Fiber Optic Probe Research Articles

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.

A Near-Infrared Plasmonic Sensor Based on Wedge Fiber-Optic for Ultra-Sensitive Hg Detection

The growing number of serious diseases caused by ever-increasing heavy metal ions pollution have necessitated the use of ion sensors in healthcare and environment monitoring systems. Even with low concentrations heavy metal ions can cause significant harm, so ultra-sensitive on-site and label-free monitoring of heavy metal ions is of great importance. In this work, a simple, portable and high sensitivity optical fiber surface plasmon resonance (SPR) sensor is demonstrated for the detection of Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> . On the basis of the investigation of the effects of different incident angles, the optical fiber sensor adopts wedged tip probe with a 75° incident angle. The plasmonic sensor exhibits a superior refractive index bulk sensitivity of up to 13830 nm/RIU in near-infrared band, which is a further step in ultrasensitive sensing detection, compared with the traditional optical fiber SPR sensors. In addition, we validate the optical fiber sensor's performance for Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> sensing. By self-assembling monolayer of 1,6-Hexanedithiol (HDT) on the sensing surface, the Au-coated fiber-optic probe is modified to capture Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> . The lowest detection limit is found to be 0.324 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf{ug}/\mathbf{mL}$</tex-math></inline-formula> for the near-infrared band and the sensitivity can reach up to 0.22 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$({\mathbf{ug}/\mathbf{mL}})$</tex-math></inline-formula> . The experimental results show the excellent promise for our sensor in applications of environmental monitoring due to high sensitivity, selectivity and low-cost.

Dental Pulp Location and Dentin Thickness Assessment in Situ with Diffuse Reflectance Spectroscopy

The modern approach to the treatment of caries requires maximum preservation of tooth tissues and pulp viability, for which it is necessary to know the residual thickness of dentin during its removal. Currently existing methods (Cone-beam Computed Tomography, electrical impedance device, and optical coherence tomography) are not widely used in clinical practice due to the laboriousness of their use or low accuracy. We evaluated the capabilities of the diffuse reflectance spectroscopy (DRS) method for determining dentine thickness in situ . Dentin tissues transmit light well in the visible and near-IR range, which makes it possible to detect the optical response of the dental pulp. The pulp contains hemoglobin and water, while dentin contains no hemoglobin, and its water content is less than 10%. Thus, the selection of the contributions of these components allows estimating the thickness of the dentin. Our results show a strong correlation (&gt; 0.9) between dentin thickness and the amplitudes of the water and hemoglobin components. However, hemoglobin content is more susceptible to changes, caused by inflammation or the action of anesthesia. Thus, the most promising approach is use the water component as a proxy. The proposed method can be the basis for the development of a fiber-optic laser probe for clinical dentistry.

Validation of a drift-corrected 3D MR temperature imaging sequence for breast MR-guided focused ultrasound treatments

Real-time temperature monitoring is critical to the success of thermally ablative therapies. This work validates a 3D thermometry sequence with k-space field drift correction designed for use in magnetic resonance-guided focused ultrasound treatments for breast cancer. Fiberoptic probes were embedded in tissue-mimicking phantoms, and temperature change measurements from the probes were compared with the magnetic resonance temperature imaging measurements following heating with focused ultrasound. Precision and accuracy of measurements were also evaluated in free-breathing healthy volunteers (N = 3) under a non-heating condition.MR temperature measurements agreed closely with those of fiberoptic probes, with a 95% confidence interval of measurement difference from −2.0 °C to 1.4 °C. Field drift-corrected measurements in vivo had a precision of 1.1 ± 0.7 °C and were accurate within 1.3 ± 0.9 °C across the three volunteers. The field drift correction method improved precision and accuracy by an average of 46 and 42%, respectively, when compared to the uncorrected data. This temperature imaging sequence can provide accurate measurements of temperature change in aqueous tissues in the breast and support the use of this sequence in clinical investigations of focused ultrasound treatments for breast cancer.

