Relationship of hyperthermia-induced hemolysis of human erythrocytes to the thermal denaturation of membrane proteins

Heating Capacity and Biocompatibility of Hybrid Nanoparticles for Magnetic Hyperthermia Treatment

Cancer is one of the deadliest diseases worldwide and has been responsible for millions of deaths. However, developing a satisfactory smart multifunctional material combining different strategies to kill cancer cells poses a challenge. This work aims at filling this gap by developing a composite material for cancer treatment through hyperthermia and drug release. With this purpose, magnetic nanoparticles were coated with a polymer matrix consisting of poly (L-co-D,L lactic acid-co-trimethylene carbonate) and a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer. High-resolution transmission electron microscopy and selected area electron diffraction confirmed magnetite to be the only iron oxide in the sample. Cytotoxicity and heat release assays on the hybrid nanoparticles were performed here for the first time. The heat induction results indicate that these new magnetic hybrid nanoparticles are capable of increasing the temperature by more than 5 °C, the minimal temperature rise required for being effectively used in hyperthermia treatments. The biocompatibility assays conducted under different concentrations, in the presence and in the absence of an external alternating current magnetic field, did not reveal any cytotoxicity. Therefore, the overall results indicate that the investigated hybrid nanoparticles have a great potential to be used as carrier systems for cancer treatment by hyperthermia.

Biomimetic Nanotherapeutics: Employing Nanoghosts to fight Melanoma

Melanoma is a cancer of melanocytes present at the basal layer of the skin. Nanomedicine has armed us with competent platform to manage such fatal neoplastic diseases. Nevertheless, it suffers from numerous pitfalls such as rapid clearance and opsonization of surface-functionalized carriers, biocompatibility and idiopathic reactions which could be difficult to predict in the patient. Biomimetic approach, a novel step towards personalized medicine bridges these drawbacks by employing endogenous cell membranes to traverse physiological barriers. Camouflaged carriers coated with natural cell membranes possess unique characteristics such as high circulatory periods, and the absence of allogenic and xenogenic responses. Proteins residing on the cell membranes render a diverse range of utilities to the coated nanoparticles including natural efficiency to identify cellular targets, homologous targeting, reticuloendothelial system evasion, biocompatibility and reduced adverse and idiopathic effects. In the present article, we have focused on cell membrane camouflaged nanocarriers for melanoma management. We have discussed various types of biomimetic systems, their processing and coating approaches, and their characterization. We have also enumerated novel avenues in melanoma treatment and the combination of biomimetic systems with smart nanoparticulate systems with the potential to bring breakthroughs in the near future. Additionally, immunotherapy-based biomimetic systems to combat melanoma have been highlighted. Hurdles towards clinical translation and ways to overcome them have been explained in detail.

Enhancement of skin permeability with thermal ablation techniques: concept to commercial products

Traditionally, the skin is considered as a protective barrier which acts as a highly impermeable region of the human body. But in recent times, it is recognized as a specialized organ that aids in the delivery of a wide range of drug molecules into the skin (intradermal drug delivery) and across the skin into systemic circulation (transdermal drug delivery, TDD). The bioavailability of a drug administered transdermally can be improved by several penetration enhancement techniques, which are broadly classified into chemical and physical techniques. Application of mentioned techniques together with efforts of various scientific and innovative companies had made TDD a multibillion dollar market and an average of 2.6 new transdermal drugs are being approved each year. Out of various techniques, the thermal ablation techniques involving chemicals, heating elements, lasers, and radiofrequency (RF) are proved to be more effective in terms of delivering the drug across the skin by disrupting the stratum corneum (SC). The reason behind it is that the thermal ablation technique resulted in improved bioavailability, quick treatment and fast recovery of the SC, and more importantly it does not cause any damage to underlying dermis layer. This review article mainly discussed about various thermal ablation techniques with commercial products and patents in each classes, and their safety aspects. This review also briefly presented anatomy of the skin, penetration pathways across the skin, and different generations of TDD.

Thermal sensitivity and haemolysis of erythrocytes with membranopathy

Measuring the impedance of heated suspensions of erythrocytes and erythrocyte ghost membranes, two thermally-induced alterations are registered in the plasma membrane at T_A (denaturation of spectrin with inducing temperature at 49,5 °C) and T_G (hyperthermic activation of basal ion permeability with inducing temperature at 60.7 °C). In this study erythrocytes from 9 healthy patients and 15 patients with hemolytic anemia were studied and divided into four groups depending on their T_A and T_G top temperatures. The T_A and T_G of erythrocytes with hemoglobinopathy were the same as those of control erythrocytes while those of erythrocytes with membranopathy were significantly reduced. In erythrocytes with severe membranopathy, the T_G was decreased by about 5 °C. In latter cells the normal value of T_G was restored and the resistance to thermal haemolysis was increased by 90% after the specific stabilization of band 3 protein by 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS). Obtained results indicate the involvement of band 3 in the membrane alteration at T_G and in the heat target responsible for thermal haemolysis.

Photothermal treatment of port-wine stains using erythrocyte-derived particles doped with indocyanine green: a theoretical study

Pulsed dye laser irradiation in the wavelength range of 585 to 600 nm is currently the gold standard for treatment of port-wine stains (PWSs). However, this treatment method is often ineffective for deeply seated blood vessels and in individuals with moderate to heavy pigmentation. Use of optical particles doped with the FDA-approved near-infrared (NIR) absorber, indocyanine green (ICG), can potentially provide an effective method to overcome these limitations. Herein, we theoretically investigate the effectiveness of particles derived from erythrocytes, which contain ICG, in mediating photothermal destruction of PWS blood vessels. We refer to these particles as NIR erythrocyte-derived transducers (NETs). Our theoretical model consists of a Monte Carlo algorithm to estimate the volumetric energy deposition, a finite elements approach to solve the heat diffusion equation, and a damage integral based on an Arrhenius relationship to quantify tissue damage. The model geometries include simulated PWS blood vessels as well as actual human PWS blood vessels plexus obtained by the optical coherence tomography. Our simulation results indicate that blood vessels containing micron- or nano-sized NETs and irradiated at 755 nm have higher levels of photothermal damage as compared to blood vessels without NETs irradiated at 585 nm. Blood vessels containing micron-sized NETs also showed higher photothermal damage than blood vessels containing nano-sized NETs. The theoretical model presented can be used in guiding the fabrication of NETs with patient-specific optical properties to allow for personalized treatment based on the depth and size of blood vessels as well as the pigmentation of the individual's skin.

