Newly emerging nanomaterials promise a major advancement of methods of nuclear and radiative medicine for cancer treatment, as they can be used as carriers of diagnostic or therapeutic radionuclides, contrast agents in nuclear imaging modalities (PET, SPECT) or sensitizers of radiative therapies (X-ray, ion beams, etc.). However, nanotechnology-based approaches have reported a limited success so far due to a lack of suitable functional nanoformulations, which are safe, non-toxic, excretable from the body and have favorable pharmacokinetics for effective accumulation in the tumor. As follows from the results of our on-going research activities, many of the above-stated problems can we solved by the employment of nanomaterials fabricated by clean laser-ablative synthesis. Here, we review our recent data on some promising nanomaterials, prepared by this method, including biodegradable silicon (Si) nanoparticles (NPs), 152Sm-enriched samarium oxide NPs, and elemental bismuth (Bi) NPs, which can be used either as carriers/agents in radionuclide therapy, or sensitizers in radiative diagnostics or therapy. Advantages of proposed approach include exceptional purity and flexibility in synthesizing of NPs of required physico-chemical parameters (controlled size, shape, composition, and surface conditioning of NPs). Advances in laser-ablative fabrication of novel nanomaterials open up avenues for future implementations of nuclear and radiative medicine approaches for safe and efficient theranostics of tumors and metastasis.
Radiation nanomedicine is an emerging field, which utilizes nanoformulations of high-Z elements and nuclear agents to improve therapeutic outcome and to reduce radiation dosage. This field lacks methods for controlled fabrication of biocompatible nanoformulations. Here, we present application of femtosecond laser ablation in liquids to fabricate stable colloidal solutions of ultrapure elemental Bi and isotope-enriched samarium oxide nanoparticles (NPs). The obtained spherical Bi and Sm oxide NPs have controllable size, while Bi NPs have remarkable absorption in the near-IR region. Exempt of any toxic by-products, laser-ablated Bi and Sm oxide NPs present a novel appealing nanoplatform for nuclear and radiotherapies.
Nanotechnology promises a major improvement of efficacy of nuclear medicine by targeted delivery of radioactive agents to tumors, but this approach still needs novel efficient nanoformulations to maximize diagnostic and therapeutic functions. Here, we present a two-step method of laser ablation and fragmentation in water to produce non-radioactive 152Sm-enriched samarium oxide nanoparticles (Sm NPs), which can be converted to radioactive form of 153Sm beta-emitters by neutron capture reaction. We found that laser ablation in deionized water leads to the formation of NPs having diverse morphology and broad size dispersion. To improve size characteristics of formed NPs, we applied additional femtosecond laser fragmentation step, which made possible a good control of mean NPs size under a drastic narrowing of size dispersion, and the spherical shape of formed NPs. Obtained colloidal solutions of Sm NPs were stable for several weeks after the synthesis. The formed NPs present a very promising object for nuclear nanomedicine.
A collaboration in education between the oldest and one of the most comprehensive Optics schools in U.S., the Institute of Optics (IO), University of Rochester (UR), and one of the most recognized Russian university, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) was started in 2015 by signing an agreement on a double-Master's degree program in optics. It was based on earlier collaboration between research groups in both universities. In summer of 2016, nine UR Optics undergraduate students participated with MEPhI students at the International School on Optics and Laser Physics in MEPhI. During five days they were immersed into the world of cutting edge research, technologies and ideas that Russian, European and U.S. scientists offered them. This School also included tours of MEPhI Nanotechnologies and Lasers Centers and Nano-bioengineering Laboratory as well as of scientific laboratories of the leading institutes in optics, photonics and laser physics of the Russian Academy of Sciences. In December of 2015, one MEPhI Master student visited IO UR for one month for a research project with results presented later at a MEPhI conference. Samples prepared by MEPhI researchers are used in IO students teaching laboratories. One Master student from MEPhI is working now towards the Master's degree at the IO UR. In this paper benefits and pitfalls of a cross-border collaboration are discussed as well as different directions of such a collaboration to provide a high-quality specialization for the students of the 21 century which includes international cooperation.
