Biotin-streptavidin Interaction Research Articles

Self-assembled biotin-phenylalanine nanoparticles for the signal amplification of surface plasmon resonance biosensors.

Astrategy for amplifying the signal of surface plasmon resonance (SPR) biosensorsis reported. Biotinylated phenylalanine (Biotin-Phe) monomers were rapidly self-assembled into nanoparticles in a mild environment. The self-assembled nanoparticles were then used as the carriers of streptavidin-antibody complexes by the streptavidin-biotin interaction. The signal was amplified because of the high molecular weight of the nanoparticle-streptavidin-antibody conjugate. With prostate-specific antigen as a model analyte, the target concentration as low as 1pgmL-1 was readily measured. The results of the nanoparticle-enhanced SPR biosensor for analysis of serum samples are well consistent with those achieved by the enzyme-linked immunosorbent assays. This work is valuable for designing of various optical and electronic biosensors through the streptavidin-biotin interaction. Graphical abstract.

Novel target capture DNA library preparation method using CircLigase-mediated hook ligation

Target capture DNA library preparation methods primarily use the biotin-streptavidin interaction to enrich target DNA, requiring complex operations and a time-consuming workflow with a series of wash steps at regulated temperatures. Here, a new method is presented termed ‘hook ligation’ for target DNA library preparation, using CircLigase to capture target DNA. The concept was validated by library preparation, sequencing, and acquisition of target DNA fragment information through bioinformatics analysis. An efficient reference point for single-strand DNA ligation to a hook sequence using CircLigase is also provided and it is shown that the efficiency can be influenced by the length and the position of the complementary area on the target DNA.

Colorimetric nanoplatform for visual determination of cancer cells via target-catalyzed hairpin assembly actuated aggregation of gold nanoparticles.

According to aptamer-mediated hairpin DNA cascade amplifier and gold nanoparticles aggregation, an optical platform for cancer cells determination has been proposed. High-affinity chimeric aptamers were used for cancer cell detection and also as an initiator for beginning hairpin assembly to construct three-way junction (3WJ) nanostructures. These three hairpins were modified at 3' ends with biotin. In the presence of target cell, chimeric aptamer binds to its ligand on cell surface and initiates 3WJ nanostructures formation. These 3WJ nanostructures interact with streptavidin-modified gold nanoparticles (AuNPs) via non-covalent biotin-streptavidin interactions and create a crossover lattice of nanoparticles. This event leads to AuNPs aggregation and red-shifting. The results were confirmed by gel electrophoresis and UV-visible spectrophotometry. The dynamic range of this assay is 25 to 107 cells with a detection limit of 10 cells which is respectively 9 and 4 times more significant than the sensitivity of AuNP-based approaches without amplification and enzyme-mediated signal amplification. Graphical abstract.

Enzyme-free electrochemical biosensor based on double signal amplification strategy for the ultra-sensitive detection of exosomal microRNAs in biological samples

Growing evidence suggests that exosomes-encapsulated miRNAs detection is of paramount significance in early diagnostics of cancer due to protection from degradation by ribonuclease. However, exosomal microRNAs with low abundance and subtle variation have restricted their clinical application. Herein, an electrochemical biosensor for highly sensitive detection of exosomal microRNAs has been fabricated based on the double signal amplification strategy. Our proposed amplifier consists of two steps: target miRNA cyclic signal amplification induced by strand displacement reaction (SDR) and subsequent deposition of silver nanoparticles induced by streptavidin-biotin interaction. Consequently, this method shows ultrahigh sensitivity to detect miRNA. Taking miRNA-21 in exosomes as a model analyte, a detection limit of 0.4 fM (S/N = 3) can be obtained. Meanwhile, the method is relatively simple and low-cost without the requirement of enzyme, which has been applied in biological samples successfully. Therefore, our miRNA assay method has shown great promise as molecular tool in the detection of exosomal miRNA and could be widely used in clinic in the future.

