Fibroin nanofibrils and gold nanoparticles composite for wearable microneedle sensors of levodopa

Silk fibroin (SF), a key component of the hierarchical structure of silkworm cocoons, can be mechanically processed into fibroin nanofibrils (FNF). This underexplored route enables fast, sustainable and scalable approach for FNF production without relying on organic solvents or costly chemicals. In this study, we employed FNF, obtained by mechanical fragmentation, combined with gold nanoparticles (AuNPs), to obtain FNF@AuNP nanohybrids, which were integrated into wearable microneedle patches for colorimetric monitoring levodopa, an essential drug for managing Parkinson's disease (PD). The approach demonstrates the potential of biobased films embedded in 3D-printed devices to serve as point-of-care wearable sensors, offering user-operated, real-time assessment of chronic conditions. Specifically, when integrated with 3D-printed microneedle (MN) platforms, the FNF@AuNP casting films acted as a colorimetric indicator of high levels of levodopa in interstitial fluid (ISF). The color changes were more evident when auxiliary paper discs were used in the analysis, combined with the FNF@AuNP films. The colorimetric study was associated with image processing, and the data analysis was performed using Interactive Document Map (IDMAP) for information visualization. In simulated interstitial fluid, the colorimetric method successfully indicated the presence of levodopa in ISF, when its concentrations were above 50 μM, with the required selectivity. Given that both sub-therapeutic and excessive levodopa doses can exacerbate motor symptoms, the proposed FNF@AuNP-based wearable sensor represents a promising strategy for supporting dose management in PD therapy, enabling first-line, personalized feedback for patients.