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Trace Ir(III) complex enhanced aggregation-induced electrochemiluminescence (AIECL) of poly-tetraphenylethene (pTPE) in aqueous media was investigated for the first time. The poly-TPE end-capped by Ir(III) complex (Ir@pTPE) and its corresponding model polymer poly-TPE (Ph@pTPE) could be synthesized by Suzuki coupling polymerization reaction of 1,2-bis(4-bromophenyl)- 1,2-diphenylethene (M-1) with 1,2-diphenyl-1,2-bis(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)ethene (M-2) and the continuous Suzuki coupling end-capped reaction of poly-TPE-pinacol boronate with (pq)2Ir(pico)Br and bromobenzene, respectively. Subsequently, the corresponding Ir@pTPE Pdots and Ph@pTPE Pdots encapsulated with poly(styrene- co-maleicanhydride) (PSMA) could be obtained by nanoprecipitation method. Compared with Ph@pTPE Pdots, the Ir@pTPE Pdots with a trace amount of Ir(III) complex (1.34‰ of Ir(III) content, wt) could exhibit 9.9-fold enhancement of the electrochemiluminescence (ECL) signal for visual emission. This work provided a novel strategy on designing highly efficient ECL materials based on trace Ir(III)-end capping AIE-active polymer dots. electrochemiluminescence, aggregation-induced emission, Ir(III) complex, polymer dots

Metal-organic frameworks (MOFs) have been successfully used as efficient quenchers for fluorescent DNA detection. However, the surface charge property of MOFs can inevitably affect their fluorescence quenching behavior. Herein, nanoscale MOFs (NMOFs), including MOF nanosheets and nanoparticles, have been employed to investigate the relationship between the fluorescence quenching and surface properties of NMOFs. We find that the positively and negatively charged NMOFs exhibited totally opposite fluorescence quenching properties toward negatively charged FAM-labeled double-stranded DNA (dsDNA). On the contrast, they show negligible influence on the sensing of positively charged TAMRA-labeled dsDNA. This study provides a new insight of the fluorescence quenching property of NMOFs and offers a new concept for construction of ratiometric fluorescence DNA biosensors.

A novel homologous surface-enhanced Raman scattering (SERS)-electrochemical (EC) dual-mode biosensor based on a 3D/2D polyhedral Au nanoparticle/MoOxnanosheet heterojunction (PAMS HJ) and target-triggered nonenzyme cascade autocatalytic DNA amplification (CADA) circuit was constructed for highly sensitive detection of microRNA (miRNA). Mixed-dimensional heterostructures were prepared by in situgrowth of polyhedral Au nanoparticles (PANPs) on the surface of MoOxnanosheets (MoOxNSs) via a seed-mediated growth method. As a detection substrate, the resulting PAMS HJ shows the synergistic effects of both electromagnetic and chemical enhancements, efficient charge transfer, and robust stability, thus achieving a high SERS enhancement factor (EF) of 4.2 × 109and strong EC sensing performance. Furthermore, the highly efficient molecular recognition between the target and smart lock probe and the gradually accelerated cascade amplification reaction further improved the selectivity and sensitivity of our sensing platform. The detection limits of miRNA-21 in SERS mode and EC mode were 0.22 and 2.69 aM, respectively. More importantly, the proposed dual-mode detection platform displayed excellent anti-interference and accuracy in the analysis of miRNA-21 in human serum and cell lysates, indicating its potential as a reliable tool in the field of biosensing and clinical analysis.

In this study, semiconducting organic polymer dots (Pdots) and inorganic quantum dots (Qdots) were firstly utilized to construct the organic-inorganic nanodots heterojunction for the photoelectrochemical (PEC) bioanalysis application. Specifically, n-type CdS Qdots, p-type CdTe Qdots and tetraphenylporphyrin (TPP)-doped poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadazole)] (PFBT) Pdots were fabricated and their energy levels, i.e., their valence band (VB)/conduction band (CB) or lowest unoccupied molecular orbital (LUMO)/highest occupied molecular orbital (HOMO) values, were also determined. Then these nanodots were integrated to construct four types p-n and p-p organic-inorganic nanodots heterojunctions, i.e., CdS Qdots/TPP-doped PFBT Pdots, TPP-doped PFBT Pdots/CdS Qdots, CdTe Qdots/TPP-doped PFBT Pdots, TPP-doped PFBT Pdots/CdTe Qdots, on the transparent glass electrode. Upon light irradiation, four heterojunctions exhibited different PEC behaviors, and some with prominent photocurrent enhancement. With the model molecule L-cysteine (L-cys) as target, the proposed PEC sensor exhibited good performances. In brief, this work presents the first semiconducting organic-inorganic nanodots heterojunction for PEC bioanalysis application, which could be easily used as a general platform for future PEC bioanalysis building. Besides, it is expected to inspire more interest in the design, development, and implementation of various organic-inorganic heterojunctions for advanced PEC bioanalysis in the future.

