Cardoon Stalk Fibre as a Sustainable Lignocellulosic Resource: Assessment of Cytotoxicity and Fungal Colonisation

The textile industry's increasing environmental impact has intensified interest in alternative fibres derived from underutilised and renewable biomass. Among these, the characteristics of lignocellulosic residues from agro-industrial processes for textile-related applications remain insufficiently understood. This study investigates the potential of cardoon ( Cynara cardunculus L.) stalk fibre as a bio-based material through the assessment of its physicochemical and biological properties. Cotton was included as a reference fibre to provide a general benchmark for comparison. Morphological and chemical analyses were performed using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR), while in vitro cytotoxicity (ISO 10993-5) and fungal colonisation assays with Aspergillus niger (ISO 13629-2 and biofilm models) were used to assess biological behaviour. Cardoon fibre exhibited similar susceptibility to fungal colonisation as cotton and showed no cytotoxicity. However, significant structural differences were observed: cardoon fibre displayed a coarser morphology and lignocellulosic composition, including lignin, which influenced its mechanical properties and degradation behaviour. This work provides the first integrated assessment of the physicochemical and biological characteristics of commercially processed cardoon stalk fibre, offering new insights into its behaviour as a lignocellulosic material. Rather than functioning as a direct substitute for cotton, cardoon fibre is better positioned as a complementary bio-based resource. The findings support its potential relevance within circular bioeconomy strategies, while highlighting the need for further optimisation of fibre processing and application-specific performance.