242 research outputs found

    Fluorescence sensing technologies for ophthalmic diagnosis

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    Personalized and point-of-care (POC) diagnoses are critical for ocular physiology and disease diagnosis. Real-time monitoring and continuous sampling abilities of tear fluid and user-friendliness have become the key characteristics for the applied ophthalmic techniques. Fluorescence technologies, as one of the most popular methods that can fulfill the requirements of clinical ophthalmic applications for optical sensing, have been raised and applied for tear sensing and diagnostic platforms in recent decades. Wearable sensors in this case have been increasingly developed for ocular diagnosis. Contact lenses, as one of the commercialized and popular tools for ocular dysfunction, have been developed as a platform for fluorescence sensing in tears diagnostics and real-time monitoring. Numbers of biochemical analytes have been examined through developed fluorescent contact lens sensors, including pH values, electrolytes, glucose, and enzymes. These sensors have been proven for monitoring ocular conditions, enhancing and detecting medical treatments, and tracking efficiency of related ophthalmic surgeries at POC settings. This review summarizes the applied ophthalmic fluorescence sensing technologies in tears for ocular diagnosis and monitoring. In addition, the cooperation of fabricated fluorescent sensor with mobile phone readout devices for diagnosing ocular diseases with specific biomarkers continuously is also discussed. Further perspectives for the developments and applications of fluorescent ocular sensing and diagnosing technologies are also provided

    Current and Emerging Technology for Continuous Glucose Monitoring

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    Diabetes has become a leading cause of death worldwide. Although there is no cure for diabetes, blood glucose monitoring combined with appropriate medication can enhance treatment efficiency, alleviate the symptoms, as well as diminish the complications. For point-of-care purposes, continuous glucose monitoring (CGM) devices are considered to be the best candidates for diabetes therapy. This review focuses on current growth areas of CGM technologies, specifically focusing on subcutaneous implantable electrochemical glucose sensors. The superiority of CGM systems is introduced firstly, and then the strategies for fabrication of minimally-invasive and non-invasive CGM biosensors are discussed, respectively. Finally, we briefly outline the current status and future perspective for CGM systems.This work was supported by the National Natural Science Foundation of China (61471233, 21504051), the Program for Professor of Special Appointment (Eastern Scholar) at SIHL, the Sailing Project and Basic Research Program from Science and Technology Commission of Shanghai Municipality (14YF1410600, 14JC1406402), Shuguang and ChenGuang project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation (14SG52, 13CG62), the key subject of Shanghai Polytechnic University (Material Science and Engineering, XXKZD1601)

    Updates of Wearing Devices (WDs) In Healthcare, And Disease Monitoring

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     With the rising pervasiveness of growing populace, aging and chronic illnesses consistently rising medical services costs, the health care system is going through a crucial change from the conventional hospital focused system to an individual-focused system. Since the twentieth century, wearable sensors are becoming widespread in medical care and biomedical monitoring systems, engaging consistent estimation of biomarkers for checking of the diseased condition and wellbeing, clinical diagnostics and assessment in biological fluids like saliva, blood, and sweat. Recently, the improvements have been centered around electrochemical and optical biosensors, alongside advances with the non-invasive monitoring of biomarkers, bacteria and hormones, etc. Wearable devices have created with a mix of multiplexed biosensing, microfluidic testing and transport frameworks incorporated with flexible materials and body connections for additional created wear ability and effortlessness. These wearables hold guarantee and are fit for a higher understanding of the relationships between analyte focuses inside the blood or non-invasive biofluids and feedback to the patient, which is fundamentally significant in ideal finding, therapy, and control of diseases. In any case, cohort validation studies and execution assessment of wearable biosensors are expected to support their clinical acceptance. In the current review, we discussed the significance, highlights, types of wearables, difficulties and utilizations of wearable devices for biological fluids for the prevention of diseased conditions and real time monitoring of human wellbeing. In this, we sum up the different wearable devices that are developed for health care monitoring and their future potential has been discussed in detail

