A linear-polymer-based lactoferrin-selective recognition element for an ELISA mimic: A proof of concept.

The synthesis of polymers with tailored properties for the recognition of macromolecules such as proteins is challenging. In this work, the synthesis of a new polymer format, a linear polymer (LP), as the selective recognition element for the globular protein lactoferrin (LF) is proposed as a proof-of-concept study. For the synthesis, a solid-phase strategy using the reversible deactivation radical polymerisation (RDRP) mechanism is proposed. This approach, which is usually used in molecular imprinting, involves the immobilisation of LF on the surface of a solid support, but, unlike classical imprinting, a cross-linker in the polymerisation mixture is not required. Consequently, the copolymer is soluble and flexible, thus overcoming the drawbacks associated with traditional synthetic polymers for macromolecule imprinting. This new polymer format has great potential for replacing natural antibodies in bioassays such as enzyme-linked immunosorbent assays (ELISA), dot blot, western blot, or pull-down. In our case, the linear polymer was used as a recognition element to replace natural antibodies in a LF-selective ELISA. The responses of the linear polymer between LF concentrations of 0.1 nM and 0.25 µM were studied, and a significant difference was observed between the non-specific signals and the signals measured in the presence of the polymeric material. Further, the response versus log concentration curves were fitted to a logistic equation, allowing estimation of the EC50 value: 11.8 ± 1.4 nM. We also confirmed the selective detection of LF using the competitive inhibition of the selective LF-biotin conjugate (LF-Bi) binding to the plastic receptor (LP) for closely related proteins (e.g. those having similar molecular weights or isoelectric points) such as human lysozyme, trypsin, and albumin, which are present in human body fluids. The system presents a cross-reactivity value or selectivity of 1.95% for lysozyme, 0.028% for trypsin, and 0.016% for albumin. The applicability of this method for the determination of urine LF levels in inflammatory and infectious diseases of the human urinary tract is also demonstrated.

Spatiotemporally resolved black carbon concentration, schoolchildren's exposure and dose in Barcelona.

At city level, personal monitoring is the best way to assess people's exposure. However, it is usually estimated from a few monitoring stations. Our aim was to determine the exposure to black carbon (BC) and BC dose for 45 schoolchildren with portable microaethalometers and to evaluate the relationship between personal monitoring and fixed stations at schools (indoor and outdoor) and in an urban background (UB) site. Personal BC concentra-tions were 20% higher than in fixed stations at schools. Linear mixed-effect models showed low R(2) between personal measurements and fixed stations at schools (R(2)  ≤ 0.28), increasing to R(2)  ≥ 0.70 if considering only periods when children were at schools. For the UB station, the respective R(2) were 0.18 and 0.45, indicating the importance of the distance to the monitoring station when assessing exposure. During the warm season, the fixed stations agreed better with personal measurements than during the cold one. Children spent 6% of their time on commuting but received 20% of their daily BC dose, due to co-occurrence with road traffic rush hours and the close proximity to the source. Children received 37% of their daily-integrated BC dose at school. Indoor environments (classroom and home) were responsible for the 56% BC dose.

Aeromonas hydrophila and its relation with drinking water indicators of microbiological quality in Argentine.

In Argentine, water municipal supplies disinfection is carried out by chlorine. We have isolated Aeromonas hydrophila from a chlorinated water supply in Buenos Aires that fulfilled Argentinean microbiological quality standards. It is an aquatic organism that could produce cytotoxins and enterotoxins associated with acute gastroenteritis and wound infections in human and hemorrhagic septicaemia of fish, reptiles and amphibians. The isolated strain produced protein bands at isoelectric point in the range of 4.6-5.3 lightly labile at 56 degrees C and heat labile at 100 degrees C non cholera antitoxin reactive in electrofocusing assay (IEF) and showed hemolytic activity thermolabile at 56 degrees C and 100 degrees C in 5% rabbit erythrocytes in phosphate buffered saline. A cytotoxic effect thermolabile at 56 degrees C and 100 degrees C and a cytotonic activity were demonstrated in Vero cell cultures. Survival assay of A. hydrophila and indicator organisms would show no correlation between their contamination sources. Biofilms production could explain the persistence of this gram negative pathogen organism in chlorinated tap water. A water system supply maintenance program and pasteurisation may be performed in spite of water chlorination.

Evaluation of heavy metal lability in polluted soils by a cation exchange batch procedure.

A new extraction procedure with cationic exchange resins is proposed for the assessment of heavy metal lability in polluted soils. This method classifies soluble metal compounds in three levels according to their lability: very labile, moderately labile and non-labile. The concept of lability is based on the use of resins with different ability to interact with metals. The proposed procedure was applied to five samples of polluted soils. In the five soils, soluble Cd was found to be very labile, soluble Ni and Pb were mostly non-labile, Mn and Zn lability depended on the soil, while Cu had a fraction of moderately labile forms in four of the five soils. The resin extraction procedure was compared with the DTPA and CaCl2 extractions.