Microfluidic-driven short peptides hydrogels with optical waveguiding property

Soft photonic elements with optical waveguiding ability based on biocompatible hydrogels have become increasingly important in optical techniques for medical diagnosis and phototherapy, among others. Supramolecular hydrogels based on peptides with interesting optical properties are rarely reported and explored. Although robust crystals based on short peptides have shown optical waveguiding capabilities, their rigidity is the main issue to overcome in the quest for soft biocompatible materials. Here, we report on a microfluidic-assisted formation of a heterochiral short peptide hydrogel that exhibit active optical waveguiding property thanks to the incorporation of two different dyes, Thioflavin T and Rhodamine B, in the hydrogel structure. Using our microfluidic platform, different parameters such as concentration of peptide, type of dye and its concentration, and flow rate have been rapidly explored, with remarkable low reagents consumption. In this way, it was possible to develop peptide hydrogel waveguides with good optical loss values, modulating the emission in diverse spectral regions. The use of microfluidics to prepare these hydrogels makes possible the preparation of structures of high length-to-diameter aspect ratio, which otherwise are hard to devise from bulk conditions. Overall, this work broadens the use of supramolecular self-assembly of peptides to create functional materials with additional versatility to polymeric hydrogels, thanks to the possibility of tuning structure by changing amino acids sequence. Additionally, the optical properties can be easily modulated by quick optimization of experimental parameters via microfluidic technology.