Compressive properties of polymer coated synthetic hydroxyapatite for bone grafting

A porous hydroxyapatite material hydrothermally converted from the calcium carbonate exoskeleton of the coral, genus Goniopora (CHAG) was either microcoated using polymethylmethacrylate (PMMA) or polylactic acid (PLA) to cover all internal surfaces, or externally coated to produce a shell, with the objective of reducing the brittleness of the material. Compressive testing showed that while CHAG, externally coated with PMMA, showed the largest increases in strength, stiffness, and energy absorption, the uncoated hydroxyapatite core cracked at low loads although the shell remained intact. CHAG internally microcoated with PMMA showed a 3.84 increase in compressive strength while specimens with internal PLA coatings had 1.81 times the compressive strength of uncoated CHAG specimens. Compared to the mechanical properties of cancellous graft material, specimens internally microcoated with either polymer could be produced having properties equivalent to or greater than those of cancellous graft.     

Activated protein C: Antithrombotic properties and influence on fibrinolysis in an animal model

The in vivo antithrombotic and profibrinolytic properties of human plasma protein C were investigated in a metallic coil induced thrombus model in the rat. Protein C, purified by immunoadsorption, was activated by thrombin and thereafter administered to the animals. Half-life of activated protein C (APC) revealed to be 15–16 min for the antigen, but only 7–8 min for the anticoagulant activity. Thrombus formation was reduced by APC in a dose-dependent statistically significant manner. A profibrinolytic effect of APC was observed when administered in combination with human tissue plasminogen activator. APC alone caused a reduction of thrombus weight. However, both effects were statistically not significant.     

Antithrombotic activity of heparin-ATP complex

The complex of high-molecular-weight heparin and ATP prevented thrombus formation in the blood flow. Repeated intramuscular injection of the complex increased total fibrinolytic activity of the blood, nonenzymatic fibrinolysis, and plasma anticoagulant activity and significantly decreased platelet aggregation. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 3, pp. 267–269, March, 2007     

Serum albumin-alginate coated beads: mechanical properties and stability.

According to a previously described method, alginate beads were prepared from a Na-alginate solution containing propylene glycol alginate (PGA) and human serum albumin (HSA). The solution was added dropwise to a CaCl2 solution. The beads were treated with NaOH, which started the formation of amide bonds between HSA and PGA at the periphery, giving a membrane. Batches of beads with increasingly thick membranes were prepared using growing concentrations of NaOH, and studied with a texture analyser. When raising NaOH concentration, the rupture strength progressively increased, and the resistance strength to a deformation of 50% of total height also increased before slightly decreasing for the highest NaOH concentration. Variations of bead elasticity were also observed. When the beads were prepared with saline reducing gelation time from 10 to 5 min, and reaction time from 15 to 5 min, mechanical properties varied more progressively with the NaOH concentration, while the results became more reproducible. A series of assays conducted with 0.01 M NaOH confirmed the importance of using a short gelation time, and saline rather than water. Stability assays were also performed. The results were compared to those of alginate-polylysine coated beads and showed the interest of the transacylation method.     

Hemolysis in needleless connectors for phlebotomy

Needleless connectors have been developed recently as a means of reducing transmission of AIDS and other blood-borne diseases by accidental needle sticks. However, the potential for hemolysis induced by fluid stresses within the connector remained to be determined. The influence of needleless connectors on hemolysis was evaluated in simulated clinical blood draws. Blood from five volunteers was drawn with vacuum tubes and syringes through 16, 18, and 22 gauge needles and PosiFlow (Becton Dickinson, Franklin Lakes, NJ) and Clave (ICU Medical, San Clemente, CA) needleless connectors. Hemolysis was measured in the samples by a spectrophotometric technique. Results showed that hemolysis increased when needleless connectors were used. The PosiFlow connector produced more hemolysis than the Clave device. Curiously, erythrocyte damage was greatest for connectors used with 18 gauge needles. Hemolysis was larger for samples drawn with vacuum tubes than with syringes. However, no combinations of connector, needle size, or blood draw device resulted in mean hemolysis values large enough to interfere with clinical assays.     

A comparison of materials for percutaneous connectors

The behavior of solid percutaneous connectors made of gold, stainless steel, vitreous carbon and titanium was studied in humans. Evaluation parameters were biocompatibility studied by conventional histochemical methods, surface degradation studied by scanning electron microscopy, and electrical impedance. The results showed after two months very slight inflammatory reaction for carbon and titanium and moderate epidermal downgrowth. In stainless steel, histology showed a somewhat more pronounced reaction, whereas in gold, there was a macroscopic inflammatory reaction. No signs of surface degradation was found in any of the materials. The electrical impedance was constant throughout the experiment. It is concluded that of the materials investigated, vitreous carbon and titanium are preferable in percutaneous connector applications. The higher impedance seen in vitreous carbon favors the use of titanium in electrical stimulation. Careful surgery with minimal trauma, controlled surface characteristics and a pure inert material are termed factors of importance to make percutaneous connector applications successful. This project was supported by The Swedish Board for Technical Development and The Neubergh Foundation.     