A Colorimetric Aptamer Sensor Based on the Enhanced Peroxidase Activity of Functionalized Graphene/Fe3O4-AuNPs for Detection of Lead (II) Ions

Lead (II) is regarded as one of the most hazardous heavy metals, and lead contamination has a serious impact on food chains, human health, and the environment. Herein, a colorimetric aptasensor based on the graphene/Fe3O4-AuNPs composites with enhanced peroxidase-like activity has been developed to monitor lead ions (Pb2+). In short, graphene/Fe3O4-AuNPs were fabricated and acted as an enzyme mimetic, so the color change could be observed by chromogenic reaction. The aptamer of Pb2+ was decorated on the surface of the amine magnetic beads by streptavidin–biotin interaction, and the complementary strands of the aptamer and target Pb2+ competed for the binding Pb2+ aptamer. In the presence of Pb2+, aptamers bonded the metal ions and were removed from the system by magnetic separation; the free cDNA was adsorbed onto the surface of the graphene/Fe3O4-AuNPs composites, thus inhibiting the catalytic activity and the color reaction. The absorbance of the reaction solution at 652 nm had a clear linear correlation with the Pb2+ concentration in the range of 1–300 ng/mL, and the limit of detection was 0.63 ng/mL. This assay is simple and convenient in operation, has good selectivity, and has been used to test tap water samples, which proves that it is capable for the routine monitoring of Pb2+.

Azide-Functional Extracellular Matrix Coatings as a Bioactive Platform for Bioconjugation.

In recent years, the development and application of decellularized extracellular matrices (ECMs) for use as biomaterials have grown rapidly. These cell-derived matrices (CDMs) represent highly bioactive and biocompatible materials consisting of a complex assembly of biomolecules. Even though CDMs mimic the natural microenvironment of cells in vivo very closely, they still lack specifically addressable functional groups, which are often required to tailor a biomaterial functionality by bioconjugation. To overcome this limitation, metabolic glycoengineering has emerged as a powerful tool to equip CDMs with chemical groups such as azides. These small chemical handles are known for their ability to undergo bioorthogonal click reactions, which represent a desirable reaction type for bioconjugation. However, ECM insolubility makes its processing very challenging. In this contribution, we isolated both the unmodified ECM and azide-modified clickECM by osmotic lysis. In a first step, these matrices were concentrated to remove excessive water from the decellularization step. Next, the hydrogel-like ECM and clickECM films were mechanically fragmentized, resulting in easy to pipette suspensions with fragment sizes ranging from 7.62 to 31.29 μm (as indicated by the mean d90 and d10 values). The biomolecular composition was not impaired as proven by immunohistochemistry. The suspensions were used for the reproducible generation of surface coatings, which proved to be homogeneous in terms of ECM fragment sizes and coating thicknesses (the mean coating thickness was found to be 33.2 ± 7.3 μm). Furthermore, they were stable against fluid-mechanical abrasion in a laminar flow cell. When primary human fibroblasts were cultured on the coated substrates, an increased bioactivity was observed. By conjugating the azides within the clickECM coatings with alkyne-coupled biotin molecules, a bioconjugation platform was obtained, where the biotin-streptavidin interaction could be used. Its applicability was demonstrated by equipping the bioactive clickECM coatings with horseradish peroxidase as a model enzyme.

Peptide-enabled receptor-binding-quantum dots for enhanced detection and migration inhibition of cancer cells

We report the efforts to construct active targeting quantum dots using receptor-binding peptide for enhanced detection and migration inhibition of cancer cells. Peptide E5 has specific binding with chemokine receptor 4 (CXCR4), which is a transmembrane G-coupled receptor involved in the metastasis of various types of cancers. E5 was introduced to the surface of CdSe/ZnS quantum dots via biotin-streptavidin interactions. The constructed CXCR4-targeting quantum dots (E5@QDs) was observed to display improved detection sensitivity and significantly enhanced binding affinity for CXCR4 over-expressed cancer cells, and the ability to inhibit cancer cells migration induced by CXCL12.

