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6. CONCLUSIONI
Sulle base dei risultati ottenuti, è possibile concludere che:
1) Tutti i lisciviati dei polimeri sottoposti alle prove di efficacia antifouling (AF) e foul release (FR) hanno mostrato assenza di tossicità verso gli organismi modello nelle condizioni di prova.
2) E' stata osservata tossicità acuta verso V. fischeri (inibizione della bioluminescenza) nei prodotti di lisciviazione del polimero S95P9.5; tuttavia il film polimerico, durante il processo di lisciviazione, è andato in incontro a delaminazione distaccandosi dal substrato di vetro, rendendo impossibili le successive prove di efficacia AF e FR. Tale aspetto potrebbe indicare che, sebbene nei blends polimerici siano assenti catalizzatori metallici favorenti la reticolazione dell'elastomero siliconico (la reticolazione è infatti indotta attraverso fotopolimerizzazione mediante un fotoiniziatore), una non corretta polimerizzazione possa consentire il rilascio di sostanze con effetti tossici sugli organismi.
3) Le prove di adesione con N. salinicola indicano che il solo polimero S95P3 (potenzialmente il più anfifilico) ha prestazioni AF sovrapponibili alla matrice silossanica di riferimento (S100), anche dopo applicazione di flusso turbolento
4) Il saggio di adesione e distacco con F. enigmatus rappresenta una novità; recentemente è reperibile in letteratura un solo lavoro (Gabilondo et al., 2013) condotto sulla medesima specie in cui è stato studiato il ciclo biologico, la produzione dei gameti, la fecondazione e la produzione di larve competenti pronte all'adesione; è stata inoltre studiata l'adesione solo su vetro ed una matrice
85
silossanica. Tuttavia, rispetto agli autori, differente è l'approccio utilizzato: mentre gli autori hanno "forzato" l'adesione applicando le larve competenti direttamente sulle superfici, in questo studio grandi quantità di larve natanti sono state lasciate "libere" di scegliere le superfici su cui aderire. Il saggio di distacco dalle superfici, effettuato per la prima volta in questo lavoro,interessa vermi di 18 giorni con tubo calcificato ben formato.
5) I risultati ottenuti sulle performance AF e FR dei polimeri con F. enigmaticus appaiono di più chiara interpretazione rispetto a quelli ottenuti con N. salinicola: il numero di tubi formati e adesi ai polimeri è all'incirca lo stesso in tutte le formulazioni analizzate, indicando assenza di selettività nel settlement e adesione su superfici di differente composizione chimica. A seguito di applicazione di flusso turbolento, diverse intensità di flusso evidenziano differenze significative nella % di distacco limitatamente ad alcuni polimeri. Considerando il massimo flusso applicato, i polimeri S95P3 ed S95P3F5/5 mostrano la migliore efficienza foul release; l'analisi di regressione lineare indica una possibile tendenza al miglioramento della prestazioni FR legata all'aumentare delle percentuali di PEG introdotte nei polimeri.
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