Poly­d,l­lactic acid­enhanced atrophic scar treatment via transdermal microjet drug delivery in Asians.

BACKGROUND: Acne vulgaris often results in permanent scars, with atrophic scars being the most common type and posing a significant therapeutic challenge due to their prevalence and impact on patients' quality of life. Various treatment options exist, including the use of poly-d,l-lactic acid delivered via different methods. OBJECTIVE: This study aimed to assess the efficacy and safety of poly-d,l-lactic acid delivered via laser-assisted needle-free microjet injection for treating atrophic scars. METHODS: Five Korean participants with atrophic facial scars were recruited. Poly-d,l-lactic acid solution was administered via the Mirajet system in five sessions, with clinical assessments conducted at baseline, before each session, and at 12-week and 22-week follow-ups. Outcome measures included the Global Aesthetic Improvement Scale and patient satisfaction scores. RESULTS: Positive results were observed at the 12-week and 22-week follow-ups, with high patient satisfaction and improvements in atrophic scars and skin texture. Mild discomfort and transient side effects were reported, with no adverse events observed during the follow-up period. CONCLUSION: Poly-d,l-lactic acid delivered by a laser-assisted needle-free microjet injector was judged to be effective for improving atrophic the facial area. Further research, particularly through randomized controlled trials, is needed to validate these findings and assess the longer-term safety and sustainability of outcomes.

Therapeutic Effectiveness of Needle Injection Versus Needle-Free Jet Injector System for Botulinum Toxin Type A in Palmar Hyperhidrosis.

BACKGROUND: The most important problem with local injections of botulinum toxin type A (BTX-A) in palmar hyperhidrosis is pain during the injections. OBJECTIVES: We evaluated therapeutic effectiveness and pain of local injections of BTX-A using needle-free direct administration system. METHODS: We performed BTX-A local injection therapy using a conventional injection needle in the left hand and a needle-free direct administration system in the right hand. RESULTS: A reduction in the quantity of perspiration was observed 4 weeks after administration of both Needle and Needle-free BTX-A, and reduction was maintained throughout 28 weeks observation period. Both hyperhidrosis Disease Severity Scale scores and Dermatology Life Quality Index for hands treated with Needle BTX-A and hands treated with Needle-free BTX-A had decreased significantly by 4 weeks after treatment. Pain visual analog scale scores and the degree of pain were significantly lower in hands treated with Needle-free BTX-A than in hands treated with Needle BTX-A. CONCLUSIONS: When the trigger of the pressurized needle-free injector device is activated, the gas powered driving pressure propels BTX-A through an orifice (0.13 mm) about four times narrower than a 30 G needle at very high speed. As most pain occurs during the needle prick itself, the advantage of a small orifice coupled with high-speed penetration of BTX-A through the pressurized device results in reduced pain during administration. The needle-free direct administration system administers the injectate under the skin without a visible needle.

A Promising Needle-Free Pyro-Drive Jet Injector for Augmentation of Immunity by Intradermal Injection as a Physical Adjuvant.

Current worldwide mRNA vaccination against SARS-CoV-2 by intramuscular injection using a needled syringe has greatly protected numerous people from COVID-19. An intramuscular injection is generally well tolerated, safer and easier to perform on a large scale, whereas the skin has the benefit of the presence of numerous immune cells, such as professional antigen-presenting dendritic cells. Therefore, intradermal injection is considered superior to intramuscular injection for the induction of protective immunity, but more proficiency is required for the injection. To improve these issues, several different types of more versatile jet injectors have been developed to deliver DNAs, proteins or drugs by high jet velocity through the skin without a needle. Among them, a new needle-free pyro-drive jet injector has a unique characteristic that utilizes gunpower as a mechanical driving force, in particular, bi-phasic pyrotechnics to provoke high jet velocity and consequently the wide dispersion of the injected DNA solution in the skin. A significant amount of evidence has revealed that it is highly effective as a vaccinating tool to induce potent protective cellular and humoral immunity against cancers and infectious diseases. This is presumably explained by the fact that shear stress generated by the high jet velocity facilitates the uptake of DNA in the cells and, consequently, its protein expression. The shear stress also possibly elicits danger signals which, together with the plasmid DNA, subsequently induces the activation of innate immunity including dendritic cell maturation, leading to the establishment of adaptive immunity. This review summarizes the recent advances in needle-free jet injectors to augment the cellular and humoral immunity by intradermal injection and the possible mechanism of action.

