Tannic acid-Aluminum (Ⅲ) coordination-enabled microcapsules for pH-responsive protein vaccine delivery / 国际生物医学工程杂志

ABSTRACT

Objective To establish a simple and gentle antigen loading method to prepare pH-responsive and biodegradable microcapsules for efficient antigen delivery.Methods Co-precipitation method was used to embed chicken egg albumin (OVA) in CaCO3 particles.Then,TA and Al (Ⅲ) were coated on the surface of CaCO3 particles template by metal-organic coordination bonds.The CaCO3 template was removed from disodium edetate to obtain TA-Al(Ⅲ) microcapsules carrying OVA,i.e.the OVA@TA-Al(Ⅲ) microcapsules.The microcapsules were characterized by field emission scanning electron microscopy,transmission electron microscopy,X-ray energy spectrometry and atomic force microscopy.The distribution of OVA in the microcapsules was observed by laser scanning confocal microscopy.The cumulative release rate of OVA in the microcapsules at different pH phosphate buffers was also investigated.The cytotoxicity of the microcapsules on immortalized mouse dendritic cells DC2.4 was observed by thiazolyl blue assay.The phagocytosis of the microcapsules by DC2.4 cells was observed by laser scanning confocal microscopy.Results The results of field emission scanning electron microscope and transmission electron microscopy showed that the OVA@TA-Al(Ⅲ) microcapsules have a intact structure and a hollow and collapsed appearance with a diameter of about 4 μm.X-ray energy spectrum showed that there are five kinds of elements,i.e.C,O,Al,Si and Na,in the microcapsules,among which C,Al and some O elements belong to the composition of the microcapsules.Atomic force microscopy showed that the microcapsules have an ultra-thin wall,and the walls of the microcapsules are uniform in thickness (about 16 nm).Laser scanning confocal microscopy showed that OVAs were evenly distributed in the CaCO3 particles.Moreover,the pH sensitivity of the coordination bond makes the OVA@TA-Al(Ⅲ) microcapsules have pH responsiveness.In addition,the microcapsules also have good biocompatibility,and the DC2.4 cells also have good phagocytic ability to the microcapsules.Conclusion A simple and gentle antigen-encapsuling method was developed to achieve effective antigen payload and pH responsive delivery.The prepared microcapsules are expected to be used as a novel antigen delivery vector for clinical research.