Self-powered optical fiber biosensor integrated with enzymes for non-invasive glucose sensing.

To alleviate the discomfort associated with frequent blood glucose detection in diabetic patients, a novel non-invasive tear glucose biosensor has been developed. This involved the design and preparation of a photoelectrochemical probe based on an optical fiber and biological enzymes. One end of the optical fiber connects to a light source, acting as an energy source and imparting, self-powered capability to the biosensor. The opposite end is loaded with nanomaterials and glucose oxidase, designed for insertion into the sample to realize photoelectrochemical sensing. This innovative configuration not only improves the integration of the biosensor but is also suitable for analyzing minuscule voluminal samples. The results show that the proposed biosensor exhibits a linear range from 10 nM to 100 µM, possesses a low detection limit of 4.1 nM and a short response time of 0.7 s. Benefiting from the high selectivity of the enzyme, the proposed biosensor demonstrates excellent resistance to the interference of common tear components. In summary, this work provides a more effective method for non-invasive glucose detection and affords valuable ideas for the design and fabrication of non-invasive and self-powered biosensors.

Co-adsorption and Fenton-like oxidation in the efficient removal of methylene blue by MIL-88B@UiO-66 nanoflowers.

Development of binary MOF-on-MOF heterostructures is a research hotspot in MOFs chemistry due to the advantages elicited by a closely connected interface, which may endow more abundant functionality and even broader applications in interface chemistry. A MOF-on-MOF heterostructure was constructed by in situ growth of MIL-88B on the outer surface of UiO-66. The resultant MIL-88B@UiO-66 produced had an interesting flower-like morphology composed of MIL-88B (petal) on tetrahedral UiO-66 (core). The MIL-88B@UiO-66 heterostructure showed adsorption and Fenton-like oxidation abilities, with distinctly improved structural stability in aqueous solution compared with that of single MIL-88B. Methylene blue (MB) was selected as the target molecule to evaluate the adsorption and Fenton-like oxidation activities. The efficiency of total removal of MB was studied systematically under various operating conditions and the influencing factors were optimized. The kinetics of adsorption and catalytic oxidation were simulated to explore the interactions between MB and MIL-88B@UiO-66. The mechanisms of enhanced adsorption and Fenton-like oxidation were suggested. The cyclic removal performance and structural stability of MIL-88B@UiO-66 were also determined.

ZnO/Cu2O heterojunction integrated fiber-optic biosensor for remote detection of cysteine.

Indium tin oxide, semiconductor nanomaterial ZnO, and Cu2O were first loaded on the surface of the optical fiber to form an optical fiber probe. Large-volume macroscopic spatial light is replaced by an optical fiber path, and remote light injection is implemented. Based on the optical fiber probe, a photoelectrochemical biosensor was constructed and remote detection of cysteine was realized. In this tiny device, the optical fiber probe not only acts as a working electrode to react with the analyte but also directs the light exactly where it is needed. Simultaneously, the electrochemical behavior of cysteine on the surface of the working electrode is dominated by diffusion-control, which provides strong support for quantitative detection. Then, under the bias potential of 0 V, the linear range of the fiber-optic-based cysteine biosensor was 0.01∼1 µM, the regression coefficient (R2) value was 0.9943. In spiked synthetic urine, the detection of cysteine was also realized by the integrated biosensor. Moreover, benefiting from the low optical fiber loss, the new structure also possesses a unique remote detection function. This work confirms that photoelectrochemical biosensors can be integrated via optical fibers and retain comparable sensing performance. Based on this property, different materials can also be loaded on the surface of the optical fiber for remote detection of other analytes. It is expected to facilitate the research on fiber-optic-based integrated biosensors and show application prospects in diverse fields such as biochemical analysis and disease diagnosis.

Differential Expression of miR-381-3p in Alzheimer's Disease Patients and Its Role in Beta-Amyloid-Induced Neurotoxicity and Inflammation.

