Layer-by-Layer assembly and humidity sensitive behavior of poly(ethyleneimine)/multiwall carbon nanotube composite films
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Layer by layer
Ethyleneimine
Layer-by-layer (LBL) films of poly(lactic acid) nanoparticles (PLA NPs) and poly(ethyleneimine) (PEI) were fabricated as a novel drug-delivery system. The PLA NPs, which encapsulated pyrene as a model drug, were prepared by nanoprecipitation methods. The assembly process of PLA NPs/PEI LBL films was monitored by UV−vis spectroscopy, and the load of pyrene in the multilayer films was verified by fluorescence spectroscopy. The morphology of the PLA NPs/PEI LBL films was observed by SEM. The release profile of pyrene from the LBL films in PBS solutions was further studied, and the result indicated that the PLA NPs/PEI films were capable of sustainably releasing pyrene as expected. The fabrication of PLA NPs/PEI LBL films provides a new facile method for drug delivery and paves the way for loading multiple types of drugs into a single LBL film.
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Abstract A layer‐by‐layer (LbL) thin film composed of poly(ethyleneimine) (PEI) and carboxymethyl cellulose (CMC) was prepared on the surface of a gold (Au) disk electrode and the LbL layer was impregnated with hemin to fabricate amperometric hydrogen peroxide (H 2 O 2 ) sensors. Hemin can be easily immobilized in the LbL layer by immersing the LbL film‐coated electrode in the hemin solution. The hemin‐modified electrode thus prepared exhibited an amperometric response to H 2 O 2 on the basis of the electrochemical reduction catalyzed by hemin. The output current of the hemin‐modified electrode depended on the concentration of H 2 O 2 over the range of 0.005–1.0 mM. Thus, the LbL film composed of PEI and CMC was found to be an excellent material for the facile preparation of hemin‐based H 2 O 2 sensors.
Hemin
Amperometry
Carboxymethyl cellulose
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Although layer–by–layer (LbL) assembly technique has been successfully used in various areas of nanobiotechnology, some LbL-assembled nanostructures have suffered from a lack of stability when they are exposed to certain changes in aqueous environments. In addition, the interlayer diffusion of polyelectrolytes throughout the film during assembly generally limits the control of film architecture and release characteristics. To overcome these limitations, we have utilized a strategy to conjugate catechol groups, largely present in mussel adhesive proteins, to branched poly(ethyleneimine) (BPEI) and poly(acrylic acid) (PAA). Only a fraction of amine or acid groups are modified with catechol groups, thereby preserving their charged nature for use in LbL assembly, while integrating the beneficial adhesive features of catechol groups into LbL films. The structure, physico–chemical properties, and stability of LbL films composing BPEI and PAA without and with catechol modifications were compared. The incorporation of catechol groups led to a doubling of the average film thickness and linear film growth. Upon exposure to PBS pH 7.4, the catechol-containing LbL films underwent far fewer changes in the degree of ionization and film thickness and exhibited stronger mechanical properties, indicative of their enhanced film stability. Finally, when LbL films with catechol modifications were used as physical barrier layers between radiolabeled 14C–dextran sulfate (14C–DS) and 3H–heparin sulfate (3H–HS), we observed two different release rates composed of an abrupt release from the surface of 3H–HS, together with a sustained release from the underlying 14C–DS. Overall, these films provide a bioinspired multifunctional platform for the systematic incorporation and assembly of biological therapeutics into controlled release films at physiological conditions for biomedical applications.
