Polymer-Encapsulated Cobalt/Gold Bimetallic Nanoclusters as Stimuli-Responsive Chemiluminescent Nanoprobes for Reactive Oxygen Species

Ultrasensitive chemiluminescence detection based on titanium-doped spinel-structured nanoparticles with abundant oxygen vacancies

We successfully synthesized spinel-structured ternary nanocatalyst Ti-Co3O4/Fe3O4 nanoparticles (NPs) for the first time. Ti-Co3O4/Fe3O4 NPs exhibited superior catalytic performance compared to the synthesized binary catalysts Co3O4/Fe3O4. Moreover, Ti-Co3O4/Fe3O4 NPs can enhance the chemiluminescence (CL) intensity of the luminol/H2O2 system by over 3800-fold, attributed to the high density of oxygen vacancies (OVs) within the structure. OVs contribute to electron delocalization, improve conductivity, and are recognized as crucial active sites in the catalytic decomposition of H2O2. Based on the inhibitory effect of L-ascorbic acid (AA) on the luminol/H2O2 CL system, we developed a sensitive, rapid, effective, and highly selective AA CL assay with a linear range of 0.1 μmol/L to 100 μmol/L and a limit of detection (LOD, S/N = 3) of 0.044 μmol/L. The method was successfully applied to quantify AA in vitamin C tablets with recoveries ranging from 99.7 % to 106.3 %. This research provides a promising prospect for the application of spinel-structured nanoparticles in CL detection platforms and offers valuable insights into nanoparticle size modulation and OV engineering for catalytic optimization.

Chemiluminescent Fe3O4@Nickel-Cobalt Double Hydroxide Magnetic Core-Shell Nanomaterial as an Analytical Interface for Label-Free CYFRA21-1 Immunosensing

Cytokeratin 19 fragment (CYFRA21-1) is considered to be a potential marker for the diagnosis and of classification of lung cancer. It is highly desired to develop rapid and highly sensitive label-free chemiluminescence (CL) immunosensors for the detection of CYFRA21-1. In this work, magnetic core-shell nanocomposite Fe3O4@nickel-cobalt double hydroxide (Fe3O4@DH) was used for the first time as a carrier to synthesize N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and gold and silver nanocluster (AuAgNC) bifunctionalized magnetic nanomaterials Fe3O4@DH/AuAgNCs-ABEI. The resulting Fe3O4@DH/AuAgNCs-ABEI demonstrated excellent CL performance, attributed to the exceptional catalytic capability of nickel-cobalt double hydroxide (NiCo-DH) and AuAgNCs, as well as the large specific surface area of NiCo-DH for AuAgNCs and ABEI enrichment. Moreover, Fe3O4@DH/AuAgNCs-ABEI exhibited superior stability compared to Fe3O4-based CL-functionalized magnetic nanomaterials, owing to the presence of NiCo-DH shells. On this basis, a label-free CL immunosensor using CYFRA21-1 antibody-modified Fe3O4@DH/AuAgNCs-ABEI as an analytical interface was constructed for the detection of CYFRA21-1 in the range from 1.0 × 10-13 to 1.0 × 10-8 g/mL. The detection limit of this CL immunosensor was 47.7 fg/mL, 4 orders of magnitude lower than existing CL methods. The CL immunosensor was able to accurately detect the concentration of CYFRA21-1 in serum samples, as evidenced by ELISA results. More importantly, it not only distinguished well between healthy persons and lung cancer patients (90.0% sensitivity and 90.0% specificity), but also effectively distinguished between patients with non-small cell lung cancer and small cell lung cancer (80.0% sensitivity and 86.7% specificity).

Levonorgestrel protected Au10 cluster for hypochlorite sensing in living organisms

BACKGROUND

Highly reactive oxygen species (ROS) could lead to serious damage in living cells and are associated with many diseases like cancers. Metal cluster with strong fluorescence has great potential in biosensing and many thiolate ligands-protected clusters have been applied in ROS sensing.

RESULTS

In this work, we synthesized levonorgestrel protected Au10 cluster with specific sensing ability for highly ROS via crystal transformation from Au8 cluster, demonstrating the significance of inner core structure on detecting performance. The detection limit of Au10 cluster for ClO- could reach as low as 0.1 μM. This fluorescent probe not only achieving detection of exogenous ClO- in living cells and zebrafish, but also successful imaging of endogenous ClO- in HeLa and HepG2 cells.

