Bubble Seeding Nanocavities: Multiple Polymer Foam Cell Nucleation by Polydimethylsiloxane-Grafted Designer Silica Nanoparticles

Hydroxyapatite, often in the form of synthetic porous blocks, has been used in the repair of bone defects for over 20 years owing to its biocompatibility and osseoconductive behaviour. Bone ingrowth requires the existence of open and interconnected pores with diameters larger than 150 µm for proper circulation of nutrients. Hence, currently available materials are characterised by poor mechanical properties. Collapse of such products is therefore a major source of concern to surgeons using these weak materials in bone surgery. There is a need to develop stronger highly porous structures through adequate control over the size, shape and volume fraction of pores. In this work, highly porous open-cell hydroxyapatite foams were fabricated by the polymer foam replication process, where two types of polyurethane (PU) foams were infiltrated with optimised slurries containing appropriate binders and ceramic particles, followed by the removal of excess slurry, burning out of the polymer to leave a ceramic replica of the polyurethane and finally high temperature sintering. Open-cell HAP foams with porosities of about 80% were obtained, i.e. 30% higher than that determined for commercial ones (50%). Many of the commercial foam cells approach 500 µm in diameter whereas the developed foam cell size ranged from 300 up to 500 µm. The ultimate compressive strength of the developed foams (1-2 MPa) was found to be higher than that recorded for the commercial ones (0.7 MPa) indicating that these foams can more easily be modelled in theatre. Both the elastic moduli and the compressive strength of the developed foams were found to increase with increasing of the relative density, in accordance with the predictions of available micro-mechanical models.

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Polymer Foam Cell Growth in Microgravity

Journal of Cellular Plastics ◽

10.1177/0021955x9202800602 ◽

1992 ◽

Vol 28 (6) ◽

pp. 536-556

Author(s):

Margaret M. Curtin ◽

Frank S. Tyler ◽

David L. Wilkinson

Keyword(s):

Cell Growth ◽

Foam Cell ◽

Polymer Foam

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Designer Core–Shell Nanoparticles as Polymer Foam Cell Nucleating Agents: The Impact of Molecularly Engineered Interfaces

ACS Applied Materials & Interfaces ◽

10.1021/acsami.1c00569 ◽

2021 ◽

Vol 13 (14) ◽

pp. 17034-17045

Author(s):

Shanqiu Liu ◽

Sissi de Beer ◽

Kevin M. Batenburg ◽

Hubert Gojzewski ◽

Joost Duvigneau ◽

...

Keyword(s):

Foam Cell ◽

Core Shell ◽

Nucleating Agents ◽

Polymer Foam ◽

Shell Nanoparticles ◽

Core Shell Nanoparticles ◽

The Impact

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Prepare Foam with Injection Molding Method in Acrylonitrile-Butadiene-Styrene (ABS) Matrix Using Chemical Foam Agent

Materials Science Advanced Composite Materials ◽

10.18063/msacm.v0i0.917 ◽

2019 ◽

Vol 2 (4) ◽

Author(s):

Akin Akinci 1 ◽

Muhammet AYCICEK 1 ◽

Sedef CAKIR 1

Keyword(s):

Injection Molding ◽

Foam Cell ◽

Acrylonitrile Butadiene Styrene ◽

Shell Layer ◽

Polymer Foam ◽

Molding Method ◽

Commercial Polymers ◽

Usage Area ◽

Butadiene Styrene ◽

Wide Usage

In this study, it is aimed to decrease the weight of the material by using polymer foam materials with lower density instead of commercial polymers which have wide usage area. For this purpose, polymer foam was produced by using an acrylonitrile butadiene styrene (ABS) matrix and an endothermic chemical foam agent using injection molding method. The foam cell morphology, shell layer thickness and mechanical properties of the final part were investigated taking into consideration the weight-changing ratios of the foam agent content (1-1,5-2-2,5-3%).

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Large Deformation Finite Element Analyses for 3D X-ray CT Scanned Microscopic Structures of Polyurethane Foams

Materials ◽

10.3390/ma14040949 ◽

2021 ◽

Vol 14 (4) ◽

pp. 949

Author(s):

Makoto Iizuka ◽

Ryohei Goto ◽

Petros Siegkas ◽

Benjamin Simpson ◽

Neil Mansfield

Keyword(s):

Mechanical Properties ◽

Finite Element ◽

Foam Cell ◽

Parent Material ◽

Polyurethane Foams ◽

Compression Tests ◽

Polymer Foam ◽

Element Analysis ◽

X Ray ◽

Wide Range

Polyurethane foams have unique properties that make them suitable for a wide range of applications, including cushioning and seat pads. The foam mechanical properties largely depend on both the parent material and foam cell microstructure. Uniaxial loading experiments, X-ray tomography and finite element analysis can be used to investigate the relationship between the macroscopic mechanical properties and microscopic foam structure. Polyurethane foam specimens were scanned using X-ray computed tomography. The scanned geometries were converted to three-dimensional (3D) CAD models using open source, and commercially available CAD software tools. The models were meshed and used to simulate the compression tests using the implicit finite element method. The calculated uniaxial compression tests were in good agreement with experimental results for strains up to 30%. The presented method would be effective in investigating the effect of polymer foam geometrical features in macroscopic mechanical properties, and guide manufacturing methods for specific applications.

