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.

Three-dimensional (3D) porous metal and metal oxide nanostructures have received considerable interest because organization of inorganic materials into 3D nanomaterials holds extraordinary properties such as low density, high porosity, and high surface area. Supramolecular self-assembled peptide nanostructures were exploited as an organic template for catalytic 3D Pt-TiO2 nano-network fabrication. A 3D peptide nanofiber aerogel was conformally coated with TiO2 by atomic layer deposition (ALD) with angstrom-level thickness precision. The 3D peptide-TiO2 nano-network was further decorated with highly monodisperse Pt nanoparticles by using ozone-assisted ALD. The 3D TiO2 nano-network decorated with Pt nanoparticles shows superior catalytic activity in hydrolysis of ammonia-borane, generating three equivalents of H2 .

Tetrameric peptide-based bioinks allow the printing of 3D cell-laden scaffolds under true physiological conditions avoiding harsh UV or chemical treatment.

The apparent rise of bone disorders demands advanced treatment protocols involving tissue engineering. Here, we describe self-assembling tetrapeptide scaffolds for the growth and osteogenic differentiation of human mesenchymal stem cells (hMSCs). The rationally designed peptides are synthetic amphiphilic self-assembling peptides composed of four amino acids that are nontoxic. These tetrapeptides can quickly solidify to nanofibrous hydrogels that resemble the extracellular matrix and provide a three-dimensional (3D) environment for cells with suitable mechanical properties. Furthermore, we can easily tune the stiffness of these peptide hydrogels by just increasing the peptide concentration, thus providing a wide range of peptide hydrogels with different stiffnesses for 3D cell culture applications. Since successful bone regeneration requires both osteogenesis and vascularization, our scaffold was found to be able to promote angiogenesis of human umbilical vein endothelial cells (HUVECs) in vitro . The results presented suggest that ultrashort peptide hydrogels are promising candidates for applications in bone tissue engineering.

An alarming increase in antibiotic-resistant bacterial strains is driving clinical demand for new antibacterial agents. One of the oldest antimicrobial agents is elementary silver (Ag), which has been used for thousands of years. Even today, elementary Ag is used for medical purposes such as treating burns, wounds, and microbial infections. In consideration of the effectiveness of elementary Ag, the present researchers generated effective antibacterial/antibiofilm agents by combining elementary Ag with biocompatible ultrashort peptide compounds. The innovative antibacterial agents comprised a hybrid peptide bound to Ag nanoparticles (IVFK/Ag NPs). These were generated by photoionizing a biocompatible ultrashort peptide, thus reducing Ag ions to form Ag NPs with a diameter of 6 nm. The IVFK/Ag NPs demonstrated promising antibacterial/antibiofilm activity against reference Gram-positive and Gram-negative bacteria compared with commercial Ag NPs. Through morphological changes in Escherichia coli and Staphylococcus aureus, we proposed that the mechanism of action for IVFK/Ag NPs derives from their ability to disrupt bacterial membranes. In terms of safety, the IVFK/Ag NPs demonstrated biocompatibility in the presence of human dermal fibroblast cells, and concentrations within the minimal inhibitory concentration had no significant effect on cell viability. These results demonstrated that hybrid peptide/Ag NPs hold promise as a biocompatible material with strong antibacterial/antibiofilm properties, allowing them to be applied across a wide range of applications in tissue engineering and regenerative medicine.

Non-healing chronic wounds are severe complications, which can often eventually lead to amputations. As such, there is a clear clinical need for dressings that promote the healing of chronic wounds. An advanced wound dressing aims to keep wound tissues moist while offering increased healing rates, preventing scar formation, reducing pain, minimizing infection, improving cosmetics, and lowering overall health care costs. We have previously developed tetrameric peptides Ac-IVZK-NH 2 (Ac-Ile-Val-Cha-Lys-NH 2 ) and Ac-IVFK-NH 2 (Ac-Ile-Val-Phe-Lys-NH 2 ) that self-assemble into nanofibrous hydrogels with biomimetic properties resembling those of collagen. In our study, we tested if these nanogels can fulfill the wound healing criteria mentioned above, and found that the nanogels are suitable scaffolds for encapsulating human dermal fibroblasts. We selected peptide nanogels Ac-IVZK-NH 2 and Ac-IVFK-NH 2 and produced silver nanoparticles in situ within the nanogels to assess their efficacy on micropigs with full-thickness excision wounds. The in situ generation of the silver nanoparticles was done solely through UV irradiation, no reducing agent was used. Application of the peptide nanogels on full thickness micropig wounds demonstrated that the scaffolds are biocompatible and did not trigger wound inflammation. This suggests that the scaffolds are safe for topical application. A comparison of the effect of both nanogels-even without the addition of the silver nanoparticles, revealed that the scaffold itself has a high potential to act as an antibacterial agent, which may suppress both the inflammatory reaction and the activity of proteases. Interestingly, the effect on wound closure of the peptide nanogels was comparable to those of standard care hydrogels. Despite our promising results, there is still much to learn about the molecular basis underlying the efficacy of tetrameric peptide nanogels in wound healing. This will support the urgent demand for advanced treatments of diabetic wounds, based on scientifically and clinically validated studies.

