Activation energy for pore opening in lipid membranes under an electric field.

The standard model of pore formation was introduced more than fifty years ago, and it has been since, despite some refinements, the cornerstone for interpreting experiments related to pores in membranes. A central prediction of the model concerning pore opening under an electric field is that the activation barrier for pore formation is lowered proportionally to the square of the electric potential. However, this has only been scarcely and inconclusively confronted to experiments. In this paper, we study the electropermeability of model lipid membranes composed of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) containing different fractions of POPC-OOH, the hydroperoxidized form of POPC, in the range 0 to 100 mol %. By measuring ion currents across a 50-µm-diameter black lipid membrane (BLM) with picoampere and millisecond resolution, we detect hydroperoxidation-induced changes to the intrinsic bilayer electropermeability and to the probability of opening angstrom-size or larger pores. Our results over the full range of lipid compositions show that the energy barrier to pore formation is lowered linearly by the absolute value of the electric field, in contradiction with the predictions of the standard model.

Negative lipid membranes enhance the adsorption of TAT-decorated elastin-like polypeptide micelles.

A cell-penetrating peptide (CPP) is a short amino-acid sequence capable of efficiently translocating across the cellular membrane of mammalian cells. However, the potential of CPPs as a delivery vector is hampered by the strong reduction of its translocation efficiency when it bears an attached molecular cargo. To overcome this problem, we used previously developed diblock copolymers of elastin-like polypeptides (ELPBCs), which we end functionalized with TAT (transactivator of transcription), an archetypal CPP built from a positively charged amino acid sequence of the HIV-1 virus. These ELPBCs self-assemble into micelles at a specific temperature and present the TAT peptide on their corona. These micelles can recover the lost membrane affinity of TAT and can trigger interactions with the membrane despite the presence of a molecular cargo. Herein, we study the influence of membrane surface charge on the adsorption of TAT-functionalized ELP micelles onto giant unilamellar vesicles (GUVs). We show that the TAT-ELPBC micelles show an increased binding constant toward negatively charged membranes compared to neutral membranes, but no translocation is observed. The affinity of the TAT-ELPBC micelles for the GUVs displays a stepwise dependence on the lipid charge of the GUV, which, to our knowledge, has not been reported previously for interactions between peptides and lipid membranes. By unveiling the key steps controlling the interaction of an archetypal CPP with lipid membranes, through regulation of the charge of the lipid bilayer, our results pave the way for a better design of delivery vectors based on CPPs.

Precise detection of trace level protein using MIP-MoS2 nanocomposite functionalized PCF based interferometer.

Fiber optic interferometry combined with recognizing elements has attracted intensive attention for the development of different biosensors due to its superior characteristic features. However, the immobilization of sensing elements alone is not capable of low-concentration detection due to weak interaction with the evanescent field of the sensing transducer. The utilization of different 2D materials with high absorption potential and specific surface area can enhance the intensity of the evanescent field and hence the sensitivity of the sensor. Here, a biosensor has been fabricated using an inline hetero fiber structure of photonic crystal fiber (PCF) and single-mode fiber (SMF) functionalized with a nanocomposite of molybodenum di-sulfide (MoS2) and molecular imprinting polymer (MIP) to detect trace levels of bovine serum albumin (BSA). The sensor showed a wide dynamic detection range with a high sensitivity of 2.34 × 107 pm/µg L-1. It shows working potential over a wide pH range with a subfemtomolar detection limit. The compact size, easy fabrication, stable structure, long detection range, and high sensitivity of this sensor would open a new path for the development of different biosensors for online and remote sensing applications.

Characterization of optical fibers doped with nanoparticles for distributed displacement sensing.

