Atomic-level design of metalloenzyme-like active pockets in metal-organic frameworks for bioinspired catalysis.

Natural metalloenzymes with astonishing reaction activity and specificity underpin essential life transformations. Nevertheless, enzymes only operate under mild conditions to keep sophisticated structures active, limiting their potential applications. Artificial metalloenzymes that recapitulate the catalytic activity of enzymes can not only circumvent the enzymatic fragility but also bring versatile functions into practice. Among them, metal-organic frameworks (MOFs) featuring diverse and site-isolated metal sites and supramolecular structures have emerged as promising candidates for metalloenzymes to move toward unparalleled properties and behaviour of enzymes. In this review, we systematically summarize the significant advances in MOF-based metalloenzyme mimics with a special emphasis on active pocket engineering at the atomic level, including primary catalytic sites and secondary coordination spheres. Then, the deep understanding of catalytic mechanisms and their advanced applications are discussed. Finally, a perspective on this emerging frontier research is provided to advance bioinspired catalysis.

Nanozyme Metabolism Controls Air Pollution over an Atomic Potassium Cyano Site.

Increasing threats of air pollution prompt the design of air purification systems. As a promising initiative defense strategy, nanocatalysts are integrated to catalyze the detoxification of specific pollutants. However, it remains a grand challenge to tailor versatile nanocatalysts to cope with diverse pollutants in practice. Here, we report a nanozyme metabolism system to realize broad-spectrum protection from air pollution. Atomic K-modified carbon nitride featuring flavin oxidase-like and peroxidase-like activities was synthesized to initiate nanozyme metabolism. In situ experiments and theoretical investigations collectively show that K sites optimize the geometric and electronic structure of cyano sites for both enzyme-like activities. As a proof of concept, the nanozyme metabolism was applied to the mask against volatile organic compounds, persistent organic pollutants, reactive oxygen species, bacteria, and so on. Our finding provides a thought to tackle global air pollution and deepens the understanding of nanozyme metabolism.

NiFe Nanoparticle Nest Supported on Graphene as Electrocatalyst for Highly Efficient Oxygen Evolution Reaction.

Designing cost-efffective electrocatalysts for the oxygen evolution reaction (OER) holds significant importance in the progression of clean energy generation and efficient energy storage technologies, such as water splitting and rechargeable metal-air batteries. In this work, an OER electrocatalyst is developed using Ni and Fe precursors in combination with different proportions of graphene oxide. The catalyst synthesis involved a rapid reduction process, facilitated by adding sodium borohydride, which successfully formed NiFe nanoparticle nests on graphene support (NiFe NNG). The incorporation of graphene support enhances the catalytic activity, electron transferability, and electrical conductivity of the NiFe-based catalyst. The NiFe NNG catalyst exhibits outstanding performance, characterized by a low overpotential of 292.3 mV and a Tafel slope of 48 mV dec-1, achieved at a current density of 10 mA cm- 2. Moreover, the catalyst exhibits remarkable stability over extended durations. The OER performance of NiFe NNG is on par with that of commercial IrO2 in alkaline media. Such superb OER catalytic performance can be attributed to the synergistic effect between the NiFe nanoparticle nests and graphene, which arises from their large surface area and outstanding intrinsic catalytic activity. The excellent electrochemical properties of NiFe NNG hold great promise for further applications in energy storage and conversion devices.

Anisotropic Dual S-Scheme Heterojunctions Mimic Natural Photosynthetic System for Boosting Photoelectric Response.

The design of heterojunctions that mimic natural photosynthetic systems holds great promise for enhancing photoelectric response. However, the limited interfacial space charge layer (SCL) often fails to provide sufficient driving force for the directional migration of inner charge carriers. Drawing inspiration from the electron transport chain (ETC) in natural photosynthesis system, we developed a novel anisotropic dual S-scheme heterojunction artificial photosynthetic system composed of Bi2O3-BiOBr-AgI for the first time, with Bi2O3 and AgI selectively distributed along the bicrystal facets of BiOBr. Compared to traditional semiconductors, the anisotropic carrier migration in BiOBr overcomes the recombination resulting from thermodynamic diffusion, thereby establishing a potential ETC for the directional migration of inner charge carriers. Importantly, this pioneering bioinspired design overcomes the limitations imposed by the limited distribution of SCL in heterojunctions, resulting in a remarkable 55-fold enhancement in photoelectric performance. Leveraging the etching of thiols on Ag-based materials, this dual S-scheme heterojunction is further employed in the construction of photoelectrochemical sensors for the detection of acetylcholinesterase and organophosphorus pesticides.

