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[Display omitted] Implantation of a biomaterial entails a form of injury where the integration of the implant into the host tissue greatly depends on the proper healing of the wound. Wound healing, itself, consists of a number of physiological processes, each occurring within a characteristic time window. A composite, multilayered polymeric drug delivery carrier for adhesion to the wound site and its supply with molecules released at precise time windows at which the stages in the healing process that they target occur is conceptualized here. We also present a simplified version of one such multilayered composite fabricated by a combination of solvent casting and dip coating, comprising the base poly(ε-caprolactone) layer reinforced with hydroxyapatite nanoparticles, poly(glutamic acid) mesolayer and poly- l -lysine surface layer, each loaded with specific small molecules and released at moderately distinct timescales, partially matching the chronology of wound healing. To that end, the base layer proved suitable for the delivery of an anti-inflammatory molecule or an angiogenic agent, the mesolayer appeared appropriate for the delivery of an epithelialization promoter or a granulation factor, and the adhesive surface layer interfacing directly with the site of injury showed promise as a carrier of a vasodilator. The drug release mechanisms were diffusion-driven, suggesting that the drug/carrier interaction is a key determinant of the release kinetics, as important as the nature of the polymer and its hydrolytic degradation rate in the aqueous medium. Morphological and phase composition analyses were performed, along with the cell compatibility ones, demonstrating solid adhesion and proliferation of both transformed and primary fibroblasts on both surfaces of the composite films. The design of the multilayered composite drug delivery carriers presented here is prospective, but requires further upgrades to achieve the ideal of a perfect timing of the sequential drug release kinetics and a perfect resonance with the physiological processes defining the chronology of wound healing. [ABSTRACT FROM AUTHOR]

Abstract: Uniform crystalline colloidal cholesterol particles of narrow size distribution were obtained by precipitation. The method consisted of adding a miscible non-solvent (water) into cholesterol solutions of different alcohols and acetone, without any additives. The properties of the resulting particles depended in a sensitive way on the concentration of all reactants, temperature, pH, ionic strength, and aging time. The major observed effects were due to the solubility of cholesterol, which was strongly affected by the solvent mixture and temperature. Precipitation in 1-propanol/water system yielded stable dispersions of well-defined particles, which were used to evaluate the effects of different experimental parameters on their properties. Aging of stable dispersions resulted in multi-layered aggregation of the primary platelets, the degree and rate of which process was strongly affected by temperature. Finally, it was shown that the colloidal cholesterol particles could be coated with homogeneous silica layers in order to alter their surface characteristics. [Copyright &y& Elsevier]

Physical adsorption of lipase from Thermomyces lanuginosus onto single-layer sheets of graphene oxide (GO) was studied using the response surface methodology to evaluate the physicochemical factors – temperature, pH, ionic strength, and concentration – affecting the enzymatic activity and the immobilization efficiency. The immobilization efficiency and the activity of the enzyme were inversely proportional to each other. Specifically, higher pH values increased the immobilization efficacy, but produced changes in the aggregation state and secondary structure of the enzyme, thus decreasing its activity. Lower pH values, in turn, reduced the immobilization efficacy, but increased the activity of the adsorbed lipase. The adsorbed and the free lipase were followed during 600 ns and 3.5 μs, respectively, in molecular dynamics (MD) simulations. MD trajectories showed that irreversible adsorption freezes the enzyme in a state with a correctly opened catalytic cavity, while the active site remains without a direct interaction with the GO adsorbent. In contrast to the interfacial activation of lipases in a hydrophobic environment, where the catalytic pocket attaches to the hydrophobic surface, the adsorption onto GO made the active site of the lipase accessible by altering the tertiary structure of the enzyme, leading to a higher catalytic efficiency. Experimental investigations confirmed that the physical adsorption onto GO induces tertiary structure changes in the lipase and protects it from H 2 O 2 by accepting the oxidative damage upon itself. In summary, the physical adsorption of the lipase onto GO is mainly affected by pH and could possibly provide a spreadable and robust catalytic interface for biotechnological applications. [ABSTRACT FROM AUTHOR]

Despite the long history of nanoparticulate calcium phosphate (CaP) as a non-viral transfection agent, there has been limited success in attempts to optimize its properties for transfection comparable in efficiency to that of viral vectors. Here we focus on the optimization of: (a) CaP nanoparticle precipitation conditions, predominantly supersaturation and Ca/P molar ratios; (b) transfection conditions, mainly the concentrations of the carrier and plasmid DNA; (c) the presence of surface additives, including citrate anion and cationic poly( l -lysine) (PLL). CaP nanoparticles significantly improved transfection with plasmid DNA encoding enhanced green fluorescent protein (eGFP) in pre-osteoblastic MC3T3-E1 cells compared to a commercial non-viral carrier. At the same time they elicited significantly lesser cytotoxicity than the commercial carrier. Plasmid DNA acted as a nucleation promoter, decreasing the nucleation lag time of metastable CaP solutions and leading to a higher rate of nucleation and a lower size of the precipitated particles. The degree of supersaturation (DS) of 15 was found to be more optimal for transfection than that of 12.5 or 17.5 and higher. Because CaP particles precipitated at DS 15 were spherical, while DS 17.5 and 21 yielded acicular particles, it was concluded that spherical particle morphologies were more conducive to transfection than the anisotropic ones. Even though the yield at DS 15 was 10 and 100 times lower than that at DS 17.5 and 21, respectively, transfection rates were higher using CaP nanoparticle colloids prepared at DS 15 than using those made at higher or lower DS, indicating that the right particle morphology can outweigh the difference in the amount of the carrier, even when this difference is close to 100×. In contrast to the commercial carrier, the concentration of CaP-pDNA delivered to the cells was directly proportional to the transfection rate. Osteosarcoma K7M2 cells were four times more easily transfectable with CaP nanoparticles than the MC3T3-E1 cells. The addition of citrate increased the transfection rate at lower concentrations; however, a complete redispersal of CaP-pDNA nanoparticles at higher concentrations of citrate coincided with a complete diminishment of transfection, implying the benefits of partial aggregation of CaP nanoparticles carrying pDNA. In contrast, PLL delayed transfection initially, but enhanced it at longer time points (⩾96 h), leading to the conclusion that both citrate and PLL could exert positive effects on transfection: citrate if added at low concentrations and PLL to extend transfection over longer periods of time. [ABSTRACT FROM AUTHOR]