Digital Quantification of Chemical Oligonucleotide Synthesis Errors

Abstract

Chemically synthesized oligonucleotides are vital to most nucleic acids-based technologies and several applications are sensitive to oligonucleotide sequence errors. However, it is challenging to identify and quantify the types and amount of errors in synthetic oligonucleotides. We applied a digital sequencing approach using unique molecular identifiers to quantify errors in chemically synthesized oligonucleotides from multiple manufacturers with different synthesis strategies, purity grades, batches, and sequence context. We detected both deletions and substitutions in chemical oligonucleotide synthesis, but deletions were 7 times more common. We found that 97.2% of all analyzed oligonucleotide molecules were intact across all manufacturers and purity grades, although the number of oligonucleotide molecules with deletions ranged between 0.2% and 11.7% for different types. Different batches of otherwise identical oligonucleotide types also varied significantly, and batch effect can impact oligonucleotide quality more than purification. We observed a bias of increased deletion rates in chemically synthesized oligonucleotides toward the 5'-end for 1 out of 2 sequence configurations. We also demonstrated that the performance of sequencing assays depends on oligonucleotide quality. Our data demonstrate that manufacturer, synthesis strategy, purity, batch, and sequence context all contribute to errors in chemically synthesized oligonucleotides and need to be considered when choosing and evaluating oligonucleotides. High-performance oligonucleotides are essential in numerous molecular applications, including clinical diagnostics.