Unravelling the nature of the α-keratin EPR signal: an ab initio study.

Fingernail as a biodosimetry material, analyzed by the EPR technique, has attracted great attention in several experimental studies. One of the most challenging issues that should be addressed is additional signals, masking the radiation-induced signals (RIS) in EPR dosimetry analyses. In this work, we conducted a theoretical study of the RIS radicals and mechanisms to propose robust methods to distinguish the original signal from the irradiated nails' unwanted noise. Also, the proposed approach includes procedures to improve the accuracy of the dosimetry measurements. In our research, three categories of cysteine, DOPA and cystine radicals were considered due to their dominant abundance during the α-keratin reduction-oxidation processes. The SOMO-HOMO inversion is observed while investigating the electronic structure in these quasi-closed-shell systems. Furthermore, we demonstrated that the SOMO-HOMO gap is proportional to the spin localization. Indeed, new peaks in the EPR signals are not observed when the amino acid sequences are different. Moreover, the studied structures' neighborhood effect merely leads to a small change in the peak broadening of the EPR signals. On-the-fly magnetic parameter calculations were used to evaluate the system dynamics' effect on the broadening of the EPR signals in a molecular dynamics simulation. Comparing the calculated parameters with computational and experimental results in other studies helps assign low dose peaks to the corresponding tyrosyl phenoxyl radical.

A New Optical Method for Online Monitoring of the Light Dose and Dose Profile in Photodynamic Therapy.

BACKGROUND AND OBJECTIVES: Photodynamic therapy (PDT) has gained widespread popularity in the last decades because of its distinctive advantages over the other commonly used cancer treatments. PDT dosimetry is a crucial factor in achieving a good optimization of PDT treatment planning. PDT dosimetry is a complex task since light dose as well as photosensitizer and oxygen concentrations in tissue need to be measured (ideally continuously) to be able to fully characterize the biological response. Light dose in PDT is routinely measured by the optical fibers that provide dose data at a limited number of discrete points and are not able to capture spatial dose profiles. The objective of this study is to propose and develop a new optical method for online monitoring of the dose profile data for PDT. STUDY DESIGN/MATERIALS AND METHODS: Using the digital holography technique, first, the general sketch of an experimental setup for PDT light dosimetry is provided. The theory behind the proposed method for using the experimental setup in PDT light dosimetry is fully described, and its limits of validity are determined. In a proof of principle study, the ability of the method for online monitoring of the absorbed light dose profile in PDT is evaluated by a simple experimental setup. RESULTS: The experimental results confirm the usefulness of the proposed method in providing continuous online dose profiles. The absorbed light dose profiles from an infrared light source in a quartz cell containing water are measured and shown. The depth-dose curves are extracted and it is shown that how these dosimetric data can be used for assisting the physicians in determining the appropriate spatiotemporal characteristics for treating the infected tissues and solid tumors with the required light dose amounts. A conversion relation is also derived for transforming the measured light dose with the proposed method to the most frequently used dose values by PDT practitioners, in terms of light power per square area. CONCLUSIONS: There is no restriction in using the method with other commonly used light sources in PDT, like light-emitting diodes and filtered lamps, with different wavelengths in visible or infrared regions of the spectrum. More complex experimental setups can be used in future studies to study the role of accumulated photosensitizers in malignant tissues. The proposed method in this study can also be used for light dose monitoring in other biomedical applications, where light is used for treating special diseases, and patients must receive sufficient amounts of light dose. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Synthesis, characterization and in vivo evaluation of [(62)Zn]-benzo-δ-sultam complex as a possible pet imaging agent.

OBJECTIVE: The development of a new tracer based on the cyclic sulfonamides (sultams) was investigated. METHODS: 3-(Methoxy-phenyl-methyl)-1,6-dimethyl-1H benzo[c][1,2] thiazine 2,2-dioxide (benzo-δ-sultam) was synthesized and characterized by elemental analysis, FT-IR spectroscopy and single crystal X-ray structure determination. The prepared cyclic sulfonamide was labeled with non-commercial (62)Zn radioisotope for fast in vivo targeting and Coincidence imaging purposes (radiochemical purity 97 % ITLC, 96 % HPLC, specific activity 20-23 GBq/mmol). In vivo biodistribution of the final complex was investigated in Sprague Dawley(®) rats bearing fibro sarcoma tumor after 2, 4 and 8 h post injection and compared with free Zn(+2) cation. RESULTS: Using instant paper chromatography method, the physicochemical properties of labeled compounds were found sufficiently stable in organic phases, e.g. a human serum, to be reliably used in bioapplications. CONCLUSIONS: The complex exhibited a rapid as well as high tumor uptake (tumor to blood ratio 4.38 and tumor to muscle ratio 9.63) resulting in an efficient tumor targeting agent.