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Engineered Nanoparticles for Drug Delivery in Cancer Therapy *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Tianmeng Sun, Yu Shrike Zhang, Pang Bo, Dong Choon Hyun, Miaoxin Yang, Younan Xia
To better use temperature variation as a stimulus for triggering drug release, Xia and coworkers introduced phase-change materials (PCMs), which are capable of undergoing reversible solid-liquid phase transitions in response to changes in temperature [311]. In the solid state, PCMs can effectively prevent any leakage of encapsulated drugs at temperatures below their melting points. However, when heated beyond their melting points, they exhibit a rapid phase change to the liquid state, thus releasing the payload. For PCMs based on fatty alcohols and fatty acids, they are particularly well-suited for drug delivery applications in vivo because of their excellent biocompatibility. Notable examples include 1-tetradecanol (melting point: 38°C–39°C), tridecanoic acid (41°C–42°C), and dodecanoic acid (43°C–46°C). In practice, the melting points of PCMs can be precisely tuned in the range of 38°C–46°C by using binary or tertiary mixtures of these compounds at appropriate ratios.
Physical and Technological Modulation of Topical and Transdermal Drug Delivery
Published in Marc B. Brown, Adrian C. Williams, The Art and Science of Dermal Formulation Development, 2019
Marc B. Brown, Adrian C. Williams
Important parameters such as intensity and duration of heat (controlled by, for example, the mass/volume of heat-generating material and the presence of a trigger such as oxygen/nucleating agent) and exposure time are known to influence heat-facilitated percutaneous absorption. Other factors such the rate of crystallisation and the level of saturation are thought to be important parameters for phase-change materials. Therefore, these parameters can be manipulated and optimised for either local or systemic drug delivery, whilst avoiding cutaneous damage or patient discomfort. Whilst there are no regulatory limits on the intensity and duration of heat produced by thermophoretic delivery systems, the scarce information on temperatures tolerated by the skin would suggest that an appropriate range for thermophoretic delivery system would be 44–47°C. Consequently, most studies investigating heat-facilitated percutaneous absorption have employed temperatures of ≤45°C, which is within the physiologically tolerable range.
Thermophysiological aspects of wearable robotics: Challenges and opportunities
Published in Temperature, 2023
The soft interface layer could include a gel-type phase change material to prevent skin temperature increase when the exoskeleton is engaged. Many phase-change materials are already used in neck and trunk cooling garments [74,81,87]. Since practically sized packets of such materials provide cooling only for a limited time, the body interface could include a mechanism for swapping out the phase-change cartridges when loosened. Finally, in principle, the body interface cooling could also be achieved using liquid cooling even within the soft part of the interface [88] or wearable thermoelectrics [89]. However, these active cooling methods require heavy support equipment that might not to be practical for exoskeleton use (e.g. based on personal measurements a typical commercial liquid cooled vest with 2.5 kg ice-filled plastic bladder and pumping system carried in a backpack has a mass of about 6 kg). Next, I discuss opportunities for systematic evaluation of the thermal performance of current and improved exoskeleton designs.
AuNPs as an important inorganic nanoparticle applied in drug carrier systems
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Wen Li, Zhiwen Cao, Rui Liu, Linlin Liu, Hui Li, Xiang Li, Youwen Chen, Cheng Lu, Yuanyan Liu
AuNPs can be modified with heat-sensitive materials to realise drug release [154]. For example, Lajunen et al. [155] developed liposomal drug carriers which were formulated using a heat-sensitive composition with star- or rod-shaped AuNPs. AuNPs convert light energy into heat and release it into the lipid bilayer, causing an increase in the local temperature that causes double leakage of the liposome and triggers drug release. Phase change material (PCM) is a material with a large latent heat of fusion that melts and solidifies at a certain temperature. There are three forms of PCM: liquid-gas, solid-solid, and solid-liquid. Solid-liquid PCM is now widely used in basic research and practical application [156]. The PCM which is applied in a drug release system should have good biocompatibility and a precise critical solution temperature with a slightly higher melting point than physiological temperature [157]. lauric acid [158], fatty acid and 1-tetradecanol [156] are frequently used PCMs. Poudel et al. [159] reported a new strategy in which hollow silver-gold nanoshells are encapsulated in hollow mesoporous silica as an effective platform for the release of anticancer drugs. The mesopores were blocked with the heat-sensitive PCM lauric acid to achieve drug-controlled release by photothermal action. In addition, there are also many dual-responsive drug release systems such as pH/near-infra-red dual-triggered drug release [160], GSH/near-infra-red dual-triggered drug release [161], GSH/pH dual-triggered drug release [146] and other responsive drug release systems [162,163].
Cooling therapy for the management of hypoxic-ischaemic encephalopathy in middle-income countries: we can, but should we?
Published in Paediatrics and International Child Health, 2019
Phase-change materials are made of salt hydride, fatty acid and esters or paraffin, melt at a set point and in theory could be effective as a semi-servo-controlled cooling device [10]. They are inexpensive (<£100 per mattress) and therefore have huge potential for wider scale-up in LMIC. The first ever pilot randomised controlled trial of whole-body cooling using PCM was undertaken in a south Indian neonatal unit in 2007 [12]. The centre had good facilities for tertiary neonatal care including invasive ventilation. Six dedicated and trained research nurses were appointed to provide 1:1 care during cooling. Despite this, there were temperature fluctuations and PCM was effective only when the ambient temperate was reduced with air-conditioning. Mortality of the PCM-cooled infants was twice that of those receiving the usual care (normothermic), although this was not statistically significant (risk ratio 1.9, 95% confidence interval 0.4–8.9). Nevertheless, the findings did not deter ambitious entrepreneurs from marketing and commercialising PCM at a 15 times higher cost (approximately £1600), claiming that the device is a life-saver [13] but without disclosing the increased mortality reported in the only randomised controlled trial of PCM.