Phong A. Tran

Carbon nanofibers and carbon nanotubes in regenerative medicine

Carbon nanotubes and carbon nanofibers have long been investigated for applications in composite structural materials, semiconductor devices, and sensors. With the recent well-documented ability to chemically modify nanofibrous carbon materials to improve their solubility and biocompatibility properties: a whole new class of bioactive carbon nanostructures has been created for biological applications. This review focuses on the latest applications of carbon nanofibers and carbon nanotubes in regenerative medicine.

Selenium nanoparticles inhibit Staphylococcus aureus growth

Staphylococcus aureus is a key bacterium commonly found in numerous infections. S. aureus infections are difficult to treat due to their biofilm formation and documented antibiotic resistance. While selenium has been used for a wide range of applications including anticancer applications, the effects of selenium nanoparticles on microorganisms remain largely unknown to date. The objective of this in vitro study was thus to examine the growth of S. aureus in the presence of selenium nanoparticles. Results of this study provided the first evidence of strongly inhibited growth of S. aureus in the presence of selenium nanoparticles after 3, 4, and 5 hours at 7.8, 15.5, and 31 μg/mL. The percentage of live bacteria also decreased in the presence of selenium nanoparticles. Therefore, this study suggests that selenium nanoparticles may be used to effectively prevent and treat S. aureus infections and thus should be further studied for such applications.

Recent advances in research applications of nanophase hydroxyapatite.

Hydroxyapatite, the main inorganic material in natural bone, has been used widely for orthopaedic applications. Due to size effects and surface phenomena at the nanoscale, nanophase hydroxyapatite possesses unique properties compared to its bulk-phase counterpart. The high surface-to-volume ratio, reactivities, and biomimetic morphologies make nano-hydroxyapatite more favourable in applications such as orthopaedic implant coating or bone substitute filler. Recently, more efforts have been focused on the possibility of combining hydroxyapatite with other drugs and materials for multipurpose applications, such as antimicrobial treatments, osteoporosis treatments and magnetic manipulation. To build more effective nano-hydroxyapatite and composite systems, the particle synthesis processes, chemistry, and toxicity have to be thoroughly investigated. In this Minireview, we report the recent advances in research regarding nano-hydroxyapatite. Synthesis routes and a wide range of applications of hydroxyapatite nanoparticles will be discussed. The Minireview also addresses several challenges concerning the biosafety of the nanoparticles.

Opportunities for nanotechnology-enabled bioactive bone implants

Until recently, traditional orthopedic implant materials termed “bioactive” have been engineered to actively promote integration with living bone. We propose to look beyond this traditional form of bioactivity (specifically for orthopedics, in which bioactivity refers to osseointegration), and introduce the use of nanoscale surface features, fabricated using various nanotechnology tools, to provide extended functionality to implants and thus create a new class of “smarter” bioactive implant materials.

Antimicrobial selenium nanoparticle coatings on polymeric medical devices

Bacteria colonization on medical devices remains one of the most serious complications following implantation. Traditional antibiotic treatment has proven ineffective, creating an increasingly high number of drug-resistant bacteria. Polymeric medical devices represent a significant portion of the total medical devices used today due to their excellent mechanical properties (such as durability, flexibility, etc). However, many polymers (such as polyvinyl chloride (PVC), polyurethane (PU) and silicone) become readily colonized and infected by bacteria immediately after use. Therefore, in this study, a novel antimicrobial coating was developed to inhibit bacterial growth on PVC, PU and silicone. Specifically, here, the aforementioned polymeric substrates were coated with selenium (Se) nanoparticles in situ. The Se-coated substrates were characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy and bacteria assays. Most importantly, bacterial growth was significantly inhibited on the Se-coated substrates compared to their uncoated counterparts. The reduction of bacteria growth directly correlated with the density of Se nanoparticles on the coated substrate surfaces. In summary, these results demonstrate that Se should be further studied as a novel anti-bacterial polymeric coating material which can decrease bacteria functions without the use of antibiotics.

Nanomaterial‐Based Treatments for Medical Device‐Associated Infections

Bacterial infections remain one of the biggest concerns to our society. Conventional antibiotic treatments showed little effect on the increasing number of antibiotic-resistant bacteria. Advances in synthetic chemistry and nanotechnology have resulted in a new class of nanometer-scale materials with distinguished properties and great potential to be an alternative for antibiotics. In this Minireview, we address the current situation of medical-device-associated infections and the emerging opportunities for antibacterial nanomaterials in preventing these complications. Several important antimicrobial nanomaterials emergent from advances in synthesis chemistry are introduced and their bactericidal mechanisms are analyzed. In addition, concerns regarding the biocompatibility of such materials are also addressed.