SIGNIFICANCE

In comparison to previously reported cluster-based sensors for ROS, this work proposes a different reaction mechanism of metal nanoclusters for ROS detection (breakage of gold-alkynyl bond and oxidation of alkynyl group). This provides new directions for designing specific ROS probes and broadens the applications of metal clusters in disease diagnostics.

A novel chemiluminescence sensor for alpha-fetoprotein detection based on an aptamer-luminol modified magnetic graphene oxide and copper-based MOF composite

Herein, an aptamer-luminol modified magnetic graphene oxide and copper-based MOF composite was prepared and used to build a novel target-triggered "turn on" chemiluminescence (CL) sensor for alpha-fetoprotein (AFP) detection. Magnetic graphene oxide (MGO) was functionalized with the complementary sequence of the AFP aptamer (cDNA), and then MGO-cDNA was linked to aptamer modified luminol (Apt-luminol) through the complementary base pairing effect. The functionalized magnetic graphene oxide (MGO-cDNA/Apt-luminol) was prepared as a specific magnetic separation and signal switch material. ZnONPs-Au@CuMOFs shows excellent catalytic performance and was used as a catalyst for the luminol-H2O2 reaction. AFP will specifically recognize and bind to Apt on MGO-cDNA/Apt-luminol when AFP is present, which causes luminol release and triggers the CL reaction. The released luminol encounters ZnONPs-Au@CuMOFs and produces strong CL intensity. Therefore, a novel target-triggered "turn on" CL method with high selectivity and sensitivity for detecting AFP has been established. The linear range and detection limit were 1.0 × 10-4-50 ng mL-1 and 4.2 × 10-5 ng mL-1, respectively. The sensor also exhibited good selectivity, reproducibility and stability, and was finally used for AFP detection in serum samples.

Ultrasensitive PD-L1-Expressing Exosome Immunosensors Based on a Chemiluminescent Nickel-Cobalt Hydroxide Nanoflower for Diagnosis and Classification of Lung Adenocarcinoma

Programmed death ligand-1 (PD-L1)-expressing exosomes are considered a potential marker for diagnosis and classification of lung adenocarcinoma (LUAD). There is an urgent need to develop highly sensitive and accurate chemiluminescence (CL) immunosensors for the detection of PD-L1-expressing exosomes. Herein, N-(4-aminobutyl)-N-ethylisopropanol-functionalized nickel-cobalt hydroxide (NiCo-DH-AA) with a hollow nanoflower structure as a highly efficient CL nanoprobe was synthesized using gold nanoparticles as a "bridge". The resulting NiCo-DH-AA exhibited a strong and stable CL emission, which was ascribed to the exceptional catalytic capability and large specific surface area of NiCo-DH, along with the capacity of AuNPs to facilitate free radical generation. On this basis, an ultrasensitive sandwich CL immunosensor for the detection of PD-L1-expressing exosomes was constructed by using PD-L1 antibody-modified NiCo-DH-AA as an effective signal probe and rabbit anti-CD63 protein polyclonal antibody-modified carboxylated magnetic bead as a capture platform. The immunosensor demonstrated outstanding analytical performance with a wide detection range of 4.75 × 103-4.75 × 108 particles/mL and a low detection limit of 7.76 × 102 particles/mL, which was over 2 orders of magnitude lower than the reported CL method for detecting PD-L1-expressing exosomes. Importantly, it was able to differentiate well not only between healthy persons and LUAD patients (100% specificity and 87.5% sensitivity) but also between patients with minimally invasive adenocarcinoma and invasive adenocarcinoma (92.3% specificity and 52.6% sensitivity). Therefore, this study not only presents an ultrasensitive and accurate diagnostic method for LUAD but also offers a novel, simple, and noninvasive approach for the classification of LUAD.

