Various techniques and methods have been emerged recently as prompt response to the COVID-19 treatment at different hospitals and research laboratories [1–5]. Among them is the use of irradiation (γ-rays), heat and UV treatment which in turn inactivate the virus effect by damaging its viral constitutes such as membrane surface RNA and DNA [1–7]. High doses of γ- or X-rays in the range of several kGy (i.e., 3–7 kGy) for different viruses including the current COVID-19, caused by the severe acute respiratory syndrome coronavirus (SARS-COV-2). The later was declared in March 2019 by the WHO as a globe pandemic. Since the early discovery of the disease around 100 millions confirmed cases have been infected and more 2 millions have passed away according to WHO recent reports at the time of writing this report. Sine high doses of 60Co γ- or X-ray can raise a destruction and loss to the lung interfacial molecules this has limit the use of this technique. On the other hand, low-energy electrons (200 keV) have replaced it for viral inactivation . Such low-energy electron beam was sufficient to stop viral growth and keep antigenic properties of the human cell membrane lung . Also, Corry et al.  has proposed that antioxidant Nacetyl-cysteine (NAC) could be used orally or within medical centers along with higher dose radiation in a clinical trial involved in COVID-19 . The research group of Mehanna et al. has adviced the use of radiation therapy as an alternative to surgery for patients in various region of the world as a way to delay surgical operations which has been adapted rapidly in medical and radiation oncology .
In the past three decades, many research works have been extensively performed on various materials to study the absorption and transmission of X and γ-rays in various important biological samples [8–13]. These experimental and theoretical studies have been emerged because it is essential to imitate their functions in living cells. Most of these "in vitro" experiments have been performed in order to realize what is happing at cell level when X- or γ-ray interacts with tissues or cell membrane . The photon energy ranged from 5 keV to a few MeV is of great importance in medical, biological or agricultural applications . However, for biologically-important elements of low Z value, the attenuation coefficients measurement studies indicated that the radiations interact predominantly by the Compton effect and photoelectric effect in the energy range E∈ [0.2,1.5] MeV (see  and the references therein). The tabulation of X-ray mass attenuation coefficients and interaction cross section coefficients for several elements, including biologically essential elements (i.e., H, C, N and O) has been undergone several developments and updates and is now available as Web-based program accessible to all scientists around the globe. This version has also undergone further development to run under the Windows operating system platform which is now called WinXCom . For the detailed and successive developments of the theoretical and experimental investigations of photon-matter interactions which have been implemented within this platform . Also, from biological and medical viewpoint γ-ray buildup factor is of great importance because of photon flux distribution and radiation dose received and buildup within the biologically essential macromolecules such as phospholipids, amino acids, peptides or proteins up to the cells or tissues. Of interest, the recognition how radiation-living matter interaction is cryptic in "buildup factors" . Namely the exposure buildup factor (EBF) and the energy absorption buildup (EABF) factor. The factors are commently evaluated by Geometric Progression fitting procedure [17, 18].
In the following we summarize previous successful contributions which based on the buildup factors that have been carried out from simple chemical elements to more complex biological macromolecules relevant in human health and medicine. The early development of calculating the mass attenuation coefficients or photon interaction cross-sections for simple elements is dated back to the seminal work of Berge and Hubbell . Since then there have been extensive theoretical and experimental research works to determine the buildup factors for complex biological macromolecules such as fatty acids, oils, carbohydrates, polypeptides or proteins and animal or plant tissues which is primarily composed of the life-essential elements H, C, N and O in varying proportions. Dried samples containing these essential elements have been reported by El-Kateb and Abdul-hamid  in the energy E∈ [54,1333] keV. Then one decade latter Sandhu et al.  have investigated a single-chain fatty acids almost in the same energy range. Then, a large body of publications have appeared in literature which is due to the WinXCom software development. This developed-software has allowed Gowda et al.  successfully measured the total attenuation and cross-sections for some sugar and amino acid macromolecules. Also, Manohara and Hanagodimth in couples of independent research reports have determined the effective electron densities and atomic numbers of certain types of amino acids in a broad range of photon energies from a few keV up to 100 GeV. A progressive investigation have also been done by Kurudirek et al.  who reported on the influence of gamma-ray radiation on human tissues by evaluating EBF and EABF. Moreover, the same research group, Kurudirek and Ozdemir  have effort the γ-ray EABF) and EBF for different biological-related molecules when the energy 0.015 < E < 15 MeV for various mpf values. In these inclusive works they have employed the five parameter G-P fitting method to deduct both EABF and EBF for amino acids, single-chain fatty acids and carbohydrates. On the other hand, Kore and Pawar  have measured the effective atomic number (Zeff), electron density (Neff) and mass attenuation coefficients of another class of amino acids which are also essential for the human body.
In the current research report work, we have focused on viral phospholipids and cholesterol the radiation effects and visus inactivation whn exposed to radiation. These molecules are in principle different from the previously investigated single-chain fatty acids with their acyl carbon double bond chains which span the cell membrane. The cell membrane is primarily a complex structure composed of phospholipid, cholesterol molecules and proteins where each of them has its own essential role or function within the cell in higher eukaryotic organisms . The organization of phospholipids into two leaflets (i.e., membrane) in eukaryote cell membrane with a typical separation of 40 nm is vital for cell-interior protection from impaired radiations [9, 26]. It is well established that the viral membrane separate the inner viral genetic materials from external surroundings. Many essentail cell living pathways accumalated at the outer viral membrane which usually prevents the whole cell from external stimuli. One of these sever stimulates is the external radiation effects exerted on the cell either by nature or in the case of medical treatments. In fact, the first barrier X-rays and γ-rays radiations encounter to penetrate into cell-interior, causing a genetic damage in its compartments (e.g., DNA and RNA) is believed to be the cell's outer-leaflet monolayer. The phospholipids investigated in this study are zwitterionic (i.e., neutral) amphiphilic molecules with saturated double bond, containing 12–20 carbon atoms along their hydrophobic chains as depicted in Scheme 1. The headgroups of these lipid molecules possess a dipole moment with zero net charge. This choice of neutral phospholipids is meant to minimize the lipid's headgroups charge effects in the buildup factors calculations performed in this work. On the other hand, cholesterol which influences the conformation order, integrity or heterogeneity of the phospholipids carbon tails and membrane viscosity . it is well known that biological membranes encapsules about 30–50 mol% of cholesterol. Furthermore, cholesterol regulate the membrane bilayer thickness due to membrane-proteins interactions [26, 27]. The molecular structure of the chosen phospholipids exemplified by DMPC and cholesterol is depicted in Scheme 1. The molecular formulas of the phospholipids and cholesterol used in the current report are listed in Table 1 (see supplementary material).