Gold Nanobipyramids as Dual-Functional Substrates for in Situ "Turn On" Analyzing Intracellular Telomerase Activity Based on Target-Triggered Plasmon-Enhanced Fluorescence

Simultaneous imaging of telomerase activity and protein tyrosine kinase 7 in living cells during epithelial-mesenchymal transformation via a near-infrared light-activatable nanoprobe

Exploring the relationship between key regulation molecules (such as telomerase and protein tyrosine kinase 7) during epithelial-mesenchymal transformation of cells is beneficial for studying malignant tumor metastasis. Fluorescence is usually used for real-time monitoring the distribution and expression of regulatory molecules in living cells. However, the recognition function of these classical nanoprobes is "always active" due to the absence of exogenous control, which leads to the amplification of both the background signal and the response signal, making it difficult to distinguish changes in biomolecule expression levels. To improve the fluorescence ratio between tumor and normal cells, we constructed near-infrared light-activatable nanoprobes by engineering the functional units of catalytic hairpin assembly and integrating upconversion luminescence nanoparticles. Under near-infrared light irradiation, the nanoparticles, serving as a near-infrared-to-ultraviolet light transducer, induced the photolysis of the photo-cleavable linkers sealed in hairpins. The recognition function of the nanoprobes can be controlled by near-infrared light, preventing them from recognizing the targets in non-irradiated regions. By employing the nanoprobes, we realized simultaneous imaging of two regulatory molecules in living cells and observed an increase in telomerase activity and a decrease in protein tyrosine kinase 7 expression during drug-induced epithelial-mesenchymal transformation. This work provides a promising method for revealing changes and relationships of regulatory molecules during tumor metastasis.

Aggregation-induced emission: Application in diagnosis and therapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a serious health issue due to its low early diagnosis rate, resistance to chemotherapy, and poor five-year survival rate. Therefore, it is crucial to explore novel diagnostic and therapeutic approaches tailored to the characteristics of HCC. Aggregation-induced emission (AIE) is a phenomenon where the luminescence of certain molecules, typically non-luminescent or weakly luminescent in solution, is significantly enhanced upon aggregation. AIE has been extensively applied in bioimaging, biosensors, and therapy. Fluorophore materials based on AIE (AIEgens) have a wide range of application scenarios and potential for clinical translation. This review focuses on recent advances in AIE-based strategies for diagnosing and treating HCC. First, the specific functional mechanism of AIE is described. Next, we summarize recent progress in the application of AIE for multimodal imaging, biosensor detection, and phototherapy. Finally, prospects and challenges for the AIE-based application in the diagnosis and therapy of HCC are discussed.

Face-to-face Assembly Strategy of Au Nanocubes: Induced Generation of Broad Hotspot Regions for SERS-Fluorescence Dual-Signal Detection of Intracellular miRNAs

While designing anisotropic noble metal nanoparticles (NPs) can enhance the signal intensity of Raman dyes, more sensitive surface-enhanced Raman scattering (SERS) probes can be designed by oriented self-assembly of noble metal nanomaterials into dimers or higher-order nanoclusters. In this study, we engineered a self-assembly strategy in living cells for real-time fluorescence and SERS dual-channel detection of intracellular microRNAs (miRNAs), using Mg2+-dependent 8-17E DNAzyme sequences as the driving motors, gold nanocubes (AuNCs) as the driver components, and three-branched double-stranded DNA as the linking tool. The assembly selects adenine in DNA as a reporter molecule, simplifying the labeling process of Raman reporter molecules and reducing the synthesis process. In addition, adenine is stably distributed between the faces of AuNCs and the wide hotspot region gives good reproducibility of the adenine SERS signal. In this strategy, the SERS channel was consistently stable and more sensitive compared to the fluorescence channel. Among them, the detection limit of the SERS channel was 2.1 pM and the coefficient of variation was 1.26% in the in vitro liquid phase and 1.49% in MCF-7 cells. The strategy successfully achieved accurate tracking and quantification of miRNA-21 in cancer cells, showing good reproducibility in complex samples as well as cells. The reported strategy provides ideas for exploring intracellular specific triggering of nanoparticles for precise control of self-assembly.

Plasmonic Gold Nanostar-Based Probes with Distance-Dependent Plasmon-Enhanced Fluorescence for Ultrasensitive DNA Methyltransferase Assay

The ultrasensitive DNA methyltransferase (Dam MTase) assay is of high significance for biomedical research and clinical diagnosis because of its profound effect on gene regulation. However, detection sensitivity is still limited by shortcomings, including photobleaching and weak signal intensities of conventional fluorophores at low concentrations. Plasmonic nanostructures with ultrastrong electromagnetic fields and fluorescence enhancement capability that can overcome these intrinsic defects hold great potential for ultrasensitive bioanalysis. Herein, a silica-coated gold nanostars (Au NSTs@SiO2)-based plasmon-enhanced fluorescence (PEF) probe with 20 "hot spots" was developed for ultrasensitive detection of Dam MTase. Here, the Dam Mtase assay was achieved by detecting the byproduct PPi of the rolling circle amplification reaction. It is worth noting that, benefiting from the excellent fluorescence enhancement capability of Au NSTs originating from their 20 "hot spots", the detection limit of Dam Mtase was reduced by nearly 105 times. Moreover, the proposed Au NST-based PEF probe enabled versatile evaluation of Dam MTase inhibitors as well as endogenous Dam MTase detection in GW5100 and JM110 Escherichia coli cell lysates, demonstrating its potential in biomedical analysis.

