Understanding myoglobin adsorption kinetics: an ex vivo model

Myoglobin is a middle-molecule protein released into the bloodstream during rhabdomyolysis, where it contributes to acute kidney injury (AKI) through hemodynamic, oxidative, and obstructive mechanisms. High cut-off membranes may enhance myoglobin clearance but carry a risk of clinically relevant albumin and other protein losses. Hemoadsorption may overcome these limitations. This study aimed to assess the adsorption capacity of a neutral microporous styrene-divinylbenzene copolymer sorbent for myoglobin.

We performed two ex vivo hemoadsorption experiments using mini modules of the HA380 cartridge. Dialysis effluent from a patient with severe rhabdomyolysis was concentrated to 1 L and circulated in a closed loop at 200 mL/min for 240 minutes. Experiments differed in sorbent mass (32 g vs 10.6 g). Myoglobin concentrations were measured at predefined time points using ELISA. Removal ratio (RR) and adsorbed mass were calculated to estimate adsorption kinetics and resin capacity.

In the first experiment (32 g sorbent), myoglobin decreased from 66,356 to 8,553 µg/L (RR 87%), with 57.8 mg adsorbed (1.8 mg/g). In the second experiment (10.6 g sorbent), concentration decreased from 76,455 to 7,043 µg/L (RR 91%), with 69.6 mg adsorbed (6.56 mg/g). In both experiments, >50% of total myoglobin was removed within the first 60 minutes, while adsorption plateaued during the last 3 hours, suggesting near saturation without complete exhaustion of binding sites.

This is the first study to evaluate the myoglobin adsorption capacity of a polystyrene-divinylbenzene sorbent, demonstrating a high affinity for myoglobin with near-complete removal in an ex vivo model. Although saturation was not fully reached, the maximal capacity of the resin is likely higher than measured. These findings provide quantitative insight into myoglobin adsorption kinetics and support further in vitro and clinical studies to optimize timing and duration of hemoadsorption in severe rhabdomyolysis.