Graphene sheets, polyaniline and AuNPs based DNA sensor for electrochemical determination of BCR/ABL fusion gene with functional hairpin probe

Noble metal nanoparticles in biosensors: recent studies and applications

The aim of this review is to cover advances in noble metal nanoparticle (MNP)-based biosensors and to outline the principles and main functions of MNPs in different classes of biosensors according to the transduction methods employed. The important biorecognition elements are enzymes, antibodies, aptamers, DNA sequences, and whole cells. The main readouts are electrochemical (amperometric and voltametric), optical (surface plasmon resonance, colorimetric, chemiluminescence, photoelectrochemical, etc.) and piezoelectric. MNPs have received attention for applications in biosensing due to their fascinating properties. These properties include a large surface area that enhances biorecognizers and receptor immobilization, good ability for reaction catalysis and electron transfer, and good biocompatibility. MNPs can be used alone and in combination with other classes of nanostructures. MNP-based sensors can lead to significant signal amplification, higher sensitivity, and great improvements in the detection and quantification of biomolecules and different ions. Some recent examples of biomolecular sensors using MNPs are given, and the effects of structure, shape, and other physical properties of noble MNPs and nanohybrids in biosensor performance are discussed.

High Sensitivity Determination of TNF-α for Early Diagnosis of Neonatal Infections with a Novel and Reusable Electrochemical Sensor

Early diagnosis is vital for the reduction of mortality caused by neonatal infections. Since TNF-α can be used as a marker for the early diagnosis, the detection of TNF-α with high sensitivity and specificity has great clinical significance. Herein, a highly sensitive and reusable electrochemical sensor was fabricated. Due to the high specificity of aptamers, TNF-α could be accurately detected from five similar cytokines, even from serum samples. In addition, Au nanoparticles (AuNPs) with a high surface area were able to combine a large number of doxorubicin hydrochloride (DOXh), which made the sensor have a high sensitivity. The sensor had a good linear relationship with TNF-α concentration in the range from 1 to 1 × 10⁴ pg/mL and the lowest detection limit is 0.7 pg/mL. More important was that the sensor could be reused 6 times by a crafty use of chain replacement reaction. Meanwhile, the detection time and cost were greatly reduced. Thus, we believe that these advantages of higher specificity and sensitivity, lower cost, and shorter detection time will provide a stronger potential for early diagnosis of neonatal infections in clinical applications.

Determination of cDNA encoding BCR/ABL fusion gene in patients with chronic myelogenous leukemia using a novel FRET-based quantum dots-DNA nanosensor

In the present study, we developed a sensitive method based on fluorescence resonance energy transfer (FRET) for the determination of the BCR/ABL fusion gene, which is used as a biomarker to confirm the clinical diagnosis of both chronic myelogenous leukemia (CML) and acute lymphocytic leukemia (ALL). For this purpose, CdTe quantum dots (QDs) were conjugated to amino-modified 18-mer oligonucleotide ((N)DNA) to form the QDs-(N)DNA nanosensor. In the presence of methylene blue (MB) as an intercalator, the hybridization of QDs-(N)DNA with the target BCR/ABL fusion gene (complementary DNA), brings the MB (acceptor) at close proximity of the QDs (donor), leading to FRET upon photoexcitation of the QDs. The enhancement in the emission intensity of MB was used to follow up the hybridization, which was linearly proportional to concentration of the target complementary DNA in a range from 1.0 × 10^-9 to 1.25 × 10^-7 M. The detection limit of the proposed method was obtained to be 1.5 × 10^-10 M. Finally, the feasibility and selectivity of the proposed nanosensor was evaluated by the analysis of derived nucleotides from both mismatched sequences and clinical samples of patients with leukemia as real samples.