Catechol
Layer by layer
Tannic acid
Ethyleneimine
Biomolecule
Acrylic acid
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Дисертaцію присвячено дослідженню проблемних питaнь aдміністрaтивно-прaвового регулювaння інвестиційної діяльності в Укрaїні. Aвтором досліджено поняття тa мехaнізм здійснення aдміністрaтивно-прaвового регулювaння у сфері інвестиційної діяльності тa визнaчено перспективні нaпрямки нaукового дослідження цієї проблеми. При цьому булa дaнa хaрaктеристикa інвестицій тa інвестиційної діяльності як об’єктів aдміністрaтивно-прaвового регулювaння. В роботі проaнaлізовaно сучaсний стaн тa перспективи розвитку інвестиційної діяльності в Укрaїні. Зокремa, подaнa хaрaктеристикa процесів зaлучення тa використaння вітчизняних тa іноземних інвестицій, тенденцій формувaння інвестиційної політики в Укрaїні тa зaсaд розвитку інвестиційного клімaту. У дисертaції тaкож досліджувaлися зaсоби тa мехaнізм реaлізaції держaвного регулювaння у сфері інвестиційної діяльності тa системa оргaнів упрaвління інвестиційною діяльністю. У дисертaції тaкож теоретично обґрунтовaні і сформульовaні пропозиції тa рекомендaції щодо вдосконaлення aдміністрaтивно-прaвового регулювaння інвестиційної діяльності. Диссертaция предстaвляет собой комплексное исследовaние aдминистрaтивно-прaвового регулювaния инвестиционной деятельности в Укрaине. Aвтором исследовaно понятие и мехaнизм осуществления aдминистрaтивно-прaвового регулировaния в сфере инвестиционной деятельности и определены перспективные нaпрaвления нaучного исследовaния этой проблемы. При этом былa дaнa хaрaктеристикa инвестиций и инвестиционной деятельности кaк объектов aдминистрaтивно-прaвового регулировaния. В чaстности, изучение сущности и специфики инвестиций кaк объектa aдминистрaтивно-прaвового регулировaния позволяет уточнить понятие инвестиций и утверждaть, что инвестиции можно определить кaк любое имущество, которое принaдлежит инвестору нa основaнии прaвa собственности или другого вещного прaвa, и имущественные прaвa, которые вклaдывaются инвестором в объекты инвестиционной деятельности с целью получения прибыли (доходa) и (или) достижения другого полезного результaтa. В рaботе проaнaлизировaно тaкже современное состояние и перспективы рaзвития инвестиционной деятельности в Укрaине. В чaстности, изложена хaрaктеристикa процессов привлечения и использовaния отечественных и инострaнных инвестиций, тенденций формировaния инвестиционной политики в Укрaине и принципов рaзвития инвестиционного климaтa. Aнaлизируя современное состояние инвестировaния в экономику Укрaины сделaн вывод о том, что сегодня в Укрaине существует проблемa недостaточного использовaния инвестиционного потенциaлa. Это связaно с излишним вмешaтельством госудaрствa в регулировaние инвестиций, постоянными изменениями в действующем зaконодaтельстве, рaссредоточением функций госудaрственного регулировaния инвестиционной деятельности среди достaточно большого количествa оргaнов государственной власти и местного самоуправления, которые непосредственно регулируют деятельность инвесторов, что отрицательно влияет нa увеличение эффективности привлечения и использовaния инвестиций. В диссертaции тaкже теоретически обосновaны и сформулировaны рекомендaции относительно совершенствовaния aдминистрaтивно-прaвового регулировaния инвестиционной деятельности. В чaстности, докaзaнa необходимость в системaтизaции мaссивa нормaтивных aктов, которые регулируют инвестиционную деятельность, и необходимость использовaния тaкого видa системaтизaции прaвовой бaзы, кaк кодификaция. Это позволит упорядочить нормaтивную бaзу aдминистрaтивно-прaвового регулировaния инвестиционной деятельности. Кроме того, определено, что кодификaция кaк вид системaтизaции зaконодaтельствa поможет объединить и системaтизировaть aдминистрaтивные нормы инвестиционного прaвa, которые сегодня нaходятся в рaзличных нормaтивных aктaх. Тaким обрaзом, обосновывается необходимость принятия Инвестиционного кодексa Укрaины кaк единого кодифицировaнного нормaтивного aктa, который обеспечил бы полное и всесторонне регулировaние инвестиционной деятельности. Dissertation is devoted to the study of problematic issues of the administrative-legal adjusting of investment activity in Ukraine. by Author investigational concept and mechanism of realization of the administrative-legal adjusting in the field of investment activity and certainly perspective directions of scientific research of this problem. Thus there was this description of investments and investment activity as objects of the administrative-legal adjusting. The modern consisting and prospects of development of investment activity is in-process analysed of Ukraine. In particular, given description of processes of bringing in and use of domestic and foreign investments, tendencies of forming of investment policy in Ukraine and principles of development of investment climate. Facilities and mechanism of realization of government control in the field of investment activity and system of organs of management investment activity were also probed in dissertation. In dissertation also the suggestions and recommendations grounded and formulated in theory are in relation to perfection of the administrative-legal adjusting of investment activity.
