A Paper‐Based Human Kidney Proximal Tubule‐on‐a‐Chip for Efficacy of SGLT2 Inhibitors and Methotrexate‐Induced Nephrotoxicity Assessment

The human kidney proximal tubule is responsible for glucose reabsorption and serves as a primary target for exogenous toxins. While conventional in vitro cell-based models offer cost-effective alternatives to animal testing, they often fail to replicate the structural and functional complexity of the native proximal tubule. Here, we developed a paper-based human kidney proximal tubule-on-a-chip that mimicked key physiological functions, bridging between traditional cell cultures and animal models. Utilizing porous paper, the chip recreated an in vivo-like three-dimensional microenvironment that supported proximal tubule-specific functions and reproduced essential physiological processes including dynamic glycogen metabolism, glucose reabsorption, and drug transport. The model enabled precise pharmacodynamics evaluation of sodium-glucose co-transporter 2 (SGLT2) inhibitors, yielding median effect concentrations of 0.954 ng/mL for dapagliflozin and 2.685 ng/mL for canagliflozin. The platform maintained consistently high glucose reabsorption inhibition rates (94.59%-95.03%) under different conditions following SGLT2 inhibitors treatment. Furthermore, the methotrexate (MTX)-induced nephrotoxicity evaluation was performed by MTT assay, LDH assay, and glucose reabsorption measurements. The chip accurately reproduced MTX transport dynamics, demonstrating its potential for pharmacokinetic studies. Thus, the paper-based model serves as a reliable platform for pharmacokinetic and nephrotoxicity assessments, offering a valuable tool to replace animal testing and support Reduce, Refine, and Replace experimentation.