Background correction in atomic absorption utilizing the Zeeman effect

Nanoparticle encapsulation of mitaplatin and the effect thereof on in vivo properties

Nanoparticle (NP) therapeutics have the potential to significantly alter the in vivo biological properties of the pharmaceutically active agents that they carry. Here we describe the development of a polymeric NP, termed M-NP, comprising poly(D,L-lactic-co-glycolic acid)-block-poly(ethylene glycol) (PLGA-PEG), stabilized with poly(vinyl alcohol) (PVA), and loaded with a water-soluble platinum(IV) [Pt(IV)] prodrug, mitaplatin. Mitaplatin, c,c,t-[PtCl2(NH3)2(OOCCHCl2)2], is a compound designed to release cisplatin, an anticancer drug in widespread clinical use, and the orphan drug dichloroacetate following chemical reduction. An optimized preparation of M-NP by double emulsion and its physical characterization are reported, and the influence of encapsulation on the properties of the platinum agent is evaluated in vivo. Encapsulation increases the circulation time of Pt in the bloodstream of rats. The biodistribution of Pt in mice is also affected by nanoparticle encapsulation, resulting in reduced accumulation in the kidneys. Finally, the efficacy of both free mitaplatin and M-NP, measured by tumor growth inhibition in a mouse xenograft model of triple-negative breast cancer, reveals that controlled release of mitaplatin over time from the nanoparticle treatment produces long-term efficacy comparable to that of free mitaplatin, which might limit toxic side effects.

Selenium in health and disease: a review

Selenium (Se) was discovered 180 years ago. The toxicological properties of Se in livestock were recognized first; its essential nutritional role for animals was discovered in the 1950s and for humans in 1973. Only one reductive metabolic pathway of Se is well characterized in biological systems, although several naturally occurring inorganic and organic forms of the element exist. The amount of Se available for assimilation by the tissues is dependent on the form and concentration of the element. Se is incorporated into a number of functionally active selenoproteins, including the enzyme glutathione peroxidase, which acts as a cellular protector against free radical oxidative damage and type 1 iodothyronine 5'-deiodinase which interacts with iodine to prevent abnormal hormone metabolism. Se deficiency has been linked with numerous diseases, including endemic cardiomyopathy in Se-deficient regions of China; cancer, muscular dystrophy, malaria, and cardiovascular disease have also been implicated, but evidence for the association is often tenuous. Information on Se levels in foods and dietary intake is limited, and an average requirement for Se in the U.K. has no been established. Available data suggest that intake in the U.K. is adequate for all, except for a few risk groups such as patients on total parenteral nutrition or restrictive diets.

Determination of selenium in biological matrices

The definitive IDMS method has the advantage of good detection limits and precision. The advent of the new, smaller, easy-to-use GC/MS system should make this method more popular. The fluorometric method remains the method of choice for the determination of selenium in many matrices if the limitations of the method are understood. The newer methods include gas chromatography, HG-AAS, and GFAAS. The gas chromatography methods show promise because of the relatively simple instrumentation needed and the fact that the analyte is separated from the matrix. HG-AAS offers good sensitivity provided care is taken to ensure complete sample digestion and conversion of selenium to selenite. The advent of Zeeman background correction systems for GFAAS has greatly facilitated selenium determinations, particularly in biological matrices where iron and phosphorus are also present. The reference materials now available, used as part of a quality assurance program, should help to ensure accurate determinations, permit method validation, and allow performance evaluation in interlaboratory trials.