The standard solution-depletion method is implemented with SDS-gel electrophoresis as a multiplexing, separation-and-quantification tool to measure competition between two proteins (i and j) for adsorption to the same hydrophobic adsorbent particles (either octyl sepharose or silanized glass) immersed in binary-protein solutions. Adsorption kinetics reveal an unanticipated slow protein-size-dependent competition that controls steady-state adsorption selectivity. Two sequential pseudo-steady-state adsorption regimes (State 1 and State 2) are frequently observed depending on i, j solution concentrations. State 1 and State 2 are connected by a smooth transition, giving rise to sigmoidally-shaped adsorption-kinetic profiles with a downward inflection near 60 minutes of solution/adsorbent contact. Mass ratio of adsorbed i, j proteins (m i m j ) remains nearly constant between States 1 and 2, even though both m i and m j decrease in the transition between states. State 2 is shown to be stable for 24 hours of continuous-adsorbent contact with stagnant solution whereas State 2 is eliminated by continuous mixing of adsorbent with solution. In sharp contrast to binarycompetition results, adsorption to hydrophobic adsorbent particles from single-protein solutions (pure i or j) exhibits no detectable kinetics within the timeframe of experiment from either stagnant or continuously-mixed solution, quickly achieving a single steady-state value in proportion to solution concentration. Comparison of binary competition between dissimilarly-sized protein pairs chosen to span a broad molecular-weight (MW) range demonstrates that selectivity between i and j scales with MW ratio that is proportional to protein-volume ratio (ubiquitin, Ub, MW = 10.7 kDa; human serum albumin, HSA, MW = 66.3 kDa; prothrombin, FII, 72 kDa; immunoglobulin G, IgG, MW = 160 kDa; fibrinogen, Fib, MW = 341 kDa). Results are interpreted in terms of a kinetic model of adsorption that has protein molecules rapidly diffusing into an inflating interphase that is spontaneously formed by bringing a protein solution into contact with a physical surface (State 1). State 2 follows by rearrangement of proteins within this interphase to achieve the maximum interphase concentration (dictated by energetics of interphase dehydration) within the thinnest (lowest volume) interphase possible by ejection of interphase water and initially-adsorbed proteins. Implications for understanding biocompatibility are discussed using a computational example relevant to the problem of blood-plasma coagulation.

Silanized-glass-particle adsorbent capacities are extracted from adsorption isotherms of human serum albumin (HSA, 66 kDa), immunoglobulin G (IgG, 160 kDa), fibrinogen (Fib, 341 kDa), and immunoglobulin M (IgM, 1000 kDa) for adsorbent surface energies sampling the observable range of water wettability. Adsorbent capacity expressed as either mass-or-moles per-unit-adsorbent-area increases with protein molecular weight (MW) in a manner that is quantitatively inconsistent with the idea that proteins adsorb as a monolayer at the solution-material interface in any physically-realizable configuration or state of denaturation. Capacity decreases monotonically with increasing adsorbent hydrophilicity to the limit-of-detection (LOD) near τo = 30 dyne/cm (θ~65o) for all protein/surface combinations studied (where τo≡γlvocosθ is the water adhesion tension, γlvo is the interfacial tension of pure-buffer solution, and θ is the buffer advancing contact angle). Experimental evidence thus shows that adsorbent capacity depends on both adsorbent surface energy and adsorbate size. Comparison of theory to experiment implies that proteins do not adsorb onto a two-dimensional (2D) interfacial plane as frequently depicted in the literature but rather partition from solution into a three-dimensional (3D) interphase region that separates the physical surface from bulk solution. This interphase has a finite volume related to the dimensions of hydrated protein in the adsorbed state (defining “layer” thickness). The interphase can be comprised of a number of adsorbed-protein layers depending on the solution concentration in which adsorbent is immersed, molecular volume of the adsorbing protein (proportional to MW), and adsorbent hydrophilicity. Multilayer adsorption accounts for adsorbent capacity over-and-above monolayer and is inconsistent with the idea that protein adsorbs to surfaces primarily through protein/surface interactions because proteins within second (or higher-order) layers are too distant from the adsorbent surface to be held surface bound by interaction forces in close proximity. Overall, results are consistent with the idea that protein adsorption is primarily controlled by water/surface interactions.

Contact activation of blood factor XII (FXII, Hageman factor) in neat-buffer solution exhibits a parabolic profile when scaled as a function of silanized-glass-particle activator surface energy (measured as advancing water adhesion tension in dyne/cm, where is water interfacial tension in dyne/cm and θ is the advancing contact angle). Nearly equal activation is observed at the extremes of activator water-wetting properties dyne/cm (0° ≤ θ < 120°), falling sharply through a broad minimum within the dyne/cm (55° < θ < 75°) range over which activation yield (putatively FXIIa) rises just above detection limits. Activation is very rapid upon contact with all activators tested and did not significantly vary over 30 minutes of continuous FXII-procoagulant contact. Results suggest that materials falling within the dyne/cm surface-energy range should exhibit minimal activation of blood-plasma coagulation through the intrinsic pathway. Surface chemistries falling within this range are, however, a perplexingly difficult target for surface engineering because of the critical balance that must be struck between hydrophobicity and hydrophilicity. Results are interpreted within the context of blood plasma coagulation and the role of water and proteins at procoagulant surfaces.

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In this article, we report a novel route for the preparation of alginate‐hydroxyapatite biocomposite. Hydroxyapatite has been nucleated on alginate chains by precipitation method to obtain a biomimetic artificial bone‐like composite. The composite was characterized by powder XRD, FTIR, TGA, DTA, and SEM to ascertain its phase homogeneity and particle size distribution. Hydroxyapatite particles on alginate matrix are around 500–1000 nm in diameter. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5162–5165, 2006

Monodispersed cerium oxide nanoparticle has been synthesized by microwave-mediated hydrothermal as well as microwave-mediated solvothermal synthesis. X-ray diffraction (XRD) data shows that the synthesized particles are single phase. SEM and TEM analysis suggest that particle synthesized by microwave-mediated solvothermal method are less agglomerated. In vitro toxicology study of the synthesized nanoceria particles has shown good free radical scavenging activity for NO and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assayed except superoxide radical within a concentration range of 25 to 75 ng ml(-1). Nanoceria particle also showed inhibition of Fe-ascorbate-induced lipid peroxidation (LPx) in chick liver mitochondrial fractions. Solvothermally synthesized nanoceria showed better protection against Fe-ascorbate-induced LPx than the hydrothermal one while the hydrothermally synthesized nanoceria showed better DPPH and NO scavenging activity. The ceria nanoparticles also prevented Fe-ascorbate-H2O2-induced carbonylation of bovine serum albumin in a dose-dependent manner. At higher concentration, i.e., 100 ng ml(-1), the synthesized nanoparticles showed a reverse trend in all the parameters measured indicating its toxicity at higher doses.