Single-molecule detection assisted by the target-triggered signal amplification strategy for ultrasensitive quantitative analysis of intracellular telomerase activity

We developed a multiplex single-molecule quantitative assay of intracellular telomerase that used target-triggered signal amplification to enhance sensitivity, substrate reaction to increase signal stability, and quantum dots to enhance signal-to-noise ratio, obtaining an LOD of 5 × 10-14 IU for intracellular telomerase and LOD of 3 cells for multiple cancer cells.

Fluorescence enhancement of surface plasmon coupled emission by Au nanobipyramids and its modulation effect on multi-wavelength radiation

Surface plasmon coupled emission (SPCE), a novel surface-enhanced fluorescence technique, can generate directional and amplified radiation by the intense interaction between fluorophores and surface plasmons (SPs) of metallic nanofilms. For plasmon-based optical systems, the strong interaction between localized and propagating SPs and "hot spot" structures show great potential to significantly improve the electromagnetic (EM) field and modulate optical properties. Au nanobipyramids (NBPs) with two sharp apexes to enhance and restrict the EM field were introduced through electrostatic adsorption to achieve a mediated fluorescence system, and the emission signal enhancement was realized by factors over 60 compared with the normal SPCE. It has been demonstrated that the intense EM field produced by the NBPs assembly is what triggered the unique enhancement of SPCE by Au NBPs, which effectively overcomes the inherent signal quenching of SPCE for ultrathin sample detection. This remarkable enhanced strategy offers the chance to improve the detection sensitivity for plasmon-based biosensing and detection systems, and expand the range of applications for SPCE in bioimaging with more comprehensive and detailed information acquisition. The enhancement efficiency for various emission wavelengths was investigated in light of the wavelength resolution of SPCE, and it was discovered that enhanced emission for multi-wavelength could be successfully detected through the different emission angles due to the angular displacement caused by wavelength change. Benefit from this, the Au NBP modulated SPCE system was employed for multi-wavelength simultaneous enhancement detection under a single collection angle, which could broaden the application of SPCE in simultaneous sensing and imaging for multi-analytes, and expected to be used for high throughput detection of multi-component analysis.

Fluorescence-Enhanced Dual-Driven "OR-AND" DNA Logic Platform for Accurate Cell Subtype Identification

Developing an endogenous stimuli-responsive and ultrasensitive DNA sensing platform that contains a logic gate biocomputation for precise cell subtype identification holds great potential for disease diagnosis and prognostic estimation. Herein, a fluorescence-enhanced "OR-AND" DNA logic platform dual-driven by intracellular apurinic/apyrimidinic endonuclease 1 (APE 1) or a DNA strand anchored on membrane protein Mucin 1 (MUC 1) for sensitive and accurate cell subtype identification was rationally designed. The recognition toehold of the traditional activated probe (TP) was restrained by introducing a blocking sequence containing an APE 1 cleavable site (AP-site) that can be either cleaved by APE 1 or replaced by Mk-apt, ensuring the "OR-AND" gated molecular imaging for cell subtype identification. It is worth noting that this "OR-AND" gated design can effectively avoid the missing logical computation caused by membrane protein heterogeneous spatial distribution as a single input. In addition, a benefit from the excellent plasmon-enhanced fluorescence (PEF) ability of Au NSTs is that the detection limit can be decreased by nearly 165 times. Based on this, not only different kinds of MCF-7, HepG2, and L02 cells, but also different breast cancer cell subtypes, including malignant MCF-7, metastatic MDA-MB-231, and nontumorigenic MCF-10A cells, can be accurately identified by the proposed "OR-AND" gated DNA logic platform, indicating the prospect of this simple and universal design in accurate cancer screening.

