Artificial blood vessels for coronary artery disease patients


Scientific Study, 2016
18 Pages, Grade: 1

Excerpt

Content

CHAPTER ONE
1.1 Overview

CHAPTER TWO
2.1 Artificial Blood Vessel
2.2 Why do we Need them?
2.3 Additive Manufacturing
2.4 3D Printing
2.5 Fused Deposition Modeling

CHAPTER THREE
3.1 Previous Researches
3.2 Artificial Vessels without the Use of the Scaffold
3.3 Current Status and Future Perspectives

CHAPTER FOUR
4.1 Coronary Heart Disease
4.2 Treatment or Management of Cardiovascular Disease
4.3 Artificial Blood Vessels
4.4 Construction of an Artificial Vessel
4.5 Tissue Engineering of Blood Vessels
4 6 Biomaterial Scaffolds
4.7 Mechanical Properties

References

CHAPTER ONE

1.1 Overview

Coronary artery disease is among the fetal disease affecting most individuals across the globe. It occurs when the coronary arteries are clogged by either clot or any substance that will lead to constriction of the lumen hence leading to stenosis. As such, patients with severe stenosis are required to undergo coronary artery bypass grafting surgery to enable efficient flow of blood to region supplied by the affected coronary artery. Coronary artery bypass surgery is an open chest operation that involves connecting the aorta to coronary artery after removal of the stenos using an artery or vein from another part of the body (Cohn, 2012).

It is preferred that a prosthetic arteries be used in the operation so as to avoid the complications that may result from the use of natural blood vessels. However, the use of a prosthetic artery has been associated with several cases of thrombus formation, poor cell growth, poor proliferations and poor adhesion. Moreover, the prosthetic artery fabrication to mimic the natural blood vessels has been reported to a challenge hence increasing chances of rejection (Fung, 2013). The purpose of this paper is to give a detailed analysis of artificial blood vessels manufacturing using techniques such as additive manufacturing (3D printing). Scaffolding designs will be studied using computer aided software and choice of bio-compatible material that matches requirements for manufacturing the artificial blood vessels will be discussed too. Finally, the paper will look into the mechanical properties of the scaffoldings designs (Fink & Helen, 2009).

CHAPTER TWO

2.1 Artificial Blood Vessel

Synthetic blood vessels were chemically produced during World War I by a French-American surgeon Alexis carrel to restore the blood circulation in the wounded soldiers. At this time, 1873, Alex was perfect in sewing ruptured blood vessels and this won him a Nobel Prize in 1912. Carrel made the artificial blood vessels using the glass and aluminium materials (Fung, 2013).

The current success in artificial blood vessels synthesis back dates to 1940s as a result of great work by Alexis. The surgical technique used by then before this great discovery was transplanting the arteries or veins from healthy donor to replace the damaged and sometimes the diseased vessels. This technique was faced with a lot of challenges, tissue rejection and development of arteriosclerosis being among them (Grassl, Barocas, & Bischof, 2004).

Materials such as vinyon, plastic Teflon and synthetic fibre Dacron were used to make artificial blood vessels and the results were encouraging. Vinyon was at some point tried on dogs and later human being in 1953 by Voorhees. The reports obtained from these studies suggested that synthetic blood vessels from these materials were rarely rejected by the human immune system. To add on the above advantage, these materials were readily available, cheap and durable. However, Dacron was found to have tendency of clogging by blood clot and research is still underway to design the interior walls of small synthetic Dacron blood vessels to eliminate the clot formations (Humphrey & Baroutaji, 2016).

The ideal artificial blood vessel graft should have the following characteristics

I. Compatible with the natural blood vessels
II. Lack the thrombogenicity associated with natural blood vessels
III. Should be resistance to infections
IV. Should have the ability to heal, contract and remodel.
V. Should be able to secrete normal blood vessels products

The above characters are necessary while structuring the artificial blood vessel scaffold from collagen or any biodegradable polymer. It should be noted that mechanical properties of artificial blood vessels is greatly enhanced by substances such as bioreactors that mimics the in vivo milieu of the blood vessels’ cells by producing pulsatile flow (Fink, Sellborn, & Krettek, 2012).

2.2 Why do we Need them?

It has been shown by various surgical reports that transplanting ones’ blood vessels to replace the diseased or damaged blood vessels lead to rejection. Moreover, transplantation required more than one surgeries, one for the healthy vessel to replace the unhealthy one and second surgery was removal of the unhealthy blood vessel (Song, Wang, Huang, & Tsung, 2014). This was consuming a lot of time, labor, and resources and also caused more harm to the patient as it led to more wounds that can easily be infected when good nursing practices are note observed. Surprising to note, these patients with poor circulation problems lacked suitable vessels that could be harvested for transplant. Therefore, discovery of artificial blood vessels synthesis and the material suitable for this was necessary and a big blessing (Grassl, Barocas, & Bischof, 2004).

The synthetic fabrics made of materials such as polyethylene and siliconized rubber had much advantage since they were porous and also flexible. Their porosity nature allowed permeation of some host blood cells into the material and this led to cell multiplication for natural tissue to emerge and the synthetic vessels get eliminated. This material seems have saved a lot of lives by preventing development of ischemia to heart parts supplied by affected coronary arteries which could have led to myocardial infarctions. The world has suffered a lot especially from complications related to rupture of coronary arteries due to high blood pressure, stenosis and aneurisms (Fink & Helen, 2009).