Feasibility study of modeling liver thermal damage using minimally invasive optical method adequate for in situ measurement

Liver thermal ablation techniques have been widely used for the treatment of liver cancer. Kinetic model of damage propagation play an important role for ablation prediction and real-time efficacy assessment. However, practical methods for modeling liver thermal damage are rare. A minimally invasive optical method especially adequate for in situ liver thermal damage modeling is introduced in this paper. Porcine liver tissue was heated by water bath under different temperatures. During thermal treatment, diffuse reflectance spectrum of liver was measured by optical fiber and used to deduce reduced scattering coefficient (μ^'_s ). Arrhenius parameters were obtained through non-isothermal heating approach with damage marker of μ^'_s . Activation energy (E_a ) and frequency factor (A) was deduced from these experiments. A pair of averaged value is 1.200 × 10⁵  J mol^-1 and 4.016 × 10¹⁷  s^-1 . The results were verified for their reasonableness and practicality. Therefore, it is feasible to modeling liver thermal damage based on minimally invasive measurement of optical property and in situ kinetic analysis of damage progress with Arrhenius model. These parameters and this method are beneficial for preoperative planning and real-time efficacy assessment of liver ablation therapy.

Feasibility of Percutaneous Intrahepatic Split by Microwave Ablation (PISA) After Portal Vein Embolization for Hypertrophy of Future Liver Remnant: The Radiological Stage-1 ALPPS

PURPOSE

To assess the feasibility of radiological stage-1 ALPPS, associating liver partition and portal vein ligation for staged hepatectomy, by combining portal vein embolization (PVE) with percutaneous intrahepatic split by ablation (PISA).

MATERIALS AND METHODS

Three patients (mean age 65.0 ± 7.3 years) underwent PVE and PISA. PISA was performed 21 days after PVE by microwave ablation to create a continuous intrahepatic cutting plane. Abdominal CT examinations were performed before and after PVE and PISA. The future liver remnant (FLR) volume was calculated by semiautomatic segmentation, and increase was reported as a percentage of the pre-procedural volume. The FLR/body weight (FLR/BW) ratio was calculated; a ratio greater than 0.8% was considered sufficient for guaranteeing adequate liver function after surgery. The liver function before and after PISA was also evaluated by 99mTc-mebrofenin hepatobiliary scintigraphy. Patients' laboratory tests, performance status, ability to walk were assessed before and after PVE and PISA procedures.

RESULTS

No procedure-related complications were recorded. The FLR volume increase in each patient was 42.0, 33.1 and 30.4% within 21 days of PVE and 109.3, 68.1 and 71.7% within 10 days after PISA. The FLR/BW ratios were 0.76, 0.66, 0.63% and 1.13, 0.83, 0.83% after PVE and PISA procedures, respectively. Two patients underwent successful right hepatectomy; in one patient, despite 1.13% FLR/BW, surgery was not performed because of the absolute rejection of blood transfusion due to the patient's religious convictions.

CONCLUSION

Radiological stage-1 ALPPS is a feasible, minimally invasive option to be further investigated to become an effective alternative to surgical stage-1 ALPPS.

Meshless bubble filter using ultrasound for extracorporeal circulation and its effect on blood

A bubble filter with no mesh structure for extracorporeal circulation using ultrasound was developed. Hemolysis was evaluated by measuring free hemoglobin (FHb). FHb in 120 mL of bovine blood was measured in acoustic standing-wave fields. With a sound pressure amplitude of 60 kPa at driving frequencies of 1 MHz, 500 kHz and 27 kHz for 15 min. FHb values were 641.6, 2575 and 8903 mg/dL, respectively. Thus, hemolysis was inhibited with higher driving frequencies when the same sound pressure amplitude was applied. An ultrasound bubble filter with a resonance frequency of 1 MHz was designed. The filtering characteristics of the flowing microbubbles were investigated with a circulation system using bovine blood with a flow rate of 5.0 L/min. Approximately 99.1% of microbubbles were filtered with 250 kPa and a flow of 5.0 L/min. Hemolysis decreased as the sound pressure decreased; FHb values were 225.8 and 490.7 mg/dL when using 150 and 200 kPa, respectively.

Physical energy for drug delivery; poration, concentration and activation

Techniques for controlling the rate and duration of drug delivery, while targeting specific locations of the body for treatment, to deliver the cargo (drugs or DNA) to particular parts of the body by what are becoming called "smart drug carriers" have gained increased attention during recent years. Using such smart carriers, researchers have also been investigating a number of physical energy forces including: magnetic fields, ultrasound, electric fields, temperature gradients, photoactivation or photorelease mechanisms, and mechanical forces to enhance drug delivery within the targeted cells or tissues and also to activate the drugs using a similar or a different type of external trigger. This review aims to cover a number of such physical energy modalities. Various advanced techniques such as magnetoporation, electroporation, iontophoresis, sonoporation/mechnoporation, phonophoresis, optoporation and thermoporation will be covered in the review. Special emphasis will be placed on photodynamic therapy owing to the experience of the authors' laboratory in this area, but other types of drug cargo and DNA vectors will also be covered. Photothermal therapy and theranostics will also be discussed.

