Validation of an in vitro model of erbB2(+) cancer cell redirection.

Overexpression of the oncoprotein erbB2/HER2 is present in 20-30% of breast cancer patients and inversely correlates with patient survival. Reports have demonstrated the deterministic power of the mammary microenvironment where the normal mammary microenvironment redirects cells of non-mammary origin or tumor-derived cells to adopt a mammary phenotype in an in vivo model. This phenomenon is termed tumor cell redirection.

Parameterization of an interfacial force field for accurate representation of peptide adsorption free energy on high-density polyethylene.

Interfacial force field (IFF) parameters for use with the CHARMM force field have been developed for interactions between peptides and high-density polyethylene (HDPE). Parameterization of the IFF was performed to achieve agreement between experimental and calculated adsorption free energies of small TGTG-X-GTGT host-guest peptides (T = threonine, G = glycine, and X = variable amino-acid residue) on HDPE, with ±0.5 kcal/mol agreement.

Experimental characterization of adsorbed protein orientation, conformation, and bioactivity.

Protein adsorption on material surfaces is a common phenomenon that is of critical importance in many biotechnological applications. The structure and function of adsorbed proteins are tightly interrelated and play a key role in the communication and interaction of the adsorbed proteins with the surrounding environment. Because the bioactive state of a protein on a surface is a function of the orientation, conformation, and accessibility of its bioactive site(s), the isolated determination of just one or two of these factors will typically not be sufficient to understand the structure-function relationships of the adsorbed layer.

Tetronic(®)-based composite hydrogel scaffolds seeded with rat bladder smooth muscle cells for urinary bladder tissue engineering applications.

Natural hydrogels such as collagen offer desirable properties for tissue engineering, including cell adhesion sites, but their low mechanical strength is not suitable for bladder tissue regeneration. In contrast, synthetic hydrogels such as poly (ethylene glycol) allow tuning of mechanical properties, but do not elicit protein adsorption or cell adhesion. For this reason, we explored the use of composite hydrogel blends composed of Tetronic (BASF) 1107-acrylate (T1107A) in combination with extracellular matrix moieties collagen and hyaluronic acid seeded with bladder smooth muscle cells (BSMC).

Manipulation of cellular spheroid composition and the effects on vascular tissue fusion.

Cellular spheroids were investigated as tissue-engineered building blocks that can be fused to form functional tissue constructs. While spheroids can be assembled using passive contacts for the fusion of complex tissues, physical forces can be used to promote active contacts to improve tissue homogeneity and accelerate tissue fusion. Understanding the mechanisms affecting the fusion of spheroids is critical to fabricating tissues.

Adsorption-induced changes in ribonuclease A structure and enzymatic activity on solid surfaces.

Ribonuclease A (RNase A) is a small globular enzyme that lyses RNA. The remarkable solution stability of its structure and enzymatic activity has led to its investigation to develop a new class of drugs for cancer chemotherapeutics. However, the successful clinical application of RNase A has been reported to be limited by insufficient stability and loss of enzymatic activity when it was coupled with a biomaterial carrier for drug delivery.

Total knee arthroplasty designed to accommodate the presence or absence of the posterior cruciate ligament.

Evidence for selecting the same total knee arthroplasty prosthesis whether the posterior cruciate ligament (PCL) is retained or resected is rarely documented. This study reports prospective midterm clinical, radiographic, and functional outcomes of a fixed-bearing design implanted using two different surgical techniques. The PCL was completely retained in 116 knees and completely resected in 43 knees.

Protein helical structure determination using CD spectroscopy for solutions with strong background absorbance from 190 to 230nm.

Conventional empirical methods for the quantification of the helical content of proteins in solution using circular dichroism (CD) primarily rely on spectral data acquired between wavelengths of 190 and 230nm. The presence of chemical species in a protein solution with strong absorbance within this range can interfere with the ability to use these methods for the determination of the protein's helical structure. The objective of this research was to overcome this problem by developing a method for CD spectral analysis that relies on spectral features above this wavelength range.

Validation of a model-based measurement of the minimum insert thickness of knee prostheses: a retrieval study.

Introduction: Wear of polyethylene inserts plays an important role in failure of total knee replacement and can be monitored in vivo by measuring the minimum joint space width in anteroposterior radiographs. The objective of this retrospective cross-sectional study was to compare the accuracy and precision of a new model-based method with the conventional method by analysing the difference between the minimum joint space width measurements and the actual thickness of retrieved polyethylene tibial inserts.

Method: Before revision, the minimum joint space width values and their locations on the insert were measured in 15 fully weight-bearing radiographs.

The Langmuir isotherm: a commonly applied but misleading approach for the analysis of protein adsorption behavior.