Nanodiamond-Based Optical-Fiber Quantum Probe for Magnetic Field and Biological Sensing.

Owing to the unique electronic spin properties, nitrogen-vacancy (NV) centers hosted in diamond have emerged as a powerful quantum tool for detecting various physical parameters and biological species. In this work, an optical-fiber quantum probe, configured by chemically modifying nanodiamonds on the surface of a cone fiber tip, is developed. Based on the continuous-wave optically detected magnetic resonance method and lock-in amplification technique, it is found that the sensing performance of probes can be engineered by varying the nanodiamond dispersion concentration and modification duration during the chemical modification process. Combined with a pair of magnetic flux concentrators, the magnetic field detection sensitivity has reached 0.57 nT/Hz1/2@1 Hz, a new record among the fiber magnetometers based on nanodiamonds. Taking Gd3+ as the demo, the capability of probes in paramagnetic species detection is also demonstrated experimentally. Our work provides a new approach to develop NV centers as quantum probes featuring high integration, multifunction, high sensitivity, etc.

Characterisation and Quenching Correction for an Al2O3:C Optical Fibre Real Time System in Therapeutic Proton, Helium, and Carbon-Charged Beams.

Real time radioluminescence fibre-based detectors were investigated for application in proton, helium, and carbon therapy dosimetry. The Al2O3:C probes are made of one single crystal (1 mm) and two droplets of micro powder in two sizes (38 μm and 4 μm) mixed with a water-equivalent binder. The fibres were irradiated behind different thicknesses of solid slabs, and the Bragg curves presented a quenching effect attributed to the nonlinear response of the radioluminescence (RL) signal as a function of linear energy transfer (LET). Experimental data and Monte Carlo simulations were utilised to acquire a quenching correction method, adapted from Birks' formulation, to restore the linear dose-response for particle therapy beams. The method for quenching correction was applied and yielded the best results for the '4 μm' optical fibre probe, with an agreement at the Bragg peak of 1.4% (160 MeV), and 1.5% (230 MeV) for proton-charged particles; 2.4% (150 MeV/u) for helium-charged particles and of 4.8% (290 MeV/u) and 2.9% (400 MeV/u) for the carbon-charged particles. The most substantial deviations for the '4 μm' optical fibre probe were found at the falloff regions, with ~3% (protons), ~5% (helium) and 6% (carbon).

Fabrication and Characterization of Novel Silk Fiber-Optic SERS Sensor with Uniform Assembly of Gold Nanoparticles.

Biocompatible optical fibers and waveguides are gaining attention as promising platforms for implantable biophotonic devices. Recently, the distinct properties of silk fibroin were extensively explored because of its unique advantages, including flexibility, process compatibility, long-term biosafety, and controllable biodegradability for in vitro and in vivo biomedical applications. In this study, we developed a novel silk fiber for a sensitive optical sensor based on surface-enhanced Raman spectroscopy (SERS). In contrast to conventional plasmonic nanostructures, which employ expensive and time-consuming fabrication processes, gold nanoparticles were uniformly patterned on the top surface of the fiber employing a simple and cost-effective convective self-assembly technique. The fabricated silk fiber-optic SERS probe presented a good performance in terms of detection limit, sensitivity, and linearity. In particular, the uniform pattern of gold nanoparticles contributed to a highly linear sensing feature compared to the commercial multi-mode fiber sample with an irregular and aggregated distribution of gold nanoparticles. Through further optimization, silk-based fiber-optic probes can function as useful tools for highly sensitive, cost-effective, and easily tailored biophotonic platforms, thereby offering new capabilities for future implantable SERS devices.

Insights into Biochemical Sources and Diffuse Reflectance Spectral Features for Colorectal Cancer Detection and Localization.

