A split-type photoelectrochemical immunosensing platform based on atom-efficient cation exchange for physiological monitoring

Ultrasensitive and accurate physiological monitoring is of great significance for disease diagnosis and treatment. In this project, an efficient photoelectrochemical (PEC) split-type sensor on the basis of controlled release strategy was established with great success. Heterojunction formation between g-C₃N₄ and Zn-doped CdS improved the visible light absorption efficiency, reduced carrier complexation, improved the PEC signal, and increased the stability of the PEC platform. Compared to the traditional model of immunosensors, the process of antigen-antibody specific binding was done in a 96 microplate, and the sensor separated the immune reaction from the photoelectrochemical conversion process, eliminating mutual interference. Cu₂O nanocubes were used to label the second antibody (Ab₂), and acid etching using HNO₃ released a large amount of divalent copper ions, which exchanged cations with Cd²⁺ in the substrate material, causing a sharp drop in photocurrent and improving the sensitivity of the sensor. Under the optimized experimental conditions, the PEC sensor based on the controlled release strategy for CYFRA21-1 target detection had a wide concentration linear range of 5 × 10^-5 to 100 ng/mL with a low detection limit of 0.0167 pg/mL (S/N = 3). This intelligent response variation pattern could also offer the possibility of additional clinical applications for other target detection.

Reticular Electrochemiluminescence Nanoemitters: Structural Design and Enhancement Mechanism

ConspectusElectrochemiluminescence (ECL) is a powerful transduction technique, which depends critically on the formation of the excited emitter through the charge transfer between the electrochemical reaction intermediates of the emitter and the co-reactant/emitter. The exploration of ECL mechanisms for conventional nanoemitters is limited due to the uncontrollable charge transfer process. With the development of molecular nanocrystals, reticular structures such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been utilized as atomically precise semiconducting materials. The long-range order in crystalline frameworks and the tunable coupling among building blocks promote the quick development of electrically conductive frameworks. Especially, the reticular charge transfer can be regulated by both interlayer electron coupling and intralayer topology-templated conjugation. By modulating intramolecular or intermolecular charge mobility, reticular structures could serve as promising candidates for enhancing ECL. Thus, reticular crystalline nanoemitters with different topologies provide a confined platform to understand ECL fundamentals for designing next-generation ECL devices.Aiming at exploring the mechanism of ECL emission, our group has developed a series of ECL nanoemitters as well as enhancement strategies of ECL emission in the past 20 years. A series of water-soluble ligand-capped quantum dots were introduced as ECL nanoemitters to create sensitive analytical methods for detecting and tracing biomarkers. The functionalized polymer dots were also designed as ECL nanoemitters for imaging of membrane proteins with signal transduction strategies of dual resonance energy transfer and dual intramolecular electron transfer. To decode the ECL fundamental and enhancement mechanisms, an electroactive MOF with accurate molecular structure was first constructed with two redox ligands as a highly crystallized ECL nanoemitter in aqueous medium. Through the mixed-ligand approach, luminophores and co-reactants were integrated into one MOF structure for self-enhanced ECL. Furthermore, several donor-acceptor COFs were developed as efficient ECL nanoemitters with tunable intrareticular charge transfer. The atomically precise structure of conductive frameworks established clear correlations between the structure and charge transport in these materials. Therefore, reticular materials as crystalline ECL nanoemitters have demonstrated both proof of concept and mechanistic innovation.In this Account, taking advantage of reticular materials with accurate molecular structure, we survey the design of the electroactive reticular materials including MOFs and COFs as crystalline ECL nanoemitters at the molecular level. The enhancement mechanisms of ECL emission of various topology frameworks are discussed via the regulation of reticular energy transfer and charge transfer and the accumulation of anion/cation radicals. Our perspective on the reticular ECL nanoemitters is also discussed. This Account provides a new avenue for designing molecular crystalline ECL nanoemitters and decoding the fundamentals of ECL detection methods.

