Nanomaterials and synergistic low-intensity direct current (LIDC) stimulation technology for orthopedic implantable medical devices

Abstract

Nanomaterials play a significant role in biomedical research and applications because of their unique biological, mechanical, and electrical properties. In recent years, they have been utilized to improve the functionality and reliability of a wide range of implantable medical devices ranging from well-established orthopedic residual hardware devices (e.g., hip implants) that can repair defects in skeletal systems to emerging tissue engineering scaffolds that can repair or replace organ functions. This review summarizes the applications and efficacies of these nanomaterials that include synthetic or naturally occurring metals, polymers, ceramics, and composites in orthopedic implants, the largest market segment of implantable medical devices. The importance of synergistic engineering techniques that can augment or enhance the performance of nanomaterial applications in orthopedic implants is also discussed, the focus being on a low-intensity direct electric current (LIDC) stimulation technology to promote the long-term antibacterial efficacy of oligodynamic metal-based surfaces by ionization, while potentially accelerating tissue growth and osseointegration. While many nanomaterials have clearly demonstrated their ability to provide more effective implantable medical surfaces, further decisive investigations are necessary before they can translate into medically safe and commercially viable clinical applications. The article concludes with a discussion about some of the critical impending issues with the application of nanomaterials-based technologies in implantable medical devices, and potential directions to address these.

Figure 1

This chart shows the projection of the 2015 US Market (in USD) and examples of implantable medical devices. Orthopaedic implantable medical devices have the most significant market share (56%). Nanomaterials and synergistic engineering technologies have the potential to impact the unmet needs and shortcomings in this market.

Figure 2

Transmission electron micrographs of (a) Escherichia coli (J53), and (b) Staphylococcus aureus (ATCC 25213) exposed to 10µg/ml of 20nm washed silver nanoparticles. Bar=200nm. Arrows depict agglomerated silver nanoparticles.

Figure 3

(a) Concept of the prophylactic technology that uses low intensity direct electric current (LIDC) stimulation for the release of oligodynamic metal (e.g. silver) ions. The potential is created through the microbe rich environment, and the antimicrobial ions that are released disrupt the bacteria cells. To demonstrate its efficacy, Mueller-Hinton agar plates have been inoculated with MRSA and exposed to (b) silver electrodes, and (c) titanium electrodes, with 20µA system current. Note the clear zone of inhibition due to the antimicrobial silver ions that were released at the anode in (b). No such zone of inhibition was observed in case of LIDC stimulated titanium in (c).^,,

Figure 3

(a) Concept of the prophylactic technology that uses low intensity direct electric current (LIDC) stimulation for the release of oligodynamic metal (e.g. silver) ions. The potential is created through the microbe rich environment, and the antimicrobial ions that are released disrupt the bacteria cells. To demonstrate its efficacy, Mueller-Hinton agar plates have been inoculated with MRSA and exposed to (b) silver electrodes, and (c) titanium electrodes, with 20µA system current. Note the clear zone of inhibition due to the antimicrobial silver ions that were released at the anode in (b). No such zone of inhibition was observed in case of LIDC stimulated titanium in (c).^,,