In this study, zinc oxide (ZnO) nanorod arrays as antibiotic agent carriers were grown on polyetheretherketone (PEEK) substrates using a chemical synthesis method. With the concentration of ammonium hydroxide in the precursor solution kept at 4 M, ZnO nanorod arrays with diameters in the range of 100–400 nm and a loading density of 1.7 mg/cm2 were grown onto the PEEK substrates. Their drug release profiles and the antibacterial properties of the antibiotic agent/ZnO/PEEK samples in the buffer solution were investigated. The results showed that the concentrations of antibiotic agents (ampicillin or vancomycin) released from the samples into the buffer solution were higher than the value of minimum inhibitory concentration of 90% for Staphylococcus aureus within the 96 h test. The bioactivities of ampicillin and vancomycin on substrates also showed around 40% and 80% on the Staphylococcus aureus, respectively. In the antibacterial activity test, sample with the suitable loading amount of antibiotic agent had a good inhibitory effect on the growth of Staphylococcus aureus.

In this study, polyetheretherketone (PEEK) materials coated with various ratios of two kinds of antibiotic agents (ampicillin and/or vancomycin salts) were prepared. A modified 3D printer based on fused deposition modeling was employed to prepare PEEK disks. Coating ampicillin and/or vancomycin salts onto the PEEK disks was carried out using the biodegradable poly (lactic-co-glycolic acid) (PLGA) polymer as a binder and a control unit for the drug release in the buffer solution. The effects of various rations of ampicillin and/or vancomycin salts in the PLGA polymer on the PEEK substrates, the release profiles of various drugs, and antibacterial activities of the samples were investigated. Temperature of the heated nozzle in a commerical 3D printer was set at 340 °C. After systemic investigations of the qualities of PEEK disks, a diameter of the heated nozzle of 0.6 mm in the 3D printer was employed for the preparation of PEEK disks. Results of drug release profiles from samples into buffer solution show that the antibacterial activities of samples can continue up to 28 days. In the inhibition zone test of samples, the release amounts of antibiotic agents from the PEEK samples can inhibit S. aureus with activity of over 40% in 30 days tests and most of them can have inhibition activities of higher than 60% during the test. These results showed that a simple and low-cost 3D printing method for the preparation of PEEK/antibiotic agents/PLGA samples can have further applications in biomedical-related technology.

This paper presents a methodology for measuring the improvements in efficiency and adjustments in the scale of R&D (Research & Development) activities. For this purpose, this study decomposes academic productivity growth into components attributable to (1) world academic frontier change, (2) R&D efficiency change, (3) human capital accumulation, and (4) capital accumulation. The world academic frontier at each point in time is constructed using data envelopment analysis (DEA). This study calculates each of the above four components of academic productivity for 27 countries over 1990-2003, and finds that the components which contribute to academic productivity growth vary with the different countries' characteristics and development stages. Human capital has more weight in terms of the quantity of academic research, and capital accumulation plays a more important role in the citation impact of academic research.