Protein-Targeted Glycan Editing on Living Cells Disrupts KRAS Signaling

The frequent mutation of KRAS oncogene in some of the most lethal human cancers has spurred incredible efforts to develop KRAS inhibitors, yet only one covalent inhibitor for the KRASG12C mutant has been approved to date. New venues to interfere with KRAS signaling are desperately needed. Here, we report a "localized oxidation-coupling" strategy to achieve protein-specific glycan editing on living cells for disrupting KRAS signaling. This glycan remodeling method exhibits excellent protein and sugar specificity and is applicable to different donor sugars and cell types. Attachment of mannotriose to the terminal galactose/N-acetyl-D-galactosamine epitopes of integrin αv β3 , a membrane receptor upstream of KRAS, blocks its binding to galectin-3, suppresses the activation of KRAS and downstream effectors, and mitigates KRAS-driven malignant phenotypes. Our work represents the first successful attempt to interfere with KRAS activity by manipulating membrane receptor glycosylation.

Electron Donor Coordinated Metal-Organic Framework to Enhance Photoelectrochemical Performance

To enhance photoelectrochemical (PEC) performance, additional electron donor/acceptor is generally required to inhibit the electron-hole recombination. However, the enhancement is limited due to the long-distance diffusion. Herein a self-supplying electron strategy is designed for PEC enhancement by coordinating an electron donor 1.4-diazabicyclo[2.2.2]octane (Dabco) in metal-organic framework (MOF). The intrareticular photoelectron transfer mechanism in mixed-ligand MOF (m-MOF) is experimentally revealed and verified by density functional theory calculations. The presence of Dabco efficiently inhibits the electron-hole recombination due to the self-supplying electrons and longer electron lifetime in the framework, and thus leads to 23.2-fold enhancement of photocurrent. As proof of concept, a simple PEC method is constructed with the designed m-MOF to demonstrate its application in sensitive bioanalysis. This work provides a new avenue for improving the PEC performance of nanomaterials.

In situ evaluation of in vivo sialylation with a dual-color imaging strategy

This work designs a functional dendrimer probe to conveniently identify newly generated sialic acid groups in vivo with a dual-color imaging strategy, which achieves in situ semiquantitative evaluation of the sialylation difference between tumor and normal tissues to reveal sialylation-related biological events and promote clinical tumor diagnosis.

Zirconium dioxide as electrochemiluminescence emitter for D-dimer determination based on dual-quenching sensing strategy

The ECL emission of simple and stable zirconium dioxide nanomaterials has always been a blank slate in the ECL sensors field. In this work, zirconium dioxide (ZrO₂)-titanium dioxide (TiO₂)-gold nanoparticle (AuNPs) composite (ZT-Au), a novel self-enhanced ECL emitter, was introduced the system of dual-quenching ECL immunosensor. The anodic luminescence of ZrO₂ in the system of tripropylamine (TPrA) as a co-reagent was first reported and explored. Meanwhile, TiO₂ was designed into the ECL scheme as a co-reaction accelerator to form the ZrO₂/TPrA/TiO₂ ternary system, which can efficiently amplify the ECL signal of the emitter. In addition, cuprous oxide-triaminophenol (Cu₂O-APF) as the quencher was devoted to the dual-quenching sensing strategy. The dual-quenching mechanism that effectively boosted the immunosensor sensitivity was adequately investigated and conjectured in this paper. The sensing model based on the luminophor ZT-Au and the quencher Cu₂O-APF was utilized for the detection of D-dimer, a reliable marker for the diagnosis and evaluation of thrombotic diseases. The short peptide ligands NARKFYKGC (NFC) with efficient biological affinity were used to site-directionally capture antibodies for adequately protecting the activity of antigen binding sites during the construction of the immunosensor. The implemented immunosensor was equipped with a broad linear range of 0.01-500 ng/mL and a low detection limit of 3.6 pg/mL. The original methodology opens up the field of vision for the detection of additional biomarkers.