Colorectal cancer (CRC) is the third most common and second most deadly type of cancer worldwide. Early detection not only reduces mortality but also improves patient prognosis by allowing the use of minimally invasive techniques to remove cancer while avoiding major surgery. Expanding the use of microsurgical techniques requires accurate diagnosis and delineation of the tumor margins in order to allow complete excision of cancer. We have used diffuse reflectance spectroscopy (DRS) to identify the main optical CRC biomarkers and to optimize parameters for the integration of such technologies into medical devices. A total number of 2889 diffuse reflectance spectra were collected in ex vivo specimens from 47 patients. Short source-detector distance (SDD) and long-SDD fiber-optic probes were employed to measure tissue layers from 0.5 to 1 mm and from 0.5 to 1.9 mm deep, respectively. The most important biomolecules contributing to differentiating DRS between tissue types were oxy- and deoxy-hemoglobin (Hb and HbO2), followed by water and lipid. Accurate tissue classification and potential DRS device miniaturization using Hb, HbO2, lipid and water data were achieved particularly well within the wavelength ranges 350-590 nm and 600-1230 nm for the short-SDD probe, and 380-400 nm, 420-610 nm, and 650-950 nm for the long-SDD probe.

Development of a coaxial DCF-GRIN fiberoptic Raman probe for enhancing in vivo epithelial tissue Raman measurements.

We report on the development of a novel, to the best of our knowledge, coaxial double-clad-fiber (DCF) and graded-index (GRIN) fiberoptic Raman probe for enhancing epithelial tissue Raman measurements in vivo. The ultra-thin (140 µm outer diameter) DCF-GRIN fiberoptic Raman probe is designed and fabricated with an efficient coaxial optical configuration, whereby a GRIN fiber is spliced onto the DCF to enhance both the excitation/collection efficiency and depth-resolved selectivity. We demonstrate that the DCF-GRIN Raman probe can be used to acquire high-quality in vivo Raman spectra from various oral tissues (e.g., buccal mucosa, labial mucosa, gingiva, mouth floor, palate, and tongue) covering both the fingerprint (800-1800 cm-1) and high-wavenumber (2800-3600 cm-1) regions within sub-seconds. The subtle biochemical differences between different epithelial tissues in the oral cavity can also be detected with high sensitivity, suggesting the potential of the DCF-GRIN fiberoptic Raman probe for in vivo diagnosis and characterization in epithelial tissue.

An optically-guided cochlear implant sheath for real-time monitoring of electrode insertion into the human cochlea

In cochlear implant surgery, insertion of perimodiolar electrode arrays into the scala tympani can be complicated by trauma or even accidental translocation of the electrode array within the cochlea. In patients with partial hearing loss, cochlear trauma can not only negatively affect implant performance, but also reduce residual hearing function. These events have been related to suboptimal positioning of the cochlear implant electrode array with respect to critical cochlear walls of the scala tympani (modiolar wall, osseous spiral lamina and basilar membrane). Currently, the position of the electrode array in relation to these walls cannot be assessed during the insertion and the surgeon depends on tactile feedback, which is unreliable and often comes too late. This study presents an image-guided cochlear implant device with an integrated, fiber-optic imaging probe that provides real-time feedback using optical coherence tomography during insertion into the human cochlea. This novel device enables the surgeon to accurately detect and identify the cochlear walls ahead and to adjust the insertion trajectory, avoiding collision and trauma. The functionality of this prototype has been demonstrated in a series of insertion experiments, conducted by experienced cochlear implant surgeons on fresh-frozen human cadaveric cochleae.

Analysis of laser Doppler flowmetry long-term recordings for investigation of cerebral microcirculation during neurointensive care.

