Polymeric heart valves: new materials, emerging hopes

doi:10.1016/j.tibtech.2009.03.002

Trends in Biotechnology

Volume 27, Issue 6, June 2009, Pages 359-367

https://doi.org/10.1016/j.tibtech.2009.03.002 Get rights and content

Heart valve (HV) replacements are among the most widely used cardiovascular devices and are in rising demand. Currently, clinically available devices are restricted to slightly modified mechanical and bioprosthetic valves. Polymeric HVs could represent an attractive alternative to the existing prostheses, merging the superior durability of mechanical valves and the enhanced haemodynamic function of bioprosthetic valves. After early unsatisfactory clinical results, polymeric HVs did not reach commercialization, mainly owing to their limited durability. Recent advances in polymers, nanomaterials and surface modification techniques together with the emergence of novel biomaterials have resulted in improved biocompatibility and biostability. Advances in HV design and fabrication methods could also lead to polymeric HVs that are suitable for long-lasting implantation. Considering all these progresses, it is likely that the new generation of polymeric HVs will find successful long-term clinical applications in future.

Section snippets

Heart valve prostheses: polymeric valves

The normal physiologic function of the heart valve (HV) is to provide unidirectional smooth blood flow through the heart chambers and the main vessels by regular opening and closing throughout each cardiac cycle. This vital function can be affected by valvular heart diseases, leading to either obstruction in the blood flow (stenosis) or backward leakage of the blood (regurgitation), or both in a worst case scenario. Although conservative medical therapy for mild and asymptomatic cases of valve

Material choice

The choice of material is a crucial element in developing polymeric HVs because it is the determining factor for durability and biocompatibility (Table 1). In theory, synthetic PVs have the potential to overcome clinical problems associated with both mechanical and bioprosthetic valves, such as thromboembolic events, anticoagulation side effects and premature failure, by providing better haemodynamic function and improved durability. However, for a polymeric HV to become a viable alternative

Surface modification: biofunctionalization and nanotopographic surfaces

The surface characteristics of biomaterials affect the interactions between the material and the biological system, and these characteristics determine the material's biocompatibility. The chemical and physical properties of the material surface (such as its hydrophobicity, hydrophilicity and surface energy) and the morphology and topography of the surface can influence biological reactions at the interface [36]. Despite the many advantages of recently developed materials, their interaction

Design issues

It is well established that the structural anatomy of the valve plays an essential part in its operative function by providing a competent and stable structure with specific anatomical and histological features [45]. Considering the complex anatomy of natural valves, it is difficult to create structures that have the exact anatomical and functional characteristics of a native valve. However, in contrast to their bioprosthetic counterparts, synthetic leaflet valves can be designed in virtually

Manufacturing strategies

The PV manufacturing process is also an important factor in PV performance because it has been shown to affect valve durability and haemodynamic function [56]. Several methods of polymeric HV manufacture have been investigated, such as dip casting, film fabrication, injection moulding and cavity moulding (Box 2).

Several studies have attempted to evaluate the impact of different fabrication techniques on the function and durability of the obtained valves, and they have suggested that valves made

Assessing valve performance

Although polymeric HVs reached clinical trials soon after the early stage of HV replacement therapy, the initial results were catastrophic and led to a high mortality rate, which was mainly due to malfunctioning and poor durability of the implanted valves 15, 57. Other early clinical problems that were encountered included the incidence of thrombotic phenomena, impaired flow dynamics, structural failures caused by leaflet stiffening and free edge conversion and calcification, leading to leaflet

Current challenges and future prospects

Currently, the most important challenge in the development of PV substitutes is their limited durability – they are susceptible to calcification, which leads to leaflet stiffening and tearing. Although considerable successes have been achieved with respect to improvements in material properties with structural and surface modifications, the problem has not yet been completely overcome. Several different factors can contribute to limited durability and premature failure of PVs, including

Acknowledgements

We would like to thank the Engineering and Physical Sciences Research Council (EPSRC) (EP/D061555) for financial support for the development of HVs and the National Institute for Health Research (NIHR) for a New and Emerging Applications of Technology (NEAT) Programme grant for the development of percutaneous HVs.