High-scattering optical fibers have emerged as a key component in distributed sensing systems, primarily due to their capacity to enhance signal-to-noise ratio. This paper presents an experimental characterization of optical fibers doped with oxide nanoparticles for displacement sensing. They were manufactured using the phase-separation technique and different doping compounds, including calcium, strontium, lanthanum and magnesium. The Rayleigh backscattering (RBS) signatures in time and frequency domains were acquired using an Optical Backscatter Reflectometer (OBR). The maximum representative length, backscattering gain and strain sensitivity were evaluated. The results indicate that the fiber co-doped with magnesium and erbium chlorides offered the best compromise between strain sensitivity (0.96 pm/µ ϵ) and maximum length (17 m). For conditions of single and multiple perturbations, strain saturation was reached at ≥7000 µm and <1500 µm, respectively. In addition, the results reveal that, under a condition of variable temperature (30-60 °C), the sensor response becomes significantly nonlinear over length, requiring a technique for temperature cross-sensitivity mitigation that accounts for nonlinearities in sensitivity and hysteresis.

Highly stabilized fiber Bragg grating accelerometer based on cross-type diaphragm.

A fiber Bragg grating (FBG) accelerometer based on cross-type diaphragm was proposed and designed, in which the cross-beam acts as a spring element. To balance the sensitivity and stability, the accelerometer structure was optimized. The experimental results show that the designed device has a resonant frequency of 556 Hz with a considerable wide frequency bandwidth of up to 200 Hz, which is consistent with the simulation. The sensitivity of the device is 12.35 pm/g@100 Hz with a linear correlation coefficient of 0.99936. The proposed FBG accelerometer has simple structure and strong anti-interference capability with a maximal cross-error less than 3.26%, which can be used for mechanical structural health monitoring.

Optical fiber immunosensors based on surface plasmon resonance for the detection of Escherichia coli.

Every year, millions of people suffer some form of illness associated with the consumption of contaminated food. Escherichia coli (E. coli), found in the intestines of humans and other animals, is commonly associated with various diseases, due to the existence of pathogenic strains. Strict monitoring of food products for human consumption is essential to ensure public health, but traditional cell culture-based methods are associated with long waiting times and high costs. New approaches must be developed to achieve cheap, fast, and on-site monitoring. Thus, in this work, we developed optical fiber sensors based on surface plasmon resonance. Gold and cysteamine-coated fibers were functionalized with anti-E. coli antibody and tested using E. coli suspensions with concentrations ranging from 1 cell/mL to 105 cells/mL. An average logarithmic sensitivity of 0.21 ± 0.01 nm/log(cells/mL) was obtained for three independent assays. An additional assay revealed that including molybdenum disulfide resulted in an increase of approximately 50% in sensitivity. Specificity and selectivity were also evaluated, and the sensors were used to analyze contaminated water samples, which verified their promising applicability in the aquaculture field.

Comparing three-dimensional endorectal ultrasound and magnification chromoendoscopy for early rectal neoplasia invasion depth assessment.

INTRODUCTION: Accurate assessment of invasion depth of early rectal neoplasms is essential for optimal therapy. We aimed to compare three-dimensional endorectal ultrasound (3D-ERUS) with magnification chromoendoscopy (MCE) regarding their accuracy in assessing parietal invasion depth (T). METHODS: Patients with middle and distal rectum neoplasms were prospectively included. Two providers blinded to each other's assessment performed 3D-ERUS and MCE, respectively. The T stage assessed through ERUS was compared to the MCE evaluation. The results were compared to the surgical specimen anatomopathological report. Sensitivity, specificity, accuracy, positive (PPV), and negative (NPV) predictive values were calculated for the T stage and for the final therapy (local excision or radical surgery). RESULTS: In 8 years, 70 patients were enrolled, and all underwent both exams. MCE and ERUS showed an accuracy of 94.3% and 85.7%, sensitivity of 83.7 and 93.3%, specificity of 96.4 and 83.6%, PPV of 86.7 and 60.9%, and NPV of 96.4 and 97.9%, respectively. Kappa for T stage assessed through ERUS was 0.64 and 0.83 for MCE. CONCLUSION: MCE and 3D-ERUS had good diagnostic performance, but the endoscopic method had higher accuracy. Both methods reliably assessed lesion extension, circumferential involvement, and distance from the anal verge.

