The biological performance of a material depends on the extent it is capable of mimicking the microenvironment of the native tissue. Based on this biomimetic approach, in last decade, scaffolds with different geometries and physical, chemical and mechanical property gradients have been investigated to promote tissue regeneration. However, little is explored about how to create electroactive scaffolds with controlled delivering electric cues to stimulate cellular response. Electroactive scaffolds which mimics the piezoelectric coefficients of natural tissue may be a suitable approach for the repair and regeneration of skeletal and neural tissues.

Piezoelectric polymers and composites based on Poly(L-Lactide) (PLLA) have emerged as a class of smart materials to fulfill this requirement. Moreover, their thermoplastic character makes them easy to be processed by advanced manufacturing techniques such as, electrospinning, extrusion based 3D printing or recently employed melt electrowriting. Blending and the incorporation of different ceramic fillers such as, hydroxyapatite (HA), zinc oxide (ZnO) particles [antimicrobial], barium titanate (BT), or cellulose nanocrystals (CNC) can help in tuning both, the piezoelectric behavior and the mechanical properties.

These characteristics are also dependent on the specific geometry of the scaffold (alignment, porosity and orientation). There are however challenges in processing and formulation of the raw material for inducing piezoelectricity. Fabricating piezoelectric scaffolds with optimized value of piezoelectric constant and mechanical properties and assessing cellular responses on polarized samples will depend on several factors: 1.-Blending composition 2.-Filler type and content, 3.-Processing variables, 4.- Structure of the scaffold; geometry (porous-like, linear channels etc.)

This project aims to fabricate 3D electroactive scaffolds with tunable piezoelectricity and mechanical properties for its application in osseous and neural tissue engineering. This objective is challenging as it is necessary to control both the material properties in bulk and the material processing parameters. This research line intends to control such characteristics at different length scales, from microstructures fabricated by 3D melt extrusion printing to nanostructures fabricated by electrowriting and electrospinning.

A number of monomers are commercially available for the synthesis of (co)polyesters, such as, lactide, glycolide and ε-caprolactone, three of the best known cyclic esters. The racemic stereochemistry, the length of straight methylenes and the ratio of ester groups will determine the biodegradation rates and properties of the copolymers obtained from them.

Our research group in science and engineering of polymeric biomaterials is committed to the study and development of biodegradable polyester based biomaterials for applications in the medical field. During the last years our group has obtained relevant results and contributions on the synthesis of (co)polyesters by Ring Opening Polymerization (ROP) of lactides, lactones and macrolactones and a number of articles and a patent have been published during our previous research in this field.

From the spectrum of monomers and copolymerization strategies we have developed in our research group (co)polymers of either high glass transition temperature (Tg) or low Tg that can be suited for medical applications involving both hard tissue and soft tissue regeneration. Crystallization ability aspects of (co)polyesters are also relevant since their effect on their mechanical properties and bodegradation rates. Some of the contributions of our group to this field are described next. The high Tg homopolymer Poly (L-lactic acid) (PLLA) and its stereocomplex, PLLA/PDLA, are semicrystalline, mechanically rigid and strong and a priori present proper mechanical properties for uses involving hard tissue regeneration (bone.) Poly (ε-caprolactone) (PCL) and Poly (ethylene brassylate) ,for example, present low Tg and are more prone to be used for regeneration of soft tissues (cartilage, neural,, urology, etc.). The proper (co)polymerization strategies allow us to have a full spectrum of (co)polyesters going from rigid and strong to elastomeric, depending on their compositions and chain microstructures, semycrystalline or amorphous in character, and with a range of biodegradation properties (faster or slower) to be used depending the different tissue regeneration strategies required.

The polymers presented in this project are therefore essentially biodegradable and biocompatible. We will particularly use specific (co)polyesters to develop novel nanostructured polymeric biomaterials and nanocomposites that present a great potential to develop medical devices with tuned mechanical and biodegradation properties applicable to both hard and soft tissue regeneration. In this research line we propose the study and development of nanostructured biodegradable (co)polyesters and nanocomposites for tissue engineering applications. Moreover, their transformation by advanced processing techniques such as 3D printing will be thoroughly studied.