Chemical Properties
Poly(DL-lactic acid) is a glassy material, occurring as white to
golden-yellow pellets or granules.
Uses
May be used to make drug delivery materials for controlled release.
Definition
ChEBI: Lactide is a member of dioxanes.
Production Methods
Lactic acid is a chiral molecule and has two optically active forms: Llactic
acid and D-lactic acid. Poly(DL-lactic acid) is produced from
the racemic mixture of lactic acid. Lactic acid is produced either
from ethylene (petrochemical pathway) or by bacterial fermentation
of D-glucose derived from food stocks. The former pathway
involves an oxidation step followed by treatment with hydrogen
cyanide and produces only racemic DL-lactic acid. In contrast, lactic
acid produced by fermentation occurs mainly as L-lactic acid. Lowmolecular-
weight poly-DL-(lactic acid) (500–10 000 Da) is produced
directly from lactic acid by condensation. Higher-molecular-weight
product is produced by one of two major pathways. The first
involves a depolymerization of low-molecular-weight polymer into
the cyclic dimer form (lactide) followed by ring-opening polymerization.
Alternatively, it can be produced by a direct condensation
using azeotropic distillation.
General Description
Resomer
? R 207 S, Poly(D,L-lactide) (PDLLA), a biodegradable and biocompatible polymer, can be used for a variety of biological applications. It shows properties like long degradation time, mechanical stiffness and hydrophobicity.
Pharmaceutical Applications
Poly(DL-lactic acid) is used in drug delivery systems in implants,
injections, and oral solid dispersions. It is also used as a coating
agent.
Safety
Poly(DL-lactic acid) degrades to produce lactic acid, which is
considered a well-tolerated nontoxic material. Several in vitro and
in vivo studies demonstrated that poly(lactic acid) in general
(including poly(DL-lactic acid)) is well tolerated and does not induce
a significant immune response.However, some studies have
illustrated signs of a mild immune response.The FDA has also
reported some rare cases of inflammatory responses in patients
treated with cosmetic poly(DL-lactic acid) injections.
storage
Poly(DL-lactic acid) is stable under dry conditions. However, it
typically biodegrades over a period of 10–15 months according to
the molecular weight. Increasing moisture and temperature
enhances biodegradation; the onset of degradation in water at
25°C is 6 months.In contrast to many other biodegradable
polymers, poly(DL-lactic acid) degrades through a two-step mechanism.
The primary degradation step involves the hydrolysis of the
ester bonds independently of microbial activity to produce a low-molecular-weight polymer. When the molecular weight drops below
10 000, microorganisms digest the polymer into carbon dioxide and
water. Poly(DL-lactic acid) is more stable than poly(L-lactic acid)
or poly(D-lactic acid) alone.Poly(DL-lactic acid) should be stored
in a dry inert environment at a temperature of －15°C to －20°C.
Incompatibilities
Incompatible with strong acids or alkaline materials.
Regulatory Status
Included in the FDA Inactive Ingredients Database (IM, powder, for
injection, suspension, and lyophilization). Poly(DL-lactic acid) is
considered as ‘not hazardous’ according to the European Directive
67/548/EEC. Included in parenteral preparations (prolongedrelease
powder for suspension for subcutaneous or intramuscular
injection) licensed in the UK.
