A Bifunctional-Blocker-Aided Hybridization Chain Reaction Lighting-Up Self-calibrating Nanocluster Fluorescence for Reliable Nucleic Acid Detection

In this work,we proposed a ratiometric silver nanoclusters(AgNCs)fluorescent assay by designing a bifunctional-blockeraided hybridization chain reaction(HCR).Hairpin probe 1(HP1)containing two special DNA fragments(5′-CAC CGC T-3′and 5′-ATT TGC CTT TTG GGG ACG GATA-3′)at two terminals creates a red-emitting AgNC nucleation sequence(rNS,5′-CAC CGC TAT TTG CCT TTT GGG GAC GGATA-3′).We found that the presence of a toehold fragment(5′-TGCCC-3′)in HP1 could silence the rNS.Upon the addition of a target nucleic acid,HCR of HP1 and hairpin probe 2(HP2)could be initiated,resulting in the formation of long chain of DNA duplexes with multibranched rNS.As the toehold fragment in HP1participated in generating duplexes,a strong emission of rNS-templated AgNCs was observed at 670 nm.More significantly,a bifunctional blocker was introduced not only to reduce the background red-emitting fluorescence but also to play as an internal green-emitting AgNCs nucleation sequence.On the one hand,the blocker could increase the signal-to-noise-ratio of the constructed biosensor,and on the other hand,the blocker also helped to prepare ratiometric HCR-AgNCs assay with self-calibrating ability to strengthen its reproducibility.Compared with the traditional HCR-AgNCs sensors,the developed ratiometric assay based on the bifunctional-blocker-aided HCR has higher reliability,which is important for the fabrication of biosensors in various fields for practical biosensing applications.

A Bright Nitrogen-doped-Carbon-Dots based Fluorescent Biosensor for Selective Detection of Copper Ions

In this work,a novel fluorescent biosensor has been constructed for rapid detection of Cu(Ⅱ)via the interaction between the fluorophore groups on the surface of nitrogen-doped-carbon-dots(N-CDs)and·OH produced from the catalytic reaction between Cu(Ⅱ)and cysteine(Cys).Specifically,Cu(Ⅱ)can catalyze the oxidation of Cys to form cystine(Cys–Cys)and hydrogen peroxide(H_(2)O_(2)),and Cu(Ⅱ)can also catalyze the decomposition of H_(2)O_(2)to produce hydroxyl radicals(·OH)by the Fenton-like reaction.·OH can oxidize and destroy the surface structure of N-CDs,resulting in the fluorescence quenching of the N-CDs.Under the optimal experimental conditions,the linear range of Cu(Ⅱ)is determined to be 0.05–25μmol L_(-1,),and the limit of detection is 23 nmol L^(-1)with the limit of quantitation of 77 nmol L^(-1).Besides,some characterizations are provided to verify the proposed principle.The method has been successfully applied for the detection of Cu(Ⅱ)in human serum and environmental water with high sensitivity and higher selectivity.

Electrochemiluminescence Sensor for Cancer Cell Detection Based on H_(2)O_(2)-Triggered Stimulus Response System

A H_(2)O_(2)-triggered stimulus response electrochemiluminescence(ECL)sensor for sensitive detection of cancer cells using mesoporous silica nanoparticles(MSNs)has been proposed.ECL signal-generating molecules(Ru(phen)32+)were encap-sulated into phenylboronic acid group-functionalized MSNs(PBA-MSNs)porous and capped by polyhydroxy functioned Au nanoparticles(AuNPs)through the interaction of carbohydrate-boronic acid first.Brunauer-Emmett-Teller(BET)and transmission electron microscopy(TEM)were applied to characterize the materials.The proposed controlled release sensing platform shows approximately no leakage from the mesoporrs of MSNs after a long time of storage.Cancer cells are initially incubated with the functionalized MSNs and then treated with ascorbic acid to endogenously produce H_(2)O_(2).Arylboronic esters in the MSNs surface can be oxidized by the produced H_(2)O_(2),causing the releasing of the molecule from MSNs and increased ECL signal.This technique displayed an excellent measurement for the breast cancer cells’sensitive diagnosis with a detection limit of 208 cells/mL.The phenomenon suggests that this sensing platform may be potentially applied for breast cancer sensitive detection in the future.