The effect of jet speed on large volume jet injection

Jet injection presents a promising alternative to needle and syringe injection for transdermal drug delivery. The controllability of recently-developed jet injection devices now allows jet speed to be modulated during delivery, and has enabled efficient and accurate delivery of volumes up to 0.3 mL. However, recent attempts to inject larger volumes of up to 1 mL using the same methods have highlighted the different requirements for successful delivery at these larger volumes. This study aims to establish the jet speed requirements for delivery of 1 mL of liquid using a controllable, voice coil driven injection device. Additionally, the effectiveness of a two-phase jet speed profile is explored (where jet speed is deliberately decreased toward the end of the injection) and compared to the constant jet speed case. A controllable jet injection device was developed to deliver volumes of 1 mL of liquid at jet speeds >140 m/s. This device was used to deliver a series of injections into post-mortem porcine tissue in single and two-phase jet speed profiles. Single-phase injections were performed over the range 80 m/s to 140 m/s. Consistent delivery success (>80% of the liquid delivered) was observed at a jet speed of 130 m/s or greater. Consistent penetration into the muscle layer coincided with delivery success. Two-phase injections of 1 mL were performed with a first phase volume of 0.15 mL, delivered at 140 m/s, while the injection of the remainder of fluid was delivered at a second phase speed that was varied over the range 60 m/s to 120 m/s. Ten two-phase injections were performed with a second phase speed of 100 m/s producing a mean delivery volume of 0.8 mL ± 0.2 mL, while the single-phase injections at 100 m/s achieved a mean delivery volume of 0.4 mL ± 0.3 mL. These results demonstrate that a reduced jet speed can be used in the later stages of a 1 mL injection to achieve delivery success at a reduced energy cost. We found that a jet speed approaching 100 m/s was required following initial penetration to successfully deliver 1 mL, whereas speeds as low as 50 m/s have been used for volumes of <0.3 mL. These findings provide valuable insight into the effect of injection volume and speed on delivery success; this information is particularly useful for devices that have the ability to vary jet speed during drug delivery.

Delivery of immunoreactive antigen using a controllable needle-free jet injector

Intradermal immunization of mice against hepatitis B surface antigen (HBsAg) using a novel real-time controlled jet injector was assessed by comparison with intradermal and subcutaneous injection of antigen using a 27G needle and syringe. Three doses of aluminium-absorbed HBsAg were delivered at 0, 14, and 28days. Antibodies to HBsAg were detected only in mice injected with antigen with antibody levels increasing with secondary injections. Mice vaccinated by intradermal injection using the jet injector or subcutaneous needle injection exhibited comparable immune responses at day 47. Differences in titer observed between intradermal jet injected and needle injected animals reflect differences in the volume of antigen delivered. With the exception of minor bleeding at the injection site in a few animals injected either by jet injection or needle, no adverse events were observed in any of the mice used in the study.

Comparison of jet injector and insulin pen in controlling plasma glucose and insulin concentrations in type 2 diabetic patients

This study is conducted to investigate efficacy of an insulin jet injector and an insulin pen in treatment of type 2 diabetic patients. Sixty patients with type 2 diabetes were treated with rapid-acting insulin (regular insulin) and insulin analog (insulin aspart) using the jet injector and the pen in 4 successive test cycles. Postprandial glucose and insulin concentrations in blood were measured over time. Areas under curves of glucose and the insulin were calculated, and efficacy of 2 injection methods in treatment of the diabetes was compared. Regular insulin and insulin aspart administration by the jet injector showed significant decreases in plasma glucose levels as compared to the pen injection (P < 0.05). Postprandial plasma glucose excursions at the time points of 0.5 to 3 hours were obviously lower in the jet-treated patients than the pen-treated ones (P < 0.05). Postprandial plasma insulin levels were markedly higher in the jet-treated patients than the pen-treated ones (P < 0.05). Area under the glucose curve in the pen-treated patients was significantly increased as compared to the jet-treated ones (P < 0.01). Efficacy of the insulin jet injector in treatment of type 2 diabetic patients is obviously superior to the insulin pen in regulating plasma glucose and insulin levels.

A device for controlled jet injection of large volumes of liquid

We present a needle-free jet injection device controllably actuated by a voice coil and capable of injecting up to 1.3 mL. This device is used to perform jet injections of ~900 μL into porcine tissue. This is the first time that delivery of such a large volume has been reported using an electronically controllable device. The controllability of this device is demonstrated with a series of ejections where the desired volume is ejected to within 1 % during an injection at a predetermined jet velocity.

Optimization of drug viscosity used in gas-powered liquid jet injectors

This paper describes the effect of drug viscosity on the performance of gas powered liquid jet injectors. The analysis is accomplished utilizing a Computational Fluid Dynamics (CFD) model that obtains the stagnation pressure at the nozzle outlet. The technique is based on previous work used to predict gas power driven injector piston velocity with time. The results depict the variation in average and peak injector stagnation pressure for three different driven pressures; driving injections which vary from 0.2 cP to 87 cP in viscosity. Furthermore, a numerical representation of jet shape is also obtained to verify the effect of viscosity on jet geometry. These results demonstrate that increasing viscosity by 10 times that of water produces only a slight decrease in injector stagnation pressure and produces jets with greater confinement, which will display better characteristics for puncturing the skin.

Jet injection of a monoclonal antibody: A preliminary study

Monoclonal antibodies (mAbs) represent a major group of biotherapeutics. The high concentration and volume of drug administered together with a shift to administration via the subcutaneous route have generated interest in alternative delivery technologies. The feasibility of using a novel, highly controllable jet injection technology to deliver a mAb is presented. The effect of delivery parameters on protein structure were evaluated and compared with delivery using a conventional needle and syringe. Injection of mAb into a rat model showed that jet injection using the device resulted in more rapid absorption and longer duration of exposure.

