A monolithic silicon based integrated signal generation and detection system for monitoring DNA hybridisation

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) modified metal-organic frameworks boosting carbon dots electrochemiluminescence emission for sensitive miRNA detection

Highly efficient luminescent materials play an important role in electrochemiluminescence (ECL) biosensing systems. Herein, the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) modified carbon dots (CDs)/zeolitic imidazolate framework-8 (ZIF-8) compositing metal-organic frameworks (MOFs) materials with excellent luminescence performance were prepared as the ECL emitters for biosensing application. In this novel ternary composites, CDs were used as emitters, ZIF-8 was used as a carrier, and the luminescent performance was finally improved by introducing PEDOT:PSS to improve the conductivity of the nanomaterials. As a result, CDs/PEDOT:PSS/ZIF-8 exhibited an approximately 8 times ECL intensity compared to CDs alone. By further modifying with AuNPs, the enhancement factor reached ≈10 in reference to the individual CDs. After combining with a DNAzyme-based two-cycle target amplification principle, an ECL biosensor was constructed to achieve high-sensitivity detection of miRNA-21 with a detection limit of 50 aM. The biosensor also demonstrated desirable selectivity, excellent stability, and quantitative ability for human serum target detection. Overall, these findings not only provide a promising pathway for high luminous efficiency ECL emitters synthesis, but also provide a platform for ultrasensitive miRNA sensing.

Carbon nanodot-based electrogenerated chemiluminescence biosensor for miRNA-21 detection

A simple carbon nanodot–based electrogenerated chemiluminescence biosensor is described for sensitive and selective detection of microRNA-21 (miRNA-21), a biomarker of several pathologies including cardiovascular diseases (CVDs). The photoluminescent carbon nanodots (CNDs) were obtained using a new synthesis method, simply by treating tiger nut milk in a microwave reactor. The synthesis is environmentally friendly, simple, and efficient. The optical properties and morphological characteristics of the CNDs were exhaustively investigated, confirming that they have oxygen and nitrogen functional groups on their surfaces and exhibit excitation-dependent fluorescence emission, as well as photostability. They act as co-reactant agents in the anodic electrochemiluminescence (ECL) of [Ru(bpy)₃]²⁺, producing different signals for the probe (single-stranded DNA) and the hybridized target (double-stranded DNA). These results paved the way for the development of a sensitive ECL biosensor for the detection of miRNA-21. This was developed by immobilization of a thiolated oligonucleotide, fully complementary to the miRNA-21 sequence, on the disposable gold electrode. The target miRNA-21 was hybridized with the probe on the electrode surface, and the hybridization was detected by the enhancement of the [Ru(bpy)₃]²⁺/DNA ECL signal using CNDs. The biosensor shows a linear response to miRNA-21 concentration up to 100.0 pM with a detection limit of 0.721 fM. The method does not require complex labeling steps, and has a rapid response. It was successfully used to detect miRNA-21 directly in serum samples from heart failure patients without previous RNA extraction neither amplification process.

Fiber bundle-based chemiluminescence array detection

Chemiluminescence (CL) is a dominant technology in clinical diagnosis. In order to meet the increasing demand for the sensitive and simultaneous detection of chemiluminescence from multiple samples, the development of multiplex analysis on a single chip is highly desired. However, most chemiluminescence detection systems for multiple samples are still simple lens-based optical imaging systems, and a compromise must always be made between a large aperture (required by the weak chemiluminescence) and a large field of view (required by the size of the sample array). In this paper, we report a fiber bundle-based chemiluminescence detection system for the simultaneous and efficient detection of multiple chemiluminescent samples. In this system, one side of the fiber bundle is directly coupled to the optically active surface of a charge-coupled device (CCD), while the other end is divided into many sub-bundles that are aligned above the samples in a chemiluminescence array to collect their chemiluminescence. Taking advantage of the large numerical aperture and high transmittance of optical fibers, this system shows about a 50 times increase in chemiluminescence collection efficiency over the lens-based imaging system. Moreover, it shows no vignetting effect that is inevitable in a lens-based imaging system with a large field of view. This work provides a promising method for multiple sample chemiluminescence detection, and should find application in bioassays.

Enhanced biosensing strategies using electrogenerated chemiluminescence: recent progress and future prospects

An overview of enhancement strategies for highly sensitive ECL-based sensing of bioanalytes enabling early detection of cancer.

Electrochemiluminescent immune-modified electrodes based on Ag2Se@CdSe nanoneedles loaded with polypyrrole intercalated graphene for detection of CA72-4

This work described a new electrochemiluminescence (ECL) immunosensor based on polypyrrole intercalated graphene and Ag2Se@CdSe nanoneedles. The novel nanomaterial Ag2Se@CdSe, with needle-like morphology, was synthesized for the first time. The prepared Ag2Se@CdSe nanoneedles exhibited good luminous performance in the presence of K2S2O8. Polypyrrole intercalated amination graphene with high specific binding sites and excellent electrochemical performance was used as the platform for the sensor. The developed ECL immunosensor was used for the detection of CA72-4 with good linear relation in the range from 10(-4) to 20 U/mL and low detection limit of 2.1 × 10(-5) U/mL (S/N = 3). The developed ECL immunosensor with high sensitivity and spectral selectivity can be used for detection of real samples. Ag2Se@CdSe nanoneedles could be promising candidate emitter for ECL biosensors in the future.

