Low Vision Practice and Service Provision Among Optometrists in Ghana: A Nationwide Survey

PURPOSE

To characterize practice patterns of low vision services among Optometrists in Ghana.

METHODS

The nationwide cross-sectional survey identified entities through the Ghana Optometrists Association (GOA) registry and utilized a semi-structured questionnaire to consolidate survey information that comprises practitioners' demographics, available services, diagnostic equipment, barriers to service provision and utilization, and interventions.

RESULTS

300 Optometrists were identified, with 213 surveyed (71% response rate). About fifty percent (52.6%) were in private practice, and more than two-thirds (77%) did not provide low vision services. Most (≥70%) reported lack of assistive devices, and basic eye care examination kits as the main barriers to low vision service provision. Similarly, practitioners reported unawareness of the presence of low vision centres (76.1%), and high cost of low vision aids (75.1%) as the prime perceived barriers for patients to utilize low vision services. Continuous professional development and public education (89-90%) were suggested as interventions to improve the uptake of low vision services. After statistical adjustment, private facility type (Adjusted odds ratio [AOR] = 0.35, p = 0.010) and lack of basic eye examination kits (AOR = 0.32, p = 0.002) were significantly associated with reduced odds of low vision service provision. Conversely, ≥15 years of work experience (AOR = 6.37, p = 0.011) was significantly associated with increased odds of low vision service provision.

CONCLUSIONS

Overall, the results indicate inadequate low vision coverage and service delivery. Government policies must be directed towards equipping practitioners with equipment and subsidize patient cost of treatment to optimize low vision care.

The Latest Sensor Detection Methods for per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFASs) have emerged as a prominent environmental pollutant in recent years, primarily due to their tendency to accumulate and magnify in both the environment and living organisms. The entry of PFASs into the environment can have detrimental effects on human health. Hence, it is crucial to actively monitor and detect the presence of PFASs. The current standard detection method of PFAS is the combination of chromatography and mass spectrometry. However, this requires expensive instruments, extra sample pretreatment steps, complicated operation and long analysis time. As a result, new methods that do not rely on chromatography and mass spectrometry have been developed and applied. These alternative methods mainly include optical and electrochemical sensor methods, which offer great potential in terms of real-time field detection, instrument miniaturization, shorter analysis time, and reduced detection cost. This review provides a summary of recent advancements in PFAS detection sensors. We categorize and explain the principles and mechanisms of these sensors, and compare their limits of detection and sensitivity. Finally, we discuss the future challenges and improvements needed for PFAS sensors, such as field application, commercialization, and other related issues.

Wireless monitoring of cell cultures based on light scattering: A novel optical scheme and portable prototype

Cell cultures are widely used in scientific research, biomedicine, and industry. When culturing, it is important to maintain certain conditions, including the concentration of cells. Monitoring of the culture growth and cell counting is an urgent task for the optimization of technological processes. Most existing methods require sampling from a culture flask. This procedure is time-consuming and associated with the risks of contamination. We present a device able to monitor the growth of cells number in a suspension noninvasively. The device uses a laser beam that pass through the culture flask and measures the intensity of scattered light as a function of coordinate along the beam. This optical scheme allows one to obtain accurate results for both high- and low-scattering samples. We constructed the wireless portable prototype for monitoring of cell culture growth directly in the incubator and demonstrated the applicability of the device for Jurkat cells and Escherichia coli bacteria.

Thermochromic Printable and Multicolor Polymeric Composite Based on Hybrid Organic-Inorganic Perovskite

Hybrid organic-inorganic perovskites (PVKs) are among the most promising materials for optoelectronic applications thanks to their outstanding photophysical properties and easy synthesis. Herein, a new PVK-based thermochromic composite is demonstrated. It can reversibly switch from a transparent state (transmittance > 80%) at room temperature to a colored state (transmittance < 10%) at high temperature, with very fast kinetics, taking only a few seconds to go from the bleached to the colored state (and vice versa). X-ray diffraction, Fourier-transform infrared spectroscopy, differential scanning calometry, rheological, and optical measurements carried out during heating/cooling cycles reveal that thermochromism in the material is based on a reversible process of PVK disassembly/assembly mediated by intercalating polymeric chains, through the formation and breaking of hydrogen bonds between polymer and perovskite. Therefore, differently from other thermochromic perovskites, that generally work with the adsorption/desorption of volatile molecules, the system is able to perform several heating/cooling cycles regardless of environmental conditions. The color and transition temperature (from 70 to 120 °C) can be tuned depending on the type of perovskite. Moreover, this thermochromic material is printable and can be deposited by cheap techniques, paving the way for a new class of smart coatings with an unprecedented range of colors.

Research Progress of Electrically Driven Multi-Stable Cholesteric Liquid Crystals

Electrically driven multi-stable cholesteric liquid crystals can be used to adjust the transmittance of incident light. Compared with the traditional liquid crystal optical devices, the multi-stable devices only apply an electric field during switching and do not require a continuous electric field to maintain the various optical states of the device. Therefore, the multi-stable devices have low energy consumption and have become a research focus for researchers. However, the multi-stable devices still have shortcomings before practical application, such as contrast, switching time, and mechanical strength. In this article, the latest research progress on electrically driven multi-stable cholesteric liquid crystals is reviewed, including electrically driven multi-stable modes, performance optimization, and applications. Finally, the challenges and opportunities of electrically driven multi-stable cholesteric liquid crystals are discussed in anticipation of contributing to the development of multi-stable liquid crystal devices.

Soft Biomimetic Fiber-Optic Tactile Sensors Capable of Discriminating Temperature and Pressure

Tactile sensors with high softness and multisensory functions are highly desirable for applications in humanoid robotics, smart prosthetics, and human-machine interfaces. Here, we report a soft biomimetic fiber-optic tactile (SBFT) sensor that offers skin-like tactile sensing abilities to perceive and discriminate temperature and pressure. The SBFT sensor is fabricated by encapsulating a macrobent fiber Bragg grating (FBG) in an elastomeric droplet-shaped structure that results in two optical resonances associated with the FBG and excited whispering gallery modes (WGMs) propagating along the bent region. Benefiting from the different thermo-optic and stress-optic effects of FBG and WGM resonances, the pressure and temperature can be fully decoupled with a high precision of 0.2 °C and 0.8 mN, respectively. To achieve a compact system for signal demodulation, a single-cavity dual-comb fiber laser is developed to interrogate the SBFT sensor based on dual-comb spectroscopy, which enables fast spectral sampling with a single photodiode. We show that the SBFT sensor is capable of perceiving pressure, temperature, and hardness in touching soft tissues and human skins, demonstrating great promise for soft tissue palpation and human-like robotic perception.