Adaptive controller for a needle free jet-injector system

A nonlinear, sliding mode adaptive controller was created for a needle-free jet injection system. The controller was based on a simplified lumped-sum parameter model of the jet-injection mechanics. The adaptive control scheme was compared to a currently-used Feed-forward+PID controller in both ejection of water into air, and injection of dye into ex-vivo porcine tissue. The adaptive controller was more successful in trajectory tracking and was more robust to the biological variations caused by a tissue load.

A compound ampoule for large-volume controllable jet injection

We present a new design for a needle-free injector ampoule, using two concentric pistons to pressurize the fluid during the injection. The smaller, inner piston is used to provide an initial high-velocity piercing jet; it then engages the outer piston to deliver the remaining drug via a low-velocity jet. The goal of this design is to enable needle-free delivery of relatively large volumes to controlled depths in tissue, a task impractical with conventional ampoules and actuators. We demonstrate this concept by constructing a 1.2mL ampoule, measuring the jet velocity it produces in free air, and performing a set of injections into post-mortem porcine tissue. The ampoule smoothly produces the two desired phases of an injection, with a smooth transition of jet velocity as the two pistons engage. The injection is able to penetrate porcine skin to a controlled depth and deliver fluid to the subcutaneous and/or intramuscular layers, though further investigation is required to ensure that all of the fluid delivered can be retained at the desired depth.

The effect of jet shape on jet injection

The effects of the dispersion pattern of a needle-free jet injector are explored. The shape of the jets were compared using a high-speed video camera and jet injections of collimated and dispersed fluid jets with a Lorentz-force actuated jet injector were made into acrylamide gel and post-mortem porcine tissue. A custom-built high-speed X-ray imaging system was used in order to observe the dynamics of the dispersion mechanism for each injection in real time. We show that a collimated jet stream results in greater tissue penetration than a dispersed jet stream.

Optimal voice coil actuators for needle-free jet injection

We present a scaling model for electrically-actuated needle free jet injectors, establishing the relationship between injection volume and motor size. Using an analytical electromagnetic model for the motor, we derive an optimal motor design, and show that this design is approximately scale-invariant. To illustrate the utility of this model, we then describe the design of a motor for use with 300 μL disposable injection ampoules with a mass of just 300 g, including a light-weight support structure. Experimental verification of the motor performance shows close agreement to model predictions, with a peak force of 1000 N/kg and a 150 m/s water jet delivered.

Needle-free interstitial fluid acquisition using a Lorentz-force actuated jet injector

The feasibility of a new method of quickly acquiring interstitial fluid (ISF) samples using a Lorentz-force actuated needle-free jet injector is demonstrated on ex vivo porcine tissue. The jet injector is used to first inject a small volume of physiological saline to breach the skin, and the back-drivability of the actuator is utilized to create a vacuum in the ampoule and collect ISF. Injection and extraction parameters are tested and optimized for minimal acquired sample dilution and extracted volume consistency. Using this method, we are able to collect a sample that contains up to 3.5% ISF in 3.1 s.

Intradermal needle-free powdered drug injection by a helium-powered device

We present a new method for needle-free powdered drug injection via a bench-top gas-powered device. This injector provides an alternative method of vaccine delivery to address the cold chain problem--the cost and risk of transporting temperature sensitive vaccines to developing countries. The device houses interchangeable nozzle inserts to vary orifice geometries and is capable of delivering polymer beads (1-5 µm diameter) into the dermal layer of porcine tissue. Results for injection shape and injection depth versus nozzle orifice diameter demonstrate the device's controllability.

Experimental analysis of the performance of an air-powered needle-free liquid jet injector

An experimental study was performed using a custom-built air-powered needle-free injector to investigate the various injector parameters governing the dynamics of jet injection. A parametric study using five different nozzle sizes at driver pressure ranging from 4 to 8 bar was carried out. The fluid stagnation pressure of the liquid jet was determined using a Honeywell force sensor. Performance plots as a function of various parameters were constructed. It was determined that as the driver pressure increased both the peak and average stagnation pressure increased almost linearly within the operating range considered. Varying the injection nozzle diameter, whilst keeping the driver pressure constant did not have any significant impact on the peak or average stagnation pressure. The chamber length was also varied and no significant influence was found on peak or average stagnation pressure.

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

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.

Patient device assessment evaluation of two insulin injection devices in a mixed cohort of insulin-treated patients with type 1 or type 2 diabetes mellitus

OBJECTIVE

FT (FlexTouch*) is a new disposable insulin injection pen device for use in insulin-treated patients with diabetes mellitus. The aim of this study was to evaluate patient perception of FT versus IL (InnoLet†) with respect to the ease of use and patient preference in a mixed patient cohort with different kinds and degrees of visual or dexterity impairments.

METHODS

Ninety patients were included into this investigation (54 male/36 female, age [mean ± SD]: 62 ± 8 yrs, disease duration: 18 ± 11 yrs, HbA1c: 7.2 ± 1.0%). After assessment of visual acuity and dexterity skills (by Jebsen-Taylor Hand Function Test), the patients were introduced to the two pen devices in random order, and were asked to perform mock injections with 10 IU, 30 IU and 50 IU doses before completing a 41 item standardized device assessment questionnaire. The questions asked were covering five topics of pen use (confidence in delivering a correct dose, dose setting, performance of the injection, general handling, and others) and could be answered with a rank scale from '1 = very easy' to '5 = very difficult'.

