Relevance of the Spectral Analysis Method of Tilted Fiber Bragg Grating-Based Biosensors: A Case-Study for Heart Failure Monitoring.

Optical fiber technology has rapidly progressed over the years, providing valuable benefits for biosensing purposes such as sensor miniaturization and the possibility for remote and real-time monitoring. In particular, tilted fiber Bragg gratings (TFBGs) are extremely sensitive to refractive index variations taking place on their surface. The present work comprises a case-study on the impact of different methods of analysis applied to decode spectral variations of bare and plasmonic TFBGs during the detection of N-terminal B-type natriuretic peptide (NT-proBNP), a heart failure biomarker, namely by following the most sensitive mode, peaks of the spectral envelopes, and the envelopes' crossing point and area. Tracking the lower envelope resulted in the lowest limits of detection (LOD) for bare and plasmonic TFBGs, namely, 0.75 ng/mL and 0.19 ng/mL, respectively. This work demonstrates the importance of the analysis method on the outcome results, which is crucial to attain the most reliable and sensitive method with lower LOD sensors. Furthermore, it makes the scientific community aware to take careful attention when comparing the performance of different biosensors in which different analysis methods were used.

Esophagomediastinal fistula: a rare case of gastrointestinal tuberculosis.

A 40-year-old male with history of HIV infection was admitted to the hospital with a one-month history of productive cough, vespertine fever, night sweats, loss of appetite and unintentional 10-Kg weight loss. Physical exam was remarkable for cachexia. Blood tests revealed a CD4+ T lymphocyte count of 23 cells/mm3 and HIV viral load of 837,678 copies/ml. Bacilloscopies were positive. Chest computed thomography (CT) showed multiple mediastinal lymph nodes, signs of esophagomediastinal fistula, pericardial effusion and multiple micronodular pulmonary opacities. Endoscopy (EGD) revealed a 10 mm deep ulcer-like lesion in the middle esophagus with pus overflow, but no bubbles were seen. The diagnosis of stage C3 HIV infection with disseminated tuberculosis was made and the patient underwent standard antituberculosis (RIPE) and antiretroviral therapy. Given the mediastinitis risk a percutaneous endoscopic gastrostomy (PEG) tube was placed for nutritional purposes.

When needles are not enough, forceps delivers!

A 35-year-old male with a history of recurrent pleuritic chest pain was referred for evaluation of a mediastinal mass detected on CT. MRI showed a 10.5 x 7 x 3 cm lesion in the posterior mediastinum. EUS revealed a multicystic lesion with thin septa and clear anechoic content that extended from the lower posterior mediastinum to the upper retroperitoneum. EUS-FNA was performed using a 22-gauge needle with aspiration of a serosanguineous fluid. Fluid analysis showed low values of amylase, triglycerides, CEA, and CA19-9. Cytology tests identified small mature lymphocytes without malignancy.

Physical Activity is Associated With Lower Arterial Stiffness in Patients With Resistant Hypertension.

BACKGROUND: Physical activity is associated with reduced arterial stiffness, although such a relationship has not been reported in those with resistant hypertension. Therefore, this study aimed to determine the association between daily physical activity and arterial stiffness in patients with resistant hypertension. METHODS: Fifty-seven (57) patients with resistant hypertension (50.9% men), aged 58.8±9.4 years, were consecutively recruited. Arterial stiffness was evaluated using carotid-femoral pulse wave velocity (cf-PWV). Daily physical activity was objectively assessed with accelerometers during 7 consecutive days. RESULTS: Patients had a body mass index of 29.0±4.0 kg/m2 (84.3% overweight/obese) and were taking an average 4.5 antihypertensive medications. Overall, the cf-PWV was 9.2±2.4 m/s and the majority of participants (n=41, 71.9%) presented a cf-PWV <10 m/s. The cf-PWV showed an inverse correlation with light-intensity physical activity (r = -0.290, p=0.029) and total daily physical activity (r = -0.287, p=0.030). The correlation between light physical activity and cf-PWV remained significant after adjustment for systolic and diastolic blood pressure, but lost significance when further adjusted for age. CONCLUSIONS: Higher daily levels of light-intensity and total physical activity were associated with lower arterial stiffness. Nonetheless, this association is weak and attenuated or abolished when adjusted for blood pressure and age. These results suggest that physical activity may play an important role as a lifestyle intervention for patients with resistant hypertension. Future studies with larger samples sizes are necessary to confirm this preliminary data.