PEGylated Polyaniline Nanofibers: Antifouling and Conducting Biomaterial for Electrochemical DNA Sensing

Biofouling arising from nonspecific adsorption is a substantial outstanding challenge in diagnostics and disease monitoring, and antifouling sensing interfaces capable of reducing the nonspecific adsorption of proteins from biological complex samples are highly desirable. We present herein the preparation of novel composite nanofibers through the grafting of polyethylene glycol (PEG) polymer onto polyaniline (PANI) nanofibers and their application in the development of antifouling electrochemical biosensors. The PEGylated PANI (PANI/PEG) nanofibers possessed large surface area and remained conductive and at the same time demonstrated excellent antifouling performances in single protein solutions as well as complex human serum samples. Sensitive and low fouling electrochemical biosensors for the breast cancer susceptibility gene (BRCA1) can be easily fabricated through the attachment of DNA probes to the PANI/PEG nanofibers. The biosensor showed a very high sensitivity to target BRCA1 with a linear range from 0.01 pM to 1 nM and was also efficient enough to detect DNA mismatches with satisfactory selectivity. Moreover, the DNA biosensor based on the PEGylated PANI nanofibers supported the quantification of BRCA1 in complex human serum, indicating great potential of this novel biomaterial for application in biosensors and bioelectronics.

Bis-three-way junction nanostructure and DNA machineries for ultrasensitive and specific detection of BCR/ABL fusion gene by chemiluminescence imaging

A novel G-quadruplex DNAzyme-driven chemiluminescence (CL) imaging method has been developed for ultrasensitive and specific detection of BCR/ABL fusion gene based on bis-three-way junction (bis-3WJ) nanostructure and cascade DNA machineries. Bis-3WJ probes are designed logically to recognize BCR/ABL fusion gene, which forms the stable bis-3WJ nanostructure for the activation of polymerase/nicking enzyme machineries in cascade, resulting in synthesis of DNAzyme subunits. These DNAzyme subunits can form integrated DNAzyme by self-assembly to catalyze CL substrate, thus providing an amplified signal for the sensing events or outputs for AND logic operation. The imaging method achieved ultrasensitive detection of BCR/ABL fusion gene with a low detection limit down to 23 fM. And this method exhibited wide linear ranges over seven orders of magnitude and excellent discrimination ability toward target. In addition, an acceptable recovery was obtained in complex matrix. It is notable that this biosensing strategy possesses merits of homogenous, isothermal and label-free assay system. Therefore, these merits endow the developed imaging method with a potential tool for CML diagnosis.

A single-bead telomere sensor based on fluorescence resonance energy transfer

We present a 200 nm in-diameter single-bead sensor for the detection of single, unlabeled DNA molecules in solution using fluorescence resonance energy transfer technology. DNA-bound Alexa 488 and Crimson 625 loaded on commercial beads served as the donor and acceptor, respectively. Binding of the target DNA to the single bead sensor induces G-quadruplex stretching, resulting in a decrease in fluorescence energy transfer. G-rich telomere sequences formed a G-quadruplex structure in the presence of ZnTCPP, as demonstrated by the detection of two strong donor and acceptor signals. The sensitivity of the sensor was 1 fM. Under optimized conditions using a polydimethylsiloxane microfluidic device, we measured the number of sensor beads by direct counting. By controlling the flow rate via the probe volume, one sensing experiment can be completed in 5 minutes. Based on these results, we propose a new parameter-dependability (RS)-as a quantitative measure to judge the quality of a bio-sensor. This parameter is based on the ratio of the sensor and sensing sample fluorescence signals. This parameter can range from 0.1 to 100, where a value of 10 represents an optimized bio-sensor.

Graphene: The Missing Piece for Cancer Diagnosis?

This paper reviews recent advances in graphene-based biosensors development in order to obtain smaller and more portable devices with better performance for earlier cancer detection. In fact, the potential of Graphene for sensitive detection and chemical/biological free-label applications results from its exceptional physicochemical properties such as high electrical and thermal conductivity, aspect-ratio, optical transparency and remarkable mechanical and chemical stability. Herein we start by providing a general overview of the types of graphene and its derivatives, briefly describing the synthesis procedure and main properties. It follows the reference to different routes to engineer the graphene surface for sensing applications with organic biomolecules and nanoparticles for the development of advanced biosensing platforms able to detect/quantify the characteristic cancer biomolecules in biological fluids or overexpressed on cancerous cells surface with elevated sensitivity, selectivity and stability. We then describe the application of graphene in optical imaging methods such as photoluminescence and Raman imaging, electrochemical sensors for enzymatic biosensing, DNA sensing, and immunosensing. The bioquantification of cancer biomarkers and cells is finally discussed, particularly electrochemical methods such as voltammetry and amperometry which are generally adopted transducing techniques for the development of graphene based sensors for biosensing due to their simplicity, high sensitivity and low-cost. To close, we discuss the major challenges that graphene based biosensors must overcome in order to reach the necessary standards for the early detection of cancer biomarkers by providing reliable information about the patient disease stage.

