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Smart biomaterials: healing thyself

Stories about George Washington having had wooden teeth abound; however, historians now say that Washington’s dentures were not wooden at all, but rather consisted of hippopotamus ivory and human teeth among other materials. Biomaterials useful in dental prostheses and other types of replacement devices have come a long way since then. A single definition for biomaterials is hard to find, but one definition is as follows: “materials intended to interface with biological systems to evaluate, treat, augment or replace any tissue, organ, or function of the body’’(D. F. Williams, The Williams Dictionary of Biomaterials, Liverpool University Press, Liverpool, 1999).

Unlike Washington’s false teeth, today’s biomaterials are functional, more compatible with the human body, lighter, stronger, and more durable. Moreover, some special materials have characteristics that can be manipulated. For instance, such materials can change shape or size with the addition of heat, or instantly convert to a solid from a liquid when near a magnet. These biomaterials with one or more alterable properties are referred to as smart materials. The potential applications of smart materials depend on variable properties such as viscosity, volume, or conductivity as the case may be.

The recent first generation biomaterials were designed with inertness in mind or to have as little interaction with the surrounding body tissue as possible. By contrast, second generation biomaterials shifted towards systems that actively reacted to bone or even soft tissue upon implantation and/or dissolved (resorbed) to be slowly replaced by tissues. Now biomaterials are developed to combine bioactivity with resorbability, which will help the body to heal itself. Biomaterials can serve as scaffolds or frameworks in conjunction with cells (tissue engineering) or growth factors to activate tissue regeneration. Additionally, other biomaterials are designed to trigger tissue formation based on physiochemical and specified dimensional properties.

One of the approaches in biomaterials science is to use genes within the body to control the regeneration process. Using novel biomaterials that are gene-activated, the tissue repair process can be specific for an individual and the disease. Also, researchers design implant materials to mimic the natural extracellular matrix (ECM) that supports cellular structure and function as well as regulates e.g., growth, cell migration, and differentiation. Eventually the implant materials are replaced by native tissue complete with a fully developed ECM.

Dr. Virgil Percec and his colleagues at the University of Pennsylvania recently led an international collaboration in the preparation of a library of synthetic biomaterials, which are functionally analogous to cellular membranes. The stable, bilayer vesicles are called dendrimersomes with properties of self-assembly and uniformity in size that show superiority over regular liposomes in the targeted delivery of proteins, genes (therapy), cancer drugs, and other chemical agents safely to the body. These biological carriers demonstrate the advances science has made in nano-sized biomaterials for practical medical applications.

References and Read-More-About-It:
Barrere F, Mahmood TA et al. 2008. Advanced biomaterials for skeletal tissue regeneration: Instructive and smart functions. R Reports:A Review Journal; Materials Science and Engineering R 59:38-71.
2. Hench LL, Thompson I. 2010. Twenty-first century challenges for biomaterials. J. R. Soc. Interface, 7:S379–S391.
3. Mieszawska AJ, Kaplan DL. 2010. Smart biomaterials-regulating cell behavior through signaling molecules. BMC Biology, 8:59
4. Institute of Nanotechnology. Synthetic biomaterials show promise in targeted delivery of cancer drugs. Source: University of Pennsylvania. Available at: Accessed July 28, 2010.
5. Percec V, Wilson DA et al. 2010. Self-assembly of Janus dendrimers into uniform dendrimersomes and other complex architectures. Science, 328(5981):1009-14.