ECL cytosensor for sensitive and label-free detection of circulating tumor cells based on hierarchical flower-like gold microstructures.

The development of sensitive and efficient cell sensing strategies to detect circulating tumor cells (CTCs) in peripheral blood is crucial for the early diagnosis and prognostic assessment of cancer clinical treatment. Herein, an array of hierarchical flower-like gold microstructures (HFGMs) with anisotropic nanotips was synthesized by a simple electrodeposition method and used as a capture substrate to construct an ECL cytosensor based on the specific recognition of target cells by aptamers. The complex topography of the HFGMs array not only catalyzed the enhancement of ECL signals, but also induced the cells to generate more filopodia, improving the capture efficiency and shortening the capture time. The effect of topographic roughness on cell growth and adhesion propensity was also investigated, while the cell capture efficiency was proposed to be an important indicator affecting the accuracy of the ECL cytosensor. In addition, the capture of cells on the electrode surface increased the steric hindrance, which caused ECL signal changes in the Ru(bpy)32+ and TPrA system, realizing the quantitative detection of MCF-7 cells. The detection range of the sensor was from 102 to 106 cells mL-1 and the detection limit was 18 cells mL-1. The proposed detection method avoids the process of separation, labeling and counting, which has great potential for sensitive detection in clinical applications.

Dark-field imaging and fluorescence dual-mode detection of microRNA-21 in living cells by core-satellite plasmonic nanoprobes.

The in situ precise quantification and simultaneous imaging of low abundance microRNAs (miRNAs) within living cells is critical for cancer diagnosis, yet it remains a significant challenge. Leveraging the excellent sensitivity and spatiotemporal resolution of dark-field microscopy (DFM) and fluorescence imaging, we have successfully devised a novel detection approach using dual-signal reporter probes (DSRPs). These probes allow for highly sensitive detection of miRNA-21 in living cells via toehold-mediated strand displacement cascades. The DSRPs were constructed by Au nanoparticles and Ag nanoclusters core-satellite nanostructures. After the recognition of miRNA-21, the strand displacement cascades were triggered, inducing the disassembly of the Au/Ag core-satellite nanostructure with apparent scattering intensity decrease and peak wavelength shifts. Additionally, the fluorescence of Ag clusters could be recovered and further enhanced when in close proximity to specific guanine-rich strands. The dual-signal response capability enables the accurate detection of miRNA-21 from 1 fM to 1 nM, with a limit of detection reached 0.75 fM. DFM and fluorescent imaging of living cells efficiently confirms the applicable detection of miRNA-21 in complex detection media. The biosensor based on DSRPs represents a promising nanoplatform for visual monitoring and imaging of biomolecules in living cells, even at the single particle level.

A Mitochondria-Targeted NIR-II Molecule Fluorophore for Precise Cancer Phototheranostics.

Subcellular organelle mitochondria are becoming a key player and a driver of cancer. Mitochondrial targeting phototheranostics has attracted increasing attention for precise cancer therapy. However, those phototheranostic systems still face great challenges, including complex and multiple components, light scattering, and insufficient therapeutic efficacy. Herein, a molecular fluorophore IR-TPP-1100 was tactfully designed by molecular engineering for mitochondria-targeted fluorescence imaging-guided phototherapy in the second near-infrared window (NIR-II). IR-TPP-1100 not only exhibited prominent photophysical properties and high photothermal conversion efficiency but also achieved excellent mitochondria-targeting ability. The mitochondria-targeting IR-TPP-1100 enabled NIR-II fluorescence and photoacoustic dual-modality imaging of mitochondria at the organism level. Moreover, it integrated photothermal and photodynamic therapy, obtaining remarkable tumor therapeutic efficacy by inducing mitochondrial apoptosis. These results indicate that IR-TPP-1100 has great potential for precise cancer therapy and provides a promising strategy for developing mitochondria-targeting NIR-II phototheranostic agents.

Robust nontarget DNA-triggered catalytic hairpin assembly amplification strategy for the improved sensing of microRNA in complex biological matrices.