Harmonizing Enzyme-like Cofactors to Boost Nanozyme Catalysis.

Engineering isolated metal sites resembling the primary coordination sphere of metallocofactors enables atomically dispersed materials as promising nanozymes. However, most existing nanozymes primarily focus on replicating specific metallocofactors while neglecting other supporting cofactors within active pockets, leading to reduced electron transfer (ET) efficiency and thus inferior catalytic performances. Herein, we report a metal-organic framework UiO-67 nanozyme with atomically dispersed iron sites, which involves multiple tailored enzyme-like nanocofactors that synergistically drive the ET process for enhanced peroxidase-like catalysis. Among them, the linker-coupled atomic iron site plays a critical role in substrate activation, while bare linkers and zirconia nodes facilitate the ET efficiency of intermediates. The synergy of three nanocofactors results in a 4.29-fold enhancement compared with the single effort of isolated metal site-based nanocofactor, holding promise in immunoassay for sensitive detection of chlorpyrifos. This finding opens a new way for designing high-performance nanozymes by harmonizing various nanocofactors at the atomic and molecular scale.

Two-Dimensional Fe-N-C Single-Atomic-Site Catalysts with Boosted Peroxidase-Like Activity for a Sensitive Immunoassay.

Single-atomic-site catalysts (SASCs) with peroxidase (POD)-like activities have been widely used in various sensing platforms, like the enzyme-linked immunosorbent assay (ELISA). Herein, a two-dimensional Fe-N-C-based SASC (2D Fe-SASC) is successfully synthesized with excellent POD-like activity (specific activity = 90.11 U/mg) and is used to design the ELISA for herbicide detection. The 2D structure of Fe-SASC enables the exposure of numerous single atomic active sites on the surface as well as boosts the POD-like activity, thereby enhancing the sensing performance. 2D Fe-SASC is assembled into competitive ELISA kit, which achieves an excellent detection performance for 2,4-dichlorophenoxyacetic acid (2,4-D). Fe-SASC has great potential in replacing high-cost natural enzymes and working on various advanced sensing platforms with high sensitivity for the detection of various target biomarkers.

Photothermal-Switched Single-Atom Nanozyme Specificity for Pretreatment and Sensing.

Various applications lead to the requirement of nanozymes with either specific activity or multiple enzyme-like activities. To this end, intelligent nanozymes with freely switching specificity abilities hold great promise to adapt to complicated and changeable practical conditions. Herein, a nitrogen-doped carbon-supported copper single-atom nanozyme (named Cu SA/NC) with switchable specificity is reported. Atomically dispersed active sites endow Cu SA/NC with specific peroxidase-like activity at room temperature. Furthermore, the intrinsic photothermal conversion ability of Cu SA/NC enables the specificity switch by additional laser irradiation, where photothermal-induced temperature elevation triggers the expression of oxidase-like and catalase-like activity of Cu SA/NC. For further applications in practice, a pretreatment-and-sensing integration kit (PSIK) is constructed, where Cu SA/NC can successively achieve sample pretreatment and sensitive detection by switching from multi-activity mode to specific-activity mode. This study sets the foundation for nanozymes with switchable specificity and broadens the application scope in point-of-care testing.

Nanobiocatalysis: a materials science road to biocatalysis.

With high activity and specificity to conduct catalysis under mild conditions, enzymes show great promise in many fields. However, they are not acclimatized to environments in practice after leaving the familiar biological conditions. Aiming at this issue, nanobiocatalysis, a fresh area integrating nanotechnology and enzymatic catalysis, is expected to design biocatalysis based on materials science. Specifically, nano-integrated biocatalysis and bio-inspired nanocatalysis are considered as two effective nanobiocatalytic systems to meet different design needs. Notably, both systems are not entirely separated, and the combination of both further sparks more possibilities. This review summarizes the type, construction, and function of nanobiocatalytic systems, analyzing the pros and cons of different strategies. Moreover, the corresponding applications in bioassay, biotherapy, and environmental remediation are highlighted. We hope that the advent of nanobiocatalysis will help in grasping the inherence of biocatalysis and propel biocatalytic applications.

