Electronic textiles (e-textiles), also known as smart textiles, explore the intersection of electronics and textile fabrication, enabling sensing, actuation, and communication within textile forms. While recent e-textile research has investigated diverse fabrication methods and novel materials, it has largely emphasized electronic sensing and actuation, with limited consideration of biological systems as integral components. In parallel, Biological Human–Computer Interaction (Bio-HCI) examines the relationships among humans, computational systems, and living or biologically derived materials, including the use of biological matter as interactive media and the development of intermediary platforms between users and biological processes. This dissertation integrates Bio-HCI with e-textiles through functional, material, and process investigations. It explores biofluid sensing for wearable interaction and energy harvesting, biodegradable and bio-based materials for sustainable textile fabrication, and bio-participatory fabrication methods that incorporate growth into making. Across these contributions, the work introduces a design space that frames biological matters and fabrication processes as interdependent dimensions of interaction. Through technical development, wearability studies, and community-based workshops, this dissertation demonstrates accessible fabrication approaches for bio-integrated textiles while examining their experiential and social implications. By situating textiles as ecologically entangled systems, the work expands the functional scope of wearable technology and proposes new directions for sustainable and more-than-human interaction design.