Recent Advances in Detection for Breast-Cancer-Derived Exosomes

Breast cancer is the most common malignant tumor in women, its incidence is secret, and more than half of the patients are diagnosed in the middle and advanced stages, so it is necessary to develop simple and efficient detection methods for breast cancer diagnosis to improve the survival rate and quality of life of breast cancer patients. Exosomes are extracellular vesicles secreted by all kinds of living cells, and play an important role in the occurrence and development of breast cancer and the formation of the tumor microenvironment. Exosomes, as biomarkers, are an important part of breast cancer fluid biopsy and have become ideal targets for the early diagnosis, curative effect evaluation, and clinical treatment of breast cancer. In this paper, several traditional exosome detection methods, including differential centrifugation and immunoaffinity capture, were summarized, focusing on the latest research progress in breast cancer exosome detection. It was summarized from the aspects of optics, electrochemistry, electrochemiluminescence and other aspects. This review is expected to provide valuable guidance for exosome detection of clinical breast cancer and the establishment of more reliable, efficient, simple and innovative methods for exosome detection of breast cancer in the future.

Spatiotemporally Controlled Ultrasensitive Molecular Imaging Using a DNA Computation-Mediated DNAzyme Platform

Programming ultrasensitive and stimuli-responsive DNAzyme-based probes that contain logic gate biocomputation hold great potential for precise molecular imaging. In this work, a DNA computation-mediated DNAzyme platform that can be activated by 808 nm NIR light and target c-MYC was designed for spatiotemporally controlled ultrasensitive AND-gated molecular imaging. Particularly, the sensing and recognition function of the traditional DNAzyme platform was inhibited by introducing a blocking sequence containing a photo-cleavable linker (PC-linker) that can be indirectly cleaved by 808 nm NIR light and thus enables the AND-gated molecular imaging. According to the responses toward three designed SDz, nPC-SDz, and m-SDz DNAzyme probes, the fluorescence recovery in diverse cell lines (MCF-7, HeLa, and L02) and inhibitor-treated cells was investigated to confirm the AND-gated sensing mechanism. It is worth noting that thanks to the strand displacement amplification and the ability of gold nanopyramids (Au NBPs) to enhance fluorescence, the fluorescence intensity increased by ∼7.9 times and the detection limit decreased by nearly 40.5 times. Moreover, false positive signals can be also excluded due to such AND-gated design. Furthermore, such a designed "AND-gate" sensing manner can also be applied to spatiotemporally controlled ultrasensitive in vivo molecular imaging, indicating its promising potential in precise biological molecular imaging.

A simple and smart AND-gate DNA nanoprobe for correlated enzymes tracking and cell-selective imaging

Accurate cancer diagnosis and effective drug therapy entail sensitive and dynamic monitoring of intracellular key enzymes, since their expression level is closely related to disease progression. Simultaneous monitoring of correlated enzymes is promising to help unveiling mystery of cytobiological events during tumor progression and drug response, while is challenged by lacking of a robust and simple simultaneous detection strategy. In order to construct a simple and smart strategy which is complex design-avoided and doesn't need other auxiliary enzyme, here we develop an AND-gate strategy for simultaneously monitoring correlated enzymes which both are upregulated in cancer cells (telomerase and apurinic/apyrimidinic endonuclease 1). An innovative AND-gate DNA nanoprobe has been designed to avoid mutual interference and background noise, guaranteeing an enhanced fluorescent signal output upon catalyzation of dual enzymes. This AND-gate strategy achieves sensitive detection of two enzymes in an individual manner in test tube, through which the diagnostic potential of bladder cancer has been validated by telomerase detection in clinical urine sample. The AND-gate strategy enables specific intracellular imaging of dual enzymes in different cancer cell lines. Importantly, in contrast to traditional single-targeting strategies, AND-gate imaging of dual enzymes significantly improves cancer cell selectivity. Moreover, this strategy dynamically monitors enzymatic activity changes during chemoresistance induced by chemotherapeutic treatment. This simple and smart strategy has foreseeable prospect in the fields of disease diagnosis, drug prognosis evaluation, and precise fluorescence-guided surgery.

Optically Programmable Plasmon Enhanced Fluorescence-Catalytic Hairpin Assembly Signal Amplification Strategy for Spatiotemporally Precise Imaging

Signal amplification strategies with spatiotemporally high sensitivity can provide more accurate information and hold great promise for improving the accuracy of disease diagnosis. Herein, a 808 nm near-infrared (NIR) light-activated plasmon enhanced fluorescence-catalytic hairpin assembly (PEF-CHA) signal amplification strategy was proposed for spatiotemporally controllable precise imaging of miRNA in vitro and in vivo with ultrasensitivity. The proposed 808 nm NIR light-activated PEF-CHA signal amplification strategy is constructed through combining up-conversion photocontrol and PEF technologies with CHA. It is worth noting that the laser irradiation-induced overheating effect could be effectively alleviated by using Nd³⁺-sensitized upconversion nanoparticles (UCNPs) to convert 808 nm NIR light to ultraviolet (UV) light, which is almost nondestructive to cells or tissues. In addition, nonspecific activation as well as false positive signals can be effectively avoided. Moreover, the detection limit can be reduced by approximate 38 times thanks to the high sensitivity of the proposed strategy. Furthermore, we demonstrate that the 808 nm NIR light-activated PEF-CHA signal amplification strategy can be expanded to sensitive and activatable imaging of intratumoral miRNAs in living mice, showing feasible prospects for precise biological and medical analysis.