MON-477 Anti-Streptavidin Interference in Multiple Hormones Immunoassays: Case Report

Automated immunoassays are the most commonly current methods used in clinicial laboratory to hormone tests, due short turnaround time and high specificity and sensibility. However immunoassays are not free from interferences. Several immunoassays use biotin-streptavidin interaction to anchor antigen-antibody complexes in solid phase and so are susceptible to biotine intake or anti-streptavidin antibody. In sample with these interferents, the results in competitive assays are falsely high and in non-competitive assays are falsely low. OBJECTIVE: To report a case of multiple hormones immunoassay interference by an anti-streptavidin antibody. MATERIAL AND METHODS: A 11-years-old boy with child obesity, and no other symptoms, had discordant laboratory results with markedly elevated free T4, total T4 and total T3 with normal TSH. Repeated measurements in the same sample and in a new collected sample confirmed the initial results and revealed low PTH and high TRAb without hypocalcemia or hyperthiroidism clinical pictures. All the parameters were measured on the automated Cobas e602, Roche plataform.The patient and your family denied biotin ingestion, so anti-streptavidin interference could explain the multiple interference.The serum was pre-incubated with streptavidin microparticles during an hour and centrifuged for 10min (3000 rpm) to removed the analytical interference. RESULTS: The results of post-incubation with microparticles were all in the normal range. Three control samples were not affected by the incubation. Since luminescence is inversely proportional to analyte concentration in competitive assays, low signals lead to falsely high levels (like in free T4, total T4, Total T3 and TRAb in our patient). The reverse occurs with immunometric assays, in which low signals result in falsely reduced values (like in PTH in our patient). CONCLUSION: In literature, streptavidin antibodies seem to be a rare occurrence. In samples with biotin or anti-streptavidin suspection, pre-incubation with streptavidin microparticles is a simple and effective procedure to remove this interference.

Self-Assembled Monolayers for Anti-Fouling and Highly Selective Electrode Interfaces

The detection, collection and/or conversion of biological-based molecules has applications to sensing, wearables, and biofuels. Flexible, wearable electronics for real-time detection of, for example, Neuropeptide Y in human sweat [1], or flagella protein in biofuels, enables deviation from bulky laboratory benchtop analyses such as ELISA. Challenges include required limits of detection, as biological materials can be present in small amounts (nM to pM concentrations) in complex high ionic strength environments[2], the need for a highly selective sensor interface that avoids non-specific binding, and a quick response to account for degradation of analytes.This work will discuss the implementation of a mixed self-assembled monolayer (SAM) interface with highly selective bio-recognition elements (BREs) on gold disk electrodes, focusing on target application for aqueous sensing in biofuels, with room for expansion to sensing in other biological fluids. The SAM composition was systematically varied to assess functionality towards preventing fouling/non-specific binding and increase the selectivity of the interface for the analyte of interest. Briefly, mixed monolayer combinations included pseudo-zwitter surfaces to prevent fouling, blocking groups similarly employed in the literature[3] to help rectify BREs, and dithiobis(succinimidyl propionate) (DSP) cross-linking chemistry[4] to attach various BREs to the gold electrode. BREs include concanavilin A, streptavidin, nanobodies, and synthetic lectins. Streptavidin and it’s interaction with biotin was chosen as a control, due to their known strong interaction. Electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV) were used to estimate changes in the resistance to charge transfer to redox mediators either immobilized or in solution. EIS is one of the most common modern techniques used in biosensing, but as a time-intensive measurement it can be undesirable for accurate sensing in analyte-degrading environments. Therefore, SWV was employed as a substitute which reduces times of measurements by an order of magnitude, and is shown to provide the same information as EIS. To corroborate these electrochemical effects with a definite surface coverage/binding event, ellipsometric experiments of functionalized electrodes are underway.Our SAM interface produces nM level detection for yeast through the employment of gold immobilized charge transfer mediators and concanavalin A with selective binding to the yeast cell wall. Specifically, a decrease in charge transfer resistance (or increase in peak current as measured in SWV) occurs upon binding of yeast cells to concanavalin A. The streptavidin-biotin interaction also manipulated the charge transfer resistance similarly, confirming our method effectiveness. Nanobodies (binding fragment of antibodies) were also shown to have some success in detecting flagella protein with redox mediators in solution.These proof-of-concept results demonstrate feasibility and indicate forward paths towards highly selective sensor electrodes with simultaneous anti-fouling properties that prevents non-specific binding. Ongoing efforts include modifying electronic device interfaces with SAMs for combined signaling and amplification, such as modification of gate electrodes in printable electrochemical transistors.