Comparative analysis of mathematical models of cell death and thermal damage processes

The standard method for assessing hyperthermia treatment has been calculation of cumulative equivalent minutes at 43 °C, CEM43 and its variations. This parameter normalises treatment thermal histories rather than predicts treatment results. Arrhenius models have been widely used in analysing higher temperature thermal treatments and successfully employed to predict irreversible thermal alterations in structural proteins. Unfortunately, in many, but not all cases they fail to represent thermally induced damage or cell death at hyperthermic temperatures, 43-50 °C, exhibiting significant over-prediction of the initial 'shoulder' region. The failure arises from the simplifying assumptions used to derive the irreversible reaction format that has been used in thermal damage studies. Several successful multi-parameter fit methods have been employed to model cell survival data. The two-state statistical thermodynamic model was derived from basic thermodynamic principles. The three-state model results from relaxing the assumptions under the Arrhenius formulation that result in an irreversible reaction. In other cell processes studied in vitro the irreversible Arrhenius model holds, and is sufficient to provide an accurate and useful estimate of thermal damage and cell death. It is essential in numerical model work to include multiple thermal damage processes operating in parallel to obtain a clear image of the likely outcome in tissues. Arrhenius and other C(t) models have that capability, while a single value for CEM43, does not.

Identification of human erythrocyte cytosolic proteins associated with plasma membrane during thermal stress

The influence of thermal stress on the association between human erythrocyte membranes and cytosolic proteins was studied by exposing erythrocyte suspensions and whole blood to different elevated temperatures. Membranes and cytosolic proteins from unheated and heat-stressed erythrocytes were analyzed by electrophoresis, followed by mass spectrometric identification. Four major (carbonic anhydrase I, carbonic anhydrase II, peroxiredoxin VI, flavin reductase) and some minor (heat shock protein 90α, heat shock protein 70, α-enolase, peptidylprolyl cis-trans isomerase A) cytosolic proteins were found to be associated with the erythrocyte membrane in response to in vitro thermal stress. Unlike the above proteins, catalase and peroxiredoxin II were associated with membranes from unheated erythrocytes, and their content increased in the membrane following heat stress. The heat-induced association of cytosolic proteins was restricted to the Triton shells (membrane skeleton/cytoskeleton). Similar results were observed when Triton shells derived from unheated erythrocyte membranes were incubated with an unheated erythrocyte cytosolic fraction at elevated temperatures. This is a first report on the association of cytosolic catalase, α-enolase, peroxiredoxin VI, peroxiredoxin II and peptidylprolyl cis-trans isomerase A to the membrane or membrane skeleton of erythrocytes under heat stress. From these results, it is concluded that specific cytosolic proteins are translocated to the membrane in human erythrocytes exposed to heat stress and they may play a novel role as erythrocyte membrane protectors under stress by stabilizing the membrane skeleton through their interactions with skeletal proteins.

Mathematical models of laser-induced tissue thermal damage

Laser sources are under increasing study for in vivo tumour ablation. Photo-thermal ablation in tissues varies tremendously in governing physical phenomena, depending on wavelength, owing to wide variation in the optical properties of tissues, specifically the dominant chromophore and degree and type of scattering. Once converted into local tissue heating, however, the governing thermodynamic principles remain the same. Observed irreversible thermal alterations range from substantial structural disruption due to steam evolution in high temperature short-term activations to low temperature rise, longer-term initiation of the complex protein cascades that result in apoptosis and/or necroptosis. The usual mathematical model in hyperthermia studies, the thermal isoeffect dose, arising from the relative reaction rate formulation, is not an effective description of the higher temperature effects because multiple processes occur in parallel. The Arrhenius formulation based on the theory of absolute reaction rates is much more useful and descriptive in laser heating since the multiple thermodynamically independent processes may be studied separately.

Anion exchanger and the resistance against thermal haemolysis

4,4'-Diiso-thiocyanato stilbene-2,2'-disulphonic acid (DIDS) is a membrane-impermeable, highly specific covalent inhibitor and powerful thermal stabiliser of the anion exchanger (AE1), the major integral protein of erythrocyte membrane (EM). Suspensions of control and DIDS-treated (15 µM, pH 8.2) human erythrocytes were heated from 20° to 70°C using various but constant heating rates (1-8°C/min). The cellular electrolyte leakage exhibited a sigmoidal response to temperature as detected by conductometry. The critical midpoint temperature of leakage, T(mo), extrapolated to low heating rate (0.5°C/min) was used as a measure for EM thermostability. T(mo) was greater for DIDS-treated erythrocytes, 63.2° ± 0.3°C, than for intact erythrocytes, 60.7° ± 0.2°C. The time, t(1/2), for 50% haemolysis of erythrocytes, exposed to 53°C was used as a measure for the resistance of erythrocytes against thermal haemolysis. The t(1/2) was also greater for DIDS-treated erythrocytes, 63 ± 3 min, than for intact erythrocytes, 38 ± 2 min. The fluorescent label N-(3-pyrenyl)maleimide and EPR spin label 3-maleimido-proxyl, covalently bound to sulphydryl groups of major EM proteins, were used to monitor the changes in molecular motions during transient heating. Both labels reported an intensification of the motional dynamics at the denaturation temperatures of spectrin (50°C) and AE1 (67°C), and, surprisingly, immobilisation of a major EM protein, presumably the AE1, at T(mo). The above results are interpreted in favour of the possible involvement of a predenaturational rearrangement of AE1 copies in the EM thermostability and the resistance against thermal haemolysis.

Thermostability of biological systems: fundamentals, challenges, and quantification

This review examines the fundamentals and challenges in engineering/understanding the thermostability of biological systems over a wide temperature range (from the cryogenic to hyperthermic regimen). Applications of the bio-thermostability engineering to either destroy unwanted or stabilize useful biologicals for the treatment of diseases in modern medicine are first introduced. Studies on the biological responses to cryogenic and hyperthermic temperatures for the various applications are reviewed to understand the mechanism of thermal (both cryo and hyperthermic) injury and its quantification at the molecular, cellular and tissue/organ levels. Methods for quantifying the thermophysical processes of the various applications are then summarized accounting for the effect of blood perfusion, metabolism, water transport across cell plasma membrane, and phase transition (both equilibrium and non-equilibrium such as ice formation and glass transition) of water. The review concludes with a summary of the status quo and future perspectives in engineering the thermostability of biological systems.

