in vasculatures in different pathologic conditions. This novel approach provides new capabilities in cancer imaging, and can be applicable to a wide range of cancers.

Plasmonic gold nanostars (NSts) demonstrate an enhanced electric field in their surrounding due to large number of ‘hot spots’ on their surface resulting in a unique ability to confine light within a nanometric volume. We are demonstrating beneficial properties of NSts as signal enhancers for tissue and cell imaging using optical coherence tomography (OCT), microscopy, surface-enhanced vibration spectroscopy (SEVS), including surface-enhanced Raman scattering (SERS), and surface-enhanced infrared absorption spectroscopy (SEIRAS) with an attenuated total reflectance (ATR) and infrared reflection-absorption spectroscopy (IRRAS) configurations. Scattering ability of gold NSts with various sizes was investigated by OCT capillary imaging and light and confocal microscopy in vitro. The variation of NSts sizes allows one to shift plasmon resonance up to 1300 nm. The most intensive scattering signals were found from the largest NSts. NSts were applied in SEVS scenarios using plasmonic chip-based systems containing self-assembled NSts on a silicon substrate both by evaporation and subsequent immobilization mediated by a gold layer and modified-dimercapto polyethylene glycol. The plasmonic substrates are able to concomitantly enhance Raman and mid-infrared signals. SERS and SEIRAS properties of such substrates were demonstrated. For SERS, by using crystal violet as a model analyte. The IR absorbance of analyte molecules placed on NSt-film deposited on a Si ATR crystal was up to 10 times higher for thioglycolic acid and 2 times higher for bovine serum albumin compared to a bare Si waveguide. For the best of our knowledge, this is the first attempt to use NSt-based substrate for SEIRAS studies.

Upconverting luminescent nanoparticles (UCNPs) represent an interesting class of nanomaterials for bioanalytical applications. Due to their excitation in the near infrared region of the spectra, no fluorescence of biological compounds is trigged. Compared to other nanomaterials like quantum dots they exhibit low cytotoxicity, high photostability, no blinking and chemical inertness. Nevertheless, UCNPs suffer from low quantum efficiency. Here we report on two different core-shell particle systems which have a core consisting of NaYF₄ doped with Yb³⁺/ Tm³⁺ and an additional inert shell (NaYF₄) or an active shell (NaYF₄ doped with Yb³⁺/Nd³⁺). Nanoparticles without Yb³⁺ as sensitizer can be excited at 980 nm. However, water has an absorption band in this region. This results in a reduction of the upconversion efficiency in aqueous systems and a heating of the solution. For bioanalytical application, more beneficial is the shifting of the wavelength to 808 nm by additional doping of the shell with Nd³⁺. Both core-shell systems were investigated in respect to the monitor enzymatic reactions of dehydrogenases and oxidases involving the generation of either NADH or FADH₂.

Subwavelength grating (SWG) ring resonators have demonstrated better sensitivity compared to the conventional silicon strip ring resonators due to the enhanced photon-analyte interaction. As the sensors are usually used in absorptive ambient environment, it is extreme challenging to further improve the sensitivity of the SWG ring resonator without deteriorating the quality factor because the coupling strength between the bus waveguide and the circular ring resonator is not sufficient to compensate the loss. To explore the full potential of the SWG ring resonator, we experimentally demonstrate a silicon-based high quality factor and low detection limit transverse magnetic (TM) mode SWG racetrack resonator around 1550 nm. A quality factor of 9800 is achieved in aqueous environment when the coupling length and gap are equal to 6.5 μm and 140 nm, respectively. The bulk sensitivity (S) is ~429.7 nm/RIU (refractive index per unit), and the intrinsic detection limit (iDL) is 3.71×10^-4 RIU reduced by 32.5% compared to the best value reported for SWG microring sensors.

Two critical, unmet needs in breast cancer are the early detection of cancer metastasis and recurrence, and the sensitive assessment of temporal changes in tumor burden in response to therapy. The present research is directed towards developing a non-invasive, ultrasensitive and specific tool that provides a comprehensive real-time picture of the metastatic tumor burden and provides a radically new route to address these overarching challenges. As the continuing search for better diagnostic and prognostic clues has shifted away from a singular focus on primary tumor lesions, circulating and disseminated biomarkers have surfaced as attractive candidates due to the intrinsic advantages of a non-invasive, repeatable “liquid biopsy” procedure. However, a reproducible, facile blood-based test for diagnosis and follow-up of breast cancer has yet to be incorporated into a clinical laboratory assay due to the limitations of existing assays in terms of sensitivity, extensive sample processing requirements and, importantly, multiplexing capability. Here, by architecting nano-structured probes for detection of specific molecular species, we engineer a novel plasmon-enhanced Raman spectroscopic platform that offers a paradigmatic shift from the capabilities of today’s diagnostic test platforms. Specifically, quantitative single-droplet serum tests reveal ultrasensitive and multiplexed detection of three key breast cancer biomarkers, cancer antigen 15-3 (CA15-3), CA27-29 and carcinoembryonic antigen (CEA), over several order of magnitude range of biomarker concentration and clear segmentation of the sera between normal and metastatic cancer levels.

