A graphene oxide-peptide fluorescence sensor tailor-made for simple and sensitive detection of matrix metalloproteinase 2

A graphene oxide-peptide based fluorescence sensor has been developed for matrix metalloproteinase 2 (MMP2), and its applicability has been demonstrated by monitoring the concentration of MMP2 secreted by HeLa cells, revealing that HeLa cells with a density of 5.48 × 10(5) cells per mL can produce 22 nM in cell culture media in 24 h.     

A cell-based biosensor for real-time detection of cardiotoxicity using lensfree imaging

A portable and cost-effective real-time cardiotoxicity biosensor was developed using a CMOS imaging module extracted from a commercially available webcam. The detection system consists of a CMOS imaging module, a white LED and a pinhole. Real-time image processing was conducted by comparing reference and live frame images. To evaluate the engineered system, the effects of two different drugs, isoprenaline and doxorubicin, on the beating rate and beat-to-beat variations of ESC-derived cardiomyocytes were measured. The detection system was used to conclude that the beat-to-beat variability increased under treatment with both isoprenaline and doxorubicin. However, the beating rates increased upon the addition of isoprenaline but decreased for cultures supplemented with doxorubicin. Moreover, the response time for both the beating rates and the beat-to-beat variability of ESC-derived cardiomyocytes under treatment of isoprenaline was shorter than for doxorubicin, although the amount of isoprenaline used in the measurement was three orders of magnitude lower than that of doxorubicin. Given its ability to perform real-time cell monitoring in a simple and inexpensive manner, the proposed system may be useful for a range of cell-based biosensing applications.     

Streptavidin-enhanced surface plasmon resonance biosensor for highly sensitive and specific detection of microRNA

We are presenting a method for sensitive and specific detection of microRNA (miRNA) using surface plasmon resonance. A thiolated capture DNA probe with a short complete complementary sequence was immobilized on the gold surface of the sensor to recognize the part sequence of target miRNA, and then an oligonucleotide probe linked to streptavidin was employed to bind the another section of the target. The use of the streptavidin-oligonucleotide complex caused a ~5-fold increase in signal, improved the detection sensitivity by a factor of ~24, and lowered the detection limit to 1.7 fmol of miR-122. This specificity allowed a single mismatch in the target miRNA to be discriminated. The whole assay takes 30 min, and the surface of the sensor can be regenerated at least 30 times without loss in performance. The method was successfully applied to the determination of miRNA spiked into human total RNA samples.

A novel reagentless glutamate microband biosensor for real-time cell toxicity monitoring

A reagentless glutamate biosensor was applied to the determination of glutamate released from liver hepatocellular carcinoma cells (HepG2) in response to toxic challenge from various concentrations of paracetamol. A screen printed carbon electrode (SPCE) containing the electrocatalyst Meldola's Blue (MB-SPCE) served as the electron mediator for the oxidation of NADH.     

Impedimetric biosensor for cancer cell detection

Electrochemical impedance spectroscopy was evaluated for the label free detection of MCF-7 cancer cell in which c-erbB-2 receptor is overexpressed on the cell surfaces. Anti-c-erbB-2, used as a specific antibody, was immobilized on electrogenerated polypyrrole-NHS on electrodes via covalent linking. The polymer formation, the grafting of the antibody, and the recognition event with the cancer cells using MCF-7 as a model cell line, were characterized by using cyclic voltammetry and fluorescence microscopy. The impedimetric sensor showed high sensitivity from 100 to 10 000 cell/mL without needing any labeling step and represents an efficient transduction method for cell selective detection.     

Increasing the detection speed of an all-electronic real-time biosensor

Biosensor response time, which depends sensitively on the transport of biomolecules to the sensor surface, is a critical concern for future biosensor applications. We have fabricated carbon nanotube field-effect transistor biosensors and quantified protein binding rates onto these nanoelectronic sensors. Using this experimental platform we test the effectiveness of a protein repellent coating designed to enhance protein flux to the all-electronic real-time biosensor. We observe a 2.5-fold increase in the initial protein flux to the sensor when upstream binding sites are blocked. Mass transport modelling is used to calculate the maximal flux enhancement that is possible with this strategy. Our results demonstrate a new methodology for characterizing nanoelectronic biosensor performance, and demonstrate a mass transport optimization strategy that is applicable to a wide range of microfluidic based biosensors.     

