scButterfly: a versatile single-cell cross-modality translation method via dual-aligned variational autoencoders.

Recent advancements for simultaneously profiling multi-omics modalities within individual cells have enabled the interrogation of cellular heterogeneity and molecular hierarchy. However, technical limitations lead to highly noisy multi-modal data and substantial costs. Although computational methods have been proposed to translate single-cell data across modalities, broad applications of the methods still remain impeded by formidable challenges. Here, we propose scButterfly, a versatile single-cell cross-modality translation method based on dual-aligned variational autoencoders and data augmentation schemes. With comprehensive experiments on multiple datasets, we provide compelling evidence of scButterfly's superiority over baseline methods in preserving cellular heterogeneity while translating datasets of various contexts and in revealing cell type-specific biological insights. Besides, we demonstrate the extensive applications of scButterfly for integrative multi-omics analysis of single-modality data, data enhancement of poor-quality single-cell multi-omics, and automatic cell type annotation of scATAC-seq data. Moreover, scButterfly can be generalized to unpaired data training, perturbation-response analysis, and consecutive translation.

Dual-source signal amplification electrochemiluminescence sensor combined with molecularly imprinted polymers for the imidacloprid detection.

A novel lanthanide metal-organic-gel (MOG)-derived material/nitrogen-doped graphdiyne (Tb-Ru-MOG/CeO2/N-GDY) composite with a dual-source signal amplification strategy was prepared and used to construct a molecularly imprinted sensor based on bifunctional monomers for the detection of imidacloprid (IMI) using electrochemiluminescence (ECL). In a green reaction environment, terbium (III) (Tb3+) can undergo multiple coordination reactions with 4'-(4-carboxyphenyl)-2,2':6',2″-terpyridine (Hcptpy) and tris(4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium (II) dichloride (Ru(dcbpy)32+), and combine with ceria nanoparticles (CeO2 NPs) to form Tb-Ru-MOG/CeO2. Within the Tb-Ru-MOG/CeO2 framework, energy transfer from the double ligands can sensitize the central Tb3+, triggering a distinct antenna effect and energy-transfer, and its polyporous configuration offered a nanoconfined space for Ce3+/Ce4+ to effectively catalyze coreactant radicals (S2O82-), leading to in-situ endogenous activation ECL reactions. The conductive N-GDY accelerated electron movement and increased the loading on the electrode surface, enhancing the exogenous excitation of the ECL signals. Leveraging the synergistic effect of the bifunctional monomer, the synthesized molecularly imprinted polymers (MIPs) ECL sensor demonstrated a wide detection range from 10 nM to 10,000 nM for IMI, with a limit of detection (LOD) of 1.37 nM, showcasing an innovative concept for the dual-source strategy of signal amplification in integrated ECL composites to analyze food and environmental hazards.

Bursting multistability induced by double-Hopf bifurcation.

We study the slow-fast dynamics of a system with a double-Hopf bifurcation and a slowly varying parameter. The model consists of coupled Bonhöffer-van der Pol oscillators excited by a periodic slow-varying AC source. We consider two cases where the slowly varying parameter passes by or crosses the double-Hopf bifurcation, respectively. Due to the system's multistability, two bursting solutions are observed in each case: single-mode bursting and two-mode bursting. Further investigation reveals that the double-Hopf bifurcation causes a stable coexistence of these two bursting solutions. The mechanism of such coexistence is explained using the slowly changing phase portraits of the fast subsystem. We also show the robustness of the observed effect in the vicinity of the double-Hopf bifurcation.

Novel poly (N-methacryloyl-L-alanine acid) grafted chitosan microspheres based solid-phase extraction coupled with ICP-MS for simultaneous detection of trace metal elements in food.

