A methodological inter-comparison study on the detection of surface contaminant sodium dodecyl sulfate applying ambient- and vacuum-based techniques.

Biomedical devices are complex products requiring numerous assembly steps along the industrial process chain, which can carry the potential of surface contamination. Cleanliness has to be analytically assessed with respect to ensuring safety and efficacy. Although several analytical techniques are routinely employed for such evaluation, a reliable analysis chain that guarantees metrological traceability and quantification capability is desirable. This calls for analytical tools that are cascaded in a sensible way to immediately identify and localize possible contamination, both qualitatively and quantitatively. In this systematic inter-comparative approach, we produced and characterized sodium dodecyl sulfate (SDS) films mimicking contamination on inorganic and organic substrates, with potential use as reference materials for ambient techniques, i.e., ambient mass spectrometry (AMS), infrared and Raman spectroscopy, to reliably determine amounts of contamination. Non-invasive and complementary vibrational spectroscopy techniques offer a priori chemical identification with integrated chemical imaging tools to follow the contaminant distribution, even on devices with complex geometry. AMS also provides fingerprint outputs for a fast qualitative identification of surface contaminations to be used at the end of the traceability chain due to its ablative effect on the sample. To absolutely determine the mass of SDS, the vacuum-based reference-free technique X-ray fluorescence was employed for calibration. Convex hip liners were deliberately contaminated with SDS to emulate real biomedical devices with an industrially relevant substance. Implementation of the aforementioned analytical techniques is discussed with respect to combining multimodal technical setups to decrease uncertainties that may arise if a single technique approach is adopted. Graphical abstract ᅟ.

Thermal denaturation produced degenerative proteins and interfered with MS for proteins dissolved in lysis buffer in proteomic analysis.

In 1-DE, proteins were traditionally mixed with the standard Laemmli buffer and boiled for several minutes. Recently, proteins dissolved in lysis buffer were used to produce better-resolved 2-DE gels, but thermal denaturation procedure still remained in some proteomic analysis. To determine the detailed effects of thermal denaturation on SDS-PAGE and MS, both 1-DE and 2-DE were performed using proteins heated at 100°C for different periods of time, and 17 protein bands/spots were positively identified by MALDI TOF/TOF MS/MS. Protein profiles on both 1-DE and 2-DE gels changed obviously and more polydisperse bands/spots were observed with increased heating time for over-heated samples. Based on these observations, an alternative protein marker-producing method was designed by directly dissolving protein standards without BSA into lysis buffer. This new kind of protein marker could be stored at room temperature for a long time, thus was more convenient for using and shipping. The identification of 17 proteins via MS and comparison of their identities revealed MASCOT-searched scores, number of both matched peptides, total searched peptides and sequence coverage became progressively lower with increasing denaturation intensity, probably due to the interference of thermal denaturation on trypsin cleavage efficiency and produced redundant modified peptides. Therefore, it was concluded that thermal denaturation not only changed the protein profiles and produced more polydisperse protein bands/spots, but also heavily interfered with the subsequent MS analysis, hence not recommended in future proteomic analysis for proteins dissolved in lysis buffer.

Method development and validation of capillary sodium dodecyl sulfate gel electrophoresis for the characterization of a monoclonal antibody.

A capillary sodium dodecyl sulfate gel electrophoresis (cSDS) method has been developed and qualified for purity and impurity analysis of monoclonal antibodies. This method was optimized and qualified for the analysis of monoclonal antibody (mAb1) under reduced and non-reduced conditions. Some of the sample preparation parameters including sample buffer pH, incubation temperature and duration, alkylation conditions with iodoacetamide (IAM), and reduction conditions with 2-mercaptoethanol (2-ME) were optimized. It was observed that under slightly acidic conditions (pH 5.5-6.5) the thermally induced fragmentation of non-reduced mAb1 was greatly decreased. As such, a citrate-phosphate buffer at pH 6.5 was used for sample preparation to replace the original Beckman sample buffer (pH 9.0). The optimal sample preparation conditions were found to be as follows: (1) incubation temperature and duration (reduced and non-reduced), 65 degrees C for 5 min; (2) alkylation condition, 10 microL of 0.25 M IAM; (3) reduction condition, 10 microL of 5-fold diluted 2-ME. The method was qualified by evaluating specificity, accuracy, precision, limit of quantitation (LOQ), and linearity. The method exhibited no interference from sample buffer matrix. The method was found to be linear, accurate, and precise in the range of 0.25-3.0mg/mL protein concentration. The LOQ of the method was determined to be 0.02 mg/mL for reduced and non-reduced mAb1. In addition, some aspects of sample stability were examined during qualification.