RESULTS

FT was ranked superior to IL with respect to the injection procedure (FT: 1.2 ± 0.1 vs. IL: 2.1 ± 0.4, p < 0.001) and general handling (1.3 ± 0.2 vs. 2.3 ± 0.7, p < 0.001), and numerically better with respect to confidence in correct dosing (1.4 ± 0.2 vs. 2.1 ± 0.9, n.s.). The two devices were ranked equally for ease of dose setting (1.6 ± 0.3 vs. 1.7 ± 0.4, n.s.). When ranked individually, FT use was recommended by 92.2% of the patients (IL: 30.0%).

KEY LIMITATIONS

Patients of this investigation were from one local area (San Jose, CA, USA) only. The subgroups may be considered small for the performed analysis.

CONCLUSIONS

In summary, FT was perceived to be easier to use than IL in this investigation.

Glycemic control, reported pain and leakage with a 4 mm × 32 G pen needle in obese and non-obese adults with diabetes: a post hoc analysis

OBJECTIVE

The shortest pen needle (PN) for subcutaneous insulin therapy is 4 mm. Clinicians may hesitate to use it in obese patients. We report a post hoc analysis of a previously published study of the 4 mm × 32 G PN, evaluating responses in obese (≥30 kg/m(2)) and non-obese (<30 kg/m(2)).

METHODS

Subjects (BMI 20 to 49 kg/m(2), 52% obese) with diabetes used 4 mm × 32 G PNs and either 5 mm or 8 mm PNs (both 31 G) in two, 3-week treatment periods in a randomized noninferiority cross-over trial. Percentage absolute change in fructosamine (%│Δ Fru│) was the primary endpoint. Equivalent glycemic control was defined as %│Δ Fru│ within 20% (including 95% CI). The impact of obesity on change in fructosamine, pain and reported insulin leakage from the skin is described.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov - identifier: NCT00928057.

LIMITATIONS

This report is a post hoc analysis of two BMI subgroups resulting in smaller sample sizes.

RESULTS

Of 168 who completed the study, 163 were included in the fructosamine analyses - 83 and 80 in the 4/5 mm and 4/8 mm groups, respectively. For the 4/5 mm group, mean BMI ± SD in non-obese and obese groups were 25.9 ± 2.3 and 35.0 ± 4.9 kg/m(2), respectively; 4/8 mm group 25.2 ± 2.6 and 35.6 ± 4.2 kg/m(2). BMI group was not significant for %│Δ Fru│ for either 4/5 mm or 4/8 mm. Between BMI groups, the difference of the means in %│Δ Fru│ was 0.4% (4/5 mm) and 0.3% (4/8 mm). The 4 mm PN was significantly less painful in all subject groups, except non-obese in 4/5 mm. Regardless of needle size, obese subjects reported more leakage events. For both BMI groups, there were fewer total reported leakage events when using the 4 mm vs 5 mm and 8 mm needles.

CONCLUSIONS

The 4 mm pen needle provided equivalent glycemic control in both obese and non-obese patients compared to 5 mm and 8 mm needles with no increase in reports of skin leakage, in this post-hoc analysis. These findings should be confirmed in a prospective randomized controlled trial.

Development of a Lorentz-force actuated intravitreal jet injector

Intravitreal injection is a common treatment in ophthalmology, but it can lead to numerous complications. Needle-free jet injection has been shown to successfully deliver fluid to various layers of skin, and, by its nature, may reduce intravitreal injection complications. From injection trials into ex vivo rabbit eyes, we find that needle-free jet injection can be used for intravitreal drug delivery. A custom-designed control scheme, characterized in this study, is crucial to this delivery. The system is capable of delivering 40 µL of fluid to the posterior vitreous humor, with an injection duration less than 100 ms and scleral entry site less than 350 µm in diameter.

A computational model of a controllable needle-free jet injector

We present a mathematical model of the dynamics of a previously developed needle-free jet injector (NFJI) that is based upon a servo-controlled Lorentz-force motor. The injector creates a fluid jet that can pierce through the skin and deliver a drug to dermal, subcutaneous and muscular tissue. We use the model to predict the jet speed achieved during an injection. The model simulates the electrical response of the motor coil, the mechanical response of the drug piston and ampoule and the friction incident upon the piston during the time course of the injection. High-speed video measurements of piston movement in response to a step input show that the model predicts piston-tip position during an injection within an RMS error of 287 µm. The corresponding jet speed is predicted to be 180 m·s(-1) with a maximum overshoot to 205 m·s(-1).

Compatibility testing of two types of pen needles with a range of injection pens for diabetes medication

Compatibility of two types of needles with a variety of durable and prefilled injection pens for diabetes medication was tested by attaching the needles according to ISO 11608-2 and verifying penetration into the cartridge using air shots and two-dimensional X-rays. NovoFine* and NovoFine Autocover† attached correctly to 20 and 19 out of 21 pen types, respectively. Neither needle type attached to Diapen 3.1/3.2, while NovoFine Autocover attached to most, but not all of OptiSet pens.

[Development of a novel liquid injection system]

A liquid jet injector employs compressed gas or spring to produce a high-velocity stream to deliver liquid drug into human body through skin. There are many clinical jet injection products available, none of which is domestic. A new liquid jet injector is designed based on a comprehensive analysis of the current products. The injector consists of an ejector, trigger and a re-positioning mechanism. The jets characteristics of sample injector are tested, and the results show that the maximum exit pressure is above 15 MPa, a threshold value for penetrating into the skin.

[The evaluation of mechanical performance of a jet injection system]

In this study, the mechanical properties of a self-made jet injector and a foreign product are tested from three aspects: penetration ability, injection completeness and injection dispersion. Correspondingly, three different experiments are designed and performed: dynamic pressure measurement, injection into silicon rubbers with fixed hardness yet different thickness and injection into polyacrylamide gels with fixed hardness. The results show similar mechanical properties between self-made system and the foreign system. The evaluation of the mechanical performance of jet injectors that consists of penetration ability, injection completeness and injection dispersion can describe the jet injection process effectively.