References (69)

A. Carpentier
Biological factors affecting long-term results of valvular heterografts
J. Thorac. Cardiovasc. Surg.
(1969)
V.E. Friedewald
The editor's roundtable: cardiac valve surgery
Am. J. Cardiol.
(2007)
P. Zilla
Prosthetic heart valves: catering for the few
Biomaterials
(2008)
L.H. Edmunds
Directions for improvement of substitute heart valves: National Heart, Lung, and Blood Institute's Working Group report on heart valves
J. Biomed. Mater. Res.
(1997)
N.S. Braunwald
Complete replacement of the mitral valve. Successful clinical application of a flexible polyurethane prosthesis
J. Thorac. Cardiovasc. Surg.
(1960)
R.Y. Kannan
Polyhedral oligomeric silsesquioxane nanocomposites: the next generation material for biomedical applications
Acc. Chem. Res.
(2005)
A.G. Kidane
Current developments and future prospects for heart valve replacement therapy
J. Biomed. Mater. Res. B Appl. Biomater.
(2009)
S.H. Daebritz
New flexible polymeric heart valve prostheses for the mitral and aortic positions
Heart Surg. Forum
(2004)
S.L. Gallocher
A novel polymer for potential use in a trileaflet heart valve
J. Biomed. Mater. Res. B Appl. Biomater.
(2006)
S.L. Hilbert
Evaluation of explanted polyurethane trileaflet cardiac valve prostheses
J. Thorac. Cardiovasc. Surg.
(1987)

F. Nistal

In vivo experimental assessment of polytetrafluoroethylene trileaflet heart valve prosthesis

J. Thorac. Cardiovasc. Surg.

(1990)

W.J. Kolff et al.

The return of elastomer valves

Ann. Thorac. Surg.

(1989)

H.B. Lo

A tricuspid polyurethane heart valve as an alternative to mechanical prostheses or bioprostheses

ASAIO Trans.

(1988)

R. Kiraly

Hexsyn trileaflet valve: application to temporary blood pumps

Artif. Organs

(1982)

B.B. Roe

Tricuspid leaflet aortic valve prosthesis

Circulation

(1966)

G.E. Chetta et al.

The design, fabrication and evaluation of a trileaflet prosthetic heart valve

J. Biomech. Eng.

(1980)

T. Akutsu

Polyurethane artificial heart valves in animals

J. Appl. Physiol.

(1959)

G.M. Bernacca

Calcification and fatigue failure in a polyurethane heart-valve

Biomaterials

(1995)

J.W. Boretos et al.

Segmented polyurethane: a new elastomer for biomedical applications

Science

(1967)

D.J. Wheatley

Polyurethane: material for the next generation of heart valve prostheses? Eur

J. Cardiothorac. Surg.

(2000)

M. Szycher

Biostability of polyurethane elastomers: a critical review

J. Biomater. Appl.

(1988)

K. Stokes

Polyurethane elastomer biostability

J. Biomater. Appl.

(1995)

E.M. Christenson

Oxidative mechanisms of poly(carbonate urethane) and poly(ether urethane) biodegradation: in vivo and in vitro correlations

J. Biomed. Mater. Res. A

(2004)

E.M. Christenson

Poly(carbonate urethane) and poly(ether urethane) biodegradation: in vivo studies

J. Biomed. Mater. Res. A

(2004)

Y.W. Tang

Enzyme-induced biodegradation of polycarbonate-polyurethanes: dependence on hard-segment chemistry

J. Biomed. Mater. Res.

(2001)

H.J. Salacinski

Thermo-mechanical analysis of a compliant poly(carbonate-urea)urethane after exposure to hydrolytic, oxidative, peroxidative and biological solutions

Biomaterials

(2002)

M. Dabagh

Effects of polydimethylsiloxane grafting on the calcification, physical properties, and biocompatibility of polyurethane in a heart valve

J. Appl. Polym. Sci.

(2005)

A. Simmons

Long-term in vivo biostability of poly(dimethylsiloxane)/poly(hexamethylene oxide) mixed macrodiol-based polyurethane elastomers

Biomaterials

(2004)

R.R. Joshi

Phosphonated polyurethanes that resist calcification

J. Appl. Biomater.

(1994)

H. Jiang

Design and manufacture of a polyvinyl alcohol (PVA) cryogel tri-leaflet heart valve prosthesis

Med. Eng. Phys.