Bio-responsive Au-miR-183 inhibitor enhances immunotherapy in hepatocellular carcinoma by inducing immunogenic cell death

The treatment of advanced hepatocellular carcinoma (HCC) is limited, and immunotherapy is the current research focus of multi-disciplinary collaborative comprehensive treatment of HCC. Herein, we constructed a bio-responsive Au-miR-183 inhibitor (Au@miR-183i) delivery system targeting liver cancer stem cells (LCSCs), and adopted the strategy of combining αPD-L1 immunotherapy. The multifunctional Au@miR-183i nanocomplexes (NCs), which self-assemble based on the tumor microenvironment, consume NADPH and H2O2, leading to redox homeostasis disturbance, ROS accumulation, regulation of the LCSC niche, and induction of stemness regression. Moreover, self-assembled Au@miR-183i NCs specifically target the delivery of miR-183i to LCSCs, triggering the immunogenic cell death (ICD) effect, promoting the maturation of dendritic cells, inducing infiltration of CD8+ T cells, and facilitating the transformation of 'cold' tumors into 'hot' tumors. More importantly, consistent with the results in vitro, Au@miR-183i NCs demonstrated effective tumor targeting and strong ICD induction in vivo, assisted in enhancing αPD-L1 immunotherapy, and activated a robust systemic anti-tumor immune response in tumor-bearing mouse models. Overall, we provide a simple and universal therapeutic strategy by constructing a multifunctional bio-responsive Au@miR-183i NCs delivery system with LCSC targeting capability. Furthermore, nanocomplex-based ICD inducers have great promise in enhancing anti-tumor immunity and the PD-1/PD-L1 blocking efficacy in HCC, which provides a theoretical basis for effectively eliminating LCSCs and achieving a high-efficiency synergistic treatment strategy for HCC.

Chiral MoSe2 Nanoparticles for Ultrasensitive Monitoring of Reactive Oxygen Species In Vivo

Reactive oxygen species (ROS) are involved in neurodegenerative diseases, cancer, and acute hepatitis, and quantification of ROS is critical for the early diagnosis of these diseases. In this work, a novel probe is developed, based on chiral molybdenum diselenide (MoSe2 ) nanoparticles (NPs) modified by the fluorescent molecule, cyanine 3 (Cy3). Chiral MoSe2 NPs show intensive circular dichroism (CD) signals at 390 and 550 nm, whereas the fluorescence of Cy3 at 560 nm is quenched by MoSe2 NPs. In the presence of ROS, the probe reacts with the ROS and then oxidates rapidly, resulting in decreased CD signals and the recovery of the fluorescence. Using this strategy, the limit of detection values of CD and fluorescent signals in living cells are 0.0093 nmol/106 cells and 0.024 nmol/106 cells, respectively. The high selectivity and sensitivity to ROS in complex biological environments is attributed to the Mo4+ and Se2- oxidation reactions on the surface of the NPs. Furthermore, chiral MoSe2 NPs are able to monitor the levels of ROS in vivo by the fluorescence. Collectively, this strategy offers a new approach for ROS detection and has the potential to inspire others to explore chiral nanomaterials as biosensors to investigate biological events.

Cobalt Species-Loaded MOFs as Chemiluminescent Catalysts for Monitoring Carbendazim

The application of active metal-based nanoscale catalysts as signal enhancers for chemiluminescent immunoassay (CLIA) is restricted by poor thermodynamic stability and ease of aggregation. For the present exploration, zirconium-based MOFs UiO-66-NH2 were adopted as supports to load cobalt species by an impregnation-reduction approach. Cobalt species were uniformly distributed in the framework architecture of the MOF materials. The prepared cobalt-loaded MOF hybrids, noted as UiO-66-NH2/Co, display superior chemiluminescence (CL) catalytic activity owing to the introduction of cobalt catalytic centers. The CL catalytic capability of UiO-66-NH2/Co hybrids is about 18 times of that of free cobalt ions at the same cobalt amount. The results of mechanism exploration manifest that the hybrids are capable of accelerating the decay of hydrogen peroxide and promoting the yield of reactive oxygen species. Based on their remarkable CL catalytic capability, a CLIA approach was proposed to monitor carbendazim by adopting the hybrids as signal probes, which showed the merits of high sensitivity and satisfactory selectivity. Carbendazim was quantitated within a concentration range of 0.05 to 60 ng mL-1, with a detection limit of 19.8 pg mL-1. The results for monitoring spiked samples verify the acceptable practicality of the proposed CLIA approach.