Hepatic osteodystrophy in cirrhosis due to alcohol-related liver disease.

INTRODUCTION: hepatic osteodystrophy, including osteoporosis, is an abnormal bone metabolism related with chronic liver diseases. Osteoporosis is associated with an increased risk of bone fractures, with a significant impact on morbidity, mortality and healthcare costs. Nevertheless, bone disorders tend to be undervalued in cirrhosis due to alcohol-related liver disease (ALD cirrhosis). This study aimed to assess the prevalence of hepatic osteodystrophy and osteoporosis in ALD cirrhosis. METHODS: a prospective observational study was performed that included patients with ALD cirrhosis, between September 2017 and December 2018. Bone mineral density was determined by dual energy X-ray absorptiometry at the lumbar spine and the femoral neck. Hepatic osteodystrophy was defined as a T-score below -1 SD and osteoporosis as a T-score below -2.5 SD. RESULTS: ninety-four patients were included; 24.5 % (n = 23) had prior fragility fractures and ten patients suffered new osteoporotic fractures during the study period. Hepatic osteodystrophy was diagnosed in 79.8 % (n = 75) and osteoporosis in 21.3 % (n = 20) of cases. Patients with hepatic osteodystrophy presented significantly worse Child-Turcotte-Pugh (p < 0.05) and Model for End-Stage Liver Disease (MELD-sodium) scores (p = 0.01). According to the multivariate analysis, lower body mass index (BMI) (OR = 0.787, 95 % CI: 0.688-0.901, p = 0.001) and vitamin D deficiency (OR = 6.798, 95 % CI: 1.775-26.038, p = 0.005) were significantly and independently associated with hepatic osteodystrophy. Patients with osteoporosis also had a lower BMI (p = 0.01). Female patients and those with prior fragility fractures were more likely to suffer from osteoporosis (p < 0.05). CONCLUSION: our study revealed a high prevalence of hepatic osteodystrophy and osteoporosis in patients with ALD cirrhosis (particularly in those with a lower BMI) and a concerning high rate of fragility fractures. Bone mineral density should be assessed in order to allow for an early diagnosis and the implementation of preventive measures.

Polymer optical fibers for mechanical wave monitoring.

This Letter presents the development of a low-cost polymer optical fiber (POF) sensor for mechanical wave monitoring. The POF is fabricated using the light polymerization spinning process (LPS-POF) with Bisphenol-A as its main component, resulting in a highly flexible fiber. The proposed LPS-POF sensor is applied on the assessment of squared waves with different amplitudes, where the amplitude and dynamic responses are compared to the ones of a piezoelectric transducer (PZT). In static conditions, a determination coefficient (R2) of 0.990 is obtained between the reference (PZT) and proposed sensors for the amplitude assessment of the wave. In dynamic analysis, the LPS-POF viscoelasticity is compensated using viscoelastic constitutive models, resulting in a R2 of 0.988 between the sensor responses, which indicate a mean error reduction of 21% when compared to the uncompensated responses in the amplitudes of different square waves. The dynamic analysis also shows the sensor capability of operating in frequencies as high as 25 Hz. Then, the sensor's responses, compared to the input squared wave, show the possibility of wave velocity measurement. Therefore, with a LPS-POF sensor array, it is possible to monitor these parameters in practical applications.

Strain, temperature, moisture, and transverse force sensing using fused polymer optical fibers.

This paper presents the characterization of polymer optical fibers (POFs) submitted to the catastrophic fuse effect towards intensity-variation-based sensing of strain, transverse force, temperature, and moisture. In the experiments, POFs with and without the fuse effect are tested and the results are compared with respect to the sensitivity, linearity, and root mean squared error (RMSE). The fused POFs have higher linearity and lower RMSE than non-fused POFs in strain and transverse force sensing. Also, the sensitivity of the fused POFs is higher in transverse force and temperature sensing, which can be related to the higher sensitivity to the curvature that the transverse force creates on the POF and to the more significant variations of the refractive index with temperature increase. Additionally, the fused POFs present lower moisture absorption than the non-fused POFs. The presented results indicate a great potential of the fused POFs intensity-variation-based sensing applications of various physical parameters.

