Direct 3D printing of monolithic ion exchange adsorbers

Abstract

Monolithic adsorbers with anion exchange (AEX) properties have been 3D printed in an easy one-step process, i.e. not requiring post-functionalization to introduce the AEX ligands. The adsorber, 3D printed using a commercial digital light processing (DLP) printer, was obtained by copolymerisation of a bifunctional monomer bearing a positively charged quaternary amine as well as an acrylate group, with the biocompatible crosslinker polyethylene glycol diacrylate (PEGDA). To increase the surface area, polyethylene glycol was introduced into the material formulation as pore forming agent. The influence of photoinitiator (Omnirad 819) and photoabsorber (Reactive Orange 16, RO16) concentration was investigated in order to optimize printing resolution, allowing to reliably 3D print features as small as 200 µm and of highly complex Schoen gyroids. Protein binding was measured on AEX adsorbers with a range of ligand densities (0.00, 2.03, 2.60 and 3.18 mmol/mL) using bovine serum albumin (BSA) and c-phycocyanin (CPC) as model proteins. The highest equilibrium binding capacity was found for the material presenting the lowest ligand density analysed (2.03 mmol/mL), adsorbing 73.7 ± 5.9 mg/mL and 38.0 ± 2.2 mg/mL of BSA and CPC, respectively. This novel 3D printed material displayed binding capacities in par or even higher than commercially available chromatographic resins. We expect that the herein presented approach of using bifunctional monomers, bearing commonly used chromatography ligands, will help overcome the material limitations currently refraining 3D printing applications in separation sciences.

Current challenges in biotherapeutic particles manufacturing

“…A new area that started to be exploited in the last couple of years, especially in the separation field, is additive manufacturing or 3D printing [143]. Simon et al, have recently described a 3D printed fully functional stationary phase for protein separations [144]. In this work, 3D printed anion exchange membrane adsorbers were evaluated for adsorption of bovine serum albumin and c-phycocyanin, showing adsorption characteristics in line with the membrane adsorbers commercially available.…”

Are we approaching a post‐monolithic era?

“… Active molding : As suggested by Tallarek and coworkers [31], active shaping of macroporous space would significantly increase transcolumn homogeneity of monoliths. Although this approach has been already demonstrated in the literature [38,39], it is necessary to introduce yet other protocols to improve radial homogeneity of polymeric separation materials. Additive manufacturing (3D printing) : Nowadays, 3D printing belongs to one of the most expanding directions in separation science [40–42], and there are already research groups devoting their potential to the development of 3D‐printed stationary phases [43–46]. A coverage of 3D‐printed scaffold by a polymeric material seems to be the simplest way to produce highly ordered stationary phases with selected surface chemistry.…”

Demonstration of protein capture and separation using three‐dimensional printed anion exchange monoliths fabricated in one‐step

“…Structures printed with the initial material formulation displayed red color [7], indicating that some of the photoabsorber, the red dye reactive orange, remained in the material despite extensive washing procedures. Reactive orange has a negative charge in its structure and binds tightly to the positive QA ligands by electrostatic interactions.…”

“…The equilibrium binding capacity of materials with different ligand density (control, 0.57, 1.14, 1.73, 2.33 mmol/mL) was investigated, with resulting adsorption isotherms displayed in Figure 3A. Adsorbers with a hollow cylindrical shape fitting into wells of a 96-well microplate were printed to facilitate the adsorption experiment (Figure 2A and B) [7]. This allowed in situ measurement of protein concentration in the liquid phase using a plate reader.…”