Influence of the Type of Biocompatible Polymer in the Shell of Magnetite Nanoparticles on Their Interaction with DPPC in Two-Component Langmuir Monolayers.

Magnetite nanoparticles (MNPs) are attractive nanomaterials for applications in magnetic resonance imaging, targeted drug delivery, and anticancer therapy due to their unique properties such as nontoxicity, wide chemical affinity, and intrinsic superparamagnetism. Their functionalization with polymers such as chitosan or poly(vinyl alcohol) (PVA) can not only improve their biocompatibility and biodegradability but it also plays an important role in their interactions with biological cells. In this work, the effect of the functionalization of MNPs with chitosan, PVA, and their blend on model cell membranes formed from 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) using a Langmuir technique was studied. The studies performed showed that the type of biocompatible polymer in the MNP shell plays a crucial role in the effectiveness of its adsorption process into the model cell membrane. Modification of MNPs with chitosan facilitates significantly more effective adsorption than coating them with PVA or with a chitosan and PVA blend. The presence of all the investigated MNPs in the DPPC monolayer at low concentrations does not affect its thermodynamic state, fluidity, or morphology, which is promising in terms of their biocompatibility. On the other hand, their high concentration (molar fraction above ≈0.05) exerts a disruptive effect on the model cell membrane and results in their aggregation, leading probably to the loss of their superparamagnetic properties essential for nanomedicine.

Probing of Interactions of Magnetite Nanoparticles Coated with Native and Aminated Starch with a DPPC Model Membrane.

Understanding the mechanism of interactions between magnetite nanoparticles and phospholipids that form cellular membranes at the molecular level is of crucial importance for their safe and effective application in medicine (e.g. magnetic resonance imaging, targeted drug delivery, and hyperthermia-based anticancer therapy). In these interactions, their surface coating plays a crucial role because even a small modification to its structure can cause significant changes to the behaviour of the magnetite nanoparticles that come in contact with a biomembrane. In this work, the influence of the magnetite nanoparticles functionalized with native and aminated starch on the thermodynamics, morphology, and dilatational elasticity of the model cell membranes was studied. The model cell membranes constituted the Langmuir monolayers formed at the air-water interface of dipalmitoylphosphatidylcholine (DPPC). The surface of the aminated starch-coated nanoparticles was enriched in highly reactive amino groups, which allowed more effective binding of drugs and biomolecules suitable for specific nano-bio applications. The studies indicated that the presence of these groups also reduced to some extent the disruptive effect of the magnetite nanoparticles on the model membranes and improved their adsorption.

Effect of Aminated Chitosan-Coated Fe3O4 Nanoparticles with Applicational Potential in Nanomedicine on DPPG, DSPC, and POPC Langmuir Monolayers as Cell Membrane Models.

An adsorption process of magnetite nanoparticles functionalized with aminated chitosan (Fe3O4-AChit) showing application potential in nanomedicine into cell membrane models was studied. The cell membrane models were formed using a Langmuir technique from three selected phospholipids with different polar head-groups as well as length and carbon saturation of alkyl chains. The research presented in this work reveals the existence of membrane model composition-dependent regulation of phospholipid-nanoparticle interactions. The influence of the positively charged Fe3O4-AChit nanoparticles on a Langmuir film stability, phase state, and textures is much greater in the case of these formed by negatively charged 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DPPG) than those created by zwitterionic 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC). The adsorption kinetics recorded during penetration experiments show that this effect is caused by the strongest adsorption of the investigated nanoparticles into the DPPG monolayer driven very likely by the electrostatic attraction. The differences in the adsorption strength of the Fe3O4-AChit nanoparticles into the Langmuir films formed by the phosphatidylcholines were also observed. The nanoparticles adsorbed more easily into more loosely packed POPC monolayer.

A detailed investigation on interactions between magnetite nanoparticles functionalized with aminated chitosan and a cell model membrane.

