Desenvolvimento de materiais luminescentes para uso como biomarcadores e agentes bactericidas: complexos de lantanídeos derivados de hidrazonas, pontos quânticos de Bi2O3/Bi2S3 e suas combinações

Abstract

The search for more effective drugs and more precise disease diagnostics has become increasingly common. In this regard, the development of bioactive compounds with luminescent properties is an interesting strategy to investigate intracellular biochemical processes. In the present work, lanthanide complexes and quantum dots were prepared to be evaluated as cellular markers as well as antibacterial agents. In the first part of the study, complexes of lanthanum, samarium, gadolinium, and ytterbium were obtained through reactions of their respective precursors with two equivalents of the ligand (1,2-diphenylethane-1,2-diylidene)di(isonicotinohydrazide) (H2L1). The lanthanum complex has the composition [LaL1(MeOH)3(NO3)]·3MeOH, with La3+ center exhibiting a coordination number of nine. On the other hand, the Sm3+, Gd3+ and Yb3+ complexes formed polymeric structures of composition [{M(L1)2}{M(L1)(H2O)2}2]n, containing two octacoordinated, but distinct, metal centers. The small Stokes shift found for the compounds, in addition to a difference in the emission intensity when comparing measurements in the presence of O2 and Ar, indicated a probable phosphorescent character. The antibacterial activity of the compounds was evaluated against the bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and their clinical resistant strains – MRSA (methicillin-resistant Staphylococcus aureus), Bacillus subtilis (strains 118 and 144). It was observed that after complexation, there was an increase in activity, with the percentage of inhibition being more pronounced on the bacterial biofilm. In the second part of this study, the synthesis of quantum dots based on nanoparticles (NPs) of Bi2O3/Bi2S3 with the presence of the stabilizing agent 1-thioglycerol was carried out through the aqueous colloidal method. The growth of Bi2O3/Bi2S3 NPs is evidenced by the results obtained, which are considered promising materials for biotechnological applications. Finally, the [{Yb(L1)2}{Yb(L1)(H2O)2}2]n complex was combined with Bi2O3/Bi2S3 nanoparticles, making it possible to characterize the formation of a new NPs/complex product by the infrared spectra, however, it was observed that this union resulted in the suppression of photoluminescence that prevented their observation in intracellular environment. The assessment of cellular internalization in Vero CCL-81 cells showed that the NPs, both in their free form and in combination, were not able of entering the cells. On the other hand, the Sm3+, Gd3+ and Yb3+ complexes revealed to be capable of crossing the cell membrane.