Recent Advances in Nanomaterial-Based Chemiluminescence Probes for Biosensing and Imaging of Reactive Oxygen Species

Reactive oxygen species (ROS) play important roles in organisms and are closely related to various physiological and pathological processes. Due to the short lifetime and easy transformation of ROS, the determination of ROS content in biosystem has always been a challenging task. Chemiluminescence (CL) analysis has been widely used in the detection of ROS due to its advantages of high sensitivity, good selectivity and no background signal, among which nanomaterial-related CL probes are rapidly developing. In this review, the roles of nanomaterials in CL systems are summarized, mainly including their roles as catalysts, emitters, and carriers. The nanomaterial-based CL probes for biosensing and bioimaging of ROS developed in the past five years are reviewed. We expect that this review will provide guidance for the design and development of nanomaterial-based CL probes and facilitate the wider application of CL analysis in ROS sensing and imaging in biological systems.

Carbon dots-mediated synthesis of gold nanodendrites with extended absorption into NIR-II window for in vivo photothermal therapy

BACKGROUND

Photothermal therapy (PTT) in the second near-infrared (NIR-II) window has attracted extensive attention due to the benefits in high maximum permissible exposure and penetration depth. Current photothermal agents generally show a broadband absorption accompanied by a gradual attenuation of absorption in the NIR-II window, leading to poor effect of PTT. It remains a great challenge to gain photothermal agents with strong and characteristic absorption in NIR-II regions. To overcome this problem, based on carbon dots (CDs)-mediated growth strategy, we proposed a simple and feasible approach to prepare plasmonic gold nanodendrites (AuNDs) with NIR-II absorption to enhance the therapeutic effect of PTT.

RESULTS

By rationally regulating the size and branch length of AuNDs, the AuNDs exhibited a broadband absorption from 300 to 1350 nm, with two characteristic absorption peaks located at 1077 and 1265 nm. The AuNDs demonstrated desired optical photothermal conversion efficiency (38.0%), which was further applied in NIR-II photoacoustic imaging (PAI) and PTT in human colon cancer cells (HCT 116)-tumor-bearing mice model. The tumor cells could be effectively eliminated in vivo under 1064 nm laser irradiation by the guidance of PAI.

CONCLUSIONS

We reported a simple but powerful synthetic method to obtain the unique AuNDs with strong and characteristic absorption peaks in the NIR-II window. This study provides a promising solution to tuning the growth of nanoparticles for bioimaging and phototherapy in the NIR-II window.

Ultrasensitive Electrochemiluminescence Biosensor Based on 2D Co3O4 Nanosheets as a Coreaction Accelerator and Highly Ordered Rolling DNA Nanomachine as a Signal Amplifier for the Detection of MicroRNA

A novel ultrasensitive electrochemiluminescence (ECL) biosensor was constructed using two-dimensional (2D) Co₃O₄ nanosheets as a novel coreaction accelerator of the luminol/H₂O₂ ECL system for the detection of microRNA-21 (miRNA-21). Impressively, coreaction accelerator 2D Co₃O₄ nanosheets with effective mutual conversion of the Co²⁺/Co³⁺ redox pair and abundant active sites could promote the decomposition of coreactant H₂O₂ to generate more superoxide anion radicals (O₂^•-), which reacted with luminol for significantly enhancing ECL signals. Furthermore, the trace target miRNA-21 was transformed into a large number of G-wires through the strand displacement amplification (SDA) process to self-assemble the highly ordered rolling DNA nanomachine (HORDNM), which could tremendously improve the detection sensitivity of biosensors. Hence, on the basis of the novel luminol/H₂O₂/2D Co₃O₄ nanosheet ternary ECL system, the biosensor implemented ultrasensitive detection of miRNA-21 with a detection limit as low as 4.1 aM, which provided a novel strategy to design an effective ECL emitter for ultrasensitive detection of biomarkers for early disease diagnosis.

