The presence of two sulfur species was detected in X-ray photoelectron spectroscopy (XPS) studies of thiol and disulfide molecules adsorbed onto gold surfaces. These species are assigned to bound thiolate (S2p3/2 binding energy of 162 eV) and unbound thiol/disulfide (S2p3/2 binding energy from 163.5 to 164 eV). These assignments are consistent with XPS data obtained from different thiols (C12, C16, C18, and C22 alkane thiols, a fluorinated thiol, and a cyclic polysiloxane thiol) and different adsorption conditions (solvent type, thiol concentration, temperature, and rinsing). In particular, the use of a poor solvent for thiol adsorption solutions (e.g., ethanol for long chain alkanethiols) and the lack of a rinsing step both resulted in unbound thiol molecules present at the surface of the bound thiolate monolayer. This has implications for recent studies asserting the presence of multiple binding sites for gold-thiolate species in organic monolayers.

Phagocytes are key cellular participants determining important aspects of host exposure to nanomaterials, initiating clearance, biodistribution and the tenuous balance between host tolerance and adverse nanotoxicity. Macrophages in particular are believed to be among the first and primary cell types that process nanoparticles, mediating host inflammatory and immunological biological responses. These processes occur ubiquitously throughout tissues where nanomaterials are present, including the host mononuclear phagocytic system (MPS) residents in dedicated host filtration organs (i.e., liver, kidney spleen, and lung). Thus, to understand nanomaterials exposure risks it is critical to understand how nanomaterials are recognized, internalized, trafficked and distributed within diverse types of host macrophages and how possible cell-based reactions resulting from nanomaterial exposures further inflammatory host responses in vivo. This review focuses on describing macrophage-based initiation of downstream hallmark immunological and inflammatory processes resulting from phagocyte exposure to and internalization of nanomaterials.

Biomaterial-associated infections occur on both permanent implants and temporary devices for restoration or support of human functions. Despite increasing use of biomaterials in an aging society, comparatively few biomaterials have been designed that effectively reduce the incidence of biomaterial-associated infections. This review provides design guidelines for infection-reducing strategies based on the concept that the fate of biomaterial implants or devices is a competition between host tissue cell integration and bacterial colonization at their surfaces.

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Extracellular matrix (ECM) proteins collectively represent a class of naturally derived proteinaceous biomaterials purified from harvested organs and tissues with increasing scientific focus and utility in tissue engineering and repair. This interest stems predominantly from the largely unproven concept that processed ECM biomaterials as natural tissue-derived matrices better integrate with host tissue than purely synthetic biomaterials. Nearly every tissue type has been decellularized and processed for re-use as tissue-derived ECM protein implants and scaffolds. To date, however, little consensus exists for defining ECM compositions or sources that best constitute decellularized biomaterials that might better heal, integrate with host tissues and avoid the foreign body response (FBR). Metrics used to assess ECM performance in biomaterial implants are arbitrary and contextually specific by convention. Few comparisons for in vivo host responses to ECM implants from different sources are published. This review discusses current ECM-derived biomaterials characterization methods including relationships between ECM material compositions from different sources, properties and host tissue response as implants. Relevant preclinical in vivo models are compared along with their associated advantages and limitations, and the current state of various metrics used to define material integration and biocompatibility are discussed. Commonly applied applications of these ECM-derived biomaterials as stand-alone implanted matrices and devices are compared with respect to host tissue responses.

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Self-assembly of thiol-terminated single-stranded DNA (HS-ssDNA) on gold has served as an important model system for DNA immobilization at surfaces. Here, we report a detailed study of the surface composition and structure of mixed self-assembled DNA monolayers containing a short alkylthiol surface diluent [11-mercapto-1-undecanol (MCU)] on gold supports. These mixed DNA monolayers were studied with X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and fluorescence intensity measurements. XPS results on sequentially adsorbed DNA/MCU monolayers on gold indicated that adsorbed MCU molecules first incorporate into the HS-ssDNA monolayer and, upon longer MCU exposures, displace adsorbed HSssDNA molecules from the surface. Thus, HS-ssDNA surface coverage steadily decreased with MCU exposure time. Polarization-dependent NEXAFS and fluorescence results both show changes in signals consistent with changes in DNA orientation after only 30 min of MCU exposure. NEXAFS polarization dependence (followed by monitoring the N 1s → π* transition) of the mixed DNA monolayers indicated that the DNA nucleotide base ring structures are oriented more parallel to the gold surface compared to DNA bases in pure HS-ssDNA monolayers. This indicates that HS-ssDNA oligomers reorient toward a more-upright position upon MCU incorporation. Fluorescence intensity results using end-labeled DNA probes on gold show little observable fluorescence on pure HSssDNA monolayers, likely due to substrate quenching effects between the fluorophore and the gold. MCU diluent incorporation into HS-ssDNA monolayers initially increases DNA fluorescence signal by densifying the chemisorbed monolayer, prompting an upright orientation of the DNA, and moving the terminal fluorophore away from the substrate. Immobilized DNA probe density and DNA target hybridization in these mixed DNA monolayers, as well as effects of MCU diluent on DNA hybridization in complex milieu (i.e., serum) were characterized by surface plasmon resonance (SPR) and 32 P-radiometric assays and reported in a related study Methods for surface-immobilizing single-strand nucleic acids that preserve their original hybridization specificity with minimized nonspecific interactions remain an important goal for improving the performance of DNA microarray and biosensor applications. As summarized in a recent review, 1 nucleic acid hybridization behavior observed between complementary probe and target DNA molecules in bulk solution differ from identical hybridization at a solid-liquid * Corresponding author. interface. In surface hybridization, nonspecific probe-surface interactions, electrostatic forces, and steric issues between adjacent DNA probes influence DNA target hybridization efficiency and capacity. For example, nucleotide primary amines on nonhybridized DNA segments can interact (e.g., covalently 2 or by acid-base adsorption) with the surface, becoming unavailable to hybridize with target DNA molecules. Effects of immobilized DNA p...

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