Poly (N-methacryloyl-L-alanine acid) grafted tartaric acid-crosslinked chitosan microspheres (PNMA-TACS) were successfully synthesized and employed as a novel adsorbent for the separation and enrichment of metal ions in the food system. PNMA-TACS microspheres-based solid phase extraction (SPE) was coupled with ICP-MS for accurate quantification of trace V(V), Cr(III), As(III), Pb(II), Cd(II) and Cu(II). The obtained PNMA-TACS microspheres were characterized, and parameters influencing the method were optimized. Under optimal conditions, the calibration curves for Cu(II) and V(V) were linear within 0.01-30 µg L-1, the linear ranges of Cr(III), As(III), Pb(II) and Cd(II) were 0.01-15 µg L-1, and the detection limit of the developed approach was 1.1-3.7 ng L-1. The results were consistent with the consensus values of method validation implemented by two standards. Moreover, standard addition recovery experiments were performed in rice and milk powder, which achieved satisfactory recovery of 86.1-103.5%.

A Smartphone-Integrated Molecularly Imprinted Fluorescence Sensor for Visual Detection of Chlortetracycline Based on N,P-Codoped Carbon Dots Decorated Iron-Based Metal-Organic Frameworks.

The residue of chlortetracycline is potentially hazardous to human health; it is meaningful to exploit a portable, rapid, sensitive, and selective method for detection of chlortetracycline (CTC). In this study, a novel fluorescence bionic sensing probe (NH2-MIL-53&N,P-CDs@MIP) was successfully prepared based on the nitrogen and phosphorus codoped carbon dots decorated iron-based metal-organic frameworks combining with molecular imprinted polymer for the detection of CTC. A fluorescence intensity-responsive "on-off" detection of CTC on account of the inner-filter effect (IFE) was achieved by NH2-MIL-53&N,P-CDs@MIP. Under the optimal conditions, the fluorescence quenching degree of NH2-MIL-53&N,P-CDs@MIP presented a good linear relationship with the CTC concentration in the range 0.06-30 µg mL-1 and the limit of detection (LOD) was 0.019 µg mL-1. The fluorescent probe was applied to detect CTC in milk samples, and experimental results showed a good recovery rate (88.73%-96.28%). Additionally, a smartphone-integrated fluorescence sensing device based on NH2-MIL-53&N,P-CDs@MIP was exploited to replace the expensive and bulky fluorescence spectrophotometer for quantitative determination of CTC with the LOD of 0.033 µg mL-1. The sensing system showed high selectivity, strong stability, high specificity, and portability, which provide a great strategy for the quantitative detection of antibiotic residue.

A Turn-Off Fluorescent Biomimetic Sensor Based on a Molecularly Imprinted Polymer-Coated Amino-Functionalized Zirconium (IV) Metal-Organic Framework for the Ultrasensitive and Selective Detection of Trace Oxytetracycline in Milk.

Developing sensitive and effective methods to monitor oxytetracycline residues in food is of great significance for maintaining public health. Herein, a fluorescent sensor (NH2-UIO-66 (Zr)@MIP) based on a molecularly imprinted polymer-coated amino-functionalized zirconium (IV) metal-organic framework was successfully constructed and first used for the ultrasensitive determination of oxytetracycline. NH2-UIO-66 (Zr), with a maximum emission wavelength of 455 nm under 350 nm excitation, was prepared using a microwave-assisted heating method. The NH2-UIO-66 (Zr)@MIP sensor with specific recognition sites for oxytetracycline was then acquired by modifying a molecularly imprinted polymer on the surface of NH2-UIO-66 (Zr). The introduction of NH2-UIO-66 (Zr) as both a signal tag and supporter can strengthen the sensitivity of the fluorescence sensor. Thanks to the combination of the unique characteristics of the molecularly imprinted polymer and NH2-UIO-66 (Zr), the prepared sensor not only exhibited a sensitive fluorescence response, specific identification capabilities and a high selectivity for oxytetracycline, but also showed good fluorescence stability, satisfactory precision and reproducibility. The fabricated sensor displayed a fluorescent linear quenching in the OTC concentration range of 0.05-40 µg mL-1, with a detection limit of 0.012 µg mL-1. More importantly, the fluorescence sensor was finally applied for the detection of oxytetracycline in milk, and the results were comparable to those obtained using the HPLC approach. Hence, the NH2-UIO-66 (Zr)@MIP sensor possesses great application potential for the accurate evaluation of trace oxytetracycline in dairy products.

