αvβ3- oder α5β1-Integrin-selektive Peptidmimetika für die Oberflächenbeschichtung

Synthesis and Evaluation of a Non-Peptide Small-Molecule Drug Conjugate Targeting Integrin αVβ3

An integrin α_Vβ₃-targeting linear RGD mimetic containing a small-molecule drug conjugate (SMDC) was synthesized by combining the antimitotic agent monomethyl auristatin E (MMAE), an enzymatically cleavable Val-Ala-PABC linker with a linear conjugable RGD mimetic. The structure proposal for the conjugable RGD mimetic was suggested upon the DAD mapping analysis of a previously synthesized small-molecule RGD mimetic array based on a tyrosine scaffold. Therefore, a diversifying strategy was developed as well as a novel method for the partial hydrogenation of pyrimidines in the presence of the hydrogenolytically cleavable Cbz group. The small-molecule RGD mimetics were evaluated in an ELISA-like assay, and the structural relationships were analyzed by DAD mapping revealing activity differences induced by structural changes as visualized in dependence on special structural motifs. This provided a lead structure for generation of an SMDC containing the antimitotic drug MMAE. The resulting SMDC containing a linear RGD mimetic was tested in a cell adhesion and an in vitro cell viability assay in comparison to reference SMDCs containing cRGDfK or cRADfK as the homing device. The linear RGD SMDC and the cRGDfK SMDC inhibited adhesion of α_Vβ₃-positive WM115 cells to vitronectin with IC₅₀ values in the low µM range, while no effect was observed for the α_Vβ₃-negative M21-L cell line. The cRADfK SMDC used as a negative control was about 30-fold less active in the cell adhesion assay than the cRGDfK SMDC. Conversely, both the linear RGD SMDC and the cRGDfK SMDC are about 55-fold less cytotoxic than MMAE against the α_Vβ₃-positive WM115 cell line with IC50 values in the nM range, while the cRADfK SMDC is 150-fold less cytotoxic than MMAE. Hence, integrin binding also influences the antiproliferative activity giving a targeting index of 2.8.

Chemically Diverse Multifunctional Peptide Platforms with Antimicrobial and Cell Adhesive Properties

Bacterial infections and incomplete biomaterial integration are major problems that can lead to the failure of medical implants. However, simultaneously addressing these two issues remains a challenge. Here, we present a chemical peptide library based on a multifunctional platform containing the antimicrobial peptide LF1-11 and the cell-adhesive motif RGD. The scaffolds were customized with catechol groups to ensure straightforward functionalization of the implant surface, and linkers of different length to assess the effect of peptide accessibility on the biological response. The peptidic platforms significantly improved the adhesion of mesenchymal stem cells and showed antimicrobial effects against Staphylococcus aureus. Of note is that peptides bearing spacers that were too long displayed the lowest efficiency. Subsequently, we designed a platform replacing linear RGD by cyclic RGD; this further enhanced eukaryotic cell adhesion while retaining excellent antimicrobial properties, thus being a suitable candidate for tissue engineering applications.

A Multifunctional Peptide-Conjugated AIEgen for Efficient and Sequential Targeted Gene Delivery into the Nucleus

Gene therapy has immense potential as a therapeutic approach to serious diseases. However, efficient delivery and real-time tracking of gene therapeutic agents have not been solved well for successful gene-based therapeutics. Herein we present a versatile gene-delivery strategy for efficient and visualized delivery of therapeutic genes into the targeted nucleus. We developed an integrin-targeted, cell-permeable, and nucleocytoplasmic trafficking peptide-conjugated AIEgen named T_D NCP for the efficient and sequential targeted delivery of an antisense single-stranded DNA oligonucleotide (ASO) and tracking of the delivery process into the nucleus. As compared with T_D NCP/siRNA-NPs (siRNA functions mainly in the cytoplasm), T_D NCP/ASO-NPs (ASO functions mainly in the nucleus) exhibited a better interference effect, which further indicates that T_D NCP is a nucleus-targeting vector. Moreover, T_D NCP/ASO-NPs showed a favorable tumor-suppressive effect in vivo.

