Materials Science , Dielectrophoresis , Dielectrophoresis and microfluidics , and Biochip. We report the development and characterization of a microfluidics-based bioimprint process using high-density microchannel arrays for cell-culture and polymer delivery. The tubeless PDMS arrays consist of multiple independent The tubeless PDMS arrays consist of multiple independent microchannels and allow for parallelized bioimprint via automated dispensing and passive pumping.
Using the microchannels, a nm thin test pattern was replicated into a methacrylate biopolymer to demonstrate process applicability. Bioimprints of cobalt chloride stimulated Ishikawa endometrial cancer cells exhibiting exocytosis-like pore structures were compared with controls using AFM to exemplify a process application. The devices can be used for high-throughput cell assays, cell developmental studies and the formation of phenotype-specific biomimetic scaffolds.
The quadrupole microelectrode design on a multilayer biochip for dielectrophoretic trapping of single cells more. However, can affect the DEP holding force on cells. To overcome this prob- excessive exposure to electric fields can deteriorate cell viability lem, the microcavity has to generate DEP force from within the on the biochip.
Therefore, a microcavity or cell trap can reduce microcavity itself. Therefore, the microcavity needs to be an elec- the DEP holding force dependency on»E2 but still maintain cell trode and structured on a different layer from the quadrupole pairs positioning [4]. Here, an insulator layer made of SU-8 is Here, we developed a new quadrupole microelectrode design to used to separate the back contact and the quadrupole microelec- trap single cells during mass loading of cells inside a microfluidic trode.
With the new electrode arrangement and the multilayer channel. The microfluidic channel regulates fluids flow i. The new design consists of arrays of quadru- can be implemented on the biochip. In the microfluidic channel, DEP force generated from microelectrode pair and the bottom of microcavity back contact.
Meanwhile, DEP force generated by the back con- through the back contact and the quadrupole microelectrode can tact is used to maintain cell positioning even when the quadrupole be left unbiased floating. Cell movements to the microcavity One advantage of this alternate biasing between layers is to re- are controlled by the AC potentials connected to the quadrupole duce damages caused by electric field in order to retain cell posi- microelectrode and the back contact.
The multilayer structure de- tioning. To realize a successful trapping event and single cell sign i. Numerical studies on the new quadrupole design fabricated using the softlithography technique. This paper de- were conducted using Comsol Multiphysics v3.
With the new quadrupole design, it is expected that single Multiphysics v3. Design and methodology A quadrupole electrode trap is established by positioning four 2. When array of quadrupole microelectrode is re- identified.
In this approximation, the tween adjacent electrodes of the quadrupole arrangement dielectric properties are ideal i. Therefore, in the only permittivity and zero conductivity. Then, the Laplace equa- new quadrupole design of Fig. This design allows AC potentials of differ- connected to the pattern. The new quadrupole biochip platform a on x-y plane and b on cross section of the SIBC platform. Table 1 Then, the master microfluidic channel pattern or mould was Simulation parameters for the quadrupole microelectrode from [12].
Parameter Polystyrene microbeads In this design straight channels are used to regulate fluids on the Relative permittivity 2. Cells were introduced onto the biochip through a Conductivity 0. The microchannels block was then manually aligned with the biochip platform in preparation for the DEP experiments shown in Fig.
Subsequently, studies on the supplied AC potentials configura- Fig. Each microelectrode arm is approximately also conducted. The microcavity is located at approximately in order to identify the optimum working combinations. In the 10 lm from the quadrupole microelectrode tips. A replication test pattern with various shapes and geometries was fabricated to evaluate the imprinting. Positive-tone photore- sist AZ, Microchemicals was spin-coated onto a glass micro- scope slide and patterned using photolithography.
A nm thick film of Cr was sputter-deposited using an Edwards Auto sput- tering system. This was followed by immersion of the sample in acetone to lift-off the Cr. Imprinting process A schematic of the bioimprint process is shown in Fig.
Ishikawa endometrial cancer cells were cultured as described previously [5]. In brief, cells were obtained from confluent cultures, trypsini- zed and diluted to the final cell density. The arrays were placed in an incubator for 5 days with regular media exchange to ensure nutrient availability. The UV-curable polymer mixture biopolymer was composed of ll of ethylene glycol dimethacrylate, Microchannels were filled by placing a droplet on the channel inlet using a pipette see Fig.
The cured biopolymer containing the bioimprints Fig. Individual channels are filled with dye-coloured water for illustration, b replacement of culture media with liquid pre-polymer in a single channel of the array, c cured imprints after removal of the PDMS microchannel array, d PDMS channel with subjacent Cr-on-glass test pattern.
The line indicates the surface profilometry scan used to characterize template and imprint, e composite SEM image of the pattern imprinted into the biopolymer after peeling off the template, f surface profilometry scans of the template solid line and imprint dashed line.
Schematic of the bioimprint process using the microchannel arrays: a Cell- culture and pre-polymer delivery, b UV-curing of the biopolymer, c imprint was removed by peeling-off the PDMS array see Fig.
Samples removal, and d sample imaging using AFM. AFM micrographs of bioimprints replicated off Ishikawa endometrial cancer cells cultured under normal conditions a and induced with cobalt chloride b. In the former standard features such as nuclei N can be observed, while in the latter cells additionally show increased secretion of vascular endothelial growth factor VEGF , which correlated well with the numbers of highly visible pores on the surface of the cell membrane arrows.
AFM Digital Instruments Nanoscope in tapping mode, as microchannel array was aligned on top and brought into reversible illustrated by Fig. All surface scans were processed using contact with the substrate see Fig. The channel was then the Gwyddion V2. After removal of the PDMS micro- channel array the bioimprint was peeled off the substrate contain- ing the test pattern.
A composite image of several SEM scans of the 3. The model contains digital pressure displays and computer integration for. Microfluidics-assisted photo nanoimprint lithography for the formation of cellular bioimprints more. Bioimprint offers a technique for the permanent capture of these features into an UV-curing, biocompatible, Bioimprint offers a technique for the permanent capture of these features into an UV-curing, biocompatible, methacrylate biopolymer.
This material shows excellent replication fidelity and fast setting times. However, the minimum reproducible feature size depends on the skillful application of the liquid prepolymer. To enable the repeatable formation of high-resolution, structurally bioactive cellular bioimprints, a modified process based on the use of microfluidics for integrated cell culture and polymer delivery has been developed.
In this article, the authors introduce the process and demonstrate its use for the culture and imaging of Ishikawa endometrial cancer cells. Initially monomer can be applied. This is currently performed by a developed to overcome challenges related to the high- delicate combination of drying through blotting and manual resolution imaging of cell surfaces and morphologies, bioim- aspiration, as any remaining fluid has the potential to distort the replication fidelity.
Related Papers Microfluidics-assisted photo nanoimprint lithography for the formation of cellular bioimprints By Maan Alkaisi. Microfluidic arrays for bioimprint of cancer cells By Lynn Murray. Bioimprinted polymer platforms for cell culture using soft lithography By Maan Alkaisi.
Fabrication of free-standing casein devices with micro- and nanostructured regular and bioimprinted surface features By Azadeh Hashemi and Isha Mutreja.
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