Dynamic analysis of DNA nanoparticle immobilization to model biomaterial substrates using combinatorial spectroscopic ellipsometry and quartz crystal microbalance with dissipation

Gene expression within cells can be altered through gene delivery approaches, which have tremendous potential for gene therapy, tissue engineering, and diagnostics. Substrate-mediated gene delivery describes the delivery of plasmid DNA or DNA complexed with nonviral vectors to cells from a surface, with the DNA immobilized to a substrate through specific or nonspecific interactions. In this work, DNA-nanoparticle (DNA–NP) adsorption to substrates is evaluated using combinatorial, in situ spectroscopic ellipsometry and quartz crystal microbalance with dissipation (SE/QCM-D), to evaluate the basic dynamic processes involved in the adsorption and immobilization of DNA–NP complexes to substrates. The concentration of DNA–NP solutions influences the adsorbed DNA–NP surface mass, which increases by a factor of approximately 6 (detected by SE) and approximately 4.5-fold (detected by QCM-D), as the DNA concentration increases from 1.5 μg/mL to 15 μg/mL, with an increase in layer porosity. In addition, SE/QCM-D analysis indicates that DNA–NP adsorption rates, surface coverage densities, and volume fractions are dependent on the type of substrate: gold (Au) and silicon dioxide substrates, proteincoated and uncoated substrates, and surfaces modified with alkanethiol self assembled monolayers (SAMs). These studies also demonstrate that the influence of an adsorbed protein layer on resulting DNA–NP immobilization efficiency is substrate dependent. For example, Au surfaces coated with fetal bovine serum (FBS) resulted in two-fold greater mass of adsorbed DNA–NPs, compared to DNA–NP adsorption to FBS-coated SAM substrates. This investigation offers insights into dynamic DNA–NP surface adsorption processes, characteristics of the immobilized DNA–NP layer, and demonstrates substrate-dependent DNA–NP adsorption.