Accumulation of styrene oligomers alters lipid membrane phase order and miscibility.

Growth of plastic waste in the natural environment, and in particular in the oceans, has raised the accumulation of polystyrene and other polymeric species in eukyarotic cells to the level of a credible and systemic threat. Oligomers, the smallest products of polymer degradation or incomplete polymerization reactions, are the first species to leach out of macroscopic or nanoscopic plastic materials. However, the fundamental mechanisms of interaction between oligomers and polymers with the different cell components are yet to be elucidated. Simulations performed on lipid bilayers showed changes in membrane mechanical properties induced by polystyrene, but experimental results performed on cell membranes or on cell membrane models are still missing. We focus here on understanding how embedded styrene oligomers affect the phase behavior of model membranes using a combination of scattering, fluorescence, and calorimetric techniques. Our results show that styrene oligomers disrupt the phase behavior of lipid membranes, modifying the thermodynamics of the transition through a spatial modulation of lipid composition.

Do spirituality and emotional intelligence improve the perception of the ability to provide care at the end of life? The role of knowledge and self-efficacy.

OBJECTIVES: Spirituality, emotional intelligence, and palliative care (PC) knowledge have a positive and direct influence on self-efficacy and on perception of preparation and ability to provide end-of-life (EOL) care. The aim of this work is to propose a conceptual model that relates spirituality, emotional intelligence, PC knowledge, self-efficacy, and the preparation and ability to provide EOL care by doctors and nurses. METHODS: Quantitative, exploratory, descriptive, and inferential study applied to doctors and nurses in a hospital in the north of Portugal, between May and July 2022. The data collection instrument includes a questionnaire. The relationships between latent variables were evaluated using structural equation models by the partial least squares method using the Smart PLS 3.0 software. It was obtained the previous authorization of the ethics committee. RESULTS: The results (n = 380) indicate that self-efficacy, spirituality, and PC knowledge have a positive influence on the ability to provide EOL care. Emotional intelligence and spirituality have a direct and positive effect on self-efficacy. There is no direct influence of emotional intelligence on the ability to provide EOL care, but emotional intelligence has an indirect effect mediated by self-efficacy. SIGNIFICANCE OF RESULTS: Spirituality, self-efficacy, and emotional intelligence are very important for the ability of doctors and nurses to provide EOL care. The identification of predictive factors of the ability to provide EOL care and the determination of the relationship between them can improve the provision of EOL care, reduction of health costs, timely and early referral of people to PC, and increase life quality.

Plasmonic sensor based on offset-splicing and waist-expanded taper using multicore fiber for detection of Aflatoxins B1 in critical sectors.

In this work, authors have developed a portable, sensitive, and quick-response fiber optic sensor that is capable of detection of Aflatoxins B1 (AFB1) quantitatively and qualitatively. Using multi-mode fiber (MMF) and multi-core fiber (MCF), the MMF-MCF-MCF-MMF fiber structure based on symmetric transverse offset splicing and waist-expanded taper is fabricated. The evanescent waves are enhanced to form a strong evanescent field by etching the fiber surface with hydrofluoric acid. To successfully excite the localized surface plasmon resonance phenomenon, gold nanoparticles are deposited on the optical fiber probe's surface. Further, to modify the fiber optic probes, Niobium carbide (Nb2CTx) MXene and AFB1 antibodies are functionalized. Nb2CTx MXene is employed to strengthen the biocompatibility of the sensor and increase the specific surface area of the fiber probe, while AFB1 antibody is used to identify AFB1 micro-biomolecules in a specific manner. The reproducibility, reusability, stability, and selectivity of the proposed fiber probe are tested and validated using various concentration of AFB1 solutions. Finally, the linear range, sensitivity, and limit of detection of the sensing probe are determined as 0 - 1000 nM, 11.7 nm/µM, and 26.41 nM, respectively. The sensor offers an indispensable technique, low-cost solution and portability for AFB1-specific detection in agricultural products and their byproducts with its novel optical fiber structure and superior detecting capability. It is also useful for marine species like fish and consequently affecting health of human body.