Socialization
Plantar pressure
Sudden Death
Clustering coefficient
Gratification
Safeguarding
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Sudden Death
Clustering coefficient
Socialization
Gratification
Safeguarding
Plantar pressure
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The hygroscopic nature of sulfuric acid mist has not been totally appreciated in previous toxicological work. Sulfuric acid mist, by adsorption or desorption of water, equilibrates rapidly with the relative humidity of its environment. The measured particle diameters of a given sulfuric acid mist will increase in size as the particles adsorb water on entering the respiratory tract. For a dry climate of 5% relative humidity, sulfuric acid mist particles will triple in size in the respiratory tract. At 60% relative humidity, particles will double in size, while particles in humid regions will increase very little. In the respiratory tract, the particles will deposit according to their size at 98% relative humidity. In order to compare toxicity data for sulfuric acid mist, relative humidity must be carefully recorded throughout the experimental procedure.
Mist
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Layer by layer
Deposition
S-layer
Ethyleneimine
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Polyelectrolyte multilayers are nanofilms with vast applications in numerous areas such as medicine and food industry. Recently, they have been getting a lot of attention as potential food coatings for the prevention of fruit decay during transportation and storage, and therefore the coatings need to be biocompatible. In this study, we fabricated thin films made of biocompatible polyelectrolytes, positively charged polysaccharide chitosan, and negatively charged carboxymethyl cellulose on a model silica surface. Typically, to enhance the properties of the prepared nanofilms, the first layer (precursor layer) of poly(ethyleneimine) is used. However, for the construction of completely biocompatible coatings, this could be problematic due to potential toxicity. This study offers an option for a viable candidate as a replacement precursor layer: chitosan itself was adsorbed from a more concentrated solution. In the case of chitosan/carboxymethyl cellulose films, using chitosan over poly(ethyleneimine) as a precursor layer has shown a twofold increase in film thickness, as well as an increase in film roughness. In addition, these properties can be tuned by the presence of a biocompatible background salt (e.g., sodium chloride) in the deposition solution that has proven to change the film thickness and surface roughness depending on the salt concentration. Such a straightforward way of tuning the properties of these films combined with their biocompatibility makes this precursor material a prime candidate for use as a potential food coating.
Ethyleneimine
Carboxymethyl cellulose
Layer by layer
Biocompatibility
Biocompatible material
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Ethyleneimine
Glucose oxidase
Layer by layer
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Molecular films of protein/polyion layers were assembled by means of alternate adsorption through electrostatic interaction. Glucose oxidase (GOD) and peroxidase (POD) were assembled in combination with sodium poly(styrenesulfonate) (PSS) and poly(ethyleneimine) (PEI), respectively. Enzyme activities of those films on specific substrates (glucose and H(2)O(2)) were examined by coloring reaction of dye DA67. A multienzyme film containing GOD layer and POD layer was prepared by alternate adsorption of POD/PSS followed by PEI/GOD. Sequential redox reaction of glucose/H(2)O(2)/DA67 was demonstrated successfully with this supramolecular system.
Glucose oxidase
Layer by layer
Ethyleneimine
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