A review on innovative optical devices for the diagnosis of human soil-transmitted helminthiasis and schistosomiasis: from research and development to commercialization

Diagnosis of soil-transmitted helminth (STH) and schistosome infections relies largely on conventional microscopy which has limited sensitivity, requires highly trained personnel and is error-prone. Rapid advances in miniaturization of optical systems, sensors and processors have enhanced research and development of digital and automated microscopes suitable for the detection of these diseases in resource-limited settings. While some studies have reported proof-of-principle results, others have evaluated the performance of working prototypes in field settings. The extensive commercialization of these innovative devices has, however, not yet been achieved. This review provides an overview of recent publications (2010–2022) on innovative field applicable optical devices which can be used for the diagnosis of STH and schistosome infections. Using an adapted technology readiness level (TRL) scale taking into account the WHO target product profile (TPP) for these diseases, the developmental stages of the devices were ranked to determine the readiness for practical applications in field settings. From the reviewed 18 articles, 19 innovative optical devices were identified and ranked. Almost all of the devices (85%) were ranked with a TRL score below 8 indicating that, most of the devices are not ready for commercialization and field use. The potential limitations of these innovative devices were discussed. We believe that the outcome of this review can guide the end-to-end development of automated digital microscopes aligned with the WHO TPP for the diagnosis of STH and schistosome infections in resource-limited settings.

Three-Dimensional Polymer Variable Optical Attenuator Based on Vertical Multimode Interference with Graphene Heater

Low-power-consumption optical devices are crucial for large-scale photonic integrated circuits (PICs). In this paper, a three-dimensional (3D) polymer variable optical attenuator (VOA) is proposed. For monolithic integration of silica and polymer-based planar lightwave circuits (PLCs), the vertical VOA is inserted between silica-based waveguides. Optical and thermal analyses are performed through the beam propagation method (BPM) and finite-element method (FEM), respectively. A compact size of 3092 μm × 4 μm × 7 μm is achieved with a vertical multimode interference (MMI) structure. The proposed VOA shows an insertion loss (IL) of 0.58 dB and an extinction ratio (ER) of 21.18 dB. Replacing the graphene heater with an aluminum (Al) electrode, the power consumption is decreased from 29.90 mW to 21.25 mW. The rise and fall time are improved to 353.85 μs and 192.87 μs, respectively. The compact and high-performance VOA shows great potential for a variety of applications, including optical communications, integrated optics, and optical interconnections.

Development and Characterisation of a Whole Hybrid Sol-Gel Optofluidic Platform for Biosensing Applications

This work outlines, for the first time, the fabrication of a whole hybrid sol-gel optofluidic platform by integrating a microfluidic biosensor platform with optical waveguides employing a standard photolithography process. To demonstrate the suitability of this new hybrid sol-gel optofluidic platform, optical and bio-sensing proof-of-concepts are proposed. A photoreactive hybrid sol-gel material composed of a photopolymerisable organically modified silicon alkoxide and a transition metal complex was prepared and used as the fabrication material for the entire optofluidic platform, including the optical waveguides, the sensing areas, and the microfluidic device. The most suitable sol-gel materials chosen for the fabrication of the cladding and core of the waveguides showed a RIC of 3.5 × 10^-3 and gave thicknesses between 5.5 and 7 μm. The material was optimised to simultaneously meet the photoreactive properties required for the photolithography fabrication process and the optical properties needed for the effective optical operability of the microstructured waveguides at 532 and 633 nm with an integrated microfluidic device. The optical proof-of-concept was performed using a fluorescent dye (Atto 633) and recording its optical responses while irradiated with a suitable optical excitation. The biosensing capability of the platform was assessed using a polyclonal primary IgG mouse antibody and a fluorescent labelled secondary IgG anti-mouse antibody. A limit of detection (LOD) of 50 ug/mL was achieved. A correlation between the concentration of the dye and the emission fluorescence was evidenced, thus clearly demonstrating the feasibility of the proposed hybrid sol-gel optofluidic platform concept. The successful integration and operability of optical and microfluidic components in the same optofluidic platform is a novel concept, particularly where the sol-gel fabrication material is concerned.

Signal and measurement considerations for human translation of diffuse in vivo flow cytometry

SIGNIFICANCE

"Diffuse in vivo flow cytometry" (DiFC) is an emerging technology for fluorescence detection of rare circulating cells directly in large deep-seated blood vessels in mice. Because DiFC uses highly scattered light, in principle, it could be translated to human use. However, an open question is whether fluorescent signals from single cells would be detectable in human-scale anatomies.

AIM

Suitable blood vessels in a human wrist or forearm are at a depth of ∼2 to 4 mm. The aim of this work was to study the impact of DiFC instrument geometry and wavelength on the detected DiFC signal and on the maximum depth of detection of a moving cell.

APPROACH

We used Monte Carlo simulations to compute fluorescence Jacobian (sensitivity) matrices for a range of source and detector separations (SDS) and tissue optical properties over the visible and near infrared spectrum. We performed experimental measurements with three available versions of DiFC (488, 640, and 780 nm), fluorescent microspheres, and tissue mimicking optical flow phantoms. We used both computational and experimental data to estimate the maximum depth of detection at each combination of settings.

RESULTS

For the DiFC detection problem, our analysis showed that for deep-seated blood vessels, the maximum sensitivity was obtained with NIR light (780 nm) and 3-mm SDS.

CONCLUSIONS

These results suggest that-in combination with a suitable molecularly targeted fluorescent probes-circulating cells and nanosensors could, in principle, be detectable in circulation in humans.

Magnetite Nanoparticles: Synthesis and Applications in Optics and Nanophotonics

Magnetite nanoparticles with different surface coverages are of great interest for many applications due to their intrinsic magnetic properties, nanometer size, and definite surface morphology. Magnetite nanoparticles are widely used for different medical-biological applications while their usage in optics is not as widespread. In recent years, nanomagnetite suspensions, so-called magnetic ferrofluids, are applied in optics due to their magneto-optical properties. This review gives an overview of nanomagnetite synthesis and its properties. In addition, the preparation and application of magnetic nanofluids in optics, nanophotonics, and magnetic imaging are described.

Thyroidectomy for Cancer: The Surgeon and the Parathyroid Glands Sparing

BACKGROUND

The diagnosis of thyroid cancer is continuously increasing and consequently the amount of thyroidectomy. Notwithstanding the actual surgical skill, postoperative hypoparathyroidism still represents its most frequent complication. The aims of the present study are to analyze the rate of postoperative hypoparathyroidism after thyroidectomy, performed for cancer by a single first operator, without any technological aid, and to compare the data to those obtained adopting the most recent technological adjuncts developed to reduce the postoperative hypoparathyroidism.

METHODS

During the period 1997-2020 at the Endocrine Surgery Unit of the Department of Clinical and Experimental Medicine of the University of Florence, 1648 consecutive extracapsular thyroidectomies for cancer (401 with central compartment node dissection) were performed. The percentage of hypoparathyroidism, temporary or permanent, was recorded both in the first period (Group A) and in the second, most recent period (Group B). Total thyroidectomies were compared either with those with central compartment dissection and lobectomies. Minimally invasive procedures (MIT, MIVAT, some transoral) were also compared with conventional. Fisher's exact and Chi-square tests were used for comparison of categorical variables. p < 0.01 was considered statistically significant. Furthermore, a literature research from PubMed^® has been performed, considering the most available tools to better identify parathyroid glands during thyroidectomy, in order to reduce the postoperative hypoparathyroidism. We grouped and analyzed them by technological affinity.

