Structural DNA nanotechnology is a rational process for the construction of new bionanostructures. One of the important physical properties of bionanostructures is their optical behavior. The optical evaluation of DNA molecules is normally performed in the ultraviolet range for quantification measurements. Here, we have fabricated four geometrically different DNA nanostructures - a ribbon, a tube, and lattices without and with hairpin loops - based on a simple duplex DNA with crossover junctions. Then we evaluated the spectroscopic properties of DNA nanostructures for quantitative classification and differentiation of DNA samples in visible light instead of ultraviolet light. In order to achieve a good spectroscopic measurement, a polymer optical fiber with a micro cuvette-based spectroscopic system was implemented for good sensitivity. (C) 2011 Elsevier B.V. All rights reserved.