Cancer immunosensor based on apo and holo transferrin binding.

An electrochemical immunosensor was developed for the determination of apo-Tf (non-iron-bound) and holo-Tf (iron-bound) using polyclonal antibody transferrin (anti-Tf) immobilized at an electrode surface as a biorecognition platform. The monitoring was based on the anti-Tf binding with both Tf forms which allows the detection of cancer cells due to the constant iron cycle and the overexpression of anti-Tf on the cancer cell surface. The immunosensor characterization was performed using electrochemical impedance spectroscopy (EIS), which evaluated the impedimetric biorecognition of the antigens-antibody by the use of K4Fe(CN)6 redox group. The immunosensor was able to detect both forms of Tf in terms of charge transfer resistance (Rct). Analytical curves showed a limit of detection of 0.049 and 0.053 ng mL-1 for apo-Tf and holo-Tf, respectively. The immunosensor was applied to the detection of the two cancer cells A549 (lung carcinoma) and MCF-7 (breast carcinoma) and compared with BHK570, a healthy cell line. The impedimetric response of healthy cells differs significantly from that of the cancerous cells, as revealed by a Dunnett's test in 95% confidence level-ca. 102 cells mL-1-indicating the feasibility of the immunosensor to discriminate both types of cells. The indirect detection of anti-Tf based on apo-Tf and holo-Tf binding can be considered an advanced approach for cancer recognition. Graphical abstract.

Optimization and validation of ultrasound-assisted extraction for the determination of micro and macro minerals in non-centrifugal sugar by F AAS.

In this work, the ultrasound-assisted extraction was employed for the first time as a sample treatment in the determination of Mn, Zn, Fe, Mg and Ca in non-centrifugal sugar by F AAS. Parameters that influence the extraction, such as composition of the extraction solvent, sample mass and sonication time were optimized in this work. The optimum condition for the extraction was the proportion of 60:40% (v/v) of HNO3:H2O2 as an extraction solution, 0.100 g of non-centrifugal sugar and 60 min of sonication. Analytical curves were built in an aqueous solution. Low quantification limits for Mn (0.021), Zn (0.008), Fe (0.030), Ca (0.389) and Mg (0.009) mg L-1 were determined, suggesting a good detectability of the methodology. Estimates of repeatability and intermediate precision demonstrated that the precision observed was within the limits recommended in the literature. Good accuracy of the method was verified through the high recovery rates (91-108%).

Ultrasound-assisted emulsification microextraction combined with graphite furnace atomic absorption spectrometry for the chromium speciation in water samples.

A simple method was proposed by ultrasound-assisted emulsification microextraction (UAEME) combined with GF AAS for Cr speciation in water samples using tributhylphosphate (TBP) as extractor solvent and dispersion with ultrasound, without disperser solvent. The selective separation and pre-concentration of Cr(VI) species in an aqueous medium with HCl and NaCl was optimized with Rotatable Central Composite Design. Total Cr was determined after oxidation of Cr(III) to Cr(VI) by KMnO4. This method resulted in detection limits of 0.85 ng L-1 for Cr(VI) and 1.82 ng L-1 for Cr(total), as well as enrichment factors around 77. The accuracy was evaluated with mineral, tap and natural water. The recovery ranged from 90% to 114%. A case study was carried out with Brazilian commercial mineral water and the total concentrations ranged from 0.47 ±â€¯0.01 µg L-1 to 3.9 ±â€¯0.19 µg L-1. The Cr(VI) values ranged from 0.02 ±â€¯0.01 µg L-1 to 2.3 ±â€¯0.13 µg L-1.

A validated fast difference spectrophotometric method for 5-hydroxymethyl-2-furfural (HMF) determination in corn syrups.

Corn syrups, important ingredients used in food and beverage industries, often contain high levels of 5-hydroxymethyl-2-furfural (HMF), a toxic contaminant. In this work, an in house validation of a difference spectrophotometric method for HMF analysis in corn syrups was developed using sophisticated statistical tools by the first time. The methodology showed excellent analytical performance with good selectivity, linearity (R2=99.9%, r>0.99), accuracy and low limits (LOD=0.10mgL-1 and LOQ=0.34mgL-1). An excellent precision was confirmed by repeatability (RSD (%)=0.30) and intermediate precision (RSD (%)=0.36) estimates and by Horrat value (0.07). A detailed study of method precision using a nested design demonstrated that variation sources such as instruments, operators and time did not interfere in the variability of results within laboratory and consequently in its intermediate precision. The developed method is environmentally friendly, fast, cheap and easy to implement resulting in an attractive alternative for corn syrups quality control in industries and official laboratories.