Transmission dynamics of Zika virus with multiple infection routes and a case study in Brazil.

The Zika virus (ZIKV) is a serious global public health crisis. A major control challenge is its multiple transmission modes. This paper aims to simulate the transmission patterns of ZIKV using a dynamic process-based epidemiological model written in ordinary differential equations, which incorporates the human-to-mosquito infection by bites and sewage, mosquito-to-human infection by bites, and human-to-human infection by sex. Mathematical analyses are carried out to calculate the basic reproduction number and backward bifurcation, and prove the existence and stability of the equilibria. The model is validated with infection data by applying it to the 2015-2016 ZIKV epidemic in Brazil. The results indicate that the reproduction number is estimated to be 2.13, in which the contributions by mosquito bite, sex and sewage account for 85.7%, 3.5% and 10.8%, respectively. This number and the morbidity rate are most sensitive to parameters related to mosquito ecology, rather than asymptomatic or human-to-human transmission. Multiple transmission routes and suitable temperature exacerbate ZIKV infection in Brazil, and the vast majority of human infection cases were prevented by the intervention implemented. These findings may provide new insights to improve the risk assessment of ZIKV infection.

Modelling the impact of human behavior using a two-layer Watts-Strogatz network for transmission and control of Mpox.

PURPOSE: This study aims to evaluate the effectiveness of mitigation strategies and analyze the impact of human behavior on the transmission of Mpox. The results can provide guidance to public health authorities on comprehensive prevention and control for the new Mpox virus strain in the Democratic Republic of Congo as of December 2023. METHODS: We develop a two-layer Watts-Strogatz network model. The basic reproduction number is calculated using the next-generation matrix approach. Markov chain Monte Carlo (MCMC) optimization algorithm is used to fit Mpox cases in Canada into the network model. Numerical simulations are used to assess the impact of mitigation strategies and human behavior on the final epidemic size. RESULTS: Our results show that the contact transmission rate of low-risk groups and susceptible humans increases when the contact transmission rate of high-risk groups and susceptible humans is controlled as the Mpox epidemic spreads. The contact transmission rate of high-risk groups after May 18, 2022, is approximately 20% lower than that before May 18, 2022. Our findings indicate a positive correlation between the basic reproduction number and the level of heterogeneity in human contacts, with the basic reproduction number estimated at 2.3475 (95% CI: 0.0749-6.9084). Reducing the average number of sexual contacts to two per week effectively reduces the reproduction number to below one. CONCLUSION: We need to pay attention to the re-emergence of the epidemics caused by low-risk groups when an outbreak dominated by high-risk groups is under control. Numerical simulations show that reducing the average number of sexual contacts to two per week is effective in slowing down the rapid spread of the epidemic. Our findings offer guidance for the public health authorities of the Democratic Republic of Congo in developing effective mitigation strategies.

Triazine-based covalent-organic framework embedded with cuprous oxide as the bioplatform for photoelectrochemical aptasensing Escherichia coli.

A superior photoelectrochemical (PEC) aptasensor was manufactured for the detection of Escherichia coli (E. coli) based on a hybrid of triazine-based covalent-organic framework (COF) and cuprous oxide (Cu2O). The COF synthesized using 1,3,5-tris(4-aminophenyl)-benzene (TAPB) and 1,3,5-triformylphloroglucinol (Tp) as building blocks acted as a scaffold for encapsulated Cu2O nanoparticles (denoted as Cu2O@TAPB-Tp-COF), which then was employed as the bioplatform for anchoring E. coli-targeted aptamer. Cu2O@Cu@TAPB-Tp-COF demonstrated enhanced separation of the photogenerated carriers and photoabsorption ability and boosted photoelectric conversion efficiency. The developed Cu2O@TAPB-Tp-COF-based PEC aptasensor exhibited a lower detection limit of 2.5 CFU mL-1 toward E. coli within a wider range of 10 CFU mL-1 to 1 × 104 CFU mL-1 than most of reported aptasensors for determining foodborne bacteria, together with high selectivity, good stability, and superior ability and reproducibility. The recoveries of E. coli spiked into milk and bread samples ranged within 95.3-103.6% and 96.6-102.8%, accompanying with low RSDs of 1.37-4.48% and 1.74-3.66%, respectively. The present study shows a promising alternative for the sensitive detection of foodborne bacteria from complex foodstuffs and pathogenic bacteria-polluted environment.

