Chemiluminescence enzyme immunoassay using magnetic nanoparticles for detection of neuron specific enolase in human serum

Label-Free Assessment of Neuron-Specific Enolase via Polydopamine over a Carbon-Nanotube-Based Flexible Immunosensor

A label-free electrochemical immunosensor was developed for the rapid and sensitive detection of neuron-specific enolase (NSE). The electropolymerization of dopamine in conjunction with highly conductive carbon nanotubes offers a simple and quick platform for the direct anchoring of antibodies without the assistance of any coupling agent as well as a blocking agent. The developed immunosensor exhibited a wider detection range from 120 pM (9 ng mL-1) to 3 nM (200 ng mL-1) for NSE with a high sensitivity of 3.9 μA pM-1 cm-2 in 0.1 M phosphate-buffered saline (PBS) at physiological pH (7.4). Moreover, the short recognition time (15 min) for the antigen enabled the detection to be fast and less invasive. Additionally, the evaluation of a rate constant at various concentrations of NSE via feedback mode of scanning electrochemical microscopy (SECM) explained the profound effect of antigen concentration on the rate of flow of electrons. Therefore, the proposed immunosensor can be a promising tool for the early detection of small cell lung cancer in a very short period of time with consistent accuracy.

Highly sensitive "off-on" sensor based on MXene and magnetic microspheres for simultaneous detection of lung cancer biomarkers - Neuron specific enolase and carcinoembryonic antigen

In this work, a highly sensitive lung cancer biomarkers detection probe was developed based on Ag and MXene co-functionalized magnetic microspheres. By using carboxyl magnetic microspheres as carrier, MXene was coated repeatedly by Poly (allylamine hydrochloride) (PAH) as interlayer adhesive, and silver particles grown on the surface of MXene in situ can efficiently improve the sensitivity of the probe. The detection of neuron specific enolase (NSE) is mainly through the formation of a specific complex between NSE antigen and antibody, and the release of antibody labeled with amino carbon quantum dots (CQDs) from the surface of Ag nanoparticles (AgNPs), so that the fluorescence is restored and "OFF-ON" is formed. The biosensor exhibits excellently wide linear range (0.0001-1500 ng/mL) and the limit of detection (LOD) is up to 0.03 pg/mL, which is superior to most tumor marker probes based on fluorescence mechanism. Furthermore, we constructed dual detection strategy for NSE and carcinoembryonic antigen (CEA) simultaneously.

Overview on the Development of Alkaline-Phosphatase-Linked Optical Immunoassays

The drive to achieve ultrasensitive target detection with exceptional efficiency and accuracy requires the advancement of immunoassays. Optical immunoassays have demonstrated significant potential in clinical diagnosis, food safety, environmental protection, and other fields. Through the innovative and feasible combination of enzyme catalysis and optical immunoassays, notable progress has been made in enhancing analytical performances. Among the kinds of reporter enzymes, alkaline phosphatase (ALP) stands out due to its high catalytic activity, elevated turnover number, and broad substrate specificity, rendering it an excellent candidate for the development of various immunoassays. This review provides a systematic evaluation of the advancements in optical immunoassays by employing ALP as the signal label, encompassing fluorescence, colorimetry, chemiluminescence, and surface-enhanced Raman scattering. Particular emphasis is placed on the fundamental signal amplification strategies employed in ALP-linked immunoassays. Furthermore, this work briefly discusses the proposed solutions and challenges that need to be addressed to further enhance the performances of ALP-linked immunoassays.

