Laser-induced thermal ablation of cancerous cell organelles.

AIM: By exploiting the physical changes experienced by cancerous organelles, we investigate the feasibility of destroying cancerous cells by single and multipulse modes of laser heating. MATERIALS & METHODS: Our procedure consists of two primary steps: determining the normal and cancerous organelles optical properties and simulating the heating of all of the major organelles in the cell to find the treatment modes for the laser ablation of cancerous organelles without harming healthy cells. RESULTS & CONCLUSION: Our simulations show that the cancerous nucleus can be selectively heated to damaging temperatures, making this nucleus a feasible therapeutic particle and removing the need for nanoparticle injection. Because of the removal of this extra step, the procedure we propose is simpler and safer for the patient.

Nanotherapy of cancer by photoelectrons emitted from the surface of nanoparticles exposed to nonionizing ultraviolet radiation.

AIM: We introduce a new method for selectively destroying cancer cell organelles by electrons emitted from the surface of intracellularly localized nanoparticles exposed to the nonionizing ultraviolet (UV) radiation. METHODS: We propose to target cancerous intracellular organelles by nanoparticles and expose them to UV radiation with energy density safe for healthy tissue. RESULTS: We simulate the number of photoelectrons produced by the nanoparticles made of various metals and radii, calculate their kinetic energy and compare it to the threshold energy for producing biological damage. CONCLUSION: Exposure of metal nanoparticles to UV radiation generates photoelectrons with kinetic energies up to 11 eV, which is high enough to produce single- to double-strand breaks in the DNA and damage the cancerous cell organelles.

Absorption efficiency and heating kinetics of nanoparticles in the RF range for selective nanotherapy of cancer.

Radio-frequency (RF) waves have an excellent ability to penetrate into the human body, giving a great opportunity to activate/heat nanoparticles delivered inside the body as a contrast agent for diagnosis and treatment purposes. However the heating of nanoparticles in the RF range of the spectrum is controversial in the research community because of the low power load of RF waves and low absorption of nanoparticles in the RF range. This study uses a phenomenological approach to estimate the absorption efficiency of metal and dielectric nanoparticles in the RF range through a study of heating kinetics of those particles in radio wave field. We also discuss the specific features of heating kinetics of nanoparticles, such as a short time scale for heating and cooling of nanoparticles in a liquid biological environment, and the effect of the radiation field structure on the heating kinetics by single-pulse and multipulse RF radiation. FROM THE CLINICAL EDITOR: In this study a phenomenological approach was applied to estimate the absorption efficiency of radiofrequency radiation (RF) by metal and dielectric nanoparticles. Such nanoparticles can be designed and used for therapeutic purposes, like for localized heating and to activate nanoparticles by RF. The authors also discuss the differences in heating kinetics using single-pulse and multi-pulse RF radiation.

X-ray optics of gold nanoparticles.

Gold nanoparticles have been investigated as contrast agents for traditional x-ray medical procedures, utilizing the strong absorption characteristics of the nanoparticles to enhance the contrast of the detected x-ray image. Here we use the Kramers-Kronig relation for complex atomic scattering factors to find the real and imaginary parts of the index of refraction for the medium composed of single-element materials or compounds in the x-ray range of the spectrum. These complex index of refraction values are then plugged into a Lorenz-Mie theory to calculate the absorption efficiency of various size gold nanoparticles for photon energies in the 1-100 keV range. Since the output from most medical diagnostic x-ray devices follows a wide and filtered spectrum of photon energies, we introduce and compute the effective intensity-absorption-efficiency values for gold nanoparticles of radii varying from 5 to 50 nm, where we use the TASMIP model to integrate over all spectral energies generated by typical tungsten anode x-ray tubes with kilovolt potentials ranging from 50 to 150 kVp.

Modeling nanophotothermal therapy: kinetics of thermal ablation of healthy and cancerous cell organelles and gold nanoparticles.

Nanoparticles are being researched as a noninvasive method for selectively killing cancer cells. With particular antibody coatings on nanoparticles, they attach to the abnormal cells of interest (cancer or otherwise). Once attached, nanoparticles can be heated with ultraviolet-visible/infrared or radiofrequency pulses, heating the surrounding area of the cell to its point of death. Researchers often use single-pulse or multi-pulse modes of laser heating when conducting nanoparticle ablation research. In this article, time-dependent simulations and detailed analyses are carried out for different nonstationary pulsed laser-nanoparticle interaction modes, and the advantages and disadvantages of single-pulse and multi-pulse (set of short pulses) laser heating of nanoparticles are shown. Simulations are performed for the metal nanoparticles in the biological surrounding medium as well as for healthy and cancerous cell organelles. FROM THE CLINICAL EDITOR: External laser pulses can be used to generate heating of targeted metal nanoparticles for thermal ablation therapy of cancers, however the approach used in individual studies is idiosyncratic. In this manuscript, time-dependent simulations and analyses are used to determine the pros and cons of single versus multiple laser pulses for differential impact of healthy versus cancerous cell organelles.

Theoretical study of bone cancer therapy by plasmonic nanoparticles.

BACKGROUND: Progress made by the scientific community in the understanding of cell receptors and metabolic pathways has led to discovery of chemical and protein agents which act as delivery vectors to specific tissues. Conjugating these agents to noble-metal nanoparticles allows for subsequent accumulation on or within targeted cells. Utilizing the unique light absorption properties of these nanoparticles then allows for photothermal heating of the particles and surrounding tissue. DISCUSSION: The heat equations are solved for the case of gold nanoparticles in biological hard tissues, such as bone, for applications to two future cancer therapies: nanophotothermolysis and nanophotohyperthermia. CONCLUSIONS: A survey of recent research in bone-targeting bioconjugates and simulations of nanoparticle thermal fields shows promise for these therapies in the near future.

Laser-induced explosion of gold nanoparticles: potential role for nanophotothermolysis of cancer.

AIMS: This article explores the laser-induced explosion of absorbing nanoparticles in selective nanophotothermolysis of cancer. METHODS: This is realized through fast overheating of a strongly absorbing target during the time of a short laser pulse when the influence of heat diffusion is minimal. RESULTS: On the basis of simple energy balance, it is found that the threshold laser fluence for thermal explosion of different gold nanoparticles is in the range of 25-40 mJ/cm(2). CONCLUSION: Explosion of nanoparticles may be accompanied by optical plasma, generation of shock waves with supersonic expansion and particle fragmentation with fragments of high kinetic energy, all of which can contribute to the killing of cancer cells.