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Highlights: [•] We examine the morphological changes of liposomes exposed to the serum environment. [•] Bare liposomes are disintegrated by serum as a result of high osmotic shock. [•] Polymer coating prevents the destruction of liposome vehicles by serum. [•] Polymer structure is crucial to the interactions of coated liposomes with serum. [•] Lipid membranes become more fluid after the addition of serum. [ABSTRACT FROM AUTHOR]

• The biological in vitro studies of silicone-stabilized liposomes are presented. • Biocompatibility of developed stabilized liposomes was demonstrated. • AFM investigation revealed better elastomechanical features of resulted liposomes. • Silicone layer brought substantial increase in elastic modulus of obtained liposomes. • Developed silicone-stabilized liposomes are promising candidates for drug nanocariers. The liposomes are among the most promising types of drug delivery systems but low stability significantly limits their application. Some approaches proposed to overcome this drawback may affect the liposomes toxicity profile. It is assumed that developed by us and presented here stabilization method involving formation of silicone network within the liposomal bilayer will improve elastomechanical properties of vesicles while not deteriorating their biocompatibility. The silicone-stabilized liposomes were prepared by base-catalyzed polycondensation process of the 1,3,5,7-tetramethylcyclotetrasiloxane (D 4 H) within the liposomal bilayer. The systematic biological in vitro studies of vesicles obtained were carried out. Moreover, the elastomechanical features investigation employing atomic force microscopy (AFM) measurements was performed. These properties of the liposome membrane are of great importance since they define the nanocarriers' stability as well as play a significant role in their cellular uptake via endocytosis. Applying the Derjaguin–Muller–Toporov (DMT) model, the elastic modulus of the silicone-stabilized liposomes was determined and compared to that characteristic for the pristine liposomes. The in vitro biological evaluation of silicone-stabilized liposomes demonstrated that these vesicles are not toxic for blood cells isolated from healthy donors and they do not induce oxidative stress in HepG2 cells. AFM results confirmed the stabilizing effect of silicone and revealed that the silicone network improves the elastomechanical properties of the resulted liposomes. This is the first report demonstrating that the silicone-stabilized liposomes retain biocompatibility of pristine liposomes' while acquire significantly better elastomechanical features. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Alkaline phosphatase was successfully incorporated into the halloysite nanoclay. • The halloysite-bound enzyme exhibits increased thermal stability. • The activity of the encapsulated enzyme was pH-independent in a wide range of pH (3–10). • Alkaline phosphatase-halloysite nanocomposite effectively promoted biomineralization. • The proposed nanocomposite may constitute an attractive biocomponent of bone scaffolds. Abstract Alkaline phosphatase (ALP) was sucessfully incorporated into the halloysite (HAL) nanotubes, as confirmed by FTIR-ATR and XRD analyses. The loading efficiency (LE) of ALP was found to be 13.5%, while its encapsulation efficiency (EE) was estimated to be around 27%, as determined using the Bradford test. The influence of the immobilization in HAL on the enzyme activity was measured using standard ALP activity assay. Immobilized ALP effectively induced the bomineralization process, as showed by SEM, EDS, and XRD studies. As a result, calcium phosphate was produced in the form of hydroxyapatite cauliflower-like structures, with a slight content of calcium hydroxide. Interestingly, the encapsulation of ALP guest molecules in the HAL nanotubes considerably increased its thermal stability, most probably due to the heat sink effect. The activity of HAL-bound ALP was also found to be pH-independent in the wide range of pH values (3–10) due to the amphoteric nature of the aluminum oxide lining the HAL nanotube internal surface. Due to an increased resistance to the unfavorable conditions, which are often encountered during scaffold preparation or sterilization, ALP-HAL nanocomposite material may constitute an attractive bioactive component of the scaffolds for bone regeneration. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Biopolymeric chemically crosslinked hydrogels were obtained and characterized. • Hydrogels’ properties can be tuned by changing hyaluronic acid and genipin content. • The in vitro cell culture study show that the hydrogels’ surfaces are biocompatible. • Obtained hydrogels can serve as a novel promising biomimetic injectable scaffolds. Abstract Studies on synthesis, physico-chemical and biological properties of novel biomimetic materials, potentially useful as injectable hydrogels are presented. These materials are in situ prepared chemically crosslinked collagen/chitosan/hyaluronic acid-based hydrogels exhibiting potential for tissue regeneration. Optimization of hydrogels involved testing the effect of various concentration of crosslinking agent (genipin) as well as different ratios of biopolymers used on their properties. The changes in the content of hyaluronic acid and in the genipin concentration used have been shown to be crucial. Employing the highest concentration of crosslinking agent studied (20 mM) the hydrogels of compact structure, characterized by good mechanical properties and prolonged degradation profile can be obtained. Changing the HA content in sol mixture the hydrogel of various wettability; more or less hydrophilic when compared to pure collagen/chitosan hydrogels can be fabricated. The in vitro cell culture study has shown that the surface of the prepared materials ensures suitable biocompatibility. These hydrogels can support the proliferation and adhesion of MG-63 cell line as it was demonstrated using Alamar Blue assay and SEM observations. It is believed that the collagen/chitosan/hyaluronic acid hydrogels crosslinked with genipin are particularly promising materials for bone regeneration procedures, especially attractive for regeneration of small bone losses. This is the first paper in the litearature presenting results of studies on that type of biopolymeric injectable hydrogels chemically crosslinked with genipin. [ABSTRACT FROM AUTHOR]

