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

Binding mechanism of the model charged dye carboxyfluorescein to hyaluronan/polylysine multilayers

Biopolymer-based multilayers become more and more attractive due to the vast span of biological application they can be used for, e.g., implant coatings, cell culture supports, scaffolds. Multilayers have demonstrated superior capability to store enormous amounts of small charged molecules, such as drugs, and release them in a controlled manner; however, the binding mechanism for drug loading into the multilayers is still poorly understood. Here we focus on this mechanism using model hyaluronan/polylysine (HA/PLL) multilayers and a model charged dye, carboxyfluorescein (CF). We found that CF reaches a concentration of 13 mM in the multilayers that by far exceeds its solubility in water. The high loading is not related to the aggregation of CF in the multilayers. In the multilayers, CF molecules bind to free amino groups of PLL; however, intermolecular CF–CF interactions also play a role and (i) endow the binding with a cooperative nature and (ii) result in polyadsorption of CF molecules, as proven by fitting of the adsorption isotherm using the BET model. Analysis of CF mobility in the multilayers by fluorescence recovery after photobleaching has revealed that CF diffusion in the multilayers is likely a result of both jumping of CF molecules from one amino group to another and movement, together with a PLL chain being bound to it. We believe that this study may help in the design of tailor-made multilayers that act as advanced drug delivery platfor

Carbon nanotubes transform soft gellan gum hydrogels into hybrid organic–inorganic coatings with excellent cell growth capability

Carbone nanotubes (CNTs) possess distinct properties, for example, hardness, which is very complementary to biologically relevant soft polymeric and protein materials. Combining CNTs with bio-interfaces leads to obtaining new materials with advanced properties. In this work, we have designed novel organic-inorganic hybrid coatings by combining CNTs with gellan gum (GG) hydrogels. The surface topography of the samples is investigated using scanning electron microscopy and atomic force microscopy. Mechanical properties of synthesized hybrid materials are both assessed at the macro-scale and mapped at the nanoscale. A clear correlation between the CNT concentration and the hardness of the coatings is revealed. Cell culture studies show that effective cell growth is achieved at the CNT concentration of 15 mg/mL. The presented materials can open new perspectives for hybrid bio-interfaces and can serve as a platform for advanced cell culture

Multi-fractional analysis of molecular diffusion in polymer multilayers by FRAP: a new simulation-based approach

Comprehensive analysis of the multifractional molecular diffusion provides a deeper understanding of the diffusion phenomenon in the fields of material science, molecular and cell biology, advanced biomaterials, etc. Fluorescence recovery after photobleaching (FRAP) is commonly employed to probe the molecular diffusion. Despite FRAP being a very popular method, it is not easy to assess multifractional molecular diffusion due to limited possibilities of approaches for analysis. Here we present a novel simulation-optimization-based approach (S-approach) that significantly broadens possibilities of the analysis. In the S-approach, possible fluorescence recovery scenarios are primarily simulated and afterward compared with a real measurement while optimizing parameters of a model until a sufficient match is achieved. This makes it possible to reveal multifractional molecular diffusion. Fluorescent latex particles of different size and fluorescein isothiocyanate in an aqueous medium were utilized as test systems. Finally, the S-approach has been used to evaluate diffusion of cytochrome c loaded into multilayers made of hyaluronan and polylysine. Software for evaluation of multifractional molecular diffusion by S-approach has been developed aiming to offer maximal versatility and user-friendly way for analysis

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

Mobility of lysozyme in poly(L-lysine)/hyaluronic acid multilayer films

The spatial and temporal control over presentation of protein-based biomolecules such as growth factors and hormones is crucial for in vitro applications to mimic the complex in vivo environment. We investigated the interaction of a model protein lysozyme (Lys) with poly(L-lysine)/hyaluronic acid (PLL/HA) multilayer films. We focused on Lys diffusion as well as adsorption and retention within the film as a function of the film deposition conditions and post-treatment. Additionally, an effect of Lys concentration on its mobility was probed. A combination of confocal fluorescence microscopy, fluorescence recovery after photobleaching, and microfluidics was employed for this investigation. Our main finding is that adsorption of PLL and HA after protein loading induces acceleration and reduction of Lys mobility, respectively. These results suggest that a charge balance in the film to a high extent governs the protein–film interaction. We believe that control over protein mobility is a key to reach the full potential of the PLL/HA films as reservoirs for biomolecules depending on the application demand

