Signal Magnification Research Articles

Target-induced activation of dual DNAzyme recycling amplifications for sensitive electrochemical fat mass and obesity-associated protein assay

The fat mass and obesity-associated protein (FTO) is vital for modulating dynamic reversible process of N6-methyladenosine (m6A) level in the nucleus and the abnormal expression of FTO correlates with generation and development of Alzheimer's disease, obesity and several cancers. The sensitive detection of FTO is therefore of significance for diagnosis of FTO-related diseases. In this work, on the basis of the demethylation enzyme capability of FTO and the dual Mg2+-dependent DNAzyme recycled signal magnification strategy, establishment of a highly sensitive electrochemical FTO biosensor is described. The target FTO molecules catalyze the demethylation of m6A-modified sequences to form effective cleavage substrates for the MboI endonuclease, leading to the release of active DNAzyme sequences to trigger subsequent dual DNAzyme recycling cycles. Many methylene blue-tagged ssDNA sequences can thus be yielded via the DNAzyme amplifications and captured on the sensor electrode to generate highly amplified currents for detecting FTO in range of 0.04 pM to 10 nM with 6.11 fM detection limit. Additionally, the sensor demonstrates high selectivity and is able to be used for detecting cell lysate FTO, showing its potential for the diagnosis and study of FTO-related diseases for various application purposes.

Engineered Fe3O4 nanoreactor as a high-performance hydrogen peroxide sensor

Nanozymes with peroxidase-mimicking activities have been extensively explored for hydrogen peroxide (H2O2) detection. However, the conventional nanozyme assay with suspensions suffer the limitations of restricted available surface, loss of short-lived radicals, and slow reaction in non-acidic conditions, thus have a greatly reduced detection sensitivity. We here proposed to overcome these drawbacks by constructing aligned nanoreactor sensor with Fe3O4 nanozymes distributed alongside the nanochannels of anodized aluminum oxide (termed as NR-Fe3O4), which allowed for a spatially confined nanozyme reactions (ca. 5 nm) operated under a filtration reaction mode. We presented the unique merits of NR-Fe3O4 on H2O2 detection compared to Fe3O4 nanozyme suspensions, together with the mechanism discussion about how the radical production and capturing got maximized under the confinement. As a result, our NR-Fe3O4 sensor featured a highly sensitive H2O2 detection with a linear concentration from 10 to 5000 nM (detection limit of 0.9 nM), expanded workable pH to neutral, and enhanced nanozyme stability for at least 8 h continuous run. We further showed the great feasibility of using NR-Fe3O4 sensor in complex water matrices for H2O2 detection, as it allowed for a pore rejection of background organics which in turn protected the internal radicals for a capturing and signal magnification. Our findings highlight the great interest of constructing confinement nanoreactors as an innovative approach of enhancing H2O2 detection sensitivity based on the nanozyme assay.

Reprogrammable Nonlinear Transmission Controls Using an Information Metasurface

AbstractNonlinearity manipulation based on electromagnetic (EM) metasurfaces has always been a hot topic, which is an important part of communication and radar systems. However, most of the existing transmission metasurfaces are mainly focused on linear processing on the incident EM waves. In this article, a reprogrammable nonlinear transmission metasurface is proposed for spatial waves using active power amplifiers. An ultrathin and compact metasurface is designed, fabricated, and measured, to achieve reprogrammable functions on the nonlinear transmissions. For EM incidence, the metasurface can not only amplify the magnification of small signals, but also control high‐energy signals nonlinearly, whose magnification is determined by different bias voltages. The simulation and experimental results show good consistency, which verifies the feasibility of the proposed method. This work can find potential applications in signal gain compression and construction of nonlinear units of diffractive deep neural networks.

One-pot wet-chemical fabrication of 3D urchin-like core-shell Au@PdCu nanocrystals for electrochemical breast cancer immunoassay.

