During this reporting period, corresponding to months 13–16 of the project, the research team completed the activities of WP3 and opened the first activities of WP4. The work focused on refining the synthesis of the bioactive glass particles, confirming their structural and morphological properties, testing their antimicrobial behaviour, and identifying the best formulations for incorporation into electrospun materials. The reporting documents state that the synthesis of the bioactive glasses was further optimised and assessed through several characterisation techniques, including SEM, EDS, TEM and XRD.
This phase was particularly important because GAiA’s filter concept depends on the successful combination of two elements: a sustainable electrospun fibre matrix and antimicrobial particles capable of acting against microorganisms captured by the filter. The project had already validated the green polymer platform in the previous work packages. The fourth phase therefore addressed the next crucial question: which bioactive glasses are the best candidates to provide the antimicrobial function inside the future filtering material?
To answer this question, the team evaluated the antimicrobial properties of functionalised bioactive glasses against both Gram-negative and Gram-positive bacterial strains. The technical report describes tests carried out on Escherichia coli, used as a Gram-negative model, and Staphylococcus aureus, used as a Gram-positive model. The materials were sterilised, extracted in culture medium and tested by measuring bacterial growth inhibition through colony-forming units. This approach allowed the researchers to compare the different Roma formulations and understand how the glass composition influenced antimicrobial performance.
The results showed that antimicrobial activity varied significantly depending on the bioactive glass formulation and on the bacterial species tested. Against E. coli, Roma 02 and Roma 05 showed the highest antibacterial activity, with an almost complete inhibition of bacterial growth. Roma 01 and Roma 03 showed intermediate activity, while Roma 04 and Roma 06 were less effective. Against S. aureus, Roma 02 again showed the strongest performance, while Roma 01, Roma 05 and Roma 06 produced moderate antimicrobial effects. These results indicated that Roma 02 was the most promising formulation across both bacterial models, while Roma 05 was also highly relevant for the Gram-negative response.
This evidence supported the completion of two central WP3 deliverables: D3.3, dedicated to the evaluation of the antimicrobial properties of the functionalised bioactive glasses, and D3.4, dedicated to the final selection of the best functionalised bioglasses for the production of loaded FFP materials. In practical terms, this meant that GAiA had completed the selection of the active antimicrobial component to be transferred into the fibre system.
At the same time, the project began the first WP4 activities, moving from particle selection to fibre loading. The fourth reporting document states that the first electrospun fibres with antimicrobial charge were produced during this period. This was the first step toward the composite material at the heart of GAiA: nonwoven electrospun fibres containing selected antimicrobial bioactive glasses.
The start of WP4 also required close coordination between the two research units involved in the project: the University Campus Bio-Medico of Rome and the University of Modena and Reggio Emilia. During this phase, the partners aligned on project progress, laboratory activities, integration between the two units, and the timing for producing prototypes and samples needed for the next stages. The same report confirms that all expected WP3 activities up to month 16 were completed, while WP4 activities included the production of electrospun fibres loaded with selected BGs, the rheology of the antimicrobial BG-loaded solution, and the morphological and mechanical characterisation of the loaded fibres.
This transition from powder to fibre was not only a technical step, but also a conceptual milestone. Until this point, the antimicrobial function had been demonstrated mainly at the level of the bioactive glass particles. From this phase onward, GAiA began testing whether those particles could be successfully integrated into a fibrous filter material without losing their functional role. This was essential because the final objective is not the production of antimicrobial powders, but the development of safer and greener filtering materials for FFP devices.
The fourth reporting period also confirmed the project’s environmental direction. GAiA continued to frame its material development around sustainable electrospinning, green chemistry and the possibility of compostability at end of use. The report highlights that, also during the development of the bioactive glasses, attention was directed toward synthesis techniques and process choices aligned as much as possible with the sustainability of the final product.
As often happens when a project moves from material discovery to material integration, this stage also required process adjustments. The report notes some delays related to the electrospinning of nonwoven fabrics with antimicrobial charge, but also states that no substantial variation from the approved project plan was recorded. The corrective measures adopted were expected to prevent deviations from the original schedule and from the expected results.
By the end of this phase, GAiA had completed a decisive bridge between WP3 and WP4. The project had identified the most promising antimicrobial bioactive glass formulations, validated their activity against both Gram-negative and Gram-positive bacteria, and started incorporating selected particles into electrospun fibres. This step opened the way to the next phase of the project: transforming loaded fibres into stable, reproducible nonwoven mats suitable for future filter prototypes.
In the evolution of GAiA, this news marks the moment when the active antimicrobial core of the project began to become an actual fibre-based material.