Signal-On Mass Spectrometric Biosensing of Multiplex Matrix Metalloproteinases with a Phospholipid-Structured Mass-Encoded Microplate

The detection of matrix metalloproteinases (MMPs) is of great importance for diagnosis and staging of cancer. This work proposed a signal-on mass spectrometric biosensing strategy with a phospholipid-structured mass-encoded microplate for assessment of multiplex MMP activities. The designed substrate and internal standard peptides were subsequently labeled with the reagents of isobaric tags for relative and absolute quantification (iTRAQ), and DSPE-PEG(2000)maleimide was embedded on the surface of a 96-well glass bottom plate to fabricate the phospholipid-structured mass-encoded microplate, which offered a simulated environment of the extracellular space for enzyme reactions between MMPs and the substrates. The strategy achieved multiplex MMP activity assays by dropping the sample in the well for enzyme cleavages, followed by adding trypsin to release the coding regions for ultrahigh performance liquid chromatography-tandem mass spectrometric (UHPLC-MS/MS) analysis. The peak area ratios of released coding regions and their respective internal standard (IS) peptides exhibited satisfied linear ranges of 0.05-50, 0.1-250, and 0.1-100 ng mL^-1 with the detection limits of 0.017, 0.046, and 0.032 ng mL^-1 for MMP-2, MMP-7, and MMP-3, respectively. The proposed strategy demonstrated good practicability in inhibition analysis and detections of multiplex MMP activities in serum samples. It is of great potential for clinical applications and can be expanded for multiplex enzyme assays.

An electrochemiluminescence insulin sensing platform based on the molecular recognition properties of cucurbit[7]uril

The establishment of new mechanisms for target identification and signal amplification continues to drive innovation in electrochemiluminescence (ECL) sensing platforms. In this paper, a novel ECL insulin sensing platform was constructed by utilizing the molecular recognition properties of cucurbit[7]uril. Specifically, the macrocyclic host molecule cucurbit[7]uril was immobilized on the surface of the sensing platform as an identification probe, which could selectively capture insulin according to the inherent properties of the protein N-terminal. Introducing the rigid molecule cucurbit[7]uril into the sensing interface could reduce the influence of the environmental parameters on the sensing system, which provides a reliable guarantee for the accurate detection of insulin. Furthermore, gold nanoclusters were modified by utilizing the molecular recognition properties of cucurbit[7]uril, and used as anode signal probes for ECL sensing platform. The macrocyclic molecules cucurbit[7]uril passivated the surface of the nanoclusters, inhibited the non-radiative relaxation and improved the physical stability of the luminophore, leading to a significant increase in the sensitivity and stability of the ECL probe. The ECL sensing platforms exhibited a linear range from 50.00 fg/mL to 100.0 ng/mL, with a detection limit of 5.44 fg/mL. This study revealed the critical role of cucurbit[7]uril in target recognition and signal amplification, extending the scope of supramolecular applications in ECL.

Regulation of Target-activated CRISPR/Cas12a on Surface Binding of Polymer Dots for Sensitive Electrochemiluminescence DNA Analysis

Polymer dots (Pdots) have emerged as a type of attractive electrochemiluminescence (ECL) emitter. However, the low ECL efficiency severely limits their practicability. In this work, we develop a sensitive ECL biosensing strategy for the detection of human papilloma virus subtype (HPV-16) DNA by using target-activated CRISPR/Cas12a to regulate the binding of Pdots-DNA to biosensor and local surface plasmon resonance (LSPR) effect of electrochemically deposited Au nanoparticles (depAuNPs) to enhance the ECL emission of Pdots bound on biosensor. The biosensor is prepared by simply assembling hairpin DNA on depAuNPs modified electrode. In the presence of target DNA, the designed specific CRISPR/Cas12a can be activated to digest single-stranded assistant DNA, which decreases the amount of hairpin DNA opened by assistant DNA to bind Pdots-DNA on the biosensor surface, thus reduces the ECL emission. The integration of target DNA-triggered catalysis and the LSPR effect of depAuNPs greatly improves the sensitivity of ECL analysis. Using HPV-16 DNA as a target model, the proposed method shows a limit of detection (LOD) of 3.2 fM at a signal-to-noise ratio of 3 and a detectable concentration range of 5.0 fM to 50 pM. The high sensitivity, excellent selectivity, good testing stability, and acceptable fabrication reproducibility of the designed ECL biosensing strategy demonstrate its potential application in DNA bioanalysis.