Schottky Junction Nanozyme Based on Mn-Bridged Co-Phthalocyanines and Ti3C2Tx Nanosheets Boosts Integrative Type I and II Photosensitization for Multimodal Cancer Therapy.

Cancer phototheranostics have the potential for significantly improving the therapeutic effectiveness, as it can accurately diagnose and treat cancer. However, the current phototheranostic platforms leave much to be desired and are often limited by tumor hypoxia. Herein, a Schottky junction nanozyme has been established between a manganese-bridged cobalt-phthalocyanines complex and Ti3C2Tx MXene nanosheets (CoPc-Mn/Ti3C2Tx), which can serve as an integrative type I and II photosensitizer for enhancing cancer therapeutic efficacy via a photoacoustic imaging-guided multimodal chemodynamic/photothermal/photodynamic therapy strategy under near-infrared (808 nm) light irradiation. The Schottky junction not only possessed a narrow-bandgap, enhanced electron-hole separation ability and exhibited a potent redox potential but also enabled improved H2O2 and O2 supplying performances in vitro. Accordingly, the AS1411 aptamer-immobilized CoPc-Mn/Ti3C2Tx nanozyme illustrated high accuracy and excellent anticancer efficiency through a multimodal therapy strategy in in vitro and in vivo experiments. This work presents a valuable method for designing and constructing a multifunctional nanocatalytic medicine platform for synergistic cancer therapy of solid tumors.

A dual-photoelectrode fuel cell-driven self-powered aptasensor based on the 1D/2D In2S3/MoS2@Fe-CNTs heterojunction for the ultrasensitive detection of Staphylococcus aureus.

A novel dual-electrode photo-fuel cell (PFC)-driven self-powered aptasensor was manufactured for the sensitive and selective detection of Staphylococcus aureus (S. aureus) using the one-dimensional (1D)/2D Schottky heterojunction comprising bimetallic indium/molybdenum sulfide nanosheets and iron-doped carbon nanotube (Fe-CNT) (denoted as In2S3/MoS2@Fe-CNTs) as the photocathode. Given the generation of a robust interface at In2S3/MoS2 and Fe-CNTs, the charge separation and transfer ability of photoexcited electron-hole pairs were enforced, thus improving the output voltage of the assembled PFC. In addition, the numerous active sites of the 1D/2D In2S3/MoS2@Fe-CNTs Schottky heterojunction enabled the immobilization of large amounts of aptamer. Accordingly, the proposed PFC-driven self-powered aptasensor exhibited a wide linear range in 10-1 × 107 CFU mL-1 with a detection limit of 1.2 CFU mL-1 toward S. aureus. High selectivity, excellent reproducibility, good stability, and acceptable regenerability, as well as great potential practicality, were also achieved for the detection of S. aureus using the developed PFC-driven self-powered aptasensor. This work not only provides a new photoactive material based on a robust 1D/2D Schottky heterojunction, but also constructs a novel PFC-based self-powered aptasensing strategy based on dual-photoelectrodes and with satisfactory performance for the detection of foodborne pathogens in diverse environments.

Universal biosensing platform based on polyMn-MOF nanosheets for efficient analysis of foodborne pathogens from diverse foodstuffs.

