肝素涂层体外循环管道抗凝血性能的研究

目的 评测3种离子键肝素涂层体外循环管道的抗凝血性能和稳定性。方法 用PT和APTT对不同浓度肝素—氯烃基二甲基代苯甲胺(HBC)复合物涂层体外循环管道的凝血性能进行评测，同时测试体外转流对3种肝素涂层管道抗凝血性能的影响。结果 3种肝素涂层方法均能够将肝素分子结合于材料表面并具有抗凝活性，其中HBC复合物和肝素—聚乙烯亚胺复合物处理的体外循环管道经体外转流96h后仍具有较佳的抗凝血活性。结论 离子键肝素涂层因结合物质不同其稳定性也不同；HBC复合物和肝素—聚乙烯亚胺复合物处理的体外循环管道肝素分子结合较牢固，能够满足临床短期使用需要。     

The activation of human plasma prekallikrein as a hemocompatibility test for biomaterials. II. Contact activation by EVAL and EVAL-SMA copolymers

The activation of human plasma prekallikrein (PKK) to kallikrein (KK), induced by the contact of blood with foreign materials, is a useful in vitro hemocompatibility test. Kallikrein is easily detected by its reaction with the chromogenic substrate H-D-Pro-Phe-Arg-pNA, which releases p-nitroaniline, revealed by its absorption at 405 nm. This test, which was already carried out by evaluating PKK activation by the 'end-point' method, has been carried out in this work by the more accurate 'initial velocity' method, i.e. by evaluating the activation from the initial rates of the KK-substrate reaction. The tests were carried out on the following materials: borosilicate glass (as a high-activation reference material), silicone (as a low-activation reference material), the commercial biomaterial Cardiothane 51, three graft copolymers synthesized in our laboratory by reacting ethylene-vinyl alcohol copolymer (EVAL) with styrene-maleic anhydride copolymer (SMA), and EVAL itself. A mathematical treatment based on a simple kinetic model has been used for a first-approximation evaluation of the PKK-activating power of the materials tested. The quite low activating power of the EVAL-SMA copolymers, which are easily processable into water-permeable hollow fibers, suggests the possibility of their use in blood dialyzers.     

Synthesis,biocompatible, and self-assembly properties of poly (ethylene glycol)/lactobionic acid-grafted chitosan

Polymers with targeted ligands are widely used as the anti-cancer drug delivery materials. For applications of chitosan as an anti-liver cancer drug delivery, poly (ethylene glycol)/lactobionic acid-grafted chitosan (PEG/LA-CS) was prepared and investigated since lactobionic acid can be specifically recognized by the hepatocytes. The structure of the PEG/LA-CS was characterized by Fourier transform infrared spectrometry and elemental analysis. The self-assembly behaviors of the PEG/LA-CS were monitored by steady-state fluorescence spectroscopy and electronic transmission microscope. The protein adsorption of the PEG/LA-CS was detected with bovine serum albumin (BSA) by electrochemical impedance spectroscopy. The results showed that the PEG/LA-CS almost did not adsorb protein. To study the effects of PEG/LA-CS on the structure of BSA, the interactions between the PEG/LA-CS and BSA were detected by ultraviolet spectrum, fluorescence spectrum, and circular dichroism. All the data gave one result that BSA maintained its original folded confirmation in PEG/LA-CS solution. The hemocompatibility of PEG/LA-CS was investigated by observing the effects of PEG/LA-CS on the hemolysis rate and the plasma recalcification time (PRT). The results showed that the PRT was prolonged greatly and the hemolysis rate was less than 5%. Furthermore, PEG/LA-CS also showed good cytocompatibility with K562, Hep G2, and LO2 cells. Therefore, the PEG/LA-CS is believed to have great potential for producing injectable anti-liver cancer drug delivery.     

Bacteriomimetic poly-γ-glutamic acid surface coating for hemocompatibility and safety of nanomaterials

