Key Engineering Materials Vols. 342-343

Abstract: In the present study, superparamagnetic maltotrionic acid-coated magnetite nanoparticles (MAM) were surface modified with doxorubicin (DOX) and RGD peptide to improve their intracellular uptake, ability to target tumor cells and antitumer effect. RGD was added to the distal end of MAM aiming to construct an enhanced tumor targeting delivery system. To test its targeting effect, DOX, a widely used anticancer drug, was immobilized on the RGD-modified magnetite nanoparticles. DOX-coated magnetite nanoparticles were also prepared as a control. KB cell culture experiment showed that both DOX-modified nanoparticles and DOX-RGD peptide-modified magnetite nanoparticles (DRMAM) were internalized into the cells. But the uptake amount of DRMAMs was higher than that of DOX-modified nanoparticles. This result indicates that DRMAMs have a great potential to be used as contrast agent and antitumor medicine.

Abstract: An anionic phospholipid copolymer PMBSSi was synthesized to construct a permanent coating with protein resistant units (2-methacryloyloxyethyl phosphorylcholine, MPC) as well as surface charges onto the silica based (quartz and glass) microchannel through a one-step modification. The coating showed a high property of minimizing the non-specific adsorption of both anionic and cationic proteins to a very low extent of less than 0.05 μg /cm2 on glass substrates. In addition, a significant cathodic EOF ((1.0±0.1) ×10-4 cm2/V·s) with approximately one-half of the EOF of the uncoated microchannel was achieved in coated microchannel at neutral pH. As a conclusion, PMBSSi coating is a simple but highly effective modification for reducing nonspecific protein adsorption, and promising to be applied in electrokinetic microfluidic systems.

Abstract: This paper presents recent activities on the surface modification of blood contacting biomaterials and devices in the author’s laboratory. Surface coating of inorganic films on materials for artificial heart valves, ventricular pumps and coronary stents, such as titanium, stainless steel and low temperature isotropic pryolitc carbon, etc, shows a significant improvement in the anticoagulation behavior. Further, the formation of functional groups such as hydroxyl or amino groups and the binding of biomolecules as well as seeding of endothelial cell shows the promise of biomimetic surface formation. Plasma grafting on materials for artificial heart valve sewing cuff, extracorporeal circulation tube, etc, such as PET, PU, PVC polymers, revealed a significant improvement of anti-platelet adhesion as well as anti-bacterial properties.

Abstract: In this study, newly synthesized zwitterionic PEG was grafted on Nitinol alloy using oxidation treatment. The surface property and blood compatibility of surface-modified Nitinols were examined. The results of surface analysis showed that the contact angle and the ratio of oxygen to carbon significantly decreased with Nitinol alloys. The total amount of fibrinogen (0.095 μg/cm2) adsorbed onto TiNi-PEG2K-N+-S- was lower than that of TiNi control (0.12 μg/cm2). The platelet adhesion decreased in the order of TiNi control > TiNi-MPEG2K > TiNi-PEG2K-N+-S. Particularly, zwitterionic PEG with PEG2K was proven better than any others. The results indicated that zwitterionic PEG surface could significantly suppress platelet adhesion and protein adsorption as compared to other samples. The present study suggested that grafted zwitterionic PEG structure may possess improved blood compatibility.

Abstract: of artificial blood catheters. This paper describes the immobilization of chitosan and heparin molecules on polyethylene terephthalate (PET) films by ozonization. The concentration of peroxide groups (-OOH) was 1.72 × 10-7 mol/cm2 on the PET surface oxidized by ozonization. The results of X-ray photoelectron spectroscopy (XPS) indicate that chains of chitosan and heparin were successfully immobilized on the PET films. The static contact angle(STA) of water decreases from 83.5° to 68.3° by immobilization of chitosan and heparin, which means that the hydrophilic properties of the modified PET is improved. The antithrombogenic property of PET surface was evaluated by a platelet-rich plasma (PRP) adhesion test. The results indicate that the number of platelet adhered on the modified-PET surface incubated with PRP for 240 min decreased significantly and platelets did not aggregate and distort.

Abstract: Nonwoven nanofiber matrices were prepared by electrospinning a solution of silk fibroin (SF) dissolved either in formic acid or in 1,1,1,3,3,3-hexafluoro-2-isopropyl alcohol (HFIP). The mean diameter of the electrospun nanofibers prepared from SF dissolved in formic acid was 80 nm with a unimodal size distribution, which was smaller than those prepared from HFIP (380 nm). SF nanofibers were then treated with an aqueous methanol solution, and structural changes due to solvent-induced crystallization of SF were investigated using IR and 13C solid-state CP/MAS NMR spectroscopy. SF nanofibers prepared from formic acid were found to have a higher proportion of β-sheet conformations than those prepared from HFIP. Methanol treatment provided a fast and effective means to alter the secondary structure of both types of SF nanofibers from a random coil form to a β-sheet form. As demonstrated in the present study, this approach to controlling the dimensions and secondary structure of proteins using various solvents may be useful for the design and tailoring of materials for biomedical applications, especially for tissue engineering applications.