What stands in the way of treating palmar hyperhidrosis as effectively as axillary hyperhidrosis with botulinum toxin type A

Botulinum Toxin type A (BTX-A) has revolutionized the treatment of focal hyperhidrosis (HH) in recent years and has dramatically reduced the invasive surgical techniques that have been performed in the past to control severe focal HH unresponsive to topical therapies. Whereas BTX-A injections are easily performed to control axillary HH with little or no analgesia, pain management is a must during the injection of palmar and plantar HH with BTX-A because of the intense pain generated with the 30 to 40 needle punctures needed on each hand or foot through the densely innervated skin present in those areas. For that reason, many physicians who contentedly treat axillary HH with BTX-A injections, refuse to do so for palmar and plantar HH. Although pain is the major stumbling block deterring patients and physicians from choosing this treatment option, it is not the only one. Many other factors may play a role in deciding whether or not to treat palmar and plantar HH with BTX-A injections. This article reviews these factors and presents some personal data from patients who have already been treated with BTX-A injections on the palms and soles and who came back once or more for repeat treatments when the effect of BTX-A started to fade away. "Jet Anesthesia" was the pain management method used in this group.

Dermal and Transdermal Drug Delivery Systems: Current and Future Prospects

The protective function of human skin imposes physicochemical limitations to the type of permeant that can traverse the barrier. For a drug to be delivered passively via the skin it needs to have adequate lipophilicity and also a molecular weight <500 Da. These requirements have limited the number of commercially available products based on transdermal or dermal delivery. Various strategies have emerged over recent years to optimize delivery and these can be categorized into passive and active methods. The passive approach entails the optimization of formulation or drug carrying vehicle to increase skin permeability. Passive methods, however do not greatly improve the permeation of drugs with molecular weights >500 Da. In contrast active methods that normally involve physical or mechanical methods of enhancing delivery have been shown to be generally superior. Improved delivery has been shown for drugs of differing lipophilicity and molecular weight including proteins, peptides, and oligonucletides using electrical methods (iontophoresis, electroporation), mechanical (abrasion, ablation, perforation), and other energy-related techniques such as ultrasound and needless injection. However, for these novel delivery methods to succeed and compete with those already on the market, the prime issues that require consideration include device design and safety, efficacy, ease of handling, and cost-effectiveness. This article provides a detailed review of the next generation of active delivery technologies.

Short communication safety, tolerability and pharmacokinetics of enfuvirtide administered by a needle-free injection system compared with subcutaneous injection

BACKGROUND

Injection site reactions (ISRs) can present a challenge to patients when using enfuvirtide (ENF). This study compared ISRs associated with use of a needle-free injection device (NFID) with those associated with a standard 27-gauge half-inch needle/syringe (NS).

METHODS

In this single-blind, crossover study, 58 ENF-naive participants were randomized to self-administer ENF with the NFID for 4 weeks (followed by 4 weeks using NS) or with the NS for 4 weeks (followed by 4 weeks using the NFID). A primary composite endpoint of painful ISR was defined as the combination of grade 1-3 ongoing pain plus either associated grade 3-4 (> or =25 mm) induration or grade 2-4 nodules/cysts (>20 mm). An ISR summary score described ISR frequency/severity. Self-reported device preference was also evaluated at baseline and at study completion.

RESULTS

Fewer participants using NFID experienced the primary composite endpoint of painful ISRs (10/28; 35.7%) compared with NS (20/28; 71.4%) (P=0.004). There was a trend towards a reduced incidence/severity of ISR signs and symptoms with NFID, with significant reductions seen in pain/discomfort and pruritus (P<0.05 and P<0.01, respectively). At the end of the study, most participants (22/25; 88%) expressed a preference for NFID. Haematoma was the sole NFID-related serious adverse event, but this did not lead to discontinuation.

CONCLUSIONS

Compared with a standard NS, use of an NFID to administer ENF was associated with a substantially lower incidence of painful ISRs, was generally safe and well-tolerated, and was preferred by most participants in the study.

Optimization of a jet-propelled particle injection system for the uniform transdermal delivery of drug/vaccine

A jet-propelled particle injection system, the biolistics, has been developed and employed to accelerate micro-particles for transdermal drug delivery. We have examined a prototype biolistic device employing a converging-diverging supersonic nozzle (CDSN), and found that the micro-particles were delivered with a wide velocity range (200-800 m/s) and spatial distribution. To provide a controllable system for transdermal drug delivery, we present a contoured shock-tube (CST) concept and its embodiment device. The CST configuration utilizes a quasi-steady, quasi-one dimensional and shock-free supersonic flow to deliver the micro-particles with an almost uniform velocity (the mean velocity and the standard deviation, 699 +/- 4.7 m/s) and spatial distribution. The transient gas and particle dynamics in both prototype devices are interrogated with the validated computational fluid dynamics (CFD) approach. The predicted results for static pressure and Mach number histories, gas flow structures, particle velocity distributions and gas-particle interactions are presented and interpreted. The implications for clinical uses are discussed.

[Needle-free injection--science fiction or comeback of an almost forgotten drug delivery system?]

The first to create a "needle-free injector" was the American anesthetist Robert A. Hingson, 65 year ago. Since that time those devices underwent a changeful history. In 1986 an outbreak of hepatitis B among patients receiving injections from a needle-free multiple-use-nozzle injector was documented and related to the use of the injector device. Due to such risk of transmission of infection with these reusable devices, their application has been restricted. In 1998 the WHO recommended that only conventional needles and syringes should be used for immunization until safe needle-free injectors are identified through independent safety testing. Since needle-free injection has shown numerous advantages in comparison to conventional injection, new systems were developed that combine the advantages of needle-free injection with sufficient safety in mass vaccination programs. As an alternative to this early injector type, the disposable-cartridge injectors were developed. The newest research field in the area of the needle-free injection systems opened with the development of powder injectors, in which the drug preparation is no longer a suspension or solution, but a powdered solid. This injector type using powder formulations shows a number of advantages in comparison with the conventional needle/syringe injection technique as well as towards the liquid jet injectors. Due to this new kind of injectors the comeback of the needle-free injection technique in large-scale vaccination programs of the WHO seems reasonable and within reach.

