Inexpensive Raft Arrays For Cell Patterning And Cloning

An easy to use, inexpensive, efficient system has been developed for the combined purpose of patterned cell culture and cell separations. The system consists of a specialized flexible array of micron-scale array elements created by a unique soft lithography process compatible with a host of biocompatible polymers, including polystyrene. Low autofluorescence, standardized tissue culture surfaces can be created and tailored to the cell type of interest. The concave array elements, termed rafts, are fabricated within poly(dimethylsiloxane) (PDMS) microwells and are individually releasable using a needle inserted through the PDMS substrate with a micromanipulator. The array enables efficient cell analysis and isolation even with small populations containing as few as 1,000 cells. Cells plated on the arrays are localized to individual rafts throughout the culture period by virtue of the PDMS microwells. While the cells are prevented from migrating and intermixing, they share a common fluidic microenvironment in contrast to standard multiwell plates. Standard microscopic imaging is used to identify and track cells or colonies over time to allow selection based on temporal or other characteristics. Those of interest are released by inserting the needle through the compliant PDMS substrate to dislodge the raft on which the cell(s) of interest lies. The hardened polymer material forming the raft protects the cells growing on its upper surface from harm by the needle. Selective release of the individual elements along with the resident cells has been enhanced with the use of polymers doped with ferromagnetic nanoparticles to achieve high collection efficiencies of viable cells under the influence of a magnetic field. In the current state of development, collection efficiency and single-cell cloning rates as high as 95% have been achieved. Among other attributes, the array enables rapid cloning to produce cell lines with desired characteristics.