Colloid dispersions of biorelated polyelectrolyte complex (PEC) particles, which are fabricated by mixing aqueous polycation and polyanion solutions, have potential applications for drug delivery and biomedicine . PEC particles can be deposited onto model and bone substitute materials (BSM), loaded by therapeutic bisphosphonates (BP), antibiotics [2, 3, 4, 5] or growth factors  and those drugs release PEC particle coatings after contact to buffer or cell culture media.
Recently, thermoresponsive PEC particles based on copolymers of N-isopropylacrylamide (NIPAM) and either cationic or anionic repeating units complexed by anionic or cationic polysaccharides were prepared. Their coatings at model and bone substitute materials were loaded either by bisphosphonates (BP) or bone morphogenetic proteins (BMP) used for systemic therapy of osteoporosis . BP and BMP could be released with slow rate at T = 37°C and with faster rate at T > 37°C. Turbidity, light scattering and FTIR measurements indicated a temperature dependent volume phase transition (VPT) known for pure PNIPAM, which results in the liberation of bound BP and BMP. Finally, results on the cytocompatibility of such thermoresponsive PEC particle coatings to human mesenchymal stromal cells and the biological activity of released BMP in myoblast cells are given.
This work is sponsored by DFG (TRR 79, Materials for tissue regeneration within systemically altered bone, part projects M7, M9, B5)
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