Intracellular targeting of CEA results in Th1-type antibody responses following intradermal genetic vaccination by a needle-free jet injection device

The route and method of immunization, as well as the cellular localization of the antigen, can influence the generation of an immune response. In general, intramuscular immunization results in Th1 responses, whereas intradermal delivery of DNA by gene gun immunization often results in more Th2 responses. Here we investigate how altering the cellular localization of the tumor antigen CEA (carcinoembryonic antigen) affects the quality and amplitude of DNA vaccine-induced antibody responses in mice following intradermal delivery of DNA by a needle-free jet injection device (Biojector). CEA was expressed either in a membrane-bound form (wild-type CEA) or in two truncated forms (CEA6 and CEA66) with cytoplasmic localization, where CEA66 was fused to a promiscuous T-helper epitope from tetanus toxin. Repeated intradermal immunization of BALB/c mice with DNA encoding wild-type CEA produced high antibody titers of a mixed IgG1/IgG2a ratio. In contrast, utilizing the DNA construct that resulted in intracellular targeting of CEA led to a reduced capacity to induce CEA-specific antibodies, but instead induced a Th1-biased immune response.

The Effects of System Parameters on In Vivo Injection Performance of a Needle-Free Injector in Human Volunteers

PURPOSE

For a novel needle-free injection (NFI) system, the relationship between frequency of wet or incomplete injections and device-related factors and subject physiological variables was examined.

MATERIALS AND METHODS

A total of 26 device configurations of a single-use pre-filled NFI system (Intraject) were used to deliver a total of 3,211 subcutaneous injections into the abdomen of 302 healthy volunteers. Two validated methods were used to determine completeness of each injection (defined as >or=90% dose delivery). Skin-fold thickness, body mass index (BMI), Fitzpatrick skin type, sex, age, and injection site were noted for each volunteer.

RESULTS

The proportion of complete injections ranged from 59-98% among the various combinations of device configurations. Two device parameters and two subject-related variables showed strong association with injection performance; Device gas mass (chamber pressure) and orifice size demonstrated statistically significant, independent effects, with increasing gas mass and larger orifice size associated with improved injection performance. BMI and site of injection on the abdomen also demonstrated statistically significant effects with increasing BMI and lateral rather than medial injection sites associated with better injections.

CONCLUSION

Both device-related factors and subject variables interact to mediate in vivo performance of a needle-free injector.

Needle-free delivery of macromolecules across the skin by nanoliter-volume pulsed microjets

Needle-free liquid jet injectors were invented >50 years ago for the delivery of proteins and vaccines. Despite their long history, needle-free liquid jet injectors are not commonly used as a result of frequent pain and bruising. We hypothesized that pain and bruising originate from the deep penetration of the jets and can potentially be addressed by minimizing the penetration depth of jets into the skin. However, current jet injectors are not designed to maintain shallow dermal penetration depths. Using a new strategy of jet injection, pulsed microjets, we report on delivery of protein drugs into the skin without deep penetration. The high velocity (v >100 m/s) of microjets allows their entry into the skin, whereas the small jet diameters (50-100 mum) and extremely small volumes (2-15 nanoliters) limit the penetration depth ( approximately 200 mum). In vitro experiments confirmed quantitative delivery of molecules into human skin and in vivo experiments with rats confirmed the ability of pulsed microjets to deliver therapeutic doses of insulin across the skin. Pulsed microjet injectors could be used to deliver drugs for local as well as systemic applications without using needles.

Selective fluid cushion in the submucosal layer by water jet: advantage for endoscopic mucosal resection

BACKGROUND/AIM

Numerous new techniques have recently been reported and described for the endoscopic mucosal resection of large superficial lesions of the gastrointestinal tract. We present here for the first time the application of a water jet dissector for mucosa elevation.

MATERIALS AND METHODS

In an ex vivo study, the effectiveness of a water jet dissector (Helix Hydro-Jet) placed directly on the stomach walls of 8 pigs was examined to create a mucosal elevation. After having determined optimal pressures, angle of application, and application times, 13 submucosal fluid cushions were produced in different areas of the stomach walls of 8 pigs in vivo, and the sizes of the resulting submucosal cushions were measured.

RESULTS

Using pressures between 30 and 70 bar, it was routinely possible to create submucosal fluid cushions in the stomach wall ex vivo as well as in vivo. Histological examination showed a selective edema in the submucosa without damage to the deeper mucosal layers of the gastric wall.

CONCLUSIONS

The capacity of a targeted high-pressure water jet to penetrate the mucosa and selectively create a fluid cushion in the submucosa facilitates endoscopic resection of the mucosa. This new method could contribute to ameliorate the endoscopic treatment of mucosal tumors which previously could not be resected endoscopically due to their size, extent, or location.

Needle-free liquid jet injections: mechanisms and applications

Liquid jet injections employ a high-speed jet to puncture the skin and deliver drugs without the use of a needle. They have been used to deliver a number of macromolecules including vaccines and insulin, as well as small molecules, such as anesthetics and antibiotics. This article reviews liquid jet injectors with respect to their historical perspective, clinical applications, mechanisms and future prospects. An overview of the use of jet injectors for delivery of vaccines, insulin and growth hormones is presented. Particular attention is paid to the mechanistic understanding of jet injections, especially the dependence of jet penetration on parameters such as nozzle diameter, velocity and jet power. Finally, gaps in the current understanding are presented and suggestions for future research and development are made.

