## 4 Conclusions  
In this study, we tried to develop modifications of a commercial 3D printer to prepare the PEEK substrates using the fused deposition modeling method. Then, the PEEK/antibiotic agent samples were prepared using dip coating with various contents of vancomycin/ampicillin salts mixed with PLGA binder in order to obtain the samples with long-term antibacterial properties. Several possible components such as the design of metal tube, the diameter of heated nozzle, and the temperatures set in the heated nozzle were examined. When the temperature of the heated nozzle was higher than 360 \({}^{\circ}\)C, a coalification was observed in the PEEK sample, which indicated that the temperature of the heated nozzle had to be set at 340 \({}^{\circ}\)C. The diameter of 0.6 mm for the heated nozzle is better than that of 0.4 mm when the PEEK materials were used for 3D printing. The part of metal tube with a diameter of 2 mm connected with the heated nozzle can also inject PEEK filament smoothly into the heated nozzle compared to the original design of a commercial 3D printer. For the drug release profile tests of antibiotic agents in the buffer solution, stable drug release profiles for ampicillin and/or vancomycin from the samples into the buffer solution were observed and made the concentrations of antibiotic agents in the buffer solution higher than the values of MIC 90 on _S. aureus_ within a 30-day  
Figure 5: Bioactivity for _S. aureus_ for **(I)** sample (A), **(II)** sample (B), **(III)** sample (C), **(IV)** sample (D), and (V) sample (E), respectively.  
tests. Bioactivities of the ampicillin and/or vancomycin loaded on the PEEK substrates can maintain at least 28 days. The loading ratio of vancomycin (50%) and ampicillin (50%) on the PEEK substrate showed good antibacterial performance compared with other samples. This study showed that a simple and low-cost 3D printing method for the preparation of PEEK/antibiotic agent material can have further applications in biomedical-related technology.  
The following are available online at [[http://www.mdpi.com/2076-3417/10/1/97/s1](http://www.mdpi.com/2076-3417/10/1/97/s1)]([http://www.mdpi.com/2076-3417/10/1/97/s1](http://www.mdpi.com/2076-3417/10/1/97/s1)): Figure S1. Printing results of PEEK sample using the (I) original 3D printer and (II) modification of our 3D printer. Figure S2. (I) Surface SEM images of PEEK sample and (II) cross-sectional images of PEEK sample. Figure S3. Short-term drug-release profiles for (I) vancomycin and (II) ampicillin salts from the samples on the PEEK substrates into the buffer solution. Figure S4. Long-term drug-release profiles for (I) vancomycin and (II) ampicillin salts from the samples on the PEEK substrates into the buffer solution.  
The designs of experiments were carried out by [PERSON] and [PERSON]. The preparation and characterization of PEEK/antibiotic agent/PLGA samples were carried out by [PERSON] and [PERSON]. The analysis of antibacterial properties of samples was carried out by [PERSON] and [PERSON]. The writing and correction were made by [PERSON] and [PERSON], and all authors have given approval to this manuscript. All authors have read and agreed to the published version of the manuscript.  
This work was sponsored by the Chang Gung Memorial Hospital, Keelung grant numbers CMRPD3G0071, CMRPD3G0072, and BMRP948.  
The authors thank Chang Gung Memorial Hospital, Keelung and Chang Gung University for supporting this study.  
The authors declare no conflict of interest.