Cerebral blood flow is monitored in the neurointensive care unit (NICU) to avoid further brain damage caused by secondary insults following subarachnoid hemorrhage and brain trauma. Current techniques are mainly snap-shot based and focus on larger vessels. However, continuous monitoring of the smaller vessels may help detect the onset of secondary insults at an earlier stage. In this study, long-term measurements of brain microcirculation with laser Doppler flowmetry (LDF) were performed and evaluated. The aim was to identify and describe physiological signal variations and separate these from movement artifacts. Fiberoptic probes for subcortical LDF recordings of perfusion and total light intensity (TLI) were implanted in three patients with subarachnoid hemorrhage. Data were successfully collected and visualized in real-time over 4 days, resulting in 34, 12, and 8.5 h per patient. Visual observation, wavelet transforms, moving medians, and peak envelopes were used to identify and describe movement artifacts and physiological changes. Artifacts occurred in <5% of the total recording time and could be identified through signal processing. Identified physiological signal patterns included a slowly increasing perfusion trend over hours, vasomotion mainly at 2 cycles/min both in the perfusion and the TLI, and rapid, synchronized changes in the TLI and the perfusion on 38 occasions. Continuous LDF recordings indicating changes in the microvascular blood flow can increase the understanding of the microcirculation in the injured brain. In the long run, this may become a complement for the detection of secondary insults at an earlier stage than possible with today's techniques.

Cutting temperature measurement using a novel near-infrared two-color pyrometer under dry and wet cutting of Ti‐6Al‐4V alloy

Due to the poor thermal properties of titanium alloys, heat generated and accumulated in the cutting area significantly affects tool life and workpiece quality. Although some methods have been proposed to measure the cutting temperature during machining titanium alloys, there still exist disadvantages including low spatial-temporal resolution, low measuring accuracy, restricted usage environment, etc. In this paper, a novel near-infrared two-color pyrometer system is developed and applied to measure the cutting zone temperature under dry and wet cutting of Ti‐6Al‐4V alloy. The developed pyrometer can eliminate the emissivity effect and shows a good linear relationship between the output signal ratio and the calibrated temperature. Meanwhile, the developed pyrometer exhibits good dynamic response and high measuring accuracy when measuring tool edge temperature and chip temperature in dry cutting conditions. In addition, a reliable sealing for cutter assembly is developed to overcome the influence of cutting fluid on the optic-fiber probe and the developed pyrometer can measure the tool edge temperature quickly and accurately in wet cutting conditions. In summary, the novel near-infrared two-color pyrometer system is validated to be quick responsiveness, high measuring accuracy, and good working stability when monitoring the cutting zone temperature under dry and wet cutting of Ti‐6Al‐4V alloy.

PHSOR03 Presentation Time: 12:40 PM: Radiation Dosimetry of a Dual-Modality Balloon Implant for Simultaneous HDR Brachytherapy and Magnetic Nanoparticle Hyperthermia to Treat Brain Tumor Resection Cavities

<h3>Purpose</h3> Glioblastoma multiforme (GBM) is an aggressive brain tumor that generally recurs locally and has a dismal median survival of less than 18 months<i>. In vivo</i> studies have shown that simultaneous hyperthermia and radiation can enhance the radiation response by a factor of up to 5. Our group developed a novel dual-modality thermobrachytherapy (TBT) balloon device to accomplish this goal. The balloon will combine magnetic fluid hyperthermia and HDR brachytherapy, which will be delivered right after brain tumor resection, so that the at-risk tissue adjacent to the tumor resection cavity will conform to the balloon shape and receive uniform radiation and thermal dose. This abstract focuses on the possible effects of hyperthermia on radiation dosimetry as well as the effects of balloon shape. <h3>Methods</h3> The current version of our TBT balloon device consists of a balloon filled with magnetic nanoparticle solution (nanofluid) and a flexible sheath with three ports to insert the HDR catheter and fiber-optic thermal probe and inject the nanofluid. We tested the balloon in air and activated the nanofluid using an external magnetic field induced by a 133 kHz induction coil. Two balloon designs were tested: a spherical one with 4 cm diameter, and a teardrop-shaped balloon with an axial diameter of 3 cm and measuring 3.7 cm along the shaft. We used Gafchromic film and RIT imaging software to analyze the in-air dose distribution of an HDR source dwell in both types of balloons, filled with distilled water and then nanofluid, as well as without and with simultaneous hyperthermia, where the coil power was escalated until reaching intra-balloon temperatures greater than 55°C. Experimental setup and radiation dose profiles can be found in Figure 1. <h3>Results</h3> The presence of the nanofluid, magnetic field and heat up to 66°C did not affect radiation dose distribution significantly in the spherical balloon (less than 10% difference). However, the teardrop-shaped balloon dose profiles showed a notable difference (about 20%) in dose magnitude with the presence of nanofluid and/or heat. Nonetheless dose distributions looked symmetrical in all cases. <h3>Conclusions</h3> The current device design is still in progress, but this study illustrated that a spherical balloon shape may be preferential for simultaneous hyperthermia and HDR brachytherapy. Furthermore, this radiation dosimetry study demonstrated compatibility and robustness of the prototype balloon components and desirable symmetrical dose distribution.

