Manfred F Maitz

Publications

• 2.82

  Impact points

  Immobilization of the direct thrombin inhibitor-bivalirudin on 316L stainless steel via polydopamine and the resulting effects on hemocompatibility in vitro.

  Lei Lu, Quan-Li Li, Manfred F Maitz, Jia-Long Chen, Nan Huang

  Journal of biomedical materials research. Part A. 05/2012;

  Bivalirudin (BV), a peptidic direct thrombin inhibitor, derived from hirudin, has gained increasing interest in clinical anticoagulant therapy in the recent years. In this work, a hemocompatible surface was prepared by immobilization of BV on 316L stainless steel (SS) using a bonding layer of polydo... [more] Bivalirudin (BV), a peptidic direct thrombin inhibitor, derived from hirudin, has gained increasing interest in clinical anticoagulant therapy in the recent years. In this work, a hemocompatible surface was prepared by immobilization of BV on 316L stainless steel (SS) using a bonding layer of polydopamine (DA). X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition of the surfaces to characterize polydopamine intermediate layer and the immobilized BV. The quantity of bound BV was measured by quartz crystal microbalance (QCM). The hemocompatibility in vitro was evaluated by coagulating time of activated partial thromboplastin time (aPTT) and prothrombin time (PT) assay, platelet adhesion and activation, fibrinogen adsorption, and activation and whole blood test. The effect of sterilizing method on the bioactivity of immobilized BV was also evaluated. The results showed that BVs were successfully immobilized on SS surface with the DA interlayer at a density of 98 ng/cm(2) . BV coating surface prolonged aPTT and PT, inhibited the activation of platelet and fibrinogen significantly. Sterilization by ultraviolet radiation was possible with only marginal loss of activity. Thus, the approach described here may provide a basis for the preparation of 316L SS surface modification for use in cardiovascular implants. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: , 2012.
• 3.02

  Impact points

  Biofunctionalization of titanium with PEG and anti-CD34 for hemocompatibility and stimulated endothelialization.

  Jialong Chen, Jianjun Cao, Juan Wang, Manfred F Maitz, Lisa Guo, Yuancong Zhao, Quanli Li, Kaiqin Xiong, Nan Huang

  Journal of colloid and interface science. 11/2011; 368(1):636-47.

  Thrombosis and restenosis are the main causes of failure of cardiovascular and other blood-contacting biomedical devices. It is recognized that rapid endothelialization is a promising method for preventing these complications. Convincing evidence in vivo has further emerged that the vascular homing ... [more] Thrombosis and restenosis are the main causes of failure of cardiovascular and other blood-contacting biomedical devices. It is recognized that rapid endothelialization is a promising method for preventing these complications. Convincing evidence in vivo has further emerged that the vascular homing of endothelial progenitor cells (EPCs) contributes to rapid endothelial regeneration. This study deals with improving the hemocompatibility and enhancing EPC colonization of titanium by covalently bonding PEG(600) or PEG(4000), then end-grafting of an anti-CD34 antibody. For this, a chemically hydroxylated titanium surface was aminosilanized, which was further used for covalent grafting of polyethylene glycol and the antibody. The grafting efficiency was verified in each step. In vitro platelet adhesion analysis confirmed superior hemocompatibility of the modified surface over the control. Affinity of EPC to the surface and inhibition of smooth muscle cell adhesion, two prerequisites for endothelialization, are demonstrated in in vitro cell culture. While the coating selectively stimulates EPC adhesion, its antifouling properties prevent formation of an extracellular matrix and proliferation of the cells. Additional affinity for matrix proteins in the coating is considered for further studies. Potent inhibitory effect on macrophage activation and the relative stability of the coating render this technique applicable.
• 7.37

  Impact points

  Impact of processing parameters on the haemocompatibility of Bombyx mori silk films.

  F Philipp Seib, Manfred F Maitz, Xiao Hu, Carsten Werner, David L Kaplan

  Biomaterials. 11/2011; 33(4):1017-23.

