1 Department of Surgery, Division of Ophthalmology, University of Sherbrooke, Sherbrooke, QC, Canada.
2 Department of Pathology & Laboratory Medicine, The University of British Columbia, Vancouver, BC, Canada.
3 Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada.
4 Department of Mechanical, Industrial, and Aerospace Engineering, Concordia University, Montreal, QC, Canada.
5 Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, QC, Canada. Electronic address: simon.tran@mcgill.ca.

Wearable biosensors are revolutionizing the landscape of modern healthcare by enabling continuous, non-invasive monitoring and real-time diagnostics across a myriad of medical applications. This chapter provides a comprehensive overview of wearable biosensors, beginning with an exploration of their fundamental components, including biological elements, transducers, and electronic interfaces. It categorizes these devices based on the types of biological matrices they utilize, such as tears and saliva, and the nanomaterials and transduction mechanisms that underpin their functionality. Highlighting state-of-the-art advancements, the chapter delves into specific applications in ophthalmology and oral health, showcasing innovative tear-based sensors for monitoring intraocular pressure and glucose levels, as well as saliva-based devices for detecting oral diseases and systemic biomarkers. Through detailed examples, such as multifunctional contact lenses and smart mouthguards, the chapter illustrates the potential of these technologies to transform disease detection, health monitoring, and personalized treatment strategies. Additionally, it addresses the current challenges in wearable biosensor development, including issues of sensor accuracy, durability, and user comfort, while outlining future directions for research and integration into everyday healthcare practices. This chapter aims to provide readers with a thorough understanding of wearable biosensors' current state, innovations, and future potential in enhancing health and wellness monitoring.