The noninvasive and specific detection of cancer cells in living subjects has been essential for the success of cancer diagnoses and treatments. Herein, we report a strategy of combining an αvβ3-integrin-receptor-targetable ligand, c-RGD, with the γ-glutamyl transpeptidase (GGT)-recognizable substrate, γ-glutamate (γ-Glu), to develop a tumor-targeting and GGT-activatable near-infrared (NIR)-fluorescent probe for the noninvasive imaging of tumors in living mice. We demonstrated that the probe’s fluorescence was off initially, but when the γ-Glu in the probe was specifically cleaved by GGT, the fluorescent product was released and could be selectively taken up by U87MG-tumor cells via αvβ3-receptor-mediated endocytosis. Remarkably, enhanced intracellular NIR fluorescence distributed mainly in the lysosomes was observed in the tumor cells only, showing that the probe was capable of differentiating the tumor cells from the GGT-positive, αvβ3-deficient normal cells. Moreover, the probe also showed a high selectivity for the real-time and noninvasive detection of GGT activity in xenograft U87MG tumors following iv administration. This study reveals the advantage of using a combination of receptor-mediated cell uptake and molecular-target-triggered activation to design molecular probes for improved cancer imaging, which could facilitate effective cancer diagnoses.

Herein we report the strategy of liposome-mediated Cu2+-induced exciton trapping upon CdS quantum dots (QDs) for amplified photoelectrochemical (PEC) bioanalysis application. Specifically, the Cu nanoclusters (NCs)-encapsulated liposomes were first fabricated and then processed with antibodies bound to their external surfaces. After the sandwich immunocomplexing, the confined liposomal labels were subjected to sequential lysis treatments for the release of Cu NCs and numerous Cu2+ions, which were then directed to interact with the CdS QDs electrode. The interaction of Cu2+ions with CdS QDs could generate CuxS and form the trapping sites to block the photocurrent generation. Since the photocurrent inhibition is closely related with the Cu NCs-loaded liposomal labels, a novel and general “signal-off” PEC immunoassay could thus be tailored with high sensitivity. Meanwhile, a complementary “signal-on” fluorescent detection could be accomplished by measuring the fluorescence intensity originated from the Cu NCs. This work features the first use of Cu NCs in PEC bioanalysis and also the first NCs-loaded liposomal PEC bioanalysis. More importantly, by using other specific ions/reagents–semiconductors interactions, this protocol could serve as a common basis for the general development of a new class of liposome-mediated PEC bioanalysis.

The small absorption cross sections of most molecules led to the low sensitivity of traditional optical absorption spectroscopy. This obstacle might be overcome by applying the near-field plasmon resonance energy transfer (PRET) between plasmonic nanoparticle and surrounding molecules. In this work, we utilized PRET-based spectroscopy on single gold nanostars to study the specific biomolecule recognition and enzyme kinetics choosing biotin-SA pair and DNase I as models. By analyzing the changes of absorption spectra for black hole quencher 3 (BHQ3), derived from spectra difference, we explored the kinetics of specific biomolecule recognition and enzyme digestion in different physiological environment, and we found that the viscosities of media and the sizes of molecules play vital role in biomolecular recognition and enzyme digestion. Compared with the traditional optical absorption spectroscopy techniques, PRET-based spectroscopy offers a nanoscopic resolution owing to the small size of the probe, is more sensitive and achieves detection on the order of hundreds or even dozens of molecules, and can achieve high selectivity due to the specific biomolecular recognition. This method might be used in the fields of molecular diagnostics, drug discovery, cell systems, and clinical diagnostics.

In this work, SiO2/CNTs photonic crystal beads were constructed by doping CNTs into SiO2photonic crystals, which have an angle-independent responsive structural color and can be used as bipolar electrodes due to their good electrical conductivity. In addition, the bipolar electrode-electrochemiluminescence (BPE-ECL) experiments and finite element simulation prove that the low driving voltage can trigger the bipolar electrode electrochemical reactions by confinement effect. Inspired by this, it is the first to combine the SiO2/CNTs structural color coding scheme with low-drive voltage induced wireless BPE-ECL imaging based on the confinement effect of microchannels to achieve simultaneous immune detection of ovarian cancer biomarkers (CA125, CEA, AFP). The detection limits of successfully constructed high-throughput BPE-ECL biosensor for AFP, CEA, and CA125 are 0.72 ng/mL, 0.95 ng/mL, and 1.03 U/mL, respectively, and have good stability and specificity, which expands the application of electrochemiluminescence and lays a foundation for the development of electrochemiluminescence coding technology.

In this paper, localized electrochemiluminescence (ECL) was visualized from nanoneedle electrodes that achieved very-high-density electrochemical sensing. The localized luminescence at the nanometer-sized tip observed was ascribed to enhanced mass transfer of the luminescence probe at the tip than on the planar surface surrounding the tip, which provided higher luminescence at the tip. The size of the luminescence spots was restricted to 15 μm permitting the electrochemical analysis with a density over 4 × 103spots/mm2. The positive correlation between the luminescence intensity at the tips and the concentration of hydrogen peroxide supported the quantitative ECL analysis using nanoneedle electrodes. The further modification of glucose oxidase at the electrode surface conceptually demonstrated that the concentration of glucose ranging from 0.5 to 5 mM could be quantified using the luminescence at the tips, which could be further applied for the detection of multiple molecules in the complex biosystem. This successful localized ECL offers a specific strategy for the development of very-high-density electrochemical arrays without the complicated chip design.