POLYMERIC BIOMATERIALS FOR SCAFFOLD-BASED BONE REGENERATIVE ENGINEERING

Abstract

Reconstruction of large bone defects resulting from trauma, neoplasm, or infection is a challenging problem in reconstructive surgery. The need for bone grafting has been increasing steadily partly because of our enhanced capability to salvage limbs after major bone loss. Engineered bone graft substitutes can have advantages such as lack of antigenicity, high availability, and varying properties depending on the applications chosen for use. These favorable attributes have contributed to the rise of scaffold-based polymeric tissue regeneration. Critical components in the scaffold-based polymeric regenerative engineering approach often include 1. The existence of biodegradable polymeric porous structures with properties selected to promote tissue regeneration and while providing appropriate mechanical support during tissue regeneration. 2. Cellular populations that can influence and enhance regeneration. 3. The use of growth and morphogenetic factors which can influence cellular migration, differentiation and tissue regeneration in vivo. Biodegradable polymers constitute an attractive class of biomaterials for the development of scaffolds due to their flexibility in chemistry and their ability to produce biocompatible degradation products. This paper presents an overview of polymeric scaffold-based bone tissue regeneration and reviews approaches as well as the particular roles of biodegradable polymers currently in use.

Keywords: Biodegradable polymers; Biomaterials; Cell-Material Interactions; Regenerative Engineering.

Fig. 1

Diagram showing cortical and trabecular bone[39]

Fig. 2

Bone matrix arranged in the form of concentric rings, lamellae, centered on Haversian canals to form osteons[39]

Fig. 3

Bone cell types and organization. Osteoblasts (OB), bone lining cells, and osteoclasts (OC) reside on the bone surface whereas osteocytes are in the interior of bone matrix. The gap junctions between all cells might provide a pathway as indicated by the arrows for the signals transduced from osteocytes in the bone matrix to OB and OC on the bone surface[30]. Reproduced with permission from reference . Copyright 2008 American Society for Clinical Investigation.

Fig. 4

Hierarchical structure of bone. Fibers, laminae, and pores are present at different size scales resulting in various macro- to sub-nanostructures. Such material hierarchical arrangement is essential for the mechanical functions of bone[46, 47]. Reproduced with permission from references and respectively. Copyright 1997 Elsevier, and copyright 1998 Annual Reviews.

Fig. 5

Chemical structure of Poly (3-hydroxybutyrate)(PHB) [10].

Fig. 6

Diagram showing the poly[pyromellitylimidoalanine-co-1,6-bis(p-carboxyphenoxy) hexane] structure [10].

Fig.7

Diagram depicting the structure of photocrosslinked polymers (a) poly(Sebacic acid) (PSA), poly(1-3 bis(p-carboxyphenoxy)propane) (PCPP) and (c) poly(1-6 bis(p-carboxy phenxoy)hexane) (PCPH)[10].

Fig. 8

Polymerization of poly (propylene fumarate) from diethyl fumarate and propylene glycol by two-step procedure [128].

Fig. 9

General structure of polyphosphazene [67].

Fig. 10

Synthetic mechanism of polyphosphazene showing the single-substituent and mixed substituent polymers [67].

Fig. 11

Time-dependent thickness change of the tissue response for PLAGA and polyphosphazene-PLAGA blends during 12 weeks of implantation. The inflammatory responses for the blends were minimal [140]. Reproduced with permission from reference . Copyright 2010 Elsevier

Fig. 12

Time-dependent thickness change of the fibrous capsules for PLAGA and polyphosphazene-PLAGA blends. The thicknesses of the fibrous capsules for the blends were minimal [140]. Reproduced with permission from reference . Copyright 2010 Elsevier

Fig. 13

Chemical structure of hyaluronic acid [10].

Fig. 14

Effects of polymer surface properties on cell function. Surfaces of the cell culture were made with vapor deposition of pHEMA onto TCPs. Proliferation was determined using the extent of uptake of [³H] thymidine. The relative cell height is represented by the size of the symbol. Cells with small heights indicate significant spreading which correspond to small symbols. Cells having large heights indicate infinitesimal spreading which correspond to large symbols [184]. Reproduced with permission from reference . Copyright 1978 Springer Nature.

Fig. 15

Design parameters that ensure optimal and favorable cell-material interactions [3]. Reproduced with permission from reference . Copyright 2016 Springer Nature.