Immobilization of oligo DNA strands on TEMPO-oxidized pulp fibers and evaluation of duplex formation

Paper fiber functionalization by modification with DNA molecules expands the applicability and specificity of paper-substrate analytical devices such as microfluidic paper-based analytical devices (µPADs). In this study, a simple amide condensation reaction was performed on 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized pulp fibers to covalently immobilize oligo DNA chains. The fluorescently labeled DNA with confocal laser scanning microscopy, revealed DNA immobilization on the pulp fiber surface and inside the pulp fiber wall. This immobilized DNA sequence-selectively recognized the complementary strand at concentrations of 10 −8 M and above. This DNA duplex formation was also explored in terms of the negative charges on the pulp surface. With greater concentrations of carboxyl groups on the pulp material, DNA duplex formation efficiency was lowered. This is proposed to be due to the negatively charged surface imposing a repulsive electrostatic interaction with the negatively charged DNA. In addition, duplex formation and melting on the pulp surface was shown to be temperature-dependent and reversible. Graphical abstract