Physical characterization of cytochrome c- and vitamin B₁₂-doped DNA thin films

DNA can be useful in the field of biological and physical sciences due to its unique features, e.g., molecular recognition and self-assembly. Here, we fabricated cytochrome C (Cy)- and vitamin B₁₂ (VB)-doped DNA thin films via a drop-casting method and explored their chemical and optoelectronic characteristics. Fourier transform infrared (FTIR), Raman, absorption, photoluminescence (PL), and electrical measurements were used to estimate critical concentrations of Cy and VB (where extremes of measured quantities occurred) in a fixed DNA concentration. These measurements focused on chemical interactions, binding modes, energy transfer mechanism, and electrical characteristics of the Cy- and VB-doped DNA thin films. We noticed that FTIR absorbance and Raman (UV–Vis) band intensities were increased (decreased), with an increase in the Cy concentration of up to 1.5 μM (= critical concentration of Cy) and a VB concentration of up to 3 mM (= critical concentration of VB) in DNA thin films. Significant band intensity changes and band position shifts of FTIR, Raman, and UV–Vis spectra were observed by varying concentrations of Cy and VB in DNA thin films. These changes provided the evidence of interaction between DNA and Cy (VB) via electrostatic bonding and intercalation interactions. The PL spectra exhibited strong red emissions at 612 nm. The changes of PL intensities revealed that effective energy transfer occurred between the VB and DNA up to critical concentration of VB, due to proper binding of VB. Finally, the current extremes for Cy- and VB-doped DNA thin films were observed at 1.5 μM of Cy and 3 mM of VB, respectively, which agreed well with the other characteristics.