A Spirulina-derived pigment extract combining phycocyanin and chlorophyll for optically responsive photopolymer architectures

The optical response of a Spirulina-derived extract (SP-E), containing phycocyanin and chlorophyll-derived pigments, was investigated in liquid and solid-state environments, deliberately exploiting extract complexity rather than pigment purification to develop a sustainable optical platform. In aqueous media, SP-E displayed the characteristic signatures of phycocyanin, whereas exposure to organic solvents, basic conditions, or oxidative agents induced pronounced blue-to-green/yellow transitions driven by attenuation of the phycocyanin contribution and enhanced visibility of chlorophyll-derived species. When incorporated into PEGDA700 photopolymers, SP-E retained chemically responsive colorimetric behavior toward both liquid and vapor/headspace chemical environments. For aqueous ammonia, a quantitative proof-of-concept response was obtained using a ratiometric signal, yielding a limit of detection of 0.41% v/v NH3, and an apparent response time of approximately 10 min. The optical response was strongly influenced by photopolymerization conditions, as high photoinitiator/SP-E ratios promoted attenuation of the phycocyanin-related signature; this behavior was supported by independent oxidation and photoinitiator-assisted irradiation experiments. Integration of SP-E into digital light processing formulations enabled fabrication of optically active 3D architectures with luminescence-based chemical indication, while the intrinsic light-attenuating properties of the multi-pigment extract contributed to printing control. Altogether, SP-E emerges as a multifunctional, sustainable additive that combines environmental optical responsiveness with photopolymer processability and compatibility with additive manufacturing, offering a resource-efficient route toward bio-derived optical indicators and functional printed materials.