1,720,963 research outputs found
Incorporation of quercetin in lipid microparticles:Effect on photo- and chemical-stability
No full textLipid microparticles loaded with the flavonoid, quercetin were developed in order to enhance its stability in topical formulations. The microparticles were produced using tristearin as the lipid material and phosphatidylcholine as the emulsifier. The obtained lipoparticles were characterized by release studies, scanning electron microscopy and powder X-ray diffractometry. The quercetin loading was 12.1% (w/w). Free or microencapsulated quercetin was introduced in a model cream formulation (oil-in-water emulsion) and irradiated with a solar simulator. The extent of photodegradation was measured by high-performance liquid chromatography. The light-induced decomposition of quercetin in the cream vehicle was markedly decreased by incorporation into the lipid microparticles (the extent of degradation was 23.1 ± 3.6% for non-encapsulated quercetin compared to 11.9 ± 2.5% for the quercetin-loaded microparticles) and this photostabilization effect was maintained over time. Moreover, the chemical instability of quercetin, during 3-month storage of the formulations at room temperature and in the dark, was almost completely suppressed by the lipid microparticle system. Therefore incorporation of quercetin in lipoparticles represents an effective strategy to enhance its stability in dermatological products
Coloading of a photostabilizer with the sunscreen agent, butyl methoxydibenzoylmethane in solid lipid microparticles
No full textThe sunscreen agent, butyl methoxydibenzoylmethane (BMDBM), one of the most widely used UV-A filter, undergoes decomposition under sunlight exposure, which is a limiting factor on its overall performance. To reduce the sunscreen photodegradation, this study investigates the incorporation into solid lipid microparticles (SLMs) of BMDBM together with the photostabilizer, 4-methylbenzylidene camphor (MBC). The microparticles were produced by the melt dispersion technique using various lipid materials (tristearin, glyceryl behenate, and stearic acid) and hydrogenated phosphatidylcholine as the surfactant. The highest retention capacity for BMDBM and MBC was achieved with tristearin microparticles. These SLMs were characterized by scanning electron microscopy and powder X-ray diffraction analyses. The BMDBM and MBC loading was 10.4 and 10.1%, respectively. The efficacy of the SLMs was evaluated after their introduction in a conventional cream (oil-in-water emulsion). The light-induced decomposition of BMDBM was decreased by encapsulation into the SLMs (the extent of degradation was 33.8 ± 5.5% for unencapsulated BMDBM/MBC and 25.3 ± 4.2% for BMDBM-loaded microparticles in conjunction with free MBC). Moreover, the co-loading of the MBC stabilizer in the SLMs produced a further reduction of the photodegradation of the UV-A filter (the BMDBM loss was 16.9 ± 5.9%) compared with the microparticles containing BMDBM without MBC. Therefore, incorporation in lipid microparticles of BMDBM together with the MBC photostabilizer is more effective in enhancing the UV-A filter photostability than the SLMs loaded with BMDBM alone
Encapsulation of the sunscreen agent, 4-methylbenzylidene camphor in lipid microparticles:effect on photostability and percutaneous penetration
No full textThe effect of solid lipid microparticles on the photostability and human stratum corneum penetration of the sunscreen agent 4-methylbenzylidene camphor was studied. The light-induced decompossition of 4-methylbenzylidene camphor in the emulsion vehicle wa significantly reduced by encapsulation into the lipoparticles. Moreover, the in vivo penetration studies demonstrated tha the permeation of 4-methylbenzylidene camphor to the deeper regions of the horny layer was markedly decreased upon application of the microencapsulated sunscreen agent
Photostabilization Effect of Quercetin on the UV Filter Combination, Butyl Methoxydibenzoylmethane–Octyl Methoxycinnamate
No full textThe aim of the study was to investigate the effect of the natural antioxidant quercetin on the photostability of the most widely used combination of UVA (320-400 nm) and UVB (290-320 nm) filters, respectively butyl methoxydibenzoylmethane (BMDBM) and octyl methoxycinnamate (OMC). In order to reproduce the conditions prevalent in commercial sunscreen products, the stabilizing efficacy of quercetin was evaluated in model creams containing BMDBM (3%, w/w) together with OMC (4%, w/w) and exposed to a solar simulator at an irradiance corresponding to natural sunlight. Quercetin was found to enhance the photostability of the two UV filters in a concentration–dependent way. Addition of quercetin to the sunscreen formulation significantly reduced the photodegradation of BMDBM and OMC from 40.3%±2.4 to 27.7%±2.6 and from 51.3%±2.1 to 42.2%±2.0, respectively. Moreover, comparative photodegradation studies demonstrated that quercetin was much more effective and at a lower concentration than commonly used stabilizer (octocrylene) and antioxidants (vitamin E, butylated hydroxyanisole). In vitro determination of the UVB and UVA protection parameters showed that the quercetin-based formulation fulfilled the official requirements on sunscreen products. Because of its photostabilizing and multiple antioxidant properties, quercetin represents a useful additive for the formulation of effective broad-spectrum sunscreens containing BMDBM and OMC
