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Publisher Summary This chapter describes the applications of multidimensional fluorescence imaging (MDFI) instrumentation. The chapter discusses fluorescence lifetime imaging (FLIM), with an emphasis on rapid wide-field time-gated imaging, including application to molecular biology, FLIM of tissue autofluorescence, and highspeed optically sectioned FLIM for live cell imaging. Optical sectioning is important to enhance image contrast and to minimize unwanted mixing of signals from axially separate fluorophores. The chapter discusses the extension to spectral FLIM, including (emission resolved) hyperspectral FLIM, implemented using line-scanning microscopy, and excitation-resolved imaging and FLIM utilizing supercontinuum generation to provide excitation throughout the visible spectrum. The combination of polarization-resolved and time resolved fluorescence imaging is described, mapping both lifetime and rotational correlation time as illustrated by an application to microfluidic devices. This chapter demonstrates that FLIM and MDFI can add significant value to microscopy, endoscopy, and assay technology. By resolving the fluorescence signal with respect to multiple dimensions including excitation and emission wavelength, lifetime, and polarization, it may be possible to enhance the fluorescence read-out for an experiment or assay, for example, in terms of improving the separation of multiple fluorophores or imaging variations in the local molecular environment.

Publisher Summary This chapter discusses systems that deliver material to the body or that remove what is unwanted. Delivery systems include: implantable capsules for slow, sustained release of a drug, and implantable drug delivery pumps that can deliver material through a catheter. Exchange devices that are external to the body include: dialyzers, which remove excess fluid and waste products from the blood, aphaeresis devices that collect fractionated blood components, and artificial gas exchangers, which are commonly used in open-chest surgery and may be used to supplement pathologically ineffective lungs. For all these devices, there must be due consideration of the materials used and particularly for those that are in contact with tissues or body fluids. These factors will include: sterility, toxicity, resistance to corrosion, the mechanical properties of the components used, and the risk of the materials causing blood clotting. The latter is particularly important for dialyzers and gas exchangers as they are in direct contact with blood. Dialyzers and gas exchangers involve a direct contact between blood and foreign materials. In these cases, the material surfaces must be highly resistant to blood clotting. It is essential that devices do not expose the blood to flow conditions that might induce clotting or damage the cells. These include the avoidance of high shear and stagnation regions.

Publisher Summary This chapter describes some of the factors underlying the effective operation of implants and extracorporeal devices. It is concerned with the physical principles by which materials are transported, either in normal tissue, or in association with devices. Tissue-engineered constructs are a special case since the living cells within them require the establishment of normal exchange processes such as occur in all other tissues. Unicellular organisms and the simplest multi-cellular organisms are able to survive since diffusion can occur sufficiently rapidly for metabolites to enter cells at the rate at which they are being used and waste products to leave as soon as they are produced. Solutions of the diffusion equations to be presented indicate that diffusional transport of a very small molecule, such as oxygen in water will take roughly 16 hours to move 1 cm and about 8 minutes to move 1 mm. These rates would be totally inadequate for larger metabolic species. Consequently, all large organisms (even plants) have additional mechanisms for moving fluids to bring metabolites close to the cells. In this context, it is useful to differentiate between pressure-driven “convective” transport and “diffusive” transport, which results from intrinsic molecular motion. In strict thermodynamic terms, these mechanisms are equivalent, since both involve a minimization of free energy in a system.

Publisher Summary This chapter provides an overview of the cardiovascular system. Blood circulation in the body is essential for the delivery to the tissues of all the nutrients that they require, including oxygen, the removal of waste products, the control of fluid levels, and the control of multiple functions through the endocrine hormone system and for thermoregulation. Blood, blood vessels, and the heart comprise the cardiovascular system, which is essential to maintain life as the movement of blood cells and plasma throughout the body provides nutrition and removes waste products from cells. Blood is the fluid that is in continuous movement through all the tissues of the body, blood vessels are the conduits for the blood, and the heart is the muscular pump that is primarily responsible for driving the flow. Failure of any components of the cardiovascular system can lead to irreversible damage to cells and organs and is one of the leading causes of death in the developed world. Thus, repair and replacement of the components of the cardiovascular system is one of the great challenges of biomaterials and bioengineering.