(2004)

W. Yin

Flow-induced platelet activation in a St. Jude mechanical heart valve, a trileaflet polymeric heart valve, and a St

Jude tissue valve. Artif. Organs

(2005)

R.Y. Kannan

Silsesquioxane nanocomposites as tissue implants

Plast. Reconstr. Surg.

(2007)

R.Y. Kannan

The antithrombogenic potential of a polyhedral oligomeric silsesquioxane (POSS) nanocomposite

Biomacromolecules

(2006)

G. Punshon

Assessment of the potential of progenitor stem cells extracted from human peripheral blood for seeding a novel vascular graft material

Cell Prolif.

(2008)

Cited by (172)

Surface modification of mechanical heart valves: A review
2024, European Polymer Journal
The prevalence of heart valve diseases and their significant impact on global mortality underscore the urgency of refining heart valve technology. Despite the crucial roles of both bioprosthetic and mechanical heart valves in restoring proper blood flow, their application is hindered by complications such as thrombosis, embolization, and structural dysfunction. The present review provides insight into various types of mechanical heart valves and their components, including the materials used in manufacturing. Common complications and defects associated with heart valves are also overviewed, highlighting the significance of surface texture in valve functionality. Central to the discussion is the emerging field of surface-modification and coating techniques. Understanding and selecting appropriate approaches are crucial in improving valve performance and mitigating complications. The review covers a range of established and innovative techniques utilized for surface modification and coating of mechanical heart valves. These techniques aim to improve hemocompatibility, reduce thrombogenicity, and promote long-term durability of mechanical heart valves.
Effect of the apron in the mechanical characterisation of hyperelastic materials by means of biaxial testing: A new method to improve accuracy
2024, Journal of the Mechanical Behavior of Biomedical Materials
Biological soft tissues and polymers used in biomedical applications (e.g. in the cardiovascular area) are hyperelastic incompressible materials that commonly operate under multi-axial large deformation fields. Their characterisation requires biaxial tensile testing. Due to the typically small sample size, the gripping of the specimens commonly relies on rakes or sutures, where the specimen is punctured at the edges of the gauge area. This approach necessitates of an apron, excess of material around the gauge region.
This work analyses the apron influence on the estimated mechanical response of biaxial tests performed by using a rakes gripping system, with the aim of verifying the test accuracy and propose improved solutions.
In order to isolate the effect of the apron, avoiding the influence of anisotropy and inhomogeneity typical of most soft tissues, homogeneous and isotropic hyperplastic samples made from a uniform sheet of casted silicone were tested. The stress-strain response of specimens with different apron sizes/shapes was measured experimentally by means of biaxial testing and digital image correlation. Tests were replicated numerically, to interpret the experimental findings.
The apron surrounding the gauge area acts as an additional annular constraint which stiffens the system, resulting in a significant overestimate in the stress values. This error can be avoided by introducing specific cuts in the apron.
The study quantifies, for the first time, the correlation between the apron size/shape and the experimental stress overestimation, proposing a research protocol which, although identified on homogeneous hyperelastic materials, can be useful in providing more accurate characterisation of both, synthetic polymers and soft tissues.
History, introduction, and physicochemical properties of silver nanoparticles
2023, Silver Nanoparticles for Drug Delivery
Silver is one of the nontoxic elements known to mankind from the ancient period. This chapter gives a brief account of the ancient history of silver and its uses in a variety of forms from ancient times. The discovery of silver nanoparticles and their physicochemical properties of silver nanoparticles related to size, and shape-dependent properties, the surface functionalization of silver nanoparticles, and their chemical properties are explained in this chapter. Application of silver nanoparticles in various fields such as environmental protection and water remediation, food processing and packaging, photocatalytic applications, photovoltaic activity, and applications, as catalysts in dye degradation, monitoring heavy metals, in the textile industry, battery, supercapacitor applications, and agriculture field are explained. Biomedical applications of silver nanoparticles in cardiovascular implants, catheters, wound dressings, orthopedic and orthodontic implants and fixations, cosmetics, dentistry, tissue engineering, protein delivery, vaccines, and adjuvants are briefed along with their antimicrobial, antihelmintic, and anticancer are also briefed in this chapter.
