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Soares, P. I. P., F. Lochte, C. Echeverria, L. C. J. Pereira, J. T. Coutinho, I. M. M. Ferreira, C. M. M. Novo, and J. P. M. R. Borges, "Thermal and magnetic properties of iron oxide colloids: influence of surfactants", Nanotechnology, vol. 26, issue 42, pp. 425704, 2015. AbstractDOI

Iron oxide nanoparticles (NPs) have been extensively studied in the last few decades for several biomedical applications such as magnetic resonance imaging, magnetic drug delivery and hyperthermia. Hyperthermia is a technique used for cancer treatment which consists in inducing a temperature of about 41–45 °C in cancerous cells through magnetic NPs and an external magnetic field. Chemical precipitation was used to produce iron oxide NPs 9 nm in size coated with oleic acid and trisodium citrate. The influence of both stabilizers on the heating ability and in vitro cytotoxicity of the produced iron oxide NPs was assessed. Physicochemical characterization of the samples confirmed that the used surfactants do not change the particles' average size and that the presence of the surfactants has a strong effect on both the magnetic properties and the heating ability. The heating ability of Fe3O4 NPs shows a proportional increase with the increase of iron concentration, although when coated with trisodium citrate or oleic acid the heating ability decreases. Cytotoxicity assays demonstrated that both pristine and trisodium citrate Fe3O4 samples do not reduce cell viability. However, oleic acid Fe3O4 strongly reduces cell viability, more drastically in the SaOs-2 cell line. The produced iron oxide NPs are suitable for cancer hyperthermia treatment and the use of a surfactant brings great advantages concerning the dispersion of NPs, also allowing better control of the hyperthermia temperature.

Soares, P. I. P., C. A. T. Laia, A. Carvalho, L. C. J. Pereira, J. T. Coutinho, I. M. M. Ferreira, C. M. M. Novo, and J. P. Borges, "Iron oxide nanoparticles stabilized with a bilayer of oleic acid for magnetic hyperthermia and MRI applications", Appl Surf Sci, vol. 383, pp. 240-247, 2016. AbstractDOI

Iron oxide nanoparticles (Fe3O4, IONPs) are promising candidates for several biomedical applications such as magnetic hyperthermia and as contrast agents for magnetic resonance imaging (MRI). However, their colloidal stability in physiological conditions hinders their application requiring the use of biocompatible surfactant agents. The present investigation focuses on obtaining highly stable IONPs, stabilized by the presence of an oleic acid bilayer. Critical aspects such as oleic acid concentration and pH were optimized to ensure maximum stability. NPs composed of an iron oxide core with an average diameter of 9 nm measured using transmission electron microscopy (TEM) form agglomerates with an hydrodynamic diameter of around 170 nm when dispersed in water in the presence of an oleic acid bilayer, remaining stable (zeta potential of −120 mV). Magnetic hyperthermia and the relaxivities measurements show high efficiency at neutral pH which enables their use for both magnetic hyperthermia and MRI.

Soares, P. I. P., I. M. M. Ferreira, and J. P. M. R. Borges, "Application of hyperthermia for cancer treatment: recent patents review", Topics in anti-cancer research, USA, Bentham Science Publishers, pp. 342-383, 2014. Abstract

Cancer is one of the main causes of death in the world and its incidence increases every
day. Current treatments are insufficient and present many breaches. Hyperthermia is an old
concept and was early established as a cancer treatment option, mainly in superficial
cancers. More recently, the concept of intracellular hyperthermia emerged wherein magnetic
particles are concentrated at the tumor site and remotely heated using an applied magnetic
field to achieve hyperthermic temperatures (42-45ºC). Many patents have been registered in
this area since the year 2000. This chapter presents the most relevant information organized
in two main categories according to the use or not of nanotechnology.

Soares, P. I. P., D. Machado, C. Laia, L. C. J. Pereira, J. T. Coutinho, I. M. M. Ferreira, C. M. M. Novo, and J. P. Borges, "Thermal and magnetic properties of chitosan-iron oxide nanoparticles", Carbohydr Polym, vol. 149, pp. 382-390, 2016. AbstractDOI

Chitosan is a biopolymer widely used for biomedical applications such as drug delivery systems, wound healing, and tissue engineering. Chitosan can be used as coating for other types of materials such as iron oxide nanoparticles, improving its biocompatibility while extending its range of applications.

In this work iron oxide nanoparticles (Fe3O4 NPs) produced by chemical precipitation and thermal decomposition and coated with chitosan with different molecular weights were studied. Basic characterization on bare and chitosan-Fe3O4 NPs was performed demonstrating that chitosan does not affect the crystallinity, chemical composition, and superparamagnetic properties of the Fe3O4 NPs, and also the incorporation of Fe3O4 NPs into chitosan nanoparticles increases the later hydrodynamic diameter without compromising its physical and chemical properties. The nano-composite was tested for magnetic hyperthermia by applying an alternating current magnetic field to the samples demonstrating that the heating ability of the Fe3O4 NPs was not significantly affected by chitosan.