The usability of an AAC pain description system for patients with acquired expressive communication disorders.

Augmentative and alternative communication (AAC) has been used by patients with acquired expressive communication disorders as an alternative to natural speech. The use of symbols to express pain, which is intangible, is challenging because designing a series of comprehensible symbols to represent personal experiences such as pain is not straightforward. This study describes (a) the development of symbols to express pain that were derived from Chinese pain-related similes and metaphors for an AAC mobile application developed specifically for this study known as PainDiary and (b) an assessment of the appropriateness of the app compared to conventional methods of collecting pain information. The symbols depicted headache pain and discomfort, which is prevalent among neurosurgical patients. The participants were 31 patients diagnosed with acquired expressive communication disorders who were receiving treatment in a neurosurgery general ward of Chang Gung Memorial Hospital in Taiwan and 14 nurses who worked on the ward. Pain information was collected by nurses using conventional methods and the PainDiary app. Assessment data, including the accuracy and efficiency of and user satisfaction with PainDiary, are compared. The results show that use of the app was effective in reporting pain and that patients required less time to report a pain event. The results further indicate that the PainDiary app was better received by younger individuals than by their older counterparts.

Single-Atomic Iron Doped Carbon Dots with Both Photoluminescence and Oxidase-Like Activity.

Multifunctional nanozymes can benefit biochemical analysis via expanding sensing modes and enhancing analytical performance, but designing multifunctional nanozymes to realize the desired sensing of targets is challenging. In this work, single-atomic iron doped carbon dots (SA Fe-CDs) are designed and synthesized via a facile in situ pyrolysis process. The small-sized CDs not only maintain their tunable fluorescence, but also serve as a support for loading dispersed active sites. Monoatomic Fe offers SA Fe-CDs exceptional oxidase-mimetic activity to catalyze 3,3',5,5'-tetramethylbenzidine (TMB) oxidation with fast response (Vmax  = 10.4 nM s-1 ) and strong affinity (Km  = 168 µM). Meanwhile, their photoluminescence is quenched by the oxidation product of TMB due to inner filter effect. Phosphate ions (Pi) can suppress the oxidase-mimicking activity and restore the photoluminescence of SA Fe-CDs by interacting with Fe active sites. Based on this principle, a dual-mode colorimetric and fluorescence assay of Pi with high sensitivity, selectivity, and rapid response is established. This work paves a path to develop multifunctional enzyme-like catalysts, and offers a simple but efficient dual-mode method for phosphate monitoring, which will inspire the exploration of multi-mode sensing strategies based on nanozyme catalysis.

Trajectories of social support are associated with health outcomes and depressive symptoms among older Taiwanese adults with diabetes following hip-fracture surgery.

OBJECTIVE: This study examined trajectories of social support and their relationships with health outcomes over 2 years post hip-fracture surgery for older adults with diabetes mellitus (DM). METHODS: This was a secondary analysis of data derived from a clinical trial, which included 158 hip fractured older adults with DM who had completed the Medical Outcomes Study Social Support Survey at 1-, 12-, 18-, and 24-months following hospital discharge. Health outcomes for self-care, physical and nutritional status, mental health, and depression were assessed at 3-month intervals up to 24-months after hospital discharge. Trajectories of social support were derived with latent class analysis while hierarchical linear models were employed to assess the associations of social-support trajectory with health outcomes. RESULTS: Four social-support trajectories were derived for persons with DM following hip-fracture surgery: poor and declining (n = 18, 11.4%), moderate and stable (n = 29, 18.4%), high but declining (n = 34, 21.5%), and high and stable (n = 77, 48.7%). Relative to those in the poor and declining group, participants in the high and stable trajectory group performed better in Activities of Daily Living and quadriceps muscle power, had better mental Health-Related Quality of Life and nutritional status, and had fewer depressive symptoms. These differences persisted over the 2 years following hospital discharge. CONCLUSIONS: These results suggest social support for persons with DM should be continually assessed following hip-fracture surgery.

