David A. Stout

Poly(lactic-co-glycolic acid): carbon nanofiber composites for myocardial tissue engineering applications.

The objective of the present in vitro research was to investigate cardiac tissue cell functions (specifically cardiomyocytes and neurons) on poly(lactic-co-glycolic acid) (PLGA) (50:50 wt.%)-carbon nanofiber (CNF) composites to ascertain their potential for myocardial tissue engineering applications. CNF were added to biodegradable PLGA to increase the conductivity and cytocompatibility of pure PLGA. For this reason, different PLGA:CNF ratios (100:0, 75:25, 50:50, 25:75, and 0:100 wt.%) were used and the conductivity as well as cytocompatibility of cardiomyocytes and neurons were assessed. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy analysis characterized the microstructure, chemistry, and crystallinity of the materials of interest to this study. The results show that PLGA:CNF materials are conductive and that the conductivity increases as greater amounts of CNF are added to PLGA, from 0 S m(-1) for pure PLGA (100:0 wt.%) to 5.5×10(-3) S m(-1) for pure CNF (0:100 wt.%). The results also indicate that cardiomyocyte density increases with greater amounts of CNF in PLGA (up to 25:75 wt.% PLGA:CNF) for up to 5 days. For neurons a similar trend to cardiomyocytes was observed, indicating that these conductive materials promoted the adhesion and proliferation of two cell types important for myocardial tissue engineering applications. This study thus provides, for the first time, an alternative conductive scaffold using nanotechnology which should be further explored for cardiovascular applications.

Novel injectable biomimetic hydrogels with carbon nanofibers and self assembled rosette nanotubes for myocardial applications

The objective of the present in vitro study was to investigate cardiomyocyte functions, specifically their adhesion and proliferation, on injectable scaffolds containing RNT (rosette nanotubes) and CNF (carbon nanofibers) in a pHEMA (poly(2-hydroxyethyl methacrylate)) hydrogel to determine their potential for myocardial tissue engineering applications. RNTs are novel biocompatible nanomaterials assembled from synthetic analogs of DNA bases guanine and cytosine that self-assemble within minutes when placed in aqueous solutions at body temperatures. These materials could potentially improve cardiomyocyte functions and solidification time of pHEMA and CNF composites. Because heart tissue is conductive, CNFs were added to pHEMA to increase the composites conductivity. Our results showed that cardiomyocyte density increased after 4 h, 1 day, and 3 days with greater amounts of CNFs and greater amounts of RNTs in pHEMA (up to 10 mg mL(-1) CNFs and 0.05 mg mL(-1) RNTs). Factors that may have increased cardiomyocyte functions include greater wettability, conductivity, and an increase in surface nanoroughness with greater amounts of CNFs and RNTs. In effect, contact angles measured on the surface of the composites decreased while the conductivity and surface roughness increased as CNFs and RNTs content increased. Lastly, the ultimate tensile modulus decreased for composites with greater amounts of CNFs. In summary, the properties of these injectable composites make them promising candidates for myocardial tissue engineering applications and should be further studied.

Carbon nanotubes for stem cell control

In the past decade, two major advancements have transformed the world of tissue engineering and regenerative medicine—stem cells and carbon nano-dimensional materials. In the past, stem cell therapy seemed like it may present a cure for all medical ailments, but problems arose (i.e., immune system clearance, control of differentiation in the body, etc.) that have hindered progress. But, with the synergy of carbon nano-dimensional materials, researchers have been able to overcome these tissue engineering and regenerative medicine obstacles and have begun developing treatments for strokes, bone failure, cardiovascular disease, and many other conditions. Here, we briefly review research involving carbon nanotubes which are relevant to the tissue engineering and regenerative medicine field with a special emphasis on carbon nanotube applications for stem cell delivery, drug delivery applications, and their use as improved medical devices.