INTRODUCTION: This study aimed to explore the diagnostic value and effect of miR-381-3p on Alzheimer's disease (AD). METHODS: RT-qPCR was used for the measurement of miR-381-3p levels. Pearson correlation coefficient was used for the correlation analysis. Receiver operating characteristic (ROC) curve was constructed to assess the distinct ability of miR-381-3p for AD. SH-SY5Y cells were treated with Aß25-35 to establish an AD cell model. The role of miR-381-3p on cell proliferation and apoptosis was detected. ELISA was applied to detect the protein levels of inflammatory cytokine expression. The target relationship of miR-381-3p with PTGS2 was verified by luciferase reporter gene assay. RESULTS: Low expression of miR-381-3p was detected in the serum of AD patients and cell models. There was a negative association of serum miR-381-3p with the serum inflammatory cytokines. The ROC curve demonstrated the distinct ability of serum miR-381-3p for AD, with the AUC value of 0.898, with a sensitivity of 87.5%, and a specificity of 77.7%. Overexpression of miR-381-3p reversed the influence of Aß25-35 on cell proliferation and apoptosis, but miR-381-3p downregulation exacerbated the influence. miR-381-3p overexpression inhibited the release of IL-6, IL-1ß, and TNF-α induced by Aß25-35 treatment, whereas miR-381-3p downregulation further promoted the release of inflammatory cytokines. PTGS2 was the target gene of miR-381-3p and was upregulated in AD cell models. CONCLUSION: miR-381-3p is less expressed in the serum of AD patients and has potential diagnostic values for AD. Overexpression of miR-381-3p may attenuate Aß25-35-induced neurotoxicity and inflammatory responses via targeting PTGS2 in SH-SY5Y cells.

Diagnostic and Prognostic Significance of serum miR-18a-5p in Patients with Atherosclerosis.

Atherosclerosis (AS) is a common vascular disease with great harm. The current study examined the expression pattern of miR-18a-5p in AS patients, and explored its clinical values. 110 AS patients and 68 healthy controls were collected clinically, and the expression pattern of miR-18a-5p in the serum of AS patients was detected using qRT-PCR. All AS patients were followed up for five years to record the adverse cardiovascular events. ROC and Kaplan-Meier (K-M) curve were plotted to assess the diagnostic ability. The multiple Cox regression analysis was performed for independent influencing factors analysis. MiR-18a-5p was at high expression in AS patients, and showed positive correlation with the CIMT value (r = 0.789, P < .001). ROC curve suggested the high diagnostic value of serum miR-18a-5p for AS, with the AUC of 0.894. The diagnostic specificity and sensitivity were 86.8% and 79.1%, respectively. K-M plot demonstrated that cases with high miR-18a-5p levels were more likely to suffer from cardiovascular events, and it is an independent influence factor for the poor clinical outcome. Serum miR-18a-5p serves as a promising biomarker for AS diagnosis, and is related to the occurrence of adverse cardiovascular events.

In situ SERS detection of quinolone antibiotic residues in a water environment based on optofluidic in-fiber integrated Ag nanoparticles.

In this paper, we present a microstructured optofluidic in-fiber Raman sensor for the detection of quinolone antibiotic residue in a water environment based on Ag surface-enhanced Raman scattering (SERS) substrate grown on the surface of the suspended core of micro-hollow optical fiber (MHF). Here, MHF has a special structure with a suspended core and a microchannel inside, which can become a natural in-fiber optofluidic device. Meanwhile, the self-assembled Ag SERS substrate can be grown on the suspended core's surface through chemical bonds, forming a microstructured optofluidic device with a Raman enhancement effect. Therefore, it can effectively detect the Raman signal of unlabeled trace quinolone antibiotic residue (ciprofloxacin and norfloxacin) inside the optical fiber. The results show that the ciprofloxacin and norfloxacin detection limits (LOD) are 10-10M and 10-11M, respectively. Compared with the maximum residue limit (3.01×10-7mol/L) stipulated by the European Union, the results are much lower, and an ideal quantitative relationship can be obtained within the detection range. Significantly, this study provides an in-fiber microstructured optofluidic Raman sensor for the label-free detection of quinolone antibiotic residue, which will have good development prospects in the field of antibiotic water pollution environmental detection.

