Variable collagen-DNA complex formation in vitro as assessed by optical anisotropy and infrared microspectroscopy.

Optical anisotropy properties and infrared spectra of collagen and DNA as individual entities have been widely described. However, they have not been studied in collagen-DNA complex biofilms. We investigated whether collagen type I and DNA birefringence evaluated using polarization microscopy, and the vibrational patterns of their chemical groups identified in Fourier transform-infrared (FT-IR) spectra are retained in collagen-DNA complexes. Collagen gel rods extruded into a DNA saline solution and films dried from drops using mixtures of a 10-μL (14 μg) collagen solution and a 50-μL (305 μg) DNA solution and of a 50-μL (70 μg) collagen solution and a 10-μL (61 μg) DNA solution were used. Changes in the collagen fibers' stereoarrangement occurred in the gel rods interacting with the DNA. Even when the DNA concentration (305 μg) was significantly higher than the collagen concentration (14 μg) and the DNA played the main role in establishing the overall oriented geometry in the collagen-DNA films (intertwisted fibrillary structure and negative birefringence), some collagen markers were present in the FT-IR spectra of the complex. When collagen and DNA concentrations were similar, DNA denaturation may occur. Present observations suggest formation of collagen-DNA complexes even if highly organized collagen macromolecules are offered to DNA.