Abstract
A narrow nozzle ejects a microjet of 150 μm in diameter with a velocity of 140 m/s a by the laser-induced bubble expansion in the designed injector. The pulsed form of the driving force at a period of 10 Hz from the connected Er:YAG laser makes it possible for multiple microjet ejections aimed at delivery of drugs into a skin target. The pulsed actuation of the microjet generation is however susceptible to the air leak which can cause the outside air to enter into the momentarily de-pressurized nozzle, leading to a significant reduction of the microjet speed during the pulsed administering of the drug. In the present study, we designed a ball-check valve injector which is less prone to an unwanted air build up inside the nozzle by controlling the nozzle pressure to remain above ambient pressure at all times. The new device is rigorously compared against the reported performance of the previous injector and has shown to maintain about 97% of the initial microjet speed regardless of the number of shots administered; likewise, the drug penetration depth into a porcine skin is improved to 1.5 to 2.25 times the previously reported penetration depths.
Highlights
A microjet drug delivery system in which a drug solution penetrates directly through the epidermis of the skin by a high-speed micro-sized jet has been investigated by various researchers.[1,2,3,4] Notably, the laser-induced bubble driven microjet injection method as shown in Fig. 1 has been recently pioneered.[5,6,7] The method utilizes a pulsed laser irradiation of 2,940 nm wavelength at 10 Hz, which ejects a drug in the form of a microjet
Aside from pulsed generation of bubbles in the diving chamber by the laser irradiation, the growing air pocket in the drug chamber nozzle has been observed in all instances,[8] in particular with the increasing number of pulsed shots
The present paper provides a detailed description of the new injection nozzle suitable for laser pulse driven microjet system for transdermal drug delivery
Summary
A microjet drug delivery system in which a drug solution penetrates directly through the epidermis of the skin by a high-speed micro-sized jet has been investigated by various researchers.[1,2,3,4] Notably, the laser-induced bubble driven microjet injection method as shown in Fig. 1 has been recently pioneered.[5,6,7] The method utilizes a pulsed laser irradiation of 2,940 nm wavelength at 10 Hz, which ejects a drug in the form of a microjet. A high-intensity laser pulse focused into a pressure chamber containing the water gives rise to an explosive bubble growth, causing the elastic membrane to push the drug out from a nozzle. With the growing size of an air pocket, the microjet speed gradually decreases until the skin penetration is no longer possible
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