Nanosensor detection of reactive oxygen and nitrogen species leakage in frustrated phagocytosis of nanofibres

Using signal off-to-on strategy for designing precise and ultrasensitive biosensor towards hepatocellular carcinoma through protein variant detection based on biocompatible bimetallic MOF

The high mortality rate of patients with hepatocellular carcinoma (HCC) is an ever-increasing worldwide concern. Fortunately, the newest research has found that the proportion of a protein variant in total alpha-fetoprotein (AFP) over 10 % can accurately predict the incidence of HCC. Therefore, a signal off-to-on strategy was designed for developing a novel precise and ultrasensitive biosensor towards HCC through protein variant detection based on bimetallic metal-organic framework (MOF). In this study, the biocompatible Fe2Ni-MOF was used as an electrochemically immobilized carrier, which provided abundant active sites and exhibited a synergistic effect between Fe and Ni ions for dramatically promoting the electron transfer and improving the electrochemical reduction efficiency, prominently facilitating signal amplification of the biosensing platform. Then, we designed a novel ordered labeling method to distinguish AFP-L3 from overall AFP and introduced a signal off-to-on strategy for achieving highly efficient determination of AFP-L3 %. This proposed biosensor demonstrated a satisfactory linear range, along with a very low detection limit of 69 pg/mL for AFP-L3, which was far below the medically relevant threshold level. Furthermore, the adopted biosensor presented preeminent specificity, and favorable reproducibility.

Tailoring the Electrocatalytic Properties of Porphyrin Covalent Organic Frameworks for Highly Selective Oxygen Sensing In Vivo

In vivo selective sensing of oxygen (O2) dynamics in the central nervous system could provide insights into energy metabolism and neural activities. Although the electrocatalytic four-electron oxygen reduction reaction (ORR) paves an effective way to the electrochemical sensing of O2 in vivo, the concurrent hydrogen peroxide reduction reaction (HPRR) within the potential windows for four-electron ORR unfortunately poses a great challenge to the conventional mechanism employed for selective electrochemical O2 sensing. In this work, we find that regulation of the linkers within the skeleton of porphyrin-based covalent organic frameworks (COFs) could improve the selectivity of the O2 sensor against hydrogen peroxide (H2O2). The electrochemical results reveal that the Co porphyrin active sites facilitate the direct four-electron pathway for ORR and that the Co porphyrin-based COF, enriched with pyrene units, shows enhanced four-electron ORR kinetics and better tolerance to HPRR. The theoretical calculation suggests that introducing pyrene units essentially weakens the adsorption of H2O2, leading to suppression of the HPRR. The microsensor fabricated with the Co porphyrin-based COF as the electrocatalyst features a high selectivity for real-time monitoring of O2 in a living rat brain.

Orbital Coupling of Dual-Atom Sites Boosts Electrocatalytic NO Oxidation and Dynamic Intracellular Response

In situ measurement of nitric oxide (NO) in living tissue and single cells is highly important for achieving a profound comprehension of cellular functionalities and facilitating the precise diagnosis of critical diseases; however, the progress is greatly hindered by the weak affinity of ultratrace concentration NO in cellular environment toward electrocatalysts. Herein, a new strategy is reported for precisely constructing orbital coupled dual-atomic sites to enhance the affinity between the metal atomic sites and NO on a class of N-doped hollow carbon matrix dual-atomic sites Co─Ni (Co1Ni1-NC) for greatly boosting electrocatalytic NO performance. The as-synthesized Co1Ni1-NC demonstrates a substantially higher current density than Ni1-NC and Co1-NC, coupled with exceptional stability with a negligible degradation rate of 0.6 µA·cm-2·h-1, which is the best among the state-of-the-art electrocatalysts for NO oxidation. Experimental and theoretical investigations collectively reveal that the pivotal role of d-d orbit coupling between Co and Ni sites enables Ni to acquire additional electrons, leading to the occupation of Ni's 3dxy/yz within the 2π orbitals of NO, thus weakening the N≡O triple bond and concurrently accelerating NO adsorption kinetics. It is demonstrated that Co1Ni1-NC-coated nanoelectrode can achieve the in situ sensing of NO in living organs and single cells.

