Microcontact printing and microspotting as methods for direct protein patterning on plasma deposited polyethylene oxide: application to stem cell patterning

A versatile and tunable bio-patterning platform for the construction of various cell array biochips

In this work, we report a versatile and tunable platform for the construction of various cell array biochips using a simple soft lithographic approach to pattern polydopamine (PDA) arrays via microcontact printing (μCP). Instead of direct polymerization of PDA on the polydimethylsiloxane (PDMS) tips, dopamine monomers were first printed on the substrate followed by a self-oxidative polymerization step facilitated by ammonia vapor to grow PDA in situ, which greatly reduced the reaction time and prevented the PDMS tips from damaging. The improved robustness and utility of the PDMS tips allows the formation of tunable PDA array chips with controllable PDA feature size and shape. As a result, single cell, multi-cells and cell line arrays can be constructed. The obtained cell array chips showed high single cell capture efficiency, providing a standardized single cell array analysis platform. Meanwhile, the adhered cells can maintain excellent viability and proliferation ability on the PDA chips. Moreover, a cytotoxicity sensor with single cell resolution was enabled on the single cell array chip. This work provides a promising cell array biochip platform for high-throughput cellular analysis and cell screening.

Mammalian Cell Interaction with Periodic Surface Nanostructures

Here, we report on the nanopatterning of different aromatic polymer substrates achieved by KrF excimer laser treatment. The conditions for the construction of the laser-induced periodic surface structures, the so-called LIPSS pattern, were established by optimized laser fluence and a number of pulses. The polymer substrates were polyethylene naphthalate (PEN), polyethersulfone (PES), and polystyrene (PS), which were chosen since they are thermally, chemically, and mechanically resistant polymers with high absorption coefficients at the excimer laser wavelength. The surface morphology of the treated substrates was investigated by atomic force microscopy and scanning electron microscopy, and the roughness and effective surface area on the modified samples were determined. Elemental concentration was characterized by energy-dispersive (EDX) analysis, surface chemistry was determined with X-ray photoelectron spectroscopy (XPS). The samples with the formation of LIPSS induced by 10 mJ·cm⁻² with 1000, 3000, and 6000 pulses were used for subsequent in vitro cytocompatibility tests using human cells from osteosarcoma (U-2 OS). The LIPSS pattern and its ability of significant cell guidance were confirmed for some of the studied samples. Cell morphology, adhesion, and proliferation were evaluated. The results strongly contribute to the development of novel applications using nanopatterned polymers, e.g., in tissue engineering, cell analysis or in combination with metallization for sensor construction.

Parallel Microdispensing Method of High-Viscous Liquid Based on Electrostatic Force

Parallel microdispensing of high-viscous liquid is a fundamental task in many industrial processes. Herein, a smart printing head is developed, including the probe array, the electric control module, the contact force measurement module, and the extra force balance module. The parallel dispensing of high-viscous liquid in nL level is achieved. The interacting effect between probes on the loading process is analyzed too. According to the result, the interacting effect between probes has a strong influence on the loading process. Therefore, the strategy of serial electrical loading and parallel transfer printing is utilized. Finally, the dependency of transfer printing volume on probe size, etc., is experimentally investigated. The volume of the loaded droplet can be controlled by the lifting velocity of the probe array, and the volume of the transferred droplet can be adjusted by the size of the probe instead of the contact force. The advantage of the proposed method is to realize the highly repeatable parallel dispensing of high-viscous liquid with a relatively simple device.

Surface patterning techniques for proteins on nano- and micro-systems: a modulated aspect in hierarchical structures

The surface patterning of protein using fabrication or the external functionalization of structures demonstrates various applications in the biomedical field for bioengineering, biosensing and antifouling. This review article offers an outline of the existing advances in protein patterning technology with a special emphasis on the current physical and physicochemical methods, including stencil patterning, trap- and droplet-based microfluidics, and chemical modification of surfaces via photolithography, microcontact printing and scanning probe nanolithography. Different approaches are applied for the biological studies of recent trends for single-protein patterning technology, such as robotic printing, stencil printing and colloidal lithography, wherein the concepts of physical confinement, electrostatic and capillary forces, as well as dielectrophoretics, are summarised to understand the design approaches. Photochemical alterations with diazirine, nitrobenzyl and aryl azide functional groups for the implication of modified substrates, such as self-assembled monolayers functionalized with amino silanes, organosilanes and alkanethiols on gold surfaces, as well as topographical effects of patterning techniques for protein functionalization and orientation, are discussed. Analytical methods for the evaluation of protein functionality are also mentioned. Regarding their selectivity, protein pattering methods will be readily used to fabricate modified surfaces and target-specific delivery systems for the transportation of macromolecules such as streptavidin, and albumin. Future applications of patterning techniques include high-throughput screening, the evaluation of intracellular interactions, accurate screening and personalized treatments.