A universal electrochemical aptasensing strategy was developed for sensitive detection of various pathogenic bacteria (such as Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella enterica) that commonly existed in food products. Diverse categories of pathogenic bacterium-targeting aptamers were separately immobilized over the polyMOF, which was prepared using the polyether polymer ligand containing 1,4-benzenedicarboxylic acid (polyH2bdc) units as building block, 4,4'-bipyridine as co-ligand, polyvinyl pyrrolidone as structural regulator, and MnCl2 as metal centers (represented by polyMn-MOF). The developed polyMn-MOF-based aptasensor illustrated ultralow limits of detection for three kinds of foodborne pathogens (2.6, 1.5, and 3.5 CFU mL-1 for SE, S. aureus, and E. coli, respectively) in a wide linear range of 10 - 1 × 108 CFU mL-1 of pathogenic bacteria concentration by differential pulse voltammetry, accompanying with high selectivity, good stability, and superior reproducibility. Considering these advantages, the fabricated polyMOF-based aptasensor demonstrated wide applications in food safety and analysis and other biosensing fields.

The intergrated nanostructure of bimetallic CoNi-based zeolitic imidazolate framework and carbon nanotubes as high-performance electrochemical supercapacitors.

In this study, a series of one-dimensional (1D)/two-dimensional (2D) heterostructure hybrids were fabricated through the in situ growth of a Co and Ni bimetallic zeolitic imidazolate framework (CoNi-ZIF) around N-doped carbon nanotubes (N-CNTs). The hybrids were further exploited as effective supercapacitor materials. The N-CNTs were prepared by carbonizing a mixture of glucose and the melamine-cyanuric acid complex at a high temperature (900 °C) under N2 atmosphere and applied as the template for the in situ synthesis of CoNi-ZIF nanosheets (NSs). The 1D N-CNTs in the hybrids can act as the high-way for charge transfer to boost the faradaic reactions. Changing the usage of metal precursors not only provided abundant redox reaction sites in 2D CoNi-ZIF NSs but also modulated the microstructures and chemical components of the hybrids. The integration of the features of N-CNTs and CoNi-ZIF NSs can result in a synergistic effect between N-CNTs and CoNi-ZIF NSs. Therefore, the obtained CoNi-ZIFs and N-CNTs hybrid (CoNi-ZIF@N-CNT) exhibited superior electrochemical capacitive performance. Comparison revealed that the CoNi-ZIF@N-CNT-2 hybrid, which was prepared with a 1:1 mass ratio of Co(NO3)2·6H2O and Ni(NO3)2·6H2O, displayed the largest specific capacitance of 1118F g-1 at 1 A g-1, which was higher than the capacitance of most reported metal-organic framework (MOF)-based supercapacitor electrodes. Moreover, the asymmetric supercapacitor based on the CoNi-ZIF@N-CNT-2 electrode exhibited a high energy density of 51.1 Wh kg-1 at the power density of 860.1 W kg-1 and good cycle stability. This work can provide a facile and effective way for the fabrication of heterostructured 1D/2D nanostructures based on 2D MOFs for advanced energy storage.

The spatiotemporal transmission dynamics of COVID-19 among multiple regions: a modeling study in Chinese provinces.

Current explosive outbreak of COVID-19 around the world is a complex spatiotemporal process with hidden interactions between viruses and humans. This study aims at clarifying the transmission patterns and the driving mechanism that contributed to the COVID-19 prevalence across the provinces of China. Thus, a new dynamical transmission model is established by an ordinary differential system. The model takes into account the hidden circulation of COVID-19 virus among/within humans, which incorporates the spatial diffusion of infection by parameterizing human mobility. Theoretical analysis indicates that the basic reproduction number is a unique epidemic threshold, which can unite infectivity in each region by human mobility and can totally determine whether COVID-19 proceeds among multiple regions. By validating the model with real epidemic data in China, it is found that (1) if without any intervention, COVID-19 would overrun China within three months, resulting in more than 1.1 billion clinical infections and 0.2 billion subclinical infections; (2) high frequency of human mobility can trigger COVID-19 diffusion across each province in China, no matter where the initial infection locates; (3) travel restrictions and other non-pharmaceutical interventions must be implemented simultaneously for disease control; and (4) infection sites in central and east (rather than west and northeast) of China would easily stimulate quick diffusion of COVID-19 in the whole country. Supplementary Information: The online version supplementary material available at 10.1007/s11071-021-07001-1.