Humanoid shaped optical fiber plasmon biosensor functionalized with graphene oxide/multi-walled carbon nanotubes for histamine detection.

Histamine is a biologically active molecule that serves as a reliable predictor of the quality of fish. In this work, authors have developed a novel humanoid-shaped tapered optical fiber (HTOF) biosensor based on the localized surface plasmon resonance (LSPR) phenomenon to detect varying histamine concentrations. In this experiment, a novel and distinctive tapering structure has been developed using a combiner manufacturing system and contemporary processing technologies. Graphene oxide (GO)/multi-walled carbon nanotubes (MWCNTs) are immobilized on the HTOF probe surface to increase the biocompatibility of biosensor. In this instance, GO/MWCNTs are deployed first, then gold nanoparticles (AuNPs). Consequently, the GO/MWCNTs help to give abundant space for the immobilization of nanoparticles (AuNPs in this case) as well as increase surface area for the attachment of biomolecules to the fiber surface. By immobilizing AuNPs on the surface of the probe, the evanescent field can stimulate the AuNPs and excite the LSPR phenomena for sensing the histamine. The surface of the sensing probe is functionalized with diamine oxidase enzyme in order to enhance the histamine sensor's particular selectivity. The proposed sensor is demonstrated experimentally to have a sensitivity of 5.5 nm/mM and a detection limit of 59.45 µM in the linear detection range of 0-1000 µM. In addition, the probe's reusability, reproducibility, stability, and selectivity are tested; the results of these indices show that the probe has a high application potential for detecting histamine levels in marine products.

Simultaneous measurement of refractive index and temperature based on a side-polish and V-groove plastic optical fiber SPR sensor.

A simple plastic optical fiber (POF) based surface plasmon resonance (SPR) sensor is proposed and demonstrated for simultaneous measurement of refractive index (RI) and temperature. The sensor consists of a series of V-grooves along the POF and a side-polish structure at the other side of the fiber. The V-groove structure can alter the SPR excitation angle and act as a mode filter, effectively enhancing the SPR effect and narrowing the SPR wavelength width. After coating a layer of thermosensitive material-polydimethylsiloxane (PDMS) film on half part of the fiber probe, a dual-parameter sensor probe is obtained for RI and temperature measurement. Experimental results show the RI sensitivity of the prepared probe can reach 1546 nm/RIU in the RI range of 1.335-1.37 RIU and the temperature sensitivity is -0.83 nm/°C in the temperature range of 20-80°C. The sensor is simple in structure and low cost, and has potential applications in the biochemical sensing fields.

Chronic pain causes Tau-mediated hippocampal pathology and memory deficits.

Persistent pain has been recently suggested as a risk factor for dementia. Indeed, chronic pain is frequently accompanied by maladaptive brain plasticity and cognitive deficits whose molecular underpinnings are poorly understood. Despite the emerging role of Tau as a key regulator of neuronal plasticity and pathology in diverse brain disorders, the role of Tau has never been studied in the context of chronic pain. Using a peripheral (sciatic) neuropathy to model chronic pain in mice-spared nerve injury (SNI) for 4 months-in wildtype as well as P301L-Tau transgenic mice, we hereby demonstrate that SNI triggers AD-related neuropathology characterized by Tau hyperphosphorylation, accumulation, and aggregation in hippocampus followed by neuronal atrophy and memory deficits. Molecular analysis suggests that SNI inhibits autophagy and reduces levels of the Rab35, a regulator of Tau degradation while overexpression of Rab35 or treatment with the analgesic drug gabapentin reverted the above molecular changes leading to neurostructural and memory recovery. Interestingly, genetic ablation of Tau blocks the establishment of SNI-induced hippocampal morphofunctional deficits supporting the mediating role of Tau in SNI-evoked hippocampal pathology and memory impairment. These findings reveal that exposure to chronic pain triggers Tau-related neuropathology and may be relevant for understanding how chronic pain precipitates memory loss leading to dementia.

