Enhanced Chemiluminescence under the Nanoconfinement of Covalent-Organic Frameworks and Its Application in Sensitive Detection of Cancer Biomarkers.

Chemiluminescence (CL) with intensive emission has been pursued for decades. It is still challenging to find a new mechanism to enhance CL. In this work, confinement-enhanced CL was developed for the first time by the coembedding of N-(aminobutyl)-N-(ethylisoluminol) (ABEI) and Co2+ into gold nanoparticle-modified covalent-organic frameworks (COFs). For the consideration of improving the hydrophilicity of COFs and facilitating subsequent biological modification, gold nanoparticles were first reduced on the COF surface (Au-COF) in situ without other reducing reagents. By virtue of the abundant imine bond and π backbones, ABEI and Co2+ were embedded in Au-COF synergistically through π-π stacking and coordination. The confinement of ABEI and Co2+ into Au-COF brought an over 20-fold enhancement of CL intensity compared to that of adding them to a liquid phase, which benefitted from the three aspects of the confinement effect, including the molecular enrichment effect, the physical constraint effect, and the molecular preorganization effect. As proof of concept, a lipid-protein dual-recognition sandwich strategy based on this CL-functionalized COF was developed for the detection of breast cancer cell line-derived extracellular vesicles (EVs) with four orders of magnitude improvement in the detection limit compared to ELISA. The successful distinction of human epidermal growth factor receptor 2 (HER2)-positive patients from HER2-negative patients indicated the great application potential of the proposed bioassay in HER2-positive breast cancer diagnosis. This work proposed a novel enhancement mechanism for CL based on crystalline porous materials, which provides a new perspective for the development of CL-functionalized materials for biosensors and bioassays.

N-(4-Aminobutyl)-N-ethylisopropanol and Co2+ Dual-Functionalized Core-Shell Fe3O4@Au/Ag Magnetic Nanomaterials with Strong and Stable Chemiluminescence for a Label-Free Exosome Immunosensor.

Recently, magnetic beads (MBs) are moving toward chemiluminescence (CL) functional magnetic nanomaterials with a great potential for constructing label-free immunosensors. However, most of the CL-functionalized MBs suffer from scarce binding sites, easy aggregation, and leakage of CL reagents, which will ultimately affect the analytical performance of immunosensors. Herein, by using core-shell Fe3O4@Au/Ag magnetic nanomaterials as a nanoplatform, a novel N-(4-aminobutyl)-N-ethylisopropanol (ABEI) and Co2+ dual-functionalized magnetic nanomaterial, namely, Fe3O4@Au/Ag/ABEI/Co2+, with strong and stable CL emission was successfully synthesized. Its CL intensity was 36 and 3.5 times higher than that of MB@ABEI-Au/Co2+ and ABEI and Co2+ dual-functionalized chemiluminescent MBs previously reported by our group, respectively. It was found that the excellent CL performance of Fe3O4@Au/Ag/ABEI/Co2+ could be attributed to the enrichment effect of the Au/Ag shell and the synergistic enhance effect of the Au/Ag shell and Co2+. A related CL mechanism has been proposed. Afterward, based on the intense and stable CL emission of Fe3O4@Au/Ag/ABEI/Co2+, a sensitive and effective label-free CL immunosensor for exosome detection was established. It exhibited excellent analytical performance with a wide detection range of 3.1 × 103 to 3.1 × 108 particles/mL and a low detection limit of 2.1 × 103 particles/mL, which were better than the vast majority of the reported CL immunosensors. Moreover, the proposed label-free CL immunosensor was successfully used to detect exosomes in human serum samples and enabled us to distinguish healthy persons and lung cancer patients. It has the potential to be a powerful tool for exosome study and early cancer diagnosis.

Label-Free Immunoassay for Sensitive and Rapid Detection of the SARS-CoV-2 Antigen Based on Functionalized Magnetic Nanobeads with Chemiluminescence and Immunoactivity.

Direct detection of SARS-CoV-2 in biological specimens is often challenging due to the low abundance of viral components and lack of enough sensitivity. Herein, we developed a new type of chemiluminescent functionalized magnetic nanomaterial for sensitive detection of the SARS-CoV-2 antigen. First, HAuCl4 was reduced by N-(aminobutyl)-N-(ethylisoluminol) (ABEI) in the presence of amino magnetic beads (MB-NH2) to generate ABEI-AuNPs, which were directly assembled on the surface of MB-NH2. Then, Co2+ was modified onto the surface to form MB@ABEI-Au/Co2+ (MAA/Co2+). MAA/Co2+ exhibited good chemiluminescence (CL) and magnetic properties. It was also found that it was easy for the antibody to be connected with MAA/Co2+. Accordingly, MAA/Co2+ was used as a sensing interface to construct a label-free immunoassay for rapid detection of the N protein in SARS-CoV-2. The immunoassay showed a linear range from 0.1 pg/mL to 10 ng/mL and a low detection limit of 69 fg/mL, which was superior to previously reported methods for N protein detection. It also demonstrated good selectivity by virtue of magnetic separation, which effectively removed a sample matrix after immunoreactions. It was successfully applied for the detection of the N protein in spiked human serum and saliva samples. Furthermore, the immunoassay was integrated with an automatic CL analyzer with magnetic separation to detect the N protein in patient serums and rehabilitation patient serums with satisfactory results. Thus, the CL immunoassay without a complicated labeling procedure is sensitive, selective, fast, simple, and cost-effective, which may be used to combat the COVID-19 pandemic. Finally, the CL quenching mechanism of the N protein in the immunoassay was also explored.