Experiences of family caregivers of persons living with dementia with and without a smart- clothes assisted home nursing program during the heightened COVID-19 alert.

BACKGROUND: The COVID-19 pandemic has required restrictions of daily activities, which has been found to impact the lives of persons living with dementia (PLWDs) and their family caregivers, who have multiple care demands. The lack of relevant studies in Taiwan emphasized the need to explore the experiences of family caregivers of older PLWDs faced with the intensified restrictions to control the spread of COVID-19, and the impact of the availability of a smart-clothes home nursing program. METHODS: This qualitative study used semi-structured interviews with family caregivers of older PLWDs. Participants were recruited from dementia clinics of a medical center in northern Taiwan from a subset of a sample from a larger study on smart-clothes assisted home nursing care. A total of 12 family caregivers who participated in the original study were interviewed during the follow-up period; seven family caregivers of a PLWD wearing a smart-vest, which transmitted information to a home care nurse; five caregivers of a PLWD not wearing a smart-vest. Interviews were conducted by telephone because the conditions of the pandemic prevented face-to-face interviews. Recorded interviews were transcribed and analyzed using content analysis. RESULTS: Interview data showed family caregivers' felt the care recipient's health was compromised and functional conditions intensified as Covid-19-related pandemic restrictions increased. Specific concerns included a lack social interactions, decreased daily activity levels, loss of interest and lack of motivation for activities, increased mood and behavioral problems, a decline in physical function and an increase in health problems. Family caregivers were also impacted by these restrictions, with significant increases in severity of caregiver role strain, including feeling trapped, a lack of in-home support, profound powerlessness, and worries about the PLWD contracting the coronavirus. The smart-clothes assisted home nursing care program offered supplementary support to family caregivers by providing on-time interactions, helping them manage health problems, enhancing predictability of the care recipient's behaviors, and providing caregivers with emotional support. CONCLUSIONS: The findings of this study support alternative care such as implementation of technology-assisted home health services to meet caregiver needs to facilitate family caregiving of PLWDs during the necessary restrictions in activities implemented during the COVID-19 pandemic. TRIAL REGISTRATION: ClinicalTrials.gov Protocol Record NCT05063045.

Single-atom catalysts boost signal amplification for biosensing.

Development of highly sensitive biosensors has received ever-increasing attention over the years. Due to the unique physicochemical properties, the functional nanomaterial-enabled signal amplification strategy has made some great breakthroughs in biosensing. However, the sensitivity and selectivity still need further improvement. Single-atom catalysts (SACs) containing atomically dispersed metal active sites demonstrate distinctive advantages in catalytic activity and selectivity for various catalytic reactions. As a consequence, the SAC-enabled signal amplification strategy holds great promise in biosensors, demonstrating satisfactory sensitivity and selectivity with the assistance of tunable metal-support interactions, coordination environments and geometric/electronic structures of active sites. In this tutorial review, we briefly discuss the structural advantages of SACs. Then, the catalytic mechanism at the atomic scale and signal amplification effects of SACs in the colorimetric, electrochemical, chemiluminescence, electrochemiluminescence, and photoelectrochemical biosensing applications are highlighted in detail. Finally, opportunities and challenges to be faced in the future development of the SAC-enabled signal amplification strategy for biosensing are discussed and outlooked.

Highly Dispersive Cerium Atoms on Carbon Nanowires as Oxygen Reduction Reaction Electrocatalysts for Zn-Air Batteries.

Highly efficient noble-metal-free electrocatalysts for oxygen reduction reaction (ORR) are essential to reduce the costs of fuel cells and metal-air batteries. Herein, a single-atom Ce-N-C catalyst, constructed of atomically dispersed Ce anchored on N-doped porous carbon nanowires, is proposed to boost the ORR. This catalyst has a high Ce content of 8.55 wt % and a high activity with ORR half-wave potentials of 0.88 V in alkaline media and 0.75 V in acidic electrolytes, which are comparable to widely studied Fe-N-C catalysts. A Zn-air battery based on this material shows excellent performance and durability. Density functional theory calculations reveal that atomically dispersed Ce with adsorbed hydroxyl species (OH) can significantly reduce the energy barrier of the rate-determining step resulting in an improved ORR activity.

