Assessment of antimicrobial activity of two Coordination Polymers based on titanium and bismuth

FEDERICO ABALLAY; MARÍA FERNANDA CASTRO; CLAUDIO DANIEL DELFINI; LILIANA BEATRIZ VILLEGAS; GOMEZ, GERMAN E.

Rosario

Congreso; LVII Reunión Anual de SAIB y el XVI Congreso Anual de la Asociación Civil de Microbiología General (SAMIGE); 2021

Universidad Nacional del Rosario

Coordination Polymers (CPs) are formed by the self-assembly process between metallic ions and organic linkers. Due to the increasing crisis of antimicrobial resistance, it is demanding to design novel CPs with potential antimicrobial activity (AMA). For this reason, we synthesized by solvothermal methods, two CPs based on titanium, bismuth and carboxylates: NH2-MIL-125 (Ti-1) and [Bi(benzene-1,2,4,5-tetracarboxilate)0.5(2,2’-bipy)(NO3)(DMF)] (Bi-1) . Previous results have shown that Ti-1 and Bi-1 have in vitro antibacterial activities against several pathogenic microorganisms. In this work, antimicrobial activities were evaluated against 14 different microorganisms using microdrop agar diffusion method in Standard Nutrient (SN) agar medium (g L-1): triptone, 15; yeast extract, 3; NaCl, 1 and agar, 15. Stock aqueous suspensions (1 mg.mL-1) of Ti-1 and Bi-1 were prepared in distilled water and autoclave sterilized. Then, 20 µL of suspensions were added in previously inoculated SN agar medium. Later on, the plates were cultured at 30ºC for 24h. Also, Minimal Inhibitory Concentrations (MICs) were studied by micro-dilution test in a 96-well plate incorporating resazurin as a cell growth indicator. Previously, pre-inoculum was prepared in SN broth for 24 h at 30ºC. Appropriate cell density for MIC assay was established using resazurin. Five dilutions (1/2, 1/4, 1/6, 1/8 and 1/10) of CP suspensions were added in semi-solid-SN medium with 160 µL of the diluted inoculum and 20 µL of each dilution. The microplate was then incubated for 24 hours at 30ºC and shaken at 120 rpm. The same procedure was carried out employing TiO2 and Bi(NO3)3.5H2O as controls. We found that neither Ti-1 nor TiO2 showed AMA against microorganisms, and both Bi-1 and Bi(NO3)3 could inhibit the growth of Candida glabrata, Candida albicans ATCC 792 and Bacillus atrophaeus A14 on solid medium. The MIC values of Bi-1 determined for B. atrophaeus and C. glabrata were 0,5 mg. mL-1 and 1 mg. mL-1, respectively. These results suggest that these selected CPs may have novel mechanisms to inhibit the microbial growth. Finally, our findings highlight the importance to study the AMA against other pathogenic Bacillus and Candida species.