Induction of Thermotolerance by Chemical Agents in Enucleate Erythrocytes

Erythrocytes treated with various chemical agents for 1 h at 37 degrees C showed resistance to a subsequent 1 h heat treatment at 53 degrees C. Maximal thermotolerance was observed 6 h after 3 mM DNP and 0.03 mM disulfiram treatment and 4 h after diamide exposure at 0.3 mM. Our results suggest that chemically induced thermotolerance to heat treatment in erythrocytes was similar to heat-induced thermotolerance.

Role of Membrane Components in Thermal Injury of Cells and Development of Thermotolerance

Exposure of cells to hyperthermia induces a transient resistance to subsequent heat treatment. The specific mechanisms responsible for hyperthermic cell killing and thermotolerance development are not well understood. It seems that heat may induce at least two different states of thermotolerance, of which one is dependent on protein synthesis. The expression of thermotolerance may include multiple cytoplasmic and membrane components. A number of studies have indicated that membranes play an important role in governing the thermal injury of cells. It seems, therefore, that heat denatured plasma membrane proteins may be a potential target for thermal stress and a trigger for the induction of thermotolerance. The localization of heat shock proteins in the plasma membrane and the suggestion of thermal resistance in enucleate erythrocytes support this suggestion. However, a direct relationship between the plasma membrane and hyperthermic killing or development of thermotolerance has not been found.

Allometric dependence of the life span of mammal erythrocytes on thermal stability and sphingomyelin content of plasma membranes

Thermal stability of erythrocyte membrane is a measure for its ability to maintain permeability barrier at deleterious conditions. Hence, it could impact the resistance of erythrocytes against detrimental factors in circulation. In this study the thermostability of erythrocyte membranes was expressed by the temperature, T(go), at which the transmembrane gradient of ion concentration rapidly dissipated during transient heating. T(go) is the inducing temperature of the membrane transition that activated passive ion permeability at hyperthermia causing thermal hemolysis. A good allometric correlation of T(go) to the resistance against thermal hemolysis and the life span of erythrocytes were found for 13 mammals; sheep, cow, goat, dog, horse, man, rabbit, pig, cat, hamster, guinea pig, rat, and mouse. For the same group, the values of T(go) were strictly related to the sphingomyelin content of erythrocyte membranes. The residual ion permeability, P, was temperature activated from 38 to 57 degrees C with activation energy of 250+/-15 kJ/mol that strongly differed from that below 37 degrees C. The projected value of P at 37 degrees C was about half that of residual physiological permeability for Na+ and K+ that build ground for possible explanation of the life span vs membrane thermostability allometric correlation.

Erythrocyte membrane defects in hemolytic anemias found through derivative thermal analysis of electric impedance

Hereditary hemolytic anemias originate mainly from defects in hemoglobin and plasma membrane proteins. Here, we propose a new method, thermal analysis of impedance, sensitive to membrane defects. It detects three processes in erythrocyte membrane; fall in membrane capacity at 49.5 degrees C and activation of passive PO(4)(2+) permeability at 37 degrees C and inorganic ions at 61.5 degrees C. The denaturation of spectrin is involved in the first process whilst the anion channel is involved in latter processes. Using this method three persons with xerocytosis were found whereby the fall in membrane capacity and spherization of erythrocytes were both postponed (53 degrees C) compared to control (49.5 degrees C). In contrast to control cells, strong activation of passive permeability for Cl(-) at 37 degrees C and sucrose at 61 degrees C were detected that were both eliminated by pre-inhibition of the anion channel with 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS). In addition, erythrocytes from 15 patients with various forms of anemia were studied in intact state and after refreshment. The results were compared with the data of clinical laboratory and osmotic fragility test. The final conclusion is that this method detects membrane defects with altered spectrin and anion channel syndrome (hereditary xerocytosis, spherocytosis, poikilocytosis and pyropoikilocytosis, elliptocytosis and stomatocytosis) and, after refreshment, helps differentiate them from the anemia with hemoglobinopathy.

Treatment of cutaneous vascular lesions using multiple-intermittent cryogen spurts and two-wavelength laser pulses: Numerical and animal studies

BACKGROUND AND OBJECTIVES

Presently, cutaneous vascular lesions are treated using a single cryogen spurt and single laser pulse (SCS-SLP), which do not necessarily produce complete lesion removal in the majority of patients. In this study, the feasibility of applying multiple cryogen spurts intermittently with multiple two-wavelength laser pulses (MCS-MTWLP) was studied using numerical and animal models.

STUDY DESIGN/MATERIALS AND METHODS

Two treatment procedures were simulated: (1) SCS+532 nm SLP; and (2) MCS+532/1064 nm MTWLP. Light transport and heat diffusion in human skin were simulated with the Monte Carlo method and finite element model, respectively. Possible epidermal damage and blood vessel photocoagulation were evaluated with an Arrhenius-type kinetic model. Blood vessels in the rodent window chamber model (RWCM) were irradiated with either SLP or MTWLP. Laser-induced structural and functional changes in the vessels were documented by digital photography and laser speckle imaging (LSI).

RESULTS

The numerical results show that the MCS-MTWLP approach can provide sufficient epidermal protection while simultaneously achieving photocoagulation of larger blood vessels as compared to SCS-SLP. Animal studies show that MTWLP has significant advantages over SLP by inducing irreversible damage to larger blood vessels without adverse effects.

CONCLUSIONS

MCS-MTWLP may be a promising approach to improve therapeutic outcome for patients with cutaneous vascular lesions featuring large blood vessels.

Electrode surface ratio optimization for thermal performance in 3-D dielectrophoretic single-cell traps

We present a systematic numerical analysis of the thermal properties of dielectrophoretic single-cell traps. The influence of the thermal conductivity of the wall material is investigated, as well as the influence of the electrical conductivity of the liquid and the applied potential. We also explore the effect of the electrode geometry on the thermal properties of the trap. We show that substrates with thermal conductivities smaller than 100 W/mK can affect significantly the temperature increase inside the traps. Our results also show, for the first time, that for flat electrodes there is an optimum electrode to trap surface area ratio for which the ratio of temperature increase in the liquid to dielectrophoretic force on a particle can be minimized. This result will be useful in the future development of optimized dielectrophoretic traps.