"Blocking-effect" detection strategy of clenbuterol by molecularly imprinted electrochemiluminescence sensor based on multiple synergistic excitation of AgNW luminophores signal with highly active BNQDs@AuNFs nanoscale co-reaction accelerator.

A molecularly imprinted electrochemiluminescence sensor (MIECLS) is constructed to selectively detect clenbuterol (CLB) based on boron nitride quantum dots@gold nanoflowers/silver nanowires (BNQDs@AuNFs/AgNWs). The abundant amino and hydroxyl groups on the surface of the BNQDs generate an electrostatic self-assembly effect with the multi-tipped spatial structure of AuNFs, constituting a novel nanoscale co-reaction accelerator (NCRA) with high activity and large load capacity. An NCRA embedded in the network structure of the AgNW luminophores significantly promotes the reduction of peroxydisulfate (S2O82-) to sulfate anion radicals (SO4-•) through the catalysis of amino groups and boron radicals (B•) and the electron acceleration of AuNFs while also reducing the reaction distance between SO4-• and AgNWs-•, realizing the multiple synergistic amplification of the electrochemiluminescence (ECL) signal. Imprinted cavities in the molecularly imprinted polymers (MIPs) prepared by electropolymerization can generate a "blocking-effect" by recognizing CLB, realizing ECL signal quenching. Analytical results indicate that the established MIECLS detects CLB in a line concentration range of 0.5-50000 nM and detection limit of 0.00693 nM. The spiked recoveries are 85.90%-97.77%, with the relative standard deviations (RSD) under 5.1%, consistent with those of high-performance liquid chromatography (HPLC). This work demonstrates that an efficient NCRA can significantly enhance the output of the ECL signal in collaboration with the original luminophore, providing a new method to realize the ultra-detection of targeted substances by MIECLS.

A molecularly imprinted fluorescence sensor for sensitive detection of tetracycline using nitrogen-doped carbon dots-embedded zinc-based metal-organic frameworks as signal-amplifying tags.

Tetracycline (TC) residues not only endanger human health, but also are detrimental to the sustainable development of aquaculture and animal husbandry. Herein, a novel fluorescence sensor with high sensitivity and selectivity was developed based on nitrogen-doped carbon dots embedded in zinc-based metal-organic frameworks and incorporating molecularly imprinted polymer (ZIF-8&N-CDs@MIP). The physical and chemical properties of the ZIF-8&N-CDs@MIP had been characterized by SEM, TEM, FTIR, XRD, BET, TGA, etc. Under optimal conditions, the limit of detection (LOD) of the novel sensor was 0.045 µg mL-1 with the concentration of TC in the range of 0.1-4.0 µg mL-1. In addition, the prepared imprinted polymers showed superior adsorption selectivity to tetracycline compared with non-imprinted polymers, and the quenching mechanism of ZIF-8&N-CDs@MIP was demonstrated to be attributed to the inner filter effect (IFE). This work provided an effective and reliable method for the specific detection of tetracycline and was successfully applied in milk and egg samples with satisfactory recoveries (80.67-95.22%).

A smartphone-assisted optosensing platform based on chromium-based metal-organic framework signal amplification for ultrasensitive and real-time determination of oxytetracycline.