Carbohydrate antigen 15-3 (CA15-3) is an important biomarker for early diagnosis of breast cancer. Herein, a label-free electrochemical immunosensor was built based on three-dimensional (3D) urchin-like core-shell Au@PdCu nanocrystals (labeled Au@PdCu NCs) for highly sensitive detection of CA15-3, where K3[Fe(CN)6] behaved as an electroactive probe. The Au@PdCu NCs were synthesized by a simple one-pot wet-chemical approachand the morphology, structures, and electrocatalytic property were investigated by several techniques. The Au@PdCu NCs preparedworked as electrode material to anchor more antibodies and as signal magnification material by virtue of its exceptional catalytic property. The developed biosensor exhibited a wide linear detection range from 0.1 to 300 U mL-1 and a low limit of detection (0.011 U mL-1, S/N = 3) for determinationof CA15-3 under the optimal conditions. The established biosensing platform exhibits some insights for detecting other tumor biomarkers in clinical assays and early diagnosis.

Hollow cage-like PtCu nanozyme-regulated photo-activity of porous CdIn2S4/SnO2 heterojunctions for ultrasensitive PEC sensing of streptomycin

Streptomycin (STR) is extensively employed for preventive and curative purposes in animals, which is accumulated in human body through food chain and induces serious health problems. Herein, highly photoactive type II heterojunctions of porous CdIn2S4/SnO2 microspheres were initially prepared, which can effectively inhibit the recombination of the charge-hole pairs. Besides, the peroxidase-mimicking catalytic property of the hollow PtCu nanocages (PtCu NCs) was carefully investigated by UV–vis spectroscopy, where catalytic oxidation of tetramethylbenzidine behaved as the benchmarked reaction. On such basis, a highly selective photoelectrochemical (PEC) aptasensor was established with the CdIn2S4/SnO2 heterojunctions for bioanalysis of streptomycin, coupled by the PtCu NCs nanozyme-catalyzed biocatalytic precipitation to achieve signal magnification. Specifically, the home-made nanozyme was applied for catalytic oxidation of 3,3’-diaminobenzidine to generate insulating precipitate in aqueous H2O2 system and thereby block the light harvesting on the photoanode, showing steeply declined PEC responses. The as-built aptasensor showed a broad linear range of 0.01–200 nM with a low limit of detection of 7.50 pM (S/N = 3) for such analysis, combined by exploring its practical detection in milk samples. This work shows excellent nanozyme-catalyzed signal amplification for fabrication of ultrasensitive PEC biosensors towards other antibiotics detection.

An electrochemiluminescence immunosensor based on signal magnification of luminol using OER-activated NiFe2O4@C@CeO2/Au as effective co-reaction accelerator

In this work, a novel, label-free electrochemiluminescence (ECL) immunosensor was constructed for the ultrasensitive detection of carbohydrate antigen 15–3 (CA15-3) by the combined use of NiFe2O4@C@CeO2/Au hexahedral microbox and luminol luminophore. The synthesis of the co-reaction accelerator (NiFe2O4@C@CeO2/Au) was related to the calcination of FeNi-based metal–organic framework (MOF), as well as the ingrowth of CeO2 nanoparticles and modification of Au nanoparticles. To be specific, the electrical conductivity will be boosted due to the Au nanoparticles, the synergetic effect generated between CeO2 and calcination FeNi-MOF could offer better activity of oxygen evolution reaction (OER). Herein, the NiFe2O4@C@CeO2/Au hexahedral microbox as a co-reaction accelerator has excellent OER activity and production of reactive oxygen species (ROS), thus increasing the ECL intensity of luminol in a neutral medium without other co-reactants such as H2O2. Because of these benefits, the constructed ECL immunosensor was applied to detect CA15-3 as an example under optimum conditions, the designed ECL immunosensor exhibited high-level selectivity and sensitivity for CA15-3 biomarker within a linear response range of 0.01–100 U mL−1 and an ultralow detection limit of 0.545 mU mL−1 (S/N = 3), demonstrating its potentially valuable application in the area of clinical analysis.

