Enzymatic control of metal deposition as key step for a low-background electrical detection for DNA chips
ABSTRACT Electrical detection of DNA using nanoparticle labels in combination with metal enhancement represents an interesting alternative to fluorescence readout schemes. This electrical method is hampered by unspecific metal deposition, resulting in a lower sensitivity of the assay. A novel enhancement technique based on an enzymatic process is introduced. This approach enables highly specific metal deposition only at the enzyme label, without the background that is typical in the case of the conventional metal enhancement process of growing nanoparticles. The enzymatic enhancement leads to a significant increase in sensitivity, and the detection of single base mismatches demonstrates the high specificity of the novel enhancement approach.
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Article: DNA-TEMPLATED NANOMATERIALS
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ABSTRACT: In this work, we presented a novel signal amplification approach to construct an electrochemical DNA biosensor for the ultrasensitive determination of sequence-specific DNA by exploiting hematin as biomimetic catalyst toward in situ metallization. Briefly, thiolated peptide nucleic acid (PNA) probes were firstly immobilized onto gold electrode through the formation of self-assembled monolayer (SAM) and then hybridization was accomplished in the ensuing step. After that, hematin molecules were introduced to the hybridized PNA/DNA heteroduplexes by employing phosphate–zirconium–carboxylate coordination chemistry. Next, the attached hematin molecules acted as catalyst in accelerating the reduction of silver ions in the presence of catechol, leading to the in situ deposition of silver particles onto the electrode. Finally, the deposited silver particles were electrochemically stripped into KCl solution and measured by square wave voltammetry (SWV). Under optimal conditions, the hematin-based electrochemical DNA biosensor presented a good linear relationship between the stripping peak currents and logarithm of single-stranded DNA (ssDNA) concentrations in the range from 0.1 fM to 0.1 nM with a low detection limit of 62.41 aM, and it rendered satisfactory analytical performance for the determination of ssDNA in serum samples. Furthermore, it exhibited good reproducibility and stability, meanwhile, it also showed excellent specificity toward single-nucleotide polymorphism (SNP). Therefore, the hematin-based signal amplification approach has great potential in clinical applications and is also suitable for quantification of biomarkers at ultralow level.Biosensors & Bioelectronics 01/2015; 63:269–275. DOI:10.1016/j.bios.2014.07.034 · 6.45 Impact Factor
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ABSTRACT: A novel colorimetric assay method based on enzyme-induced metallization has been proposed for detection of alkaline phosphatase (ALP), and it was further applied to high sensitive detection of avian influenza virus particles coupled with immunomagnetic separation. The enzyme-induced metallization-based color change strategy combined the amplification of the enzymatic reaction with the unique optical properties of metal nanoparticles (NPs), which could lead to a great enhancement in optical signal. The detection limit for ALP detection was 0.6 amol/50 μL which was 4-6 orders of magnitude more sensitive than other metal NP-based colorimetric method. Moreover, this technique was successfully employed to colorimetric viral immunosensor which could be applied to complex samples without complicated sample pretreatment and sophisticated instruments, and a detection limit as low as 17.5 pg mL-1 was achieved. This work not only provides a simple and sensitive sensing approach for ALP and virus detection, but also offers an effective signal enhancement strategy for development of high sensitive non-aggregation metal NP-based colorimetric assay method.Analytical Chemistry 01/2014; 86(5). DOI:10.1021/ac404177c · 5.83 Impact Factor