PDA Films Research Articles

Cell response to PEGylated poly(dopamine) coated liposomes considering shear stress

BackgroundLiposomes have gained immerse attention in the field of drug delivery as carriers of therapeutic molecules. Their modification with a polymer either to make them stealth (e.g. using PEG) and/or more stable (e.g. using poly(dopamine) (PDA)) is a crucial aspect to improve their performance e.g. the blood circulation time. Despite their potential, there are only a few commercialized liposome-based formulations for intravenous drug delivery. Hence, there is still considerable need to address the challenges involved in the design and characterization of liposomal therapeutics. In the latter case, it is of paramount importance to consider the dynamic in vivo environment, e.g. the interstitial fluidic pressure in tumors, blood flow, or bile flow in the liver. MethodsThe PEGylation of PDA films was characterized by quartz crystal microbalance with dissipation monitoring, and the optimized protocol was used to assemble PEGylated PDA coated liposomes (LPDA_PEG). Dynamic light scattering, a plate reader, a flow cytometer and a cytotoxicity assay were used to characterize the liposomes and quantify cellular association/uptake and cell viability in the presence and absence of shear stress after 30min and 4h. The immortalized skeletal mouse myoblast (C2C12) cell line was chosen as model cancer cells, and a hepatic cell line (HepG2) was selected due to their importance in nanosized drug carrier clearance from the system in the liver. ResultsThe presence of hydrophilic cargo did not affect the PDA assembly process. In the absence of shear stress, there was no difference in cellular uptake/association of both PDA coated liposomes (LPDA) and LPDA_PEG for hepatocytes while myoblasts preferentially internalized/associated with LPDA. In the presence of shear stress, hepatocytes preferentially internalized/associated with LPDA after 30min, while there was only a significant difference for myoblasts after 4h. The cell viability remained unaffected in all cases. ConclusionsLPDA_PEG are a promising platform towards drug delivery. The nature of cells and fluidic flow are important factors to be considered in their characterization using cell cultures. General significanceThese findings will contribute in the better understanding of polymer coated liposomes with cells. The importance of microfluidics in cell culture based characterization is demonstrated, and this will eventually affect the way advanced drug delivery vehicles are designed and characterized prior to animal experiments.

Stability and interactions in mixed monolayers of fatty acid derivatives on Artificial Sea Water

We studied the formation and stability of fatty acid and derivatives films on aqueous sub-phases by means of Langmuir trough experiments. Films were prepared from pure stearic acid (SA), stearyl amine (SAm) and 12-phenyldodecanoic acid (PDA), and from binary systems of SA with either SAm or PDA. For the aqueous sub-phase, multicomponent salt solutions (‘Artificial Sea Water’) at various concentrations (cASW, 0–100%) and pH values (3–7) were explored. SAm and SA differ most strongly at pH 7, where they can dissociate into oppositely charged species. For SA:SAm mixtures at this pH, pressure-area isotherms indicate mixing on a molecular scale. Increase of salt concentration from 0.05 to 0.5M causes significant contraction of the layer, which is ascribed to (enhanced) electrostatic attractions between the head-groups. Relaxation experiments with these films indicate that dissolution of SAm into the sub-phase is suppressed by SA. The most stable films are formed at xSA=0.5, in agreement with the calculated excess free energy of mixing. PDA is much less amphiphilic than SA. (Meta-) stable mixed films of SA and PDA are formed only at high salt concentration and low pH, where the solubility of PDA into the sub-phase is the lowest. Under these conditions, SA appears to have a stabilizing effect, which is however not strong enough to prevent expulsion of PDA from interface. Isobars of SA:PDA films corroborate this picture. The weak interactions between SA and PDA are confirmed by the excess free energies of mixing, which are close to those of ideal mixtures.

Assembly of Poly(dopamine) Films Mixed with a Nonionic Polymer

Poly(dopamine) (PDA) coatings have recently attracted considerable interest for a variety of applications. Here, we investigate the film deposition of dopamine mixed with a nonionic polymer (i.e., poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA), and poly(N-vinyl pyrrolidone) (PVP)) onto silica substrates using X-ray photoelectron spectroscopy and quartz crystal microbalance. Furthermore, we assess the possibility of coating silica colloids to yield polymer capsules and liposomes with these mixtures. We found that mixed PDA/PEG and PDA/PVA films are deposited without the need for a covalent linker such as an amine or thiol. We also discovered the first material, namely, PVP, that can suppress PDA film assembly. These fundamental findings give further insight into PDA film properties and contribute to establish PDA as a widely applicable coating.

