Biocompatibility

A biocompatible material is not toxic, nor does it generate an adverse reaction in the body or tissue it is in contact with.

Biocompatibility is a key property of materials used in medical devices and is measured in accordance with ISO 10993. The range of tests to be carried out for a biocompatibility evaluation depends on the nature and the duration of the contact between the device and the body. Hence, the tests to be performed will be different for a dental aligner material and a bone implant material.

In DLP 3D-printing, the development of biocompatible photopolymer resins is a prerequisite for the expansion of this technology in the fields of biofabrication and bioprinting. Recent developments in material research have enabled the emergence of new non-toxic photopolymer formulations and photopolymerization techniques that pave the way for promising applications in tissues engineering ang regenerative medicine.

Key Aspects of Biocompatibility

Biocompatibility is determined based on two primary factors:

1. Biofunctionality – The material must perform its intended function effectively and safely within the body.
2. Biological Safety – It should not cause toxicity, immune rejection, excessive inflammation, or long-term complications.

These factors depend on material composition, surface properties, degradation behavior, and interaction with biological systems.

Biocompatibility Assessment and Testing

Biocompatibility is evaluated through a series of tests that comply with ISO 10993 (Biological Evaluation of Medical Devices) and FDA (Food and Drug Administration) regulations. Testing is classified into three main categories:

(A) Cytotoxicity Testing (Cellular Level)

• Evaluates direct toxic effects on living cells.
• Common tests: MTT assay, Neutral Red Uptake, and Agar Diffusion Test.

(B) In Vitro and In Vivo Testing

• In Vitro (Lab-based): Tests for cellular response, protein adsorption, and hemocompatibility.
• In Vivo (Animal Models): Assesses tissue response, systemic toxicity, immune reaction, and biodegradability.

(C) Long-Term Biocompatibility Studies

• Chronic toxicity: Evaluates effects over months or years.
• Genotoxicity: Assesses the potential to cause DNA damage.
• Carcinogenicity: Checks for cancer-causing properties.
• Reproductive toxicity: Examines effects on fertility and fetal development.

Types of Biocompatible Materials

Materials used in biomedical applications must be non-toxic, non-carcinogenic, and non-immunogenic.

(A) Metals

• Titanium & Titanium Alloys – High corrosion resistance, strength, and biocompatibility (used in orthopedic and dental implants).
• Stainless Steel (316L) – Used in surgical instruments, bone plates.
• Cobalt-Chromium Alloys – Strong and wear-resistant (e.g., heart valves).

(B) Polymers

• Polytetrafluoroethylene (PTFE, Teflon) – Used in vascular grafts.
• Polyethylene (UHMWPE) – Wear-resistant, used in joint replacements.
• Polylactic Acid (PLA) & Polyglycolic Acid (PGA) – Biodegradable, used in sutures and tissue scaffolds.

(C) Ceramics

• Zirconia & Alumina – High biocompatibility, hardness, and wear resistance (e.g., dental implants).
• Hydroxyapatite (HA) – Mimics bone structure, used in bone grafts and coatings.

(D) Natural Biomaterials

• Collagen, Chitosan, Alginate – Used in tissue engineering and wound healing.
• Silk Fibroin – Used in biodegradable sutures and scaffolds.