Nanoporous membranes for medical and biological applications

Abstract

Synthetic nanoporous materials have numerous potential biological and medical applications that involve sorting, sensing, isolating, and releasing biological molecules. Nanoporous systems engineered to mimic natural filtration systems are actively being developed for use in smart implantable drug delivery systems, bioartificial organs, and other novel nano-enabled medical devices. Recent advances in nanoscience have made it possible to precisely control the morphology as well as physical and chemical properties of the pores in nanoporous materials that make them increasingly attractive for regulating and sensing transport at the molecular level. In this work, an overview of nanoporous membranes for biomedical applications is given. Various in vivo and in vitro membrane applications, including biosensing, biosorting, immunoisolation, and drug delivery, are presented. Different types of nanoporous materials and their fabrication techniques are discussed with an emphasis on membranes with ordered pores. Desirable properties of membranes used in implantable devices, including biocompatibility and antibiofouling behavior, are discussed. The use of surface modification techniques to improve the function of nanoporous membranes is reviewed. Despite the extensive research carried out in fabrication, characterization, and modeling of nanoporous materials, there are still several challenges that must be overcome in order to create synthetic nanoporous systems that behave similarly to their biological counterparts.

Figure 1

A schematic diagram of key membrane characteristics that affect the performance.

Figure 2

SEM image of ordered porous structures of alumina. The intervals of 100 nm (a), 150 nm (b) and 200 nm (c). Reused with permission from Hideki Masuda, Applied Physics Letters, 71, 2770 (1997). Copyright 1997, American Institute of Physics.

Figure 3

Biological applications of nanoporous materials.

Figure 4

Scanning electron micrograph of anodized diamond-like carbon-coated alumina membrane exposed to platelet rich plasma. The pulsed laser deposition method was used for the coating. The surface contains sodium chloride crystals; however, the pores remain free of fouling. Reprinted with permission from R. Narayan et al., Journal of Nanoscience and Nanotechnology, 7, 1486 (2007) Copyright @ American Scientific Publishers, http://www.aspbs.com.

Figure 5

Twenty-four hour MTT viability assays conducted in human epidermal keratinocytes for uncoated (Al), gold-coated (Au), silicon-coated (Si), and diamond-like-carbon (DLC)-coated nanoporous alumina membranes. Si, Au, and DLC coatings were deposited on nanoporous alumina membranes using ultraviolet (wavelength = 248 nm) pulsed laser deposition.