Cell-free systems for low-cost diagnostics

Cell-free systems have also become a revolutionary platform for low-cost diagnostics, providing fast, flexible, and scalable solutions to the conventional cell-based assays. Such systems, which utilize the fundamental biochemical machinery of cells without the intricacies of living organisms, have been of great use in point-of-care (POC) diagnostics, particularly in resource-poor environments. This chapter offers a broad overview of the basic principles, design approaches, and technological breakthroughs behind cell-free diagnostic development. It discusses the biochemical underpinnings of cell-free expression, such as ribosomal function, transcriptional control, and energy regeneration, with emphases on the leading platforms including E. coli lysates, wheat germ extracts, and PURE systems. The application of synthetic biology in the form of gene circuits, CRISPR-Cas tools, and RNA aptamers is presented here in the framework of improving the sensitivity and specificity of diagnostics. The chapter further discusses recent innovations in paper-based assays, microfluidic biosensors, and wearable biosensors, which are capable of offering real-time and field-deployable diagnostics. Major challenges in the form of reagent stability, scalability, and regulatory implications are analyzed carefully along with recent trends such as AI-based system design and personalization of diagnostics. In extensive case studies, the chapter highlights the promise of cell-free systems in filling diagnostic gaps, enhancing access to healthcare, and revolutionizing global health. This book strives to offer an encyclopedic sourcebook for researchers, clinicians, and innovators interested in bringing cell-free diagnostics forward.