Evaluation of the impact of sodium lauryl sulfate source variability on solid oral dosage form development.

OBJECTIVE: The objective of this study was to investigate the effects of sodium lauryl sulfate (SLS) from different sources on solubilization/wetting, granulation process, and tablet dissolution of BILR 355 and the potential causes. METHODS: The particle size distribution, morphology, and thermal behaviors of two pharmaceutical grades of SLS from Spectrum and Cognis were characterized. The surface tension and drug solubility in SLS solutions were measured. The BILR 355 tablets were prepared by a wet granulation process and the dissolution was evaluated. RESULTS: The critical micelle concentration was lower for Spectrum SLS, which resulted in a higher BILR 355 solubility. During wet granulation, less water was required to reach the same end point using Spectrum than Cognis SLS. In general, BILR 355 tablets prepared with Spectrum SLS showed a higher dissolution than the tablets containing Cognis SLS. Micronization of SLS achieved the same improved tablet dissolution as micronized active pharmaceutical ingredient. CONCLUSIONS: The observed differences in wetting and solubilization were likely due to the different impurity levels in SLS from two sources. This study demonstrated that SLS from different sources could have significant impact on wet granulation process and dissolution. Therefore, it is critical to evaluate SLS properties from different suppliers, and then identify optimal formulation and process parameters to ensure robustness of drug product manufacture process and performance.

Toxicity of organic compounds to marine invertebrate embryos and larvae: a comparison between the sea urchin embryogenesis bioassay and alternative test species.

This study investigated the toxic effects of the insecticides lindane and chlorpyrifos, the herbicide diuron, the organometallic antifoulant tributyltin (TBT), and the surfactant sodium dodecyl sulfate (SDS) on the early life stages of Paracentrotus lividus (Echinodermata, Euechinoidea), Ciona intestinalis (Chordata, Ascidiacea), Maja squinado and Palaemon serratus (Arthropoda, Crustacea) in laboratory acute toxicity tests. The assays studied embryogenesis success from fertilized egg to normal larvae in P. lividus (48 h incubation at 20 degrees C) and C. intestinalis (24 h incubation at 20 degrees C), and larval mortality at 24 and 48 h in M. squinado and P. serratus. For P. lividus, the median effective concentrations (EC50) reducing percentages of normal larvae by 50% were: 350 microg l(-1) for chlorpyrifos, 5500 microg l(-1) for diuron, 4277 microg l(-1) for SDS, and 0.309 microg l(-1) for TBT. For C. intestinalis, the EC50 values affecting embryogenesis success were 5666 microg l(-1) for chlorpyrifos, 24,397 microg (l-1) for diuron, 4412 microg l(-1) for lindane, 5145 microg I(-1) for SDS, and 7.1 microg l(-1) for TBT. The median lethal concentrations (LC50) for M. squinado larval survival were 0.84 microg l(-1) (24 h) and 0.79 microg l(-1) (48 h) for chlorpyrifos, 2.23 microg(l(-1) (24 h) and 2.18 microg l(-1) (48 h) for lindane, and 687 microg l(-1) (48 h) for SDS. For P. serratus the LC50 values obtained were 0.35 microg l(-1) (24 h) and 0.22 microg l(-1) (48 h) for chlorpyrifos, 3011 microg l(-1) (24 h) and 3044 microg l(-1) (48 h) for diuron, 5.20 microg l(-1) (24 h) and 5.59 microg l(-1) (48 h) for lindane, and 22.30 microg l(-1) (24 h) and 17.52 microg l(-1) (48 h) for TBT. Decapod larvae, as expected, were markedly more sensitive to the insecticides than sea urchins and ascidians, and SDS was the least toxic compound tested for these organisms. Lowest observed effect concentrations (LOEC) of TBT for sea urchin and ascidian embryos, chlorpyrifos and lindane for crustacean larvae, and SDS, were similar to those found in many coastal areas indicating that there would be a risk to invertebrate embryos and larvae from exposure in the field to these pollutants.

Solute-solvent interactions in micellar electrokinetic chromatography. 6. Optimization of the selectivity of lithium dodecyl sulfate-lithium perfluorooctanesulfonate mixed micellar buffers.

