Biofunctional materials: fundamentals and classification

The term biomaterial is widely used to describe materials associated with biological systems, but often fails to distinguish whether a material merely exists within a biological environment or actively participates in regulating biological processes. This ambiguity has created a subtle conceptual gap, making it difficult to distinguish passive materials from those deliberately engineered to trigger biological responses. This Editorial addresses this gap by introducing a foundational framework for defining and classifying biofunctional materials. Accordingly, biofunctional materials are defined as deliberately engineered material systems designed to engage biological environments and produce measurable and reproducible biological outcomes. To conceptualize this concept, biofunctionality is defined and described as a multidimensional continuum governed by four foundational pillars including structural, physicochemical, biological signaling, and adaptive functionality. Together, these pillars form a conceptual biofunctionality landscape, enabling materials to be interpreted according to the maturity of their functional mechanisms and the degree of integration across domains. By clarifying the distinction between passive biomaterials and actively biofunctional systems, this framework aims to provide a milestone, thereby to support clearer terminology, more rigorous evaluation, and more rational design of materials that decisively interact with living systems.