Ti3C2-MXene decorated with nanostructured silver as a dual-energy acceptor for the fluorometric neuron specific enolase detection

Nanohybrids of two-dimensional (2D) layered materials have shown fascinating prospects towards the fabrication of highly efficient fluorescent immunosensor. In this context, a nanohybrid of ultrathin Ti₃C₂-MXene nanosheets and silver nanoparticles (Ag@Ti₃C₂-MXene) has been reported as a dual-energy acceptor for ultrahigh fluorescence quenching of protein-functionalized graphene quantum dots (anti-NSE/amino-GQDs). The Ti₃C₂-MXene nanosheets are decorated with silver nanoparticles (AgNPs) to obsolete the agglomeration and restacking through a one-pot direct reduction method wherein the 2D Ti₃C₂-MXene nanosheets acted both as a reducing agent and support matrix for AgNPs. The as-prepared nanohybrid is characterized by various techniques to analyze the optical, structural, compositional, and morphological parameters. The quenching efficiency and energy transfer capability between the anti-NSE/amino-GQDs (donor) and Ag@Ti₃C₂-MXene (acceptor) have been explored through steady state and time-resolved spectroscopic studies. Interestingly, the Ag@Ti₃C₂-MXene nanohybrid exhibits better quenching and energy transfer efficiencies in contrast to bare Ti₃C₂-MXene, AgNPs and previously reported AuNPs. Based on optimized donor-acceptor pair, a fluorescent turn-on biosensing system is constructed that revealed improved biosensing characteristics compared to Ti₃C₂-MXene, graphene and AuNPs for the detection of neuron-specific enolase (NSE), including higher sensitivity (∼771 mL ng^-1), broader linear detection range (0.0001-1500 ng mL^-1), better LOD (0.05 pg mL^-1), and faster response time (12 min). Besides, remarkable biosensing capability has been observed in serum samples, with fluorescence recovery of ∼98%.

An enhanced enzyme-linked aptamer assay for the detection of zearalenone based on gold nanoparticles

A novel enhanced enzyme-linked aptamer assay (ELAA) for the detection of zearalenone (ZEN) was developed based on gold nanoparticles (AuNPs) modified with an aptamer and horseradish peroxidase (HRP). In this assay, the aptamer was used as a recognition probe to competitively bind with coated ZEN-BSA on a microplate and ZEN in samples. AuNPs with high surface areas were used as a carrier to immobilize more amounts of HRP labelled aptamer probe, which can amplify the colorimetric signal by enhancing catalysis of the HRP enzyme compared with the traditional enzyme-linked method. Under the optimal conditions, the enhanced ELAA presented a good linearity in the range of 0.1-160 ng mL-1 and the limit of detection was 0.08 ng mL-1 for ZEN detection. In addition, the enhanced ELAA had no cross reactivity with other mycotoxins and showed good recoveries in spiked corn oil samples. These results indicated that the AuNP enhanced ELAA provided a new approach with simplicity, and high sensitivity and specificity for the detection of ZEN in foodstuff.

Multifunctional neuron-specific enolase: its role in lung diseases

Neuron-specific enolase (NSE), also known as gamma (γ) enolase or enolase-2 (Eno2), is a form of glycolytic enolase isozyme and is considered a multifunctional protein. NSE is mainly expressed in the cytoplasm of neurons and neuroendocrine cells, especially in those of the amine precursor uptake and decarboxylation (APUD) lineage such as pituitary, thyroid, pancreas, intestine and lung. In addition to its well-established glycolysis function in the cytoplasm, changes in cell localization and differential expression of NSE are also associated with several pathologies such as infection, inflammation, autoimmune diseases and cancer. This article mainly discusses the role and diagnostic potential of NSE in some lung diseases.

Photoelectrochemical immunoassay platform based on MoS2 nanosheets integrated with gold nanostars for neuron-specific enolase assay

