Thermoresponsive Polymer Micropatterns Fabricated by Dip-Pen Nanolithography for a Highly Controllable Substrate with Potential Cellular Applications (original) (raw)
Related papers
Cool Microcontact Printing To Fabricate Thermosensitive Microgel Patterns
Langmuir, 2013
A facile method, cool microcontact printing (cool μCP), of fabricating microgel patterns under ambient conditions is developed. By using spontaneously condensed water on the surface of cold items and the phase transition of polymer microgels below the lower critical solution temperature (LCST), a cool poly(dimethylsiloxane) (PDMS) stamp can be easily decorated with a thin layer of water ink and its pattern can substantially transfer to a substrate that is assembled with microgels. As a proof of concept, one kind of thermosensitive microgel (i.e., poly(N-isopropylacrylamide) (pNIPAM)) is selected to demonstrate our method. A series of pNIPAM microgel patterns with various geometries can be easily generated by featured PDMS stamps through a cool μCP method. The results of control experiment using room-temperature PDMS stamps or patterning the pNIPAM microgel-incorporated fluorescent probe reveal that condensed cold water on a cool PDMS stamp plays an important role when microgel particles are lifted off. In addition, it is also observed that both humidity and contact pressure have effects on the shapes of the pattern fabricated by cool μCP, and more precise or sophisticate patterns can be obtained by adjusting the conditions. It is envisioned that this practically available method, as a good extension to μCP, can facilitate the design of complex patterns, affording great convenience for many inherent applications ranging from photonics to chemical sensing to biotechnology.
Controlled synthesis of responsive hydrogel nanostructures via microcontact printing and ATRP
2011
Surfaces that are spatially functionalized with intelligent hydrogels, especially at the micro-and nanoscale, are of high interest in the diagnostic and therapeutic fields. Conventional methods of the semiconductor industry have been successfully employed for the patterning of hydrogels for various applications, but methods for fabricating precise 3 D patterns of hydrogels at the micro-and nanoscale over material surfaces remain limited. Herein, microcontact printing (mCP) followed by atom transfer radical polymerization (ATRP) was applied as a platform to synthesize temperature responsive poly(N-isopropylacrylamide) hydrogels with varied network structures (e.g. different molecular weight crosslinkers) over gold surfaces. The XY control of the hydrogels was achieved using mCP, and the Z (thickness) control was achieved using ATRP. The controlled growth and the responsive behavior of hydrogels to temperature stimuli were characterized using Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The results demonstrate that this platform allows for the controlled growth of hydrogel nanostructures using the controlled ATRP mechanism. It is also shown that the molecular weight of the crosslinker affects the rate of hydrogel growth. These PNIPAAm-based crosslinked hydrogel patterns were also demonstrated to have a temperature-dependent swelling response. Using this technique, it is possible to synthesize responsive hydrogel patterns over various surfaces for potential applications in the biomedical field.
Functional extensions of Dip Pen NanolithographyTM: active probes and microfluidic ink delivery
Smart materials and …, 2006
Dip Pen Nanolithography (DPN TM) is an important technique for nanotechnology and a fundamental new tool for studying the consequences of miniaturization. In this scanning probe technique a sharp tip is coated with a functional molecule (the 'ink') then brought into contact with a surface where it deposits ink via a water meniscus. The DPN process is a direct-write pattern transfer technique with nanometer resolution and is inherently general with respect to usable inks and substrates, including biomolecules such as proteins and oligonucleotides. We present functional extensions of the basic DPN process by showing multiple active probes along with the ability to load different inks onto probe tips. We present the fabrication process and characterization of thermomechanically actuated probes that use the bimorph effect to induce deflection of individual cantilevers as well as the integration of these probes with control electronics and an interface module. As an additional improvement to DPN functionality, we developed the capability to write with different inks on the probe array, permitting the fabrication of multicomponent nanodevices in one writing session. For this purpose, we fabricate passive microfluidic devices and present the microfluidic behavior and ink loading performance of these components.
Macromolecules, 2004
Sequential surface chemical reactions of poly(acrylic acid-coN -isopropylacrylamide) [poly-(AAc-co-NIPAAm)] with AAc contents of 5, 10, and 15 mol %, of which carboxyl groups were previously activated by 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride (EDC), plus poly(vinylamine hydrochloride) through amide linkages produced ultrathin films on a solid substrate. Assembly processes were quantitatively monitored by a quartz crystal microbalance as substrates. Assembled amounts increased with decreasing both AAc and EDC amounts. Subsequent immersion of ultrathin films into aqueous media resulted in the thickness increases, producing ultrathin hydrogels. Swelling ratios were estimated by percent increases in the thickness and increased with increasing AAc and EDC amounts. Swelling ratios were regularly changed by varying the ionic strength and pH of aqueous media. Swelling properties were interpreted on the basis of structural information on ultrathin hydrogels. Cyclic voltammetries using potassium ferricyanide revealed that ions permeated ultrathin hydrogels, and permeabilities were clearly suppressed above a lower critical solution temperature (LCST) of polyNIPAAm. Reversible on-off changes in permeabilities below and above a LCST were potentially observed. Not only structural control but also stimuli responsive functions of ultrathin hydrogels were realized within the present study.
