Abstract
In this work, an economical and easy-to-use microcapsule array fabricated by ice printing technique has been realized for ultrasensitive fluorescence quantification of copper ions employing functional nucleic acid strategy. With ice printing, the detection reagents are sealed by polystyrene (PS) film isolation and photopolymer, which guarantees a stable and contamination-free environment for functional nucleic acid reaction. Our microcapsule arrays have shown long-term stability (20 days) under −20 °C storage in frozen form before use. During the Cu2+ on-site detection, 1 μL sample is simply injected into the thawy microcapsule by a microliter syringe under room temperature, and after 20 minutes the fluorescence result can be obtained by an LED transilluminator. This method can realize the detection limit to 100 nM (100 fmol/μL) with high specificity.
Highlights
~20 μM) is the maximum of copper ion in drinking water
The detailed fabrication procedure can be concluded as five steps. (1) 10 μL reaction solution composing of Cu-substrate, Cu-enzyme, ascorbate and corresponding buffer is printed onto a certain spot of the polyethylene terephthalate (PET) substrate determined by 3D platform
When the controller sends the printing command, the nozzle starts to print the reaction solution from about 2 mm above the PET substrate and moves upwards slowly to ensure the reaction solution continuously falling onto the droplet surface
Summary
~20 μM) is the maximum of copper ion in drinking water. low-cost on-site chips which can offer people quantitative real-time detection of copper ions with identifiable signals are clearly imminent. The previously developed microcapsule array chip is not suitable in this assay, because when the microcapsules melt for application the residual of photo-polymerization may intrude into liquid-phase reaction solution from solidified photopolymer damaging the bioactive DNA-based reagents, and interfere the quantification sensitivity and accuracy. To deal with this issue, we improve the ice printing fabrication process with an addition of polystyrene (PS) film forming procedure, which isolates the fragile reagents from photopolymer. The PS film isolating the reaction solution and photopolymer efficiently protects DNAzyme system contributing to the realization of on-chip ultrasensitive fluorescence quantification of copper ions
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