  Silk has traditionally been used for surgical sutures due to its lasting strength and durability; however, the use of purified silk proteins as a scaffold material for vascular tissue engineering goes beyond traditional use and requires application-orientated biocompatibility testing. For this study... [more] Silk has traditionally been used for surgical sutures due to its lasting strength and durability; however, the use of purified silk proteins as a scaffold material for vascular tissue engineering goes beyond traditional use and requires application-orientated biocompatibility testing. For this study, a library of Bombyx mori silk films was generated and exposed to various solvents and treatment conditions to reflect current silk processing techniques. The films, along with clinically relevant reference materials, were exposed to human whole blood to determine silk blood compatibility. All substrates showed an initial inflammatory response comparable to polylactide-co-glycolide (PLGA), and a low to moderate haemostasis response similar to polytetrafluoroethylene (PTFE) substrates. In particular, samples that were water annealed at 25 °C for 6 h demonstrated the best blood compatibility based on haemostasis parameters (e.g. platelet decay, thrombin-antithrombin complex, platelet factor 4, granulocytes-platelet conjugates) and inflammatory parameters (e.g. C3b, C5a, CD11b, surface-associated leukocytes). Multiple factors such as treatment temperature and solvent influenced the biological response, though no single physical parameter such as β-sheet content, isoelectric point or contact angle accurately predicted blood compatibility. These findings, when combined with prior in vivo data on silk, support a viable future for silk-based vascular grafts.
• 7.37

  Impact points

  The effect of coimmobilizing heparin and fibronectin on titanium on hemocompatibility and endothelialization.

  Guicai Li, Ping Yang, Wei Qin, Manfred F Maitz, Shuo Zhou, Nan Huang

  Biomaterials. 04/2011; 32(21):4691-703.

  Currently available cardiovascular implants, such as heart valves and stents, exhibit suboptimal biocompatibility because of the incomplete endothelialization and sequential thrombosis formation especially after a long-term implantation. To improve the blood compatibility and endothelialization simu... [more] Currently available cardiovascular implants, such as heart valves and stents, exhibit suboptimal biocompatibility because of the incomplete endothelialization and sequential thrombosis formation especially after a long-term implantation. To improve the blood compatibility and endothelialization simultaneously and ensure the long-term effect of the cardiovascular implants, a technique of combining electrostatic interaction and coimmobilization was developed to form heparin and fibronectin (Hep/Fn) films on aminosilanized titanium (Ti) surfaces. The Hep/Fn coimmobilized films were stable after immersion in PBS for five days, probed by wettability studies and by the release kinetics of heparin and fibronectin. Blood compatibility tests showed that the coimmobilized Hep/Fn films displayed lower hemolysis rate, prolonged blood coagulation time, higher AT III binding density, less platelets activation and aggregation, and less fibrinogen conformational change compared with Ti surface. Endothelial cells (ECs) seeding and fibronectin bioactivity results showed more attached and proliferated ECs and exposed cell-binding sites on the Hep/Fn immobilized samples than that on Ti surfaces. Thus, the Hep/Fn coimmobilized films kept excellent bioactivity even after immersion in PBS for five days. Systemic evaluation suggests that the coimmobilization of Hep/Fn complex improves the blood compatibility and promotes the endothelialization simultaneously. We envisage that this method will provide a potential and effective selection for biomaterials surface modification of cardiovascular implants.

• Shaped hemocompatible aerogels from cellulose phosphates: preparation and properties

  F. Liebner, R. Dunareanu, M. Opietnik, E. Haimer, M. Wendland, C. Werner, M. Maitz, P. Seib, M.-A. Neouze, A. Potthast, T. Rosenau

  Holzforschung. 01/2011; accepted.

  Hemocompatible-shaped cellulose phosphate aerogels were obtained from phosphorylated cellulosic pulps of low degree of phosphorylation (DSP≤0.20) by dissolution in stabilized NMMO×H2O, shaping, reprecipitation with ethanol and subsequent scCO2 drying. The novel aerogels were found to be promising ma... [more] Hemocompatible-shaped cellulose phosphate aerogels were obtained from phosphorylated cellulosic pulps of low degree of phosphorylation (DSP≤0.20) by dissolution in stabilized NMMO×H2O, shaping, reprecipitation with ethanol and subsequent scCO2 drying. The novel aerogels were found to be promising materials for cell scaffolding and bone grafting. Special features include their interconnected and spread porosity, highly porous surface and microstructure, good hemocompatibility, and suitable hydroxyl apatite-binding environment. Adsorption of Ca2+ ions to the phosphate groups did not invert the negative inflammatory response observed after phosphorylating cellulose, but increased platelet-dependent parameters of hemostasis.
• 2.82

  Impact points

  Immobilization of the irreversible thrombin inhibitor D-Phe-Pro-Arg-chloromethylketone: a concept for hemocompatible surfaces?