Synthesis and sensing applications of polyaniline nanocomposites: a review

A comprehensive review on the synthesis of PANI nanocomposites and their applications as gas sensors and biosensors has been presented.

Identification of Chinese Herbs Using a Sequencing-Free Nanostructured Electrochemical DNA Biosensor

Due to the nearly identical phenotypes and chemical constituents, it is often very challenging to accurately differentiate diverse species of a Chinese herbal genus. Although technologies including DNA barcoding have been introduced to help address this problem, they are generally time-consuming and require expensive sequencing. Herein, we present a simple sequencing-free electrochemical biosensor, which enables easy differentiation between two closely related Fritillaria species. To improve its differentiation capability using trace amounts of DNA sample available from herbal extracts, a stepwise electrochemical deposition of reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) was adopted to engineer a synergistic nanostructured sensing interface. By using such a nanofeatured electrochemical DNA (E-DNA) biosensor, two Chinese herbal species of Fritillaria (F. thunbergii and F. cirrhosa) were successfully discriminated at the DNA level, because a fragment of 16-mer sequence at the spacer region of the 5S-rRNA only exists in F. thunbergii. This E-DNA sensor was capable of identifying the target sequence in the range from 100 fM to 10 nM, and a detection limit as low as 11.7 fM (S/N = 3) was obtained. Importantly, this sensor was applied to detect the unique fragment of the PCR products amplified from F. thunbergii and F. cirrhosa, respectively. We anticipate that such a direct, sequencing-free sensing mode will ultimately pave the way towards a new generation of herb-identification strategies.

Gold-graphene nanocomposites for sensing and biomedical applications

Recent developments in materials science and nanotechnology have propelled the development of a plethora of materials with unique chemical and physical properties for biomedical applications. Graphitic nanomaterials such as carbon nanotubes, fullerenes and, more recently, graphene oxide (GO) and reduced graphene oxide (rGO) have received a great deal of interest in this domain. Besides the exceptional physico-chemical features of these materials, another advantage is that they can be easily produced in good quantities. Moreover, the presence of abundant functional groups on their surface and good biocompatibility make them highly suitable for biomedical applications. Many research groups have utilized GO and rGO nanocargos to effectively deliver insoluble drugs, nucleic acids and other molecules into cells for bioimaging and therapeutic purposes. Gold nanostructures (Au NSs), on the other hand, have also attracted great attention owing to their applications in biomedical fields, organic catalysis, etc. Loading of GO and rGO sheets with Au NSs generates a new class of functional materials with improved properties and thus provides new opportunities in the use of such hybrid materials for catalytic biosensing and biomedical applications. This review article is aimed at providing an insight into the important features of gold-graphene nanocomposites, the current research activities related to the different synthetic routes to produce these nanocomposites, and their potential applications in sensing and biomedical therapy, notably photothermal therapy (PTT).

An electrochemical biosensor for sensitive detection of microRNA-155: combining target recycling with cascade catalysis for signal amplification

In this work, a new electrochemical biosensor based on catalyzed hairpin assembly target recycling and cascade electrocatalysis (cytochrome c (Cyt c) and alcohol oxidase (AOx)) for signal amplification was constructed for highly sensitive detection of microRNA (miRNA). It is worth pointing out that target recycling was achieved only based on strand displacement process without the help of nuclease. Moreover, porous TiO2 nanosphere was synthesized, which could offer more surface area for Pt nanoparticles (PtNPs) enwrapping and enhance the amount of immobilized DNA strand 1 (S1) and Cyt c accordingly. With the mimicking sandwich-type reaction, the cascade catalysis amplification strategy was carried out by AOx catalyzing ethanol to acetaldehyde with the concomitant formation of high concentration of H2O2, which was further electrocatalyzed by PtNPs and Cyt c. This newly designed biosensor provided a sensitive detection of miRNA-155 from 0.8 fM to 1 nM with a relatively low detection limit of 0.35 fM.