Electrochemiluminescence based on quantum dots and their analytical application

This review presents a general description of the electrochemiluminescence (ECL) related to quantum dots (QDs) and their analytical application. It briefly overviews the synthetic route of quantum dots. The basic mechanisms are given for QDs ECL behavior. Finally, new developments and improvements of its application in inorganic substance analysis, organics analysis, immunoassay and aptasensing assay are discussed.

An aptamer-based electrochemiluminescent biosensor for ATP detection

An aptamer-based electrochemiluminescent (ECL-AB) biosensor for ATP detection with high sensitivity and specificity was developed. The biosensor was assembled based on several steps. First, a complementary DNA (cDNA) of the ATP-binding aptamer, which has six complementary bases at both its ends, was hybridized with the aptamer molecule to form a rigid, linear double-stranded DNA (ds-DNA). The ds-DNA was then labeled with a ruthenium complex at the 3' terminus of cDNA, followed by the immobilization of this ds-DNA onto Au electrode surface through the 5'-HS on the cDNA. In the presence of ATP, due to the ATP binding to the aptamer, the aptamer molecules dissociated from the ds-DNA complex, which resulted in the formation of stem-loop structure of the single-stranded cDNA and led to the increase of the ECL signal. The increased ECL intensity was found linearly to the logarithm of the concentration of ATP ranging from 0.05 nM to 10 nM with a detection limit of 0.02 nM. Different from other ECL-AB biosensors with aptamers as the probes, this sensing system proposed here is based on the utilization of the cDNA of aptamers as the probes for ECL sensing. Therefore, such sensing system could provide a promising label-free and more readily regenerated model for aptamer-based small-molecules detection.

Nanostructured materials for electrochemiluminescence (ECL)-based detection methods: recent advances and future perspectives

This review presents a general picture of the last advances and developments (2003-2008) related to novel nanostructured materials for electrochemiluminescence-based biosensors using. It briefly covers the basic mechanisms of ECL detection, and the recent developments in fabrication of solid-state ECL sensors using nanostructured materials such as carbon nanotubes, metal nanoparticles, quantum dots, thin films of metallopolymers and of inorganic metal complexes. Finally, challenges and perspectives of the use of such materials for biomedical diagnostics are discussed.

DNA biosensor based on the electrochemiluminescence of Ru(bpy)32+ with DNA-binding intercalators

This paper reports a novel detection method for DNA hybridization based on the electrochemiluminescence (ECL) of Ru(bpy)(3)(2+) with a DNA-binding intercalator as a reductant of Ru(bpy)(3)(3+). Some ECL-inducible intercalators have been screened in this study using electrochemical methods combined with a chemiluminescent technique. The double-stranded DNA intercalated by doxorubicin, daunorubicin, or 4',6-diamidino-2-phenylindole (DAPI) shows a good ECL with Ru(bpy)(3)(2+) at +1.19 V (versus Ag/AgCl), while the non-intercalated single-stranded DNA does not. In order to stabilize the self-assembled DNA molecules during ECL reaction, we constructed the ECL DNA biosensor separating the ECL working electrode with an immobilized DNA probe. A gold electrode array on a plastic plate was assembled with a thru-hole array where oligonucleotide probes were immobilized in the side wall of thru-hole array. The fabricated ECL DNA biosensor was used to detect several pathogens using ECL technique. A good specificity of single point mutations for hepatitis disease was obtained by using the DAPI-intercalated Ru(bpy)(3)(2+) ECL.

Electrochemiluminescent hybridization chip with electric field aided mismatch discrimination

This paper describes a heterogeneous DNA-hybridization assay based on electrochemiluminescence (ECL) detection on gold electrodes. Short, 15-mer oligonucleotides were conjugated with a synthesized electrochemiluminescent label, bis(2,2'-bipyridine)-5-isothiocyanato-1,10-phenanthroline ruthenium(II) at the amino-modified 5'-end. Gold electrodes were derivatized with 15-mer oligonucleotide probes via 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) cross-linking reaction and hybridized with Ru-labeled strands. Two types of self-assembled-monolayers have been utilized for the immobilization reaction, 3-mercaptopropanoic acid (3-MHA) and 16-mercaptohexadecanoic acid (16-MHA). Longer thiols were more stable at high electrode potentials needed for the ECL generation. The system was sensitive down to 1 fmol of labeled complementary strand, detected in 30 microL of buffer. Mismatch discrimination was achieved both passively by washing and actively by application of negative electrode potential on electrodes prior to detection, but active denaturing lead to better results. Two base-pair mismatches were discriminated at room temperature.

Dual polarization interferometry size and density characterisation of DNA immobilisation and hybridisation

Investigation of nucleic acid interactions was performed using dual polarization interferometry, a novel approach to elucidating molecular interactions. This paper presents a preliminary study of adsorption of single stranded DNA onto functionalised silicon oxynitride, compared with covalent linkage, and avidin-biotin immobilisation. The effect of probe concentration on hybridisation efficiency was also examined. We found that increasing the electrolyte concentration resulted in a decrease of adsorbed DNA and that capture of a biotinylated duplex DNA on an adsorbed avidin layer resulted in four times fewer molecules per cm(2) than for duplex DNA covalently bound via an amine end terminal. The rate of thickness increase of a biotin probe layer on an adsorbed avidin capture layer increased 10-fold when the probe concentration was increased from 0.1 microM to 1 microM. The close grafting density of the higher concentration probe meant that the immobilised probes were unavailable for hybridisation.