RESULTS

On the 1648 thyroidectomies enrolled for the study, the histotype was differentiated in 93.93 % of cases, medullary in 4% and poorly differentiated in the remaining 2.06%. Total extracapsular thyroidectomy and lobectomy were performed respectively in 95.45% and 4.55%. We recorded a total of 318 (19.29%) cases of hypocalcemia, with permanent hypoparathyroidism in 11 (0.66%). In regard to the literature, four categories of tools to facilitate the identification of the parathyroids were identified: (a) vital dye; (b) optical devices; (c) autofluorescence of parathyroids; and (d) autofluorescence enhanced by contrast media. Postoperative hypoparathyroidism had a variable range in the different groups.

CONCLUSIONS

Our data confirm that the incidence of post-surgical hypoparathyroidism is extremely low in the high volume centers. Its potential reduction adopting technological adjuncts is difficult to estimate, and their cost, together with complexity of application, do not allow immediate routine use. The trend towards increasingly unilateral surgery in thyroid carcinoma, as confirmed by our results in case of lobectomy, is expected to really contribute to a further reduction of postsurgical hypoparathyroidism.

3D printing of glass by additive manufacturing techniques: a review

Additive manufacturing (AM), which is also known as three-dimensional (3D) printing, uses computer-aided design to build objects layer by layer. Here, we focus on the recent progress in the development of techniques for 3D printing of glass, an important optoelectronic material, including fused deposition modeling, selective laser sintering/melting, stereolithography (SLA) and direct ink writing. We compare these 3D printing methods and analyze their benefits and problems for the manufacturing of functional glass objects. In addition, we discuss the technological principles of 3D glass printing and applications of 3D printed glass objects. This review is finalized by a summary of the current achievements and perspectives for the future development of the 3D glass printing technique.

Integration of Colloidal Quantum Dots with Photonic Structures for Optoelectronic and Optical Devices

Colloidal quantum dot (QD), a solution-processable nanoscale optoelectronic building block with well-controlled light absorption and emission properties, has emerged as a promising material system capable of interacting with various photonic structures. Integrated QD/photonic structures have been successfully realized in many optical and optoelectronic devices, enabling enhanced performance and/or new functionalities. In this review, the recent advances in this research area are summarized. In particular, the use of four typical photonic structures, namely, diffraction gratings, resonance cavities, plasmonic structures, and photonic crystals, in modulating the light absorption (e.g., for solar cells and photodetectors) or light emission (e.g., for color converters, lasers, and light emitting diodes) properties of QD-based devices is discussed. A brief overview of QD-based passive devices for on-chip photonic circuit integration is also presented to provide a holistic view on future opportunities for QD/photonic structure-integrated optoelectronic systems.

Light Technology for Efficient and Effective Photodynamic Therapy: A Critical Review

Photodynamic therapy (PDT) is a cancer treatment with strong potential over well-established standard therapies in certain cases. Non-ionising radiation, localisation, possible repeated treatments, and stimulation of immunological response are some of the main beneficial features of PDT. Despite the great potential, its application remains challenging. Limited light penetration depth, non-ideal photosensitisers, complex dosimetry, and complicated implementations in the clinic are some limiting factors hindering the extended use of PDT. To surpass actual technological paradigms, radically new sources, light-based devices, advanced photosensitisers, measurement devices, and innovative application strategies are under extensive investigation. The main aim of this review is to highlight the advantages/pitfalls, technical challenges and opportunities of PDT, with a focus on technologies for light activation of photosensitisers, such as light sources, delivery devices, and systems. In this vein, a broad overview of the current status of superficial, interstitial, and deep PDT modalities-and a critical review of light sources and their effects on the PDT process-are presented. Insight into the technical advancements and remaining challenges of optical sources and light devices is provided from a physical and bioengineering perspective.

Ultrathin Diamond Nanofilms-Development, Challenges, and Applications

Diamond is a highly attractive material for ample applications in material science, engineering, chemistry, and biology because of its favorable properties. The advent of conductive diamond coatings and the steady demand for miniaturization in a plethora of economic and scientific fields resulted in the impetus for interdisciplinary research to develop intricate deposition techniques for thin (≤1000 nm) and ultra-thin (≤100 nm) diamond films on non-diamond substrates. By virtue of the lowered thickness, diamond coatings feature high optical transparency in UV-IR range. Combined with their semi-conductivity and mechanical robustness, they are promising candidates for solar cells, optical devices, transparent electrodes, and photochemical applications. In this review, the difficulty of (ultra-thin) diamond film development and production, introduction of important stepping stones for thin diamond synthesis, and summarization of the main nucleation procedures for diamond film synthesis are elucidated. Thereafter, applications of thin diamond coatings are highlighted with a focus on applications relying on ultrathin diamond coatings, and the excellent properties of the diamond exploited in said applications are discussed, thus guiding the reader and enabling the reader to quickly get acquainted with the research field of ultrathin diamond coatings.

Optical Devices Constructed From Responsive Microgels for Polyphenols Detection

Polyphenols are used as antioxidants in various foods and beverages, which are considered to be a health benefit. The measurement of polyphenols contents is of great interest in food chemistry and health science. This work reported a microgels based photonic device (etalon) to detect polyphenols. Dopamine was used as a model compound of polyphenols. Herein, we proposed a “block” concept for dopamine detection. The dopamine was oxidized and formed dopamine films catalyzed by tyrosinase on the surface of etalon. As the etalon was immersed in ZnCl₂, the dopamine films blocked the ZnCl₂ diffusion into etalon that caused optical property changes. The film thickness is associated with the concentration of dopamine which can be readout via optical signals.

Short-Term Circulating Tumor Cell Dynamics in Mouse Xenograft Models and Implications for Liquid Biopsy

MOTIVATION

Circulating tumor cells (CTCs) are widely studied using liquid biopsy methods that analyze fractionally-small peripheral blood (PB) samples. However, little is known about natural fluctuations in CTC numbers that may occur over short timescales in vivo, and how these may affect detection and enumeration of rare CTCs from small blood samples.

METHODS

We recently developed an optical instrument called "diffuse in vivo flow cytometry" (DiFC) that uniquely allows continuous, non-invasive counting of rare, green fluorescent protein expressing CTCs in large blood vessels in mice. Here, we used DiFC to study short-term changes in CTC numbers in multiple myeloma and Lewis lung carcinoma xenograft models. We analyzed CTC detections in over 100 h of DiFC data, and considered intervals corresponding to approximately 1%, 5%, 10%, and 20% of the PB volume. In addition, we analyzed changes in CTC numbers over 24 h (diurnal) periods.

