Nitrogen, boron-doped Ti3C2 MXene quantum dot-based ratiometric fluorescence sensing platform for point-of-care testing of tetracycline using an enhanced antenna effect by Eu3

The Ti₃C₂ MXene quantum dots (Ti₃C₂ MQDs) derived from Ti₃C₂ MXene have received much attention because of their remarkable advantages in biosensing. Nevertheless, the functionalization of Ti₃C₂ MQDs to improve their properties is just in its infant stage. Herein, we firstly synthesized nitrogen and boron co-doped Ti₃C₂ MQDs (N, B-Ti₃C₂ MQDs) with good water solubility, strong stability, and high optical characteristics. The N, B-Ti₃C₂ MQDs exhibit excitation wavelength-dependent blue photoluminescence with optimal excitation/emission peaks at 335/439 nm. Nowadays, the development of fast and real-time detection of tetracycline (TC) in animal derived food is very essential. In this work, a novel point-of-care testing (POCT) platform was established based on ratiometric fluorescence method using N, B-Ti₃C₂ MQDs coupled with Eu³⁺. Upon addition of TC in the Eu³⁺/N, B-MQDs system, blue fluorescence emission of N, B-Ti₃C₂ MQDs was quenched and red fluorescence emission of Eu³⁺ was enhanced gradually, which was ascribed to the synergistic inner filter effect and antenna effect. Moreover, we prepared test papers with N, B-Ti₃C₂ MQDs and Eu³⁺ for TC detection based on the change of fluorescence color, which could be recognized by color recognizer app installed in the smartphone. Therefore, great promise for POCT of TC is given with the merits of simplicity and visible detection possibility. The proposed method demonstrated a low detection limit of 20 nM. Application of the platform for TC quantification in milk samples opened a novel means for the potential use of N, B-Ti₃C₂ MQDs in food safety.

Ultrathin boron nanosheets as an emerging two-dimensional photoluminescence material for bioimaging

Two-dimensional (2D) metal-free sheets with atomic thickness have been highly considered as promising candidates for fluorescent probes, due to their intriguing characteristics. In this work, 2D ultrathin boron nanosheets (B NSs) with a surface defect nanolayer can be effectively prepared by modified liquid phase exfoliation. The as-prepared ultrathin B NSs show blue fluorescence characteristics even with a quantum yield efficiency of up to 10.6%. Such luminescent behavior originates from the quantum confinement effect and the existence of a surface defect layer. In light of the advantages of being environmentally friendly, having high photostability and good biocompatibility, for the first time we have shown that ultrathin B NSs can be used as an emerging fluorescent probe for application in cellular bioimaging. It is believed that this work will open new avenues for ultrathin B NSs in biomedical fields, and it will also inspire the development of other elemental 2D nanomaterials.

Neutron Autoradiography Combined With UV-C Sensitization: Toward the Intracellular Localization of Boron

Our group has reported the imprint formation of biological material on polycarbonate nuclear track detectors by UV-C exposure, which is used as an approach to simultaneously visualize cell imprints and nuclear tracks coming from the boron neutron capture reaction. Considering that the cell nucleus has a higher UV-C absorption than the cytoplasm and that hematoxylin preferentially stains the nucleus, we proposed to enhance the contrast between these two main cell structures by hematoxylin staining before UV-C sensitization. In this study, several experiments were performed in order to optimize UV-C exposure parameters and chemical etching conditions for cell imprint formation using the SK-BR-3 breast cancer cell line. The proposed method improves significantly the resolution of the cell imprints. It allows clear differentiation of the nucleus from the rest of the cell, together with nuclear tracks pits. Moreover, it reduces considerably the UV-C exposure time, an important experimental issue. The proposed methodology can be applied to study the boron distribution independently from the chosen cell line and/or boron compounds.

