Controlling Protein Immobilization over Poly(3-hydroxybutyrate) Microparticles Using Substrate Binding Domain from PHA Depolymerase

Biointerface decoration with ligands is a crucial requirement to modulate biodistribution, increase half-life, and provide navigation control for targeted micro- or nanostructured systems. To better control the process of ligand functionalization over three-dimensional (3D) polyester surfaces, we report the characterization of hybrid proteins developed to enhance the anchoring efficiency over polymeric surfaces and preserve optimal spatial orientation: sfGFP, mRFP1, and the RBD proteins were attached to a polyester substrate binding domain (SBD) formed by the C-terminus region of PHA depolymerase. The binding ability was evaluated over poly(3-hydroxybutyrate) (PHB) microparticles (MP) and two-dimensional (2D) surfaces. The PHB interfaces revealed a high affinity toward the proteins linked with SBD, displaying higher protein contents compared to untagged proteins. The MP decorated with RBD-SBD exhibited limited MRC5 internalization and cytotoxicity without a significant impact caused by the RBD protein, suggesting that the system might be adapted for targeted drug delivery and vaccine applications.