Poly (lactide-co-glycolide)

Poly (lactide-co-glycolide), PLGA, is a copolymer composed of D.L-lactic acid and glycolic acid monomers that can be easily degraded by the human organism. In medicine, PGLA is widely used in different polymerisation ratios, sometimes also in mixtures with other substances (e.g. hyaluronic acid in tissue fillers used for tissue augmentation). The polyester compounds of D, L-lactic acid and glycolic acid are converted and degraded in tissues without reaction.

PGLA is used for various indications. For example in surgical sutures (Vicryl), in cardiology for stents, in neurosurgery as a guide for nerve regeneration after traumatic nerve injuries. PGLA is also widely used in orthopaedic surgery, for example in interference screws used to fix cruciate ligament implants. For example, the use of biodegradable fixation screws (which consist mainly of lactose polymers) is the method of choice for the fixation of cruciate ligament implants. The biodegradation and remodelling of the copolymer takes 6 months to 6 years in the bone.

PLGA copolymers are also used orthopedically in combination with methacrylates.

PLGA microparticles: In the pharmaceutical industry, PLGA is used as an excipient for the production of depot drug forms, such as implants, microparticles or in-situ systems. In in-situ systems, the depot drug form is only formed after the drug has been administered to the patient's body, for example by solidifying an injected solution or suspension to form an in-situ implant. PGLA is used in filler materials, sometimes as a mixture with hyaluronic acid for tissue augmentation.

PLGA and allergy: PLGA is well tolerated during orthopaedic surgery (Barber FA et al. 2017). Little is known about sensitization after implantation of PLGA-containing materials. Experiments have shown (Schöll I et al. 2004) that biocompatible and biodegradable PLGA nanoparticles modulate the immunological response to type I allergens (see alsoimplant intolerance).

PLGA products for hyposensitization are now in clinical trials. Here, allergens are incorporated into PLGA nanoparticles and supplied to the organism in well-dosed quantities. PLGA acts like a Trojan horse, which infiltrates the allergen into the organism undercover, so to speak, and releases it only after a certain time, whereby it is only then presented to the immune system. (Salari F et al. 2015). The immunological reactivity of such allergens (e.g. house dust mite extracts) introduced into the organism depends on the size of the PLGA particles (Joshi VB et al. 2014).

1. Barber FA et al (2017) Biocomposite Implants Composed of Poly(Lactide-co-Glycolides) /β-Tricalcium Phosphates: Systematic Review of Imaging, Complication, and Performance Outcomes. Arthroscopy 33:683-689.
2. Joshi VB et al (2014) Development of a poly (lactic-co-glycolic acid) particle vaccine to protect against house dust mite induced allergy. AAPS J 16:975 985.
3. alari F et al (2015) Down-regulation of Th2 immune responses by sublingual administration of poly(lactic-co-glycolic) acid (PLGA)-encapsulated allergen in BALB/c mice. Int Immunopharmacol 29:672-678.
4. Schöll I et al (2004) Allergen-loaded biodegradable poly(d, l-lactic-co-glycolic) acid nanoparticles down-regulate an ongoing Th2 response in the BALB/c mouse model. Clinical & Experimental Allergy 34: 315-321