High throughput discovery of new fouling-resistant surfaces

Abstract

A novel high throughput method for synthesis and screening of customized protein-resistant surfaces was developed. This method is an inexpensive, fast, reproducible and scalable approach to synthesize and screen protein-resistant surfaces appropriate for a specific feed. The method is illustrated here by combining a high throughput platform (HTP) approach together with our patented photo-induced graft polymerization (PGP) method developed for facile modification of commercial poly(aryl sulfone) membranes. We demonstrate that the HTP-PGP approach to synthesize and screen fouling-resistant surfaces is general, and thus provides the capability to develop surfaces optimized for specific feeds. Surfaces were prepared via graft polymerization onto poly(ether sulfone) (PES) membranes and were evaluated using a protein adsorption assay followed by pressure-driven filtration. We have employed the HTP-PGP approach to confirm previously reported successful monomers and to develop new antifouling surfaces from a library of 66 monomers for four different challenges of interest to the biotechnology community: hen egg-white lysozyme, supernatant from Chinese Hamster Ovary (CHO) cells in phosphate buffered saline (PBS) solution as a model cell suspension, and immunoglobulin G (IgG) precipitated in the absence and presence of bovine serum albumin (BSA) in high salt solution as a model precipitation process.

Fig. 1

The PGP method (center box) illustrating radical formation from UV radiation on PES membranes and subsequent graft polymerization of vinyl monomers. Sixty-six vinyl monomers (in nine classes based on functionality, surrounding boxes) were grafted onto PES using the HTP–PGP platform and tested for protein adhesion and filtration. In the text the following abbreviations in parenthesis are used for the monomers in the outer 9 boxes in clockwise direction: charged (Basic and Zwitterionic or Zwit), hydrophobic methacrylates (HPO MA), amines (Amines), aromatic (Aromatic), hetero ring (Hetero ring), monomers that do not easily fit into the other categories (Others), strong and weak acids (Acid), polyethylene glycols (PEGs) and hydroxyl monomers (Hydroxy).

Fig. 2

Measured (histogram) and best fit General Extreme Value (lines) fouling index distributions for (a) hen egg lysozyme solution in PBS at 1 mg ml⁻¹; (b) Chinese hamster ovary cell supernatant in PBS at ~4 mg ml⁻¹ total protein with 1 mg ml⁻¹ IgG; (c) IgG precipitate with 0.5 mg ml⁻¹ IgG; (d) IgG precipitate with 0.25 mg ml⁻¹ IgG in the presence of 0.25 mg ml⁻¹ of BSA; (e) BSA solution in PBS at 1 mg ml⁻¹; and (f) comparison of fitted distributions. Points on the x-axis show location of measured fouling indices. Histogram bin size shown corresponds approximately to one standard deviation in the fouling index data over the range 0 to ±2.

Fig. 3

Number of monomers with specific ratings for different monomer classes for fouling-resistant surfaces due to challenges from (a) hen egg lysozyme solution in PBS at 1 mg ml⁻¹; (b) Chinese hamster ovary cell supernatant in PBS at ~4 mg ml⁻¹ total protein with 1 mg ml⁻¹ IgG; (c) IgG precipitate with 0.5 mg ml⁻¹ IgG; (d) IgG precipitate with 0.25 mg ml⁻¹ IgG in the presence of 0.25 mg ml⁻¹ of BSA. Monomers: purple: charged (Basic and Zwitterionic or Zwit), red: hydrophobic methacrylates (HPO MA), light blue: amines (Amines), yellow: aromatic (Aromatic), orange: hetero ring (Hetero ring), rose: monomers that do not easily fit into the other categories (Others), dark blue: strong and weak acids (Acid), light green: polyethylene glycols (PEGs) and dark green: hydroxyl monomers (Hydroxy). ND = not determined due to low modified membrane permeability.