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EM of human atherosclerosis: Aortic fatty streaks with transitional lesion features

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100123519 ◽

1992 ◽

Vol 50 (1) ◽

pp. 622-623

Author(s):

K. Florian Klemp ◽

J.R. Guyton

Keyword(s):

Foam Cell ◽

Cell Formation ◽

Processing Technique ◽

Foam Cell Formation ◽

Tissue Preparation ◽

Electron Microscopic ◽

Extracellular Lipid ◽

Electron Microscopic Cytochemistry ◽

Human Atherosclerosis ◽

Clinically Significant

The earliest distinctive lesions in human atherosclerosis are fatty streaks (FS), characterized initially by lipid-laden foam cell formation. Fibrous plaques (FP), the clinically significant lesions, differ from FS in several respects. In addition to foam cells, the FP also exhibit fibromuscular proliferation and a necrotic core region rich in extracellular lipid. The possible transition of FS into mature FP has long been debated, however. A subset of FS described by Katz etal., was intermediate in lipid composition between ordinary FS and FP. We investigated this hypothesis by electron microscopic cytochemistry by employing a tissue processing technique previously described by our laboratory. Osmium-tannic acid-paraphenylenediamine (OTAP) tissue preparation enabled ultrastructural analysis of lipid deposits to discern features characteristic of mature fibrous plaques.

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Acetaminophen: Macula densa hypersecretory activity by induced hepatotoxicity

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012895x ◽

1987 ◽

Vol 45 ◽

pp. 934-935

Author(s):

S.S. Poolsawat ◽

C.A. Huerta ◽

S.TY. Lae ◽

G.A. Miranda

Keyword(s):

Cell Proliferation ◽

Liver Function ◽

Chronic Inflammation ◽

Foam Cell ◽

Term Effect ◽

Short Term ◽

Drug Induced ◽

Experimental Induction ◽

Tissue Alterations ◽

Toxic Responses

Introduction. Experimental induction of altered histology by chemical toxins is of particular importance if its outcome resembles histopathological phenomena. Hepatotoxic drugs and chemicals are agents that can be converted by the liver into various metabolites which consequently evoke toxic responses. Very often, these drugs are intentionally administered to resolve an illness unrelated to liver function. Because of hepatic detoxification, the resulting metabolites are suggested to be integrated into the macromolecular processes of liver function and cause an array of cellular and tissue alterations, such as increased cytoplasmic lysis, centrilobular and localized necroses, chronic inflammation and “foam cell” proliferation of the hepatic sinusoids (1-4).Most experimentally drug-induced toxicity studies have concentrated primarily on the hepatic response, frequently overlooking other physiological phenomena which are directly related to liver function. Categorically, many studies have been short-term effect investigations which seldom have followed up the complications to other tissues and organs when the liver has failed to function normally.

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The Anti-Atherogenic Properties of Sesamin are Mediated via Improved Macrophage Cholesterol Efflux Through PPARγ1-LXRα and MAPK Signaling

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000195 ◽

2014 ◽

Vol 84 (1-2) ◽

pp. 79-91 ◽

Cited By ~ 7

Author(s):

Amin F. Majdalawieh ◽

Hyo-Sung Ro

Keyword(s):

Cholesterol Efflux ◽

Transcriptional Activity ◽

Molecular Mechanisms ◽

Foam Cell ◽

Mapk Signaling ◽

Luciferase Reporter ◽

Foam Cell Formation ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Macrophage Cholesterol Efflux

Background: Foam cell formation resulting from disrupted macrophage cholesterol efflux, which is triggered by PPARγ1 and LXRα, is a hallmark of atherosclerosis. Sesamin and sesame oil exert anti-atherogenic effects in vivo. However, the exact molecular mechanisms underlying such effects are not fully understood. Aim: This study examines the potential effects of sesamin (0, 25, 50, 75, 100 μM) on PPARγ1 and LXRα expression and transcriptional activity as well as macrophage cholesterol efflux. Methods: PPARγ1 and LXRα expression and transcriptional activity are assessed by luciferase reporter assays. Macrophage cholesterol efflux is evaluated by ApoAI-specific cholesterol efflux assays. Results: The 50 μM, 75 μM, and 100 μM concentrations of sesamin up-regulated the expression of PPARγ1 (p< 0.001, p < 0.001, p < 0.001, respectively) and LXRα (p = 0.002, p < 0.001, p < 0.001, respectively) in a concentration-dependent manner. Moreover, 75 μM and 100 μM concentrations of sesamin led to 5.2-fold (p < 0.001) and 6.0-fold (p<0.001) increases in PPAR transcriptional activity and 3.9-fold (p< 0.001) and 4.2-fold (p < 0.001) increases in LXR transcriptional activity, respectively, in a concentration- and time-dependent manner via MAPK signaling. Consistently, 50 μM, 75 μM, and 100 μM concentrations of sesamin improved macrophage cholesterol efflux by 2.7-fold (p < 0.001), 4.2-fold (p < 0.001), and 4.2-fold (p < 0.001), respectively, via MAPK signaling. Conclusion: Our findings shed light on the molecular mechanism(s) underlying sesamins anti-atherogenic effects, which seem to be due, at least in part, to its ability to up-regulate PPARγ1 and LXRα expression and transcriptional activity, improving macrophage cholesterol efflux. We anticipate that sesamin may be used as a therapeutic agent for treating atherosclerosis.

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