Ultrasensitive Photoelectrochemical Biosensor for Dual-miRNAs Detection Based on Molecular Logic Gates and Methylene Blue Sensitized ZnO@CdS@Au Nanorods.

The occurrence of cancer is often closely related to multiple tumor markers, so it is important to develop multitarget detection methods. By the proper design of the input signals and logical operations of DNA logic gates, detection and diagnosis of cancer at different stages can be achieved. For example, in the early stages, specific input signals can be designed to correspond to early specific tumor markers, thereby achieving early cancer detection. In the late stage, logic gates for multitarget detection can be designed to simultaneously detect multiple biomarkers to improve diagnostic accuracy and comprehensiveness. In this work, we constructed a dual-target-triggered DNA logic gate for anchoring DNA tetrahedra, where methylene blue was embedded in the DNA tetrahedra to sensitize ZnO@CdS@Au, achieving ultrasensitive detection of the target substance. We tested the response of AND and OR logic gates to the platform. For AND logic gates, the sensing platform only responds when both miRNAs are present. In the concentration range of 10 aM to 10 nM, the photoelectric signal gradually increases with an increase of the target concentration. Subsequently, we used OR logic gates for miRNA detection. Even if only one target exists, the sensing platform exhibits excellent performance. Similarly, within the concentration range of 10 aM to 10 nM, the photoelectric signal gradually increases with an increase of the target concentration. The minimum detection limit is 1.10 aM. Whether it is the need to detect multiple targets simultaneously or only one of them, we can achieve it by selecting the appropriate logic gate. This strategy holds promising application prospects in fields such as biosensing, medical diagnosis, and environmental monitoring.

Fabrication of versatile Fe3O4/GO/Au composite nanomaterial as SERS-active substrate for detection of pesticide residue.

Highly active Fe3O4/GO/Au composite nanomaterial was fabricated as a substrate of surface-enhanced Raman spectroscopy (SERS) and applied for pesticide residue detection. The three-layer multifunctional Fe3O4/GO/Au nanoparticles (NPs) were designed by facile method, with high hotspots, and were characterized by various techniques, including ultraviolet spectrophotometry (UV), X-ray diffraction (XRD), infrared absorption spectrometer (IR), and transmission electron microscopy (TEM). The performance of Fe3O4/GO/Au was evaluated by Raman spectroscopy with R6G as a probe molecule to verify its enhancement effect. It exhibited a strong Raman signal with 10-6 M of R6G. Furthermore, the presence of Fe3O4/GO/Au nanohybrid enabled the SERS-based method to detect mancozeb and showed an excellent linear relationship in the range of 0.25-25 ppm, with a low limit of detection (0.077 ppm), satisfactory EF, stability, and repeatability. In addition, the mechanism of SERS enhancement with electromagnetic mechanism (EM) and chemical mechanism (CM) was discussed in detail. Therefore, the proposed SERS approach holds promise as an auxiliary technique for screening contaminated agricultural products, environmental sample, and food in the future.

Design of Cellulose Nanocrystal-Based Self-Healing Nanocomposite Hydrogels and Application in Motion Sensing and Sweat Detection.

Hydrogels, as flexible materials, have been widely used in the field of flexible sensors. Human sweat contains a variety of biomarkers that can reflect the physiological state of the human body. Therefore, it is of great practical significance and application value to realize the detection of sweat composition and combine it with human motion sensing through a hydrogel. Based on mussel-inspired chemistry, polydopamine (PDA) and gold nanoparticles (AuNPs) were coated on the surface of cellulose nanocrystals (CNCs) to obtain CNC-based nanocomposites (CNCs@PDA-Au), which could simultaneously enhance the mechanical, electrochemical, and self-healing properties of hydrogels. The CNCs@PDA-Au was composited with poly(vinyl alcohol) (PVA) hydrogel to obtain the nanocomposite hydrogel (PVA/CNCs@PDA-Au) by freeze-thaw cycles. The PVA/CNCs@PDA-Au has excellent mechanical strength (7.2 MPa) and self-healing properties (88.3%). The motion sensors designed with PVA/CNCs@PDA-Au exhibited a fast response time (122.9 ms), wide strain sensing range (0-600.0%), excellent stability, and fatigue resistance. With the unique electrochemical redox properties of uric acid, the designed hydrogel sensor successfully realized the detection of uric acid in sweat with a wide detection range (1.0-100.0 µmol/L) and low detection limit (0.42 µmol/L). In this study, the dual detection of human motion and uric acid in sweat was successfully realized by the designed PVA/CNCs@PDA-Au nanocomposite hydrogel.