Understanding osteoblast responses to stiff nanotopographies through experiments and computational simulations

An increasing number of studies have demonstrated the positive role nanotopographies can have toward promoting various cell functions. However, the relevant mechanism(s) behind this improvement in biological interactions at the cell-material interface is not well understood. For this reason, here, osteoblast (bone forming cell) functions (including adhesion, proliferation, and differentiation) on two carefully-fabricated diamond films with dramatically-different topographies were tested and modeled. The results over all the time periods tested revealed greater cell responses on nanocrystalline diamond (NCD, grain sizes <100 nm) compared to submicron crystalline diamond (SMCD, grain sizes 200-1000 nm). To understand this positive impact of cell responses per stiff nanotopographies, cell filopodia extension and cell spreading were studied through computational simulations and the results suggested that increasing the lateral dimensions or height of nanometer surface features could inhibit cell filopodia extension and, ultimately, decrease cell spreading. The computational simulation results were further verified by live cell imaging (LCI) experiments. This study, thus, describes a possible new approach to investigate (through experiments and computational simulation) the mechanisms behind nanotopography-enhanced cell functions.

Antibacterial properties and toxicity from metallic nanomaterials

The era of antibiotic resistance is a cause of increasing concern as bacteria continue to develop adaptive countermeasures against current antibiotics at an alarming rate. In recent years, studies have reported nanoparticles as a promising alternative to antibacterial reagents because of their exhibited antibacterial activity in several biomedical applications, including drug and gene delivery, tissue engineering, and imaging. Moreover, nanomaterial research has led to reports of a possible relationship between the morphological characteristics of a nanomaterial and the magnitude of its delivered toxicity. However, conventional synthesis of nanoparticles requires harsh chemicals and costly energy consumption. Additionally, the exact relationship between toxicity and morphology of nanomaterials has not been well established. Here, we review the recent advancements in synthesis techniques for silver, gold, copper, titanium, zinc oxide, and magnesium oxide nanomaterials and composites, with a focus on the toxicity exhibited by nanomaterials of multidimensions. This article highlights the benefits of selecting each material or metal-based composite for certain applications while also addressing possible setbacks and the toxic effects of the nanomaterials on the environment.

Nano-BaSO4: a novel antimicrobial additive to pellethane.

Hospital-acquired infections remain a costly clinical problem. Barium sulfate (BaSO4, in micron particulate form) is a common radiopacifying agent that is added to catheters and endotracheal tubes. Due to the recently observed ability of nanostructured surface features to decrease functions of bacteria without the aid of antibiotics, the objective of this in vitro study was to incorporate nano-barium sulfate into pellethane and determine the antimicrobial properties of the resulting composites. The results demonstrated for the first time that the incorporation of nano-barium sulfate into pellethane enhanced antimicrobial properties (using Staphylococcus aureus and Pseudomonas aeruginosa) compared to currently used pellethane; properties that warrant further investigation for a wide range of clinical applications.

Growth characteristics of different heart cells on novel nanopatch substrate during electrical stimulation

During a heart attack, the hearts oxygen supply is cut off, and cardiomyocytes perish. Unfortunately, once these tissues are lost, they cannot be replaced and results in cardiovascular disease-the leading cause of deaths worldwide. Advancements in medical research have been targeted to understand and combat the death of these cardiomyocytes. For example, new research (in vitro) has demonstrated that one can expand cardiomyocyte adhesion and proliferation using polylactic-co-glycolic acid (PLGA) (50:50 (weight percent)) supplemented with carbon nanofibers (CNFs) to create a cardiovascular patch. However, the examination of other cardiovascular cell types has not been investigated. Therefore, the purpose of this present in vitro study was to determine cell growth characteristics of three different important cardiovascular cell types (aortic endothelial, fibroblast and cardiomyocyte) onto the substrate. Cells were seeded onto different PLGA:CNF ratio composites to determine if CNF density has an effect on cell growth, both in static and electrically stimulated environments. During continuous electrical stimulation (rectangle, 2 nm, 5 V/cm, 1 Hz), cardiomyocyte cell density increased in comparison to its static counterparts after 24, 72 and 120 hours. A minor rise in Troponin I excretion in electrical stimulation compared to static conditions indicated nominal cardiomyocyte cell function during cell experiments. Endothelial and fibroblast cell growth experiments indicated the material hindered or stalled proliferation during both static and electrical stimulation experiments, thus supporting the growth of cardiomyocytes onto the dead tissue zone. Furthermore, the results specified that CNF density did have an effect on PLGA:CNF composite cytocompatibility properties with the best results coming from the 50:50 [PLGA:CNF (weight percent:weight percent)] composite. Therefore, this study provides further evidence that a conductive scaffold using nanotechnology should be further research for various cardiovascular applications.