An optical fiber probe based on multi-optical well particle capture

An optical fiber probe based on multi-optical well particle capture

Spectrally Resolved Fiber Photometry for In Vivo Multi-Color Fluorescence Measurements.

This article describes how to assemble and operate a spectrometer-based fiber photometry system for in vivo simultaneous measurements of multiple fluorescent biosensors in freely moving mice. The first section of the article describes the step-by-step procedure to assemble a basic single-spectrometer fiber photometry system and how to expand it into a dual-spectrometer system that allows for simultaneous recordings from two sites. The second part describes the steps for a typical fiber probe implantation surgery. The last section describes how to acquire and analyze the time-lapsed spectral data. This article is intended for teaching labs how to build their own fiber photometry systems (with a video tutorial) from commercially available parts and perform in vivo recordings in behaving mice. © Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Basic Protocol 1: Assembling a dual-laser, single-spectrometer fiber photometry system Support Protocol: Dual-spectrometer fiber photometry assembly Basic Protocol 2: Optical fiber probe implantation Basic Protocol 3: Data acquisition and analysis.

Electro-plasmonic-assisted biosensing of proteins and cells at the surface of optical fiber

An electro-plasmonic biosensor is used to attract proteins and cells on the surface of a fiber optic probe by controlled biomolecular migration. Concentrating targets on a high performance plasmon-assisted fiber grating sensor leads to a drastic enhancement of the limit of detection. This architecture relies on a biofunctionalized gold coated tilted fiber Bragg grating (TFBG) that operates as a working electrode to enable electrophoresis in the probed medium. The applied electric field triggers the attraction of proteins over a distance of almost 250 μm from the sensor surface, which is more than two orders of magnitude larger than the intrinsic penetration depth of the plasmon wave. Quantitative determination of target analytes was performed by cyclic voltammetry measurements using the gold coated fiber as an electrode, simultaneously with optical transmission measurements of the underlying fiber grating. In our work, these electro-plasmonic optrodes were used against a clinically-relevant biomarker in breast cancer diagnosis, namely HER2 (Human Epidermal Growth Factor Receptor-2). In vitro assays confirm that their limit of detection lies in the subpicomolar range for proteins, which is beyond reach of similar sensors without voltammetry. The improved detection limit is further facilitated by an improvement of the signal-to-noise ratio of the read-out process. Whole cell capture is finally demonstrated by the same micro-system.

Highly sensitive and selective colorimetric sensing of CO2 for biomedical applications

The concentration of carbon dioxide (CO2) in unhealthy people differs greatly from healthy people. High-precision CO2 detection with a quick response time is essential for many biomedical applications. A major focus of this research is on the detection of CO2, one of the most important health biomarkers. We investigated a low-cost, flexible, and reliable strategy by using dyes for colorimetric CO2 sensing in this study. The impacts of temperature, pH, reaction time, reusability, concentration, and dye selectivity were studied thoroughly. This study described real-time CO2 analysis. Using this multi-dye method, we got an average detection limit of 1.98 ppm for CO2, in the range of 50–120 ppm. A portable colorimetric instrument with a smartphone-assisted unit was constructed to determine the relative red/green/blue values for real-time and practical applications within 15 s of interaction and the readings are very similar to those of an optical fiber probe. Environmental and biological chemistry applications are likely to benefit greatly from this unique approach.

