Emerging diseases such as influenza have the potential to cause global pandemics; a key intervention will be vaccination. In fact, most infectious diseases remained as major health risks, due to the lack of vaccine or the lack of facilities to deliver the vaccines. Plasmid DNA (pDNA) vaccines provide an antigen-specific protective immunity by expressing a foreign protein within the hots cells. This is mimicking intracellular pathogenic infection, and can induce both humoral and cellular immune responses. Thus, nonviral systems, particularly a synthetic DNA delivery system, are highly desirable in both research and clinical applications. Nasal delivery of vaccines has been an area of interest for the pharmaceutical industries in recent years to overcome the alarming pattern of unsafe injection practices and the poor availability of orally administrated and injectable vaccines. DNA prime-protein boost immunization involves priming with DNA vaccines and boosting with protein or recombinant protein. This strategy aims to augment immune responses to pathogens.

In this study, a microencapsulation method using ultrasonic atomization is used to synthesize biodegradable polymer microspheres (10-20µm) that encapsulate both the pDNA and the mesoporous silica spheres loaded with protein. Adhesive properties of biodegradable polymer make them suitable for transmucosal delivery applications and prolong the contact time of vaccines with the nasal surface. The embedding of biopharmaceutical compounds into biodegradable polymer microspheres has gained considerable interest over the last decade. Vaccines can be released from such microparticles in a sustained and controlled fashion, while non-release biopharmaceuticals are protected from rapid in vivo degradation.