Nanoparticles are becoming ubiquitous in applications including diagnostic assays, drug delivery and therapeutics. However, there remain challenges in the quality control of these products. Here we present methods for the orthogonal measurement of these parameters by tracking the motion of the nanoparticle in all three special dimensions as it interacts with an optical waveguide. These simultaneous measurements from a single particle basis address some of the gaps left by current measurement technologies such as nanoparticle tracking analysis, ζ-potential measurements, and absorption spectroscopy. As nanoparticles suspended in a microfluidic channel interact with the evanescent field of an optical waveguide, they experience forces and resulting motion in three dimensions: along the propagation axis of the waveguide (x-direction) they are propelled by the optical forces, parallel to the plane of the waveguide and perpendicular to the optical propagation axis (y-direction) they experience an optical gradient force generated from the waveguide mode profile which confines them in a harmonic potential well, and normal to the surface of the waveguide they experience an exponential downward optical force balanced by the surface interactions that confines the particle in an asymmetric well. Building on our Nanophotonic Force Microscopy technique, in this talk we will explain how to simultaneously use the motion in the y-direction to estimate the size of the particle, the comparative velocity in the x-direction to measure the polydispersity of a particle population, and the motion in the z-direction to measure the potential energy landscape of the interaction, providing insight into the colloidal stability.

Optimally coupling light in an integrated Photonic crystal (PhC) cavity is challenging, but crucial for improving their sensing properties. Here we experimentally investigate the impact of side coupling and in-line coupling on the transmission properties of integrated silicon PhC based air-slot cavities by probing the near field of the cavity mode with a nano fiber tip. These cavities were fabricated with standard deep UV lithography. Positioning this nano-tip near and inside 130 nm wide PhC slot cavity modifies the dielectric map of the cavity which perturbs the intensity scattered from the cavity surface. We show that the mapping of the nano tip induced intensity variations provides some insight about the nature of the confinement of electric field of the various modes of slot cavities. Such intensity maps carry moreover information about the cavity light coupling, which is useful for maximizing the intensity of PhC slot cavity modes.

We propose using the time multiplexing super resolution method in order to extend the depth of focus of an imaging system. In standard time multiplexing the super resolution is achieved by generating duplication of the optical transfer function in the spectrum domain by using moving gratings. By changing the grating's frequency, and by that changing the duplication positions, it is possible to obtain an extended depth of focus. Using the same concept, it is also possible to correct geometrical aberrations of the imaging lens. The proposed method is presented analytically, demonstrated via numerical simulations, and validated by a laboratory experiments.

Super-resolution localization microscopy can overcome the diffraction limit and achieve a tens of order improvement in resolution. It requires labeling the sample with fluorescent probes followed with their repeated cycles of activation and photobleaching. This work presents an alternative approach that is free from direct labeling and does not require the activation and photobleaching cycles. Fluorescently labeled gold nanoparticles in a solution are distributed on top of the sample. The nanoparticles move in a random Brownian motion, and interact with the sample. By obscuring different areas in the sample, the nanoparticles encode the sub-wavelength features. A sequence of images of the sample is captured and decoded by digital post processing to create the super-resolution image. The achievable resolution is limited by the additive noise and the size of the nanoparticles. Regular nanoparticles with diameter smaller than 100nm are barely seen in a conventional bright field microscope, thus fluorescently labeled gold nanoparticles were used, with proper

The mechanisms of super-resolution imaging by contact microspherical or microcylindrical nanoscopy remain an enigmatic question since these lenses neither have an ability to amplify the near-fields like in the case of far-field superlens, nor they have a hyperbolic dispersion similar to hyperlenses. In this work, we present results along two lines. First, we performed numerical modeling of super-resolution properties of two-dimensional (2-D) circular lens in the limit of wavelength-scale diameters, λ ≤ D ≤ 2λ, and relatively high indices of refraction, n=2. Our preliminary results on imaging point dipoles indicate that the resolution is generally close to λ/4; however on resonance with whispering gallery modes it may be slightly higher. Second, experimentally, we used actin protein filaments for the resolution quantification in microspherical nanoscopy. The critical feature of our approach is based on using arrayed cladding layer with strong localized surface plasmon resonances. This layer is used for enhancing plasmonic near-field illumination of our objects. In combination with the magnification of virtual image, this technique resulted in the lateral resolution of actin protein filaments on the order of λ/7.