Hierarchical Metal-Organic Framework-Confined CsPbBr3 Quantum Dots and Aminated Carbon Dots: A New Self-Sustaining Suprastructure for Electrochemiluminescence Bioanalysis.

All-inorganic lead halide perovskites have become promising alternatives to traditional semiconductor electrochemiluminescence (ECL) emitters because of their appealing optoelectronic attributes, but major challenges remain in improving their stability and enhancing charge injection/transfer capacities. Herein, a self-sustaining suprastructure was constructed by successively loading aminated carbon dots (NCDs) and CsPbBr3 perovskite quantum dots (PeQDs) in situ into hierarchical zeolite imidazole framework-8 (HZIF-8). The elaborated architecture guarantees not only improved stability via the peripheral HZIF-8 protective barrier but also accelerated charge transport and efficient self-enhanced ECL between PeQDs and the surrounding NCDs in a confined structure. As a result, the ternary nanocomposite is endowed with greatly improved stability and ECL efficiency. Based on this ternary nanocomposite as an electrode substrate, a novel ECL sensing strategy is further proposed for the first time to evaluate T4 polynucleotide kinase activity and screen its inhibitors. This work opens an avenue for the advancement of perovskite-based ECL emitters as well as the development of corresponding applications in the ECL domain.

Smartphone-Based Dual-Channel Immunochromatographic Test Strip with Polymer Quantum Dot Labels for Simultaneous Detection of Cypermethrin and 3-Phenoxybenzoic Acid.

Currently, gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-MS (LC-MS) are the primary methods used to detect pesticides and their metabolites for biomonitoring of exposure. Although GC-MS and LC-MS can provide accurate and sensitive measurements, these techniques are not suitable for point-of-care or in-field biomonitoring applications. The objective of this work is to develop a smartphone-based dual-channel immunochromatographic test strip (ICTS) for on-site biomonitoring of exposure to cypermethrin by simultaneous detection of cypermethrin and its metabolite, 3-phenoxybenzoic acid (3-PBA). Polymer carbon dots (PCDs) with ultrahigh fluorescent brightness were synthesized and used as a signal amplifier in ICTS assay. Cypermethrin (a representative pyrethroid pesticide) and its major metabolite 3-PBA were simultaneously detected to provide more comprehensive analysis of cypermethrin exposure. After competitive immunoreactions between the target sample and the coating antigens preloaded on the test line, the tracer antibody (PCD-conjugated antibody) was quantitatively captured on the test lines. The captured PCDs were inversely proportional to the amount of the target compound in the sample. The red fluorescence on the test line was then recorded using a smartphone-based device capable of conducting image analysis and recording. Under optimal conditions, the sensor showed excellent linear responses for detecting cypermethrin and 3-PBA ranging from 1 to 100 ng/mL and from 0.1 to 100 ng/mL, respectively, and the limits of detection were calculated to be ∼0.35 ng/mL for cypermethrin and ∼0.04 ng/mL for 3-PBA. The results demonstrate that the ICTS device is promising for accurate point-of-care biomonitoring of pesticide exposure.

Single-Atomic Site Catalyst with Heme Enzymes-Like Active Sites for Electrochemical Sensing of Hydrogen Peroxide.

Heme enzymes, with the pentacoordinate heme iron active sites, possess high catalytic activity and selectivity in biosensing applications. However, they are still subject to limited catalytic stability in the complex environment and high cost for broad applications in electrochemical sensing. It is meaningful to develop a novel substitute that has a similar structure to some heme enzymes and mimics their enzyme activities. One emerging strategy is to design the Fe-N-C based single-atomic site catalysts (SASCs). The obtained atomically dispersed Fe-Nx active sites can mimic the active sites of heme enzymes effectively. In this work, a SASC (Fe-SASC/NW) is synthesized by doping single iron atoms in polypyrrole (PPy) derived carbon nanowire via a zinc-atom-assisted method. The proposed Fe-SASC/NW shows high heme enzyme-like catalytic performance for hydrogen peroxide (H2 O2 ) with a specific activity of 42.8 U mg-1 . An electrochemical sensor based on Fe-SASC/NW is developed for the detection of H2 O2 . This sensor exhibits a wide detection concentration range from 5.0 × 10-10 m to 0.5 m and an excellent limit of detection (LOD) of 46.35 × 10-9 m. Such excellent catalytic activity and electrochemical sensing sensitivity are attributed to the isolated Fe-Nx active sites and their structural similarity with natural metalloproteases.

