The isolation of circulating tumor cells (CTCs) from the blood of patients afflicted with solid malignant tumors becomes increasingly important as it may serve as a ‘liquid biopsy’ with the potential of monitoring the course of the cancer disease and its response to cancer therapy, with subsequent molecular characterization. For this purpose, we functionalized a structured medical Seldinger guidewire (FSMW), normally used to obtain safe access to blood vessels and other organ cavities, with a chimeric monoclonal antibody directed to the cell surface expressed epithelial cell surface adhesion molecule (EpCAM). This medical device was optimized in vitro and its biocompatibility was tested according to the regulations for medical devices and found to be safe with no noteworthy side effects. Suitability, specificity and sensitivity of the FSMW to catch and enrich CTCs in vivo from circulating peripheral blood were tested in 24 breast cancer or non-small cell lung cancer (NSCLC) patients and in 29 healthy volunteers. For this, the FSMW was inserted through a standard venous cannula into the cubital veins of healthy volunteers or cancer patients for the duration of 30 min. After removal, CTCs were identified by immunocytochemical staining of EpCAM and/or cytokeratins and staining of their nuclei and counted. The FSMW successfully enriched EpCAM-positive CTCs from 22 of the 24 patients, with a median of 5.5 (0–50) CTCs in breast cancer (n=12) and 16 (2–515) CTCs in NSCLC (n=12). CTCs could be isolated across all tumor stages, including early stage cancer, in which distant metastases were not yet diagnosed, while no CTCs could be detected in healthy volunteers. In this observatory study, no adverse effects were noted. Evidently, the FSMW has the potential to become an important device to enrich CTCs in vivo for monitoring the course of the cancer disease and the efficacy of anticancer treatment.

We describe the formation and characterization of surface-passivating poly(ethylene glycol) (PEG) films on indium tin oxide (ITO) glass substrates. PEG chains with a molecular weight of 2000 and 5000 D were covalently attached to the substrates in a systematic approach using different coupling schemes. The coupling strategies included the direct grafting with PEG-silane, PEG-methacrylate, and PEG-bis(amine), as well as the two-step functionalization with aldehyde-bearing silane films and subsequent coupling with PEG-bis(amine). Elemental analysis by X-ray photoelectron spectroscopy (XPS) confirmed the successful surface modification, and XPS and ellipsometry provided values for film thicknesses. XPS and ellipsometry thickness values were almost identical for PEG-silane films but differed by up to 400% for the other PEG layers, suggesting a homogeneous layer for PEG-silane but an inhomogeneous distribution for other PEG coatings on the molecularly rough ITO substrates. Atomic force microscopy (AFM) and water contact angle goniometry confirmed the different degrees of surface homogeneity of the polymer films, with PEG-silane reducing the AFM rms surface roughness by 50% and the water contact angle hysteresis by 75% compared to uncoated ITO. The ability of the PEG layers to passivate the substrate against the nonspecific adsorption of biopolymers was tested using fluorescence-labeled immunoglobulin G and DNA oligonucleotides in combination with fluorescence microscopy. The results indicate a positive relationship between film density and homogeneity on one hand and the ability to passivate against biopolymer adhesion on the other hand. The most homogeneous layers prepared with PEG-silane reduced the nonspecific adsorption of fluorescence-labeled DNA by a factor of 300 compared to uncoated ITO. In addition, the study finds that the ratio of film thicknesses derived by ellipsometry and XPS is a useful parameter to quantify the structural integrity of PEG layers on molecularly rough ITO surfaces. The findings may be applied to characterize PEG or other polymeric films on similarly coarse substrates.

Indium tin oxide (ITO) substrates were modified with a layer of poly(amidoamine) (PAMAM) dendrimers to change their surface properties and, in particular, the substrates' work function. The functionalization procedure involved the electrostatic adsorption of positively charged PAMAM dendrimers of generation five onto negatively polarized ITO surfaces. Three different PAMAM dendrimers were used: PAMAM-NH2 and PAMAM-OH with terminal amine and hydroxyl groups, respectively, as well as Q-PAMAM-NH2, which had been prepared from PAMAM-NH2 by quaternization of the dendrimer's terminal and internal amine groups with methyl iodide. The resulting organic films were analyzed by contact angle goniometry, X-ray photoelectron spectroscopy, ellipsometry, and Kelvin probe force microscopy to confirm the presence of a dense layer. A Langmuir isotherm was derived from surface densities of fluorescence-labeled PAMAM-NH2 dendrimers from which we deduced an equilibrium binding constant, K(eq), of (1.3 +/- 0.3) x 10(5) M(-1). Kelvin probe measurements of the contact potential difference revealed a high reduction of the work function from 4.9 eV for bare ITO to 4.3 eV for ITO with a dense film of PAMAM-NH2 of generation five. PAMAM-OH and Q-PAMAM-NH2 resulted in slightly smaller work function changes. This study illustrates that the work function of ITO can be tuned by adlayers composed of PAMAM dendrimers.