Additive manufacturing of poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] scaffolds for engineered bone development

Abstract

A wide range of poly(hydroxyalkanoate)s (PHAs), a class of biodegradable polyesters produced by various bacteria grown under unbalanced conditions, have been proposed for the fabrication of tissue-engineering scaffolds. In this study, the manufacture of poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (or PHBHHx) scaffolds, by means of an additive manufacturing technique based on a computer-controlled wet-spinning system, was investigated. By optimizing the processing parameters, three-dimensional scaffolds with different internal architectures were fabricated, based on a layer-by-layer approach. The resulting scaffolds were characterized by scanning electron microscopy, which showed good control over the fibre alignment and a fully interconnected porous network, with porosity in the range 79-88%, fibre diameter 47-76 µm and pore size 123-789 µm. Moreover, the resulting fibres presented an internal porosity connected to the external fibre surface as a consequence of the phase-inversion process governing the solidification of the polymer solution. Scaffold compressive modulus and yield stress and strain could be varied in a certain range by changing the architectural parameters. Cell-culture experiments employing the MC3T3-E1 murine pre-osteoblast cell line showed good cell proliferation after 21 days of culture. The PHBHHx scaffolds demonstrated promising results in terms of cell differentiation towards an osteoblast phenotype. Copyright © 2014 John Wiley & Sons, Ltd.

Recent Progress in Polyhydroxyalkanoates‐Based Copolymers for Biomedical Applications

“…Although PHBHHx has good properties, it still cannot escape the limitations of the PHA family due to the complicated production process and expensive raw materials. Relative to other members of the PHA family, there are relatively few bacterial species capable of synthesizing PHBHHx . Fukui's team biosynthesized a high‐yield P(3HB‐ co ‐3HHx) by using an artificially modified Ralstonia eutropha and unrelated fructose as a raw material, with 3HHx fragment molar fraction of 22%.…”

Switching from petro-plastics to microbial polyhydroxyalkanoates (PHA): the biotechnological escape route of choice out of the plastic predicament?

“…Particularly for the biomedical use, traditional processing techniques for production of PHA-based items, such as melt-spinning, melt extrusion, or solvent evaporation, get more and more outperformed by new emerging processing techniques such as additive manufacturing (3D-printing) to produce scaffolds for tissue engineering (124) or bone development (125), scaffold design by electrospinning (126) or computer-aided wet-spinning (127), or laser perforation (128) and plasma treatment (129) to enhance adhesion and attachment of stem cells and other cells to PHA surfaces. In vivo applicability of PHA can also be enhanced by post-synthetic functionalization of the biopolyesters; only recently, it was shown by Bhatia et al that PHA functionalized with ascorbic acid provides a new biomaterial with decreased crystallinity, enhanced hydrophilicity, increased thermal degradation temperature, and superior biodegradability; these authors proposed this new product as powerful in vivo radical scavenger (130).…”

Wet-spinning of biomedical polymers: from single-fibre production to additive manufacturing of three-dimensional scaffolds

“…A number of studies have shown that this technique is well suited for the layered manufacturing of polymeric scaffolds with a predefined network of pores customized in terms of geometry and size, as well as with a given external shape that can resemble an anatomical part. The investigation of the CAWS fabrication process has led to the development of a set of layered scaffold prototypes made of biodegradable polyesters obtained from synthetic routes, such as PCL (Figs (c)–(f)), or from natural sources, such as poly[( R )‐3‐hydroxybutyrate‐ co ‐( R )‐3‐hydroxyhexanoate)] (PHBHHx) (Figs (g)–(i)).…”

“…Representative (c) photograph and (d, e) SEM micrographs of PCL scaffolds, and (f) confocal laser scanning microscopy (CLSM) micrograph of MC3T3‐E1 preosteoblast cells cultured in vitro on PCL scaffolds (day 35) . Representative (g) photograph, and (h) top view and (i) cross‐section SEM micrographs of PHBHHx scaffolds …”