Fabrication of microparticles from three-armed, biodegradable macromers by oil-in-water emulsion and subsequent photo-cross-linking

Abstract text (incl. figure legends and references)

Introduction
Macromers, macromolecules with at least one oligo- or polymeric block and two or more reactive groups, are a suitable basis for adaptable biomaterials. Previously, we developed the TriLGA macromers with lactic (LA) and glycolic acid (GA) in the biodegradable oligoesters [1]. Films from the macromers were used as models for subsequent surface modifications [2].

Fig.1: TriLGA macromer

Objectives
Injectable microparticles can potentially translate our TriLGA-based material concept with modifiable surfaces into a medical device. To that end, fabrication of microparticles from the TriLGA macromers was investigated.

Materials and methods
The macromer was dissolved in an organic solvent along with a photo-initiator and, optionally, an anchor molecule for surface modification. In an oil-in-water emulsion technique, this organic phase was added dropwise to a stirred aqueous phase containing poly(vinyl alcohol) (PVA). The formed particles were cross-linked by UV light and subsequently characterized for size (laser diffraction) and morphology (visual, SEM).

Results
The reference formulation, with butyl acetate as the solvent, Tri134(LA6) as the macromer at 1 g/mL (m/V) and 2% (m/m) PVA in the aqueous phase, reproducibly yielded spherical porous particles with sizes between 60 and 160 µm. Glycidyl methacrylate or methacrylic acid as anchor molecules for surface modifications could be co-polymerized. Other TriLGA variants were also examined for particle fabrication. Choice of organic solvent as well as PVA concentration significantly affected microparticle size and morphology.

Conclusion
Using an O/W emulsion technique and cross-linking with UV light, TriLGA macromers were successfully used for microparticle fabrication. The TriLGA particles can be investigated as vehicles for subsequent surface modifications for therapeutic approaches.

References:
[1] Krieghoff J et al., Polym Degrad Stab 2022, 195, 109775
[2] Mueller B et al., Acta Biomater. 2017, 51, 148–160