The mechanism of catalase loading into porous vaterite CaCO3 crystals by co-synthesis

Porous vaterite CaCO3 crystals are nowadays extensively used as high-capacity bio-friendly sacrificial templates for the fabrication of such protein-containing nano- and micro-particles as capsules and beads. The first step in the protein encapsulation is performed through loading of the protein molecules into the crystals. Co-synthesis is one of the most useful and simple methods proven to effectively load crystals with proteins; however, the loading mechanism is still unknown. To understand the mechanism, in this study, we focus on the loading of a model protein catalase into the crystals by means of adsorption into pre-formed crystals (ADS) and co-synthesis (COS). Analysis of the physico-chemical characteristics of the protein in solution and during the loading and simulation of the protein packing into the crystals are performed. COS provides more effective loading than ADS giving protein contents in the crystals of 20.3 and 3.5 w/w%, respectively. Extremely high loading for COS providing a local protein concentration of about 550 mg mL−1 is explained by intermolecular protein interactions, i.e. formation of protein aggregates induced by CaCl2 during the co-synthesis. This is supported by a lower equilibrium constant obtained for COS (5 × 105 M−1) than for ADS (23 × 105 M−1), indicating a higher affinity of single protein molecules rather than aggregates to the crystal surface. Fitting the adsorption isotherms by classical adsorption models has shown that the Langmuir and BET models describe the adsorption phenomenon better than the Freundlich model, proving the aggregation in solution followed by adsorption of the aggregates into the crystals. We believe that this study will be useful for protein encapsulation through CaCO3 crystals using the COS method

Biodegradation-resistant multilayers coated with gold nanoparticles. Toward a tailor-made artificial extracellular matrix

Polymer multicomponent coatings such as multilayers mimic extracellular matrix (ECM) that attracts significant attention for their use as functional supports for advanced cell culture and tissue engineering. Herein, biodegradation and molecular transport in hyaluronan/polylysine multilayers coated with gold nanoparticles was described. Nanoparticle coating acts as semipermeable barrier that governs molecular transport into/from the multilayers and makes them biodegradation resistant. Model protein lysozyme (mimics of ECM soluble signals) diffuses in the multilayers as fast and slow diffusing populations existing in an equilibrium. Such composite system may have high potential to be exploited as degradation-resistant drug delivery platforms suitable for cell-based applications. The extracellular matrix (ECM) provides not only a structural support for cell-based applications

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

Temperature effect on the build-up of exponentially growing polyelectrolyte multilayers. An exponential-to-linear transition point

In this study, the effect of temperature on the build-up of exponentially growing polyelectrolyte multilayer films was investigated. It aims at understanding the multilayer growth mechanism as crucially important for the fabrication of tailor-made multilayer films. Model poly(L-lysine)/hyaluronic acid (PLL/HA) multilayers were assembled in the temperature range of 25–85 1C by layer-by-layer deposition using a dipping method. The film growth switches from the exponential to the linear regime at the transition point as a result of limited polymer diffusion into the film. With the increase of the build-up temperature the film growth rate is enhanced in both regimes; the position of the transition point shifts to a higher number of deposition steps confirming the diffusion-mediated growth mechanism. Not only the faster polymer diffusion into the film but also more porous/permeable film structure are responsible for faster film growth at higher preparation temperature. The latter mechanism is assumed from analysis of the film growth rate upon switching of the preparation temperature during the film growth. Interestingly, the as-prepared films are equilibrated and remain intact (no swelling or shrinking) during temperature variation in the range of 25–45 1C. The average activation energy for complexation between PLL and HA in the multilayers calculated from the Arrhenius plot has been found to be about 0.3 kJ mol 1 for monomers of PLL. Finally, the following processes known to be dependent on temperature are discussed with respect to the multilayer growth: (i) polymer diffusion, (ii) polymer conformational changes, and (iii) inter-polymer interactions

Biopolymer-based multilayer capsules and beads made via templating : advantages, hurdles and perspectives

One of the undeniable trends in modern bioengineering and nanotechnology is the use of various biomolecules, primarily of a polymeric nature, for the design and formulation of novel functional materials for controlled and targeted drug delivery, bioimaging and theranostics, tissue engineering, and other bioapplications. Biocompatibility, biodegradability, the possibility of replicating natural cellular microenvironments, and the minimal toxicity typical of biogenic polymers are features that have secured a growing interest in them as the building blocks for biomaterials of the fourth generation. Many recent studies showed the promise of the hard-templating approach for the fabrication of nano- and microparticles utilizing biopolymers. This review covers these studies, bringing together up-to-date knowledge on biopolymer-based multilayer capsules and beads, critically assessing the progress made in this field of research, and outlining the current challenges and perspectives of these architectures. According to the classification of the templates, the review sequentially considers biopolymer structures templated on non-porous particles, porous particles, and crystal drugs. Opportunities for the functionalization of biopolymer-based capsules to tailor them toward specific bioapplications is highlighted in a separate section

Hybrids of polymer multilayers, lipids, and nanoparticles: mimicking the cellular microenvironment

