Biocomposite films synthesized at a fluid/fluid interface

Abstract

In the synthesis of mesostructured particles and films, the cooperative self-organization of amphiphilic molecules in the presence of reactive species is a key factor in the reaction mechanism. This paper presents a method for preparing structured collagen films synthesized at fluid/fluid interfaces. This work is an extension of previous efforts in our group to synthesize structured silica films in a reaction system confined at the interface between two immiscible fluid phases, providing an additional level of control over the structural evolution that occurs during reaction. Synthesis at a liquid/liquid interface was shown to provide excellent control over the mesostructure of the final product, avoiding a major problem encountered in many film synthesis techniques in which the reaction occurs at a liquid/solid interface: namely, the undesired effect of the solid surface on the film structure. The focus of this paper is the synthesis of structured composite films containing amphiphilic phospholipids and collagen. These films provide a way to pattern cell growth on biocompatible surfaces and a model system for studying the self-assembly mechanism of lipids and collagen. Self-assembled monolayers and bilayers composed of phosphatidylethanolamine (PE) lipids and collagen were investigated to determine how regularly patterned films can be prepared in a manner that preserves the bioactive properties of the collagen. Mixtures of PEs and acid-soluble collagen were spread on an aqueous subphase in a Langmuir trough. Surface pressure-area compression isotherms for the composite lipid/collagen monolayers provide information about interactions between these components. Langmuir-Blodgett (LB) techniques were utilized to transfer the composite films onto freshly cleaved mica. The mica-supported films were characterized by atomic force microscopy. The lipid/collagen ratio in the composite films was found to be the most important factor in determining how the collagen is assembled and distributed. The temperature and pH of the aqueous subphase, the process for spreading collagen on the subphase, the deposition speed, and the deposition pressure are factors that can be used to selectively control the film patterning. For most of these experimental factors, the range over which a highly structured uniform film can be fabricated over significant length scales is generally very narrow. Based on the experimental results and understanding of the fundamental interactions involved, a mechanism for the co-self-assembly of phospholipids and collagen is suggested. The adhesion and growth of Chinese hamster ovary (CHO) cells on the patterned film surfaces demonstrates the biocompatibility of these composite films.

Compressibility study of quaternary phospholipid blend monolayers

“…The graph in Fig. 1 shows the pressure-area (˘-A) isotherms for pure DOPE and pure DSPE monolayers at room temperature, which are in reasonable agreement when compared with equivalent ones found in the literature [15][16][17][18], some differences being due to variations in temperature, compression speed, impurities or other instabilities of polar lipid systems. The area per molecule is more difficult to reproduce while the shape of the isotherm should be reproducible and is characteristic of each material or mixture.…”

Fabrication of biofunctional nanomaterials via Escherichia coli OmpF protein air/water interface insertion/integration with copolymeric amphiphiles

“…In the case of subphase OmpF addition to the 4METH, lower starting pressures (eg, 2 mN/m and 4 mN/m) may have allowed for so much protein insertion that the film was destabilized during compression. Such phenomena have also previously been observed with collagen-copolymer composites, wherein optimal film pressures were reached depending on the ratio of collagen to copolymer [14,15].…”

“…More recently, however, block copolymer membranes have been used as biomimetic membranes for potential protein-based device fabrication because of their enhanced mechanical stability as well as versatility in composition and dimension [9][10][11][12]. In addition, polymers and lipids have been used as amphiphilic substrates for the deposition of biomolecules directly onto the liquid subphase [13][14][15]. In the planar form, block copolymer membranes can be integrated with various integral proteins to make large-area films to achieve cellular surface mimicry and applications in coating bioimplants for enhanced biocompatibility.…”

The effect of neutral helper lipids on the structure of cationic lipid monolayers

“…Close agreement from the comparison of the thickness of the DODAB monolayers obtained in the present study with half the bilayer thickness of the same lipid systems when in the form of vesicles lends support to the use of monolayer studies to aid in understanding the molecular architecture of the corresponding bilayers. As the lateral surface pressure in the biological membrane is widely considered to be of the order of 30-35 mN m 21 (reviewed in [38][39][40]), it is most pertinent to compare the structure of the various DODAB-containing monolayers at surface pressures between 30 and 40 mN m [52] and determined by ourselves).…”