Biotin-Derivatized Poly(l-lysine)-g-poly(ethylene glycol):  A Novel Polymeric Interface for Bioaffinity Sensing

Abstract

A novel biosensor interface exploiting the spontaneous surface assembly of a polycationic, PEG-grafted, biotinylated copolymer was developed and tested on optical waveguide chips in a model immunoassay based on sequential immobilization of (strept)avidin and biotinylated goat antirabbit immunoglobulin (RRIgG-biotin) as a capture molecule to sense the rabbit immunoglobulin (RIgG) target molecule. Optical waveguide lightmode spectroscopy with niobium oxide waveguiding layers was used to monitor quantitatively and in situ the spontaneous adsorption of the (biotinylated) copolymer onto the waveguide surface, the resistance of the resulting adlayer to nonspecific protein adsorption, and the mass uptakes in each step of the model immunoassay. Poly(L-lysine)-g-poly(ethylene oxide) (PLL-g-PEG) is a polycationic copolymer that adsorbs spontaneously from aqueous solutions onto negatively charged surfaces via electrostatic interactions. It forms monolayers with densely packed PEG chains. PLL-g-PEG graft copolymers carrying terminal biotin groups on 0, 20, 30, or 50% of the PEG chains were synthesized and assembled onto the surface of niobium oxide (negatively charged at neutral pH). The surface concentration of biotin was tailored by adjusting the biotin grafting ratio in the polymeric molecule or by assembling mixed [PLLg-PEG/PEGbiotin + PLL-g-PEG] adlayers from the corresponding mixed solutions. These biotinylated surfaces are shown to be highly resistant to nonspecific adsorption from serum while still allowing for the specific surface binding of the linkage proteins: streptavidin, avidin, or neutral avidin. The amount of immobilized linkage protein is shown to be closely related to the biotin surface concentration. The subsequent adsorption behavior of RRIgG-biotin and RIgG, however, depends in a more complex manner on each individual surface modification step and is discussed in the light of specific and nonspecific interactions, as well as of orientational and steric repulsion effects within the adlayers. In terms of the sensing signalto-background ratio, the [PLL-g-PEG/PEGbiotin//NeutrAvidin//RRIgG-biotin] architecture demonstrated particularly promising performance as an interface architecture for bioaffinity sensing of proteins.

Construction of a densely poly(ethylene glycol)-chain-tethered surface and its performance

“…The long-term stability of oligoamine-ended PEG on gold surfaces was confirmed by using gold colloid under physiological conditions. 28,39,40,53,54 Modified N6-PEG can be applied for other surfaces, especially for active-ester surfaces. 16,55,56 Because of the covalent conjugation of PEG on active-ester surfaces, mono-amine-ended PEG is commonly used.…”

“…The present review describes the effect of mixed PEG on the non-biofouling character and also hybrid construction of a PEG/biopolymer mixture on substrate surfaces for versatile applications. Because many excellent reviews on PEG surface coating have been previously published, [15][16][17][18][19][20][21][22][23][24][25][26][27][28] this review mainly introduces our work. BACKGROUND PEG has long been manufactured industrially and utilized in many applications such as nonionic surfactants, lubricants, an intermediate for urethane composition, adhesives and cosmetics.…”

“…This is especially true regarding the versatile techniques for surface coating using PEG that have been developed since the 1980s to improve blood and bio-compatibility. Figure 1 summarizes several methods for the immobilization of PEG on substrate surfaces: PEG gels, 19,20,36 the physical and chemical immobilization of PEG 13,21,37 (so-called grafting-to method), the adsorption of block [22][23][24][25][26][27]38 and graft 27,28,39,40 copolymers, polymerization from the surface 41 (the so-called grafting-from method), the immobilization of star-shape polymers and micelles, [42][43][44] and other methods.…”

Surface Presentation of Bioactive Ligands in a Nonadhesive Background Using DOPA-Tethered Biotinylated Poly(ethylene glycol)

“…A. Woodlam, Inc.). The reported thickness, before and after the adsorption of streptavidin and biotinylated IgG 1 (5-8 biotin molecules per IgG 1 ; biotin (5)(6)(7)(8) -IgG 1 ; BD Biosciences, San Jose, CA), was the average from 3 surfaces with 3 different spots measured on each surface. XPS spectra were collected on an Omicron ESCALAB (Omicron, Taunusstein, Germany) with a monochromatic Al Kα (1486.6 eV) 300-W X-ray source.…”

“…We examined sequential adsorption of streptavidin and biotin (5)(6)(7)(8) -IgG 1 to characterize the binding activity of DPB/DP surfaces. Nonspecific adsorption of streptavidin and biotin (5)(6)(7)(8) IgG 1 was very low for surfaces coated with 100% DP (DPB0) (Fig.…”