Assessing different interventions against Avian Influenza A (H7N9) infection by an epidemiological model.

This paper aims at evaluating the effectiveness of different intervention measures against the infection of avian influenza A (H7N9) by using an epidemiological model. The model formulates the intrinsic interactions of domestic poultry (DP), H7N9 virus and humans by ordinary differential equations and couples the essential roles of various interventions (including culling, vaccinating, screening, disinfecting, and reducing contact rate, etc). Qualitative analysis indicates that when the recruiting poultry is virus-free, there is a transmission threshold denoted by basic reproduction number which can determine the invasion of H7N9; and there is always a stable H7N9 endemic in case of persistent import of virus-carrying poultry, under which only complete vaccination or cutting off poultry-to-poultry/human contacts can stop H7N9 transmission. By performing numerical analysis of the model with biological background parameters, the intervention outcomes against H7N9 infection are further quantified. It is found that (1) reducing poultry-human/poultry interaction and per-contact infection probability, as well as culling DP, are highly effective in diminishing the infections of humans and DP; (2) the disease is prevented when larger than (1 - 0.1λ p ) proportion of DP is vaccinated, where λ p is the DP-to-DP transmission rate; (3) cleaning and disinfecting environment play limited role in reducing the risk of infection; and (4) screening imported poultry is quite important for stopping disease diffusion, but it works little when local epidemic is prevailing. Combing these measures with real situations would be necessary for controlling H7N9 epidemics and reaching one health purpose.

Determination of VEGF165 using impedimetric aptasensor based on cyclohexanehexone-melem covalent-organic framework.

A porous nanostructured covalent-organic framework (COF) has been prepared via condensation polymerization between the two building blocks of melem and hexaketocyclohexane octahydrate (represented as M-HO-COF). Basic characterizations revealed that the M-HO-COF network was composed of C=N and highly conjugated aromatic moieties, along with a high surface area, large pore size, remarkable electrochemical activity, and strong bioaffinity toward aptamer strands. Given that the vascular endothelial growth factor 165 (VEGF165)-targeted aptamer was stably anchored over M-HO-COF via weak intermolecular forces, the prepared M-HO-COF network exhibited great potential as a sensitive and selective platform for the impedimetric VEGF165 aptasensor. Consequently, the M-HO-COF-based aptasensor displayed an ultralow limit of detection of 0.18 fg mL-1 within a wide range of VEGF165 concentrations from 1 fg mL-1 to 10 ng mL-1. Considering its strong fluorescence performance, excellent biocompatibility, and small nanosheet-like structure, the obtained COF-based aptasensor showed a superior sensing performance and regeneration capability after 7 regeneration cycles for the detection of osteosarcoma cells (K7M2 cells), which overexpressed with VEGF165, with a low limit of detection of 49 cells mL-1. For real f human serum samples, the obtained COF-based aptasensor exhibits acceptable mean apparent recoveries of 97.41% with a relative standard deviation of 4.60%. Furthermore, the proposed bifunctional aptasensor for the detection VEGF165 and K7M2 cells exhibited good stability, appropriate selectivity toward other biomarkers or normal cells, acceptable reproducibility, and applicability. A bifunctional sensing system was constructed for detecting osteosarcoma cells (K7M2 cells) and VEGF165 based on the a porous nanostructured covalent-organic framework (M-HO-COF) via condensation polymerization between melem and hexaketocyclohexane octahydrate. The M-HO-COF-based aptasensor displayed ultralow detection limit of 0.18 fg mL-1 toward VEGF165 and 49 cell mL-1 for K7M2 cells with high selectivity, acceptable reproducibility, and good stability.

Novel impedimetric sensing strategy for detecting ochratoxin A based on NH2-MIL-101(Fe) metal-organic framework doped with cobalt phthalocyanine nanoparticles.