    Ophthalmic sensing technologies for ocular disease diagnostics

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    Point-of-care diagnosis and personalized treatments are critical in ocular physiology and disease. Continuous sampling of tear fluid for ocular diagnosis is a need for further exploration. Several techniques have been developed for possible ophthalmological applications, from traditional spectroscopies to wearable sensors. Contact lenses are commonly used devices for vision correction, as well as for other therapeutic and cosmetic purposes. They are increasingly being developed into ocular sensors, being used to sense and monitor biochemical analytes in tear fluid, ocular surface temperature, intraocular pressure, and pH value. These sensors have had success in detecting ocular conditions, optimizing pharmaceutical treatments, and tracking treatment efficacy in point-of-care settings. However, there is a paucity of new and effective instrumentation reported in ophthalmology. Hence, this review will summarize the applied ophthalmic technologies for ocular diagnostics and tear monitoring, including both conventional and biosensing technologies. Besides applications of smart readout devices for continuous monitoring, targeted biomarkers are also discussed for the convenience of diagnosis of various ocular diseases. A further discussion is also provided for future aspects and market requirements related to the commercialization of novel types of contact lens sensors

    Ophthalmic sensors and drug delivery

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    Advances in multifunctional materials and technologies have allowed contact lenses to serve as wearable devices for continuous monitoring of physiological parameters and delivering drugs for ocular diseases. Since the tear fluids comprise a library of biomarkers, direct measurement of different parameters such as concentration of glucose, urea, proteins, nitrite, and chloride ions, intraocular pressure (IOP), corneal temperature, and pH can be carried out non-invasively using contact lens sensors. Microfluidic contact lens sensor based colorimetric sensing and liquid control mechanisms enable the wearers to perform self-examinations at home using smartphones. Furthermore, drug-laden contact lenses have emerged as delivery platforms using a low dosage of drugs with extended residence time and increased ocular bioavailability. This review provides an overview of contact lenses for ocular diagnostics and drug delivery applications. The designs, working principles, and sensing mechanisms of sensors and drug delivery systems are reviewed. The potential applications of contact lenses in point-of-care diagnostics and personalized medicine, along with the significance of integrating multiplexed sensing units together with drug delivery systems, have also been discussed

    Photonic hydrogel sensors

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    Hydrogels are an important tools for sensing because of their sensitivity to small adjustments and reactions to physical, biological, and chemical changes. They have been used in wide range of applications such as biomedical fields for drug delivery and in diagnostics. Hydrogel-based systems are a reusable sensing platform to quantify biomarkers in high-risk patients at clinical and point-of-care settings. In this thesis, two fabrication methods have been developed to successfully detect glucose concentration, pH changes and intraocular pressure (IOP). Continuous glucose monitoring aims to achieve accurate control of blood glucose concentration to prevent hypo/hyperglycaemia in diabetic patients. Also, the development of pH changes sensing device is the key to prevent the fatal implications. The Increasing of intraocular pressure (IOP) is the main risk factor for glaucoma, which is the second major source of losing sight in the world. The first method is to developed hydrogel-based sensor by using stamping technique. A novel glucose sensor based on hydrogel with a micro-imprinted hexagonal structure was fabricated here. Our method utilized diffraction properties of a hexagonally photonic microscale concavities to detect the changes in the glucose concentration from 1 mM to 200 mM. In addition, same method was used to design a new pH hydrogel-based sensor with imprinted Fresnel lens. The sensor was able to monitor the pH changes with respond time of 5 minutes. The sensor had pH range from 4.5 to 7 and showed an increase in the sensitivity after 10 days storage in PBS solution of pH 7.4. Also, when the effect of temperature changes was investigated in the study, the temperature effect was negligible in the performance the sensor. The second method is Laser ablation of commercial contact lenses. Initially, CO2 laser (HPC LS 3040) was used to modify the surface properties of the lens at selective areas by creating 1D and 2D patterns. Laser parameters (space gap between the patterns and laser power, and scan speed) were examined to find the optimal laser setting. We managed to improve the wettability properties of the lens by increasing the density of the surface. After that, we engraved two circular micro-channels on the contact lens using CO2 laser (Rayjet laser). Three different lenses were fabricated with various spacing gap between the channels (1 mm, 1.5 mm and 2 mm). The lenses had maximum channel depth of up to 20 µm. By using laser treated lenses, a change in pressure from 12 mmHg to 22 mmHg, normal eye IOP and glaucoma patients IOP, was detect by the lenses. In summary, this thesis presents important findings that can be recommended for application in medical point-of-care diagnostics, implantable chips, and wearable continuous monitoring devices to quantify biomarkers. These methods offer sensing devices that are easy and fast to manufacture, cost effective, fast response and noninvasive sensors