Here we address research directions and trends developed following novel concepts in 2D/3D self-assembled polymer structures established in the department led by Helmuth Möhwald. These functional structures made of hybrids of polymer multilayers, lipids, and nanoparticles stimulated research in the design of the cellular microenvironment. The composition of the extracellular matrix (ECM) and dynamics of biofactor presentation in the ECM can be recapitulated by the hybrids. Proteins serve as models for protein-based biofactors such as growth factors, cytokines, hormones, and so forth. A fundamental understanding of complex intermolecular interactions and approaches developed for the externally IR-light-triggered release offers a powerful tool for controlling the biofactor presentation. Pure protein beads made via a mild templating on vaterite CaCO3 crystals can mimic cellular organelles in terms of the compartmentalization of active proteins. We believe that an integration of the approaches developed and described here offers a strong tool for engineering and mimicking both extra- and intracellular microenvironments

A “cell-friendly” window for the interaction of cells with hyaluronic acid/poly-L-lysine multilayers

Polyelectrolyte multilayers assembled from hyaluronic acid (HA) and poly-L-lysine (PLL) are most widely studied showing excellent reservoir characteristics to host molecules of diverse nature; however, thick (HA/PLL)n films were often found cell-repellent. By a systematic study of the adhesion and proliferation of various cells as a function of bilayer number ‘n’ a correlation with the mechanical and chemical properties of films is developed. The following cell lines have been studied: mouse 3T3 and L929 fibroblasts, human foreskin primary fibroblasts VH-Fib, human embryonic kidney HEK-293, human bone cell line U-2-OS, Chinese hamster ovary CHO-K and mouse embryonic stem cells. All cells adhere and spread well in a narrow ‘cell-friendly’ window, identified in the range of n=12-15. At n15, the film is cell-repellent for all cell lines. Cellular adhesion correlates with the mechanical properties of the films showing that softer films at higher ‘n’ number exhibiting a significant decrease of the Young’s modulus below 100 kPa are weakly adherent to cells. This trend cannot be reversed even by coating a strong cell-adhesive protein fibronectin onto the film. This indicates that mechanical cues plays a major role for cell behaviour, also in respect to biochemical ones

A sense of place. Narratives of memory and identity as told through image and place

Drawing upon participatory artistic practices and using the capacity of documentary photography and moving image both to construct and unsettle official discourses, I advance through my practice a collective exploration of memory and identity as embedded in designated places, and in turn make visible the memories of place. I am looking particularly at the identity of place in the post-Soviet context to explore notions of belonging, identity and migration. The research is structured around two case studies, which provide an in-depth analysis of two different methodological approaches to the study of a place, each situated in specified locations. The first case study, Out of Place, examines the phenomenon of national identity as found within Baltic Russian emigrants now living in the UK. Focusing on a network of Russian-speaking emigrants from Latvia, I establish an audio-visual archive of the objects and memorabilia brought with the emigrants as they move from Latvia to the UK. Ten participants were invited to contribute to the project by telling a story about the object of their own selection. The case study aims to look at how the identity with a place can be constructed through people’s experience, and how place manifests itself through the objects and artefacts. The second case study, The Landscapes of Nizny Novgorod produced in collaboration with sociologist Olga Chernyavskaya, emerged out of the question of how identity of/with place can be constructed through representation of landscape. The case study is aimed at exploring the identity of Nizhny Novgorod (Russia), through tracing the distinctive features of its eight districts. Eight walks were organised, each one dedicated to a particular district. These walks were organised as field studies, though they carried elements of the Situationists’ dérives, they were designed to document the city and gather ‘the field data’, but also create a situation where new and unintended encounters could take place. The contribution this MPhil seeks to make is situated in both methodological and artistic fields, in a reconsideration of the underlying principles and artistic practices in representing and constructing the identity of/with a place. The use of oral history as a method in the Out of Place case study allowed me to create an identity of a place based on plurality and multiplicity. In the Landscapes of Nizhny Novgorod the identity of a place was constructed through the means of photography, by giving voice to those parts of the city that are usually considered to be too banal or not interesting enough to be photographed

Naturally derived nano- and micro-drug delivery vehicles: halloysite, vaterite and nanocellulose

Recent advances in drug delivery and controlled release had a great impact on bioscience, medicine and tissue engineering. Consequently, a variety of advanced drug delivery vehicles either have already reached the market or are approaching the phase of commercial production. Progressive growth of the drug delivery market has led to the necessity to earnestly concern about economically viable, up-scalable and sustainable technologies for a large-scale production of drug delivery carriers. We have identified three attractive natural sources of drug carriers: aluminosilicate clays, minerals of calcium carbonate, and cellulose. Three classes of drug delivery carriers derived from these natural materials are halloysite nanotubes, vaterite crystals and nanocellulose. These carriers can be produced using “green” technologies from some of the most abundant sources on the Earth and have extremely high potential to meet all criteria applied for the manufacture of modern delivery carriers. We provide an up-to-date snapshot of these drug delivery vehicles towards their use for bioapplications, in particular for drug delivery and tissue engineering. The following research topics are addressed: (i) the availability, sources and methodologies used for production of these drug delivery vehicles, (ii) the drug loading and release mechanisms of these delivery vehicles, (iii) in vitro, in vivo, and clinical studies on these vehicles, and (iv) employment of these vehicles for tissue engineering. Finally, the prospects for vehicles’ further development and industrialisation are critically assessed, highlighting most attractive future research directions such as the design of third generation active biomaterials