A simple but robust fluorescence strategy based on a nontarget DNA-triggered catalytic hairpin assembly (CHA) was constructed to probe microRNA-21 (miR-21). A short ssDNA rather than degradable target miRNA was employed as an initiator. Two molecular beacons needed to assist the CHA process were simplified to avoid unfavorable nonspecific interactions. In the presence of the target, the initiator was released from a partially duplex and triggered the cyclic CHA reaction, resulting in a significantly amplified optical readout. A wide linear range from 0.1 pM to 1000 pM for the sensing of miR-21 in buffer was achieved with a low detection limit of 0.76 pM. Fortunately, this strategy demonstrated an obviously improved performance for miR-21 detection in diluted serum. The fluorescence signals were enhanced remarkably and the sensitivity was further improved to 0.12 pM in 10% serum. The stability for miR-21 quantification and the capability for the analysis of single nucleotide polymorphisms (SNPs) were also improved greatly. More importantly, the biosensor could be applied to image miR-21 in different living tumor cells with high resolution, illustrating its promising potential for the assay of miRNAs in various complex situations for early-stage disease diagnosis and biological studies in cells.

A multi-stage group decision making approach for sustainable supplier selection based on probabilistic linguistic time-ordered incentive operator.

This study proposes a novel multi-stage multi-attribute group decision making method under a probabilistic linguistic environment considering the development state and trend of alternatives. First, the probabilistic linguistic term set (PLTS) is used by decision makers (DMs) to describe qualitative evaluation information. Subsequently, the weights of DMs for different attributes in different periods are determined by the credibility degree, which is combined with the hesitancy degree and the similarity degree. The evaluations of different DMs for alternatives and the evaluations of DMs' intentions to reward or punish are then aggregated. Later, the trend change level and the trend change stability of alternatives are measured through the means of reward and punishment incentives. Additionally, the probabilistic linguistic time-ordered incentive operator is proposed to aggregate the development state evaluation information and development trend evaluation information in different periods, and alternatives are prioritized by the extended TOPSIS method in the probabilistic linguistic environment. Finally, the practical use of the proposed decision framework is validated by using a sustainable supplier selection problem, and the effectiveness and the applicability of the framework are discussed through comparative analysis. The results show that the proposed approach can select suitable sustainable suppliers by considering their development state and trend in multiple stages.

Self-delivery of metal-coordinated NIR-II nanoadjuvants for multimodal imaging-guided photothermal-chemodynamic amplified immunotherapy.

The effectiveness of phototheranostics induced immunotherapy is still hampered by limited light penetration depth, the complex immunosuppressive tumor microenvironment (TME) and the low efficiency of immunomodulator drug delivery. Herein, self-delivery and TME responsive NIR-II phototheranostic nanoadjuvants (NAs) were fabricated to suppress the growth and metastasis of melanoma through the integration of photothermal-chemodynamic therapy (PTT-CDT) and immune remodeling. The NAs were constructed by the self-assembly of ultrasmall NIR-II semiconducting polymer dots and the toll-like receptor agonist resiquimod (R848) utilizing manganese ions (Mn2+) as coordination nodes. Under acidic TME, the NAs responsively disintegrated and released therapeutic components, which enable NIR-II fluorescence/photoacoustic/magnetic resonance imaging-guided tumor PTT-CDT. Moreover, the synergistic treatment of PTT-CDT could induce significant tumor immunogenic cell death and evoke highly efficacious cancer immunosurveillance. The released R848 stimulated the maturation of dendritic cells, which both amplified the antitumor immune response by modulating and remodeling the TME. The NAs present a promising integration strategy of polymer dot-metal ion coordination and immune adjuvants for precise diagnosis and amplified anti-tumor immunotherapy against deep-seated tumors. STATEMENT OF SIGNIFICANCE: The efficiency of phototheranostics induced immunotherapy is still limited by insufficient light penetration depth, low immune response and the complex immunosuppressive tumor microenvironment (TME). In order to improve the efficacy of immunotherapy, self-delivery NIR-II phototheranostic nanoadjuvants (PMR NAs) were successfully fabricated via the facile coordination self-assembly of ultra-small NIR-II semiconducting polymer dots and toll-like receptor agonist resiquimod (R848) utilizing manganese ions (Mn2+) as coordination nodes. PMR NAs not only enable TME responsive cargo release and NIR-II fluorescence/photoacoustic/magnetic resonance imaging mediated precise localization of tumors, but also achieve synergistic photothermal-chemodynamic therapy, evoking an effective anti-tumor immune response by ICD effect. The responsively released R848 could further amplify the efficiency of immunotherapy by reversing and remodeling the immunosuppressive tumor microenvironment, thereby effectively inhibiting tumor growth and lung metastasis.

