Micro-competition system for Raman quantification of multiple glycans on intact cell surface

A micro-competition system integrated functionalized silica bubbles and Raman encoded nanoprobes to simultaneously assay multiple glycans on intact cell surfaces.

A micro-competition system is designed for simultaneous quantification of multiple glycans on intact cell surfaces, by integrating two-surface–one-molecule competition with surface enhanced Raman scattering (SERS). The micro-competition is achieved among multiple-polysaccharide-coated gold nanostars functionalized silica bubbles, target cells and gold nanoprobes at a micron scale. The gold nanoprobes are prepared by coating distinct Raman molecules and lectins on gold nanoparticles for signal resolution and glycan recognition, respectively. The silica bubble surface serves as an artificial glycan surface and a SERS substrate. Upon the competitive recognition of lectin to the corresponding glycan, the gold nanoprobes can be specifically captured by the bubbles and cells in a homogeneous system, and the amounts of different gold nanoprobes on bubbles are simultaneously detected by SERS to reflect the corresponding glycan amounts on the cell surface. This micro-competition system with multiple quantification capability provides a powerful tool for investigation of the complex glycan-related biological processes.

A peptide nucleic acid-functionalized carbon nitride nanosheet as a probe for in situ monitoring of intracellular microRNA

A novel probe for recognition of both cancer cells and intracellular microRNA (miRNA) is designed by functionalizing a carbon nitride nanosheet (f-CNNS) with a Cy5-labeled peptide nucleic acid (Cy5-PNA) and folate. The interaction between Cy5-PNA and CNNS quenches the fluorescence of Cy5, and the presence of folate endows the probe with good specificity to folate acceptor overexpressed cells. The probe can be specifically taken up by cancer cells with an incubation step. Upon the recognition of the PNA to complementary miRNA, the hybridization product is released from the CNNS surface, which leads to the fluorescence recovery and provides a specific method for sensing of miRNA. Thus, this probe can be used for cell-specific intracellular miRNA sensing with a confocal microscope. Using miRNA-18a as a target model, the dynamic changes of its expression level inside living cells can be monitored with the proposed method. This method possesses promising applications in the study of miRNA related bioprocesses and biomedicine.

Porphyrinic metal-organic framework as electrochemical probe for DNA sensing via triple-helix molecular switch

An electrochemical DNA sensor was developed based on the electrocatalysis of porphyrinic metal-organic framework (MOF) and triple-helix molecular switch for signal transduction. The streptavidin functionalized zirconium-porphyrin MOF (PCN-222@SA) was prepared as signal nanoprobe via covalent method and demonstrated high electrocatalysis for O2 reduction. Due to the large steric effect, the designed nanoprobe was blocked for the interaction with the biotin labeled triple-helix immobilized on the surface of glassy carbon electrode. In the presence of target DNA, the assistant DNA in triple-helix will hybridize with target DNA, resulting in the disassembly of triple-helix molecular. Consequently, the end biotin away from the electrode was ''activated'' for easy access to the signal nanoprobe, PCN-222@SA, on the basis of biotin-streptavidin biorecognition. The introduction of signal nanoprobe to a sensor surface led to a significantly amplified electrocatalytic current towards oxygen reduction. Integrating with DNA recycling amplification of Exonuclease III, the sensitivity of the biosensor was improved significantly with detection limit of 0.29 fM. Moreover, the present method has been successfully applied to detect DNA in complex serum matrix. This porphyrinic MOF-based strategy has promising application in the determination of various analytes for signal transduction and has great potential in bioassays.

Reversibly extracellular pH controlled cellular uptake and photothermal therapy by PEGylated mixed-charge gold nanostars

Shielding nanoparticles from nonspecific interactions with normal cells/tissues before they reach and after they leave tumors is crucial for the selective delivery of NPs into tumor cells. By utilizing the reversible protonation of weak electrolytic groups to pH changes, long-chain amine/carboxyl-terminated polyethylene glycol (PEG) decorated gold nanostars (GNSs) are designed, exhibiting reversible, significant, and sensitive response in cell affinity and therapeutic efficacy to the extracellular pH (pHe) gradient between normal tissues and tumors. This smart nanosystem shows good dispersity and unimpaired photothermal efficacy in complex bioenvironment at pH 6.4 and 7.4 even when their surface charge is neutral. One PEGylated mixed-charge GNSs with certain surface composition, GNS-N/C 4, exhibits high cell affinity and therapeutic efficacy at pH 6.4, and low affinity and almost "zero" damage to cells at pH 7.4. Remarkably, this significant and sensitive response in cell affinity and therapeutic efficacy is reversible as local pH alternated. In vivo, GNS-N/C 4 shows higher accumulation in tumors and improved photothermal therapeutic efficacy than pH-insensitive GNSs. This newly developed smart nanosystem, whose cell affinity reversibly transforms in response to pHe gradient with unimpaired biostability, provides a novel effective means of tumor-selective therapy.