Syntheses and characterizations of biocompatible superparamagnetic iron oxide nanoparticles with embedded curcumin and coated with ultrathin layer of hyaluronic acid-curcumin (HA-Cur) conjugate have been reported. Zeta potential measurements confirmed effective coating of native iron oxide nanoparticles stabilized by cationic derivative of chitosan (SPION-CCh) with the synthesized HA-Cur conjugate. Both SPIONs with embedded curcumin and the ones coated with HA-Cur (SPION-CCh/HA-Cur) revealed desired magnetic characteristics while fluorescent properties were much better for the coated nanoparticles. SPION-CCh/HA-Cur nanoparticles were shown to be very promising candidates for T 2 MRI contrast agents as they can easily penetrate cell membrane and their relaxivity is exceptionally high (ca. 470 mM −1 s −1 ). They may be also tracked using confocal fluorescence microscopy due to the presence of fluorescent curcumin in the coating. In vitro studies indicated that the obtained SPIONs-CCh/HA-Cur were non-toxic for EA.hy926 endothelial cells. [ABSTRACT FROM AUTHOR]

The present work aims at development of novel hybrid materials from genipin crosslinked collagen or collagen/chitosan hydrogels containing various types of TiO 2 nanoparticles characterized with different anatase/rutile ratios. Collagen and chitosan were selected as hydrogel components since they are biopolymers being, like collagen, the major compound present in extracellular matrix or exhibit structural similarity to glycosaminoglycans, like chitosan. TiO 2 nanoparticles were introduced to the hydrogel matrices to improve their mechanical properties as well as bioactivity. A series of twelve novel hybrid materials were prepared and their physicochemical, mechanical and biological properties were evaluated. It was found that TiO 2 nanostructures introduced to the hydrogels have significant influence on the swelling properties of the synthesized hybrids and their impact is strongly dependent on the type of matrices. The surfaces of hybrid materials were found to be more hydrophilic than these of corresponding hydrogel matrix. It was also observed that, the storage modulus values of the hybrids based on collagen-chitosan hydrogel are comparable to these for plain hydrogels what indicates that the mechanical properties of the materials obtained are satisfactory for possible biomedical application. The in vitro cell culture studies have shown that prepared materials are biocompatible as they can support mitochondrial activity of MEFs as well as MG-63 cells. In vitro experiments performed under simulated body fluid (SBF) conditions have revealed that all studied TiO 2 nanoparticles present in hydrogel matrices, regardless of anatase/rutile ratio, successfully induced formation of apatite-like structures. The hybrid materials developed here are promising candidates for preparation of bioactive, injectable scaffolds for tissue engineering. [ABSTRACT FROM AUTHOR]

Development of silicone stabilized liposomes which can serve as novel drug nanocarriers is presented. Silicone precursor 1,3,5,7-tetramethylcyclotetrasiloxane (D 4 H ) was introduced into the bilayer of the cationic liposomes prepared from egg yolk phosphatidylocholine (PC) and double-tailed dimethyldioctadecylammonium bromide (DODAB). The silicone material was created inside of the liposomal bilayer in the base-catalyzed polycondensation process of the D 4 H what was confirmed employing 29 Si solid-state MAS NMR and FTIR measurements. Surfactant lysis experiments revealed that resulted systems can be effectively stabilized. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements demonstrated that the silicone-stabilized liposomes have typical lipid vesicle’s morphology and mean hydrodynamic diameters in the range of about 110 nm. They have considerably lower tendency for aggregation than the pristine liposomes. The permeability of vesicles can be tuned by introducing various amounts of silicone precursor into the liposome bilayer, as confirmed in calcein-release studies. The effect of fetal bovine serum (FBS) on the stability of liposomes was also tested in in vitro studies. Biological studies revealed that resulted liposomes can be considered as possible drug nanocarriers because they are not toxic to human skin fibroblasts (HSFs) and mouse embryonic fibroblasts (MEFs). [ABSTRACT FROM AUTHOR]

