Safety Testing of Needle Free, Jet Injection Devices to Detect Contamination with Blood and Other Tissue Fluids

JAMES M. SWEAT^a,b, MARK ABDY^b, BRUCE G. WENIGER^c, ROBERT HARRINGTON^d, BERNARD COYLE^d, RAM A. ABUKNESHA^e and E. PAUL J. GIBBS^b

^bDepartment of Pathobiology, College of Veterinary Medicine, University of Florida, Gainesville, Florida 32608, USA ^cCenters for Disease Control and Prevention, Atlanta, Georgia, USA
^dAmerican Jet Injector Inc., Lansdale, Pennsylvania, USA
^eKing's College, London, UK
 

^aAddress for correspondence: J. Mark Sweat, Department of Pathobiology, College of Veterinary Medicine, University of Florida, 2015 S.W. 16th Avenue, Gainsville, FL 52608. Voice: 352-392-4700x5883; fax: 352-392-5793.
sweatm@mail.vetmed.ufl.edu
 

	ABSTRACT

 
Needle free jet injection guns have been used extensively in both veterinary and human health to deliver both vaccine and drugs, but in recent years, concerns have mounted for their potential to transmit blood borne disease agents among consecutive vaccinates. A Ped-O-Jet^® type jet injection device was used to deliver serial subcutaneous injections of 0.5 mL saline (as a surrogate for vaccine) into calves and pigs, with intervening ejectates collected in vials to represent what the next vaccinate would have received. An enzyme linked immunosorbant assay was developed to detect species specific albumin as a marker for blood, using calibration standards from known dilutions of bovine or porcine blood. Assay sensitivity of 20 pL/mL corresponded to the estimated minimal chimpanzee infectious dose of 10 pL for hepatitis B virus. The methodology and available results for evaluating the safety of jet injector devices are reported.

	STUDY DESIGN

 
Safety testing of a Ped-O-Jet^® type jet injection (JI) device was conducted as a prospective clinical trial. Five different procedures were used to administer injections to calves and pigs: (1) following compliance protocol (device nozzle is swabbed with alcohol between vaccinates), (2) non-compliance with a standard JI nozzle, (3) compliance and (4) non-compliance with a redesigned JI check-valve, and (5) using a plastic disposable nozzle.

	ANIMAL MODELS

Calves and pigs, as a model for human skin, has variable attributes. Calf skin is less like human skin when compared to the pig, and requires clipping of the injection site three days prior to testing.

Pigs were sedated (Telazol, 4.4 mg/kg) and positioned to receive injections within a marked, 2-cm2 grid. Blanching and saline "backsplash" was noted at the injection site following injection. Blanching diminished after approximately two minutes. Whether the fluid loss immediately following the injection is a result of the JI nozzle, or check valve design, or qualities unique to pig skin is not clear. After two days postinjection, the circular pattern of arrhythmia diminished. It was interesting to note that the amount of backsplash resulting from injection using a disposable plastic nozzle was slightly less than that from the metal type.
 

	SAMPLE COLLECTION

 All materials, including the parafilm-covered collection vials, JI device, and cryogenic storage-vials were handled with latex rubber gloves to minimize exposure to exogenous albumin. Samples were frozen at -80°C until the time of analysis. Control samples consisted of floor, mouth, and skin as likely positives and negative, respectively.

	ELISA

Albumin was detected by an ELISA using a rabbit-anti-pig whole serum polyclonal antibody. The sensitivity of this assay detects about 5 pL/mL. If albumin is detected in test samples (at more than 10 pL/mL), the conclusion is that the device is responsible for transmitting volumes of blood sufficient to contain pathogenic agents.

	CONCLUSIONS

Pigs offer a better model of human skin for the testing of JIs than calves. The cause for the difference between the models relative to the "backsplash" of injection fluid is unclear. The sensitivity of the ELISA is sufficient to detect clinically significant levels of blood products.

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