We review our recently obtained data on the employment of Si nanoparticles as sensitizers of radiofrequency (RF) - induced hyperthermia for mild cancer therapy tasks. Such an approach makes possible the heating of aqueous suspensions of Si nanoparticles by tens of degrees Celsius under relatively low intensities (1–5 W/cm2) of 27 MHz RF radiation. The heating effect is demonstrated for nanoparticles synthesized by laser ablation in water and mechanical grinding of porous silicon, while laser-ablated nanoparticles demonstrate a remarkably higher heating rate than porous silicon-based ones for the whole range of the used concentrations. The observed RF heating effect can be explained in the frame of a model considering the polarization of Si NPs and electrolyte in the external oscillating electromagnetic field and the corresponding release of heat by electric currents around the nanoparticles. Our tests evidence relative safety of Si nanostructures and their efficient dissolution in physiological solutions, suggesting potential clearance of nanoparticles from a living organism without any side effects. Profiting from Si nanoparticle-based heating, we finally demonstrate an efficient treatment of Lewis Lung carcinoma in vivo. The obtained data promise a breakthrough in the development of mild, non-invasive methods for cancer therapy.
We examine absorption of electromagnetic radio-frequency (RF) radiation in aqueous suspensions of semiconductor (silicon) and metal (gold) nanoparticles (NPs) and theoretically investigate the heat release in these systems. The absorption of RF radiation is considered in both bulk electrolyte and the region around the NPs. Simulations show a strong dependence of the heating rate on electrical conductivity of the electrolyte rather than on that of NPs properties. The obtained results indicate that NPs can act as sensitizers of the RF induced hyperthermia for biomedical applications.
The results of theoretical studies are reported for threshold characteristics of a metal ablation by ultrashort laser pulses.
Two possible mechanisms of the laser ablation at laser fluence F≥Fth are considered: thermal mechanism of ablation
connected with a kinetics of a metal-vacuum surface evaporation and mechanism of ablation connected with a
hydrodynamics of a dense matter. The analysis has been made within the framework of a two-temperature model of
metals for two region of laser pulse duration-femtosecond and picosecond, and the extended of a two-temperature model
of the metal. Analytical expressions for the ablation-threshold fluency Fth as well as the threshold values of the lattice time temperature Tth(Fth) are obtained.
The nonlinear absorption mechanisms in transparent materials under ultrashort laser pulses irradiation are
considered theoretically. Nitride semiconductor, sapphire and others transparent dielectrics was investigated. The
ablation threshold for theses materials is in multi-TW/cm2 range. The model is used based on the tunneling
absorption under the irradiation by high intensity ultrashort pulses in terms of theory of ionization of solid in a
field of strong electromagnetic wave. Sartisfactory explanation is found of the influence of the material energy
bandgap on the laser ablation threshold.
The results of theoretical studies are reported for threshold characteristics of a metal ablation by picosecond and femtosecond laser pulse. Two possible mechanisms of the laser ablation at laser fluence F ≤ Fth are considered: thermal mechanism of ablation connected with a kinetics of a metal-vacuum surface evaporation and the mechanism of ablation connected with a hydrodynamics of a dense matter. The analysis has been made within the framework of a two-temperature model of metals for femtosecond and picosecond region of laser pulse duration and the extended of a two-temperature model of the metal in the case when the surface temperature Ti more than the critical temperature of metals. Analytical expressions for the ablation-threshold fluency Fth as well as the threshold values of the lattice temperature and the characteristic time of lattice temperature decay td(Fth) are obtained. This analytical description is in satisfactory agreement with particular numerical calculations.
The applicability of hydrodynamic models for theoretical description of UV laser ablation of polymers is studied. The plume formation is considered as a first-kind phase transition. In case of strongly absorbing polymers this phase transition occurs as a surface evaporation, and in case of weakly absorbing polymers as a bulk evaporation. The vapor plume is assumed to be transparent for laser radiation, and its expansion is described by the isoentropic hydrodynamic equations. New analytical expressions for ablation (etch) depths per pulse are obtained, which are in a good agreement with the available experimental data.
Metal ablation taking into account the hydrodynamics of a dense ablated material with ion temperature close to critical is considered. An extended two-temperature model taking into account hydrodynamic plasma expansion and degeneracy of the electron gas is developed. The new version of the RAPID code is used to perform calculations of ablation rates for several metal targets under conditions where the electron degeneracy is important.
Laser ablation of metals by femto- and picosecond pulses is analytically and numerically studied within the framework of different models for the ablated material. Within the plasma model ablation is initiated by high-power thermal and hydrodynamic waves which propagate into the irradiated material. Analytical expressions for the thermal ablation and for the ablation by the shock wave are obtained. Numerical simulations with the computer code RAPID are in a good agreement with analytical results.
Metal ablation taking into account hydrodynamics of a dense ablated material with ion temperature close to the critical one is considered. The extended two-temperature model taking into account the hydrodynamic plasma expansion, degeneracy of the electron gas, cold pressure of ions and interaction between the electron and ion subsystems (nonideality of the metal plasma) is developed. The new version of the RAPID code is used to perform calculations of ablation rates for several metal targets under conditions where the electron degeneracy is important.
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