A site-specific branching poly-glutamate tag mediates intracellular protein delivery by cationic lipids.

Intracellular protein delivery is of significance for cellular protein analysis and therapeutic development, but remains challenging technically. Herein, we report a general and highly potent strategy for intracellular protein delivery based on commercially available cationic lipids. In this strategy, a designed double branching poly-glutamate tag is site-specifically attached onto the C-terminal of protein cargos via expressed protein ligation (EPL), which mediates the entrapment of proteins into cationic liposomes driven by electrostatic interaction. The resultant protein-lipid complexes can enter into cytosol with a high efficiency even at the low protein concentration while maintaining protein's biological activity.

Self-assembled branched polypeptides as amelogenin mimics for enamel repair.

The regeneration of demineralized enamel holds great significance in the treatment of dental caries. Amelogenin (Ame), an essential protein for mediating natural enamel growth, is no longer secreted after enamel has fully matured in childhood. Although biomimetic mineralization based on peptides or proteins has made significant progress, easily accessible, low-cost, biocompatible and highly effective Ame mimics are still lacking. Herein, we construct a series of amphiphilic branched polypeptides (CAMPs) by facile coupling of the Ame's C-terminal segment and poly(γ-benzyl-L-glutamate), which serves to simulate the Ame's hydrophobic N-terminal segment. Among them, CAMP15 is the best biomimetic mineralization template with great self-assembly performance to guide the oriented crystallization of hydroxyapatite and is capable of inhibiting the adhesion of Streptococcus mutans and Staphylococcus aureus on the enamel surfaces. This work highlights the potential application of amphiphilic branched polypeptide as Ame mimics in repairing defected enamel, providing a promising strategy for prevention and treatment of dental caries.

Recent Advances in Post-polymerization Modifications on Polypeptides: Synthesis and Applications.

Polypeptides, a kind of very promising biomaterial, have shown a wide range of applications due to their excellent biocompatibility, easy accessibility, and structural variability. To synthesize polypeptides with desired functions, post-polymerization modification (PPM) plays an important role in introducing novel chemical structure on their side-chains. The key to PPM strategy is to develop highly selective and efficient reactions that can couple the additional functional moieties with pre-installed side-chain functionalities on polypeptides. In this minireview, classic PPM approaches and their recent progresses are summarized and categorized into five sections, including various reactions on unsaturated alkyl, oxygen-, nitrogen-, sulfur-containing and other special functional groups. In addition, we also highlight the applications of the resultant structure-diversified polypeptides in the field of biomaterial.

Phosphorylated and Phosphonated Low-Complexity Protein Segments for Biomimetic Mineralization and Repair of Tooth Enamel.

Biomimetic mineralization based on self-assembly has made great progress, providing bottom-up strategies for the construction of new organic-inorganic hybrid materials applied in the treatment of hard tissue defects. Herein, inspired by the cooperative effects of key components in biomineralization microenvironments, a new type of biocompatible peptide scaffold based on flexibly self-assembling low-complexity protein segments (LCPSs) containing phosphate or phosphonate groups is developed. These LCPSs can retard the transformation of amorphous calcium phosphate into hydroxyapatite (HAP), leading to merged mineralization structures. Moreover, the application of phosphonated LCPS over phosphorylated LCPS can prevent hydrolysis by phosphatases that are enriched in extracellular mineralization microenvironments. After being coated on the etched tooth enamel, these LCPSs facilitate the growth of HAP to generate new enamel layers comparable to the natural layers and mitigate the adhesion of Streptococcus mutans. In addition, they can effectively stimulate the differentiation pathways of osteoblasts. These results shed light on the potential biomedical applications of two LCPSs in hard tissue repair.

Comparison of processing and sectioning methodologies for arteries containing metallic stents.

The histological study of arteries with implanted metallic scaffolding devices, known as stents, remains a technical challenge. Given that the arterial response to stent implantation can sometimes lead to adverse outcomes, including the re-accumulation of tissue mass within the stent (or in-stent restenosis), overcoming these technical challenges is a priority for the advancement of research and development in this important clinical field. Essentially, the task is to section the stent-tissue interface with the least amount of disruption of tissue and cellular morphology. Although many methacrylate resin methodologies are successfully applied toward the study of endovascular stents by a variety of research laboratories, the exact formulations, as well as subsequent processing and sectioning methodology, remain largely coveted. In this paper, we describe in detail a methyl methacrylate resin-embedding methodology that can successfully be applied to tungsten carbide blade, as well as saw and grinding sectioning methods and transmission electron microscopy. In addition, we present a comparison of the two sectioning methodologies in terms of their effectiveness with regard to morphological, histochemical, and immunohistochemical analyses. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.