乌拉坦对大鼠肾脏滤过功能的影响

以９９ｍＴｃ－ＤＴＰＡ颈静脉“弹丸”式注入，用ＳＰＥＣＴ技术研究乌拉坦麻醉大鼠的肾脏滤过功能。结果表明乌拉坦麻醉大鼠肾脏滤过功能明显降低（Ｐ＜０．０５），与给药途径无关。     

Catalyst‐Free Ring Opening Synthesis of Biodegradable Poly(ester‐urethane)s Using Isosorbide Bio‐Based Initiator

Polycaprolactones are obtained via ring opening polymerization of ε‐caprolactone in catalyst‐free condition. The polymerization is initiated in bulk, using isosorbide‐based amino‐alcohol as a biosourced initiator. The ratio of initiator to ε‐caprolactone, as well as to temperature, is optimized in order to tune the hydroxyl number (Nr. OH) and the average molecular weight of the polymers. In addition, these biocompatible polyesters are used as soft‐block to prepare thermoplastic poly(esterurethane)s elastomers via a simple one‐pot catalyst‐free polymerization. The successful synthesis of poly(esterurethane)s is confirmed by Fourier transform‐infrared spectroscopy, and the thermal properties are studied by differential scanning calorimetry. These novel materials exhibit glass transition temperatures ranging from 7 to 38 °C. The biodegradability of these elastomers is evaluated by enzymatic degradation tests performed at rt in phosphate buffer solution (pH ≈ 7.4). The mass loss of polymer films is around 3% after 4 weeks. Scan electron as well as atomic force microscopies are used to show the degradation patterns.     

Synthesis,Characterization and Biomedical Properties of UV-Cured Polyurethane Acrylates Containing a Phosphorylcholine Structure

Abstract

In order to develop a simple, economical and rapid approach to incorporate 2-methacryloyloxyethyl phosphorylcholine (MPC) with other monomers without any solvent, we prepared a series of ultraviolet cured poly(urethane acrylate) (PUA) membranes containing different MPC content. Their chemical structure and surface properties were investigated by FT-IR, XPS, water swelling ratio and water contact angle measurement, while the biocompatibilities were evaluated through fibrinogen adsorptions, platelet adhesion and plasma recalcification time determination. The results demonstrate that the phosphorylcholine (PC) groups were successfully introduced into the PUA system by the UV-curing approach and the all PC-containing membranes showed better biocompatibility than those without PC moiety. The UV-curing method is potentially to be applied in the coating of medical devices which require biocompatibility and manufacturing efficiency.     

Biodegradable poly(ester urethane) urea scaffolds for tissue engineering: Interaction with osteoblast-like MG-63 cells

Porous three-dimensional scaffolds with potential for application as cancellous bone graft substitutes were prepared from aliphatic segmented poly(ester urethane) urea using the phase-inverse technique. Proton nuclear magnetic resonance, size-exclusion chromatography, electron spectroscopy for chemical analysis, secondary ion mass spectrometry, infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, computed tomography and mechanical tests were carried out, to characterize the scaffolds’ physicochemical properties. Human osteosarcoma MG-63 cells were seeded into the scaffolds for 1, 2, 3 and 4 weeks to evaluate their potential to support attachment, growth and proliferation of osteogenic cells. The scaffold–cell interaction was assessed by analysis of DNA content, total protein amount, alkaline phosphatase activity and WST-1 assay. The scaffolds supported cell attachment, growth and proliferation over the whole culture period of 4 weeks (DNA, total protein amount). There was, however, a reduction in the WST-1 assay values at 4 weeks, which might suggest a reduction in the rate of cell proliferation at this time.     