Dual-quenching electrochemiluminescence resonance energy transfer system from CoPd nanoparticles enhanced porous g-C3N4 to FeMOFs-sCuO for neuron-specific enolase immunosensing

For the diagnosis and therapy of small cell lung cancer (SCLC), the accurate and sensitive determination of neuron-specific enolase (NSE) content is crucial. This work outlines a dual-quenching electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor based on the double quenching effects of iron base metal organic frameworks (FeMOFs) loaded with small sized CuO nanoparticles (FeMOFs-sCuO) towards CoPd nanoparticles (CoPdNPs) enhanced porous g-C₃N₄ (P-C₃N₄-CoPdNPs). To be specific, we prepared a porous g-C₃N₄ (P-C₃N₄) which has a rich porous structure, and significantly increased the specific surface area and the number of reaction sites of P-C₃N₄. Meanwhile, the CoPdNPs were loaded onto P-C₃N₄ to improve the ECL luminescence property of P-C₃N₄/K₂S₂O₈ system through acting as a coreaction accelerator. In addition, the ultraviolet-visible (UV-vis) absorption spectra of FeMOFs and small sized CuO nanoparticles (sCuO) showed considerable overlap with the ECL emission spectra of P-C₃N₄ appropriately. Therefore, FeMOFs with high specific surface area were prepared and well combined with sCuO to effectively dual-quenching the ECL emission of P-C₃N₄ based on resonance energy transfer. Hence, a new type ECL-RET couple made up of P-C₃N₄-CoPdNPs (donor) and FeMOFs-sCuO (acceptor) were developed for the first time. A certain amount of P-C₃N₄-CoPdNPs, Ab₁, BSA, NSE were modified layer by layer onto the electrode surface. Then FeMOFs-sCuO-Ab₂ bioconjugates was incubated through the immune recognition binding. As a result, a sandwich-type ECL biosensor was manufactured successfully for NSE immunoassay. Under optimal experimental conditions, the limit of detection (LOD) and the limit of quantitation (LOQ) of the prepared ECL sensor for NSE analysis was 20.4 fg mL^-1 and 7.99 fg mL^-1, respectively, with the relative standard deviation (RSD) of 1.68%. The linear detection range was 0.0000500-100 ng mL^-1. The studied immunosensor had satisfactory sensitivity, specificity and reproducibility, manifesting the suggested sensing strategy might offer a good technical means and theoretical basis for the sensitivity analysis of NSE and has a potential application in clinical diagnosis analysis.

Special Issue "Feature Papers in Biosensors Section 2022"

Biosensors are devices composed of a biorecognition part and of a transduction part [...].

Enhanced anode electrochemiluminescence in split aptamer sensor for kanamycin trace monitoring

Covalently modifying electrochemiluminescence (ECL) luminophores to alter their energy levels or generate energy/electron transfer processes for improved performance is hindered by the complex design and fabrication processes. In this study, non-covalent bond self-assembly was employed to enhance the ECL property of gold nanoclusters with tryptophan (Try) and mercaptopropionic acid (MPA) as ligands (Try-MPA-gold nanoclusters). Specifically, through the molecular recognition of Try by cucurbit[7]uril, some non-radiative transition channels of the charge carriers on the surface of the Try-MPA-gold nanoclusters were restricted, resulting in a significant enhancement of the ECL intensity of the nanoclusters. Furthermore, rigid macrocyclic molecules acted on the surface of the nanoclusters through self-assembly, forming a passive barrier that improved the physical stability of the nanoclusters in the water-phase and indirectly improved their luminescent stability. As an application, cucurbit[7]uril-treated Try-MPA-gold nanoclusters (cucurbit[7]uril@Try-MPA-gold nanoclusters) were used as signal probes, and Zn-doped SnO₂ nanoflowers (Zn-SnO₂ NFs) with high electron mobility were used as electrode modification material to establish an ECL sensor for kanamycin (KANA) detection, utilizing split aptamers as capture probes. The advanced split aptamer sensor demonstrated excellent sensitivity analysis for KANA in complex food substrates with a recovery rate of 96.2 to 106.0%.