Toward Angiogenesis Inhibitors Based on the Conjugation of Organometallic Platinum(II) Complexes to RGD Peptides

A novel conjugate between a cyclometalated platinum(II) complex with dual antiangiogenic and antitumor activity and a cyclic peptide containing the RGD sequence (-Arg-Gly-Asp-) has been synthesized by combining solid- and solution-phase methodologies. Although peptide conjugation rendered a non-cytotoxic compound in all tested tumor cell lines (± α_V β₃ and α_V β₅ integrin receptors), the antiangiogenic activity of the Pt-c(RGDfK) conjugate in human umbilical vein endothelial cells at sub-cytotoxic concentrations opens the way to the design of a novel class of angiogenesis inhibitors through conjugation of metallodrugs with high antiangiogenic activity to cyclic RGD-containing peptides or peptidomimetic analogues.

About Chemical Strategies to Fabricate Cell-Instructive Biointerfaces with Static and Dynamic Complexity

Properly functioning cell-instructive biointerfaces are critical for healthy integration of biomedical devices in the body and serve as decisive tools for the advancement of our understanding of fundamental cell biological phenomena. Studies are reviewed that use covalent chemistries to fabricate cell-instructive biointerfaces. These types of biointerfaces typically result in a static presentation of predefined cell-instructive cues. Chemically defined, but dynamic cell-instructive biointerfaces introduce spatiotemporal control over cell-instructive cues and present another type of biointerface, which promises a more biomimetic way to guide cell behavior. Therefore, strategies that offer control over the lateral sorting of ligands, the availability and molecular structure of bioactive ligands, and strategies that offer the ability to induce physical, chemical and mechanical changes in situ are reviewed. Specific attention is paid to state-of-the-art studies on dynamic, cell-instructive 3D materials. Future work is expected to further deepen our understanding of molecular and cellular biological processes investigating cell-type specific responses and the translational steps toward targeted in vivo applications.

Insights into the Binding of Cyclic RGD Peptidomimetics to α5β1 Integrin by using Live-Cell NMR And Computational Studies

The interaction of a small library of cyclic DKP-RGD peptidomimetics with α5β1 integrin has been investigated by means of an integrated experimental and computational approach. Bioaffinity NMR techniques, including saturation transfer difference (STD) and transferred NOESY, were applied to the ligands in a suspension of intact MDA-MB-231 breast cancer cells, in which integrin α5β1 is highly expressed. The NMR data were compared with the docking calculations of the RGD ligands in the crystal structure of the α5β1 binding site, and were integrated with competitive binding assays to the purified α5β1 integrin. Ligand binding epitopes involve protons of both the RGD moiety and the DKP scaffold, although the stereochemistry and the functionalization of the DKP scaffold as well as the macrocycle conformation determine a great variability in the interaction. The ligand showing the highest number of STD signals is also the most potent α5β1 ligand of the series, displaying a nanomolar IC50 value.

Guiding hMSC Adhesion and Differentiation on Supported Lipid Bilayers

Mesenchymal stem cells (MSCs) are intensively investigated for regenerative medicine applications due to their ease of isolation and multilineage differentiation capacity. Hence, designing instructive microenvironments to guide MSC behavior is important for the generation of smart interfaces to enhance biomaterial performance in guiding desired tissue formation. Supported lipid bilayers (SLBs) as cell membrane mimetics can be employed as biological interfaces with easily tunable characteristics such as biospecificity, mobility, and density of predesigned ligand molecules. Arg-Gly-Asp (RGD) ligand functionalized SLBs are explored for guiding human MSC (hMSC) adhesion and differentiation by studying the effect of changes in ligand density and mobility. Cellular and molecular analyses show that adhesion occurs through specific interactions with RGD ligands where the extent is positively correlated to changes in ligand density. Furthermore, cell area is significantly regulated by ligand density on ligand-mobile SLBs when compared to ligand-immobile SLBs. Finally, the osteogenic differentiation capacity of hMSCs is positively correlated to ligand density on ligand-mobile SLBs indicating that regulation of cell spreading is linked to cell differentiation capacity. These results demonstrate that hMSC behavior can be directed on SLBs by molecular design and presents SLBs as versatile platforms for future engineering of smart biomaterial coatings.