Iron-based metal-organic framework, NH2-MIL-101(Fe), was doped with different dosages of cobalt phthalocyanine nanoparticles (CoPc) to synthesize a series of NH2-MIL-101(Fe)@CoPc nanocomposites. The NH2-MIL-101(Fe)@CoPc nanocomposites were then employed to construct novel impedimetric aptasensors for the detection of ochratoxin A (OTA). Combining the intrinsic advantages of NH2-MIL-101(Fe) (highly porous structure and excellently electrochemical activity) and CoPc (good physiochemical stability and strong bioaffinity), the NH2-MIL-101(Fe)@CoPc nanocomposites show promising properties, which are beneficial for immobilizing OTA-targeted aptamer strands. Amongst, the developed impedimetric aptasensor based on NH2-MIL-101(Fe)@CoPc6:1, prepared using the mass ratio of NH2-MIL-101(Fe):CoPc of 6:1, exhibits the best amplified electrochemical signal and highest sensitivity for detecting OTA. The detection limitation is 0.063 fg·mL-1 within the OTA concentration of 0.0001-100 pg·mL-1, accompanying with high selectivity, good reproducibility and stability, acceptable regenerability, and wide applicability in diverse real samples. Consequently, the proposed sensing strategy can be applied for detecting OTA to cope with food safety.

Quantification of EGFR and EGFR-overexpressed cancer cells based on carbon dots@bimetallic CuCo Prussian blue analogue.

A new bimetallic CuCo Prussian blue analogue (CuCo PBA) loaded with carbon dots (CDs) was prepared (represented by CD@CuCoPBA) and developed as a scaffold for anchoring the epidermal growth factor receptor (EGFR) aptamer to detect EGFR and living EGFR-overexpressed cancer cells. The basic characterizations revealed CuCo PBA exhibited nanocube shape and still remained its nanostructure and physical/chemical properties after coupling with large amounts of CDs. As compared with the pristine CuCo PBA, the CD@CuCoPBA displayed good electrochemical activity, strong binding interaction toward aptamer, and high stability of aptamer-EGFR G-quadruplex in aqueous solution. As such, the results of electrochemical impedance spectroscopy measurements indicated that the CD@CuCoPBA-based aptasensor displayed an ultra-low detection limit toward EGFR (0.42 fg mL-1) and living EGFR-overexpressed MCF-7 cancer cells (80 cell per mL), as well as high selectivity, good reproducibility, high stability, repeatability, and acceptable applicability. Consequently, the constructed CD@CuCoPBA-based aptasensor can be extended to be a promising universal method for early diagnosis of cancers.

A γ-cyclodextrin-based metal-organic framework embedded with graphene quantum dots and modified with PEGMA via SI-ATRP for anticancer drug delivery and therapy.

The γ-cyclodextrin-based metal-organic framework (γ-CD-MOF) composite was designed and prepared toward targeted anticancer drug delivery and cancer therapy. Large amounts of graphene quantum dots (GQDs) were embedded in the γ-CD-MOF matrix (denoted as GQDs@γ-CD-MOF) to endow the γ-CD-MOF with strong fluorescence, which was then modified by pH responsive poly(ethyleneglycol)dimethacrylate (PEGMA) through surface initiated atom transfer radical polymerization (SI-ATRP) to fabricate the PEGMA@GQDs@γ-CD-MOF composite. Then, the cancer cell-targeted probe was obtained by immobilizing the AS1411 aptamer over it (denoted as AS1411@PEGMA@GQDs@γ-CD-MOF) and it exhibits pH-responsive release function and excellent targeting ability. Large amounts of antitumour drug, doxorubicin hydrochloride (DOX), could be encapsulated within this composite due to the chemical-rich functionality, and the resultant pH-responsive DOX delivery system (denoted as DOX/AS1411@PEGMA@GQDs@γ-CD-MOF) displayed a higher DOX loading of 89.1% with sustained release than the pristine γ-CD-MOF and GQDs@γ-CD-MOF. The targeting specificity investigation revealed that this DOX delivery system was effectively internalized via receptor mediated endocytosis with high selectivity. The in vivo antitumour study with tumour-bearing mice illustrated that the tumour growth can be effectively suppressed and partially ablated with negligible side effects after treatments. Therefore, the proposed AS1411@PEGMA@GQD@γ-CD-MOF composite is promising for effective DOX delivery and tumour growth inhibition both in vitro and in vivo, showing great potential for anticancer therapy.

