Structure and properties variations of regenerated cellulose fibers induced by metal ion impurity.

In the ionic liquids (ILs) method for processing regenerated cellulose fiber (RCF), which is a high-performance ecologically benign product, metal ion impurities (such as Fe3+ and Cu2+) of cellulose might inevitably remain in the recycled ILs and coagulation bath. The presence of metal ions might negatively impact the properties of the manufactured RCFs and obstruct their applications, which are urgent to be made clear. For this research, the solvent for dissolving wood pulp cellulose (WPC) was 1-ethyl-3-methylimidazolium diethyl phosphate ([Emim]DEP) with various metal ion concentrations. The effect of metal ions in IL on the dissolution of cellulose was investigated by Molecular Dynamics simulations. Rheological analysis and degree of polymerization (DP) analysis were adopted to evaluate the influence on fiber spinnability of different spinning solution metal ion concentrations and various dissolving times. Further, the morphology and mechanical performances of the RCFs variation regulation were also thoroughly researched. The findings showed that the presence of metal ions in the spinning solution affected the DP, crystallinity, and orientation factor of RCFs, which will influence their stress more sensitively than the strain. These findings can serve as a practical guide for the commercial manufacture of emerging fiber.

Therapeutic drug monitoring and the therapeutic reference range of levetiracetam for Chinese patients: Problems and issues.

BACKGROUND: Levetiracetam (LEV) is widely used in the clinical monotherapy or multi-drug combination treatment of seizures due to its good tolerability and efficacy. Due to a lack of large-scale clinical studies, the relationship between levetiracetam concentrations, disease activity and adverse is unclear, limiting the usefulness of therapeutic drug monitoring (TDM) based LEV plasma levels. This study was intended to investigate factors influencing the pharmacokinetics of and the appropriate reference range of LEV concentration using available LEV TDM data. METHODS: A rapid, accurate and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS) method was established to determine LEV plasma concentrations. In this study, the levetiracetam plasma concentration monitoring data from 352 samples (taken from 248 patients) were used to explore the relationship between levetiracetam dose, age, combined administration with other antiseizure medications in patients with epilepsy. RESULTS: Age and combined administration emerged as important affecting factors for the correlation of LEV concentration and dose. The correlation between concentration and dose was better in monotherapy. Combined administration may affect LEV concentration, especially when LEV is combined with oxcarbazepine, which might decrease the LEV concentration. CONCLUSION: These findings emphasize the need to monitor LEV routinely LEV, especially among children and older adults when other antiseizure comedications are prescribed in the treatment regimen. LEV TDM is a well-established tool for the management of patients with epilepsy.