Investigating skin penetration depth and shape following needle-free injection at different pressures: A cadaveric study.

BACKGROUND AND OBJECTIVES: The effectiveness of needle-free injection devices in neocollagenesis for treating extended skin planes is an area of active research. It is anticipated that needle-free injection systems will not only be used to inject vaccines or insulin, but will also greatly aid skin rejuvenation when used to inject aesthetic materials such as hyaluronic acid, botulinum toxin, and placental extracts. There has not been any specific research to date examining how materials penetrate the skin when a needle-free injection device is used. In this study, we investigated how material infiltrates the skin when it is injected into a cadaver using a needle-free device. STUDY DESIGN/MATERIALS AND METHODS: Using a needle-free injector (INNOJECTOR™; Amore Pacific, Seoul, Korea), 0.2 ml of 5% methylene blue (MB) or latex was injected into cheeks of human cadavers. The device has a nozzle diameter of 100 µm and produces a jet with velocity of 180 m/s. This jet penetrates the skin and delivers medicine intradermally via liquid propelled by compressed gasses. Materials were injected at pressures of 6 or 8.5 bars, and the injection areas were excised after the procedure. The excised areas were observed visually and with a phototrichogram to investigate the size, infiltration depth, and shape of the hole created on the skin. A small part of the area that was excised was magnified and stained with H&E (×40) for histological examination. RESULTS: We characterized the shape, size, and depth of skin infiltration following injection of 5% MB or latex into cadaver cheeks using a needle-free injection device at various pressure settings. Under visual inspection, the injection at 6 bars created semi-circle-shaped hole that penetrated half the depth of the excised tissue, while injection at 8.5 bars created a cylinder-shaped hole that spanned the entire depth of the excised tissue. More specific measurements were collected using phototrichogram imaging. The shape of the injection entry point was consistently spherical regardless of the amount of pressure used. When injecting 5% MB at 6 bars, the depth of infiltration reached 2.323 mm, while that at 8.5 bars reached 8.906 mm. The area of the hole created by the 5% MB injection was 0.797 mm(2) at 6 bars and 0.242 mm(2) at 8.5 bars. Latex injections reached a depth of 3.480 mm at 6 bars and 7.558 mm at 8.5 bars, and the areas were measured at 1.043 mm(2) (6 bars) and 0.355 mm(2) (8.5 bars). Histological examination showed that the injection penetrated as deep as the superficial musculoaponeurotic system at 6 bars and the masseter muscle at 8.5 bars. CONCLUSION: When injecting material into the skin using a pneumatic needle-free injector, higher-pressure injections result in a hole with smaller area than lower-pressure injections. The depth and shape of skin penetration vary according to the amount of pressure applied. For materials of low density and viscosity, there is a greater difference in penetration depth according to the degree of pressure. Lasers Surg. Med. 48:624-628, 2016. © 2016 Wiley Periodicals, Inc.

Immunogenic Comparison of Nucleic Acid-Based Vaccines Administered by Pyro-Drive Jet Injector.

mRNA vaccines were successfully developed and approved for emergency use to fight coronavirus disease 2019. However, the effect of DNA vaccines against SARS-CoV-2 is considerably lower than that of mRNA vaccines. A pyro-drive jet injector (PJI) efficiently delivers plasmid DNA intradermally into animal models. Here, we compared the immunogenic potential of DNA and mRNA vaccines in mice using the same platform. PJI was used to deliver naked mRNA and pDNA and their efficacy in inducing antigen expression and immune responses was assessed. Our results showed that PJI efficiently delivered mRNA into the skin, and a smaller effective dose than that of pDNA injection was required to achieve similar levels of antigen expression. The PJI-delivered CpG-free pDNA vaccine efficiently induced antigen-specific antibody production and a cell-mediated IFN-γ response compared to the mRNA vaccine, as well as the upregulation of inflammatory cytokines (IL-6, IFN-γ, and IL-1ß) in the skin and lymph nodes. However, the intradermal mRNA vaccine was significantly less immunogenic than the standard intramuscular mRNA-lipid nanoparticle vaccine, despite equivalent mRNA dosages. Improvements in lipid nanoparticle and mRNA technology have revolutionized mRNA vaccines, and DNA vaccines can be similarly modified for higher clinical efficacy.

