Needle-free delivery of fluids from compact laser-based jet injector

Effective improvement methods for striae distensae: A novel approach utilizing laser-induced micro-jet injectors with poly-d,l-lactic acid

INTRODUCTION

Striae distensae (SD), or stretch marks, result from rapid stretching of the skin due to various factors. Conventional treatments often yield unsatisfactory results, leading to the exploration of alternative methods. Laser-induced microjet technology offers a promising approach for drug delivery to target areas. This study investigates the efficacy of using a microjet injector with poly-d,l-lactic acid for treating SD.

METHODS

Four female participants with SD were treated with poly-d,l-lactic acid solution using a microjet injector over five sessions. Patients were assessed based on severity scales before and after treatment. Topical anesthetics were applied to minimize discomfort. Injection techniques were optimized to reduce side effects such as bleeding and pain.

RESULTS

All patients showed significant improvement in SD appearance after 5-7 treatments. Assessment scales indicated positive outcomes both immediately after treatment and at the 32-week follow-up. Minimal side effects, primarily petechiae, were observed.

DISCUSSION

Laser-induced microjet technology offers several advantages, including rapid drug delivery and mechanotransduction effects, promoting skin regeneration. Poly-d,l-lactic acid injections demonstrated effectiveness in treating SD, particularly when delivered via microjet injectors. Patients expressed high satisfaction due to the procedure's minimal invasiveness and quick recovery.

CONCLUSION

Utilizing a needleless microjet injector with poly-d,l-lactic acid shows promise as a treatment for SD, typically requiring 5-7 sessions for optimal results. Mild petechiae may occur as a common side effect. This approach offers an effective and minimally invasive alternative for addressing this common cosmetic concern.

3D printed needleless injector based on thermocavitation: analysis of impact and penetration depth in skin phantoms in a repetitive regime

A global issue that requires attention is the duality between the shortage of needles for regular vaccination campaigns and the exponential increase in syringe and needle waste from such campaigns, which has been exacerbated by the COVID-19 pandemic. In response to this problem, this study presents a 3D printed needleless injector based on thermocavitation. The work focused on investigating the interaction of the resulting liquid jets with skin phantoms at different concentrations (1-2%), emphasizing their impact and penetration depth in a repetitive regime. The injector was designed and fabricated from a semi-transparent polymer using a high-resolution 3D printer, allowing the ejection of liquid jets with velocities up to ~ 73 m/s. The impact of these jets on skin phantoms was evaluated using a high-speed camera. After 6 consecutive liquid jets (1% concentration), a maximum penetration depth of ~ 2.5 mm was achieved, delivering approximately 4.7 µL. For the highest concentration (2.0%) and the same number of shots, the penetration depth was reduced to ~ 0.6 mm with a delivered volume of ~ 0.7 µL. An important finding of this study is that the liquid jet with the highest pressure does not cause the maximum penetration depth, but is the result of a series of successive shots. In addition, the velocity and shape of the ejected jet are determined by the amount of solution and the meniscus formed inside the injector. These findings advance the development of precise and efficient thermocavitation-based injectors with broad potential applications in medical and pharmaceutical fields.

Needleless laser injector versus needle injection for skin enhancement and rejuvenation effect of dermal filler

BACKGROUND AND OBJECTIVES

A needleless laser-induced microjet injector is a novel transdermal drug delivery system that can rapidly inject a very small and precise drug dose into the skin with minimal pain and downtime. In this study, we aimed to compare the laser-induced microjet injection versus needle injection of polylactic acid/hyaluronic acid filler for skin enhancement and rejuvenation.

PATIENTS AND METHODS

A 24-week prospective, single-center, assessor-blinded, randomized, split-face study was conducted. The enrolled patients underwent one treatment session of dermal filler injection using a laser-induced microjet injector on one half of the face or a traditional needle injection on the other half of the face. Evaluation was conducted at baseline before treatment and at 4, 12, and 24 weeks after treatment.

RESULTS

A single treatment of filler injection with a laser-induced microjet injector resulted in similar improvements in skin hydration and elasticity as a single treatment of filler injection by using manual needle injection, with reduced pain, side effects, and decreased treatment time.

CONCLUSIONS

Laser-induced microjet injector enabled not only the application of a controlled dose and filler depth but also even distribution, improved clinical efficacy, reduced pain and side effects, and sufficient time for clinicians to perform treatment.

Bubble dynamics and speed of jets for needle-free injections produced by thermocavitation

Significance

The number of injections administered has increased dramatically worldwide due to vaccination campaigns following the COVID-19 pandemic, creating a problem of disposing of syringes and needles. Accidental needle sticks occur among medical and cleaning staff, exposing them to highly contagious diseases, such as hepatitis and human immunodeficiency virus. In addition, needle phobia may prevent adequate treatment. To overcome these problems, we propose a needle-free injector based on thermocavitation.