  Manfred F Maitz, Claudia Sperling, Carsten Werner

  Journal of biomedical materials research. Part A. 09/2010; 94(3):905-12.

  The irreversible thrombin inhibitor D-Phe-Pro-Arg-chloromethylketone (PPACK) was covalently immobilized to PEGylated polymer thin films at its primary alpha-amino group. Activity assays and capture of radioconjugated thrombin reveal that the PPACK-decorated surfaces could bind thrombin forming up to... [more] The irreversible thrombin inhibitor D-Phe-Pro-Arg-chloromethylketone (PPACK) was covalently immobilized to PEGylated polymer thin films at its primary alpha-amino group. Activity assays and capture of radioconjugated thrombin reveal that the PPACK-decorated surfaces could bind thrombin forming up to 30% of a monolayer density. Back-calculation of this high thrombin-inhibiting capacity indicated that the surface immobilization of the inhibitor was still associated with more than two orders of magnitude of loss of activity; increasing activity was observed at higher surface densities. PPACK-containing polymer films almost duplicated the plasma coagulation time when compared with the reference substrate without inhibitor. In whole blood, however, the anticoagulant properties were below those previously found for benzamidine-type reversible thrombin inhibitors; in addition, the surface exhibited inflammatory properties. It is concluded that immobilized reversible thrombin inhibitors are more effective by passivating higher amounts of thrombin in a cooperative action with antithrombin III.
• 7.37

  Impact points

  The covalent immobilization of heparin to pulsed-plasma polymeric allylamine films on 316L stainless steel and the resulting effects on hemocompatibility.

  Zhilu Yang, Jin Wang, Rifang Luo, Manfred F Maitz, Fengjuan Jing, Hong Sun, Nan Huang

  Biomaterials. 12/2009;

  For an improved hemocompatibility of 316L stainless steel (SS), we develop a facile and effective approach to fabricating a pulsed-plasma polymeric allylamine (P-PPAm) film that possesses a high cross-linking degree and a high density of amine groups, which is used for subsequent bonding of heparin.... [more] For an improved hemocompatibility of 316L stainless steel (SS), we develop a facile and effective approach to fabricating a pulsed-plasma polymeric allylamine (P-PPAm) film that possesses a high cross-linking degree and a high density of amine groups, which is used for subsequent bonding of heparin. The P-PPAm film as a stent coating shows good resistance to the deformation behavior of compression and expansion of a stent. Using deionized water as an aging medium, it is demonstrated that the heparin-immobilized P-PPAm (Hep-P-PPAm) surface has a good retention of heparin. The systematic in vitro hemocompatibility evaluation reveals lower platelet adhesion, platelet activation and fibrinogen activation on the Hep-P-PPAm surface, and the activated partial thromboplastin time prolongs for about 15 s compared with 316L SS. The P-PPAm surface significantly promotes adhesion and proliferation of endothelial cells (ECs). For the Hep-P-PPAm, although EC adhesion and proliferation is slightly suppressed initially, after cultivation for 3 days, the growth behavior of ECs is remarkably improved over 316L SS. In vivo results indicate that the Hep-P-PPAm surface successfully restrain thrombus formation by growing a homogeneous and intact shuttle-like endothelium on its surface. The Hep-P-PPAm modified 316L SS shows a promising application for vascular devices.
• 7.37

  Impact points

  Blood coagulation on biomaterials requires the combination of distinct activation processes.

  Claudia Sperling, Marion Fischer, Manfred F Maitz, Carsten Werner

  Biomaterials. 07/2009;

