Real-time monitoring of heat transfer between gold nanoparticles and tethered bilayer lipid membranes.

Plasmon resonance frequency irradiated gold nanoparticles (GNPs) have gained interest as a laser-targeted treatment for infections, tumors and for the controlled release of drugs in situ. Questions still remain, however, as to the efficiency of heat delivery within biological tissues and how this can be reliably determined. Here, we demonstrate how a nanomaterial-electrode interface that mimics cell membranes can detect the localized heat transfer characteristics arising from plasmon resonance frequency-matched laser excitation of GNPs. We demonstrate that the lipid bilayer membrane can be affected by conjugated GNP induced hyperthermia when irradiated with a laser power output as low as 135 nW/µm2. This is four orders of magnitude lower power than previously reported. By restricting the lateral movement of the lipids in the bilayer membrane, it was shown that the change in membrane conductance as a result of the heat transfer was due to the creation of transient lipidic toroidal pores within the membrane. We further demonstrate that the heat transfer from the GNPs alters diffusion rates of monomers of the gramicidin-A peptide within the lipid leaflets. This work highlights how targeted low laser power GNP hyperthermia treatments, in vivo, could play a dual role of interfering with both cell membrane morphology and dynamics, along with membrane protein function.

Thermal modelling of controlled scalp hypothermia using a thermoelectric cooling cap.

This study presents a novel, thermoelectric cryotherapy cap that aims to provide effective and controlled scalp cooling to prevent hair loss for chemotherapy patients. The cap's design consists of multiple thermoelectric coolers (TECs) evenly spaced and bonded to a soft thermal interface material, tightly fitted to a patient's head. A numerical model is developed to assess the performance of alternative cap designs in relation to their ability to achieve hair follicle hypothermia. Under ideal conditions, 26.5 W of heat removal from the scalp is required to achieve the clinically-significant follicle temperature target of 22 °C. Temperature maps of the subcutaneous tissue are generated to visualise the development of hypothermic follicles, and thereby assess the effectiveness of the cap design. Transient studies show that cooling to the therapeutic temperature can be achieved within 40 min. To avoid the possibility of cold-induced tissue damage, individual thermoelectric cooling modules should not be operated at a cooling flux beyond approximately 3175 W/m2. This may be achieved with 38 modules evenly spaced in a checkerboard arrangement, each providing 0.7 W of cooling to the scalp.

Soft and Moldable Mg-Doped Liquid Metal for Conformable Skin Tumor Photothermal Therapy.

As a class of emerging multifunctional soft materials, gallium-based liquid metal (LM) amalgams, metal/nonmetal particles dispersed in an LM environment, suggest a combination of intriguing properties. In this article, Mg particles in gallium-indium alloy for making new conceptual biomedical materials, which can adapt to any irregular skin surface, are introduced, and superior photothermal effect with a 61.5% photothermal conversion (PTC) increase with respect to that of the LM is realized. The formation of a new intermetallic phase Mg2 Ga5 and adjustable surface roughness, which guarantees a rapid temperature increase when illuminated by laser, are found to be responsible for the photothermal effect enhancement. The obtained soft metallic mixtures also possess excellent thermal conductivity, favorable formability, together with benign biocompatibility. The potential use of the currently produced LM mixtures for conformable photothermal therapy (PTT) of skin tumors, which is hard to precisely heat otherwise via conventional ways, is explored. The soft Mg-GaIn mixtures can adapt to irregular tumor shapes to achieve conformable and minimal invasive tumor treatment. In vivo experiments on skin-tumor-bearing mice show obvious tumor growth suppression and life span extension after PTT treatment. As a novel functional PTC material, the Mg-GaIn mixtures exhibit promising potentials in the coming clinical cancer theranostics.

Heat transfer from nanoparticles for targeted destruction of infectious organisms.

Whereas the application of optically or magnetically heated nanoparticles to destroy tumours is now well established, the extension of this concept to target pathogens has barely begun. Here we examine the challenge of targeting pathogens by this means and, in particular, explore the issues of power density and heat transfer. Depending on the rate of heating, either hyperthermia or thermoablation may occur. This division of the field is fundamental and implies very different sources of excitation and heat transfer for the two modes, and different strategies for their clinical application. Heating by isolated nanoparticles and by agglomerates of nanoparticles is compared: hyperthermia is much more readily achieved with agglomerates and for large target volumes, a factor which favours magnetic excitation and moderate power densities. In contrast, destruction of planktonic pathogens is best achieved by localised thermoablation and very high power density, a scenario that is best delivered by pulsed optical excitation.

A critical review on liquid-gas mass transfer models for estimating gaseous emissions from passive liquid surfaces in wastewater treatment plants.

Emission models are useful tools for the study and management of atmospheric emissions from passive liquid surfaces in wastewater treatment plants (WWTPs), which are potential sources of odour nuisance and other environmental impacts. In this work, different theoretical and empirical models for the gas-side (kG) and liquid-side (kL) mass transfer coefficients in passive surfaces in WWTPs were critically reviewed and evaluated against experimental data. Wind forcing and the development of the wind-wave field, especially the occurrence of microscale wave breaking, were identified as the most important physical factors affecting mass transfer in these situations. Two approaches performed well in describing the available data for kG for water vapour. One is an empirical correlation whilst the other consists of theoretical models based on the description of the inner part of the turbulent boundary layer over a smooth flat plate. We also fit to the experimental data set a new, alternate equation for kG, whose performance was comparable to existing ones. However, these three approaches do not agree with each other in the whole range of Schmidt numbers typical for compounds found in emissions from WWTPs. As to kL, no model was able to satisfactorily explain the behaviour and the scatter observed in the whole experimental data set. Excluding two suspected biased sources, the WATER9 (US EPA, 1994. Air Emission Models for Waste and Wastewater. North Carolina, USA. EPA-453/R-94-080A) approach produced the best results among the most commonly used kL models, although still with considerably high relative errors. For this same sub-set, we propose a new, alternate approach for estimating kL, which resulted in improved performance, particularly for longer fetches. Two main gaps were found in the literature, the understanding of the evolution of the mass transfer boundary layer over liquid surfaces, and the behaviour of kL for larger fetches, especially in the range from 40 to 60 m.