Silica-based nanohybrids containing europium complexes covalently grafted: structural, luminescent, and cell labeling investigation

Author(s)

Mutti, Alessandra M. G. ; Canisares, Felipe S. M. ; Santos, Joao A. O. ; Santos, Bruno C. ; Cavalcante, Dalita G. S. M. ; Job, Aldo E. ; Pires, Ana M. ; Lima, Sergio A. M.

• Document type: Journal article
• Source: Journal of Sol-Gel Science and Technology; v. 107, n. 3, p. 17-pg., 2023-05-29.

Abstract

Designing luminescent nanohybrids for bioimaging proposes has been explored by different approaches in the literature. In this context, here silica luminescent nanohybrids containing Eu3+-complexes were synthesized in three different approaches to determine the better methodology to obtain the most efficient emissive final hybrid and its applicability in cell imaging by using the Eu3+ luminescent probe properties. For this, the synthesized dense Stober silica nanoparticles, SiO2, had their surface functionalized with APTES, in which its amine group reacted with salicylaldehyde to form a Schiff base ligand (SB), yielding the SiO2-SB system. Then, Eu3+ ion was coordinated to the SB, followed by the displacement of coordinated water molecules by dibenzoylmethane (dbm), resulting in the SiO2-[Eu1] hybrid. SiO2-[Eu2] hybrid, in turn, was obtained from tris-[Eu(dbm)(3)] complexes coordinated to the imine groups grafted on the SiO2-SB surface. For the third hybrid, SiO2-[Eu3], a new Eu3+-Schiff base complex displaying a triethoxysilyl group was grafted onto the SiO2 surface. The three luminescent hybrids are spheroidal shaped with 100 nm-size and they are red emitters with long lifetime (0.34-0.61 ms) and high photostability when exposed to continuous 340 nm UV radiation. Quantum efficiency (Q(Eu)(Eu)) as well as the number of coordinated water molecules (q(H2O)) to the Eu3+ was estimated using the LUMPAC software package and Horrocks equation, respectively. Although the three strategies exhibited suitable photophysical results, SiO2-[Eu1] was classified as the best hybrid considering its higher Q(Eu)(Eu) and color purity values, and it was evaluated as non-toxic according to its bio-viability in CHO-k1 cells in different doses. Exploratory cell imaging tests using such hybrid indicated cell marking near the nucleus with the internalization of nanoparticles in the cell confirmed by Eu3+ (D-5(0) -> F-7(J)) narrow emission bands. Therefore, SiO2-[Eu1] hybrid manifested suitable shape and size, optical, and biocompatibility features that make it promising to be applied as a luminescent stain for cell imaging. (AU)

• FAPESP's process: 19/26103-7 - Silica particles decorated with luminescent complexes for application in sensors and cellular imaging
• Grantee: Sergio Antonio Marques de Lima
• Support Opportunities: Regular Research Grants