Tissue reaction to jet injection

Jet-induced Tissue Disruption for Blood Release

OBJECTIVE

Needle free jet injection is a drug delivery technique that uses the momentum of the fluid drug to break through the skin. This technique has recently also been applied to blood release, aiming to collect samples from capillaries in the skin without needing a lancet prick. This work provides new information about the wound geometry and tissue disruption caused by shallow jet injection with circular shaped and slot shaped jets.

METHODS

We use histological analysis to compare the disruption of tissue, including blood vessels, caused by lancet-pricking and jet injection with a circular shaped jet and a lancet-inspired slot shaped jet.

RESULTS

Intradermal injection into porcine skin using a slot shaped jet disrupted more vascular endothelium in the tissue than a circular shaped jet and did so at a smaller penetration depth with smaller wound volume. Our results suggest that shallow jet injections may have the potential to release more capillary blood than a lancet prick.

CONCLUSION

These findings demonstrate that a reversible jet injector might be used in diabetes management as a device to release and collect blood samples, in addition to being used to deliver insulin.

SIGNIFICANCE

Tissue disruption is crucial to consider when using jet injection to deliver drug and release capillary blood.

Blood Collection from The Porcine Ear Using a Jet Injector. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020;2020:5119-5123. [PMID: 33019138 DOI: 10.1109/embc44109.2020.9175421]

We present a new lancet-free method of capillary blood collection for the measurement of blood glucose concentration using a needle-free jet injector. This technique is tested on living animals and directly compared to the current best practice, lancet prick. Shallow jet injection into porcine outer-ear was performed using a portable needle-free jet injector with a slot-shaped nozzle. The jet injections presented used about 25 µL of injectate to penetrate porcine skin to about 1.4 mm, which is within the WHO standards for capillary blood sampling. The blood and fluid released by the jet injections and lancet pricks was collected. The volume and colour of these samples were analysed. The results demonstrate that jet injection is a feasible technique for the collection of capillary blood, despite the small volume of blood samples retrieved from all four pigs. Jet injection may be used in the future to retrieve capillary blood samples from human fingertips.

Jet-induced skin puncture and its impact on needle-free jet injections: experimental studies and a predictive model

Needle-free jet injections constitute an important method of drug delivery, especially for insulin and vaccines. This report addresses the mechanisms of interactions of liquid jets with skin. Liquid jets first puncture the skin to form a hole through which the fluid is deposited into skin. Experimental studies showed that the depth of the hole significantly affects drug delivery by jet injections. At a constant jet exit velocity and nozzle diameter, the hole depth increased with increasing jet volume up to an asymptotic value and decreased with increasing values of skin's uniaxial Young's modulus. A theoretical model was developed to predict the hole depth as a function of jet and skin properties. A simplified model was first verified with polyacrylamide gels, a soft material in which the fluid mechanics during hole formation is well understood. Prediction of the hole depth in the skin is a first step in quantitatively predicting drug delivery by jet injection.

New Way to Deliver Fluids: Endoscopic Jet Injection Into the Beagle Prostate

PURPOSE

Local therapy of the prostate could have a role in the treatment of benign prostatic hyperplasia as well as prostate cancer. Endoscopic jet injection could simplify these treatments. We evaluated the tissue effects of endoscopic jet injection in an animal model.

MATERIALS AND METHODS

An endoscopic jet injector was developed. In 12 beagle dogs the prostate was injected with single shot and continuous mode jet injection. Macroscopic and histological analysis was performed 0, 2 and 14 days after jet injection.

RESULTS

Jet injection allowed complete penetration of the beagle prostate. The single shot technique resulted in only minimal tissue effects. However, the continuous mode led to major tissue damage, even complete aseptic necrosis, in the injected area.

CONCLUSIONS

A new method for endoscopic application of fluids is described. Depending on the jet injection technique it could be used to apply pharmaceutical agents or plasmids, and/or induce aseptic necrosis.

Transdermal drug delivery by jet injectors: energetics of jet formation and penetration

PURPOSE

Pressure-driven jets have been used for intradermal delivery of a variety of drugs. Despite their introduction into clinical medicine, variability and occasional bruising have limited their widespread acceptance. Although numerous clinical studies of jet injectors have been reported in the literature, surprisingly little is known about the mechanisms of jet penetration into the skin. In this article, we report results of our studies aimed at determining the dependence of drug delivery on jet velocity and diameter. These studies were performed using two experimental models, porcine skin and human skin. Our rationale for using two models was to explore the possibility of using porcine skin as a model for human skin.

