| Adsorption at interface and self-assembly in aqueous solution are two basic behaviors of surfactants and endow surfactants all kinds of application performances. Request for environmental friendiness and growing special need of application on rising fields with rapid development are driving demand for new types of functional surfactants, such as cleavable, biosurfactants, switchable, regulated etc. And switchability and regulation are hot topic for amphiphilic system in recent years. This paper is aimed at developing a kind of surfactant with high surface activity, good biocompatibility, and pH-regulation characteristics.Symmetric N,N'-dialkyl-N,N'-diacetate ethylenediamine (Ace(n)-2-Ace(n), n=8,10,12) and asymmetric Ace(m)-2-Ace(n) (m or n=8,10,12,14,16 and three different asymmetric degrees of 2,4,6 CH2) were designed synthesized. pKal and pKa2 of Ace(n)-2-Ace(n) and Ace(m)-2-Ace(n) were systematically measured. Surface activity and self-assembly properties were studied at-strong alkaline, weak alkaline, neutral, and weak acidic-four different pH intervals according to pKa values. At strong alkaline pH, Ace(n)-2-Ace(n) owns high surface activity, cmc and c?mc increase with carbon chain lengthening; at weak alkaline and neutral pH, surface activity worsens but self-assembly ability enhances, a large quantity of vesicles materialize and the colloidal system can be stable for at least six monts; at acidic pH, acid structure deprive the surfactant of surface activity and precipitate as white solid. pH-transmittance and pH-DLS cycle measurments demonstrate that not only control the switch between "on" and "off" surfactant activity, pH can reversibly regulate the self-assembly bhehavior of Ace(n)-2-Ace(n). By contrast, the pKa2 of Ace(m)-2-Ace(n) is obviously lower than that of Ace(n)-2-Ace(n), meaning the wider pH range avaibale for surface acitivity. The cmc of each Ace(m)-2-Ace(n) stays at 10-5 mN/m order of magnitude at strong alkaline pH. As pH decreases or alkyl chain lengthens, the increase degree of Ace(m)-2-Ace(n)'s cmc is far less obvious than Ace(n)-2-Ace(n); accordingly, the decrease of cac indicates the improved ability of self-assembly. The regulation of pH on self-assembly of Ace(m)-2-Ace(n) reflects as the more featured aggregation transition process-vesicles materialize from nothing, and then from large to small size.Deduced from the ?-potential of the colloidal system formed by gemini surfactant at different pH values and DLS research in differen solvents of H2O and CH3OH mixtures, it is concluded that the protonation between H+ and-N-CH2COO- neutralizes part of the negative charges on the colloid particles and then generates the effect similar to catanionic surfactant. That determines whether pH-regulation is available or not. From the fluorescence spectra of aqueous surfactant solution containing pyrene or Coumarin 153, it is demonstrated that pH regulates Ace(n)-2-Ace(n) or Ace(m)-2-Ace(n) to form considerable vesicles with bilayers arranged more tightly within the isoelectric point pH range. Moreover, FRET from hydrophobic C153 to hydrophilic R6G is effectively promoted in surfactant solutions.Dissolove hydrophobic Coenzyme Q10 and Vitamine D3 in vesicle bilayers and prepare as nano-CoQ10-capsule and nano-VD3-capsule, take SDS and 1631 as comparison. The PDI and stability of the nanocapsules fabcriating by Ace(n)-2-Ace(n) or Ace(m)-2-Ace(n) is superior to SDS or 1631. The internalization study of C153-loaded-vesicles of Ace(10)-2-Ace(16) to MCF-7 demonstrates the vesicles can transport into cellular internal. MTT results show that the cytotoxicity of Ace(n)-2-Ace(n) or Ace(m)-2-Ace(n) is obviously lower than that of 1631. Thus, N,N'-dialkyl-N,N'-diacetate ethylenediamine holds potential for drug delivery. |
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