Components of compulsory service program for health professionals in low- and middle-income countries: a scoping review.

AIMS: The global health landscape has been characterized by shortfalls and imbalances in human resources for health (HRH), with more health workers concentrated in urban than rural areas. To address this maldistribution, some countries resorted to the implementation of a compulsory service policy for HRH. However, there is no comprehensive documentation describing the different components of such policies. This scoping review aims to determine the components for compulsory service for selected health professionals in low- and middle-income countries (LMICs). METHODS: A search was conducted in MEDLINE, PLoS, Scopus, and ProQuest Central, using keywords for 'compulsory service', 'return service', 'mandatory service', 'physician', 'dentist', 'nurse', 'midwife', 'physical therapist', 'occupational therapist', and identified LMICs. A total of 6757 records were retrieved and assessed, from which 41 relevant records were included in the study. RESULTS AND CONCLUSIONS: Common elements of a compulsory service program are the following: a comprehensive master plan, clearly articulated program goals, appropriate education and training, transparent recruitment and placement, strong institutional and system support, competitive benefits and incentives, and active management of exit from the program. Results presented in this article can serve to inform LMICs on policy, guide program development and management, and direct future research in the area of HRH to address challenges in maldistribution.

Halogen bonding for increasing efficiency in liquid-liquid microextraction: Application to the extraction of hexabromocyclododecane enantiomers in river water.

Halogen bonding (XB) was here proposed, for the first time, as a solubilization mechanism for increasing efficiency in the liquid-liquid microextraction of halogenated compounds. The approach was illustrated by the extraction of hexabromocyclododecane (HBCD) enantiomers in natural waters with a supramolecular solvent (SUPRAS) made up of inverted hexagonal aggregates of decanoic acid. The XB and dispersion interactions offered by the SUPRAS were able to extract the six HBCD enantiomers (i.e. (+)-α-, (-)-α- (+)-ß-, (-)-ß-, (+)-γ- and (-)-γ-) quantitatively (e.g. recoveries in the range 89-106%) and reach concentration factors as high as 720 without the need for solvent evaporation. HBCD enantiomers in the SUPRAS extract were directly analysed by chiral liquid chromatography coupled to tandem mass spectrometry (LCMS/MS). Quantitation limits of the method (0.09-0.9 ng L-1) were below the quality standard stablished by the European Union for HBCDs in inland surface water samples (1.6 ng L-1), and the precision, expressed as relative standard deviation (n = 6), was below 9% for all the HBCD enantiomers at concentrations within the range 50-500 ng L-1. The method was successfully applied to the enantioselective determination of HBCDs in the dissolved and the particle-bound fractions of river waters containing different concentration of suspended particles (10-57.8 mg L-1) that were spiked at two concentration levels (10 and 100 ng L-1). The results here obtained prove that XB is a valuable mechanism for the solubilisation of halogenated compounds that can effectively increase their recovery from liquid and solid samples.

Characterization of a ß-galactosidase from Bacillus subtilis with transgalactosylation activity.

Microbial ß-galactosidases (EC 3.1.2.23) have applications in the production of galacto-oligosaccharides, which are established prebiotic food ingredients. The ß-galactosidase from Bacillus subtilis (YesZ) was expressed as a heterologous protein in Escherichia coli, and presented an optimum activity at pH 6.5 and 40 °C. The catalytic constants Km and Vmax of the enzyme were 8.26 mM and 1.42 µmol·min-1·mg-1 against pNP-ß-d-galactopyranoside, respectively. Structural characterization revealed that YesZ is a homotrimer in solution, and homology modeling suggested that the YesZ conserves a Cys cluster zinc binding site. Flame photometry experiments confirmed the presence of bound zinc in the recombinant enzyme, and YesZ activity was inhibited by 1 mM zinc, copper and silver ions. Transgalactosylation activity of YesZ was observed with the synthetic substrate p-NP-ßGal in the presence of a d-xylose acceptor, producing a ß-d-galactopyranosyl-(1 → 4)-d-xylopyranose disaccharide. Analysis of this disaccharide by MALDI-ToF-MS/MS suggested a ß-1,4 glycosidic linkage between a non-reducing galactose residue and the xylose. The ß-galactosidase YesZ from B. subtilis is a candidate for enzymatic synthesis showing favorable thermostability (with residual activity of 50% after incubation at 30 °C for 25 h) and transgalactosylation activity.

Speeding up the extraction of hexabromocyclododecane enantiomers in soils and sediments based on halogen bonding.