MoS₂ nanosheets were prepared by exfoliating MoS₂ bulk crystals with ultrasonication in N-methylpyrrolidone and were integrated with gold nanostars (AuNS) to fabricate an AuNS/MoS₂ nanocomposite. All nanomaterials were characterized by transmission electron microscope, scanning electron microscope, ultraviolet-visible spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. AuNS/MoS₂ nanocomposites were coated onto a glassy carbon electrode (GCE) surface to construct a nanointerface for immobilizing neuron-specific enolase antibody (anti-NSE) thus forming a photoelectrochemical immunoassay system. AuNS can significantly promote the photoelectric conversion of MoS₂ nanosheets improving the performance for a photoelectrochemical assay. Being illuminated with white light LED and controlling the potential at 0.05 V (vs. SCE), the photocurrent generated from anti-NSE(BSA)/AuNS/MoS₂/GCE using 0.15 mol L^-1 ascorbic acid as electron donor can be recorded with amperometry and used as an output signal for NSE quantitative assay. Under optimized experimental conditions, the photocurrent variation for the affinity-binding NSE is proportional to the logarithm of NSE concentration in the range 5.0 pg mL^-1   to 1.5 ng mL^-1 with a detection limit of 3.5 pg mL^-1 (S/N = 3). The practicability of the PEC immunoassay system was evaluated by determining NSE in clinical serum samples. The recoveries ranged from 93.0 to 103% for the determination of NSE in serum samples with a standard addition method. The PEC immunoassay system possesses good accuracy for determining NSE in real samples. Graphical abstract.

Enzyme-free amplified SERS immunoassay for the ultrasensitive detection of disease biomarkers

We developed an enzyme-free, amplified SERS immunoassay by combining AgNP-linked immunoreaction and SERS transduction for the ultrasensitive detection of disease biomarkers.

Evaluation of serum biomarkers and efficacy of MTX in women with ectopic pregnancy

Ectopic pregnancy occurs when a fertilized ovum attaches outside the uterus. As a complication in approximately 1‑2% of all pregnancies, ectopic pregnancies may cause catastrophic hemorrhage as a result of invading maternal blood vessels. Therefore, early diagnosis and timely treatment are crucial for women with ectopic pregnancy. In this study, we aimed to identify and determine the efficacy of serum biomarkers for the prompt diagnosis of ectopic pregnancy. For this purpose, the serum concentrations of progesterone, β human chorionic gonadotropin (β‑hCG) and cancer antigen‑125 (CA125) were detected by solid‑phase, competitive binding chemiluminescent enzyme immunoassays. Flow cytometry was used to analyze the percentage of CD3+ T cells in women with ectopic pregnancy. Pathological analysis of tubal and villus tissues was performed by hematoxylin and eosin (H&E) staining. After receiving an injection of methotrexate (MTX), patients were examined by transvaginal ultrasound to detect the size of the echogenic mass. The results revealed that the serum levels of progesterone, β‑HCG and CA125 were significantly decreased in women with ectopic pregnancy, whereas the percentage of CD3+ T cells was increased in women with ectopic pregnancy. Histopathological examination revealed blood clots with small tissue fragments of a tubal‑type epithelium and incomplete pile structures. Five days after the MTX injection, an echogenic mass was found with a size of 1.7x1.2x1.6 cm that contained a gestational sac‑like structure and a yolk sac. On the whole, the findings of this study indicate the at the joint detection of progesterone, β‑HCG, CA125 serum levels and the CD3+ T cell percentage could be applied as a reliable indicator for the early diagnosis of ectopic pregnancy. MTX administration was determined to be an efficacious approach for the treatment of ectopic pregnancy.

In Situ Generation of Prussian Blue with Potassium Ferrocyanide to Improve the Sensitivity of Chemiluminescence Immunoassay Using Magnetic Nanoparticles as Label

Using magnetic nanoparticles (MNPs) as a label in immunoassay (IA) possesses advantages such as high specific surface area, simple modification process. However, the catalytic activity of MNPs is low, which limits their applications in IA. The present study found it interesting that potassium ferrocyanide reacts with MNPs, leading to the in situ generation of Prussian blue. The produced Prussian blue shows high catalytic activity on a luminol chemiluminescent (CL) reaction. Therefore, a simple and sensitive immunoassay for rabbit IgG (rIgG) as model analyte using MNPs as label was developed. The CL intensity had a linear increase with the concentration of rIgG that ranged from 0.625 to 20 ng mL^-1. The limit of detection was calculated to be 0.59 ng mL^-1. In addition, the applicability of this method was evaluated using the standard addition method. The recovery ranged from 80.0% to 115.0%. What's more, the proposed CLIA method based on in situ generation of Prussian blue with MNPs was also applied to the detection of carcinoembryonic antigen (CEA) and hepatitis B virus (HBV)-related sequence-specific DNA. The LOD for the detection of CEA and sequence-specific DNA was estimated to be 0.28 ng mL^-1 and 0.044 pmol, respectively.

