TY - JOUR A1 - Kovach, Ildyko A1 - Kosmella, Sabine A1 - Prietzel, Claudia Christina A1 - Bagdahn, Christian A1 - Koetz, Joachim T1 - Nano-porous calcium phosphate balls JF - Colloids and surfaces : an international journal devoted to fundamental and applied research on colloid and interfacial phenomena in relation to systems of biological origin ; B, Biointerfaces N2 - By dropping a NaH2PO4 center dot H2O precursor solution to a CaCl2 solution at 90 degrees C under continuous stirring in presence of two biopolymers, i.e. gelatin (G) and chitosan (C), supramolecular calcium phosphate (CP) card house structures are formed. Light microscopic investigations in combination with scanning electron microscopy show that the GC-based flower-like structure is constructed from very thin CP platelets. Titration experiments indicate that H-bonding between both biopolymers is responsible for the synergistic effect in presence of both polymers. Gelatin chitosan water complexes play an important role with regard to supramolecular ordering. FTIR spectra in combination with powder X-ray diffraction show that after burning off all organic components (heating up >600 degrees C) dicalcium and tricalcium phosphate crystallites are formed. From high resolution transmission electron microscopy (HR-TEM) it is obvious to conclude, that individual crystal platelets are dicalcium phosphates, which build up ball-like supramolecular structures. The results reveal that the GC guided crystal growth leads to nano-porous supramolecular structures, potentially attractive candidates for bone repair. (c) 2015 Elsevier B.V. All rights reserved. KW - Calcium phosphates KW - Bone repair material KW - Biomineralization KW - Supramolecular ball structure Y1 - 2015 U6 - https://doi.org/10.1016/j.colsurfb.2015.05.021 SN - 0927-7765 SN - 1873-4367 VL - 132 SP - 246 EP - 252 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kovach, Ildyko A1 - Koetz, Joachim A1 - Friberg, Stig E. T1 - Janus emulsions stabilized by phospholipids JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Janus emulsions were formed by mixing three immiscible liquids; this implies two oil components (i.e. olive oil (00) and silicone oil (SiO)) with water in presence of interfacial active components. The morphology and size of Janus droplets formed strongly depended on the type of surfactant used. In presence of a non-ionic surfactant, i.e. Tween 80, large engulfed Janus droplets were formed. By adding phospholipids to the system the droplet size was decreased and more stable Janus droplets formed. Interfacial tension measurements carried out using a spinning drop apparatus and a ring tensiometer demonstrate that interfacial tension is the most important factor controlling the size, morphology and stability of Janus droplets. When the interfacial tension between oil and water becomes <= 1 mN/m, smaller Janus droplets are formed. Such conditions are fulfilled when phospholipids are used in combination with non-ionic surfactant Tween 80. The morphology of the double droplets is predominantly controlled by the viscosity and interfacial tension between the two oil phases. By using different types of phospholipids, i.e. asolectin and lecithin instead of a more concentrated phosphatidylcholine (phospholipon), the interfacial tension is decreased and different morphologies of engulfing can be observed. KW - Janus emulsions KW - Spinning drop KW - Interfacial tension KW - Phospholipids Y1 - 2014 U6 - https://doi.org/10.1016/j.colsurfa.2013.08.065 SN - 0927-7757 SN - 1873-4359 VL - 441 SP - 66 EP - 71 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hasinovic, H. A1 - Friberg, S. E. A1 - Kovach, Ildyko A1 - Koetz, Joachim T1 - Destabilization of a dual emulsion to form a Janus emulsion JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - A vegetable oil (VO) was added to an emulsion of silicone oil in water (SO/W) with mixing limited to once turning the test tube upside down. Initially, the VO was dispersed into virtually centimeter-sized drops and the emulsion contained effectively no Janus drops, while after 1 h of agitation at a low level to prevent creaming, drops of 50-100-mu m size of the two oils were observed: in addition to an insignificant number of Janus drops. The topology of the latter showed them to emanate from flocculated individual drops of the two oils, but with no discernible effect by the interfacial tension equilibrium on the drop topology. Continued gentle mixing gave increasing fraction of Janus drops of increased size with a topology gradually approaching the one expected from the interfacial equilibrium at the contact line. The spontaneous formation of Janus drops indicated a reduction of the interfacial free energy in the process and the interfacial energy difference between separate and Janus drops was calculated for an appropriate range of interfacial tensions and for all oil fractions. The calculations enabled a distinction of the decrease due to interfacial area changes from the reduction of interfacial tensions per se, with the latter only a minor fraction. KW - Emulsion destabilization KW - Janus emulsions KW - Interfacial equilibrium KW - Microfluidics Y1 - 2014 U6 - https://doi.org/10.1007/s00396-014-3263-3 SN - 0303-402X SN - 1435-1536 VL - 292 IS - 9 SP - 2319 EP - 2324 PB - Springer CY - New York ER - TY - JOUR A1 - Hasinovic, Hida A1 - Friberg, Stieg E. A1 - Kovach, Ildyko A1 - Koetz, Joachim T1 - Janus emulsion drops - equilibrium calculations JF - Journal of dispersion science and technology N2 - Experimental results indicated the contact angles in the drops of Janus emulsions formed in a one-step mixing process to be invariant within a significant range the oil volume ratios, similar to the results from microfluidics emulsification. Since this result points to a connection between the kinetically formed emulsions and the local equilibrium topology of emulsion drops, the effect of interfacial tensions on the morphology of Janus emulsions was estimated from the equilibrium interfacial tensions at the line of contact. Realistic values of the tensions revealed the limited range of these to obtain Janus drops and also offered correlation between the equilibrium entities and the curvature of the interface between the two oils. KW - Drop morphology KW - equilibrium topology KW - Janus emulsions KW - microfluidics KW - multiple emulsion preparation Y1 - 2013 U6 - https://doi.org/10.1080/01932691.2013.763728 SN - 0193-2691 SN - 1532-2351 VL - 34 IS - 12 SP - 1683 EP - 1689 PB - Taylor & Francis Group CY - Philadelphia ER -