A visible and near-infrared light dual responsive "signal-off" and "signal-on" photoelectrochemical aptasensor for prostate-specific antigen

A visible and near-infrared light dual responsive "signal-off" and "signal-on" photoelectrochemical aptasensor was constructed for determining prostate-specific antigen (PSA) based on MoS₂ nanoflowers and gold nanobipyramids. The dual responsive photoelectrochemical aptasensor can provide accurate results for PSA determination. For the photoelectrochemical aptasensor fabrication, amino-group functionalized aptamers were immobilized on a MoS₂ nanoflowers modified glassy carbon electrode surface for the specific recognition, and thus to achieve a "signal-off" aptasensor for PSA under visible light illumination. Subsequently, gold nanobipyramids integrated with thiol-functional aptamer were introduced to the "signal-off" aptasensing interface after PSA recognition. Under excitation with near-infrared light at 808 nm, the photocurrent response can be amplified significantly due to the excellent conductivity and local surface plasmon resonance effect of gold nanobipyramids, thus to producing a "signal-on" model for determining PSA. Under the optimized conditions, the dual-responsive photoelectrochemical aptasensor shows a linear response to the logarithm of PSA concentration in the range of 0.005-100 ng/mL. The detection limits for PSA determination with a "signal-off" or a "signal-on" mode are 1.75 pg mL^-1 and 0.39 pg mL^-1, respectively. The dual-responsive photoelectrochemical aptasensor was also employed for determining PSA in clinical serum samples with satisfactory selectivity and excellent accuracy.

Near-Infrared-Fluorescent Probe for Turn-On Lipopolysaccharide Analysis Based on PEG-Modified Gold Nanorods with Plasmon-Enhanced Fluorescence

Lipopolysaccharide (LPS), as the major component of the outer membrane of Gram-negative bacteria, can trigger a variety of biological effects such as sepsis, septic shock, and even multiorgan failure. Herein, we developed a near-infrared-fluorescent probe for fluorescent turn-on analysis of LPS based on plasmon-enhanced fluorescence (PEF). Gold nanorods (Au NRs) modified polyethylene glycol (PEG) was used as PEF materials. Au NRs were prepared with different longitudinal surface plasmon resonance (LSPR), and their fluorescence enhancement was investigated. Three kinds of molecular weights (1000, 5000, and 10000) of polyethylene glycol (PEG) were employed to control the distance between the Au NRs and the fluorescence substances of cyanine 7 (Cy7). Experimental analysis showed that the enhancement was related to the spectral overlap between the plasmon resonance of Au NRs and the extinction/emission of fluorophore. The three-dimensional finite-difference time-domain (3D-FDTD) simulation further revealed that the enhancement was caused by local electric field enhancement. Furthermore, the probe was used for the ultrasensitive analysis of LPS with a detection limit of 3.85 ng/mL and could quickly distinguish the Gram-negative bacterium-Escherichia coli (E. coli) (with LPS in the membrane) from Gram-positive bacterium-Staphylococcus aureus (S. aureus) (without LPS), as well as quantitative determination of E. coli with a detection limit of 1.0 × 10⁶ cfu/mL. These results suggested that the prepared probe has great potential for biomedical diagnosis and selective detection of LPS from different bacterial strains.

Target-triggered and controlled release plasmon-enhanced fluorescent AIE probe for conformational monitoring of insulin fibrillation

In this work, we constructed a target-triggered and controlled-release plasmon-enhanced fluorescent AIE probe to realize the purpose of conformational monitoring of insulin fibrillation. We synthesized a novel water-soluble anthracene derivative, 4,4',4'',4'''-(anthracene-9,10-diylbis(ethene-2,1,1-triyl))tetrakis(N,N,N-trimethylbenzenaminium) iodide (BDVAI), with AIE properties, high biocompatibility and good self-assembly effect. Gold nanocages (AuNCs) were selected as the substrate for PEF, and the inner space of hollow AuNCs was filled with BDVAI. Thiol-modified DNA chains were bonded to the surface of AuNCs by Au-S bonds, and an insulin aptamer was combined with the sulfhydryl chain to seal the AuNCs. This PEF-AIE sensor produces different fluorescence signals when interacting with native insulin and fibrillar insulin; thus, monitoring conformational changes in insulin can be realized by detecting fluorescence intensity changes during insulin fibrillation. Based on this design, this system realized sensitive detection of fibrillar insulin with a detection limit of 23.6 pM. This AIE molecular-based PEF fluorescence enhancement system improves the optical properties of fluorescent substances, which is of great significance in improving the detection sensitivity of amyloid fibrils conformational changes and providing a reliable basis for further understanding the pathogenesis of amyloidosis.