Needle-free injection of DNA vaccines: a brief overview and methodology

The development of needle-free injection originally stemmed from a general apprehension of needle injections, disease transmission by accidental needle-sticks, and the need for effective mass immunization. Naked DNA vaccines, as attractive and universal as they appear, have not produced robust immune responses in test systems. However, proof of principle for DNA vaccines has been validated with a number of vaccine candidates in a variety of test systems, and the concept of DNA vaccines as a generic platform for vaccines still remains viable and attractive. Many avenues are being explored to enhance the immunogenicity of DNA vaccines. The easiest and most straightforward approach that can be quickly transitioned to a clinical trial setting is vaccine delivery by a needle-free jet injector. This approach has shown much potential in a number of cases and should become the lead method for enhancing DNA vaccines. This approach requires no additional development, and with an expanding market and willingness from jet injector manufacturers to produce prefilled syringes, the technique should become feasible for larger phase II/phase III trials.

Children's preferences concerning the physical appearance of dental injectors

PURPOSE

This pilot study was carried out to assess how the physical appearance of dental injectors influenced children's choice.

METHODS

The study group consisted of 34 randomly selected children (17 boys, 17 girls) between the ages of 7 and 11 (mean age=8.6 +/- 1.4), who had been registered for treatment at the School of Dentistry, Marmara University. A combination of tests-the Children's Fear Survey Schedule-Dental Subscale (CFSS-DS), Venham Picture Test (VPT), and facial image scale (FIS)-were used to assess the multi-dimensional character of children's dental anxiety. Dental injectors (Wand, Citoject, traditional metal injector [MI], and plastic injector [PI]) were displayed on a tray and introduced to the children. The children were asked to consider which injectors they would choose "if their tooth had to be put to sleep," and their preferences were noted starting with their first choice.

RESULTS

The children's first choice was: (1) the Wand (56%); (2) PI (29%); (3) Citoject (12%); and (4) MI (3%). The anxious children (n= 13) preferred the Wand with significantly higher ratings (Wand=84%; Citoject=8%; MI=8%; PI=0%).

CONCLUSION

The physical appearance of dental injectors is important to children and even more important for children who are anxious.

Novel delivery of botulinum toxin for the treatment of anal fissures

OBJECTIVE

Botulinum toxin A (Botox) has been used as a local treatment for anal fissure since 1994. It effects a reversible chemical sphincterotomy without the need for patient compliance. This study examines the feasibility of injecting the treatment using a needle-less system.

PATIENTS AND METHODS

The optimal angle for injection was determined in a preclinical study using fresh porcine specimens. Ten patients with chronic anal fissures were then injected with 20 units Botox at the site of the fissure. They underwent assessment with a visual analogue pain scale, incontinence score and anal manometry pre-injection, at 48 h postinjection and at six and 12 weeks postinjection. They were also examined at the initial and final visits.

RESULTS

The optimal angle for injection was 60 degrees . All 10 patients (5 male; median age 40.5 years (range 26-68 years)) attended the 48 h follow up visit but only seven attended the six and 12 week visits. Six of seven patients healed their fissures. The remaining three were contacted by telephone at six months post injection and two of three remained asymptomatic without further treatment. In seven patients who underwent full follow up the median pain score pre-injection was 5.5 out of 10 (range 1-10) and this dropped to a median of 1 (range 0-6) at 12 weeks. The median drop in resting pressure was 47 cm H2O or 37% at six weeks.

CONCLUSION

No needle injection of Botox is feasible with similar healing rates and reduction of resting pressure to conventional injection techniques.

Enfuvirtide plasma levels and injection site reactions using a needle-free gas-powered injection system (Biojector)

OBJECTIVES

To assess the use of the Biojector B2000 needle-free gas-powered injection system for subcutaneous administration of enfuvirtide in HIV-infected patients and to compare this system with standard needles and syringes with respect to ease of use, severity of injection site reactions (ISR), and enfuvirtide plasma levels.

DESIGN

An observational study among 32 treatment-experienced HIV clinic patients receiving enfuvirtide.

METHODS

Adult patients were assessed before and after switching from standard needles to the Biojector for enfuvirtide administration. Patients used the Biojector for up to 24 weeks and rated ease of use from 0 (easy) to 3 (difficult). ISR were graded from 0 to 31 for signs and symptoms (erythema, induration, pruritus, nodules/cysts, ecchymosis), duration of individual lesions, and number of lesions. Plasma was collected pre-dose and 1 h post-dose for enfuvirtide measurement. The high-pressure liquid chromatography with tandem mass spectrometry method used was specific for enfuvirtide over its known plasma metabolite. Wilcoxon rank sum tests were used to compare needle-based and Biojector outcomes.

RESULTS

The Biojector was rated as being significantly easier to use (P < 0.001) and reduced the occurrence of ISR compared with standard needles (P < 0.001). Enfuvirtide plasma levels were not statistically different between the two administration methods at either pre-dose trough (P = 0.41) or 1 h post-dose (P = 0.74).

CONCLUSIONS

The Biojector needle-free injection system was easy to use for enfuvirtide administration and was associated with a decreased severity of ISR. Plasma enfuvirtide levels pre-dose and 1 h post-dose were comparable when injecting with standard needles or the Biojector.