I review our latest advances in wide-field interferometric imaging of biological cells with molecular specificity, obtained by time-modulated photothermal excitation of gold nanoparticles. Heat emitted from the nanoparticles affects the measured phase signal via both the nanoparticle surrounding refractive-index and thickness changes. These nanoparticles can be bio-functionalized to bind certain biological cell components; thus, they can be used for biomedical imaging with molecular specificity, as new nanoscopy labels, and for photothermal therapy. Predicting the ideal nanoparticle parameters requires a model that computes the thermal and phase distributions around the particle, enabling more efficient phase imaging of plasmonic nanoparticles, and sparing trial and error experiments of using unsuitable nanoparticles. We thus developed a new model for predicting phase signatures from photothermal nanoparticles with arbitrary parameters. We also present a dual-modality technique based on wide-field photothermal interferometric phase imaging and simultaneous ablation to selectively deplete specific cell populations labelled by plasmonic nanoparticles. We experimentally demonstrated our ability to detect and specifically ablate in vitro cancer cells over-expressing epidermal growth factor receptors (EGFRs), labelled with plasmonic nanoparticles, in the presence of either EGFR under-expressing cancer cells or white blood cells. This demonstration established an initial model for depletion of circulating tumour cells in blood. The proposed system is able to image in wide field the label-free quantitative phase profile together with the photothermal phase profile of the sample, and provides the ability of both detection and ablation of chosen cells after their selective imaging.

We present long period fiber gratings which are constructed of periodic changes in the fiber diameter. Our long period fiber gratings induce strong coupling between the different modes and as such have wider bandwidth and even off-resonance spectral response. We present both calculated and measured results of these long period fiber gratings.

Microsphere-assisted microscopy can be incorporated onto conventional light microscopes allowing wide-field and flourescence imaging with enhanced resolution. The refractive index of the background medium in which the microsphere is placed plays an important role in imaging. In this work, we investigated the effect of the background medium containing the microsphere on imaging properties of the microspheres. We used finite-difference timedomain numerical simulation to investigate the photonic nanojet formation in a microlens. We showed that by fine tuning the refractive index of the background medium, the nanojet properties of a microlens can be optimized for applications where sharp focusing of light is needed. Our results provide a guideline for design optimization of novel microparticle-embedded optical devices.

Our group had previously established that nanoscale three-dimensional refractive index (RI) fluctuations of a linear, dielectric, label-free medium can be sensed in the far field through spectroscopic microscopy, regardless of the diffraction limit of optical microscopy. Adopting this technique, Partial Wave Spectroscopic (PWS) Microscopy was able to sense nanoarchitectural alterations in early-stage cancers. With the success of PWS on detecting cancer from healthy clinical samples, we further investigated whether and how histological staining can enhance the performance of PWS by both finite difference time domain (FDTD) simulations and experiments. In this investigation, the dispersion models of hematoxylin and eosin were extracted from the absorption spectra of H and E stained cells. Using these models, the effect of staining were studied via FDTD simulations of unstained versus stained samples with various nanostructures. We observed that, the spectral variance was increased and the spectral variance difference between two samples with distinct nanostructures was enhanced in stained samples by over 200%. Furthermore, we investigated with FDTD whether molecule-specific staining can be used to enhance signals from a medium composing of the desired molecule. Samples with two mixed random media were created and the desired medium was either stained or unstained. Our results showed that the difference between the nanostructures of only the desired medium was enhanced in stained samples. We concluded that, with molecule-specific staining, PWS can selectively target the nanoarchitecture of a desired molecule. Lastly, these results were validated by experiments using human buccal cells from healthy or lung cancer patients. This study has significant impact in improving the performance of PWS on quantifying nanoarchitectural alterations during cancer.

