Search

Yttrium iron garnet and calcium titanate (Y3Fe5O12-CaTiO3, YIG-CTO) ceramic composite were obtained according to the well-established solid-state route. This system was studied by complex impedance spectroscopy as a function of temperature. All samples showed a thermo-activated relaxation with energy activation between 1.10 and 1.70 eV. The CaTi0.6Fe0.4O2.8 phase is formed during sintering process, which influences in the electrical behavior of the samples. Nyquist diagrams were adjusted by two equivalent circuits in series to represent electric response. The YIG-CTO system was also used to design a dielectric resonator antenna (DRA) for microwave applications. The results indicate that DRA YIG-CTO-based presented an operation frequency range around 1–7 GHz, and reflection coefficient below −38 dB. From obtained results, the YIG-CTO composite is a great candidate for usage in electronic devices, operating in the C-band, such as WiFi and ISM band applications.

Magnetic nanocomposites were synthesized for the targeted delivery of hydrophilic bioactives through guidance generated by a magnetic field. Superparamagnetic iron oxide nanoparticles (SPIONs) were used to generate hydroxyethyl starch magnetic nanocapsules (HES MNCs). This synthesis allowed the co-encapsulation of oncocalyxone A (onco A) and surface-modified magnetite nanoparticles (Fe3O4@citrate) into the same nanostructure. The synthesized nanocapsules exhibited a core-shell morphology, with an average diameter of 143 nm. This nanocomposite showed potential anticancer activity (IC50) against four human tumor cell lines: glioblastoma SNB-19 (1.010 μgmL−1), colon carcinoma HCT-116 (2.675 μgmL−1), prostate PC3 (4.868 μgmL−1), and leukemia HL-60 (2.166 μgmL−1). Additionally, in vivo toxicity and locomotor activity were evaluated in a zebrafish (Danio rerio) model. The nanocomposite exhibited in vitro cytotoxicity, prolonged drug release profile and also responded to an applied magnetic field, representing a versatile compound with perspectives for highest concentration of different hydrophilic bioactives in a target tissue through magnetic vectorization.

Magneto-dielectric composites are interesting advanced materials principally due to their potential applications in electronic fields, such as in microstrip antennas substrates. In this work, we developed superparamagnetic polymer-based films using the biopolymeric matrices chitosan (Ch), cellulose (BC) and collagen (Col). For this proposal, we synthesized superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with polyethyleneimine with a cheap method using sonochemistry. Further, the SPIONs were dispersed into polymer matrices and the composites were evaluated regarding morphology, thermal, dielectric and magnetic properties and their application as microstrip antennas substrates. Microscopically, all tested films presented a uniform dispersion profile, principally due to polyethyleneimine coating. Under an operating frequency (fo) of 4.45 GHz, Ch, BC and Col-based SPION substrates showed moderate dielectric constant (&epsilon, &prime, ) values in the range of 5.2&ndash, 8.3, 6.7&ndash, 8.4 and 5.9&ndash, 9.1, respectively. Furthermore, the prepared films showed no hysteresis loop, thereby providing evidence of superparamagnetism. The microstrip antennas showed considerable bandwidths (3.37&ndash, 6.34%) and a return loss lower than &minus, 10 dB. Besides, the fo were modulated according to the addition of SPIONs, varying in the range of 4.69&ndash, 5.55, 4.63&ndash, 5.18 and 4.93&ndash, 5.44 GHz, for Ch, BC and Col-based substrates, respectively. Moreover, considering best modulation of &epsilon, and fo, the Ch-based SPION film showed the most suitable profile as a microstrip antenna substrate.