Clinical safety and efficacy of a powdered Hepatitis B nucleic acid vaccine delivered to the epidermis by a commercial prototype device

This clinical delivery system bridging study evaluated the performance of a single-use disposable, commercial prototype device (designated ND 5.5) for particle-mediated epidermal delivery (PMED) of a nucleic acid vaccine against Hepatitis B virus (HBV). Healthy adults, previously immunized with licensed HBV vaccine, received a single boost vaccination of HBV nucleic acid vaccine administered by ND 5.5 or XR-1, the clinical research device used in previous clinical trials. Similar increases in anti-HBV surface antigen serum antibody titers and cell-mediated immune responses were produced by ND 5.5 and XR-1 when delivering comparable effective doses of the vaccine. The overall intensity of the immune response was lower in those subjects vaccinated with two, rather than 4 administrations of vaccine delivered by ND 5.5. Skin reactions at sites of vaccine administration were equivalent with both devices. This is the first clinical demonstration of the safe and effective PMED of a nucleic acid vaccine with the ND 5.5 device.

A Lorentz-force actuated autoloading needle-free injector

The advantages of delivering injections via needle-free methods are numerous. However, conventional methods for needle-free injection lack sufficient control over depth of penetration and shape of injection. Thus, a needle-free injector was designed, constructed, and tested, using a controllable linear Lorentz-force actuator. This actuator allows rapid control of the injection pressure during injections. Using this device, precise control over delivery parameters can be achieved. The injector design was tested for repeatability and evaluated for depth control using acrylamide gel and dye.

[Comparison of the systems used for providing local anesthesia in dentistry--the Wand (Milestone Scientific) and Injex (Rosch)]

Local anesthesia is one of the basic and the most often executed interventions in dentistry. This procedure is very stressful for the patients because it is combined with pain. The new systems for delivering local anesthesia in dentistry have revolutionized the technique considerably by its simplify as well as reduction in pain.

THE AIM

this study presents the comparison between the local anesthesia delivery systems used in dentistry--The Wand and Injex, taking into consideration pain intensity during performing anesthesia and the intensification of fear before executed anesthesia with the given system.

MATERIAL AND METHODS

the Visual Analogue Scale (VAS), verbal scale and questionnaires were used to evaluate pain and fear.

RESULTS

On the basis of our investigations it can be concluded that there were statistically important differences between men and women in fear intensity combined with the anesthesia procedure--men were less afraid than women. The patients who were anaesthetized with system The WAND declared less fear before similar anesthesia in future. The average value of intensity of pain analyzed with both verbal and visual scales during anaesthetizing with the system Injex (independently from sex) was statistically significantly higher than for system The WAND--respectively 0.57 and 8.55 for The WAND, 2.02 and 32.18 for Injex (p = 0.001).

CONCLUSION

on the basis of the results of this study it can be concluded that the less stressful and painful local anesthesia delivery system is the WAND.

The penetration of a soft solid by a liquid jet, with application to the administration of a needle-free injection

Liquid jet injections have been performed on human skin in vivo and silicone rubber using Intraject needle-free injectors. The discharge characteristics of the liquid jet were measured using a custom-built test instrument. The experiments reveal that a high-speed liquid jet penetrates a soft solid by the formation and opening of a planar crack. The fluid stagnation pressure required for skin penetration decreases with increasing diameter of the liquid jet. These findings are consistent with the slow-speed penetration of a soft solid by a sharp-tipped punch. It is demonstrated that the Shergold-Fleck sharp-tipped punch penetration model [Shergold, O.A., Fleck, N.A., 2004. Mechanisms of deep penetration of soft solids. Proc. Roy. Soc. Lond. A 460, 3037-3058.] gives adequate predictions for the pressure required to penetrate a soft solid by a high-speed liquid jet.

No-needle jet anesthetic technique for no-scalpel vasectomy

PURPOSE

We describe a new, modified jet injection technique for local anesthesia for no-scalpel vasectomy without the use of a needle, which may minimize the fear of vasectomy in men due to the needle involved in local anesthesia.

MATERIALS AND METHODS

A MadaJet Medical Injector (MADA Medical Products, Carlstadt. New Jersey) was used in this study to deliver a high pressure spray of 0.1 cc local anesthetic solution directly through the scrotal skin down onto the tissue around the vas. Two or 3 jet injections are delivered to each vas and a total of 4 to 6 suffice for the entire vasectomy.

RESULTS

No-needle jet injection is remarkably effective for local anesthesia for no-scalpel vasectomy. The average volume of anesthetic solution per jet injection is 0.1 cc with 0.2 to 0.3 cc for each vas. Onset is almost immediate, within 10 to 20 seconds after injection. About 465 patients were anesthetized by the jet injection technique with great satisfaction. The average visual analog scale score for the pain of the jet injection itself was 1.71 of 10. The average visual analog scale score for the pain of subsequent vasectomy during the surgical procedure was 0.66 of 10 (median 0.2). No hematomas were noted. Patients experience the mild discomfort of a pinch, not unlike a rubber band, with the first injection.

CONCLUSIONS

No-needle anesthesia with jet injection is a new technique to deliver rapid onset of profound local anesthesia to the patient undergoing vasectomy. It is a simple and safe approach with high patient satisfaction, as reflected in low pain scores. The benefit of this technique without a needle is that it may decrease the fear of pain in men and enhance the popularity of vasectomy worldwide.