Impact of a Routine Colorectal Endoscopic Submucosal Dissection in the Surgical Management of Nonmalignant Colorectal Lesions Treated in a Referral Cancer Center.

BACKGROUND: Recent data show an increasing number of abdominal surgeries being performed for the treatment of nonmalignant colorectal polyps in the West but in settings in which colorectal endoscopic submucosal dissection is not routinely performed. This study evaluated the number of nonmalignant colorectal lesions referred to surgical treatment in a tertiary cancer center that incorporated magnification chromoendoscopy and endoscopic submucosal dissection as part of the standard management of complex colorectal polyps. OBJECTIVE: The study aimed to estimate the number of patients with nonmalignant colorectal lesions referred to surgical resection at our institution after the standardization of routine endoscopic submucosal dissection and to describe outcomes for patients undergoing colorectal endoscopic submucosal dissection. DESIGN: Single-center retrospective study from a prospectively collected database of endoscopic submucosal dissections and colorectal surgeries performed between January 2016 and December 2019. SETTING: Reference cancer center. PATIENTS: Consecutive adult patients with complex nonmalignant colorectal polyps were included. INTERVENTIONS: Patients with nonmalignant colorectal polyps were treated by endoscopic submucosal dissection or surgery (elective colectomy, rectosigmoidectomy, low anterior resection, or proctocolectomy). MAIN OUTCOMES MEASURES: The primary outcome measure was the percentage of patients referred to colorectal surgery for nonmalignant lesions. RESULTS: In the study period, 1.1% of 825 colorectal surgeries were performed for nonmalignant lesions, and 97 complex polyps were endoscopically removed by endoscopic submucosal dissection. The en bloc, R0, and curative resection rates of endoscopic submucosal dissection were 91.7%, 83.5%, and 81.4%, respectively. The mean tumor size was 59 (SD 37.8) mm. Perforations during endoscopic submucosal dissection occurred in 3 cases, all treated with clipping. One patient presented with a delayed perforation 2 days after the endoscopic resection and underwent surgery. The mean follow-up period was 3 years, with no tumor recurrence in this cohort. LIMITATIONS: Single-center retrospective study. CONCLUSIONS: A workflow that includes assessment of the lesions with magnification chromoendoscopy and resection through endoscopic submucosal dissection can lead to a very low rate of abdominal surgery for nonmalignant colorectal lesions. See Video Abstract at http://links.lww.com/DCR/C123 . IMPACTO DE LA DISECCIN SUBMUCOSA ENDOSCPICA COLORRECTAL DE RUTINA EN EL MANEJO QUIRRGICO DE LESIONES COLORRECTALES NO MALIGNAS TRATADAS EN UN CENTRO ONCOLGICO DE REFERENCIA: ANTECEDENTES:Datos recientes muestran un número cada vez mayor de cirugías abdominales realizadas para el tratamiento de pólipos colorrectales no malignos en Occidente, pero no en los entornos donde la disección submucosa endoscópica colorrectal se realiza de forma rutinaria. El estudio evaluó el número de lesiones colorrectales no malignas referidas a tratamiento quirúrgico en un centro oncológico terciario, que incorporó cromoendoscopia de aumento y disección submucosa endoscópica como parte del manejo estándar de pólipos colorrectales complejos.OBJETIVO:Estimar el número de pacientes con lesiones colorrectales no malignas referidos para resección quirúrgica en nuestra institución, después de la estandarización de la disección submucosa endoscópica de rutina y describir los resultados para los pacientes sometidos a disección submucosa endoscópica colorrectal.DISEÑO:Estudio retrospectivo de un solo centro, a partir de una base de datos recolectada prospectivamente de disecciones submucosas endoscópicas y cirugías colorrectales realizadas entre enero de 2016 y diciembre de 2019.AJUSTE:Centro oncológico de referencia.PACIENTES:Pacientes adultos consecutivos con pólipos colorrectales no malignos complejos.INTERVENCIONES:Pacientes con pólipos colorrectales no malignos tratados mediante disección submucosa endoscópica o cirugía (colectomía electiva, rectosigmoidectomía, resección anterior baja o proctocolectomía).PRINCIPALES MEDIDAS DE RESULTADO:La medida de resultado primario fue el porcentaje de pacientes remitidos a cirugía colorrectal por lesiones no malignas.RESULTADOS:En el período, 1,1% de 825 cirugías colorrectales fueron realizadas por lesiones no malignas y 97 pólipos complejos fueron extirpados por. disección submucosa endoscópica. Las tasas de resección en bloque, R0 y curativa de disección submucosa endoscópica fueron 91,7%, 83,5% y 81,4%, respectivamente. El tamaño tumoral medio fue de 59 (DE 37,8) mm. Se produjeron perforaciones durante la disección submucosa endoscópica en 3 casos, todos tratados con clipaje. Un paciente presentó una perforación diferida 2 días después de la resección endoscópica y fue intervenido quirúrgicamente. El seguimiento medio fue de 3 años, sin recurrencia tumoral en esta cohorte.LIMITACIONES:Estudio retrospectivo de un solo centro.CONCLUSIONES:Un flujo de trabajo que incluye la evaluación de las lesiones con cromoendoscopia de aumento y resección a través de disección submucosa endoscópica, puede conducir a una tasa muy baja de cirugía abdominal para lesiones colorrectales no malignas. Consulte Video Resumen en http://links.lww.com/DCR/C123 . (Traducción-Dr. Fidel Ruiz Healy ).

