X-ray Photoelectron Spectroscopy and Radiometry Studies of Biotin-Derivatized Poly(l-lysine)-grafted-Poly(ethylene glycol) Monolayers on Metal Oxides

Abstract

This paper describes the first detailed analytical characterization of the surface properties of a new class of biomolecular interfaces based on derivatized poly(L-lysine)-grafted-poly(ethylene glycol) (PLL-g-PEG) copolymers. Such copolymers spontaneously adsorb to negatively charged surfaces under physiological pH and efficiently repel nonspecific protein adsorption while providing PEG-tethered functional/active sites for specific biomolecular recognition. As a model system, we synthesized biotin-derivatized (PLL-g-PEG) copolymers, PLL-g-[(PEG)1-x(PEG-biotin)x], where x varies from 0 to 1. The copolymers were adsorbed on titanium dioxide substrates. Surface characteristics and biorecognition properties were investigated using X-ray photoelectron spectroscopy and radiometry. We show that the monolayer formed is ∼20-25 Å in thickness. It is organized with its PLL backbone located within the first 10 Å on the substrate and with the PEG side chains located above the PLL. The resulting biotin surface concentration depends linearly on the biotin concentration in the bulk copolymer. This aspect implies that the surface concentration of functional groups can be adjusted by adapting their concentration within the bulk copolymer. The PLLg-PEG(-biotin) monolayers are efficient in repelling nonspecific protein adsorption but can specifically bind streptavidin (SA). Within the biotin range considered, the SA surface concentration increases linearly with the biotin surface concentration of the monolayer.

Selective streptavidin bioconjugation on silicon and silicon carbide nanowires for biosensor applications

“…Samples analyzed after SA immobilization show C 1s peaks (C*-C at 285.0 eV, C*-O at 286.5 eV, and C* 5 O at 288.3 eV, see Fig. 2, upper-center inset) consistent with SA immobilization 22 as well as a N 1s peak [see Fig. 2(d)].…”

Immobilization of Peroxidase on SiO2 Surfaces with the Help of a Dendronized Polymer and the Avidin‐Biotin System

“…One exception are layers composed of polycationic polymers such as polylysine and polylysinebased copolymers which easily and with relatively high stability adsorb on metal oxides or SiO 2 via a multitude of non-covalent interactions. [22][23][24][25] Compared with polycationic denpols, however, in polylysine the number of functional groups that can interact with the surface and that can be modified with biotin is much lower. Therefore, the use of polycationic denpols for non-covalently immobilizing enzymes on a solid surface may have several advantages as compared to polylysine.…”

“…The ease of the denpol-mediated HRP immobilization and the high stability of the immobilized enzyme are promising for bioanalytical applications. dendrimers [17][18][19][20][21] and polymers [22][23][24] have been used as soft layer to bind various proteins via the biotin-avidin system. To our knowledge, among the various possibilities, layers of partially biotinylated polyamidoamine dendrimers showed the highest avidin loading capacity (up to 520 ng avidin Á cm À2 were reported).…”

Biofunctional polyethylene glycol coatings on titanium: An in vitro-based comparison of functionalization methods

“…Polishing, solvent cleaning and plasma activation was done for all samples UK) was used for the determination of atomic elemental composition applying the manufacturer set of relative sensitivity factors. Two samples per condition were analyzed.Film thickness was estimated by the attenuation of the XPS titanium signal according to the equation 1, where is the intensity of Ti2p from the clean surface (Ti-PA), 0 is the intensity of the Ti2p from PEG coated substrate, is the electron attenuation length for Ti peaks and θ is the take-off angle for XPS measurements.Electron attenuation length was assumed as 2.8Å according to Ruiz-Taylor et al63 and the takeoff angle was 90º for all the measurements. Protein adsorption on the titanium surfaces was tested by immersing the samples in bovine serum albumin (BSA, Sigma Aldrich).…”