306 research outputs found
Zein encapsulation of amphiphilic compounds
No full textFunctional compounds including flavors, essential oils, antioxidants or nutraceuticals are widely added into food system to enhance sensory properties or for health purposes. However, these compounds might not be stable in food systems during processing, storage and food preparation. Encapsulation has been proposed as a practical approach to stabilize these compounds and control their release. Zein is an amphiphilic protein originally obtained from corn. Its film-forming and coating ability make it potentially useful as a wall material for encapsulation. Amphiphilic compounds have been recognized to form well defined microspheres by evaporation induced self-assembly (EISA) in binary solvents, which is useful in encapsulation. The goals of this research were to improve our understanding of the development of zein encapsulation structures. The main objective was to investigate the effect of the hydrophobicity of core materials as measured by contact angle on the formation and structure of zein encapsulates obtained by evaporation induced self-assembly of ethanol-water systems. A second objective was to apply the knowledge learned in the above objective to propose a strategy to capture and encapsulate flavors generated in frying oils. Results showed that citral was effectively encapsulated with zein. Zein encapsulation morphology was related to the droplet formation ability of core materials in ethanol-water systems. Amphiphilic compounds were believed to form stable droplets in ethanol-water, which favored zein encapsulation. Hydrophobic compounds showed phase separation in ethanol-water which led to the formation of films rather than closed structures. A model system consisting of mixtures of a flavor and a hydrophobic carrier was used to study the effect of carriers on encapsulation ability of zein by the self-assembly process. The presence of the carrier negatively affected encapsulation effectiveness. Citral was recovered from the flavor-carrier mixture by extraction and phase separation at sub-freezing temperatures. Recovered citral was effectively encapsulated by zein. Fried chips flavors were also recovered from frying oil and encapsulated in zein by ethanol extraction and phase separation at low temperatures. Sensory ranking test was used to confirm the presence of recovered flavors after zein encapsulation.Item withdrawn by Mark Zulauf ([email protected]) on 2012-06-19T21:58:37Z
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MODAL POLITIK BENY YUSRIAL DALAM PEMILIHAN LEGISLATIF (DPRD) KOTA BUKITTINGGI TAHUN 2014
No full textABSTRAK
Ramadhani Zein. 1010833004. Jurusan Ilmu Politik, Fakultas Ilmu Sosial dan Ilmu Politik, Universitas Andalas, dengan judul Skripsi “”. Pembimbing: (1) Irawati S.IP, MA. (2) Ilham Aldelano Azre S.IP, MA. 128 Halaman, 12 Buku, 3 Skripsi, 1 Tesis, 3 Jurnal, 8 Transkip Wawancara.
Penelitian ini mendeskripsikan dan menganalisa . Penelitian ini di latar belakangi oleh Beny Yusrial orang baru (New Comer) mencalonkan diri dan berhasil terpilih dengan memperoleh suara terbanyak dan menjadi Anggota Legislatif DPRD Kota Bukittinggi periode 2014-2019. Peneliti menggunakan Teori Modal Politik Kimberly L Casey yaitu Modal Kelembagaan, Modal Ekonomi, Modal Sosial, Modal Moral dan Modal Simbolik, kemudian Teori Strategi Politik Adman Nursal yaitu Strategi Segmentasi, Strategi Targeting dan Strategi Positioning. Penelitian ini menggunakan metodelogi penelitian kualitatif, jenis penelitian studi kasus dengan tipe deskriptif. Teknik pengumpulan data yang di lakukan oleh peneliti dengan wawancara mendalam, dokumentasi dan observasi. Dalam pemilihan informan, peneliti menggunakan teknik purposive sampling. Data yang di peroleh dianalisis menggunakan etik dan emik.