Molecular Dynamics Simulations of Soft and Reactive Landing of Proteins Desorbed by Argon Cluster Bombardment.

Reactive molecular dynamics (MD) simulations were conducted to investigate the soft and reactive landing of hyperthermal velocity proteins transferred to a vacuum using large argon clusters. Experimentally, the interaction of argon cluster ion beams (Ar1000-5000+) with a target biofilm was previously used in such a manner to transfer lysozymes onto a collector with the retention of their bioactivity, paving the way to a new solvent-free method for complex biosurface nanofabrication. However, the experiments did not give access to a microscopic view of the interactions needed for their full understanding, which can be provided by the MD model. Our reactive force field simulations clarify the landing mechanisms of the lysozymes and their fragments on collectors with different natures (gold- and hydrogen-terminated graphite). The results highlight the conditions of soft and reactive landing on rigid surfaces, the effects of the protein structure, energy, and incidence angle before landing, and the adhesion forces with the collector substrate. Many of the obtained results can be generalized to other soft and reactive landing approaches used for biomolecules such as electrospray ionization and matrix-assisted laser desorption ionization.

Multienzyme Active Nanozyme for Efficient Sepsis Therapy through Modulating Immune and Inflammation Inhibition.

Sepsis, a life-threatening condition caused by a dysregulated immune response to infection, leads to systemic inflammation, immune dysfunction, and multiorgan damage. Various oxidoreductases play a very important role in balancing oxidative stress and modulating the immune response, but they are stored inconveniently, environmentally unstable, and expensive. Herein, we develop multifunctional artificial enzymes, CeO2 and Au/CeO2 nanozymes, exhibiting five distinct enzyme-like activities, namely, superoxide dismutase, catalase, glutathione peroxidase, peroxidase, and oxidase. These artificial enzymes have been used for the biocatalytic treatment of sepsis via inhibiting inflammation and modulating immune responses. These nanozymes significantly reduce reactive oxygen species and proinflammatory cytokines, achieving multiorgan protection. Notably, CeO2 and Au/CeO2 nanozymes with enzyme-mimicking activities can be particularly effective in restoring immunosuppression and maintaining homeostasis. The redox nanozyme offers a promising dual-protective strategy against sepsis-induced inflammation and organ dysfunction, paving the way for biocatalytic-based immunotherapies for sepsis and related inflammatory diseases.

Antibacterial Property and Mechanisms of Au@Ag Core-Shell Nanoparticles with Near-Infrared Absorption Against E. faecalis Infection of Dentin.