Use of surface plasmon resonance to investigate lateral wall deposition kinetics and properties of polydopamine films

Dopamine (DA) is a particularly important neurotransmitter. Polydopamine (pDA) films have been demonstrated to be important materials for the immobilization of biomolecules onto almost any type of solid substrate. In this study, a surface plasmon resonance (SPR)-based sensor system with the sensor chip surface parallel to the direction of gravity was used to investigate the lateral wall deposition kinetics and properties of pDA films. The deposition kinetics of pDA Films are limited by the oxidation process. The pDA film could not be removed from the sensor chip completely by a strongly alkaline solution, indicating that the pDA film was heterogeneous in the direction of deposition. The pDA film formed near the interior of the solution was less stable than the film formed near the gold–solution interface. Adsorption of proteins on pDA film was studied compared with that on bare gold and dextran sensor chip. The reduction of Au(111) cations by the pDA film, forming a layer of gold particles, was monitored using SPR.

Regulation of Supramolecular Chirality in Co‐Assembled Polydiacetylene LB Films with Removable Azobenzene Derivatives

Herein, we report a novel model that combines supramolecular chemistry and the LB technique for the chirality regulation of the PDA films. The helical packing of PCDA molecules and the chiroptical properties of the resulting PDA LB films can be easily modulated by different azobenzene derivatives. Moreover, the effect of the photo-isomerization of azobenzene chromophores on the helical formation of PCDA assemblies is investigated in detail.

Preparation of Surface Molecularly Imprinted Poly(dopamine) Film for 4-Hydroxybenzoic Acid (4-BA) Recognition by One-Step Method

In this paper, we present a one-step aqueous self-polymerization strategy to prepare surface molecularly imprinted poly(dopamine) (PDA) film. The method is simple and convenient compared with the “template-guided” surface molecularly imprinted synthesis method and the layer-by-layer self-assembly and the surface-grafted molecularly imprinted synthesis methods. The molecularly imprinted PDA films could selectively bind the template molecules (4-Hydroxybenzoic acid as a model), and bisphenol A (BPA) imprinted PDA films were also investigated. Meanwhile, the 2-dimension imprinted film material was used very conveniently.

Electrochemistry of Fe-Phenylenediamine Derived Cathode Catalysts Supported on Carbon

The primary goal of this work has been to better understand the oxygen reduction (ORR) activity of a series of Fe-N-C catalysts, formed by mixing Fe chloride with o-phenylenediamine (PDA) followed by heat treatment (HT). It is shown that, for HT at less than 500oC, significant redox chemistry, typical of a o-PDA redox polymer, is revealed in fully deaerated acidic solutions. This redox chemistry disappears at higher HT temperatures, arguing that the ORR active site arises from the thermal decomposition product of the PDA surface polymer. By electrodepositing PDA, either from a solution of o-PDA or from one also containing Fe3+, followed by ORR studies, it is demonstrated that the presence of Fe in the PDA film serves to enhance the ORR activity.

Induced Optical Chirality of Poly(diacetylene) Film by Circularly Polarized Light and Its Control by Changing Substrate Temperature

The strength of chirality of a blue-phase poly(diacetylene) (PDA) film polymerized from achiral monomers using circularly polarized light (CPL) was effectively controlled by changing substrate temperature (313 and 273 K). The obtained absorption spectra did not show a difference between PDA films polymerized using left- and right-CPL, whereas the chiral PDA films with opposite chirality were selectively produced by left- and right-CPL irradiations. The PDA film prepared at 313 K showed stronger chirality than that prepared at 273 K. Microscopy observation clearly indicates that the strength of chirality depends on the domain size.

