A stereocomplex platform efficiently detecting antigen-antibody interactions

Effect of poly(tert-butyl methacrylate) stereoregularity on polymer film interactions with peptides, proteins, and bacteria

The impact of polymer stereoregularity on its interactions with peptides, proteins and bacteria strains was studied for three stereoregular forms of poly(tert-butyl methacrylate) (PtBMA): isotactic (iso), atactic (at) and syndiotactic (syn) PtBMA. Principal component analysis of the time-of-flight secondary ion mass spectrometry data recorded for thin polymer films indicated a different orientation of ester groups, which in the case of iso-PtBMA are exposed away from the surface whereas for at-PtBMA and syn-PtBMA these are located deeper within the film. This arrangement of chemical groups modified the interactions of iso-PtBMA with biomolecules when compared to at-PtBMA and syn-PtBMA. For peptides, the affected interactions were explained by the preferential hydrogen bonding and electrostatic interaction between the exposed polar ester groups of iso-PtBMA and positively charged peptides. In turn, for protein adsorption no impact on the amount of adsorbed proteins was observed. However, the polymer stereoregularity influenced the orientation of immunoglobulin G and induced conformational changes in bovine serum albumin structure. Moreover, the impact of polymer stereoregularity occurred equally for their interactions with Gram-positive bacteria (S. aureus), which absorbed preferentially onto iso-PtBMA films as compared to two other stereoregularities.

Hydrophilic Polyelectrolyte Multilayers Improve the ELISA System: Antibody Enrichment and Blocking Free

In this study, polyelectrolyte multilayers were fabricated on a polystyrene (PS) plate using a Layer-by-Layer (LbL) self-assembly technique. The resulting functional platform showed improved performance compared with conventional enzyme-linked immunosorbent assay (ELISA) systems. Poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were used as cationic and anionic polyelectrolytes. On the negatively-charged (PDDA/PAA)₃ polyelectrolyte multilayers the hydrophilic PAA surface could efficiently decrease the magnitude of the noise signal, by inhibiting nonspecific adsorption even without blocking reagent adsorption. Moreover, the (PDDA/PAA)₃ substrate covalently immobilized the primary antibody, greatly increasing the amount of primary antibody adsorption and enhancing the specific detection signal compared with a conventional PS plate. The calibration curve of the (PDDA/PAA)₃ substrate showed a wide linear range, for concentrations from 0.033 to 33 nM, a large specific signal change, and a detection limit of 33 pM, even though the conventional blocking reagent adsorption step was omitted. The (PDDA/PAA)₃ substrate provided a high-performance ELISA system with a simple fabrication process and high sensitivity; the system presented here shows potential for a variety of immunosensor applications.

Polyelectrolyte multilayers-modified polystyrene plate improves conventional immunoassay: full covering of the blocking reagent

In this study, we fabricated polyelectrolyte multilayers (PEMs) on a polystyrene (PS) plate by a simple and novel alternate drop coating process (Acta Biomaterialia 2008, 4, 1255-1262), leading to the construction of a functional platform for improving conventional enzyme-linked immunosorbent assay (ELISA) systems. Poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS) were used as cationic and anionic polyelectrolytes, and then positively or negatively charged surfaces were obtained on the PEMs. The PDDA/PSS PEMs on the PS plate had the following favorable characteristics. On the positive PEMs, the coverage of the blocking reagent (ovalbumin from egg white: OVA) was over 100% by electrostatic interaction between the protein and PEMs, hence, nonspecific adsorption from the secondary antibody was efficiently suppressed. Moreover, the positive PEMs showed higher sensitivity on the ELISA than the negative PEMs, including the PS plate. Regularly oscillating behavior for sensitivity (specific signal-to-noise ratio) was observed on 1-10-step assemblies. The calibration curves for antigen detection on the positive PEMs had wide range of concentration from 0.002 to 5 microg/mL, and largest change in signal as compared with the negative PEMs and the PS plate. In summary, we discovered that positive PEMs possessed excellent performance for ELISA systems, and PEMs could easily improve the immunoassay with a convenient process and diverse substrates.