Recognition of protein biomarkers using epitope-mediated molecularly imprinted films: Histidine or cysteine modified epitopes?

This research aims to engineer molecularly imprinted polymer (MIP)-based synthetic receptors for the molecular recognition of neuron specific enolase (NSE) biomarker. The synthetic peptide derived from the NSE was synthesized along with its cysteine and histidine modified versions. The modified peptides were utilized as templates for molecular imprinting, which was achieved by combination of epitope- and electrochemical surface imprinting strategy. The subsequently generated imprinted cavities were used for the detection of the NSE derived peptide and NSE. The imprints created with cysteine (CME) and histidine modified epitopes (HME) could detect the peptide in a concentration range of 2-128 µM and 15.6 nM to 128 µM, respectively. The recognition of NSE was achieved by the same imprints in a linear range of 1-64 ng mL^-1 (CME) and 0.25-64 ng mL^-1 (HME), respectively. The target molecules bound to the control polymer very weakly, confirming the high selectivity of the MIP cavities. Selectivity studies resulted in imprinting factors of 8.8 and 11 for the CME and HME imprints, respectively. The affinity analyses provided dissociation constants of 2.3 × 10^-10 M and 3 × 10^-11 M for NSE recognition using the corresponding epitope imprints. Cross-reactivity studies with non-specific molecules proved high specificity of the artificial receptors for the targets.

The fabrication of magnetic particle-based chemiluminescence immunoassay for human epididymis protein-4 detection in ovarian cancer

The magnetic particles have a significant influence on the immunoassay detection and cancer therapy. Herein, the chemiluminescence immunoassay combined with the magnetic particles (MPCLIA) was presented for the clinical determination and analysis of human epididymis protein 4 (HE4) in the human serum. Under the optimized experiment conditions, the secure MPCLIA method can detect HE4 in the broader range of 0–1000 pmol/L, with a lower detection limit of 1.35 pmol/L. The satisfactory recovery rate of the method in the serum ranged from 83.62% to 105.10%, which was well within the requirement of clinical analysis. Moreover, the results showed the good correlation with enzyme-linked immunosorbent assay (ELISA), with the correlation coefficient of 0.9589. This proposed method has been successfully applied to the clinical determination of HE4 in the human serum.

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A high-sensitivity, relatively simple and rapid MPCLIA has been successfully developed for the clinical determination of HE4 in human serum.

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The quantitative determination for HE4 in the serum samples was with satisfactory recoveries ranging from 83% to 105%.

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The magnetic particle-based chemiluminescence immunoassays could be used for the quantitative detection of other tumor markers.

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This assay provides apparent advantages and shows great potential in the clinical diagnosis.

Paper-Based Surface-Enhanced Raman Scattering Lateral Flow Strip for Detection of Neuron-Specific Enolase in Blood Plasma

An inexpensive and disposable paper-based lateral flow strip (PLFS) has been developed as an immunoassay, in which surface-enhanced Raman scattering (SERS) is utilized for sensing signal transduction. The Au nanostar@Raman Reporter@silica sandwich nanoparticles are developed as the SERS probes, which is the key to the high sensitivity of the device. Compared with a colorimetric PLFS, the SERS-PLFS exhibits superior performance in terms of sensitivity and limit of detection (LOD) in a blood plasma-containing sample matrix. In addition, the SERS-PLFS has been successfully used for detection of neuron-specific enolase (NSE), a traumatic brain injury (TBI) protein biomarker, in diluted blood plasma samples, achieving a LOD of 0.86 ng/mL. Moreover, the SERS-PLFS was successfully employed to measure the NSE level in clinical blood plasma samples taken from deidentified TBI patients. This work demonstrates that the SERS-PLFS has great potential in assisting screening of TBI patients in the point-of-care setting.