Oxidative graft polymerization of aniline on the modified surface of polypropylene films

AbstractA novel method for preparing electrically conductive polypropylene‐graft‐polyacrylic acid/polyaniline (PP‐g‐PAA/PANI) composite films was developed. 1,4‐Phenylenediamine (PDA) was introduced on the surface of PP‐g‐PAA film, and then, chemical oxidative polymerization of aniline on PP‐g‐PAA/PDA film was carried out to prepare PP‐g‐PAA/PANI electrically conductive composite films. After each step of reaction, the PP film surface was characterized by attenuated total reflectance Fourier transform infrared spectroscopy. Static water contact angles of the PP, PP‐g‐PAA, and PP‐g‐PAA/PANI films were measured, and the results revealed that graft reactions took place as expected. The morphology of the PP‐g‐PAA film and the PP‐g‐PAA/PANI composite film were observed by atomic force microscopy. The conductivity and the thickness of the PP‐g‐PAA/PANI composite films with 1.5 wt % PANI were around 0.21 S/cm and 0.4 μm, respectively. The PANI on the PP‐g‐PAA/PANI film was reactivated and chain growing occurred to further improve the molecular weight of PANI. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2442–2450, 2007

Characterization of saturable absorbers using an open-aperture Gaussian-beamZscan

We present a theoretical investigation on the open-aperture Gaussian-beam $Z$-scan technique for two dominant saturable absorption models, by using the Adomian decomposition method. Analytic expressions of the $Z$-scan traces are deduced for a cw laser and a pulsed laser, respectively; in particular, for performable simulations, the optimal sum upper limit is found. We give an experimental demonstration, in which a side-chain azobenzene polymer poly [6-[1-(4-(4-nitrophenylazo)phenyl) piperazine] hexyl methacrylate] (Pda) film behaves as a test sample. The results manifest that our theory is reasonable and the Pda film is a good saturable absorber at the wavelength of $532\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$.

Polymorph and Orientation Controls of Calcium Carbonate Crystals Achieved by Organic Matrices

Crystallographic properties such as polymorphs and crystal orientations of calcium carbonate formed in biological systems can be controlled by interactions between organic matrices and inorganic substances. We have attempted to reveal such control mechanisms, using a polymerized Langmuir-Blodgett film of 10,12-pentacosadiynoic acid (PDA) as an organic matrix with highly regulated molecular alignment. Only calcite crystals were precipitated on the polymerized PDA film, even though in presence of Mg 2+ ions which were reported to enhance aragonite formation in previous works. The calcite precipitates were aligned on the PDA film with their a-axes in parallel to the polymerization direction. Calcite structure does not give a reasonable match over the molecular alignment of the PDA film along its a-axis. A concerted mechanism of geometric matching and stereochemical effect should determine the polymorphs and directions of calcium carbonate crystals on the organic matrices.

Physical and chemical characterization of enolase immobilized polydiacetylene Langmuir–Blodgett film

Hexa histidine tagged recombinant Plasmodium falciparum enolase (His6-Pfen) was covalently immobilized on a Langmuir–Blodgett film of a self assembled mixture of 10,12-pentacosadiynoic acid and its N-succinimidyl ester derivative (PDA LB-film). The film was polymerized with a UV-lamp at 254nm to obtain a blue coloured, protein hooked polydiacetylene film. Atomic force microscopy (AFM) was used to characterize the surface morphology of the protein-immobilized film. The colorimetric response (CR) of the His6-Pfen hooked PDA LB-film to 2-phosphoglyceric acid (2-PGA), the substrate of enolase, in the presence of magnesium ions was studied spectrophotometrically. The CR of glutathione S-transferase-Pfen (GST-Pfen) immobilized film prepared by using similar procedure was also examined. The results suggest that binding of Mg (II) to the enzyme facilitates the interaction of the enzyme with 2-phosphoglycerate. This ligand-binding event could be detected by an observed increase in colorimetric response of the film by ∼10%. Thus the incorporation of enolase on a PDA film resulted in the formation of a novel material, which can serve as a biosensor.

Cyclodextrin-induced Color Changes in Polymerized Diacetylene Langmuir-Schaefer Films

Abstract We have observed the first example of a cyclodextrin-induced color change of polymerized diacetylene film sensor. The PDA film, prepared from a diacetylene monomer containing a terminal anilide moiety was found to preferentially interact with α-cyclodextrin causing a color transition which is both time and concentration dependent.