Hemocompatible polymers for medical applications
2023, Handbook of Polymers in Medicine
Hemocompatibility is a critical condition for the application of materials in the field of biomedicine. The presence of biomaterials in contact with blood immediately caused the absorbance of platelets and eventually, the coagulation cascade is initiated and forms a fibrin structure. Medical applications require a various range of biomaterials especially polymers that are hemocompatible, which means that they can prevent thrombi formation when they come into contact with blood, even for a short time, which could lead to device failure. Hemocompatible polymers have been used in medical applications such as heart valves, vascular grafts, hemodialysis membranes, extracorporeal blood circulation systems, and stents, those that depend on the free flow of blood over their surfaces. In this chapter the definition of hemocompatibility and the coagulation cascade are summarized. Following, the use of polymers as numerous coatings methods on the surface of devices produced with different materials, even polymers will be discussed. Most polymers themselves also need modifications including the addition of functional groups or nanomaterials in their bulk or surface which are the common aims of many studies for improving the hemocompatibility of the blood-contacting applications.
Green synthesis of silver nanoparticles and their potenial biological applications
2023, Nanotechnology and in Silico Tools: Natural Remedies and Drug Discovery
Since the introduction of the concept in the late 1950s, nanotechnology provides new ways of thinking for solving problems at the nanoscale level. Currently, many advancements in nanotechnology are taking place worldwide to help deal with various problems at our hands. Nanotechnology allows the manipulation of matter at a molecular or atomic level to produce novel materials and devices with new extraordinary properties. Various methods of production are broadly classified into three methods, i.e., physical, chemical, and biological. Green synthesis of the nanoparticles focuses on environmentally compatible materials such as bacteria, fungi, and plants for production. Nanoparticles previously produced by physical or chemical methods are now produced using biological materials, enhancing their properties and reducing their toxic effects. Due to recent advancements and the variety of uses for nanoparticles, interest has increased. Metal oxide nanoparticles have been identified as therapeutic agents with an extended half-life and therapeutic index, as well as less immunogenic properties. This review discusses the various synthesis methodologies, as well as various biomedical applications of NPs.
The evolution of polyurethane heart valve replacements: How chemistry translates to the clinic
2022, Materials Today Communications
Current heart valve replacements (HVRs) fail to comprehensively capture the physiological behavior of native heart valve tissues, allowing the burden of valvular heart disease to persist after surgical intervention. Through extensive research and clinical experience, it has become evident that material selection is central to the success of HVRs. One outstanding candidate material for next-generation HVRs is polyurethane. These polymers exhibit a unique segmented chemical structure that can imitate the mechanical strength and elasticity of soft biological tissues. Consequently, polyurethanes have long been investigated as HVR materials, however, progression to clinical utility has historically been impaired by the material’s susceptibility to biodegradation and calcification. This review presents a concise and critical analysis of past and recent investigations to elucidate the contemporary potential of polyurethane HVRs. Importantly, the overwhelming clinical failure of past prototypes necessitated a detailed examination to validate any further use of polyurethanes in HVR development. Recently, advancements in polyurethane chemistry have contributed towards addressing the shortcomings of polyurethane HVRs, encouraging progress towards clinical translation.