    Soft and flexible material-based affinity sensors

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    Recent advances in biosensors and point-of-care (PoC) devices are poised to change and expand the delivery of diagnostics from conventional lateral-flow assays and test strips that dominate the market currently, to newly emerging wearable and implantable devices that can provide continuous monitoring. Soft and flexible materials are playing a key role in propelling these trends towards real-time and remote health monitoring. Affinity biosensors have the capability to provide for diagnosis and monitoring of cancerous, cardiovascular, infectious and genetic diseases by the detection of biomarkers using affinity interactions. This review tracks the evolution of affinity sensors from conventional lateral-flow test strips to wearable/implantable devices enabled by soft and flexible materials. Initially, we highlight conventional affinity sensors exploiting membrane and paper materials which have been so successfully applied in point-of-care tests, such as lateral-flow immunoassay strips and emerging microfluidic paper-based devices. We then turn our attention to the multifarious polymer designs that provide both the base materials for sensor designs, such as PDMS, and more advanced functionalised materials that are capable of both recognition and transduction, such as conducting and molecularly imprinted polymers. The subsequent content discusses wearable soft and flexible material-based affinity sensors, classified as flexible and skin-mountable, textile materials-based and contact lens-based affinity sensors. In the final sections, we explore the possibilities for implantable/injectable soft and flexible material-based affinity sensors, including hydrogels, microencapsulated sensors and optical fibers. This area is truly a work in progress and we trust that this review will help pull together the many technological streams that are contributing to the field

    Recent developments in minimally and truly non-invasive blood glucose monitoring techniques

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    The aim of this paper is to introduce the recent research and commercial developments in minimally and non invasive blood glucose monitoring technique

