Rheo-NMR studies of an enzymatic reaction: evidence of a shear-stable macromolecular system

Shear stress as a driver of degradation for protein-based therapeutics: More accomplice than culprit

Protein degradation is a major concern for protein-based therapeutics. It may alter the biological activity of the product and raise the potential for undesirable effects on the patients. Among the numerous drivers of protein degradation, shear stress has been the focus around which much work has revolved since the 1970s. In the pharmaceutical realm, the product is often processed through several unit operations, which include mixing, pumping, filtration, filling, and atomization. Nonetheless, the drug might be exposed to significant shear stresses, which might cooperatively contribute to product degradation, together with interfacial stress. This review presents fundamentals of shear stress about protein structure, followed by an overview of the drivers of product degradation. The impact of shear stress on protein stability in different unit operations is then presented, and recommendations for limiting the adverse effects on the biopharmaceutical formulations are outlined. Finally, several devices used to explore the effects of shear stress are discussed.

Rheo-NMR Spectroscopy for Cryogenic-Probe-Equipped NMR Instruments to Monitor Protein Aggregation

Cryogenic-probe-based Rheo-NMR spectroscopy is a recently developed methodology to obtain solution NMR spectra of protein samples in situ under external shear. It is applicable to atomic-resolution monitoring of protein aggregation in situ, thereby aiding understanding of the transient structural changes and state conversion of amyloidogenic proteins, which are strongly associated with the both the onset and the progression of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Here, we present detailed experimental procedures for the instrumental setup and practical tips for preparation of NMR measurement to analyze protein aggregation by this technique. This protocol will thus aid future Rheo-NMR spectroscopic studies not only of protein aggregation but also of other phenomena related to shear stress, such as shear-induced viscosity increase and shear-enhanced crystallization. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Setup of a Rheo-NMR Instrument Basic Protocol 2: Adjustment of the Vertical and Horizontal Positions of the Glass Stick Basic Protocol 3: Monitoring Protein Aggregation by Rheo-NMR Spectroscopy.

In-vial printing and drying of biologics as a personalizable approach

This study addressed the need for a flexible (personalizable) production of biologics, allowing their stabilization in the solid state and processing of small batch volumes. Therefore, inkjet printing into vials followed by a gentle vacuum drying step at ambient temperature was investigated by screening different formulations with a 2²-full factorial design of experiments regarding printability. Human Serum Albumin (HSA) was used as a model protein in a wide range of concentrations (5 to 50 mg/ml), with (10 w/v%) and without the surfactant polysorbate 80 (PS80). PS80 was identified to positively affect the formulations by increasing the Ohnesorge number and stabilizing the printing process. The dispensed volumes with a target dose of 0.5 mg HSA were dried and analyzed concerning their residual moisture (RM) and protein aggregation. All investigated formulations showed an RM < 10 wt% and no significant induced protein aggregation as confirmed by Size Exclusion Chromatography (<2.5%) and Dynamic Light Scattering (Aggregation Index ≤ 2.5). Additionally, long-term printability and the available final dose after reconstitution were investigated for two optimized formulations. A promising formulation providing ∼93% of the targeted dose and a reconstitution time of 30 s was identified.

2D and 3D inkjet printing of biopharmaceuticals - A review of trends and future perspectives in research and manufacturing

There is an ongoing global shift in pharmaceutical business models from small molecule drugs to biologics. This increase in complexity is in response to advancements in our diagnoses and understanding of diseases. With the more targeted approach coupled with its inherently more costly development and manufacturing, 2D and 3D printing are being explored as suitable techniques to deliver more personalised and affordable routes to drug discovery and manufacturing. In this review, we explore first the business context underlying this shift to biopharmaceuticals and provide an update on the latest work exploring discovery and pharmaceutics. We then draw on multiple disciplines to help reveal the shared challenges facing researchers and firms aiming to develop biopharmaceuticals, specifically when using the most commonly explored manufacturing routes of drop-on-demand inkjet printing and pneumatic extrusion. This includes separating out how to consider mechanical and chemical influences during manufacturing, the role of the chosen hardware and the challenges of aqueous formulation based on similar challenges being faced by the printing industry. Together, this provides a review of existing work and guidance for researchers and industry to help with the de-risking and rapid development of future biopharmaceutical products.