The optimization of the composition of mixed surfactants used as micellar electrokinetic chromatography (MEKC) pseudostationary phases is proposed as an effective method for the separation of complex mixtures of analytes. The solvation parameter model is used to select two surfactants (lithium dodecyl sulfate, LDS, and lithium perfluorooctanesulfonate, LPFOS) with contrasting solvation properties. Combination of these two surfactants allows variations of the solvation properties of MEKC pseudostationary phase along a wide range. Thus, the convenient variation of the proportion of both surfactants allows an effective control of the selectivity in such systems. An algorithm that predicts the overall resolution of a given mixture of compounds is described and applied to optimize the composition of the mixed surfactant for the separation of the mixture. The algorithm is based on the calculation of peak purities on simulated chromatograms as a function of the composition of the mixed LDS/LPFOS micellar buffer from data at several micellar buffer compositions. Successful separations were achieved for mixtures containing up to 20 compounds, in less than 12 min.

Dissolution media for in vitro testing of water-insoluble drugs: effect of surfactant purity and electrolyte on in vitro dissolution of carbamazepine in aqueous solutions of sodium lauryl sulfate.

The intrinsic dissolution rate and solubility of carbamazepine was measured in aqueous solutions of sodium lauryl sulfate (SLS) prepared with two different grades of purity, 95 and 99%, and 95% SLS in 0.15 M NaCl to determine the effect of surface-active impurities and electrolytes. Four significant observations resulted from this work: (1) the equilibrium coefficients calculated from the solubility experiments in the 99% SLS, 95% SLS, and 95% with 0.15 M NaCl SLS solutions were 295, 265, and 233 L/mol, respectively; (2) the dissolution rate enhancement in the 99% SLS was 10% greater than that in the 95% SLS and 95% with 0.15 M NaCl solutions, which were not significantly different; (3) the diffusion coefficients of the drug-loaded micelles estimated from the dissolution experiments were 8.4 x 10(-7) cm2/s for the 99% SLS, 9.5 x 10(-7) cm2/s for the 95% SLS, and 1.2 x 10(-6) cm2/s for the 95% with 0.15 M NaCl; and (4) the critical micelle concentrations for the 99% SLS, 95% SLS, and 95% SLS with 0.15M NaCl were 6.8, 4.2, and 0.35 mM, respectively. The results of this study clearly illustrate the sensitivity of the micelle to impurities and electrolytes with regard to size and loading capacity and the effect these changes have on the solubility and dissolution rate. Therefore, when using surfactants in dissolution media for in vitro testing of dosage forms, consideration must be given to the level of impurities present so that the results are consistent and reliable. Intrinsic dissolution rate, surface tension, or solubility measurements may be useful, convenient methods for identifying changes in the surfactant due to either degradation or lot-to-lot variability.

Variability in electrophoretic mobility of Gi-like proteins: effect of SDS.

Two forms of Gi-like protein are resolved in both somatic cells and mouse gametes when Sigma SDS (95% grade) is used during polyacrylamide gel electrophoresis, whereas only a single species is resolved when Bio-Rad SDS (electrophoresis grade) is used. These two Gi-like proteins are likely to reflect two distinct species, since (i) the two species resolved in the presence of Sigma SDS migrate with the same electrophoretic mobility upon re-electrophoresis in the presence of Sigma SDS and (ii) exchanging Sigma SDS for Bio-Rad SDS resolves a single species, whereas exchanging Bio-Rad SDS for Sigma SDS resolves two species.

Importance of sodium dodecyl sulfate source to electrophoretic separations of thylakoid polypeptides.

Electrophoretic banding patterns of Chlamydomonas reinhardtii thylakoid polypeptides differ depending on whether impure, or pure sodium dodecyl sulfate (SDS) is used. Bands of Mr 45,000 and 36,000 were found when impure sodium dodecyl sulfate was used, but the Mr 45,000 band was absent when pure sodium dodecyl sulfate was used. Seven thylakoid polypeptides were isolated using preparative polyacrylamide gel electrophoresis, and the pure sodium dodecyl sulfate. Polypeptide (Mr 36,000) reran as a single band in pure sodium dodecyl sulfate, but yielded Mr 45,000 and 36,000 bands in impure sodium dodecyl sulfate. Although the Rf of most of the six other polypeptides differed, depending on whether pure or impure sodium dodecyl sulfate was used, the Mr of these polypeptides was the same with both. Thus, the banding pattern difference due to SDS source results from differences in Rf without changes in apparent Mr and a marked change in Mr of one polypeptide.