The antithrombotic and antimicrobial properties of PEG-protected silver nanoparticle coated surfaces

Cardiovascular implant-associated complications such as infection and thrombosis may be reduced by modification of device surfaces using antimicrobial and antithrombotic agents. Silver nanoparticles (SNPs) are well accepted for its broad-spectrum antimicrobial effect. A recent report suggested its antiplatelet effect also. So the hypothesis of this study is that polyethylene glycol (PEG) protected SNPs can be incorporated with biomaterials to attain dual properties; and by adjusting an optimum concentration, its cytotoxicity to tissues and cells can be prevented. To prove this, detailed study of PEG-SNP was done at three levels: (i) direct inhibitory effect on platelet activation, aggregation and biochemical pathways when PEG-SNP is added into platelet suspension; (ii) inhibition of platelet adhesion to PEG-SNP incorporated biological matrix and polymer scaffold and (iii) non-cytotoxic behavior of immobilized PEG-SNP in fibrin matrix. Inhibitory effects demonstrated are on: platelet function by aggregometry, exposure of activation and apoptosis markers by flow cytometry, biochemical pathway by malondealdehyde (MDA) estimation and protein phosphorylation by Western blot. Reduced platelet adhesion onto PEG-SNP incorporated scaffold is shown using scanning electron microscopy (SEM). Non-toxic behavior of endothelial cells (EC) and smooth muscle cells (SMC) grown on PEG-SNP-fibrin disc is shown by fluorescence microscopy and cell phenotype stability by real-time polymerase chain reaction (PCR).     

Mechanical properties of a dental ceramic coated by RF magnetron sputtering

Metal and ceramic thin film coatings were deposited onto a dental ceramic via radio frequency (RF) magnetron sputtering. The objectives of the study were to determine if a coherent interface could be produced between the coating and the substrate and if the coating significantly would improve the mechanical properties of the ceramic. Thin films of Au, Al, and AlN were deposited in this study. Mechanical testing results indicated that a significant improvement in flexural strength was observed with both Au and Al coatings while significant improvements in the flexural modulus were observed with all three materials. SEM analysis indicated that the interfaces were coherent and also suggested two mechanisms (crack bridging and crack blunting) that could be responsible for the enhanced mechanical properties.     

Antithrombotic treatment of acute coronary syndrome

After we have become aware that arteriosclerosis provokes thrombotic and thromboembolic process, which is the most common cause of occlusion of coronary arteries, in the past 30 years significant improvements have been made in antithrombotic treatment of acute coronary syndrome. Antithrombotic therapy of acute coronary syndrome has been explored in few directions. These are thrombolytic multidrug therapy, anticoagulant therapy with nonfractional and low molecular heparin, therapy with glycoprotein IIb/IIIa receptor antagonists and antiaggregation therapy with acetylsalicylic acid and tienopyrid. Research results and clinical experience point to a conclusion that antithrombotic therapy is the cornerstone in the mariagement of acute coronary syndrome. In this paper, results of major studies and main antithrombotic treatment guidelines in acute coronary syndrome accepted by international professional associations are presented.     

Structured sleeve for repair of implantable in-line connectors

A structured miniature repair sleeve has been designed for implantable in-line connectors that develop small current leaks post-implant. The repair sleeve has been successfully utilised in one subject following the development of current leakage in connectors on an implanted joint angle sensor.     

Evaluation of interfacial properties of hyaluronan coated poly(methylmethacrylate) intraocular lenses

Polymethylmethacrylate intraocular lenses (IOLs) were surface-modified by the linking of a overlayer of hyaluronan. In vitro experiments show that the hydrophilic HA overlayer prevents fibroblasts adhesion and greatly reduces Staphyloccous epidermidis adhesion to the IOL surface. To gain insights into the interfacial properties of untreated and hyaluronan-coated PMMA IOLs, force-distance curves were obtained by atomic force microscopy, using standard and modified tips. These measurements allow clear appreciation of the marked difference between the mechanical and chemico-physical properties at the aqueous interface of the uncoated and hyaluronan-coated lenses.     

Evaluation of interfacial properties of hyaluronan coated poly(methylmethacrylate) intraocular lenses

Polymethylmethacrylate intraocular lenses (IOLs) were surface-modified by the linking of a overlayer of hyaluronan. In vitro experiments show that the hydrophilic HA overlayer prevents fibroblasts adhesion and greatly reduces Staphyloccous epidermidis adhesion to the IOL surface. To gain insights into the interfacial properties of untreated and hyaluronan-coated PMMA IOLs, force-distance curves were obtained by atomic force microscopy, using standard and modified tips. These measurements allow clear appreciation of the marked difference between the mechanical and chemico-physical properties at the aqueous interface of the uncoated and hyaluronan-coated lenses.     

Photocatalytic and antibacterial properties of medical-grade PVC material coated with TiO2 film

The TiO(2) film was coated on poly vinyl chloride (PVC) surface by dip-coating process from TiO(2)-PVC-THF suspension. The morphology and crystal structure of the as-synthesized samples were characterized by SEM and XRD. The photocatalytic properties were measured by the photodegradation reaction of RhB and the anti-adhesion and anti-bacteria for Escherichia coli. The results show that the resultant TiO(2) film is well-conglutinated on PVC surface and has the same crystal structure as the original TiO(2) powder. The TiO(2)/PVC shows excellent photocatalytic activity for the degradation of aqueous RhB and the activity increases with increasing reaction time and tends toward stable after accumulative illumination for 11.5 h. The TiO(2) film shows good bacterial anti-adhesion activity following photo-activation and sterilization property under UV irradiation. The E. coli can be killed completely after UV irradiation for 1.5 h.     

Correspondence: Potential equalization connectors for medical equipment

Dear Sir

You have solicited the views of safety and standards experts on the paper by Ezawa and Futami [1].

My main comment would be that there are considerable differences of viewpoint and practice between different countries on the role of potential equalization for medical equipment. The authors correctly observe that the subject has been discussed in IEC for several years (I would say rather for many years), without conclusion.