Design and characterization of a curvature sensor using fused polymer optical fibers.

This Letter demonstrates the application of polymer optical fibers (POFs) damaged by the fiber fuse effect to curvature sensing and dynamic angular monitoring. The curvature sensing performance using the fused-POF is compared to POF without the fuse effect. Both POFs are submitted to angles of up to 90 deg in flexion/extension cycles with angular velocities ranging from 0.48 rad/s to 5.61 rad/s. The fused POF is found to show higher performance with respect to sensitivity, correlation coefficient with linear regression, and hysteresis. For instance, at the angular velocity of 0.48 rad/s, the fused POF shows >3 times higher sensitivity and significantly lower hysteresis than those of the non-fused POF. In addition, the fused POFs have lower cross-sensitivity and hysteresis variations on the tests with different angular velocities. These results indicate that the fused POFs are potential candidates to develop curvature sensors with various advantages over non-fused POFs, for applications such as gait analysis and wearable robotics.

Gait Shear and Plantar Pressure Monitoring: A Non-Invasive OFS Based Solution for e-Health Architectures.

In an era of unprecedented progress in sensing technology and communication, health services are now able to closely monitor patients and elderly citizens without jeopardizing their daily routines through health applications on their mobile devices in what is known as e-Health. Within this field, we propose an optical fiber sensor (OFS) based system for the simultaneous monitoring of shear and plantar pressure during gait movement. These parameters are considered to be two key factors in gait analysis that can help in the early diagnosis of multiple anomalies, such as diabetic foot ulcerations or in physical rehabilitation scenarios. The proposed solution is a biaxial OFS based on two in-line fiber Bragg gratings (FBGs), which were inscribed in the same optical fiber and placed individually in two adjacent cavities, forming a small sensing cell. Such design presents a more compact and resilient solution with higher accuracy when compared to the existing electronic systems. The implementation of the proposed elements into an insole is also described, showcasing the compactness of the sensing cells, which can easily be integrated into a non-invasive mobile e-Health solution for continuous remote gait monitoring of patients and elder citizens. The reported results show that the proposed system outperforms existing solutions, in the sense that it is able to dynamically discriminate shear and plantar pressure during gait.

POFBG-Embedded Cork Insole for Plantar Pressure Monitoring.

We propose a novel polymer optical fiber (POF) sensing system based on fiber Bragg gratings (FBGs) to measure foot plantar pressure. The plantar pressure signals are detected by five FBGs, in the same piece of cyclic transparent optical polymer (CYTOP) fiber, which are embedded in a cork insole for the dynamic monitoring of gait. The calibration and measurements performed with the suggested system are presented, and the results obtained demonstrate the accuracy and reliability of the sensing platform to monitor the foot plantar pressure distribution during gait motion and the application of pressure. This architecture does not compromise the patient's mobility nor interfere in their daily activities. The results using the CYTOP fiber showed a very good response when compared with solutions using silica optical fibers, resulting in a sensitivity almost twice as high, with excellent repeatability and ease of handling. The advantages of POF (e.g., high flexibility and robustness) proved that this is a viable solution for this type of application, since POF's high fracture toughness enables its application in monitoring patients with higher body mass compared with similar systems based on silica fiber. This study has demonstrated the viability of the proposed system based on POF technology as a useful alternative for plantar pressure detection systems.

Low-Cost Interrogation Technique for Dynamic Measurements with FBG-Based Devices.

Fiber Bragg gratings are widely used optical fiber sensors for measuring temperature and/or mechanical strain. Nevertheless, the high cost of the interrogation systems is the most important drawback for their large commercial application. In this work, an in-line Fabry-Perot interferometer based edge filter is explored in the interrogation of fiber Bragg grating dynamic measurements up to 5 kHz. Two devices an accelerometer and an arterial pulse wave probe were interrogated with the developed approach and the results were compared with a commercial interrogation monitor. The data obtained with the edge filter are in agreement with the commercial device, with a maximum RMSE of 0.05 being able to meet the requirements of the measurements. Resolutions of 3.6 pm and 2.4 pm were obtained, using the optical accelerometer and the arterial pulse wave probe, respectively.

