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.
The cellular environment plays a significant role in cell phenotype and function. As such, physical properties of cell culture substrates including topography, roughness, and elasticity may be utilized to investigate the influence of these physical cues on the cellular response. In this review, 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 are highlighted, with a particular emphasis on elastic substrates.
The ability to reversibly modulate macroscopic surface properties is an important requirement for numerous biomedical applications, such as cell culture, tissue engineering, biosensors, biofouling ...and microfluidics. While dynamic remodeling of materials and interfaces is a widely observed phenomenon in nature, examples of synthetic systems that can be switched on-demand are scarce. Recently, numerous active model systems have emerged, which rely on conformational transitions in molecularly defined films driven by external stimuli. In this article, we review recent advances in stimuli-responsive materials specifically focusing on monolayers formed by molecules such as peptides and oligonucleotides and their applications in biotechnology.
Stem cells have a host of applications in regenerative medicine and basic research. However, clinical translation hinges on the availability of effective stem cell expansion. Stem cell expansion has ...been limited due to the use of xenogenic factors in the culture system, batch-to-batch variation, and processes that do not readily lend themselves to scale-up. Synthetic substrates represent attractive alternatives to standard feeder layer culture, as they address many of these pressing limitations. Specifically, we use a grafting-to approach to create a zwitterionic hydrogel capable of maintaining human pluripotent stem cells in long-term culture. This approach enables the control of substrate physiochemical properties, is relatively inexpensive, and results in a substrate with good storage and sterilization stability. In this feature, we focus on the contributions of our culture system to prolonged stem cell culture and compare it to other culture systems currently available.
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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.
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 2.2paracyclophanes 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.
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.
A new method for generating and modeling reduced‐scale copolymer gradients by CVD is reported. By exploiting diffusion through confined channels, functionalized 2.2paracyclophanes are copolymerized ...into their poly(p‐xylylene) (PPX) analogues as a composition gradient. Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS) are used to verify the gradient composition profiles. Gradients are deposited on both flat substrates and 3‐dimensional cylinders. Both the thickness and compositional profiles are fitted to a diffusion‐based model using realistic physical parameters. The derived equation can be generalized and optimized for any copolymerization gradient through a confined geometry, thus allowing for broad applicability to other copolymer systems.
A method for depositing reduced‐scale polymer surface composition gradients is described. The method applies to both flat and three‐dimensional substrates. A transport model fits the experimental measurements to physical parameters, enabling the calculation of gradient properties.
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