Understanding the Differences Between Bioactive and Biocompatible Materials

The study of biomaterials — substances that are engineered to interact with biological systems for medical purposes — is a relatively novel field but has facilitated numerous treatments and discoveries.

As the field has quickly grown, numerous new terms have been used to describe biomedical devices and materials. In this article, two of the most common adjectives in the field, bioactive and biocompatible, are discussed as well as how they are used to describe a series of highly specialized materials.

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‘Biocompatible’ is used to depict a material that is accepted by the biological system it has contact with. At a minimum, the majority of biocompatible materials are chemically inert.

In practice, biocompatibility for a given application can be dependent upon any number of other characteristics, such as elastic modulus, mechanical strength, or adhesion with the surrounding cellular matrix.

It is worth noting that biocompatibility is application-specific; materials may be biocompatible in one specific use case, but not biocompatible in another.

Bioactive materials go even further. Bioactive materials induce a local physiological response, typically through chemical or physical action. A common example of bioactive material is bioactive glass. This material is typically silicate-based glass-ceramic, which often readily degrades within the body.

Used for bone repair, ion exchange at the surface of bioactive glass results in the formation of bone-like hydroxyapatite, which natural bone will readily grow around.¹ Applied in this way, bioactive glass can actively promote the regeneration of a patient’s bone.

“Bioactive” is the opposite of “bioinert” which refers to materials that do not induce a physiological reaction.

Definitions and Distinctions

If choosing an official definition for “biocompatible” and “bioactive,” we would likely apply The International Union of Pure and Applied Chemistry (IUPAC) definitions – a global authority on standardized scientific nomenclature.²

Bioactive is defined as a “Qualifier for a substance which provokes any response from a living system.” The IUPAC also states that the term can also be used positively, such as to reflect a beneficial change.

Biocompatibility is defined as “The ability to be in contact with a living system without producing an adverse effect.”

These definitions appear simple, but some subtleties can frequently cause confusion. These can be clarified by applying the terms to a familiar medical device: a contact lens.

Biocompatibility without Bioactivity

Modern contact lenses are produced from soft, inert synthetic polymers known as silicone hydrogels. Silicone hydrogel contact lenses are permeable to oxygen, wettable, and cause negligible irritation to the tissues of the eye.

Therefore, we can say with confidence that modern contact lenses are incredibly biocompatible when used properly.

However, is a contact lens bioactive? Although a contact lens modifies the light as it enters the eye (resulting in improved vision), a physiological response is not induced within the eye tissue. Thus, we cannot refer to an ordinary contact lens as bioactive.

“Biocompatible” is usually only used to refer to materials, while the term “bioactive” refers to materials or drugs. Therefore, a drug without negative side effects and well-tolerated would not usually be described as “biocompatible,” even though it meets the IUPAC criteria.

Mechanisms of Bioactivity

The mechanisms by which bioactivity can occur are often complex and numerous.³ Efforts to engineer bioactive materials often include mimicking intra-cellular signaling, using coatings of peptides or proteins to modulate cell interactions.

There are also numerous bioactive materials, mostly bioactive ceramics and glasses, which induce a local physiological response through the exchange of simple ions, i.e., fluoride, calcium, and silver.⁴

Such “therapeutic ions” can activate, enhance or inhibit a vast array of cellular pathways. This can result in antibacterial activity and the stimulation of blood vessels and bone formation.

As research develops and scientists discover more about how different materials can influence cellular processes, we can expect more bioactive and biocompatible materials to find their way into mainstream medical treatment.

Mo-Sci has extensive experience in the manufacturing of bioactive glass. Mo-Sci produces standard compositions, such as 13-93, S53P4, and 45S5, and can research, develop and manufacture glass that is customized to a specific application.

References

1. Ferraris, S. et al. Bioactive materials: In vitro investigation of different mechanisms of hydroxyapatite precipitation. Acta Biomaterialia 102, 468–480 (2020).
2. Vert, M. et al. Terminology for biorelated polymers and applications (IUPAC Recommendations 2012). Pure and Applied Chemistry 84, 377–410 (2012).
3. Meyers, S. R. & Grinstaff, M. W. Biocompatible and Bioactive Surface Modifications for Prolonged In Vivo Efficacy. Chem. Rev. 112, 1615–1632 (2012).
4. Baino, F., Hamzehlou, S. & Kargozar, S. Bioactive Glasses: Where Are We and Where Are We Going? JFB 9, 25 (2018).

This information has been sourced, reviewed and adapted from materials provided by Mo-Sci Corp.

For more information on this source, please visit Mo-Sci Corp.