Magnetite nanoparticles are promising materials for application in magnetic resonance imaging, targeted drug delivery, enzyme immobilization and cancer therapies based on hyperthermia thanks to their biocompatibility, wide chemical affinity and superparamagnetic properties. However, there is still the lack of the knowledge of interactions between magnetite nanoparticles covered with the bioactive polymers and biological cells. In order to fulfil this gap, we have investigated interactions of newly synthetized magnetite nanoparticles functionalized with aminated chitosan (Fe3O4-aminated chitosan) and a model biological membrane made of dipalmitoylphosphatidylcholine (DPPC) using a Langmuir technique. Surface pressure-mean area per DPPC molecule isotherms and Brewster angle microscope images (BAM) recorded during compression of the two-component Fe3O4-aminated chitosan:DPPC films revealed the strong influence of the Fe3O4-aminated chitosan nanoparticles on the stability, phase state and structure of the phospholipid membrane. The studies on the adsorption/incorporation process of the Fe3O4-aminated chitosan nanoparticles showed that they can adsorb/incorporate into the DPPC model membrane at the surface pressure corresponding to this present in the cellular membrane under the biological conditions (35 mN·m-1). The number of the adsorbed/incorporated Fe3O4-aminated chitosan nanoparticles can be regulated by the nanoparticles concentration in the neighbourhood of the DPPC model membrane even at high surface pressure of 35 mN·m-1.

Influence of chlorine atoms in bay positions of perylene-tetracarboxylic acids on their spectral properties in Langmuir-Blodgett films.

The influence of chlorine atoms in the bay positions of the perylene-3,4,9,10-tetracarboxylic acids with the different alkyl chains length on their spectral properties in monomolecular films has been studied. The chlorinated (PCln) and for comparison non-chlorinated (Pn) perylene derivatives were deposited onto quartz plates using a Langmuir-Blodgett (LB) technique. The absorption spectra showed that the PCln and Pn dyes form in monolayers the I- and J-type aggregates, respectively. In turn, their steady-state and time-resolved emission spectra revealed presence of two emitter types, which we assigned to monomers and excimers. The luminescence lifetimes of the PCln monomers and excimers determined with a time-correlated single photon counting method (TCSPC) are significantly shorter than these obtained for the same emitter types in the Pn monolayers. In the case of the chlorinated dyes, the contribution of the monomer emission dominates over the excimer emission and is almost independent from the alkyl chain length. By contrast, the share of the Pn monomer emission increases strongly with a number of carbon atoms in their hydrocarbon chains. The luminescence quantum yields (LQY) of the Pn and PCln monolayers measured in an integrating sphere are in the range of 0.06-0.11. The presented results reveal that the PCln dyes exhibit lower tendency for aggregation than the non-chlorinated derivatives. It can be explained by limited intermolecular interaction between neighbouring PCln molecules caused by deformation of the perylene core as a result of strongly electronegative chlorine atoms in the bay positions of these dyes. Moreover, the strong influence of the alkyl chain length on the Pn aggregation contrary to the case of the PCln derivatives was observed.

Photo-switching of a non-ionic azobenzene amphiphile in Langmuir and Langmuir-Blodgett films.

The concept of programmable and reconfigurable soft matter has emerged in science in the last few decades and can be realized by photoisomerization of azobenzene derivatives. This possibility results in great application potential of these compounds in optical storage devices, molecular junctions of electronic devices, command layers of liquid crystal displays or holographic gratings. In this paper, we present the results of a study on the organization and isomerization of the non-ionic and amphiphilic methyl 4-[(E)-2-[4-(nonyloxy)phenyl]diazen-1-yl]benzoate (LCA) in a 2D layer architecture of Langmuir and Langmuir-Blodgett (LB) films supported by spectroscopic studies on LCA chloroform solutions. Our investigation has shown a significantly different molecular organization of LCA depending on the ratio of trans and cis isomers in the monolayers. Taking advantage of a relatively low packing density and aggregation strength in the cis-LCA monolayer, we demonstrated the reversible isomerization in the LB film initially formed of LCA molecules in the cis form, while in the trans-LCA monolayer this effect was not observed. Our approach allows the formation of a switchable monolayer made of the amphiphilic LCA showing liquid crystalline properties without introducing an ionic group into the molecule structure, mixing with another compound or changing the subphase pH to provide free space for the molecules' isomerization.

Morphology and molecular arrangement of perylene-3,4,9,10-(n-pentylester) in thin layers obtained by zone-casting.

Liquid-crystalline perylene-3,4,9,10-tetra-(n-pentylester) zone-casted on hydrophilic glass substrates forms characteristic belt-like structures which are observed under optical microscope and atomic force microscope. Polarised Raman scattering spectra reveal the presence of anisotropic alignment of the molecules inside the obtained structures. Moreover, the absorption and fluorescence spectra confirm molecular aggregation in the belt-like structures. The research shows, that the belt-like structures are created by columns of molecules with the edge-on alignment on the glass substrate. Such organisation of the molecules is confirmed by spectroscopic methods. These structures can be interesting from the point of view of organic electronics.