In BioSMaLL, novel water-soluble polypeptides (polymers of amino acids) were developed and optimised using pragmatic chemistries to form hydrogels with the ability to change their physical state through light-based crosslinking (photocrosslinking) for different 3D printing methods. Two distinct light reactive polypeptide systems were prepared via synthetic strategies which used pre (system 1) and post polymerisation modification (system 2). System 1 polypeptides were synthesised from novel monomers with light reactive vinyl bonds, to create 3D printable photocrosslinkable water-based formulations. The polypeptides could successfully undergo a rapid transformation from liquid to solid following exposure to a cell-friendly wavelength of light (405 nm). These polymers were suitable for DLP, stereolithography (SLA) and direct laser writing (DLW) 3D printing techniques, forming 3D structures with tailored mechanical properties and high-resolution features on µm scales. System 2 polypeptides were designed to have high solid-like viscosities, along with reactive vinyl bonds, where peptide secondary structure allowed for assembly into soft hydrogels. The materials were used in direct ink writing (DIW) based 3D bioprinting with embedded genetically engineered bacteria (E. coli), where they could be extruded and photocrosslinked (at 405 nm) into ‘‘living’’ 3D shapes. These 3D printed biocomposites demonstrated high viability with E.coli growth dependent on the mechanical properties of polypeptides over time scales which were indicated by green fluorescent protein (GFP) induction. Further advances on these polypeptides have been made in mammalian cell bioprinting, with 2D cell studies showing good viability with embedded fibroblast cells and human mesenchymal stem cells. Initial studies demonstrated good bioprintability, and final studies are underway to assess their functionality as cartilage scaffolds. The results of BioSMaLL have been dissemination in a number of forms including journal publications and conference presentations. Specifically, 3 research manuscripts have been peer reviewed and published, and 3 others are currently in late stages of manuscript drafting. The progress of the BioSMaLL project has also been disseminated at 3 different conferences via oral presentations; in 2022 at American Chemical Society Spring (ACS, San Diego, USA) and Bordeaux Polymer Conference (BPC, Bordeaux, France), and in 2023 at the Society of Polymer Science Japan International Polymer Conference (SPSJ IPC, Sapporo, Japan).