Fabrication of a ratiometric electrochemiluminescence biosensor using single self-enhanced nanoluminophores for the detection of spermine

A ratiometric electrochemiluminescence strategy using a single luminophore for accurate and sensitive biomolecule detection could be immensely valuable in bioanalysis. Herein, an ultrasensitive ratiometric electrochemiluminescence sensing system was fabricated using a self-enhanced luminophore with dual-signal emission for the detection of spermine. A nanocomposite was synthesized by the covalent attachment of N, N-diisopropylethylenediamine onto glutathione-protected Au-Ag bimetallic nanoclusters (DPEA-GSH@Au/Ag BNCs). The nanocomposite exhibited efficient intra-cluster charge transfer to produce strong anodic self-enhanced electrochemiluminescence emission at 0.8 V without external co-reactants. Interestingly, the DPEA@GSH@Au-Ag BNCs exhibited cathodic electrochemiluminescence emission upon the addition of the co-reactant potassium persulfate at -1.6 V, exhibiting stable and efficient dual-signal electrochemiluminescence emission features at a continuous potential window of -1.75 to 1.2 V. Thus, they were used to fabricate a single-luminophore electrochemiluminescence sensor with dual emission. The cathodic emission of the biosensor gradually increased with increasing concentrations of spermine, whereas the anodic electrochemiluminescence intensity remained almost constant, enabling the ratiometric detection of spermine. The fabricated biosensor, with an internal standard, significantly improved the accuracy and reliability of spermine detection in a wide concentration range of 0.85 pM-100 μM, with a low limit of detection of 0.12 pM (S/N = 3) under optimum conditions. This single-luminophore electrochemiluminescence sensing system could be used for the detection of spermine and could guide the construction of ratiometric electrochemiluminescence sensors in the future.

Synergetic Dual-Site Atomic Catalysts for Sensitive Chemiluminescent Immunochromatographic Test Strips

In view of the outstanding catalytic efficiency, single-atom catalysts (SACs) have shown great promise for the construction of sensitive chemiluminescent (CL) platforms. However, the low loading amount of active sites dramatically obstructs the improved catalytic activity of these metal SACs. Benefiting from the exceedingly unique catalytic properties of the metal-metal bonds, atomic clusters may give rise to enhancing the catalytic properties of SACs based on the synergistic effects of dual atomic-scale sites. Inspired by this, atomic Co₃N clusters-assisted Co SACs (Co₃N@Co SACs) were synthesized through a facile doping method. Through X-ray absorption spectroscopy, the active metal sites in the synergetic dual-site atomic catalysts of Co₃N@Co SACs were confirmed to be Co-O₄ and Co₃-N moieties. Co₃N@Co SACs served as a superior co-reactant to remarkably enhance the luminol CL signal by 2155.0 times, which was prominently superior to the boosting effect of the pure Co SACs (98.4 times). The synergetic dual-site atomic catalysts contributed to accelerating the decomposition of H₂O₂ into singlet oxygen as well as superoxide radical anions to display superb catalytic performances. For a concept employment, Co₃N@Co SACs were attempted to utilize as CL probes for establishing a sensitive immunochromatographic assay to quantitate pesticide residues, in which imidacloprid was adopted as the model analyte. The quantitative range of imidacloprid was 0.05-10 ng mL^-1 with a detection limit of 1.7 pg mL^-1 (3σ). Furthermore, the satisfactory recovery values in mock herbal medicine samples demonstrated the effectiveness of the proposed Co₃N@Co SAC-based CL platform. In the proof-of-concept work, synergetic dual-site atomic catalysts show great perspectives on trace analysis and luminescent biosensing.

New advanced oxidation progress with chemiluminescence behavior based on NaClO triggered by WS2 nanosheets

As one integral part of coping strategies for addressing water pollution, advanced oxidation progresses (AOPs) get enormous attentions in recent years. However, the complex synthesis and high cost of H₂O₂ and K₂S₂O₈ hampered their developments. Herein, a novel AOP with the chemiluminescence (CL) property based on economic NaClO and WS₂ nanosheets was proposed to achieve efficient decomposition of organic pollutants. In this AOP, WS₂ nanosheets exhibited a dual-function feature of the catalyst and energy acceptor. It demonstrated that the reaction order of WS₂ nanosheets was equal to 0.8271 and enormous singlet oxygen (¹O₂),·ClO and hydroxyl radical (·OH) were generated in rhodamine B (RhB) degradation process. Interestingly, a strong CL emission was observed and reflected the relative concentration of ¹O₂ and·OH for adjusting the oxidizing capability in WS₂ nanosheets-NaClO system. Through a series of degradation tests, RhB, methylene blue (MB), p-nitrophenol and phenol were decomposed and the degradation efficiency of over 90% was achieved. Therefore, this study not only builds a chemiluminescent AOPs to eliminate organic pollutants, but also broadens the applications of WS₂ nanomaterials and CL in environmental field.