Relationship between damaged fraction and reflected spectra of denaturing tissues

BACKGROUND AND OBJECTIVES

During thermal therapy of tissue, such as induced by microwave heating, the initiation of denaturation should be monitored for proper thermal dosage. Additionally, denaturation should be confined to the pathologic volume, while preserving surrounding healthy tissue. The relationship between the damaged fraction and reflected spectra of denaturing tissues was investigated for a variation of the temperature of the tissues.

STUDY DESIGN/MATERIALS AND METHODS

Denaturation of muscle, liver, and milk was studied in vitro by measuring the temperature-varying reflectance spectrum as heating occurs. A high-resolution fiber optic spectrometer was used to measure the reflectance changes. Temperature was monitored using a thermocouple embedded within the tissue along the side of the optical fiber probe.

RESULTS

The values of average free energy to initiate denaturation in muscle and liver at about 60 degrees C were 94.8 and 96.3 kJ/mole, respectively. The reflectance spectra increased in amplitude for muscle and liver, and the peak shifted from approximately 700 to 720 nm in accordance with the damage fraction of tissue. The reflectance spectrum for milk was essentially unchanged.

CONCLUSIONS

Spectral changes from heated muscle and liver reflect denaturation of proteins contained therein. The spectral information at 800 nm can be used to determine the average free energy for the initiation of denaturation.

Improvement of port wine stain laser therapy by skin preheating prior to cryogen spray cooling: A numerical simulation

BACKGROUND AND OBJECTIVES

Although cryogen spray cooling (CSC) in conjunction with laser therapy has become the clinical standard for treatment of port wine stain (PWS) birthmarks, the current approach does not produce complete lesion blanching in the vast majority of patients. The objectives of this study are to: (1) experimentally determine the dynamic CSC heat flux when a skin phantom is preheated, and (2) numerically study the feasibility of using skin preheating prior to CSC to improve PWS laser therapeutic outcome.

STUDY DESIGN/MATERIALS AND METHODS

A fast-response thin-foil thermocouple was used to measure the surface temperature and thus heat flux of an epoxy skin phantom during CSC. Using the heat flux as a boundary condition, PWS laser therapy was simulated with finite element heat diffusion and Monte Carlo light distribution models. Epidermal and PWS blood vessel thermal damage were calculated with an Arrhenius-type kinetic model.

RESULTS

Experimental results show that the skin phantom surface can be cooled to a similar minimum temperature regardless of the initial temperature. Numerical simulation indicates that upon laser irradiation, the epidermal temperature increase is virtually unaffected by preheating, while higher PWS blood vessel temperatures can be achieved. Based on the damage criterion we assumed, the depth and maximum diameter of PWS vessels that can be destroyed irreversibly with skin preheating are greater than those without.

CONCLUSIONS

Skin preheating prior to CSC can maintain epidermal cooling while increasing PWS blood vessel temperature before laser irradiation. Numerical models have been developed to show that patients may benefit from the skin preheating approach, depending on PWS vessel diameter and depth.

Thermal Stability of Proteins

Protein stability is critical to the outcome of nearly all thermally mediated applications to biomaterials such as thermal therapies (including cryosurgery), burn injury, and biopreservation. As such, it is imperative to understand as much as possible about how a protein loses stability and to what extent we can control this through the thermal environment as well as through chemical or mechanical modification of the protein environment. This review presents an overview of protein stability in terms of denaturation due to temperature alteration (predominantly high and some low) and its modification by use of chemical additives, pH modification as well as modification of the mechanical environment (stress) of the proteins such as collagen. These modifiers are able to change the kinetics of protein denaturation during heating. While pH can affect the activation energy (or activation enthalpy) and the frequency factor (or activation entropy) of the denaturation kinetics, many other chemical and mechanical modifiers only affect the frequency factor (activation entropy). Often, the modification affecting activation entropy appears to be linked to the hydration of the protein. While the heat-induced denaturation of proteins is reasonably well understood, the heat denaturation of structural proteins (e.g., collagen) within whole tissues remains an area of active research. In addition, while some literature exists on protein denaturation during cold temperatures, relatively little is known about the kinetics of protein denaturation during both freezing and drying. Further understanding of this kinetics will have an important impact on applications ranging from preservation of biomaterials and pharmaceutics to cryosurgery. Interestingly, both freezing and drying involve drastic shifts in the hydration of the proteins. It is clear that understanding protein hydration at the molecular, cellular, and tissue level will be important to the future of this evolving area.

The Kinetics of Thermal Injury in Human Renal Carcinoma Cells

In this study, the thermal injury behavior of both suspended and attached SN12 human renal carcinoma cells (RCC) under thermal therapy conditions (i.e., heating cells to elevated temperature for seconds to minutes) was investigated using a non-isothermal method. This non-isothermal method entailed heating the cells using a programmable heating stage from room temperature at 130 degrees C min(-1) to various peak temperatures from 45 to 70 degrees C, held for 0-10 min, and then cooling down to room temperature at 65 degrees C min(-1). It was found that the suspended SN12 cells are more heat susceptible than attached ones. The non-isothermal portions (i.e., the heat-up and cool-down portions) of the thermal histories were found to be able to cause significant injury (> 10%) in both suspended and attached SN12 cells when the peak temperature is above 60 degrees C. Therefore, a non-isothermal method, which accounts for both the isothermal and non-isothermal portions of the thermal histories, was used to extract the kinetic parameters (i.e., the activation energy and frequency factor) in the Arrhenius injury model for SN12 cells. Furthermore, these results suggest that this non-isothermal method can be used to extract kinetic parameters from in vivo heating studies using minimally invasive surgical probes, where it is very difficult to get a thermal history in tissue with a dominant isothermal portion.

