Characterizing the Adsorption of Proteins on Glass Capillary Surfaces Using Electrospray-Differential Mobility Analysis

Abstract

We quantify the adsorption and desorption of a monoclonal immunoglobulin-G antibody, rituxamab (RmAb), on silica capillary surfaces using electrospray-differential mobility analysis (ES-DMA). We first develop a theory to calculate coverages and desorption rate constants from the ES-DMA data for proteins adsorbing on glass capillaries used to electrospray protein solutions. This model is then used to study the adsorption of RmAb on a bare silica capillary surface. A concentration-independent coverage of ≈4.0 mg/m(2) is found for RmAb concentrations ranging from 0.01 to 0.1 mg/mL. A study of RmAb adsorption to bare silica as a function of pH shows maximum adsorption at its isoelectric point (pI of pH 8.5) consistent with literature. The desorption rate constants are determined to be ≈10(-5) s(-1), consistent with previously reported values, thus suggesting that shear forces in the capillary may not have a considerable effect on desorption. We anticipate that this study will allow ES-DMA to be used as a "label-free" tool to study adsorption of oligomeric and multicomponent protein systems onto fused silica as well as other surface modifications.

Electrospray–differential mobility analysis of bionanoparticles

“…On the other hand for IgM desorption from bare silica is 0.004 ± 0.0025 min -1 and 0.00035 ± 0.00007 min -1 for monomers and dimers respectively. These values are well within the wide range of desorption rate constants (≈10 -4 min -1 to ≈1 min -1 ) found in the literature [120,[144][145][146]. Clearly, there are two important inferences: the monomer desorbs faster than the dimer for both surfaces, and the propensity for both the monomers and dimers of IgM to stay adsorbed on the gelatin-passivated surface is lower.…”

“…As one of the peer reviewers pointed out: "The systematic study undertaken of the phenomenon is of considerable interest, as it establishes a relatively powerful method for protein adsorption 174 studies." The reviewer in this case was referring to section 4.1 which was published in Langmuir [144]. Section 4.2 extended this to oligomeric proteins.…”

Quantifying Ligand Adsorption to Nanoparticles Using Tandem Differential Mobility Mass Analysis

“…In these experiments, the coverage of RmAb adsorbed on 60 nm PSL nanoparticles as a function of pH was determined using ES-DMA–APM (Supporting Information S4, Figure S2). The coverage reaches a maximum at pH ≈ 8.5 which is close to the isoelectric point (pI) of RmAb . There are at least two possibilities that may explain the maximum coverage near the pI: (i) net zero charge of a RmAb molecule would mean the decreased electrostatic repulsions between neighboring molecules allows for more compact packing on the surface and (ii) the RmAb molecules interact with each other and the PSL surface through hydrophobic interactions; denature significantly; and promote nonspecific adsorption of more RmAb molecules, creating multiple layers.…”

Electrospray–Differential Mobility Analysis as an Orthogonal Tool to Size-Exclusion Chromatography for Characterization of Protein Aggregates

“…We have found that different IgGs tend to adsorb to the capillary walls of the ES capillaries, which is problematic because it leads to a time‐variant size distribution and may affect quantification of different oligomers,30 but can be significantly reduced by passivating the capillaries with gelatin. Prior to ES of protein samples, 0.5–1.0 mol/L H 2 SO 4 , deionized (18 MΩ/cm) ultrapure water, and 20 mmol/L ammonium actetate buffer solutions were eluted sequentially for 20–30 min through 25‐µm fused silica capillaries (TSI Inc.).…”