An Activatable Phototheranostic Nanoplatform for Tumor Specific NIR-II Fluorescence Imaging and Synergistic NIR-II Photothermal-Chemodynamic Therapy.

The phototheranostics in the second near-infrared window (NIR-II) have proven to be promising for the precise cancer theranostics. However, the non-responsive and "always on" imaging mode lacks the selectivity, leading to the poor diagnosis specificity. Herein, a tumor microenvironment (TME) activated NIR-II phototheranostic nanoplatform (Ag2 S-Fe(III)-DBZ Pdots, AFD NPs) is designed based on the principle of Förster resonance energy transfer (FRET). The AFD NPs are fabricated through self-assembly of Ag2 S QDs (NIR-II fluorescence probe) and ultra-small semiconductor polymer dots (DBZ Pdots, NIR-II fluorescence quencher) utilizing Fe(III) as coordination nodes. In normal tissues, the AFD NPs maintain in "off" state, due to the FRET between Ag2 S QDs and DBZ Pdots. However, the NIR-II fluorescence signal of AFD NPs can be rapidly "turn on" by the overexpressed GSH in tumor tissues, achieving a superior tumor-to-normal tissue (T/NT) signal ratio. Moreover, the released Pdots and reduced Fe(II) ions provide NIR-II photothermal therapy (PTT) and chemodynamic therapy (CDT), respectively. The GSH depletion and NIR-II PTT effect further aggravate CDT mediated oxidative damage toward tumors, achieving the synergistic anti-tumor therapeutic effect. The work provides a promising strategy for the development of TME activated NIR-II phototheranostic nanoprobes.

Near-infrared-II light excitation thermosensitive liposomes for photoacoustic imaging-guided enhanced photothermal-chemo synergistic tumor therapy.

Despite the great success of photothermal therapy (PTT), it still suffers from many obstacles, such as the limited penetration depth of light, thermoresistance of tumors, and limitations of mono-therapeutic modalities. Herein, second near-infrared (NIR-II, 1064 nm) light excitation thermosensitive liposomes (DG@TLs) were fabricated for photoacoustic imaging (PAI) guided enhanced PTT-chemotherapy. DG@TLs were constructed by encapsulating NIR-II light excitation semiconducting polymers into liposomes composed of phase change materials (PCMs), along with gambogic acid (GA) with chemotherapeutic and heat shock protein inhibition effects. Under 1064 nm laser irradiation, DG@TLs exhibited superior NIR-II PAI and PTT performances with deep tissue penetration while triggering the thermoresponsive release of GA based on the phase transition of PCMs from solid to liquid. The released GA could enhance the NIR-II PTT efficacy by inhibiting the activity of HSP90, reducing the thermoresistance of tumors, exhibiting significant chemotherapeutic effects, and achieving synergistic anti-tumor efficiency. This work provides a new strategy for achieving on-demand drug release and effective theranostics in deep-seated tumor regions.

NIR-II Excitation Phototheranostic Nanomedicine for Fluorescence/Photoacoustic Tumor Imaging and Targeted Photothermal-Photonic Thermodynamic Therapy.

