Porous biomaterials for tissue engineering: a review

The field of biomaterials has grown rapidly over the past decades. Within this field, porous biomaterials have played a remarkable role in: (i) enabling the manufacture of complex three-dimensional structures; (ii) recreating mechanical properties close to those of the host tissues; (iii) facilitating interconnected structures for the transport of macromolecules and cells; and (iv) behaving as biocompatible inserts, tailored to either interact or not with the host body. This review outlines a brief history of the development of biomaterials, before discussing current materials proposed for use as porous biomaterials and exploring the state-of-the-art in their manufacture. The wide clinical applications of these materials are extensively discussed, drawing on specific examples of how the porous features of such biomaterials impact their behaviours, as well as the advantages and challenges faced, for each class of the materials.

Equisetum hyemale-derived unprecedented bioactive composite for hard and soft tissues engineering

Although Bioactive Glasses (BGs) have been progressively optimized, their preparation often still involves the use of toxic reagents and high calcination temperatures to remove organic solvents. In the present work, these synthesis related drawbacks were overcome by treating the ashes from the Equisetum hyemale plant in an ethanol/water solution to develop a bioactive composite [glass/carbon (BG-Carb)]. The BG-Carb was characterized by scanning electron microscopy, and transmission electron microscopy; and its chemical composition was assessed by inductively coupled plasma-optical emission spectroscopy. Brunauer-Emmett-Teller gas adsorption analysis showed a specific surface area of 121 m² g^-1. The formation of hydroxyapatite (HA) surface layer in vitro was confirmed by Fourier-transform infrared spectroscopy analysis before and after immersion in simulated body fluid (SBF) solution. The Rietveld refinement of the XRD patterns and selected area electron diffraction analyses confirmed HA in the sample even before immersing it in SBF solution. However, stronger evidences of the presence of HA were observed after immersion in SBF solution due to the surface mineralization. The BG-Carb samples showed no cytotoxicity on MC3T3-E1 cells and osteo-differentiation capacity similar to the positive control. Altogether, the BG-Carb material data reveals a promising plant waste-based candidate for hard and soft tissue engineering.

Highly Structured Polyvinyl Alcohol Porous Carriers: Tuning Inherent Stability and Release Kinetics in Water

Polyvinyl alcohol (PVA) porous carriers were prepared by means of ice templating of aqueous solutions containing of 90 kD and/or 16 kD PVA. The carriers were loaded with traces of a colored probe (methyl orange) to screen their release properties, once immersed in water. The carriers prepared from solutions containing 90 kD and 16 kD PVA resulted in intimate polymer mixtures, exhibiting physical properties that stand in between those of the bare 90 kD or 16 kD PVA end members. The freezing protocols employed were adapted to prepare carriers textured in the form of either monolithic scaffolds (directional constant freezing rate) or millimetric pellets (flash-freeze). Monolithic carriers remain stable in aqueous solution, and the probe release is governed by a swelling-diffusion mechanism. The kinetics of probe release can be tuned from minutes to hours by either increasing the total PVA content or the 90 kD-to-16 kD PVA ratio in the parent solution. In contrast, pellets (millimetric carriers) immersed in water release the probe on the scale of minutes, irrespective of the PVA content or composition. However, the PVA content and the 90 kD-to-16 kD PVA ratio dramatically affect the stability of the carriers. Depending on the formulation, these small carriers can develop swelling, erosion, or eventually massive dissolution.