Effective visible light-active boron and europium co-doped BiVO4 synthesized by sol-gel method for photodegradion of methyl orange

Eu-B co-doped BiVO4 visible-light-driven photocatalysts have been synthesized using the sol-gel method. The resulting materials were characterized by a series of joint techniques, including XPS, XRD, SEM, BET, and UV-vis DRS analyses. Compared with BiVO4 and B-BiVO4 photocatalysts, the Eu-B-BiVO4 photocatalysts exhibited much higher photocatalytic activity for methyl orange (MO) degradation under visible light irradiation. The optimal Eu doping content is 0.8 mol%. It was revealed that boron and europium were doped into the lattice of BiVO4 and this led to more surface oxygen vacancies, high specific surface areas, small crystallite size, a narrower band gap and intense light absorbance in the visible region. The doped Eu(III) cations can help in the separation of photogenerated electrons. The synergistic effects of boron and europium in doped BiVO4 were the main reason for improving visible light photocatalytic activity.

Time-resolved interferometry of femtosecond-laser-induced processes under tight focusing and close-to-optical breakdown inside borosilicate glass

We use an interferometric time-resolved observation of a femtosecond-laser pulse (800 nm/45 fs) interaction with glass from 100 fs to 10 ns at spatial lateral resolution down to the wavelength of the pulse. The phase and amplitude images reveal sequence of events after the irradiation of a single ultra-short laser pulse at close-to-threshold intensity when permanent refractive index changes occur. The proposed method is applicable to characterization of the processes induced by tightly focused fs-laser pulses during three-dimensional structuring of glasses and crystals for fundamental studies and optical applications. Generation of carriers, thermal expansion, generation and propagation of shockwaves, and formation of refractive index changes are experimentally observed and resolved in time and space with the highest resolution. Quantitative estimations of the threshold energies of different processes are achieved. The threshold energy of carrier generation is found the same as that of shockwave generation while the threshold energy of refractive index changes was by 40% higher. Application potential of the method is discussed.

Ionisation chamber containing boron as a neutron detector in medical accelerator fields

A combination of the recombination principle of H(10) measurements with the use of the ionisation chambers containing boron has been presented, in order to increase the relative sensitivity of the chamber to neutrons by a factor close to the radiation quality factor of photoneutrons. Three types of the chambers were investigated. Two of them were filled with BF(3) and the third one contained electrodes covered with B(4)C. All the chambers were placed in paraffin moderators. The response of the chambers was investigated, depending on gas pressure and polarising voltage. The results showed that it was possible to obtain nearly the same response of the chamber to H(10) for photons and neutrons in a restricted energy range; however, further investigations are needed to make an optimum design.

Combined TL and 10B-alanine ESR dosimetry for BNCT

The dosimetric technique described in this paper is based on electron spin resonance (ESR) detectors using an alanine-boric compound acid enriched with (10)B, and beryllium oxide thermoluminescent (TL) detectors; with this combined dosimetry, it is possible to discriminate the doses due to thermal neutrons and gamma radiation in a mixed field. Irradiations were carried out inside the thermal column of a TRIGA MARK II water-pool-type research nuclear reactor, also used for Boron Neutron Capture therapy (BNCT) applications, with thermal neutron fluence from 10(9) to 10(14) nth cm(-2). The ESR dosemeters using the alanine-boron compound indicated ESR signals about 30-fold stronger than those using only alanine. Moreover, a negligible correction for the gamma contribution, measured with TL detectors, almost insensitive to thermal neutrons, was necessary. Therefore, a simultaneous analysis of our TL and ESR detectors allows discrimination between thermal neutron and gamma doses, as required in BNCT.