A major challenge in tissue imaging is the degradation of resolution with increased depth, due to multiple scattering and refraction. By using long-wavelength lasers, penetration depth can be improved, while resolution further degrades. Recently, superresolution techniques emerged to enhance spatial resolution by switching or saturation of fluorescence. However, fluorescence suffers from photobleaching, and current techniques do not provide deep-tissue imaging capability due to the lack of optical sectioning or the requirement of special beam manipulation. We have recently demonstrated that scattering from a single gold nanoparticle exhibits saturation behavior, which was adopted to significantly enhance resolution by saturated excitation (SAX) microscopy. Compared to fluorophores, scattering from plasmonic nanoparticles is free from bleaching, the cross-section is much larger, and the plasmonic resonance band is broadly tunable with particle shape and size, making it an ideal and robust contrast agent for long-term observation. On the other hand, SAX microscopy does not need any beam engineering and provides intrinsic sectioning with its confocal scheme, suitable for deep-tissue imaging. In this work, we combine the advantages of plasmonics and SAX microscopy to demonstrate resolution enhancement underneath a very deep tissue. One general concern of scattering-based imaging is the background from the strong scattering of the surrounding tissue. Since tissue scattering is linear, and SAX allows the extraction of only nonlinear responses, the background can be fully eliminated, leaving only nanoparticle visible. Therefore, such combination provides a novel tool for not only high-resolution, but also high-contrast, background-free, and long-term imaging deep inside biological tissues.

A colorimetric biosensing system based on a porous silicon (PSi) rugate filter is demonstrated. Using an imaged-based technique that monitors RGB intensity, a spectral shift less than 0.25nm can be reliably detected. The porous silicon rugate filter demonstrates a sensitivity of 310 nm/RIU, which corresponds to a detection limit near 7×10^-4 RIU. In this work, an external light source and camera are employed for proof-of-concept demonstration. By utilizing a smartphone camera LED and smartphone camera as the light source and detector, respectively, this system could serve as an effective, low-cost, point-of-care diagnostic tool.

The cell membrane is composed of phospholipids, glycolipids, cholesterol and proteins that are dynamic and heterogeneous distributed in the bilayer structure and many researches have showed that the plasma membrane in eukaryotic cells contains microdomains termed “lipid raft” in which cholesterol, sphingolipids and specific membrane proteins are enriched. Cholesterol extraction induced lipid raft disruption is one of the most widely used methods for lipid raft research and MβCD is a type of solvent to extract the cholesterol from cell membranes. In this study, the effect of MβCD treatment on the membrane nanostructure in MCF-7 living cells was investigated by atomic force microscopy. Different concentrations of MβCD were selected to deplete cholesterol for 30 min and the viability of cells was tested by MTT assay to obtain the optimal concentration. Then the nanostructure of the cell membrane was detected. The results show that an appropriate concentration of MβCD can induce the alteration of cell membranes nanostructure and the roughness of membrane surface decreases significantly. This may indicate that microdomains of the cell membrane disappear and the cell membrane appears more smoothly. Cholesterol can affect nanostructure and inhomogeneity of the plasma membrane in living cells.

Human tissue is one of the most complex optical media since it is turbid and nonhomogeneous. In our poster, we suggest a new type of skin phantom and an optical method for sensing physiological tissue condition, basing on the collection of the ejected light at all exit angles, to receive the full scattering profile. Conducted experiments were carried out on an unique set-up for noninvasive encircled measurement. Set-up consisted of a laser, a photodetector and new tissues-like phantoms made with a polyvinyl chloride-plastisol (PVCP), silicone elastomer polydimethylsiloxane (PDMS) and PDMS with glycerol mixture. Our method reveals an isobaric point, which is independent of the optical properties. Furthermore, we present the angular distribution of cylindrical phantoms, in order to sense physiological tissue state.

Plasmonic nanostructures enable field confinement which is locally amplified within sub-diffraction limited volume. The localized near-field can be useful in many biomedical sensing and imaging applications. In this research, we present the near-field characteristics localized by plasmonic nano-post arrays for biomedical spectroscopy. Circular gold nano-post arrays were modeled on gold and chrome films fabricated on a glass substrate whose thickness was 50, 20 and 2 nm, respectively. The nano-post arrays were fabricated with an e-beam lithography and a diameter of the post was 250 nm with periods varied as 500, 700, and 900 nm. The field localization produced by nano-posts was induced by angled illumination with a total internal reflection fluorescence microscope objective lens and measured by a near-field scanning optical microscope (NSOM). The NSOM has a tapered fiber probe with a 70-nm aperture and was a continuous-wave laser whose wavelength is 532 nm as light source. Incident TM-polarized light exhibited field localization on one side of an individual gold nano-post. When the direction of light incidence was changed opposite, localized field was switched to the opposite edge of the circular nano-post. We performed 3D finite difference time domain s for the field calculation and confirmed the localized field distribution at given illumination angles. We also discuss the potential applications of plasmonic field localization for analysis of biomolecules, cells, and tissues.

We present fusing of fiber micro-knot by CO2 laser which fixes the micro-fibers in place and stabilizing the micro-knot shape, size and orientation. This fusing enables tuning of the coupling strength, the free-spectral range and the birefringence of the fiber micro-knot. Fused micro-knots are superior over regular micro-knots and we believe that fusing of micro-knots should be a standard procedure in fabricating fiber micro-knots.