Crosslinked albumin-manganese nanoaggregates with sensitized T1 relaxivity and indocyanine green loading for multimodal imaging and cancer phototherapy

Albumin-manganese-based nanocomposites (AMNs) characterized by simple preparation and good biocompatibility have been widely used for in vivo T₁-weighted magnetic resonance imaging (MRI) and cancer theranostics. Herein, an aggregation and crosslinking assembly strategy was proposed to achieve the sensitization to T₁ relaxivity of the albumin-manganese nanocomposite. At a relatively low Mn content (0.35%), the aggregation and crosslinking of bovine serum albumin-MnO₂ (BM) resulted in a dramatic increase of T₁ relaxivity from 5.49 to 67.2 mM^-1 s^-1. Upon the loading of indocyanine green (ICG) into the crosslinked BM nanoaggregates (C-BM), the T₁ relaxivity of the C-BM/ICG nanocomposite (C-BM/I) was further increased to 97.3 mM^-1 s^-1, which was much higher than those reported previously even at high Mn contents. Moreover, the presence of C-BM greatly enhanced the photoacoustic (PA) and photothermal effects of ICG at 830 and 808 nm, respectively, and the second near infrared fluorescence (NIR-II FL) of ICG also showed better stability. Therefore, the synthesized C-BM/ICG nanocomposite exhibited remarkable performance in in vivo multimodal imaging of tumors, such as T₁-weighted MRI, NIR-II FL imaging and PA imaging, and cancer phototherapy with little side effects. This work provided a highly efficient and promising multifunctional nanoprobe for breaking through the limits of cancer theranostics, and opened a new avenue for the development of high-relaxivity AMNs and multimodal imaging methodology.

Cell-Selective Multifunctional Surface Covalent Reconfiguration Using Aptamer-Enabled Proximity Catalytic Labeling

Cell surface engineering provides access to custom-made cell interfaces with desirable properties and functions. However, cell-selective covalent labeling methods that can simultaneously install multiple molecules with different functions are scarce. Herein, we report an aptamer-enabled proximity catalytic covalent labeling platform for multifunctional surface reconfiguration of target cells in mixed cell populations. By conjugating peroxidase with cell-selective aptamers, the probes formed can selectively bind target cells and catalyze target-cell-localized covalent labeling in situ. The universal applicability of the platform to different phenol-modified functional molecules allows us to perform a variety of manipulations on target cells, including labeling, tracking, assembly regulation, and surface remodeling. In particular, the platform has the ability of multiplexed covalent labeling, which can be used to install two mutually orthogonal click reactive molecules simultaneously on the surface of target cells. We thus achieve "multitasking" in complex multicellular systems: programming and tracking specific cell-cell interactions. We further extend the functional molecules to carbohydrates and perform ultrafast neoglycosylation on target living cells. These newly introduced sugars on the cell membrane can be recognized and remodeled by a glycan-modifying enzyme, thus providing a method package for cell-selective engineering of the glycocalyx.

Cancer Cell-Selective Membrane Receptor Clustering Driven by VEGF Secretion for In Vivo Therapy

Clustering of cell membrane receptors regulates cell behaviors. Although receptor clustering plans have achieved wide applications in cancer therapy, it still remains challenging to manipulate receptor clustering selectively for cancer cells with little influence on normal cells. Here, we design a Raji cell Selective MAnipulation of Receptor Clustering (SMARC) strategy for CD20, which is driven by endogenous secretion of Raji cells. Retractable DNA nanostrings with repeating hairpin-structured units are anchored to the cell membrane CD20, which contract in response to Raji cell-secreted vascular endothelial growth factor (VEGF) with corresponding CD20 clustering. The contraction of DNA nanostrings is intensified via a VEGF amplifier including DNA cyclic reactions to continuously trigger the foldings of hairpin-structured units in DNA nanostrings. The SMARC strategy shows selective and efficient apoptosis of Raji cells with little interference to normal B cells and demonstrates good in vivo therapeutic efficacy, which provides a promising tool for precise cancer therapy.