RESULTS

For rare CTCs (fewer than 1 CTC per ml of blood), the use of short DiFC intervals (corresponding to small PB samples) frequently resulted in no detections. For more abundant CTCs, CTC numbers frequently varied by an order of magnitude or more over the time-scales considered. This variance in CTC detections far exceeded that expected by Poisson statistics or by instrument variability. Rather, the data were consistent with significant changes in mean numbers of CTCs on the timescales of minutes and hours.

CONCLUSIONS

The observed temporal changes can be explained by known properties of CTCs, namely, the continuous shedding of CTCs from tumors and the short half-life of CTCs in blood. It follows that the number of cells in a blood sample are strongly impacted by the timing of the draw. The issue is likely to be compounded for multicellular CTC clusters or specific CTC subtypes, which are even more rare than single CTCs. However, we show that enumeration can in principle be improved by averaging multiple samples, analysis of larger volumes, or development of methods for enumeration of CTCs directly in vivo.

Optical Waveguides and Integrated Optical Devices for Medical Diagnosis, Health Monitoring and Light Therapies

Optical waveguides and integrated optical devices are promising solutions for many applications, such as medical diagnosis, health monitoring and light therapies. Despite the many existing reviews focusing on the materials that these devices are made from, a systematic review that relates these devices to the various materials, fabrication processes, sensing methods and medical applications is still seldom seen. This work is intended to link these multidisciplinary fields, and to provide a comprehensive review of the recent advances of these devices. Firstly, the optical and mechanical properties of optical waveguides based on glass, polymers and heterogeneous materials and fabricated via various processes are thoroughly discussed, together with their applications for medical purposes. Then, the fabrication processes and medical implementations of integrated passive and active optical devices with sensing modules are introduced, which can be used in many medical fields such as drug delivery and cardiovascular healthcare. Thirdly, wearable optical sensing devices based on light sensing methods such as colorimetry, fluorescence and luminescence are discussed. Additionally, the wearable optical devices for light therapies are introduced. The review concludes with a comprehensive summary of these optical devices, in terms of their forms, materials, light sources and applications.

Full-field swept-source optical coherence tomography and neural tissue classification for deep brain imaging

Optical coherence tomography can differentiate brain regions with intrinsic contrast and at a micron scale resolution. Such a device can be particularly useful as a real-time neurosurgical guidance tool. We present, to our knowledge, the first full-field swept-source optical coherence tomography system operating near a wavelength of 1310 nm. The proof-of-concept system was integrated with an endoscopic probe tip, which is compatible with deep brain stimulation keyhole neurosurgery. Neuroimaging experiments were performed on ex vivo brain tissues and in vivo in rat brains. Using classification algorithms involving texture features and optical attenuation, images were successfully classified into three brain tissue types.

OptCAM: An ultra-fast all-optical architecture for DNA variant discovery

Nowadays, the accelerated expansion of genetic data challenges speed of current DNA sequence alignment algorithms due to their electrical implementations. Essential needs of an efficient and accurate method for DNA variant discovery demand new approaches for parallel processing in real time. Fortunately, photonics, as an emerging technology in data computing, proposes optical correlation as a fast similarity measurement algorithm; while complexity of existing local alignment algorithms severely limits their applicability. Hence, in this paper, employing optical correlation for global alignment, we present an optical processing approach for local DNA sequence alignment to benefit both high-speed processing and operational parallelism, inherently exist in optics. The proposed method, named as OptCAM, utilizes amplitude and wavelength of the optical signals, to accurately locate mutations through three main procedures. Furthermore, an all-optical implementation of the OptCAM method is proposed consisting of three units, corresponding to the three OptCAM procedures. Performing considerably fast processes by passing optical signals through high-throughput photonic devices, OptCAM avoids various limitations of electrical implementations. Accuracy and efficiency of the OptCAM method and its optical implementation are validated through numerical simulation by a gold standard simulation benchmark. The results indicate the proposed method is significantly faster than its electrical counterparts, in both single node and grid computation.

Determining the thermomechanical image shift for the MIGHTI instrument on the NASA-ICON satellite

The Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) instrument on NASA's Ionospheric Connection Explorer's mission will measure neutral winds in the Earth's thermosphere. We investigate how thermal changes to the instrument's optical bench affect the relative position of the image recorded by the camera. The thermal shift is measured by fitting the image of a series of reference notches and determining their current position on the camera with subpixel precision. Analyzing ground-based calibration data, we find that the image position is not affected within the uncertainty of the analysis for the applied thermal changes. We also address the question of the analysis uncertainty with signal-to-noise ratio.

Stretchable and Highly Sensitive Optical Strain Sensors for Human-Activity Monitoring and Healthcare

Flexible and stretchable strain sensors are essential to developing smart wearable devices for monitoring human activities. Such sensors have been extensively exploited with various conductive materials and structures, which, however, are normally in need of complex manufacturing processes and confronted with the challenge to achieve both large stretchability and high sensitivity. Here, we report a simple and low-cost optical strategy for the design of stretchable strain sensors which are capable of measuring large strains of 100% with a low detection limit (±0.09%), a fast responsivity (<12 ms), and high reproducibility (over 6000 cycles). The optical strain sensor (OS²) is fabricated by assembling plasmonic gold nanoparticles (GNPs) in stretchable elastomer-based optical fibers, where a core/cladding structure with step-index configuration is adopted for light confinement. The stretchable, GNP-incorporated optical fiber shows strong localized surface plasmon resonance effects that enable sensitive and reversible detection of strain deformations with high linearity and negligible hysteresis. The unique mechanical and sensing properties of the OS² enable its assembling into clothing or mounting on skin surfaces for monitoring various human activities from physiological signals as subtle as wrist pulses to large motions of joint bending and hand gestures. We further apply the OS² for quantitative analysis of motor disorders such as Parkinson's disease and demonstrate its compatibility in strong electromagnetic interference environments during functional magnetic resonance imaging, showing great promises for diagnostics and assessments of motor neuron diseases in clinics.

Fluorescence monitoring of rare circulating tumor cell and cluster dissemination in a multiple myeloma xenograft model in vivo

Circulating tumor cells (CTCs) are of great interest in cancer research because of their crucial role in hematogenous metastasis. We recently developed “diffuse in vivo flow cytometry” (DiFC), a preclinical research tool for enumerating extremely rare fluorescently labeled CTCs directly in vivo. In this work, we developed a green fluorescent protein (GFP)-compatible version of DiFC and used it to noninvasively monitor tumor cell numbers in circulation in a multiple myeloma (MM) disseminated xenograft mouse model. We show that DiFC allowed enumeration of CTCs in individual mice overtime during MM growth, with sensitivity below 1  CTC mL  −  1 of peripheral blood. DiFC also revealed the presence of CTC clusters (CTCCs) in circulation to our knowledge for the first time in this model and allowed us to calculate CTCC size, frequency, and kinetics of shedding. We anticipate that the unique capabilities of DiFC will have many uses in preclinical study of metastasis, in particular, with a large number of GFP-expressing xenograft and transgenic mouse models.