  The rational design of hemocompatible materials requires a mechanistic understanding of activation processes induced at the blood-material interface. Binary self-assembled monolayers of alkyl thiols (SAMs) with various ratios of -CH(3) and -COOH terminations were used to study the relevance of hydro... [more] The rational design of hemocompatible materials requires a mechanistic understanding of activation processes induced at the blood-material interface. Binary self-assembled monolayers of alkyl thiols (SAMs) with various ratios of -CH(3) and -COOH terminations were used to study the relevance of hydrophobic and negatively charged surfaces for the initiation of blood coagulation. Platelet adhesion and activation of the intrinsic coagulation pathway scaled with the surface composition: the numbers of adherent platelets were highest on the 100%-CH(3) surface whereas the greatest contact activation was seen on 100%-COOH surfaces. In vitro whole blood incubation assays showed, however, that the surfaces exposing either -CH(3)or -COOH groups induced comparably low levels of thrombin formation while the surfaces with intermediate contents of both terminating groups had significantly higher values. These results reveal that contact activation and platelet adhesion have a strong synergistic effect on coagulation on blood-contacting materials even though these events in isolation are not sufficient to induce substantial thrombin formation. Successful surface design strategies for hemocompatible materials therefore need to carefully consider the interplay of both processes.

• Actively anticoagulant surfaces targeting Protein C

  M. Maitz, L. de Morais Schmittgens, C. Sperling, C. Werner

  Hämostaseologie. 01/2009; 29:A22.

  Background: Surface modifications are frequently applied to provide anticoagulant properties biomedical devices in contact with streaming blood. They mainly consist of surface passivation or are direct or indirect inhibitors of the coagulation factors thrombin or FXa. The present study intends to im... [more] Background: Surface modifications are frequently applied to provide anticoagulant properties biomedical devices in contact with streaming blood. They mainly consist of surface passivation or are direct or indirect inhibitors of the coagulation factors thrombin or FXa. The present study intends to impart the properties of the anticoagulant enzyme activated protein C to a surface. Method: Recombinant human activated protein C (Drotrecogin Alpha) and a direct Protein C activator from snake venom (Protac) were immobilized covalently via spacer molecules to model surfaces. The activity of the immobilized enzymes was probed by a chromogenic substrate. The efficiency as anticoagulant surface was tested by incubation with plasma and whole blood. Results: Both enzymes could be immobilized in active form to the surface. For drotrecogin about 8% of the theoretical maximal activity of a monolayer was obtained. The efficiency of Protac immobilization was reduced due to the immobilization of bulking proteins in the applied formulation. In whole blood incubation, immobilized drotrecogin exhibited anti-hemostatic effects on the coagulation cascade and on blood platelets. It further reduced the inflammatory response of leukocytes. Despite the reported rapid inhibition of the enzyme, the effects still could be observed after two hours incubation. Beneficial effects of Protac apparently were superposed by the co-immobilized bulking proteins. Conclusion: Targeting the physiological anticoagulant protein C system is an innovative and promising approach to form actively anticoagulant surfaces.

• Relevance of tissue factor for biomaterial associated blood coagulation

  C. Sperling, M. Fischer, M. Maitz, C. Werner

  Hämostaseologie. 01/2009; 29:A33.

  Objectives: The initiation of blood coagulation on biomaterial surfaces usually is attributed to the activation of the contact phase. Tissue factor (TF) up to now is not thought to be relevant for material associated blood coagulation. Regarding new insights into the presence of TF in whole blood th... [more] Objectives: The initiation of blood coagulation on biomaterial surfaces usually is attributed to the activation of the contact phase. Tissue factor (TF) up to now is not thought to be relevant for material associated blood coagulation. Regarding new insights into the presence of TF in whole blood this should be reconsidered. Design and methods: Model materials with clearly defined surface groups (Self assembled monolayers of alkylthiols (SAMs) displaying various ratios of -CH3, –OH, and –COOH terminations) were used for studying the relevance of surface properties for the initiation of blood coagulation. An in vitro assay using fresh heparinized whole human blood was used to determine blood reactivity and TF expression and release. Results: The transcription of TF mRNA showed clear differences related to surface properties and increased over time for up to 3 hours (relative expression to initial: hydrophobic -CH3: 125±1; negatively charged -COOH: 181±11; hydrophilic –OH: 590±50) A positive correlation between TF transcription and presence on leukocytes (microscopic analysis using antibody to VIC7), leukocyte activation (CD11b on granulocytes) and complement activation (C5a in plasma) was shown. A correlation between coagulation activation (plasmatic TAT) and TF mRNA was not yet found in our experimental model. Conclusions: Material related differences for TF transcription and release were found. These differences did not relate to the activation of coagulation as studied, which might relate to methodological limitations like the short incubation time (2 to 3 hours). This set up will be further optimised and more TF related parameters will be analyzed.
• 2.19

  Impact points

  Surface endotoxin contamination and hemocompatibility evaluation of materials.