Chronic Stress, Depression, and Alzheimer's Disease: The Triangle of Oblivion.

Chronic stress and high levels of the main stress hormones, and glucocorticoids (GC), are implicated in susceptibility to brain pathologies such as depression and Alzheimer's disease (AD), as they promote neural plasticity damage and glial reactivity, which can lead to dendritic/synaptic loss, reduced neurogenesis, mood deficits, and impaired cognition. Moreover, depression is implicated in the development of AD with chronic stress being a potential link between both disorders via common neurobiological underpinnings. Hereby, we summarize and discuss the clinical and preclinical evidence related to the detrimental effect of chronic stress as a precipitator of AD through the activation of pathological mechanisms leading to the accumulation of amyloid ß (Aß) and Tau protein. Given that the modern lifestyle increasingly exposes individuals to high stress loads, it is clear that understanding the mechanistic link(s) between chronic stress, depression, and AD pathogenesis may facilitate the treatment of AD and other stress-related disorders.

What is the association between gender and self-perceived health status when controlling for disease-specific conditions? A retrospective data analysis of pre- and post-operative EQ-5D-5L differences in total hip and knee arthroplasty.

BACKGROUND: The self-perceived health status of patients undergoing total hip and knee arthroplasty (THA and TKA) might differ post-operatively due to gender, age, or comorbidities. Patient-reported outcome measures (PROMs) such as the EQ-5D-5L measure the self-perceived health status. This study investigates whether the index score of the EQ-5D-5L is a valid tool for interpreting gender differences in outcomes for patients undergoing THA and TKA. METHODS: Routine and PROM-data of elective primary THA or TKA patients in two German hospitals between 2016 and 2018 were analyzed. Univariate analysis with Pearson's chi-square was conducted to identify control variables for gender. To quantify the association between gender and the EQ-5D-5L dimensions, a cumulative odds ordinal logistic regression with proportional odds was conducted. RESULTS: Two thousand three hundred sixty-eight​​ THA patients (m = 978; f = 1390) and 1629 TKA patients (m = 715; f = 914) were considered. The regression analysis of the individual EQ-5D-5L dimensions showed that female gender was significantly associated with better self-care (THA and TKA) and better post-operative mobility (THA). In contrast, male gender was significantly associated with less pain/discomfort (TKA) and less anxiety/depression (THA) pre-surgery and 3-months post-surgery. CONCLUSION: Our results confirmed that the self-perceived health status improved after surgery. However, due to the different associations of gender to the individual dimensions of the EQ-5D-5L, the weighted index score clouds the comparability between patients with different gender undergoing THA or TKA. Therefore, we argue to use the individual five dimensions for health status analysis, to reveal relevant additional information.

