Effect of bupivacaine liposome suspension administered as a local anesthetic block on indicators of pain and distress during and after surgical castration in dairy calves

Castration is a routine procedure performed on beef and dairy operations in the U.S. All methods of castration cause behavioral, physiologic, and neuroendocrine changes associated with pain. The American Veterinary Medical Association and the American Association of Bovine Practitioners recommend that anesthesia and analgesia be administered at castration. The objective of this study was to evaluate the effectiveness of bupivacaine liposome suspension a novel, long-acting, local anesthetic administered as a nerve block at castration. The authors chose to investigate this novel formulation as an alternative to current industry standards using lidocaine nerve blocks alone, or in combination with meloxicam. Thirty male Holstein calves, 16-20 weeks of age, were enrolled and randomly assigned to 1 of 4 treatment groups prior to surgical castration: 1) bupivacaine liposome suspension block + oral placebo (BUP); 2) lidocaine block + oral placebo (LID); 3) lidocaine block + oral meloxicam (1 mg/kg) (LID + MEL); and 4) saline block + oral placebo (CON). Biomarkers were collected at -24 h and from 0 to 120 hours post-castration and included infrared thermography, pressure mat gait analysis, chute defense and behavior scoring (pain and activity), and blood sampling for serum cortisol and prostaglandin E2 metabolites (PGEM). Responses were analyzed using repeated measures, with calf nested in treatment as a random effect, and treatment, time, and their interaction designated as fixed effects. Results from pressure mat gait analysis show the CON had a shorter front limb stance time from baseline (-8.73%; 95% CI: -24.84 to 7.37%) compared to BUP and LID + MEL (> 5.70%; 95% CI: -22.91 to 23.79%) (P < 0.03). The CON tended to have an increase in front limb force from baseline (6.31%; 95% CI: -1.79 to 14.41%) compared to BUP, LID, and LID + MEL (< -5.06%; 95% CI: -14.22 to 0.95%) (P < 0.04). The CON displayed higher counts of hunched standing (2.00; 95% CI: 1.68 to 2.32) compared to LID + MEL (1.43; 95% CI: 1.13 to 1.72) (P = 0.05). The CON had higher cortisol concentrations at 24 h (7.70 ng/mL; 95% CI: 1.52 to 13.87 ng/mL) relative to BUP (3.11 ng/mL; 95% CI: -2.56 to 8.79 ng/mL) (P = 0.002). At 4 and 24 h, LID + MEL had lower PGEM concentrations from baseline (-32.42% and -47.84%; 95% CI: -78.45 to -1.80%) compared with CON (27.86% and 47.63%; 95% CI: 7.49 to 82.98%) (P < 0.02). Administration of bupivacaine liposome suspension as a local anesthetic block at the time of castration was as effective at controlling pain as a multi-modal approach of lidocaine and meloxicam.

Preparation of liposomal nanocarrier by extruder to enhance tumor accumulation of paclitaxel

Despite the wide-spectrum and effective anti-cancer activity of paclitaxel (PTX), their low solubility and side effects are the main challenges in their clinical application. In this study, a model paclitaxel-encapsulated nanoliposome (NLips-PTX) carrier was synthesized to enhance PTX solubility and increase its passive accumulation at the tumor site. Soy lecithin and cholesterol at a 9:1 ratio were used to prepare the nano-sized liposomes through the thin-film hydration followed by extrusion technique. The prepared spherical NLips-PTX liposomes with an average size of about 150 nm and high uniformity were characterized by DLS and TEM. PTX load efficiency of NLips was determined at about 85% by HPLC. NLips-PTX also showed a therapeutic effect toward breast cancer cells (MCF-7) in a dose- and time-dependent manner via in vitro cellular uptake and a cytotoxicity study. This research indicates that extrusion is a simple and convenient method for nano-sizing and homogenising liposome suspension for potentially effective delivery of drug to target tumor sites.

