Biocompatible photocrosslinked poly(ester anhydride) based on functionalized poly(epsilon-caprolactone) prepolymer shows surface erosion controlled drug release in vitro and in vivo.

Star-shaped poly(epsilon-caprolactone) oligomers functionalized with succinic anhydride were used as prepolymers to prepare photocrosslinked poly(ester anhydride) to evaluate their in vivo drug delivery functionality and biocompatibility. Thus, in this work, erosion, drug release and safety of the photocrosslinked poly(ester anhydride) were examined in vitro and in vivo. A small water-soluble drug, propranolol HCl (M(w) 296 g/mol, solubility 50 mg/ml), was used as the model drug in an evaluation of the erosion controlled release. Drug-free and drug-loaded (10-60% w/w) poly(ester anhydride) discoids eroded in vitro (pH 7.4 buffer, +37 degrees C) linearly within 24-48 h. A strong correlation between the polymer erosion and the linear drug release in vitro was observed, indicating that the release had been controlled by the erosion of the polymer. Similarly, in vivo studies (s.c. implantation of discoids in rats) indicated that surface erosion controlled drug release from the discoids (drug loading 40% w/w). Oligomers did not decrease cell viability in vitro and the implanted discoids (s.c., rats) did not evoke any cytokine activity in vivo. In summary, surface erosion controlled drug release and the safety of photocrosslinked poly(ester anhydride) were demonstrated in this study.

Piperazine-based buffers for liposome coating of capillaries for electrophoresis.

Anionic liposomes can be coated on fused-silica capillaries for electrophoresis in the presence of N-(hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) (HEPES) as background electrolyte (BGE) solution. In this work, the interaction of various compounds with zwitterionic and anionic phospholipid coatings was studied with HEPES at pH 7.4 as BGE solution. The chromatographic and electrophoretic behavior of three test sample solutions (anionic, cationic, and neutral) was investigated for evaluation of the phospholipid coatings. Our results show that hydrophobic interactions between analytes and the phospholipid coating are important for the migration of charged analytes. In addition, the performances of other piperazine-based buffers, i.e., N-(2-hydroxyethyl)piperazine-N'-(2-hydroxypropanesulfonic acid), piperazine-N,N'-bis(2-ethanesulfonic acid), and piperazine-N,N'-bis(hydroxypropane sulfonic acid), at pH 7.4, as liposome solvent and BGE solution were evaluated and compared with the performance of HEPES at pH 7.4. The anionic liposome solution comprised 80/20 mol% phosphatidylcholine/phosphatidylserine. A simple test solution was selected and the chromatographic and electrophoretic migration behavior of the analytes was evaluated. The results show that, in addition to HEPES, other piperazine-based buffers at pH 7.4 are suitable for coating of fused-silica capillaries with anionic liposomes.

Stabilization of phosphatidylcholine coatings in capillary electrophoresis by increase in membrane rigidity.

Divalent cations affect the stability and structure of phospholipid vesicles and also the binding and immobilization of proteins into phospholipid membranes. The effect of calcium, magnesium, and zinc on zwitterionic phosphatidylcholine (PC) coatings in fused silica capillaries for electrophoresis was the primary interest in this work. In addition, the effect of temperature on the coating stability was investigated by coating 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes at temperatures above and below the gel- to fluid-state transition. All coatings were performed with PC large unilamellar vesicles (LUV) in 40 mM N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) (HEPES) at pH 7.4 as basic solution. HEPES (40 mM) at pH 7.4 was used as background electrolyte (BGE) throughout the study. The stability of the coating was studied by measuring the electroosmotic flow. A molar ratio of 1:3 PC/Ca2+ or PC/Mg2+ gave the best coating stability owing to the increased rigidity of the phospholipid membrane furnished by the divalent metal ions. Better results were obtained with DPPC in the more rigid gel state than in the fluid state: the electroosmotic flow was much suppressed and the PC coating was stabilized. Coating the fused silica capillary with PC liposome-metal ion buffer solutions resulted in good electrophoretic separation of basic model proteins (pI-values 7.8-11.0). The electrophoretic results demonstrate the importance of stabilizing the phospholipid coating on fused silica capillaries, either by the addition of divalent metal ions (Ca2+, Mg2+, or Zn2+) or by working in the gel-state region of the phospholipid.

Cytokine balance and lipid antigen presentation in the NOD mouse pancreas during development of insulitis.

The role of cytokine balance and lipid antigen presentation in the development of diabetes was studied using immunohistochemistry of cytokines in the pancreas of non-obese diabetic mice (NOD) and BALB/c mice at various ages. In both the NOD and BALB/c mice, interleukin 10 (IL-10) was expressed in the islets. IL-10 was also present in the epithelial cells of the exocrine tissue in both strains. In the NOD mice, IL-10 disappeared from both the islets and the exocrine tissue at 16 weeks of age. At this age, IL-10 was still present in the islets and exocrine tissue of the BALB/c pancreata. IL-10 was not present in the pancreata of diabetic NOD mice. IL-6 first appeared in the pancreas at 10 weeks of age and disappeared at the age of 16 weeks in both NOD and BALB/c mice. It was present in the endothelial cells. Neither the pancreata of normal BALB/c mice nor NOD mice at 2-16 weeks of age contained tumor necrosis factor alpha (TNF-alpha), interferon gamma (IFN-gamma), IL-4, or IL-12. At 8 weeks of age, a few IL-2+ cells were found in the pancreas of one of three NOD mice. CD1d was already present in both strains at 2 weeks of age but disappeared from the NOD mice at 16 weeks of age. CD1d localized to walls of tubular structures probably representing collecting tubules. These results suggest that in the NOD mice the disappearance of the T(H0), T(H1), and T(H2) responses inhibiting IL-10 from the islets at the age of 16 weeks may trigger the final stage of the immune response leading to overt diabetes. The simultaneous disappearance of CD1d suggests that activation of immune responses against lipid antigens does not play a role in this stage of the disease.