Scalable purification of single stranded DNA scaffolds for
biomanufacturing DNA-origami nanostructures: exploring anion-exchange
and multimodal chromatography
Abstract
DNA-origami biomanufacturing relies in many cases on the use of
asymmetric PCR (aPCR) to generate 500-3500 base, object-specific,
single-stranded DNA (ssDNA) scaffolds. Each scaffold is usually purified
by agarose gel extraction, a technique that is laborious, limited, not
scalable, presents low recovery yields and a low-quality product.
Alternatively, we present a chromatography-based method to purify ssDNA
scaffolds from aPCR mixtures, which can be used in the context of
DNA-origami techniques. aPCR was performed to generate single and
double-stranded DNA (dsDNA) from the M13mp18 genome. To isolate the
target ssDNA from dsDNA and other PCR impurities, anion-exchange
(Q-ligand) and multimodal chromatography (CaptoTM adhere ImpRes) were
explored using stepwise gradients with increasing NaCl concentrations.
In anion exchange chromatography, the less-charged ssDNA eluted before
the dsDNA. In multimodal chromatography, however, the elution pattern
was reversed, highlighting the importance played by hydrophobicity. In
either case, collected ssDNA-containing fractions were homogeneous and
impurity free. Finally, 8.4 μg of a 1000-nt ssDNA fragment were purified
and used alongside with site-specific short oligonucleotides (staples)
to assemble 63-bp edge length tetrahedrons. Gel electrophoresis showed
high assembly yield and purity, whereas fluorescence correlation
spectroscopy confirmed that the tetrahedrons had a diffusion coefficient
(26.7 μm2 s-1) consistent with the
expected size (20 nm).