Functionalization of Metal and Carbon Nanoparticles with Potential in Cancer Theranostics

Cancer theranostics is a new concept of medical approach that attempts to combine in a unique nanoplatform diagnosis, monitoring and therapy so as to provide eradication of a solid tumor in a non-invasive fashion. There are many available solutions to tackle cancer using theranostic agents such as photothermal therapy (PTT) and photodynamic therapy (PDT) under the guidance of imaging techniques (e.g., magnetic resonance-MRI, photoacoustic-PA or computed tomography-CT imaging). Additionally, there are several potential theranostic nanoplatforms able to combine diagnosis and therapy at once, such as gold nanoparticles (GNPs), graphene oxide (GO), superparamagnetic iron oxide nanoparticles (SPIONs) and carbon nanodots (CDs). Currently, surface functionalization of these nanoplatforms is an extremely useful protocol for effectively tuning their structures, interface features and physicochemical properties. This approach is much more reliable and amenable to fine adjustment, reaching both physicochemical and regulatory requirements as a function of the specific field of application. Here, we summarize and compare the most promising metal- and carbon-based theranostic tools reported as potential candidates in precision cancer theranostics. We focused our review on the latest developments in surface functionalization strategies for these nanosystems, or hybrid nanocomposites consisting of their combination, and discuss their main characteristics and potential applications in precision cancer medicine.

Development of FL/MR dual-modal Au nanobipyramids for targeted cancer imaging and photothermal therapy

Multifunctional nanodrugs have emerged as an effective platform to integrate multiple imaging and therapeutic functions for tremendous biomedical applications. However, the development of a simple potent theranostic nanoplatform is still an intractable challenge. Herein, a novel theranostic nanoplatform was developed by coupling prepared Au nanobipyramids with Gd₂O₃, Au nanoclusters and denatured bovine serum albumin (AuNBP-Gd₂O₃/Au-dBSA) for FL/MR dual-modal imaging guided photothermal therapy. AS1411 aptamers were conjugated to enhance its targetability towards breast cancer. The AS1411-AuNBP-Gd₂O₃/Au-dBSA suspension could be readily heated above 40 °C at a low concentration (2 mg/L) and NIR density (1 W/cm²). The AS1411-AuNBP-Gd₂O₃/Au-dBSA revealed a fluorescence quantum yield of 4.2% and higher longitudinal relaxivity rate of 6.75 mM^-1 s^-1 compared to Gd-DTPA of 4.45 mM^-1 s^-1. As a result, the AS1411-AuNBP-Gd₂O₃/Au-dBSA functions as a multimodal nanoprobe of photothermal, fluorescence and MR imaging for specific tumor diagnosis and guidance of therapy, which was validated via in vitro and in vivo tests. Moreover, AS1411-AuNBP-Gd₂O₃/Au-dBSA nanoparticles indicated excellent photothermal anticancer effect more than 95% in both in vitro and in vivo tests. Besides, the low toxicity of AS1411-AuNBP-Gd₂O₃/Au-dBSA nanocomposites was further confirmed in vitro and in vivo. Thus, these results demonstrated the AS1411-AuNBP-Gd₂O₃/Au-dBSA nanocomposites as a rational design of multifunctional nanoplatform to enable multimodal imaging guided photothermal therapy.

Recent progress in sensing application of metal nanoarchitecture-enhanced fluorescence

Fluorescence analytical methods, as real time and in situ analytical approaches to target analytes, can offer advantages of high sensitivity/selectivity, great versatility, non-invasive measurement and easy transmission over long distances. However, the conventional fluorescence assay still suffers from low specificity, insufficient sensitivity, poor reliability and false-positive responses. By exploiting various metal nanoarchitectures to manipulate fluorescence, both increased fluorescence quantum yield and improved photostability can be realized. This metal nanoarchitecture-enhanced fluorescence (MEF) phenomenon has been extensively studied and used in various sensors over the past years, which greatly improved their sensing performance. Thus in this review, we primarily give a general overview of MEF based sensors from mechanisms to state-of-the-art applications in environmental assays, biological/medical analysis and diagnosis areas. Finally, their pros and cons as well as further development directions are also discussed.

Functionalized nanoprobes for in situ detection of telomerase

Telomerase, a special ribonucleoprotein reverse transcriptase, can maintain the length and stability of telomeres and plays an important role in cell proliferation and differentiation. Due to the distinguishable expression level in normal cells and cancer cells, telomerase has become an important biomarker for cancer diagnosis and prognosis evaluation. Despite major breakthroughs in the field of telomerase detection, the extracts in the cell lysate are still the first choice as the analyte nevertheless, which will bring serious inaccuracies compared with the real intracellular activity. With the development of nanotechnology and nanomaterials, extraordinary progress has been made in telomerase detection by employing different versatile nanoprobes. In this review, we list the superiority of nanoprobes and systematically summarize the applications of nanoprobes in telomerase detection from the aspects of various nanomaterials and discuss the current challenges and potential trends in the future design of nanoprobes.