Jet injection into polyacrylamide gels: investigation of jet injection mechanics

Jet injectors employ high-velocity liquid jets that penetrate into human skin and deposit drugs in the dermal or subdermal region. Although jet injectors have been marketed for a number of years, relatively little is known about the interactions of high-speed jets with soft materials such as skin. Using polyacrylamide gels as a model system, the mechanics of jet penetration, including the dependence of jet penetration on mechanical properties, was studied. Jets employed in a typical commercial injector, (orifice diameter: 152 microm, velocity: 170-180 m/s) were used to inject fluid into polyacrylamide gels possessing Young's moduli in the range of 0.06-0.77 MPa and hardness values in the range of 4-70 H(OO). Motion analysis of jet entry into polyacrylamide gels revealed that jet penetration can be divided into three distinct events: erosion, stagnation, and dispersion. During the erosion phase, the jet removed the gel at the impact site and led to the formation of a distinct cylindrical hole. Cessation of erosion induced a period of jet stagnation ( approximately 600 micros) characterized by constant penetration depth. This stage was followed by dispersion of the liquid into the gel. The dispersion took place by crack propagation and was nearly symmetrical with the exception of injections into 10% acrylamide (Young's modulus of 0.06 MPa). The penetration depth of the jets as well as the rate of erosion decreased with increasing Young's modulus. The mechanics of jet penetration into polyacrylamide gels provides an important tool for understanding jet injection into skin.

Treatment of plantar hyperhidrosis with botulinum toxin type A

BACKGROUND

Hyperhidrosis (excessive, uncontrollable sweating) can be embarrassing and disabling, significantly impacting social and professional performance and quality of life. Treatments aim to reduce sweating, but few are effective, often carrying the risk of significant side-effects. The aims of this study were to evaluate the efficacy and safety of botulinum toxin type A (BTX-A) for plantar hyperhidrosis and to investigate the role of the Dermojet as a potential injection technique.

METHODS

Ten adult patients (five men, five women), aged 19-51 years, with severe, previously unresponsive, plantar hyperhidrosis, were recruited to this single-center, open-label, noncomparative study. The hyperhidrotic area of each foot was injected over 15-20 sites without analgesia with 50 U BTX-A + 5 mL sterile saline using a Dermojet. Patients were followed up for 8 months with monthly sweat reduction assessments using Minor's iodine-starch test. Patients provided a treatment self-assessment after completion of follow-up.

RESULTS

Within 7 days post-treatment, eight patients reported significantly decreased sweating, and seven patients were symptom free for up to 5 months. Patient self-assessment showed that seven of the 10 patients were satisfied with their treatment. One minor adverse event was reported comprising a temporary localized hematoma (one patient).

CONCLUSIONS

Intracutaneous BTX-A injection using the Dermojet offers a simple, safe, and effective alternative for treatment of plantar hyperhidrosis.

Needle-free jet injections: dependence of jet penetration and dispersion in the skin on jet power

Jet injection is a needle-free drug delivery method in which a high-speed stream of fluid impacts the skin and delivers drugs. Although a number of jet injectors are commercially available, especially for insulin delivery, a quantitative understanding of the energetics of jet injection is still lacking. Here, we describe the dependence of jet injections into human skin on the power of the jet. Dermal delivery of liquid jets was quantified using two measurements, penetration of a radiolabeled solute, mannitol, into skin and the shape of jet dispersion in the skin which was visualized using sulforhodamine B (SRB). The power of the jet at the nozzle was varied from 1 to 600 W by independently altering the nozzle diameter (30-560 microm) and jet velocity (100-200 m/s). The dependence of the amount of liquid delivered in the skin and the geometric measurements of jet dispersion on nozzle diameter and jet velocity was captured by a single parameter, jet power. Additional experiments were performed using a model material, polyacrylamide gel, to further understand the dependence of jet penetration on jet power. These experiments demonstrated that jet power also effectively describes gel erosion due to liquid impingement.

Assessment of the biological performance of the needle-free injector INJEX using the isolated porcine forelimb

BACKGROUND

The development and utilization of novel needle-free injection devices in order to minimize needle stick injuries make increasing demands for suitable assay systems, which reflect the physiological situation in humans as close as possible.

OBJECTIVES

It was therefore the goal of the present study to test the biological performance of a needle-free injector (INJEX) by the use of porcine skin as a model with a high predictive value for the feasibility in humans because of its close similarity to human skin.

METHODS

In order to use porcine skin in the context of the underlying tissues, the isolated porcine forelimb was chosen as an assay model for use with the INJEX injector. Ink or the fluorescent dye fluorescein-isothiocyanate was injected and the penetration depth was determined metrically and dye distribution histologically. To assess the resorption of heparin, needle injection was compared with needle-free injection in a perfused limb model.

RESULTS

Increasing amounts of ink increasingly penetrated into subcutaneous tissue layers in a cone-shaped manner mainly following lead structures. Penetration was hampered by skin thickness and by the deep muscle fascia, which served as a penetration barrier. Resorption of heparin was similar irrespective of injection by the use of a needle or the INJEX device.

CONCLUSIONS

The isolated porcine forelimb serves as a versatile tool for the assessment of the biological performance of needle-free injection devices such as INJEX. Further studies are necessary to correlate the model for drug delivery in humans.

[Clinical evaluation of the INJEX system, a local anesthesia system without needles: a comfort evaluation study]

The use of needless local anaesthesia systems in dentistry can be of a help in treating needle phobia patients. The aim of this comfort study was to compare a classical local infiltration anaesthesia with a needle-free system. INJEX (ROSCH AG Germany). A split mouth design study was performed. All patients in this study needed 2 restorations. In order to receive objective information on both systems needle-phobia patients were banned. Therefore the first restoration was performed with the classical system (with needle) and the well-acceptance was evaluated. The second restoration was done with the needle-free system. Both patient and dental practitioner performed an evaluation after each treatment. Evaluation by the patient was given by a questionnaire on the comfort of the treatment using Faces Pain Scale, Lickert Scale and a modified version of the Abbreviated Acceptability Rating Profile. By the dental practitioner the comfort of the treatment and the amount of local anaesthesia needed was evaluated. The study was approved by the ethical committee of Ghent University Hospital Belgium.

CONCLUSION

The INJEX system can be a valuable alternative to use in paediatric dentistry, although non needle phobia patients in this study did not preferred the needle free INJEX system above the classical local 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.