Background: Enterococcus faecalis (E. faecalis) is one of the main pathogens responsible for refractory root canal infections in the teeth and shows resistance against various antibacterial managements. Effective control of E. faecalis infection is a prerequisite for successful treatment of refractory apical periodontitis. This study aimed to analyze the antibacterial activity and mechanisms of Au@Ag nanoparticles (NPs) combined with photothermal therapy (PTT) against the original and Ag+-resistant E. faecalis. Methods: Au@AgNPs with optimal shell thicknesses were synthesized and characterized. The antibacterial activity of Au@AgNPs with PTT against the original or Ag+-resistant E. faecalis was evaluated, and the antibiofilm activity was tested on E. faecalis biofilm on the dentin of teeth. The potential antibacterial mechanisms of Au@AgNPs combined with PTT against E. faecalis have also been studied. Moreover, its influence on dentin microhardness and cytotoxicity was assessed. Results: This study revealed that Au@AgNPs combined with PTT showed enhanced antibacterial and antibiofilm effects, no negative effects on dentin microhardness, and low cytotoxicity toward human periodontal ligament cells (hPDLCs). Moreover, Au@AgNPs combined with PTT effectively inhibited the growth of Ag+-resistant E. faecalis. Its antibacterial effects may be exerted through the release of silver ions (Ag+), destruction of the cell membrane, production of reactive oxygen species (ROS) and inhibition of adenosine triphosphate (ATP) production. Hyperthermia generated by Au@AgNPs with PTT reduced membrane fluidity and enhanced Ag+ sensitivity by downregulating fabF expression. The upregulated expression of heat shock genes demonstrated that the Ag+ released from Au@AgNPs compromised the heat adaptation of E. faecalis. Conclusion: PTT significantly enhanced Ag+ sensitivity of the original and Ag+-resistant E. faecalis. Au@AgNPs combined with PTT may have the potential to be developed as a new antibacterial agent to control E. faecalis infections in teeth.

Gold nanoparticles-based biosensors: pioneering solutions for bacterial and viral pathogen detection-a comprehensive review.

Gold Nanoparticles (AuNPs) have gained significant attention in biosensor development due to their unique physical, chemical, and optical properties. When incorporated into biosensors, AuNPs offer several advantages, including a high surface area-to-volume ratio, excellent biocompatibility, ease of functionalization, and tunable optical properties. These properties make them ideal for the detection of various biomolecules, including proteins, nucleic acids, and bacterial and viral biomarkers. Traditional methods for detecting bacteria and viruses, such as RT-PCR and ELISA, often suffer from complexities, time consumption, and labor intensiveness. Consequently, researchers are continuously exploring novel devices to address these limitations and effectively detect a diverse array of infectious pathogenic microorganisms. In light of these challenges, nanotechnology has been instrumental in refining the architecture and performance of biosensors. By leveraging advancements in nanomaterials and strategies of biosensor fabrication the sensitivity and specificity of biosensors can be enhanced, enabling more precise detection of pathogenic bacteria and viruses. This review explores the versatility of AuNPs in detecting a variety of biomolecules, including proteins, nucleic acids, and bacterial and viral biomarkers. Furthermore, it evaluates recent advancements in AuNPs-based biosensors for the detection of pathogens, utilizing techniques such as optical biosensors, lateral flow immunoassays, colorimetric immunosensors, electrochemical biosensors, and fluorescence nanobiosensors. Additionally, the study discusses the existing challenges in the field and proposes future directions to improve AuNPs-based biosensors, with a focus on enhancing sensitivity, selectivity, and their utility in clinical and diagnostic applications.

The GoldX Fiducial Eraser.

Gold nanoparticles with sizes in the range of 5-15 nm are a standard method of providing fiducial markers to assist with alignment during reconstruction in cryogenic electron tomography. However, due to their high electron density and resulting contrast when compared to standard cellular or biological samples, they introduce artifacts such as streaking in the reconstructed tomograms. Here, we demonstrate a tool that automatically detects these nanoparticles and suppresses them by replacing them with a local background as a post-processing step, providing a cleaner tomogram without removing any sample relevant information or introducing new artifacts or edge effects from uniform density replacements.

Construction of UCNPs-aptamer-AuNPs luminescence energy transfer probe for ratio detection of Staphylococcus aureus.