Intradermal Inoculation of Inactivated Foot-and-Mouth Disease Vaccine Induced Effective Immune Responses Comparable to Conventional Intramuscular Injection in Pigs.

All pigs in the Republic of Korea are given the foot-and-mouth disease virus (FMDV) vaccine intramuscularly (IM) as part of the country's vaccination policy. However, the IM administration of the FMDV vaccine to pig results in residual vaccine components in the muscle and undesirable changes in muscle and soft tissues, causing economic losses in swine production. In this study, we evaluated whether intradermal (ID) vaccination could be proposed as an alternative to IM administration. ID vaccination (0.2 mL on each side of the neck muscle) and IM vaccination (2 mL on each side of the neck muscle) were performed twice, separated by 14 days, using a commercial FMD vaccine in specific-pathogen-free pigs. We observed growth performance, gross and microscopic lesions at the inoculation site, FMDV-specific antibodies, and neutralizing antibodies for 35 days after vaccination. Side effects on the skin grossly appeared following ID administration, but most were reduced within two weeks. All ID-vaccinated pigs showed inflammatory lesions limited to the dermis, but IM-vaccinated pigs had abnormal undesirable changes and pus in the muscle. ID-vaccinated pigs performed comparably to IM-vaccinated pigs in terms of growth, FMD virus-specific antibodies, protection capability against FMDV, and T-cell induction. This study demonstrated that the ID inoculation of the inactivated FMD vaccine induced immune responses comparable to an IM injection at 1/10 of the inoculation dose and that the inoculation lesion was limited to the dermis, effectively protecting against the formation of abnormal undesirable changes in muscle and soft tissues.

Poly-d,l-Lactic Acid Via Transdermal Microjet Drug Delivery for Treating Rosacea in Asian Patients.

BACKGROUND: Rosacea, a chronic inflammatory skin condition, is marked by enduring redness, visible blood vessels, and inflammatory eruptions in facial areas. Managing rosacea remains a persistent challenge for dermatologists, especially in cases unresponsive to conventional treatments. Injectable poly-d,l-lactic acid (PDLLA) has shown promise in treating erythema and telangiectasia associated with rosacea in addition to age-related concerns. Employing Mirajet, a laser-induced microjet system, for administering PDLLA is a novel and promising treatment for rosacea. AIMS: We aimed to evaluate the efficacy and safety of injectable PDLLA delivered via a needle-free microjet system for managing rosacea. METHODS: Four Korean women with persistent and refractory rosacea received five monthly sessions of PDLLA needle-free injections. Clinical assessments were conducted using the Clinician's Erythema Assessment and Patient's Self-Assessment (PSA) at baseline, 4 weeks post-treatment, and 22 weeks post-final treatment. Adverse events were monitored throughout the study period. RESULTS: At 4 weeks post-treatment, both Clinician's Erythema Assessment and PSA scores indicated significant improvements in erythema that were sustained up to the 22-week follow-up. Patients reported high satisfaction with resolution of redness and improved skin texture. Mild swelling, redness, and petechiae were observed post-treatment but resolved spontaneously. No product-related adverse events were noted during the study period. CONCLUSION: Injectable PDLLA delivered via laser-induced microjet injection demonstrated promising efficacy in improving rosacea symptoms and skin quality for up to 22 weeks without significant adverse effects. Larger randomized controlled trials are needed to confirm these findings and evaluate long-term safety and sustainability of outcomes.

Advances in Large Volume Subcutaneous Injections: A Pilot Tolerability Study of an Innovative Needle-Free Injection Platform.

Many medical conditions require chronic treatment with subcutaneous injectable biologics often exceeding 1.0 mL. However, subcutaneous administration of volumes of 2.0 mL or greater using a standard needle and syringe or auto-injector proves challenging, and patients often must administer two separate injections to achieve their full dose or endure injection times in excess of 10 s if using a mechanical autoinjector. In addition, needle-based injections often cause patient anxiety and discomfort. In this article, we describe an approach to meet these needs with a needle-free medication delivery device capable of rapidly delivering up to 2.0 mL with minimal discomfort. A pilot study was conducted with this needle-free injection system to evaluate the delivery of a 2.0 mL volume in human subjects. The results demonstrated that injections of up to 2.0 mL were well tolerated and often preferred over two separate 1.0 mL injections using the needle-free injection system.

Non-Inferiority Field Study Comparing the Administrations by Conventional Needle-Syringe and Needle-Free Injectors of a Trivalent Vaccine Containing Porcine Circovirus Types 2a/2b and Mycoplasma hyopneumoniae.

