Population-wide vaccination is the most promising long-term COVID-19 disease management strategy. However, the protection offered by the currently available COVID-19 vaccines wanes over time, requiring boosters to be periodically given, which represents an unattainable challenge, especially if it is necessary to apply several doses per year. Therefore, it is essential to design strategies that contribute to maximizing the control of the pandemic with the available vaccines. Achieving this objective requires knowing, as precisely and accurately as possible, the changes in vaccine effectiveness over time in each population group, considering the eventual dependence on age, sex, etc. Thus, the present work proposes a novel approach to calculating realistic effectiveness profiles against symptomatic disease. In addition, this strategy can be adapted to estimate realistic effectiveness profiles against hospitalizations or deaths. All such time-dependent profiles allow the design of improved vaccination schedules, where each dose can be administrated to the population groups so that the fulfillment of the containment objectives is maximized. As a practical example for this analysis, vaccination against COVID-19 in Mexico was considered. However, this methodology can be applied to other countries’ data or to characterize future vaccines with time-dependent effectiveness values. Since this strategy uses aggregated observational data collected from massive databases, assumptions about the data validity and the course of the studied epidemic could eventually be necessary.

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A ferrofluid with 1,2-Benzenediol-coated iron oxide nanoparticles was synthesized and physicochemically analyzed. This colloidal system was prepared following the typical co-precipitation method, and superparamagnetic nanoparticles of 13.5 nm average diameter, 34 emu/g of magnetic saturation, and 285 K of blocking temperature were obtained. Additionally, the zeta potential showed a suitable colloidal stability for cancer therapy assays and the magneto-calorimetric trails determined a high power absorption density. In addition, the oxidative capability of the ferrofluid was corroborated by performing the Fenton reaction with methylene blue (MB) dissolved in water, where the ferrofluid was suitable for producing reactive oxygen species (ROS), and surprisingly a strong degradation of MB was also observed when it was combined with H2O2. The intracellular ROS production was qualitatively corroborated using the HT-29 human cell line, by detecting the fluorescent rise induced in 2,7-dichlorofluorescein diacetate. In other experiments, cell metabolic activity was measured, and no toxicity was observed, even with concentrations of up to 4 mg/mL of magnetic nanoparticles (MNPs). When the cells were treated with magnetic hyperthermia, 80% of cells were dead at 43 °C using 3 mg/mL of MNPs and applying a magnetic field of 530 kHz with 20 kA/m amplitude.

The physical characterization of a colloidal system of superficially modified magnetic nanoparticles (MNPs) is presented. The system consists of oleic acid-coated iron oxide nanoparticles (OAMNP) suspended in water. A structural analysis is carried out by using standard physical techniques to determine the diameter and shape of the MNPs and also the width of the coating shell. The colloidal stability and the polydispersity index of this ferrofluid are determined by using Zeta potential measurements. Additionally, the magnetic characterization is conducted by obtaining the DC magnetization loops, and the blocking temperatures are determined according to the ZFC–FC protocol. Finally, the values of power absorption density P of the ferrofluid are estimated by using a magneto-calorimetric procedure in a wide range of magnetic field amplitude H and frequency f. The experimental results exhibit spherical-like shape of OAMNP with (20 ± 4) nm in diameter. Due to the use of coating process, the parameters of the magnetization loops and the blocking temperatures are significantly modified. Hence, while the uncoated MNPs show a blocking state of the magnetization, the OAMNP are superparamagnetic above room temperature (300 K). Furthermore, the reached dependence P versus f and P versus H of the ferrofluid with coated MNPs are clearly fitted to linear and quadratic correlations, respectively, showing their accordance with the linear response theory.

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