Hasil penelitian ini adalah Beny Yusrial memanfaatkan modal politik yang di milikinya dalam menggunakan strategi politik untuk mendapatkan suara dari para konstituennya agar dapat memperoleh kursi di lembaga legislatif DPRD Kota Bukittinggi. Dalam penggunaan strategi segmentasi Beny Yusrial mengabungkan dengan modal sosial; dukungan dari kelompok PKK, Majelis taqlim, dan Organisasi Kepemudaan (GEMSIA), kemudian modal simbolik; Yusrial sebagai ayah Beny Yusrial dan Ria Amelia sebagai istri Beny Yusrial seorang publik figur. Serta modal moral; dari Beny Yusrial yang di pandang oleh masyarakat sebagai pribadi yang sopan, ramah dan peduli terhadap sesama. Dalam menggunakan strategi targetting Beny Yusrial mnggunakan modal ekonomi; untuk melengkapi kebutuhan kampanye seperti baliho,spanduk, dan kalender kemudian mengajak masyarakat untuk pergi refresing ke Mifan di Padang Panjang. sementara itu dalam penggunaan strategi positioning Beny Yusrial menggunakan modal kelembagaan; citra Partai Gerindra bersih dari KKN dan membuat acara KIM dengan para masyarakat, kemudian menggunakan modal simbolik dan modal moral. Dengan kepemilikan modal politik yang baik membantu Beny Yusrial dalam menerapkan strategi politik dalam memenangkan pemilu legislatif DPRD Kota Bukittinggi tahun 2014.
Kata Kunci: Modal Politik, Legislatif, Pemilihan Umu
Pengaruh Konsentrasi Minyak Atsiri Daun Cengkeh (Syzygium aromaticum L) Terhadap Aktivitas Antioksidan Nanopartikel Zein-Minyak Atsiri
No full textMinyak atsiri daun cengkeh (Syzygium aromaticum) digunakan sebagai bahan baku pada bidang industri maupun bidang kesehatan karena berperan sebagai antioksidan dan antibakteri. Minyak atsiri memiliki senyawa aktif yang mudah menguap pada suhu ruang sehingga tidak stabil terhadap perubahan lingkungan. Untuk melindungi senyawa aktif yang terkandung dalam minyak atsiri dapat dilakukan dengan menjadikan ukuran partikel minyak atsiri dalam bentuk nano. Minyak atsiri daun cengkeh yang ditambahkan dengan zein dan tween yang berguna untuk melindungi serta berfungsi sebagai penstabil. Nanopartikel zein-minyak atsiri dibuat dengan memvariasikan konsentrasi penambahan minyak cengkeh (0, 2, 4, 6, 8 dan 20 mg/mL) pada 1,5 mg/mL zein dan 1 mL tween 20 yang disonikasi selama 20 menit. Aktivitas antioksidan dari NPZSA yang terbentuk diuji dengan metode DPPH, nilai aktivitas antioksidan yang tinggi ditunjukkan pada formula 5 dengan penambahan konsentrasi minyak atsiri daun cengkeh 8 mg/mL menunjukkan aktivitas antioksidan yang terbaik dengan nilai persen inhibisi yaitu 71,13 %, didukung oleh hasil dari sinar laser dimana banyaknya sinar yang dihamburkan oleh larutan tersebut. Spektrum UV-Vis NPZSA menunjukkan serapan maksimum pada panjang gelombang 280,0 nm. Analisis komponen kimia yang terdapat di dalam NPZSA hasil analisis Gas Chromatography Mass Spectrometry (GC-MS) menunjukkan adanya 32 senyawa dengan tiga senyawa utama yaitu trans-β-caryophyllene (46,69%), chavibetol (25,80%) dan α-humulene (10,84%)
Development of novel zein-cellulose nanocomposite films
