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New ways of providing assistive care to fractures and damaged tissues are key areas in nanomedicine and tissue engineering. There is a wide class of materials known as bio-ceramics, which are excellent materials for many types of reconstructive and regenerative medicine. In this article, we look at what they are and some of the application areas where they are used.
What Are Bio-Ceramics
Bio-ceramics are a class of materials composed of biocompatible ceramics and bioglasses, with some of the most common bio-ceramics being calcium phosphate, hydroxyapatite, polymer composites, bioactive glasses, zirconia, titania and alumina. The materials in this class range are often harder in structure but can either be densely packed or porous depending on the required application. It should be noted that the ceramic-like materials bear no resemble to porcelain-type ceramics, rather, they are materials that mimic the body’s own biomaterials (or are durable metal oxide materials).
Applications of Bio-Ceramics
Many of the applications are in assistive repair, so there are certain characteristics that bio-ceramic materials need to exhibit for them to be used in clinical applications. The most important is biocompatibility, so that they can help to prevent the body’s natural defence system from breaking them down and they are not toxic to the cellular environment when they are used.
Other properties include a high wear resistance which utilizes a materials high hardness and a lack of plastic and elastic deformation under a load, a low friction coefficient, a high compressional strength, a high fatigue resistance, high biological and chemical corrosion resistance, high electrical insulating properties to prevent galvanic reactions from occurring and the ability to synthesize a highly pure material.
Scaffolds that can help to proliferate cells in a target area to regrow tissues, and then biodegrade so that they can be excreted, is one of the current trends in the field of tissue engineering. Scaffolds of this type have been created from various materials, including calcium phosphate and polymer composites, to help with the growth of both tissue and bone cells. In general, it is the porous bio-materials that are used for scaffold related applications.
These scaffold applications can be twofold, in-vivo and in-vitro. In-vivo applications generally involve delivering the scaffold to a target area of interest within the body, whereupon the cells can grow in a controlled manner at the direct point of affliction. These approaches often involve loading the scaffold with stem cells (or the specific cell type), whereupon they proliferate and attach to the native tissue. When the scaffold has done its job, it will degrade and be excreted by the body.
By comparison, in-vitro scaffolds are an external cell proliferation approach. Scientist will grow a large culture of cells outside of the body and direct the growth in two ways – either from a small amount of stem cells to a larger amount of stem cells, or by increasing the growth and controlling the types of cell formed, so that they can be used in a specific area. The cell cultures can then be introduced to a patient.
Bone Regeneration and Reconstruction
A wide range of materials can be employed in bone regeneration and reconstruction approaches, depending on the bone in question and the level of damage. To date, alumina, metal bioglass, bioglass-metal fiber composites, polymer-carbon fibre composites, calcium phosphate and hydroxy apatite have been used in these approaches.
These materials have been used for a wide range of functions, including as both dense materials for direct implants and reconstruction materials (plates etc) and as porous materials to help the native bone cells to regrow naturally.
As a class of materials, bio-ceramics can be used in reconstructive approaches as a total artificial replacement for the hip, knee, shoulder, elbow and wrist, as bone plates, bone screws and bone wires, as intramedullary nails to repair fractures, Harrington rods to correct spinal curvature, vertebrae spacers and extensors to correct congenital deformity, as a way a fusing the spine to protect the spinal cord, alveolar bone replacements, mandibular reconstruction, dental implants to replace damaged, removed or decaying teeth and as orthodontic anchors.
On the more regenerative side, hydroxy apatite can be used to create biomimetic films that help with bone growth. Hydroxy apatite can be stabilized and functionalized with a wide range of groups that provide a biomimetic control to mimic bodily fluids and make them highly biocompatible. These films can then be loaded and introduced at early stages of bone calcification to help with the proliferation of bone cells (osteoblasts).
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