Duloxetine: an effective treatment for fibromyalgia syndrome?

Duloxetine hydrochloride (duloxetine) is a powerful selective serotonin and norepinephrine reuptake inhibitor (SSRI), which in recent years has shown measurable success in treating a wide variety of disorders, including fibromyalgia syndrome (FMS). Among the clinical symptoms of FMS is the dysfunction of the monoamine systems in the nervous system, and since those are what duloxetine regulates, it is successful in managing its symptoms.1 Therefore, the United States Food and Drug Administration has cleared it for treating major depressive disorder, generalized anxiety disorder, for managing diabetic peripheral neuropathic pain and chronic musculoskeletal pain2. FMS is prevalent worldwide and affects nearly 1 in 20 people globally, including about 3 million adults in the United States3. Usually, patients diagnosed with FMS also have other chronic overlapping pain conditions and mental disorders, therefore it is uncommon to have FMS as an independent diagnosis4. Chronic stress exacerbates neuropathic pain by integrating stress affect–related information with nociceptive information in the amygdala’s central nucleus5,6. Its symptoms include restless sleep, fatigue, anxiety, depression, and problems regulating mood. There is a central magnification of pain signals, which evidence suggests is caused by the fact that both the ascending and descending pain pathways are functioning abnormally7. Although there is little evidence supporting this, it is believed that the symptoms are caused by neural over-sensitization, decreased conditioned pain modulation, combined with cognitive dysfunction, memory impairment, and altered information processing caused by negative events, stressful environments, or physical/emotional trauma8,9. Patients suffering from FMS have also been reported to experience a phenomenon known as fibrofog, which entails a decreased ability to think and process new information. The inference that disruptions in the perception of physiological pain, sleep, fatigue, cognition, and mood (hallmark symptoms of patients with FMS) may be consequences of abnormalities in serotonin and norepinephrine metabolism and transmission is supported by the fact they are both important regulators of these functions in healthy individuals10. Duloxetine works by reinforcing the serotonergic and adrenergic pathways involved in descending inhibition of pain at the dorsal horn of the spinal cord. The subsequent increased threshold for pain stimuli to reach the brain results in significant neuropathic pain relief. In a study, Write et al11 concluded that because the average FMS patient is on 3–6 medications to manage the symptoms, there may be an increased risk for the drug-to-drug interactions. Serotonin toxicities can develop from using serotonergic drugs and duloxetine simultaneously as it can lead to adverse drug-drug interactions12. Furthermore, little is known about how it may affect pregnancies or lead to complications for the mother and child before and after delivery. SSRIs increase the possibility of developing suicidality in children and young adults aged 18–24, which is one of its more tendentious side effects. Thus, the FDA has released a black box warning for duloxetine use13. Furthermore, duloxetine increases both levels of serotonin and norepinephrine, which directly results in tachycardia and hypertension14. Even though systematic reviews have proven its effectiveness in pain management, improving symptoms in up to 80% of patients, a careful examination of its adverse effects and advantages must be taken into consideration when prescribing SSRIs to any patient13,14. Diagnosis and eventual management of this disease are delayed because patients usually present with a variety of symptoms15. FMS patients must spend up to $35,920 on health care every year in the United States to treat the various symptoms of this disease16. Frequent physical therapy appointments to reduce stiffness, frequent blood work, and hospital visits take up significant time and place a financial strain on the patient. In a recent study, it was found that most patients with FMS view themselves as being moderate to severely disabled. The intensity of pain they experience and psychological factors (alexithymia and depression) were found to be the main reasons for this17. Clear, distinct guidelines for its diagnosis should be established so as not to delay the beginning of treatment, and awareness needs to be created among clinicians in third-world countries about this disease as well. Newer, more effective drugs need to be designed to not only improve the patient’s quality of life but to reduce the burden on the already overwhelmed health care systems as well. Ethical approval None. Sources of funding None. Authors’ contribution N.E.: wrote the article, suggested a topic, conducted a literature search A.E.: conducted a final review and corrections Conflicts of interest disclosure The authors declare that they have no financial conflict of interest with regard to the content of this report. Research registration unique identifying number (UIN) None. Guarantor Naz Elahi.

