Plants, invertebrate animals, amphibians and even reptiles have the ability to regenerate lost or damaged body parts. In the case of lizards, for example, this is a defensive mechanism. When a predator attacks, the lizard can break off its own tail as a means of distraction. While the predator is busy eating the tail, the lizard escapes and regenerates the body part later on. Mammals can regenerate some skin and liver tissue, but our regenerative abilities stop there. Unlike lizards, which have nature to thank for their regenerative capabilities, we are dependent on scientists, physicians and the business community to develop new technologies that will help us repair and replace damaged tissue.

How do lizards and other animals regenerate tissue? Part of the answer has to do with stem cells. When an amphibian loses its tail, for example, stem cells in the spinal cord migrate into the regrowing tail and differentiate into several cell types, including muscle and cartilage. This occurs simultaneously with the growth and differentiation of cells in the tail stump. Eventually, this process results in a new, fully-functional and anatomically-correct tail.

The exact reasons why mammals are so limited when it comes to regenerative potential is still not known. However, there have been significant levels of investment into stem cell research over the past several years in the hope of developing new technologies that will offer the ability to grow lost or damaged tissue, and perhaps even organs. Although there have been a number of recent breakthroughs in stem cell research, technologies that will actually regenerate human tissue are still several years away from fully coming to market. In the meantime, a new market is developing for products that have the ability to interact with living tissue and in some cases promote cellular migration and growth. While these products stop well short of growing new limbs and organs, they do provide some solutions for many of the problems associated with traditional surgical and treatment options.

The surgical biomaterials market is currently one of the largest and fastest growing global medical markets. It encompasses a number of surgical specialties and has reached a market capitalization of several billions dollars. The rapid growth of surgical biomaterials has to do with their capacity to reduce procedure times, recovery times and complication rates, while providing clinicians with innovative approaches to improving the level of patient care. Medical device companies worldwide are racing to bring to market biomaterial implants and devices that are designed to help repair defects in soft tissue, skin and bones.

What are biomaterials? A very broad definition of surgical biomaterials may include any substance that has the capacity to function in contact with living tissue and not be rejected by the body. This would include products made from metals, alloys and polyester-based materials such as orthopedic implants, and a number of other products traditionally used for the reconstruction or repair of tissue. The modern definition of surgical biomaterials, however, focuses on substances and products that not only evade rejection by the body, but that can interact with living tissue. These biomaterials do the job they are meant to perform, and then are either absorbed naturally by the body over time and eliminated by biological processes or become a permanent part of the surrounding tissue.

The use of nonviable materials to repair or replace defects in the human body dates back thousands of years. Early civilizations such as the Egyptians, Romans and Aztecs used wood, ivory, gem stones and other objects to replace missing teeth and fill in bone defects more than 2,500 years ago. Since then, scientific developments have led to the use of a number of different synthetics and natural materials in the human body. From World War I through World War II a number of natural rubbers, celluloids, vinyl polymers and polyurethanes were used for grafts, artificial hearts and catheters. During World War II, silicon was used in Japan to enhance the breasts of prostitutes and polymethylmethacrylate (PMMA), the main component in many of todays bone cements, was used in dental and craniofacial applications. Alloys have been used as pins and plates in the human body since the early nineteenth century. The use of steel and other alloys, which have the tendency to discolor, eventually led to the development and introduction of stainless steel and titanium, materials that are still commonly used in the production of orthopedic implants today.

Biomaterials can be made either from synthetic compounds or natural substances. Synthetic materials such as hydroxyapatite and tricalcium phosphate have been used for years in dental, craneo-maxilofacial and orthopedic procedures. The use of natural substances such as human or animal tissue in the manufacture of surgical biomaterials is a more recent development. A number of years of research and development in this area have led to technological advances in the processing of natural tissue to remove its toxicity and improve its clinical properties. Natural substances generally have complex structures that are difficult to replicate with synthetic compounds, and therefore can interact with human tissue in ways that synthetic products cannot. The ongoing development of surgical biomaterials is now resulting in a number of hybrid products that integrate both natural and synthetic substances in an effort to provide products that offer the clinical benefits of both materials.

Some of the benefits of biomaterials can be seen in their use in surgeries that typically use autografts. This is when surgeons take tissue (or bone) from one part of the patients body and then place it in another part of their body in order to repair a defect or replace diseased tissue. One of the most common procedures in which autografts are used is spinal fusion, a surgery in which one or more vertebrae of the spine are welded together with the aim of eliminating painful motion. During a spinal fusion, the surgeon makes an incision in the patients hip and removes a piece of bone from the pelvis, which is then implanted in the space between the vertebrae and held in place by metal fasteners. The pain and problems associated with motion are reduced over time, as the implanted bone and vertebrae grow into a single, solid bone. Some of the major disadvantages of autografts in these procedures are the additional operating time it takes the surgeon to harvest the graft, the extra postoperative recovery time needed and the added pain the patient must endure at the harvest site. Synthetic or animal based biomaterial bone substitutes provide surgeons and their patients with an option that lessens time under anesthesia and cuts down on recovery time.

Collagen implants for tissue repair and augmentation is another area where biomaterials may offer substantial benefits over traditional treatments. In recent years, the use of membranes made from natural substances such as porcine and bovine dermis or pericardium has gained in popularity with surgeons. Synthetic membranes made from materials such as polypropylene, polyester, silicone or polytetrafluoroethylene (PTFE) have been widely used in facial aesthetic and reconstructive surgery, hernia repair, neurosurgery and other surgical procedures. While synthetic surgical meshes have good strength characteristics, they remain in the body as permanent implants and sometimes can cause adverse reactions when the surrounding tissue identifies these materials as foreign bodies. A handful of companies in Europe and the U.S. have developed new ways of collecting and processing animal collagen to produce membranes that offer the same strength characteristics as synthetic membranes, but are completely biocompatible and provide a permanent solution for the repair and augmentation of tissue. Since the structure of this collagen is so similar to human tissue, once it is implanted the membrane provides the basis for cellular ingrowth and revascularization.

Bone graft substitutes and collagen implants do not have the capacity to help us grow new limbs or organs. However, they are an important step in the ongoing developments being made in the fields of tissue engineering and regenerative medicine. Progress continues to be made into stem cell research and, just like amphibians and lizards, one day new technologies may be available to help us regenerate our bodies. In the meantime, the market for surgical biomaterials continues to evolve and new technologies are continuously coming to market that have the capacity to improve the quality of life of mammals around the world.