Encapsulation of the UV Filters Ethylhexyl Methoxycinnamate and Butyl Methoxydibenzoylmethane in Lipid Microparticles: Effect on in vivo Human Skin Permeation
No full text<i>Background:</i> Lipid microparticles loaded with the UVB filter ethylhexyl methoxycinnamate (EHMC) and the UVA filter butyl methoxydibenzoylmethane (BMDBM) were evaluated for their effect on the sunscreen agent’s percutaneous penetration. <i>Methods:</i> Microparticles loaded with EHMC or BMDBM were prepared by the melt emulsification technique using stearic acid or glyceryl behenate as lipidic material, respectively, and hydrogenate phosphatidylcholine as the surfactant. Nonencapsulated BMDBM and EHMC in conjunction with blank microparticles or equivalent amounts of the 2 UV filters loaded in the lipid microparticles were introduced into oil-in-water emulsions and applied to human volunteers. Skin penetration was investigated in vivo by the tape-stripping technique. <i>Results:</i> For the cream with the nonencapsulated sunscreen agents, the percentages of the applied dose diffused into the stratum corneum were 32.4 ± 4.1% and 30.3 ± 3.3% for EHMC and BMDBM, respectively. A statistically significant reduction in the in vivo skin penetration to 25.3 ± 5.5% for EHMC and 22.7 ± 5.4% for BMDBM was achieved by the cream containing the microencapsulated UV filters. The inhibiting effect on permeation attained by the lipid microparticles was more marked (45–56.3% reduction) in the deeper stratum corneum layers. <i>Conclusions:</i> The reduced percutaneous penetration of BMDBM and EHMC achieved by the lipid microparticles should preserve the UV filter efficacy and limit potential toxicological risks.</jats:p
Solid lipid budesonide microparticles for controlled release inhalation therapy
No full textA solid-lipid microparticle system containing budesonide was prepared. The solid-lipid system was studied in terms of morphology, particle-size distribution, crystallinity, thermal properties, aerosol performance and dissolution/diffusion release. In addition, the microparticle system was compared to conventional spray-dried crystalline and amorphous budesonide samples. The particle size distributions of the crystalline, amorphous and solid-lipid microparticles, measured by laser diffraction, were similar; however, the microparticle morphology was more irregular than the spray dried drug samples. The thermal response of the solid-lipid microparticles suggested polymorphic transition and melting of the lipid, glycerol behenate (at ~48°C and ~72°C). No budesonide melting or crystallisation peaks were observed (as was seen in the drug only samples) suggesting that the budesonide was integrated into the matrix. X-ray powder diffraction patterns of the crystalline and amorphous budesonide were consistent with previous studies while the solid-lipid microparticles showed two peaks, at approximately 21.3 and 23.5 2θ suggesting the metastable sub-α and primarily β’ form. Analysis of the in vitro diffusion/dissolution of the formulations was studied using a flow through model and the curves analysed using difference/similarity factors and fitted using the Higuchi model. Regression analysis of this data set indicated differences in the t0.5, where values of 49.7, 35.3 and 136.9 mins were observed for crystalline, amorphous and the solid-lipid microparticles, respectively. The aerosol performance (<5μm), measured by multistage-liquid-impinger, was 29.5% and 27.3%, 21.1% ± 0.6% for the crystalline, amorphous and the solid-lipid microparticles, respectively. This study has shown solid-lipid microparticles may provide a useful approach to controlled release respiratory therapy
Novel inhalable controlled release particles for inhalation
No full textThis study evaluate the potential of using lipid microparticles as a delivery vehicle for controlled release to the lung . In addition, the development of the most suitable methodologies for their in vitro testing was also examine
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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