Sialic acid (SA) is a monosaccharide usually linked to the terminus of glycan chains on the cell surface. It plays a crucial role in many biological processes, and hypersialylation is a common feature in cancer. Lectins are widely used to analyze the cell surface expression of SA. However, these protein molecules are usually expensive and easily denatured, which calls for the development of alternative glycan-specific receptors and cell imaging technologies. In this study, SA-imprinted fluorescent core-shell molecularly imprinted polymer particles (SA-MIPs) were employed to recognize SA on the cell surface of cancer cell lines. The SA-MIPs improved suspensibility and scattering properties compared with previously used core-shell SA-MIPs. Although SA-imprinting was performed using SA without preference for the α2,3- and α2,6-SA forms, we screened the cancer cell lines analyzed using the lectins Maackia Amurensis Lectin I (MAL I, α2,3-SA) and Sambucus Nigra Lectin (SNA, α2,6-SA). Our results show that the selected cancer cell lines in this study presented a varied binding behavior with the SA-MIPs. The binding pattern of the lectins was also demonstrated. Moreover, two different pentavalent SA conjugates were used to inhibit the binding of the SA-MIPs to breast, skin, and lung cancer cell lines, demonstrating the specificity of the SA-MIPs in both flow cytometry and confocal fluorescence microscopy. We concluded that the synthesized SA-MIPs might be a powerful future tool in the diagnostic analysis of various cancer cells.

Cancer cell behaviour such as motility, migration and adhesion are important parameters to study, in order to understand the properties of metastasis. The sialylation of proteins and lipids on cell surfaces is central for movement of cells. We have investigated two different cell lines with and without sialylation, MDAMB-231 and PC-3 Wild type (WT) and Simple Cells (SC) and used digital holographic cytometry (DHC) to monitor the morphological changes of these cells in vitro. DHC is a convenient method to monitor different cell types and to collect morphological data such as area and thickness. MDA-MB-231 and PC-3WT cells differed morphologically as shown by DHC. In terms of proliferation, after incubation for 30 h a significant difference was observed between the genetically engineered breast MDA-MB-231 SC line and the MDA-MB-231 WT cell line, while no significant differences in proliferation patterns were observed between prostate PC-3 WT and SC. The cellular area could be compared with data generated by conventional flow cytometry. Differences between the analyzed cell lines are also demonstrated by feature diagrams. Wound healing assays were conducted, and the MDA-MB-231 WT cell line significantly outperformed the PC-3 WT cell line during 24 h of incubation. For MDA-MB-231 WT/SC and the PC-3 WT/SC lines, respectively, no significant difference was observed in this assay. Furthermore, a motility analysis using DHC indicateda significant difference between MDA-MB-231 and PC-3 cells. A significant difference over time could be demonstrated between MDA-MB-231 SC and WTcells, as MDA-MB-231 WT cells accumulated further compared to MDA-MB-231 SC. A significant difference was also observed between PC-3 WT and PC-3SC, where the PC-3 SC motility increased over time.

Digital holographic cytometry (DHC) is a state-of-the-art quantitative phase imaging (QPI) method that permits time-lapse imaging of cells without induced cellular toxicity. DHC platforms equipped with semi-automated image segmentation and analysis software packages for assessing cell behavior are commercially available. In this study we investigate the possible uptake of nanoprobes in macrophages in vitro over time.

Molecularly imprinted polymers (MIPs) against sialic acid (SA) have been developed as a detection tool to target cancer cells. Before proceeding to in vivo studies, a better knowledge of the overall effects of MIPs on the innate immune system is needed. The aim of this study thus was to exemplarily assess whether SA-MIPs lead to inflammatory and/or cytotoxic responses when administered to phagocytosing cells in the innate immune system. The response of monocytic/macrophage cell lines to two different reference particles, Alhydrogel and PLGA, was compared to their response to SA-MIPs. In vitro culture showed a cellular association of SA-MIPs and Alhydrogel, as analyzed by flow cytometry. The reference particle Alhydrogel induced secretion of IL-1β from the monocytic cell line THP-1, whereas almost no secretion was provoked for SA-MIPs. A reduced number of both THP-1 and RAW 264.7 cells were observed after incubation with SA-MIPs and this was not caused by cytotoxicity. Digital holographic cytometry showed that SA-MIP treatment affected cell division, with much fewer cells dividing. Thus, the reduced number of cells after SA-MIP treatment was not linked to SA-MIPs cytotoxicity. In conclusion, SA-MIPs have a low degree of inflammatory properties, are not cytotoxic, and can be applicable for future in vivo studies.