Semiempirical Model for the Ion Impact Ionization of Complex Biological Media

Vera, Pablo de; García-Molina, Rafael; Abril, Isabel; Solov’yov, Andrey V.

doi:10.1103/physrevlett.110.148104

Cited by 82 publications

(148 citation statements)

References 31 publications

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“…Our present results of ionization potential are compared with available previous work for dry DNA (I= 81.02 eV) [8] good agreement is achieved in previous work [16]. [25] 75 [9] 77.01 PMMA 68.37 [9] 74 [9] 79.55 H2O 72.5 [9] 75 [9] 76.32…”

Section: Resultssupporting

confidence: 77%

Proton Impact of Bimolecular Targets

Khalaf¹,

Ahmad²,

Al-Ani³

2017

Journal of Asian Scientific Research

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Article HistoryFor a better control and understanding of the effects of radiation damage in living tissues by using the irradiation of biological systems by energetic ion beams have multiple applications in medical physics and space radiation health, such as hadron therapy for cancer treatment and it is necessary to advance an accurate description of the energy loss from the ion beam to the target. In the present work the dielectric formalism like Drude has been used to calculate the probability for an energetic proton and to produce electronic excitations in five targets of high biological interest, namely, liquid water, DNA, PMMA, Adenine and Guanine. Also, the effects of ionization fraction on the mean excitation energy, average energy and Inelastic mean free path studied taking in to consideration electronic excitation in the target. Good agreement achieved with previous work. Contribution/ Originality:This study document an empirical method of obtaining the energy loss function which is the key quantity to study the energy deposited in targets of biological interest by swift projectiles such as protons, so it contains all the information about the electron excitation spectrum of the target.,. The model used through (ELF), namely the extended-Drude ELF. Each term in the sum of Drude-type functions has three adjustable parameters. The parameters a, b and c can be obtained by a fit of Eq. (1) to the ELF for compounds. The energy delivered by a swift proton beam in materials of interest to hadron therapy in 5 compounds is investigated.

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Section: Resultssupporting

confidence: 77%

Proton Impact of Bimolecular Targets

Khalaf¹,

Ahmad²,

Al-Ani³

2017

Journal of Asian Scientific Research

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“…Figure 2 presents the number of electrons per unit length per unit energy produced via the plasmon excitation mechanism by the 1 nm spherical NPs due to 1 MeV proton irradiation. We have also compared the electron production by the NPs and by the equivalent volume of pure water medium [38]. Comparative analysis of the spectra demonstrates that the number of LEE (with the kinetic energy of about a few eV) produced due to the plasmon excitations in the noble metal NPs is about one order of magnitude higher than that by liquid water.…”

Section: Fig 1 (Color Online)mentioning

confidence: 99%

“…Number of electrons per unit length per unit energy produced via the plasmon excitations in the Au, Pt, Ag and Gd NPs irradiated by a 1 MeV proton. Open circles represent the number of electron generated from the equivalent volume of water [38]. Inset: contributions of the surface (dashed) and the volume (dash-dotted) plasmons to the electron yield from the AuNP.…”

Section: Fig 2 (Color Online)mentioning

confidence: 99%

Revealing the Mechanism of the Low-Energy Electron Yield Enhancement from Sensitizing Nanoparticles