Wortmannin enhances the induction of micronuclei by low and high LET radiation

In mammalian cells, the repair of DNA double-strand breaks (DSBs) is mainly mediated by DNA non-homologous end joining. DNA-dependent protein kinase (DNA-PK), a nuclear serine-threonine kinase and a member of the phosphaditylinositol-3 kinase-related kinase family that is activated by DSBs, is a key component of this pathway. Wortmannin (WM) is known to be an irreversible and potent inhibitor of DNA-PK and has thus been proposed as an effective sensitizer for ionizing radiation and for radiomimetic compounds. The present study, using the cytokinesis block micronucleus assay, reports on the differential effect of WM on the repair of the DNA damage induced by low LET ((60)Co gamma-radiation) and high LET radiation by the boron neutron capture reaction (alpha and Li particles) in V79 Chinese hamster cells. Significant increases in the number of micronuclei per binucleated cell as well as in the frequency of micronucleated binucleated cells were observed in the presence of different concentrations of WM for high LET radiation from the boron neutron capture reaction. The increases observed reached a maximum of approximately 2-fold in comparison with the respective controls. WM, however, had a more pronounced effect on (60)Co gamma-radiation-induced micronuclei, increasing the genotoxic damage from this radiation by approximately 3- to 4-fold. These results are in general in agreement with the concept that DSBs induced by high LET radiation are not a more suitable substrate for the end joining processes mediated by DNA-PK, yet they do not preclude a role for DNA-PK in high LET-induced damage repair.

Thermal neutron capture therapy of malignant melanoma using 10B-monoclonal antibodies: in vitro and in vivo analysis

We have established methods of targeting a sufficient number of 10B atoms on human melanoma cells to allow selective destruction of the cancer cells by thermal neutron irradiation. Thermal neutron capture therapy (NCT)1-3 requires the presence of at least 10(9) 10B atoms on each target cell for specific killing of that cell without injuring normal tissues. In order to accumulate an adequate number of 10B atoms on target cells, we first created an effective compound containing 12 atoms of 10B per molecule (10B12-chlorpromazine) and 10B-dopa analogue (10B1-paraboronophenylalanine). In the present study, about three molecules of our newly synthesized 10B12-compound were conjugated to an avidin molecule. The resulting 10B38.5-avidin compound can be specifically directed to human melanoma cells by biotinated monoclonal antibodies (MAbs) specific for the cells. We were able to accumulate 2.6 x 10(8) 10B atoms on a melanoma cell using this method. Cultured human melanoma cells treated with 10B-avidin-biotin-MAb (10B-AB-MAb) were selectively damaged by thermal neutron irradiation in vitro. This is the first study to indicate that thermal neutrons selectively damage target cells boronated by MAbs.

Inhibition of tumor growth in a glioma model treated with boron neutron capture therapy

This investigation attempts to determine whether increased survival time seen when the F98 glioma model is treated with boron neutron capture therapy (BNCT) is a result of inhibition of tumor growth caused by radiation-induced alterations in endothelial cells and normal tissue components. This indirect effect of radiation has been called the tumor bed effect. A series of tumor-bearing rats was studied, using a standardized investigational BNCT protocol consisting of 50 mg/kg of Na2B12H11SH injected intravenously 14 to 17 hours before neutron irradiation at 4 x 10(12) n/cm2. Ten rats, serving as controls, received no treatment either before or after tumor implantation. A second group of 10 rats was treated with BNCT 4 days before tumor implantation; these animals received no further treatment. The remaining group of 10 rats received no pretreatment but was treated with BNCT 10 days after implantation. Histological and ultrastructural analyses were performed in 2 animals from each group 17 days after implantation. Survival times of the untreated control animals (mean, 25.8 days) did not differ statistically from the survival times of the rats in the pretreated group (mean, 25.5 days). The rats treated with BNCT after implantation survived significantly longer (P less than 0.02; mean, 33.2 days) than the controls and the preirradiated animals. Tumor size indices calculated from measurements taken at the time of death were similar in all groups. These results indicate that, with this tumor model, BNCT does not cause a tumor bed effect in cerebral tissue. The therapeutic gains observed with BNCT result from direct effects on tumor cells or on the peritumoral neovascularity.