Three-dimensional (3D) porous metal and metal oxide nanostructures have received considerable interest because organization of inorganic materials into 3D nanomaterials holds extraordinary properties such as lowd ensity, high porosity,a nd high surface area. Supramolecular selfassembled peptide nanostructures were exploited as an organic template for catalytic 3D Pt-TiO 2 nano-network fabrication. A 3D peptide nanofiber aerogel was conformally coated with TiO 2 by atomic layer deposition (ALD) with angstrom-level thickness precision. The 3D peptide-TiO 2 nano-network was further decorated with highly monodisperse Pt nanoparticles by using ozone-assisted ALD.T he 3D TiO 2 nano-network decorated with Pt nanoparticles shows superior catalytic activity in hydrolysis of ammonia-borane,g enerating three equivalents of H 2 .The three-dimensional (3D) porous metal and metal oxide aerogels have recently attracted enormous interest, because assembly of bulk inorganic materials into 3D nanomaterials generates exciting features such as low density,high porosity, and high surface area.[1] Porous 3D aerogels allow rapid flow of electrons,i ons,a nd molecules,w hich makes them extremely attractive for applications such as catalysis, [2] sensing, [3] fuel cells, [4] and supercapacitors.[5] Numerous techniques have been developed to prepare porous metal and metal oxide nanomaterials,including templating,combustion, cathodic corrosion, and aerogel formation.[4b] However, as ignificant challenge exists to synthesize metal and metal oxide 3D nanomaterials in controlled and reproducible manner.T herefore,uniform and highly controlled deposition of metals and metal oxides at ambient temperatures on soft organic templates,which can assemble into desired structures (1D,2D, and 3D), shape and morphology,could be apromising strategy to prepare variety of porous inorganic 3D nanomaterials.S elf-assembling peptides are ac lass of supramolecular polymers,w hich exploit noncovalent interactions such as hydrogen bonding,h ydrophobic, electrostatic, p-p, and van der Waals interactions to generate well-defined supramolecular nanostructures including nanospheres,n anosheets,n anotubes,a nd nanofibers.[6] These versatile supramolecular polymers can encapsulate large amounts of water to form gels,w hich have been extensively utilized as 2D and 3D scaffolds.[7] Critical and air-dried self-assembled peptide nanofiber gels can form self-standing porous 3D aerogels and xerogels,w hich are made up of highly dense 1D nanofibers. These 3D aerogels can be used as soft templates to deposit and support various inorganic nanomaterials from 1D to 3D. [8] Atomic layer deposition (ALD) is ac hemical vapor deposition technique based on sequential, self-limiting surface reactions between gaseous precursors and asolid surface to deposit materials in an atomic layer-by-layer fashion, which paves the way for controlling the film thickness and size of nanoparticles by the number of growth cycles.[9] It provides unmatched capabilities for highly uniform c...

Blood vessel generation is an essential process for tissue formation, regeneration, and repair. Notwithstanding, vascularized tissue fabrication in vitro remains a challenge, as current fabrication techniques and biomaterials lack translational potential in medicine. Naturally derived biomaterials harbor the risk of immunogenicity and pathogen transmission, while synthetic materials need functionalization or blending to improve their biocompatibility. In addition, the traditional top-down fabrication techniques do not recreate the native tissue microarchitecture. Self-assembling ultrashort peptides (SUPs) are promising chemically synthesized natural materials that self-assemble into three-dimensional nanofibrous hydrogels resembling the extracellular matrix (ECM). Here, we use a modular tissue-engineering approach, embedding SUP microgels loaded with human umbilical vein endothelial cells (HUVECs) into a 3D SUP hydrogel containing human dermal fibroblast neonatal (HDFn) cells to trigger angiogenesis. The SUPs IVFK and IVZK were used to fabricate microgels that gel in a water-in-oil emulsion using a microfluidic droplet generator chip. The fabricated SUP microgels are round structures that are 300–350 μm diameter in size and have ECM-like topography. In addition, they are stable enough to keep their original size and shape under cell culture conditions and long-term storage. When the SUP microgels were used as microcarriers for growing HUVECs and HDFn cells on the microgel surface, cell attachment, stretching, and proliferation could be demonstrated. Finally, we performed an angiogenesis assay in both SUP hydrogels using all SUP combinations between micro- and bulky hydrogels. Endothelial cells were able to migrate from the microgel to the surrounding area, showing angiogenesis features such as sprouting, branching, coalescence, and lumen formation. Although both SUP hydrogels support vascular network formation, IVFK outperformed IVZK in terms of vessel network extension and branching. Overall, these results demonstrated that cell-laden SUP microgels have great potential to be used as a microcarrier cell delivery system, encouraging us to study the angiogenesis process and to develop vascularized tissue-engineering therapies.