A ratio luminescence probe was developed for detecting Staphylococcus aureus (S. aureus) based on luminescence energy transfer (LET) using double-wavelength emission (550 nm and 812 nm) upconversion nanoparticles (UCNPs) as donor, gold nanoparticles (AuNPs) as acceptor and the aptamer for S. aureus as the specific recognition and link unit. The LET process could cause luminescence quenching because of the spectral overlap between the acceptor and the donor at 550 nm. In the presence of S. aureus, S. aureus selectively combined with the aptamer, and the AuNPs left the surface of UCNPs, which weakened the quenching effect and restored the luminescence of UCNPs. Based on this, the ratio detection was realized by monitoring the change of the luminescence signal of the probe at 550 nm and taking the luminescence signal at 812 nm as the reference signal. Crucially, the probe has a fast reaction speed, with a reaction time of 25 min, and the detection of S. aureus is realized in the concentration range of 5.0 × 103-3.0 × 105 CFU/ml, with the detection limit of 106 CFU/ml. Therefore, the ratio probe has great potential for detecting of S. aureus in food because of its high sensitivity, fast speed and good selectivity.

Plasmonic trimers designed as SERS-active chemical traps for subtyping of lung tumors.

Plasmonic materials can generate strong electromagnetic fields to boost the Raman scattering of surrounding molecules, known as surface-enhanced Raman scattering. However, these electromagnetic fields are heterogeneous, with only molecules located at the 'hotspots', which account for ≈ 1% of the surface area, experiencing efficient enhancement. Herein, we propose patterned plasmonic trimers, consisting of a pair of plasmonic dimers at the bilateral sides and a trap particle positioned in between, to address this challenge. The trimer configuration selectively directs probe molecules to the central traps where 'hotspots' are located through chemical affinity, ensuring a precise spatial overlap between the probes and the location of maximum field enhancement. We investigate the Raman enhancement of the Au@Al2O3-Au-Au@Al2O3 trimers, achieving a detection limit of 10-14 M of 4-methylbenzenethiol, 4-mercaptopyridine, and 4-aminothiophenol. Moreover, single-molecule SERS sensitivity is demonstrated by a bi-analyte method. Benefiting from this sensitivity, our approach is employed for the early detection of lung tumors using fresh tissues. Our findings suggest that this approach is sensitive to adenocarcinoma but not to squamous carcinoma or benign cases, offering insights into the differentiation between lung tumor subtypes.

An Immunochromatographic Test Strip for Rapid Quantitative Control of Monoclonal Antibodies against Programmed Cell Death Protein 1.

Cancer is one of the major public health challenges in the world, which is characterized by rapid progression and high mortality. Immunotherapy, represented by PD-1 monoclonal antibody, has significantly improved the efficacy of malignant tumors and has become one of the most popular immunotherapy methods at present. Therefore, there is an increasing demand for novel detection methods for PD-1 monoclonal antibodies. The aim of this work was to establish a rapid, simple, and sensitive immunochromatographic test strip (ICTS) based on the AuNPs enlargement for both visual and instrumental detection of the PD-1 monoclonal antibody concentration. The mixed solution of NH2OH·HCl and HAuCl4 was used as an enhancement solution to lower the detection limit and achieve higher sensitivity. A test strip reader was used to construct a visualized quantitative detection standard curve for the PD-1 monoclonal antibody concentration. The LOD was 1.58 ng/mL through a triple signal-to-noise ratio. The detection time was within 10 min. The constructed test strips can rapidly, accurately, and efficiently detect the concentration of PD-1 monoclonal antibody in real samples.

A lateral flow assay strip for simultaneous detection of miRNA and exosomes in liver cancer.

By employing an aptamer as the bridge and combining catalytic hairpin assembly with the Au aggregation amplification effect, a lateral flow assay (LFA) is designed for simultaneous detection of liver cancer-associated miRNA and exosomes. The LFA can differentiate between liver cancer patients and healthy individuals with simple operation and high accuracy.

Structure-activity relationship of anticancer and antiplasmodial gold bis(dithiolene) complexes.