A Simple Yet Parameter-Less and Cost-Effective Rotor Speed-Cum-Position Estimator for Encoder-Free Control of Doubly-Fed Induction Generator

A hybrid process for estimating rotor speed and position is proposed for the doubly-fed induction generator (DFIG) in connection with its stator flux-oriented vector control. The improved characteristics of the proposed method are: (i) unlike existing schemes, this method does not exhibit error due to discrepancy in the machine’s parameters, and (ii) The number of sensors is reduced in comparison with the other estimators. As a result, the estimation model achieves parameter independence while also using fewer sensors, i.e., a cost-effective, reliable, and compact scheme is suggested due to the reduction of physical element and parameter dependency. In the proposed case, it is not necessary to calculate fluxes or intermediate variables, as well as to use fewer measured input quantities, which reduces the calculation burden. Differentiation and integration of variables are absent. This prevents the magnification of noise and low-frequency signals on the primary signal. The operations of the proposed estimator under diverse conditions are tested by means of a real-time working prototype. The performances here support the theoretical conclusions. The comparisons with other state-of-art techniques indicate the superiority of the proposed estimation scheme.

Nucleic acid amplification with specific signal filtration and magnification for ultrasensitive colorimetric detection

Recently, sensitive, fast and low cost nucleic acid isothermal amplification technologies (such as loop-mediated isothermal amplification, LAMP) have attracted great attention in the urgent needs of point-of-care testing (POCT) and regular epidemic prevention and control. However, unlike PCR which usually employs TaqMan probe to report specific signals, specific-signal-output strategies in isothermal amplification are immature and visual detection even rare, which limits their popularity in POCT. We hypothesize to address this issue by designing a visual-signal-report system to both filtrate and magnify the target information in isothermal amplification. In this work, we developed a specific signal filtration and magnification colorimetric isothermal sensing platform (SFMC for short) for ultrasensitive detection of DNA and RNA. SFMC consists of two processes: an isothermal amplification with specific signal filtration and a self-replication catalyzed hairpin assembly (SRCHA) for rapid target-specific signal magnification and outputting. With these unique properties, this biosensing platform could detect target DNA as low as 5 copies per reaction and target RNA as low as 10 copies per reaction by naked eyes. Benefited from the excellent colorimetric detection performance, this biosensing platform has been successfully used for African swine fever virus (ASFV) and SARS-CoV-2 detection.

Development of Poly(L-arginine)/PSSA/QDs Modified Biosensor for Simultaneous Detection of Different Glucocorticoids in Wastewater

Due to poor electro-active and less structural differences of glucocorticoids, it is still a challenge to realize simultaneous electrochemical detection of different glucocorticoids in wastewater. In this study, an electrochemical biosensing platform was constructed through electrochemical in situ polymerization. A poly(sulphosalicylic acid) (PSSA) composite electrode was prepared based on polymerized L-arginine (Arg) doped with carbon quantum dots (QDs) and GCE-Arg-PSSA-QD sensor was obtained. Transmission electron microscopy, scanning electron microscopy and energy dispersive spectrometer were used to characterize the morphology and physical property of obtained electrodes. The PSSA layer mimics the sulfonated metabolism of glucocorticoids in vivo, allowing for direct reduction of glucocorticoids on the surface of electrode, thus enabling the capture of different glucocorticoids. Meanwhile, the fast electron transfer of QDs and the signal magnification effect of Arg allow a sensitive and direct detection of dexamethasone (DXM) and hydrocortisone (HC) simultaneously. Differential pulse voltammetry was used to investigate the analytical properties of prepared biosensing platform. The results show that GCE-Arg-PSSA-QD sensor delivered an analytical performance for both DXM and HC with a limit of detection of 9 nM and 37 nM. Then, the method was utilized for simultaneous detection of DXM and HC in real wastewater samples with favorable results.