A rare cause of intestinal bleeding: duodenal metastasis from endometrial cancer.

With this report we alert to an extremely rare case of duodenal metastases, from an endometrial adenocarcinoma by lymphatic spread and whose primary manifestation was with gastrointestinal bleeding. We think this is the first case reported of duodenal metastases from endometrial carcinoma and with this presentation.

Internal and External Temperature Monitoring of a Li-Ion Battery with Fiber Bragg Grating Sensors.

The integration of fiber Bragg grating (FBG) sensors in lithium-ion cells for in-situ and in-operando temperature monitoring is presented herein. The measuring of internal and external temperature variations was performed through four FBG sensors during galvanostatic cycling at C-rates ranging from 1C to 8C. The FBG sensors were placed both outside and inside the cell, located in the center of the electrochemically active area and at the tab-electrode connection. The internal sensors recorded temperature variations of 4.0 ± 0.1 °C at 5C and 4.7 ± 0.1 °C at 8C at the center of the active area, and 3.9 ± 0.1 °C at 5C and 4.0 ± 0.1 °C at 8C at the tab-electrode connection, respectively. This study is intended to contribute to detection of a temperature gradient in real time inside a cell, which can determine possible damage in the battery performance when it operates under normal and abnormal operating conditions, as well as to demonstrate the technical feasibility of the integration of in-operando microsensors inside Li-ion cells.

Detection of NT-proBNP Using Optical Fiber Back-Reflection Plasmonic Biosensors.

Heart failure (HF) is a clinical entity included in cardiovascular diseases affecting millions of people worldwide, being a leading cause of hospitalization of older adults, and therefore imposing a substantial economic burden on healthcare systems. HF is characterized by dyspnea, fatigue, and edema associated with elevated blood levels of natriuretic peptides, such as N Terminal pro-B-type Natriuretic Peptide (NT-proBNP), for which there is a high demand for point of care testing (POCT) devices. Optical fiber (OF) biosensors offer a promising solution, capable of real-time detection, quantification, and monitoring of NT-proBNP concentrations in serum, saliva, or urine. In this study, immunosensors based on plasmonic uncladded OF tips were developed using OF with different core diameters (200 and 600 µm). The tips were characterized to bulk refractive index (RI), anddetection tests were conducted with NT-proBNP concentrations varying from 0.01 to 100 ng/mL. The 200 µm sensors showed an average total variation of 3.6 ± 2.5 mRIU, an average sensitivity of 50.5 mRIU/ng·mL-1, and a limit of detection (LOD) of 0.15 ng/mL, while the 600 µm sensors had a response of 6.1 ± 4.2 mRIU, a sensitivity of 102.8 mRIU/ng·mL-1, and an LOD of 0.11 ng/mL. Control tests were performed using interferents such as uric acid, glucose, and creatinine. The results show the potential of these sensors for their use in biological fluids.

Aerobic exercise improves central blood pressure and blood pressure variability among patients with resistant hypertension: results of the EnRicH trial.