    Optical biosensors

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    Continuous glucose monitoring facilitates the stringent control of blood glucose concentration in diabetic and intensive care patients. Low-cost, robust, and reusable continuous glucose monitoring systems that can provide quantitative measurements at point-of-care settings is an unmet medical need. Phenylboronic acids (PBAs) have emerged as synthetic receptors that can reversibly bind to cis-diols such as glucose molecules. The incorporation of phenylboronic acids in hydrogels offer exclusive attributes as the binding process with glucose induces Donnan potential that leads to osmotic pressure, resulting in volumetric changes in the hydrogel matrix. Optical glucose sensors based on PBA-functionalized hydrogels have emerged as strong candidates for commercialization; however, their complex and time-consuming fabrication process, and their bulky and expensive readouts methods made them undesirable for quantitative analyses. In this dissertation, optical hydrogel sensors have been developed and attached to contact lenses for continuous glucose detection in physiological conditions. A simple fabrication method was utilized, and smartphone technology was employed for recording the output signals. A 1D photonic structure was replicated on a PBA-functionalized hydrogel to function as a transducer and to improve the sensor performance. Upon binding glucose with boronate anions immobilized in the hydrogel matrix, a positive volumetric shift occurred modifying the periodic constant of the photonic structure, consequently its diffraction properties altered. A correlation has been established between the sensor’s periodic constant and glucose concentration in the range of 0-50 mM. The hydrogel sensor was attached to a soft commercial contact lens (ACUVUE) and was interrogated for glucose detection in artificial tears. The ambient light sensor of a smartphone captured the intensity of the laser diffracted signals and was correlated with glucose concentrations. The smart contact lens showed very short response time (3 s), and a saturation time of near 4 minutes in continuous monitoring conditions. However, a laser beam was necessary to interrogate the contact lens which is uncomfortable, and the frequent exposure might be harmful to the eye cornea. Alternatively, a novel transducer has been introduced to enable interrogating the smart contact lens by using a white light beam. Light diffusing microstructures (LDMs) have been introduced for the first time for the sensing applications. The LDMs can be considered as densely-packed microparticles of different shapes and dimensions which have the capacity to diffuse the polychromatic and monochromatic light in the forward and backward directions. The LDMs were imprinted on the glucose -responsive hydrogel to monitor the volumetric shift due to glucose complexation. The volumetric modification of the hydrogel upon glucose complexation induced a change in the dimensions and refractive index of the LDMs, resulting in a variation in the diffusion efficiency. The glucose sensor was attached to a commercial contact lens and a smartphone measured the optical output signals. The alternative transducer enabled interrogating the smart contact lens by a white light beam and retained on the simplicity of the fabrication and the readout methodology; however, the response time of the senor increased significantly. The proposed smart contact lenses can be considered as a non-invasive way for continuous glucose monitoring, and can detect many other biomarkers that are beneficial for medical diagnostic applications. For implantable and remote monitoring of glucose concentration, fiber optic probes have been developed. Fiber optics have inherent advantages such as immunity to electromagnetic interference, miniaturization, and small volumes of samples. These merits candidate them for biosensing applications; however, complexity of the manufacturing process, poor mechanical properties, unpracticality of the readout methodology have hindered their practical applications. We have developed fiber optic probes for glucose detection that overcome the limitations mentioned above. Capability of the LDMs to scatter/diffuse the incident light beam in the forward and backward directions was exploited. The glucose responsive hydrogel imprinted with the LDMs was attached to the tip of a multimode silica fiber. Swelling of the attached hydrogel led to a decrease in the refractive index of the LDMs, inducing a decrease in the light scattering angles. Whereas the numerical aperture of the optical fiber indicates the range of the angles of the incident rays those satisfy the total internal reflection condition. Accordingly, swelling the hydrogel attached to the fiber result in more incident rays fall within the accepted range of angles to be guided in the optical fiber. Hence, the optical power guided in the fiber increased with glucose concentration. The fabricated fiber probe was interrogated for glucose detection in transmission configuration and the smartphone was utilized to pick up the fiber’s signals. Also, the probe was tested in reflection configuration which is a more practical mode for implantable biosensing applications. The probe overcame some limitations of the existing probes such as interferometric, SPR, and fluorescent probes in terms of ease of the fabrication and the interrogation processes. Additionally, the probe showed high sensitivity, rapid response, and selectivity for glucose over lactate. The lactate interference was found to be ~ 0.1% in the physiological condition. Furthermore, biocompatible hydrogel fibers were introduced to prevent or reduce the immune reaction in the implantation sites. The probes were tested for glucose detection and showed similar response to that of silica fiber probes; however, they presented lower sensitivity which might be the result of a higher light loss in the hydrogel fiber. In order to emphasize the variety of applications of these novel fiber optic probes that we developed, two more probes were fabricated for alcohol detection and pH measurements. The alcohol probe showed real-time sensing of ethanol, propanol, and dimethyl sulfoxide with a response time in seconds and a saturation time around 60 s. Also, the pH probe showed high sensitivity and rapid response in the acidic region with a sensitivity near 20% pH-1. For medical applications, the pH sensor was attached to a biocompatible fiber optic and was tested for pH sensing in reflection configuration. The probe can be recommended for gastric pH detection. The fabricated optical fiber sensors may also have applications in wearable and implantable point-of-care and intensive-care continuous monitoring systems

    Soft, smart contact lenses with integrations of wireless circuits, glucose sensors, and displays

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    Recent advances in wearable electronics combined with wireless communications are essential to the realization of medical applications through health monitoring technologies. For example, a smart contact lens, which is capable of monitoring the physiological information of the eye and tear fluid, could provide real-time, noninvasive medical diagnostics. However, previous reports concerning the smart contact lens have indicated that opaque and brittle components have been used to enable the operation of the electronic device, and this could block the user???s vision and potentially damage the eye. In addition, the use of expensive and bulky equipment to measure signals from the contact lens sensors could interfere with the user???s external activities. Thus, we report an unconventional approach for the fabrication of a soft, smart contact lens in which glucose sensors, wireless power transfer circuits, and display pixels to visualize sensing signals in real time are fully integrated using transparent and stretchable nanostructures. The integration of this display into the smart lens eliminates the need for additional, bulky measurement equipment. This soft, smart contact lens can be transparent, providing a clear view by matching the refractive indices of its locally patterned areas. The resulting soft, smart contact lens provides real-time, wireless operation, and there are in vivo tests to monitor the glucose concentration in tears (suitable for determining the fasting glucose level in the tears of diabetic patients) and, simultaneously, to provide sensing results through the contact lens display
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