Patients could one day self-administer vaccines using a needleless, pill-sized technology that jet-releases a stream of vaccine inside the mouth, according to a proof-of-concept study conducted at UC Berkeley.

MucoJet is a 15-by-7-milimeter cylindrical, two-compartment plastic device. The exterior compartment holds 250 mililiters of water. The interior compartment is composed of two reservoirs separated by a porous plastic membrane and a movable piston. One interior compartment is a vaccine reservoir, containing a 100-ml chamber of vaccine solution with a piston at one end and a sealed 200-micrometer (m) diameter delivery nozzle at the other end. The other interior compartment is the propellant reservoir, which contains a dry chemical propellant (citric acid and sodium bicarbonate) and is separated from the vaccine reservoir at one end by the built-in porous membrane and movable piston and is sealed at the other end from the exterior compartment with a dissolvable membrane

To administer the MucoJet, a patient clicks together the interior and exterior compartments. The membrane dissolves, water contacts the chemical propellant and the ensuing chemical reaction generates carbon dioxide gas. The gas increases the pressure in the propellant chamber, causing the piston to move. The free-moving piston ensures uniform movement of the ejected drug and blocks the exit of fizz from the carbon dioxide through the nozzle. When the pressure in the propellant chamber is high enough, the force on the piston breaks the nozzle seal of the vaccine reservoir. The vaccine solution is then ejected from the MucoJet nozzle, penetrates the mucosal layer of the buccal tissue, and delivers the vaccine to underlying vaccine targets, called antigen-presenting cells.

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