Removal of cytokines from HAS-containing solutions by adsorption onto silica.

Septic shock syndrome is a potentially fatal medical condition that is associated with elevated blood levels of low molecular weight proteins known as cytokines. Adsorption was investigated as a potential method for removing cytokines from blood. Saline with 50 mg/mL human serum albumin (HAS) spiked with pathological concentrations (ng-pg/mL) of radiolabeled cytokine was used to study cytokine adsorption. Adsorption isotherms were linear in the pathological concentration range, with adsorption constants ranging from 33.0 mL/g to 173 mL/g for tumor necrosis factor (TNF-alpha), interleukin-8 (IL-8),interleukin-6 (IL-6), and C3a. Adsorption constants were also determined for interleukin-1alpha (IL-1alpha), IL-1beta, and interferon-gamma (IFN-gamma). The adsorption of cytokines by several different silica adsorbents was investigated. Increased concentrations of NaCl reduced cytokine adsorption, but did not completely eliminate adsorption even at high concentrations, suggesting that adsorption wads not entirely electrostatic in nature. Possible mechanisms of cytokine adsorption are discussed. Data for batch adsorption for TNF-alpha was used to estimate the minimum amount of silica required to treat septic shock. It was concluded that a silica adsorbent has a sufficiently high capacity to be used for hemoperfusion. Adsorption of myoglobin and cytochrome c was also investigated as possible marker proteins for future dynamic adsorption studies in hemoperfusion devices.

Plasma separator for encapsulating fluorescent probe in erythrocytes.

Using a plasma separator, it is possible to wash large volumes of whole blood free of plasma proteins in short periods. The novelty, however, is that the same apparatus can be used to reversibly hemolyze and reseal the red blood cells (RBCs) using hypotonic and hypertonic dialysates, respectively. This technique was assessed using the fluorescent exogenous agent uranin (fluorescein sodium). Results indicate that the encapsulation of the RBCs can be completed in under 2 h. The encapsulation efficiency of the RBCs was approximately 80% with a RBC recovery rate of 75%.

Efficient continuous flow washing of red blood cells for exogenous agent loading using a hollow fiber plasma separator.

Red blood cells (RBCs) are naturally occurring and biodegradable and are therefore ideal in vivo exogeneous agent (EA) carriers. Before being loaded with the EAs, the RBCs are washed, a process that normally involves repeated centrifugation with an iso-osmotic solution. Washing the RBCs can be achieved more efficiently and rapidly using a capillary hollow fiber plasma separator until the blood is 99.5% protein free. Here, a separator area of 0.25 m2 was preferentially selected over a 0.5 m2 device because the reduction in RBC washing time associated with the latter was considered insufficient to justify the use of the more costly (0.5 m2) separator. Mathematical modelling of this continuous flow system indicates that washing time is mainly dependent on the volume of blood to be processed and the filtration rate. Using the separator, 300 ml of blood can be washed in less than 15 min.

Laboratory-scale finned-rotor impeller for dialysis.

Dialysis of blood and other fluids may be accomplished using semi-permeable membranes. Most commonly used are the commercially available hollow-fibre dialysers, which have large priming volumes, an important consideration especially when laboratory techniques are being developed. With dialysis tubing (DT), however, priming volumes are readily controlled. To ensure adequate mass transfer, mixing of both dialysate and DT content is necessary. An impeller-based dialyser which consists of two open-boxed finned rotors facilitates both dialysate and DT content mixing. The operation of this device relies on the difference in hydrodynamic forces acting on opposite ends of the rotors, causing rotation in the vertical plane. This laboratory device was assessed via mass-transfer trials in which saline and washed-packed erythrocytes were dialysed against hypo- and hypertonic dialysate, allowing estimation of the DT's overall mass-transfer coefficient. Experimental correlation between the angular speeds of the impeller's rotation in the horizontal plane omega H and finned rotors' rotation in the vertical plane omega V were also established. Results indicate that the osmolality of the DT's content follows an exponential decay, and that omega V is strongly dependent on both omega H and the submergence depth of the impeller.