The whole blood contains red cells, white cells, and platelets suspended in plasma. In the following study we investigated an impact of nanodiamond particles on blood elements over various periods of time.The material used in the study consisted of samples taken from ten healthy canines (Canis lupus f. domestica) of various age, different blood types and both sexes. The markings were conducted by adding to the blood unmodified diamonds (SND), modified O₂ (SO₂) suspended in 0,9% NaCl. The blood was put under an impact of two diamond concentrations: 20μl and 100μl. The amount of abnormal cells increased with time. The percentage of echinocytes as a result of interaction with nanodiamonds in various time periods for individual specimens was scarce. In the examined microscopic image a summary was made for 100 white blood cells. Following cells were included in said group: band neutrophils, segmented neutrophils, eosinophils, basophils, lymphocytes, monocytes, lymphocytes with granulates, stimulated lymphocytes, lymphocytes with vacuoles, metamielocytes and smudge cells. The impact of the three diamond types had no clinical importance on red blood cells. After the diamonds mixed with white blood cells, atypical cells came into being, in the range of agranulocytes in stimulated form or with granulates and/or vacuoles. It is supposed that as a result of longlasting exposure a stimulation and vacuolisation takes place, because of the function of the cells.

We present an surface-enhanced Raman spectroscopy (SERS) approach for detection of drugs of abuse in whole human blood. We utilize a near infrared laser with 830 nm excitation wavelength in order to reduce the influence of fluorescence on the spectra of blood. However, regular plasmon resonance peak of plasmonic nanoparticles, such as silver or gold fall in a much lower wavelength regime about 400 nm. Therefore, we have shifted the plasmon resonance of nanoparticles to match that of an excitation laser wavelength, by fabrication of the silver-core gold-shell nanoparticles. By combining the laser and plasmon resonance shift towards longer wavelengths we have achieved a great reduction in background fluorescence of blood. Great enhancement of Raman signal coming solely from drugs was achieved without any prominent lines coming from the erythrocytes. We have applied chemometric processing methods, such as Principal Component Analysis (PCA), to detect the elusive differences in the Raman bands which are specific for the investigated drugs. We have achieved good classification for the samples containing particular drugs (e.g., butalbital, α-hydroxyalprazolam). Furthermore, a quantitative analysis was carried out to assess the limit of detection (LOD) using Partial Least Squares (PLS) regression method. In conclusion, our LOD values obtained for each class of drugs was competitive with the gold standard GC/MS method.

In this paper we present the usage of photonic remote laser based device for sensing nano-vibrations for detection of muscle contraction and fatigue, eye movements and in-vivo estimation of glucose concentration. The same concept is also used to realize a remote optical stethoscope. The advantage of doing the measurements from a distance is in preventing passage of infections as in the case of optical stethoscope or in the capability to monitor e.g. sleep quality without disturbing the patient. The remote monitoring of glucose concentration in the blood stream and the capability to perform opto-myography for the Messer muscles (chewing) is very useful for nutrition and weight control. The optical configuration for sensing the nano-vibrations is based upon analyzing the statistics of the secondary speckle patterns reflected from various tissues along the body of the subjects. Experimental results present the preliminary capability of the proposed configuration for the above mentioned applications.

Cell therapy provides a promising approach for diseases and injuries that conventional therapies cannot cure effectively. Mesenchymal stem cells (MSCs) can be used as effective targeted therapy, as they exhibit homing capabilities to sites of injury and inflammation, exert anti-inflammatory effects, and can differentiate in order to regenerate damaged tissue. Despite the potential efficacy of cell therapy, applying cell-based therapy in clinical practice is very challenging; there is a need to uncover the mystery regarding the fate of the transplanted cells. Therefore, in this study, we developed a method for longitudinal and quantitative in vivo cell tracking, based on the superior visualization abilities of classical X-ray computed tomography (CT), and combined with gold nanoparticles as labeling agents. We applied this technique for non-invasive imaging of MSCs transplanted in a rat model for depression, a highly prevalent and disabling neuropsychiatric disorder lacking effective treatment. Our results, which demonstrate that cell migration could be detected as early as 24 hours and up to one month post-transplantation, revealed that MSCs specifically navigated and homed to distinct depression related brain regions. This research further reveals that cell therapy is a beneficial approach for treating neuropsychiatric disorders; Behavioral manifestations of core symptoms of depressive behavior, were significantly attenuated following treatment. We expect This CT-based technique to lead to a significant enhancement in cellular therapy both for basic research and clinical applications of brain pathologies.