Endometrial Thermal Balloon Ablation Using a High Temperature, Pulsed System: A Mathematical Model

A new endometrial thermal balloon ablation treatment for menorrhagia is modeled mathematically to predict its efficacy and safety. A device preheats a fluid to 173°C within a reservoir external to the uterus, and then pulses this fluid without further heating between the reservoir and the balloon for 2.1 min of treatment time. The model predicted this treatment to result in consistent immediate tissue death (coagulation) depths of 3.4±0.1 mm for uterine cavities of 7 to 26 mL, and that eventual necrosis (tissue death that would occur 1–5 days post burn) may occur to depths of 6.5±0.2 mm. Whereas, burn depths varied with uterine cavity volume when a low temperature treatment (constant 75°C for 15 min) was modeled (2.3–2.9 mm and 6.8–8.2 mm, for immediate tissue death and eventual necrosis respectively). Similarly, the high temperature, pulsed treatment was less sensitive to blood perfusion rate than the low temperature treatment. Predicted eventual necrosis depth was 1.5 mm less for the high temperature, pulsed treatment than that predicted for a low temperature treatment (constant 87°C for 7 min) for the same immediate tissue death depth (3.5 mm), indicating that the new high temperature treatment may result in less damage to non targeted tissues.

Indicators of erythrocyte damage after microwave warming of packed red blood cells

BACKGROUND

Localized overheating of packed red blood cells (PRBCs) after microwave warming with consequent damage to erythrocytes has been reported. We therefore compared possible cellular markers of erythrocyte damage, as measured by flow cytometry, with laboratory indicators of hemolysis to evaluate the effects of microwave warming on PRBCs.

METHODS

PRBC samples were warmed to room temperature or to 37, 42, 47, 52, or 57 degrees C in a water bath. Flow cytometry was performed after fluorescein labeling using antibodies to spectrin, Ca(2+)-ATPase, and Na(+)-K(+)-ATPase. The forward-to-sideward scatter (FSC/SSC) ratio and antibody binding were evaluated. Plasma free hemoglobin (FHb) and alpha-hydroxybutyrate dehydrogenase (HBDH) were measured immediately after heating and after 48 h. In addition, all measurements were made before and after the heating of PRBCs to 35 degrees C by a microwave blood warmer.

RESULTS

Analysis of 15000 erythrocytes showed a decrease in the FSC/SSC ratio and antibody binding above 47 degrees C [at 37 degrees C, median (SD) of 94.2 (7.4) with 0.07 (0.05)% fluorescein-positive; at 52 degrees C, median (SD) of 177.0 (19.0) with 18.5 (6.4)% positively gated; P <0.001]. FHb [room temperature, 0.3 (0.2) g/L] was increased 2-fold at 37 and 42 degrees C, 4-fold at 47 degrees C, and 25-fold at 52 degrees C. HBDH increased in parallel. Hemolysis markers showed an additional twofold increase 48 h after heating to 42 and 47 degrees C. Microwave heating to 35 degrees C did not produce significant changes of any marker.

CONCLUSIONS

All markers of cellular damage were altered after heating to >47 degrees C, and a substantial part of hemolysis was delayed. The methodology can be used for future testing of other blood warming devices.

Relation between K+ leakage and damage to band 3 in photodynamically treated red cells

Potassium leakage is one of the first events that appear after photosensitization of red blood cells. This event may subsequently lead to colloid osmotic hemolysis. The aim of our study was to determine which photodynamically induced damage is responsible for increased membrane cation permeability. This was done by studying the effect of dimethylmethylene blue (DMMB)-mediated photodynamic treatment (PDT) on different membrane transport systems. Inhibition of band 3 activity (anion transport) showed a comparable light dose dependency as PDT-induced potassium leakage, whereas glycerol transport activity was inhibited only at higher light doses. Dipyridamole (DIP), an inhibitor of anion transport, protects band 3 against DMMB-induced damage, and prevents the increase in cation permeability of the membrane. Damage to glycerol transport was partially reduced when PDT was performed in the presence of DIP. Because DIP has no affinity for the glycerol transporter, this protection might result from the reduced photodamage to band 3. These results support the hypothesis that band 3 might be involved in glycerol transport. Glucose transport was not affected by DMMB-mediated PDT. The present results are the first to show a causal relationship between DMMB-mediated photodamage to band 3 and increased cation permeability of red blood cells.

Photothermal coagulation of blood vessels: a comparison of high-speed optical coherence tomography and numerical modelling

Optical-thermal models that can accurately predict temperature rise and damage in blood vessels and surrounding tissue may be used to improve the treatment of vascular disorders. Verification of these models has been hampered by the lack of time- and depth-resolved experimental data. In this preliminary study, an optical coherence tomography system operating at 4-30 frames per second was used to visualize laser irradiation of cutaneous (hamster dorsal skin flap) blood vessels. An argon laser was utilized with the following parameters: pulse duration 0.1-2.0 s, spot size 0.1-1.0 mm, power 100-400 mW. Video microscopy images were obtained before and after irradiations, and optical-thermal modelling was performed on two irradiation cases. Time-resolved optical coherence tomography and still images were compared with predictions of temperature rise and damage using Monte Carlo and finite difference techniques. In general, predicted damage agreed with the actual blood vessel and surrounding tissue coagulation seen in images. However, limitations of current optical-thermal models were identified, such as the inability to model the dynamic changes in blood vessel diameter that were seen in the optical coherence tomography images.