High-throughput imaging assay of multiple proteins via target-induced DNA assembly and cleavage

This work integrates target-induced DNA assembly and cleavage on a DNA chip to design a versatile imaging strategy as an assay for multiple proteins. The DNA assembly is achieved via immunological recognition to trigger the proximity hybridization for releasing a DNA sequence, which then hybridizes with FITC-DNA1 immobilized on the chip to induce the enzymatic cleavage of DNA1 and thus decrease the signals. The signal readout is performed with both fluorescent imaging of the left FITC and chemiluminescent (CL) imaging, by adding peroxidase labelled anti-FITC in assembly solution and CL substrates to produce CL emission. This one-step incubation can be completed in 30 min. The imaging method shows wide detection ranges and detection limits down to pg mL-1 for the simultaneous detection of 4 protein biomarkers. This high-throughput strategy with good practicability can be easily extended to other protein analytes, providing a powerful protocol for protein analysis and clinical diagnosis.

In situ activation and monitoring of the evolution of the intracellular caspase family

An intergrated nano-platform is designed to achieve in situ activation, monitoring and signal feedback of the caspase family evolution from upstream to downstream.

The evolution of the intracellular caspase family is crucial in cell apoptosis. To evaluate this process, a universal platform of in situ activation and monitoring of the evolution of intracellular caspase is designed. Using well-known gold nanostructure as a model of both nanocarrier and matter inducing the cell apoptosis for photothermal therapy, a nanoprobe is prepared by assembly of two kinds of dye-labelled peptides specific to upstream caspase-9 and downstream caspase-3 as the signal switch, and folic acid as a targeting moiety. The energy transfer from dyes to the gold nanocarrier at two surface plasmon resonance absorption wavelengths leads to their fluorescence quenching. Upon endocytosis of the nanoprobe to perform the therapy against cancer cells, the peptides are successively cleaved by intracellular caspase activation with the evolution from upstream to downstream, which lights up the fluorescence of the dyes sequentially, and can be used to quantify both caspase-9 and caspase-3 activities in cancer cells and to monitor their evolution in living mice. The recovered fluorescence could also be used to assess therapeutic efficiency. This work provides a novel powerful tool for studying the evolution of the intracellular caspase family and elucidating the biological roles of caspases in cancer cell apoptosis.

Strand displacement activated peroxidase activity of hemin for fluorescent DNA sensing

The toehold-mediated DNA strand displacement was utilized to regulate the catalytic activity of the peroxidase mimic hemin and design a fluorescent DNA sensing method with high specificity.

A novel and versatile nanomachine for ultrasensitive and specific detection of microRNAs based on molecular beacon initiated strand displacement amplification coupled with catalytic hairpin assembly with DNAzyme formation

A simple and versatile strategy for ultrasensitive and specific detection of microRNAs based on strand displacement amplification and catalytic hairpin assembly.

A new mode for highly sensitive and specific detection of DNA based on exonuclease III-assisted target recycling amplification and mismatched catalytic hairpin assembly

Schematic representation of the designed strategy for target DNA detection.

A porphyrin photosensitized metal–organic framework for cancer cell apoptosis and caspase responsive theranostics

A photosensitized and caspase-responsive nanoprobe was designed with metal–organic frameworks for cancer therapy andin situtherapeutic monitoring.

Supramolecular interaction of labetalol with cucurbit[7]uril for its sensitive fluorescence detection

The supramolecular interaction between labetalol and cucurbit[7]uril is studied for simple and sensitive fluorescence detection of labetalol through its competitive interaction with berberine, palmatine or coptisine for occupancy of the cucurbit[7]uril cavity.

Porphyrin functionalized porous carbon derived from metal–organic framework as a biomimetic catalyst for electrochemical biosensing

A novel biomimetic catalyst was designed by the assembly of porphyrin on porous carbon derived from metal–organic frameworks for electrochemical biosensing.

