Anchoring of Aminophosphonates on Titanium Oxide for Biomolecular Coupling

Aminophosphonates were chosen for a first step functionalization of TiO2 grown on titanium, as they possess a phosphonate group on one end, that can be exploited for coupling with the oxide surface, and an amino group on the other end to enable further functionalization of the surface. The deposition of aminophosphonates with different chain lengths (6 and 12 methylenes) was investigated. Oxygen plasma treatment proved useful in increasing the number of −OH groups at the TiO2 surface, thus helping to anchor the aminophosphonates. By combining different surface-sensitive experimental techniques, we found the existence of a discontinuous monolayer where the molecules are covalently coupled to the TiO2 surface. For the molecules with longer chains, we find evidence of their covalent coupling to the surface through Ti–O–P bond formation, of the exposure of the amino groups at the outer surface, and of an increase in the order of the layer upon thermal annealing

Self-Assembly of 1,4-Benzenedimethanethiol Self-Assembled Monolayers on Gold

A study of the self-assembly of 1,4-benzenedimethanethiol (BDMT; HS−CH2−(C6H4)−CH2−SH) monolayers on gold is presented. Self-assembled monolayers (SAMs) are characterized by reflection−absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE) measurements. The ensemble of measurements consistently shows that well-organized BDMT SAMs, with “standing-up” molecules, can be obtained on high quality gold films with incubation in n-hexane provided that N2-degassed solutions are used and all preparation steps are performed at 60 °C in the absence of ambient light. SE data indicate that the optical interface properties of the BDMT−Au system are different from those of simple alkanethiol SAMs. A possible mechanism for the formation of the “standing-up” phase from the lying-down phase via a hydrogen exchange reaction involving chemisorbed lying-down and free dithiol molecules is discussed

Optical Properties of Disulfide-Functionalized Diacetylene Self-Assembled Monolayers on Gold: a Spectroscopic Ellipsometry Study

Spectroscopic ellipsometry (SE) has been applied to study the optical properties of thiolate polydiacetylene (PDA) self-assembled monolayers (SAMs) deposited on low-roughness polycrystalline gold. A systematic investigation of methyl-terminated diacetylene (dihexacosa-7,9-diyn disulfide, DS9) SAMs is presented. The results have been compared with experiments on carbazolyl-derivatized diacetylene (14-(9H-9-carbazolyl)tetradeca-10,12-diyn-1-yl disulfide, CDS9) SAMs and with findings recently obtained on SAMs of alkanethiols. The SE measurements have been complemented with X-ray photoelectron spectroscopy and atomic force microscopy data. The difference between SE spectra measured after and before the monolayer assembly (δΨ = ΨSAM − ΨAu and δΔ = ΔSAM − ΔAu) showed specific absorptions of the adsorbed molecules, including narrow features in the 500−700 nm wavelength range which have been interpreted as markers of the SAM polymerization state. To our knowledge, these results represent the first unambiguous optical detection of polymer-induced absorptions in the case of diacetylene SAMs. Polymerization mainly occurred in the so-called red phase (absorption peak around 550 nm) on very flat surface regions obtained by flame-annealing the sample. The polymeric phase was stable against moderate UV irradiance. The detection of the blue phase was questionable as specific absorptions (around 640 nm) overlap with an absorption band related to the formation of the S−Au interface

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 3

MALDI measurements to determine the mass of PEG 6000 produced by S.A. (green), Merck (blue), C.E. (red).</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 6

Micrographs of HT-29 (A-C) and Hela (D-F) cells without treatment (A, D), or incubated for 5 mins in PEG6000 from C.E. (B, E) and S.A. (C, F) and imaged 48 h after seeding. The scale bars indicate 200 μm.</p

Triple SEC measurement with PEG6000 from S.A., C.E., and Merck.

Triple SEC measurement with PEG6000 from S.A., C.E., and Merck.</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 2

Micrographs of (A) HeLa, (B) PANC-1; and (C) Caco-2 cells imaged 72 h after seeding on PEG60000 (C.E.) pre-treated surfaces.</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 4

HT29 imaged by transmission light microscopy 96 h after plating in a 96 well plate treated for 1 h at 37°C with (A) PEG6000 from C.E., (B) PEG4000 (4000), (C) PEG6000 from S.A. (D) a mixture of 4000/S.A. 1/5 PRE diluted, (E) a mixture of 4000/S.A. 1/5, (F) mixture of 4000/S.A. 1/10, (G) PEG6000 from MERCK, (H) 4000/MERCK 1/5 pre-diluted, (J) 4000/MERCK 1/5, (K) 4000/MERCK 1/10, and (L) as control HT29 cells on an untreated surface. The scale bar in a) is valid for all images.</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 1

Microscopic images of HT29 cells on surfaces (1 h; 37°C) treated with PEG6000 from A) C.E.; B) Acros; C) Merck; and D) S.A.. The images were recorded 48 h after cell plating.</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 5

AFM micrograph of Petri dish surfaces incubated for 1 h with 3% PEG6000 from (A) C.E.; (B) Merck; and (C) S.A. The images were recorded after replacing the PEG solution with Milli-Q water. The scale bars indicate 5 μm.</p