Assessing the ABCG2 Protein Interactome: a Potential Strategy to Disrupt ABCG2 Function

The ATP‐binding cassette sub‐family G member 2, ABCG2, is an important plasma membrane transporter that removes potentially harmful endogenous toxins and xenobiotics from cells. ABCG2 was identified as an important contributor to the multidrug resistance phenotype in cancer cells because it exported a wide variety of structurally diverse chemotherapeutic agents, including mitoxantrone, topotecan and the tyrosine kinase inhibitors. High ABCG2 expression in a variety of tumours is associated with poor clinical outcomes. In our present study, we hypothesized that proteins that interact with ABCG2 modulate its function. This knowledge would allow us to discover novel therapeutic targets that could be exploited to alter ABCG2 expression and/or function.To identify interacting proteins for ABCG2, we employed a site‐specific biotinylation system utilizing a 15 amino acid peptide tag known as AviTag, fused to ABCG2. In the presence of the E. coli biotin ligase (BirA), biotin can be covalently attached to the AviTag peptide and the complex can be purified using the non‐covalent streptavidin‐biotin interaction. A plasmid harboring both AviTag‐ABCG2 and an IRES directed BirA was constructed. We stably expressed it in HEK293 cells and confirmed that AviTag ABCG2 was expressed at the plasma membrane and retained typical ABCG2 transport activity. Importantly, the cells expressing the AviTag‐ABCG2 and BirA readily labelled AviTag‐ABCG2 with biotin. The AviTag‐ABCG2 protein complexes captured by streptavidin agarose beads were purified and eluted according to an empirically developed protocol.Using a proteomic approach with mass spectrometry, we identified 39 proteins (both known and novel ABCG2 interacting proteins) at a p‐value threshold of 0.05 in the AviTag‐ABCG2 protein complex compared to the negative control. As expected, ABCG2 was one of the top 10 proteins in abundance (high spectral counts). Among the 39 interacting proteins, we confirmed by immunoblotting that several important cancer‐related proteins interact with ABCG2. These proteins appear capable of regulating ABCG2 function in cancer cells.Future studies will elucidate how these interactions affect ABCG2 function. These findings might aid in the development of new strategies for blocking ABCG2 function in multidrug resistant cancers, which could have important implications in improving patient’s response to chemotherapy.Support or Funding InformationThis work was supported by NIH and ALSAC

Competitive HRP-Linked Colorimetric Aptasensor for the Detection of Fumonisin B1 in Food based on Dual Biotin-Streptavidin Interaction.

Fumonisin B1 (FB1) is the most prevalent and toxic form among fumonisin homologues which are produced by fusarium species and it contaminates various types of food products, posing serious health hazards for humans and animals. In this work, a colorimetric assay for the detection of FB1 has been developed based on competitive horseradish peroxidase (HRP)-linked aptamer and dual biotin-streptavidin interaction. In short, a biotinylated aptamer of FB1 was immobilized on the microplate by biotin-streptavidin binding; the complementary strand (csDNA) of the aptamer was ligated with HRP by biotin-streptavidin binding again to form a csDNA-HRP sensing probe, competing with FB1 to bind to the aptamer. The color change can be observed after the addition of chromogenic and stop solution, thereby realizing the visual detection of FB1. Under optimal conditions, good linearity was observed within the concentration range of 0.5 to 300 ng/mL, with a detection of limit of 0.3 ng/mL. This assay is further validated by spike recovery tests towards beer and corn samples, it provides a simple, sensitive and reliable method for the screening of FB1 in food samples and may be potentially used as an alternative to conventional assays.

