The Use of Silica Microparticles to Improve the Efficiency of Optical Hyperthermia (OH)

Although optical hyperthermia could be a promising anticancer therapy, the need for high concentrations of light-absorbing metal nanoparticles and high-intensity lasers, or large exposure times, could discourage its use due to the toxicity that they could imply. In this article, we explore a possible role of silica microparticles that have high biocompatibility and that scatter light, when used in combination with conventional nanoparticles, to reduce those high concentrations of particles and/or those intense laser beams, in order to improve the biocompatibility of the overall procedure. Our underlying hypothesis is that the scattering of light caused by the microparticles would increase the optical density of the irradiated volume due to the production of multiple reflections of the incident light: the nanoparticles present in the same volume would absorb more energy from the laser than without the presence of silica particles, resulting either in higher heat production or in the need for less laser power or absorbing particles for the same required temperature rise. Testing this new optical hyperthermia procedure, based on the use of a mixture of silica and metallic particles, we have measured cell mortality in vitro experiments with murine glioma (CT-2A) and mouse osteoblastic (MC3T3-E1) cell lines. We have used gold nanorods (GNRs) that absorb light with a wavelength of 808 nm, which are conventional in optical hyperthermia, and silica microparticles spheres (hereinafter referred to as SMSs) with a diameter size to scatter the light of this wavelength. The obtained results confirm our initial hypothesis, because a high mortality rate is achieved with reduced concentrations of GNR. We found a difference in mortality between CT2A cancer cells and cells considered non-cancer MC3T3, maintaining the same conditions, which gives indications that this technique possibly improves the efficiency in the cell survival. This might be related with differences in the proliferation rate. Since the experiments were carried out in the 2D dimensions of the Petri dishes, due to sedimentation of the silica particles at the bottom, whilst light scattering is a 3D phenomenon, a large amount of the energy provided by the laser escapes outside the medium. Therefore, better results might be expected when applying this methodology in tissues, which are 3D structures, where the multiple reflections of light we believe will produce higher optical density in comparison to the conventional case of no using scattering particles. Accordingly, further studies deserve to be carried out in this line of work in order to improve the optical hyperthermia technique.This study was partially supported by CIBER-BBN (Spain) and the NEUROCENTRO-CM (B2017/BMD-3760) Consortium. Characterization of the MNPs was performed by the ICTS ‘NANBIOSIS’, Unit 15, Functional Characterization of Magnetic Nanoparticles of the CIBER in Bioengineering, Biomaterials & Nanomedicine (CIBER-BBN) at the Center for Biomedical Technology (CTB) of the ‘Universidad Politécnica de Madrid’ (UPM). This work was carried out as a part of Project PGC2018-097531-B-I00, funded by the Ministry of Science of Spain

Democratisation of AAC symbol choices using technology

The use of an online voting system has been developed to enable democratic choices of newly designed symbols to support speech, language and literacy skills in a localisation situation. The system works for those using and supporting Augmentative and Alternative Communication (AAC) symbols on electronic systems by the provision of simplified scales of acceptance and adapted grids. The methodology and results highlighted the importance of user participation at the outset and concrete examples of symbol adaptations that were found necessary to ensure higher levels of user satisfaction. Design changes included appropriate local dress codes, linguistic nuances, social settings, the built environment and religious sensitivities

Artificial synovial fluid and artificial cerebrospinal fluid development and tests using QCR based biosensor for medical diagnosis

Quartz Crystal Resonators are devices with high capabilities in sensing systems due to their accuracy, efficiency and low cost. In this work we present a prototype of biosensor based on the use of QCR with the objective of measure the viscosity of small samples of biological fluids for medical diagnosis. In order to observe the response of the system in a biomedical application, two artificial fluids were developed for simulate healthy and pathological fluids. These measurements were compared with a professional viscometer to observe the similarity between both measurement methods. These tests may be used to observe the viability of the device and to calibrate the system before testing with real fluids

Preliminary Glycerine Tests using Quartz Crystal Resonator based biosensor for medical diagnosis

Quartz crystal resonators (QCR) are piezoelectric elements that, when excited with a sinusoidal signal at its resonance frequency, their impedance will reach a minimum value. According to Sauerbrey [1] and Kanazawa [2], when the crystal is in contact with a mass (solidf ilm) or with a fluid, its resonance frequency changes. These properties allow QCR to have applications in the field of biomedicine [3]. With this prototype it will be possible to measure the viscosity of biological fluids for medical diagnosis, for example, synovial fluid, since the viscosity is a factor in diagnosing diseases such as osteoarthritis or arthritis [4, 5]. On a first stage, we must make sure that the device is capable of measuring viscosity. For this purpose, tests were developed to measure the viscosity of a Newtonian fluid such as a mixture of vegetable glycerin with distilled water

Viscosity Measurement Sensor: A Prototype for a Novel Medical Diagnostic Method Based on Quartz Crystal Resonator

Viscosity variation in human fluids, such as Synovial Fluid (SF) or Cerebrospinal Fluid (CSF), can be used as a diagnostic factor; however, the sample volume obtained for analysis is usually small, making it difficult to measure its viscosity. On the other hand, Quartz Crystal Resonators (QCR) have been used widely in sensing applications due to their accuracy, cost, and size. This work provides the design and validation of a new viscosity measurement system based on quartz crystal resonators for low volume fluids, leading to the development of a sensor called “ViSQCT” as a prototype for a new medical diagnostic tool. The proposed method is based on measuring the resonance frequency at the crystal’s maximum conductance point through a frequency sweep, where crystals with 10 MHz fundamental resonance frequency were used. For validation purposes, artificial fluids were developed to simulate SFs and CFs in healthy and pathological conditions as experiment phantoms. A commercial QCR based system was also used for validation since its methodology differs from ours. A conventional rotational viscometer was used as a reference for calibration purposes. ViSQCT demonstrates the capability to measure the sample’s viscosity differentiation between healthy and pathological fluid phantoms and shows that it can be used as a basis for a diagnostic method of several pathologies related to the studied biological fluids. However, some performance differences between both QCR-based systems compared to the reference system deserves further investigation

Enhancing Magnetic Hyperthermia Nanoparticle Heating Efficiency with Non-Sinusoidal Alternating Magnetic Field Waveforms

For decades now, conventional sinusoidal signals have been exclusively used in magnetic hyperthermia as the only alternating magnetic field waveform to excite magnetic nanoparticles. However, there are no theoretical nor experimental reasons that prevent the use of different waveforms. The only justifiable motive behind using the sinusoidal signal is its availability and the facility to produce it. Following the development of a configurable alternating magnetic field generator, we aim to study the effect of various waveforms on the heat production effectiveness of magnetic nanoparticles, seeking to prove that signals with more significant slope values, such as the trapezoidal and almost-square signals, allow the nanoparticles to reach higher efficiency in heat generation. Furthermore, we seek to point out that the nanoparticle power dissipation is dependent on the waveform’s slope and not only the frequency, magnetic field intensity and the nanoparticle size. The experimental results showed a remarkably higher heat production performance of the nanoparticles when exposed to trapezoidal and almost-square signals than conventional sinusoidal signals. We conclude that the nanoparticles respond better to the trapezoidal and almost-square signals. On the other hand, the experimental results were used to calculate the normalized power dissipation value and prove its dependency on the slope. However, adjustments are necessary to the coil before proceeding with in vitro and in vivo studies to handle the magnetic fields required