The success of phototheranostics is hampered by some intrinsic defects, such as limited light penetration depth, heat resistance of tumor cells to photothermal therapy (PTT) induced by heat shock protein (HSP) and stress resistance against photodynamic therapy (PDT) caused by hypoxia microenvironment of tumor. Herein, a second near infrared (NIR-II) light excitation phototheranostic nanomedicine has been fabricated by integrating the semiconducting polymer, azo compound, and HSP inhibitor into a thermosensitive liposome, followed by modification with targeting aptamer, forming Lip(PTQ/GA/AIPH) for multimodal phototheranostics of triple-negative breast cancer (TNBC). The phototheranostic nanomedicine provides tumor targeting NIR-II fluorescence and photoacoustic dual-modal imaging, as well as NIR-II PTT. The released HSP inhibitor can effectively inhibit the activity of HSP for enhanced NIR-II PTT. Moreover, azo compound can be decomposed by the NIR-II photothermal activation, generating cytotoxic free radicals and realizing oxygen-irrelevant photonic thermodynamic therapy (PTDT) effects. Under the NIR-II laser irradiation, NIR-II fluorescence/photoacoustic dual-modal imaging guided enhanced NIR-II PTT and PTDT by Lip(PTQ/GA/AIPH), can achieve precise diagnosis and effective suppression of deep-seated TNBC with negligible side effects. This work develops a promising NIR-II excitation phototheranostic nanomedicine for spatiotemporally specific diagnosis and combination therapy of TNBC.

NIR-II fluorescence imaging guided tumor-specific NIR-II photothermal therapy enhanced by starvation mediated thermal sensitization strategy.

Photothermal therapy (PTT) is hampered by limited light penetration depth and cell thermoresistance induced by over-expressed heat shock proteins (HSPs). Herein, we proposed a tumor-specific enhanced NIR-II PTT through the starvation mediated thermal sensitization strategy. A semiconducting polymer with superior NIR-II fluorescence imaging (FI) performance and NIR-II PTT efficacy was synthesized and encapsulated into folate modified liposomes, together with a glycolysis inhibitor, 2-deoxy-d-glucose (2DG). Upon specifically targeting folate receptors and guidance of NIR-II FI, spatiotemporal 2DG release could be achieved by the trigger of NIR-II photothermal effect. The released 2DG could not only deplete the energy supply of tumor cells by inhibiting tumor anaerobic glycolysis, but also decrease the ATP levels and hamper the production of HSPs, ultimately enhancing the tumor thermal sensitivity toward PTT. Owing to the sensitization effect of 2DG, tumor cells with overexpressed folate receptors could be significantly damaged by NIR-II PTT with an enhanced therapeutic efficiency. The work provided a promising strategy for specific starvation/NIR-II PTT synergistic therapy towards tumors.

Injectable and Thermosensitive Liposomal Hydrogels for NIR-II Light-Triggered Photothermal-Chemo Therapy of Pancreatic Cancer.

An injectable hydrogel sustained drug release system could be a promising technique for in situ treatment. Herein, an injectable hydrogel was prepared for photothermal-chemo therapy of cancer based on the thermosensitive liposomal hydrogel (Lip-Gel). The Lip-Gel system was fabricated by encapsulation of the NIR-II photothermal agent (DPP-BTz) and chemotherapy drugs (GEM) in thermosensitive liposomes and then combined with hydrogel precursor solution. The hydrogel precursor was used as an injectable flowing solution at room temperature and transferred into a cross-linked gel structure at physiological temperature. After being injected into the tumor, DPP-BTz in the Lip-Gel system can generate heat under irradiation of 1064 nm laser, breaking the thermosensitive liposomes and releasing GEM to kill tumor cells. From the treatment results, the Lip-Gel system showed a significant antitumor effect through chemo-/photothermal therapy combination therapy triggered by the NIR-II laser. This work provides a useful scheme for the development of drug delivery and drug treatment directions for local cancer therapy.

Tumor Microenvironment-Responsive Fe(III)-Porphyrin Nanotheranostics for Tumor Imaging and Targeted Chemodynamic-Photodynamic Therapy.

