Ultrashort Peptide Bioinks Support Automated Printing of Large-Scale Constructs Assuring Long-Term Survival of Printed Tissue Constructs

Abstract

We report about rationally designed ultrashort peptide bioinks, overcoming severe limitations in current bioprinting procedures. Bioprinting is increasingly relevant in tissue engineering, regenerative and personalized medicine due to its ability to fabricate complex tissue scaffolds through an automated deposition process. Printing stable large-scale constructs with high shape fidelity and enabling long-term cell survival are major challenges that most existing bioinks are unable to solve. Additionally, they require chemical or UV-cross-linking for the structure-solidifying process which compromises the encapsulated cells, resulting in restricted structure complexity and low cell viability. Using ultrashort peptide bioinks as ideal bodylike but synthetic material, we demonstrate an instant solidifying cellembedding printing process via a sophisticated extrusion procedure under true physiological conditions and at cost-effective low bioink concentrations. Our printed large-scale cell constructs and the chondrogenic differentiation of printed mesenchymal stem cells point to the strong potential of the peptide bioinks for automated complex tissue fabrication.

Enhancing Peptide Biomaterials for Biofabrication

“…However, in the translation of synthetic peptide materials to bioinks, these key predictors are often under-reported and seemingly inconsistent. In reported studies of SAP bioinks, measures of printability such as viscosity [ 80 , 81 , 82 , 104 ], loss tangent [ 80 , 81 , 102 ], shear-thinning [ 81 , 82 , 103 ], achievable height [ 81 , 82 , 99 , 103 ] and filament assessments [ 81 , 82 , 103 ], were briefly discussed. This demonstrates the adoption of printability measures into the SAP bioink field; however, the lack of standard printability outcomes and the inconsistency in relationships of printability and predictors such as viscosity [ 81 , 82 ] limit the understanding of key material properties for future development.…”

“…This has required the development of novel fabrication setups to enhance gelation. Bioprinting techniques amenable to SAP bioinks include droplet printing [ 98 , 99 , 100 , 101 ], or the generation of droplets which are then extruded [ 100 , 101 ], extrusion printing [ 80 , 81 , 102 , 103 , 104 ], and the customisation of extrusion printing setups, such as coaxial nozzles to mix salt solutions [ 80 , 81 ], printing onto salt-covered substrates [ 82 ], or removing excess fluid with a vacuum print-bed [ 105 ]. This demonstrates that the unique properties of SAP materials can be exploited for bioprinting.…”

“…Progress into biomaterial molecular modelling and design principles may improve the clinical translation of materials by predicting outcomes without significant labour-intensive bench time. Molecular modelling [ 80 , 81 , 82 , 83 , 84 ], design principles [ 85 , 86 , 87 , 88 , 89 , 90 , 91 ] and predictive gelation models [ 90 ] of synthetic peptide materials are being increasingly reported, indicating a future ramp-up of high-throughput peptide biomaterial discovery. Synthetic self-assembling peptide (SAP) hydrogels are peptide sequences that self-assemble via supramolecular interactions to spontaneously immobilise fluid, creating a highly hydrated scaffold [ 92 ].…”

“…Synthetic peptide materials give rise to complex biomimetic structures with bioactivity, resulting in controlled cell-scaffold interactions [ 96 , 97 ]. Furthermore, recent reports have demonstrated the translation of synthetic SAP biomaterials into bioinks [ 80 , 81 , 82 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 ]. This demonstrates the potential of synthetic SAP design for biofabrication of organs and tissues, and ultimately clinical translation ( Figure 1 ).…”

Time-dependent pulsing of microfluidic pumps to enhance 3D bioprinting of peptide bioinks

“…Bioinks based on ultrashort peptides composed of 3-7 natural amino acids boast great potential due to their natural but synthetic properties and their salt-enhanced instantaneous gelation [6][7][8][9][10] . Unlike polymers or gelatin and alginate-based bioinks, these peptide bioinks eliminate harmful processes of UV light and chemical exposures for post-printed crosslinking of the bioinks.…”