2015

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We provide a physical explanation for enhancement of the low-energy electron production by sensitizing nanoparticles due to irradiation by fast ions. It is demonstrated that a significant increase in the number of emitted electrons arises from the collective electron excitations in the nanoparticle. We predict a new mechanism of the yield enhancement due to the plasmon excitations and quantitatively estimate its contribution to the electron production. Revealing the nanoscale mechanism of the electron yield enhancement, we provide an efficient tool for evaluating the yield of emitted electron from various sensitizers. It is shown that the number of low-energy electrons generated by the gold and platinum nanoparticles of a given size exceeds that produced by the equivalent volume of water and by other metallic (e.g., gadolinium) nanoparticles by an order of magnitude. This observation emphasizes the sensitization effect of the noble metal nanoparticles and endorses their application in novel technologies of cancer therapy with ionizing radiation.PACS numbers: 36.40. Gk, Radiotherapy is currently one of the frequently used methods to treat cancer, which is a major health concern of nowadays. However, it has the side effects induced by the radiation in surrounding healthy tissues. One of the promising modern treatment techniques is ion-beam cancer therapy [1][2][3]. It allows one to deliver a higher dose to the target region, as compared to conventional photon therapy, and also to minimize the exposure of healthy tissue to radiation [1]. Approaches that enhance radiosensitivity within tumors relative to normal tissues have the potential to become advantageous radiotherapies. A search for such approaches is within the scope of several ongoing multidisciplinary projects [4,5].Metal nanoparticles (NPs) were proposed recently to act as sensitizers in cancer treatments with ionizing radiation [6][7][8]. Injection of such nanoagents into a tumor can increase relative biological effectiveness of ionizing radiation. It is defined as a ratio of the dose delivered by photons to that by a different radiation modality, leading to the same biological effects such as the probability of an irradiated cell death. During the past years, application of gold NPs acting as dose enhancers, in combination with photons, revealed an increase of cancer cell killing [9][10][11], while an advantage of using NPs in ion-beam cancer therapy is still to be thoroughly substantiated.It is currently acknowledged [3,[12][13][14]] that a substantial portion of biodamage by incident ions is related to the secondary electrons and free radicals produced due to ionization of the medium by the projectiles. Refs. [15][16][17] have explored the possibility of the low-energy electrons (LEE), having the kinetic energy from a few eV to several tens of eV, to be important agents of biodamage.In this Letter, we reveal the physical mechanism of enhancement of the LEE production by sensitizing (noble metal, in particular) NPs. We demonstrate that a significant inc...

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“…Solid and dashed blue curves represent the results obtained recently within the dielectric formalism [80,81]. This approach is based on the experimental measurements of the energy-loss function of the target medium, Im[−1/ǫ(ω, q)], where ǫ(ω, q) is the complex dielectric function, with ω and q being the energy and the momentum transferred to the electronic excitation, respectively.…”

Section: Electron Production Via the Plasmon Excitation Mechanismmentioning

confidence: 99%

“…Figure 10 shows the relative enhancement of the electron yield from the Au 32 cluster as compared to pure water. The data for the gold nanoparticle are normalized to the spectrum for liquid water [81]. The solid line shows the contribution of the plasmon excitations to the electron yield, while the dashed line presents the contribution from the atomic 5d giant resonance, estimated using Eq.…”

Section: Contribution Of Individual Atomic Excitations To Electronmentioning

confidence: 99%

Electron Production by Sensitizing Gold Nanoparticles Irradiated by Fast Ions

2014

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The yield of electrons generated by gold nanoparticles due to irradiation by fast charged projectiles is estimated. The results of calculations are compared to those obtained for pure water medium. It is demonstrated that a significant increase in the number of emitted electrons arises from collective electron excitations in the nanoparticle. The dominating enhancement mechanisms are related to the formation of (i) plasmons excited in a whole nanoparticle, and (ii) atomic giant resonances due to excitation of d electrons in individual atoms. Decay of the collective electron excitations in a nanoparticle embedded in a biological medium thus represents an important mechanism of the low-energy electron production. Parameters of the utilized model approach are justified through the calculation of the photoabsorption spectra of several gold nanoparticles, performed by means of time-dependent density-functional theory.

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Semiempirical Model for the Ion Impact Ionization of Complex Biological Media

Cited by 82 publications

References 31 publications

Proton Impact of Bimolecular Targets

Proton Impact of Bimolecular Targets

Revealing the Mechanism of the Low-Energy Electron Yield Enhancement from Sensitizing Nanoparticles

Electron Production by Sensitizing Gold Nanoparticles Irradiated by Fast Ions

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