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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 1.25 nm/RIU (refractive index unit) at the beginning of the process, up to 23.38 nm/RIU at the end of the etching, for a RI range from 1.3418 to 1.4419 RIU. The proposed aptasensor showed improved RI sensitivity as compared to the unetched TFBG, without requiring metal depositions on the fiber surface or polarization control during the measurements. The proposed sensor was tested for the detection of thrombin-aptamer interactions based on silane-coupling surface chemistry, with thrombin concentrations ranging from 2.5 to 40 nM. Functionalized eTFBGs provided a competitive platform for biochemical interaction measurements, showing sensitivity values ranging from 2.3 to 3.3 p.m./nM for the particular case of thrombin detection.

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). Subsequently, in order to perform a selective detection of thrombin, the EFBG has been functionalized with silane-coupling agent 3-(aminopropyl)triethoxysilane (APTES) and a cross-linker, glutaraldehyde, for the immobilization of thrombin-binding aptamer. The biosensor has been validated for thrombin detection in concentrations ranging from 10 nM to 80 nM. The proposed sensor presents advantages with respect to other sensor configurations, based on plasmonic resonant tilted FBG or Long Period Grating (LPG), for thrombin detection. Firstly, fabricating an EFBG only requires chemical etching. Moreover, the functionalization method used in this study (silanization) allows the avoidance of complicated and expensive fabrications, such as thin film sputtering or chemical vapor deposition. Due to their characteristics, EFBG sensors are easier to multiplex and can be used in vivo. This opens new possibilities for the detection of thrombin in clinical settings.

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 CO2 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. The ball resonators behaved as weak interferometers with a shallow fringe and a spectrum that appeared close to a random signal, and RI sensitivity could be measured either through wavelength shift or amplitude change. In this work, we reported four samples having sensitivity ranges 48.9–403.3 nm/RIU and 256.0–566.2 dB/RIU (RIU = refractive index unit). Ball resonators appeared as a sensitive and robust platform for RI sensing in liquid and can be further functionalized for biosensing.

BackgroundRecent 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. Molecular levels of various proteins have also been examined.MethodsTo evaluate and assess the effect of antiviral treatment on morphometric, migratory and other cellular characteristics of MCF7 breast cancer cells, the following experiments were performed: (i) MTT assay to measure the viability of MCF7 cells; (ii) Colony formation ability by soft agar assay; (iii) Morphometric characterization by immunofluorescent analysis using confocal microscopy; (iv) wound healing and transwell membrane assays to evaluate migration and invasion capacity of the cells; (v) ELISA colorimetric assays to assess expression levels of caspase-3, E-cadherin and enzymatic activity of aldehyde dehydrogenase (ALDH).ResultsWe demonstrate the suppressive effect of acyclovir on breast cancer cells. Acyclovir treatment decreases the growth and the proliferation rate of cells and correlates with the upregulated levels of apoptosis associated cytokine Caspase-3. Moreover, acyclovir inhibits colony formation ability and cell invasion capacity of the cancer cells while enhancing the expression of E-cadherin protein in MCF7 cells. Breast cancer cells are characterized by high ALDH activity and associated with upregulated proliferation and invasion. According to this study, acyclovir downregulates ALDH activity in MCF7 cells.ConclusionsThese results are encouraging and demonstrate the possibility of partial suppression of cancer cell proliferation using an antiviral agent. Acyclovir antiviral agents have a great potential as an adjuvant therapy in the cancer treatment. However, more research is necessary to identify relevant biochemical mechanisms by which acyclovir induces a potent anti-cancer effect.Electronic supplementary materialThe online version of this article (doi:10.1186/s13027-017-0128-7) contains supplementary material, which is available to authorized users.