Gold nanostar-enhanced surface plasmon resonance biosensor based on carboxyl-functionalized graphene oxide

A new high-sensitivity surface plasmon resonance (SPR) biosensor based on biofunctional gold nanostars (AuNSs) and carboxyl-functionalized graphene oxide (cGO) sheets was described. Compared with spherical gold nanoparticles (AuNPs), the anisotropic structure of AuNSs, which concentrates the electric charge density on its sharp tips, could enhance the local electromagnetic field and the electronic coupling effect significantly. cGO was obtained by a diazonium reaction of graphene oxide (GO) with 4-aminobenzoic acid. Compared with GO, cGO could immobilize more antibodies due to the abundant carboxylic groups on its surface. Testing results show that there are fairly large improvements in the analytical performance of the SPR biosensor using cGO/AuNSs-antigen conjugate, and the detection limit of the proposed biosensor is 0.0375 μg mL⁻¹, which is 32 times lower than that of graphene oxide-based biosensor.     

Detection of a biomarker for Alzheimer's disease from synthetic and clinical samples using a nanoscale optical biosensor

A nanoscale optical biosensor based on localized surface plasmon resonance (LSPR) spectroscopy has been developed to monitor the interaction between the antigen, amyloid-beta derived diffusible ligands (ADDLs), and specific anti-ADDL antibodies. Using the sandwich assay format, this nanosensor provides quantitative binding information for both antigen and second antibody detection that permits the determination of ADDL concentration and offers the unique analysis of the aggregation mechanisms of this putative Alzheimer's disease pathogen at physiologically relevant monomer concentrations. Monitoring the LSPR-induced shifts from both ADDLs and a second polyclonal anti-ADDL antibody as a function of ADDL concentration reveals two ADDL epitopes that have binding constants to the specific anti-ADDL antibodies of 7.3 x 10(12) M(-1) and 9.5 x 10(8) M(-1). The analysis of human brain extract and cerebrospinal fluid samples from control and Alzheimer's disease patients reveals that the LSPR nanosensor provides new information relevant to the understanding and possible diagnosis of Alzheimer's disease.     

A novel hydrazine electrochemical sensor based on the high specific surface area graphene

An ultrasensitive platform is presented for the determination of hydrazine by combining the high specific surface area and higher electrical conductivity of poly(sodium styrenesulfonate) (PSS) graphene nanocomposite film with amperometric detection. The PSS-graphene were synthesized by the Hummers method and used to modify a glassy carbon electrode. The material was characterized by scanning electron microscopy and is found to be suitable for sensing hydrazine. The overpotential of hydrazine on the modified electrode is 0.31 V which is lower than in many electrochemical sensors. The calibration curve for hydrazine is linear in the range from 3.0 to 300 µmol L^?1, and the detection limit is as low as 1 µmol L^?1. This is the first report in which such a high sensitivity and low limit of detection has been achieved. It is concluded that PSS graphene represents an efficient electron mediator for sensing hydrazine.     

A nano-functionalized real-time electrochemiluminescent biosensor for alanine transaminase assay

An electrochemiluminescent (ECL) biosensor was constructed for selective assay of alanine aminotransferase (ALT) based on the enzymatically catalyzed oxidation of pyruvate by pyruvate oxidase (PYOD). The composite of potassium ferricyanide and carbon nanotube was adopted to pre-functionalize the basal platinum electrode while the potassium ferricyanide acted as the activator of PYOD. The ALT catalyzed the reaction of L-alanine and-ketoglutarate to produce pyruvate which could be further enzymatically oxidiz...     

A flexible giant magnetoimpedance-based biosensor for the determination of the biomarker C-reactive protein

We report on a method for the determination of magnetic bead-labeled C-reactive protein (CRP), a biomarker of cardiovascular diseases and inflammations. It is using a flexible giant magnetoimpedance (GMI)-based platform. Micro-patterned GMI sensing elements were prepared from a cobalt-based commercial amorphous ribbon (Metglas® 2714A) using micro electro-mechanical system (MEMS) technology. A gold film was then deposited on the GMI sensing element to act as a support for the immuno platform. Sandwich assays are performed using antibody-antigen combinations and biotin-streptavidin interactions on the gold film substrate surface via self-assembled layers. The GMI ratios of the sensors with different concentrations of antigen against CRP were investigated. The results show that the presence of CRP antigens on the biosensor improves the GMI effect owing to the induced magnetic dipole of superparamagnetic beads, and that the GMI ratios show distinct changes at high frequency. This bioassay for CRP has a linear detection range between 1 to 10 ng·mL⁻¹. This new method in our perception provides a widely applicable basis for rapid diagnostic testing and will pave the way for future development of electrochemical point-of-care diagnostic devices for cardiac diseases.