2.3 Additive Manufacturing

Rapid prototyping has been applied in industrial manufacturing of commercial products. It is a quick means to ensure mass production of substances which may be needed in bulk. It gives a prototype of the object required which finally will be modified to give the final product that looks almost similar to the natural one (Froelich et al., 2010). The whole process is known as 3D printing of additive manufacturing. The process involves fabricating the parts of the prototype product with additional materials hence additive approach. The principle behind this great technology is production of initial pro-product termed as prototype with aid of three dimensional computer aided design system. Once the pro-product is obtained, it is then remodeled without process planning by adding other substance to get a complete final product (Fink, Sellborn, & Krettek, 2012).

The other form of manufacturing artificial substances for commercial purposes in the industry is Rapid manufacturing. The method is mainly suitable for rapid processing of low volume products which are not required in bulk. The products of rapid manufacturing are commonly customized and have complex shapes. They are good for emergency. Rapid manufacturing have the following advantages: safer working environment, no need of tooling, assurance of dimensional accuracy and geometrical freedom. It should be noted that a lot of material are wasted in this technique making it more costly; it is slow and has a low surface finish (Fung, 2013).

2.4 3D Printing

Previous section had discussed the three dimensional printing technique and how it works. This section will reinforce the available mechanisms used to achieve production of plastic materials and other substances relevant to the topic of this paper. Three dimensional printing popularly known as additive manufacturing is a slow process that involves building product in layers. The initial step is always computer aided design sketch which is later developed to STL file which can be easily interpreted by the 3D printers (Froelich et al., 2010).

The available technologies using 3D printing system include stereo lithography (SLA), selective laser sintering (SLS), inject modeling (IJM), electronic beam melting (EBM), fused deposition modeling (FDM) among others. 3D printers can be dismantled to obtain five main parts, cartridge, coolant, electronics, print heads and finally built table. The 3D printers systems have been documented to posses the ability to build multi-material parts. Such examples include, Z-Corp 3D Printing and Object Inkjet Printing. Synthesis of artificial blood vessels requires high technology to ensure that the structure of the unhealthy natural blood vessels is replaced with almost similar artificial blood vessels to avoid the side effects that may result from too much deviation from the natural ones. For the purpose of this paper, only fused deposition modeling will be discussed in details (Humphrey & Baroutaji, 2016).

2.5 Fused Deposition Modeling

Fused deposition modeling as a technique of 3Dprinting technology can give the final products without synthesizing the intermediate termed prototype. The blood vessels are manufactured by extruding individual layers of the material using the nozzles and build them in layers as per the structures desired. It is capable of producing thermoplastic blood vessels with good mechanical strength that can withstand an elevated blood pressure (Dabiri, Schmid, & Tryggvason, 2014).

It should be noted that while using fused deposition modeling technique of 3D printing, the following parameters must be taken into consideration: the part build orientations, raster angles, thickness of the layers, road width and air gap. The extruded material is which is in thermoplastic state is drawn into head using a wheel drive attached in a motor moving horizontally hence molding the exact cross section of each layer (Fink, Sellborn, & Krettek, 2012). The plastic substance then hardens within a short period of time to form a union with previously molded layer. The substance holding the product is removed by soaking in a solution. The build styles that can be applied in fused deposition modeling technique include solid normal, sparse-doubled and spars. The layers should be filled completely using solid materials to avoid vacuums. The raster width and raster angle should be as low as possible to enable more bonding which will enhance the strength of the final product (Dabiri, Schmid, & Tryggvason, 2014).

Fused deposition modeling is composed of three main stages which include creation of` a prototype using a computer aided design file, heating the thermoplastic prototype to make it a semisolid and lastly printing the substance and socking to get rid of the supporting material (Snowhill & Silver, 2005). FDM technique is described to have anisotropic structures which other molded structures do not have. Because the technique is not hygroscopic, the final products are stable hence fit for use as artificial blood vessels to replace the diseased or damaged natural blood vessels. Fused deposition modeling makes use of materials such as polycarbonates, ABS, polyphenylsulfone, nylon and ULTEM9085. These materials yield the best structures that qualify to be used as artificial blood vessels (Dabiri, Schmid, & Tryggvason, 2014).

The benefits of artificial blood vessels manufactured via fused deposition modeling technique includes lack of toxicity, durability, cleanliness and environmental friendly, flexibility in design and high accuracy. However, the products and the technique face the following challenges: support of the product during synthesis is required, extrusion of the head must be kept moving without which the material will bump up, the process and the machine is costly (Dabiri, Schmid, & Tryggvason, 2014).

CHAPTER THREE

3.1 Previous Researches

The first in vitro arteries were constructed by Weinberge and Bellwere. The components of the artery were collagens and bovine aortic SMCs casted together to obtain an annular mold. The inner parts of the artery graft were made of bovine ECs while the outer surface fabricated with bovine adventitial fibroblasts. To maintain the mechanical strength of the artery, Weignberge and Bellwere used the Dacron mesh to furnish the walls of the artificial artery (Froelich et al., 2010). The researchers discovered that without the Dacron mesh, the synthesized artery would bursts at intraluminal pressure which is greater than 10mmHg. The more the Dacron mesh layers, the more strong the vessels and alternating the Dacron mesh with collagen lattice was enough to make the artery much stronger and it would need a pressure of 120 to 180mmHg to burst (Grassl, Barocas, & Bischof, 2004).

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Details

Title
Artificial blood vessels for coronary artery disease patients
College
Federation University Australia  (Biomedical Engineering)
Course
BE543
Grade
1
Author
Year
2016
Pages
18
Catalog Number
V340642
ISBN (eBook)
9783668304031
ISBN (Book)
9783668304048
File size
529 KB
Language
English
Notes
This text was written by a non-native English speaker. Please excuse any errors or inconsistencies.
Tags
artificial blood vessels, coronary artery disease, 3D printing
Quote paper
Marvin Namanda (Author), 2016, Artificial blood vessels for coronary artery disease patients, Munich, GRIN Verlag, https://www.grin.com/document/340642

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