Dual-signal amplification electrochemical sensing for the sensitive detection of uranyl ion based on gold nanoparticles and hybridization chain reaction-assisted synthesis of silver nanoclusters.

Herein, a dual-signal amplification electrochemical sensing has been proposed for the ultrasensitive detection of uranyl ions (UO22+) by integration of gold nanoparticles (AuNPs) and hybridization chain reaction (HCR)-assisted synthesis of silver nanoclusters (AgNCs). In this sensing platform, AuNPs are used as an ideal signal amplification carrier, aiming at increasing the loads of UO22+-specific DNAzyme on the gold electrode. In the presence of UO22+, UO22+-specific DNAzyme can be activated, leading to the cleavage of substrate strands (S-DNA). Then, HCR is triggered to produce long dsDNA through hybridization the probe with the ssDNA on the electrode surface. As a result, an amplified electrochemical response can be detected by inserting a large amount of AgNCs generated in situ using dsDNA as template. Featured with amplification efficiency, good specificity and high sensitivity, the strategy could quantitatively detect UO22+ down to 6.2 pM with a linear calibration range from 20 pM to 5000 pM. The proposed sensing platform has been also successfully demonstrated the practical application of detecting UO22+, indicating that the developed method has the potential applications and can open up a new avenue for highly sensitive detection of UO22+ in environmental monitoring.

Exosomes and exosomal microRNA in non-targeted radiation bystander and abscopal effects in the central nervous system.

Localized cranial radiotherapy is a dominant treatment for brain cancers. After being subjected to radiation, the central nervous system (CNS) exhibits targeted effects as well as non-targeted radiation bystander effects (RIBE) and abscopal effects (RIAE). Radiation-induced targeted effects in the CNS include autophagy and various changes in tumor cells due to radiation sensitivity, which can be regulated by microRNAs. Non-targeted radiation effects are mainly induced by gap junctional communication between cells, exosomes containing microRNAs can be transduced by intracellular endocytosis to regulate RIBE and RIAE. In this review, we discuss the involvement of microRNAs in radiation-induced targeted effects, as well as exosomes and/or exosomal microRNAs in non-targeted radiation effects in the CNS. As a target pathway, we also discuss the Akt pathway which is regulated by microRNAs, exosomes, and/or exosomal microRNAs in radiation-induced targeted effects and RIBE in CNS tumor cells. As the CNS-derived exosomes can cross the blood-brain-barrier (BBB) into the bloodstream and be isolated from peripheral blood, exosomes and exosomal microRNAs can emerge as promising minimally invasive biomarkers and therapeutic targets for radiation-induced targeted and non-targeted effects in the CNS.

Colorimetric determination of lead(II) or mercury(II) based on target induced switching of the enzyme-like activity of metallothionein-stabilized copper nanoclusters.

It is shown that metallothionein-stabilized copper nanoclusters (MT-CuNCs) display catalase-like activity. In the presence of either lead(II) or mercury(II), the catalase-like activity is converted to a peroxidase-like activity. On addition of Pb(II) or Hg(II), the inhibitory effect of MT-CuNCs on the chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) with H2O2 is weakened. On the other hand, the catalytic effect of the nanoclusters on the chromogenic reaction is increased. The system MT-CuNCs-Pb(II)/Hg(II) exhibits high affinity for the substrates TMB and H2O2. Their catalytic behavior follows Michaelis-Menten kinetics. Based on these findings, a method was developed for visual detection (via the blue coloration formed) and spectrophotometric determination (at 450 nm) of Pb(II) and Hg(II). The linear range for Pb(II) extends from 0.7 to 96 µM, and the linear ranges for Hg(II) from 97 nM to 2.3 µM and from 3.1 µM to 15.6 µM. The detection limits are 142 nM for Pb(II) and 43.8 nM for Hg(II). Graphical abstract Metallothionein-stabilized copper nanoclusters (MT-CuNCs) display catalase-like activity. On addition of Pb(II) or Hg(II), the catalase-like activity is converted to a peroxidase-like activity. The latter catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2.

Detection of radon with biosensors based on the lead(II)-induced conformational change of aptamer HTG and malachite green fluorescence probe.

The aim of this paper is to assemble a new biosensor for detecting the accumulated radon dose in the environment to achieve rapid monitor of radon. Based on the correlation between radon and its stable decay daughter 210Pb, a biosensor using the lead-induced specific aptamer HTG conformational changes, and the organic dye malachite green (MG) as a fluorescent probe was assembled. In these studies, we explored a novel, sensitive, label-free, fluorescence biosensing method for the detection of both radon and lead. The fluorescence intensity difference has a linear relationship with Pb2+ and the accumulated radon concentration from 6.87 × 103 Bq·h/m3 to 3.49 × 105 Bq·h/m3. The lead and radon detection limits of this method are 6.7 nmol/L and 2.06 × 103 Bq·h/m3, respectively. The student's t-test results indicated that the new method was reliable and stable. The detection method is sensitive, accurate, easy to operate, has a wide linear range and is highly selective. In the sampling and determination processes of radon, the radiation harm to human health can be effectively avoided.

