The adsorption of human IgG at the air/water interface was monitored both by the in situ radiotracer technique using [14C] labeled IgG and by surface tension measurements. The results reveal that adsorption of IgG from single protein systems displays bimodality due to mol. rearrangements at the interface. Above the threshold value of 1.5×10-2 mg/mL soln. concn., adsorbed IgG mols. reoriented from the side-on to the end-on configuration. The existence of a lag time which did not appear in Γ=f(t) curves, was obsd. in Π=f(t) relationships at low protein concns. and was due to the limits of the surface pressure technique to detect protein adsorption. The adsorption of native IgG was also carried out in the presence of a hydrophobized IgG obtained by grafting capryloyl residues to its lysine groups by reaction with N-hydroxysuccinimide ester of caprylic acid, which yielded 19 covalently bound alkyl chains to the IgG mol. (19C8-IgG). This modified IgG exhibited enhanced adsorption at the air/water interface, as manifested by its increased adsorption efficiency relative to the native protein. Sequential and competitive adsorption expts. from binary mixts. of native IgG and 19C8-IgG clearly demonstrate that the displacement of the native protein from the air/water interface strongly depended on the manner of how 19C8-IgG and native IgG competed with each other. When the two proteins competed simultaneously, 19C8-IgG predominantly occupied the available area but when native IgG was adsorbed first, for 2 h, the sequentially adsorbed 19C8-IgG was incapable of substantially displacing it from the interface. (c) 2001 Academic Press. [on SciFinder(R)]

The in situ adsorption/desorption studies of 14C-labeled human IgG were performed at the polyethylene (PE)/aq. soln. interface. The results reveal that the adsorbed protein mols. were predominantly packed in the end-on orientation. Desorption expts. showed that upon rinsing with buffer only minute fractions of adsorbed IgG could be removed from the PE surface. Both the competitive and the sequential adsorption measurements from the binary mixts. of hydrophobic IgG modified by attachment of 19 caprylic chains (19C8-IgG) and [14C]IgG confirm that native IgG strongly adhered to the PE films. The specific recognition ability of adsorbed human IgG layers was studied by using specific (goat anti-human) IgG and nonspecific (goat anti-rabbit) IgG. It was shown that the prevailing effect of the interaction of [14C]IgG adsorbed onto PE with the specific antibody was the increase in the surface radioactivity, which was attributed to the formation of a more densely packed layer of IgG mols. at the PE surface. It was also demonstrated that, whereas the specific antibody preadsorbed onto PE films retained the recognition ability relative to human IgG, its hydrophobic modification resulted in a substantial decrease in this ability. (c) 2001 Academic Press. [on SciFinder(R)]

Adsorption onto silica of native human IgG and its hydrophobized forms prepd. by covalent attachment of 11, 25, and 52 C8 alkyl chains was studied. All hydrophobized IgGs spontaneously form micelle-like aggregates (nanoclusters) in aq. solns. with a mean diam. of 40 nm. Adsorption isotherms are of a high affinity type. The plateau surface concn. of the isotherms depends on the degree of the protein modification, increasing for 11C8-IgG and 25C8-IgG and decreasing for 52C8-IgG as compared with the native protein. The isothermal enthalpies of adsorption for the native and modified IgGs at all degrees of silica surface coverage were endothermic, i.e., the adsorption process is entropically driven. For the native IgG, the adsorption isotherm is apparently reversible, while the isotherms for the modified forms display distinct hysteresis. The biol. (immunol.) activity of the desorbed mols. was evaluated, and it was found that all forms of IgG which were desorbed from silica display reduced ability to react with a specific antibody, goat anti-human IgG, compared to the corresponding forms before adsorption. The immunoassay on desorbed IgGs indicated that hydrophobic modification of the mol. reduced structural alterations obsd. on adsorption of the native IgG. The decrease in activity was much less pronounced in the range of surface coverage close to the plateau values. Possible mechanisms of adsorption of the hydrophobized forms of IgG are discussed. [on SciFinder(R)]

An ink-jet ink compn. for piezoelec. in-jet printing comprises: (a) a hydrophobic dye; (b) an oil-in-water microemulsion including: (i) a volatile oil; (ii) water; (iii) a co-solvent; (iv) at least one surfactant; and (v) a binder, wherein upon application of the ink to a substrate surface, the volatile oil evaps. and nanoparticles are formed. The invention addnl. discloses a printing process using the ink compn. [on SciFinder(R)]

A therapeutic or cosmetic compn. for topical application, capable of stabilizing an active ingredient and delivering said ingredient, comprising a plurality of microcapsules having a core-shell structure and a diam. of approx. 0.1-100 μ. The core of each microcapsule includes at least one active ingredient, and is encapsulated within a microcapsular shell. The shell is comprised of at least one inorg. polymer obtained by a sol-gel process, and the shell protects the active ingredient before topical application and releases the ingredient after topical application. This compn. is useful to encapsulate active ingredients that are unstable in formulation, or are irritating to the skin. The present invention further discloses a process for the encapsulation of an active ingredient in the form of a dispersion within a hydrophobic phase. For example, combinations of erythromycin and benzoyl peroxide are useful in the treatment of acne but usually must be formulated as a two component system because of incompatibility of the two active ingredients. Thus, erythromycin was encapsulated in silica; 1.7 g of erythromycin was mixed with 14.9 g of octylmethoxy cinnamate, and 19.5 g of tetraethoxy silane (TEOS) was added. This oil phase was emulsified and the emulsion was poured into a basic soln. of pH 11.5. The mixt. was stirred at 50-240 rpm. Flocculation was induced by the addn. of MgSO4 at a final concn. of 0.1% by wt. The ppt. was collected by filtration and a product obtained was a paste with a particle size distribution of 1-12 μ (an av. size of 6.2 μ). Encapsulation of benzoyl peroxide (30 g of 7% soln. in diisopropyl sebacate) was carried out by mixing it with 20 g of TEOS. The org. phase was emulsified in 200 g of an aq. soln. contg. 1% CTAC under high shear. The emulsion obtained was poured into a reactor contg. 200 g NaOH aq. soln. at pH 10 and stirred. The final product was re-suspended in water to obtain a dispersion contg. a 3% benzoyl peroxide encapsulated in silica particles of 0.5015 μ. [on SciFinder(R)]

A review. This review describes the interfacial behavior of biomols., which were converted to more hydrophobic derivs. by covalent attachment of hydrophobic chains. The mols. presented are proteins (glucose oxidase, IgG, gelatin, ovalbumin) and polysaccharides (CM-cellulose, pullulan). In general, it was found that such hydrophobically modified biomols. have enhanced surface activity and ability to penetrate into phospholipid monolayers. In addn., it has been demonstrated, that such mols. can be used as efficient emulsifiers and foaming agents, and in unique biomedical application based on combining the surface activity and recognition ability. [on SciFinder(R)]