Microelectrodes for pain management, neural prosthesis or assistances have a huge medical demand, such as the application of pain management chip or retinal prosthesis addressed on age-related macular degeneration (AMD) and the retinitis pigmentosa (RP). Due to lifelong implanted in human body and direct adhesion of neural tissues, the electrodes and associated insulation materials should possess an ideal bio-compatibility, including non-cytotoxicity and no safety concern elicited by immune responses. Our goal intended to develop retinal prosthesis, an electrical circuit chip used for assisting neural electrons transmission on retina and ameliorating the retinal disability. Therefore, based on the ISO 10993 guidance for implantable medical devices, the electrode prosthesis with insulation material has to conduct bio-compatibility assessment including cytotoxicity, hemolysis, (skin) irritation and pathological implantation examinations. In this study, we manufactured inter-digitated electrode (IDE) chips mimic the electrode prosthesis through photolithography. The titanium and platinum composites were deposited onto a silicon wafer to prepare an electric circuit to mimic the electrode used in retinal prosthesis manufacture, which further be encapsulated to examine the bio-compatibility in compliance with ISO 10993 and ASTM guidance specifically for implantable medical devices. Parylene-C, polyimide and silicon carbide were selected as materials for electrode encapsulation in comparison. Our data revealed parylene-C coating showed a significant excellence on bio-insulation and bio-compatibility specifically addressed on implantable neuron stimulatory devices and provided an economic procedure to package the electrode prosthesis. Therefore, parylene C encapsulation should serve as a consideration for future application on retinal prosthesis manufacture and examination.

Background: The aqueous solubility of indomethacin, a poorly water-soluble anti-inflammatory drug, was enhanced by co-crystallization with co-formers. The co-crystals were characterized and compared by an X-ray diffraction (XRD) analysis, terahertz (THz) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. Methods: Indomethacin co-crystals with either amides (saccharin, nicotine amide, and urea) or amino acids (lysine and histidine) as co-formers were prepared through the solvent evaporation method. The co-crystals were characterized by XRD, THz, and FT-IR analyses, followed by solubility tests to examine the solubility enhancement. Results: Both the XRD and THz analyses were capable of distinguishing co-crystals from physical mixtures; however, the THz spectra were relatively simpler and clearer than the XRD analysis. Furthermore, the solubility of indomethacin was successfully increased by two to three times that of pure indomethacin after co-crystallization with the above five co-formers. Conclusion: Five kinds of indomethacin co-crystals (with enhanced solubility) were successfully prepared and confirmed by the three spectroscopy techniques, XRD, THz, and FT-IR. The identification of co-crystals was achieved by a THz analysis, giving relatively simpler and clearer spectra with less noise. Hence, in addition to an XRD analysis, a THz analysis (a non-destructive, non-ionizing radiative, and relatively rapid measurement technique which is convenient and safe to use) is a good alternative method to characterize co-crystals.

Back pain resulted from spine disorders reaches 60–80% prevalence in humans, which seriously influences life quality and retards economic production. Conventional electrical pain relief therapy uses radiofrequency to generate a high temperature of 70–85 °C on the electrode tip to destroy the neural transmission and stop the pain. However, due to the larger area of stimulation, eliciting significant side effects, such as paralysis, contraction, and a slightly uncomfortable feeling, our study aimed to design a tiny and stretchable neural stimulatory electrode that could be precisely anchored adjacent to the dorsal root ganglion which needs therapy and properly interfere with the sensory neural transmission. We also designed a subcutaneously implantable wireless power transmission (WPT) device to drive the neural stimulatory electrode. Through the study, we elaborated the design concept and clinical problems, and achieved: (1) the architecture design and simulation of the transdermal wireless power transferred device, (2) a wrap-able pulsed radiofrequency (PRF) stimulatory electrode, (3) an insulation packaging design of the titanium protection box. The feasibility study and hands-on prototype were also carried out.