View all citing articles on Scopus

View full text

Trends in Biotechnology

ReviewPolymeric heart valves: new materials, emerging hopes

Section snippets

Heart valve prostheses: polymeric valves

Material choice

Surface modification: biofunctionalization and nanotopographic surfaces

Design issues

Manufacturing strategies

Assessing valve performance

Current challenges and future prospects

Acknowledgements

Biological factors affecting long-term results of valvular heterografts

J. Thorac. Cardiovasc. Surg.

The editor's roundtable: cardiac valve surgery

Am. J. Cardiol.

Prosthetic heart valves: catering for the few

Biomaterials

Directions for improvement of substitute heart valves: National Heart, Lung, and Blood Institute's Working Group report on heart valves

J. Biomed. Mater. Res.

Complete replacement of the mitral valve. Successful clinical application of a flexible polyurethane prosthesis

J. Thorac. Cardiovasc. Surg.

Polyhedral oligomeric silsesquioxane nanocomposites: the next generation material for biomedical applications

Acc. Chem. Res.

Current developments and future prospects for heart valve replacement therapy

J. Biomed. Mater. Res. B Appl. Biomater.

New flexible polymeric heart valve prostheses for the mitral and aortic positions

Heart Surg. Forum

A novel polymer for potential use in a trileaflet heart valve

J. Biomed. Mater. Res. B Appl. Biomater.

Evaluation of explanted polyurethane trileaflet cardiac valve prostheses

J. Thorac. Cardiovasc. Surg.

In vivo experimental assessment of polytetrafluoroethylene trileaflet heart valve prosthesis

J. Thorac. Cardiovasc. Surg.

The return of elastomer valves

Ann. Thorac. Surg.

A tricuspid polyurethane heart valve as an alternative to mechanical prostheses or bioprostheses

ASAIO Trans.

Hexsyn trileaflet valve: application to temporary blood pumps

Artif. Organs

Tricuspid leaflet aortic valve prosthesis

Circulation

The design, fabrication and evaluation of a trileaflet prosthetic heart valve

J. Biomech. Eng.

Polyurethane artificial heart valves in animals

J. Appl. Physiol.

Calcification and fatigue failure in a polyurethane heart-valve

Biomaterials

Segmented polyurethane: a new elastomer for biomedical applications

Science

Polyurethane: material for the next generation of heart valve prostheses? Eur

J. Cardiothorac. Surg.

Biostability of polyurethane elastomers: a critical review

J. Biomater. Appl.

Polyurethane elastomer biostability

J. Biomater. Appl.

Oxidative mechanisms of poly(carbonate urethane) and poly(ether urethane) biodegradation: in vivo and in vitro correlations

J. Biomed. Mater. Res. A

Poly(carbonate urethane) and poly(ether urethane) biodegradation: in vivo studies

J. Biomed. Mater. Res. A

Enzyme-induced biodegradation of polycarbonate-polyurethanes: dependence on hard-segment chemistry

J. Biomed. Mater. Res.

Thermo-mechanical analysis of a compliant poly(carbonate-urea)urethane after exposure to hydrolytic, oxidative, peroxidative and biological solutions

Biomaterials

Effects of polydimethylsiloxane grafting on the calcification, physical properties, and biocompatibility of polyurethane in a heart valve

J. Appl. Polym. Sci.

Long-term in vivo biostability of poly(dimethylsiloxane)/poly(hexamethylene oxide) mixed macrodiol-based polyurethane elastomers

Biomaterials

Phosphonated polyurethanes that resist calcification

J. Appl. Biomater.

Design and manufacture of a polyvinyl alcohol (PVA) cryogel tri-leaflet heart valve prosthesis

Med. Eng. Phys.

Flow-induced platelet activation in a St. Jude mechanical heart valve, a trileaflet polymeric heart valve, and a St

Jude tissue valve. Artif. Organs

Silsesquioxane nanocomposites as tissue implants

Plast. Reconstr. Surg.

The antithrombogenic potential of a polyhedral oligomeric silsesquioxane (POSS) nanocomposite

Biomacromolecules

Assessment of the potential of progenitor stem cells extracted from human peripheral blood for seeding a novel vascular graft material

Cell Prolif.

Review
Polymeric heart valves: new materials, emerging hopes