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search.filters.applied.f.access: openAccess × Subject: Thermoresponsive polymers ×

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    Switchable Release of Bone Morphogenetic Protein from Thermoresponsive Poly(NIPAM-co-DMAEMA)/Cellulose Sulfate Particle Coatings
    (Basel : MDPI, 2018) Müller, Martin; Urban, Birgit; Reis, Berthold; Yu, Xiaoqian; Grab, Anna Luise; Cavalcanti-Adam, Elisabetta Ada; Kuckling, Dirk
    Thermoresponsive coatings of poly(N-isopropylacrylamide-co-DMAEMA)/cellulose sulfate (PNIPAM-DMAEMA/CS) complexes are reported eluting bone-morphogenetic-protein-2 (BMP-2) on demand relevant for implant assisted local bone healing. PNIPAM-DMAEMA/CS dispersions contained colloid particles with hydrodynamic radii RH = 170–288 nm at T = 25 °C shrinking to RH = 74–103 nm at T = 60 °C. Obviously, PNIPAM-DMAEMA/CS undergoes volume phase transition (VPT) analogously to pure PNIPAM, when critical VPT temperature (VPTT) is exceeded. Temperature dependent turbidity measurements revealed broad VPT and VPTT 47 °C for PNIPAM-DMAEMA/CS colloid dispersions at pH = 7.0. FTIR spectroscopy on thermoresponsive PNIPAM-DMAEMA/CS particle coatings at germanium model substrates under HEPES buffer indicated both wet-adhesiveness and VPT behavior based on diagnostic band intensity increases with temperature. From respective temperature courses empirical VPTT ≈ 42 °C for PNIPAM-DMAEMA/CS coatings at pH = 7.0 were found, which were comparable to VPTT found for respective dispersions. Finally, the PNIPAM-DMAEMA/CS coatings were loaded with BMP-2 and model protein papain (PAP). Time dependent FTIR spectroscopic measurements showed, that for T = 37 °C there was a relative protein release of ≈30% for PAP and ≈10% for BMP-2 after 24 h, which did not increase further. Heating to T = 42 °C for PAP and to 47 °C for BMP-2 further secondary protein release of ≈20% after 24 h was found, respectively, interesting for clinical applications. BMP-2 eluted even at 47 °C was found to be still biologically active
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    Cononsolvency of the responsive polymer poly(N-isopropylacrylamide) in water/methanol mixtures: a dynamic light scattering study of the effect of pressure on the collective dynamics
    (Berlin ; Heidelberg : Springer, 2022) Niebuur, Bart-Jan; Deyerling, André; Höfer, Nicole; Schulte, Alfons; Papadakis, Christine M.
    The collective dynamics of 25 wt% poly(N-isopropylacrylamide) (PNIPAM) solutions in water or an 80:20 v/v water/methanol mixture are investigated in the one-phase region in dependence on pressure and temperature using dynamic light scattering. Throughout, two dynamic modes are observed, the fast one corresponding to the relaxation of the chain segments within the polymer blobs and the slow one to the relaxation of the blobs. A pressure scan in the one-phase region on an aqueous solution at 34.0 °C, i.e., slightly below the maximum of the coexistence line, reveals that the dynamic correlation length of the fast mode increases when the left and the right branch of the coexistence line are approached. Thus, the chains are rather swollen far away from the coexistence line, but contracted near the phase transition. Temperature scans of solutions in neat H2O or in H2O/CD3OD at 0.1, 130, and 200 MPa reveal that the dynamic correlation length of the fast mode shows critical behavior. However, the critical exponents are significantly larger than the value predicted by mean-field theory for the static correlation length, ν = 0.5, and the exponent is significantly larger for the solution in the H2O/CD3OD mixture than in neat H2O.