Neutral red

A PSF ultrafiltration support membrane with a MWCO around 20 000 g mol⁻¹ was purchased from Hunan Keensen, China. Monomers including TMC (>99.0%) and PIP (>99.5%) for interfacial polymerization were purchased from J&K Products Catalog. Methyl blue, semixylenol orange, safranine T and neutral red, used as the dye molecules to evaluate the separation performance of the membranes, were purchased from MACKLIN. Analytical standard bovine serum albumin (BSA) was purchased from Shanghai Aladdin Reagent Company and used as a model foulant. All other chemicals were analytical reagents and used directly without further purification.

As described in section 2.1, we assembled two UR3 robot-based bioprinters on the diagonal margins of a stable working table, and simultaneously controlled the motion of both robots through Arduino board with in-house developed C++ scripts. The two robots were individually loaded with different bioinks: one was loaded with hCMEC/d3 cells (5 × 10⁶ cells/ml in RPMI-1640 + 10% FBS + 1% Matrigel) stained by 1% Fast Green (Sigma #F7252), the other was loaded with H9-differentiated cardiomyocytes (5 × 10⁶ cells/ml in RPMI-1640 + 10% FBS + 1% Matrigel) stained by 1% Neutral Red (Macklin #N814728). We programmed the two robots to collaboratively print cells onto a complex-shaped coronary scaffold submerged under oil bath. The moving speed of both robots was set as 1 mm/s.