Construction of Tb-MOF-on-Fe-MOF conjugate as a novel platform for ultrasensitive detection of carbohydrate antigen 125 and living cancer cells.

Combining different metal-organic frameworks (MOFs) into a conjugate material can integrate the properties of each MOF component and further lead to emergent properties from the synergistic heterostructured units. In this work, two kinds of bimetallic TbFe-MOFs have been designed by MOF-on-MOF strategy and utilized as a platform for anchoring carbohydrate antigen 125 (CA125) aptamer to detect CA125 and living michigan cancer foundation-7 (MCF-7) cells. Although the integrated MOF-on-MOF architectures show similar chemical and structural features to that of the top layer, the Fe-MOF-on-Tb-MOF and Tb-MOF-on-Fe-MOF have different surface nanostructures to their parent MOFs. The developed aptasensor based on Tb-MOF-on-Fe-MOF displays higher stability of the formed G-quadruplex between aptamer and CA125 than that based on Fe-MOF-on-Tb-MOF, owing to stronger immobilization behavior of the aptamer for the Tb-MOF-on-Fe-MOF composite. The developed aptasensor provides an extremely low detection limit of 58 µU·mL-1 towards CA125 within a wide linear range from 100 µU·mL-1 to 200 U·mL-1, which is significantly lower than those of all reported sensors. This aptasensor also has high selectivity, good stability, acceptable reproducibility, and excellent applicability in human serum. Moreover, the Tb-MOF-on-Fe-MOF nanoarchitecture demonstrates superior biocompatibility and good endocytosis. As a result, the developed aptasensor illustrates high sensitivity for detection of MCF-7 cells with an extremely low detection limit of 19 cell·mL-1. Therefore, the proposed aptasensor based on Tb-MOF-on-Fe-MOF exhibits great potentials for early diagnosis of tumors.

Bimetallic cerium and ferric oxides nanoparticles embedded within mesoporous carbon matrix: Electrochemical immunosensor for sensitive detection of carbohydrate antigen 19-9.

A label-free electrochemical immunosensor was successfully developed for sensitively detecting carbohydrate antigen 19-9 (CA19-9) as a cancer marker. To achieve this, a series of bimetallic cerium and ferric oxide nanoparticles embedded within the mesoporous carbon matrix (represented by CeO2/FeOx@mC) was obtained from the bimetallic CeFe-based metal organic framework (CeFe-MOF) by calcination at different high temperatures. The formed CeO2 or FeOx nanoparticles were uniformly distributed within the highly graphitized mesoporous carbon matrix at the calcination temperature of 500 °C (represented by CeO2/FeOx@mC500). However, the obtained nanoparticles were aggregated into large size when calcined at the temperatures of 700 and 900 °C. The CA 19-9 antibody can be anchored to the CeO2/FeOx@mC network through chemical absorption between carboxylic groups of antibody and CeO2 or FeOx by ester-like bridging. The CeO2/FeOx@mC500-based immunosensor displayed superior sensing performance to the pristine CeFe-MOF, CeO2/FeOx@mC700- and CeO2/FeOx@mC900-based ones. Electrochemical impedance spectroscopy results showed that the developed immunosensor exhibited an extremely low detection limit of 10 µU·mL-1 (S/N = 3) within a wide range from 0.1 mU·mL-1 to 10 U·mL-1 toward CA 19-9. It also illustrated excellent specificity, good reproducibility and stability, and acceptable application analysis in the human serum solution which was diluted 100-fold with 0.01 M PBS solution (pH 7.4) and spiked with different amounts of CA19-9. Consequently, the proposed electrochemical immunosensor is capable enough of determining CA 19-9 in clinical diagnostics.