Dual Immunomagnetic Nanobeads-Based Lateral Flow Test Strip for Simultaneous Quantitative Detection of Carcinoembryonic Antigen and Neuron Specific Enolase

A novel immunomagnetic nanobeads -based lateral flow test strip was developed for the simultaneous quantitative detection of neuron specific enolase (NSE) and carcinoembryonic antigen (CEA), which are sensitive and specific in the clinical diagnosis of small cell lung cancer. Using this nanoscale method, high saturation magnetization, carboxyl-modified magnetic nanobeads were successfully synthesized. To obtain the immunomagnetic probes, a covalent bioconjugation of the magnetic nanobeads with the antibody of NSE and CEA was carried out. The detection area contained test line 1 and test line 2 which captured the immune complexes sensitively and formed sandwich complexes. In this assay, cross-reactivity results were negative and both NSE and CEA were detected simultaneously with no obvious influence on each other. The magnetic signal intensity of the nitrocellulose membrane was measured by a magnetic assay reader. For quantitative analysis, the calculated limit of detection was 0.094 ng/mL for NSE and 0.045 ng/mL for CEA. One hundred thirty clinical samples were used to validate the test strip which exhibited high sensitivity and specificity. This dual lateral flow test strip not only provided an easy, rapid, simultaneous quantitative detection strategy for NSE and CEA, but may also be valuable in automated and portable diagnostic applications.

The Establishment of an HE4-CLIA Method and the Combined Analysis of HE4 and CA125 in Ovarian Cancer

BACKGROUND

The human epididymal secretory protein 4 (HE4) is a novel, verified biomarker for the early diagnosis of ovarian cancer.

METHODS

Magnetic beads were coated with capture antibodies and were used with acridinium ester labeled detection antibodies in a sandwich-type immunoassay. The patient's HE4 serum levels were measured simultaneously with the chemiluminescence immunoassay (CLIA) kit we developed and electrochemiluminescence immunoassay (ECLIA) kit from Roche (Mannheim, Germany). CA125 was also detected by time-resolved fluoroimmunoassay. The diagnostic value was analyzed.

RESULTS

The assay demonstrated a linear range from 2.5 to 2,000 pmol/l, with an analytical sensitivity of 2.5 pmol/l. The reproducibility, recovery, and specificity of the immunoassay were demonstrated to be acceptable. Compared with the ECLIA kit from Roche in 124 serum samples (40 patients with ovarian cancer, 35 patients with benign gynecological diseases, and 49 health controls), there is a satisfied correlation coefficient of 0.875. The area under the receiver-operating curve (ROC-AUC) was 0.903 (95% CI was 0.839-0.966, P < 0.001) for HE4, 0.787 (95% CI was 0.694-0.879, P < 0.001) for CA125, and 0.914 (95% CI was 0.866-0.962, P < 0.001) for combined analysis of HE4 and CA125.

CONCLUSIONS

A quantitative method (HE4-CLIA) for detecting HE4 in serum was successfully established. Preliminary clinical sample analysis showed HE4-CLIA has a certain clinical value in the screening and diagnosis of ovarian cancer. Moreover, in distinguishing benign from malignant ovarian lesions, HE4 has higher demonstrated accuracy than CA125.