Recapitulating complex biological signaling environments using a multiplexed, DNA-patterning approach

Elucidating how the spatial organization of extrinsic signals modulates cell behavior and drives biological processes remains largely unexplored because of challenges in controlling spatial patterning of multiple microenvironmental cues in vitro. Here, we describe a high-throughput method that directs simultaneous assembly of multiple cell types and solid-phase ligands across length scales within minutes. Our method involves lithographically defining hierarchical patterns of unique DNA oligonucleotides to which complementary strands, attached to cells and ligands-of-interest, hybridize. Highlighting our method's power, we investigated how the spatial presentation of self-renewal ligand fibroblast growth factor-2 (FGF-2) and differentiation signal ephrin-B2 instruct single adult neural stem cell (NSC) fate. We found that NSCs have a strong spatial bias toward FGF-2 and identified an unexpected subpopulation exhibiting high neuronal differentiation despite spatially occupying patterned FGF-2 regions. Overall, our broadly applicable, DNA-directed approach enables mechanistic insight into how tissues encode regulatory information through the spatial presentation of heterogeneous signals.

Bio-orthogonal fluorinated resist for biomolecules patterning applications

The patterning of organic materials on solid substrate surfaces has been demonstrated by several methods, such as photolithography, soft lithography, imprint lithography and ink-jet printing. Fluorinated polymers and solvents provide attractive material systems to develop new patterning approaches, as they are chemically orthogonal to non-fluorinated organic molecules, allowing their efficient incorporation in different devices and systems. Moreover, fluorinated polymers are soluble in hydrofluoroether solvents, benign to biomolecules, and can be properly engineered to enable efficient photolithographic patterning. In this work, we report the development of a new photolithographic process for patterning biomolecules on any kind of surfaces either by physical adsorption or covalent bonding. The photoresist is based on a fluorinated material and hydrofluoroether solvents that have minimum interactions with biomolecules and thus they can be characterized as orthogonal to the biomolecules (bio-orthogonal). In both cases, the creation of patterns with dimensions down to 2 μm was achieved. The implementation of the developed photolithographic procedure for the creation of a multi-protein microarray is demonstrated.

Improved Multiprotein Microcontact Printing on Plasma Immersion Ion Implanted Polystyrene

Multiprotein micropatterning allows the creation of complex, controlled microenvironments for single cells that can be used for the study of the localized effects of various proteins and signals on cell survival, development, and functions. To enable analysis of cell interactions with microprinted proteins, the multiprotein micropattern must have low cross-contamination and high long-term stability in a cell culture medium. To achieve this, we employed an optimized plasma ion immersion implantation (PIII) treatment to provide polystyrene (PS) with the ability to covalently immobilize proteins on contact while retaining sufficient transparency and suitable surface properties for contact printing and retention of protein activity. The quality and long-term stability of the micropatterns on untreated and PIII treated PS were compared with those on glass using confocal microscopy. The protein micropattern on the PIII treated PS was more uniform and had a significantly higher contrast that was not affected by long-term incubation in cell culture media because the proteins were covalently bonded to PIII treated PS. The immunostaining of mouse pancreatic β cells interacting with E-cadherin and fibronectin striped surfaces showed phosphorylated paxillin concentrated on cell edges over the fibronectin stripes. This indicates that multiprotein micropatterns printed on PIII treated PS can be used for high-resolution studies of local influence on cell morphology and protein production.

Bioengineering of the Human Neural Stem Cell Niche: A Regulatory Environment for Cell Fate and Potential Target for Neurotoxicity

Human neural stem/progenitor cells of the developing and adult organisms are surrounded by the microenvironment, so-called neurogenic niche. The developmental processes of stem cells, such as survival, proliferation, differentiation, and fate decisions, are controlled by the mutual interactions between cells and the niche components. Such interactions are tissue specific and determined by the biochemical and biophysical properties of the niche constituencies and the presence of other cell types. This dynamic approach of the stem cell niche, when translated into in vitro settings, requires building up "biomimetic" microenvironments resembling natural conditions, where the stem/progenitor cell is provided with diverse extracellular signals exerted by soluble and structural cues, mimicking those found in vivo. The neural stem cell niche is characterized by a unique composition of soluble components including neurotransmitters and trophic factors as well as insoluble extracellular matrix proteins and proteoglycans. Biotechnological innovations provide tools such as a new generation of tunable biomaterials capable of releasing specific signals in a spatially and temporally controlled manner, thus creating in vitro nature-like conditions and, when combined with stem cell-derived tissue specific progenitors, producing differentiated neuronal tissue structures. In addition, substantial progress has been made on the protocols to obtain stem cell-derived cell aggregates such as neurospheres and self-assembled organoids.In this chapter, we have assessed the application of bioengineered human neural stem cell microenvironments to produce in vitro models of different levels of biological complexity for the efficient control of stem cell fate. Examples of biomaterial-supported two-dimensional and three-dimensional (2D and 3D) complex culture systems that provide artificial neural stem cell niches are discussed in the context of their application for basic research and neurotoxicity testing.