Development of a Tissue‐Engineered Lymphatic Graft Using Nanocomposite Polymer for the Treatment of Secondary Lymphedema

Damage of the lymphatic vessels, commonly due to surgical resection for cancer treatment, leads to secondary lymphedema. Tissue engineering approach offers a possible solution to reconstruct this damage with the use of lymphatic graft to re‐establish the lymphatic flow, hence preventing lymphedema. The aim of this study is to develop a tissue‐engineered lymphatic graft using nanocomposite polymer and human dermal lymphatic endothelial cells (HDLECs). A nanocomposite polymer, the polyhedral oligomeric silsequioxane‐poly(carbonate‐urea)urethane (POSS‐PCU), which has enhanced mechanical, chemical, and physical characteristics, was used to develop the lymphatic graft. POSS‐PCU has been used clinically for the world's first synthetic trachea, lacrimal duct, and is currently undergoing clinical trial for coronary artery bypass graft. Two designs and fabrication methods were used to manufacture the conduits. The fabrication method, the mechanical and physical properties, as well as the hydraulic conductivity were tested. This is followed by in vitro cell culture analysis to test the cytocompatibility of HDLEC with the polymer surface. Using the casted extrusion method, the nanocomposite lymphatic graft demonstrates desirable mechanical property and hydraulic conductivity to re‐establish the lymphatic flow. The conduit has high tensile strength (casted: 74.86 ± 5.74 MPa vs. coagulated: 31.33 ± 3.71 MPa; P < 0.001), favorable kink resistance, and excellent suture retention property (casted vs. coagulated, P < 0.05). Cytocompatibility study showed that the POSS‐PCU scaffold supports the attachment and growth of HDLECs. This study demonstrates the feasibility of developing a tissue‐engineered lymphatic graft using the nanocomposite polymer. It displays excellent mechanical property and cytocompatibility to HDLECs, offering much promise for clinical applications and as a new treatment option for secondary lymphedema.     

Utilization of 1-hydroxybenzotriazole in mixed anhydride coupling reactions

The coupling of Boc-Val-OH to either H-Pro-OBzl or H-Pro-Gly-Val-Gly-OBzl by the mixed anhydride method leads to the formation of a urethane by-product in yields of 40–60%. This side reaction can be suppressed by the addition of HOBt to the reaction mixture before the amino component is added. This results in a substantially increased yield of the desired peptide.     

Interactions between N-acetylcysteine and sodium selenite in modulating the clastogenicity of urethane and 2-acetylaminofluorene in mice

Combined treatment with different agents represents a promising approach in cancer chemoprevention. Therefore, it is useful to assess in preclinical models the efficacy of combinations that are selected by taking into account mechanistic considerations. We designed 2 studies evaluating the interaction between N-acetylcysteine (NAC) and sodium selenite (Se), both given with the drinking water to Balb/c mice, in modulating clastogenic effects in bone marrow polychromatic erythrocytes. In a first study, a single i.p. injection of urethane considerably enhanced the frequency of micronucleated cells. While NAC produced a significant inhibition, Se further enhanced urethane clastogenicity. When given in combination at the same doses, NAC prevented the adverse effect of Se. In a second study, a single i.p. injection of 2-acetylaminofluorene enhanced the frequency of micronucleated cells. Se did not reduce this effect to a significant extent, while NAC produced a dose-dependent inhibition. When tested at the lower dose in combination with Se, the protective effect of NAC was unchanged. Especially in association with Se, NAC also prevented the toxicity of 2-acetylaminofluorene by normalizing the ratio of polychromatic to normochromatic erythrocytes. In conclusion, NAC attenuated the clastogenicity of both urethane and 2-acetylaminofluorene and the toxicity of this aromatic amine. In addition, NAC prevented the clastogenic and toxic effects resulting from the interaction of Se with urethane. Together with the findings of previous studies, it appears that, besides its intrinsic protective properties in carcinogenesis, NAC is capable of attenuating the adverse effects of several cytotoxic drugs and chemopreventive agents.     

Somatovesical and vesicovesical excitatory reflexes in urethane-anaesthetized rats

The effect of spinal cord transection on excitatory somato- and vesicovesical micturition reflexes have been investigated in urethane-anaesthetized rats. In adult rats, 3 distinct types of excitatory reflexes to the bladder may be observed: a somatovesical reflex organized at spinal level and two vesicovesical reflexes organized at spinal and supraspinal level, respectively. In agreement with results of lesion experiments (Neurosci. Lett., 8 (1978) 27-33), bladder voiding is abolished following spinal cord transection although both somato- and vesicovesical reflexes may be demonstrated in acute spinal rats. Occurrence of the spinal vesicovesical reflex during the collecting phase of the cystometrogram appears to be inhibited by a supraspinal inhibitory pathway.