Miniaturized fiber optic ultrasound sensor with multiplexing for photoacoustic imaging

A miniaturized ultrasound sensor based on optical fiber is designed and realized for multichannel parallel ultrasound detection and photoacoustic imaging. The fiber optic sensor is composed of a polymer coating, a reflective mirror and a single-mode optical fiber, with only 125 µm in diameter. By integrating the coherent demodulation technology and multiplexing technology, which using a relatively cheap fixed wavelength laser, hundreds of sensors could work simultaneously. Meanwhile, highly sensitive ultrasound detection has been demonstrated with the noise equivalent pressure as low as 0.46 kPa and the sensor exhibits a nearly omnidirectional directivity. Furthermore, a photoacoustic imaging system based on three sensors working in parallel is demonstrated. High lateral resolutions of 165–217 µm and axial resolutions of 112–131 µm over a depth range of larger than 5 mm are obtained. A three-dimensional phantom imaging experiment is also demonstrated. Benefited from parallel detection, the imaging speed is three times faster than that of a single sensor. The miniaturized fiber optic ultrasound sensor probe provides a competitive alternative for mechanically scanning-free endoscopic imaging, which is beneficial from small size, omnidirectional directivity and parallel detection capability.

Effect of bed material size on gas-solid flow characteristics in a CFB at low solid recirculation rates

The gas–solid flow characteristics greatly influence the heat transfer, combustion and pollutant formation processes in a circulating fluidized bed (CFB) boiler. The effects of particle size on the gas–solid flow characteristics, including flow structure, axial pressure and bed density profiles were studied in a two-dimensional CFB cold apparatus under low solid circulation rates (Gs’s). At the same time, an optical fiber probe was used to assess the particle size effect on the formation of particle clusters and their properties under different operating conditions. Results revealed that when the averaged size of bed materials decreased from ∼200 μm to ∼100 μm, at the same operating condition, the bottom dense bed became remarkably higher, and the upper dilute zone had stronger pressure fluctuation, more even axial and horizontal particle distributions, and higher solid density. Gs was more sensitive to the variation of the superficial gas velocity than the bed inventory. In addition, the standard deviation and power spectrum density of instantaneous pressure decreased in the dense bed and increased in the dilute zone. The particle velocity was slightly lower in the lower section of the riser but noticeably greater in the upper riser section. In addition, the clusters formed more frequently and lasted significantly longer. The study showed that flow characteristics in the bed qualitatively changed from that of Type B particles to that Type A particles in the Geldart’s classification, even at a small Gs, and previous studies with Type B particles could very likely not apply in the CFB boilers operating with fine bed materials.

Miniaturized 7-in-1 fiber-optic Raman probe.

This Letter reports a miniature 7-in-1 fiber-optic Raman probe that eliminates the inelastic background Raman signal from a long-fused silica fiber. Its foremost purpose is to enhance a method for investigating extraordinarily tiny substances and effectively capturing Raman inelastic backscattered signals using optical fibers. We successfully used our home-built fiber taper device to combine seven multimode fibers into a single fiber taper with a probe diameter of approximately 35 µm. By experimentally comparing the traditional bare fiber-based Raman spectroscopy system with the miniaturized tapered fiber-optic Raman sensor using liquid solutions, the novel probe's capability is demonstrated. We observed that the miniaturized probe effectively removed the Raman background signal originating from the optical fiber and confirmed expected outcomes for a series of common Raman spectra.