Poly-γ-glutamic acid (PGA), a major component of the bacterial capsule, is known to confer hydrophilicity to bacterial surfaces and protect bacteria from interactions with blood cells. We tested whether applying a bacteriomimetic surface coating of PGA modulates interactions of nanomaterials with blood cells or affects their safety and photothermal antitumor efficacy. Amphiphilic PGA (APGA), prepared by grafting phenylalanine residues to PGA, was used to anchor PGA to reduced graphene oxide (rGO) nanosheets, a model of hydrophobic nanomaterials. Surface coating of rGO with bacterial capsule-like APGA yielded APGA-tethered rGO nanosheets (ArGO). ArGO nanosheets remained stable in serum over 4?weeks, whereas rGO in plain form precipitated in serum within 5?minutes. Moreover, ArGO did not interact with blood cells, whereas rGO in plain form or as a physical mixture with PGA formed aggregates with blood cells. Mice administered ArGO at a dose of 50?mg/kg showed 100% survival and no hepatic or renal toxicity. No mice survived exposure at the same dose of rGO or a PGA/rGO mixture. Following intravenous administration, ArGO showed a greater distribution to tumors and prolonged tumor retention compared with other nanosheet formulations. Irradiation with near-infrared light completely ablated tumors in mice treated with ArGO. Our results indicate that a bacteriomimetic surface modification of nanomaterials with bacterial capsule-like APGA improves the stability in blood, biocompatibility, tumor distribution, and photothermal antitumor efficacy of rGO. Although APGA was used here to coat the surfaces of rGO, it could be applicable to coat surfaces of other hydrophobic nanomaterials.     

Biocompatible implant mimicking cartilage: A new horizon for reconstructive facial field

Cartilage is avascular with limited to no regenerative capacity, so its loss could be a challenge for reconstructive surgery. Current treatment options for damaged cartilage are also limited. In this aspect there is a tremendous need to develop an ideal cartilage-mimicking biomaterial that could repair maxillofacial defects. Considering this fact in this study we have prepared twelve silicone-based materials (using Silicone 40, 60, and 80) reinforced with hydroxyapatite, tri-calcium phosphate, and titanium dioxide which itself has proven their efficacy in several studies and able to complement the shortcomings of using silicones. Among the mechanical properties (Young’s modulus, tensile strength, percent elongation, and hardness), hardness of Silicone-40 showed similarities with goat ear (P > .05). Silicone peaks have been detected in FTIR. Both AFM morphology and SEM images of the samples confirmed more roughed surfaces. All the materials were nonhemolytic in hemocompatibility tests, but among the twelve materials S2, S3, S5, and S6 showed the least hemolysis. For all tested bacterial strains, adherence was lower on each material than that grown on the plain industrial silicone material which was used as a positive control. S2, S3, S5, and S6 samples were selected as the best based on mechanical characterizations, surface characterizations, in vitro hemocompatibility tests and bacterial adherence activity. So, outcomes of this present study would be promising when developing ideal cartilage-mimicking biocomposites and their emerging applications to treat maxillofacial defects due to cartilage damage.     

Cellulose Carbamates and Derivatives as Hemocompatible Membrane Materials for Hemodialysis

Dialysis membranes made from regenerated cellulose are under dispute because of their alleged lack of hemocompatibility. The introduction of membranes from synthetically modified cellulose, like cellulose acetate or Hemophan, has proven, however, that hemocompatible membranes can be fabricated from cellulose by means of chemical surface modifications. In addition to membranes made from modified cellulose like ethers or esters, which were investigated in earlier experiments, we looked for further cellulose modifications to be assessed for their hemocompatibility. For this purpose, we synthesized a series of cellulose carbamate derivatives to profit from the excellent hemocompatibility pattern of the urethane family. In vitro investigations on membranes made from these cellulose modifications proved a direct relationship between the degree of modification and hemocompatibility. This was proven for the following 3 representative hemocompatibility parameters: complement C5a generation, thrombin-antithrombin (TAT) III formation, and platelet count (PC). As already shown for modifications made from cellulose esters, a direct dependency between improved hemocompatibility and the degree of substitution (DS) in the cellulose molecule could be found. In our experiments, a degree of substitution below a value of 0.1 led to a nearly complete suppression of complement activation for all cellulose carbamates under investigation. In contrast to data on cellulose esters, we observed that molecular weight or molecular conformation of chemical substituents exerted only a minor effect on the hemocompatibility pattern. In addition, data on cellulose carbamate esters (e.g., cellulose succinate-phenyl-carbamate) show that a simultaneous but balanced substitution with hydrophilic and hydrophobic groups at the surface of the cellulose polymer is a further prerequisite for optimal hemocompatibility. It seems that the carbamate configuration per se has a positive effect on the hemocompatibility pattern of synthetically modified cellulose membranes.     

