Briefly, the circuit consisted of a custom-designed reservoir, two mechanical roller pumps (Baoding Shenchen peristaltic pump company, China) and a 30-ml dialyzer for hemodialysis (AEF-03), which were all connected via homemade tubing (TianJing Hanaco medical company, China).

To test the clearance, Cy5-labeled aptamers (TBA15 or HD22, 1 µM) or Aptarrays (origami ~28 nM, containing 1 µM TBA15 and 1 µM HD22) were injected through an infusion port into PBS solutions that filled in the circuit. After 1 h period of continuous dialysis circulations, solutions were collected via the infusion port at indicated time points (0, 1, 2, 5, 10, 20, 30, 60 min). The samples were analyzed for fluorescence intensity at 650 nm on a fluorescence spectrophotometer (Agilent Technologies).

Blood was pumped via a roller pump to dialyzer through the closed extracorporeal circuit; while dialysate (TRHD company, TR-2, Liquid A: Na+ 138 mM, K+ 2.0 mM, Ca2+ 1.5 mM, Mg2+ 0.5 mM, Cl 109.5 mM, HCO3 32 mM, CH3OO 3.0 mM; Liquid B: Na+ 35 mM, HCO3 35 mM) flowed through the device and disposed. To provide temperature control, a constant temperature water bath was used to contain the dialyzer, and a thermostatic magnetic stirrer was used to hold a flask that contained the dialysate solution. The temperature of the circulating blood was maintained at ~30 °C. Blood flow rate was 10 ml/min, while dialysate flow rate was 50 ml/min. Prior to the addition of blood and dialysate, the circuit was primed with PBS and circulated continuously at a flow rate of 10 ml/min for ~30 min.

Fifty milliliters of whole blood was collected from individual healthy donors and anticoagulated with 3.2% sodium citrate. After draining the PBS from the circuit, equivalent volume buffer, the mixture of aptamers and origami (Ori + H + T) or Aptarray-treated blood was added. CaCl2 (1 M, 322.5 µl) was injected into the circuit through the infusion port and mixed with the blood for 5 min to neutralize sodium citrate. The circulation was initiated (time = 0 min) at a flow rate of 10 ml/min with dialysate flowed through the filter device in an opposite direction at 50 ml/min. Blood samples (~2 ml) were withdrawn from the circuit at 1, 5, 10, 20 min after circulation was initiated for APTT measurement. After 60 min of circulation, circuit blood was removed and the dialyzer was then rinsed with PBS and fixed overnight with 2.5% glutaraldehyde.

Prefixed dialyzer was mechanical crashing and the hollow filters were separated. These fibers were cut into pieces and dehydrated by gradient ethanol (10%, 30%, 60%, 90%, 100%). The fibers were subsequently submerged in liquid nitrogen for 5 min, and then were affixed to circular metal stubs. The samples were obtained Pt-sputtering in an ion sputter coater for 20 s. The micrographs were obtained with scanning electron microscope (SEM, Hitachi SU8200, Japan). The data were collected and processed using Hitachi SU8200 ver.1.18.

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