The objective of this study was to assess the clinical, immunological, microbiological, and pathological evaluation of trivalent vaccine containing porcine circovirus types 2a/b (PCV2a/b) and Mycoplasma hyopneumoniae given by two different needle-free injection devices compared with conventional needle-syringe injection in a herd with subclinical PCV2d infection and enzootic pneumonia. A total of 240 21-day-old pigs, which weighed between 5 to 6 kg, were randomly divided into four groups (60 pigs per group, 30 = male and 30 = female per group). Injection site reactions in the pigs were minimal for the two needle-free injection devices and needle-syringe injection. Trivalent vaccination of pigs with two needle-free injection devices was not inferior to conventional needle-syringe injection for growth performance. Trivalent vaccination of pigs with two different needle-free injection devices reduced levels of PCV2d loads in serum and M. hyopneumoniae loads in the larynx equally compared to the conventional needle-syringe injection. The amount of PCV2d load in serum from the needle-free Pulse FX injection device at 49 days post vaccination showed non-inferiority to conventional needle-syringe injection. The immune response against PCV2 and M. hyopneumoniae to trivalent vaccine given with the needle-free Pulse FX injection device was non-inferior to conventional needle-syringe injection. The pigs from the two needle-free injection device and conventional needle-syringe injection had significantly (p < 0.05) lower macroscopic and microscopic lung lesion scores, and microscopic lymphoid lesions than from unvaccinated. The results of this study demonstrated that vaccination of trivalent vaccine by the two needle-free Pulse injection devices used in the study was non-inferior to that by conventional needle-syringe injection for growth performance, immune response against PCV2 and M. hyopneumoniae, and reduction of PCV2 viremia.

Mechanism and clinical applications of needle-free injectors in dermatology: Literature review.

BACKGROUND: Needle-free jet injectors are devices that deliver drugs using a high-speed jet without a needle. Recent studies have significantly increased our understanding of the mechanisms of needle-free jet injectors, and technical advancements have broadened the scope of application of the device. AIMS: We aimed to provide an up-to-date review of previous literature regarding the mechanism of action and clinical applications of needle-free jet injectors in dermatology field. METHODS: We conducted a PUBMED search for studies on needle-free jet injectors using the following parameters: "Pneumatic injector" OR "needleless injector" OR "needle-free injector" OR "jet injector." Among 191 results, 72 articles focusing on their mechanisms of action, cutaneous delivery patterns, and clinical applications in dermatology were selected for review. RESULTS: Significant clinical evidence has been published confirming the potential of needle-free jet injectors in treating various dermatologic conditions. In particular, these devices have the potential to be used in various skin remodeling treatment, especially in skin rejuvenation procedures by injecting various esthetic materials. CONCLUSION: As proven by accumulated experience, the applications of NFJIs are not restricted to vaccine or insulin delivery in dermatology field. However, this literature review shows that until now, there are no clinical guidelines that standardize the optimal parameters when using NFJIs on various clinical settings. Therefore, further studies should be performed in order to investigate the full potential of these devices in dermatology, to ensure safe and effective outcomes in clinical practice.

Advances in subcutaneous injections: PRECISE II: a study of safety and subject preference for an innovative needle-free injection system.

Needle-free injection is a desirable goal for many reasons, including reducing pain, anxiety, and eliminating safety risks associated with needle-stick injuries. However, development of a safe, reliable needle-free device optimized for at-home use has been met with many challenges. Portal Instruments Inc. has been developing needle-free medication delivery using a well-designed hand-held device, PRIME, that is safe, intuitive to use, and utilizes advanced electronic control of a focused, high velocity, pressurized liquid injection stream. The PRECISE II human study demonstrated that the PRIME needle-free injection system was safe, well tolerated, and strongly preferred by participants for self-injections over a standard needle and syringe. In addition, the study was able to be completed early for superiority following the success of the pre-defined interim analysis.

Insulin delivery with a needle-free insulin injector versus a conventional insulin pen in Chinese patients with type 2 diabetes mellitus: A 16-week, multicenter, randomized clinical trial (the FREE study).