Aim

Experimentally study the dynamics of vapor bubbles produced by thermocavitation inside a fully buried 3D fused silica chamber and the resulting high-speed jets emerging through a small nozzle made at the top of it. The injected volume can range from ∼ 0.1 to 2    μ L per shot. We also demonstrate that these jets have the ability to penetrate agar skin phantoms and ex-vivo porcine skin.

Approach

Through the use of a high-speed camera, the dynamics of liquid jets ejected from a microfluidic device were studied. Thermocavitation bubbles are generated by a continuous wave laser (1064 nm). The 3D chamber was fabricated by ultra-short pulse laser-assisted chemical etching. Penetration tests are conducted using agar gels (1%, 1.25%, 1.5%, 1.75%, and 2% concentrations) and porcine tissue as a model for human skin.

Result

High-speed camera video analysis showed that the average maximum bubble wall speed is about 10 to 25 m/s for almost any combination of pump laser parameters; however, a clever design of the chamber and nozzle enables one to obtain jets with an average speed of ∼ 70    m / s . The expelled volume per shot (0.1 to 2    μ l ) can be controlled by the pump laser intensity. Our injector can deliver up to 20 shots before chamber refill. Penetration of jets into agar of different concentrations and ex-vivo porcine skin is demonstrated.

Conclusions

The needle-free injectors based on thermocavitation may hold promise for commercial development, due to their cost and compactness.

Design and Analysis: Servo-Tube-Powered Liquid Jet Injector for Drug Delivery Applications

The current state of commercially available needle-free liquid jet injectors for drug delivery offers no way of controlling the output pressure of the device in real time, as the driving mechanism for these injectors provides a fixed delivery pressure profile. In order to improve the delivery efficiency as well as the precision of the targeted tissue depth, it is necessary to develop a power source that can accurately control the plunger velocity. The duration of a liquid jet injection can vary from 10 to 100 ms, and it generate acceleration greater than 2 g (where g is the gravity); thus, a platform for real-time control must exhibit a response time greater than 1 kHz and good accuracy. Improving the pioneering work by Taberner and others whereby a Lorentz force actuator based upon a voice coil is designed, this study presents a prototype injector system with greater controllability based on the use of a fully closed-loop control system and a classical three-phase linear motor consisting of three fixed coils and multiple permanent magnets. Apart from being capable of generating jets with a required stagnation pressure of 15–16 MPa for skin penetration and liquid injection, as well as reproducing typical injection dynamics using commercially available injectors, the novelty of this proposed platform is that it is proven to be capable of shaping the real-time jet injection pressure profile, including pulsed injection, so that it can later be tailored for more efficient drug delivery.

High-Speed Jet Injector for Pharmaceutical Applications

A shock wave-driven needle-free syringe was developed and tested for liquid jet delivery into an artificial skin model and porcine skin samples. The device could deliver an adequate volume of liquid to a depth sufficient for drug dissemination in skin samples. The device is equipped with a splash-proof conduit and a silencer for smooth operation. The concept is expected to minimize the pain of liquid injection by a) minimally breaching the blood vessels in the skin, b) reducing trauma, inflammation and aiding regeneration of the incised spot by the liquid of the jet, and c) preserving most of the micro-circulation system in the target, enabling an effective drug uptake. A theoretical model that predicts jet penetration into viscoelastic targets is derived and presented. A sound agreement has been observed between the experimental jet penetration depths and the corresponding theoretical predictions. The development can offer a cost-effective, minimally invasive health care solution for immunization and drug delivery.

Jet injectors: Perspectives for small volume delivery with lasers

Needle-free jet injectors have been proposed as an alternative to injections with hypodermic needles. Currently, a handful of commercial needle-free jet injectors already exist. However, these injectors are designed for specific injections, typically limited to large injection volumes into the deeper layers beneath the skin. There is growing evidence of advantages when delivering small volumes into the superficial skin layers, namely the epidermis and dermis. Injections such as vaccines and insulin would benefit from delivery into these superficial layers. Furthermore, the same technology for small volume needle-free injections can serve (medical) tattooing as well as other personalized medicine treatments. The research dedicated to needle-free jet injectors actuated by laser energy has increased in the last decade. In this case, the absorption of the optical energy by the liquid results in an explosively growing bubble. This bubble displaces the rest of the liquid, resulting in a fast microfluidic jet which can penetrate the skin. This technique allows for precise control over volumes (pL to µL) and penetration depths (µm to mm). Furthermore, these injections can be tuned without changing the device, by varying parameters such as laser power, beam diameter and filling level of the liquid container. Despite the published research on the working principles and capabilities of individual laser-actuated jet injectors, a thorough overview encompassing all of them is lacking. In this perspective, we will discuss the current status of laser-based jet injectors and contrast their advantages and limitations, as well as their potential and challenges.