Central blood pressure (BP) and BP variability are associated with cardiovascular disease risk. However, the influence of exercise on these hemodynamic parameters is unknown among patients with resistant hypertension. The EnRicH (The Exercise Training in the Treatment of Resistant Hypertension) was a prospective, single-blinded randomized clinical trial (NCT03090529). Sixty patients were randomized to a 12-week aerobic exercise program or usual care. The outcome measures include central BP, BP variability, heart rate variability, carotid-femoral pulse wave velocity, and circulating cardiovascular disease risk biomarkers including high-sensitivity C-reactive protein, angiotensin II, superoxide dismutase, interferon gamma, nitric oxide, and endothelial progenitor cells. Central systolic BP decreased by 12.22 mm Hg (95% CI, -1.88 to -22.57, P = 0.022) as did BP variability by 2.85 mm Hg (95% CI, -4.91 to -0.78, P = 0.008), in the exercise (n = 26) compared to the control group (n = 27). Interferon gamma -4.3 pg/mL (95%CI, -7.1 to -1.5, P = 0.003), angiotensin II -157.0 pg/mL (95%CI, -288.1 to -25.9, P = 0.020), and superoxide dismutase 0.4 pg/mL (95%CI, 0.1-0.6, P = 0.009) improved in the exercise compared to the control group. Carotid-femoral pulse wave velocity, heart rate variability, high-sensitivity C-reactive protein, nitric oxide, and endothelial progenitor cells were not different between groups (P > 0.05). In conclusion, a 12-week exercise training program improved central BP and BP variability, and cardiovascular disease risk biomarkers in patients with resistant hypertension. These markers are clinically relevant as they are associated with target organ damage and increased cardiovascular disease risk and mortality.

Respiratory and heart rate monitoring using an FBG 3D-printed wearable system.

This work proposes a 3D-printed sensor based on fiber Bragg grating (FBG) technology for respiratory rate (RR) and heart rate (HR) monitoring. Each sensor is composed of a single FBG fully encapsulated into a 3D-printable Flexible, during the printing process. Sensors with different material thicknesses and infill densities were tested. The sensor with the best metrological properties was selected and preliminary assessed in terms of capability of monitoring RR and HR on three users. Preliminary results proved that the developed sensor can be a valuable easy-to-fabricate solution, with high reproducibility and high strain sensitivity to chest wall deformations due to breathing and heart beating.

Cost-Effective Fiber Optic Solutions for Biosensing.

In the last years, optical fiber sensors have proven to be a reliable and versatile biosensing tool. Optical fiber biosensors (OFBs) are analytical devices that use optical fibers as transducers, with the advantages of being easily coated and biofunctionalized, allowing the monitorization of all functionalization and detection in real-time, as well as being small in size and geometrically flexible, thus allowing device miniaturization and portability for point-of-care (POC) testing. Knowing the potential of such biosensing tools, this paper reviews the reported OFBs which are, at the moment, the most cost-effective. Different fiber configurations are highlighted, namely, end-face reflected, unclad, D- and U-shaped, tips, ball resonators, tapered, light-diffusing, and specialty fibers. Packaging techniques to enhance OFBs' application in the medical field, namely for implementing in subcutaneous, percutaneous, and endoscopic operations as well as in wearable structures, are presented and discussed. Interrogation approaches of OFBs using smartphones' hardware are a great way to obtain cost-effective sensing approaches. In this review paper, different architectures of such interrogation methods and their respective applications are presented. Finally, the application of OFBs in monitoring three crucial fields of human life and wellbeing are reported: detection of cancer biomarkers, detection of cardiovascular biomarkers, and environmental monitoring.

Label-free plasmonic immunosensor for cortisol detection in a D-shaped optical fiber.

Measuring cortisol levels as a stress biomarker is essential in many medical conditions associated with a high risk of metabolic syndromes such as anxiety and cardiovascular diseases, among others. One technology that has a growing interest in recent years is fiber optic biosensors that enable ultrasensitive cortisol detection. Such interest is allied with progress being achieved in basic interrogation, accuracy improvements, and novel applications. The development of improved cortisol monitoring, with a simplified manufacturing process, high reproducibility, and low cost, are challenges that these sensing mechanisms still face, and for which solutions are still needed. In this paper, a comprehensive characterization of a D-shaped fiber optic immunosensor for cortisol detection based on surface plasmon resonance (SPR) enabled by gold coating is reported. Specifically, the sensor instrumentation and fabrication processes are discussed in detail, and a simulation with its complete mathematical formalism is also presented. Moreover, experimental cortisol detection tests were performed for a detection range of 0.01 to 100 ng/mL, attaining a logarithmic sensitivity of 0.65 ± 0.02 nm/log(ng/mL) with a limit of detection (LOD) of 1.46 ng/mL. Additionally, an investigation of signal processing is also discussed, with the main issues addressed in order to highlight the best way to extract the sensing information from the spectra measured with a D-shaped sensor.