The development of effective and safe tumor nanotheranostics remains a research imperative. Herein, tumor microenvironment (TME)-responsive Fe(III)-porphyrin (TCPP) coordination nanoparticles (FT@HA NPs) were prepared using a simple one-pot method followed by modification with hyaluronic acid (HA). FT@HA NPs specifically accumulated in CD44 receptor-overexpressed tumor tissues through the targeting property of HA and upon endocytosis by tumor cells. After cell internalization, intracellular acidic microenvironments and high levels of glutathione (GSH) triggered the rapid decomposition of FT@HA NPs to release free TCPP molecules and Fe(III) ions. The released Fe(III) ions could trigger GSH depletion and Fenton reaction, activating chemodynamic therapy (CDT). Meanwhile, the fluorescence and photodynamic effects of the TCPP could be also activated, achieving controlled reactive oxygen species (ROS) generation and avoiding side effects on normal tissues. Moreover, the rapid consumption of GSH further enhanced the efficacy of CDT and photodynamic therapy (PDT). The in vivo experiments further demonstrated that the antitumor effect of these nanotheranostics was significantly enhanced and that their toxicity and side effects against normal tissues were effectively suppressed. The FT@HA NPs can be applied for activated tumor combination therapy under the guidance of dual-mode imaging including fluorescence imaging and magnetic resonance imaging, providing an effective strategy for the design and preparation of TME-responsive multifunctional nanotheranostics for precise tumor imaging and combination therapy.

Endogenous oxygen generating multifunctional theranostic nanoplatform for enhanced photodynamic-photothermal therapy and multimodal imaging.

Phototherapy, including photothermal therapy (PTT) and photodynamic therapy (PDT), has been considered as a noninvasive option for cancer therapy. However, insufficient penetration depth, tumor hypoxia, and a single treatment method severely limit the effectiveness of treatment. Methods: In this study, a multifunctional theranostic nanoplatform has been fabricated based on Au/Ag-MnO2 hollow nanospheres (AAM HNSs). The Au/Ag alloy HNSs were first synthesized by galvanic replacement reaction and then the MnO2 nanoparticles were deposited on the Au/Ag alloy HNSs by the reaction between Ag and permanganate (KMnO4), finally obtained the AAM HNSs. Then, SH-PEG was modified on the surface of AAM HNSs by the interaction of sulfhydryl and Au/Ag alloy, which improved the dispersibility and biocompatibility of the HNS. Next, the PDT photosensitizer Ce6 was loaded into AAM HNSs, benefiting from the hollow interior of the structure, and the AAM-Ce6 HNSs were obtained. Results: The AAM HNSs exhibit broad absorption at the near infrared (NIR) biological window and remarkable photothermal conversion ability in the NIR-II window. The MnO2 nanoparticles can catalyze endogenous H2O2 to generate O2 and enhance the therapeutic effect of PDT on tumor tissue. Simultaneously, MnO2 nanoparticles intelligently respond to the tumor microenvironment and degrade to release massive Mn2+ ions, which introduce magnetic resonance imaging (MRI) properties. When AAM-Ce6 HNSs are loaded with Ce6, the AAM-Ce6 HNSs can be used for triple-modal imaging (fluorescence/photoacoustic/magnetic resonance imaging, FL/PAI/MRI) guided combination tumor phototherapy (PTT/PDT). Conclusion: This multifunctional nanoplatform shows synergistic therapeutic efficacy better than any single therapy by achieving multimodal imaging guided cancer combination phototherapy, which are promising for the diagnosis and treatment of cancer.

Multifunctional Theranostic Liposomes Loaded with a Hypoxia-Activated Prodrug for Cascade-Activated Tumor Selective Combination Therapy.

Photodynamic therapy (PDT) is becoming a promising therapeutic regimen but is limited by the hypoxic microenvironment in solid tumors and the undesirable post-treatment phototoxicity side effects on normal tissues. To overcome these restrictions and enhance the antitumor therapeutic effect, near-infrared (NIR) light-activated, cancer cell-specific, hypoxia prodrug-loaded chlorin e6 liposomes were developed for tumor selective combination therapy guided by multimodal imaging. The photothermal agent indocyanine green (ICG) and hypoxia-activated prodrug tirapazamine (TPZ) were coencapsulated into the liposomes, followed by modification with cRGD and conjugation with GdIII to form ICG/TPZ@Ce6-GdIII theranostic liposomes (ITC-GdIII TLs). In the ITC-GdIII TLs, both the fluorescence and photodynamic effect of Ce6 were quenched by ICG via fluorescence resonance energy transfer. The ITC-GdIII TLs can effectively reach the tumor site through the enhanced permeability and retention effect as well as the cRGD-mediated active targeting ability. The fluorescence and photodynamic effect of Ce6 can be activated by the photothermal effect of ICG under NIR light. Upon subsequent irradiation with a 660 nm laser, the released Ce6 could kill cancer cells by generating cytotoxic singlet oxygen. Furthermore, the PDT process would induce hypoxia, which in turn activated the antitumor activity of the codelivered hypoxia-activated prodrug TPZ for a combination antitumor effect. The TLs could be utilized for multimodal imaging (fluorescence/photoacoustic/magnetic resonance imaging)-guided cascade-activated tumor inhibition with optimized therapeutic efficiency and minimized side effects, holding great potential for constructing intelligent nanotheranostics.