An Ion-Imprinting Derived Strategy to Synthesize Single-Atom Iron Electrocatalysts for Oxygen Reduction.

Carbon-based single-atom catalysts (CSACs) have recently received extensive attention in catalysis research. However, the preparation process of CSACs involves a high-temperature treatment, during which metal atoms are mobile and aggregated into nanoparticles, detrimental to the catalytic performance. Herein, an ion-imprinting derived strategy is proposed to synthesize CSACs, in which isolated metal-nitrogen-carbon (Me-N4 -Cx ) moiety covalently binds oxygen atoms in Si-based molecular sieve frameworks. Such a feature makes Me-N4 -Cx moiety well protected/confined during the heat treatment, resulting in the final material enriched with single-atom metal active sites. As a proof of concept, a single-atom Fe-N-C catalyst is synthesized by using this ion-imprinting derived strategy. Experimental results and theoretical calculations demonstrate high concentration of single FeN4 active sites distributed in this catalyst, resulting in an outstanding oxygen reduction reaction (ORR) performance with a half-wave potential of 0.908 V in alkaline media.

Finding a balance in family caregiving for people with dementia: A correlational longitudinal study.

AIMS: The "Finding a Balance Point" framework was used to explore the caregiving process over time for family caregivers of people with dementia in Taiwan. This study aimed to: (a) identify Taiwanese caregivers' different balance trajectories; (b) explore predictors of trajectory group membership; and (c) examine associations of different balance trajectories with caregiving outcomes. DESIGN: A correlational longitudinal design was used. METHODS: Data were collected from 200 family caregivers' self-completed questionnaires and they were followed over 2 years (June 2015-May 2017). Discrete balance trajectories were identified by group-based trajectory modelling. Predictors of trajectory group membership were identified from potential predictors of caregiving characteristics and caregiving factors using multivariate logistic regression. Associations of trajectory groups with caregiving outcomes (depressive symptoms and health-related quality of life) were explored using the generalized estimating equation. RESULTS: Balance trajectories best fit a two-group trajectory model (poor and good). Caregivers with a poor sense of balance between competing needs were more likely to have more depressive symptoms (b = 11.71, 95% CI [9.04, 14.38], p < .001), worse physical health (b = -6.22, 95% CI [-8.71, -3.74], p < .001), and worse mental health (b = -11.1, 95% CI [-13.58, -8.63], p < .001) than caregivers with a good sense of balance. Caregivers experiencing lower role strain (b = -1.45, SE = 0.48, p = .003) or higher predictability (b = 2.83, SE = 0.76, p < .001) were more likely to belong to the good-balance group. CONCLUSIONS: Caregivers with poor balance between competing needs are more likely to have worse caregiving outcomes. Role strain and predictability significantly predicted balance trajectory groups. Family caregivers with lower caregiving task difficulty and/or better knowledge of the care receiver were more likely to be in the good balance trajectory group. IMPACT: Our findings support the framework, "Finding a Balance Point," and clarify the family caregiving process for people with dementia. This framework could be used to tailor interventions for home care nurses to improve family caregivers' caregiving outcomes.

Controlled Synthesis of EDTA-Modified Porous Hollow Copper Microspheres for High-Efficiency Conversion of CO2 to Multicarbon Products.

Electrochemical reduction of CO2 into value-added products is an effective approach to relieve environmental and energetic issues. Herein, EDTA anion-modified porous hollow copper microspheres (H-Cu MPs) were constructed by EDTA-2Na-assisted electrodeposition. The faradic efficiency (FE) of ethylene doubled from 23.3% to 50.1% at -0.82 V vs RHE in nearly neutral 0.1 M KHCO3 solution, one of the highest values among copper-based electrodeposited catalysts. Apart from the favorable influence from morphology regulated by EDTA-2Na, theoretical calculations revealed that the adsorbed EDTA anions were able to create a local charged copper surface to stabilize the transition state and dimer and to assist in the stabilization by interacting with OCCO adsorbate synergistically, which contributed to the outstanding catalytic performance together.