An efficient polymeric micromotor doped with Pt nanoparticle@carbon nanotubes for complex bio-media

A highly efficient polymeric tubular micromotor doped with Pt nanoparticle@carbon nanotubes is fabricated by template-assisted electrochemical growth.

In situ generation of electron acceptor for photoelectrochemical biosensing via hemin-mediated catalytic reaction

A novel photoelectrochemical sensing strategy is designed for DNA detection on the basis of in situ generation of an electron acceptor via the catalytic reaction of hemin toward H2O2. The photoelectrochemical platform was established by sequential assembly of near-infrared CdTe quantum dots, capture DNA, and a hemin-labeled DNA probe to form a triple-helix molecular beacon (THMB) structure on an indium tin oxide electrode. According to the highly catalytic capacity of hemin toward H2O2, a photoelectrochemical mechanism was then proposed, in which the electron acceptor of O2 was in situ-generated on the electrode surface, leading to the enhancement of the photocurrent response. The utilization of CdTe QDs can extend the absorption edge to the near-infrared band, resulting in an increase in the light-to-electricity efficiency. After introducing target DNA, the THMB structure is disassembled and releases hemin and, thus, quenches the photocurrent. Under optimized conditions, this biosensor shows high sensitivity with a linear range from 1 to 1000 pM and detection limit of 0.8 pM. Moreover, it exhibits good performance of excellent selectivity, high stability, and acceptable fabrication reproducibility. This present strategy opens an alternative avenue for photoelectrochemical signal transduction and expands the applications of hemin-based materials in photoelectrochemical biosensing and clinical diagnosis.

Catalytic activity of a dual-hemin labelled oligonucleotide: conformational dependence and fluorescent DNA sensing

The conformation-dependent peroxidase activity of a dual-hemin labelled oligonucleotide was identified and conveniently utilized to design a sensitive homogenous fluorescent method for DNA sensing.

Label-free triple-helix aptamer as sensing platform for "signal-on" fluorescent detection of thrombin

The design of a label-free aptamer for separation of recognition sequence from signal reporter is significant to ensure the high-efficiency affinity between aptamer and target. This work develops a label-free triple-helix aptamer (THA) as sensing platform for "signal-on" fluorescent detection of thrombin. THA was composed of aptamer sequence and help DNA 1 (H1), which contained the complementary sequence of hexachloro-fluorescein (HEX) labeled help DNA 2 (H2). The specific recognition event between aptamer and thrombin triggered the dismission of THA to release H1. The released H1 then reacted with the signal probe of H2/graphene oxide (GO) nanocomposite to form H1-H2 duplex, leading to the fluorescence recovery of H2 due to the detachment of H1-H2 duplex from the surface of GO. With employment of THA as a signal transducer and GO as a "superquencher", this method shows a sensitive response to thrombin with a wide concentration range from 5 to 1200 nM. The limit of detection is 1.8 nM (S/N=3) with excellent selectivity. Considering the universality of THA, the proposed aptasensor would provide a platform for homogeneous fluorescent detection of a wide range of analytes.

Nitrogen-doped porous carbon derived from metal-organic gel for electrochemical analysis of heavy-metal ion

A nitrogen-doped porous carbon material (N@MOG-C) was prepared by simple pyrolysis of polypyrrole-doped Al-based metal-organic gel (PPy@MOG) at 800 °C. The N@MOG-C possessed a uniform three-dimensional (3-D) interconnected mesoporous structure with a high surface area of 1542.6 m(2) g(-1) and a large pore volume of 0.76 cm(3) g(-1). By using an ionic liquid (IL) to immobilize N@MOG-C on electrode surface, the N@MOG-C was further used for sensitive detection of heavy metal ion. The doping of nitrogen-endowed N@MOG-C with faster electron transfer kinetics than other carbon materials such as MOG-C, multiwalled carbon nanotubes, and graphene. The N@MOG-C-modified electrode showed a high effective area, because of the porous structure. Under optimized conditions, the N@MOG-C-based sensor could detect Cd ions present in concentrations of 0.025-5 μM, with a detection limit of 2.2 nM. The mesoporous structure, fast electron transfer ability, and simple and green synthesis of N@MOG-C made it a promising electrode material for practical applications in heavy-metal-ion sensing.