  Manfred F Maitz, Juliane Teichmann, Claudia Sperling, Carsten Werner

  Journal of biomedical materials research. Part B, Applied biomaterials. 11/2008;

  To evaluate the blood compatibility of new materials, a clear distinction between properties of the materials and effects due to surface contamination by adsorbed endotoxins is essential. This study compares direct contact approaches and elution methods with water, organic solvents, nonionic, and zw... [more] To evaluate the blood compatibility of new materials, a clear distinction between properties of the materials and effects due to surface contamination by adsorbed endotoxins is essential. This study compares direct contact approaches and elution methods with water, organic solvents, nonionic, and zwitterionic detergents for determination of surface-adsorbed endotoxin by the limulus amoebocyte lysate (LAL) test and determines the blood compatibility of various surfaces with controlled endotoxin contamination in vitro. The LAL test in direct contact with an endotoxin-contaminated surface was concluded to be not practicable for most devices and its sensitivity showed a high dependence on surface characteristics. Among the elution methods, 0.2% Tween-20 showed most stable elution characteristics and appears therefore preferable. Biological reactions at in vitro blood exposure were found to be only minimally influenced by adsorbed endotoxin during the time window of 2 h, allowing for a straightforward discrimination between materials and endotoxin-dependent reactions. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2009.

• Surface modification of Ni-Ti alloys for biomedical applications

  Manfred F. Maitz

  01/2008: pages 173-193;

  ISBN: 1 84569 344 2
• 7.88

  Impact points

  In vitro blood reactivity to hydroxylated and non-hydroxylated polymer surfaces.

  Claudia Sperling, Manfred F Maitz, Sandra Talkenberger, Marie-Françoise Gouzy, Thomas Groth, Carsten Werner

  Biomaterials. 10/2007; 28(25):3617-25.

  Complement activation on hydroxyl-group-bearing surfaces is regarded as the main reason for granulocyte activation in applications of blood-contacting medical devices such as extracorporeal blood purification. However, the factors inducing the cell adhesion so far remained ambiguous. For a dedicated... [more] Complement activation on hydroxyl-group-bearing surfaces is regarded as the main reason for granulocyte activation in applications of blood-contacting medical devices such as extracorporeal blood purification. However, the factors inducing the cell adhesion so far remained ambiguous. For a dedicated research, whole blood was incubated with a set of structurally similar polymer coatings on glass with either hydroxy or ether functionalities. By co-incubation of an activating with a non-activating surface, the reaction of granulocytes activated by complement fragments on non-activating surfaces could be evaluated. As expected, hydroxyl-terminated polymer layers induced much higher levels of complement activation than those with ether functionalities. Leukocyte activation, as measured by the expression of CD11b, correlated closely with the presence of free complement fragment C5a. However, adhesion of leukocytes was rather associated with the adsorption of activated fragments of C3 than with the activation level of the cells. Moreover, it was found that adsorbed quantities of fibrin and fibrinogen had little influence on leukocyte adhesion. It is concluded that the activation of leukocytes is triggered by soluble complement factors such as C5a while their adhesion on hydroxy-bearing surfaces is mainly triggered by the presence of surface-bound complement fragment C3b.
• 2.32

  Impact points

  The effect of the major components of Salvia Miltiorrhiza Bunge on bone marrow cells.

  Y R Liu, S X Qu, M F Maitz, R Tan, J Weng

  Journal of ethnopharmacology. 06/2007; 111(3):573-83.

  Salvia Miltiorrhiza Bunge (SMB), a traditional Chinese medicinal herb, has been alleged to support bone healing. However, the effects of the isolated major components of SMB on osseous cells and their corresponding effective doses are still unclear. In the present study, the effects of three compone... [more] Salvia Miltiorrhiza Bunge (SMB), a traditional Chinese medicinal herb, has been alleged to support bone healing. However, the effects of the isolated major components of SMB on osseous cells and their corresponding effective doses are still unclear. In the present study, the effects of three components of SMB, including tanshinone IIA (Ts), salvianolic acid B (salB) and protocatechuic aldehyde (Pca), on mesenchymal bone marrow cells with the potential for osteoblastic differentiation were investigated. Various concentrations of Ts, salB and Pca were added to a rat bone marrow cell culture. The total metabolic activity and differentiation of bone marrow cells were evaluated by a metabolic assay and alkaline phosphatase (ALP) activity, respectively. The morphology and number of cells was observed by phase contrast microscopy and fluorescent microscopy after propidium iodide staining, respectively. Ts suppressed the growth and differentiation of bone precursor cells. SalB exhibited a biphasic effect: the high concentration of 160 microg/mL significantly depressed the population of bone marrow cells, however, lower concentrations (3-80 microg/mL) enhanced the total metabolic activity and their ALP expression. Pca suppressed the bone marrow cell population in a dose-dependent manner. Therefore, SalB has the potential to ameliorate bone healing by stimulating both the total metabolic activity and ALP activity of osteoblastic cells. Aqueous extracts, which preferably contain salB over Pca and are free of Ts therefore are recommended for bone formation.
• 3.11