No full textZein is a hydrophobic biopolymer, which naturally forms biodegradable films. These films are rigid, brittle, and lack good mechanical and barrier properties for packaging applications. This study aims at improving the mechanical and barrier properties of zein films by the development of zein-cellulose nanocomposites. A ‘nanocomposite’ is a mixture of polymer matrix, which forms the continuous phase and the filler (having at least one dimension less than 100nm), which forms the dispersed phase. Zein-cellulose nanocomposites have zein as the matrix and cellulose as the filler. Nano-sized cellulose was prepared using wet-media milling machine and mass ratios of 1%, 3%, 5% and 10% of both, naked (not stabilized) nano-cellulose and GA - stabilized nano-cellulose were used in the film formulation. Tributyl citrate (TBC) was used as the plasticizer. The films were prepared using solvent-cast technique and characterized to test their mechanical and barrier properties. The controls were pure zein films and films with only plasticizer. Texture Analysis showed that filler loading of 5% was most effective in increasing the elongation-at-break to about 16 to 20 times of the controls. However, the tensile strength did not change. Water vapor permeability of the nanocomposites was minimum at 1% by wt. of naked cellulose (~4 times less than control) or at 5% by wt. of stabilized cellulose (~6 times less than control). Water absorption results showed that the rate of water uptake decreased as the filler loading increased. DSC and FTIR suggested that there is no interaction between the zein and the nano-cellulose in the films. The AFM results showed that the films’ surface is flat, but the thickness of the films increased with filler loading. Therefore, incorporation of nano-cellulose improved the flexibility and water barrier properties of the films. Gum Arabic, which was used as a stabilizer for nano-cellulose, seemed to have aided the even distribution of cellulose in the zein matrix. Thus, these films can be a good starting point to further study the arrangement of cellulose within the zein matrix and test its potential applications on food systems and as edible films.M.S.Includes bibliographical referencesby Seema Lakshmana Ra
Fabrication, characterization, and applications of zein-based colloidal particles
No full textWith an increasing trend on the development of "clean-label" food products, environmental friendly materials have attracted more and more attentions during the recent years. As a natural biodegradable protein from maize, zein has a good potential to be used to develop new carrier systems due to its Generally Recognized as Safe (GRAS) status, abundant source, commercial availability, low cost, and low digestion properties. The water-insoluble and amphiphilic characteristic of zein makes it a perfect candidate to form colloidal particles to stabilize Pickering emulsions. The successful assembly of particles at emulsion interface largely relies on their surface activities, which can be tuned through the modification of surface charges and hydrophobicities.
In this study, zein was hydrophilically modified with sodium caseinate (SC) to form zein/SC complexes and hydrophobically modified with saturated fatty acids (FA) to form zein/FA complexes. The obtained zein/SC complexes displayed good emulsification capacities, which were suitable to stabilize a wide range of oils with middle or low polarities including toluene, n-octane, hexane, and general cooking oils extracted from vegetables. The fluorescence image of fluorescein isothiocyanate (FITC)-labeled zein particles indicated that the emulsions were stabilized mainly by zein-based colloidal particles. With the presence of polyglycerol polyricinoleate, zein/SC complexes were able to stabilize W/O/W double emulsions either through magnetic stirring method or through high speed homogenization method. The Pickering emulsions stabilized by zein/SC complexes were further utilized to encapsulate resveratrol, a plant phytoalexin extracted from grape, peanut and other few plants.