Covalent organic framework-based electrochemical aptasensors for the ultrasensitive detection of antibiotics.

We designed and synthesized a novel covalent organic framework (COF) by condensation polymerization of 1,3,6,8-tetrakis(4-formylphenyl)pyrene and melamine through imine bonds (represented by Py-M-COF). The basic characterizations revealed that the Py-M-COF not only exhibited an extended π-conjugation framework, a large specific surface area (495.5 m2 g-1), big pore cavities, and nanosheet-like structure but also possessed rich functional groups, such as CË­C, CË­N, CË­O, and NH2. These features endowed the Py-M-COF with high charge carrier mobility, further improving the strong immobilization of DNA aptamer strands via π-π stacking interaction and electrostatic interaction. As such, the Py-M-COF-based electrochemical aptasensors are ultrasensitive in detecting different antibiotics, including enrofloxacin (ENR) and ampicillin (AMP), yielding extremely low detection limits of 6.07 and 0.04 fg mL-1 (S/N = 3) toward ENR and AMP, respectively, along with other excellent sensing performances. This biosensing platform based on Py-M-COF has potential applications for the sensitive detection of antibiotics or other analytes by replacing the corresponding aptamers.

Bimetallic cerium/copper organic framework-derived cerium and copper oxides embedded by mesoporous carbon: Label-free aptasensor for ultrasensitive tobramycin detection.

We reported a novel bimetallic cerium/copper-based metal organic framework (Ce/Cu-MOF) and its derivatives pyrolyzed at different temperatures, followed by exploiting them as the scaffold of electrochemical aptamer sensors for extremely sensitive detection of trace tobramycin (TOB) in human serum and milk. After the calcination at high temperature, the meal coordination centers (Ce and Cu) were transferred to metal oxides containing various chemical valences, such as Ce(III), Ce(IV), Cu(II) and Cu(0), which were embedded within the mesoporous carbon network originated from the organic ligands (represented by CeO2/CuOx@mC). Owning to the strong synergistic effect among the metal oxides, mesoporous carbon, and small cavities and open channels of MOF, the as-prepared CeO2/CuOx@mC nanocomposites not only possess good electrochemical activity but also exhibit strong bioaffinity toward the aptamer strands. By comparing the electrochemical biosensing peroformances using on the Ce/Cu-MOF- and the series of CeO2/CuOx@mC-based aptasensors, the constructed CeO2/CuOx@mC900-based (calcinated at 900 °C) aptasensor exhibits an extremely low detection limit of 2.0 fg mL-1 within a broad linear TOB concentration range from 0.01 pg mL-1 to 10 ng mg L-1. It demonstrates that the proposed aptasensor is substantially superior to those previously reported in the literature, along with high selectivity, good stability and reproducibility, and acceptable applicability in human serum and milk. Thereby, the newly fabricated aptasensing approach based on bimetallic CeO2/CuOx@mC has a considerable potential for the quantitative detection of antibiotics in the food safety and biomedical field.

Two-dimensional oriented growth of Zn-MOF-on-Zr-MOF architecture: A highly sensitive and selective platform for detecting cancer markers.