Thermosensitivity of red blood cells from Down's syndrome individuals

Biochemical disturbances of the reactive oxygen species metabolism revealed in subjects with Down's syndrome (DS), and the findings indicating that heat-induced cell alterations have been, at least, partly mediated by reactive oxygen species, made the elucidation of the response of trisomic cells to elevated temperatures of special interest. Kinetic analysis of cell-survival curves, accompanied by the flow cytometry and the scanning electron microscopy (SEM) examinations, and their relationship with the cell membrane fluidity, were undertaken. At each temperature (48-54 degrees C), Dq parameters, representing the ability to accumulate sublethal damages, were similar for both cell groups. D0 parameters (inverse leakage rates; D0 = 1/k) were greater for DS cells at each temperature below 54 degrees C. The haemolysis sensitivity ratio (HSR) showed that DS erythrocytes were, in average, 1.60 times more resistant to heat injury than those from normal subjects. Activation energies of haemolysis, calculated according to the Arrhenius equation, were similar both for normal (290.8 +/- 6.5 [kJ/mol]) and DS erythrocytes (288.0 +/- 5.5 [kJ/mol]). Flow cytometry studies showed that the scattering properties of intact DS erythrocytes (reflecting size, volume, shape and cell membrane surface morphology) were different than those of normal cells. Scanning electron micrographs and scattering diagrams obtained for cells submitted to heat stress (51 degrees C) confirmed that DS erythrocytes were more resistant, to a certain extent, to heat-induced disruption than normal cells. The steady-state fluorescence anisotropy of TMA-DPH (1-(4-trimethyl-ammoniumphenyl)-6-phenyl-1,3,5-hexatriene) showed that untreated DS erythrocytes had substantially lower fluidity (r = 0.356 +/- 0.008) of the outer monolayer of cell membranes as compared to normal cells (r = 0.324 +/- 0.011). The increase of the cell membrane fluidity during exposure to heat was observed. The greatest elevation of cell membrane fluidity occurred during the preleakage period, immediately upon the heat treatment and was considered as a rate-limiting step of heat-induced haemolysis.

Bioheat transfer analysis of cryogen spray cooling during laser treatment of port wine stains

BACKGROUND AND OBJECTIVE

The thermal response of port wine stain (PWS) skin to a combined treatment of pulsed laser irradiation and cryogen spray cooling (CSC) was analyzed through a series of simulations performed with a novel optical-thermal model that incorporates realistic tissue morphology.

STUDY DESIGN/MATERIALS AND METHODS

The model consisted of (1) a three-dimensional reconstruction of a PWS biopsy, (2) a Monte Carlo optical model, (3) a finite difference heat transfer model, and (4) an Arrhenius thermal damage calculation. Simulations were performed for laser pulses of 0.5, 2, and 10 ms and a wavelength of 585 nm. Simulated cryogen precooling spurts had durations of 0, 20, or 60 ms and terminated at laser onset. Continuous spray cooling, which commenced 60 ms before laser onset and continued through the heating and relaxation phases, was also investigated.

RESULTS

The predicted response to CSC included maximal pre-irradiation temperature reductions of 27 degrees C at the superficial surface and 12 degrees C at the dermoepidermal junction. For shorter laser pulses (0.5, 2 ms), precooling significantly reduced temperatures in superficial regions, yet did not effect superficial vessel coagulation. Continuous cooling was required to reduce significantly thermal effects for the 10-ms laser pulse.

CONCLUSIONS

For the PWS morphology and treatment parameters studied, optimal damage distributions were obtained for a 2-ms laser pulse with a 60-ms precooling spurt. Epidermal and vascular morphology as well as laser pulse duration should be taken into account when planning CSC/laser treatment of PWS. Our novel, realistic-morphology modeling technique has significant potential as a tool for optimizing PWS treatment parameters.

Pulsed laser-induced thermal damage in whole blood

An investigation of the effects of laser irradiation with a wavelength of 532 nm and pulse duration of 10 ms on whole blood was performed in vitro. Threshold radiant exposures for coagulation were quantified and transient radiometric temperatures were measured. The progression of effects with increasing radiant exposure--from evaporation to coagulation-induced light scattering to aggregated coagulum formation to ablation--is described. Results indicate that coagulation and ablation occur at temperatures significantly in excess of those assumed in previous theoretical studies. An Arrhenius rate process analysis based on hemoglobin data indicates good agreement with experimental results.

Thermal destabilization of transmembrane proteins by local anaesthetics

Local anaesthetics, in addition to anaesthesia, induce the synthesis of heat shock proteins (HSPs), sensitize cells to hyperthermia, and increase the aggregation of nuclear proteins during heat shock. Anaesthetics are membrane active agents, and anaesthesia appears to be due to altered ion channel activity; however, the direct effect of heat shock is protein denaturation. These observations suggest that local anaesthetics may sensitize cells to hyperthermia by interacting with and destabilizing membrane proteins such that protein denaturation is increased. It is shown, using differential scanning calorimetry (DSC), that the local anaesthetics procaine, lidocaine, tetracaine and dibucaine destabilize the transmembrane domains of the Ca2+ -ATPase of sarcoplasmic reticulum and the band III anion transporter of red blood cells. The transmembrane domain of the Ca2+ -ATPase has a transition temperature (Tm) of denaturation of 61 degrees C which is decreased, for example, to 53 degrees C by 15 mM lidocaine. The degree of destabilization (deltaTm) by each anaesthetic is proportional to the lipid to water partition coefficient, and the increased sensitization by anaesthetics with larger partition coefficients and at higher pH suggests that the uncharged forms of the anaesthetics are responsible for destabilization. A Hill analysis of deltaTm for the Ca2+ -ATPase as a function of the concentration of anaesthetic in water gives dissociation constants (Kd) on the order of 10(-4) M, if binding occurs directly from the aqueous phase. This demonstrates moderate affinity binding. However, dissociation constants of 1-3 M are obtained, if binding occurs through the lipid phase, which demonstrates low affinity binding. Thus, the interaction of local anaesthetics with the Ca2+ -ATPase may be moderately specific or non-specific depending on the mechanism of interaction. The observation that local anaesthetics also destabilize the transmembrane domain of the band III protein of erythrocytes suggests that destabilization of transmembrane proteins is a general property of anaesthetics, which is at least in part a mechanism of sensitization to hyperthermia.