Amplified colorimetric sensor for detecting radon by its daughter lead based on the free-fixed auto-assembly structure of Duplex-hemin/G-quadruplex.

A novel signal amplification strategy based on a Pb2+-dependent DNAzyme is proposed for detecting Pb2+ and radon through Pb2+-induced DNAzyme cleavage and the auto-assembly of a duplex-hemin/G-quadruplex with two loop-stem structures and enzyme-mimicking catalytic activity. First, the Pb2+-specific DNAzyme cleaves a primer sequence, which induces assembly of the hairpin probe Hp1/Hp2 into a double helix structure. Subsequently, a G-quadruplex forms after the insertion of hemin into the free G-rich sequences; this G-quadruplex possesses the catalytic activity of horseradish peroxidase and changes colorless TMB to its deeply colored oxidized state. lead-dependent DNAzymes were constantly sheared by Pb2+, and the free primer strands were continuously assembled into double chains by hybridization with hairpin probes, providing amplification for the detection of lead (II) and radon. Under the optimum conditions, there was a good linear relationship between ΔA and the lead concentration for Pb2+ concentrations ranging from 2.58 to 18 nM, and the detection limit was 0.77 nM. Analysis of actual samples indicated that when the radon concentration was in the range of 5.41 × 103- 1.65 × 105 Bq·h/m3, the radon concentration and the absorbance were linearly correlated with a detection limit of 1.62 × 103 Bq·h/m3. During the process of radon sampling and detection, radiation damage from the radioactive gas radon can be avoided. In this study, the primer dissociated by the DNAzyme was in a free state. Compared with the fixed-state primer chain, this system will be more convenient for the biological analysis of ultratrace metal ions. Therefore, this strategy has good application prospects for biosensors and is expected to become a novel platform for the amplification and detection of metal ion signals.

Novel and label-free colorimetric detection of radon using AuNPs and lead(II)-induced GR5 DNAzyme-based amplification strategy.

Radioactive radon decays into a stable daughter product, 210Pb, which was used as the detection target to determine the radon radiation dose in a new technique. Pb2+ triggers DNAzyme to cleave a molecular beacon (MB), resulting in the stem-loop structure opening and forming two single DNA strands (ssDNA). The ssDNA binds to unmodified gold nanoparticles and effectively prevents their aggregation in a salt solution. The detached enzyme strands continue to complement the remaining MB to amplify the response signal. The method proposed in this study exhibited a good linear relationship for Pb2+ and radon concentrations in the range of 6.22 × 102-1.02 × 105 Bq h/m3 with a detection limit of 186.48 Bq h/m3 using an ultraviolet-visible spectrometer. In practical applications, this sensitive method can avoid radioactive damage in field testing, and the detection limit meets the national standard in China. Importantly, this simple, highly sensitive strategy uses simple equipment and has a strong anti-interference ability. Graphical abstract.

A novel detection of radon based on its decay product inducing conformational changes of an aptamer probe.

This study proposes a novel method for the detection of inert gas radon using a label-free, specific, fluorescence-sensing aptamer in the context of PW17-OG system. This method utilizes the cyanine dye OliGreen (OG) as a signal reactor and the aptamer PW17 as a fluorescent identification probe. When OG integrates into the free curling PW17, a strong fluorescence signal is generated. After radon decays, the long lived naturally occurring radon progeny Pb being disposed and introduced to the system. Lead ions induce PW17 to form a stable G-quadruplex, thereby inhibiting the interaction between OG and PW17 and resulting in a reduction of the fluorescence intensity. The fluorescence intensity show a good linear relationship with lead ion and the radon concentration (D), thereinto, We fitted linear regression of radon concentration in the range of 0.92-4.22 (×10(4) Bqhm(-3)) to receive a good relationship between ΔF and the concentration of radon with the detection limit of 1963 Bqhm(-3). This method has been successfully applied for detecting standard cumulative concentration of radon and the detection limit reached the national standard of China. This sensitive method can exclude radiation damage in field testing, furthermore, it explores a new field in biological analysis using an aptamer to detected inorganic, gaseous, and radioactive materials.

A new method for determining the absorbed dose in a radiation field by using a thiamine hydrochloride aqueous solution.

This research investigated the ionizing radiation effect on thiamine hydrochloride (TH) and its usability as an irradiation dosimeter. The fundamental principle is to determine the concentration variations of TH solutions with high-performance liquid chromatography (HPLC) after exposing to γ-rays. The decreasing peak area of TH in the HPLC chromatogram forms a linear relationship with the rising radiation dose. We investigated the characteristics and suitable application range of the TH as a new radiation dosimeter. The influence factors and mechanism of the reaction induced by radiation were also discussed. According to the correlation between the concentration and the radiation dose, 0.3 g/L of a TH solution is suitable for the 0.1-10 kGy dose range, and 2 g/L is appropriate for 0.1-20 kGy. The easy availability and the simple, but stable, chemical structure of thiamine makes it a potential candidate for radiation dose research. Also, the preparation proceeding for sampling is easy, and the result can be automatic monitored by liquid chromatography.