Resveratrol has been widely reported for its health beneficial potentials, such as anti-oxidation, anti-inflammation, anti-obesity, anti-tumor activities, etc. However, the applications of resveratrol in the food industries are quite limited because of its low chemical stability, low oral bioavailability, and poor water solubility. In this study, a series of delivery systems were developed to compare their delivery efficacy and bioaccessibility of resveratrol using in vitro models. Zein/SC complexes were utilized to fabricate Pickering emulsions through high speed homogenization, while conventional emulsions were stabilized by lecithin using high pressure homogenization. The Simulator of the Human Intestinal Microbial Ecosystem (SHIME) and TNO gastro-Intestinal Model (TIM-1) were utilized to mimic the digestion in the upper GI tract. The results from TIM-1 indicated that conventional emulsions displayed the highest bioaccessibility compared with Pickering emulsions and bulk oil solutions. In SHIME experiment, the structure of Pickering emulsions was still observable after 2-hour digestion in the stomach, which explained why Pickering emulsion showed slower release effect of RES compared with conventional emusions. After 180 min digestion in the jejunum by the TIM-1 model, the digested samples were loaded on Franz Cell Diffusion apparatus to see the permeability of various formulations through porcine small intestine membrane. It was found that Pickering emulsions had significantly lower permeability as compared with conventional emulsions and bulk oil solutions (P < 0.05). The permeability of resveratrol was driven by concentration gradients between donor compartment and receptor compartment. Through anaerobic fermentation study, it was found that lecithin stabilized emulsions after SHIME digestion retarded the growth of probiotics, Lactobacillus rhamnosus GG, while zein/SC complexes stabilized Pickering emulsions even promoted its growth, since zein and sodium caseinate could serve as a protein source for bacteria. Conclusively, Pickering emulsions are more suitable for target delivery of RES into colon, while conventional emulsions can be used to improve the bioaccessibility in small intestine.
Besides Pickering emulsion, zein/SC complexes were further utilized to fabricate colloidosomes that are characterized by their hollow shell structures through layer-by-layer (LbL) self-assembling technique. Quartz crystal microbalance equipped with dissipation monitoring (QCM-D) was applied to simulate the deposition process of polyelectrolytes (chitosan, sodium alginate, and zein) on the zein/SC surface. The result from QCM-D analysis showed that the adlayer on zein/SC surface had a soft and viscoelastic property. This presented method successfully produced robust colloidosomes, which not only survived from multiple washing steps, but also did not show flocculation and coalescence phenomenon during the LbL coating process. And the polysaccharide coatings strengthened the structure of shells, and offered them a viscoelastic property to stand harsh dehydration conditions.
In the following section, fatty acid (FA)/zein (Z) complexes were prepared by using FAs with different chain lengths (i.e. lauric acid (LA), myristic acid (MA), palmitic acid (PA), stearic acid (SA) and oleic acid (OA)), different FA/Z ratios (i.e. 0.1:1, 0.2:1, 0.4:1, and 1:1), and different pH values (i.e. 3.5, 5.0, 8.0, 10.5) in order to precisely tune the surface activities of zein. Results showed that stable FA/Z complexes were able to be formed under alkaline condition, rather than acidic or neutral pH, which was due to the film forming property of zein in acidic conditions. According to the contact angle (CA) measurement, the CA increased gradually from 64.88 ± 4.09˚ (LA/Z, 0.5:1) to 85.25 ± 2.00˚ (SA/Z, 0.5:1) with an increase of the carbon chain length. However, oleic acid, a monounsaturated omega-9 fatty acid, reduced the hydrophobicity, giving the lowest CA of 61.08 ± 6.14˚. Scanning electron microscopic (SEM) images indicated that FAs could lead to the partial fusion of the particles, which explained why FAs could reduce the brittleness and increase the plasticity of zein. The SA/Z complexes showed good emulsification capacity to stabilize O/W/O double emulsions through handshaking. The LA/Z complexes were further applied to improve the bioavailability of lipophilic ingredients, i.e. hesperidin in this study. Based on in vitro study conducted through the TIM-1 model, the bioavailability of hesperidin was successfully enhanced from 53% to around 70% as compared with bulk oil solutions. This study indicated the good potentials of using zein as an environmental friendly particle emulsifier to develop novel delivery systems for various nutraceuticals.Ph.D.Includes bibliographical reference
Applications of zein-based material in nano-encapsulation, pickering emulsions, microspheres and amorphous solid dispersions
No full textWith the increasing environmental concerns about the synthetic plastic materials, prolamine originated from grains have come back to people’s sight due to their unique characteristics: GRAS (Generally Recognized as Safe) nature with good biocompatibility and biodegradability, highly hydrophobic but soluble in 60%-80% aqueous alcohol, easy fabrication of particulate carrier at micro even nano level, and relatively slower digestibility for oral route-controlled release design, etc. Among them, zein is the first commercial prolamine originated from maize byproduct, which is usually produced as a white or light yellowish powder. As one of the historically manufactured plant proteins, zein has various applications in the industry like coatings, binders, fibers, etc. In the decade, zein’s advantages make it one potential biomaterial with intensive explorations in nutraceutical and medical delivery use, as well as an environmental friendly structural material for the soft matter. However, there is still the specific limitation or scarce study for zein based materials to fulfill its application potentials in each trending field, including nano-encapsulation, Pickering emulsions, microspheres and amorphous solid dispersions.