An Entropy-Driven Multipedal DNA Walker Microsensor for In Situ Electrochemical Detection of ATP

Microelectrode- and nanoelectrode-based electrochemistry has become a powerful tool for the in situ monitoring of various biomolecules in vivo. However, two challenges limit the application of micro- and nanoelectrodes: the difficulty of highly sensitive detection of nonelectroactive molecules and the specific detection of target molecules in complex biological environments. Herein, we propose an electrochemical microsensor based on an entropy-driven multipedal DNA walker for the highly sensitive and selective detection of ATP. An ATP aptamer was immobilized on the microelectrode surface to form the DNA walker track for selective ATP recognition. Multiple walking "legs" were attached to quantum dots to create the multipedal DNA walker. ATP was selectively captured by the ATP aptamer, triggering the autonomous movement of the multipedal DNA walker on the microelectrode interface, which brought methylene blue (MB) closer to the microelectrode interface, realizing a cascade signal amplification. Additionally, ATP release induced by hypotonic conditions in BV2 cells was successfully monitored, indicating that increased cell volume enhances ATP release. This multipedal DNA walker microsensor offers a novel strategy for in situ, highly sensitive, and selective monitoring of nonelectroactive biomolecules in vivo, which is crucial for investigating the neurochemical processes involved in neurological diseases.

Nanosensor quantitative monitoring of ROS/RNS homeostasis in single phagolysosomes of macrophages during bactericidal processes

Reactive oxygen and nitrogen species (ROS/RNS) in macrophages have a potent killing effect on pathogens that infect the host. Here, we achieved in situ, quantitative detection of the homeostasis of four primary ROS/RNS (ONOO-, H2O2, NO, and NO2-) and their precursors (O2˙-, NO) in phagolysosomes of single RAW 264.7 macrophages after phagocytosis of Escherichia coli with platinum-black nanoelectrodes. Enhanced bactericidal activity of the macrophages was observed by an increase in the total amount of ROS/RNS as well as the level and proportion of ONOO-, a potent bactericidal species of RNS. Moreover, both the bactericidal process and the steady-state replenishment process were dominated by the production of RNS (NO-based), revealing differences in the enzyme kinetics of the bactericidal process.

Bifunctional nanoprobe for simultaneous detection of intracellular reactive oxygen species and temperature in single cells

Living cells can rapidly adjust their metabolic activities in response to external stimuli, leading to fluctuations in intracellular temperature and reactive oxygen species (ROS) levels. Monitoring these parameters is essential for understanding cellular metabolism, particularly during dynamic biological processes. In this study, we present a bifunctional nanoprobe capable of simultaneous measurement of ROS levels and temperature within single cells. The nanoprobe features two individually addressable nanoelectrodes, with platinum (Pt) and nickel (Ni) coatings on both sides. At the tip, these two metal layers form a nano-thermocouple, enabling precise intracellular temperature measurements, while the Pt layer facilitates selective ROS detection. This dual functionality allows for real-time monitoring of cellular responses during synergistic chemo-photothermal therapy of cancer cells and zebrafish embryos subjected to mitochondrial toxic stress. Our results demonstrate that the nanoprobe effectively measures increases in temperature and ROS levels in HeLa cells undergoing chemo-photothermal therapy, as well as in chemically stimulated zebrafish embryos. By providing detailed analysis of submicrometer-scale temperature and ROS variations within living cells, this nanoprobe offers valuable insights into cellular processes and holds promise for early disease detection and drug development.

Unlocking the electrochemical functions of biomolecular condensates

Biomolecular condensation is a key mechanism for organizing cellular processes in a spatiotemporal manner. The phase-transition nature of this process defines a density transition of the whole solution system. However, the physicochemical features and the electrochemical functions brought about by condensate formation are largely unexplored. We here illustrate the fundamental principles of how the formation of condensates generates distinct electrochemical features in the dilute phase, the dense phase and the interfacial region. We discuss the principles by which these distinct chemical and electrochemical environments can modulate biomolecular functions through the effects brought about by water, ions and electric fields. We delineate the potential impacts on cellular behaviors due to the modulation of chemical and electrochemical environments through condensate formation. This Perspective is intended to serve as a general road map to conceptualize condensates as electrochemically active entities and to assess their functions from a physical chemistry aspect.

