Papers by Author: Thomas J. Webster

Abstract: Selenium (Se) nanoclusters were coated on three different orthopedic materials: Titanium, stainless steel and ultra high molecular weight polyethylene (UHMWPE). There different coating densities were achieved on each type of substrate. The uncoated and coated Ti and SS substrates were then used in experiments with either normal healthy osteoblasts (bone-forming cells) or cancerous osteoblasts (osteosarcoma) or a combination of both. For the first time, it was shown that the substrates coated with Se nanoclusters promoted (or at least maintained) normal osteoblast proliferation and inhibited cancerous osteoblast growth in both separate culture experiments and co-culture experiments. Thus, this study introduced to the orthopedic cancer community for the first time a coating material (Se) which may inhibit bone cancer growth and promote normal bone growth.

Abstract: Magnetic nanoparticles have been used extensively as drug delivery materials in recent years [1,2]. The present research goal is to treat bone diseases (such as osteoporosis and infection) by using surface modified magnetic nanoparticles. Magnetite (Fe3O4) and maghemite (Fe2O3) were synthesized and coated with calcium phosphate (CaP). The resulting nanoparticles were treated hydrothermally to change the crystalline properties of CaP. Nanoparticles were characterized via transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). TEM was also used to study the uptake of nanoparticles into osteoblasts (OB) and bacteria. OB proliferation experiments were conducted after 1, 3 and 5 days in the presence of the various iron oxide nanoparticles alone and CaP coated iron oxide magnetic nanoparticles. OB proliferation experiments were also conducted after 1, 3 and 5 days in the presence of various concentrations of CaP coated nanoparticles to examine a possible concentration dependent trend on OB density. Staph epidermidis were incubated with different doses of Fe3O4 to determine the effect of these nanoparticles on bacteria activity. Results of this in vitro study demonstrated greater OB functions and inhibited bacteria functions in the presence of select magnetic nanoparticles. In summary, the results of this study showed that magnetic nanoparticles should be further studied for various orthopedic applications.

Abstract: Implant infection leading to revision surgery can be avoided by incorporating controllable antibiotic release from titanium (Ti) implant surfaces. In this study, penicillin/streptomycin (P/S) and dexamethasone (Dex) were successfully immobilized via electropolymerization within polypyrrole membranes coated on the surface of Ti, which is widely used in orthopedic applications. In vitro results showed that greater numbers of osteoblasts adhered on these polymer-coated substrates than on currently-used unmodified Ti. X-ray photoelectron spectroscopy was used to monitor and compare the reaction effectiveness and the yield of electropolymerization. Polypyrrole membranes conjugated with P/S and Dex, and then coated with PLGA, all possessed nanometer scale roughness, as analyzed by atomic force microscopy. In summary, this study demonstrated that drugs incorporated within electroactive polypyrrole membranes, whose release was controlled by applying voltages, supported osteoblast adhesion and could potentially fight bacterial infection.

Abstract: Atherosclerosis, which is caused by endothelial dysfunction, vascular inflammation, and the build-up of lipids, cholesterol, calcium, and cellular debris within the intima of the vessel wall, is one of the most important complications of health. Vascular stenting is the procedure of implanting a thin tube into the site of a narrow or blocked artery due to atherosclerosis. However, the application of vascular stents using conventional metals is limited because the implantation process will cause significant injury to the vascular wall and endothelium, which functions as a protective biocompatible barrier between the tissue and the circulating blood, resulting in neointima hyperplasia followed by the development of long-term restenosis. The objective of this in vitro study was to investigate the endothelial cell function, especially their adhesion behaviour, on highly controllable features on nanostructured surface. Considering the importance of the endothelium and its properties, highly controllable nanostructured surface features of titanium, a popular vascular stent metal, were created using E-beam evaporation to promote endothelialization and to control the direction of endothelial cells on vascular stents. Endothelial cells are naturally aligned with the blood flow in the body. In this manner, the present in vitro study provides much promise for the use of nanotechnology for improving metallic materials for vascular stent applications.

Abstract: Superficial bladder cancer is often treated by removing the cancerous portion of the bladder wall combined with immuno-chemotherapy; in more extreme cases, it is often necessary to remove the entire bladder wall. This diagnosis brings an obvious need for bladder tissue replacement designs with a high degree of efficacy. Since bladder cells are accustomed to interacting with extracellular matrix proteins having dimensions on the nanometer scale, this study aimed to design the next generation of tissue-engineered bladder replacement constructs with nanometer (less than 100 nm) surface features. For this purpose, porous and biodegradable PLGA and PU scaffolds were treated with various concentrations of NaOH or HNO3, respectively, for various periods of time to create nanometer surface roughness. Resulting surface properties were characterized using SEM (to visualize scaffold properties) and BET. Cell experiments conducted on these polymeric scaffolds provided evidence of enhanced bladder smooth muscle cell attachment, growth, and elastin/collagen production (critical extracellular matrix proteins in the bladder tissue regeneration process) as surface feature dimensions were reduced into the nanometer regime. In vivo augmentation surgeries with nano-structured PLGA and PU patches will provide further information regarding total bladder capacity, anastomotic integrity, burst pressure, epithelialization, muscular ingrowth, and neovascularization. In vitro and in vivo proof of material usefulness and technique would provide urologists with a readily accessible graft for bladder tissue replacement applications.

Abstract: Nanotechnology is being used to mimic structural components of our tissues in synthetic materials intended for various implant applications. Recent studies have highlighted that when compared to flat or micron rough surfaces, surfaces with nanofeatures promote optimal initial protein interactions necessary to mediate cell adhesion and subsequent tissue regrowth. This has been demonstrated for a wide range of implant chemistries (from ceramics to metals to polymers) and for a wide range of tissues (including bone, vascular, cartilage, bladder, and the central and peripheral nervous system). Importantly, these results have been seen at the in vitro and in vivo level. This short review paper will cover some of the more significant advancements in creating better implants through nanotechnology efforts.

Abstract: Nanotechnology is defined as the use of materials with at least one dimension less than 100 nm. Although nanotechnology has revolutionized many fields to date, it use in medical applications remains at it infancy. This manuscript describes recent promising studies made towards increasing tissue regeneration through the use of nano compared to conventional materials.

Abstract: Success in surgical joint replacements has resulted in a huge demand amongst patients. Coupled with the lowered average age of patients requiring hip replacements, younger patients are demanding longer life expectancy from such devices. The increasing need and demand for more durable implants have led to new formulations of high performance nanomaterials (materials with basic structural units of 1-100 nm). Nanotubes in particular have shown great promise because they: 1) have sizes that approach biological structures and 2) possess efficient channels for displaying chemistries relevant to living systems at high densities and well-controlled spatial distribution. Helical rosette nanotubes (HRN) are a new class of soft organic nanomaterials composed of a guanine-cytosine building block that self-assembles in aqueous environments into stable nanotubular structures with an inner diameter of ~1.1 nm. HRN can be decorated with biologically active chemical functionalities such as cell attracting peptide fragments. Previously, we have showed that HRN coated Ti can enhance OB attachment. In addition, proteins were seen to interact favorably with HRN networks in a manner favorable toward OB attachment. Furthermore, in the absence of proteins, HRN were seen to play the role of proteins in promoting OB attachment. The studies herein, attempt to understand the role of the lysine clusters on HRN toward OB attachment. Results show that OB do respond to lysine and molecular orientation considerations were shown to be important. Detailed structural considerations from molecular modeling further present the possibility of topographical influences (nanotube network architecture) towards OB attachment.