A novel self-enhanced electrochemiluminescence immunosensor based on hollow Ru-SiO2@PEI nanoparticles for NSE analysis

Poly(ethylenimine) (PEI) and Ru(bpy)3(2+)-doped silica (Ru-SiO2) nanoparticles were simply mixed together to prepare a novel self-enhanced electrochemiluminescence (ECL) composite of Ru-SiO2@PEI. The hollow Ru-SiO2@PEI nanoparticles were used to build an ECL immunosensor for the analysis of neuron specific enolase (NSE). PEI not only assembled on the surface of Ru-SiO2 nanoparticles through the electrostatic interaction to act as co-reactant for Ru(bpy)3(2+) ECL, but also provided alkaline condition to etch the Ru-SiO2 nanoparticles to form the hollow Ru-SiO2@PEI nanoparticles with porous shell. The unique structure of the Ru-SiO2@PEI nanoparticles loaded both a large amount of Ru(bpy)3(2+) and its co-reactant PEI at the same time, which shortened the electron-transfer distance, thereby greatly enhanced the luminous efficiency and amplified the ECL signal. The developed immunosensor showed a wide linear range from 1.0 × 10(-11) to 1.0 × 10(-5) mg mL(-1) with a low detection limit of 1.0 × 10(-11) mg mL(-1) for NSE. When the immunosensor was used for the determination of NSE in clinical human serum, the results were comparable with those obtained by using enzyme-linked immunosorbent assay (ELISA) method. The proposed method provides a promising alternative for NSE analysis in clinical samples.

Evaluation of a magnetic particles-based chemiluminescence enzyme immunoassay for Golgi protein 73 in human serum

BACKGROUND

Golgi protein 73 (GP73) is regarded as a potential serum biomarker for early diagnosis of hepatocellular carcinoma (HCC). We developed a rapid magnetic particles-based chemiluminescence enzyme immunoassay (MPs-CLEIA) for the determination of serum GP73.

METHODS

Fluorescein isothiocyanate (FITC) and alkaline phosphatase (ALP) were used to label 2 different monoclonal antibodies to GP73. Serum GP73 was captured with labeled antibodies and formed a sandwiched immunoreaction. The magnetic particles (MPs) coated with anti-FITC antibody were used as a means of separation of the GP73 protein from other serum proteins. After adding the enzyme substrate solution, the relative light unit (RLU) was measured. A MPs-CLEIA for serum GP73 was established and evaluated.

RESULTS

The RLU was directly proportional to the concentration of GP73. The method linearity was 5-600 μg/l. Limit of the blank was 2.19 μg/l. The intra- and inter-assay imprecision was <3% and <5%, respectively. The average recoveries were between 95% and 105%. The proposed method showed a good correlation with a commercial ELISA assay (r=0.983, p<0.001). We also evaluated the efficiency of serum GP73 measurement for the diagnosis of HCC using this assay. The area under the receiver operating characteristic curve was 0.822 (95% CI, 0.73-0.89), and the sensitivity and specificity, with cut-off value of 115.6 μg/l, were 75.4% and 92.1%, respectively.

CONCLUSIONS

The proposed method demonstrates an acceptable performance for quantifying serum GP73. This assay could be appropriate for routine use in clinical laboratories.

Neuron-Specific Enolase as a Biomarker: Biochemical and Clinical Aspects

Neuron-specific enolase (NSE) is known to be a cell specific isoenzyme of the glycolytic enzyme enolase. In vertebrate organisms three isozymes of enolase, expressed by different genes, are present: enolase α is ubiquitous; enolase β is muscle-specific and enolase γ is neuron-specific. The expression of NSE, which occurs as γγ- and αγ-dimer, is a late event in neural differentiation, thus making it a useful index of neural maturation.NSE is a highly specific marker for neurons and peripheral neuroendocrine cells. As a result of the findings of NSE in specific tissues under normal conditions, increased body fluids levels of NSE may occur with malignant proliferation and thus can be of value in diagnosis, staging and treatment of related neuroendocrine tumours (NETs).NSE is currently the most reliable tumour marker in diagnosis, prognosis and follow-up of small cell lung cancer (SCLC), even though increased levels of NSE have been reported also in non-small cell lung cancer (NSCLC). The level of NSE correlates with tumour burden, number of metastatic sites and response to treatment.NSE can be also useful at diagnosis of NETs and gastroenteropancreatic (GEP)-NETs.Raised serum levels of NSE have been found in all stages of neuroblastoma, although the incidence of increased concentration is greater in widespread and metastatic disease. Moreover, NSE determination in cord blood offers an early postnatal possibility of confirming the diagnosis of neuroblastoma in newborns.NSE has been demonstrated to provide quantitative measures of brain damage and/or to improve the diagnosis and the outcome evaluation in ischaemic stroke, intracerebral hemorrhage, seizures, comatose patients after cardiopulmonary resuscitation for cardiac arrest and traumatic brain injury.Increased NSE serum levels have also been found associated with melanoma, seminoma, renal cell carcinoma, Merkel cell tumour, carcinoid tumours, dysgerminomas and immature teratomas, malignant phaechromocytoma, Guillain-Barré syndrome and Creutzfeldt-Jakob disease.