Spectrofluorometric and microcalorimetric study of the thermal poration relevant to the mechanism of thermohaemolysis

This study sheds light on the structural changes in erythrocyte membrane during thermally induced poration, an event involved in thermohaemolysis. Two major membrane disturbing events can be induced during transient heating, the denaturation of spectrin and thermoporation. The first one precedes the latter but is not involved in it. Ethanol linearly reduces the onset temperature of both events but with different efficiencies. Thermoporation efficiency exceeds by 3.5 fold that of spectrin denaturation. Thus, at a specific concentration of ethanol (18% v/v), the poration occurs at 39.5 degrees C, which precedes the denaturation of spectrin by 6 degrees C. To induce and study the poration avoiding spectrin denaturation, cells were put in contact with preheated (39 degrees C) isotonic (60mM) NaCl) media containing 18% v/v ethanol and sucrose as an osmotic protectant. After 3 min heating, the porated cells were washed, their membranes isolated and studied. The control cells were processed similarly except that they were incubated at 23 degrees C, thus avoiding thermoporation. Using scanning microcalorimetry, the enthalpy and the temperature of denaturation of spectrin were found to be the same in control as well as in porated membranes which indicates similar spectrin structure in both membranes. While the enthalpy of denaturation of the anion channel was preserved, its denaturation temperature was lowered by 2.5 degrees C after poration. These results confirmed that the heat denaturation of the main membrane proteins was not needed and not involved in thermoporation and, hence, in thermohaemolysis. Analysis of the fluorescence of membrane bound ANS gave an apparent increase in the number of binding sites for ANS in membranes after poration. In relation to the control, the eximerization of pyrene in porated membranes changed, depending on the location of the probe: in the domain of free lipids it decreased by 18% but it increased by 60% in the lipid milieu proximal to membrane proteins. Likewise, the eximerization of N-(3-Pyrene) maleimide bound to membrane proteins increased by 67% after poration, which proves increased intramolecular mobility of proteins following poration. The maximal efficiency for transferring energy from tryptophans to neighbouring pyrene was determined to be 0.93 in control, which is almost the same as in intact membranes, and 0.70 in porated membranes, indicating a strong decrease in the lipid/protein contact zone. This data suggests a mild conformational change, possibly an irreversible perturbance of the transbilayer distribution of membrane proteins in porated membranes in comparison to the control and intact ones.

Correlation between the n-alkanols-induced sensitization of erythrocytes to hyperthermia and the fluidization of their membrane

It was reported recently that the thermohaemolysis of mammalian erythrocytes is related to a thermo-induced membrane event of permeability barrier impairment in which the inactivation of membrane proteins is implicated. Here, the influence of different n-alkanols, methanol to octanol, on the onset temperature Tm of this barrier impairment event was compared with the changes in the dynamic properties of the membrane lipid region for human erythrocytes. The potencies of these n-alkanols to decrease Tm, to fluidize and disorder the lipid region were strongly related to their lipid solubilities. With respect to their membrane concentration, all the applied n-alkanols were roughly equipotent in decreasing Tm and in fluidizing and disordering the membrane lipids. Since Tm corresponds to the stability of erythrocytes against hyperthermia, this result indicates that the heat sensitization of these cells, induced by the n-alkanols employed, strongly correlated the fluidization (disordering) of the lipid region of their membranes.

Impact of moisture on thermally induced denaturation and decomposition of lyophilized bovine somatotropin

The nonisothermal transitions of lyophilized recombinant bovine somatotropin (rbSt) as seen via differential scanning calorimetry were evaluated with respect to moisture content. The transition peak temperature of rbSt decreased with increasing moisture from 161 degrees C in the dry state to a plateau of 65 degrees C at 28% moisture, which is similar to that of rbSt in solution. Using high performance liquid chromatography, this irreversible endothermic transition consisted primarily of unfolding, hydrophobic aggregation, and some covalent modifications. In the dry state, covalent modifications, including polymerization into compounds of higher molecular weight, were more prominent, while in the presence of moisture, hydrophobic aggregation was most prominent. The irreversibility and scan rate dependence of the endothermic phenomena supports the kinetic nature of the transition rather than a simple equilibrium between globular and unfolded states. The apparent activation energy for the net transition (i.e., unfolding, hydrophobic aggregation, and covalent modifications) was 57 kcal/mol for rbSt at 9.9% moisture. The observed enthalpy of the transition increased, decreased, then approximately leveled off as a function of increasing moisture content. This can be explained by the increasingly significant contribution of the exothermic aggregation at higher moisture contents.

Loss of red blood cell viability associated with limited thermal inactivation of extracellular HIV-1

The effects of incubation at mildly elevated temperatures on HIV-1 inactivation and in vitro red blood cell properties were investigated. Red cells (55% Hct) were leukodepleted (3 log10) by filtration, maintained at 45 or 47 degrees C for 4 or 8 h, and then stored at 4 degrees C. Hemolysis was twice that of controls after 42-day storage for samples treated for 4 h at 45 degrees C, and five times larger for samples heated at 47 degrees C. There was also a significant increase in the rate of potassium loss, an early decrease in ATP levels, and an initial drop in pH for samples treated at either temperature. Larger differences were observed for samples exposed to these elevated temperatures for 8 h. Osmotic deformability curves obtained by ektacytometry showed dramatic decreases in red cell deformability at both temperatures and for both time periods. HIV-1 inactivation in red cells treated at 45 degrees C (approximately 0.25 log10/h) was considerably less than that obtained in tissue culture medium (1-2 log10/h). Since the decrease in red cell deformability is likely to indicate reduced red cell function and survival, and the rate of HIV-1 inactivation is low, mild heat treatment is not an adequate process for viral inactivation of red cell products.

Hyperthermia (heat shock)-induced protein denaturation in liver, muscle and lens tissue as determined by differential scanning calorimetry

Protein denaturation has been shown to occur in cells during heat shock and is closely correlated with the cellular responses to hyperthermia; however, little is known about protein denaturation in tissue. This study describes an analysis of endothermic transitions in the hyperthermic region using differential scanning calorimetry (DSC) in liver, white muscle, and lens tissue from Wistar rat, New Zealand white rabbit, and Rainbow trout. Complex DSC profiles consisting of several transitions were obtained for each tissue. Evidence is given that these transitions are due primarily to protein denaturation. Onset temperatures of denaturation (Tl) for rat liver, muscle, and lens are about 38, 39 and 48 degrees C, respectively. Thus, significant protein denaturation occurs in liver and muscle during mild hyperthermia (40-45 degrees C) with lens considerably more stable. The values of Tl for the same tissue from the different animals correlates well with body temperature (rabbit 39.4, rat 38.2, and trout grown at 11 degrees C); Tl increased in the same order as the body temperature for each tissue. Thus, there is correlation between the onset temperature for protein denaturation in these tissues and body temperature.