Spatial-Division Multiplexing Approach for Simultaneous Detection of Fiber-Optic Ball Resonator Sensors: Applications for Refractometers and Biosensors.

Fiber-optic ball resonators are an attractive technology for refractive index (RI) sensing and optical biosensing, as they have good sensitivity and allow for a rapid and repeatable manufacturing process. An important feature for modern biosensing devices is the multiplexing capacity, which allows for interrogating multiple sensors (potentially, with different functionalization methods) simultaneously, by a single analyzer. In this work, we report a multiplexing method for ball resonators, which is based on a spatial-division multiplexing approach.

Cost-Effective Fiber Optic Solutions for Biosensing.

In the last years, optical fiber sensors have proven to be a reliable and versatile biosensing tool. Optical fiber biosensors (OFBs) are analytical devices that use optical fibers as transducers, with the advantages of being easily coated and biofunctionalized, allowing the monitorization of all functionalization and detection in real-time, as well as being small in size and geometrically flexible, thus allowing device miniaturization and portability for point-of-care (POC) testing. Knowing the potential of such biosensing tools, this paper reviews the reported OFBs which are, at the moment, the most cost-effective.

Ultra-wide, attomolar-level limit detection of CD44 biomarker with a silanized optical fiber biosensor.

Measuring cancer biomarkers at ultralow detection limit and high sensitivity could be a promising tool for early diagnosis, monitoring treatment and post-treatment recurrence. Soluble CD44 is a promising diagnostic and prognostic biomarker in several types of cancer including gastric, colon and breast cancer. Several highly sensitive biosensors have been built to measure this important biomarker.

Optical Fiber Ball Resonator Sensor Spectral Interrogation through Undersampled KLT: Application to Refractive Index Sensing and Cancer Biomarker Biosensing.

Optical fiber ball resonators based on single-mode fibers in the infrared range are an emerging technology for refractive index sensing and biosensing. These devices are easy and rapid to fabricate using a CO laser splicer and yield a very low finesse reflection spectrum with a quasi-random pattern. In addition, they can be functionalized for biosensing by using a thin-film sputtering method.

Label-free fiber-optic spherical tip biosensor to enable picomolar-level detection of CD44 protein.

Increased level of CD44 protein in serum is observed in several cancers and is associated with tumor burden and metastasis. Current clinically used detection methods of this protein are time-consuming and use labeled reagents for analysis. Therefore exploring new label-free and fast methods for its quantification including its detection in situ is of importance.

Shallow-Tapered Chirped Fiber Bragg Grating Sensors for Dual Refractive Index and Temperature Sensing.

In this work, we present a gold-coated shallow-tapered chirped fiber Bragg grating (stCFBG) for dual refractive index (RI) and temperature sensing. The stCFBG has been fabricated on a 15-mm long chirped FBG, by tapering a 7.29-mm region with a waist of 39 μm.

Fiber Optic Refractive Index Sensors Based on a Ball Resonator and Optical Backscatter Interrogation.

In this work, we introduced fabrication and interrogation of simple and highly sensitive fiber-optic refractive index (RI) sensors based on ball resonators built on the tip of single-mode fibers. The probes have been fabricated through a CO fiber splicer, with a fast (~600 s) and repeatable method. The ball resonator acted as a weak interferometer with a return loss below -50 dB and was interrogated with an optical backscatter reflectometer measuring the reflection spectrum.

Functionalized etched tilted fiber Bragg grating aptasensor for label-free protein detection.

An aptasensor based on etched tilted fiber Bragg grating (eTFBG) is developed on a single-mode optical fiber targeting biomolecule detection. TFBGs were chemically etched using hydrofluoric acid (HF) to partially remove the fiber cladding. The sensor response was coarsely interrogated, resulting on a sensitivity increase from 1.

Wavelet-Based Demodulation of Multimode Etched Fiber Bragg Grating Refractive Index Sensor.