Monoanionic gold bis(dithiolene) complexes were recently shown to display activity against ovarian cancer cells, Gram-positive bacteria, Candida strains and the rodent malaria parasite, P. berghei. To date, only monoanionic gold(III) bis(dithiolene) complexes with a thiazoline backbone substituted with small alkyl chains have been evaluated for biomedical applications. We now analyzed the influence of the length and the hydrophobicity vs. hydrophilicity of these complexes' alkyl chain on their anticancer and antiplasmodial properties. Isomer analogues of these monoanionic gold(III) bis(dithiolene) complexes, this time with a thiazole backbone, were also investigated in order to assess the influence of the nature of the heterocyclic ligand on their overall chemical and biological properties. In this report we present the total synthesis of four novel monoanionic gold(III) bis(dithiolene) complexes with a long alkyl chain and a polyoxygenated (PEG) chain aiming to improve their solubility and biological properties. Our results showed that the complexes with a PEG chain showed promising anticancer and antiplasmodial activities beside improved solubility, a key parameter in drug discovery and development.

Superlarge, Rigidified DNA Tetrahedron with a Y-Shaped Backbone for Organizing Biomolecules Spatially and Maintaining Their Full Bioactivity.

A major impediment to the clinical translation of DNA tiling nanostructures is a technical bottleneck for the programmable assembly of DNA architectures with well-defined local geometry due to the inability to achieve both sufficient structural rigidity and a large framework. In this work, a Y-backbone was inserted into each face to construct a superlarge, sufficiently rigidified tetrahedral DNA nanostructure (called RDT) with extremely high efficiency. In RDT, the spatial size increased by 6.86-fold, and the structural rigidity was enhanced at least 4-fold, contributing to an ∼350-fold improvement in the resistance to nucleolytic degradation even without a protective coating. RDT can be mounted onto an artificial lipid-bilayer membrane with molecular-level precision and well-defined spatial orientation that can be validated using the fluorescence resonance energy transfer (FRET) assay. The spatial orientation of Y-shaped backbone-rigidified RDT is unachievable for conventional DNA polyhedrons and ensures a high level of precision in the geometric positioning of diverse biomolecules with an approximately homogeneous environment. In tests of RDT, surface-confined horseradish peroxidase (HRP) exhibited nearly 100% catalytic activity and targeting aptamer-immobilized gold nanoparticles showed 5.3-fold enhanced cellular internalization. Significantly, RDT exhibited a 27.5-fold enhanced structural stability in a bodily environment and did not induce detectable systemic toxicity.

Redox cycling-based signal amplification at alkanethiol modified nanoporous gold interdigitated microelectrodes.

Interdigitated electrodes (IDEs) enable electrochemical signal enhancement through repeated reduction and oxidation of the analyte molecule. Porosity on these electrodes is often used to lower the impedance background. However, their high capacitive current and signal interferences with oxygen reduction limit electrochemical detection ability. We present utilization of alkanethiol modification on nanoporous gold (NPG) electrodes to lower their background capacitance and chemically passivate them from interferences due to oxygen reduction, while maintaining their fast electron transfer rates, as validated by lower separation between anodic and cathodic peaks (ΔE) and lower charge transfer resistance (Rct) values in comparison to planar gold electrodes. Redox amplification based on this modification enables sensitive detection of various small molecules, including pyocyanin, p-aminophenol, and selective detection of dopamine in the presence of ascorbic acid. Alkanethiol NPG arrays are applied as a multiplexed sensor testbed within a well plate to screen binding of various peptide receptors to the SARS COV2 S-protein by using a sandwich assay for conversion of PAPP (4-aminophenyl phosphate) to PAP (p-aminophenol), by the action of AP (alkaline phosphatase), which is validated against optical ELISA screens of the peptides. Such arrays are especially of interest in small volume analytical settings with complex samples, wherein optical methods are unsuitable.

An ultrasensitive electrochemical/colorimetric dual-mode self-powered biosensing platform for lung cancer marker detection by multiple-signal amplification strategy.

