Novel DFO-SAM on mesoporous silica for iron sensing. Part I. Synthesis optimization and characterization of the material

Abstract

The synthesis and the physico-chemical characterisation of a novel solid phase, designed for iron(iii) sorption, are presented. The solid (indicated in the following as DFO-SAMMS) is made with a hydroxamate siderophore, the deferoxamine (DFO), covalently bound on a self-assembled monolayer on mesoporous silica (SAMMS). The data demonstrate that the DFO molecules are bound to the solid material, grafted on the surface and do not enter the silica pores. A new one-pot synthesis is presented in which DFO is dissolved in DMSO, and left to react with GPTMS with stirring overnight. In the same mixture, SAMMS is added to get the final product. The optimisation of experimental conditions of this novel one-pot synthesis is presented, with results indicating that a temperature of 90 °C, for the reaction between DFO and GPTMS, and the use of MCM-41 silica are the most convenient conditions. The kinetics of sorption reveals that the iron uptake is relatively fast, around 100 min at pH = 2.5, and from the sorption profile of iron(iii), the estimated capacity of the product obtained under optimized conditions was higher than 0.3 mmol g(-1). The results found in the present research are very promising for application in real biological samples.

Simple solid-phase spectrophotometric method for free iron(III) determination

“…The characterization of the Fe(III) sorption on DFO SAMMS and the possibility to apply the functionalized material as sorbent in Solid Phase Extraction (SPE) processes were already discussed (Biesuz et al, 2014;Alberti et al, 2014b).…”

“…We decide to perform experiments according to a 2 3 full factorial design, similar to that presented in the previous work (Biesuz et al, 2014). The model is described by the following equation:…”

“…In a previous study (Biesuz et al, 2014), a similar approach was used and in that case the maximum sorption capacity q max (mmol g À1 ) was selected as the response for a factorial experimental design. It was highlighted that, to achieve the q max value for each experiment, a complete sorption isotherm is needed and the measurements are quite time-consuming.…”

“…DFO mesoporous silica (MS) self assembled monolayer (DFO SAMMS) was prepared according to a previously described one-pot pathway (Biesuz et al, 2014), as schematically shown in Fig. 1.…”

“…The terminal amino group is not implicated in iron complexation, therefore it is suitable to anchor DFO onto a solid phase. On the basis of this strategy, we had already prepared two different solid products: the DFO Self-Assembled Monolayers on Mesoporous Silica (DFO SAMMS) and the DFO-immobilized paper (Alberti et al, 2014b;Biesuz et al, 2014). It was noted that these solid phases became brownish after sorption of Fe(III), and the colour has a maximum absorption at 425 nm, similar to the DFO/Fe(III) complex in aqueous solution, with an extinction coefficient of about 2500-2800 M À1 cm À1 (Monzyk and Crumbliss, 1982;Murphy et al, 2003;Duckworth and Sposito, 2005).…”