Novel DFO-functionalized mesoporous silica for iron sensing. Part 2. Experimental detection of free iron concentration (pFe) in urine samples

Abstract

Successful in vivo chelation treatment of iron(iii) overload pathologies requires that a significant fraction of the administered drug actually chelates the toxic metal. Increased mobilization of the iron(iii) in experiments on animals or humans, most often evaluated from urinary output, is usually used as an assessment tool for chelation therapy. Alternatively, the efficiency of a drug is estimated by calculating the complexing ability of a chelating agent towards Fe(iii). The latter is calculated by the pFe value, defined as the negative logarithm of the concentration of the free metal ion in a solution containing 10 μM total ligand and 1 μM total metal at a physiological pH of 7.4. In theory, pFe has to be calculated taking into account all the complexation equilibria involving the metal and the possible ligands. Nevertheless, complexation reactions in complex systems such as serum and urine may hardly be accurately modelled by computer software. The experimental determination of the bioavailable fraction of iron(iii) in biological fluids would therefore be of the utmost relevance in the clinical practice. The efficiency of the therapy could be more easily estimated as well as the course of overload pathologies. In this context, the aim of the present work was the development of a sensor to assess the free iron directly in biological fluids (urine) of patients under treatment with chelating agents. In the proposed device (DFO-MS), the strong iron chelator deferoxamine (DFO) is immobilized on the MCM-41 mesoporous silica. The characterization of the iron(iii) sorption on DFO-MS was undertaken, firstly in 0.1 M KNO3, then directly in urine samples, in order to identify the sorption mechanism. The stoichiometry of the reaction in the solid phase was found to be: with an exchange constant (average value) of log βex = 40(1). The application of DFO-MS to assess pFe in SPU (Simulating Pathology Urine) samples was also considered. The results obtained were very promising for a future validation and subsequent application of the sensor in samples of patients undergoing chelation therapy.

A Simple Small Size and Low Cost Sensor Based on Surface Plasmon Resonance for Selective Detection of Fe(III)

“…The complexation of Fe(III) by DFO in solution is strong even at this high acidity [26], as it is in the case of DFO covalently linked to a solid phase (silica) [6]. The fact that Fe(III) is able to interact with the DFO-SAM-POF here considered has been shown by Shervedani et al [3,27] by electrochemical detection.…”

Deferoxamine–paper for iron(III) and vanadium(V) sensing

“…In particular, cellulose (Wenk et al, 2001;Takagai et al, 2007a), nylon (Takagai et al, 2007b), acrylate polymers (Rossi et al, 2008), sepharose (Yehuda et al, 2003) and silica *Corresponding author, e-mail: galberti@unipv.it Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 6/21/15 4:25 PM materials (Wanunu et al, 2006;Roy et al, 2008;Su et al, 2011;Alberti et al, 2014) have been considered.…”

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).…”

“…With these data, it is possible to calculate the theoretic values of a Mt , reported in the fifth column. The partition coefficients K * between Fe(III) and DFO SAMMS reported in the sixth column, were previously calculated by independent experiments (Alberti et al, 2014b).…”

“…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).…”