Biosensors and Bioelectronics 20 (2004) 773–779 A comparison of microscope slide substrates for use in transfected cell microarrays James B. Delehanty ∗ , Kara M. Shaffer, Baochuan Lin Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC 20375-5348, USA Available online 24 May 2004 Abstract Transfected cell microarrays, arrays of mammalian cells expressing defined genes, offer enormous potential for the development of high-throughput cell-based detection technologies to monitor the presence of biological agents or environmental toxicants. The signals generated from these arrays are intimately linked to the efficiency of DNA uptake by the cells located on the micrometer-sized spots. However, quantitative analysis of the transfection efficiency on cellular microarrays has been limited. Further, little regard has been given to the role of the substrate in influencing the transfection efficiency of mammalian cells on transfected microarrays. In this report, we have quantified the transfection efficiency of mammalian cells on different microscope slide substrates. Using commercially available microscope slides bearing substrates that mediate cellular attachment (polystyrene, 3-aminopropylsilane, and poly-l-lysine), we have demonstrated the role of substrate hydrophobicity in determining the resulting spot size and the local DNA concentration when plasmid DNA is dispensed in a printing buffer containing gelatin and sucrose using a noncontact microarray printer. The mean spot diameter varied inversely with the substrate water contact angle (r 2 = 0.970). Further, the relative local plasmid DNA concentration was a function of the mean spot diameter. The deposition of Rhodamine Red-labeled plasmid DNA revealed that, across all substrates, the average fluorescence signal within the spots varied inversely with the mean spot diameter (r 2 = 0.976). The transfection efficiency of HEK 293T/17 cells varied in accord with the mean spot diameter, demonstrating that the uptake of DNA was a function of the local DNA concentration on each substrate. © 2004 Elsevier B.V. All rights reserved. Keywords: Cellular microarray; Transfection efficiency; Piezoelectric; Fluorescence; Biosensor 1. Introduction With advances in cell and tissue culture has emerged the ability to use biological cells as sensing platforms for the detection of biological warfare agents and environmental toxicants (Pancrazio et al., 1999; Aravanis et al., 2001; Gilchrist et al., 2001; Stenger et al., 2001). Cell-based sen- sors carry out functional assays as cells not only possess the ability to detect the presence of an agent, but they are also capable of responding in a manner that can offer insight into the physiological effect of the analyte. One can view cells as a vehicle by which receptors of interest are expressed in their native environment and conformation. Further, these receptors are often linked to highly sensitive and specific signaling cascades that allow for signal amplification. In this manner, biosensors with living cells as the recognition ∗ Corresponding author. Tel.: +1-202-767-0291; fax: +1-202-767-9594. E-mail address: jbd@cbmse.nrl.navy.mil (J.B. Delehanty). elements offer distinct advantages over more traditional sensing platforms (e.g., immunoassays) which function largely by the immobilization of recognition molecules and provide only binding information. As the list of potential threats including chemical and biological agents has become increasingly diverse, the need has arisen for the development of detection technologies that depart from single analyte detection and move toward sensing platforms that can achieve multiplex detection. In similar fashion to DNA and protein microarrays, which deliver multiplex detection via the high-density spatial ar- rangement of molecular recognition elements (Ekins and Chu, 1992; Schena et al., 1995), the ability to create arrays of cells at high-density offers the potential for the develop- ment of cell-based sensors with extremely high-throughput and multiplex capability. Further, the expression of recep- tors of interest within these arrays could yield cell-based sensors with defined specificities. Recently, a method for the production of high-density arrays of cells expressing defined genes was described (Ziauddin and Sabatini, 2001; 0956-5663/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2004.04.016