The detection of circulating tumor cells (CTCs) in the blood of cancer patients is a challenging task. CTCs are, especially at the early stages of cancer development, extremely rare cells hidden in a vast background of regular blood cells. We describe a new strategy for the isolation of CTCs from whole blood. The key component is a medical wire coated with a multilayer assembly that allows highly specific capture of EpCAM (epithelial cell adhesion molecule) positive CTCs from blood. The assembly is generated in a layer-by-layer fashion through photochemically induced C,H insertion reactions and consists of a protective layer, which shields the contacting solution from the metal, a protein resistant layer, which prevents nonspecific interactions with proteins and a layer containing the EpCAM antibodies. In vitro experiments show that these surfaces can capture tumor cells from whole blood with enrichment factors (specifically vs nonspecifically bound cells) of up to about 3000 compared to the number of leucocytes in the blood. The purity of the isolated cells is greater than 90%. After "fishing" them from the blood, the cells, still bound to the wire, can be genetically analyzed. This demonstrates that this strategy might prove useful for next generation sequencing.
This work describes a novel technique for the deposition of surface‐attached hydrogels, which is based on a combination of spray coating and CH‐insertion cross‐linking (CHic) to create a protein repellent surface. To this, hydrogel precursor polymers are spray coated onto the surface to be modified, dried, and photo cross‐linked in the solid state. Spray coating allows the application of the hydrogel precursors in a fast and flexible way, so that even geometrically challenging substrates can be coated, such as the round surfaces present in the inside of blood collection tubes. Characterization of the coatings shows that the layer thickness and roughness can be controlled in the sub micrometer range by varying coating parameters. Interestingly, the ability for the deposited and attached layer to repel proteins is highly affected by these parameters. For layers with an identical chemical composition, protein repellent and adsorbing layers can be formed depending on the spraying conditions. Finally, protein and human serum repellency of spray coated layers in glass blood collection tubes is investigated and show a drastic improvement over uncoated tubes.
In bioanalytical applications, many coating strategies have been established for so-called "blocking" of the surfaces. However, most of the procedures developed so far require additional processing steps for surface blocking and small variations in the blocking efficiency result in increased background noise, which lowers the overall sensitivity of an assay. In this study, we demonstrate the preparation of a bioanalytical surface with a thin film of a photo-cross-linkable copolymer that is transformed photochemically into a surface-attached hydrogel network. The presented coating is directly applicable to various plastic substrates that are used for bioassays without the need for any prior surface modification. Such a strategy allows facile one-step immobilization of biomolecules for bioanalysis and protein-repellent properties for avoiding unspecific adsorption of analyte molecules during the assay. The protein adsorption behavior of the hydrogel-coated and blank surfaces is measured by SPR with human serum and physisorption of labeled detection antibodies. We show that the hydrogel surfaces used lower unspecific background signals and background noise and thus increase the sensitivities of the microarray immunoassays.
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