Abstract: β-tricalcium phosphate (TCP) ceramic nanofibers via electrospinning route have been produced using β-TCP sol, which was prepared by the mixing of calcium nitrate tetrahydrate and triethyl phosphate as Ca sand P precursors, respectively. The as-prepared sol was tightly caped and aged in a drying oven at 90 °C for 16 hrs. The aged sol was evaporated in opened containers at 35 °C to reach a proper value of viscosity (100 cPs). Viscous solution was prepared by the mixing of β-TCP sol and high-molecular weight PVP to obtain appropriate viscosity for electrospinning. The mixed solution of β-TCP and PVP with various ratios were vigorously mixed using hot plate/stirrer for 24 hrs and then electrospun. The as-electrospun β-TCP nanofibers were dried in a drying oven at 60°C for 12 hrs and then heat-treated at 500, 600, 700 and 800 °C at 1°C/min heating rate in air. Surface morphology and phase identification of as-spun and heat-treated β-TCP nanofibers were studied. The results have shown that ratio between PVP and β-TCP sol and heat-treatment conditions significantly affected the crystalline phase and morphology of β-TCP nanofibers.

Abstract: Exposed dentine with patent tubules allows the movement of the tubule fluid leading to dentine sensitivity. An occlusion of patent dentinal tubules can effectively reduce the state of dentine hypersensitivity. Strontium chloride (SrCl2) has been known as a representative component of a desensitizing dentifrice. Recently, a desensitizing dentifrice containing nano-sized Carbonated Apatites (n-CAPs) was released onto the market. The aim of this in vitro study was to evaluate the occlusion effects of dentinal tubules in dentifrices containing several concentrations of the n-CAPs. One hundred human dentine specimens were embedded into a Teflon mold and ground with silicone carbide papers to expose the dentin surface. The dentin surface was etched with 37% phosphoric acid for 60 seconds and washed ultrasonically for 1 hour. The dentifrices were classified into five groups: experimental dentifrices Group 1: n-CAPs 5%, group 2: n-CAPs 15%, group 3: n- CAPs 0% and group 4: n-CAPs 30%, and the control dentifrice group 5: SrCl2 10%. The dentifrice slurries were prepared as 20 grams of dentifrice in 80 ml of distilled water. Fifty specimens were brushed with the dentifrice slurries using a V8 Cross Brushing Machine. Tooth brushing was performed 5,000 times using a back-and–forth stroke. Images showing the sizes of the dentinal tubules were taken by scanning electron microscopy (×3000) and the changes in the tubule sizes were analyzed using a digital analyzer. The n-CAPs used in this study had a high solubility and affinity to bone minerals. In addition, the n-CAPs were well deposited on patent dentinal tubules. The group 1 dentifrice (n-CAPs 5% and silica 25%) showed the highest dentinal tubule occlusion, and there was a statistically significant difference between group 4 and the control (p<0.05). Overall, the dentifrice containing 5% nano carbonated apatite and 25% silica is the most effective in occluding dentinal tubules.

Abstract: The aim of this study was to set up a SPR sensor and to investigate protein adsorption onto biomaterial surface using it. Methods: The adsorption of human albumin (Alb), fibrinogen (Fib) and immunoglobulin G (IgG) onto polyurethane (PU) H50-50 and Au surface were measured using this SPR sensor. Results: The results of protein adsorption showed that the amount of Alb, Fib and IgG adsorbed on PU (H50-50) are smaller than Au, and on these two material surfaces, the amount sequence of adsorbed protein is: IgG> Fib > Alb. Both the Alb/Fib ratio and Alb/IgG ratio on PU (H50-50) surface are higher than Au. Conclusion: The antithrombogenicity of PU (H50-50) is better than Au.

Abstract: Stress concentration is one of the main mechanical problems leading to the failure of clinical application for osteointegrated implant of percutaneous osteointegrated prosthesis, which is especially marked for higher amputated leg prosthesis. Traditionally design was composed of only the distal part. To improve the biomechanical safety, a new design with the lag part similar to the lag screw was introduced. Based on CT scan data, relatively accurate model of femur for finite element analysis (FEA) were obtained. The FEA results with the new implant demonstrated that compared to traditional design, the declination of bone stress peak ranged from 15.68% to 28.67%, perpendicular deformation from 34.73% to 72.16%, and maximal stress of implant from 14.51% to 23.36% with the increasing of loads from 3750N to 2000N. So the new design of osteointegrated implant would be more secure mechanically, in the case of higher amputated leg attachment.