A multicolor DNA tetrahedron nanoprobe for analyzing human telomerase in living cells

Herein, we report the in situ analysis of human telomerase by a multicolor DNA tetrahedron nanoprobe. The elongated telomeric repeats can hybridize with settled molecular beacons in order, accompanied by sequentially lighted up fluorescence. Imaging telomerase activity, real-time monitoring telomerase action and determining product length distribution in living cells are realized. It detects multiple information of intracellular telomerase and provides deeper insights into the function of telomerase.

A multi-colorimetric immunosensor for visual detection of ochratoxin A by mimetic enzyme etching of gold nanobipyramids

A multi-colorimetric immunosensor basing on the mimetic enzyme etching of gold nanobipyramids (Au NBPs) was established to detect ochratoxin A (OTA). Octahedral Cu₂O nanoparticles were successfully synthesized through a selective surface stabilization strategy, which can exhibit a peroxidase-like ability to oxidize 3,3',5,5'-tetramethylbenzidine (TMB). Au NBPs can be etched by the product, TMB²⁺, to form a significant longitudinal peak blue shift of local surface plasmon resonance. During the construction of the immunosensor, the microplate was coated with dopamine to immobilized OTA antigens, followed by the immunoreaction of OTA antibody and the Cu₂O-labled secondary antibody. A linear relationship can be found between the local surface plasmon resonance (LSPR) peak changes with the logarithm of OTA concentration in a wide range from 1 ng/L to 5 μg/L, while the detection limit was 0.47 ng/L. Meanwhile, the approximate OTA concentration can be conveniently and intuitively observed by the vivid color changes. Benefiting from the high specificity, the proposed multi-colorimetric immunoassay detection of OTA in millet samples was achieved, indicating the available potential of the immunoassay for the determination of OTA in real samples.

Core-Shell Multifunctional Nanomaterial-Based All-in-One Nanoplatform for Simultaneous Multilayer Imaging of Dual Types of Tumor Biomarkers and Photothermal Therapy

Versatile all-in-one nanoplatforms that inherently possess both diagnostic imaging and therapeutic capabilities are highly desirable for efficient tumor diagnosis and treatment. Herein, we have developed a novel core-shell multifunctional nanomaterial-based all-in-one nanoplatform composed of gold nanobipyramids@polydopamine (Au NBPs@PDA) and gold nanoclusters (Au NCs) for simultaneous in situ multilayer imaging of dual types of tumor biomarkers (using a single-wavelength excitation) with different intracellular spatial distributions and fluorescence-guided photothermal therapy. The competitive combination between target transmembrane glycoprotein mucin1 (MUC1) and its aptamer caused Au NCs (620 nm) labeled with MUC1 aptamer to detach from the surface of Au NBPs@PDA, turning on the red fluorescence. Meanwhile, the hybridization between microRNA-21 (miRNA-21) and its complementary single-stranded DNA triggered the green fluorescence of Au NCs (515 nm). Based on this, simultaneous in situ multilayer imaging of dual types of tumor biomarkers with different intracellular spatial distributions was achieved. In addition, the potential of Au NBPs@PDA/Au NCs was also confirmed by simultaneous multilayer in situ imaging within not only three cell lines (MCF-7, HepG2, and L02 cells) with different expression levels of MUC1 and miRNA-21 but also cancer cells treated with different inhibitors. Moreover, the remarkable photothermal properties of Au NBPs@PDA resulted in the more efficient killing of cancer cells, demonstrating the great promise of the all-in-one nanoplatform for accurate diagnosis and tumor therapy.

Functional Self-Assembled DNA Nanohydrogels for Specific Telomerase Activity Imaging and Telomerase-Activated Antitumor Gene Therapy

Engineering a functional nanoplatform that integrates dynamic monitoring of endogenous biomarkers and a stimuli-activated therapeutic mode is promising for early diagnosis and treatment of cancers. In this study, we developed an intelligent DNA nanohydrogel with specific targeting capability that can be stimuli-activated for both in vitro telomerase detection and in vivo telomerase-triggered gene therapy. The DNA nanohydrogel was formed simply by the self-assembly of two Y-shaped DNA units and a double-stranded DNA linker labeled with fluorophores and loaded with therapeutic siRNA. When intracellular telomerase was overexpressed, the DNA nanohydrogel collapsed owing to the prolongation of the telomeric primer at the terminal sequence of one of the Y-shaped DNA units. As a result, the quenched fluorescence due to fluorescence resonance energy transfer (FRET) of the DNA nanohydrogel recovered and the trapped siRNA was released, enabling the accurate detection and imaging of intracellular telomerase activity as well as effective gene therapy of tumors. Benefiting from the great biocompatibility, specificity, and stimuli-responsive property, the developed DNA nanoplatform provides a new opportunity for precise cancer diagnosis and treatment as well as other biological applications.

