Polymers

Degradation of biodegradable polymers

Degradation of Inion Optima^TM polymers in the body is a two-phase process: simple chemical hydrolysis of the polymer backbone and active metabolism.

During the first phase, water penetrates the biodegradable device, preferentially attacking the chemical bonds in the amorphous phase and converting the long polymer chains into shorter water-soluble fragments. The reduction in molecular weight is soon followed by a reduction in physical properties as water begins to fragment the biodegradable device.

In the second phase, enzymes released from white blood cells attack these fragments causing the further degradation of the polymer to natural monomeric acids found in the body, such as lactic acid. These acids enter the citric acid cycle and are excreted as water and carbon dioxide.

Inion polymers

Inion products use a combination of four polymers – trimethylene carbonate (TMC), L-polylactic acid (LPLA), D,L-polylactic acid (DLPLA) and polyglycolic acid (PGA). Since the 1970s, the biocompatibility of these polymers has been well documented, and these same polymers have been used clinically for more than 30 years in biodegradable sutures and osteosynthesis devices.

Creating the right degradation profile

Inion scientists have used their expertise in blending well known biocompatible polymers to design and produce a range of products with varying strength and degradation profiles that can be tailored for specific use in many surgical practices.

Of the currently available biodegradable polymers, highly crystalline LPLA and PGA homopolymers have the highest strength and stiffness. LPLA is a slow-degrading hydrophobic polymer, that takes more than 24 months to fully biodegrade, whereas PGA is more hydrophilic and biodegrades faster, within 6 - 12 months.

By combining (co-polymerising) LPLA and PGA monomers in varying proportions, Inion has extended the range of polymer properties. The addition of DLPLA, which takes 12 - 16 months to fully biodegrade, also has an effect on the degradation profile.

By combining (co-polymerising) The properties can be tailored further by incorporating TMC (trimethylene carbonate) into the polymer backbone. The presence of TMC has a strong impact on the malleability (flexibility) of the final products and contributes to the product’s ease of use by surgeons.

Further important variables are the physical appearance of  the implant, the manufacturing processes and the sterilisation method.