Distinctive Adsorption Mechanism and Kinetics of Immunoglobulin G on a Nanoscale Polymer Surface

Abstract

Elucidation of protein adsorption beyond simple polymer surfaces to those presenting greater chemical complexity and nanoscopic features is critical to developing well-controlled nanobiomaterials and nanobiosensors. In this study, we repeatedly and faithfully track individual proteins on the same nanodomain areas of a block copolymer (BCP) surface and monitor the adsorption and assembly behavior of a model protein, immunoglobulin G (IgG), over time into a tight surface-packed structure. With discrete protein adsorption events unambiguously visualized at the biomolecular level, the detailed assembly and packing states of IgG on the BCP nanodomain surface are subsequently correlated to various regimes of IgG adsorption kinetic plots. Intriguing features, entirely different from those observed from macroscopic homopolymer templates, are identified from the IgG adsorption isotherms on the nanoscale, chemically varying BCP surface. They include the presence of two Langmuir-like adsorption segments and a nonmonotonic regime in the adsorption plot. Via correlation to time-corresponding topographic data, the unique isotherm features are explained with single biomolecule level details of the IgG adsorption pathway on the BCP. This work not only provides much needed, direct experimental evidence for time-resolved, single protein level, adsorption events on nanoscale polymer surfaces but also signifies mutual linking between specific topographic states of protein adsorption and assembly to particular segments of adsorption isotherms. From the fundamental research viewpoint, the correlative ability to examine the nanoscopic surface organizations of individual proteins and their local as well as global adsorption kinetic profiles will be highly valuable for accurately determining protein assembly mechanisms and interpreting protein adsorption kinetics on nanoscale surfaces. Application-wise, such knowledge will also be important for fundamentally guiding the design and development of biomaterials and biomedical devices that exploit nanoscale polymer architectures.

Self-Assembled Block Copolymers as a Facile Pathway to Create Functional Nanobiosensor and Nanobiomaterial Surfaces

“…A distinct adsorption pathway of a single to double-file IgG assembly was revealed on the BCP surface. Additionally, unique adsorption characteristics such as the presence of two Langmuir-like segments and an undulating nonmonotonic regime were identified on the nanoscale BCP surface [76]. On the control surfaces of PS and PMMA homopolymers, the kinetic profile of IgG adsorption exhibited a single Langmuir-like segment with no undulating regime [76,77].…”

“…Additionally, unique adsorption characteristics such as the presence of two Langmuir-like segments and an undulating nonmonotonic regime were identified on the nanoscale BCP surface [76]. On the control surfaces of PS and PMMA homopolymers, the kinetic profile of IgG adsorption exhibited a single Langmuir-like segment with no undulating regime [76,77]. The IgG adsorption kinetics on the BCP surface of PS-b-PMMA versus on the homopolymer surfaces of PS and PMMA are presented in Figure 7A,B.…”

“…Despite these hurdles, the exact adsorption pathways and kinetics of IgG were determined successfully by tracking individual IgG molecules on the striped nanodomains of PS-b-PMMA [76]. Owing to the direct measurements of the same IgG molecules over time, it was possible to establish meaningful correlations between various topological states of the IgG assembly and specific adsorption kinetic regimes on the BCP surface.…”

“…The drastic surface-induced changes can be best evidenced in research efforts that systematically compared the interaction behaviors of the same proteins on BCP nanodomains relative to homopolymers, random copolymers, and polymer blends [35,[76][77][78]85,87,156,158]. Salient features such as high protein density and tight 2D-packing represent those behaviors distinctively observed from nanoscale BCP platforms.…”

“…The focus of this Review is to provide a comprehensive and detailed overview of those research efforts pertaining to nanoscale surface assembly of functional biomolecules, biomolecular interaction properties at nanoscale polymer interfaces, functionality of nanoscale surface-bound biomolecules, as well as specific examples in biosensing. [75] [76,77] [78] [79] Poly(styrene-co-4-bromostyrene)-block-polyethylene oxide (P(S-co-BrS)-b-PEO) 3.1.3. [80] Poly(2-methacryloyloxyethyl phosphorylcholine)-block-poly(dimethylsiloxane) (PMPC-b-PDMS) PS-b-PEO 3.1.2.…”