Oligomer Length Defines the Self-Assembly of Single-Stranded DNA-Collagen Complex Fibers

Self-assembled VEGF-R2 targeting DNA aptamer-collagen fibers stimulate an angiogenic-like endothelial cell phenotype

Vascularization of engineered tissue is one of the hallmark challenges of tissue engineering. Leveraging self-assembled nucleic acid-collagen complexes (NACCs), we mixed a VEGF-R2 targeting aptamer or its receptor agonist divalent assembly with type I collagen to assemble NACC microfibers. Human umbilical vein endothelial cells (HUVECs) quickly remodeled these fibers into tubulogenic-like structures over 48 h. Moreover, NACCs made with the receptor agonist divalent aptamer assembly promoted enhanced expression of von Willebrand factor (vWF), angiopoietin-2 (ANGPT-2), and matrix metalloproteinase-2 (MMP-2) by HUVECs as measured by either immunocytochemistry or ELISA. The findings suggest, endothelial cell phenotype was directed by both biochemical cues afforded by the agonist behavior of the divalent aptamer assembly as well as by the biophysical cues afforded by the fibrous topography. Collectively, these results support the development of an angiogenic endothelial cell phenotype stimulated by the VEGF-R2 agonist NACC fibers. Thus, the combination of engineered DNA aptamer nanotechnology and DNA-collagen complexation phenomena is a promising biofunctional natural scaffold material system for tissue engineering and regenerative medicine applications.

Mineralized DNA-collagen complex-based biomaterials for bone tissue engineering

DNA is a highly polyanionic biomolecule that complexes with both collagen and hydroxyapatite. By combining these complexes, we synthesized nucleic-acid collagen complexes (NACC) mineralized with hydroxyapatite. The composite complexes were made using a short, monodisperse single-stranded DNA, type I collagen, and mineralizing medium. They rapidly self-assembled into both mineralized NACC microfibers and 3D NACC gels. At the nanoscale, these complexes are hierarchical, interwoven, curly nanofibrils resembling native extracellular matrix, which mineralized an interpenetrating nanocrystalline hydroxyapatite phase. Mineralization was able to be done either before or after NACC formation enabling temporal control of the process. In response to the NACC material, primary human osteoblasts took on an osteocyte-like morphology. Moreover, the cells agglomerated and remodeled the NACC gels into densified, tissue-like structures within 3 days. NACC fibers and gels have promise not only as osteoconductive coatings and scaffolds, but as coatings and scaffolds for any tissue using this new form of naturally-derived biomaterials.