Halogen bonding (XB), a highly energetic and directional interaction, is here proposed as a new mechanism to increase solute solubilisation in solvent extractions. The approach is illustrated by the extraction of hexabromocyclododecane (HBCD) enantiomers in soils and sediments using supramolecular solvents (SUPRAS) containing XB donors in their structure. SUPRAS consisting of inverted hexagonal aggregates of decanoic acid, synthesized by water-induced coacervation of the amphiphile in tetrahydrofuran (THF), were explored for this purpose. Sample treatment involved the extraction of 400 mg of soil or sediment with 250 µL of SUPRAS for 5 min and then centrifugation for 10 min. SUPRAS extracts were directly analyzed by chiral liquid chromatography tandem mass spectrometry (LC-MS/MS) and quantification was carried out using isotopically labelled internal standards. Quantitative recoveries (93-102%) were obtained for the six HBCD enantiomers in both fresh and aged spiked samples. The mild experimental conditions required for extraction (room temperature and atmospheric pressure), the low SUPRAS volume/sample amount ratio needed (0.6 mL g─1), the short time required for sample treatment (15 min), and the simplicity of the procedure (use of conventional equipment and the possibility of treating several samples simultaneously), makes this method clearly superior to those previously reported. Method quantitation limits were in the intervals 0.58-2.23 ng g─1, and the relative standard deviations (n = 18, HBCD stereoisomer concentration = 50 ng g─1) obtained under repeatability and reproducibility conditions varied within the ranges 1.0-4% and 2.5-5%, respectively. The approach here described could be easily extended to the extraction of brominated flame retardants in different types of matrices.

Functionalization of paramagnetic nanoparticles for protein immobilization and purification.

A paramagnetic nanocomposite coated with chitosan and N-(5-Amino-1-carboxy-pentyl) iminodiacetic acid (NTA) that is suitable for protein immobilization applications has been prepared and characterized. The nanoparticle core was synthesized by controlled aggregation of Fe3O4 under alkaline conditions, and Transmission Electron Microscopy revealed a size distribution of 10-50 nm. The nanoparticle core was coated with chitosan and derivatized with glutaraldehyde and NTA, as confirmed by Fourier Transform Infrared Spectroscopy. The final nanoparticles were used as a metal affinity matrix to separate a recombinant polyhistidine-tagged ß-galactosidase from Bacillus subtilis directly from E. coli cell lysates with high purity (>95%). After loading with Ni2+, nanoparticles demonstrated a binding capacity of 250 µg of a polyhistidine-tagged ß-galactosidase per milligram of support. The immobilized enzyme retained 80% activity after 9 cycles of washing, and the immobilized recombinant protein could be eluted with high purity with imidazole. The applications for these nanomagnetic composites extend beyond protein purification, and can also be used for immobilizing enzymes, where the ß-galactosidase immobilized on the nanomagnetic support was used in multiple cycles of catalytic reactions with no significant loss of catalytic activity.

Enantiomer-specific determination of hexabromocyclododecane in fish by supramolecular solvent-based single-step sample treatment and liquid chromatography-tandem mass spectrometry.

A single-step, environmentally friendly sample treatment was developed and used in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the quantitation of hexabromocyclododecane (HBCD) stereoisomers in fish. It was based on the microextraction of the stereoisomers with a supramolecular solvent (SUPRAS) made up of reverse aggregates of decanoic acid (DeA). The procedure involved the stirring of the fish sample (750 mg) with 600 µL of SUPRAS for five minutes, subsequent centrifugation for extract separation from matrix components and direct analysis of the extract after dilution 1:1 with methanol. Individual enantiomers of α-, ß- and γ-HBCD were separated on a chiral stationary phase of ß-cyclodextrin and quantified by monitoring of the [M-H](-)→Br(-) transition at m/z 640.9→80.9. Driving forces for the microextraction of HBCD in the SUPRAS involved both dispersion and dipole-dipole interactions. Quantitation limits for the determination of individual HBCD enantiomers in hake, cod, sole, panga, whiting and sea bass were within the intervals 0.5-3.4 ng g(-1), 0.9-2.5 ng g(-1), 0.6-1.4 ng g(-1), 1.0-5.6 ng g(-1), 0.8-1.3 ng g(-1) and 0.5-3.5 ng g(-1), respectively. Recoveries for fish samples fortified at the ng g(-1) level ranged between 87 and 114% with relative standard deviations from 1 to 10%. The sample treatment proposed greatly simplifies current procedures for extraction of HBCD stereoisomers and is a useful tool for the development of a large scale database for their presence in fish.