Temperature-induced molecular transport through polymer multilayers coated with PNIPAM microgels

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Polyelectrolyte multilayers serve as effective reservoirs for bioactive molecules which are stored and released from the multilayers for cellular applications. However, control over the release without significantly affecting the multilayers and biomolecules is still a challenge. On the other hand, externally stimulated release would make the multilayers promising for the development of stimuli-sensitive planar carriers with release performance switched on demand. In this study soft composite films are designed by coating hyaluronic acid/poly-L-lysine (HA/PLL) multilayers with temperature responsive poly( N-isopropylacrylamide) (PNIPAM) microgels. Microgels are flattened and immersed into the multilayers to maximize the number of contacts with the surrounding polyelectrolytes (HA and PLL). The microgel coating serves as an efficient switchable barrier for the PLL transport into the multilayers. PLL diffusion into the film is significantly hindered at room temperature but is dramatically enhanced at 40 degrees C above the volume phase transition temperature (VPTT) of PNIPAM at 32 degrees C associated with microgel shrinkage. Scanning force microscopy micrographs show that the mechanism of volume phase transition on soft surfaces cannot be directly deduced from the processes taking place at solid substrates

Surface modification with particles coated or made of polymer multilayers

The coating of particles or decomposable cores with polyelectrolytes via Layer-by-Layer (LbL) assembly creates free-standing LbL-coated functional particles. Due to the numerous functions that their polymers can bestow, the particles are preferentially selected for a plethora of applications, including, but not limited to coatings, cargo-carriers, drug delivery vehicles and fabric enhancements. The number of publications discussing the fabrication and usage of LbL-assembled particles has consistently increased over the last vicennial. However, past literature fails to either mention or expand upon how these LbL-assembled particles immobilize on to a solid surface. This review evaluates examples of LbL-assembled particles that have been immobilized on to solid surfaces. To aid in the formulation of a mechanism for immobilization, this review examines which forces and factors influence immobilization, and how the latter can be confirmed. The predominant forces in the immobilization of the particles studied here are the Coulombic, capillary, and adhesive forces; hydrogen bonding as well as van der Waal’s and hydrophobic interactions are also considered. These are heavily dependent on the factors that influenced immobilization, such as the particle morphology and surface charge. The shape of the LbL particle is related to the particle core, whereas the charge was dependant on the outermost polyelectrolyte in the multilayer coating. The polyelectrolytes also determine the type of bonding that a particle can form with a solid surface. These can be via either physical (non-covalent) or chemical (covalent) bonds; the latter enforcing a stronger immobilization. This review proposes a fundamental theory for immobilization pathways and can be used to support future research in the field of surface patterning and for the general modification of solid surfaces with polymer-based nano- and micro-sized polymer structures

Key indicators of innovation activity of Russia (From 2011 to 2017)

© 2019, Allied Business Academies. All rights reserved. Innovation as a priority for development Russia's economy became relevant relatively recently. Management of innovation processes federal and regional level requires knowledge of their patterns, problems and the specifics of innovation in Russia, as well as the problems and specifics of the innovation activities of enterprises in the context of economic activities. Official federal statistics contain extremely limited number of indicators characterizing innovative processes in business. The innovation sphere is currently the subject of a study of various branches of scientific knowledge and is actualized in numerous scientific publications. However, they do not have common conceptual foundations, and for the most part they have only economic content. In the literature there is no single definition of the concept of "innovation", we tried to give a single comprehensive definition of the concept of "innovation", consider different points of view, identified two main approaches to the definition of the concept of innovation. In the article we tried to analyze the basic indicators of the innovative development of the Russian Federation over the past 7 years

Key indicators of innovation activity of Russia (From 2011 to 2017)