Ultrasensitive and onsite detection of oxytetracycline (OTC) is of vital significance for ensuring public health. Herein, a novel and versatile fluorescence biomimetic nanosensor, Mg,N-CDs@MIL-101@MIP, was elaborately tailored for the assay of OTC. MIL-101 with extraordinarily high surface area and porosity, as a favorable supporter, suppressed self-quenching of Mg,N-CDs and boosted mass transfer rate, realizing signal amplification. As an ultrasensitive signal transducer, high luminescent Mg,N-CDs yielded conspicuous fluorescence responses for OTC, enhancing the sensitivity of Mg,N-CDs@MIL-101@MIP. High-affinity imprinting sites further endowed Mg,N-CDs@MIL-101@MIP with superior anti-interference ability and reusability. Given prominent merits, Mg,N-CDs@MIL-101@MIP demonstrated a good linear range (0.05-40 µg mL-1) with a lower limit of detection (16.8 ng mL-1), supplying high accessibility to realize ultrasensitive and highly selective measurement of OTC in samples. Additionally, to attain precise onsite profiling of OTC, an intelligent sensing platform was developed by integrating Mg,N-CDs@MIL-101@MIP with a portable smartphone-assisted optical device. As both signal reader and analyzer, smartphone can instantly capture concentration-dependent fluorescent images and accurately digitize them, accomplishing quantitative analysis of OTC. More delightfully, the portable platform was utilized for visual determination of OTC in milk samples with satisfactory results, offering a promising tool for the high-performance onsite evaluation of food safety and environmental health.

Construction of an ECL Detection Platform for Sensitive Detection of Carbaryl Based on an Eu3+-Functionalized Metal-Organic Framework Encapsulated with Nanogold.

In this work, an Eu3+-MOF-253@Au electrochemiluminescence sensor was successfully constructed for the first time by encapsulating nanogold in the metal-organic frameworks (MOFs) backbone and pore channels, and assembling Eu3+ on the MOF backbone. Firstly, the introduction of nanogold overcomes the weakness of MOFs, which was difficult to achieve, and enhances its catalytic performance, followed by the modification of Eu3+ to confer the electrochemiluminescence performance and the function of target detection on the sensor. Moreover, carbaryl was placed in an alkaline working solution to enhance the intensity of electrochemiluminescence signal, as well as to promote the hydrolysis of carbaryl into 1-naphthol, which caused the burst of Eu3+-MOF-253@Au electrochemiluminescence sensor, thereby achieving the sensitive detection of carbaryl. On this basis, the electrochemiluminescence detection conditions were optimized, the performance was analyzed, and finally it was successfully used for the detection of carbaryl with good linearity in the range of 0.2-200 µg L-1 and a low detection limit (0.14 µg L-1).

A molecularly imprinted fluorescence nanosensor based on upconversion metal-organic frameworks for alpha-cypermethrin specific recognition.

A sensitive molecularly imprinted fluorescent nanosensor based on zeolitic imidazolate frameworks-8 (ZIF-8) and upconversion nanoparticles (UCNPs) was developed for the determination of trace alpha-cypermethrin (α-CPM) for the first time. The sensor was synthesized by a layer-by-layer self-assembly strategy. UCNPs with a maximum emission wavelength of 544.5 nm under 980 nm excitation were firstly prepared as the luminous core. Then, ZIF-8 with the large specific surface and porosity was introduced, which not only improved the mass transfer and adsorption capacity of the sensor but also increased the fluorescence intensity of UCNPs as a protective layer. Finally, molecularly imprinted polymers (UCNPs@ZIF-8@MIPs) were fabricated in mixed solutions containing UCNPs@ZIF-8 (support material), α-CPM (template), acrylamide (functional monomer), and divinylbenzene (cross-linker). Under the optimal condition, the fluorescence intensity of UCNPs@ZIF-8@MIP was linearly quenched with increasing concentration of α-CPM in the range 0.10-12 mg L-1 with a detection limit of 0.03 mg L-1 (S/N = 3). The developed UCNPs@ZIF-8@MIP probe was used to detect α-CPM in real samples; the satisfactory results obtained were consistent with those obtained by GC-MS.Graphical abstract.