Improvements to an optical scintillator imaging-based tissue dosimetry system

Previous work has shown that capturing optical emission from plastic discs attached directly to the skin can be a viable means to accurately measure surface dose during total skin electron therapy. This method can provide accurate dosimetric information rapidly and remotely without the need for postprocessing. The objective of this study was to: (1) improve the robustness and usability of the scintillators and (2) enhance sensitivity of the optical imaging system to improve scintillator emission detection as related to tissue surface dose. Baseline measurements of scintillator optical output were obtained by attaching the plastic discs to a flat tissue phantom and simultaneously irradiating and imaging them. Impact on underlying surface dose was evaluated by placing the discs on-top of the active element of an ionization chamber. A protective coating and adhesive backing were added to allow easier logistical use, and they were also subjected to disinfection procedures, while verifying that these changes did not affect the linearity of response with dose. The camera was modified such that the peak of detector quantum efficiency better overlapped with the emission spectra of the scintillating discs. Patient imaging was carried out and surface dose measurements were captured by the updated camera and compared to those produced by optically stimulated luminescence detectors (OSLD). The updated camera was able to measure surface dose with < 3 %   difference compared to OSLD–Cherenkov emission from the patient was suppressed and scintillation detection was enhanced by 25 × and 7 ×  , respectively. Improved scintillators increase underlying surface dose on average by 5.2  ±  0.1 %   and light output decreased by 2.6  ±  0.3 %  . Disinfection had < 0.02 %   change on scintillator light output. The enhanced sensitivity of the imaging system to scintillator optical emission spectrum can now enable a reduction in physical dimensions of the dosimeters without loss in ability to detect light output.

Graphene Oxide as an Optical Biosensing Platform: A Progress Report

A few years ago, crucial graphene oxide (GO) features such as the carbon/oxygen ratio, number of layers, and lateral size were scarcely investigated and, thus, their impact on the overall optical biosensing performance was almost unknown. Nowadays valuable insights about these features are well documented in the literature, whereas others remain controversial. Moreover, most of the biosensing systems based on GO were amenable to operating as colloidal suspensions. Currently, the literature reports conceptually new approaches obviating the need of GO colloidal suspensions, enabling the integration of GO onto a solid phase and leading to their application in new biosensing devices. Furthermore, most GO-based biosensing devices exploit photoluminescent signals. However, further progress is also achieved in powerful label-free optical techniques exploiting GO in biosensing, particularly using optical fibers, surface plasmon resonance, and surface enhanced Raman scattering. Herein, a critical overview on these topics is offered, highlighting the key role of the physicochemical properties of GO. New challenges and opportunities in this exciting field are also highlighted.

Integrative microendoscopic system combined with conventional microscope for live animal tissue imaging

Intravital optical imaging technology is essential for minimally invasive optical diagnosis and treatment in small animal disease models. High-resolution imaging requires high-resolution optical probes, and high-resolution optical imaging systems based on highly precise and advanced technologies and therefore, associated with high-system costs. Besides, in order to acquire small animal live images, special types of animal imaging setups are indispensable. In this paper, a microendoscopic system is designed as an add-on to existing conventional imaging microscopes, reducing the price of complete confocal endomicroscopic systems. The proposed attachable system can be configured for confocal microscopes from common manufacturers and this enables users to acquire live animal cellular images from a conventional system. It features a 4f optical plane relay system, a rotary stage for side-view endoscopic probes, and an endoscopic probe mount which swings between the horizontal and the vertical. The system could be widely useful for biological studies of animal physiology and disease models.

Fibre Bragg Grating Based Strain Sensors: Review of Technology and Applications

Fibre Bragg grating (FBG) strain sensors are not only a very well-established research field, but they are also acquiring a bigger market share due to their sensitivity and low costs. In this paper we review FBG strain sensors with high focus on the underlying physical principles, the interrogation, and the read-out techniques. Particular emphasis is given to recent advances in highly-performing, single head FBG, a category FBG strain sensors belong to. Different sensing schemes are described, including FBG strain sensors based on mode splitting. Their operation principle and performance are reported and compared with the conventional architectures. In conclusion, some advanced applications and key sectors the global fibre-optic strain sensors market are envisaged, as well as the main market players acting in this field.

Direct Laser Writing of Nanophotonic Structures on Contact Lenses

Contact lenses are ubiquitous biomedical devices used for vision correction and cosmetic purposes. Their application as quantitative analytical devices is highly promising for point-of-care diagnostics. However, it is a challenge to integrate nanoscale features into commercial contact lenses for application in low-cost biosensors. A neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (1064 nm, 3 ns pulse, 240 mJ) in holographic interference patterning mode was utilized to produce optical nanostructures over the surface of a hydrogel contact lens. One-dimensional (925 nm) and two-dimensional (925 nm × 925 nm) nanostructures were produced on contact lenses and analyzed by spectroscopy and angle-resolve measurements. The holographic properties of these nanostructures were tested in ambient moisture, fully hydrated, and artificial tear conditions. The measurements showed a rapid tuning of optical diffraction from these nanostructures from 41 to 48°. The nanostructures were patterned near the edges of the contact lens to avoid any interference and obstruction to the human vision. The formation of 2D nanostructures on lenses increased the diffraction efficiency by more than 10%. The versatility of the holographic laser ablation method was demonstrated by producing four different 2D nanopattern geometries on contact lenses. Hydrophobicity of the contact lens was characterized by contact angle measurements, which increased from 59.0° at pristine condition to 62.5° at post-nanofabrication. The holographic nanostructures on the contact lens were used to sense the concentration of Na⁺ ions. Artificial tear solution was used to simulate the conditions in dry eye syndrome, and nanostructures on the contact lenses were used to detect the electrolyte concentration changes (±47 mmol L^-1). Nanopatterns on a contact lens may be used to sense other ocular diseases in early stages at point-of-care settings.

Response characteristics of the cat somatosensory cortex following the mechanical stimulation to non-vital and vital canine

Patients sometimes complain that non-vital teeth after root canal treatment (RCT) are paresthesia compared with vital teeth, and previous psychological studies on the tactile sensibility of non-vital teeth remained controversial. In the present study, intrinsic signal optical imaging, which served as an objective tool, was employed to compare the cortex response characteristics following forces applied to the cat non-vital and vital canines. Based on the evoked cortical responses, the response threshold, signal strength, spatial pattern, temporal dynamics and the preference of force direction, they were not significantly different between vital and non-vital canines. It seemed that the tactile sensibility of vital and non-vital teeth was comparable at the cortical response level, and pulpal receptors were not concerned in tactile function.