Sensitive detection of intracellular telomerase activity via double signal amplification and ratiometric fluorescence resonance energy transfer

As an important and universal tumor marker, the reliable and in situ detection of intracellular telomerase activity is crucial for cancer diagnosis. Herein, a ratiometric fluorescence resonance energy transfer (FRET) method was developed for detecting intracellular telomerase activity. It takes full advantage of manganese dioxide nanosheets (MnO2NS) that can carry DNA probes with different conformations into cells and then completely release the DNA probes via decomposition of MnO2NS by intracellular reduced glutathione (GSH). In the presence of telomerase, a telomere substrate (TS) could be extended to form long telomerase extension products (TEPs), which trigger the cycling strand displacement reaction (SDR) between two fluorophore-labeled hairpin DNA probes to form lots of DNA duplexes. The close contact of two fluorophores led to an effective ratiometric FRET for reliable detection of telomerase activity. Fluorescence confocal imaging demonstrated that the activity of telomerase in tumor cells was reliably detected. The inhibition of telomerase activity by an inhibitor resulted in a decrease in FRET signal. For extracellular detection, the FRET ratio (FA/FD) shows a good linear relationship with the number of HeLa cells in the range of 20-1000 cells. Therefore, it offers a more facile method for reliable and sensitive detection of intracellular telomerase activity.

Non-template synthesis of porous carbon nanospheres coated with a DNA-cross-linked hydrogel for the simultaneous imaging of dual biomarkers in living cells

A fluorescent nanoprobe was designed based on porous-carbon nanospheres and DNA hybrid hydrogel for the simultaneous imaging of triphosadenine and biothiol in living cells.

Simultaneously Enhanced Singlet Oxygen and Fluorescence Production of Nanoplatform by Surface Plasmon Resonance Coupling for Biomedical Applications

Photodynamic therapy (PDT) and fluorescence imaging offer the possibility of precise and personalized treatment of cancer, but low singlet oxygen production of a commercial photosensitizer and the quenching effect of fluorescent dyes limit the further application of PDT treatment and fluorescence imaging. In addition, the single nanoplatform that simultaneously achieved singlet oxygen and fluorescence enhancement is rare. In this paper, a novel simultaneously enhanced singlet oxygen and fluorescence production nanoplatform of AuNR@mSiO₂-Ce6-Cy5.5 has been successfully designed and synthesized by surface plasmon resonance coupling. The as-synthesized nanoplatform achieved a 1.8-fold enhancement of the singlet oxygen production of Ce6 and a 5.0-fold enhancement of the fluorescence production of Cy5.5 by surface plasmon resonance coupling. The as-synthesized nanoplatform simultaneously enhances the photodynamic therapy and fluorescence imaging of cancer, which will have great potential in biomedical applications.

Beyond the Concentration Limitation in the Synthesis of Nanobipyramids and Other Pentatwinned Gold Nanostructures

Gold nanoparticles offer unique optoelectronic properties relevant for a wide range of processes and products, in biology and medicine (therapeutic agents, diagnostic, drug delivery), as well as in electronics, photovoltaics, and catalysis. So far, various synthesis methods proposed have led to rather limited concentration and purity of the colloidal suspensions, severely hindering their use. Here, we present a simple and versatile procedure for the synthesis of gold pentatwinned nanostructures, including nanobipyramids based on a seed-mediated growth process that overcomes the concentration limitations of current methods by 2 orders of magnitude. Moreover, our novel process offers quantitative yields while easily allowing a fine control of the particles' shape, size (with a high monodispersity), and plasmonic properties. Finally, we demonstrate that our method can be easily upscaled to produce large amounts of nanostructures, up to the gram scale, with minimal waste and postprocessing, thus facilitating their use for further applications and industrial developments.

Target-induced formation of multiple DNAzymes in solid-state nanochannels: Toward innovative photoelectrochemical probing of telomerase activity

Solid-state nanochannels have great potentials in the vibrant field of photoelectrochemical (PEC) bioanalysis. This work herein demonstrates the innovative use of DNA-decorated nanoporous anodic alumina (NAA) nanochannels for sensitive PEC bioanalysis of telomerase (TE) activity. Specifically, telomerase primer sequences (TS) were initially immobilized within the NAA nanochannels and then extended by TE in the presence of deoxyribonucleoside triphosphates (dNTPs). The as formed single-strand DNA was then directed to hybrid with many partially matched single-strand assisting DNA (aDNA), leading to the formation of multiple DNAzymes by the unmatched parts and the subsequent DNAzyme-stimulated biocatalytic precipitation (BCP) within the nanochannels. Because the inhibited signals of the photoelectrode could be correlated with TE-enabled TS extension, an innovative nanochannels PEC bioanalysis could be realized for probing TE activity. This work features the ingenious use of DNA-associated nanochannels for PEC bioanalysis of TE activity. Given the versatile functions of DNA molecules, the extension of this strategy easily allows for addressing numerous other targets of interest. Also, we envision this work could inspire more interest for the further development of nanochannels PEC bioanalysis.

