Biocompatibility, biodegradation and excretion of polylactic acid (PLA) in medical implants and theranostic systems

Abstract

Polylactic acid (PLA) is the most commonly used biodegradable polymer in clinical applications today. Examples range from drug delivery systems, tissue engineering, temporary and long-term implantable devices; constantly expanding to new fields. This is owed greatly to the polymer's favorable biocompatibility and to its safe degradation products. Once coming in contact with biological media, the polymer begins breaking down, usually by hydrolysis, into lactic acid (LA) or to carbon dioxide and water. These products are metabolized intracellularly or excreted in the urine and breath. Bacterial infection and foreign-body inflammation enhance the breakdown of PLA, through the secretion of enzymes that degrade the polymeric matrix. The biodegradation occurs both on the surface of the polymeric device and inside the polymer body, by diffusion of water between the polymer chains. The median half-life of the polymer is 30 weeks; however, this can be lengthened or shortened to address the clinical needs. Degradation kinetics can be tuned by determining the molecular composition and the physical architecture of the device. Using L-or D-chirality of the LA will greatly slow or lengthen the degradation rates, respectively. Despite the fact that this polymer is more than 150 years old, PLA remains a fertile platform for biomedical innovation and fundamental understanding of how artificial polymers can safely coexist with biological systems.

Magnesium Alloys for Open-Pored Bioresorbable Implants

“…29 Although PLA has high biocompatibility and can be used in drug delivery systems as well, calcium phosphate further enhances the activity of osteoblasts and the bone growth. 30,31 Only considering the degradation rate, the additional PLA coating is the more effective variant as compared with the calcium phosphate coating. Tomographic images of LAE442 implants with the same coatings as used in the present study showed another benefit of the PLA coating: The effect of the grain size on the corrosion rate could be successfully suppressed.…”

Facile preparation of a novel biogenic silver-loaded Nanofilm with intrinsic anti-bacterial and oxidant scavenging activities for wound healing

“…The degradation of PLA is further enhanced by enzymes secreted by a bacterial infection or inflammation cells. Disintegration takes place both on the surface and inside the polymer through water diffusion between polymer chains 62 . However, features such as poor toughness, low degradation rate, and high hydrophobicity limit the implementation of PLA in wound dressings.…”

Effect of poly(D‐lactic acid) and cooling temperature on heat resistance and antibacterial performance of stereocomplex poly(L‐lactic acid)

“…Poly(lactic acid) (PLA), a biodegradable polymer, can be synthesized from lactic acid in fermented starch or sugar to L and D lactic acids, polymerized in forms of poly(L‐lactic acid) (PLLA), poly(D‐lactic acid) (PDLA) and poly(DL‐lactic acid) (PDLLA) . PLA has gained attention from many researchers in packaging and medical applications . However, the crystallization of PLA is slow, resulting in poor thermal stability and heat resistance.…”