A chemiluminescence aptasensor for sensitive detection of alpha-fetoprotein based on hemin@ZIF-67

In this work, hemin@ZIF-67 composites were prepared and were used to construct a chemiluminescence (CL) aptasensor for alpha-fetoprotein (AFP) detection. Hemin is a catalytic porphyrin with two carboxylate groups that can covalently bond to metal ions. A hemin/ZIF-67 composite was prepared via covalent bonding between the carboxyl groups of hemin and the cobalt ion of ZIF-67, and these materials were characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR), and X-ray diffraction (XRD). Hemin@ZIF-67 was used as the peroxidase material, and the aptamer of alpha-fetoprotein was modified on its surface by electrostatic adsorption. Then a simple CL aptasensor was constructed based on the CL system of luminol-H₂O₂-NaOH. Under the optimal conditions, the CL intensity value was linearly proportional to the concentration of AFP in the range of 4 × 10^-10 to 200 × 10^-10 mg/mL. The detection limit was 1.3 × 10^-10 mg/mL. Thus the aptasensor enables highly sensitive and selective detection of AFP.

Europium functionalized black phosphorus quantum dots as a CRET platform for synergistically enhanced chemiluminescence

In this work, we synthesize stable europium ion modified black phosphorus quantum dots (Eu-BPQDs) using a microwave irradiation technique, which can react with organic amines exhibiting unique chemiluminescence (CL). The mechanism of the Eu-BPQDs/organic amines CL system accounting for the efficient CRET is induced by the chelation of organic amines with the surface functionalized europium.

Tianma Gouteng Decoction Exerts Pregnancy-Protective Effects Against Preeclampsia via Regulation of Oxidative Stress and NO Signaling

Preeclampsia (PE), a pregnancy-specific syndrome with the major molecular determinants of placenta-borne oxidative stress and consequently impaired nitric oxide (NO) generation, has been considered to be one of the leading causes of maternal morbidity as well as mortality and preterm delivery worldwide. Several medical conditions have been found to be associated with increased PE risk, however, the treatment of PE remains unclear. Here, we report that Tianma Gouteng Decoction (TGD), which is used clinically for hypertension treatment, regulates oxidative stress and NO production in human extravillous trophoblast-derived TEV-1 cells. In human preeclamptic placental explants, reactive oxygen species (ROS) levels were elevated and NO production was inhibited, while TGD treatment at different periods effectively down-regulated the H2O2-induced ROS levels and significantly up-regulated the H2O2-suppressed NO production in human TEV-1 cells. Mechanistically, TGD enhanced the activity of total nitric oxide synthase (TNOS), which catalyze L-arginine oxidation into NO, and simultaneously, TGD promoted the expression of neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS), two isoforms of nitric oxide synthetases (NOS) in human placenta, resulting in the increased NO generation. More importantly, TGD administration not only increased the weight gain during pregnancy and revealed a hypotensive effect, but also improved the placental weight gain and attenuated fetal growth restriction in an NG-nitro-L-arginine methyl ester (L-NAME)-induced mouse PE-like model. Our results thereby provide new insights into the role of TGD as a potentially novel treatment for PE.

Trimetallic AuPtCo Nanopolyhedrons with Peroxidase- and Catalase-Like Catalytic Activity for Glow-Type Chemiluminescence Bioanalysis

Chemiluminescence (CL) with stable and glowing light emission is vital for the accurate detection of biomarkers. Moreover, the catalyst plays an important role in CL systems. Herein, the trimetallic AuPtCo nanopolyhedrons with peroxidase- and catalase-like catalytic activities are readily synthesized via a one-step reduction method. After reaction with the substrate ABEI and oxidant H₂O₂, the AuPtCo nanozyme can catalyze the CL emission in a flash type. Interestingly, it has been found that the biofunctionalization of the AuPtCo surface can endow the catalytic interface with a slow-diffusion effect, thereby prolonging the emission of glow-type CL. On this basis, two biofunctionalized AuPtCo nanocomposites, named as AuPtCo@Cys and AuPtCo@Ab, are prepared, achieving sensitive and selective detection of H₂O₂ and lipoprotein-associated phospholipase A₂ (Lp-PLA₂), respectively. Further, the proposed glow-type CL assays are successfully applied for the determination of H₂O₂ and Lp-PLA₂ in female vaginal discharge and human serum samples, respectively, which exhibit good correlation with the clinical results. Overall, the trimetallic AuPtCo nanozyme-based glow-type CL analysis has demonstrated as a powerful and robust tool for biomarker analysis, which holds great promise in clinical applications.