EXPERIMENTAL METHODS AND IN VITRO CYTOXICITY AND GENOTOXICITY OF NANOMATERIALS

Exposure to nanosized materials (specifically, materials with one dimension less than 100 nm) is nothing new. Humans have long been exposed to nanomaterials from various earth related processes, like forest fires and volcanoes, as well as naturally occurring events, such as sea spray. Due to the advent of modern nanotechnology research, however, the arrival of the industrial nanotechnology age is upon us where large quantities of various synthetic nanomaterials are formulated and exposed to humans on a daily basis. As such, there is an on-going need for more researchers to determine human and environmental toxicity of nanomaterials. This review paper will assess the current knowledge on the in vitro cytotoxicity and genotoxicity of nanomaterials while summarizing the exploration of nanotechnology within the specific world of biomaterials. An overview of material characterization studies as well as various biological assays currently used to evaluate cytotoxicity and genotoxicity will also be addressed. Specifically, after defining some basic definitions of biomaterials and biocompatibility, commonly used cytotoxicity assays are summarized, and some examples of nanomaterial cytotoxicity studies presented. Next, an understanding of genotoxicity assays and associated mechanisms with nanomaterials are presented. Finally, some future thoughts on nanobiomaterial (that is, nanomaterials used as biomaterials) cytotoxicity and genotoxicity are presented. Such an overview reflects a comprehensive effort to gain an understanding of the toxicity of nanobiomaterials at the molecular level requiring the use of a battery of toxicological assays. The purpose of this review article is to serve as reference for those new to the field of nanotoxicity and to encourage others to conduct accurate and meaningful nanotoxicity studies.

Nanomaterials for Spinal Cord Injury Recovery

Nanotechnology and nanomaterials have had a significant positive impact within the biomedical field for quite some time, and have included cardiovascular, cartilage, and neural tissue engineering applications. Due to its potential for treating neural tissue, current research is investigating the use of nanomaterials for spinal cord injury (SCI), an injury characterized by tissue damage and the disruption of communication between the brain to the body. To treat such an injury, cell-based therapy has shown promising results, and the following papers are recommended. This communication will focus on nanoparticle, carbon nanotubes, and self-assembling peptide approaches for treating SCI, as well as concerns of toxicity.

Nanophase magnesium for orthopedic applications

Magnesium has gained interest as a biomaterial for orthopedic applications because of its biocompatibility, biodegradability, and positive effect on bone formation. Likewise, studies have shown nanophase material increase osteoblast (bone-forming cell) function compared to conventional materials, but the two have not been studied together. The purpose of this study was to determine if altering magnesium surface features into the nanometer scale promotes greater osteoblast functions. Nanorough magnesium surfaces were created by a novel treatment with sodium hydroxide at 1N, 5N, and 10N concentrations for 10, 20, and 30 minutes. Material characterization by scanning electron microscopy showed increased roughness on all treated samples compared to the control magnesium. Contact angle measurements indicated greater hydrophilicity on treated magnesium and no significant effect of ultraviolet sterilization on the surface energy of the material. Osteoblasts were seeded onto treated and untreated surfaces and adhesion at 4hrs were assessed through the MTT assay. Results indicated increased osteoblast adhesion on nano-treated samples compared to untreated samples. These findings support previous studies indicating the promise of magnesium as a biomaterial for orthopedic applications and suggest further experiments examining the long-term effects of nanophase magnesium on osteoblast proliferation and function.