Ultraviolet Absorption and Circular Dichroism Spectroscopy of Nonviral Gene Delivery Complexes

A powerful, yet often underutilized tool available to probe the structure of macromolecules is absorption spectroscopy. The first of the various spectroscopic techniques to be widely developed, data from absorption spectroscopy is commonly viewed as low in overall information content compared to modern forms of X-ray diffraction, nuclear magnetic resonance, fourier-transformed infrared, and circular dichroism (CD) spectroscopies. With the development of diode array spectrophotometers and analysis software capable of quickly and simply producing high-definition derivative spectra, however, ultraviolet-visible spectroscopy remains a useful analytical technique, especially when applied to nucleic acids. This approach offers significant advantages in terms of flexibility, accuracy, speed, low expense, and instrumental availability. Thus, the technique can be productively applied to the analysis of nonviral gene delivery vectors, focusing primarily on the oligonucleotide component. Here are presented applications of derivative absorbance spectroscopy to the analysis of nucleic acid-cationic polymer complexes. Additionally, a brief overview of the theory, instrumentation, and general applications of zero and second-derivative absorption spectroscopy is presented, followed by a discussion of the complementary absorptive technique of circular dichroism in the same context.