Improving Internal Cell Colonization of Porous Scaffolds with Chemical Gradients Produced by Plasma Assisted Approaches

Cell colonization of the surrounding environment is a very significant process in both physiological and pathological events. In order to understand the tissue regeneration process and thereby provide guidance principles for designing new biomaterials, it is of paramount importance to study the cell colonization in the presence of physical, chemical, and biological cues. Flat "gradient" materials are generally used with this purpose. Three dimensional gradient scaffolds mimicking more precisely the situation in vivo are somewhat more complex to fabricate and characterize. Scaffolds for Tissue Engineering (TE) made of hydrophobic synthetic polymers do not allow good cell colonization: far from their periphery, in fact, internal cell colonization is usually low. In this research poly-ε caprolactone (PCL) scaffolds have been "decorated" with chemical gradients both on top and along their thickness by means of cold plasma processes, in order to improve cell colonization of their core. Plasma treatments with a mixture of argon and oxygen (Ar/O₂), as well as plasma deposition of differently cross-linked poly(ethylene oxide) (PEO)-like coatings, have been performed. This study establishes that cross-linked PEO-like domains interspaced with native PCL ones deposited only on top of the scaffold (i.e., coating that penetrates less than 300 μm inside the scaffold) are more effective in promoting cell colonization across the scaffolds than the other tested materials including superhydrophilic samples and that ones produced by tested double step approaches. Last but not least, one result of this research is that, in the case of plasma coatings with low deposition rates and porous materials with a low pore interconnectivity, it is possible to improve penetration of low pressure plasma active species inside the scaffold's core thorough a pretreatment of the porous materials (i.e., penetration up to 4500 mm far from topside).

Multiplex cell microarrays for high-throughput screening

Microarray technology was developed in the early 1990s to measure the transcription levels of thousands of genes in parallel. The basic premise of high-density arraying has since been expanded to create cell microarrays. Cells on chip are powerful experimental tools for high-throughput and multiplex screening of samples or cellular functions. Miniaturization increases assay throughput while reducing both reagent consumption and cell population heterogeneity effect, making these systems attractive for a wide range of assays, from drug discovery to toxicology, stem cell research and therapy. It is usual to functionalize the surface of a substrate to design cell microarrays. One form of cell microarrays, the transfected cell microarray, wherein plasmid DNA or siRNA spotted on the surface of a substrate is reverse-transfected locally into adherent cells, has become a standard tool for parallel cell-based analysis. With the advent of technology, cells can also be directly spotted onto functionalized surfaces using robotic fluid-dispensing devices or printed directly on bio-ink material. We are providing herein an overview of the latest developments in optical cell microarrays allowing high-throughput and high-content analysis.

Protein patterning by a DNA origami framework

A spatial arrangement of proteins provides structural and functional advantages in vast technological applications as well as fundamental research. Most protein patterning procedures employ complicated, time consuming and very costly nanofabrication techniques. As an alternative route, we developed a fully biomolecular self-assembly method using DNA Origami Frames (DOF) as a template for both small and large scale protein patterning. We employed a triangular DOF (tDOF) to arrange the Bovine Serum Albumin (BSA) protein. Our in situ protein patterning strategy provides a novel, fully organic platform using a fast and low-cost surface approach with possible utilization in fundamental science and technological applications.

Surface-printed microdot array chips coupled with matrix-assisted laser desorption/ionization mass spectrometry for high-throughput single-cell patterning and phospholipid analysis

RATIONALE

Single-cell analysis is very important in several research fields for the heterogeneity of individual cells, which has been well accepted. However, restricted by the size and low content of a single cell, current studies have encountered challenges in high-throughput, high-space resolution and sensitivity, and multicomponent analysis. A methodology of a surface-printed microdot array chip coupled with matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is presented in this study for high-throughput single-cell patterning and phospholipid analysis.

