Photoacoustic Spectroscopy as a Method for Detecting Phycocyanin in Complex Biopolymeric Matrices

Phycocyanin (PC), a bioactive phycobiliprotein from Arthrospira maxima, exhibits strong antioxidant and therapeutic potential; however, its spectroscopic characterization becomes challenging when PC is incorporated into complex biopolymeric matrices due to matrix-induced signal interference. In this study, photoacoustic spectroscopy (PAS) was evaluated as an alternative, matrix-tolerant technique for detecting PC encapsulated within polysaccharide-based polymeric matrices, including alginate, agavins, κ-carrageenan, and carboxymethyl cellulose. PC-loaded matrices were characterized by using PAS, UV-vis spectrophotometry, FTIR spectroscopy, and optical microscopy to assess optical absorption, structural features, and potential matrix-analyte interactions. PAS successfully reproduced the characteristic PC absorption band near 620 nm across all matrices and PC concentrations, even in optically dense or highly scattering samples, where UV-Vis transmission measurements are unreliable. FTIR spectra enabled differentiation among polymer matrices and revealed formulation-dependent variations attributable to physicochemical interactions with PC. Morphometric analysis showed substantial differences in encapsulate size and surface characteristics among formulations, although these differences did not affect PAS detection. Overall, the results demonstrate that PAS is a reliable, nondestructive method for identifying PC regardless of matrix composition, morphology, or optical heterogeneity, highlighting its potential as an analytical tool for nutraceutical characterization in biopolymeric delivery systems.