Metal nanoshells are a class of nanoparticles with tunable optical resonances. In this article, an application of this technology to thermal ablative therapy for cancer is described. By tuning the nanoshells to strongly absorb light in the near infrared, where optical transmission through tissue is optimal, a distribution of nanoshells at depth in tissue can be used to deliver a therapeutic dose of heat by using moderately low exposures of extracorporeally applied near-infrared (NIR) light. Human breast carcinoma cells incubated with nanoshells in vitro were found to have undergone photothermally induced morbidity on exposure to NIR light (820 nm, 35 W/cm2), as determined by using a fluorescent viability stain. Cells without nanoshells displayed no loss in viability after the same periods and conditions of NIR illumination. Likewise, in vivo studies under magnetic resonance guidance revealed that exposure to low doses of NIR light (820 nm, 4 W/cm2) in solid tumors treated with metal nanoshells reached average maximum temperatures capable of inducing irreversible tissue damage (DeltaT = 37.4 +/- 6.6 degrees C) within 4-6 min. Controls treated without nanoshells demonstrated significantly lower average temperatures on exposure to NIR light (DeltaT < 10 degrees C). These findings demonstrated good correlation with histological findings. Tissues heated above the thermal damage threshold displayed coagulation, cell shrinkage, and loss of nuclear staining, which are indicators of irreversible thermal damage. Control tissues appeared undamaged.

https://www.pnas.org/content/pnas/100/23/13549.full.pdf

Nanoshell-mediated near-infrared thermal therapy of tumors under magnetic resonance guidance

With the rapid development of clinical hyperthermia for the treatment of cancer either alone or in conjunction with other modalities, a means of measuring a thermal dose in terms which are clinically relevant to the biological effect is needed. A comparison of published data empirically suggests a basic relationship that may be used to calculate a "thermal dose." From a knowledge of the temperature during treatment as a function of time combined with a mathematical description of the time-temperature relationship, an estimate of the actual treatment calculated as an exposure time at some reference temperature can be determined. This could be of great benefit in providing a real-time accumulated dose during actual patient treatment. For the purpose of this study, a reference temperature of 43 degrees C has been arbitrarily chosen to convert all thermal exposures to "equivalent-minutes" at this temperature. This dose calculation can be compared to an integrated calculation of the "degree-minutes" to determine its prognostic ability. The time-temperature relationship upon which this equivalent dose calculation is based does not predict, nor does it require, that different tissues have the same sensitivity to heat. A computer program written in FORTRAN is included for performing calculations of both equivalent-minutes (t43) and degree-minutes (tdm43). Means are provided to alter the reference temperature, the Arrhenius "break" temperature and the time-temperature relationship both above and below the "break" temperature. In addition, the effect of factors such as step-down heating, thermotolerance, and physiological conditions on thermal dose calculations are discussed. The equations and methods described in this report are not intended to represent the only approach for thermal dose estimation; instead, they are intended to provide a simple but effective means for such calculations for clinical use and to stimulate efforts to evaluate data in terms of therapeutically useful thermal units.

Thermal dose determination in cancer therapy

In oncology, the term 'hyperthermia' refers to the treatment of malignant diseases by administering heat in various ways. Hyperthermia is usually applied as an adjunct to an already established treatment modality (especially radiotherapy and chemotherapy), where tumor temperatures in the range of 40-43 degrees C are aspired. In several clinical phase-III trials, an improvement of both local control and survival rates have been demonstrated by adding local/regional hyperthermia to radiotherapy in patients with locally advanced or recurrent superficial and pelvic tumors. In addition, interstitial hyperthermia, hyperthermic chemoperfusion, and whole-body hyperthermia (WBH) are under clinical investigation, and some positive comparative trials have already been completed. In parallel to clinical research, several aspects of heat action have been examined in numerous pre-clinical studies since the 1970s. However, an unequivocal identification of the mechanisms leading to favorable clinical results of hyperthermia have not yet been identified for various reasons. This manuscript deals with discussions concerning the direct cytotoxic effect of heat, heat-induced alterations of the tumor microenvironment, synergism of heat in conjunction with radiation and drugs, as well as, the presumed cellular effects of hyperthermia including the expression of heat-shock proteins (HSP), induction and regulation of apoptosis, signal transduction, and modulation of drug resistance by hyperthermia.