The Langmuir adsorption isotherm provides one of the simplest and most direct methods to quantify an adsorption process. Because isotherm data from protein adsorption studies often appear to be fit well by the Langmuir isotherm model, estimates of protein binding affinity have often been made from its use despite that fact that none of the conditions required for a Langmuir adsorption process may be satisfied for this type of application. The physical events that cause protein adsorption isotherms to often provide a Langmuir-shaped isotherm can be explained as being due to changes in adsorption-induced spreading, reorientation, clustering, and aggregation of the protein on a surface as a function of solution concentration in contrast to being due to a dynamic equilibrium adsorption process, which is required for Langmuir adsorption.

Clinical Outcomes of Tibial Components with Modular Stems Used in Primary TKA.

Due to the known potential for fretting and corrosion at modular junctions in orthopaedic implants, this retrospective study evaluated radiographic and clinical outcomes of 85 primary TKA patients implanted with modular stemmed tibial components and followed up for an average of 82 months. There was low incidence of tibial radiolucent lines, excellent functional outcomes, and no complications associated with stem modularity. The findings were comparable to the historical control study involving 107 TKA with a nonmodular tibial stem design.

Development and initial characterization of a chemically stabilized elastin-glycosaminoglycan-collagen composite shape-memory hydrogel for nucleus pulposus regeneration.

Nucleus pulposus (NP) is a resilient and hydrophilic tissue which plays a significant role in the biomechanical function of the intervertebral disc (IVD). Destruction of the NP extracellular matrix (ECM) is observed during the early stages of IVD degeneration. Herein, we describe the development and initial characterization of a novel biomaterial which attempts to recreate the resilient and hydrophilic nature of the NP via the construction of a chemically stabilized elastin-glycosaminoglycan-collagen (EGC) composite hydrogel.

Determination of orientation and adsorption-induced changes in the tertiary structure of proteins on material surfaces by chemical modification and peptide mapping.

The labeling of amino acid residues followed by peptide mapping via mass spectrometry (AAL/MS) is a promising technique to provide detailed information on the adsorption-induced changes in its solvent accessibility. However, the potential of this method for the study of adsorbed protein structure is largely undeveloped at this time. The objective of this research was therefore to extend these capabilities by developing and applying AAL/MS techniques for a range of amino acid types to identify the dominant configurations of an adsorbed protein on a material surface.

Biological magnetic cellular spheroids as building blocks for tissue engineering.

Magnetic nanoparticles (MNPs), primarily iron oxide nanoparticles, have been incorporated into cellular spheroids to allow for magnetic manipulation into desired shapes, patterns and 3-D tissue constructs using magnetic forces. However, the direct and long-term interaction of iron oxide nanoparticles with cells and biological systems can induce adverse effects on cell viability, phenotype and function, and remain a critical concern. Here we report the preparation of biological magnetic cellular spheroids containing magnetoferritin, a biological MNP, capable of serving as a biological alternative to iron oxide magnetic cellular spheroids as tissue engineered building blocks.

Efficacy of reversal of aortic calcification by chelating agents.

Elastin-specific medial vascular calcification, termed "Monckeberg's sclerosis," has been recognized as a major risk factor for various cardiovascular events. We hypothesize that chelating agents, such as disodium ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and sodium thiosulfate (STS) might reverse elastin calcification by directly removing calcium from calcified tissues into soluble calcium complexes. We assessed the chelating ability of EDTA, DTPA, and STS on removal of calcium from hydroxyapatite (HA) powder, calcified porcine aortic elastin, and calcified human aorta in vitro.

Quantification of the influence of protein-protein interactions on adsorbed protein structure and bioactivity.

While protein-surface interactions have been widely studied, relatively little is understood at this time regarding how protein-surface interaction effects are influenced by protein-protein interactions and how these effects combine with the internal stability of a protein to influence its adsorbed-state structure and bioactivity. The objectives of this study were to develop a method to study these combined effects under widely varying protein-protein interaction conditions using hen egg-white lysozyme (HEWL) adsorbed on silica glass, poly(methyl methacrylate), and polyethylene as our model systems. In order to vary protein-protein interaction effects over a wide range, HEWL was first adsorbed to each surface type under widely varying protein solution concentrations for 2h to saturate the surface, followed by immersion in pure buffer solution for 15h to equilibrate the adsorbed protein layers in the absence of additionally adsorbing protein.

Evaluation of normal and metastatic mammary cells grown in different biomaterial matrices: establishing potential tissue test systems.

