Additive Manufacturing Approaches for Hydroxyapatite‐Reinforced Composites

Abstract

Additive manufacturing (AM) techniques have gained interest in the tissue engineering field, thanks to their versatility and unique possibilities of producing constructs with complex macroscopic geometries and defined patterns. Recently, composite materials-namely, heterogeneous biomaterials identified as continuous phase (matrix) and reinforcement (filler)-have been proposed as inks that can be processed by AM to obtain scaffolds with improved biomimetic and bioactive properties. Significant efforts have been dedicated to hydroxyapatite (HA)-reinforced composites, especially targeting bone tissue engineering, thanks to the chemical similarities of HA with respect to mineral components of native mineralized tissues. Herein, applications of AM techniques to process HA-reinforced composites and biocomposites for the production of scaffolds with biological matrices, including cellular tissues, are reviewed. The primary outcomes of recent investigations in terms of morphological, structural, and in vitro and in vivo biological properties of the materials are discussed. The approaches based on the nature of the matrices employed to embed the HA reinforcements and produce the tissue substitutes are classified, and a critical discussion is provided on the presented state of the art as well as the future perspectives, to offer a comprehensive picture of the strategies investigated as well as challenges in this emerging field of materiomics.

In-vivo vascular application via ultra-fast bioprinting for future 5D personalised nanomedicine

“…Thanks to the high scaffold customisation potential (NP or functionalised matrix for a gradual drug release), we can design and bioprint 5D personalised medical devices. In detail, modifying the composite biomaterial [42][43][44][45] and the manufacturing methods, the interaction 45,46 of the transplanted structures with the biological substrate can be varied accordingly to experimental needs. When it is possible to graft biocompatible objects (prosthesis, STENT, etc.)…”

De novo topology optimization of total ossicular replacement prostheses

“…Silk, on the other hand, is a natural protein fiber that can be easily used as an ink for Direct Ink Writing or, once solidified, shaped via ultraprecision milling. The good biocompatibility and tunable degradability of devices made of silk have made it a concrete alternative to synthetic materials for clinical applications [35,38,39]. Finally, Collagen/HA is a composite that resembles bone tissues as it contains the two most important constituents of bone.…”

“…However, although the mineralization of cortical bone reaches about 70%, researchers have not overcome the upper limit of 40% due to embrittlement of the material [41]. Collagen/HA has been successfully shaped through molding and Direct Ink Writing to create replacements for tissues with features in the order of millimeters, but, to the best of the authors' knowledge, applications in otology have not been pursued so far [35].…”

“…Finally, we assess the mechanical response of four selected optimized prosthesis geometries in a more complex simulation environment mimicking the middle ear under dynamic sound pressure loads, investigating four different materials: titanium, cortical bone, silk, and a Collagen/hydroxyapatite (HA) composite. The last two, so far not used for otological applications, represent a potential alternative to the traditional materials: silk is a bioinert material that can be properly shaped via 3D printing and/or ultraprecision machining [35,38,39]; Collagen/HA is a composite that mimics the bone tissue through its main components [35,40,41].…”

Fabrication of Three-Dimensional Composite Scaffold for Simultaneous Alveolar Bone Regeneration in Dental Implant Installation

“…However, the block-type bone grafts composed of HA and/or β-TCP are brittle because of their mechanical characteristics, which could result in a sudden decrease in the mechanical stiffness during decomposition in the body [24][25][26][27]. To overcome the brittleness of these ceramic block-type bone grafts, bone graft scaffolds mixed with synthetic biocompatible/biodegradable polymers and osteoconductive ceramic particles (HA and β-TCP) have been fabricated [28][29][30][31]. Many researchers have developed polymer/ceramic composites and also demonstrated their osteoconductive effects such as osteoblast activity and structural the reinforcement [32,33].…”