Unique aggregation of conjugated amphotericin B and its interaction with lipid membranes.

The purpose of this paper was to investigate the aggregation of amphotericin B (AMB) and AMB-arabinogalactan conjugate (AMB-AGC), and the interactions of these drugs with free and membrane-embedded sterols. Aggregation of AMB and AMB-AGC was studied by circular dichroic (CD) and UV absorbance spectroscopic techniques. The effect of liposomes on the spectra was utilized to investigate the interactions of aggregates with membrane-embedded sterols. Interaction with free sterols was studied by measuring sterols' effect on AMB/AMB-AGC susceptibility test. The results demonstrated that AMB-AGC forms unique aggregates in aqueous solution which differ from those formed by free AMB. Ergosterol and cholesterol embedded in liposomes, affected the CD spectra obtained for both AMB and AMB-AGC, indicating interactions of these sterols with both drugs. Interaction with both cholesterol and ergosterol resulted in an increase of AMB-AGC's minimal inhibitory concentration (MIC) in Candida albicans. In conclusion, AMB-AGC forms unique aggregates in aqueous solution; these aggregates interact with membrane-embedded cholesterol and ergosterol and with free sterols. These results indicate that the selectivity of AMB-AGC to fungal cells may not occur due to inability to bind cholesterol but probably as a result of this unique aggregation. Understanding this mechanism may help to develop a safer AMB formulation for therapy.

Interspecies differences in reaction to a biodegradable subcutaneous tissue filler: severe inflammatory granulomatous reaction in the Sinclair minipig.

Soft tissue filler products have become very popular in recent years, with ever-increasing medical and aesthetic indications. While generally considered safe, the number of reported complications with tissue fillers is growing. Nevertheless, there is no specific animal model that is considered as the gold standard for assessing safety or efficacy of tissue fillers, and there are very little data on interspecies differences in reaction to these products. Here, we report on interspecies differences in reaction to a subcutaneous injectable co-polyester, composed of castor oil and citric acid. Comparison of the histopathological local tissue changes following 1-month postimplantation, indicated that in rats the reaction consisted of cavities, surrounded by relatively thin fibrotic enveloping capsule. In contrast, an unexpected severe inflammatory granulomatous reaction was noticed in Sinclair minipigs. To our knowledge, this is the first report on significant interspecies differences in sensitivity to tissue fillers. It emphasizes the importance of using the appropriate animal model for performing preclinical biocompatibility assays for biodegradable polymers, tissue fillers, and implanted medical devices in general. It also makes the Sinclair minipig subject for scrutiny as an animal model in future biocompatibility studies.

Activity, reduced toxicity, and scale-up synthesis of amphotericin B-conjugated polysaccharide.

Amphotericin B (AMB) arabinogalactan (AG) conjugate was synthesized by the conjugation of AMB to oxidized AG by reductive amination. The conjugate was evaluated for in vitro antifungal activity and in vivo toxicity. Optimization of the conjugation process was investigated using large batches of 100 g, which are 20 times larger than previously reported for AMB-AG conjugation. The efficacy of AMB-AG conjugates was studied as a function of reaction conditions and time, aldehyde/reducing agent mole ratio, and purification procedure. The most potent AMB-AG conjugate having low minimal inhibitory concentration (MIC) and high maximal tolerated dose (MTD) was obtained following reduction with NaBH4 at 1:2 mol ratio (AG units/NaBH4) at 25 °C for 24 h. AMB-AG conjugate prepared under these conditions demonstrated MIC of 0.5 mg/L (equiv of AMB) in Candida albicans, and an MTD of 60 mg/kg (equiv of AMB) in mice, while AMB clinical formulation (Fungizone) demonstrated high toxicity (MTD = 3 mg/kg). These findings confirm the simplicity and reproducibility of the conjugation allowing this method to be applied on larger scale production.

Extended release local anesthetic agents in a postoperative arthritic pain model.

Local anesthetics play an important role in postoperative pain management in orthopedic joint procedures. The aim of this study was to determine the effect of an intraoperative extra-articular injection of poly(DL-lactic acid co castor oil 3:7), p(DLLA:CO) 3:7 loaded with 15% bupivacaine, for postoperative analgesia following knee arthroplasty. Prolonged release local anesthetic formulation was synthesized by mixing p(DLLA:CO) 3:7 with bupivacaine base. Under anesthesia, the knee joint of Sprague-Dawley rats was exposed, a hole drilled in the femoral trochlea. 0.2 mL of either 15% polymer-bupivacaine formulation or plain bupivacaine (control) was injected locally and compared with a nonsurgery control group. Mechanical hyperalgesia was determined by counting the vocalizations and leg withdrawal after joint squeezing. Behavioral assessments over a day postoperative period revealed a reduction in rearing and ambulation in an open-field apparatus in animals of both experimental groups compared with the nonsurgery control. The vocalizations during the hyperalgesia test increased compared with the control at 24 h. At 48 h, 3.667 ± 0.5138, p = 0.0076 vocalizations were recorded for the plain bupivacaine group versus 1.417 ± 0.5138, p < 0.0001 in the 15% polymer-bupivacaine formulation. Bupivacaine encapsulated in p(DLLA:CO) 3:7 extended the duration of the analgesia compared with plain drug in rats and could represent effective postoperative analgesic in orthopedic joint procedures.

In vivo degradation and elimination of injectable ricinoleic acid-based poly(ester-anhydride).

The in vivo degradation and elimination after subcutaneous implantation of injectable p(SA-RA) 3:7 copolymer in rats, followed by characterization of the polymer matrix composition during hydrolysis and erosion, is reported. Major chemical changes were observed during the first few days post implantation, the anhydride bonds hydrolyzed along with about 45% weight loss and a significant decrease in the molecular weight. 1H NMR spectral analysis was used to determine the structures and content of ricinoleic acid containing oligomeric chains present in the degraded polymer. The polymer degrades into ester oligomers of 2-4 ricinoleic acid units which further degrade to ricinoleic acid, a natural fatty acid. The polymer hydrolytic degradation process fit the in vitro degradation process.