Clinical biochemistry

The use of 5-fluorouracil (5-FU) is associated with multifaceted challenges and poor pharmacokinetics. Accordingly, our study was designed to prepare 5-FU nanogel as a new form of the colon cancer chemotherapeutic drug 5-FU using polyacrylic acid and gelatin hybrid nanogel as efficient drug carriers. Alongside the in vivo chemotherapeutic evaluation, the anti-proliferative and anti-apoptotic efficacy were carried out for 5-FU nanogel against 1,2-dimethylhydrazine (DMH, 20 mg/kg) and γ-radiation (4 Gy)-prompted colon dysplasia in rats compared to 5-FU. The morphology and size of 5-FU nanogel were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS) in addition to cytotoxicity assay. The expression of phosphoinositide-3-kinase (PI3K)/Akt, mammalian target of rapamycin (mTOR); Toll-like receptor2 (TLR2)/nuclear factor kappa B), adenosine monophosphate (AMP)-activated protein kinase (AMPK) and its downstream autophagy-related genes in addition to ap...

We report the effect of the DNA hydration level on damage yields induced by soft X-rays and photoemitted low-energy electrons (LEEs) in thin films of plasmid DNA irradiated in N 2 at atmospheric pressure under different humidity levels. Contrary to a dilute solution of DNA, the number of H 2 O molecules per nucleotide (Γ) in these films can be varied from Γ = 2.5 to ∼33, where Γ ≤ 20 corresponds to layers of hydration and Γ = 33 to an additional bulk-like water layer. Our results indicate that DNA damage induced by LEEs does not increase significantly until the second hydration shell is formed. However, this damage increases dramatically as DNA coverage approaches bulk-like hydration conditions. A number of phenomena are invoked to account for these behaviors, including dissociative electron transfer from water−interface electron traps to DNA bases, quenching of dissociative electron attachment to DNA, and quenching of dissociative electronically excited states of H 2 O in contact with DNA. SECTION: Biophysical Chemistry and Biomolecules T he discovery that low-energy electrons (LEEs, E < 30 eV) can directly damage the DNA molecule with considerable efficiency 1−3 has established that almost all of the secondary electrons (SEs) produced by ionizing radiation can be lethal to the genome. 4 As a result, the new concepts that were developed during the studies of the mechanisms of action of LEEs 1,5 are starting to be applied to the development of new anticancer drugs 6−8 and the modification of clinical protocols. 9−12 Whereas the mechanisms of the direct action of LEEs on biomolecules are now fairly well understood, 4,5 the indirect effect of these electrons in irradiated cells remains unknown, owing essentially to the experimental difficulties associated with the production and observation of LEEs in aqueous media. Direct-type damage results from radiation energy being deposited directly into the DNA, whereas indirect damage occurs when the species created by the interaction of the primary radiation and SEs within the molecular environment surrounding the DNA (e.g., salts, proteins, oxygen and water) react with the molecule. 13,14 SEs with energies below 30 eV (i.e., LEEs) can attach to DNA components and thus form transient negative ions (TNIs) of DNA subunits (a base, sugar, or phosphate group). In this manner, LEEs induce direct damage to DNA, such as single and double strand breaks (SSBs and DSBs) principally via the decay of TNIs into dissociating electronically excited states and dissociative electron attachment (DEA). 4,15 Because cells contain 70−80% water, 16 LEEs also react with water molecules near DNA in the cell nucleus and create reactive species to produce indirect damage. To estimate the relative contribution of the indirect and direct modes of damage of LEEs in cells, experiments were undertaken with thin films of short single DNA strands (i.e., oligonucleotides) embedded into biomolecular environments under ultrahigh vacuum (UHV). The oligonucleotides were embedded into multilayer films of amorphous ice to simulate the water molecules surrounding cellular DNA. 17−19 The presence of water around DNA was found to modify the TNI manifold, the corresponding decay channels, and thus the SSB and DSB yield functions. 20,21 More recently, theoretical studies indicated that the solvation of DNA molecules (i.e., immersion in an environment of polar molecules such as water) could significantly increase their ability to capture electrons with energies near zero or lower via the modification of adiabatic electron affinity of solvated DNA bases in bulk water. 22,23 Owing to recent advances in LEE techniques, 24 we present in this work the first results of a study on the indirect effect of LEEs with liquid water condensed on and within plasmid DNA. The experiments are performed at standard ambient temperature and pressure (SATP) in a N 2 atmosphere under different humidity levels up to solvation. We report the yields of DNA strand breaks induced by soft X-rays. The damage yields for DNA deposited on glass are due to X-rays, whereas those arising from DNA on tantalum (Ta) are due to the interaction of both X-rays and photoemitted LEEs from the metal. Varying the hydration level of DNA, up to a bulk-like water

We report the effect of DNA hydration level on damage yields induced by soft X-rays and photoemitted low energy electrons (LEEs) in thin films of plasmid DNA irradiated in N 2 at atmospheric pressure under different humidity levels. Contrary to a dilute solution of DNA, the number of H 2 O molecules per nucleotide (Γ) in these films can be varied from Γ=2.5 to ~33, where Γ≤20 corresponds to layers of hydration and Γ=33 to an additional bulk-like water layer. Our results indicate that DNA damage induced by LEEs does not increase significantly until the second hydration shell is formed. However, this damage increases dramatically as DNA coverage approaches bulk-like hydration conditions. A number of phenomena are invoked to account for these behaviors including: dissociative electron transfer from water-interface electron traps to *

EFFECT OF GAMMA RADIATION AND LOW ENERGY ELECTRON ON THE DNA FUNCTIONALITY By Saloua Sahbani Program of Radiation Sciences and Biomedical Imaging Thesis submitted to the Faculty of Medicine and Health Sciences for the degree of Doctorate of Philosophy (PhD) in Radiation Sciences and Biomedical Imaging, Faculty of Medicine and Health Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, Canada It is generally accepted that DNA double-strand breaks (DSB) are among the most toxic lesions induced by ionizing radiation (IR). Unrepaired or misrepaired DSB can lead to genomic instability and cell death. It is known that concomitant chemoradiation therapy is one of the most preferred methods for the treatment of certain cancers especially in advanced stage. The yield of DSBs was increased when DNA was irradiated with low energy electron (LEEs). The aims of our study was to reassess the contribution of DSBs and other lesions induced by indirect and direct effect of IR in cell lethality. Th...