Electrochemiluminescence Imaging at a Single Nanoparticle Scale to Elucidate Diffusion-Accelerated Charge Transfer and Monitor Cell Permeability

Accelerating the charge transfer between electroactive species and the electrode is always a hot topic. Here, we report a finding of Ru(bpy)₃³⁺ diffusion-induced acceleration of charge transfer from Ru(bpy)₃²⁺-doped silica nanoparticles (RDSNs) to the electrode via electrochemiluminescence (ECL) imaging at a single nanoparticle scale. Ru(bpy)₃²⁺ in the electrolyte can act as an enhancer of RDSN ECL emission in the presence of coreactant tripropylamine, which amplifies the RDSN ECL by 478 times at 10 μM free Ru(bpy)₃²⁺. According to percolation theory, the diffusion of electro-generated Ru(bpy)₃³⁺ near a single RDSN brings much quicker charge transfer to the electrode than electron hopping in RDSN, which is demonstrated by spatial and temporal interaction imaging of the RDSN and the Ru(III) diffusion layer. Taking advantage of this new mechanism, a real-time ECL imaging method has been constructed to monitor the rapid change of cell permeability during surfactant treatment.

Chimeric Biocatalyst Combining Peptidic and Nucleic Acid Components Overcomes the Performance and Limitations of the Native Horseradish Peroxidase

Chimeric peptide-DNAzyme (CPDzyme) is a novel artificial peroxidase that relies on the covalent assembly of DNA, peptides, and an enzyme cofactor in a single scaffold. An accurate control of the assembly of these different partners allows for the design of the CPDzyme prototype G4-Hemin-KHRRH, found to be >2000-fold more active (in terms of conversion number k_cat) than the corresponding but non-covalent G4/Hemin complex and, more importantly, >1.5-fold more active than the corresponding native peroxidase (horseradish peroxidase) when considering a single catalytic center. This unique performance originates in a series of gradual improvements, thanks to an accurate selection and arrangement of the different components of the CPDzyme, in order to benefit from synergistic interactions between them. The optimized prototype G4-Hemin-KHRRH is efficient and robust as it can be used under a wide range of non-physiologically relevant conditions [organic solvents, high temperature (95 °C), and in a wide range of pH (from 2 to 10)], thus compensating for the shortcomings of the natural enzymes. Our approach thus opens broad prospects for the design of ever more efficient artificial enzymes.

PB@PDA nanocomposites as nanolabels and signal reporters for separate-type cathodic photoelectrochemical immunosensors in the detection of carcinoembryonic antigens

Photoelectrochemical (PEC) immunoassays exhibiting high sensitivity and decent operability have considerable potential in areas such as cancer diagnostics. In particular, cathodic PEC configurations can prevent interference from reductive substances, which can occur in biological samples; however, challenges remain in terms of sensitivity and operability. In this study, separate-type PEC immunoassays were developed for carcinoembryonic antigen (CEA) by combining microplate-based immune recognition and off-on cathodic PEC detection. Polydopamine (PDA)-coated Prussian blue (PB) nanoparticles (PB@PDA NPs) were used as signal tags to label the detection antibody. The PB NPs and PDA captured on the microplates both disassembled under strongly alkaline conditions to generate redox-active electron acceptors. The disassembled products were quantitatively transferred to PEC detection cells and synergistically enhanced the PEC current with microstructured BiOI, which operated as a cathodic semiconductor electrode. As proof of principle, carcinoembryonic antigen (CEA) was applied to elucidate the potential application of PEC immunoassay in clinical diagnosis, and the obtained linear range of the sensor was 0.001-100 ng mL^-1 with the detection limit of 54.9 fg mL^-1 (S/N = 3). The proposed separate-type off-on PEC strategy showed high sensitivity and decent operability for CEA detection, indicating its potential for the identification of other tumor markers.

DNAzyme-Powered DNA Walker for Cooperative Expression Imaging of Mutant p53 and Telomerase in Cancer Cells

Cooperative expression of multiple cancer biomarkers is of great significance in influencing cell pathways and drug treatment. However, the simultaneous analysis of low-abundance biomarkers in living cells remains a challenge. Here, we report a DNAzyme-powered DNA walker to visualize the cooperative expression of mutant p53 and telomerase in living cells. The activation of the DNA walker is orthogonally powered by mutated p53 and telomerase, which enables the unlocking of the walking strand and the subsequently repeated substrate cleavage, producing fluorescence recovery for the imaging of the two target molecules in living cells. The DNA walker allows for real-time monitoring of the expression profile of mutant p53 and active telomerase in cancer cells under various antitumor drug treatments, and the results demonstrate the cooperative expression of mutant p53 and telomerase via the Akt pathway, which may bring new insights into the study of cancer pathway-relevant biomarkers.

