In-vivo study

To confirm the applicability of the chip to practical uses, the hybrid hydrogel with a composition of GP1.5TEOS54 was selected because of its sufficiently mechanical reliability and drug elution capability, according to in-vitro test, Fig. 10(b). In this preliminary in-vivo study, a unique design by integrating the biological self-detection and response-induced features of the chip on epileptic treatment was demonstrated. The architecture of the whole drug delivery system is shown in Fig. 11. The drug delivery system consists of four units: (a) signal acquisition and amplification unit, (b) 8051 micro-processor and wireless data transmission unit, (c) electric field and drug delivery chip, (d) host system for data storage and real-time display.

It can be observed in Fig. 11(a) that electroencephalogram (EEG) signal of the rat’s frontal cortex is amplified and band-pass filtered (1000x, 0.3-80 Hz) by the op-amp, and then the amplified EEG is positive-biased to the input voltage range of an analog-to-digital converter (ADC) (Texas Instrument CC2430 chip). Thus, several tasks were implemented on the microcontroller board (MCU) (refer to Fig. 11(b)), including analog-to-digital conversion of EEG signals, execution of seizure detection, generation of trigger to the drug releasing chip, and EEG data wireless transmission. The MCU was programmed to control the sampling period of the ADC and the generation of trigger, retrieved the direct memory access (DMA) data, and started a series of feature extraction and seizure detection. The system detected epileptic seizures and immediately feedbacks to stimulate electric at the drug releasing chip (refer to Fig. 11(c)) to induce drug elution. Electric filed activated the structural change of the hybrid hydrogel in the chip to release drugs accordingly. Therefore, the controlled release system is regarded as a closed-loop drug delivery system on epilepsy control, as shown in Fig. 11(a)-(c). Furthermore, in order to achieve real-time monitoring, the real-time on-line seizure monitoring was developed using National Instrument LabVIEW to create a graphical user interface (GUI) VI to monitor and store the EEG data(refer to Fig. 11(d)).

A complete view of the backpack and of its placement on a rat is given in Fig. 12(a). There are two batteries in the backpack. In order to minimize the weight of head mounted devices for a rat, the backpack was mounted on the rat’s jacket which was connected to the neural interface by short soft wires. Generally, the shorter the wires, the lower the noise picked from the environment.

The detailed caption was given in Fig. 12(b), the neural interface consists of op-amplifier and constant voltage circuits. On the other hand, the microcontroller board used Texas Instrument CC2430 chip to compute detection epileptic seizure. When the MCU detects epileptic seizures, it would feedback immediately to trigger chip to release drug into the rat during eight minutes. The funnel chip can be demonstrated in the inset of Fig. 11(c).

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Fig. 11. Schematic illustration of the controlled release system. (a) signal acquisition and amplification unit, (b) 8051 micro-processor and wireless data transmission unit, (c) drug releasing chip, (d) host system for data storage and real-time display.

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Microcontroller board (TI CC2430)

Neural interface board

Chip Connect device and constant

current power

Fig. 12. Experimental setup of the animal study and the illustration of the drug release system, where the “chip” (b) indicates the drug delivery device.

Fig. 13 represents one example of the SWD of the rats in this experiment. We recorded 40-minutes spontaneous brain activity during released process and 20-minutes spontaneous brain activity after treatment. Fig. 13 demonstrates that the SWD of the rats reached ~120 times without drug administration while the SWD of the rats reduced by nearly 50% while ESM was released from the self-detection drug delivery system. Although it is hard to quantify the exact amount of the ESM release into the rats during the in-vivo operation, it is truly indicated that certain effective dose of ESM was released into the rats from the chip-based drug delivery system, which, for the first time, proved the concept of the integrated system designed based on the electrical-responsive hybrid hydrogel. Although this in vivo study has far from being optimized in terms of operation parameters among different parts of the integral system, drug dose, and time of dosing, the preliminary in-vivo outcomes do provide promising perspective toward further investigation. It is highly expected by combing photolithography technology frequently employed in semi-conductor industry, the implantation of the chip-based system would be expected to offer self-detection and effective therapeutic treatment for epileptic patients, and those who suffers from chronic diseases, in the future.

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0 20 40 60 80 100 120 140 160

Drug release process Without Drug

released process

SWD number

Fig. 13. Comparison of SWD number of the rats (n=6) with and without (as control group) drug elution from the chip-based drug delivery system.

4. CONCLUSION

This study demonstrates the synthesis of a hybrid hydrogel consisted of a modified chitosan and inorganic silica gel via a sol-gel route. The hybrid hydrogel showed improved thermal stability and mechanical swelling behavior, indicating an interaction evolved between the modified chitosan, i.e., carboxyl groups, and inorganic siliate phases, i.e., hydroxyl groups. An anticonvulsant drug, ESM, released from the hybrid, was evaluated in vitro under DC electric field of various voltages, showing different release profiles. The field-induced release mechanism from the hybrid hydrogels appeared to be a combined contribution between electrophoretic and electro-osmotic operations upon the electric field stimulus. While integrating the electric-responsive hybrid hydrogel, as a drug reservoir, into a self-detection system, we have successfully demonstrated a real-time responsive drug delivery operation in an epileptic rat model where the number of seizure was reduced considerably by ~50%, from automatic seizure detection to a subsequent release of anti-epileptic drug from the hybrid hydrogel, achieved in tens of seconds.

Acknowledgment

The authors gratefully acknowledge the financial support of the National Science Council in Taiwan through Contract NSC-98-2627-B-009-001.

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Part-IV. 計畫執行績效:

就研究成果而言，目前本子計畫在2009~2010 已發表三篇論文著作於High-impact 國際期 刊如下與一項專利申請:

Published Papers:

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1. Yen-Po Chang, Kun-Ho Liu, Chih-Shin Chao, San-Yuan Chen*, Dean-Mo Liu, Synthesis and characterization of mesoporous Gd2O3 nanotube and its use as a drug-carrying vehicle, Acta Biomaterialia 6 (2010) 3713–3719. (IF=3.98, N/M=5.1%)

2. Shang-Hsiu Hu, Kuan-Ting Kuo, Wei-Lin Tung, Dean-Mo Liu,and San-Yuan Chen* , A Multifunctional Nanodevice Capable of Imaging, Magnetically Controlling, and In Situ Monitoring Drug Release, Advanced Functional Materials, 19, 3396–3403 (2009) (IF=6.99, N/M=4.21%)

3. Wei-Chen Huang, Kun-Ho Liu, Shang-Hsiu Hu, San-Yuan Chen* and Dean-Mo Liu, “A Flexible Drug Delivery Chip for Magnetically-Controlled Release of Anti-Epileptic Drug”, Journal of Controlled Release 139 (3), 221-228, NOV (2009) (IF=5.949, N/M=5.90%) Patent Application:

應用於慢性疾病的生物自我偵測及回饋誘導藥物釋放系統 申 請 日：民國99 年9 月15 日

申請國家：中華民國、美國 案件類型：發明

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