Transcutaneous immunization is becoming an attractive non-invasive vaccination strategy, though it is still challenging. This study evaluates the potential of transcutaneous delivery of antigens in mice through niosomal and elastic niosomal carbomer hydrogels. Ovalbumin was encapsulated into niosomes prepared by Span 80/cholesterol/stearylamine through reverse-phase evaporation. Ethanol was added into niosomal mixtures for elastic niosomes formation, then embedded in carbopol 934 hydrogel. Encapsulation efficiency and other physiochemical properties of the prepared niosomal vesicles such as particle size, stability, in vitro release and cytotoxicity were determined. In vivo immunizations of niosomal and elastic niosomal gel were carried out in mice. The optimal niosomal formulation loads 48.6 ± 5.2% ovalbumin with a vesicle size below 300 nm. A simple BCA method was used to determine the encapsulation efficiency of niosome. The cumulative permeation of proteins of niosomal gel was 15~20%. Both gels were stable at room temperature; however, elastic niosomal gel deteriorated at 60 ℃. Compared to free antigen, the topical administration of niosomal or elastic niosomal gel to mice displayed significant IgG titers. From the findings, compared to elastic niosomal gel, the niosomal hydrogel platform exhibited enhanced antigen delivery. Therefore, niosomal hydrogel may be considered a promising transcutaneous antigen delivery carrier.
In this study, stable sodium carboxymethyl cellullose (CMC-Na) coated niosomal vesicles was successfully prepared through an electrostatic deposition method. The interaction of CMC-Na with two types of gemini alkyl O -glucosides based vesicles was thermodynamically characterized by means of isothermal titration calorimetry (ITC). The thermodynamic parameters suggested that the binding process was entropy driven and energetically favourable, thereby leading to the further stabilization of vesicles suspension. Based on the data from ζ-potential and dynamic light scattering, the concentration of polyelectrolyte required to afford stable secondary niosomes was estimated by applying an empirical model and was found to be in excellent agreement with our experimental results. Vesicles were unstable when polyelectrolyte concentration below or above the optimum range owing to bridging flocculation or depletion flocculation, respectively. The prepared secondary vesicles exhibited significantly improved resistance to pH variation, thermal and osmotic stress compared with bare ones. This study would facilitate application of polyelectrolyte deposition to produce stable secondary niosomal vesicles with better performance, which holds a great promise as nano-carriers for bioactive compounds .
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