Stirring rate affects thermodynamics and unfolding kinetics in isothermal titration calorimetry

Isothermal titration calorimetry (ITC) directly provides thermodynamic parameters depicting the energetics of intermolecular interactions in solution. During ITC experiments, a titration syringe with a paddle is continuously rotating to promote a homogeneous mixing. Here, we clarified that the shape of the paddles (flat, corkscrew and small-pitched corkscrew) and the stirring rates influence on the thermodynamic parameters of protein-ligand interaction. Stirring with the flat paddle at lower and higher rate both yielded a lower exothermic heat due to different reasons. The complete reaction with no incompetent fractions was achieved only when the stirring was performed at 500 or 750 rpm using the small-pitched corkscrew paddle. The evaluation of the protein solution after 1,500 rpm stirring indicated that proteins in the soluble fraction decreased to 94% of the initial amount, among which 6% was at an unfolded state. In addition, a significant increase of micron aggregates was confirmed. Furthermore, a new approach for the determination of the unfolding kinetics based on the time dependence of the total reaction heat was developed. This study demonstrates that a proper stirring rate and paddle shape are essential for the reliable estimation of thermodynamic parameters in ITC experiments.

High-Sensitivity Rheo-NMR Spectroscopy for Protein Studies

Shear stress can induce structural deformation of proteins, which might result in aggregate formation. Rheo-NMR spectroscopy has the potential to monitor structural changes in proteins under shear stress at the atomic level; however, existing Rheo-NMR methodologies have insufficient sensitivity to probe protein structure and dynamics. Here we present a simple and versatile approach to Rheo-NMR, which maximizes sensitivity by using a spectrometer equipped with a cryogenic probe. As a result, the sensitivity of the instrument ranks highest among the Rheo-NMR spectrometers reported so far. We demonstrate that the newly developed Rheo-NMR instrument can acquire high-quality relaxation data for a protein under shear stress and can trace structural changes in a protein during fibril formation in real time. The described approach will facilitate rheological studies on protein structural deformation, thereby aiding a physical understanding of shear-induced amyloid fibril formation.

Hydrodynamic effects in proteins

Experimental and numerical results pertaining to flow-induced effects in proteins are reviewed. Special emphasis is placed on shear-induced unfolding and on the role of solvent mediated hydrodynamic interactions in the conformational transitions in proteins.

Rheo-NMR studies of the behavior of a nematic liquid crystal in a low-shear-rate regime: the transition from director alignment to reorientation

Deuterium NMR spectroscopy has been used to study the director dynamics of the nematic liquid-crystal system cetyl trimethylammonium bromide/D2O under the action of applied viscous torques. Shear forces were applied using a custom-built Couette cell that was introduced into an NMR superconducting magnet, so that its rotational axis was parallel to the magnetic field direction, along which the liquid-crystal director originally aligned. Subsequently, the inner cylinder of the cell was rotated continuously at different rates using a stepper motor. The resulting time evolution and ultimate steady-state orientation of the director, governed by the competition between the applied viscous torque with elastic and magnetic terms, was measured via observed changes in the deuterium spectrum. Using a simple gearbox allowed unprecedented access to a low-shear-rate regime in which, above a threshold shear rate, the director of part of the sample was observed to reorient, while the remaining part still aligned with the magnetic field. Subsequent increases in the applied rotational rate were found to increase the relative proportion of the orienting fraction. Spatially resolved NMR spectra showed that the orienting and field-aligned fractions formed separated bands across the gap of the Couette cell, with director reorientation being initiated at the moving inner wall. The behavior was found to be consistent with the often ignored variation in velocity gradient manifest across the gap of a cylindrical cell, so that as the angular frequency of the inner cylinder was increased the radial location of the critical shear rate required for reorientation traversed the gap. Once the applied rotational rate was sufficient to reorient the director of the entire sample, the dependence of the exhibited steady-state orientation on the average applied shear rate was measured. These results could be fitted to an analytical solution of the force-balance equation, made tractable by the assumption that the elasticity term was of minor significance and could be ignored. Additionally, the use of a numerical solution of the full force-balance equation, which explicitly includes elasticity and secondary flow and additionally allows the time evolution of the director orientation to be calculated, was investigated.