Endowing a plain fluidic chip with micro-optics: a holographic microscope slide

Lab-on-a-Chip (LoC) devices are extremely promising in that they enable diagnostic functions at the point-of-care. Within this scope, an important goal is to design imaging schemes that can be used out of the laboratory. In this paper, we introduce and test a pocket holographic slide that allows digital holography microscopy to be performed without an interferometer setup. Instead, a commercial off-the-shelf plastic chip is engineered and functionalized with this aim. The microfluidic chip is endowed with micro-optics, that is, a diffraction grating and polymeric lenses, to build an interferometer directly on the chip, avoiding the need for a reference arm and external bulky optical components. Thanks to the single-beam scheme, the system is completely integrated and robust against vibrations, sharing the useful features of any common path interferometer. Hence, it becomes possible to bring holographic functionalities out of the lab, moving complexity from the external optical apparatus to the chip itself. Label-free imaging and quantitative phase contrast mapping of live samples are demonstrated, along with flexible refocusing capabilities. Thus, a liquid volume can be analyzed in one single shot with no need for mechanical scanning systems.

A top-down approach for fabricating three-dimensional closed hollow nanostructures with permeable thin metal walls

We report on a top-down method for the controlled fabrication of three-dimensional (3D), closed, thin-shelled, hollow nanostructures (nanocages) on planar supports. The presented approach is based on conventional microelectronic fabrication processes and exploits the permeability of thin metal films to hollow-out polymer-filled metal nanocages through an oxygen-plasma process. The technique is used for fabricating arrays of cylindrical nanocages made of thin Al shells on silicon substrates. This hollow metal configuration features optical resonance as revealed by spectral reflectance measurements and numerical simulations. The fabricated nanocages were demonstrated as a refractometric sensor with a measured bulk sensitivity of 327 nm/refractive index unit (RIU). The pattern design flexibility and controllability offered by top-down nanofabrication techniques opens the door to the possibility of massive integration of these hollow 3D nano-objects on a chip for applications such as nanocontainers, nanoreactors, nanofluidics, nano-biosensors and photonic devices.

Real-time three-dimensional jaw tracking in temporomandibular disorders

When a dysfunction occurs in any component of the stomatognathic system, temporomandibular disorders (TMD) may originate. The aim of this study was to compare the deviations, displacement and the execution speed of mandibular movements among asymptomatic participants and those with TMD. Convenience sampling was used; forty participants diagnosed by clinical evaluation following the Research Diagnostic Criteria for Temporomandibular Disorders were divided into three groups: arthropathy (GART, 10 participants, 40% men), myopathy (GMYO, 10 participants, 30% men), and the control group (CG, 20 asymptomatic participants, 25% men). Participants were asked to perform the movements of free maximal mouth opening and closing, right and left lateral excursions, and protrusion with sliding teeth contacts. The mandibular trajectory was recorded using opto-electronic devices tracking reflective markers placed in front of the 'soft tissue pogonion point'. The movements were analysed on the following axis: x - medial-lateral, y - vertical, z - antero-posterior. Significative differences were found in CGxGART - unassisted maximal mouth opening and closing projection on y-axis (OCY), CGxGMYO - unassisted maximal mouth opening and closing projection on x-axis (OCX), and in the measures Opening lateral deviation on x-axis (OLDX), closing lateral deviation on x-axis (CLDX) and in the measures of speed for both. In regard to GARTxGMYO, a significative difference was found in Protrusion lateral deviation on x-axis (PLDX) 'Conover-Iman Test of Multiple Comparisons Using Rank Sums' using Bonferroni correction (P < 0·05). In conclusion, the total opening movements in individuals with TMD tended to have higher deviation than in those asymptomatic individuals and a reduction in the speed of movements.

Influence of Connecting Two Standalone Mobile Three-Dimensional Scanners on Accuracy Comparing with a Standard Device in Facial Scanning

Objectives

In this study is investigated if bundling of two scanners leads to better accuracy in recording faces than a standard face-scanning device.

Material and Methods

In a group of 28 volunteers, two test specimens were attached to their faces: one on their forehead and one turned 90° on their cheek. Each volunteer was scanned by FaceScan3D^® and two bundled Artec EVA^® scanners. The scans were aligned to a three-dimensional model of the test specimen, and the mean error was recorded. Length, width and angles between the test specimen’s planes were compared.

Results

The mean deviation is significantly lower for the cheek test specimen in alignment (P < 0.001), length and width (P < 0.001) but not for the forehead test specimen in alignment and length and width (P > 0.05) using FaceScan3D^®. The aberration from the original angle between two sides of the test specimen is significantly lower measured with Artec EVA^® for the angle between the front and the bottom plane of both test specimens (P < 0.01). Besides the angle between the right plane and the bottom plane as well as the top plane of the test specimen mounted to the cheek, the deviation of the angle between the other side planes to each other is significantly lower (P > 0.05) scanned with Artec EVA^®.

Conclusions

Compared to FaceScan3D^®, two bundled Artec EVA^® scanners provide different accuracies depending on the location of the measured parameters. The accuracy measured for both scanners is inside the range found in the literature.

Optical Devices Constructed from Ferrocene-Modified Microgels for H2O2 Sensing

Ferrocene-modified poly(N-isopropylacrylamide)-based microgels were synthesized, characterized, and used to construct optical devices (etalons). The response of the microgels and etalons to H₂O₂ was investigated, and we show that both the microgel diameter and the optical properties of the etalons depend on the solution concentration of H₂O₂ from 0.6 to 35 mM. This behavior is a direct result of the oxidation of ferrocene, which influences the microgel diameter. This was also demonstrated by electrochemical-mediated oxidation/reduction of ferrocene using cyclic voltammetry. We go on to show that these materials could be used to monitor H₂O₂ that is generated from enzymatic reactions. Specifically, we show that the H₂O₂ generated from the oxidation of glucose catalyzed by glucose oxidase could be quantified. Finally, the devices can be reused multiple times via a regeneration process. This investigation illustrates the versatility of the etalon system to detect species of broad relevance and how they could potentially be used to quantify products of biological reactions.

Population response characteristics of intrinsic signals in the cat somatosensory cortex following canine mechanical stimulation

Intrinsic signal optical imaging has been widely used to measure functional maps in various sensory cortices due to better spatial resolution and sensitivity for detecting cortical neuroplasticity. However, application of this technique in dentistry has not been reported. In this study, intrinsic signal optical imaging was used to investigate mechanically driven responses in the cat somatosensory cortex, when punctate mechanical stimuli were applied to maxillary canines. The global signal and its spatial organization pattern were obtained. Global signal strength gradually increased with stimulus strength. There was no significant difference in response strength between contralateral and ipsilateral mechanical stimulation. A slightly greater response was recorded in the sigmoidal gyrus than in the coronal gyrus. The cat somatosensory cortex activated by sensory inputs from mechanical stimulation of canines lacks both topographical and functional organization. It is not organized into columns that represent sensory input from each tooth or direction of stimulation. These results demonstrate that intrinsic signal optical imaging is a valid tool for investigating neural responses and neuroplasticity in the somatosensory cortex that represents teeth.

Structured Organic-Inorganic Perovskite toward a Distributed Feedback Laser

A general strategy for the in-plane structuring of organic-inorganic perovskite films is presented. The method is used to fabricate an industrially relevant distributed feedback (DFB) cavity, which is a critical step toward all-electrially pumped injection laser diodes. This approach opens the prospects of perovskite materials for much improved optical control in LEDs, solar cells, and also toward applications as optical devices.