Direct Conjugation of Streptavidin to Encoded Hydrogel Microparticles for Multiplex Biomolecule Detection with Rapid Probe-Set Modification.

Encoded hydrogel microparticles synthesized via flow lithography have drawn attention for multiplex biomarker detection due to their high multiplex capability and solution-like hybridization kinetics. However, the current methods for preparing particles cannot achieve a flexible, rapid probe-set modification, which is necessary for the production of various combinations of target panels in clinical diagnosis. In order to accomplish the unmet needs, streptavidin was incorporated into the encoded hydrogel microparticles to take advantage of the rapid streptavidin–biotin interactions that can be used in probe-set modification. However, the existing methods suffer from low efficiency of streptavidin conjugation, cause undesirable deformation of particles, and impair the assay capability. Here, we present a simple and powerful method to conjugate streptavidin to the encoded hydrogel microparticles for better assay performance and rapid probe-set modification. Streptavidin was directly conjugated to the encoded hydrogel microparticles using the aza-Michael addition click reaction, which can proceed in mild, aqueous condition without catalysts. A highly flexible and sensitive assay was developed to quantify DNA and proteins using streptavidin-conjugated encoded hydrogel microparticles. We also validated the potential applications of our particles conducting multiplex detection of cancer-related miRNAs.

Perillaldehyde 1,2-epoxide Loaded SLN-Tailored mAb: Production, Physicochemical Characterization and In Vitro Cytotoxicity Profile in MCF-7 Cell Lines.

We have developed a new cationic solid lipid nanoparticle (SLN) formulation, composed of Compritol ATO 888, poloxamer 188 and cetyltrimethylammonium bromide (CTAB), to load perillaldehyde 1,2-epoxide, and surface-tailored with a monoclonal antibody for site-specific targeting of human epithelial growth receptor 2 (HER2). Perillaldehyde 1,2-epoxide-loaded cationic SLN (cPa-SLN), with a mean particle size (z-Ave) of 275.31 ± 4.78 nm and polydispersity index (PI) of 0.303 ± 0.081, were produced by high shear homogenization. An encapsulation efficiency of cPa-SLN above 80% was achieved. The release of perillaldehyde 1,2-epoxide from cationic SLN followed the Korsemeyer–Peppas kinetic model, which is typically seen in nanoparticle formulations. The lipid peroxidation of cPa-SLN was assessed by the capacity to produce thiobarbituric acid-reactive substances, while the antioxidant activity was determined by the capacity to scavenge the stable radical DPPH. The surface functionalization of cPa-SLN with the antibody was done via streptavidin-biotin interaction, monitoring z-Ave, PI and ZP of the obtained assembly (cPa-SLN-SAb), as well as its stability in phosphate buffer. The effect of plain cationic SLN (c-SLN, monoterpene free), cPa-SLN and cPa-SLN-SAb onto the MCF-7 cell lines was evaluated in a concentration range from 0.01 to 0.1 mg/mL, confirming that streptavidin adsorption onto cPa-SLN-SAb improved the cell viability in comparison to the cationic cPa-SLN.

G-triplex molecular beacon‒based fluorescence biosensor for sensitive detection of small molecule-protein interaction via exonuclease III‒assisted recycling amplification

