Ganesan Balasundaram

A perspective on nanophase materials for orthopedic implant applications

In the past, synthetic conventional materials have not served as satisfactory implants. As an example, the current average lifetime of an orthopedic implant (such as hip, knee, ankle, etc.) is only 10 to 15 years. Clearly, such conventional materials (or those materials with constituent dimensions greater than 1 micron) have not invoked suitable cellular responses to regenerate enough bone to allow these devices to be successful for long periods of time. In contrast, due to their ability to mimic the dimensions of constituent components of natural bone (like proteins and hydroxyapatite), nanophase materials may be an exciting successful alternative orthopedic implant material. Nanophase materials are defined as materials with constituent dimensions (and/or associated surface features) less than 100 nm in at least one direction. This review article discusses recent studies that have been conducted to determine the efficacy of nanophase materials as orthopedic implants. In doing so, compared with conventional orthopedic implant materials, it is suggested that nanophase materials can be synthesized to possess similar nanometer dimensions as components of natural bone to promote new bone formation; a criterion critical to orthopedic implant success.

Nanotechnology and biomaterials for orthopedic medical applications

Future prospects for nanotechnology and biomaterials in medical applications appear to be excellent. In orthopedic applications, there is a significant need and demand for the development of a bone substitute that is bioactive and exhibits material properties (mechanical and surface) comparable with those of natural, healthy bone. Particularly, in bone tissue engineering, nanometer-sized ceramics, polymers, metals and composites have been receiving much attention recently. This is a result of current conventional materials (or those materials with constituent dimensions >1 microm) that have not invoked suitable cellular responses to promote adequate osteointegration to enable these devices to be successful for long periods. By contrast, owing to their ability to mimic the dimensions of constituent components of natural bone (e.g., proteins and hydroxyapatite), nanophase materials may be an exciting successful alternative orthopedic implant material. In this article, the ability of novel nanomaterials that promote osteointegration is discussed. Potential pitfalls or undesirable side effects associated with the use of nanomaterials in orthopedic applications are also reviewed.

Molecular plasma deposited peptides on anodized nanotubular titanium: An osteoblast density study

A large amount of work is currently being conducted to design, fabricate, and characterize materials coated or immobilized with bioactive molecules for tissue engineering applications. Here, a novel method, molecular plasma deposition (MPD), is introduced with can efficiently coat materials with numerous bioactive peptides. Specifically, here, RGDS (arginine-glycine-aspartic acid-serine), KRSR (lysine-arginine-serine-arginine), and IKVAV (isoleucine-lysine-valine-alanine-valine) were coated on anodized nanotubular titanium using MPD. The anodized nanotubular titanium surfaces were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle measurements. Peptide coatings were examined by X-ray photoelectron spectroscopy (XPS) and an amine reactive fluorescence molecule, 3-(4 carboxybenzoyl)quinoline 2-carboxaldehyde (CBQCA). Electrospray ionization (ESI) was used to confirm peptide integrity. Osteoblast (bone-forming cell) density was determined on the materials of interest. Results confirmed peptide coatings and showed that the MPD RGDS and KRSR coatings on anodized nanotubular titanium increased osteoblast density compared with uncoated substrates and those coated with IKVAV and a control peptide (RGES) after 4 h and 7 days. SEM confirmed differences in the morphology of the attached cells. These results, to the best of our knowledge, are the first reports using MPD to efficiently create peptide coatings to increase osteoblast density on metals commonly used in orthopedics. Since MPD represents a quick, inexpensive, and versatile technique to coat implants with peptides, it should be further studied for numerous implant applications.

Molecular plasma deposition: biologically inspired nanohydroxyapatite coatings on anodized nanotubular titanium for improving osteoblast density

In order to begin to prepare a novel orthopedic implant that mimics the natural bone environment, the objective of this in vitro study was to synthesize nanocrystalline hydroxyapatite (NHA) and coat it on titanium (Ti) using molecular plasma deposition (MPD). NHA was synthesized through a wet chemical process followed by a hydrothermal treatment. NHA and micron sized hydroxyapatite (MHA) were prepared by processing NHA coatings at 500°C and 900°C, respectively. The coatings were characterized before and after sintering using scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The results revealed that the post-MPD heat treatment of up to 500°C effectively restored the structural and topographical integrity of NHA. In order to determine the in vitro biological responses of the MPD-coated surfaces, the attachment and spreading of osteoblasts (bone-forming cells) on the uncoated, NHA-coated, and MHA-coated anodized Ti were investigated. Most importantly, the NHA-coated substrates supported a larger number of adherent cells than the MHA-coated and uncoated substrates. The morphology of these cells was assessed by scanning electron microscopy and the observed shapes were different for each substrate type. The present results are the first reports using MPD in the framework of hydroxyapatite coatings on Ti to enhance osteoblast responses and encourage further studies on MPD-based hydroxyapatite coatings on Ti for improved orthopedic applications.