Stability of Protein Pharmaceuticals: Recent Advances.

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

Application of Formulation Principles to Stability Issues Encountered During Processing, Manufacturing, and Storage of Drug Substance and Drug Product Protein Therapeutics.

The field of formulation and stabilization of protein therapeutics has become rather extensive. However, most of the focus has been on stabilization of the final drug product. Yet, proteins experience stress and degradation through the manufacturing process, starting with fermentaition. This review describes how formulation principles can be applied to stabilize biopharmaceutical proteins during bioprocessing and manufacturing, considering each unit operation involved in prepration of the drug substance. In addition, the impact of the container on stabilty is discussed as well.

Analysis of Peptides using Asymmetrical Flow Field-flow Fractionation (AF4).

While asymmetrical flow field-flow fractionation (AF4) has been widely used for separation of high molecular weight species and even particles, its ability to resolve lower molecular weight species has rarely been explored. Over the course of many projects, we have discovered that AF4 can be an effective analytical method for separating peptides from oligomers and higher molecular weight aggregates. The methodology can be used even for peptides as small as 2 kD in molecular weight. Using multi-angle laser light scattering (MALLS) detection, accurate masses of the parent peptide can be obtained, provided accurate extinction coefficients are provided. It was shown that AF4 can be stability-indicating, suggesting that AF4-MALLS may be a suitable alternative to the use of SEC to monitor the aggregation of peptides.

Deposition of amorphous CN(x) materials in BrCN plasmas: exploring adhesion behavior as an indicator of film properties.

Adhesion and delamination behavior of amorphous carbon nitride (a-CN(x)) is critical to development of wear resistant materials and protective coatings. Here, the composition and delamination behavior of a-CN(x) films was explored utilizing BrCN, CH3CN, and CH4 as film precursors, either alone or in combination with one another. Film delamination depends on film thickness and plasma composition as well as post deposition treatment conditions. Delamination is not observed with films deposited from 100% CH3CN discharges, whereas films of similar thickness deposited from 100% BrCN plasmas delaminate almost immediately upon exposure to atmosphere. Exploration of these differences in delamination behavior is discussed relative to contributions of humidity, hydrocarbon species, and ion bombardment during deposition in conjunction with compositional studies using X-ray photoelectron spectroscopy (XPS).

Gas phase energetics of CN radicals in radio frequency discharges: influence on surface reaction probability during deposition of carbon nitride films.

The CN radical has been implicated as an important contributor to the plasma deposition of amorphous carbon nitride. Here, laser-induced fluorescence and optical emission spectroscopy were used to explore in greater detail the gas phase energetics of CN in CH(3)CN, BrCN, and CH(4)/N(2) plasmas. Measurements of CN internal temperatures from these systems yield rotational temperatures well above 300 K, with notably higher ones for CN formed in BrCN plasmas, and vibrational temperatures of 4500-6000 K in all three systems. The data agree with the results of literature photodissociation experiments, and extension of those results to the plasma systems studied here provides insight into both the mechanisms for CN formation as well as the disposal of energy during fragmentation of the parent molecules. The internal energies of these species may influence their surface behavior; this issue is discussed in the context of previous work from our lab as well as others. The apparent trends not only offer a valuable perspective on the chemical dynamics of CN during the plasma deposition of a-CN(x) films but are also suggestive of a more general relationship between the energetics of plasma species and their behavior at surfaces.

Plasma diagnostics for unraveling process chemistry.

This review focuses on the use of diagnostic tools to examine plasma processing chemistry, primarily plasma species energetics, dynamics, and molecule-surface reactions. We describe the use of optical diagnostic tools, mass spectrometry, and Langmuir probes in measuring species densities, rotational and kinetic energies, and plasma-surface reactions. Molecule-surface interactions for MX(n) species (M = C, Si, N; X = H, F, Cl) are presented and interpreted with respect to the molecule's electronic configuration and dipole moments.