Etched fiber Bragg grating (EFBG)-based sensors are used as evanescent field sensors for refractive index detection. When the fiber thickness is thin and the refractive index sensitivity increases, the number of propagating modes increases, resulting in a spectral enlargement that complicates the interrogation of the sensor. In this work, we present a method to analyze the spectrum of a multimode etched fiber Bragg grating (MMEFBG) in the wavelet domain, which analyzes the amount of spectral density independently from the peak reflectivity value.

Etched Fiber Bragg Grating Biosensor Functionalized with Aptamers for Detection of Thrombin.

A biosensor based on an etched Fiber Bragg Grating (EFBG) for thrombin detection is reported. The sensing system is based on a Fiber Bragg Grating (FBG) with a Bragg wavelength of 1550 nm, wet-etched in hydrofluoric acid (HF) for ~27 min, to achieve sensitivity to a refractive index (RI) of 17.4 nm/RIU (refractive index unit).

Fiber optic refractive index sensors through spectral detection of Rayleigh backscattering in a chemically etched MgO-based nanoparticle-doped fiber.

We demonstrate and experimentally validate a fiber optic refractive index (RI) sensor obtained by simply etching a high-scattering MgO-based nanoparticle-doped single-mode fiber in hydrofluoric acid (HF). The fiber has 32.3 dB stronger Rayleigh scattering than a standard fiber, allowing a detection of scattering spectral signatures with an optical backscatter reflectometer, even when the core is exposed to the outer RI.

Fabrication and Interrogation of Refractive Index Biosensors Based on Etched Fiber Bragg Grating (EFBG).

We discuss the fabrication and interrogation of a fiber-optic refractive index sensors based on wet-etched fiber Bragg grating (EFBG). The fabrication is based on chemical etching of an FBG through an HF-free etching solution (ammonium fluoride and sulfuric acid), which progressively depletes the fiber cladding exposing the core to the outer medium. Microscope inspection of the fiber and real-time detection of the Bragg wavelength allow controlling the sensitivity.

Partially etched chirped fiber Bragg grating (pECFBG) for joint temperature, thermal profile, and refractive index detection.

In this work, a partially etched chirped fiber Bragg grating (pECFBG) is introduced, as a compact sensor for multi-parametric measurement of temperature, thermal gradients over the active length, and refractive index. The sensor is fabricated by wet-etching a portion of a 14-mm linearly chirped FBG with linear chirp profile. The resulting device has two active areas: the unetched part of the grating (2 mm) can be used either as a uniform temperature sensor, or to detect thermal gradients experienced through the grating length by means of a spectral reconstruction technique; the etched part (12 mm), besides having a similar thermal sensitivity, is exposed to refractive index sensing through the introduction of a sensitivity to external refractive index.

Biocompatible scaffolds based on natural polymers for regenerative medicine.

The chitosan and gelatine are commonly used biopolymers for the tissue engineering applications. In the previous methods for the cryogels synthesis, multistep preparation methods using toxic cross-linking agents such as glutaraldehyde are reported. Here, we present a two-step preparation method of gelatin macroporous cryogels and one-step preparation method of chitosan or gelatin cryogels.

The effects of antiviral treatment on breast cancer cell line.

Background: Recent studies have revealed the positive antiproliferative and cytotoxic effects of antiviral agents in cancer treatment. The real effect of adjuvant antiviral therapy is still controversial due to the lack of studies in biochemical mechanisms. Here, we studied the effect of the antiviral agent acyclovir on morphometric and migratory features of the MCF7 breast cancer cell line.

Disruption of Bcl-2 and Bcl-xL by viral proteins as a possible cause of cancer.

The Bcl proteins play a critical role in apoptosis, as mutations in family members interfere with normal programmed cell death. Such events can cause cell transformation, potentially leading to cancer. Recent discoveries indicate that some viral proteins interfere with Bcl proteins either directly or indirectly; however, these data have not been systematically described.