Ultrathin “one-component” multilayer polymeric films for potential biomedical applications were designed based on polyvinyl alcohol,—a non-toxic, fully degradable synthetic polymer. Good uniformity of the obtained film and adequate adsorption properties of the polymeric layers were achieved by functional modification of the polymer, which involved synthesis of cationic and anionic derivatives. Synthesized polymers were characterized by FTIR, NMR spectroscopy, dynamic light scattering measurements and elemental analysis. The layer by layer assembly technique was used to build up a multilayer film and this process was followed using UV–Vis spectroscopy and ellipsometry. The morphology and thickness of the obtained multilayered film material was evaluated by atomic force microscopy (AFM). Preliminary studies on the application of the obtained multilayer film for coating of liposomal nanocarriers containing phenytoin, an antiarrhythmic drug, were performed. The coating effectively stabilizes liposomes and the effect increases with an increasing number of deposited layers until the polymeric film reaches the optimal thickness. The obtained release profiles suggest that bilayer-coated liposomes release phenytoin less rapidly than uncoated ones. The cytotoxicity studies performed for all obtained nanocarriers confirmed that none of them has negative effect on cell viability. All of the performed experiments suggest that liposomes coated with ultrathin film obtained from PVA derivatives can be attractive drug nanocarriers. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cationic, hydrophobic and cationic–hydrophobic derivatives of chitosan were obtained and characterized. [•] Curcumin-containing liposomes were successfully stabilized by effective coating with these derivatives. [•] Liposomes coated with cationic–hydrophobic chitosan are most promising for curcumin delivery. [•] Such coated liposomes easily penetrate cell membrane and release curcumin in a controlled manner. [•] These curcumin-loaded liposomal systems are non-toxic for normal cells, but toxic for murine melanoma. [Copyright &y& Elsevier]

Abstract: Curcumin shows huge potential as an anticancer and anti-inflammatory agent. However, to achieve a satisfactory bioavailability and stability of this compound, its liposomal form is preferable. Our detailed studies on the curcumin interaction with lipid membranes are aimed to obtain better understanding of the mechanism and eventually to improve the efficiency of curcumin delivery to cells. Egg yolk phosphatidylcholine (EYPC) one-component monolayers and bilayers, as well as mixed systems containing additionally dihexadecyl phosphate (DHP) and cholesterol, were studied. Curcumin binding constant to EYPC liposomes was determined based on two different methods: UV/Vis absorption and fluorescence measurements to be 4.26×104 M−1 and 3.79×104 M−1, respectively. The fluorescence quenching experiment revealed that curcumin locates in the hydrophobic region of EYPC liposomal bilayer. It was shown that curcumin impacts the size and stability of the liposomal carriers significantly. Loaded into the EYPC/DPH/cholesterol liposomal bilayer curcumin stabilizes the system proportionally to its content, while the EYPC/DPH system is destabilized upon drug loading. The three-component lipid composition of the liposome seems to be the most promising system for curcumin delivery. An interaction of free and liposomal curcumin with EYPC and mixed monolayers was also studied using Langmuir balance measurements. Monolayer systems were treated as a simple model of cell membrane. Condensing effect of curcumin on EYPC and EYPC/DHP monolayers and loosening influence on EYPC/DHP/chol ones were observed. It was also demonstrated that curcumin-loaded EYPC liposomes are more stable upon interaction with the model lipid membrane than the unloaded ones. [Copyright &y& Elsevier]

Abstract: A system of poly(ethylene glycol) bound tetraarylporphyrin entrapped in liposomal membranes was investigated. The interactions between the 5-(4-hydroxymethylphenyl)-10,15,20-tritolylporphyrin (Po) covalently attached to the poly(ethylene glycol) chain (PEG-Po), and phosphatidylcholine liposomes in the aqueous solution were studied. The adsorption of the investigated polymer to lipid vesicles was confirmed by measurements of dynamic light scattering and zeta potential. Experimental results demonstrate that the diameter of liposomes increased and the absolute value of the zeta potential decreased after addition of PEG-Po. The binding constants (K b) of Po chromophores to liposome in pH range from 5.2 to 9.0 were determined using fluorescence spectroscopy. The degree of binding was found to be pH-independent and the average value was 24.6±0.9mgml−1. The acid–base properties of the porphyrin chromophores and their aggregation in an aqueous solution were also studied. pK values associated with imine-N protonation of the porphyrin core were found to be 2.59 and 0.68 at the ionic strength of 0.1M. The equilibrium constant for dimerization, K D, was found to be 5×103 M−1. [Copyright &y& Elsevier]