Biomaterial

A biomaterial is a substance that has been engineered to interact with biological systems for a medical purpose – either a therapeutic (treat, augment, repair, or replace a tissue function of the body) or a diagnostic one.

[needs update] It has experienced steady growth over its history, with many companies investing large amounts of money into the development of new products.

[2][a][b][c] Biomaterials can be derived either from nature or synthesized in the laboratory using a variety of chemical approaches utilizing metallic components, polymers, ceramics or composite materials.

They are often used and/or adapted for a medical application, and thus comprise the whole or part of a living structure or biomedical device which performs, augments, or replaces a natural function.

For example, a construct with impregnated pharmaceutical products can be placed into the body, which permits the prolonged release of a drug over an extended period of time.

[6] Self-assembly is the most common term in use in the modern scientific community to describe the spontaneous aggregation of particles (atoms, molecules, colloids, micelles, etc.)

This includes an emerging class of mechanically superior biomaterials based on microstructural features and designs found in nature.

These tropocollagen molecules are intercalated with the mineral phase (hydroxyapatite, calcium phosphate) forming fibrils that curl into helicoids of alternating directions.

These "osteons" are the basic building blocks of bones, with the volume fraction distribution between organic and mineral phase being about 60/40.

Calcium sulfate (its α- and β-hemihydrates) is a well known biocompatible material that is widely used as a bone graft substitute in dentistry or as its binder.

The mechanics involve two semicircular discs moving back and forth, with both allowing the flow of blood as well as the ability to form a seal against backflow.

The valve is coated with pyrolytic carbon and secured to the surrounding tissue with a mesh of woven fabric called Dacron (du Pont's trade name for polyethylene terephthalate).

[23] As discussed previously, biomaterials are used in medical devices to treat, assist, or replace a function within the human body.

[25][26] The in vivo functionality and longevity of any implantable medical device is affected by the body's response to the foreign material.

The acute phase occurs during the initial hours to days of implantation, and is identified by fluid and protein exudation[28] along with a neutrophilic reaction.

[29] During the acute phase, the body attempts to clean and heal the wound by delivering excess blood, proteins, and monocytes are called to the site.

Immuno-informed biomaterials that direct the immune response rather than attempting to circumvent the process is one approach that shows promise.

It can manifest in either acute or chronic form, affecting multiple organs and tissues and causing serious complications in clinical practice, both during transplantation and implementation of biocompatible materials.

[34] A biomaterial should perform its intended function within the living body without negatively affecting other bodily tissues and organs.

[36] One recent study states: "Advanced nanobiomaterials, including liposomes, polymers, and silica, play a vital role in the codelivery of drugs and immunomodulators.

[39] Some of the most commonly-used biocompatible materials (or biomaterials) are polymers due to their inherent flexibility and tunable mechanical properties.

Medical devices made of plastics are often made of a select few including: cyclic olefin polymer (COP), cyclic olefin copolymer (COC), polycarbonate (PC), polyetherimide (PEI), medical grade polyvinylchloride (PVC), polyethersulfone (PES), polyethylene (PE), polyetheretherketone (PEEK) and even polypropylene (PP).

[43] Surface engineering and modification allows clinicians to better control the interactions of a biomaterial with the host living system.

Important surface properties:[44] In addition to a material being certified as biocompatible, biomaterials must be engineered specifically to their target application within a medical device.

Matching the elastic modulus makes it possible to limit movement and delamination at the biointerface between implant and tissue as well as avoiding stress concentration that can lead to mechanical failure.

Since flexural rigidity depends on the thickness of the material, h, to the third power (h3), it is very important that a biomaterial can be formed into thin layers in the previously mentioned applications where conformality is paramount.

Macrostructure refers to the overall geometric properties that will influence the force at failure, stiffness, bending, stress distribution, and the weight of the material.

Biomaterials can be constructed using only materials sourced from plants and animals in order to alter, replace, or repair human tissue/organs.

Cellulose and starch, proteins and peptides, and DNA and RNA are all examples of biopolymers, in which the monomeric units, respectively, are sugars, amino acids, and nucleotides.

[61][62] On a similar manner, silk (proteinaceous biopolymer) has garnered tremendous research interest in a myriad of domains including tissue engineering and regenerative medicine, microfluidics, drug delivery.