Free-standing nanomembranes based on selective CVD deposition of functional poly-p-xylylenes.

The precise engineering of ultrathin nanofilms with variable functionality remains an unmet challenge in nanotechnology. We report a strategy for generating free-standing nanomembranes based on the selective chemical vapor deposition polymerization of functional [2.2]paracyclophanes on micropatterned self-assembled monolayers of alkanethiolates on gold. This fabrication strategy can yield microstructured nanofilms that are between 2 and 5 nm thick. Subsequent release from the substrate results in free-standing nanoscale membranes with controlled pore size and geometry. The process allows for modification of important functional parameters, such as ultrasmall membrane thickness, membrane pore geometry, and chemical functionality.

Co-immobilization of biomolecules on ultrathin reactive chemical vapor deposition coatings using multiple click chemistry strategies.

Immobilization of biomolecules, such as proteins or sugars, is a key issue in biotechnology because it enables the understanding of cellular behavior in more biological relevant environment. Here, poly(4-ethynyl-p-xylylene-co-p-xylylene) coatings have been fabricated by chemical vapor deposition (CVD) polymerization in order to bind bioactive molecules onto the surface of the material. The control of the thickness of the CVD films has been achieved by tuning the amount of precursor used for deposition. Copper-catalyzed Huisgen cycloaddition has then been performed via microcontact printing to immobilize various biomolecules on the reactive coatings. The selectivity of this click chemistry reaction has been confirmed by spatially controlled conjugation of fluorescent sugar recognizing molecules (lectins) as well as cell adhesion onto the peptide pattern. In addition, a microstructured coating that may undergo multiple click chemistry reactions has been developed by two sequential CVD steps. Poly(4-ethynyl-p-xylylene-co-p-xylylene) and poly(4-formyl-p-xylylene-co-p-xylylene) have been patterned via vapor-assisted micropatterning in replica structures (VAMPIR). A combination of Huisgen cycloaddition and carbonyl-hydrazide coupling was used to spatially direct the immobilization of sugars on a patterned substrate. This work opens new perspectives in tailoring microstructured, multireactive interfaces that can be decorated via bio-orthogonal chemistry for use as mimicking the biological environment of cells.

Physical aspects of cell culture substrates: topography, roughness, and elasticity.

The cellular environment impacts a myriad of cellular functions by providing signals that can modulate cell phenotype and function. Physical cues such as topography, roughness, gradients, and elasticity are of particular importance. Thus, synthetic substrates can be potentially useful tools for exploring the influence of the aforementioned physical properties on cellular function. Many micro- and nanofabrication processes have been employed to control substrate characteristics in both 2D and 3D environments. This review highlights strategies for modulating the physical properties of surfaces, the influence of these changes on cell responses, and the promise and limitations of these surfaces in in-vitro settings. While both hard and soft materials are discussed, emphasis is placed on soft substrates. Moreover, methods for creating synthetic substrates for cell studies, substrate properties, and impact of substrate properties on cell behavior are the main focus of this review.

Chemical-vapor-deposition-based polymer substrates for spatially resolved analysis of protein binding by imaging ellipsometry.

Biomolecular interactions between proteins and synthetic surfaces impact diverse biomedical fields. Simple, quantitative, label-free technologies for the analysis of protein adsorption and binding of biomolecules are thus needed. Here, we report the use of a novel type of substrate, poly-p-xylylene coatings prepared by chemical vapor deposition (CVD) polymerization, for surface plasmon resonance enhanced ellipsometry (SPREE) studies and assess the reactive coatings as spatially resolved biomolecular sensing arrays. Prior to use in binding studies, reactive coatings were fully characterized by Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy, and ellipsometry. As a result, the chemical structure, thickness, and homogeneous coverage of the substrate surface were confirmed for a series of CVD-coated samples. Subsequent SPREE imaging and fluorescence microscopy indicated that the synthetic substrates supported detectable binding of a cascade of biomolecules. Moreover, analysis revealed a useful thickness range for CVD films in the assessment of protein and/or antigen-antibody binding via SPREE imaging. With a variety of functionalized end groups available for biomolecule immobilization and ease of patterning, CVD thin films are useful substrates for spatially resolved, quantitative binding arrays.