An electrochemical DNA sensor based on polyaniline/graphene: high sensitivity to DNA sequences in a wide range

In the platform constructed by a polyaniline/graphene composite, double-stranded DNA, resulting from hybridization of a DNA probe, was escaping from or remaining on the sensor surface.

Electrochemically reduced graphene oxide supported poly(indole-5-carboxylic acid) nanocomposite for genosensing application

An ultrasensitive DNA electrochemical biosensing interface was developed for rapid determination of BCR/ABL fusion gene by employing ERGNO supported PICA.

Enzymatic amplification detection of peanut allergen Ara h1 using a stem-loop DNA biosensor modified with a chitosan-mutiwalled carbon nanotube nanocomposite and spongy gold film

In this paper, a highly sensitive biosensor was constructed for peanut allergen Ara h1 detection. The biosensor was constructed by coating a glassy carbon electrode with a chitosan-mutiwalled carbon nanotube nanocomposite and then adding a spongy gold film via electro-deposition to increase the effective area. The probe switched from an "on" to an "off" state in the presence of target DNA, which detached biotin from the electrode surface. This also detached streptavidin-horseradish peroxidase (HRP-SA), which was bound to the electrode via specific interaction with biotin. The HRP-SA catalyzed chemical oxidation of hydroquinone by H2O2 to form benzoquinone, and when it was detached, electrochemical reduction of the signal of benzoquinone could be used to monitor DNA hybridization via chronoamperometry. Under optimum conditions, a wide dynamic detection range (3.91 × 10(-17)-1.25 × 10(-15) mol L(-1)) and a low detection limit (1.3 × 10(-17) mol L(-1)) were achieved for the complementary sequence. Furthermore, the DNA biosensor exhibited an excellent ability to discriminate between a complementary target and a one-base mismatch or non-complementary sequence. The sensor was successfully applied to Ara h1 analysis in peanuts.

Integrated graphene/nanoparticle hybrids for biological and electronic applications

The development of novel graphene/nanoparticle hybrid materials is currently the subject of tremendous research interest. The intrinsic exceptional assets of both graphene (including graphene oxide and reduced graphene oxide) and nanoparticles render their hybrid materials synergic properties that can be useful in various applications. In this feature review, we highlight recent developments in graphene/nanoparticle hybrids and their promising potential in electronic and biological applications. First, the latest advances in synthetic methods for the preparation of the graphene/nanoparticle hybrids are introduced, with the emphasis on approaches to (1) decorate nanoparticles onto two-dimensional graphene and (2) wrap nanoparticles with graphene sheets. The pros and cons of large-scale synthesis are also discussed. Then, the state-of-the-art of graphene/nanoparticle hybrids in electronic and biological applications is reviewed. For electronic applications, we focus on the advantages of using these hybrids in transparent conducting films, as well as energy harvesting and storage. Biological applications, electrochemical biosensing, bioimaging, and drug delivery using the hybrids are showcased. Finally, the future research prospects and challenges in this rapidly developing area are discussed.

Chemical Polymerization Kinetics of Poly-O-Phenylenediamine and Characterization of the Obtained Polymer in Aqueous Hydrochloric Acid Solution Using K2Cr2O7as Oxidizing Agent

The oxidative chemical polymerization of o-phenylenediamine (OPDA) was studied in hydrochloric acid solution using potassium dichromate as oxidant at 5°C. The effects of potassium dichromate, hydrochloric acid, and monomer concentrations on the polymerization reaction were investigated. The order of reaction with respect to potassium dichromate, hydrochloric acid, and monomer concentration was found to be 1.011, 0.954, and 1.045, respectively. Also, the effect of temperature on the polymerization rate was studied and the apparent activation energy of the polymerization reaction was found to be 63.658 kJ/mol. The obtained polymer was characterized using XPS, IR, UV-visible, and elemental analysis. The surface morphology of the obtained polymers was characterized by X-ray diffraction and transmission electron microscopy (TEM). The TGA analysis was used to confirm the proposed structure and number of water molecules in each polymeric chain unit. The ac conductivity(σac)of (POPDA) was investigated as a function of frequency and temperature. The ac conductivity was interpreted as a power law of frequency. The frequency exponent (s) was found to be less than unity and decreased with the increase of temperature, which confirms that the correlated barrier hopping model was the dominant charge transport mechanism.