Programmable hybridization assemble nicked displacement amplification for detecting ricin toxin

Isothermal amplification, such as hybridization chain reaction (HCR), is a simple and reliable method for detecting signal amplification. However, the hairpin in HCR will not fully participate in the reaction. And after the hairpin is opened, the distance between the fluorophore and the quencher does not change much. Therefore, the signal magnification is limited. Here, we designed a new isothermal amplification method named hybridization assemble nicked displacement amplification (HANDA), combining HCR and strand displacement amplification (SDA) ingeniously. HANDA first triggers HCR through the target sequence to form long double-strand DNA (dsDNA) with gaps. Then SDA is performed from the gap to obtain a large amount of single-stranded DNA (ssDNA), so as to achieve the purpose of double signal amplification. The base sequence of DNA hairpin had also been optimized. The best sequence design rule was found and had universal applicability. We have demonstrated that HANDA combined with DNA barcodes can be used for trace detection of ricin. This new isothermal amplification method provides an effective and universal platform for the trace detection of various toxic substances.

Dual signal magnification for ultrasensitive biosensing based on well-regulated SERS of AuNTs@AuHg and DSN-assisted amplification.

AuNTs@AuHg alloy with well-regulated SERS properties was proposed, which displayed wonderful SERS intensity and effective salt resistance. Using miRNA-21 as a model analyte and combining with DSN-assisted amplification, a dual signal amplification strategy for ultrasensitive miRNA biosensing with a low detection limit (0.53 fM) and satisfactory selectivity was designed.

Benchmarking Electrolyte‐Gated Monolayer MoS2 Field‐Effect Transistors in Aqueous Environments

Most electrical sensor and biosensor elements require reliable transducing elements to convert small potential changes into easy to read out current signals. Offering inherent signal magnification and being operable in many relevant environments field‐effect transistors (FETs) are the element of choice in many cases. In particular, using electrolyte gating, numerous sensors and biosensors have been realized in aqueous environments. Over the past years, electrolyte‐gated FETs have been fabricated using a variety of semiconducting materials, including graphene, ZnO, as well as conjugated molecules and polymers. Above all, using conducting polymers top‐performing devices have been achieved. Herein, an approach to use a transition metal dichalcogenide (TMDC)‐based monolayer device as a transducing element is presented. Using MoS2 monolayers, it is shown that such electrolyte‐gated devices may be regarded as very promising transducing elements for sensor and biosensor applications, enabled by their high sensitivity for environmental changes and the possibility of using the naturally occurring sulfur vacancies as grafting points of biorecognition layers. Furthermore, the behavior of such a device under prolonged operation in a dilute biologically relevant electrolyte such as phosphate buffered saline solution (PBS) is reported.

A label-free electrochemical immnunosensor based on signal magnification of oxygen reduction reaction catalyzed by uniform PtCo nanodendrites for highly sensitive detection of carbohydrate antigen 15-3

Developing a highly sensitive immunoassay for tumor biomarkers is particularly important in bioanalysis and early disease diagnosis. In this work, a simple one-pot solvothermal method was developed for controllable synthesis of well-dispersed PtCo alloyed nanodendrites (PtCo NDs) by using l-carnosine as the co-structure-directing agent. The PtCo NDs had a large specific surface area and provided abundant active sites available for electrocatalytic oxygen reduction reaction (ORR). Based on the highly enhanced currents of the ORR, a novel label-free electrochemical immunosensor was fabricated for highly sensitive assay of carbohydrate antigen 15–3 (CA15-3). The sensor showed a wide linear range of 0.1–200 U mL−1 and a low limit of detection (LOD) down to 0.0114 U mL−1 (S/N = 3), in turn exploring its application to diluted human serum samples with satisfactory results. This study provides a feasible platform for monitoring other tumor markers in clinical diagnosis.