  Impact points

  Sulfated glycopolymer thin films - preparation, characterization, and biological activity.

  Ringo Grombe, Marie F Gouzy, Manfred F Maitz, Uwe Freundenberg, Stefan Zschoche, Frank Simon, Tilo Pompe, Claudia Sperling, Carsten Werner

  Macromolecular bioscience. 03/2007; 7(2):195-200.

  The impact of heparinoid characteristics on model surfaces obtained from immobilization of sole sulfate groups as well as sulfated glycosides, sulfated cellulose, and definite heparin has been investigated. The obtained layers were physico-chemically characterized regarding film thickness, chemical ... [more] The impact of heparinoid characteristics on model surfaces obtained from immobilization of sole sulfate groups as well as sulfated glycosides, sulfated cellulose, and definite heparin has been investigated. The obtained layers were physico-chemically characterized regarding film thickness, chemical composition, wettability, and surface morphology. Antithrombin adsorption, studied by fluorescence labeling, revealed a strong dependence on the presence of glycosidic structures and on the molecular weight of the grafted saccharide. On contact with whole blood, the coatings resulted in a diminished plasmatic and cellular coagulation in vitro, which did not reflect well the antithrombin binding. Therefore, more complex activating pathways are discussed.
• 5.21

  Impact points

  Conformational changes during protein adsorption. FT-IR spectroscopic imaging of adsorbed fibrinogen layers.

  Gerald Steiner, Sibel Tunc, Manfred Maitz, Reiner Salzer

  Analytical chemistry. 03/2007; 79(4):1311-6.

  The influence of hydrophobicity of the substrate surface on structural changes during protein adsorption was investigated. Plasma fibrinogen was chosen to model this effect as it is the most important protein in the body that adsorbs to foreign surfaces. Only conformations of adsorbed fibrinogen sim... [more] The influence of hydrophobicity of the substrate surface on structural changes during protein adsorption was investigated. Plasma fibrinogen was chosen to model this effect as it is the most important protein in the body that adsorbs to foreign surfaces. Only conformations of adsorbed fibrinogen similar to that of the protein in solution do not activate the process of blood coagulation. Small spots on the substrate surface with conformational changes within the adsorbed protein are already sufficient to deteriorate biocompatibility. Mid-infrared hyperspectral imaging permits the identification of coagulated spots down to a few micrometers in size. The spectra of the FT-IR images that were assessed to be of suitable quality were clustered by a fuzzy c-means algorithm. The determination of the appropriate number of clusters was based on cluster variance. Subsequent evaluation of the centroid spectra of each cluster showed that their amide I band was separated into contributions from different structural units, with the alpha-helix content always being dominant. Significant differences between hydrophobic and hydrophilic surfaces were observed for turn and sheet contributions. Lower sheet/turn ratios appear to indicate inferior biocompatibility. Spots on hydrophilic surfaces could be identified, which exhibit structural changes similar to those on hydrophobic surfaces.

• Biological evaluation of sirolimus-loaded PLGA films

  L. Ren, J. Wang, J.J. Tang, Ch.J. Pang, M. Maitz, N. Huang

  Key Engineering Materials. 01/2007; 342-343:537-40.