On-line SERS detection of bilirubin based on the optofluidic in-fiber integrated GO/Ag NPs for rapid diagnosis of jaundice.

In this paper, we propose a self-assembled graphene oxide (GO)/Ag NPs SERS Raman sensor based on a novel type of optofluidic MHF as a point-of-care testing (POCT) device. This device is used to diagnose jaundice and its related diseases through on-line detection of free bilirubin content in human serum. This optofluidic Raman sensor is composed of a microstructured hollow fiber (MHF) with a microstructured channel and a suspended core, which allows the sample solution to flow in the channel while interacting with the strong evanescent field on the suspended core. Here, the suspended core was modified by a GO/Ag NPs SERS substrate. When the sample flows through the channel, and interacts with the strong evanescent field generated by the suspended core, the on-line SERS signal is generated and can be coupled back to the suspended core to be detected. In addition, both the electrostatic interaction and interference between GO/Ag NPs with the target enriched bilirubin. The results show that the detection concentration range of bilirubin aqueous, bilirubin in albumin and bilirubin in human blood are all in the range of 2 µM-100 µM, and all have a good linear response. The limit of detection reaches the order of 10-6 M. This rapid, sensitive and label-free SERS Raman sensor of free bilirubin in blood can detect excessive levels of bilirubin in the actual blood environment of the human body, providing a broad prospect for clinically accurate diagnosis of jaundice and related diseases.

All-fiber bidirectional optical modulator derives from the microfiber coated with ITO electrode.

A cheap, compact, and simply prepared all-fiber bidirectional optical modulator based on the Pockels effect of water and the band population effect was first, to the best of our knowledge, proposed and demonstrated. The transparent conductive oxide indium-tin-oxide (ITO) was coated on the surface of a nonadiabatic microfiber and first used as a modulating electrode on the microfiber. The device was realized by just submerging the microfiber in water. With supplying an electric field perpendicular to the interface between the microfiber and water, the refractive index was modulated in the electric double layer near the tapered region of the microfiber, under the Pockels effect of water. Subsequently, the interference spectrum was modulated. Meanwhile, the intensity of the light was modulated due to the band population effect in the space-charge layer. In this Letter, the proposed all-fiber optical modulator can realize simultaneous bidirectional modulation of the phase and intensity of output light. Experimentally, the maximum phase shift and the extinction ratio were 4.38 nm and 4.87 dB at 1550 nm, respectively. Significantly, the work used the Pockels effect of water and the band population effect to realize an all-fiber optical modulator, showing great potential in the optical phase modulators, optical switches, and electric field sensors.

In-fiber optofluidic online SERS detection of trace uremia toxin.

In this Letter, we propose a microstructured in-fiber optofluidic surface-enhanced Raman spectroscopy (SERS) sensor for the initial inspection of uremia through the detection of unlabeled urea and creatinine. As a natural microfluidic device, microstructured hollow fiber has a special structure inside. Through chemical bonds, the SERS substrate can be modified and grown on the surface of the suspended core. Here, the silver nanoparticles (Ag NPs) are embedded on the poly diallyl dimethyl ammonium chloride-modified graphene oxide sheet to achieve the self-assembled SERS substrate. The reduced distance between Ag NPs can increase the strong hot spots that generate enhanced Raman signals. Therefore, it can effectively detect the Raman signal of unlabeled trace uremic toxin analytes (urea, creatinine) inside the optical fiber. The results show that under simulated biophysical conditions, the limit detection (LOD) for urea is 10-4M and the linearity is good, especially at the clinical conventional concentration range (2.5-6.5×10-3M). In addition, the online Raman detection of creatinine aqueous solution LOD is 10-6M, which also has good linearity. Significantly, this Letter provides a microstructured optofluidic in-fiber Raman sensor for the preliminary detection of uremia, which will have good development prospects in the field of clinical biomedicine.

All-fiber phase modulator and switch based on local surface plasmon resonance effect of the gold nanoparticles embedded in gel membrane.

