Begell House Inc.
Critical Reviews™ in Biomedical Engineering
CRB
0278-940X
38
6
2010
Responding to Change: Thermo- and Photoresponsive Polymers as Unique Biomaterials
487-509
10.1615/CritRevBiomedEng.v38.i6.10
Laura A.
Wells
Department of Chemical Engineering, McMaster University, Hamilton, Ontario, Canada
Frances
Lasowski
School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada
Scott D.
Fitzpatrick
School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada
Heather
Sheardown
Department of Chemical Engineering and School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada
stimuli responsive; intelligent materials; thermo-responsive; light responsive; drug delivery
Responsive polymer systems that react to thermal and light stimuli have been a focus in the biomaterials literature because they have the potential to be less invasive than currently available materials and may perform well in the in vivo environment. Natural and synthetic polymer systems created to exhibit a temperature-sensitive phase transition lead to in situ forming hydrogels that can be degradable or non-degradable. These systems typically yield physical gels whose properties can be manipulated to accommodate specific applications while requiring no additional solvents or cross-linkers. Photo-responsive isomerization, dimerization, degradation, and triggered processes that are reversible and irreversible may be used to create unique gel, micelle, liposome, and surface-modified polymer systems. Unique wavelengths induce photo-chemical reactions of polymer-bound chromophores to alter the bulk properties of polymer systems. The properties of both thermo- and photo-responsive polymer systems may be taken advantage of to control drug delivery, protein binding, and tissue scaffold architectures. Systems that respond to both thermo- and photo-stimuli will also be discussed because their multi-responsive properties hold the potential to create unique biomaterials.
Ablation of Chronic Total Occlusions Using Kilohertz-Frequency Mechanical Vibrations in Minimally Invasive Angioplasty Procedures
511-531
10.1615/CritRevBiomedEng.v38.i6.20
Garrett B.
McGuinness
School of Mechanical and Manufacturing Engineering, Dublin City University, Ireland
M. P.
Wylie
School of Manufacturing and Design Engineering, Dublin Institute of Technology ; and Biomedical Devices and Assistive Technologies Research Group, Dublin Institute of Technology, Ireland
G. P.
Gavin
School of Manufacturing and Design Engineering, Dublin Institute of Technology ; and Biomedical Devices and Assistive Technologies Research Group, Dublin Institute of Technology, Ireland
Certain minimally invasive cardiology procedures, such as balloon angioplasty and stent implantation, critically require that the site of an arterial blockage be crossed by an intraluminal guidewire. Plaques resulting in near or totally occluded arteries are known as chronic total occlusions, and crossing them with conventional guidewires is a significant challenge. Among the most promising proposed solutions is the delivery of high-power, low-frequency ultrasonic vibrations to the occlusion site via an intraluminal wire waveguide. The vibrating distal tip of the ultrasound wire waveguide is used to transmit energy to the surrounding plaques, tissues, and fluids to ablate or weaken atherosclerotic plaque. Potential mechanisms of interaction with the plaque and adjacent fluids identified in the literature include: (i) direct contact with the waveguide distal tip, (ii) subcavitational acoustic fluid pressure fluctuations, (iii) cavitation, and (iv) acoustic streaming. We summarize developments in this area over more than two decades, describing experimental methods for device performance characterization, preclinical tests, early clinical investigations, and, later, full clinical trials. The article also reviews theoretical foundations and numerical models suitable for device design and analysis. Finally, important issues for future research and for the development of this technology will be considered.
Mathematical Foundations of Biomechanics
533-577
10.1615/CritRevBiomedEng.v38.i6.30
Peter F.
Niederer
Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
biomechanics; modeling; mechanobiology; biomathematics
The aim of biomechanics is the analysis of the structure and function of humans, animals, and plants by means of the methods of mechanics. Its foundations are in particular embedded in mathematics, physics, and informatics. Due to the inherent multidisciplinary character deriving from its aim, biomechanics has numerous connections and overlapping areas with biology, biochemistry, physiology, and pathophysiology, along with clinical medicine, so its range is enormously wide. This treatise is mainly meant to serve as an introduction and overview for readers and students who intend to acquire a basic understanding of the mathematical principles and mechanics that constitute the foundation of biomechanics; accordingly, its contents are limited to basic theoretical principles of general validity and long-range significance. Selected examples are included that are representative for the problems treated in biomechanics. Although ultimate mathematical generality is not in the foreground, an attempt is made to derive the theory from basic principles. A concise and systematic formulation is thereby intended with the aim that the reader is provided with a working knowledge. It is assumed that he or she is familiar with the principles of calculus, vector analysis, and linear algebra.