Agarose Stamp Research Articles

Initiation of waves in the Belousov–Zhaboyinsky system via the reaction-diffusion process of wet stamping

Periodic waves were studied via the process of wet stamping, in a heterogeneous media soaked in different solutions of the Belousov–Zhabotinsky (BZ) reaction system containing ferroin and malonic acid. The experiments were performed by making an initial contact of soaked polyacrylamide (PAA) gel with agarose stamp for a short period of time, and then placing the gel onto the glass plate after exposing both of its surfaces. This led to the development of propagating waves on the surface of the gel. The results show that patterns have a dependence on the concentration of individual species, which are represented in the form of bifurcation diagrams. The behavioral trend of this system is also compared with the current perspectives of the reaction diffusion system.

Polyelectrolyte Micropatterning Using Agarose Plane Stamp and a Substrate Having Microscale Features on Its Surface

We have introduced polyelectrolyte micro-patterning technique employing agarose plane stamp and a hard substrate having microscale features on its surface. With this method, chemically micropatterned surfaces with both positive and negative functionalities were successfully embedded in well-defined microstructures, and selective impartment of charge functionalities was confirmed by patterning bead bearing surface charge. Furthermore, this technique allows highly sensitive immobilization of protein onto targeted surface simply by endowing functionalities, which extends the potential of its use as a tool for high-throughput protein microarray and proteomics. Because plane agarose stamp is free of structures on its surface, there is no concern for pattern collapse, and the combination of agarose plane stamp with patterned substrate is more suited for selective protein patterning compared with adopting surface-patterned agarose stamp with flat substrate. Our technique using agarose plane stamp and a substrate having microscale features on its surface suggests a range of possible applications, including the micropatterning of biofunctionalized copolymer having polyelectrolyte block, immobilization of micro- and nanoparticle with biofunctionalities such as biotin and streptavidine, and establishing optoelectronic microstructures with micro-beads on various surfaces.

Direct patterning of mammalian cells onto porous tissue engineering substrates using agarose stamps

This paper describes simple, inexpensive, and potentially generic methodology for generating patterns of mammalian cells on porous scaffolds for tissue engineering using replica printing. Circular patterns (diameter: 200, 700, and 1000 μm) of human osteoblasts were transferred directly from topographically patterned agarose stamps onto porous hydroxyapatite scaffolds or onto fibronectin-coated glass slides. The use of hydrogel stamps provided a “wet”, biocompatible surface and maintained the viability of cells adsorbed on stamps during the patterning process. Stamps inked once with suspensions of cells allowed the repeated patterning of substrates. Direct stamping of human osteoblasts (and, potentially other mammalian cells) can be used to control the size, spacing, and geometry of patterns of cells printed on porous tissue engineering substrates. This approach may find use in controlling the spatial invasion of scaffolds, promoting the hierarchical organization of cells, and in controlling cell–cell interactions as a step in preservation of phenotypes of cells.

Bacterial Printing Press that Regenerates Its Ink: Contact-Printing Bacteria Using Hydrogel Stamps

This paper describes the use of micropatterned agarose stamps prepared by molding against PDMS masters to print patterns of bacteria on agar plates. Topographically patterned agarose stamps were inked with suspensions of bacteria; these stamps generated patterns of bacteria with features as small as 200 microm over areas as large as 50 cm2. Stamps with many small features (>200 microm) were used to study patterns of bacteria growing on media containing gradients of small molecules; stamps with larger features (>750 microm) were used to print different strains of bacteria simultaneously. The stamp transfers only a small percentage of cells that are on its surface to the agar at a time; it is thus possible to replica-pattern hundreds of times with a single inking. The use of soft stamps provides other useful functions. Stamps are easily customized to provide a range of patterns. When culture media is included in the agarose stamp, cells divide and thrive on the surface. The resulting "living stamp" regenerates its "ink" and can be used to pattern surfaces repetitively for a month. This method is rapid, reproducible, convenient, and can be used to control the pattern, spacing, and orientation between colonies of different bacteria.