Small molecule-protein interaction plays a significant role in disease diagnosis and biomedical research. Most of the reported fluorescence strategies for small molecule-protein interaction still involve the use of costly fluorophore-labelled probes. In this work, a label-free fluorescent method for sensitive detection of small molecule-protein interaction is proposed. It is based on G-triplex‒based molecular beacon (G3-MB) and exonuclease III (Exo III)‒aided DNA recycling amplification. Biotin-streptavidin interaction is selected as one model for proof-of-concept. The biotin-linked double-strand DNA (dsDNA) is used as the binding probe. In the presence of streptavidin, Exo III hydrolyzes the binding probe to release the trigger DNA, and the released trigger DNA can hybridize G3-MB to trigger the Exo III cleavage process, accompanied by releasing the trigger DNA and G3 sequences. The trigger DNA can recycle, generating a large number of G3 sequences. The generated G3 sequences bind thioflavin T (ThT) to produce strong fluorescence emission. The interaction between small molecule–protein can be detected by the fluorescence reader. This method exhibits low detection limit (5.6 pg/mL), and owns the merits of the simplicity, high specificity and satisfactory applicability in serum sample.

A colorimetric method for determination of theprostate specific antigen based on enzyme-free cascaded signal amplification via peptide-copper(II) nanoparticles.

Biotinylated peptide-Cu2+ nanoparticles (Cu-P NPs) were synthesized via "one-pot" self-assembly. The peptide P conststs ofa hydrophobic dipeptide (FF), a tripeptide (KGH), and a biotin moiety attached to the terminal amino group of the Lys residue.The Cu-P NPs contain abundant catalytically active Cu2+ ions which are liberated by acid-induced dissolution. The released Cu2+ ions catalyze the oxidization of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 because of their intrinsic peroxidase activity, and thisresults in the formation of a blue-green coloration. Based on the streptavidin-biotin interaction, the Cu-P NPs were employed to establish an enzyme-free colorimetric method for determination of prostate-specific antigen (PSA) as a model biomarker. Under optimal conditions, the linear response range is 0.001-1 ng mL-1, with a limit of detection as low as 1 pg mL-1. Graphical abstract Schematic illustration of a colorimetric immunoassay for the prostate specific antigen (PSA) with biotinylated peptide-Cu2+ nanoparticle (Cu-P NP) as the signal label based on the streptavidin (SA)-biotin interaction. The signal was produced by Cu2+-catalyzed oxidization of 3,3',5,5'-tetramethylbenzidine (TMB).P: KGHFF.

A magnetism/laser-auxiliary cascaded drug delivery to pulmonary carcinoma

Although high-efficiency targeted delivery is investigated for years, the efficiency of tumor targeting seems still a hard core to smash. To overcome this problem, we design a three-step delivery strategy based on streptavidin–biotin interaction with the help of c(RGDfK), magnetic fields and lasers. The ultrasmall superparamagnetic iron oxide nanoparticles (USIONPs) modified with c(RGDfK) and biotin are delivered at step 1, followed by streptavidin and the doxorubicin (Dox) loaded nanosystems conjugated with biotin at steps 2 and 3, respectively. The delivery systems were proved to be efficient on A549 cells. The co-localization of signal for each step revealed the targeting mechanism. The external magnetic field could further amplify the endocytosis of USPIONs based on c(RGDfK), and magnify the uptake distinctions among different test groups. Based on photoacoustic imaging, laser-heating treatment could enhance the permeability of tumor venous blood vessels and change the insufficient blood flow in cancer. Then, it was noticed in vivo that only three-step delivery with laser-heating and magnetic fields realized the highest tumor distribution of nanosystem. Finally, the magnetism/laser-auxiliary cascaded delivery exhibited the best antitumor efficacy. Generally, this study demonstrated the necessity of combining physical, biological and chemical means of targeting.

Chemistry of Biotin-Streptavidin and the Growing Concern of an Emerging Biotin Interference in Clinical Immunoassays.