  Sirolimus-loaded poly (lactic acid-co-glycol acid) (PLGA) films were prepared by a casting method. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to determine the optimal concentration of sirolimus for vascular smooth muscle cell (VSMC) inhibition effect. Base... [more] Sirolimus-loaded poly (lactic acid-co-glycol acid) (PLGA) films were prepared by a casting method. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to determine the optimal concentration of sirolimus for vascular smooth muscle cell (VSMC) inhibition effect. Based on the results of MTT, three samples of different weight percent loaded-sirolimus (2wt%, 6wt%, 15wt%) PLGA films were selected. The release of lactate dehydrogenase (LDH) was used to evaluate the immediate toxicity of the sirolimus-loaded PLGA films and it was shown that the three different concentrations of sirolimus-loaded films have low toxicity. Alamar blue results indicate that the sirolimus-loaded films have better antiproliferation effect than 316 stainless steel (SS). The higher the sirolimus concentration in the film is, the better is the antiproliferation effect. These films may be used for stent coating to inhibit in-stent restenosis induced by VSMC proliferation.
• 0.21

  Impact points

  Bioactive composite ceramics in the hydroxyapatite–tricalcium phosphate system

  O. L. Kubarev, V. S. Komlev, M. Maitz, S. M. Barinov

  Doklady Chemistry. 01/2007; 413(1):72-4.

  Synthetic materials based on hydroxyapatite (HA), an analogue of the mineral component of the bone tissue, are used in medicine for the repair of damaged bone tissue [1–3]. A new repair technology is based on implanting porous ceramic scaffolds containing cultivated cells and proteins into the bone ... [more] Synthetic materials based on hydroxyapatite (HA), an analogue of the mineral component of the bone tissue, are used in medicine for the repair of damaged bone tissue [1–3]. A new repair technology is based on implanting porous ceramic scaffolds containing cultivated cells and proteins into the bone tissue [4]. The formation of new bone tissue is a complex process that includes protein adsorption as an important stage [5, 6]. Scaffolds should be resorbable with time in the human body with gradual replacement by newly formed bone tissue and should ensure a high protein-adsorption capacity. Hydroxyapatite is stable against dissolution by body fluids, whereas tricalcium phosphate (TCP) has a much higher resorption rate compared to that of HA. By varying the component ratio in an HA/TCP composite, one can control the resorption rate. The problems of design of such composite materials have been considered in reviews [7, 8]. Two-phase composites (TCMs) are produced by thermal decomposition of calcium-deficient HA followed by sintering [8]. Using this method, it is difficult to control the component ratio in the material. Some aspects of the influence of the phase composition on the biological behavior of TCMs remain obscure. This study is devoted to the production of TCMs with specified composition and porosity and elucidation of the question of which factor, porosity or phase composition, is more important for protein adsorption.
• 4.80

  Impact points

  Current strategies towards hemocompatible coatings

  Carsten Werner, Manfred F. Maitz, Claudia Sperling

  Journal of Materials Chemistry. 01/2007; 17:3376-84.

  A wide range of biomedical devices is applied clinically in contact with blood. Tailoring the surface properties of the involved biomaterials is a common approach to enhance performance and to limit adverse reactions. This review summarizes current trends in coating technologies developed for that p... [more] A wide range of biomedical devices is applied clinically in contact with blood. Tailoring the surface properties of the involved biomaterials is a common approach to enhance performance and to limit adverse reactions. This review summarizes current trends in coating technologies developed for that purpose. Inorganic coatings were shown to substantially improve the durability and inertness of biomaterials while a number of advanced polymer coatings were demonstrated to be very effective by targeting specific biochemical pathways. However, to fully utilize the power of these bioactive coatings safety issues need to be thoroughly addressed in future studies.
• 1.79

  Impact points

  Reactive plasma immersion ion implantation for surface passivation

  R. A. Yankov, N. Shevchenko, A. Rogozin, M. F. Maitz, E. Richter, W. Möller, A. Donchev, M. Schütze

  Surface and Coatings Technology. 01/2007; 201:6752-8.

  Plasma immersion ion implantation (PIII) using halogen or oxygen plasmas has been employed for the surface passivation of advanced alloys with a view to their applications for high-temperature oxidation protection and in medicine. Special devices have been designed to ensure efficient plasma generat... [more] Plasma immersion ion implantation (PIII) using halogen or oxygen plasmas has been employed for the surface passivation of advanced alloys with a view to their applications for high-temperature oxidation protection and in medicine. Special devices have been designed to ensure efficient plasma generation and reduce sample contamination arising from the interaction of the aggressive plasmas with the chamber components under bias. The paper addresses two main applications of PIII, namely oxidation protection of gamma-titanium aluminides (