Device integration of electrochemical biosensors

Electrochemical biosensors incorporate a recognition element and an electronic transducer for the highly sensitive detection of analytes in body fluids. Importantly, they can provide rapid readouts and they can be integrated into portable, wearable and implantable devices for point-of-care diagnostics; for example, the personal glucose meter enables at-home assessment of blood glucose levels, greatly improving the management of diabetes. In this Review, we discuss the principles of electrochemical biosensing and the design of electrochemical biosensor devices for health monitoring and disease diagnostics, with a particular focus on device integration into wearable, portable and implantable systems. Finally, we outline the key engineering challenges that need to be addressed to improve sensing accuracy, enable multiplexing and one-step processes, and integrate electrochemical biosensing devices in digital health-care pathways.

AuNPs@MoSe2 heterostructure as a highly efficient coreaction accelerator of electrocheluminescence for amplified immunosensing of DNA methylation

Electrocheluminescence analysis amplified by coreaction accelerators has experienced breakthrough in ultrasensitive detection of biomarkers. Herein, a highly efficient coreaction accelerator, two-dimensional layered MoSe₂ nanosheets loaded with gold nanoparticles (AuNPs@MoSe₂ heterostructure), is proposed to enhance the ECL efficiency of Ru(bpy)₃²⁺/tripropylamine (TPrA) system. The presence of AuNPs avoids the aggregation of MoSe₂ nanosheets, and improves the electrical conductivity of modified surface. The AuNPs@MoSe₂ modified electrode also provides a large area for loading of abundant capture probe. MoSe₂ as an electroactive substrate can remarkably accelerate the generation of TPrA^•+ radicals to react with electrooxidized Ru(bpy)₃²⁺, which achieves about 3.4-fold stronger ECL intensity. Thus, an enhanced ECL immunoassay method can be achieved after Ru(bpy)₃²⁺-doped silica nanoparticle labeled antibody (Ab₂-Ru@SiO₂) is captured to the modified electrode via immunological recognition. Using methylated DNA as a target, the immunosensor was prepared by binding capture DNA on AuNPs@MoSe₂ modified electrode to successively capture the target, anti-5-methylcytosine antibody (anti-5mC) and Ab₂-Ru@SiO₂. The proposed strategy could detect 0.26 fM 5 mC (3σ) with a detectable concentration range of 1.0 fM - 10 nM at methylated DNA. This immunosensor showed excellent selectivity, good stability and reproducibility, and acceptable recovery, indicating the broad prospects of the novel coreaction accelerator in clinical diagnosis.

Biomimetic retractable DNA nanocarrier with sensitive responsivity for efficient drug delivery and enhanced photothermal therapy

BACKGROUND

The coalition of DNA nanotechnology with diversiform inorganic nanoparticles offers powerful tools for the design and construction of stimuli-responsive drug delivery systems with spatiotemporal controllability, but it remains challenging to achieve high-density oligonucleotides modification close to inorganic nanocores for their sensitive responsivity to optical or thermal signals.

RESULTS

Inspired by Actinia with retractable tentacles, here we design an artificial nano-Actinia consisted of collapsible DNA architectures attached on gold nanoparticle (AuNP) for efficient drug delivery and enhanced photothermal therapy. The collapsible spheroidal architectures are formed by the hybridization of long DNA strand produced in situ through rolling circle amplification with bundling DNA strands, and contain numerous double-helical segments for the intercalative binding of quercetin as the anti-cancer drug. Under 800-nm light irradiation, the photothermal conversion of AuNPs induces intensive localized heating, which unwinds the double helixes and leads to the disassembly of DNA nanospheres on the surface of AuNPs. The consequently released quercetin can inhibit the expression of heat shock protein 27 and decrease the thermal resistance of tumor cells, thus enhancing photothermal therapy efficacy.

CONCLUSIONS

By combining the deformable DNA nanostructures with gold nanocores, this Actinia-mimetic nanocarrier presents a promising tool for the development of DNA-AuNPs complex and opens a new horizon for the stimuli-responsive drug delivery.

