Optical time domain reflectometry based on a self-chaotic circular-sided microcavity laser.

A self-chaotic circular-sided square microcavity laser, with a chaos bandwidth of 12.9 GHz and a flatness of ±3d B, was applied in optical time domain reflectometry (OTDR). Using the broadband chaos laser, we demonstrated a range resolution of 4.5 mm and a 25-km detection distance experimentally. The solitary wide-bandwidth microcavity chaos laser, without the extra correlation peaks in optical feedback chaotic lasers, has shown potential advantages for correlation OTDR in practical application.

Feedback insensitivity in a self-chaotic microcavity laser.

Insensitivity to external optical feedback is experimentally demonstrated in a self-chaotic deformed square microcavity laser for the first time, to the best of our knowledge. Both the optical and radio frequency (RF) spectra of the microlaser remain unaffected for external optical feedback with feedback strength as high as 9.9 dB. In addition, the autocorrelation function curve exhibits no time-delayed peaks. The insensitivity makes the self-chaotic microcavity laser promising for applications in feedback-insensitive optical sources.

Blood compatibility and interaction with endothelial cells of titanium modified by sequential immobilization of poly (ethylene glycol) and heparin.

In this study, poly(ethylene glycol) (PEG) and heparin were sequentially immobilized on a titanium surface by the carbodiimide covalent coupling method with the aim to improve the blood compatibility of titanium and enhance endothelial cell adhesion and proliferation. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed that PEG and heparin were successfully immobilized on the titanium surface. Compared to the pristine titanium, a highly hydrophilic layer was achieved after the immobilization, and the resulting heparin-PEG layer can significantly prevent human plasma fibrinogen adsorption. Analysis of platelet attachment to the modified surfaces, via scanning electron microscopy (SEM), showed strikingly fewer platelets attached to the PEG and heparin modified surfaces, compared to the control. The immobilized PEG and heparin effectively prolonged the activated partial thromboplastin time (APTT) and inhibit platelet activation significantly. Furthermore, the modified samples showed good cytocompatibility. Endothelial cells exhibited improved proliferative profiles in terms of a CCK-8 assay, as compared to those on the pristine titanium. The modified samples showed a better endothelial cell adhesion and spreading, than the pristine titanium. Therefore, the blood compatibility and cytocompatibility of the titanium surface can be enhanced by PEG immobilization and further, by subsequent heparin grafting. It could be concluded that the negatively charged heparin-PEG layer with excellent hydrophilicity could obviously improve the blood compatibility and enhance the endothelial cell adhesion and proliferation, and the approach of the present study is considered as an effective method to improve the hemocompatibility and cytocompatibility of biomaterials.

Improved anticoagulation of titanium by sequential immobilization of oligo(ethylene glycol) and 2-methacryloyloxyethyl phosphorylcholine.

Titanium and its alloys have been widely used for blood-contacting biomedical devices; however, their blood compatibility needs to be improved. In this study, titanium surface was modified by sequential immobilization of oligo(ethylene glycol) (OEG) and 2-methacryloyloxyethyl phosphorylcholine (MPC) to improve its anticoagulation. Water contact angle results showed an excellent hydrophilic surface after the immobilization. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) confirmed that OEG and MPC were successfully immobilized on titanium surface. Static platelet adhesion and APTT (activated partial thromboplastin time) experiments suggested that the anticoagulation of titanium was significantly enhanced by the immobilization of OEG and further by subsequent MPC grafting. The approach in the present study opens up a window of promising an effective and efficient method to improve the anticoagulation of blood-contact biomedical devices such as coronary stents.

Extracellular matrix protein patterns guide human chondrocytes adhesion and alignment characterized by vimentin and matrilin-3.

The main purpose of the present study is to investigate the influences of collagen VI (col-VI) patterns on human chondrocytes behaviors. To this end, col-VI stripes with varying width and interstripe spacing are created on polystyrene (PS) surfaces by microcontact printing (µCP). Human chondrocytes are then seeded on these protein patterns and the cell adhesion and alignment are investigated by staining the vimentin and matrilin-3 secreted by seeded chondrocytes. The results indicate that the cells preferentially attach onto the protein areas, rendering cell patterns and the elongated cell shapes. The pattern dimensions can significantly influence cell adhesion, spreading and orientation. The stripe protein patterns can guide cell adhesion and alignment. The cell morphologies can be controlled by carefully designing the pattern shapes and sizes. Our results suggest that the protein patterns can be used to modify biomaterials' surfaces for selective cell-binding and cell alignment. It could provide some cues for the development of novel implantable biomaterials, such as tissue-engineered scaffolds for cartilage replacement, where specific cell alignment is needed.

Enhancing the antibacterial activity of biomimetic HA coatings by incorporation of norvancomycin.

BACKGROUND: Bacterial infections associated with the use of biomaterials remain a great challenge for orthopedic surgery. The main purpose of the work discussed in this paper was to improve the antibacterial activity of a biomimetic calcium phosphate (CP) coating widely used in orthopedic biomaterials by incorporation of norvancomycin in the biomimetic process. METHODS: CP coating and CP coating containing norvancomycin were produced on a titanium alloy (Ti6Al4V) surface by a biomimetic process. The morphology, surface crystal structure, and concentrations of elements in the coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), respectively. The amount of norvancomycin and its release were investigated by UV-visible spectroscopy. MTT was used to investigate cell behavior. The morphology of adhered bacteria was observed by SEM. Antibacterial activity was expressed as inhibition zone by using Staphylococcus aureus (ATCC 25923) as model bacteria. RESULTS: Results from SEM, EDX, and XRD revealed formation of a hydroxyapatite (HA) coating. The amount of antibiotic in the CP coating increased with increasing concentration of norvancomycin in the coating solution, followed by a plateau when the concentration of norvancomycin in the coating solution reached 600 mg/l. Approximately 2.16 µg norvancomycin per mg coating was co-precipitated with the CP layer onto titanium alloy discs when 600 mg/l norvancomycin coating solution was applied. The norvancomycin had a fast release profile followed by slow release. The MTT test of osteoblast cell cultures suggested that coatings containing norvancomycin did not cause any cytotoxicity compared with the CP coating and control titanium plate. The antibacterial activity test showed that the norvancomycin released from the coatings inhibited the growth of Staphylococcus aureus; more bacteria were found on the CP coating than on the norvancomycin-loaded coating. CONCLUSIONS: A norvancomycin-loaded HA-like coating was successfully obtained on titanium surfaces. The norvancomycin incorporated had no negative effects on osteoblast cell behavior. The released norvancomycin results in excellent antibacterial activity of Ca-P coatings. Therefore, incorporation of norvancomycin can enhance antibacterial activity and the norvancomycin-loaded CP coating can be used to inhibit post-surgical infections in orthopaedics.