METHODS

The poly-L-lysine (PLL) used as ink molecule was printed on an oxygen plasma processed indium tin oxide (ITO)-coated glass slide to form a microdot array by micro-contact printing technology. The cell array was then formed on the PLL microarray through electrostatic adsorption force. 9-Aminoacridine (9-AA) matrix was applied on the cell array before it was analyzed by MALDI-TOF MS. MALDI mass spectrometry imaging (MALDI-MSI) was then used for high-throughput, quick measurement, and multicomponent analysis of the cell array.

RESULTS

The single-cell capture efficiency of the cell array formed on the PLL microarray was about 40%. Twelve phospholipids were detected at the single-cell level, and the structures were further confirmed by MS/MS. The MALDI-MSI of selected ions showed a conformity with the cell array. The relative signal intensity data of selected ions were extracted from every pixel in the image within several minutes. The heterogeneity between individual cells was revealed from the relative signal intensity of phospholipids in 1-3 cells.

CONCLUSIONS

Compared to the existing related approaches, high-throughput, quick measurement, and multicomponent single-cell analysis have been realized by our method. Through different ink molecules used for micro-contact printing, the established platform could have the potential to capture and analyze specific cells. Copyright © 2016 John Wiley & Sons, Ltd.

Fabrication of Thickness-Controllable Micropatterned Polyelectrolyte-Film/Nanoparticle Surfaces by Using the Plasma Oxidation Method

We have demonstrated a novel way to form thickness-controllable polyelectrolyte-film/nanoparticle patterns by using a plasma etching technique to form, first, a patterned self-assembled monolayer surface, followed by layer-by-layer assembly of polyelectrolyte-films/nanoparticles. Octadecyltrimethoxysilane (ODS) and (3-aminopropyl)triethoxysilane (APTES) self-assembled monolayers (SAMs) were used for polyelectrolyte-film and nanoparticle patterning, respectively. The resolution of the proposed patterning method can easily reach approximately 2.5 μm. The height of the groove structure was tunable from approximately 2.5 to 150 nm. The suspended lipid membrane across the grooves was fabricated by incubating the patterned polyelectrolyte groove arrays in solutions of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) giant unilamellar vesicles (GUVs). The method demonstrated here reveals a new path to create patterned 2D or 3D structures.

Micropatterned fabrication of chitosan-based thermoresponsive membranes for improving cell adhesion and gene expression

A simple, rapid, and economical method to fabricate micropatterned thermoresponsive chitosan membranes was developed. Porous polystyrene films were prepared by liquid-induced phase separation. The size of pores on polystyrene films could be regulated by adjusting the composition of coagulation bath and changing the solvent evaporation rate. Subsequently, chitosan-based thermoresponsive membranes with island protrusions were fabricated using porous polystyrene films as templates. The effects of the micropatterns on the behaviors of mouse fibroblast L929 were investigated. The presence of micropatterns altered the cell cycle distribution and enhanced the gene expression of cyclin D1 and integrin β1. The micro-convex surface could promote the adhesion and proliferation of L929 cells. These results provided valuable guidance to design appropriate topographic surfaces for tissue engineering applications.

Modulation of surface bio-functionality by using gold nanostructures on protein repellent surfaces

A simple and straightforward nanofabrication method for the creation of gold nanoparticles patterns on a biologically inert plasma-deposited poly(ethyleneoxide) film for sensing and cell culture applications.

Nanotopographical manipulation of focal adhesion formation for enhanced differentiation of human neural stem cells

Manipulating neural stem cell (NSC) fate is of great importance for improving the therapeutic efficacy of NSCs to treat neurodegenerative disorders. Biophysical cues, in addition to biochemical factors, regulate NSC phenotype and function. In this study, we assessed the extent to which surface nanotopography of culture substrates modulates human NSC (hNSC) differentiation. Fibronectin-coated polymer substrates with diverse nanoscale shapes (groove and pillar) and dimensions (ranging from 300 to 1500 nm groove width and pillar gap) were used to investigate the effects of topographical cues on hNSC morphology, alignment, focal adhesion, and differentiation. The majority of nanopatterned substrates induced substantial changes in cellular morphology and alignment along the patterned shapes, leading to alterations in focal adhesion and F-actin reorganization. Certain types of nanopatterned substrates, in particular the ones with small nanostructures (e.g., 300-300 nm groove ridges and 300-300 nm pillar diameter gaps), were found to effectively enhance focal adhesion complex development. Consequently, these substrates enhanced hNSC differentiation toward neurons and astrocytes. Nanotopographical-induced formation of focal adhesions in hNSCs activates integrin-mediated mechanotransduction and intracellular signaling pathways such as MEK-ERK, which may ultimately promote gene expression related to NSC differentiation. This strategy of manipulating matrix surface topography could be applied to develop culture substrates and tissue engineered scaffolds that improve the efficacy of NSC therapeutics.