(a) Graphical illustration of CRP test setup. (b) Magnetic field arrangement of the beads under an applied magnetic field. (c) GMI changes in relation to the concentration of the CRP

     

A surface topography assisted droplet manipulation platform for biomarker detection and pathogen identification

This paper reports a droplet microfluidic, sample-to-answer platform for the detection of disease biomarkers and infectious pathogens using crude biosamples. The platform exploited the dual functionality of silica superparamagnetic particles (SSP) for solid phase extraction of DNA and magnetic actuation. This enabled the integration of sample preparation and genetic analysis within discrete droplets, including the steps of cell lysis, DNA binding, washing, elution, amplification and detection. The microfluidic device was self contained, with all reagents stored in droplets, thereby eliminating the need for fluidic coupling to external reagent reservoirs. The device incorporated unique surface topographic features to assist droplet manipulation. Pairs of micro-elevations were created to form slits that facilitated efficient splitting of SSP from droplets. In addition, a compact sample handling stage, which integrated the magnet manipulator, the droplet microfluidic device and a Peltier thermal cycler, was built for convenient droplet manipulation and real-time detection. The feasibility of the platform was demonstrated by analysing ovarian cancer biomarker Rsf-1 and detecting Escherichia coli with real time polymerase chain reaction and real time helicase dependent amplification.     

A novel amperometric biosensor for the detection of nitrophenol

We report on a novel amperometric biosensor for detecting phenolic compounds based on the co-immobilization of horseradish-peroxidase (HRP) and methylene blue (MB) with chitosan on Au-modified TiO₂ nanotube arrays. The titania nanotube arrays were directly grown on a Ti substrate using anodic oxidation first; a gold thin film was then coated onto the TiO₂ nanotubes by an argon plasma technique. The morphology and composition of the fabricated Au-modified TiO₂ nanotube arrays were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry and amperometry were used to study the proposed electrochemical biosensor. The effect of pH, applied electrode potential and the concentration of H₂O₂ on the sensitivity of the biosensor have been systemically investigated. The performance of the proposed biosensor was tested using seven different phenolic compounds, showing very high sensitivity; in particular, the linearity of the biosensor for the detection of 3-nitrophenol was observed from 3 × 10⁻⁷ to 1.2 × 10⁻⁴ M with a detection limit of 9 × 10⁻⁸ M (based on the S/N = 3).     

A SERS DNAzyme biosensor for lead ion detection

SERS biosensor for sensitive and selective detection of lead ions (Pb(2+)) based on DNAzyme was developed by taking advantage of the specific catalytic reaction of DNAzyme upon binding to Pb(2+) ions. Detection was accomplished by SERS nanoprobe labeled with DNA and Raman reporters for signal amplification.     

A novel electrochemical biosensor for detection of cholesterol

We report on a highly sensitive electrochemical biosensor for determination of cholesterol. The biosensor was fabricated by co-immobilizing bi-enzymes, cholesterol oxidase (ChOx), and horseradish peroxidase (HRP). Voltammetric technique such as cyclic voltammetry and impedance experiment were used to study the characterization of modified electrode step by step. The developed sensor is cheap, disposable, portable and exhibits higher sensitivity. The biosensor expressed a wide linear range up to 300 mg dL^–1 in a physiological condition (pH 7.0), with a correlation coefficient of 0.9969. A sensitivity of 13.28 μA mg^–1 dL cm^?2 which makes it very promising for the clinical determination of cholesterol.     

一种锌配合物用于炭疽生物标志物的检测

采用溶剂热合成方法,合成了一种新型金属配位聚合物{[Zn₂(L)(H₂O)(DMA)]·DMA·2.3H₂O}_n (1),其中L^4-为完全脱去质子的N,N''-二(4-羧基苄基)-5-氨基间苯二甲酸,DMA为N,N-二甲基乙酰胺。单晶X射线衍射结果显示,该配合物属于三斜晶系,空间群为P$overline{1}$,a=0.989 6(5) nm,b=1.370 5(5) nm,c=1.382 1(5) nm,α=80.067(5)°,β=76.729(5)°,γ=76.611(5)°,结构是由二维金属有机层通过π…π相互作用而扩展成的三维超分子骨架。红外光谱验证了锌离子与L^4-配体成功配位。粉末X射线衍射(PXRD)实验证实了配合物1具有较高的纯度。热重分析结果显示配合物1在室温至416.9 ℃区间内具有较好的热稳定性。在273 nm的激发光下,配合物1在437 nm处有较强的荧光发射,可以在30 s内快速检测乙醇溶液中的炭疽生物标志物——吡啶-2,6-二甲酸,具有选择性高、抗干扰能力强、检测限低(约为15 μmol·L^-1)等特点。结合PXRD图和紫外可见吸收光谱揭示了其检测机理为晶体骨架坍塌而诱导的荧光猝灭。