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.