Biomedical subjects

Scott M Husson

Publications and source records attributed to Scott M Husson.

8 recordsLinked to original sources

PubMed2006

Two-dimensional molecular imprinting approach to produce optical biosensor recognition elements.

This article describes a new two-step methodology for preparing thiol monolayers having artificial recognition sites for dansylated amino acids on gold optical biosensor surfaces. Nepsilon-Dansyl-L-lysine (DK) was used as the template molecule to form molecularly imprinted monolayers (MIMs). Impact factors that were studied were the concentration of DK in step one (template deposition) and the time and method for thiol monolayer formation in step two (backfilling). Compared to a prior method that used the simultaneous adsorption of the template and thiol from solution, this new approach provides the flexibility to imprint template molecules that have low binding energies on gold. Control over the surface density of imprinting sites can be achieved by this approach, and rebinding studies done using surface plasmon resonance spectroscopy confirmed that the MIMs prepared against DK showed selectivity for that template over didansyl-L-lysine.

Biosensing Techniques↗

PubMed2006

The role of independently variable grafting density and layer thickness of polymer nanolayers on peptide adsorption and cell adhesion.

This contribution demonstrates a simple and reproducible method for fabricating surface-tethered polymer brushes that vary in grafting density and layer thickness for peptide adsorption and cell-adhesion studies. Surface-initiated atom transfer radical polymerization was used together with thiol self-assembly to generate these nanothin polymer brush layers of poly((polyethylene glycol) methacrylate). A kinetic study was done to measure the layer thickness growth rate at room temperature from flat gold substrates presenting different polymerization initiator molecule surface densities. The polymer brush layers transition from mushroom to brush regimes with increasing grafting density. A crossover density of 0.038+/-0.005 chains/nm(2) was determined for the PPEGMA polymer brushes. The results described in this paper show that layer properties such as wettability and dry layer thickness depend strongly on initiator surface density. Ultimately, the adsorbed concentration of an RGD-containing synthetic peptide Gly-Arg-Gly-Asp-Ser and the adhesion and spreading of cells were correlated with surface properties, which continues to be a major research theme in biomedical and biomaterials research.

3T3 Cells↗

PubMed2006

Adsorption thermodynamics of short-chain peptides on charged and uncharged nanothin polymer films.

The present work describes experimental measurements of submolecular-level interaction energies involved in the process of peptide adsorption on polymer films using surface plasmon resonance spectroscopy. Gibbs energy change on adsorption (DeltaG(ad)) for tyrosine, phenylalanine, and glycine homopeptides were measured at 25 degrees C and pH 7 on highly uniform, nanothin polymer films, and the results were used to predict DeltaG(ad) for homologous homopeptides with a larger number of residue units. Nanothin poly(2-vinylpyridine), poly(styrene), and poly(1-benzyl-2-vinylpyridinium bromide) films were used for the adsorption studies; they were prepared using a graft polymerization methodology. In-situ swelling experiments were done with ellipsometry to examine the uniformity of the surfaces and to ensure that the graft densities of the different polymer films were similar to facilitate the comparison of adsorption results on these surfaces. The swelling experiments showed that the films were uniform, and the grafting densities were found to be 0.14-0.17 chains/nm(2). For uncharged surfaces, predicted and measured DeltaG(ads) values for homopeptides deviated by < or =4.9%. To extend this approach to a mixed-residue peptide, measurements were made for glycine, phenylalanine, and tyrosine-leucine subunits found in leucine enkephalin. The predicted DeltaG(ads) values for leucine enkephalin deviated by 3.0% and -9.1% for poly(2-vinylpyridine) and poly(styrene) films, respectively. Deviations between measured and predicted adsorption energies were larger for the charged poly(1-benzyl-2-vinylpyridinium bromide) surface relative to uncharged surfaces. While the adsorption energies were found to be additive within experimental uncertainties for the charged surface, generally speaking, measured uncertainty values were also larger for the charged surface.

Adsorption↗

PubMed2006

Adsorption of dansylated amino acids on molecularly imprinted surfaces: a surface plasmon resonance study.

Surface plasmon resonance spectroscopy (SPR) was used to measure the adsorption kinetics and isotherms of dansylated amino acids onto surface-confined molecularly imprinted polymer films (MIP-Fs) and the corresponding non-imprinted polymer control films (NIP-Fs). The surface-confined polymer films were grafted from flat gold surfaces using atom transfer radical polymerization (ATRP). This approach allowed uniform nanothin films to be grown, thereby ensuring that the amino acids see a uniform surface during adsorption. N,N'-Didansyl-l-cystine (DDC) and didansyl-l-lysine (DDK) were used as the template molecules to form the MIP-Fs. Adsorption kinetics data were analyzed using single- and dual-site Langmuir adsorption models. It was found that, within the experimental measurement range, adsorption isotherm data were well described by any of four isotherm models: Langmuir, dual-site Langmuir, Freundlich, or Langmuir-Freundlich (LF). The relatively high heterogeneity index values regressed using the Freundlich and LF isotherms suggest the formation of fairly homogeneous MIP-Fs; although Scatchard analysis reveals binding site heterogeneity does exist. Selectivity studies showed that the MIP-Fs display cross-reactivity between DDC and DDK; nevertheless, MIP-Fs prepared against one template showed selectivity for that template. Solution pH and polymer layer thickness were studied as independent parameters to determine their impacts on amino acid adsorption, as monitored by SPR.

Adsorption↗

PubMed2006

Adsorption of fluorescently labeled protein residues on poly(ethylene-co-acrylic acid) films modified with affinity functionalities.

