Nowadays, the application of nanoparticles for biomedical purposes is a promising and innovative tool for the thermal therapy of tumors. Gold nanoparticles are distinguished by their tunable optical properties, biocompatibility, and ease of synthesis. The ability of gold nanoparticles to absorb light at near-infrared region (NIR) to generate localized heat allows temperature elevation and optimizing the temperature distribution during short-time laser ablation. The synthesized 20-nm gold nanoparticles injected on the surface of the tissue demonstrated rapid and diffused heat increase enlarging the shape of the treated region compared to the pristine tissue. Another advantage of this work is the proposed optical fiber distributed sensing network over the laser ablation assisted with nanomaterials. The sensing system uses single-mode enhanced-backscattering optical fibers doped with MgO nanoparticles; it achieves narrow spatial resolution, which demonstrates accurate temperature distribution monitoring in real time, in 2-dimensions over 5.4 cm2 area at 16 sensing points per fiber. The obtained sensing data allowed to calculate the treated area and provided the information when the ablation process should be terminated in order to avoid the vaporization of tissue after reaching the temperature of 100 °C. The calculated damage threshold (>60 °C) areas are 2.57 cm2 with gold nanoparticles, compared to 1.33 mm2 pristine. The results of this work provide the solution to two issues existing during laser ablation that are possible damage of undesired area and the ability to precisely monitor the temperature in real time that is compatible to MRI.
In this work, the investigation of thrombin concentration using microresonator functionalized with thiol-modified thrombin-binding aptamer (TBA) is reported. Resonator is a ball shaped structure on a tip of an optical fiber. Thrombin is a serine protease that plays an important role during blood coagulation; therefore, it is substantial to detect its levels in blood of the patient. The structure has been manufactured using standard single-mode fibers on CO2 laser splicing system. Further, the resonator of diameter 518 µm has been calibrated with sucrose for refractive index changes with optical backscatter reflectometer. Changes in sensitivity and reflectivity in wavelength shift and amplitude fluctuation were measured. This was followed by coating the resonator with gold and functionalizing surface with TBA. Following aptamer immobilization, the performance of 518 µm resonator was examined in different concentrations of thrombin protein from 4.01 nM to 66.84 nM. We report here a sample presenting a sensitivity of (122.65 nm/RIU, RIU = refractive index units), which allows thrombin detection with an average wavelength shift of 1.034 nm.
Laser ablation (LA) has shown promising results in selective treatment of solid tumors. Recently, nanomaterials, in particular nanoparticles (NPs), have been proposed as mediators for laser tissue ablation due to their high optical absorption coefficients. In this work, we report distributed fiber optic temperature sensors for monitoring of NPmediated LA in ex-vivo porcine liver. This study aims at improving the outcomes of LA through magnetite NPsenhanced LA with in-situ thermal profiling. Such thermal profiling is achieved with optical backscatter reflectometer interrogating a set of custom-made MgO-doped optical fibers exhibiting enhanced scattering profiles. Fiber optic sensors, providing spatially resolved measurements, significantly outperform conventional thermocouples and imaging techniques. A minimally invasive LA setup is based on high power fiber coupled diode laser operating at 980 nm wavelength, with output power up to 30 W. Magnetite (Fe3O4) NPs are synthetized and locally injected within the tissue before performing LA. The sensing setup utilizes optical backscatter reflectometer that exploits Rayleigh backscattering to measure the temperature distribution with submillimeter spacing. Thermal maps, i.e. temperature distribution as a function of space and time, are reported highlighting thermal distribution within the ablated lesion and in off-target adjacent tissue. The influence of laser power and of NPs concentrations on the outcomes of LA is also investigated. Results demonstrate that injection of NPs into targeted area helps enhance conversion of light energy into thermal energy, thus increasing the efficacy of the ablation within the treated area, without overheating the adjacent off-target tissue.
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