TiO2 is a common inorganic filter used in sunscreens due to its photoprotective effect on the skin against UV radiation. However, the use of this kind of material in cosmetics is limited by its inherent photocatalytic activity. It is known that coating on TiO2 surface can improve some features. Although, many of the methodologies used for this purpose are still laborious and time-consuming. Thus, this work reports a novel, easy, cheap and fast strategy to coat TiO2 particles by using a sonochemistry approach, aiming to decrease photocatalytic activity and to enhance colloidal stability. For this proposal, SiO2, Al2O3, ZrO2 and sodium polyacrylate (PAANa) were used to tune the surface of commercial TiO2 particles and they were applied in a sunscreen formulation. The samples were characterized by XRPD, FT-IR, DLS, EDS, SEM and TEM. The photocatalytic activity and UV-shielding ability were also evaluated. The sunscreen formulations were prepared and characterized by zeta potential, DLS, and Sun Protection Factor (SPF). FT-IR, EDS, and charge surface of the particles confirmed the success of the sonochemistry coating. Additionally, TiO2@Al2O3, TiO2@SiO2 and TiO2@PAANa show a lower photocatalytic activity than original TiO2 with similar UV-shielding ability. The sunscreens produced with the coated TiO2 have similar SPF to the one with commercial TiO2. Specifically, the sunscreen with TiO2@PAANa shows an increase in colloidal stability. Herein, the incorporation of the sonochemical-coated TiO2 particles in sunscreen formulations may produce sunscreens with better aesthetic appearance and a greater health security due to its lower free radicals production.

A robust fluorescence-based sensing strategy was designed considering relevance of analyzing chemical additives in industrialized food. In this study, a sensing approach was developed using fluorescent carbon quantum dots (CQDs) as a chemometric tool. CQDs were synthesized by a simple one-step hydrothermal route using the American natural seed Caelsalpinia pulcherrima, and further characterized regarding their chemical structure. Five food additives were identified, citric acid, lactic acid, ascorbic acid, sodium benzoate and potassium sorbate, which showed a highly sensitive response with a limit of detection (LOD) as low as 252 ng mL−1. The sensing platform was designed using the supervised method for recognizing patterns of linear discriminant analysis (LDA), where we could identify different concentrations of additives, after optimization of experimental parameters. Furthermore, the sensing strategy successfully identified all tested additives in a pickled olives sample with 95 % of confidence, where 100 % of combinations were correctly identified based on classification matrix. Overall, the obtained results evidence the accuracy and potential of CQDs-based fluorescence sensing in the identification of food additives.

The great performance of functionalized Fe3O4 nanoparticles (NPs) as contrast agent for magnetic resonance imaging (MRI) is related to the functionalizing agents, once can tune colloidal properties, chemical stability, hydrophilicity, overall toxicity, as well as, dipole interparticle interactions. Phosphonate derivatives have proven to be excellent capping agents due to their ability to control the above parameters. However, the available functionalizing agents do not provide enough both attached and free-form phosphoric acid groups on NPs surface. Herein, we report the use of a commercially available amino-phosphonate compound, diethylenetriaminepenta (methylene phosphonic acid, DTPMP), to functionalize Fe3O4 NPs to be potentially applied as MRI contrast agent. For the synthesis of DTPMP-coated Fe3O4 NPs, two methodologies were applied, hydrothermal and sonochemical approaches. Several characterization techniques were performed, confirming the success of surface functionalization, which allowed a deep chemical discussion involving the interactions between DTPMP and Fe3O4 NPs. Furthermore, relaxivity and cytotoxicity analyses confirmed the MRI contrast agent potential of the DTPMP-coated Fe3O4 NPs, presenting non-cytotoxicity profile and high values of transverse relaxivity (357–417 mM−1 s−1). Therefore, this work presents a novel and excellent alternative magnetic material for biological and technological application, mainly considering MRI contrast agent.

Mangiferin-loaded F127/PEG micellar systems were evaluated regarding the effect of PEG addition at different molecular weights, where the system with best mangiferin solubility response (0.5 wt% of PEG in 1 wt% F127 aqueous solution) was chosen to be a potential drug delivery system (DDS), which solubilized 7.92 mg dL−1 of mangiferin. Subsequently, the chosen mangiferin-loaded DDS was evaluated in regard the inhibition of enzyme α-glucosidase, which showed a more effective inhibition, around 95.42%, when compared to the standard acarbose (92.59%) and to the free-form mangiferin (90.42%). The same micellar system was also evaluated for its cytotoxicity, where no significative values of LDH activity was observed. No study has been done yet with both mangiferin and DDSs regarding in vitro α-glucosidase inhibitory activity. This work proposes a “new” alternative towards diabetes treatment.