© 2019, Allied Business Academies. All rights reserved. Innovation as a priority for development Russia's economy became relevant relatively recently. Management of innovation processes federal and regional level requires knowledge of their patterns, problems and the specifics of innovation in Russia, as well as the problems and specifics of the innovation activities of enterprises in the context of economic activities. Official federal statistics contain extremely limited number of indicators characterizing innovative processes in business. The innovation sphere is currently the subject of a study of various branches of scientific knowledge and is actualized in numerous scientific publications. However, they do not have common conceptual foundations, and for the most part they have only economic content. In the literature there is no single definition of the concept of "innovation", we tried to give a single comprehensive definition of the concept of "innovation", consider different points of view, identified two main approaches to the definition of the concept of innovation. In the article we tried to analyze the basic indicators of the innovative development of the Russian Federation over the past 7 years

Alterations in the immuno-skeletal interface drive bone destruction in HIV-1 transgenic rats

Osteoporosis and bone fractures are increasingly recognized complications of HIV-1 infection. Although antiretroviral therapy itself has complex effects on bone turnover, it is now evident that the majority of HIV-infected individuals already exhibit reduced bone mineral density before therapy. The mechanisms responsible are likely multifactorial and have been difficult to delineate in humans. The HIV-1 transgenic rat recapitulates many key features of human AIDS. We now demonstrate that, like their human counterparts, HIV-1 transgenic rats undergo severe osteoclastic bone resorption, a consequence of an imbalance in the ratio of receptor activator of NF-κB ligand, the key osteoclastogenic cytokine, to that of its physiological decoy receptor osteoprotegerin. This imbalance stemmed from a switch in production of osteoprotegerin to that of receptor activator of NF-κB ligand by B cells, and was further compounded by a significantly elevated number of osteoclast precursors. With the advancing age of individuals living with HIV/AIDS, low bone mineral density associated with HIV infection is likely to collide with the pathophysiology of skeletal aging, leading to increased fracture risk. Understanding the mechanisms driving bone loss in HIV-infected individuals will be critical to developing effective therapeutic strategies

Temperature-induced molecular transport through polymer multilayers coated with PNIPAM microgels

Polyelectrolyte multilayers serve as effective reservoirs for bioactive molecules which are stored and released from the multilayers for cellular applications. However, control over the release without significantly affecting the multilayers and biomolecules is still a challenge. On the other hand, externally stimulated release would make the multilayers promising for the development of stimuli-sensitive planar carriers with release performance switched on demand. In this study soft composite films are designed by coating hyaluronic acid/poly-l-lysine (HA/PLL) multilayers with temperature responsive poly(N-isopropylacrylamide) (PNIPAM) microgels. Microgels are flattened and immersed into the multilayers to maximize the number of contacts with the surrounding polyelectrolytes (HA and PLL). The microgel coating serves as an efficient switchable barrier for the PLL transport into the multilayers. PLL diffusion into the film is significantly hindered at room temperature but is dramatically enhanced at 40 °C above the volume phase transition temperature (VPTT) of PNIPAM at 32 °C associated with microgel shrinkage. Scanning force microscopy micrographs show that the mechanism of volume phase transition on soft surfaces cannot be directly deduced from the processes taking place at solid substrates

Temperature-induced molecular transport through polymer multilayers coated with PNIPAM microgels

Polyelectrolyte multilayers serve as effective reservoirs for bioactive molecules which are stored and released from the multilayers for cellular applications. However, control over the release without significantly affecting the multilayers and biomolecules is still a challenge. On the other hand, externally stimulated release would make the multilayers promising for the development of stimuli-sensitive planar carriers with release performance switched on demand. In this study soft composite films are designed by coating hyaluronic acid/poly-l-lysine (HA/PLL) multilayers with temperature responsive poly(N-isopropylacrylamide) (PNIPAM) microgels. Microgels are flattened and immersed into the multilayers to maximize the number of contacts with the surrounding polyelectrolytes (HA and PLL). The microgel coating serves as an efficient switchable barrier for the PLL transport into the multilayers. PLL diffusion into the film is significantly hindered at room temperature but is dramatically enhanced at 40 °C above the volume phase transition temperature (VPTT) of PNIPAM at 32 °C associated with microgel shrinkage. Scanning force microscopy micrographs show that the mechanism of volume phase transition on soft surfaces cannot be directly deduced from the processes taking place at solid substrates