Selective Potential Response of a Poly(N,N-dimethylaniline)/Poly(o-chloroaniline) Dual-Layer Coated Electrode to Dissolved Iodide Ions

Abstract Poly(N,N-dimethylaniline) (PDA) was easily obtained by an anodic oxidation of N,N-dimethylaniline in acidic media. PDA is a semiconductor having positively charged sites as quaternary ammonium groups in its polymeric backbone. It was possible for a PDA-film coated electrode to incorporate I− electrostatically; I− in the film was then oxidized electrochemically. Further, the oxidized products of I− still remained in the film. Although the electrode responded to dissolved I− potentiometrically, the response was disturbed by the presence of other redox species. On the other hand, poly(o-chloroaniline) (PCA) was also easily prepared by the electro-oxidation of o-chloroaniline in acidic solutions. On a PCA-film coated electrode, only the redox wave of I2/I− was observed, though PCA, itself, was electroinactive. In other words, the PCA film responded to I− selectively. The dual-layer (a PDA film incorporated oxidized products of I− and PCA film) showed a selective Nernstian response to dissolved I−.

Selective Nernstian Response of Poly(N,N-dimethylaniline)/Poly(o-chloroaniline) Dual-layer Coated Electrode to Dissolved Iodide Ion

Abstract Poly(N,N-dimethylaniline)(PDA) is a semiconductor having positively charged sites in the polymeric backbone. A PDA coated electrode can capture I− electrostatically and the I− in the PDA film can also be oxidized electrochemically. Poly(o-chloroaniline)(PCA) responses to dissolved I− selectively, though it is quite an insulator. A PDA/PCA dual-layer coated electrode shows selective Nernstian response to dissolved I−.

Optical properties of Langmuir-Blodgett polydiacetylene thin films

The colour phase transition of Langmuir-Blodgett polydiacetylene (LB PDA) films is investigated as a function of annealing temperature. A new reversible colour change is observed for a short annealing time. Such a reversible property has not previously been reported in LB PDA films. The X-ray diffraction patterns show that the reversible property is closely related to the layer structure of the LB films. Furthermore, the ratio of the line intensities of the Raman peaks due to C≡C and C=C stretch modes changes with the annealing temperature. The colour phase transition of the LB PDA films is correlated with this ratio. Such phase transitions have also been observed in laser-annealed points of LB PDA films. From these results, a new optical device based on LB PDA films is proposed. Furthermore, the electrical properties of ion-irradiated LB PDA films are briefly reported.

Lateral interactions among phospholipid head groups at the heptane/water interface

For the photoresist in the semiconductor photolithography, the study was extended to the five LB films for EX laser, Le., TDA, PDA, HDA, OAA, and w-TCA. Especially, fabrication of resist pattern with the KrF EX stepper and spectroscopic evaluation were carried out. (1) In terms of the pattern shape and photosensitivity, PDA for EX laser gave the best result. With PDA films, a 0.3-pm pattern could be fabricated by the EX stepper. (2) The photoreactivity with the molecular arrangement of LB films was investigated in detail. It was demonstrated that the photoreactivity of PDA LB f ibs for KrF EX laser was influenced strongly by the molecular arrangement. Future studies will include the impermeability to plasma under various conditions, and, for the purpose of a detailed study of photoreaction processes of PDA LB films, IR or Raman spectroscopic analysis will be carried out. This technique should become useful for the fabrication of 64-Mbit D-RAMS, if higher efficiency can be achieved in the preparation of LB films.

Raman Scattering and Photoluminescence of Pristine and Ion Implanted Langmuir-Blodgett Polydiacetylene Thin Films

AbstractFundamental optical properties of Langmuir-Blodgett polydiacetylene (LB PDA) ultra thin films are investigated. The LB films exhibit a strong absorption peak at about 16000 cm-1 and a weak and broad peak at about 17500 cm-1; the color of the film is blue. After annealing at 90°C, a blue shift of the absorption peaks is observed; that is, the color of the LB films changes from blue to red. The phase transition corresponding to the color change is studied using Raman spectroscopy as a function of annealing temperature. For annealing temperatures between 50 and 60°C, the results show significant change in the ratio of Raman line intensities due to C≡C and C=C stretch modes. Such a transition is also observed for laser annealed LB PDA films. Furthermore, the photoluminescence (PL) properties of pristine (blue), annealed (red) and ion implanted (red) LB PDA films are investigated. The photoluminescence of both pristine and annealed LB PDA films show sharp peaks at about 15500 cm-1. The annealed LB PDA films have an additional small peak or shoulder at about 18000 cm-1. The photoluminescence peaks of red films implanted with 200keV As+ ions are observed at about 16000 cm-1 and become broad with increasing ion implantation dose in the range 1012–1015 cm-2.