No abstract

Surface-imprinted polymers allow for specific cell detection based on simultaneous recognition of the cell shape, cell size, and cell membrane functionalities by macromolecular cell imprints. In this study, the specificity of detection and the detection sensitivity for target cells within a pool of non-target cells were analyzed for a cell-specific surface-imprinted polymer combined with a heat-transfer-based read-out technique (HTM). A modified Chinese hamster ovarian cell line (CHO-ldlD) was used as a model system on which the transmembrane protein mucin-1 (MUC1) could be excessively expressed and for which the occurrence of MUC1 glycosylation could be controlled. In specific cancer cells, the overexpressed MUC1 protein typically shows an aberrant apical distribution and glycosylation. We show that surface-imprinted polymers discriminate between cell types that (1) only differ in the expression of a specific membrane protein (MUC1) or (2) only differ in the membrane protein being glycosylated or not. Moreover, surface-imprinted polymers of cells carrying different glycoforms of the same membrane protein do target both types of cells. These findings illustrate the high specificity of cell detection that can be reached by the structural imprinting of cells in polymer layers. Competitiveness between target and non-target cells was proven to negatively affect the detection sensitivity of target cells. Furthermore, we show that the detection sensitivity can be increased significantly by repetitively exposing the surface to the sample and eliminating non-specifically bound cells by flushing between consecutive cell exposures.

Previous work has indicated that surface imprinted polymers (SIPs) allow for highly specific cell detection through macromolecular cell imprints. The combination of SIPs with a heat-transfer-based read-out technique has led to the development of a selective, label-free, low-cost, and user-friendly cell detection assay. In this study, the breast cancer cell line ZR-75-1 is used to assess the potential of the platform for monitoring the quality of a cell culture in time. For this purpose, we show that the proposed methodology is able to discriminate between the original cell line (adherent growth, ZR-75-1a) and a descendant cell line (suspension growth, ZR-75-1s). Moreover, ZR-75-1a cells were cultured for a prolonged period of time and analyzed using the heat-transfer method (HTM) at regular time intervals. The results of these experiments demonstrate that the thermal resistance (Rth) signal decays after a certain number of cell culture passages. This can likely be attributed to a compromised quality of the cell culture due to cross-contamination with the ZR-75-1s cell line, a finding that was confirmed by classical STR DNA profiling. The cells do not express the same functional groups on their membrane, resulting in a weaker bond between cell and imprint, enabling cell removal by mechanical friction, provided by flushing the measuring chamber with buffer solution. These findings were further confirmed by HTM and illustrate that the biomimetic sensor platform can be used as an assay for monitoring the quality of cell cultures in time.

Phone: þ32 (011) 26 88 93, Fax: þ32 (011) 26 88 99 † K. Eersels and B. van Grinsven contributed equally to this work.In this article, we increased the sensitivity of the heat-transfer method (HTM) for the detection of breast cancer cells (ZR-75-1 cells, see figure) in phosphate buffered saline (PBS). The effect of small technological changes on the limit of detection (LoD) of the methodology was examined. To this extent, polished aluminum substrates with a mirror finish were used, replacing the unpolished chips used in previous studies. These chips were coated with a polyurethane layer and imprinted for the target cell type, creating a so-called surface imprintedpolymer (SIP). Binding of target cells to the SIP resulted in an increase of the thermal resistance at the solid-liquid interface under study. Background thermal resistance measurements were performed with polished and unpolished aluminum substrates. In addition, the effect of using silver paste as thermal coupling between the aluminum chip and the copper heat provider was analyzed. The results of these experiments reveal that optimal thermal contact is achieved when directly coupling the copper heat provider to the polished side of the aluminum substrate as evidenced by a decrease in the baseline thermal resistance. In addition, noise levels on the heat-transfer resistance (R th ) signal decreased by a factor in the optimal configuration. Dose-response curves were obtained using the optimized methodology and were compared with results obtained with the original substrates. These quantitative experiments demonstrated an improvement of the LoD by approximately thirty percent.ZR-75-1 cells applied onto a home-made rubber stamp.