Self-Immolative Fluorescent and Raman Probe for Real-Time Imaging and Quantification of γ-Glutamyl Transpeptidase in Living Cells

Characterizing over-expressed enzymes or biomarkers in living cells is critical for the molecular understanding of disease pathology and consequently for designing precision medicines. Herein, a "switch-on" probe is designed to selectively detect γ-glutamyl transpeptidase (GGT) in living cells via a unique ensemble of enhanced fluorescence and surface-enhanced Raman scattering (SERS). In the presence of GGT, the γ-glutamyl bond in the probe molecule is cleaved, thereby activating a fluorescent probe molecule as well as a Raman reporter molecule. Consequently, the detection of GGT is achieved based on both plasmonic fluorescent enhancement and SERS with a detection limit as low as 1.2 × 10^-3 U/L (normal range for GGT levels in the blood is 9-48 U/L). The main advantage of this platform is that on the occasion of fluorescence signal interference, especially in the presence of free metal ions in cells, the SERS signals still hold high stability as a backup. This work highlights the benefits of the marriage of two complimentary sensing techniques into one platform that can overcome the major obstacles of detection of real-time biomarkers and imaging in living cells.

Non-invasive diagnosis of bladder cancer by detecting telomerase activity in human urine using hybridization chain reaction and dynamic light scattering

Cystoscopy and histology are the gold standards for detection of bladder cancer. However, these methods are highly subjective, expensive, and invasive. We have developed a non-invasive method for the diagnosis of bladder cancer by detecting telomerase activity in human urine. Telomerase substrate (TS) primer is elongated with repeating sequences of (TTAGGG)n in the presence of telomerase. The elongated primer can trigger hybridization chain reaction between two hairpins H1 and H2, result in the aggregation of AuNPs due to the hybridization between the tail sequence on H1 (or H2) and DNA-AuNPs probe, and accompany with the increase of hydrodynamic diameter of AuNPs, which can be measured with dynamic light scattering (DLS). The biosensor displayed a detection limit of 4 MCF-7 cells (a signal-to-noise ratio of 3) and a dynamic range of 10-1000 cells. Moreover, only urine specimens from bladder cancer patients induced a significant change in the average hydrodynamic diameter, indicating its specificity for the non-invasive diagnosis of bladder cancer.

Advances in optical assays for detecting telomerase activity

Telomerase uses its RNA as template and its protein unit as reverse transcriptase to synthesize TTAGGG repeats at the ends of the eukaryotic chromosome to maintain the lengths of telomeres. Telomerase activity up-regulates in about 85% of human tumors compared with somatic cells, which indicates that telomerase is a tumor biomarker. Reliable assay of telomerase activity is thus essential in diagnosis and management of malignant tumors. In this review, recent developed optical assays are summarized based on the readout signal, including chemiluminescence assay, colorimetric assay, and fluorescence assay.

FRET investigation toward DNA tetrahedron-based ratiometric analysis of intracellular telomerase activity

Ratiometric sensing of telomerase activity is realized at a single-cell level based on a novel DNA nanoprobe reconciling an extension primer, a DNA tetrahedron and a flare probe.

Hybrid Silver Nanocubes for Improved Plasmon-Enhanced Singlet Oxygen Production and Inactivation of Bacteria

Plasmonic nanoparticles can strongly interact with adjacent photosensitizer molecules, resulting in a significant alteration of their singlet oxygen (¹O₂) production. In this work, we report the next generation of metal-enhanced ¹O₂ nanoplatforms exploiting the lightning rod effect, or plasmon hot spots, in anisotropic (nonspherical) metal nanoparticles. We describe the synthesis of Rose Bengal-decorated silica-coated silver nanocubes (Ag@SiO₂-RB NCs) with silica shell thicknesses ranging from 5 to 50 nm based on an optimized protocol yielding highly homogeneous Ag NCs. Steady-state and time-resolved ¹O₂ measurements demonstrate not only the silica shell thickness dependence on the metal-enhanced ¹O₂ production phenomenon but also the superiority of this next generation of nanoplatforms. A maximum enhancement of ¹O₂ of approximately 12-fold is observed with a 10 nm silica shell, which is among the largest ¹O₂ production metal enhancement factors ever reported for a colloidal suspension of nanoparticles. Finally, the Ag@SiO₂-RB NCs were benchmarked against the Ag@SiO₂-RB nanospheres previously reported by our group, and the superior ¹O₂ production of Ag@SiO₂-RB NCs resulted in improved antimicrobial activities in photodynamic inactivation experiments using both Gram-positive and -negative bacteria model strains.