The cellular and molecular basis of hyperthermia.

The current status of the use of nanoparticles for photothermal treatments is reviewed in detail. The different families of heating nanoparticles are described paying special attention to the physical mechanisms at the root of the light-to-heat conversion processes. The heating efficiencies and spectral working ranges are listed and compared. The most important results obtained in both in vivo and in vitro nanoparticle assisted photothermal treatments are summarized. The advantages and disadvantages of the different heating nanoparticles are discussed.

Nanoparticles for photothermal therapies.

A progress report is presented on a selection of scientific, technological and commercial advances in the biomedical applications of magnetic nanoparticles since 2003. Particular attention is paid to (i) magnetic actuation for in vitro non-viral transfection and tissue engineering and in vivo drug delivery and gene therapy, (ii) recent clinical results for magnetic hyperthermia treatments of brain and prostate cancer via direct injection, and continuing efforts to develop new agents suitable for targeted hyperthermia following intravenous injection and (iii) developments in medical sensing technologies involving a new generation of magnetic resonance imaging contrast agents, and the invention of magnetic particle imaging as a new modality. Ongoing prospects are also discussed.

/pdf/progress-in-applications-of-magnetic-nanoparticles-in-1fdltiiz5p.pdf

Progress in applications of magnetic nanoparticles in biomedicine

In general, the survival of Chinese hamster ovary cells exposed to hyperthermic temperatures of 42.5–46.0° decreases exponentially as a function of duration of heat exposure in a manner quite similar to survival as a function of radiation dose. The data indicate that above 43° a 1° change in temperature requires a 2-fold change in time to achieve the same degree of killing, whereas below 43° the same 2-fold change in time requires only a 0.5° change in temperature for the same effect. An Arrhenius-type plot of the logarithm of the rate of killing as a function of reciprocal temperature exhibits linearity with a change in slope at 43°. This change in slope suggests either a change in the mechanism of cell killing below this temperature or a manifestation of thermal tolerance that is readily observed when the duration of heating exceeds 4 to 5 hr. Thermotolerance to 45.5°, as evidenced by a 3- to 4-fold increase in D0, is observed in synchronous G1 cells exposed to heat 20 hr after an initial heat dose. This thermotolerance develops, although no progression of cells into S phase occurs during this period. In addition, thermotolerance develops in both asynchronous and synchronous G1 cells exposed to single heat doses between 41.5 and 42.5° for periods exceeding 4 to 5 hr, i.e., survival decreases exponentially as a function of duration of heating up to 4 to 5 hr, after which survival decreases very little. At 42.0–42.5°, survival is extremely sensitive to changes in temperature, with as much as a 10-fold difference in survival for a 0.1° difference in temperature with heat exposures greater than 4 hr. The above data indicate the importance of careful treatment design and precise temperature control if hyperthermia is to be used for cancer therapy. No progression of synchronous G1 cells into S phase is observed for cells continuously exposed to temperatures of 42.0° and above. However, computer simulation of sequential DNA histograms from flow cytometry of synchronous cells continuously exposed to 41.5° indicates that cell cycle delays of 5.4 and 2.4 hr for G1 and S, respectively, occurred for cells for which exposure began in G1, and delays of 0.5 and 5.4 hr for S and G2 plus mitosis, respectively, occurred for cells for which exposure began in late S. Normal cell cycle phase transit times for G1, S, and G2 plus mitosis are 4.3, 7.1, and 2.4 hr, respectively. In addition, mitotic indices and increases in cell number of asynchronous populations of cells continuously exposed to 41.5° indicate that entry into mitosis is delayed for approximately 2 hr. Following this delay, cells begin to enter mitosis and accumulate from 2 to 6 hr in metaphase; after about 6 hr, they begin to progress into G1. However, comparison of flow cytometry data and mitotic index data suggests that during the initial 6 hr of heating, the majority of cells accumulating in G2 plus mitosis are actually delayed in G2.

