PEGylated polyplexes had been proved to improve the stability of DNA complexes. However, the conjugation reaction might reduce the capacity of efficient DNA complexation. Herein we described an easy and favorable approach to construct PEGylated polyplexes via entrapping poly(ethylene glycol) cholesterol ether (CPEG) into polyplexes. It was of interest to find the addition sequence of CPEG had great effect on the stability of polyplexes in physiological salt concentration. The addition of CPEG into the formed PEI25k/DNA polyplexes had no effect to improve the stability. Whereas by the “CPEG first” method of adding CPEG and PEI25k mixture into the DNA solution, the PEI25k/CPEG/DNA polyplexes showed excellent anti-aggregation effect and enhanced transfection efficiency in physiological condition. The difference performance might be explained by the possibility of CPEG entrapment. By the “CPEG first” method, PEGylated polyplexes was constructed due to the hydrophobic interaction between the cholesterol group of CPEG and hydrophobic charged-compensated core. The PEG coating significantly improved the stability of polyplexes in physiological condition. This facile entrapment approach to prepare PEGylated polyplexes might have great potential in non-viral gene delivery research and application. 相似文献
A novel comb‐like derivative CPEG‐g‐cholesterol was prepared by the reaction of cholesteryl chloroformate with hydroxyl groups of CPEG. The TEM and SEM results showed that CPEG‐cholesterol spontaneously aggregated vesicles with the membrane thickness of 4.27 ± 0.48 nm. Compared with the vesicles formed by comb‐like PEG (CPEG), the derivation of cholesteryl chloroformate increased the thickness of vesicle membrane and developed corrugations. The hydrophobic doxorubicin (Dox) was added into the solution of CPEG and CPEG‐g‐cholesterol to test their vesicle stability. The drug‐loaded vesicles of CPEG‐g‐cholesterol still existed but those of CPEG disappeared, which indicated that stability of vesicles was enhanced by the derived cholesteryl chloroformate. The vesicles were further cross‐linked by the reaction between divinyl sulfone (DVS) and the hydroxy groups in the side chains of the CPEG and CPEG‐g‐cholesterol. Both cross‐linked vesicles of CPEG and CPEG‐g‐cholesterol entrapped considerable hydrophobic Dox in the vesicles membrane. The spontaneous vesicles of CPEG‐g‐cholesterol and the crosslinked vesicles of CPEG and CPEG‐g‐cholesterol might have great potential as a cargo of the hydrophobic drug.
We have developed a new hydrolytically stable amide-embedded stationary phase via a simple and effective synthetic method. The preparation of the new phase involves the synthesis of multifunctional silane ligands and the surface modification of porous silica particles via multiple attachments of these ligands to the silica surface. A hydrolytically stable coating was produced as a result of multiple covalent linkages formed between silane ligands and the silica surface, and cross-linking between adjacent ligands. The resulting amide-embedded stationary phase showed excellent hydrolytic stability over a wide pH range. Like other existing amide-embedded columns, this new stationary phase exhibits higher retention for polar compounds and different selectivity as compared to conventional C18 columns. The new phase is compatible with 100% aqueous mobile phases, and also provides high column efficiency and good peak shapes for both acidic and basic compounds. 相似文献
The surface of a titanium (Ti) alloy substrate was modified by a simple and quick process using a water-soluble polymer, and the effects of 3,4-dihydroxyphenyl (DHP) groups in the polymer side chain on the modification process were examined. The polymers (PMDP) composed of both 2-methacryloyloxyethyl phosphorylcholine (MPC) unit and 3,4-dihydroxyphenyl methacrylate unit were synthesized for surface anchoring. The Ti alloy substrate was coated with PMDP using an aqueous solution of the polymer. A PMDP layer with a thickness of 20 nm was formed on the Ti alloy substrate simply by dip coating for 10 s without drying. Even when the Ti alloy substrate with PMDP coating was immersed in the aqueous medium for 1 week, no change in the thickness was observed, i.e., the PMDP layer was bound to the surface very stably. Oxidation of the DHP groups reduced the stability of the polymer layer significantly. Thus, the DHP groups play a significant role in achieving stable binding. Protein was adsorbed on the Ti alloy substrate; however, this was not observed for the PMDP-coated Ti alloy substrate. In conclusion, we confirmed the effects of DHP groups in PMDP on the stability of the coating on the Ti alloy substrate. Moreover, we found that surface treatment using PMDP was simple, quick, and reliable, and thus, it has great potential for improving biofouling of Ti alloy substrates used in medical devices. 相似文献
Nano-encapsulation of a poorly soluble anticancer drug was demonstrated with a sonication assisted layer-by-layer polyelectrolyte coating (SLbL). We changed the strategy of LbL-encapsulation from making microcapsules with many layers in the walls for encasing highly soluble materials to using a very thin polycation/polyanion coating on low solubility nanoparticles to provide them with good colloidal stability. SLbL encapsulation of paclitaxel resulted in stable 100-200 nm diameter colloids with a high electrical surface ξ-potential (of -45 mV) and drug content in the nanoparticles of 90 wt%. In the top-down approach, nanocolloids were prepared by rupturing a powder of paclitaxel using ultrasonication and simultaneous sequential adsorption of oppositely charged biocompatible polyelectrolytes. In the bottom-up approach paclitaxel was dissolved in organic solvent (ethanol or acetone), and drug nucleation was initiated by the addition of aqueous polyelectrolyte assisted by ultrasonication. Paclitaxel release rates from such nanocapsules were controlled by assembling multilayer shells with variable thicknesses and were in the range of 10-20 h. 相似文献
