This paper describes a new bioassay surface chemistry that effectively inhibits non-specific biomolecular and cell binding interactions, while providing a capacity for specific immobilization of desired biomolecules. Poly(ethylene glycol) (PEG) as the primary component in nonfouling film chemistry is well-established, but the multicomponent formulation described here is unique in that it (1) is applied in a single, reproducible, solution-based coating step; (2) can be applied to diverse substrate materials without the use of special primers; and (3) is readily functionalized to provide specific attachment chemistries. Surface analysis data are presented, detailing surface roughness, polymer film thickness, and film chemistry. Protein non-specific binding assays demonstrate significant inhibition of serum, fibrinogen, and lysozyme adsorption to coated glass, indium tin oxide, and tissue culture polystyrene dishes. Inhibition of S. aureus and K. pneumoniae microbial adhesion in a microfluidic flow cell, and inhibition of fibroblast cell adhesion from serum-based cell culture is shown. Effective functionalization of the coating is demonstrated by directing fibroblast adhesion to polymer surfaces activated with an RGD peptide. Batch-to-batch reproducibility data are included. The in situ cross-linked PEG-based coating chemistry is unique in its formulation, and its surface properties are attractive for a broad range of in vitro bioassay applications.

Eu3+ fluorescence spectroscopy is used to investigate the clustering of rare-earth ions and the effectiveness of aluminum codoping in dispersing and isolating rare-earth ions in solgel silica monoliths. Fluorescence line-narrowing (FLN) studies are demonstrated as a useful tool in identifying clustered and isolated Eu3+. Clustered Eu3+ is identified by the lack of a line-narrowing effect, which is attributed to energy transfer between adjacent Eu3+ ions.Clustering is shown to be significant, even in transparent samples with Eu3+ concentrations as low as 0.5 wt % Eu3+. Addition of Al3+ as a codopant has a profound impact on the bonding and structure of Eu3+ in silica. Significant fluorescence line narrowing is observed, which suggests that Al3+ codoping is effective in dispersing and isolating Eu3+ ions in the silica matrix. Fluorescence decay studies provide evidence of increased Eu3+ hydroxylation in the Al3+-containing samples.

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Charged organic-aqueous interface electrostatics are assessed in order to clarify potential electrostatic contributions to oriented mineral nucleation at planar organic surfaces. Fatty acid and acidic phospholipid monolayers contacting aqueous solutions of sparingly soluble salts serve as model systems. Monolayer electrostatic parameters and ion distributions in the interfacial aqueous solution are calculated using a GouyChapman-Stern electric double-layer model that incorporates the multiple, multivalent cations and anions found in mineralizing solutions. The calculations provide insight into the relationship between surface-directed crystallization and factors such as ion binding, surface charge density, and interfacial ion concentrations. Variations in crystal nucleation, phase, and morphology observed at charged monolayers are interpreted in terms of calculated departures from lattice ion stoichiometry and pH lowering within the interfacial aqueous solution. Lattice matching is addressed in terms of Stern layer calculations of Ca 2+ ion binding at carboxylic acid monolayers. Arguments are presented suggesting that near negatively charged surfaces, soluble ionic species concentrations are enhanced relative to free anion concentrations, and a link between interfacial anion speciation and oriented mineral nucleation is proposed. Implications for biomineralization and templatedirected crystallization at planar surfaces are discussed.

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SummarySamples from >750 patients with presumptive TB in two continents were tested with a field-based IgG serological assay incorporating 57 M. tuberculosis antigens, and showed that responses to single antigens or multiple antigen sets have no clinically useful discriminating power.

Diagnosis of opportunistic infections in HIV-