Fabricating novel bimetallic metal organic framework (MOF) architectures and exploiting them as aptasensor scaffolds for detecting diverse analytes, especially cancer markers, have aroused widespread research attention. Herein, we report a novel strategy for obtaining ZnZr bimetallic MOFs via the MOF-on-MOF method and exploit them as an aptasensor platform for detecting the cancer marker protein tyrosine kinase-7 (PTK7). Basic characterizations reveal that the chemical structure, crystalline properties, and surface functionality of bimetallic ZnZr-MOFs can be modulated by changing the order of addition of metal precursors and organic ligands. The Zn-MOF-on-Zr-MOF hybrid exhibits a hierarchically decussated foliace, whereas Zr-MOF-on-Zn-MOF demonstrates a multilayered nanosheet structure. The electrochemical results reveal that Zr-MOF facilitates aptamer strand immobilization, whereas the Zn-MOF stabilizes the G-quadruplex formed by aptamer strands and PTK7. The Zn-MOF-on-Zr-MOF-based aptasensor outperforms the Zr-MOF-on-Zn-MOF-based one, providing ultralow detection limits of 0.84 and 0.66 pg mL-1, as obtained by electrochemical impedance spectroscopy and differential pulse voltammetry, respectively, within the PTK7 concentration range of 1.0 pg mL-1 to 1.0 ng mL-1. The proposed Zn-MOF-on-Zr-MOF-based aptasensor exhibits high selectivity in the presence of various interferences, good stability, reproducibility, and acceptability in human serum. The proposed strategy provides a new approach for fabricating ultrasensitive and selective bimetallic MOFs-based aptasensors and contributes to efforts to broaden their applications in early cancer diagnosis.

Tunable Hollow Bimetallic MnFe Prussian Blue Analogue as the Targeted pH-Responsive Delivery System for Anticancer Drugs.

Owning to the improved ability of selectivity and penetration toward cancer cells, drug delivery systems (DDSs) play essential roles in chemotherapy for solid tumors. Herein, a series of bimetallic MnFe Prussian blue analogues (PBAs) with a tunable nanostructure was prepared by using sodium citrate (SC) as a structure regulator (represented by MnFe-PBA-SC). An advanced targeted drug delivery system was obtained by adding folic acid (FA) to the preparation system of MnFe-PBA-SC nanospheres (denoted as MnFe-PBA-SC-FA). The shape of pure MnFe PBA was changed from a typical nanocube to a hollow nanosphere when adding SC, leading to the formation of the core-shell nanospheres of the MnFe-PBA-SC-FA composite. The hollow nanostructures and intrinsic cavities in PBA can carry large amounts of doxorubicin (DOX), showing a high loading efficiency of MnFe-PBA-SC1.0-FA (91.8%), which was higher than that in MnFe-PBA-SC0.5 (63.2%). Additionally, the series of MnFe-PBAs showed pH-responsive drug release behaviors. A cell viability assay illustrated no remarkable cytotoxicity of MnFe-PBA-SC-FA against human breast cancer cells, Michigan Cancer Foundation-7 (MCF-7) cells, for 24 h. Confocal laser scanning showed that the MnFe-PBA-SC1.0-FA/DOX system significantly entered FA receptor-expressing MCF-7 cells in vitro and in vivo, while an increased DOX release was observed in the cytoplasm of the MCF-7 cells. In consequence, this novel anticancer delivery system based on bimetallic PBAs can be potentially applied to drug delivery.

Bimetallic NiFe oxide structures derived from hollow NiFe Prussian blue nanobox for label-free electrochemical biosensing adenosine triphosphate.

We designed and constructed a novel aptasensor based on the porous nanostructured bimetallic NiFe-oxides embedded with the mesoporous carbon (represented by NiOxFeOy@mC) for sensitively detecting adenosine triphosphate (ATP), of which the porous NiOxFeOy@mC was derived from the hollow NiFe Prussian blue analogue (hollow NiFe PBA) by calcinating under high temperature. Owning to the excellent electrochemical activity originated from the metal oxides and mesoporous carbon and the strong binding interaction between the aptamer strands and the nanostructure hybrid, the formed porous NiOxFeOy@mC composite calcinated at 900 °C exhibited superior sensitivity toward ATP determination in comparison with other porous nanocubes obtained at 500 and 700 °C. The proposed aptasensor not only revealed a wide linear range from 5.0 fg·mL-1 to 5.0 ng mL-1 with a extremely low detection limit of 0.98 fg·mL-1 (1.62 fM) (S/N = 3), but also displayed high selectivity towards other interferences, good stability and reproducibility, and acceptable applicability. Therefore, this proposed approach provides a promising platform for ultra-sensitive detection of ATP, further having the potential applications on diagnosis of ATP-related diseases.