Multi- doped hydroxyapatite within porous poly(L-lactide-co-D,L-lactide): functional biomaterials for bone tissue engineering

Abstract

Event Abstract Back to Event Multi- doped hydroxyapatite within porous poly(L-lactide-co-D,L-lactide): functional biomaterials for bone tissue engineering Marija Vukomanović1 and Danilo Suvorov1 1 Jožef Stefan Institute, Advanced Materials Department, Slovenia Introduction: For ideal 3D bone scaffold it is crucial to mimic natural bone. For that purpose it is essential to find artificial material with composition, structure and mechanical characteristics similar to the natural bone [1]. It can be achieved by formation of the nanocomposites of bioactive materials (including hydroxyapatite (HAp)) and biodegradable polymers with good mechanical properties (like poly(L-lactide-co-D,L-lactide) (PLLA)). Doping the structure of inorganic part of the composite and functionalization of its surface opens a great possibility to design its bioactivity and affinity to stimulate cellular growth, along with ability for prevention of bacterial growth [2]. Materials and methods: Multi-doped HAp was synthesized with homogeneous sonochemical precipitation method [3]; its surface was modified by functionalized Au nanoparticles using ultrasonic processing [4] and the material was incorporated within 3D PLLA matrix, formed by gelation/crystallization in acetonitrile/water, followed by freeze drying. Results and discussion: To obtain similarity with the bone our first idea was to mimic its composition by formation of the multi-doped HAp. For that purpose we simultaneously incorporated Mg2+, Sr2+, Zn2+ and/or Ga3+ within HAp structure (Fig. 1a). Doping provided increase of the specific surface area which was particularly pronounced for the multi-doped material. High surface area of doped HAp was used to attach amino acid functionalized Au nanoparticles. That enabled to the inorganic part of a material additional function related to the ability for antimicrobial response along with improved bioactivity. Figure 1: XRD patterns of HAp doped by different ions (a); 3D PLLA matrix physical appearance (b) and morphology (c). Another approach that we used to obtain similarity with the natural bone was to mimic its structure. For that purpose we formed a 3D PLLA matrix, namely a disc with height of 1 cm and diameter about 2 cm that contained both macroscopic and microscopic porosity along with nano-roughness (Figs. 1b and 1c). These characteristics are essential for interactions of the material with stem cells, their attachment to the material and spreading over its surface. Good interconnectivity of the inner pores which was formed is very important for transport of the nutrients and oxygen required for survival of the cells inside the matrix. Conclusions: Porous 3D structures composed of multi-doped HAp with functionalized surface incorporated within PLLA matrix is a functional biomaterial applicable in bone tissue engineering. The material joins ability for improved bioactivity along with strong antimicrobial activity. In addition, the structure and nature of porous polymeric matrix join together high porosity with structural integrity. Joining together all listed characteristics newly developed material represent a synthetic scaffold which possesses characteristics of the natural bone. It provides intelligent tool that can be used in advanced engineering of the bone tissue.