My Ph.D. thesis exploits the solutions to break through the instability limitations of zein-based material in nano encapsulation and Pickering emulsions via chemical modification, and also fills its research gap for scaling up bioactive compound encapsulation using microsphere system and amorphous solid dispersions. Firstly, hydrophilic modification was successfully performed on zein material, in order to improve its colloidal stability by intrinsically enhancing its amphiphilic nature. The zein was conjugated with hydrophilic carboxymethyl dextran (CMD) through covalent linking, and a novel amphiphilic zein-based material, zein-carboxymethyl dextran (Zein-CMD), was successfully synthesized to self-assemble nano-micelles for delivery potential application. The results suggested that about 2 CMD molecules were conjugated per zein chain, which resulted in the transformation from secondary α-helix to β-sheet and random coil structure. After modification, Zein-CMD still took a rod-like conformation but more elongated than pristine zein in aqueous alcohol solution. The modified zein-based material could self-assemble spherical nano-micelles by conventional anti-solvent method, with a good control on colloidal stability and particle size within a physiological pH environment, regardless of zein’s precipitation tendency due to its isoelectric point of ~ 6.2.
Secondly, hydrophilic modified zein-based material was self-assembled into nano-sized micelles to enhance the encapsulation efficiency of lipophilic phytochemicals. Dihydromyricetin (DMY) loaded Zein-CMD nano-micelles, DMY/Zein-CMD, was prepared through anti-solvent method. The Dihydromyricetin load was up to 30 wt.%, and a better colloidal stability was achieved overwhelming solely zein carrier or zein with CMD as the outer. In addition, DMY encapsulated in the Zein-CMD carrier was confirmed as amorphous status, with hydrogen bonding found to synergistically prevent recrystallization of DMY with hydrophobic interactions. In comparison, dissolution profile of DMY/Zein-CMD was significantly improved as compared to pristine zein in bio-relevant media.
In the following section, hydrophobic modification on zein material was also conducted to resolve the unstable issues of Pickering emulsions (PE) based on pristine zein particles. The typical hydrophobic lauryl chains were successfully grafted onto zein to adjust its hydrophile-lipophile balance (HLB) to better stabilize PE. It is indicated that the HLB of lauryl-zein conjugate could be tuned by 1-8 lauryl chains per zein chain, which was visually quantified by water contact angle as well. Through anti-solvent and ultrasonic treatments, modified zein conjugate particles were successfully prepared with narrowly size distribution. These particles at low concentration of 1 wt% could better stabilize 70% oil internal phase than that at 50% oil phase, and overwhelmed the breakage of pristine zein based Pickering emulsions after 1 week’s storage at the ambient environment. The potential mechanism was discussed that the increase of hydrophobicity through the lauryl grafting correspondingly enhanced the surface tension. A new insight was introduced on PE stabilization containing high oil internal phase, using hydrophobic modified zein conjugate particles without other additives.
Besides chemical modification on zein material, encapsulation of poor soluble bioactive compounds at scale-up level was also discussed on zein-based microsphere delivery system and amorphous solid dispersions. A novel zein-based microsphere delivery system containing amorphous resveratrol was prepared by anti-solvent method and following freeze drying technology. The results showed that up to 20 wt% of amorphous resveratrol was stabilized in zein microspheres possibly via hydrogen bonding, and the amorphous formulation could maintain stable for 3 months. A better dissolution performance with enhanced solubility from amorphous resveratrol was achieved from zein microspheres as compared to equivalent crystalline resveratrol. Free drying technology can be a way to manufacture hydrophobic phytochemical loaded microspheres based on zein material, but a limit of the initial load could be a concern regarding on the high crystallization tendency.
