Membrane foaming is a new method of foaming. To enlarge the knowledge about the influencing factors and to know how to vary the structure of the resulting foam, different factors were evaluated. A whey protein solution with 10% protein was foamed as a model solution by means of a tubular cross-flow filtration membrane. The pore size of the membrane was varied. The smaller the pore size, the smaller the bubbles produced. As a result, the foam firmness increases and less drainage was observed when smaller pore sizes were applied.
An important factor is that the added amount of gas must be stabilised as completely as possible in the foam. In order to achieve this, both the process and the product parameters were varied. Raising the foaming temperature increased the quantity of stabilised gas. The whey proteins then diffuse faster to the bubble surfaces and stabilise these by unfolding and networking reactions to prevent the coalescence of the bubbles.
The product parameter viscosity was found to influence the foaming result in such a way that up to a viscosity of 40 mPa s the incorporated gas bubbles are stabilised by the higher viscosity. At viscosities higher than 40 mPa s it is difficult to incorporate in the bubbles, and the foam structure becomes coarser due to increased coalescence at the pores of the membrane. The foam stability is enhanced with higher viscosities. 相似文献
Surface modification by poly(ethylene glycol) (PEGylation) has been acknowledged as a powerful strategy in minimizing non-specific reactions for biomedical devices. Once applied into manufacture of drug/gene delivery systems, PEGylation has demonstrated to significantly improve their biocompatibility and stealthiness in physiological environment. Nonetheless, reluctant cell membrane affinities thus cellular uptake efficiencies owing to PEGylation brought up further issues that are imperative to be resolved. Pertain to this PEGylation dilemma, we attempted to introduce peptide (GPLGVRG) linkage between block copolymer of PEG-poly{N'-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} PAsp(DET), wherein the cationic PAsp(DET) could self-assemble with pDNA into nanoscaled complex core. Noteworthy was the peptide linkage whose amino acids sequence could be specifically recognized and degraded by matrix metalloproteinases (MMPs) (overexpressed in extracellular milieu of tumors). Therefore, our subsequent studies validated facile detachment of PEGylation from the aforementioned polyplex micelles upon treatment of MMPs, which elicited improved cytomembrane affinities and cellular uptake efficiencies. In addition, promoted escape from endosome entrapment was also confirmed through direct endosome membrane destabilization by PAsp(DET), which was further elucidated to be attributable to dePEGylation as well as elevated charged density of PAsp(DET) in acidic endosomes. These benefits from dePEGylation eventually contributed to promoted gene expression at the affected cells and potent tumor growth suppression based on anti-angiogenic approach. Therefore, our developed strategy has provided a facile approach in overcoming the dilemma of PEGylation, which could be informative in design of drug/gene delivery systems. 相似文献
A rosin-based ester tertiary amine salt (RETAS) cationic surfactant was obtained using natural rosin as raw material. GC-MS of RETAS was detailed analyzed. The pH-responsive mechanism of rosin-based ester tertiary amine (RETA) and RETAS was confirmed by applying theoretical calculations about electrostatic potential maps of RETA and RETAS cation using Gaussian software. Mixed system surfactants were obtained by blending RETAS cationic surfactant with sodium dodecyl benzene sulfonate (SDBS) anionic surfactant. The binary mixed surfactant systems of RETAS and SDBS had obvious synergistic effect. The γcmc and CMC were 39.40?mN/m and 0.56?mmol/L at the optimum molar fraction of RETAS (α)?=?0.6, respectively. The stability time of emulsion with the optimum mixed system as emulsifier increased to 309?s at α?=?0.6. The emulsifying capacity of RETAS was much better than that of RETA. RETAS had pH-responsive targeted release and the optimum mixed system showed a relatively sustained drug release by using doxorubicin (DOX) as a model drug. These results indicate that RETAS surfactant and mixed system surfactant are both promising for applications in drug delivery and emulsification. 相似文献