This study aims to explore the fundamental surface characteristics of polydopamine (pDA)-coated hydrophobic polymer films. A poly(vinylidene fluoride) (PVDF) film was surface modified by dip coating in an aqueous solution of dopamine on the basis of its self-polymerization and strong adhesion feature. The self-polymerization and deposition rates of dopamine on film surfaces increased with increasing temperature as evaluated by both spectroscopic ellipsometry and scanning electronic microscopy (SEM). Changes in the surface morphologies of pDA-coated films as well as the size and shape of pDA particles in the solution were also investigated by SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM). The surface roughness and surface free energy of pDA-modified films were mainly affected by the reaction temperature and showed only a slight dependence on the reaction time and concentration of the dopamine solution. Additionally, three other typical hydrophobic polymer films of polytetrafluoroethylene (PTFE), poly(ethylene terephthalate) (PET), and polyimide (PI) were also modified by the same procedure. The lyophilicity (liquid affinity) and surface free energy of these polymer films were enhanced significantly after being coated with pDA, as were those of PVDF films. It is indicated that the deposition behavior of pDA is not strongly dependent on the nature of the substrates. This information provides us with not only a better understanding of biologically inspired surface chemistry for pDA coatings but also effective strategies for exploiting the properties of dopamine to create novel functional polymer materials. 相似文献
Among various coating processes, slot die coating belongs to a class of pre-metered coating, in which the coating film thickness can be predetermined. In the past, most research works on slot die coating have focused mainly on polymer solutions; very little information is available using suspensions as coating fluids. In this study, the effect of adding TiO2 and SiO2 in aqueous polyvinyl alcohol (PVA) solutions on slot die coating is investigated. It was found that the stable coating window was enlarged with the addition of particles, and its size increased with solids concentration. This is due to the strong interaction between polymer and particles, resulting in a higher viscosity and surface tension. As a result, the upstream coating bead is more stable and the maximum coating speed is extended to a high value, hence the coating window becomes larger. Although both viscosity and surface tension appear to contribute to the stability of coating flow, the effect of surface tension is more dominant. The surface tension of a suspension with porous particles was higher than one with hard solid particles. Consequently, the coating window obtained with the former was significantly larger than the latter. Flow visualization revealed that under the same operating conditions, the upstream dynamic contact angle for the suspension was smaller than for the aqueous polymer solution. This observation could be related to the stability of the upstream coating bead, and hence the coating window. The experimental flow fields were verified numerically with the aid of a numerical simulation package (Flow-3D). 相似文献
A polyacrylic acid film was synthesized on titanium substrates from aqueous solutions via an electroreductive process for
the first time. This work was done in order to develop a versatile coating for titanium-based orthopaedic implants that acts
as both an effective bioactive surface and an effective anti-corrosion barrier. The chemical structure of the PAA coating
was investigated by X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was employed to evaluate the
effect of annealing treatment on the morphology of the coatings in terms of their uniformity and porosity. Inductively coupled
plasma mass spectrometry was used to measure ion concentrations in ion release tests performed on Ti-6Al-4V sheets modified
with PAA coatings (annealed and unannealed). Results indicate that the annealing process produces coatings that possess considerable
anti-corrosion performance. Moreover, the availability and the reactivity of the surface carboxylic groups were exploited
in order to graft biological molecules onto the PAA-modified titanium implants. The feasibility of the grafting reaction was
tested using a single aminoacid residue. A fluorinated aminoacid was selected, and the grafting reaction was monitored both
by XPS, using fluorine as a marker element, and via quartz crystal microbalance (QCM) measurements. The success of the grafting
reaction opens the door to the synthesis of a wide variety of PAA-based coatings that are functionalized with selected bioactive
molecules and promote positive reactions with the biological system interfacing the implant while considerably reducing ion
release into surrounding tissues.
Figure Vanadium release from bare Ti-6Al-4V sheets compared with the release from sheets coated with annealed and unannealed electrosynthesised
PAA
Dedicated to Professor P.G. Zambonin on the occasion of his 72nd birthday. 相似文献