Evaluation of direct versus multi-layer passivation and capture chemistries for nanoparticle-based biosensor applications

Nanoparticles used in biosensor applications often fail when deployed directly in complex biological fluids. This is due to surface fouling and interference from the large concentration of non-specific binders (proteins, lipids, nucleic acids and saccharides) in the matrix. We systematically investigate four orthogonal approaches for decorating nanoparticle surfaces with affinity probes and evaluate their performance in buffer and serum. Carbodiimide coupling, cooper-mediated 'click' coupling, copper-free click coupling and thiol-maleimide coupling were quantitatively controlled during the fabrication process. Analyte mediated aggregation of fluorescent reporters and paramagnetic nanoparticle in a sandwich immunoassay was then used to probe assay sensitivity and specificity using an early biomarker of dengue fever, NS-1, as an exemplar and clinically relevant analyte. The type of surface functionalization played a vital role in assay performance in buffer versus serum at the assay sensitivity limit (3 ng/mL in serum) and over the linearity of response of the assay's dynamic range. There was a 10 fold increase on the dynamic range of the detection of NS1 comparing copper free click coupling to carbodiimide coupling, one of the most common approaches for nanoparticle functionalization. By tuning their size, we could carefully monitor the evolution of nanoparticle populations by flow cytometer and discriminate between unbound and fluorescent nanoparticles. This subtle control on each assay component resulted in more than a 10-fold reduction in fluorescence background and improved the sensitivity of almost two orders of magnitude compared to endpoint measurements.

Stochastic microsensors as screening tools for neuron specific enolase

Stochastic microsensors based on nanostructured materials from the classes of porphyrins and cyclodextrins, and carbon onions were used for new screening tools of whole blood samples for neuron specific enolase, a lung cancer biomarker.

Novel chemiluminescence immunoassay for the determination of zearalenone in food samples using gold nanoparticles labeled with streptavidin-horseradish peroxidase

A novel highly sensitive chemiluminescence immunoassay (CLIA) was developed to detect zearalenone in food samples by using both biotinylated zearalenone conjugates and gold (Au) nanoparticles labeled with streptavidin-horseradish peroxidase for signal amplification. Biotinylated zearalenone-ovalbumin conjugates and Au nanoparticles labeled with streptavidin-horseradish peroxidase were synthesized separately. The concentrations of immunoreagents and the reaction times of these immunoreagents were optimized to improve the performances of analytical methods. For the CLIA based on biotinylated zearalenone conjugates and Au nanoparticles labeled with streptavidin-horseradish peroxidase, the limit of detection was 0.008 ng/mL and the IC50 was 0.11 ng/mL. The linear working range was 0.02-0.51 ng/mL. The cross-reactivities with the zearalenone analogues (α-zearalanol, zearalanone, α-zearalenol, β-zearalanol, and β-zearalenol) were 32, 17, 12, 0.3, and 0.1%, respectively. The recovery rates in spiked food samples were 97-117%, and the intraday and interday relative standard deviations were both <10%. Parallel analysis of natural food samples showed a good correlation between this novel CLIA and liquid chromatography-tandem mass spectrometry. This method provides a rapid, accurate, and highly sensitive method to determine levels of zearalenone in food samples.