[Integrated optical sensor for rapid analysis of biological samples]

INTRODUCTION

In the medical diagnostics of bacteria, the rapid detection of pathogenic microorganisms from body fluids is one of the most important tasks. The majority of the modern measuring techniques are based on specific labels bound to the bacteria. However, this strategy usually assumes a rather time-consuming procedure involving several steps (e.g., the widely used enzyme-linked immunosorbent assay normally consists of 5 consecutive steps). Hence, there is an urgent need for the elaboration of rapid, "label-free" techniques, that are often based on Lab-on-a-chip devices.

AIM

In this paper, the authors report on the development of a biosensor based on a miniature, integrated optical Mach-Zehnder interferometer.

METHOD

Functionalization of the measuring arm of the sensor by antibodies, made the rapid and specific label-free detection of pathogens feasible.

RESULTS

Using the combination of the interferometer with a microfluidic system, the device was able to detect Escherichia coli bacteria at concentrations as low as 10(6) colony forming unit/ml within minutes.

CONCLUSIONS

This makes the newly developed biosensor a promising device for a wide range of applications, not only in medical microbiology, but microbial forensics, criminal investigations, bio-terrorism threats and in environmental studies as well.

Low vision aid-A ray of hope for irreversible visual loss in the pediatric age group

Purpose:

To analyze visual acuity (VA) improvement, causes of low vision (LV), and quality of life (QOL) following the use of low vision aids (LVAs) in children with LV.

Methods:

A prospective analysis was conducted on children with LV aged between 4 years and 18 years between March 2013 and October 2013. Children were recruited from both urban schools and rural schools. LVAs were tried for visual improvement, and improved VA was noted. All children were trained to use the aid and followed up monthly for 3 consecutive months for VA improvement; QOL through a questionnaire was analyzed after the use of LVAs.

Results:

A total of 74 children (148 eyes; 50% male; mean age, 11.8 ± 3.2 years) were analyzed, where 34 children were recruited from rural areas and 40 from urban schools. After LVA use, 101 (68.24%) eyes of 59 (79.72%) children improved for distance with telescope and 81 (54.72%) eyes of 51 (68.91%) children improved for near with magnifiers. LV due to retinal problems, optic atrophy, congenital anomalies, and amblyopia drastically reduced after use of LVA. A statistically significantly higher proportion of children had either “excellent” or “good” QOL, and a significantly lower proportion of children had either “not satisfactory” or “poor” QOL after the use of LVA (p < 0.0001).

Conclusion:

LVA is essential and effective in improving VA and QOL in children with LV.

Optical reading aids for children and young people with low vision

BACKGROUND

Low vision in childhood is a significant barrier to learning and development, particularly for reading and education. Optical low vision aids may be used to maximise the child's functional vision. The World Health Organization (WHO) has previously highlighted the importance of the use of low vision aids in managing children with visual impairment across the world.

OBJECTIVES

To assess the effect of optical low vision aids on reading in children and young people with low vision.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to January 2015), EMBASE (January 1980 to January 2015), the Health Technology Assessment Programme (HTA) (www.hta.ac.uk/), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 8 January 2015.We also used manual searching to check the references listed in retrieved articles. Manufacturers of low vision aids were contacted to request any information about studies or research regarding their products.

SELECTION CRITERIA

We planned to include randomised controlled trials (RCTs) and quasi-RCTs where any optical low vision aid was compared to standard refractive correction in children and young people aged between 5 and 16 years of age with low vision as defined by the WHO. We planned to include within-person design studies where the order of presentation of devices was randomised.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed the search results for eligibility .

MAIN RESULTS

No studies met the inclusion criteria for this review.

AUTHORS' CONCLUSIONS

There is a lack of good quality evidence regarding the use of optical low vision aids in children and young people. As such, no implications for practice can be drawn. We believe future research should include functional outcome measures such as reading speed, accuracy and comprehension, as well as the effect of low vision aids on quality of life, in order to truly assess and compare the effect of these devices on a child's life and development.

A high-sensitivity optical device for the early monitoring of plant pathogen attack via the in vivo detection of ROS bursts

Biotic stressors, especially pathogenic microorganisms, are rather difficult to detect. In plants, one of the earliest cellular responses following pathogen infection is the production of reactive oxygen species (ROS). In this study, a novel optical device for the early monitoring of Pseudomonas attack was developed; this device measures the ROS level via oxidation-sensitive 2', 7'-dichlorodihydrofluorescein diacetate (H2DCFDA)-mediated fluorescence, which could provide early monitoring of attacks by a range of plant pathogen; ROS bursts were detected in vivo in Arabidopsis thaliana with higher sensitivity and accuracy than those of a commercial luminescence spectrophotometer. Additionally, the DCF fluorescence truly reflected early changes in the ROS level, as indicated by an evaluation of the H2O2 content and the tight association between the ROS and Pseudomonas concentration. Moreover, compared with traditional methods for detecting plant pathogen attacks based on physiological and biochemical measurements, our proposed technique also offers significant advantages, such as low cost, simplicity, convenient operation and quick turnaround. These results therefore suggest that the proposed optical device could be useful for the rapid monitoring of attacks by plant pathogen and yield results considerably earlier than the appearance of visual changes in plant morphology or growth.

Acquisition of Visual Perception in Blind Adults Using the BrainPort Artificial Vision Device

OBJECTIVE

We sought to determine whether intensive low vision rehabilitation would confer any functional improvement in a sample of blind adults using the BrainPort artificial vision device.

METHOD

Eighteen adults ages 28-69 yr (n=10 men and n=8 women) who had light perception only or worse vision bilaterally spent up to 6 hr per day for 1 wk undergoing structured rehabilitation interventions. The functional outcomes of object identification and word recognition were tested at baseline and after rehabilitation training.

RESULTS

At baseline, participants were unable to complete the two functional assessments. After participation in the 1-wk training protocol, participants were able to use the BrainPort device to complete the two tasks with moderate success.

CONCLUSION

Without training, participants were not able to perform above chance level using the BrainPort device. As artificial vision technologies become available, occupational therapy practitioners can play a key role in clients' success or failure in using these devices.

Particle size distribution of exosomes and microvesicles determined by transmission electron microscopy, flow cytometry, nanoparticle tracking analysis, and resistive pulse sensing

BACKGROUND

Enumeration of extracellular vesicles has clinical potential as a biomarker for disease. In biological samples, the smallest and largest vesicles typically differ 25-fold in size, 300,000-fold in concentration, 20,000-fold in volume, and 10,000,000-fold in scattered light. Because of this heterogeneity, the currently employed techniques detect concentrations ranging from 10(4) to 10(12) vesicles mL(-1) .

OBJECTIVES

To investigate whether the large variation in the detected concentration of vesicles is caused by the minimum detectable vesicle size of five widely used techniques.

METHODS

The size and concentration of vesicles and reference beads were measured with transmission electron microscopy (TEM), a conventional flow cytometer, a flow cytometer dedicated to detecting submicrometer particles, nanoparticle tracking analysis (NTA), and resistive pulse sensing (RPS).