Lastly, amorphous solid dispersions (ASD) containing felodipine and polymeric carrier zein were produced by spray drying technology. The solid state characterization results demonstrated that amorphous origin of ASD was maintained under 3 months’ accelerated stability study, with spherical particles of about 1 um were observed without any birefringence in the micro condition. Only one single glass transition (Tg) was detected around 128.6 °C without exotherms or endotherms, indicating the good miscibility of felodipine in polymeric zein through spray drying. Based on cumulative bioaccessibility of felodipine through TIM-1 in vitro digestion model, a 6-8 times increased bioaccessibility from ASD was achieved as compared to equivalent crystalline felodipine mixed with zein. The spray dried amorphous solid dispersions using zein as polymeric excipient was proved to maintain saturation status of felodipine and enhance its bioaccessibility in simulated upper intestinal tract.Ph.D.Includes bibliographical reference
Development of zein-based ice nucleator films for frozen food applications
No full textThis research aimed at developing zein-based ice nucleation films for the applications of frozen foods. Acetic acid was chosen as the solvent to cast zein films with flawless surface. Tributyl citrate (TBC) was mixed into zein films to various proportions and 10% TBC was most effective on improving mechanical properties resulting in 2.3-fold more flexibility and 5.8-fold more toughness compared to unplasticized zein films. But incorporation of 20% TBC significantly decreased the water absorption by 19% compared to 10% TBC. Thus, zein films with 20% TBC with good flexibility and water resistance was used in following experiments. The activity of ECINs was stable at pH between 4.0 and 9.0 and ionic strength between 0.01 M and 0.10 M. In the development of INFs, the optimum adsorption of ECINs on zein films surface occurred through layer-by-layer method at pH 7.0 and ionic strength of 0.05 M on UV/ozone-treated zein. A novel method was developed to quantify the activity of INFs, which revealed that the highest activity of zein-based INFs reached 175 units/mm2. The zein-based ice nucleation films (INFs) were used to wrap frozen bread dough during five freeze/thaw cycles. The high-activity INF was as effective as blending ECINs in improving the yeast survival by 40%, and consequently increased the specific volume of bread loaf by 25%. Furthermore, high-activity INFs prevented the dehydration of frozen dough and thus significantly reduced the crumb hardness by 36% and increased the crumb springiness by 1.25 times. On energy saving, zein-based INFs were less potential than blended ECINs. INFs only reduced the time of freezing by 6% compared to the 20% by blended ECINs. However, the total amount of ECINs used on wrapping a piece of dough was only about 1/200 of the amount through blending. In addition, ECINs immobilized on the zein films showed desirable stability to sustain at least fifteen repetitive uses on freezing water.Ph. D.Includes bibliographical referencesIncludes vitaby Ke Sh
Encapsulation of naringenin using zein nanoparticles
No full textNaringenin (4’,5,7-‐‑trihydroxyflavanone) is a flavanone known to have many health benefits including antitumor, antioxidant, anti-‐‑inflammatory, and hepatoprotective properties. It is naturally found in citrus fruits, predominantly in grapefruits. However, when naringenin is orally ingested, the health benefits are limited due to its low solubility in water, which causes low bioavailability. In an effort to improve the bioavailability of naringenin, various nanoparticle systems were investigated and optimized to counter this problem. Zein, a corn based protein, was chosen as the primary encapsulation material due to its capability of forming self-‐‑assembled nanoparticles and sustained release. To minimize the immunogenicity effects of zein, the nanoparticles were further treated with a polysaccharide to produce a more hydrophilic surface coating. Three polysaccharides, carboxymethyl cellulose (CMC), carboxymethyl chitosan (CMCH), and carboxymethyl dextran (CMD), were individually explored with the naringenin