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We derivatized low molecular weight chitosan (LMWC) with 3-mercaptopropanoic acid (3-MPA) by a coupling reaction. The chemical modification of LMWC was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance,1HNMR. We researched the influence of 3-MPA on the nanoparticles formation by ionic gelation method using sodium tripolyphosphate (TPP) as cross-linker reagent. In order to optimize the nanoparticles formation, we studied the effect of the pH solution and molar ratio on nanoparticles stability. Analyses of particle size, morphology, and surface charge were determined by dynamic light scattering, Atomic Force Microscopy, and zeta potential, respectively. It was found that formation of semispherical and stable nanoparticles was improved due to the chemical modification of chitosan. Optimized semispherical nanoparticles of thiolated chitosan were synthesized with the parameters (pH 4.7, molar ratios 1 : 106). Additionally, we reported the thermodynamic profile of the nanoparticles formation determined by isothermal titration calorimetry (ITC). The aggregation process achieved to form nanoparticles of thiolated and nonmodified chitosan consisted of two stages, considering one binding site model. Gibbs free energy(ΔG)and binding constant (Ka) describe the aggregation process of thiolated chitosan/TPP, which is an initial reaction and followed by an endothermic stage. These results are promising for the possible application of these nanoparticles as nanocarriers and delivery systems.

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Purpose Spain has been one of the most affected countries by the COVID-19 pandemic, being among the countries with worse numbers, including the death rate. However, most patients are asymptomatic, although they are very contagious. The objective of this study was to investigate the incidence in oncological patients infected with SARS-CoV-2 that are asymptomatic for COVID-19 and at home and that undergo PET/CT for oncologic indications, nonrelated to COVID-19, finding in the PET/CT lung alterations that are suggestive of SARS-CoV-2 infection. Methods During the period of maximum incidence of the global pandemic in one of the most affected regions of Spain, there were 145 patients that met inclusion and exclusion criteria and were included in the study. Imaging findings previously described such as ground-glass opacities with low [ 18 F]-FDG uptake were considered images suspicious for SARS-CoV-2 infection. Patients with these findings were referred to RT-PCR testing and close follow-up to confirm the presence or absence of COVID-19. Results Suspicious lung imaging findings were present in 7 of 145 patients (4.8%). Five of these 7 patients were confirmed as presenting SARS-CoV-2 infection, this is, COVID-19. In the remaining two, it was not possible to confirm the presence of COVID-19 with RT-PCR, although in one of them, PET/CT allowed an early diagnosis of a lung infection related to a bacterial pneumonic infection that was promptly and adequately treated with antibiotics. Conclusion These results confirm that the prevalence of SARS-CoV-2 infection is higher than suspected and that there are asymptomatic patients that are attending imaging departments to be explored for their baseline oncologic processes. In these patients, PET/CT allows an early diagnosis of COVID-19.