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Development of Benign Metal Alkoxide Initiators for Stereoselective Synthesis of Polyesters for Application as Scaffolds in Tissue Engineering

Final Report Summary - DGV (Development of benign metal alkoxide initiators for stereoselective synthesis of polyesters for application as scaffolds in tissue engineering)

Project objectives

According to the original proposal and the Annex I of the Grant Agreement, we divided the research objectives of the present project in three main areas: synthetic chemistry, polymer synthesis and processing, and tissue engineering. Training aspects of the fellowship were explained in the personal career development plan.

Project results

Following our planned work, during the initial part of the project we synthesised a range of metal complexes with potential application as initiators for the ring-opening polymerisation (ROP) of cyclic esters. We managed to isolate and structurally characterise a family of group 1 metal derivatives of this ligand family which exhibited quite novel structural motifs, including the participation of a 'metallic' hydrogen atom in the typical cubic array of a lithium or sodium phenolate. Then, turning our attention to the development of new initiators for the ROP reaction we prepared an extensive library of group 1 (Li and Na) metal aryloxide complexes stabilised by polyamine ligands, including the first application of the tripodal Me6-TREN ligand to group 1 metal chemistry.

Some of these Group 1 metal complexes were found to be very good initiators for the ROP of rac-lactide. In particular, lithium derivatives showed very fast polymerisation reactions but only yielded low molecular weight cyclic polymers. Sodium derivatives showed much more controlled reactions yielding polymers which a much more predictable properties. We have also carried out polymerisations using the less studied cyclic ester rac-beta-butyrolactone. Interestingly, besides its good catalytic activities, some of the metal complexes evaluated in the ROP of rac-beta-butyrolactone yielded polymers exhibiting a high degree of stereocontrol. Doubtless, these encouraging initial results will open new research lines within the group. Given the results obtained in the firsts two parts of the project the evaluation of the new polymeric materials as scaffolds has remained largely unexplored. However, in collaboration with the group of Tony D. James (University of Bath) during the final part of the project we prepared new polymeric materials with potential application as sensors for biologically relevant molecules. These new exciting results will have a great impact in the development of novel biocompatible sensors.

Dissemination of results and project impact

The results obtained from the project have been promptly published and also presented at numerous national and international conferences. In particular, we have already published four articles in peer-reviewed international journals of high impact factor. Approximately 40 % of the work is being prepared for publication. The researcher has participated in 6 major national and international conferences, including two oral presentations.

Personal and professional development of the researcher

The researcher received training in nuclear magnetic resonance (NMR), mass spectrometry, X-ray, etc., and has received a hands-in training in polymer synthesis and characterisation. Group and literature meetings during the two-year period focused the research work, identified new research areas of potential interest and increased the chemical knowledge of the researcher.

The researcher has also been involved in the active supervision of graduate and undergraduate students working in Prof. Davidson's group and has been able to participate in teaching undergraduate students by carrying out tutorials.

In summary, the excellent research results obtained together with the very good quality of the training and new skills acquired by the researcher provided him with an exceptional opportunity for the development. As a result, Dr García has recently been awarded with a Marie Curie Reintegration Grant (ERG) sponsored by the Seventh Framework Programme (FP7) of the European Commission (EC) to facilitate his reintegration to the University of Oviedo (EUR 45 000).