All-fiber modulators and switches have drawn great interest in the photonics domain, and they are applied in viable photonic and optoelectronic devices. In this work, with the assistance of an agarose membrane, aspherical gold nanoparticles are embedded on the surface of the microfiber treated with the piranha solution. An all-fiber Mach-Zehnder interferometer was used to realize a low-cost, low-loss, and conveniently prepared all-fiber phase modulator. By taking advantage of the local surface plasmon resonance effect of gold nanoparticles embedded in the agarose membrane, under the excitation of near-infrared region light, the gold nanoparticles were excited to change the effective refractive index of one arm of the Mach-Zehnder interferometer. A maximum phase shift of ∼6π at 1550 nm was obtained from the device. In addition, an all-optical switch was achieved with a rising edge time of 47 ms and falling edge time of 14 ms. The proposed all-fiber modulator and switch based on the local surface plasmon resonance effect of gold nanoparticles embedded in agarose membrane will provide great potential in all-optical fiber systems.

Optofluidic in-fiber integrated surface-enhanced Raman spectroscopy detection based on a hollow optical fiber with a suspended core.

In this Letter, we propose, to the best of our knowledge, the first in-fiber optofluidic Raman surface-enhanced Raman spectroscopy (SERS) sensor based on a microstructured hollow fiber (MHF) with a suspended core. Taking advantage of the unique internal structure, we immobilize silver nanoparticles with an SERS effect in the MHF by chemical bonding. The Raman signal of the microfluidic sample is excited by the excitation light in the suspended core through an evanescent field. Then the online SERS signal can be coupled back into the core and detected. To demonstrate the feasibility of the device, rhodamine 6G is chosen as the analyte, and high-quality SERS spectra are detected with the limit of detection of 1×10-14 M. Furthermore, an online optofluidic test is conducted on ceftriaxone (C18H18N8O7S3) to examine its capabilities in antibiotic sensing. The results show that the LOD of the samples is 10-6 M. Significantly, this Letter provides an integrated optofluidic in-fiber SERS sensor with a microchannel that can be integrated with chip devices without spatial optical coupling, which has a broad application in medicine and food safety, as well as various aspects of biological in-fiber sensing.

On-line dynamic detection in the column chromatography separation based on an optical fiber surface plasmon resonance sensor.

In this design, we introduced a surface plasmon resonance (SPR) fiber-sensing probe into a column chromatography (CC) system to realize on-line dynamic detection in sample separation. The refractive index of the gel around the probe would be adjusted dynamically by the concentration change of the sample during CC separation. To demonstrate the separation and on-line detection process, bovine serum albumin (BSA) and riboflavin-5-phosphate sodium (FMN-Na) are chosen as the analytes in a Sephadex gel filtration chromatography system. The results show that the apparent reversible shift of the SPR spectrum can characterize the separation process. Specifically, the separated BSA with an outflow time of 8 min can cause a resonance wavelength shift of 15.5 nm, and the FMN-Na with an outflow time of 26 min can cause a shift of 8.4 nm. This on-line dynamic detection of SPR spectra has great potential to save time and simplify the analysis process compared to the complex thin layer chromatography detection steps in traditional manual CC.

An in-fiber integrated optofluidic device based on an optical fiber with an inner core.

A new kind of optofluidic in-fiber integrated device based on a specially designed hollow optical fiber with an inner core is designed. The inlets and outlets are built by etching the surface of the optical fiber without damaging the inner core. A reaction region between the end of the fiber and a solid point obtained after melting is constructed. By injecting samples into the fiber, the liquids can form steady microflows and react in the region. Simultaneously, the emission from the chemiluminescence reaction can be detected from the remote end of the optical fiber through evanescent field coupling. The concentration of ascorbic acid (AA or vitamin C, Vc) is determined by the emission intensity of the reaction of Vc, H2O2, luminol, and K3Fe(CN)6 in the optical fiber. A linear sensing range of 0.1-3.0 mmol L(-1) for Vc is obtained. The emission intensity can be determined within 2 s at a total flow rate of 150 µL min(-1). Significantly, this work presents information for the in-fiber integrated optofluidic devices without spatial optical coupling.