Thermoresponsive microgel-based materials
With the continued development of thermoresponsive colloidal hydrogel particles, a number of groups have begun to exploit their properties to create dynamic materials self-assembled from those components. The fundamental details of how those building blocks are assembled, the component functionality, and the geometry or length-scales present in the assemblies contribute to the behavior of the resultant material. In this tutorial review, we examine recent progress in the assembly of responsive hydrogel colloids in two and three dimensions, highlighting their potential applications, especially in the domain of biotechnology.
Responsive Micromolds for Sequential Patterning of Hydrogel Microstructures
Journal of the American Chemical Society, 2011
Microscale hydrogels have been shown to be beneficial for various applications such as tissue engineering and drug delivery. A key aspect in these applications is the spatial organization of biological entities or chemical compounds within hydrogel microstructures. For this purpose, sequentially patterned microgels can be used to spatially organize either living materials to mimic biological complexity or multiple chemicals to design functional microparticles for drug delivery. Photolithographic methods are the most common way to pattern microscale hydrogels but are limited to photocrosslinkable polymers. So far, conventional micromolding approaches use static molds to fabricate structures, limiting the resulting shapes that can be generated. Herein, we describe a dynamic micromolding technique to fabricate sequentially patterned hydrogel microstructures by exploiting the thermoresponsiveness of poly(N-isopropylacrylamide)based micromolds. These responsive micromolds exhibited shape changes under temperature variations, facilitating the sequential molding of microgels at two different temperatures. We fabricated multicompartmental striped, cylindrical, and cubic microgels that encapsulated fluorescent polymer microspheres or different cell types. These responsive micromolds can be used to immobilize living materials or chemicals into sequentially patterned hydrogel microstructures which may potentially be useful for a range of applications at the interface of chemistry, materials science and engineering, and biology.
Sensors and Actuators B: Chemical, 2008
This paper presents a simple method to create protein micropattern on the poly(ethylene glycol) (PEG) hydrogels through the surface graft polymerization and photolithography. The modification of the protein-repellent PEG hydrogel surface was achieved by a two-step process using immobilization of benzophenone on the PEG hydrogel as surface initiator and subsequent surface-initiated polymerization of acrylic acid by UV irradiation. Surface modification of PEG hydrogels was demonstrated with FTIR/ATR spectroscopy and XPS by confirming the presence of carboxyl groups in the poly(acrylic acid) (PAA). The photograft polymerization through the designed photomask produced well-defined, pH-responsive PAA micropatterns with diameters ranging from 50 to 300 m on the PEG hydrogels. The size of PAA micropatterns was controlled by changing the environmental pH, such that a 300 m diameter and 17 m thick PAA micropattern at pH 4 swelled to 480 m diameter and 80 m thick at pH 7. Activation of the carboxyl groups in PAA allowed covalent immobilization of proteins only on the PAA micropatterns due to the nonadhesivity of PEG. Based on these results, biotin was micropatterned on the PEG hydrogels and binding of streptavidin was qualitatively and quantitatively investigated, demonstrating the possibility of micropatterned PEG hydrogels for various biosensor systems.
Polymers
For the effective use of live cells in biomedicine as in vitro test systems or in biotechnology, non-invasive cell processing and characterisation are key elements. Thermoresponsive polymer coatings have been demonstrated to be highly beneficial for controlling the interaction of adherent cells through their cultivation support. However, the widespread application of these coatings is hampered by limitations in their adaptability to different cell types and because the full range of applications has not yet been fully explored. In the work presented here, we address these issues by focusing on three different aspects. With regard to the first aspect, by using well-defined laminar flow in a microchannel, a highly controllable and reproducible shear force can be applied to adherent cells. Employing this tool, we demonstrate that cells can be non-invasively detached from a support using a defined shear flow. The second aspect relates to the recent development of simple methods for patterning thermoresponsive coatings. Here, we show how such patterned coatings can be used for improving the handling and reliability of a wound-healing assay. Two pattern geometries are tested using mouse fibroblasts and CHO cells. In terms of the third aspect, the adhesiveness of cells depends on the cell type. Standard thermoresponsive coatings are not functional for all types of cells. By coadsorbing charged nanoparticles and thermoresponsive microgels, it is demonstrated that the adhesion and detachment behaviour of cells on such coatings can be modulated. cells from synthetic cultivation substrates or scaffolds is crucial for making these cells available for cell-based approaches in the fields mentioned above.