Browsing by Author "Cisternas Fruns, Marcelo Andrés"

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    AFM Study of Elastic Module of Physical-Vapor-Deposited Phospholipid Membranes
    (2018) Volkmann, Ulrich Georg; Catalán López, Rodrigo Esteban; Retamal Ponce, María José; Cisternas Fruns, Marcelo Andrés; Moraga Vent, Nicolás Andrés; Díaz Díaz, Diego Ignacio; Corrales, Tomás P.; Pérez-Acle, Tomás; Soto Arriaza, Marco Antonio; Huber, Patrick
    The physical study of artificial phospholipid membranes on solid substrates has become a relevant way to gain insights into the physical behavior of cell membranes. The study of mechanical properties of artificial membranes (lab-made) has become possible with the use of atomic force microscopy. Here, we analyze the Young's modulus and adhesion force of several phospholipidic membranes as a function of temperature using Scanning Force Spectroscopy (SFS). Phospholipids were deposited onto double-polished silicon substrates by physical vapor deposition (PVD), as we have recently reported [1, 2]. We have used Raman spectroscopy to show that the chemical structure of our deposited phospholipid remains unaltered after PVD. After PVD we performed AFM and SFS measurements on the following phospholipids: DPPC, DMPC and DSPC. Measurements using AFM in liquid confirm the self-assembly of the phospholipid bilayer. By using SFS of the deposited membrane in liquid, we observe 2 phase transitions, both in Younǵs Modulus, as well as adhesion channels. The measured phase transitions are consistent with the ripple-gel transition and the gel-liquid crystalline phases. Furthermore, we have studied the frequency dependence of these phase transitions by changing the tip velocity in SFS experiments. Supported by FONDECYT grant # 1141105 (UGV), FONDECYT INICIACION grant # 11160664 (TPC), CONICYT Fellowships (RC and MC), Postdoctoral Fellowship FONDECYT 3160803 (MJR) and CONICYT-PIA ACT 1409. [1] María J. Retamal, Marcelo A. Cisternas, Sebastian E. Gutierrez-Maldonado, Tomas Perez-Acle, Birger Seifert, Mark Busch, Patrick Huber and Ulrich G. Volkmann, J. Chem. Phys. 141, 104201 (2014). [2] María Jose Retamal, Tomas P. Corrales, Marcelo A. Cisternas, Nicolas H. Moraga, Diego I. Diaz, Rodrigo E. Catalan, Birger Seifert, Patrick Huber, and Ulrich G. Volkmann. Biomacromolecules 17 (3), 1142 (2016).
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    Dry two-step self-assembly of stable supported lipid bilayers on silicon substrates
    (2020) Cisternas Fruns, Marcelo Andrés; Palacios-Coddou, F.; Molina, S.; Retamal Ponce, María José; Gómez Vierling, Nancy Catalina; Moraga Alarcón, Nicolás; Zelada, H.; Soto Arriaza, Marco; Corrales, T. P.; Volkmann, Ulrich
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    Formation and Morphology of Single Phospholipid Bilayers Formed by Velocity-Controlled Dip-Coating
    (2018) Cisternas Fruns, Marcelo Andrés; Soto Arriaza, Marco Antonio; Retamal Ponce, Maria Jose; Moraga Alarcón, Nicolás Hernán; Catalán Lopez, Rodrigo Esteban; Volkmann, Ulrich Georg; Diaz, Diego; Corrales, Tomas P.
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    Spontaneous formation in air of DPPC Supported Lipid Bilayers (SLBs) evaporated in a solvent free process on silicon substrates
    (2021) Cisternas Fruns, Marcelo Andrés; Volkmann, Ulrich; Pontificia Universidad Católica de Chile. Instituto de Física
    Artificial membranes are models for biological systems and are important to gain deeper insight into biological membranes and for various applications. We introduce a dry two-step self-assembly method consisting of the high-vacuum evaporation of phospholipid molecules over silicon, followed by a subsequent annealing step in air. We evaporate dipalmitoylphosphatidylcholine (DPPC) molecules over bare silicon without the use of polymer cushions or solvents. High-resolution ellipsometry and AFM temperature-dependent measurements are performed in air to detect the characteristic phase transitions of DPPC bilayers. Complementary AFM force-spectroscopy breakthrough events are induced to detect single- and multi-bilayer formations. These combined experimental methods confirm the formation of stable non-hydrated lipid bilayers with phase transitions between gel to ripple phases at 311.5 ± 0.9 K, ripple to liquid crystalline phases at 323.8 ± 2.5 K and liquid crystalline to fluid disordered phases at 330.4 ± 0.9 K, which was consistent with such structures reported in wet environments. We find that the AFM tip induces a restructuring or intercalation of the bilayer that is strongly related to the applied tip-force. These dry supported lipid bilayers show long-term stability. These findings are relevant for the development of functional biointerfaces, specifically for fabrication of biosensors and membrane protein platforms. The observed stability is relevant in the context of lifetimes of such systems protected by bilayers in dry environments, such as e.g. SARS-CoV-2 virus.
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    Study of nitrogen implantation in Ti surface using plasma immersion ion implantation & deposition technique as biocompatible substrate for artificial membranes
    (2020) Cisternas Fruns, Marcelo Andrés; Bhuyan, Heman; Retamal Ponce, María José; Casanova Morales, N.; Favre Domínguez, Mario; Volkmann, Ulrich; Díaz, Donovan; Moraga Jaramillo, Luis; Mandl, S.; Manova, D.; Chandía Cristi, América Valeska; Alvarez, A.; Guzmán, F.; Saikia, P.
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