Biomimetic Peptide Coating on Bioresorbable Magnesium Metal A. Patil (Pitt), C. Sfeir (Pitt) E. Beniash (Pitt) Fig 1 is not labeled Corrosion is not a disadvantage, this is why Mg was chosen as a resorbable material, I have rephrased the sentence in fundamental questions/challenges In the results, can you place the amino acid frequency for 23 biopanning against WX41 into Figure 2 to show the alloy specificity. Also in the summary you mention a number of unique properties. Please list them in the bottom of left collumn, i.e. hydrophobicity, charge, lack of negatively charged AAs et cetera, see the progress report for 99.9% Mg and look at the Selected peptides against WX41 Surface Morphology of Peptide Coated Mg Surface SEM study confirms the peptide coating is fairly homogeneous and thin. The surface topography of the coated discs was smoother than of bare Mg discs. Surface features are muted due to the peptide coating Project Goals The aim of this study was to develop high affinity synthetic peptide coating for an orthopedic fixation device made of Mg using Phage Display Technology to control the corrosion rate and increase its biocompatibility A B Target Surface Linker Peptide Osteogenic Peptide Figure 1 Schematic of peptide coating on a target surface The Project’s Support of Strategic Plan One of the goals of ES1 of the ERC “Revolutionizing Metallic Biomaterials” is to achieve corrosion control of Mg based alloys using various approaches. In this project, we propose to create biomimetic coating onto the Mg alloys surface to control its corrosion rate of an orthopedic fixation device. Figure 3 SEM images of Mg surface without (A) and with (B) peptide coating Mg Corrosion Rate Study The corrosion study demonstrated that both peptides have significantly slowed the rate of corrosion, when compared to the control Fundamental Questions/Challenges Magnesium (Mg) and its alloys are currently being investigated as resorbable orthopedic implant material. Mg has excellent biocompatibility, light weight and density matching to bone. However it is necessary to control the rate of corrosion to prevent forming hydrogen pockets at the implantation site and to match the resorption and regeneration rates. Currently different coating strategies have been used to control the corrosion rate of Mg and its alloys. Among many strategies, bioactive high affinity peptide coating of to resorbable Mg alloys is a promising method. One of the fundamental questions/ challenges here is to develop the coatings for highly unstable corroding Mg alloy surfaces. We have phage display selection strategies identify high affinity peptide sequences to overcome this problem. The next step in our peptide design is to select osteoinductive signaling peptides and designing a hybrid peptide ass shown in Fig 1. Figure 4 A) Schema of the H2 evolution experiment, B) Plot showing H2 release over time as a measure of Mg corrosion kinetics (n=3, mean ± SE) Summary of Achievements The first round of biopanning experiments against Mg and its alloy (WX41 & AZ31) surfaces have been completed and our sequence analysis has revealed a number of unique features of these sequences. Homogenous thin layer of peptide coating can be created on Mg and its alloys surfaces. Demonstrated that these peptides can regulate the rate of Mg metal corrosion. Currently starting in vivo studies to test biocompatibility and corrosion control properties of the selected peptides We anticipate that this work will lead to development of biomimetic coating layers for resorbable orthopedic implant devices Year 5 Research Results Mg Biopanning Experiments with 99.9% Pure Mg Our analysis of Mg- selected sequences show threefold increase in Pro frequency in comparison to naïve Ph.D. 7 library, indicating a strong selection for this amino acid in the peptides binding to Mg surface. Compared to the naïve library, the 99.9% Mg selected peptides lacked negatively charged amino acids Asp and Glu, but were rich in Pro and contained more hydrophobic amino acids such as Leu, Ile, Val and Tyr (Figure 2). In case of WX41 alloy selected sequences, high frequency of Asp (D) is observed, which was absent in the 99.9% Mg selected sequences. Future Research Plans Years 5 6 7 8 Design, synthesis and characterization of Mg-alloys binding peptides Tissue culture test for biocompatibility and osteogenic properties Selection, synthesis and design of bio-inspired peptides with osteogenic properties: SSD3, SSD5 with and without RGD motif, BMP2 active domain KIPKASSVPTELSAISTLYL In-vivo subcutaneous testing of Mg-alloy discs coated with selected peptides MicroCT, histology and chemical analyses of the implants In vivo testing of the Mg fixation plates coated with selected peptides MicroCT, histology and chemical analyses of the implants Relationships between main aims and the timetable of the project Figure 2 Frequencies of AA occurrence in peptide sequences (%) ES1: Craniofacial and Orthopedic Applications