Structural Consequences of Introducing Bioactive Domains to Designer ß-Sheet Peptide Self-Assemblies.

We applied solid- and solution-state nuclear magnetic resonance spectroscopy to examine the structure of multidomain peptides composed of self-assembling ß-sheet domains linked to bioactive domains. Bioactive domains can be selected to stimulate specific biological responses (e.g., via receptor binding), while the ß-sheets provide the desirable nanoscale properties. Although previous work has established the efficacy of multidomain peptides, molecular-level characterization is lacking. The bioactive domains are intended to remain solvent-accessible without being incorporated into the ß-sheet structure. We tested for three possible anticipated molecular-level consequences of introducing bioactive domains to ß-sheet-forming peptides: (1) the bioactive domain has no effect on the self-assembling peptide structure; (2) the bioactive domain is incorporated into the ß-sheet nanofiber; and (3) the bioactive domain interferes with self-assembly such that nanofibers are not formed. The peptides involved in this study incorporated self-assembling domains based on the (SL)6 motif and bioactive domains including a VEGF-A mimic (QK), an IGF-mimic (IGF-1c), and a de novo SARS-CoV-2 binding peptide (SBP3). We observed all three of the anticipated outcomes from our examination of peptides, illustrating the unintended structural effects that could adversely affect the desired biofunctionality and biomaterial properties of the resulting peptide hydrogel. This work is the first attempt to evaluate the structural effects of incorporating bioactive domains into a set of peptides unified by a similar self-assembling peptide domain. These structural insights reveal unmet challenges in the design of highly tunable bioactive self-assembling peptide hydrogels.

Antiviral fibrils of self-assembled peptides with tunable compositions.

The lasting threat of viral pandemics necessitates the development of tailorable first-response antivirals with specific but adaptive architectures for treatment of novel viral infections. Here, such an antiviral platform has been developed based on a mixture of hetero-peptides self-assembled into functionalized ß-sheets capable of specific multivalent binding to viral protein complexes. One domain of each hetero-peptide is designed to specifically bind to certain viral proteins, while another domain self-assembles into fibrils with epitope binding characteristics determined by the types of peptides and their molar fractions. The self-assembled fibrils maintain enhanced binding to viral protein complexes and retain high resilience to viral mutations. This method is experimentally and computationally tested using short peptides that specifically bind to Spike proteins of SARS-CoV-2. This platform is efficacious, inexpensive, and stable with excellent tolerability.

Injectable Peptide Hydrogels Loaded with Murine Embryonic Stem Cells Relieve Ischemia In Vivo after Myocardial Infarction.

Myocardial infarction (MI) is a major cause of morbidity and mortality worldwide, especially in aging and metabolically unhealthy populations. A major target of regenerative tissue engineering is the restoration of viable cardiomyocytes to preserve cardiac function and circumvent the progression to heart failure post-MI. Amelioration of ischemia is a crucial component of such restorative strategies. Angiogenic ß-sheet peptides can self-assemble into thixotropic nanofibrous hydrogels. These syringe aspiratable cytocompatible gels were loaded with stem cells and showed excellent cytocompatibility and minimal impact on the storage and loss moduli of hydrogels. Gels with and without cells were delivered into the myocardium of a mouse MI model (LAD ligation). Cardiac function and tissue remodeling were evaluated up to 4 weeks in vivo. Injectable peptide hydrogels synergized with loaded murine embryonic stem cells to demonstrate enhanced survival after intracardiac delivery during the acute phase post-MI, especially at 7 days. This approach shows promise for post-MI treatment and potentially functional cardiac tissue regeneration and warrants large-scale animal testing prior to clinical translation.

Self-Assembling Peptides with Insulin-Like Growth Factor Mimicry.

Growth factor (GF) mimicry involves recapitulating the signaling of larger molecules or cells. Although GF mimicry holds considerable promise in tissue engineering and drug design applications, difficulties in targeting the signaling molecule to the site of delivery and dissociation of mimicking peptides from their target receptors continue to limit its clinical application. To address these challenges, we utilized a self-assembling peptide (SAP) platform to generate synthetic insulin-like growth factor (IGF)-signaling, self-assembling GFs. Our peptide hydrogels are biocompatible and bind target IGF receptors in a dose-dependent fashion, activate proangiogenic signaling, and facilitate formation of angiogenic microtubules in vitro. Furthermore, infiltrated hydrogels are stable for weeks to months. We conclude that the enhanced targeting and long-term stability of our SAP/GF mimicry implants may improve the efficacy and safety of future GF mimic therapeutics.

How to Design Peptides.

Novel design of proteins to target receptors for treatment or tissue augmentation has come to the fore owing to advancements in computing power, modeling frameworks, and translational successes. Shorter proteins, or peptides, can offer combinatorial synergies with dendrimer, polymer, or other peptide carriers for enhanced local signaling, which larger proteins may sterically hinder. Here, we present a generalized method for designing a novel peptide. We first show how to create a script protocol that can be used to iteratively optimize and screen novel peptide sequences for binding a target protein. We present a step-by-step introduction to utilizing file repositories, data bases, and the Rosetta software suite. RosettaScripts, an .xml interface that allows for sequential functions to be performed, is used to order the functions for repeatable performance. These strategies may lead to more groups venturing into computational design, which may result in synergies from artificial intelligence/machine learning (AI/ML) to phage display and screening. Importantly, the beginner is expected to be able to design their first peptide ligand and begin their journey in peptide drug discovery. Generally, these peptides potentially could be used to interact with any enzyme or receptor, for example, in the study of chemokines and their interactions with glycosoaminoglycans and their receptors.