Patients undergoing total hip and knee arthroplasty (THA and TKA) can fill out standardized questionnaires pre- and post-surgery, such as the EQ-5D-5L, to measure the improvement in the self-perceived health status. The EQ-5D-5L includes mobility, self-care, usual activity, pain/discomfort, and anxiety/depression. We do not know whether male and female patients experience the same improvement in the dimensions or whether significant differences exist. Currently, only index scores of the EQ-5D-5L are used for the comparison of pre- and post-operative health status. However, due to the questionnaire's weighted composition, relevant changes in individual dimensions might be easily missed. Thus, we investigated whether significant differences between gender and the EQ-5D-5L dimensions in patients undergoing TKA and TKA are observable. We found that female patients reported significantly better scores in self-care (THA and TKA) and post-operative mobility (THA). In contrast, male gender was significantly associated with less pain/discomfort (TKA) and less anxiety/depression (THA) pre-surgery and 3-months post-surgery. The EQ-5D-5L's weighted index score, however, does not directly represent these differences. Therefore, we argue to use the individual five dimensions for health status analysis, as relevant additional information on improvement over time would otherwise be missed.

Development of Fiber-Bragg-Grating-Integrated Artificial Embedded Tendon for Multifunctional Assessment of Temperature, Strain, and Curvature.

This paper presents the development and application of an optical fiber-embedded tendon based on biomimetic multifunctional structures. The tendon was fabricated using a thermocure resin (polyurethane) and the three optical fibers with one fiber Bragg grating (FBG) inscribed in each fiber. The first step in the FBG-integrated artificial tendon analysis is the mechanical properties assessment through stress-strain curves, which indicated the customization of the proposed device, since it is possible to tailor the Young's modulus and strain limit of the tendon as a function of the integrated optical fibers, where the coated and uncoated fibers lead to differences in both parameters, i.e., strain limits and Young's modulus. Then, the artificial tendon integrated with FBG sensors undergoes three types of characterization, which assesses the influence of temperature, single-axis strain, and curvature. Results show similarities in the temperature responses in all analyzed FBGs, where the variations are related to the heterogeneity on the polyurethane matrix distribution. In contrast, the FBGs embedded in the tendon presented a reduction in the strain sensitivity when compared with the bare FBGs (i.e., without the integration in the artificial tendon). Such results demonstrated a reduction in the sensitivity as high as 77% when compared with the bare FBGs, which is related to strain field distributions in the FBGs when embedded in the tendon. In addition, the curvature tests indicated variations in both optical power and wavelength shift, where both parameters are used on the angle estimation using the proposed multifunctional artificial tendon. To that extent, root mean squared error of around 3.25° is obtained when both spectral features are considered. Therefore, the proposed approach indicates a suitable method for the development of smart structures in which the multifunctional capability of the device leads to the possibility of using not only as a structural element in tendon-driven actuators and devices, but also as a sensor element for the different structures.

Static and Dynamic Multiparameter Assessment of Structural Elements Using Chirped Fiber Bragg Gratings.

