Biocompatible polymers for antibody support on gold surfaces

Monolayers prepared with polar or ionic amino acids with short side chains have a reduced nonspecific adsorption of serum proteins compared to that of hydrophobic amino acids and organic monolayers immobilized on the gold surface of surface plasmon resonance (SPR) biosensors. Proteins contained in biological samples adsorb on most surfaces, which in the case of biosensors causes a nonspecific response that hinders the quantification of biomarkers in these biological samples. To circumvent this problem, self-assembled monolayers (SAM) of N-3-mercaptopropyl-amino acids (3-MPA-amino acids) were prepared from 19 natural amino acids. These SAM were investigated to limit the nonspecific adsorption of proteins contained in biological fluids and to immobilize molecular receptors (i.e., antibodies) that are necessary in the construction of biosensors. SPR and Ge attenuated total reflection (GATR) FTIR spectroscopy were employed to characterize the formation of the amino acid SAMs. Monolayers of 3-MPA-amino acids densely packed on the surface of the SPR biosensors result in a surface concentration of approximately 10 (15) molecules/cm (2). SPR also quantifies the surface concentration of serum proteins nonspecifically adsorbed on 3-MPA-amino acids following the exposure of the biosensor to undiluted bovine serum. The concentration of nonspecifically bound proteins ranged from approximately 400 ng/cm (2) with polar and ionic amino acids to approximately 800 ng/cm (2) with amino acids of increased hydrophobicity. The nonspecific adsorption of serum proteins on the 3-MPA-amino acids increases in the following order: Asp < Asn < Ser < Met < Glu < Gln < Thr < Gly < His < Cys < Arg < Phe < Trp < Val < Pro < Ile < Leu < Ala < Tyr. The analysis of the adsorption and desorption curves for serum proteins on the SPR sensorgram has demonstrated the strong irreversibility of the protein adsorption on each surface. The effective hydrophilicity of the SAMs was measured from the contact angle with a saline buffer and has demonstrated that surfaces minimizing the contact angle with PBS performed better in serum. The antibody for beta-lactamase was immobilized on a 3-MPA-glycine SAM, and beta-lactamase was detected in the nanomolar range. The presence of beta-lactamase is an indicator of antibiotic resistance.

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“…To obtain experimentally the surface concentration (Γ) for each SAM from ∆λ SPR , the equation from Jung et al was employed. 13,44 …”

Section: Resultsmentioning

confidence: 99%

Monolayers of 3-Mercaptopropyl-amino Acid to Reduce the Nonspecific Adsorption of Serum Proteins on the Surface of Biosensors

2008

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“…Polymers such as poly(vinyl alcohol), poly(acrylamide), dextran, and poly(ethylene glycol) (PEG) have been used as coating materials to prevent nonspecific adsorption. [3][4][5][6][7] The elimination or minimization of nonspecific binding itself may not be enough for certain applications. The development of biosensors for biomedical diagnostics requires controlled immobilization of bioactive species so that the specific recognition ligands are bound to the sensor surface in a favorable orientation.…”

Section: Introductionmentioning

confidence: 99%

Preventing Nonspecific Adsorption on Polymer Brush Covered Gold Electrodes Using a Modified ATRP Initiator

et al. 2009

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Biological systems have a tendency to adsorb nonspecifically onto a solid substrate, thus reducing the efficacy of the interface being used in biorecognition. This nonspecific adsorption is a common problem in the development of biosensors as it typically reduces the efficacy of the sensor platform. In this manuscript we report the synthesis of an oligo(ethylene glycol) (OEG) containing ATRP (atom transfer radical polymerization) thiol initiator and demonstrate the role of this initiator in preventing nonspecific adsorption of IgG antibodies on chemically functionalized gold electrode surfaces using cyclic voltammetry. A new synthetic route for the synthesis of the new ATRP thiol initiator in high yields has been reported. Surface initiated poly(acrylic acid) brushes grown off the gold surface with modified OEG containing and conventional ATRP thiol initiators were chemically modified with 2,4-dinitrophenyl (DNP) groups. Amperometric studies were carried out on gold electrodes modified with DNP-PAA brushes using DNP-specific and nonspecific IgG antibodies. The cyclic voltammograms of an osmium redox mediator recorded over time suggest that the chemical modification of the gold electrodes with DNP-PAA brushes using the OEG-containing ATRP initiator is much more effective in preventing nonspecific adsorption of antibodies than polymer brushes grown from the conventional initiator. Finally, we confirmed these results with the quartz crystal microbalance (QCM) technique by quantitatively evaluating the adsorption of nonspecific IgG antibodies on DNP-PAA functionalized QCM surfaces. The use of this modified ATRP thiol initiator to chemically functionalize macro/microelectrode surfaces will help develop reproducible, reliable, and robust electrochemical biosensors with minimized nonspecific adsorption.

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“…The designs of biosensor devices often call for biomolecular recognition elements, such as enzymes, antibodies, or oligonucleotides, to be immobilized in or on a substrate [1][2][3][4][5][6][7][8][9]. Immobilization in hydrogels is commonly used to protect the sensing elements in applications involving exposure to fouling environments [10,11]. By minimizing convection, gel immobilization introduces a significant analyte mass transfer resistance, yet the structure of the gel precludes mechanical intra-gel mixing schemes.…”

Section: Introductionmentioning

confidence: 99%

Enhanced mixing in polyacrylamide gels containing embedded silica nanoparticles as internal electroosmotic pumps

Matos

White

Tilton

2008

Colloids and Surfaces B: Biointerfaces

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Biocompatible polymers for antibody support on gold surfaces

Cited by 72 publications

References 39 publications

Monolayers of 3-Mercaptopropyl-amino Acid to Reduce the Nonspecific Adsorption of Serum Proteins on the Surface of Biosensors

Monolayers of 3-Mercaptopropyl-amino Acid to Reduce the Nonspecific Adsorption of Serum Proteins on the Surface of Biosensors

Preventing Nonspecific Adsorption on Polymer Brush Covered Gold Electrodes Using a Modified ATRP Initiator

Enhanced mixing in polyacrylamide gels containing embedded silica nanoparticles as internal electroosmotic pumps

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