DNA crosslinked alginate hydrogels: Characterization, microparticle development and applications in forensic science

DNA-based hydrogels are attractive materials due to the integration of highly specific DNA sequences that can perform targeted functions for multiple fields. In this work we present a suite of materials with covalently bound ssDNA to an alginate-based hydrogel for targeted forensic applications. These crosslinked materials not only promote a more stable 3D polymeric network, but also achieve localization of functional ssDNA, a more desirable feature compared to previous DNA encapsulated versions. Specifically, dual amine terminated ssDNA (N-DNA-N) of three different concentrations was bound to alginate using carbodiimide chemistry. Rheological characterization showed that each DNA-crosslinked material forms similar structures, but the higher DNA concentration behaved like a dynamic viscoelastic material. FTIR analysis confirmed the formation of amide bonds, indicative of successful crosslinking between the N-DNA-N and alginate. SEM visualization also showed that each material had distinct topographies, where the covalent crosslinked alginate-DNA materials had more ordered particles and networked structures. We also investigated ssDNA with three different amine functionalities to understand the amine reactivity, which revealed that the N-DNA-N attaches primarily from the terminal primary amines on the DNA strands. From this, microparticles (MPs) using the DNA-crosslinked materials were developed, and the particle morphology and sizes were measured. It was determined that MPs made using DNA-crosslinked materials had larger particle diameters compared to the non-DNA controls, which is ideal for the generation of white blood cell (WBC) mimetics in forensic materials. In addition, these MPs could be successfully processed in a relevant forensic scenario through extraction, amplification, and genotyping, demonstrating the functionality of these materials to forensic blood simulants.