Organ-Specific Strategies in Bioprinting: Addressing Translational Challenges in the Heart, Liver, Kidney, and Pancreas.

Organ bioprinting is a rapidly evolving field designed to address the persistent shortage of donor organs by engineering patient-specific tissues that replicate the function and structure of natural organs. Despite significant technological advancements, bioprinting still faces major obstacles, including tissue rejection, inadequate vascularization, limited physiological functionality, and various ethical and translational challenges. In this review, we assess current bioprinting modalities, particularly extrusion-based printing, inkjet printing, laser-assisted bioprinting (LAB), and stereolithography/digital light processing (SLA/DLP), highlighting their individual strengths and limitations. We also explore different bioink formulations, focusing especially on hybrid bioinks as promising solutions to traditional bioink constraints. Additionally, this article thoroughly evaluates bioprinting strategies for four major organs: heart, liver, kidney, and pancreas. Each organ presents unique anatomical and physiological complexities, from cardiomyocyte immaturity and electromechanical mismatch in cardiac tissues to vascularization and zonation challenges in liver structures, intricate nephron patterning in kidney constructs, and immune rejection issues in pancreatic islet transplantation. Regulatory and ethical considerations critical for clinical translation are also addressed. By systematically analyzing these aspects, this review clarifies current gaps, emerging solutions, and future directions, providing a comprehensive perspective on advancing organ bioprinting toward clinical application.