Early osteoarthritis diagnosis based on near-infrared spectroscopy combined with aquaphotomics.

Osteoarthritis (OA) is the most common joint disease and the leading cause of disability in elderly individuals. Despite rapid advances in imaging techniques, early OA diagnosis remains a clinical challenge. In the present study, the feasibility of early OA diagnosis was explored via near-infrared spectroscopy (NIRS) combined with aquaphotomics. Synovial fluid samples from 65 cases of OA categorized as mild, moderate, and severe according to theKellgrenandLawrence classification criteria were analyzed via NIRS. The 1st overtone of water (1300-1600 nm) was considered as the research object for an aquaphotomics model, and aquagrams of the mild, moderate, and severe OA cases were generated using 12 water absorption patterns for early OA diagnosis.The aquaphotomics results exhibited clear differences in the region of 1300-1500 nm, and the number of hydrogen bonds of different water species (1412,1424, 1482, and 1496 nm) evidently correlated with OA occurrence and development. With OA progression, the absorption intensity of water molecules without hydrogen bonds (1412 nm/1424 nm) became stronger, while the absorption intensity of water molecules with four hydrogen bonds (1482 nm/1496 nm) decreased.These results together reveal that the established accurate and rapid early OA diagnosis model based on NIRS combined with aquaphotomics is effective and feasible, and that the number of hydrogen bonds can be used as a biomarker for early OA diagnosis.

Large dynamic strain range slope-assisted Brillouin optical time domain reflectometry based on a graded-index multi-mode fiber.

A slope-assisted Brillouin optical time domain reflectometry system with large dynamic strain range was proposed and demonstrated using graded-index multi-mode fiber (GI-MMF) as sensing fiber. Analysis of the simulated and experimental results indicated that the Brillouin gain spectrum in GI-MMF could be broadened by controlling the coupling efficiency of optical and acoustic modes. The coupling efficiency could be controlled by adjusting lateral offset between single mode fiber (SMF) and GI-MMF. The system realized the maximum strain dynamic measurement of 3000 µÉ› with the spatial resolution of 5 m along ∼1 km GI-MMF, and exhibited significant linear relationship between signal intensity and strain at vibrational frequency of 7.83 and 15.47 Hz. The measured error of vibration frequency was less than 0.2 and 1.5 Hz, respectively. The measured strain range of this system was more than three times that of traditional systems based on SMF and could be achieved at relatively low cost.

In-line reflected fiber sensor for simultaneous measurement of temperature and liquid level based on tapered few-mode fiber.

An in-line reflective dual-parameters fiber-optic sensor is proposed in this work, whereas it is experimentally verified by measuring both the liquid level and the local temperature distribution simultaneously. The proposed sensor configuration comprises a single-mode fiber (SMF), a tapered few-mode fiber (TFMF), as well as a silver-coated capillary tube. The extracted experimental results indicate that the liquid level only affects the power of the resonant dips, while having little impact on the wavelength. On the other hand, both the wavelength and the power of the resonant dips vary with the temperature change. Therefore, the simultaneous measurement of the liquid level and temperature can be realized according to the different responses of the resonant dips to the liquid level and temperature. The obtained liquid level and temperature sensitivities can reach the values of 0.106 dB/mm and 0.029 dB/°C, 35 pm/°C, respectively. The sensor exhibits the advantages of high stability and low cost, the demodulation relates on only one wavelength which can shorten the scanning wavelength range during measurement. The proposed sensor can be potentially applied where accurate and simultaneous measurements of both temperature and liquid level are required.

Au-NPs signal amplification ultra-sensitivity optical microfiber interferometric biosensor.

An optical microfiber interferometric biosensor for the low concentration detection of sequence-specific deoxyribonucleic acid (DNA) based on signal amplification technology via oligonucleotides linked to gold nanoparticles (Au-NPs) is proposed and experimentally analyzed. The sensor uses a "sandwich" detection strategy, in which capture probe DNA (DNA-c) is immobilized on the surface of the optical microfiber interferometer, the reporter probe DNA (DNA-r) is immobilized on the surface of Au-NPs, and the DNA-c and DNA-r are hybridized to the target probe DNA (DNA-t) in a sandwich arrangement. The dynamic detection of the DNA-t was found to range from 1.0×10-15 M to 1.0×10-8 M, and the limit of detection (LOD) concentration was 1.32 fM. This sensor exhibited not only a low LOD but also excellent selectivity against mismatched DNA-t, and it can be further developed for application in various sensing platforms.

Development of an optical microfiber immunosensor for prostate specific antigen analysis using a high-order-diffraction long period grating.

Fiber-optic biosensors are of great interest to many bio/chemical sensing applications. In this study, we demonstrate a high-order-diffraction long period grating (HOD-LPG) for the detection of prostate specific antigen (PSA). A HOD-LPG with a period number of less than ten and an elongated grating pitch could realize a temperature-insensitive and bending-independent biosensor. The bio-functionalized HOD-LPG was capable of detecting PSA in phosphate buffered saline with concentrations ranging from 5 to 500 ng/ml and exhibited excellent specificity. A limit of detection of 9.9 ng/ml was achieved, which is promising for analysis of the prostate specific antigen.

Temperature and liquid refractive index sensor using P-D fiber structure-based Sagnac loop.

A cost-efficient P-D fiber structure-based Sagnac loop sensor is proposed and experimentally demonstrated for measuring temperature and liquid refractive index (RI). The P-D structure is fabricated by fusion splicing a section of polarization-maintaining fiber (PMF) to a piece of multimode D-shaped optical fiber (MMDF). Then the P-D structure is built into a Sagnac loop using a 3dB coupler. The temperature and RI characteristics of the sensor are investigated experimentally. The results show that two resonant dips have different spectral responses of temperature and RI, which indicate that the sensor can realize simultaneous temperature and RI measurement. The high sensitivities of -1.804nm/°C and -131.49nm/RIU are achieved. The obtained resolutions of temperature and RI of the proposed sensor can reach 0.01°C and 2.46 × 10-4RIU, respectively. The proposed sensor has the potential application in biological and chemical fields.