BACKGROUND: In recent years, miRNAs have emerged as potentially valuable tumor markers, and their sensitive and accurate detection is crucial for early screening and diagnosis of tumors. However, the analysis of miRNAs faces significant challenges due to their short sequence, susceptibility to degradation, high similarity, low expression level in cells, and stringent requirements for in vitro research environments. Therefore, the development of sensitive and efficient new methods for the detection of tumor markers is crucial for the early intervention of related tumors. RESULTS: An ultrasensitive electrochemical/colorimetric dual-mode self-powered biosensor platform is established to detect microRNA-21 (miR-21) via a multi-signal amplification strategy. Gold nanoparticles (AuNPs) and VS4 nanosheets self-assembled 3D nanorods (VS4-Ns-Nrs) are prepared for constructing a superior performance enzyme biofuel cell (EBFC). The double-signal amplification strategy of Y-shaped DNA nanostructure and catalytic hairpin assembly (CHA) is adopted to further improve enhance the strength and specificity of the output signal. In addition, a capacitor is matched with EBFC to generate an instantaneous current that is amplified several times, and the output detection signal is improved once more. At the same time, electrochemical and colorimetric methods are used for dual-mode strategy to achieve the accuracy of detection. The linear range of detection is from 0.001 pg/mL to 1000 pg/mL, with a relatively low limit of detection (LOD) of 0.16 fg/mL (S/N = 3). SIGNIFICANCE: The established method enables accurate and sensitive detection of markers in patients with lung cancer, providing technical support and data reference for precise identification. It is anticipated to offer a sensitive and practical new technology and approach for early diagnosis, clinical treatment, and drug screening of cancer and other related major diseases.

Field-deployable viral diagnostic tools for dengue virus based on Cas13a and Cas12a.

The diagnosis of dengue virus (DENV) has been challenging particularly in areas far from clinical laboratories. Early diagnosis of pathogens is a prerequisite for the timely treatment and pathogen control. An ideal diagnostic for viral infections should possess high sensitivity, specificity, and flexibility. In this study, we implemented dual amplification involving Cas13a and Cas12a, enabling sensitive and visually aided diagnostics for the dengue virus. Cas13a recognized the target RNA by crRNA and formed the assembly of the Cas13a/crRNA/RNA ternary complex, engaged in collateral cleavage of nearby crRNA of Cas12a. The Cas12a/crRNA/dsDNA activator ternary complex could not be assembled due to the absence of crRNA of Cas12a. Moreover, the probe, with 5' and 3' termini labeled with FAM and biotin, could not be separated. The probes labeled with FAM and biotin, combined the Anti-FAM and the Anti-Biotin Ab-coated gold nanoparticle, and conformed sandwich structure on the T-line. The red line on the paper strip caused by clumping of AuNPs on the T-line indicated the detection of dengue virus. This technique, utilizing an activated Cas13a system cleaving the crRNA of Cas12a, triggered a cascade that amplifies the virus signal, achieving a low detection limit of 190 fM with fluorescence. Moreover, even at 1 pM, the red color on the T-line was easily visible by naked eyes. The developed strategy, incorporating cascade enzymatic amplification, exhibited good sensitivity and may serve as a field-deployable diagnostic tool for dengue virus.

A DNA walker based on hairpin-shaped DNA aligner and fueled by nicking endonuclease for sensitive and rapid miRNA analysis.