Poly(ethylene-co-acrylic acid) (EAA) films were reacted with glycine, 12-aminododecanoic acid, aspartic acid, 5-aminoisophthalic acid, ethanolamine, diethylamine, dimethylamine, N-isopropylamine, and dimethylaminoethyleneamine to prepare EAA films with negatively charged, non-charged, hydrophilic, and hydrophobic functionalities. Attenuated total reflectance Fourier transform infrared spectroscopy, differential scanning calorimetry, and contact angle measurements were used to characterize the modified EAA films. Analyses revealed that the films were modified on the surfaces and also in the bulk; therefore, bulk properties such as cohesive energy density were changed even though the surfaces remained hydrophobic. Adsorption studies were performed for two fluorescently labeled protein residues, dansyl-L-phenylalanine (dansyl-F) and dansyl-L-glutamine (dansyl-Q), from pH 7.4 buffer solutions. The adsorption results revealed that dimethylaminoethyleneamine functionality gave the highest uptake among the functionalities studied, and adsorption was more favorable for dansyl-F than dansyl-Q. Adsorption behavior is discussed in terms of hydrophobic-hydrophobic (dispersion) interactions and Coulombic interactions.

Acrylic Resins↗

PubMedDate not supplied

Thermodynamic studies on the adsorption of fibronectin adhesion-promoting peptide on nanothin films of poly(2-vinylpyridine) by SPR.

This paper describes a methodology for preparing uniform, nanothin polymer films for the study of biomolecule adsorption by surface plasmon resonance spectroscopy (SPR). The methodology combines molecular self-assembly of alkanethiols on gold with surface-confined atom transfer radical polymerization (ATRP). Poly(2-vinylpyridine) was chosen to demonstrate the methodology, and growth kinetics were studied by ex situ ellipsometry. Atomic force microscopy (AFM) indicated that the polymer films were uniform with RMS roughness of approximately 0.5 nm. Subsequent SPR measurements were done to determine thermodynamic adsorption properties (deltaG, deltaH, and deltaS) between fibronectin adhesion-promoting peptide and the surface-confined poly(2-vinylpyridine) at 15, 20, and 25 degrees C. The flexibility in synthesis conditions and the opportunities for manipulating film thicknesses and graft densities that ATRP provides to grow polymer films from gold surfaces holds advantages over conventional spin-coating and grafting to approaches in the design of model polymer films for biomolecule adsorption studies. These advantages are described.

Adsorption↗

PubMedDate not supplied

Thermodynamic measurements and predictions of the adsorption of short-chain peptides on nanothin polymer films.

This contribution describes experimental measurements of submolecular-level interaction energies involved in the process of peptide adsorption on polymer films. The objective of this study was to use surface plasmon resonance (SPR) spectroscopy to measure the Gibbs energy change on adsorption (DeltaG(ad)) for pairs of various homopeptides on highly uniform, nanothin polymer films and to use these data, along with the principle of additivity, to predict DeltaG(ad) for homologous homopeptides, as well as for a mixed-residue peptide. By using a graft polymerization methodology, a nanothin poly(2-vinylpyridine) film was prepared and adsorption energies were measured first for a homologous series of tyrosine (Y) homopeptides on this film to determine submolecular-level interaction energies. By using SPR, adsorption isotherms were measured for YY and YYY peptides; analysis of these isotherms provided DeltaG(ad) data for a midchain tyrosine unit and a set of chain-end tyrosine units; values were -0.75 +/- 0.07 kcal/mol and -2.12 +/- 0.04 kcal/mol, respectively. Combining the thermodynamic contributions for adsorption of individual tyrosine units allowed a predictive estimate of -5.12 +/- 0.32 kcal/mol for the adsorption energy for YYYYYY; this estimate deviated by only 2.3% from its measured value of -5.24 +/- 0.06 kcal/mol. Similarly, adsorption energies were found for phenylalanine, glycine, and tyrosine-leucine peptides. Combining the thermodynamic contributions for adsorption of individual residue units allowed a predictive estimate of -3.24 +/- 0.38 kcal/mol for a pentapeptide, leucine enkephalin; this estimate deviated by only 3.0% from its measured value of -3.34 +/-0.11 kcal/mol.

Adsorption↗

PubMedDate not supplied

Surface molecular imprinting by atom transfer radical polymerization.

Results are presented that demonstrate the successful preparation of ultrathin (< 10 nm), surface-confined, molecularly imprinted polymer (MIP) films on model gold substrates using atom transfer radical polymerization (ATRP). 2-Vinylpyridine (2Vpy) was investigated as the functional monomer, and ethylene glycol dimethacrylate (EGDMA) was the cross-linking monomer. Fluorescently labeled N,N'-didansyl-L-cystine and N,N'-didansyl-L-lysine were used as the template molecules to form the MIPs. Spectroscopic and ellipsometric results are presented that follow film formation and growth rates. Results are also presented from fluorescence experiments used to quantify and compare the adsorption capacities of MIP surface films and nonimprinted (NIP) control films. MIP films exhibited higher binding capacities than the control NIP films at all solution concentrations of N,N'-didansyl-L-cystine and N,N'-didansyl-L-lysine. Furthermore, template removal from these imprinted films appears to be 100% efficient. Selectivity studies showed that the MIPs display some cross-reactivity between these two molecules; nevertheless, MIPs prepared against one template showed selectivity for that template. A selectivity coefficient of 1.13 was achieved for MIP surfaces prepared against N,N'-didansyl-L-lysine; a value of 1.51 was observed for MIP surfaces prepared against N,N'-didansyl-L-cystine.

Adsorption↗