RESULTS

Each technique gave a different size distribution and a different concentration for the same vesicle sample.

CONCLUSION

Differences between the detected vesicle concentrations are primarily caused by differences between the minimum detectable vesicle sizes. The minimum detectable vesicle sizes were 70-90 nm for NTA, 70-100 nm for RPS, 150-190 nm for dedicated flow cytometry, and 270-600 nm for conventional flow cytometry. TEM could detect the smallest vesicles present, albeit after adhesion on a surface. Dedicated flow cytometry was most accurate in determining the size of reference beads, but is expected to be less accurate on vesicles, owing to heterogeneity of the refractive index of vesicles. Nevertheless, dedicated flow cytometry is relatively fast and allows multiplex fluorescence detection, making it most applicable to clinical research.

Tear film measurement by optical reflectometry technique

Evaluation of tear film is performed by an optical reflectometer system with alignment guided by a galvanometer scanner. The reflectometer system utilizes optical fibers to deliver illumination light to the tear film and collect the film reflectance as a function of wavelength. Film thickness is determined by best fitting the reflectance-wavelength curve. The spectral reflectance acquisition time is 15 ms, fast enough for detecting film thickness changes. Fast beam alignment of 1 s is achieved by the galvanometer scanner. The reflectometer was first used to evaluate artificial tear film on a model eye with and without a contact lens. The film thickness and thinning rate have been successfully quantified with the minimum measured thickness of about 0.3 μm. Tear films in human eyes, with and without a contact lens, have also been evaluated. A high-contrast spectral reflectance signal from the precontact lens tear film is clearly observed, and the thinning dynamics have been easily recorded from 3.69 to 1.31 μm with lipid layer thickness variation in the range of 41 to 67 nm. The accuracy of the measurement is better than ±0.58% of the film thickness at an estimated tear film refractive index error of ±0.001. The fiber-based reflectometer system is compact and easy to handle.

Shear-sensitive regulation of neutrophil flow behavior and its potential impact on microvascular blood flow dysregulation in hypercholesterolemia

OBJECTIVE

Shear stress-induced pseudopod retraction is an anti-inflammatory measure that minimizes neutrophil activity and is regulated by membrane cholesterol. We tested the hypothesis that a hypercholesterolemic impairment of shear mechanotransduction alters the neutrophil flow behavior leading to microvascular dysfunction.

APPROACH AND RESULTS

We examined the shear effects on the flow behavior of human leukocytes. When subjected to shearing during cone-plate viscometry, leukocyte suspensions exhibited parallel time-dependent reductions in viscosity and pseudopod activity. Shear-induced reductions in suspension viscosity were attenuated by membrane cholesterol enrichment. We also showed that enhanced pseudopod activity of leukocyte suspensions in 10% hematocrit significantly (P<0.05) raised the flow resistance of microvascular mimics. These results implicate an impaired neutrophil pseudopod retraction response to shear in hypercholesterolemic microvascular dysfunction. We confirmed this using near-infrared diffuse correlation spectroscopy to assess skeletal muscle blood flow regulation in the hindlimbs of mice subjected to reactive hyperemia. Using a custom protocol for the mouse, we extrapolated an adjusted peak flow and time to adjusted peak flow to quantify the early phase of the blood flow recovery response during reactive hyperemia when shear mechanobiology likely has a maximal impact. Compared with mice on normal diet, hypercholesterolemic mice exhibited significantly (P<0.05) reduced adjusted peak flow and prolonged time to adjusted peak flow which correlated (r=0.4 and r=-0.3, respectively) with neutrophil shear responsiveness and were abrogated by neutropenia.

CONCLUSIONS

These results provide the first evidence that the neutrophils contribute to tissue blood flow autoregulation. Moreover, a deficit in the neutrophil responsiveness to shear may be a feature of hypercholesterolemia-related microvascular dysfunction.

High-sensitivity, real-time, ratiometric imaging of surface-enhanced Raman scattering nanoparticles with a clinically translatable Raman endoscope device

Topical application and quantification of targeted, surface-enhanced Raman scattering (SERS) nanoparticles offer a new technique that has the potential for early detection of epithelial cancers of hollow organs. Although less toxic than intravenous delivery, the additional washing required to remove unbound nanoparticles cannot necessarily eliminate nonspecific pooling. Therefore, we developed a real-time, ratiometric imaging technique to determine the relative concentrations of at least two spectrally unique nanoparticle types, where one serves as a nontargeted control. This approach improves the specific detection of bound, targeted nanoparticles by adjusting for working distance and for any nonspecific accumulation following washing. We engineered hardware and software to acquire SERS signals and ratios in real time and display them via a graphical user interface. We report quantitative, ratiometric imaging with nanoparticles at pM and sub-pM concentrations and at varying working distances, up to 50 mm. Additionally, we discuss optimization of a Raman endoscope by evaluating the effects of lens material and fiber coating on background noise, and theoretically modeling and simulating collection efficiency at various working distances. This work will enable the development of a clinically translatable, noncontact Raman endoscope capable of rapidly scanning large, topographically complex tissue surfaces for small and otherwise hard to detect lesions.

Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy

We present near-infrared spectroscopy measurement of absolute cerebral hemoglobin concentration and saturation in a large sample of 36 healthy elderly (mean age, 85 ± 6 years) and 19 young adults (mean age, 28 ± 4 years). Non-invasive measurements were obtained on the forehead using a commercially available multi-distance frequency-domain system and analyzed using a diffusion theory model for a semi-infinite, homogeneous medium with semi-infinite boundary conditions. Our study included repeat measurements, taken five months apart, on 16 elderly volunteers that demonstrate intra-subject reproducibility of the absolute measurements with cross-correlation coefficients of 0.9 for absorption coefficient (μa), oxy-hemoglobin concentration ([HbO2]), and total hemoglobin concentration ([HbT]), 0.7 for deoxy-hemoglobin concentration ([Hb]), 0.8 for hemoglobin oxygen saturation (StO2), and 0.7 for reduced scattering coefficient (μ's). We found significant differences between the two age groups. Compared to young subjects, elderly subjects had lower cerebral [HbO2], [Hb], [HbT], and StO2 by 10 ± 4 μM, 4 ± 3 μM, 14 ± 5 μM, and 6%±5%, respectively. Our results demonstrate the reliability and robustness of multi-distance near-infrared spectroscopy measurements based on a homogeneous model in the human forehead on a large sample of human subjects. Absolute, non-invasive optical measurements on the brain, such as those presented here, can significantly advance the development of NIRS technology as a tool for monitoring resting/basal cerebral perfusion, hemodynamics, oxygenation, and metabolism.

Alq3 nanorods: promising building blocks for optical devices

Monodisperse Alq3 nanorods with hexagonal-prism-like morphology are produced via a facile, emulsion based synthesis route. The photoluminescence of individual nanorods differs from the bulk material. These nanorods are promising building blocks for novel optical devices.