Construction of a Bifunctional Nanoelectrode for Intracellular Natural Product Delivery and Monitoring Anticancer Efficiency in Single Cells

Natural products play a significant role in new drug discovery and anticancer therapy, making the evaluation of their anticancer efficiency crucial for clinical application. However, delivering natural products to single cells and in situ monitoring of induced signaling molecule fluctuation to evaluate anticancer efficiency remain significant challenges. Hence, we proposed a universal and straightforward strategy to construct a bifunctional nanoelectrode that integrates drug loading and monitoring of signal molecule fluctuations at the single-cell level. Platinum (Pt) nanoparticles/reduced graphene oxide (rGO) composites were first electrochemically deposited on the carbon fiber nanoelectrode (CFNE@Pt/rGO) to serve as electrocatalytic materials for the monitoring of natural-product-induced reactive oxygen species (ROS) generation. The GO/natural product complex, formed by π-π stacking and hydrophobic interactions, was further electrochemically reduced on the surface of CFNE@Pt/rGO to enable the CFNE drug-loading function. Using this bifunctional functional nanoelectrode, a series of natural products (such as capsaicin, curcumin, and chrysin) were delivered into single cancer cells, and their anticancer efficiency was evaluated by measuring ROS generation. The results showed that intracellular ROS production induced by chrysin was 1.5-fold greater than that of curcumin and 2.1-fold greater than that of capsaicin. This work proposes an effective tool to evaluate the anticancer efficiency of various natural products. Additionally, this nanotool can be expanded to monitor the fluctuation of other biomolecules (such as RNS, GSH, NADH, etc.) by replacing Pt nanoparticles with other electrocatalytic materials, which is significant for comprehensively exploring the anticancer efficiency of new drugs and for the clinical treatment of various diseases.

In Vitro Toxicity and Modeling Reveal Nanoplastic Effects on Marine Bivalves

Nanoplastics (NPs) represent a growing concern for global environmental health, particularly in marine ecosystems where they predominantly accumulate. The impact of NPs on marine benthic organisms, such as bivalves, raises critical questions regarding ecological integrity and food safety. Traditional methods for assessing NP toxicity are often limited by their time-intensive nature and ethical considerations. Herein, we explore the toxicological effects of NPs on the marine bivalve Ruditapes philippinarum, employing a combination of in vitro cellular assays and advanced modeling techniques. Results indicate a range of adverse effects at the organismal level, including growth inhibition (69.5-108%), oxidative stress, lipid peroxidation, and DNA damage in bivalves, following exposure to NPs at concentrations in the range of 1.6 × 109-1.6 × 1011 particles/mL (p/mL). Interestingly, the growth inhibition predicted by models (54.7-104%), based on in vitro cellular proliferation assays, shows strong agreement with the in vivo outcomes of NP exposure. Furthermore, we establish a clear correlation between cytotoxicity observed in vitro and the toxicological responses at the organismal level. Taken together, this work suggests that the integration of computational modeling with in vitro toxicity assays can predict the detrimental effects of NPs on bivalves, offering insightful references for assessing the environmental risk assessment of NPs in marine benthic ecosystems.

Aggregation-Enabled Electrochemistry in Confined Nanopore Capable of Complementary Faradaic and Non-Faradaic Detection

Electrochemistry that empowers innovative nanoscopic analysis has long been pursued. Here, the concept of aggregation-enabled electrochemistry (AEE) in a confined nanopore is proposed and devised by reactive oxygen species (ROS)-responsive aggregation of CdS quantum dots (QDs) within a functional nanopipette. Complementary Faradaic and non-Faradaic operations of the CdS QDs aggregate could be conducted to simultaneously induce the signal-on of the photocurrents and the signal-off of the ionic signals. Such a rationale permits the cross-checking of the mutually corroborated signals and thus delivers more reliable results for single-cell ROS analysis. Combined with the rich biomatter-light interplay, the concept of AEE can be extended to other stimuli-responsive aggregations for electrochemical innovations.