Loading...
3 results
Search Results
Now showing 1 - 3 of 3
- New Quantum-Dot-Based Fluorescent Immunosensor for Cancer Biomarker DetectionPublication . Sousa, Mariana P.; Piloto, Ana Margarida L.; Pereira, Ana Cláudia; Schmitt, Fernando; Fernandes, Ruben; Moreira, Felismina T. C.Cancer antigen 15-3 (CA 15-3) is a biomarker for breast cancer used to monitor response to treatments and disease recurrence. The present work demonstrates the preparation and application of a fluorescent biosensor for ultrasensitive detection of the cancer antigen CA 15-3 protein tumor marker using mercaptopropionic-acid-functionalized cadmium telluride (CdTe@MPA) quantum dots (QDs) conjugated with CA 15-3 antibodies. First, the QDs were synthesized by the hydrothermal route, resulting in spherical nanoparticles up to 3.50 nm in diameter. Subsequently, the QD conjugates were characterized by Fourier transform infrared spectroscopy (FTIR), UV absorption, and fluorescence. The interaction between the conjugates and the protein was studied by fluorescence spectroscopy in buffer and in 10-fold diluted commercial human serum. Calibration in spiked serum samples gave a detection limit of 0.027 U/mL, 1000-fold lower than the clinical limit for CA 15-3 (25 U/mL to 30 U/mL), indicating that this is an ultrasensitive technique. In addition, a rapid response was obtained within 10 min. The biosensor was selective in the presence of the interfering serum proteins BSA, CEA, and CA-125, with a maximum interference of 2% for BSA. The percent recovery was close to 100% with maximum relative standard deviation (RSD%) values of 1.56. Overall, the developed CA 15-3 biosensor provides a simple and sensitive method for ultrasensitive monitoring of breast cancer, as well as the ability to detect other molecules of interest in human serum matrices.
- Oxidative stress genes involved in the virulence-dependent susceptibility to antibiotics in Pseudomonas aeruginosaPublication . Coelho, Pedro Barata; Fernandes, Ruben; Silva, Carina; Oliveira, Marco; Veiga, Marlene; Sá, Sara; Vieira, André; Guedes, Carla; Baylina, PilarPseudomonas aeruginosa is a Gram-negative opportunistic pathogen which rarely causes disease in healthy people. P. aeruginosa, in particular strain PAO1 is also a biological model for studying virulence and bacterial social traits, such as quorum sensing, SOS response among other. Antibiotic response is dependent, among several other factors, to the response to environmental stress conditions. The present study aims to understand the role of 10 PAO1 oxidative gene mutants in the response to antibiotic stress in elastase, protease and pyocyanin-dependent virulence factors. PAO1 was stressed to several antibiotics (penicilins, cephalosporins, macrolides, and quinolones), and the virulence proteins were measured by means of spectroscopic methods. Viability was measured by means of Erythrosin B. PAO1 GGT, GLO1, RubA2, GSH A mutants were the most susceptible to the production of virulence-dependent factors.
- Phylogenetic Insights of β-lactam resistance of the CTX-M familyPublication . Coelho, Pedro Barata; Mendonça, Jacinta; Silva, Carina; Baylina, Pilar; Fernandes, Ruben; Guedes, CarlaBacterial resistance is a major public health concern, particularly against β-lactam antibiotics, one of the most widely used antibacterial drugs. The production of extended-spectrum β-lactamases (ESBLs) is the main defense mechanism found in Gram negative bacteria. Among all the ESBLs, the CTX-M enzymes appear as the most efficient in terms of diffusion in different epidemiological contexts, outnumbering the others. Originated in chromosomal genes of Klyvera spp., the blaCTX-M genes have become associated with mobile genetic elements, such as plasmids, that have mediated inter-replication and dissemination. CTX-M enzymes exhibit a striking plasticity, with a large number of allelic variants belonging to several sub-lineages, which can be associated with functional heterogeneity of clinical relevance. This observational analytical study provides an update of this family, currently with more than 200 variants described, from a phylogenetic, molecular and structural point of view through homology in amino acid sequences. There are currently 6 defined clusters (CTX-M-1, CTX-M-2, CTX-M-8, CTX-M-9, CTX-M-25 and CTX-M-151), with the domains CTX -M-1 and CTX-M-9 presenting subgroups, composed mainly of variants identified as hybrids between them (particularly between CTX-M-14 and CTX-M-15).