Characterization and cytotoxicity assessment of cadmium sulfide quantum dots synthesized with Fusarium oxysporum f. sp. lycopersici.

The potential of CdS quantum dots for biomedical and bioimaging applications depends on their cytotoxicity, which can be modulated by coating molecules. Using sulfur as a precursor can be used along with cadmium nitrate to synthesize CdS quantum dots with the fungus Fusarium oxysporum f. sp. lycopersici. The latter replaces pure chemical sulfur as a precursor for CdS quantum dot synthesis, thus transforming waste into a value-added product, increasing sustainability, reducing the environmental impact of the process through the implementation of green synthesis techniques, and contributing to the circular economy. Therefore, we compared the cytotoxicity on HT-29 cells of biogenic, and chemical CdSQDs, synthesized by a chemical method using pure sulfur. Biogenic and chemical CdSQDs had diameters of 4.08 ± 0.07 nm and 3.2 ± 0.20 nm, Cd/S molar ratio of 43.1 and 1.1, Z-potential of - 14.77 ± 0.64 mV and - 5.52 ± 1.11 mV, and hydrodynamic diameters of 193.94 ± 3.71 nm and 152.23 ± 2.31 nm, respectively. The cell viability improved 1.61 times for biogenic CdSQDs over chemical CdSQDs, while cytotoxicity, measured as IC50, diminished 1.88-times. The lower cytotoxicity of biogenic CdSQDs was attributed to their organic coating consisting of lipids, amino acids, proteins, and nitrate groups that interacted with CdS through -OH and -SH groups. Therefore, the biogenic synthesis of CdSQDs has repurposed a pathogenic fungus, taking advantage of the biomolecules it secretes, to transform hazardous sulfur waste and metal ions into stable CdSQDs with advantageous structural and cytotoxic properties for their potential application in biomedicine and bioimaging.

In vitro toxicity assessment of fungal-synthesized cadmium sulfide quantum dots using bacteria and seed germination models.

There is currently controversy over the use of quantum dots (QDs) in biological applications due to their toxic effects. Therefore, the purpose of the present study was to evaluate the toxic effect of chemical and biogenic (synthesized by Fusarium oxysporum f. sp. lycopersici) cadmium sulfide quantum dots (CdSQDs) using a bacterial model of Escherichia coli and sprouts of Lactuca sativa L. with the aim to foresee its use in the near future in biological systems. Physicochemical properties of both types of CdSQDs were determined by TEM, XRD, zeta potential and fluorescence spectroscopy. Both biogenic and chemical CdSQDs showed agglomerates of spherical CdSQDs with diameters of 4.14 nm and 3.2 nm, respectively. The fluorescence analysis showed a band around 361 nm in both CdSQDs, the zeta potential was -1.81 mV for the biogenic CdSQDs and -5.85 mv for the chemical CdSQDs. Results showed that chemical CdSQDs, presented inhibition in the proliferation of E. coli cell in a dose-dependent manner, unlike biogenic CdSQDs, that only at its highest concentration showed an antibacterial activity. Also, it was observed that after incubation with chemical and biogenic CdSQDs of L. sativa L. seeds, only the biogenic CdSQDs showed no inhibition on seed germination. In summary, our results suggest that the production route has a significant effect on the toxicity of QDs; in addition, it seems that the biological coating of the CdSQDs from F. oxysporum f. sp. lycopersici inhibit their toxic effect on bacterial strains and plant seeds.

Environmental and Anthropogenic Influences on Coliform Concentrations in the Octopus insularis Production Chain in the Veracruz Reef System, Gulf of Mexico.

Coliforms are relatively common in aquatic environments, but their concentrations can be increased by environmental changes and anthropogenic activities, thus impacting fisheries resources. To determine the microbiological quality in the octopus production chain (capture, post-capture, processing and commercialization), total (TC) and fecal (FC) coliforms were quantified in sea water, fresh octopus, fresh water, ice and octopus in two presentations: packed in ice and boiled. Samples came from fishing zones Enmedio, Chopa and La Gallega at the Veracruz Reef System (VRS) during dry, rainy and windy seasons. The coliforms were determined using the most probable number technique (MPN). The most relevant results indicated that octopus packed in ice coming from the commercialization stage had FC levels >540 MPN/100 g, which exceeded the permissible limits (230 MPN/100 g). Therefore, these products present a risk for human consumption. Differences in FC were observed in octopuses between the three fishing zones (H = 8.697; p = 0.0129) and among the three climatic seasons, increasing during the rainy season, highlighting La Gallega with 203.33 ± 63 MPN (H = 7.200; p = 0.0273). The results provide evidence of the environmental and anthropogenic influences on coliform concentrations and the urgent need to implement an efficient cold chain throughout octopus production stages with adequate handling practices to reverse this situation.

Genomic epidemiology analysis of drug-resistant Mycobacterium tuberculosis distributed in Mexico.

Genomics has significantly revolutionized pathogen surveillance, particularly in epidemiological studies, the detection of drug-resistant strains, and disease control. Despite its potential, the representation of Latin American countries in the genomic catalogues of Mycobacterium tuberculosis (Mtb), the bacteria responsible for Tuberculosis (TB), remains limited. In this study, we present a whole genome sequencing (WGS)-based analysis of 85 Mtb clinical strains from 17 Mexican states, providing insights into local adaptations and drug resistance signatures in the region. Our results reveal that the Euro-American lineage (L4) accounts for 94% of our dataset, showing 4.1.2.1 (Haarlem, n = 32), and 4.1.1.3 (X-type, n = 34) sublineages as the most prevalent. We report the presence of the 4.1.1.3 sublineage, which is endemic to Mexico, in six additional locations beyond previous reports. Phenotypic drug resistance tests showed that 34 out of 85 Mtb samples were resistant, exhibiting a variety of resistance profiles to the first-line antibiotics tested. We observed high levels of discrepancy between phenotype and genotype associated with drug resistance in our dataset, including pyrazinamide-monoresistant Mtb strains lacking canonical variants of drug resistance. Expanding the Latin American Mtb genome databases will enhance our understanding of TB epidemiology and potentially provide new avenues for controlling the disease in the region.