Synergistic effect of heterogeneous single atoms and clusters for improved catalytic performance

Electrocatalytic water splitting provides an efficient method for the production of hydrogen.In electrocatalytic water splitting,the oxygen evolution reaction(OER)involves a kinetically sluggish four-electron transfer process,which limits the efficiency of electrocatalytic water splitting.Therefore,it is urgent to develop highly active OER catalysts to accelerate reaction kinetics.Coupling single atoms and clusters in one system is an innovative approach for developing efficient catalysts that can synergistically optimize the adsorption and configuration of intermediates and improve catalytic activity.However,research in this area is still scarce.Herein,we constructed a heterogeneous single-atom cluster system by anchoring Ir single atoms and Co clusters on the surface of Ni(OH)_(2)nanosheets.Ir single atoms and Co clusters synergistically improved the catalytic activity toward the OER.Specifically,Co_(n)Ir_(1)/Ni(OH)_(2)required an overpotential of 255 mV at a current density of 10 mA·cm^(−2),which was 60 mV and 67 mV lower than those of Co_(n)/Ni(OH)_(2)and Ir1/Ni(OH)_(2),respectively.The turnover frequency of Co_(n)Ir_(1)/Ni(OH)_(2)was 0.49 s^(−1),which was 4.9 times greater than that of Co_(n)/Ni(OH)_(2)at an overpotential of 300 mV.

Nanomechanical assay for ultrasensitive and rapid detection of SARS-CoV-2 based on peptide nucleic acid

The massive global spread of the COVID-19 pandemic makes the development of more effective and easily popularized assays critical.Here,we developed an ultrasensitive nanomechanical method based on microcantilever array and peptide nucleic acid(PNA)for the detection of severe acute respiratory syndrome-coronavirus-2(SARS-CoV-2)RNA.The method has an extremely low detection limit of 0.1 fM(105 copies/mL)for N-gene specific sequence(20 bp).Interestingly,it was further found that the detection limit of N gene(pharyngeal swab sample)was even lower,reaching 50 copies/mL.The large size of the N gene dramatically enhances the sensitivity of the nanomechanical sensor by up to three orders of magnitude.The detection limit of this amplification-free assay method is an order of magnitude lower than RT-PCR(500 copies/mL)that requires amplification.The non-specific signal in the assay is eliminated by the in-situ comparison of the array,reducing the false-positive misdiagnosis rate.The method is amplification-free and label-free,allowing for accurate diagnosis within 1 h.The strong specificity and ultrasensitivity allow single base mutations in viruses to be distinguished even at very low concentrations.Also,the method remains sensitive to fM magnitude lung cancer marker(miRNA-155).Therefore,this ultrasensitive,amplification-free and inexpensive assay is expected to be used for the early diagnosis of COVID-19 patients and to be extended as a broad detection tool.

Nanomechanical vibration profiling of oocytes

The beginning of a mammalian life commences with a fertilized oocyte.The study of oocytes is certainly one of the most intriguing scientific questions of our time.Herein,we studied oocytes from a mechanical perspective and characterized the typical life activities of oocytes by nanomechanical vibrations.During the development of oocytes from the germinal vesicle(GV)stage to the zygotes,the GV stage oocytes induced a significant nanomechanical vibration,compared with the oocytes in meiosis I(MI)and meiosis II(MII)stages and zygotes.We analyzed the characteristics of mechanical vibrations of oocytes,including the amplitude as well as the frequency.It showed that the amplitude and frequency of nanomechanical vibrations induced by oocytes were caused by the cytoskeleton(microfilaments)and the distribution of metabolic characteristics(mitochondria)within oocytes.This work provides a new perspective for clinical quality assessment and basic research of oocytes,and can open new doors for development of life science.

Quantifying 3D cell-matrix interactions during mitosis and the effect of anticancer drugs on the interactions

The mechanical force between cells and the extracellular microenvironment is crucial to many physiological processes such as cancer metastasis and stem cell differentiation. Mitosis plays an essential role in all these processes and thus an in-depth understanding of forces during mitosis gains insight into disease diagnosis and disease treatment. Here, we develop a traction force microscope method based on monolayer fluorescent beads for measuring the weak traction force (tens of Pa) of mitotic cells in three dimensions. We quantify traction forces of human ovarian granulosa (KGN) cells exerted on the extracellular matrix throughout the entire cell cycle in three dimensions. Our measurements reveal how forces vary during the cell cycle, especially during cell division. Furthermore, we study the effect of paclitaxel (PTX) and nocodazole (NDZ) on mitotic KGN cells through the measurement of traction forces. Our results show that mitotic cells with high concentrations of PTX exert a larger force than those with high concentrations of NDZ, which proved to be caused by changes in the structure and number of microtubules. These findings reveal the key functions of microtubule in generating traction forces during cell mitosis and explain how dividing cells regulate themselves in response to anti-mitosis drugs. This work provides a powerful tool for investigating cell-matrix interactions during mitosis and may offer a potential way to new therapies for cancer.

Nanomechanical sensor for rapid and ultrasensitive detection of tumor markers in serum using nanobody

Early cancer diagnosis requires ultrasensitive detection of tumor markers in blood.To this end,we develop a novel microcantilever immunosensor using nanobodies(Nbs)as receptors.As the smallest antibody(Ab)entity comprising an intact antigen-binding site,Nbs achieve dense receptor layers and short distances between antigen-binding regions and sensor surfaces,which significantly elevate the generation and transmission of surface stress.Owing to the inherent thiol group at the C-terminus,Nbs are covalently immobilized on microcantilever surfaces in directed orientation via one-step reaction,which further enhances the stress generation.For microcantilever-based nanomechanical sensor,these advantages dramatically increase the sensor sensitivity.Thus,Nb-functionalized microcantilevers can detect picomolar concentrations of tumor markers with three orders of magnitude higher sensitivity,when compared with conventional Ab-functionalized microcantilevers.This proof-of-concept study demonstrates an ultrasensitive,label-free,rapid,and low-cost method for tumor marker detection.Moreover,interestingly,we find Nb inactivation on sensor interfaces when using macromolecule blocking reagents.The adsorption-induced inactivation is presumably caused by the change of interfacial properties,due to binding site occlusion upon complex coimmobilization formations.Our findings are generalized to any coimmobilization methodology for Nbs and,thus,for the construction of high-performance immuno-surfaces.

Dynamic nanomechanical characterization of cells in exosome therapy

Exosomes derived from mesenchymal stem cells(MSCs)have been confirmed to enhance cell proliferation and improve tissue repair.Exosomes release their contents into the cytoplasmic solution of the recipient cell to mediate cell expression,which is the main pathway through which exosomes exert therapeutic effects.The corresponding process of exosome internalization mainly occurs in the early stage of treatment.However,the therapeutic effect of exosomes in the early stage remains to be further studied.We report that the three-dimensional cell traction force can intuitively reflect the ability of exosomes to enhance the cytoskeleton and cell contractility of recipient cells,serving as an effective method to characterize the therapeutic effect of exosomes.Compared with traditional biochemical methods,we can visualize the early therapeutic effect of exosomes in real time without damage by quantifying the cell traction force.Through quantitative analysis of traction forces,we found that endometrial stromal cells exhibit short-term cell roundness accompanied by greater traction force during the early stage of exosome therapy.Further experiments revealed that exosomes enhance the traction force and cytoskeleton by regulating the Rac1/RhoA signaling pathway,thereby promoting cell proliferation.This work provides an effective method for rapidly quantifying the therapeutic effects of exosomes and studying the underlying mechanisms involved.