Transdermal Delivery of High Molecular Weight Antibiotics to Deep Tissue Infections via Droplette Micromist Technology Device (DMTD).

Wound infection by multidrug-resistant (MDR) bacteria is a major disease burden. Systemic administration of broad-spectrum antibiotics colistin methanesulfonate (CMS) and vancomycin are the last lines of defense against deep wound infections by MDR bacteria. However, systemic administration of CMS and vancomycin are linked to life-threatening vital organ damage. Currently there are no effective topical application strategies to deliver these high molecular weight antibiotics across the stratum corneum. To overcome this difficulty, we tested if high molecular weight antibiotics delivered by Droplette micromist technology device (DMTD), a transdermal delivery device that generates a micromist capable of packaging large molecules, could attenuate deep skin tissue infections. Using green fluorescent protein-tagged E. coli and live tissue imaging, we show that (1) the extent of attenuation of deep-skin E. coli infection was similar when treated with topical DMTD- or systemic IP (intraperitoneal)-delivered CMS; (2) DMTD-delivered micromist did not spread the infection deeper; (3) topical DMTD delivery and IP delivery resulted in similar levels of vancomycin in the skin after a 2 h washout period; and (4) IP-delivered vancomycin was about 1000-fold higher in kidney and plasma than DMTD-delivered vancomycin indicating systemic toxicity. Thus, topical DMTD delivery of these antibiotics is a safe treatment for the difficult-to-treat deep skin tissue infections by MDR bacteria.

Specialized Pro-Resolving Mediators Reduce Scarring After Cleft Lip Repair.

Objective: Residual scarring after cleft lip repair surgery remains a challenge for both surgeons and patients and novel therapeutics are critically needed. The objective of this preclinical experimental study was to evaluate the impact of the methyl-ester of pro-resolving lipid mediator lipoxin A4 (LXA4-ME) on scarring in a novel rabbit model of cleft lip repair. Methods: A defect of the lip was surgically created and repaired in eight six-week old New Zealand white rabbits to simulate human cleft lip scars. Rabbits were randomly assigned to topical application of PBS (control) or 1 ug of LXA4-ME (treatment). 42 days post surgery all animals were euthanized. Photographs of the cleft lip area defect and histologic specimens were evaluated. Multiple scar assessment scales were used to compare scarring. Results: Animals treated with LXA4-ME exhibited lower Visual Scar Assessment scores compared to animals treated with PBS. Treatment with LXA4-ME resulted in a significant reduction of inflammatory cell infiltrate and density of collagen fibers. Control animals showed reduced 2D directional variance (orientation) of collagen fibers compared to animals treated with LXA4-ME demonstrating thicker and more parallel collagen fibers, consistent with scar tissue. Conclusions: These data suggest that LXA4-ME limits scarring after cleft lip repair and improves wound healing outcomes in rabbits favoring the resolution of inflammation. Further studies are needed to explore the mechanisms that underlie the positive therapeutic impact of LXA4-ME on scarring to set the stage for future human clinical trials of LXA4-ME for scar prevention or treatment after cleft lip repair.

Performance and Consistency of Circulating Warm Water Blankets for Rodents.

General anesthesia as used for rodent research can have adverse effects on physiologic mechanisms. Thermoregulation is often greatly inhibited, with resultant deleterious effects on cardiac and respiratory function. These potential effects can be mitigated by providing external heat support. The circulating warm water blanket and associated heat pump are often used in rodent procedures. The current study demonstrated that the heating pump and water blanket require quality control assessment to ensure adequate function. Our data showed that of the 6 pumps tested, 5 were able to achieve a temperature that met or exceeded the documented thermoneutral zone for mice. Pumps required 20 min of warming to reach their maximal attainable temperatures for the designated user setting. Although the pumps reached a temperature that was sufficient to provide external thermal support, only 1 of the 6 pumps reached the temperature that was set by the user during the trial. Surface temperatures across the water blanket were recorded to analyze whether a difference in heat support was influenced by animal placement along the water blanket; however, the location points did not yield statistically different results. Two pumps were eliminated from the study due to failure to pass the preparation phase of the trial. The results of this study support the need for facilities to establish quality control measures to ensure that heat support systems are functioning at a level required to maintain normothermia during anesthetic procedures.