Sonochemiluminescence Using Apertureless USB Piezoelectric Ultrasonic Transducer and Its Applications for the Detection of Hydrogen Peroxide, Glucose, and Glucose Oxidase Activity

The mesh-type USB piezoelectric ultrasonic transducer (USB-PUT) used in household humidifiers and inhalation therapy devices is very cheap, small, and energy saving. It holds great promise for sonochemistry. However, the microtapered apertures in the center of the stainless steel substrate of mesh-type USB-PUT can lead to rapid atomization of solution, leakage of solutions containing surfactants and organic solvent through the apertures, and high background emission. Herein, we design a new type of USB-PUT by replacing the meshed stainless steel substrate with an apertureless stainless steel substrate. We have found that this apertureless USB-PUT can not only induce intense sonochemiluminescence (SCL) but can also enable sensitive luminol SCL detection of hydrogen peroxide which is practically impossible using mesh-type PUT because of the strong background SCL emission. By using this apertureless device to induce SCL and using smart phone as a detector, a visual hydrogen peroxide SCL detection method with a linear range of 0.5-50 μM and a detection limit of 0.32 μM is established. Moreover, the device can achieve the detection of glucose oxidase (GOD) activity and glucose by enzymatic conversion of glucose to hydrogen peroxide. The linear range of GOD detection is 1-200U/L with a detection limit of 0.86 U/L. The linear range of glucose detection is 0.5-70 μM with a detection limit of 0.43 μM. The cheap (a few dollars) and user-friendly apertureless USB-PUT is promising for sonochemistry applications and chemical education.

In Situ Monitoring of Hydrogen Peroxide Released from Living Cells Using a ZIF-8-Based Surface-Enhanced Raman Scattering Sensor

Hydrogen peroxide (H₂O₂) widely involves in intracellular and intercellular redox signaling pathways, playing a vital role in regulating various physiological events. Nevertheless, current analytical methods for the H₂O₂ assay are often hindered by relatively long response time, low sensitivity, or self-interference. Herein, a zeolitic imidazolate framework-8 (ZIF-8)-based surface-enhanced Raman scattering (SERS) sensor has been developed to detect H₂O₂ released from living cells by depositing ZIF-8 over SERS active gold nanoparticles (AuNPs) grafted with H₂O₂-responsive probe molecules, 2-mercaptohydroquinone. Combining the superior fingerprint identification of SERS and the highly efficient enrichment and selective response of H₂O₂ by ZIF, the ZIF-8-based SERS sensor exhibits a high anti-interference ability for H₂O₂ detection, with a limit of detection as low as 0.357 nM. Satisfyingly, owing to the enhanced catalytic activity derived from the successful integration of AuNPs and ZIF, the response time as short as 1 min can be obtained, demonstrating the effectiveness of the SERS sensor for rapid H₂O₂ detection. Furthermore, the developed SERS sensor enables real-time detection of H₂O₂ secreted from living cells under phorbol myristate acetate stimulation, as cells can be cultured on-chip. This study will pave the way toward the development of a metal-organic framework-based SERS platform for application in the fields of biosensing and early disease diagnosis associated with H₂O₂ secretion, thus exhibiting promising potential for future therapies.

