International standards for evaluating antibacterial, antiviral, and antibiofilm properties of surface-finished materials: a critical review

International standards such as ISO 22196, ISO 21702, and ISO 4768:2023 provide essential frameworks for evaluating the antibacterial, antiviral, and antibiofilm properties of plastics and other non-porous surfaces. Although these standards have greatly contributed to reproducible performance assessment, they remain primarily endpoint-based biological assays and do not fully integrate the physicochemical characteristics of engineered material surfaces. This critical review compares the scientific basis, experimental assumptions, and practical limitations of the three standards from a surface engineering perspective. Particular attention is given to the film-contact principle, crystal violet staining, metal ion dissolution, wettability, surface roughness, intermolecular forces, and extracellular polymeric substances (EPS). The discussion encompasses representative biofilm-forming organisms – including Pseudomonas aeruginosa and Staphylococcus aureus, fungal species such as Candida albicans and Rhodotorula mucilaginosa, and industrially relevant Bacillus and Micrococcus species – whose behaviour on engineered surfaces underpins the rationale for each standard. The review argues that antibacterial, antiviral, and antibiofilm evaluations should not be treated as isolated test categories, because all are governed by common surface – microorganism interactions. At the same time, important gaps remain, including the lack of standardised flow-based antibiofilm testing, insufficient treatment of mixed-species biofilms, and limited requirements for surface characterisation. Future standardisation should therefore move beyond pass/fail biological activity values and incorporate materials descriptors, real-time monitoring, and predictive approaches such as electrochemical impedance spectroscopy, image analysis, and digital twin modelling. Such integration will strengthen the scientific basis of anti-infective surface design and improve the reliability of performance claims for practical applications.