The prognostic value of splenic abnormalities in pretreatment 18F-FDG PET/CT in patients with complete response diffuse large B-cell lymphoma

AIM

To investigate whether spleen imaging characteristics of baseline 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron-emission tomography (PET)/computed tomography (CT) can help to predict the clinical outcome in complete response (CR) diffuse large B-cell lymphoma (DLBCL).

MATERIALS AND METHODS

Three hundred and six patients with DLBCL were enrolled in the study and divided into recurrence and non-recurrence groups. The splenic abnormalities were compared using the chi-square test and quantitative indexes were compared using the t-test. The Cox proportional hazard regression model was used for univariate and multivariate analysis. Kaplan-Meier curves and log-rank tests were used to compare progression-free survival (PFS). Propensity score matching (PSM) was used to match patients with and without splenic abnormalities according to age, gender, and initial Ann Arbor stage at a 1:2 ratio (52:104); then the recurrence and PFS results were compared again.

RESULTS

Age, international prognostic index (IPI), stage, splenomegaly, and focal splenic lesions were significantly different between the recurrence and non-recurrence groups. IPI, stage, baseline spleen mean standard uptake value (SUVmean)/liver SUVmean, splenomegaly, and focal lesions were selected by Cox single-factor analysis, and only focal lesions showed a statistical difference in terms of Cox multivariate analysis (p=0.022, hazard ratio [HR]: 2.843). After PSM, focal splenic lesions (n=20) were still statistically different (p=0.003) between the recurrence and non-recurrence groups, and this played an essential role in PFS forecasting (p=0.0004, HR: 3.767).

CONCLUSION

Focal splenic lesions were identified as an independent risk factor for the prognosis of DLBCL. Pretreatment splenomegaly and focal splenic lesions appeared to be related to the relapse and PFS of DLBCL patients. Focal splenic lesions still showed meaningful predictive value even with propensity matching.

Electrochemiluminescence nanoemitters for immunoassay of protein biomarkers

The family of electrochemiluminescent luminophores has witnessed quick development since the electrochemiluminescence (ECL) phenomenon of silicon nanoparticles was first reported in 2002. Moreover, these developed ECL nanoemitters have extensively been applied in sensitive detection of protein biomarker by combining with immunological recognition. This review firstly summarized the origin and development of various ECL nanoemitters including inorganic and organic nanomaterials, with an emphasis on metal-organic frameworks (MOFs)-based ECL nanoemitters. Several effective strategies to amplify the ECL response of nanoemitters and improve the sensitivity of immunosensing were discussed. The application of ECL nanoemitters in immunoassay of protein biomarkers for diagnosis of cancers and other diseases, especially lung cancer and heart diseases, was comprehensively presented. The recent development of ECL imaging with the nanoemitters as ECL tags for detection of multiplex protein biomarkers on single cell membrane also attracted attention. Finally, the future opportunities and challenges in the ECL biosensing field were highlighted.

Tumor identification via in vivo portable Raman detection of sialic acid with a dual gold nanoprobe system

A dual gold nanoprobe system was designed for in vivo portable Raman detection of sialic acid (SA) for tumor identification. The dual gold nanoprobe system contained two gold nanoprobes, Au10-DTTC/PEG-PBA and Au40-PEG-SA. Au10-DTTC/PEG-PBA was constructed on a 10 nm gold nanoparticle modified with 3,3'-diethylthia tricarbocyanine iodide (DTTCI) as the Raman reporter and 3-aminophenylboronic acid (APBA) through a thiol PEG succinimidyl carboxymethyl ester (HS-PEG-NHS) linker for specific recognition of SA. Au40-PEG-SA was constructed on a 40 nm gold nanoparticle modified with SA through HS-PEG-NHS. For in vivo detection of SA, Au10-DTTC/PEG-PBA and Au40-PEG-SA were subsequently injected into tumor xenografted mice with optimal interval and retention times. Through the specific recognition between PBA and SA, the conjugates of Au10-DTTC/PEG-PBA and Au40-PEG-SA formed in the tumor region emitted strong SERS signals of DTTC, which could be detected by a portable Raman detector. This work provides a convenient and portable method to detect SA in tumor xenografted mice, which is useful for family-stay identification and clinical cleavage of tumors.