RESOURCES

Abstract
Drug-induced liver injury (DILI) remains a major cause of acute liver failure, clinical trial attrition, and post-marketing drug withdrawal, yet predictive in vitro models are limited in accuracy, scalability, and human relevance. Here, we present a Liver-on-Micropillar (LoM) platform a fully animal-free, high-throughput, miniaturized human liver model designed for early-stage hepatotoxicity screening. The system combines a xeno-free medium with a xeno-free bioink to support co-culture of four human liver-relevant cell types: differentiated HepaRG, LX-2, HMEC-1, and differentiated THP-1 cells. Microlivers are bioprinted onto micropillar arrays compatible with standard 96-well plate formats. Functional characterization confirmed stable cell viability, albumin and urea production, as well as inducible CYP expression. To evaluate DILI predictivity, ten reference drugs were tested using assays to measure ATP content, XTT metabolic activity, and albumin secretion. Half-maximal inhibitory concentrations (IC50) were experimentally determined, and margins of safety (MOS) were calculated by dividing IC50 by clinical maximum plasma concentration (Cmax). The LoM platform correctly classified 90% of the tested compounds using a MOS threshold of 100. This scalable and reproducible model provides a human-relevant, regulatory-aligned alternative to animal testing and supports broader efforts to implement non-animal methodologies in drug safety evaluation.

Abstract
Abstract 3D bioprinting enables the fabrication of human organ models that can be used for various fields of biomedical research, including oncology and infection biology. An important challenge, however, remains the generation of vascularized, perfusable 3D models that closely simulate natural physiology. Here, a novel direct ink writing (DIW) approach is described that can produce vascularized organ models without using sacrificial materials during fabrication. The high resolution of the method allows the one-step generation of various sophisticated hollow geometries. This sacrificial-free DIW (SF-DIW) approach is used to fabricate hepatic metastasis models of various cancer types and different formats for investigating the cytostatic activity of anti-cancer drugs. To this end, the models are incorporated into a newly developed perfusion system with integrated micropumps and an agar casting step that improves the physiological features of the bioprinted tissues. It is shown that the hepatic environment of the tumor models is capable of activating a prodrug, which inhibits breast cancer growth. This versatile SF-DIW approach is able to fabricate complicated perfusable constructs or microfluidic chips in a straightforward and cost-efficient manner. It can also be easily adapted to other cell types for generating vascularized organ tissues or cancer models that may support the development of new therapeutics.