Split-Type Electrochemical Immunoassay System Triggering Ascorbic Acid-Mediated Signal Magnification Based on a Controlled-Release Strategy.

This research put forward a novel split-type electrochemical (EC) immunosensor which integrated the controlled-release strategy with EC detection for application in the field of biosensing. Concretely, ascorbic acid (AA) was packaged in a cadmium sulfide (CdS)-capped spherical mesoporous bioactive glass (SBG) nanocarrier (SBGCdS) on account of encapsulation technology. To reduce the complexity of the bioanalysis, the detection antibody-labeled SBGCdS-AA bioconjugate was applied in a 96-well microplate for the immunoreaction process, which is independent of the EC determination procedure. Thus, the immune interference and steric hindrance caused by the accumulation of nanomaterials on the electrode could be minimized. Subsequently, AA was released efficiently via the destruction effect of dithiothreitol on the disulfide bond. In addition, for the as-prepared FcAI/l-Cys/gold nanoparticles (GNPs)/porous BiVO4 (p-BVO)/ITO EC sensing platform in the detection solution, the synergetic catalysis of Fc and GNPs/p-BVO toward the oxidation of the released AA could be realized, which triggered AA-mediated significant signal magnification throughout this study. In particular, p-BVO with an ordered nanoarray structure could accelerate the electron transfer to assist in sensitivity improvement of this system. This novel biosensor was capable of assaying the neuron-specific enolase (NSE) biomarker sensitively, from which a linear range of 0.001-100 ng/mL was derived along with a low detection limit of 1.08 pg/mL. An innovative way could be paved in the bioanalysis of NSE and other biomarkers.

Au/In2O3 Nanocubes Based Label‐free Aptasensor for Ultrasensitive and Rapid Recognition of Cardiac Troponin I

AbstractCardiac Troponin I (cTnI) is a preferred biomarker to diagnose acute myocardial infarction which is one of the leading risks to health globally due to its short term. However, clinical analyzers are difficult to achieve its on‐site quantitative detection. A novel label‐free aptasensor was constructed to realize ultrasensitive and rapid recognition of cTnI. A nanocubic AuNPs/In2O3 composite was designed to provide synergistic effects of abundant active sites and signal magnification for aptamers grafting. Relying on a conductance‐dependence strategy, this aptasensor can achieve the quantitative detection within 10 min, which is much faster than state‐of‐the‐art analyzers, as well as exhibiting an ultrawide linear range of 0.1–1000 ng/mL and a low detection limit of 0.06 ng/mL with an excellent selectivity in the analysis of human serum.

A facile ratiometric electrochemical strategy for ultrasensitive monitoring HER2 using polydopamine-grafted-ferrocene/reduced graphene oxide, Au@Ag nanoshuttles and hollow Ni@PtNi yolk-shell nanocages

Abstract Human epidermal growth factor receptor 2 (HER2) is believed as a clinically important breast cancer marker, and thereby it is extremely imperative to develop a highly sensitive and effective strategy for specific recognition and assay of HER2. In this work, a facile ratiometric electrochemical immunosensor was fabricated for sensitively monitoring HER2 as a model analyte, in which reduced graphene oxide-polydopamine-grafted-ferrocene/Au@Ag nanoshuttles (Au@Ag NSs) performed as electrode material and hollow Ni@PtNi yolk-shell nanocages-thionine (Ni@PtNi HNCs) as signal tags, which provided two distinct electrochemical signals from Fc and Thi, respectively. The Au@Ag NSs endowed the rGO-PDA-Fc with improved biocompatibility and dramatic magnification of the Fc signals upon sensing interface. Also, by integration of the hollow structure, enlarged specific surface area and superior catalytic ability together, the Ni@PtNi HNCs-Thi achieved substantial amplification in the detection signals from Thi. Benefiting from the above, the as-developed immunosensor exhibited a broad linear range (0.01 ∼ 100 ng mL–1) and a low detection limit (3.3 pg mL–1) for HER2 (S/N = 3), followed by exploring its application in actual serum samples with acceptable results. It holds great potential for clinical screening of cancer biomarkers and point of-care assays.

