Protein adsorption on Ion exchange resin: Estimation of equilibrium isotherm parameters from batch kinetic data

Determination of the Serum Concentrations of the Monoclonal Antibodies Bevacizumab, Rituximab, and Panitumumab Using Porous Membranes Containing Immobilized Peptide Mimotopes

Effective monoclonal antibody (mAb) therapies require a threshold mAb concentration in patient serum. Moreover, the serum concentration of the mAb Bevacizumab should reside in a specific range to avoid side effects. Methods for conveniently determining the levels of mAbs in patient sera could allow for personalized dosage schedules that lead to more successful treatments. This work utilizes microporous nylon membranes functionalized with antibody-binding peptides to capture Bevacizumab, Rituximab, or Panitumumab from diluted (25%) serum. Modification of the capture-peptide terminus is often crucial to creating the affinity necessary for effective binding. The high purity of eluted mAbs allows for their quantitation using native fluorescence, and membranes are effective in spin devices that can be used in any laboratory. The technique is effective over the therapeutic range of Bevacizumab concentrations. Future work aims at further modifications to develop rapid point-of-care devices and decrease detection limits.

Non-invasive determination of ionizable ligand group density on high internal phase emulsion derived polymer

Stepwise change between low and high salt concentration buffers of the same pH results in pH transition, the length of which was demonstrated to be proportional to the quantity of ion-exchange groups present on the matrix. In this work, we analyzed the effect of the ligand type, density, and buffer concentration on the pH transition shape for typical ion-exchange groups (QA, DEAE, SO3, and COOH) and ligands acting as metal-chelators, such as IDA, TAEA, and EDA. It was demonstrated that pH transition can occur either as a chromatographic or flat-top peak. pH transition peaks were evaluated by their length, height, and peak center parameters. While no parameter can describe the ligand density accurately with a single linear correlation for both peak types, all parameters can be used for the description of one peak type. Peak length and height exhibited the same accuracy, while their sensitivity depended on the pH transition shape: length being more sensitive for the flat-top peaks, while height for the chromatographic peaks. pH height can be obtained faster, at lower elution volume, and seems to be more suitable for the determination of low amounts of ligand, when typically chromatographic peak type pH transitions occur.

Interference: A Much-Neglected Aspect in High-Throughput Screening of Nanoparticles

Despite several studies addressing nanoparticle (NP) interference with conventional toxicity assay systems, it appears that researchers still rely heavily on these assays, particularly for high-throughput screening (HTS) applications in order to generate "big" data for predictive toxicity approaches. Moreover, researchers often overlook investigating the different types of interference mechanisms as the type is evidently dependent on the type of assay system implemented. The approaches implemented in the literature appear to be not adequate as it often addresses only one type of interference mechanism with the exclusion of others. For example, interference of NPs that have entered cells would require intracellular assessment of their interference with fluorescent dyes, which has so far been neglected. The present study investigated the mechanisms of interference of gold NPs and silver NPs in assay systems implemented in HTS including optical interference as well as adsorption or catalysis. The conventional assays selected cover all optical read-out systems, that is, absorbance (XTT toxicity assay), fluorescence (CytoTox-ONE Homogeneous membrane integrity assay), and luminescence (CellTiter Glo luminescent assay). Furthermore, this study demonstrated NP quenching of fluorescent dyes also used in HTS (2',7'-dichlorofluorescein, propidium iodide, and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzamidazolocarbocyanin iodide). To conclude, NP interference is, as such, not a novel concept, however, ignoring this aspect in HTS may jeopardize attempts in predictive toxicology. It should be mandatory to report the assessment of all mechanisms of interference within HTS, as well as to confirm results with label-free methodologies to ensure reliable big data generation for predictive toxicology.

A Flow-Through Chromatographic Strategy for Hepatitis C Virus-Like Particles Purification

Biopharmaceuticals are currently becoming one of the fastest growing segments of the global pharmaceutical industry, being used in practically all branches of medicine from disease treatment to prevention. Virus-like particles (VLP) hold tremendous potential as a vaccine candidate due to their anticipated immunogenicity and safety profile when compared to inactivated or live attenuated viral vaccines. Nevertheless, there are several challenges yet to be solved in the development and manufacturing of these products, which ultimately can increase time to market. Suchlike virus-based products, the development of a platform approach is often hindered due to diversity and inherent variability of physicochemical properties of the product. In the present work, a flow-through chromatographic purification strategy for hepatitis C VLP expressed using the baculovirus-insect cell expression system was developed. The impact of operational parameters, such as residence time and ionic strength were studied using scaled-down models and their influence on the purification performance was described. The flow-through strategy herein reported made use of radial-flow chromatography columns packed with an anion exchanger and was compared with a bind and elute approach using the same chromatography media. Overall, by selecting the optimal operational setpoints, we were able to achieve higher VLP recoveries in the flow-through process (66% versus 37%) with higher removal of DNA, baculovirus and host-cell protein (92%, 99% and 50% respectively).

Optimization of Process Parameters forε-Polylysine Production by Response Surface Methods

ε-Polylysine (ε-PL) is a highly safe natural food preservative with a broad antimicrobial spectrum, excellent corrosion resistances, and great commercial potentials. In the present work, we evaluated theε-PL adsorption performances of HZB-3B and D155 resins and optimized the adsorption and desorption conditions by single-factor test, response surface method, and orthogonal design. The complexes of resin andε-PL were characterized by SEM and FITR. The results indicated that D155 resin had the bestε-PL adsorption performance and was selected for the separation and purification ofε-PL. The conditions for the static adsorption ofε-PL on D155 resin were optimized as follows:ε-PL solution 40 g/L, pH 8.5, resins 15 g/L, and absorption time 14 h. The adsorption efficiency ofε-PL under the optimal conditions was 96.84%. Theε-PL adsorbed on the D155 resin was easily desorbed with 0.4 mol/L HCl at 30°C in 10 h. The highest desorption efficiency was 97.57% and the overall recovery ofε-PL was 94.49% under the optimal conditions. The excellentε-PL adsorption and desorption properties of D155 resin including high selectivity and adsorption capacity, easy desorption, and high stability make it a good candidate for the isolation ofε-PL from fermentation broths.