Use of Air-activated Thermal Devices during Recovery after Surgery in Mice.

Laboratory mice (Mus musculus) are susceptible to hypothermia, especially during anesthetic events, disease states, and exposure to environmental stressors. Thermal support devices for small mammals are numerous, but often require a power source and may be impractical to use for cages on a rack. Air-activated thermal devices (AATD) are mixtures of chemicals that cause an exothermic reaction. In this study, we examined the environmental effects of AATD on internal cage temperatures without the use of additional equipment as well as the physiologic effects of AATD as postoperative thermal support in mice. For environmental experiments, temperatures measured inside the cage and above the AATD peaked at 35.6 ± 2.5 °C (13.4 °C higher than control cages). We also demonstrated that the amount of heat produced by AATD and its temporal distribution are dependent on cage and rack types. For physiologic experiments, mice were surgically implanted with an intraperitoneal temperature telemetry device in a static cage setting. Recovery times and final body temperature at 5 h postoperatively did not differ significantly between mice with and without AATD. During the first 0 to 3 h after mice returned to their home cages, body temperature dropped markedly in mice without AATD but not in mice with AATD. Based on this result the physiologic results of our study support that AATD can be useful in providing extended thermal support for mice housed in static microisolation cages to help maintain body temperature postsurgically. Environmental results of our studies demonstrated that AATD provide local clinically relevant thermal support for 2.5 to 6 h, depending on cage set-up.

Duodenal Cannulation in Pigs (Sus scrofa) as a Drug Delivery Method.

Currently available animal models for delivery of drug capsules and pharmacokinetic testing are limited by either intersubject variability in gastric emptying time or the need to sedate animals when using targeted delivery methods of drug capsules. With the increasing development of large-molecule biologics, better in vivo models for testing the pharmacokinetics of capsule-delivered drugs are urgently needed. To this end, we made engineering modifications to an existing bovine surgical cannula device, successfully implanted this modified cannula into pigs, and delivered drug capsules directly to the proximal duodenum. In our porcine model, capsule insertion and serial blood samples were all acquired without the use of sedatives. Furthermore, we were able to maintain cannulated pigs for weekly pharmacokinetic testing for more than 18 mo, with minimal postoperative complications. This study demonstrates a novel and effective porcine model of sedation-free drug delivery and blood collection that eliminates inconsistencies associated with models that require either gastric emptying or animal sedation.

Hemodynamic effects of left atrial or left ventricular cannulation for acute circulatory support in a bovine model of left heart injury.

Our objective was to examine the hemodynamic effects of a trans-aortic axial flow catheter (Impella CP) in the left ventricle (LV) versus left atrial (LA) to femoral artery bypass using a centrifugal pump (TandemHeart: TH) in a bovine model of acute LV injury. In three male calves, we performed sequential activation of a CP then TH device in each animal. After 60 minutes of left anterior descending artery ligation, a CP was activated at maximal power. The CP was then removed and the TH activated at 5,500 then a maximum of 7,500 rotations per minute (RPM). The CP generated a maximum 3.1 ± 0.2 L/minute (LPM) of flow, whereas the TH at 5,500 and 7,500 RPM generated 3.1 ± 0.4 and 4.4 ± 0.3 LPM. At 3.1 LPM, the CP and TH reduced LV stroke work (LVSW) similarly. The TH reduced stroke volume, whereas the CP did not. The CP reduced end-systolic pressure, whereas the TH did not. At a maximum flow of 4.4 LPM, the TH provided a greater reduction in LVSW than maximal CP activation. This is the first report to compare the hemodynamic effects of trans-aortic LV unloading versus LA-to-femoral artery (FA) bypass.