Self-Assembly of Polymers

Nowadays, polymer self-assembly has become extremely attractive for both biological (drug delivery, tissue engineering, scaffolds) and non-biological (packaging, semiconductors) applications. In nature, a number of key biological processes are driven by polymer self-assembly, for instance protein folding. Impressive morphologies can be assembled from polymers thanks to a diverse range of interactions involved, e.g., electrostatics, hydrophobic, hots-guest interactions, etc. Both 2D and 3D tailor-made assemblies can be designed through modern powerful techniques and approaches such as the layer-by-layer and the Langmuir-Blodgett deposition, hard and soft templating. This Special Issue highlights contributions (research papers, short communications, review articles) that focus on recent developments in polymer self-assembly for both fundamental understanding the assembly phenomenon and real applications

Bioapplications of light-sensitive polymer films and capsules assembled using the layer-by-layer technique

This review covers the area of bioapplications of layer-by-layer assembled polymer planar films and microcapsules-biologically relevant responses stimulated by light. We present recent progress in light-stimulated release of bioactive molecules from the assembled structures. Functionalization of the films with metal nanoparticles and bioactive molecules that provide the films with light sensitivity and reservoir properties is also described. The use of these films in the delivery of bioactive molecules is closely related to light-induced cargo release from capsules; this promising method of intracellular delivery is also addressed

Encapsulation of Low-Molecular-Weight Drugs into Polymer Multilayer Capsules Templated on Vaterite CaCO3 Crystals

Polyelectrolyte multilayer capsules (PEMCs) templated onto biocompatible and easily degradable vaterite CaCO3 crystals via the layer-by-layer (LbL) polymer deposition process have served as multifunctional and tailor-made vehicles for advanced drug delivery. Since the last two decades, the PEMCs were utilized for effective encapsulation and controlled release of bioactive macromolecules (proteins, nucleic acids, etc.). However, their capacity to host low-molecular-weight (LMW) drugs (<1–2 kDa) has been demonstrated rather recently due to a limited retention ability of multilayers to small molecules. The safe and controlled delivery of LMW drugs plays a vital role for the treatment of cancers and other diseases, and, due to their tunable and inherent properties, PEMCs have shown to be good candidates for smart drug delivery. Herein, we summarize recent progress on the encapsulation of LMW drugs into PEMCs templated onto vaterite CaCO3 crystals. The drug loading and release mechanisms, advantages and limitations of the PEMCs as LMW drug carriers, as well as bio-applications of drug-laden capsules are discussed based upon the recent literature findings

Microfluidics meets layer-by-layer assembly for the build-up of polymeric scaffolds

The Layer-by-Layer (LbL) assembly of polymers and microfluidics belong to a category of the most useful and promising techniques emerged within the last three-to-four decades. Despite the high promise to combine LbL deposition with microfluidic techniques for the formulation of polymeric scaffolds, this combination is limited thus far, and is only presented by few literature reports only. This combination holds the ability to aid in assembling advanced scaffolds with programmable and highly controlled properties. Here we highlight the advantages and disadvantages for both LbL assembly onto 2D and 3D substrates, and of microfluidic techniques observed in the literature thus far. Firstly, LbL assembly is presented, focusing upon its basic principles, hard-templating and multilayer capsule formation, followed by deposition technical aspects. The basics of microfluidics is described in view of the formulation of polymer structures, whereby examples of microfluidic-assisted scaffold fabrication via LbL assembly are provided. This review seeks to provide the reader with a critical view on the application of microfluidic techniques, in combination with LbL assembly for the production of polymer scaffolds