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Issue 4, 2015
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Imaging and spectroscopic comparison of multi-step methods to form DNA arrays based on the biotin–streptavidin system

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Abstract

Three multi-step multi-molecular approaches using the biotin–streptavidin system to contact-print DNA arrays on SiO2 surfaces modified with (3-glycidoxypropyl)trimethoxysilane are examined after each deposition/reaction step by atomic force microscopy, X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry. Surface modification involves the spotting of preformed conjugates of biotinylated oligonucleotides with streptavidin onto surfaces coated with biotinylated bovine serum albumin b-BSA (approach I) or the spotting of biotinylated oligonucleotides onto a streptavidin coating, the latter prepared through a reaction with immobilized b-BSA (approach II) or direct adsorption (approach III). AFM micrographs, quantified by autocorrelation and height histogram parameters (e.g. roughness), reveal uniform coverage after each modification step with distinct nanostructures after the reaction of biotinylated BSA with streptavidin or of a streptavidin conjugate with biotinylated oligonucleotides. XPS relates the immobilization of biomolecules with covalent binding to the epoxy-silanized surface. Protein coverage, estimated from photoelectron attenuation, shows that regarding streptavidin the highest and the lowest immobilization efficiency is achieved by following approaches I and III, respectively, as confirmed by TOF-SIMS microanalysis. The size of the DNA spot reflects the contact radius of the printed droplet and increases with protein coverage (and roughness) prior to the spotting, as epoxy-silanized surfaces are hardly hydrophilic. Representative TOF-SIMS images show sub-millimeter spots: uniform for approach I, doughnut-like (with a small non-zero minimum) for approach II, both with coffee-rings or peak-shaped for approach III. Spot features, originating from pinned contact lines and DNA surface binding and revealed by complementary molecular distributions (all material, DNA, streptavidin, BSA, epoxy, SiO2), indicate two modes of droplet evaporation depending on the details of each applied approach.

Graphical abstract: Imaging and spectroscopic comparison of multi-step methods to form DNA arrays based on the biotin–streptavidin system

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Publication details

The article was received on 22 May 2014, accepted on 09 Dec 2014 and first published on 09 Dec 2014


Article type: Paper
DOI: 10.1039/C4AN00929K
Citation: Analyst, 2015,140, 1127-1139
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    Imaging and spectroscopic comparison of multi-step methods to form DNA arrays based on the biotin–streptavidin system

    K. Gajos, P. Petrou, A. Budkowski, K. Awsiuk, A. Bernasik, K. Misiakos, J. Rysz, I. Raptis and S. Kakabakos, Analyst, 2015, 140, 1127
    DOI: 10.1039/C4AN00929K

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