DeepMag

Many important physical phenomena involve subtle signals that are difficult to observe with the unaided eye, yet visualizing them can be very informative. Current motion magnification techniques can reveal these small temporal variations in video, but require precise prior knowledge about the target signal, and cannot deal with interference motions at a similar frequency. We present DeepMag, an end-to-end deep neural video-processing framework based on gradient ascent that enables automated magnification of subtle color and motion signals from a specific source, even in the presence of large motions of various velocities. The advantages of DeepMag are highlighted via the task of video-based physiological visualization. Through systematic quantitative and qualitative evaluation of the approach on videos with different levels of head motion, we compare the magnification of pulse and respiration to existing state-of-the-art methods. Our method produces magnified videos with substantially fewer artifacts and blurring whilst magnifying the physiological changes by a similar degree.

HER2 breast cancer biomarker detection using a sandwich optical fiber assay

Optical fiber-based surface plasmon resonance (OF-SPR) sensors have demonstrated high versatility and performances over the last years, which propelled the technique to the heart of numerous and original biosensing concepts. In this work, we contribute to this effort and present our recent findings about the detection of breast cancer HER2 biomarkers through OF-SPR optrodes. 1 cm-long sections of 400 μm core-diameter optical fibers were covered with a sputtered gold film, yielding enhanced sensitivity to surface refractive index changes. Studying the impacts of the gold film thickness on the plasmonic spectral response, we improved the quality and reproducibility of the sensors. These achievements were correlated in two ways, using both the central wavelengths of the plasmon resonance and its influence on the bulk refractive index sensitivity. Our dataset was fed by additional biosensing experiments with a direct and indirect approach, relying on aptamers and antibodies specifically implemented in a sandwich layout. HER2 biomarkers were specifically detected at 0.6 μg/mL (5.16 nM) in label-free while the amplification with HER2-antibodies provided a nearly hundredfold signal magnification, reaching 9.3 ng/mL (77.4 pM). We believe that these results harbinger the way for their further use in biomedical samples.

Co3O4@β-cyclodextrin with synergistic peroxidase-mimicking performance as a signal magnification approach for colorimetric determination of ascorbic acid

Transition metal oxides nanoparticles have shown enzyme-mimetic performance. It was demonstrated that the Co3O4@β-cyclodextrin nanoparticles (Co3O4@β-CD NPs) showed a higher peroxidase-mimicking catalytic activity than pure Co3O4 NPs. β-CD molecules were coated onto the surface of Co3O4 NPs via a one-pot synthesis method. Co3O4@β-CD NPs displayed higher affinity to 3,3′,5,5′-tetramethylbenzidine (TMB) through Michaelis-Menten mechanism after modification with β-CD. The catalytic efficiency of Co3O4@β-CD NPs for TMB oxidation was 9.5-fold higher than that of the pure Co3O4 NPs because of the effective host-guest interactions between Co3O4@β-CD NPs and TMB. Further, the hydrophobic cavity of β-CD while hosting TMB could reduce the transfer distance of electrons between TMB and Co3O4 catalyst, which could lead to faster oxidation of TMB. The synergistic effects between Co3O4 and β-CD enhanced the peroxidase-mimicking property. The efficient and visual colorimetric determination of Ascorbic Acid (AA) assay was achieved. The limit of detection was 1.09 μM (S/N = 3) and the linear range was 10–60 μM based on the Co3O4@β-CD NPs peroxidase-mimicking-mediated 3.0-fold signal magnification strategy. Moreover, the outstanding selectivity toward the detection of AA was achieved, which could exhibit prospects in biomedical analysis.