Abstract: Introduction: The incidence of infectious diseases caused by microorganisms has been a constant concern in hospital settings, resulting in serious global damage. In recent years, various drugs have been developed as an option to combat pathogenic microorganisms, including viruses, fungi, and bacteria. Due to their applications, nanostructured materials have aroused interest among various scientific research groups. Among these nanomaterials, titanate nanotubes have been the subject of extensive investigation. Objective: The aim of this study was to evaluate sodium, strontium, and gallium-modified titanate nanotubes and analyze their antibacterial activity and antibiotic modification against bacterial strains. Methodology: In order to determine the minimum inhibitory concentration (MIC) in direct antibacterial activity and the modifying effect of antibacterial activity of Na-TiNT, Sr-TiNT, and Ga-TiNT, the microdilution procedure in 96-well plates was adopted. In both tests, inoculants were prepared from 24-hour cultures of bacterial strains in Heart Infusion Agar (HIA) and subsequently diluted in 0.9% physiological saline, with turbidity adjusted to McFarland scale 0.5 (1 × 108 CFU/mL). In the direct antibacterial activity test, the methodology proposed by Javadpour et al. (1996) was used. Microdilution plates were filled with a solution consisting of 10% Brain Heart Infusion (BHI) broth and bacterial inoculum in a 10% volume ratio. The wells were then microdiluted with Na-TiNT, Sr-TiNT, and Ga-TiNT at concentrations ranging from 512??g/mL to 8??g/mL. In the antibiotic modification activity test, the methodology proposed by Coutinho et al. (2008) was used. In this test, the plate wells were filled with a solution equivalent to that used in the direct activity test, plus Na-TiNT, Sr-TiNT, and Ga-TiNT at subinhibitory concentrations. The plates were then microdiluted with antibiotics at concentrations ranging from 512??g/mL to 0.5??g/mL. Both tests were performed in triplicate, with readings taken using the colorimetric method, adding 20??L of resazurin to each well after 24 hours of incubation at 37°CThe standard and multi-resistant strains of Gram-negative and Gram-positive models (Escherichia coli ATCC 25922, Escherichia coli 06, Staphylococcus aureus ATCC 25923, Staphylococcus aureus 10, Pseudomonas aeruginosa ATCC 9023, and Pseudomonas aeruginosa 24) were used in this assay, cultivated at the Laboratory of Microbiology and Molecular Biology (LMBM) of the Cariri Regional University (URCA). All compounds used, antibiotics, and products were diluted in sterile water to a concentration of 1024 ?g/ml. For compounds that required pre-dilution in DMSO, the maximum limits for this substance were respected according to the Clinical and Laboratory Standards Institute. The geometric means of the triplicates were used as central data in the analyses?±?standard deviation of the mean. For the statistical analysis, a two-way ANOVA test was performed followed by a Bonferroni post hoc test, using the statistical program GraphPad Prism 5.0. Values of p?<?0.05 were considered significant. Results: Na-TiNT, Sr-TiNT, and Ga-TiNT nanotubes did not exhibit direct antibacterial activity against the tested strains. However, their combination with the tested antibiotics showed significant values for TiNTs Na, Ga, and Sr with ampicillin against the S. aureus 10 microorganism compared to the antibiotic control, thereby reducing its inhibitory concentration. The same was observed for gentamicin. Na-TiNT in combination with gentamicin exhibited a reduced inhibitory concentration compared to the control for P. aeruginosa 24. In E. coli 06, Na, Sr, and Ga TiNTs showed a reduction in concentration when combined with gentamicin, indicating a potential potentiating effect. Conclusion: We can conclude that the nanotubes, when used alone, did not exhibit direct antibacterial activity. However, when combined with antibiotics, a potentiating effect was observed, thus enhancing their ability to interact with them.
Comissão Organizadora
Francisco Mendonça Junior
Pascal Marchand
Teresinha Gonçalves da Silva
Isabelle Orliac-Garnier
Gerd Bruno da Rocha
Comissão Científica
Ricardo Olimpio de Moura
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