BACKGROUND: Insulin therapy is poorly accepted by patients with type 2 diabetes mellitus (T2DM). A needle-free insulin injector has been developed for patients who fear injections or are reluctant to initiate insulin therapy when it is clearly indicated. The objective of this trial was to evaluate the glucose-lowering effect, tolerability, patient satisfaction and compliance with insulin treatment via a needle-free insulin injector (NFII) compared with insulin treatment via a conventional insulin pen (CIP) in patients with T2DM. METHODS: A total of 427 patients with T2DM were enrolled in a prospective, multicenter, randomized, open-label study, and were randomly assigned 1:1 to receive 16 weeks' treatment with basal insulin or premixed insulin administered either by a NFII or CIP. TRIAL REGISTRATION: ClinicalTrials.gov (NCT03243903). FINDINGS: In the 412 patients who completed the study, the adjusted mean reduction of HbA1c from baseline at week 16 in the NFII group was 0.55% (95% CI -0.71, -0.39), which was non-inferior and statistically superior to the HbA1c reduction in the CIP group (0.26%, 95% CI -0.42, -0.11). Patients in the NFII group showed significantly higher treatment satisfaction scores than those in the CIP group (mean scores, 8.17 ± 1.78 vs. 7.21 ± 2.22, respectively; p<0.0001). The occurrence of hypoglycemia was similar in the two groups, and the NFII group showed reduced incidences of skin scratches, indurations and lower VAS pain scores. INTERPRETATION: Insulin therapy through needle-free injector showed a non-inferior glycemic-lowering effect and a significantly enhanced level of patient satisfaction with insulin treatment compared with conventional insulin therapy through needle injections. In addition, the needle-free injector also had a better safety profile. FUNDING: This study were funded by Beijing QS Medical Technology Co., Ltd, as well as The Major Chronic Non-communicable Disease Prevention and Control Research.

Study Protocol for a Prospective, Multicenter, Randomized, Open-Label, Parallel-Group Clinical Trial Comparing the Efficacy and Safety of a Needle-Free Insulin Injector and a Conventional Insulin Pen in Controlling Blood Glucose Concentrations in Chinese Patients with Type 2 Diabetes Mellitus (The FREE Study).

INTRODUCTION: China has the largest number of diabetic patients in the world. In the past 2 decades, the prevalence of diabetes in China has increased dramatically, and the current status of diabetes control in the diabetic population is not satisfactory. Although insulin is currently recognized in diabetes treatment guidelines as the therapeutic option for patients not adequately controlled by diet/exercise and oral agents, the proportion of patients with type 2 diabetes using insulin is still very low, and the time when insulin therapy is initiated is relatively late. In using insulin injections, concerns about the complexity of the treatment regimen, a fear of needles, and other psychological barriers can affect insulin treatment, impacting on patient compliance and potentially resulting in a poor treatment response. Another type of insulin injection device that has become available recently, the needle-free injector, is now being used in clinical practice because of its unique features and patients' injection experiences. The aims of this study are to investigate the efficacy and safety of the needle-free injector-based insulin treatment in blood glucose control in patients with type 2 diabetes, as compared with a conventional needle-based insulin treatment, and to evaluate patient satisfaction with the different insulin delivery methods. METHODS AND PLANNED OUTCOMES: A prospective, multicenter, randomized, open-label, parallel-group clinical trial was designed and implemented in China. A total of 420 patients with type 2 diabetes from ten research centers will be enrolled in the study. The primary efficacy endpoint is the change in the glycosylated hemoglobin (HbA1c) level from baseline to after 16 weeks of treatment after randomization. Secondary efficacy endpoints include measurements of blood glucose concentrations, the rate of achieving the target HbA1c level of less than 7%, patients' quality-of-life (as determined by the SF-36 questionnaire), the insulin dose administered, compliance with insulin therapy, and patients' satisfaction with their injection device. ETHICS AND DISSEMINATION: The study was approved by the Independent Ethics Committee (IEC) of Peking University Peoples Hospital and was conducted in accordance with the moral, ethical, and scientific principles of the declaration of Helsinki and the provisions of good clinical practice (GCP) in China. Written informed consent will be obtained from all participants before any study-related procedures are implemented. It is hoped that the study will provide evidence for the clinical application of the needle-free injector by providing data on its efficacy and safety, as compared with a conventional insulin pen, in the Chinese type 2 diabetes population. When available, the results will be published in an international peer-reviewed journal. TRIAL REGISTRATION: ClinicalTrials.gov Identifier, NCT03243903. Registration date, August 9, 2017. FUNDING: Beijing QS Medical Technology Co., Ltd.