Multifunctional Thermosensitive Liposomes Based on Natural Phase-Change Material: Near-Infrared Light-Triggered Drug Release and Multimodal Imaging-Guided Cancer Combination Therapy.

Multifunctional theranostic nanoplatforms (NPs) in response to environment stimulations for on-demand drug release are highly desirable. Herein, the near-infrared (NIR)-absorbing dye, indocyanine green (ICG), and the antitumor drug, doxorubicin (DOX), were efficiently coencapsulated into the thermosensitive liposomes based on natural phase-change material. Folate and conjugated gadolinium (Gd) chelate-modified liposome shells enhance active targeting and magnetic resonance performance of the NPs while maintaining the size of the NPs. The ICG/DOX-loaded and gadolinium chelate conjugated temperature-sensitive liposome nanoplatforms (ID@TSL-Gd NPs) exhibited NIR-triggered drug release and prominent chemo-, photothermal, and photodynamic therapy properties. With the coencapsulated ICG, DOX, and the conjugated gadolinium chelates, the ID@TSL-Gd NPs can be used for triple-modal imaging (fluorescence/photoacoustic/magnetic resonance imaging)-guided combination tumor therapy (chemotherapy, photothermotherapy, and photodynamic therapy). After tail vein injection, the ID@TSL-Gd NPs accumulated effectively in subcutaneous HeLa tumor of mice. The tumor was effectively suppressed by accurate imaging-guided NIR-triggered phototherapy and chemotherapy, and no tumor regression and side effects were observed. In summary, the prepared ID@TSL-Gd NPs achieved multimodal imaging-guided cancer combination therapy, providing a promising platform for improving diagnosis and treatment of cancer.

Dynamic Single Molecular Rulers: Toward Quantitative Detection of MicroRNA-21 in Living Cells.

Innovative techniques to measure microRNA (miRNA) in vivo could greatly improve the fundamental understanding of complex cellular processes. Herein, we report a novel method for real-time, quantitative miRNA detection inside living cells based on core-satellite plasmon rulers (PRs). This approach allows for the statistical analysis of single hybridization event caused by target miRNA. We investigated hundreds of satellite leaving events and found that the distribution of the time range for one strand displacement event is miRNA concentration-dependent, which obeyed Poisson statistics. Probing several such PRs under dark-field microscopy would provide precise determination of miRNA in vitro and in living cells, without photobleaching or blinking of the fluorophores. We believe the simple and practical approach on the basis of dynamic PRs with single-molecule sensitivity combined with statistical analysis hold promising potential to visualize native nucleic acids with short sequence and low-abundance.

Multi-segmented CdS-Au nanorods for electrochemiluminescence bioanalysis.

In this study, we have developed a programmable electrochemiluminescence (ECL) system based on multi-segmented CdS-Au nanorod arrays with a sequential and highly tunable structure. The nanorod arrays were synthesized by an electrodeposition method using anodic aluminum oxide (AAO) as the template in which the Au and CdS segments were alternately electrodeposited. Compared to pure CdS nanorod arrays, multi-segmented CdS-Au nanorod arrays have showed a better ECL performance, which can be attributed to two factors: the favorable electron transfer and the surface plasma resonance (SPR) effect of the Au segment. On the one hand, we demonstrated that the Au segment can increase the charge transfer rate of CdS, which is beneficial for the ECL process because the generation of the radical state needs to accept electrons and then generate the radical state. On the other hand, the SPR of Au plasmon-induced local electromagnetic field enhancement can increase the radiative decay rate of CdS which makes the ECL process more efficient and lead to a higher ECL intensity. And also, an ECL sensor with multi-segmented CdS-Au nanorod arrays was constructed to detect prostate protein antigen (PSA). This study provides some basis for designing high-performance ECL emission materials and the construction of biosensors.

