Milena Mattes Cerveira

Foodborne illnesses, particularly those caused by Salmonella spp., represent a major global health concern, with S. typhimurium being a significant contributor to outbreaks. The persistence of S. typhimurium in food production environments and its resistance to conventional disinfectants highlight the need for alternative antimicrobial solutions. Essential oils (EOs) from Eucalyptus globulus (EGEO) and Cymbopogon flexuosus (CFEO) have shown antimicrobial potential against S. typhimurium , but their mechanisms of action and cytotoxic effects on eukaryotic cells require further investigation to assess their safety for food applications, particularly in situ. We evaluated cytotoxicity in erythrocytes and zebrafish liver (ZF-L) cells using hemolysis (HA), MTT, and NR uptake assays. Additionally, we investigated the antimicrobial behavior of EGEO and CFEO against S. typhimurium ATCC 14,028 through MIC/MBC tests, time-kill assays, and a newly designed TSI-adapted test to assess the EOs’ impact on bacterial metabolism. An in situ experiment was also conducted to evaluate the preservative effects of EGEO and CFEO on pork sirloin contaminated with an infectious dose of S. typhimurium and treated with EO-based brines for 7 days under refrigeration. We monitored the presence of Salmonella spp., as well as pH, calcium (Ca²⁺), and magnesium (Mg²⁺) concentrations in the brined samples. Results indicated that CFEO was hemolytic above 0.73 mg/mL and EGEO above 0.45 mg/mL. The MTT assay showed that CFEO did not impair mitochondrial function from 2.941 mg/mL and EGEO from 14.36 mg/mL. NR uptake assay showed that both EOs did not impaired lysossomal function in ZF-L. The MICs and MBCs for CFEO and EGEO were 0.37 mg/mL and 1.79 mg/mL, respectively. Time-kill assays revealed bactericidal effects for CFEO at 4x and 2x MIC within 6 h, while EGEO showed a bactericidal effect only at 4x MIC. The EO-TSI agar assay demonstrated that EGEO inhibited sugar fermentation and sulfur metabolism, while CFEO impacted peptone oxidation and protein metabolism. In situ analyses showed CFEO caused more significant changes in color and odor of the pork samples than EGEO, while both maintained pH levels around 6. Ca²⁺ and Mg²⁺ levels were lower in CFEO-treated samples. Microbiological data confirmed the absence of Salmonella spp. in all samples except for two in the CFEO-brine group. None of the samples showed signs of autolysis or putrefaction, suggesting that both CFEO and EGEO, particularly EGEO, are feasible alternatives as food preservatives, depending on the desired application.

The employment of metal nanoparticles for biomedical applications is gaining visibility as a result of their excellent properties. Niobium oxide (Nb ₂ O ₅ ) possesses interesting physicochemical properties that can be modified for its use in prosthetic coatings. However, there are only a limited number of studies in the literature concerning its characterization as a pure powder, its surface modification and their cytotoxicity. Therefore, the purpose of this study was to evaluate nine different Nb ₂ O ₅ samples synthesized using the microwave technique, each with a different surfactant. x-ray diffraction results indicated that all samples were amorphous, and the addition of surfactants did not seem to cause any alterations, as indicated by Raman and FTIR. Scanning electron microscopy (SEM) images revealed that the particles tended to form aggregates; modification of parameters such as surface area and acid sites was also observed, with pure Nb ₂ O ₅ having the highest area (230.4 m ² g ⁻¹ ) and NbSDS5 having the highest total acidity (3141 µmol g ⁻¹ ). We assessed the cytotoxicity in sheep’s erythrocytes and the Zebrafish Liver (ZF-L) cell line. Pure Nb ₂ O ₅ exhibited high cytotoxicity at 10 mg ml ⁻¹ in red blood cells with an erythrocyte survival rate of 15%. The MTT assay that revealed that NbCA1 showed only 27.1% cell viability, while NbSDS1 was able to increase cell proliferation (101.1%) even at a lower pH. Compounds were also able to interfere with the intrinsic coagulation pathway, with several samples exceeding the clotting time (>120 s). Nb ions leaching to the medium does not seem to directly affect cytotoxicity. Pearson’s correlation does not indicate a direct relationship between surface area, acid sites, and cytotoxicity assays.

The COVID-19 pandemic has caused an unprecedented health and economic crisis, highlighting the importance of developing new molecular tools to monitor and detect SARS-CoV-2. Hence, this study proposed to employ the carrageenan extracted from Gigartina skottsbergii algae as a probe for SARS-CoV-2 virus binding capacity and potential use in molecular methods. G. skottsbergii specimens were collected in the Chilean subantarctic ecoregion, and the carrageenan was extracted —using a modified version of Webber’s method—, characterized, and quantified. After 24 h of incubation with an inactivated viral suspension, the carrageenan’s capacity to bind SARS-CoV-2 was tested. The probe-bound viral RNA was quantified using the reverse transcription and reverse transcription loop-mediated isothermal amplification (RT-LAMP) methods. Our findings showed that carrageenan extraction from seaweed has a similar spectrum to commercial carrageenan, achieving an excellent proportion of binding to SARS-CoV-2, with a yield of 8.3%. Viral RNA was also detected in the RT-LAMP assay. This study shows, for the first time, the binding capacity of carrageenan extracted from G. skottsbergii, which proved to be a low-cost and highly efficient method of binding to SARS-CoV-2 viral particles.