亚硫酸氢钠处理后牛心包的血液相容性

目的评价经亚硫酸氢钠(SOB)溶液抗钙化处理后的牛心包的血液相容性。方法对戊二醛处理后再经SOB溶液处理的牛心包,采用体外动态凝血实验、血小板黏附实验、D-二聚体测定和补体激活实验进行血液相容性评价;仅经过戊二醛处理者作为对照组。结果SOB处理后牛心包的凝血性能和血小板黏附性能与对照组相比无明显差异;D-二聚体含量两组均在正常范围内,且SOB处理组显著低于对照组(P<0.05);补体激活实验中SOB处理组补体C3a水平显著低于对照组(P<0.05)。结论经SOB抗钙化处理后的生物材料体外血液相容性符合临床应用要求。     

两种钛合金成品表面特性表征及血液相容性的对比研究

目的对两种不同加工工艺生产的钛合金成品(白色和黑色)进行表面特性鉴定,并评价其血液相容性,为选择合适的工艺流程提供理论依据。方法使用扫描电子显微镜(scanning electron microscopy,SEM)、能谱分析(energy dispersive spectroscopy,EDS)、原子力显微镜(atomic force microscopy,AFM)、X射线衍射仪(X-ray diffraction,XRD)、X射线光电子能谱仪(X-ray photoelectron spectrometer,XPS)对两种钛合金的表面结构、表面物理和化学性能进行表征。通过体外纤维蛋白原吸附、血小板黏附与激活、凝血时间的测定等实验,以及植入狗右心房10 d观察血栓形成情况,系统评价两种钛合金的血液相容性。结果白色钛合金表面为粗且深的犁沟,成分为Ti、Al、V,黑色钛合金表面呈孔样层状叠加分布,且成分除了Ti、Al、V外,还有Si、Na、Ca、Fe等杂质。XRD结果显示两种钛合金物相结构均为钛。XPS结果显示两种钛合金表层都形成极薄的TiO_2薄膜,但黑色钛合金形成的TiO_2薄膜略厚于白色钛合金。体外纤维蛋白原吸附、血小板黏附与激活及凝血时间结果均显示两种钛合金血液相容性无明显差异。体内植入实验结果显示两种钛合金表面均形成了血栓,但黑色钛合金有明显异物反应,形成了增生的肉芽组织,且电镜下显示,白色钛合金表面黏附的有形成分少于黑色钛合金。结论结合体内、体外实验,白色钛合金的生物相容性优于黑色钛合金。     

Study on the Hemostasis Characteristics of Biomaterial Frustules Obtained from Diatom Navicula australoshetlandica sp.

Diatoms, known as photosynthetic unicellular algae, can produce natural biosilica frustules that exhibit great biocompatibility, superhydrophilicity, and superhemophilicity. In our study, the diatom Navicula australoshetlandica sp. was isolated from aquaculture wastewater and pretreated to obtain frustules so as to explore their hemostasis characteristics. A special “porous web” (6–8 nm) substructure in the ordered nanopores (165–350 nm) of boat-shaped diatom frustule was observed in Navicula australoshetlandica sp. using SEM and TEM analysis. Moreover, X-ray, N₂ adsorption–desorption isotherms, and BET analysis showed that the diatom frustule is a mesoporous material with a surface area of 401.45 m² g⁻¹ amorphous silica. FTIR analysis showed that Navicula australoshetlandica sp. frustules possessed abundant OH functional groups. A low hemolysis ratio was observed for 1–5 mg mL⁻¹ diatom frustules that did not exceed 1.55 ± 0.06%, which indicates favorable hemocompatibility. The diatom frustules exhibited the shortest clotting time (134.99 ± 7.00 s) with a hemostasis material/blood (mg/μL) ratio of 1:100, which is 1.83 times (112.32 s) shorter than that of chitosan. The activated partial thromboplastin time (aPTT) of diatom frustule was also 44.53 s shorter than the control. Our results demonstrate the potential of Navicula australoshetlandica sp. diatom frustules to be used as medical hemostasis material.     

The Effect of Coumadin Upon Thrombus Forming on Foreign Surfaces

Experience with the Stagnation Point Flow Experiment has revealed the earliest microscopic events surrounding thrombus inception and growth on foreign surfaces in a perfectly defined flow field. Using 40 and 80 × magnification, the effects of Coumadin upon these events was studied. These events include leukocyte adherence, fibrin deposition and platelet aggregation, deviation of flow streamlines around these aggregates, and subsequent downstream thrombus growth. Surface density of leukocytes was measured as a function of time and shear, and served as an index of the quantity of thrombus on the surface, which in turn, allowed direct comparisons of thrombus growth rate between experiments. Coumadin decreases the adhesive force between leukocytes or thrombi and the foreign surface. Emboli are more frequent with Caumadin, but are smaller. Thrombus inception is not altered. These results suggest that clinical benefit obtained from use of Coumadin derives from reduction in size of emboli.