Color Micropatterning with Reconfigurable Stamps

A two-phase, reaction−diffusion (RD) system is described in which printing stamps of the same geometries produce different micropatterns when applied to different surfaces. Initial outflow of water from an agarose stamp into a dry gelatin “paper” causes redistribution of a chemical “ink” contained in the stamp. Depending on the gelatin's water absorptivity, the ink is printed at different locations and develops into different types of color patterns. The mechanism of formation of these patterns is studied using stamps with polygonal tiling surface reliefs. Scaling arguments are derived that explain formation of different pattern types for different geometrical parameters of the system.

Color Micro‐ and Nanopatterning with Counter‐Propagating Reaction–Diffusion Fronts

Thin films of ionically doped gelatin have been color-patterned with submicrometer precision using the wet-stamping technique. Inorganic salts are delivered onto the gelatin surface from an agarose stamp, and diffuse into the gelatine layer, producting deeply colored precipitates. Reaction fronts originating from different features of the stamp cease within < 1 μm of each other, leaving sharp, transparent regions in between.

Self-assembling protein arrays | Assay for interactions requiring PTMs | Brain peptidomics | 15N-labeled rat | Singling out proteins in mixtures | NMR of proteins in bilayer nanotube arrays | Environment affects proteomes | Oligosaccharides labeled with cyanine dyes | Plant-specific proteins | Proteome analysis of ovarian epithelial cancer | Agarose stamps for protein microarrays

Self-assembling protein arrays | Assay for interactions requiring PTMs | Brain peptidomics | 15N-labeled rat | Singling out proteins in mixtures | NMR of proteins in bilayer nanotube arrays | Environment affects proteomes | Oligosaccharides labeled with cyanine dyes | Plant-specific proteins | Proteome analysis of ovarian epithelial cancer | Agarose stamps for protein microarrays

One-Step Multilevel Microfabrication by Reaction−Diffusion

A new experimental technique is described that uses reaction--diffusion phenomena as a means of one-step microfabrication of complex, multilevel surface reliefs. Thin films of dry gelatin doped with potassium hexacyanoferrate are chemically micropatterned with a solution of silver nitrate delivered from an agarose stamp. Precipitation reaction between the two salts causes the surface to deform. The mechanism of surface deformation is shown to involve a sequence of reactions, diffusion, and gel swelling/contraction. This mechanism is established experimentally and provides a basis of a theoretical lattice-gas model that allows prediction surface topographies emerging from arbitrary geometries of the stamped features. The usefulness of the technique is demonstrated by using it to rapidly prepare two types of mold for passive microfluidic mixers.

Multicolour micropatterning of thin films of dry gels.

Micropatterning of surfaces with several chemicals at different spatial locations usually requires multiple stamping and registration steps. Here, we describe an experimental method based on reaction-diffusion phenomena that allows for simultaneous micropatterning of a substrate with several coloured chemicals. In this method, called wet stamping (WETS), aqueous solutions of two or more inorganic salts are delivered onto a film of dry, ionically doped gelatin from an agarose stamp patterned in bas relief. Once in conformal contact, these salts diffuse into the gelatin, where they react to give deeply coloured precipitates. Separation of colours in the plane of the surface is the consequence of the differences in the diffusion coefficients, the solubility products, and the amounts of different salts delivered from the stamp, and is faithfully reproduced by a theoretical model based on a system of reaction-diffusion partial differential equations. The multicolour micropatterns are useful as non-binary optical elements, and could potentially form the basis of new applications in microseparations and in controlled delivery.

Micropatterned agarose gels for stamping arrays of proteins and gradients of proteins.

We describe a method for repetitive and rapid formation of planar microarrays and gradients of proteins using patterned agarose stamps. It demonstrates: (i) micropatterning of agarose gels with feature sizes as small as 2 microm; (ii) inking of posts (diameter 50-1000 microm) on patterned agarose stamps with one or multiple (here, eight) proteins and repetitive stamping of patterns (>100 times in the case of one protein) and arrays (20 times in the case of eight proteins) without the need for intermediate re-inking; (iii) transferring spots of proteins with good homogeneity in surface coverage to glass slides; (iv) applying this technique to surface-based immunoassays; (v) stamping that requires only sub-nanomolar amounts of protein (typically approximately 3 microg in approximately 0.6 microL of solution); (vi) stamping without the need for drying of the proteins, as opposed to stamping with stamps made of poly(dimethylsiloxane); and (vii) patterning gradients of proteins by allowing two proteins to diffuse toward each other in an agarose stamp, followed by printing the protein gradients onto a surface.