Flexible Fabrication of Microarrays of Microwells

Abstract

Microwell technology, although in its infancy, has already shown enormous potential. Microwells have for example been applied in a number of optoelectronics-related applications [1,2] where microwells were able to offer fine control over, and manipulation of, crystal nucleation. In the biological arena [3] microwells have been produced that have allowed the selection and immobilization of single cells; while micro-patterned wells that maintain human embryonic stem cells (hESC) undifferentiated for up to three weeks, and limit colony growth have been reported. [4] A number of approaches have been used to generate the required structures. This includes a variety of soft-lithographic techniques, [3][4][5][6][7][8][9][10] often using a combination of polydimethylsiloxane (PDMS) based materials and photolithography [11][12][13][14][15][16][17][18] to produce "stamps" which can be coated with various polymers, biochemicals, gels etc., prior to stamping onto the receiving substrate to yield the desired microwell pattern. Photolithographic methods [11][12][13][14][15][16][17][18] have also been used to transfer images from a mask to a metal surface, with subsequent selective etching to generate the desired microwells. Several templating methods, based on self-assembly, have been used to create patterned substrates with sub-micron features. This includes the use of ordered arrays of colloidal particles, [19] microporous materials, [20,21] polymers with rod-coil architecture [22] or honeycomb structures, [23] self-organized surfactants, [24] and microphase-separated block copolymers. [25,26]

Rapid Prototyping of Concave Microwells for the Formation of 3D Multicellular Cancer Aggregates for Drug Screening

“…In addition, PS is the most commonly used material in tissue and cell culture research, [11a, 18] and has previously been used for thermal molding by a CO 2 laser for various biological applications. [11a] The PS chosen in this study is from untreated cell culture dishes, which are intended for growing cells in stationary suspension, and are therefore both economical and readily available.…”

Versatile Biocompatible Polymer Hydrogels: Scaffolds for Cell Growth

“…Chitosan and poly(ethylenimine) are two widely used polymers (Figure 1 a). Chitosan is a polysaccharide derived from chitin, and is an attractive material for use in the biomedical field [13] because of its controlled biodegradability [14] and biocompatibility.[15] Chitosan forms so-called "hydrogels" by the neutralization of acidic solutions of chitosan, although the resulting materials are opaque, with a granular crystalline morphology.[16] Poly(ethylenimine) (PEI) is a linear-branch polymer which has been extensively used in the gene delivery field [17] and as a coating material in biosensor applications.[18] Chitosan and PEI have been chemically grafted to give materials with enhanced gene-carrier abilities.[19] Herein we report the preparation of quite remarkable hydrogels that support 3D cell growth by the simple expedient of mixing solutions of these two cationic polymers.Polymer blends were generated by mixing chitosan (partially hydrolyzed, Mw = 250 kDa, 1 % aqueous acetic acid, pH % 4.0) and poly(ethylenimine) (Mw = 300 kDa, 10 % in water, pH % 11) in various molar ratios (90:10 to 10:90). The resulting solutions (pH % 7.5) became, over a period of 5 minutes, gels that were stable to inversion and manipulation.…”

Fabrication of polymeric biomaterials: a strategy for tissue engineering and medical devices

“…The microwells that have been generated allowed various cell types manipulation, encapsulation and growth, 80 for example, cervical carcinoma (HeLa) and human leukemia (K562) cells, and DNA transfection to the cells have been demonstrated in Fig. 6.…”