Uptake of polystyrene beads bearing functional groups by macrophages and fibroblasts

Biomaterials bearing functional groups can be important for designing colloidal drug carriers or optimising implants and medical devices. Particle dissolution or the wear of biomaterials can cause inflammation mediated by macrophages and fibroblasts. We have investigated the in vitro uptake of standard and functionalised (COO- or R3N+) 0.4 mum polystyrene (PS) beads by J774.2 macrophages and L929 fibroblasts. Both COO- and R3N+ beads decreased the number of J774.2 cells after 48 h. Charged (especially R3N+) but not standard beads are toxic for L929. An increase in cell size was correlated with cytotoxicity in every case. Both cell types produced increased IL6 secretion, measured by ELISA, when incubated for 24 h with standard PS or R3N+ beads. Uptake of COO- and R3N+ bead by J774.2 cells caused a dramatic increase in TNFalpha release. Internalisation at 6 and 24 h was determined by measuring granularity by flow cytometry; it showed that L929 cells take up beads more slowly than J774.2 cells, but that they rapidly and avidly internalise R3N+ beads. Macrophages internalise roughly same amounts of all bead types. Cell morphology and intracellular bead arrangement change with the surface properties of the PS beads. Both cytochalasin D (2.5 muM) and colchicine (10 muM) inhibited, standard bead uptake at 6 h by J774.2 and L929 cells. The uptake of charged beads was also decreased with cytochalasin D, but colchicine did not inhibit the uptake of carboxylated beads. We evidenced that the functional groups on the bead surface influence bead uptake and the subsequent cell reactions. Analysis of serum protein adsorption onto beads could well help identify the cellular mechanisms underlying these regulations. (C) 2003 Elsevier B.V. All rights reserved.