Dynamic mechanical interaction between injection liquid and human tissue simulant induced by needle-free injection of a highly focused microjet

This study investigated the fluid-tissue interaction of needle-free injection by evaluating the dynamics of the cavity induced in body-tissue simulant and the resulting unsteady mechanical stress field. Temporal evolution of cavity shape, stress intensity field, and stress vector field during the injection of a conventional injection needle, a proposed highly focused microjet (tip diameter much smaller than capillary nozzle), and a typical non-focused microjet in gelatin were measured using a state-of-the-art high-speed polarization camera, at a frame rate up to 25,000 f.p.s. During the needle injection performed by an experienced nurse, high stress intensity lasted for an order of seconds (from beginning of needle penetration until end of withdrawal), which is much longer than the order of milliseconds during needle-free injections, causing more damage to the body tissue. The cavity induced by focused microjet resembled a funnel which had a narrow tip that penetrated deep into tissue simulant, exerting shear stress in low intensity which diffused through shear stress wave. Whereas the cavity induced by non-focused microjet rebounded elastically (quickly expanded into a sphere and shrank into a small cavity which remained), exerting compressive stress on tissue simulant in high stress intensity. By comparing the distribution of stress intensity, tip shape of the focused microjet contributed to a better performance than non-focused microjet with its ability to penetrate deep while only inducing stress at lower intensity. Dynamic mechanical interaction revealed in this research uncovered the importance of the jet shape for the development of minimally invasive medical devices.

Degradation study on molecules released from laser-based jet injector

Development of needle-free methods to administer injectable therapeutics has been researched for a few decades. We focused our attention on a laser-based jet injection technique where the liquid-jet actuation mechanism is based on optical cavitation. This study investigates the potential damage to therapeutic molecules which are exposed to nanosecond laser pulses in the configuration of a compact laser-based jet injection device. Implementation of a pulsed laser source at 1574 nm wavelength allowed us to generate jets from pure water solutions and circumvent the need to reformulate therapeutics with absorbing dyes. We performed H1-NMR analysis on exposed samples of Lidocaine and δ-Aminolevulinic acid. We made several tests with linear and plasmid DNA to assess the structural integrity and functional potency after ejection with our device. The tests showed no significant degradation or detectable side products, which is promising for further development and eventually clinical applications.

Miniaturized Needle Array-Mediated Drug Delivery Accelerates Wound Healing

A major impediment preventing normal wound healing is insufficient vascularization, which causes hypoxia, poor metabolic support, and dysregulated physiological responses to injury. To combat this, the delivery of angiogenic factors, such as vascular endothelial growth factor (VEGF), has been shown to provide modest improvement in wound healing. Here, the importance of specialty delivery systems is explored in controlling wound bed drug distribution and consequently improving healing rate and quality. Two intradermal drug delivery systems, miniaturized needle arrays (MNAs) and liquid jet injectors (LJIs), are evaluated to compare effective VEGF delivery into the wound bed. The administered drug's penetration depth and distribution in tissue are significantly different between the two technologies. These systems' capability for efficient drug delivery is first confirmed in vitro and then assessed in vivo. While topical administration of VEGF shows limited effectiveness, intradermal delivery of VEGF in a diabetic murine model accelerates wound healing. To evaluate the translational feasibility of the strategy, the benefits of VEGF delivery using MNAs are assessed in a porcine model. The results demonstrate enhanced angiogenesis, reduced wound contraction, and increased regeneration. These findings show the importance of both therapeutics and delivery strategy in wound healing.

Challenges and opportunities for small volumes delivery into the skin

Each individual's skin has its own features, such as strength, elasticity, or permeability to drugs, which limits the effectiveness of one-size-fits-all approaches typically found in medical treatments. Therefore, understanding the transport mechanisms of substances across the skin is instrumental for the development of novel minimal invasive transdermal therapies. However, the large difference between transport timescales and length scales of disparate molecules needed for medical therapies makes it difficult to address fundamental questions. Thus, this lack of fundamental knowledge has limited the efficacy of bioengineering equipment and medical treatments. In this article, we provide an overview of the most important microfluidics-related transport phenomena through the skin and versatile tools to study them. Moreover, we provide a summary of challenges and opportunities faced by advanced transdermal delivery methods, such as needle-free jet injectors, microneedles, and tattooing, which could pave the way to the implementation of better therapies and new methods.