Heterogeneity in Lateral Distribution of Polycations at the Surface of Lipid Membrane: From the Experimental Data to the Theoretical Model

Natural and synthetic polycations of different kinds attract substantial attention due to an increasing number of their applications in the biomedical industry and in pharmacology. The key characteristic determining the effectiveness of the majority of these applications is the number of macromolecules adsorbed on the surface of biological cells or their lipid models. Their study is complicated by a possible heterogeneity of polymer layer adsorbed on the membrane. Experimental methods reflecting the structure of the layer include the electrokinetic measurements in liposome suspension and the boundary potential of planar bilayer lipid membranes (BLM) and lipid monolayers with a mixed composition of lipids and the ionic media. In the review, we systematically analyze the methods of experimental registration and theoretical description of the laterally heterogeneous structures in the polymer layer published in the literature and in our previous studies. In particular, we consider a model based on classical theory of the electrical double layer, used to analyze the available data of the electrokinetic measurements in liposome suspension with polylysines of varying molecular mass. This model suggests a few parameters related to the heterogeneity of the polymer layer and allows determining the conditions for its appearance at the membrane surface. A further development of this theoretical approach is discussed.

The Elucidation of the Molecular Mechanism of the Extrusion Process

Extrusion is a popular method for producing homogenous population of unilamellar liposomes. The technique relies on forcing a lipid suspension through cylindrical pores in a polycarbonate membrane. The quantification of the extrusion and/or recalibration processes make possible the acquisition of experimental data, which can be correlated with the mechanical properties of the lipid bilayer. In this work, the force needed for the extrusion process was correlated with the mechanical properties of a lipid bilayer derived from other experiments. Measurements were performed using a home-made dedicated device capable of maintaining a stable volumetric flux of a liposome suspension through well-defined pores and to continuously measure the extrusion force. Based on the obtained results, the correlation between the lipid bilayer bending rigidity and extrusion force was derived. Specifically, it was found that the bending rigidity of liposomes formed from well-defined lipid mixtures agrees with data obtained by others using flicker-noise spectroscopy or micromanipulation. The other issue addressed in the presented studies was the identification of molecular mechanisms leading to the formation of unilamellar vesicles in the extrusion process. Finally, it was demonstrated that during the extrusion, lipids are not exchanged between vesicles, i.e., vesicles can divide but no membrane fusion or lipid exchange between bilayers was detected.

179 A Comparison of Local Anesthetic Effectiveness in Reducing Pain Associated with Dehorning in Dairy Calves

Dehorning is performed on a high percentage of dairies in the United States. Concern for animal welfare has led to investigating pain mitigation during dehorning. The objective was to compare the effectiveness of bupivacaine liposome suspension, lidocaine, or lidocaine + meloxicam administered at dehorning. Fifty male Holstein calves, 10–14 weeks of age were enrolled and randomly assigned to 1 of 5 treatment groups: 1) bupivacaine liposome suspension block, oral placebo, cautery dehorn (BUP); 2) lidocaine block, oral placebo, cautery dehorn (LID); 3) lidocaine block, oral meloxicam, cautery dehorn (LID + MEL); 4) saline block, oral placebo, cautery dehorn (CON); and 5) saline block, oral placebo, sham dehorn (SHAM). Biomarkers were collected from 0 to 120 hours post-dehorning and included infrared thermography (IRT), mechanical nociceptive threshold (MNT), and pressure mat gait analysis. Biomarkers were statistically analyzed using repeat measures with the calf being the repeated measure. There were no significant treatment differences for IRT measures. A treatment effect was observed for the mean difference of the right horn bud minus a control point which were -1.21 kgF, -1.41 kgF, -1.56 kgF, -1.65 kgF, and -1.68 kgF for the SHAM, CON, BUP, LID + MEL, and LID groups, respectively (P = 0.004). The BUP group did not differ from CON (P = 0.78) or SHAM (P = 0.07). A treatment effect was observed for gait distance means which were 182.05 cm, 189.69 cm, 195.77 cm, 199.54 cm, and 200.59 cm for the SHAM, BUP, LID + MEL, LID and CON groups, respectively (P = 0.04). The CON group did not differ from BUP, LID, or LID + MEL (P > 0.05) but did differ from SHAM (P = 0.02). These data show that administration of bupivacaine liposome suspension at the time of dehorning was not different than lidocaine or lidocaine + meloxicam.

Drop coating deposition of a liposome suspension on surfaces with different wettabilities: “coffee ring” formation and suspension preconcentration

A study of “coffee ring” formation and preconcentration of a liposome suspension dropped on six surfaces with different physico-chemical characteristics.