Exploration of the Kinetics of Toehold-Mediated Strand Displacement via Plasmon Rulers.

DNA/RNA strand displacement is one of the most fundamental reactions in DNA and RNA circuits and nanomachines. In this work, we reported an exploration of the dynamic process of the toehold-mediated strand displacement via core-satellite plasmon rulers at the single-molecule level. Applying plasmon rulers with unlimited lifetime, single-strand displacement triggered by the invader that resulted in stepwise leaving of satellite from the core was continuously monitored by changes of scattering signal for hours. The kinetics of strand displacement in vitro with three different toehold lengths have been investigated. Also, the study revealed the difference in the kinetics of strand displacement between DNA/RNA and DNA/DNA duplexes. For the kinetics study in vivo, influence from the surrounding medium has been evaluated using both phosphate buffer and cell lysate. Applying core-satellite plasmon rulers with high signal/noise ratio, kinetics study in living cells proceeded for the first time, which was not possible by conventional methods with a fluorescent reporter. The plasmon rulers, which are flexible, easily constructed, and robust, have proven to be effective tools in exploring the dynamical behaviors of biochemical reactions in vivo.

Plasmon-Enhanced Electrochemiluminescence for Nucleic Acid Detection Based on Gold Nanodendrites.

Gold nanodendrites (Au NDs) exhibit extremely strong electromagnetic field located around multiple tip branches due to a plasmon coupling effect. In this work, a novel LSPR-enhanced ECL emission from CdTe nanocrystals (NCs) by Au NDs for the detection of nucleic acid is reported. This system is composed of a thin film of CdTe NCs on glassy carbon electrode (GCE) as anodic ECL emitter and Au NDs as plasmon enhancer. DNA tetrahedron embedded with a stem-loop hairpin structure on one edge was applied as a switch to regulate the distance between CdTe NCs and Au NDs. At original state, the hairpin structure was closed and DNA tetrahedron played in a relaxed state on CdTe NCs film. The ECL emission of CdTe NCs was quenched by proximal Au NDs due to Förster resonance energy transfer (FRET), which was defined as the "turn-off" mode. After the complementary hybridization with target DNA, the hairpin structure changed to a rodlike configuration, resulting in an increased distance between CdTe NCs and Au NDs, and a significant enhancement of ECL induced by LSPR of Au NDs, which was defined as a "turn-on" mode. Along with the asymmetric modification method, a controllable and versatile pathway for modifying nanomaterials, the ECL sensor performed well with great stability and repeatability for nucleic acid detection in the range from 1.0 to 500 fM. Considering the high sensitivity and selectivity in the serum sample assay, this proposed method indicates a great potential for bioassay application.

Ultrasensitive MicroRNA Assay via Surface Plasmon Resonance Responses of Au@Ag Nanorods Etching.

Quantification of trace serum circulate microRNAs is extremely important in clinical diagnosis but remains a great challenge. Herein we developed an ultrasensitive platform for microRNA 141 (miR-141) detection based on a silver coated gold nanorods (Au@Ag NRs) etching process accompanied by surface plasmon resonance (SPR) shift. Both SPR absorption and scattering responses were monitored. Combined amplification cascades of catalyzed hairpin assembly (CHA) and hybridization chain reaction (HCR) with the sensitive SPR responses of plasmonic Au@Ag NRs, the proposed bioassay exhibited ultrahigh sensitivity toward miRNA-141 with dynamic range from 5.0 × 10-17 M to 1.0 × 10-11 M. With target concentration higher than 1.0 × 10-13 M, the color of the solution changed obviously that could be observed with naked eyes. Under dark-field microscopy observation of individual particle, a limit of detection down to 50 aM could be achieved. Owing to the superior sensitivity and selectivity, the proposed method was applied to detecting trace microRNA in serum. Similar SPR assays could be developed simply by redesigning the switching aptamer for the detections of other microRNAs or targets such as small molecule, DNA, or protein. Considering the convenient operation, good performance and simple observation modes of this method, it may have great potential in trace bioanalysis for clinical applications.