Er:YAG laser pulse for small-dose splashback-free microjet transdermal drug delivery

Abstract

The microjet injector system accelerates drugs and delivers them without a needle, which is shown to overcome the weaknesses of existing jet injectors. A significant increase in the delivered dose of drugs is reported with multiple pulses of laser beam at lower laser energy than was previously used in a Nd:YAG system. The new injection scheme uses the beam wavelength best absorbable by water at a longer pulse mode for elongated microjet penetration into a skin target. A 2.9 μm Er:YAG laser at 250 μs pulse duration is used for fluorescent staining of guinea pig skin and for injection controllability study. Hydrodynamic theory confirms the nozzle exit jet velocity obtained by the present microjet system.

Continuous-wave laser generated jets for needle free applications

“…Another pulsed laser-based jet injector with speeds up to 50 m/s and volume of 2100 nL has been developed to prevent this issue. [26][27][28][29][30] Here, the container where cavitation occurs, and the nozzle where the drug is stored, were separated by a thermal resistant membrane.…”

“…31 However, the jet speed ( 10 m/s) was still insufficient to cross the skin barrier (stratum corneum). 27 In this work we present, to the best of our knowledge, the first microfluidic device to produce elongated liquid jets by CW-laser induced thermocavitation with speeds above the threshold to break the stratum corneum (uttermost epidermal layer), which is the major barrier to chemical transfer through the skin. For a typical skin strength of 20 MPa, a minimum jet velocity of 14 m/s is needed.…”

“…For a typical skin strength of 20 MPa, a minimum jet velocity of 14 m/s is needed. 27 The device focuses the bubble expansion with a specially designed geometry, leading to a liquid jet of 29 m/s. Thermocavitation produces jet speeds comparable with those by pulsed laser, opening the possibility to develop an inexpensive portable and needle free injector.…”

Towards clinical use of a laser-induced microjet system aimed at reliable and safe drug delivery

“…[1][2][3] One possible remedy is a system based on the microjet, [4][5][6][7][8][9] whereby the generation of needle-free injection relies on the bubble dynamics within the injector. 10,11 Both jet characteristics and bubble behavior determined by the laser beam properties such as wavelength and pulse duration have been studied.…”

“…9 For general use of a laser-induced microjet injector as a clinical device, the delivery of drugs into the human tissue must be assured by a zero side effect associated with any type of drug damage done by strong thermal and inertial effects of the laser ablation-based mechanism for ejecting a microjet. 8 In order to address these potential concerns addressed by the medical practitioners, the injector design is evolved around the use of two separate chambers that independently contain driving water (in the upper chamber) and the drug (in the lower reservoir), separated by a thermally resistant silicon rubber membrane. The laser ablation occurs within the upper driving chamber only, whereas the drug solution beneath the membrane is protected from the laser ablation.…”