filled zein nanoparticles. ii Optimized ratios with the highest load and the smallest particle size were identified for each nanoparticle system. The optimized ratios for each polysaccharide were as follows: 0.1N: 5Z: 15CMC, 3N: 5Z: 15CMCH, 3N: 5Z: 15CMD. MTT testing identified cytotoxicity thresholds for each formulation. Pure naringenin was found to be not cytotoxic at <50 μg/mL. The 0.1N: 5Z: 15CMC formulation was not cytotoxic at 10 fold dilution. For 3N: 5Z: 15CMCH and 3N: 5Z: 15CMD, each formulation was not cytotoxic at 20 fold dilution. Across the polysaccharide sets, carboxymethyl chitosan was found to be smallest in particle size. Further investigation was done on this polysaccharide to see whether further reductions of particle size could be achieved. The addition of a calcium chloride coating reduced the particle size further compared to the original carboxymethyl chitosan ratio. This research showed that the combination of carboxymethyl chitosan with calcium chloride resulted in the most promising system of encapsulating naringenin with zein nanoparticles.M.S.Includes bibliographical referencesby Elizabeth Joseffy Chrzaste
On the association between high temperature and mortality in warm climates
No full textWe conducted a time-series analysis of 1997-1999 data records of air temperature and all-cause mortality in Greater Beirut, using bi-linear Poisson auto-regressive models, and published our findings in the Science of the Total Environment [El-Zein, A., Tewtel-Salem, M., Nehme, G., 2004. A time-series analysis of mortality and air temperature in Greater Beirut. Sci. Total Environ. 330, 71-80]. We compared our results to those of Curriero et al. [Curriero, F.C., Heiner, K.S., Samet, J.M., Zeger, S.L., Strug, L., Patz, J.A., 2002. Temperature and mortality in 11 cities of the Eastern United States. Am. J. Epidemiol. 155(1) 80-87.], who subsequently reported that their original results were inaccurate and published new results [Curriero, F.C., Heiner, K.S., Samet, J.M., Zeger, S.L., Strug, L., Patz, J.A., 2002. Temperature and mortality in 11 cities of the Eastern United States. Am. J. Epidemiol. 155(1) 80-87; Curriero, F.C., Samet, J.M., Zeger, S.L., 2003. Letter to the Editor re. On the Use of Generalized Additive Models in Time-Series Studies of Air Pollution and Health and Temperature and Mortality in 11 Cities of the Eastern United States. Am. J. Epidemiol. 158(1) 93-94.]. In this letter, we report two changes in the interpretation of our findings as a result of the change in the results of Curriero et al. [Curriero, F.C., Heiner, K.S., Samet, J.M., Zeger, S.L., Strug, L., Patz, J.A., 2002. Temperature and mortality in 11 cities of the Eastern United States. Am. J. Epidemiol. 155(1) 80-87]. Their newly-reported results reinforce our conclusion that heat-related mortality can be a significant public health issue even in temperate to warm climates. However, our findings raise a question concerning the ability of socioeconomic indicators to explain differences in vulnerability to heat between high-income and low-income countries. © 2004 Elsevier B.V. All rights reserved.BAJU R, 2002, EPIDEMIOL REV, V24, P190; Ballester F, 1997, INT J EPIDEMIOL, V26, P551, DOI 10.1093-ije-26.3.551; Curriero FC, 2002, AM J EPIDEMIOL, V155, P80, DOI 10.1093-aje-155.1.80; Curriero FC, 2003, AM J EPIDEMIOL, V158, P93, DOI 10.1093-aje-kwg105; Dominici F, 2002, AM J EPIDEMIOL, V156, P193, DOI 10.1093-aje-kwf062; El-Zein A, 2004, SCI TOTAL ENVIRON, V330, P71, DOI 10.1016-j.scitotenv.2004.02.02710111
Design of self-assembled zein-based nanoparticles as an effective drug carrier and transporter
No full textCancer is the second leading cause of death in the world. General characteristics of tumors include abnormal blood vessels and lack of lymphatic system. Due to large sizes, drug-loaded delivery systems cannot diffuse out the tumor blood vessels, as a result of progressive accumulation: the EPR effect. That’s the main reason to utilize nanoparticles in cancer therapy. Besides, the size, shape, surface chemistry and targeting groups of nanoparticles are important in controlling biodistribution and cellular internalization of engineered nanoparticles.