Hydrazine Hydrate and Dissolved Oxygen-Triggered Near-Infrared Chemiluminescence from CuInS2@ZnS Nanocrystals for Bioassays

The overwhelming majority of commercially available chemiluminescence (CL) assays are conducted in the eye-visible region. Herein, a near-infrared (NIR) aqueous CL strategy was proposed with CuInS₂@ZnS nanocrystals (CIS@ZnS NCs) as emitters. Hydrazine hydrate (N₂H₄·H₂O) could inject electrons into the conduction band of the CIS@ZnS NCs and simultaneously transformed to the intermediate radical N₂H₃^•. N₂H₃^• reduced dissolved oxygen (O₂) to O₂^-•, while the O₂^-• could inject holes into the valence band of the CIS@ZnS NCs. The recombination of electrons and holes at Cu⁺ defects in CIS@ZnS NCs eventually yielded efficient NIR CL at around 824.1 nm, which is the longest waveband for NCs CL to the best of our knowledge. The NIR CL could be conveniently performed in the neutral aqueous medium (pH 7.0) with a quantum yield of 0.0155 Einstein/mol and was successfully employed for constructing a signal-off CL biosensor with ascorbic acid as the analyte as well as a signal-on CL biosensor for determining ascorbate oxidase, which indicates that this NIR CL system has a promising potential for bioassays in diverse ways.

A novel copper-based metal-organic framework as a peroxidase-mimicking enzyme and its glucose chemiluminescence sensing application

A novel copper-based metal-organic framework (Cu-MOF) with a large specific surface area and high porosity was synthesized. The Cu-MOF was a good peroxidase-mimicking enzyme and showed a high affinity with hydrogen peroxide in a wide pH range. The catalytic mechanism of Cu-MOF has been studied further based on comparing the characteristic of the Cu-MOF with some isomorphic MOFs. The catalytic activity center of Cu-MOF was determined to be the cupric ion rather than the ligand, which effectively promoted the generation of free radicals and electron transfer in the reaction progress. The high affinity of Cu-MOF to hydrogen peroxide proved it as an ideal catalyst for the chemiluminescence (CL) reaction involving hydrogen peroxide. Therefore, the CL method with high sensitivity could be established for detecting various substrates. A double-enzyme CL glucose biosensing platform was constructed for the determination of serum glucose employing the peroxidase-mimicking properties of Cu-MOF as well as glucose oxidase (GOx).

Disordered Assembly of Donors and Acceptors on Layered Double Hydroxides for High-Efficiency Chemiluminescence Resonance Energy Transfer

High-efficiency chemiluminescence (CL) resonance energy transfer (CRET) can be obtained by shortening the donor-acceptor distance and/or improving the luminescence efficiency of CRET acceptors. However, careful design and stringent experimental conditions are usually required for the ordered assembly of CRET acceptors on support materials to avoid aggregation-caused quenching problems. In this work, an aggregation-induced emission (AIE)-active fluorophore was disorderly adsorbed on the surface of layered double hydroxides (LDHs), which could exhibit high-efficiency luminescence. On the other hand, the positively charged LDHs can further adsorb peroxynitrite (ONOO^-) on the surface of LDHs. Therefore, the LDH-supported AIE fluorophore could dramatically amplify weak CL signals from ONOO^- donors as a result of ultra-high CRET efficiency by coupling the shorter donor-acceptor distance with efficient CRET acceptors. The proposed CL system has been successfully applied for the detection of NaNO₂ in the concentration range from 1.0 to 100 μM with a detection limit as low as 0.5 μM. Satisfactory recoveries (98-106%) and good accuracy were achieved for sausage samples. Our success will open new avenues for the convenient design of high-efficiency CRET systems.

Aggregation-induced chemiluminescence system for sensitive detection of mercury ions

As mercury ions (Hg²⁺) are emanated to surroundings in the course of various natural events and human activities, an accurate sensing of Hg²⁺ is essential for human health and environmental protection. Herein, a new aggregation-induced chemiluminescence (CL) sensor for fast, sensitive, and selective detection of Hg²⁺ is developed, based on the CL enhancement of bis(2,4,6-trichlorophenyl)oxalate (TCPO)-H₂O₂ system by thiolate-protected gold complexes (Au(I)-thiolate complexes) in the aggregated state. Because Hg²⁺ has a strong interaction with hydrosulfuryl (-SH) groups in Au(I)-thiolate complexes, the aggregation is disrupted and the CL is quenched. The decrease of CL intensity is proportional to Hg²⁺ contents with a linear range of 0.005-10 μg mL^-1 and the limit of detection (LOD) is 3 ng mL^-1. To the best of our knowledge, this is the first AIE CL sensor for Hg²⁺ detection. The study opens up attractive perspectives for developing simple and rapid aggregation-induced CL methods in monitoring heavy metals.