Soares, P. I. P., A. M. R. Alves, L. C. J. Pereira, J. T. Coutinho, I. M. M. Ferreira, C. M. M. Novo, and J. P. M. R. Borges, "Effects of surfactants on the magnetic properties of iron oxide colloids", J. Colloid Interface Sci., vol. 419, pp. 46-51, 2014. AbstractDOI

Iron oxide nanoparticles are having been extensively investigated for several biomedical applications such as hyperthermia and magnetic resonance imaging. However, one of the biggest problems of these nanoparticles is their aggregation.

Taking this into account, in this study the influence of three different surfactants (oleic acid, sodium citrate and Triton X-100) each one with various concentrations in the colloidal solutions stability was analyzed by using a rapid and facile method, the variation in the optical absorbance along time.

The synthesized nanoparticles through chemical precipitation showed an average size of 9 nm and a narrow size distribution. X-ray diffraction pattern and Fourier Transform Infrared analysis confirmed the presence of pure magnetite. SQUID measurements showed superparamagnetic properties with a blocking temperature around 155 K. In addition it was observed that neither sodium citrate nor Triton X-100 influences the magnetic properties of the nanoparticles. On the other hand, oleic acid in a concentration of 64 mM decreases the saturation magnetization from 67 to 45 emu/g. Oleic acid exhibits a good performance as stabilizer of the iron oxide nanoparticles in an aqueous solution for 24 h, for concentrations that lead to the formation of the double layer.

Soares, P. I. P., A. I. Sousa, J. C. Silva, I. M. M. Ferreira, C. M. M. Novo, and J. P. Borges, "Chitosan-based nanoparticles as drug delivery systems for doxorubicin: Optimization and modelling", Carbohydr Polym, vol. 147, pp. 304-312, 2016. AbstractDOI

In the present work, two drug delivery systems were produced by encapsulating doxorubicin into chitosan and O-HTCC (ammonium-quaternary derivative of chitosan) nanoparticles. The results show that doxorubicin release is independent of the molecular weight and is higher at acidic pH (4.5) than at physiological pH. NPs with an average hydrodynamic diameter bellow 200 nm are able to encapsulate up to 70% and 50% of doxorubicin in the case of chitosan and O-HTCC nanoparticles, respectively. O-HTCC nanoparticles led to a higher amount of doxorubicin released than chitosan nanoparticles, for the same experimental conditions, although the release mechanism was not altered. A burst effect occurs within the first hours of release, reaching a plateau after 24 h. Fitting mathematical models to the experimental data led to a concordant release mechanism between most samples, indicating an anomalous or mixed release, which is in agreement with the swelling behavior of chitosan described in the literature.

Soares, P. I. P., A. I. Sousa, I. M. M. Ferreira, C. M. M. Novo, and J. P. Borges, "Towards the development of multifunctional chitosan-based iron oxide nanoparticles: Optimization and modelling of doxorubicin release", Carbohydr Polym, vol. 153, pp. 212-221, 2016. AbstractDOI

In the present work composite nanoparticles with a magnetic core and a chitosan-based shell were produced as drug delivery systems for doxorubicin (DOX). The results show that composite nanoparticles with a hydrodynamic diameter within the nanometric range are able to encapsulate more DOX than polymeric nanoparticles alone corresponding also to a higher drug release. Moreover the synthesis method of the iron oxide nanoparticles influences the total amount of DOX released and a high content of iron oxide nanoparticles inhibits DOX release. The modelling of the experimental results revealed a release mechanism dominated by Fickian diffusion.

Soares, Í., J. Faria, A. Marques, I. A. C. Ribeiro, C. Baleizão, A. Bettencourt, I. Ferreira, and A. C. Baptista, "Drug Delivery from PCL/Chitosan Multilayer Coatings for Metallic Implants", ACS omega, vol. 7, pp. 23096-23106, 2022.
Sousa, D. M., J. C. Lima, and I. Ferreira, "Synthesis of Cadmium Selenide Quantum Dots, Using 2, 2‐Bipyridine as a Capping and Phase Transfer Agent", ChemistrySelect, vol. 2, issue 3, pp. 1271-1274, 2017. AbstractDOI

Cadmium selenide quantum dots (CdSe QDs), were synthesized by one‐pot or water‐to‐organic phase transfer and capped with molten 2,2′‐bipyridine (bipy). The obtained CdSe QDs by the two‐step procedure, reveal average sizes of 2 nm while the one‐pot are mixed with secondary salt products and bipy and are undetectable by TEM. However the absorption peak of both CdSe QDs was at 425 nm and the emission band is centered at 535 nm, with a band width at half height of 77 nm, when excited with 425 nm light. The two‐step CdSe QDs synthesis has the great advantage of capping the CdSe QDs with bipy, forming a solid phase, which is easily stored and dispersed in most of the organic solvents. On the other hand, the one‐pot procedure requires an extra step to remove the secondary products.

Sousa, D. M., W. Chiappim, J. P. Leitão, J. C. Lima, and I. Ferreira, "Microwave synthesis of silver sulfide and silver nanoparticles: light and time influence", ACS omega, vol. 5, pp. 12877-12881, 2020.