Zein specifically acts as reservoirs for lipophilic bioactive substances or drugs due to the strong hydrogen bond and hydrophobic interaction between nutraceutical and proteins. Zein nanoparticles (NPs) are commonly prepared via phase separation method. Although it is a relatively easy technique, the resultant zein colloidal dispersion usually form poorly redispersable aggregates and sediments after drying. Also, individual zein NPs exhibited a burst drug release profile at physiological conditions due to the swelling of the zein NPs and the drug cannot tightly bind to zein particles. Therefore, we aim to design novel zein-based NPs to enhance the stability and sustained release of individual zein NPs. At the meantime, the cellular uptake and bioefficacy of the encapsulated drug were also discussed in this work.
In the first part of this work, hydrophilic carboxymethyl konjac glucomannan and calcium ion crosslinking were used to modify the surface of zein nanoparticles, therefore zein- carboxymethyl konjac glucomannan-calcium (ZCC) NPs were assembled. As a result, ZCC NPs showed good stabilities in cell culture medium at 37 °C, and enhanced pH stability at a range from 5.0 to 8.5 and lower surface hydrophobicity. The endocytic pathway of ZCC NPs is cell-line dependent, and ZCC NPs enhanced the cellular uptake through dynamin- mediated endocytosis can be assigned to clathrin-mediated endocytosis in HT29 cells. And the stability and cellular uptake were enhanced compared to individual zein NPs.
Because of the anti-inflammation and anti-cancer properties, andrographolide (AG) and its derivatives, which are labdane diterpenoid compounds extracted from Andrographis paniculata Nees, are often used as herbal drugs in Asian countries. AG sparingly soluble in water (3.29μg/ml at 25 °C), which restricts its therapeutic use due to low bioavailability by oral administration. ZCC NPs was used as a drug carrier for AG to enhance the water solubility and the bioefficacy. Importantly, ZCC NPs loaded AG were shown effectively decreasing the cancer cell population and resulting cell death. The efficacy of AG to regulate the in vitro NF-κB expression was notably enhanced by the ZCC nanoparticle delivery system due to enhanced dose efficiency resulting from better solubility, transportability and reduced toxicity. In these preliminary studies, ZCC NPs were proved to be appealing delivery systems for hydrophobic bioactive compounds.
Efficient pH-sensitive delivery systems sensitively response to subtle pH variations in the tumor microenvironment. In this paper, we utilized the acid-sensitive bonds between metal ions and dihydromyricetin (DMY) and designed a pH-sensitive zein-based delivery system. The self-assembled zein NPs were coated with a DMY-Zn2+ coordinated bonding layer. Z-DMY/ZnII NPs not only acted as an efficient drug carrier, but also a highly pH-responsive drug release system. Therefore, Z-DMY/ZnII NPs had a better sustained release compared with individual zein NPs. Moreover, Z-DMY/ZnII NPs demonstrated excellent cellular uptake by HeLa cells. Z-DMY/ZnII NPs effectively inhibited the cancer cell growth and exhibited an efficient anti-cancer activity toward HeLa cells. As a result, Z-DMY/ZnII NPs acts as a promising pH-responsive food-grade colloidal delivery system encapsulating hydrophobic nutraceuticals in cancer therapy.Ph.D.Includes bibliographical referencesby Xunan Zh
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