Automatic label-free immunoassay with high sensitivity for rapid detection of SARS-CoV-2 nucleocapsid protein based on chemiluminescent magnetic beads.

Accurate and efficient early diagnosis is crucial for the control of COVID-19 pandemic. However, methods that can balance sensitivity, high throughput, detection speed and automation simultaneously are still scarce. Here, we report an automatic label-free chemiluminescence immunoassay (CLIA) for rapid SARS-CoV-2 nucleocapsid protein (NP) detection with high sensitivity and throughput. N-(4-aminobutyl)-N-ethylisoluminol and Co2+ dual-functionalized chemiluminescent magnetic beads (dfCL-MB) were first applied to the detection of protein by a novel and simple strategy. Sulphydryl polyethylene glycol was coated on the surface of dfCL-MB so as to assemble dfCL-MB and antibody conjugated gold nanoparticles through Au-S bond. Considering the high-risk application scenarios, the immunosensor was integrated with an automatic chemiluminescence analyzer so that the whole testing procedure could be carried out automatically without manual operation. A linear correlation between CL intensities and the logarithm of NP concentration was obtained in the range of 0.1-10,000 pg/mL with a detection limit of 21 fg/mL. The whole process cost 25 min and the sample compartment can bear 24 samples simultaneously. The spiked human serum samples and serum samples from COVID-19 patients were determined with satisfactory recoveries of 91.1-109.4%, suggesting that the proposed label-free CLIA is of great potential for SARS-CoV-2 NP detection in practice.

Deep Learning-Assisted Three-Dimensional Fluorescence Difference Spectroscopy for Identification and Semiquantification of Illicit Drugs in Biofluids.

The fast identification and quantification of illicit drugs in biofluids are of great significance in clinical detection. However, existing drug detection strategies cannot fully meet clinical needs, and the on-site identification and quantification of various illicit drugs in biofluids remain a great challenge. Here, we report the development of a deep learning-assisted three-dimensional (3D) fluorescence difference spectroscopy for rapid identification and semiquantification of illicit drugs in biofluids. This strategy introduces highly fluorescent silver nanoclusters into the biofluids with illicit drugs as signal sources. The interaction between silver nanoclusters and drug molecules changed the fluorescence performance of the mixture. Deep learning methods were applied to grasp the subtle fingerprint information from the 3D fluorescence difference spectra to identify and semiquantify various illicit drugs in biofluids, including codeine, 4,5-methylene-dioxy amphetamine, 3,4-methylene dioxy methamphetamine, meperidine, and methcathinone. This approach can achieve a high prediction accuracy rate of 88.07% and a broad detection range from 2 µg/mL to 100 mg/mL. It opens up a new way for the detection of small molecules with or without fluorescence in complicated matrixes.

Effect analysis of pore wall thickness, pore size, and functional group of activated carbon on adsorption behavior based on molecular simulation.

To effectively investigate the influence of activated carbon on the adsorption of volatile organic compounds (VOCs), physical and chemical factors of activated carbon including pore wall thickness, pore size, and functional groups were studied using grand canonical Monte Carlo (GCMC) simulation. In addition, benzene and acetone were taken as two representative components of VOCs. Simulation results was presented by the changes in characteristics of benzene and acetone. The results show that at the saturated vapor pressure (P0), the adsorption density hardly varies with the mentioned factors of activated carbon. Differently, the saturated adsorption capacity increases considerably with the rise of pore size or the reduction of pore wall thickness, and the rise of pore size also leads to a dramatic increase in adsorption layer and a subsequent fall in ordering. However, when the pressure is less than 0.001P0, the monomolecular interaction energy and the isosteric heat are strengthened greatly with the addition of carboxyl and amino groups, while the threshold pressure shows an opposite change to the monomolecular interaction energy. In the meantime, the decrease of pore size or the increase of pore wall thickness will result in the same results. Findings in this paper can provide valuable insights into the microscopic mechanisms of the adsorption between activated carbon and VOCs.