Metal-on-Metal Hip Arthroplasty: A Review of Adverse Reactions and Patient Management.

Recent alarming joint registry data highlighting increased revision rates has prompted further research into the area of metal-on-metal hip replacements and resurfacings. This review article examines the latest literature on the topic of adverse reactions to metal debris and summarises the most up-to-date guidelines on patient management. Adverse reactions to metal debris can cause significant damage to soft tissue and bone if not diagnosed early. Furthermore, not every patient with an adverse reaction to metal debris will be symptomatic. As such, clinicians must remain vigilant when assessing and investigating these patients in order to detect failing implants and initiate appropriate management.

Differential effects of nanoselenium doping on healthy and cancerous osteoblasts in coculture on titanium

In the present study, selenium (Se) nanoclusters were grown through heterogeneous nucleation on titanium (Ti) surfaces, a common orthopedic implant material. Normal healthy osteoblasts (bone-forming cells) and cancerous osteoblasts (osteosarcoma) were cultured on the Se-doped surfaces having three different coating densities. For the first time, it is shown that substrates with Se nanoclusters promote normal osteoblast proliferation and inhibit cancerous osteoblast growth in both separate (mono-culture) and coculture experiment. This study suggests that Se surface nanoclusters can be properly engineered to inhibit bone cancer growth while simultaneously promoting the growth of normal bone tissue.

Enhanced osteoblast adhesion on nanostructured selenium compacts for anti-cancer orthopedic applications

Metallic bone implants possess numerous problems limiting their long-term efficacy, such as poor prolonged osseointegration, stress shielding, and corrosion under in vivo environments. Such problems are compounded for bone cancer patients since numerous patients receive orthopedic implants after cancerous bone resection. Unfortunately, current orthopedic materials were not originally developed to simultaneously increase healthy bone growth (as in traditional orthopedic implant applications) while inhibiting cancerous bone growth. The long-term objective of the present research is to investigate the use of nano-rough selenium to prevent bone cancer from re-occurring while promoting healthy bone growth for this select group of cancer patients. Selenium is a well known anti-cancer chemical. However, what is not known is how healthy bone cells interact with selenium. To determine this, selenium, spherical or semispherical shots, were pressed into cylindrical compacts and these compacts were then etched using 1N NaOH to obtain various surface structures ranging from the micron, submicron to nano scales. Changes in surface chemistry were also analyzed. Through these etching techniques, results of this study showed that biologically inspired surface roughness values were created on selenium compacts to match that of natural bone roughness. Moreover, results showed that healthy bone cell adhesion increased with greater nanometer selenium roughness (more closely matching that of titanium). In this manner, this study suggests that nano-rough selenium should be further tested for orthopedic applications involving bone cancer treatment.

In situ formation of antimicrobial silver nanoparticles and the impregnation of hydrophobic polycaprolactone matrix for antimicrobial medical device applications

Bacterial infection associated with medical devices remains a challenge to modern medicine as more patients are being implanted with medical devices that provide surfaces and environment for bacteria colonization. In particular, bacteria are commonly found to adhere more preferably to hydrophobic materials and many of which are used to make medical devices. Bacteria are also becoming increasingly resistant to common antibiotic treatments as a result of misuse and abuse of antibiotics. There is an urgent need to find alternatives to antibiotics in the prevention and treatment of device-associated infections world-wide. Silver nanoparticles have emerged as a promising non-drug antimicrobial agent which has shown effectiveness against a wide range of both Gram-negative and Gram-positive pathogen. However, for silver nanoparticles to be clinically useful, they must be properly incorporated into medical device materials whose wetting properties could be detrimental to not only the incorporation of the hydrophilic Ag nanoparticles but also the release of active Ag ions. This study aimed at impregnating the hydrophobic polycaprolactone (PCL) polymer, which is a FDA-approved polymeric medical device material, with hydrophilic silver nanoparticles. Furthermore, a novel approach was employed to uniformly, incorporate silver nanoparticles into the PCL matrix in situ and to improve the release of Ag ions from the matrix so as to enhance antimicrobial efficacy.