Overconsumption of biotin (5–100 mg daily) as a supplement by the general population poses a significant problem for clinical immunoassays (IAs) based on biotin–streptavidin (SA) interactions. This affinity pair has been exploited in immunoassays because of its avidity, sensitivity, specificity, and stability. The elevated biotin level in plasma varies from patient to patient, and its severe interference cannot easily be predicted and quantified. Thus, immunoassay manufacturers must investigate the biotin interference in the developed immunoassays to satisfy the threshold of 3510 ng/mL (14 367 nM), as stipulated by the FDA. There is no concrete solution to circumvent the biotin interference without extra costs and technical difficulties, albeit different strategies have been attempted. They include the IA format with biotinylated reagents prebound to streptavidin, the removal of biotin from the specimen, sample treatment, and biotin interference-free assays. The general public has been instructed to stop taking biotin supplements for 48 h or even weeks before the test, depending on the specific test, dose, and frequency of biotin uptake. As lab-based techniques cannot accommodate an enormous number of public samples, a rapid analytical procedure for biotin is urgently needed to quantify for its interference in immunoassays.

Precision Anisotropic Brush Polymers by Sequence Controlled Chemistry.

The programming of nanomaterials at molecular length-scales to control architecture and function represents a pinnacle in soft materials synthesis. Although elusive in synthetic materials, Nature has evolutionarily refined macromolecular synthesis with perfect atomic resolution across three-dimensional space that serves specific functions. We show that biomolecules, specifically proteins, provide an intrinsic macromolecular backbone for the construction of anisotropic brush polymers with monodisperse lengths via grafting-from strategy. Using human serum albumin as a model, its sequence was exploited to chemically transform a single cysteine, such that the expression of said functionality is asymmetrically placed along the backbone of the eventual brush polymer. This positional monofunctionalization strategy was connected with biotin–streptavidin interactions to demonstrate the capabilities for site-specific self-assembly to create higher ordered architectures. Supported by systematic experimental and computational studies, we envisioned that this macromolecular platform provides unique avenues and perspectives in macromolecular design for both nanoscience and biomedicine.

La prise de biotine à fortes doses : une cause d’hyperthyroïdie biologique factice

IntroductionMany hormone immunoassays use the biotin streptavidin interaction to immobilize immune complexes. The intake of high dose biotin can interfere with immunoassays using the biotin streptavidin interaction. The biotin-immunoassay interference generates falsely low or falsely high tests of hormones according to the type of immunoassay used. Case reportA 70-year-old patient, with progressive multiple sclerosis, was referred to our hospital for thyrotoxicosis. She was found to have markedly elevated thyroid hormones level (T3-T4) and decreased thyrotropin (TSH) level but she had no symptoms of hyperthyroidism. An ingestion of biotin, that is more and more frequent in patients with progressive multiple sclerosis, was found. Thyroid function tests normalized after discontinuation of biotin treatment. ConclusionThe discrepancy between a clinical exam which is not indicative of thyrotoxicosis and markedly abnormal thyroid function tests should lead to a search for biotin intake, which can interfere with thyroid function tests.

Sensitive electrochemical aptasensor for detecting EpCAM with silica nanoparticles and quantum dots for signal amplification

The epithelial cell adhesion molecule (EpCAM) is a known biomarker of circulating tumor cells that plays an important role in tumor metastasis. The detection of EpCAM is vital for personalized diagnosis and therapy but is challenging because of its extremely low concentration in peripheral blood. In our work, an electrochemical aptasensor has been developed to quantitatively detect EpCAM at low concentrations. A gold electrode modified with an aptamer can capture EpCAM, which can then be further recognized by a second aptamer acting as a signal reporter. To amplify the signal, a silica nanoparticle/CdSe complex has been designed to enhance the detection system. First, silica nanoparticles were synthesized to act as carriers for loading many CdSe quantum dots which are capable of binding with the second aptamer by biotin-streptavidin interactions. A molecule of EpCAM can bind with numerous CdSe quantum dots (QDs) to realize significant signal amplification. By stripping square wave voltammetry (SSWV), concentrations down to 10 aM EpCAM can be successfully detected and quantified based on the newly developed aptasensor. The detection linear range is from 10 aM to 100 pM. This principle can also be extended to other biomarkers when a suitable aptamer or antibody is available. This aptasensor is expected to be a potential tool for the diagnosis, therapeutic evaluation and personalized medical care of cancer patients.