The in vitro growth and differentiation of normal mammalian cells is quite different than the growth of cells derived from tumors. Additionally, cells of the same origin (tissue) behave differently depending on the biomaterial matrix in or on which they are grown in vitro. We examined both Matrigel(TM) and a collagen/agarose blend and demonstrated that two murine mammary derived cells lines, 4T1 and NMuMG, derived from a metastatic mammary tumor or a normal mammary gland, respectively, exhibit different growth and differentiation patterns depending on the three-dimensional matrix in which they are grown.

Prosthesis alignment affects axial rotation motion after total knee replacement: a prospective in vivo study combining computed tomography and fluoroscopic evaluations.

Background: Clinical consequences of alignment errors in total knee replacement (TKR) have led to the rigorous evaluation of surgical alignment techniques. Rotational alignment in the transverse plane has proven particularly problematic, with errors due to component malalignment relative to bone anatomic landmarks and an overall mismatch between the femoral and tibial components' relative positions. Ranges of nominal rotational alignment are not well defined, especially for the tibial component and for relative rotational mismatch, and some studies advocate the use of mobile-bearing TKR to accommodate the resulting small rotation errors.

Peptide-surface adsorption free energy comparing solution conditions ranging from low to medium salt concentrations.

Multi-technique methods involving surface plasmon resonance spectroscopy and atomic force microscopy provide experimental data for the characterization of peptide adsorption on self-assembled monolayers. A comparative study is carried out in phosphate-buffered saline (PBS) and potassium phosphate-buffered (PPB) water to determine the influence of the salt concentration on the adsorption behavior (see figure; ΔG(0)(ads) : free energy of peptide adsorption, F(des) : force required for peptide desorption).

Development of a tuned interfacial force field parameter set for the simulation of protein adsorption to silica glass.

Adsorption free energies for eight host-guest peptides (TGTG-X-GTGT, with X = N, D, G, K, F, T, W, and V) on two different silica surfaces [quartz (100) and silica glass] were calculated using umbrella sampling and replica exchange molecular dynamics and compared with experimental values determined by atomic force microscopy. Using the CHARMM force field, adsorption free energies were found to be overestimated (i.e.

Neomycin enhances extracellular matrix stability of glutaraldehyde crosslinked bioprosthetic heart valves.

Glutaraldehyde (GLUT) crosslinked porcine aortic heart valves are continued to be extensively used in heart valve replacement surgeries. GLUT does not crosslink glycosaminoglycans in the tissue and we have demonstrated that GAG loss is associated with tissue degeneration. In this study, we examined the ability of neomycin to enhance GLUT crosslinking to stabilize GAGs, as well as provide evidence of improved functional integrity.

Design and Testing of a Pulsatile Conditioning System for Dynamic Endothelialization of Polyphenol-Stabilized Tissue Engineered Heart Valves.

Heart valve tissue engineering requires biocompatible and hemocompatible scaffolds that undergo remodeling and repopulation, but that also withstand harsh mechanical forces immediately following implantation. We hypothesized that reversibly stabilized acellular porcine valves, seeded with endothelial cells and conditioned in pulsatile bioreactors would pave the way for next generations of tissue engineered heart valves (TEHVs). A novel valve conditioning system was first designed, manufactured and tested to adequately assess TEHVs.

Tannic acid cross-linked collagen scaffolds and their anti-cancer potential in a tissue engineered breast implant.

Tannic acid (TA) is a hydrolysable plant tannin, and it has been determined that TA functions as a collagen cross-linking agent through hydrogen-bonding mechanisms and hydrophobic effects. Since TA may have anti-tumor properties, it may be a viable cross-linking agent for collagen-based breast tissue scaffolds. The goal of this work was to determine if TA cross-linked scaffolds induce apoptotic processes in MCF-7 cancer cells, with minimal toxic effect on healthy D1 mesenchymal stem-like stromal cells.

Examining the role of mechanosensitive ion channels in pressure mechanotransduction in rat bladder urothelial cells.

Until recently, the bladder urothelium had been thought of only as a physical barrier between urine and underlying bladder tissue. Recent studies, however, have demonstrated that the urothelium is sensitive to mechanical stimuli and responds by releasing signaling molecules (NO, ATP). This study sought to investigate the role of select ion channels in urothelial cell (UC) pressure mechanotransduction.

Correlation between desorption force measured by atomic force microscopy and adsorption free energy measured by surface plasmon resonance spectroscopy for peptide-surface interactions.

Surface plasmon resonance (SPR) spectroscopy is a useful technique for thermodynamically characterizing peptide-surface interactions; however, its usefulness is limited to the types of surfaces that can readily be formed as thin layers on the nanometer scale on metallic biosensor substrates. Atomic force microscopy (AFM), on the other hand, can be used with any microscopically flat surface, thus making it more versatile for studying peptide-surface interactions. AFM, however, has the drawback of data interpretation due to questions regarding peptide-to-probe-tip density.