PLLA and PDLLA Fillers: Linking Crystallinity and Mechanical Stability to Aggregation, Redispersion, and Collagen...

Area of Science:

• Biomaterials Science
• Dermatology
• Polymer Chemistry

Background:

• Poly lactic acid (PLA) microsphere fillers stimulate neocollagenesis.
• Microsphere aggregation can lead to heterogeneous tissue remodeling.
• Stereochemistry influences PLA filler properties and performance.

Purpose of the Study:

• Compare poly-L-lactic acid (PLLA) and poly-D,L-lactic acid (PDLLA) fillers.
• Correlate stereochemistry with microsphere stability, dispersion, and in vivo outcomes.
• Evaluate the impact of filler properties on neocollagenesis and inflammation.

Main Methods:

• Analysis of PLA/sodium hyaluronate composite fillers using SEM, NMR, DSC, and micro-compression.
• Quantification of dispersion-aggregation-redispersion in saline via optical microscopy.
• In vivo assessment in SKH mice, measuring projection volume (PRIMOS) and tissue response (H&E, Masson's trichrome, macrophage immunofluorescence).

Main Results:

• PLLA microspheres maintained discrete structure, while PDLLA particles deformed and aggregated.
• PLLA particles were larger and exhibited semicrystalline features; PDLLA was amorphous.
• In vivo, PLLA fillers showed more uniform volume rebound, greater collagen area, and weaker inflammatory signals compared to PDLLA.

Conclusions:

• PLLA's crystallinity and mechanical robustness enhance re-dispersibility and homogeneous collagen remodeling.
• PDLLA aggregation is associated with increased inflammation and reduced collagen deposition.
• Microsphere integrity and dispersion are critical for uniform biostimulatory outcomes with PLA fillers.