Application note Optimization of process conditions for Vk fragment capture and purification using MiMode PuraBead® HX2 The expanding range of therapeutic modalities, including monoclonal antibodies (mAbs) and their derivatives, present purification challenges due to the diversity of their physical properties and expression systems. This application note demonstrates the potential of MiMode PuraBead® HX2 for antibody fragment capture using an E. coli-derived variable kappa light chain (Vk) fragment as a model feedstock.
Purification of mAbs and their derivatives typically starts with a capture step using either Protein A, which binds the antibody Fc region, or Protein L ligands, which have specificity for the kappa light chain. The performance of these resins can be limited, however, by a lack of base stability and, for Protein L, its narrow specificity.
Unoptimized MiMode PuraBead® HX2 purification buffers Equilibration:
25 mM Tris
Elution:
50 mM sodium citrate, pH 3.0
Clean-in-place: MiMode PuraBead® HX2 is a mixed-mode chromatography resin with a synthetic ligand that has broad specificity for both antibody kappa and lambda chains. The synthetic ligand allows for robust base stability, and the PuraBead® 6HF base matrix offers stable flow properties even for largescale manufacturing. These attributes make it an appealing alternative to Protein L as a platform technology. This application note demonstrates the potential of MiMode PuraBead® HX2 for capturing and purifying antibody fragments using an E. coli-derived variable kappa light chain (Vk) fragment as a model feedstock. The optimized workflow showed superior host cell protein (HCP) clearance for Vk fragments compared to a Protein L adsorbent and serves as a guide for purifying antibody fragments using MiMode PuraBead® HX2.
Table 1: Unoptimized MiMode PuraBead® HX2 purification buffers. The capacity, recovery, and purity results for best-performing screening conditions and the predicted results for the in-silico model optimal conditions for Vk fragment purification are shown in Table 2. These two load conditions were selected for further verification in 1 mL column mode. Capacity (mg/mL adsorbent) 8
6 8
12
10
®
Screening was performed using a high-throughput system (Biomek i7) with a Captiva Plate® containing 16 x 0.25 mL MiMode PuraBead® HX2 adsorbent. Vk capacity, recovery and purity were assessed by densitometry. The DOE showed that binding capacity, recovery, and purity were optimized at high pH and low-NaCl concentration in the binding buffer (Figure 1).
Recovery (mg/mL adsorbent)
4
10
Optimization of MiMode PuraBead® HX2 load step The MiMode PuraBead HX2 load step was optimized using a design of experiments (DOE) screen to scout binding conditions for capture of the Vk fragment from an E. coliderived feedstock. The full factorial design assessed the impact of pH (7.5–9.0) and NaCl concentration (0–500 mM) on binding capacity, recovery, and purity. MiMode PuraBead® HX2 purification buffers are shown in Table 1.
0.5 M NaOH
Purity (%)
Figure 1: Impact of pH (7.5–9.0) and NaCl concentration (0–500 mM) on binding capacity, recovery, and purity of the Vk fragment.
40 50
60 70 80 90