https://cancerres.aacrjournals.org/content/canres/38/2/393.full.pdf

Effects of Hyperthermia on Survival and Progression of Chinese Hamster Ovary Cells

A total of 130 dogs and cats with squamous cell carcinomas, melanomas, fibrosarcomas, mammary adenocarcinomas, or mast cell sarcomas were randomized to receive radiation (XRT) or heat plus XRT Time-temperature data for each monitored tumor location were converted to degree-minutes or equivalent min at 43° (Eq43) Response rates and durations of response were compared for subgroups of histology, volume, site, and heat treatment method Thermal gradients existed in all heated tumors The influence of these gradients on tumor response was examined by correlation of response with degree-minutes and Eq43 minima, maxima, averages, and ranges A pattern emerged from these analyses linking dose minima, maxima, and ranges with prognostic subgroups as classified by volume, site, or treatment method The data indicated that the coolest part of the tumor governed the biological response to combined heat + XRT Tumors which received a minimum of 35 Eq43 had significantly longer durations of response than did those receiving XRT alone or

https://cancerres.aacrjournals.org/content/canres/44/1/43.full.pdf

Importance of Minimum Tumor Temperature in Determining Early and Long-Term Responses of Spontaneous Canine and Feline Tumors to Heat and Radiation

Synchronous Chinese hamster cells in vitro were obtained by mitotic selection. The cells were heated at 45.5°C for 4 min in mitosis, 11 min in G1, or 7 min in S sphase and then X-irradiated immediately thereafter. Colony survival from heat alone was 0.30 to 0.45, and the frequency of chromosomal aberrations induced by heat was 0.00, 0.14, or 0.97 for heat treatments during M, G1, or S, respectively. As shown previously, lethality from hyperthermia alone is due to chromosomal aberrations only when the cells are heated during S phase. The log survival $(D_{0}^{\sim}=80\ \text{rad})$ and aberration frequency curves for cells irradiated during mitosis were linear, and the only effect of hyperthermia was to shift the curves in accord with the effect from heat alone. Thus, hyperthermia did not radiosensitize the mitotic cells. The cells irradiated in G1 were more resistant $(D_{0}^{\sim}=100\ \text{rad})$ than those irradiated in mitosis, and the survival and aberration...

Hyperthermic radiosensitization of synchronous Chinese hamster cells: relationship between lethality and chromosomal aberrations.

M. W. DEWHIRST, D.V.M., PH.D.,* T. L. PHILLIPS, M.D.,+ T. V. SAMULSKI, PH.D.,+ P. STAUFFER, MSEE,? P. SHRIVASTAVA, PH.D.,+ B. PALIWAL, PH.D.,+ T. PAJAK, PH.D.,+ M. GILLIM, PH.D.,+ M. SAPOZINK, M.D., PH.D.,+ R. MYERSON, M.D., PH.D.,+ F. M. WATERMAN, PH.D.,+ S. A. SAPARETO, PH.D.,+ P. CORRY, PH.D.,+ T. C. CETAS, PH.D.,+ D. B. LEEPER, PH.D.,+ P. FESSENDEN, PH.D.,+ D. KAPP, M.D., PH.D.,+ J. R. OLESON, M.D., PH.D.+ AND B. EMAMI, M.D.*

Stephen A. Sapareto

Papers

Thermal dose determination in cancer therapy

Effects of Hyperthermia on Survival and Progression of Chinese Hamster Ovary Cells

Importance of Minimum Tumor Temperature in Determining Early and Long-Term Responses of Spontaneous Canine and Feline Tumors to Heat and Radiation

Hyperthermic radiosensitization of synchronous Chinese hamster cells: relationship between lethality and chromosomal aberrations.

RTOG quality assurance guidelines for clinical trials using hyperthermia.