This paper presents the development, analysis, and application of chirped fiber Bragg gratings (CFBGs) for dynamic and static measurements of beams of different materials in the single-cantilever configuration. In this case, the beams were numerically analyzed using the finite-element method (FEM) for the assessment of the natural frequencies and vibration modes of the beam for the dynamic analysis of the structural element. Furthermore, the static numerical analysis was performed using a load at the free end of the beam, where the maximum strain and its distribution along the beam were analyzed, especially in the region at which the FBG was positioned. The experimental evaluation of the proposed CFBG sensor was performed in static conditions for forces from 0 to 50 N (in 10 N steps) applied at the free end of the beam, whereas the dynamic evaluation was performed by means of positioning an unbalanced motor at the end of the beam, which was excited at 16 Hz, 65 Hz, 100 Hz, and 131 Hz. The results showed the feasibility of the proposed device for the simultaneous assessment of the force and strain distribution along the CFBG region using the wavelength shift and the full-width at half-maximum (FWHM), respectively. In these cases, the determination coefficients of the spectral features as a function of the force and strain distribution were higher than 0.99 in all analyzed cases, where a potential resolution of 0.25 N was obtained on the force assessment. In the dynamic tests, the frequency spectrum of the sensor responses indicated a frequency peak at the excited frequency in all analyzed cases. Therefore, the proposed sensor device is a suitable option to extend the performance of sensors for structural health assessment, since it is possible to simultaneously measure different parameters in dynamic and static conditions using only one sensor device, which, due to its multiplexing capabilities, can be integrated with additional optical fiber sensors for the complete shape reconstruction with millimeter-range spatial resolution.

Convex fiber-tapered seven core fiber-convex fiber (CTC) structure-based biosensor for creatinine detection in aquaculture.

The purpose of this article is to propose an optical fiber sensor probe based on the localized surface plasma resonance (LSPR) technique for the detection of creatinine in aquaculture. The sensing probe is functionalized through the use of gold nanoparticles (AuNPs), niobium carbide (Nb2CTx) MXene, and creatinase (CA) enzyme. The intrinsic total internal reflection (TIR) mechanism is modified to increase the evanescent field intensity using a heterogeneous core mismatch and tapering probe structure (i.e., convex fiber-tapered seven core fiber-convex fiber (CTC) structure). Strong evanescent fields can stimulate AuNPs and induce the LSPR effect, thereby increasing probe sensitivity. The specific recognition is enhanced by Nb2CTx MXene adsorbing more active CA enzymes. The developed sensor probe has a sensitivity and limit of detection of 3.1 pm/µM and 86.12 µM, respectively, in the linear range of 0-2000 µM. Additionally, the sensor probe's reusability, reproducibility, stability, and selectivity were evaluated, with satisfactory results obtained with impact for areas like food protein, marine life and healthcare.

Tear of lipid membranes by nanoparticles.

Health concerns associated with the advent of nanotechnologies have risen sharply when it was found that particles of nanoscopic dimensions reach the cell lumina. Plasma and organelle lipid membranes, which are exposed to both the incoming and the engulfed nanoparticles, are the primary targets of possible disruptions. However, reported adhesion, invagination and embedment of nanoparticles (NPs) do not compromise the membrane integrity, precluding direct bilayer damage as a mechanism for toxicity. Here it is shown that a lipid membrane can be torn by small enough nanoparticles, thus unveiling mechanisms for how lipid membrane can be compromised by tearing from nanoparticles. Surprisingly, visualization by cryo transmission electron microscopy (cryo-TEM) of liposomes exposed to nanoparticles revealed also that liposomal laceration is prevented by particle abundance. Membrane destruction results thus from a subtle particle-membrane interplay that is here elucidated. This brings into a firmer molecular basis the theorized mechanisms of nanoparticle effects on lipid bilayers and paves the way for a better assessment of nanoparticle toxicity.