METHODS

Dermal penetration of jets possessing a range of diameters from 76 microm to 559 microm and a range of velocities from 80 m/s to 190 m/s was studied into human and porcine skin. Penetration was quantified using radiolabeled mannitol. Pressure and velocity of the jets were measured using a calibrated pressure transducer and high-speed photography.

RESULTS

Penetration of the jet into the skin was determined by two main parameters, jet diameter and average jet velocity. Substantial variation in jet penetration into porcine skin was observed for skin pieces obtained from different anatomic locations. For porcine skin, a parabolic dependence of jet delivery on velocity and diameter was observed. The threshold velocity is suggested to be between 80 and 100 m/s for a jet diameter of 152 microm. Above the threshold velocity, the delivery increased for velocities up to 150 m/s, after which delivery decreased with increasing velocity. At a constant velocity of 150 m/s, jet delivery exhibited a maximum at a diameter of 152 microm. Results obtained with human skin were qualitatively similar but quantitatively different. The threshold velocity for jet penetration into human skin was comparable with that in porcine skin; however, the maxima observed in jet delivery into porcine skin with respect to jet velocity was not apparent for human skin over the range of velocities explored.

CONCLUSIONS

These studies offer a quantitative analysis of jet penetration into the skin.

Safety, tolerability, and lack of antibody responses after administration of a PfCSP DNA malaria vaccine via needle or needle-free jet injection, and comparison of intramuscular and combination intramuscular/intradermal routes

Introduction of a new vaccine requires choosing a delivery system that provides safe administration and the desired level of immunogenicity. The safety, tolerability, and immunogenicity of three monthly 2.5-mg doses of a PfCSP DNA vaccine were evaluated in healthy volunteers as administered intramuscularly (IM) by needle, IM by jet injection (Biojector or IM/intradermally (ID) by jet injection. Vaccine administration was well-tolerated. Adverse events were primarily mild and limited to the site of injection (98%). Jet injections (either IM or ID) were associated with approximately twice as many adverse events per immunization as needle IM, but nevertheless were strongly and consistently preferred in opinion polls taken during the study. No volunteers had clinically significant biochemical or hematologic changes or detectable anti-dsDNA antibodies. In conclusion, the injection of Plasmodium falciparum circumsporozoite (PfCSP) DNA vaccine appeared to be safe and well-tolerated when administered by any of the three modes of delivery. However, despite improved antibody responses following both jet injection and ID delivery in animal models, no antibodies could be detected in volunteers by immunofluorescence antibody test (IFAT) or enzyme-linked immunosorbent assay (ELISA) after DNA vaccination.

The efficacy and acceptability of using a jet injector in performing digital blocks

This prospective, nonblinded study, comparing jet injection with needle-syringe injection of lidocaine in performing digital blocks, tested the hypothesis that jet injection can be used effectively as a less painful way to perform digital blocks. Twenty-four adult patients with injuries of the middle or distal phalanges of the fingers received digital blocks using a jet injector on one side of the finger and a needle-syringe on the other side; pain was assessed at 0, 1, 3, 6, 12, and 24 hours using visual analog scales. Differences in pain scores for the two procedures (jet injector vs needle) were tested at each time period using nonparametric statistical procedures for paired or matched data (paired Wilcoxon). At the time of injection (time 0) and at 12 hours, the jet had a significantly lower pain score than the needle. Comparisons made at the other points were statistically nonsignificant at .05. The anesthesia achieved using the jet injector was considered adequate in 23 of 24 patients. We conclude that the jet injector can be used effectively in performing digital blocks and is less painful than standard needle-syringe methods.

Application of a versatile instrument for production of cutaneous anesthesia without needle penetration of the skin

A self-contained jet injector, the Syrjet Mk II, can be used for needleless injection of anesthetic agents into the skin and subcutaneous tissues. Although designed for dental use, its compact size, simplicity, and versatility make it suited for many medical applications where a relatively small anesthetic field is desired, especially in children. It provides an anesthetic area for the introduction of standard hypodermic needles for more extensive tissue infiltration, or for definitive anesthesia for procedures such as marrow aspiration, biopsies, small lesion excision, and in certain field blocks such as digital or facial sensory. It is significantly free of side effects and complications.