BACKGROUND: DNA walker-based strategies have gained significant attention in nucleic acid analysis. However, they face challenges related to balancing design complexity, sequence dependence, and amplification efficiency. Furthermore, most existing DNA walkers rely on walking and lock probes, requiring optimization of various parameters like DNA probe sequence, walking-to-lock probe ratio, lock probe length, etc. to achieve optimal performance. This optimization process is time-consuming and adds complexity to experiments. To enhance the performance and reliability of DNA walker nanomachines, there is a need for a simpler, highly sensitive, and selective alternative strategy. RESULTS: A sensitive and rapid miRNA analysis strategy named hairpin-shaped DNA aligner and nicking endonuclease-fueled DNA walker (HDA-NE DNA walker) was developed. The HDA-NE DNA walker was constructed by modifying hairpin-shaped DNA aligner (HDA) probe and substrate report (SR) probe on the surface of AuNPs. Under normal conditions, HDA and SR remained stable. However, in the presence of miR-373, HDA underwent a conformational transition to an activated structure to continuously cleave the SR probe on the AuNPs with the assistance of Nt.AlwI nicking endonuclease, resulting in sensitive miRNA detection with a detection limit as low as 0.23 pM. Additionally, the proposed HDA-NE DNA walker exhibited high selectivity in distinguishing miRNAs with single base differences and can effectively analyze miR-373 levels in both normal and breast cancer patient serums. SIGNIFICANCE: The proposed HDA-NE DNA walker system was activated by a conformational change of HDA probe only in the presence of the target miRNA, eliminating the need for a lock probe and without sequence dependence for SR probe. This strategy demonstrated a rapid reaction rate of only 30 min, minimal background noise, and a high signal-to-noise ratio (S/B) compared to capture/lock-based DNA walker. The method is expected to become a powerful tool and play an important role in disease diagnosis and precision therapy.

Simultaneous Hg2+ and Pb2+ detection in water samples using an electrochemical aptasensor with dual signal amplification by exonuclease III and metal-organic frameworks.

Heavy metal pollution in the environment has become a significant global concern due to its detrimental effects on human health and the environment. In this study, we report an electrochemical aptasensor for the simultaneous detection of Hg2+ and Pb2+. Gold nanoflower/polyethyleneimine-reduced graphene oxide (AuNFs/PEI-rGO) was introduced on the surface of a gold electrode to improve sensing performance. The aptasensor is based on the formation of a T-Hg2+-T mismatch structure and specific cleavage of the Pb2+-dependent DNAzyme, resulting in a dual signal generated by the Exo III specific digestion of methylene blue (MB) labeled at the 3' end of probe DNA-1 and the reduction of the substrate ascorbic acid (AA) catalyzed by the signal label. The decrease of MB signal and the increase of AA oxidation peak was used to indicate the content of Hg2+ and Pb2+, respectively, with detection limits of 0.11 pM (Hg2+) and 0.093 pM (Pb2+). The aptasensor was also used for detecting Hg2+ and Pb2+ in water samples with good recoveries. Overall, this electrochemical aptasensor shows promising potential for sensitive and selective detection of heavy metals in environmental samples.

Weakly ionized gold nanoparticles amplify immunoassays for ultrasensitive point-of-care sensors.

Gold nanoparticle-based lateral flow immunoassays (AuNP LFIAs) are widely used point-of-care (POC) sensors for in vitro diagnostics. However, the sensitivity limitation of conventional AuNP LFIAs impedes the detection of trace biomarkers. Several studies have explored the size and shape factors of AuNPs and derivative nanohybrids, showing limited improvements or enhanced sensitivity at the cost of convenience and affordability. Here, we investigated surface chemistry on the sensitivity of AuNP LFIAs. By modifying surface ligands, a surface chemistry strategy involving weakly ionized AuNPs enables ultrasensitive naked-eye LFIAs (~100-fold enhanced sensitivity). We demonstrated how this surface chemistry-amplified immunoassay approach modulates nanointerfacial bindings to promote antibody adsorption and higher activity of adsorbed antibodies. This surface chemistry design eliminates complex nanosynthesis, auxiliary devices, or additional reagents while efficiently improving sensitivity with advantages: simplified fabrication process, excellent reproducibility and reliability, and ultrasensitivity toward various biomarkers. The surface chemistry using weakly ionized AuNPs represents a versatile approach for sensitizing POC sensors.