Different Mechanisms of DNA Radiosensitization by 8-Bromoadenosine and 2′-Deoxy-2′-fluorocytidine Observed on DNA Origami Nanoframe Supports

Abstract

DNA origami nanoframes with two parallel DNA sequences are used to evaluate the effect of nucleoside substituents on radiation-induced DNA damage. Double strand breaks (DSB) of DNA are counted using atomic force microscopy (AFM), and total number of lesions is evaluated using real-time polymerase chain reaction (RT-PCR). Enhanced AT or GC content does not increase the number of DNA strand breaks. Incorporation of 8bromoadenosine results in the highest enhancement in total number of lesions; however, the highest enhancement in DSB is observed for 2′-deoxy-2′-fluorocytidine, indicating different mechanisms of radiosensitization by nucleoside analogues with the halogen substituent on base or sugar moieties, respectively. "Bystander" effects are observed, when the number of DSB in a sequence is enhanced by a substituent in the parallel DNA sequence. The present approach eliminates limitations of previously developed methods and motivates detailed studies of poorly understood conformation or bystander effects in radiation induced damage to DNA.

Electron-Induced Damage by UV Photolysis of DNA Attached to Gold Nanoparticles

“…5,26,27 Halogenated bases containing F, Br, and I are more efficient than natural DNA bases toward capturing and undergoing DEA with hot electrons, much like their reactions with solvated electrons. 28,29 The above interesting results elicit further investigation of the effects of SPR on DNA.…”

“…SPR in both AuNPs and AgNPs was activated by 530 nm of light from a laser. They showed that transfer of hot electrons to 8-bromoadenine, 8-bromoguanine, and 5-bromouracil imbedded within double-stranded DNA resulted in dissociative electron attachment (DEA) at the C–Br bond leading to halogen extrusion as inferred by surface-enhanced Raman spectroscopy. ,, Halogenated bases containing F, Br, and I are more efficient than natural DNA bases toward capturing and undergoing DEA with hot electrons, much like their reactions with solvated electrons. , The above interesting results elicit further investigation of the effects of SPR on DNA.…”

Lab-on-a-DNA origami: nanoengineered single-molecule platforms

“…The absolute quantification of radiation-induced DNA strand breaks with other methods is very challenging, and another advantage of the use of DNA origami platforms is the possibility of comparing two different DNA sequences in a single irradiation experiment. A complementary approach has been developed by Sala et al 95 using a DNA origami nanoframe to quantify double strand breaks in DNA that are spanned between two sides of the frame and exposed to different types of radiation, as illustrated in Fig. 8A .…”

“…Irradiation with 16 MeV electrons does not only lead to enhanced strand breakage in the modified DNA double strand but also in a larger number of strand breaks in the neighboring, unmodified control strand. 95 This is probably due to a generation of secondary reactive products from 8-bromoadenine that can also damage the surrounding. Such effects can be very well studied using DNA origami platforms and are important for developing efficient radiosensitizers for radiation therapy and need further fundamental investigations in the future.…”

Light-induced damage to DNA origami nanostructures in the 193 nm–310 nm range

“…However, such experiments are size-limited to molecular sub-units of DNA such as nucleobases or nucleotides [2,3]. To overcome these limitations, we recently implemented DNA origami in our laboratories as a versatile tool to study precisely defined DNA segments [4]. * Authors to whom any correspondence should be addressed.…”