Efficacy and safety of a needle-free injector in Chinese patients with type 2 diabetes mellitus treated with basal insulin: a multicentre, prospective, randomised, crossover study.

Objective: To evaluate the efficacy and safety of a needle-free injector in Chinese patients with type 2 diabetes mellitus treated with basal insulin. Methods: 62 patients with type 2 diabetes were enrolled in a multicenter, randomised, prospective, open-label, crossover study. All patients received subcutaneous insulin glargine administered by a needle-free injector or a glargine pen for 7 ~ 14 days, and were then crossed over after wash out. Results: Patients in the insulin needle-free injector (NFI) and glargine pen (GP) groups achieved similar fasting blood glucose control . However, the dosage of insulin required to achieve the target FBG level in the NFI group was lower than in the GP group (16.14 ± 5.13 U/day vs 19.25 ± 6.20 U/day, respectively; p = 0.0046). This difference was more significant in patients who received higher insulin dosages compared with those receiving lower dosages. Use of the needle-free injector was also associated with significantly less pain (p < 0.001) and less fear of injection (p < 0.001) than glargine pens. Conclusion: The use of a needle-free injector can significantly lower the dosage of insulin required to achieve good glycemic control and reduce topical adverse reactions and the fear of injections as well, which help to improve patient compliance. Clinical Trial Registration Number KY20172077-1; NCT03420040.

Needle-free jet injector intradermal delivery of fractional dose inactivated poliovirus vaccine: Association between injection quality and immunogenicity.

INTRODUCTION: The World Health Organization recommends that as part of the polio end-game strategy a dose of inactivated poliovirus vaccine (IPV) be introduced by the end of 2015 in all countries currently using only oral poliovirus vaccine (OPV). Administration of fractional dose (1/5 of full dose) IPV (fIPV) by intradermal (ID) injection may reduce costs, but its conventional administration is with Bacillus Calmette-Guerin (BCG) needle and syringe (NS), which is time consuming and technically challenging. We compared injection quality achieved with BCG NS and three needle-free jet injectors and assessed ergonomic features of the injectors. METHODS: Children between 12 and 20 months of age who had previously received OPV were enrolled in the Camaguey, Cuba study. Subjects received a single fIPV dose administered intradermally with BCG NS or one of three needle-free injector devices: Bioject Biojector 2000® (B2000), Bioject ID Pen® (ID Pen), or PharmaJet Tropis® (Tropis). We measured bleb diameter and vaccine loss as indicators of ID injection quality, with desirable injection quality defined as bleb diameter ≥5mm and vaccine loss <10%. We surveyed vaccinators to evaluate ergonomic features of the injectors. We further assessed the injection quality indicators as predictors of immune response, measured by increase in poliovirus neutralizing antibodies in blood between day 0 (pre-IPV) and 21 (post-vaccination). RESULTS: Delivery by BCG NS and Tropis resulted in the highest proportion of subjects with desirable injection quality; health workers ranked Biojector2000 and Tropis highest for ergonomic features. We observed that vaccine loss and desirable injection quality were associated with an immune response for poliovirus type 2 (P=0.02, P=0.01, respectively). CONCLUSIONS: Our study demonstrated the feasibility of fIPV delivery using needle-free injector devices with high acceptability among health workers. We did not observe the indicators of injection quality to be uniformly associated with immune response.

Needle-free transdermal delivery using PLGA nanoparticles: effect of particle size, injection pressure and syringe orifice diameter.

The aim of this study is to investigate the effects of particle size and other injection factors on the skin penetration of nanoparticles delivered with a needle-free injector. Experimental and simulation tests were carried out at various parameters. In addition to testing different sizes of nanoparticles, we also observed the effects of several injection pressures and syringe orifice diameters (SOD) on the dispersion pattern of the nanoparticles after injection. Our results showed that as the nanoparticle size increased from 45 nm to 452 nm, the resulting puncture opening, channel diameter, and depth of the nanoparticle dispersion decreased, but the width of the dispersion increased. Conversely, as the SOD increased, the puncture opening, channel diameter, and depth of the dispersion increased, but width of the dispersion decreased. Increasing the injection pressure also decreased the size, depth, and width of the puncture opening. These results identify how these three parameters affect nanoparticle delivery from a needle-free injector; therefore, our findings will be beneficial for optimization and further study of needle-free injectors as a mechanism for transdermal delivery of nanoparticles.