Recently, Zhong Chao's team from the National Key Laboratory of Quantitative Synthetic Biology of the Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences (hereinafter referred to as "Shenzhen Advanced Institute"), Liu Zhiyuan's team from the Neuroengineering Center of the Shenzhen Institute of Advanced Technology, and Wang Renheng's team from Shenzhen University published their latest research results in Advanced Materials. They used 3D printing living hydrogel technology to successfully develop a micro-portable microbial fuel cell with a diameter of only 20 mm, innovatively integrated a bioelectric stimulation device, and achieved precise regulation of electrophysiology and blood pressure by stimulating neurons, which has great application potential in disease treatment. This research has promoted the development of portable biological devices and expanded the research frontier of living energy materials.

Interdisciplinary development of biobatteries that can be recycled

In this study, the research team developed an innovative 3D printed living hydrogel material based on Shewanella. This biomaterial has unique elastic properties, which enables it to form complex structures ranging from one to three dimensions, including fine spider webs and leaf shapes, through 3D printing technology. To ensure that the microorganisms remain active in the device, the researchers first encapsulated the microorganisms in a solution state in alginate hydrogels, and optimized the system by adding nanocellulose and graphene oxide, which significantly improved the mechanical strength and conductivity of the material.

Designing and making biobatteries requires the integration of multidisciplinary knowledge, involving fields such as synthetic biology, materials science and biomedicine. At the Shenzhen Institute of Advanced Technology, interdisciplinary cooperation has a natural advantage. Based on breakthrough materials, Zhong Chao's team cooperated with Liu Zhiyuan's team, a researcher at the Neuroengineering Center of the Shenzhen Institute of Advanced Technology, to jointly develop a micro-biobattery system.

Inspired by traditional lithium battery manufacturing technology, the research team adopted an optimized design of anode-cathode separation: using living hydrogel as the "anode" and alginate hydrogel containing potassium ferrocyanide as the "cathode", a high-performance electrode structure was prepared through 3D printing technology, and finally a micro-biobattery system with a diameter of only 20 mm was successfully constructed.

Experimental results show that this micro-battery can stably output 450 millivolts and achieve up to 10 complete "self-charging-discharging" energy supply cycles. Further performance tests show that the biobattery has excellent cycle stability and extremely low energy loss. At the same time, it completely avoids the use of scarce metals such as cobalt and lithium and toxic electrolytes in traditional batteries, and has significant advantages in environmental protection.

Achieving precise blood pressure regulation

"Research needs to break through 'paper innovation' and find practical application scenarios." Wang Xinyu, the first author of the research paper, introduced that although the technical concept of biobatteries is novel, there are two major limitations of power and output voltage fluctuations (affected by bacterial activity), which makes biobatteries difficult to cope with scenarios that require continuous and stable power supply.

Based on these characteristics, the team targeted the field of precision medicine, instantaneous neural stimulation, and successfully developed a bio-battery application solution suitable for neural regulation by integrating capacitor systems to achieve precise regulation of electrical energy.

The results of the rat sciatic nerve stimulation experiment showed that as the gradient of the output intensity of the bio-battery increased, the induced action potential and electromyographic signal amplitude showed a significant dose-dependent enhancement. In addition, by adjusting the output of the bio-battery, the blood pressure of the rats successfully decreased significantly, with systolic blood pressure (high pressure) decreasing by 23.5% and diastolic blood pressure (low pressure) decreasing by 18.7%. After the stimulation stopped, the blood pressure of the rats returned to the baseline level autonomously.

These data not only verified the effectiveness of bio-batteries in neural intervention therapy, but also revealed their unique advantages - the natural fluctuation characteristics of bacterial metabolism are highly consistent with the needs of instantaneous neural stimulation, providing an innovative solution for precise neural regulation of diseases such as hypertension.

According to Wang Xinyu, the team plans to develop implantable bio-batteries based on living hydrogels in the future, using human blood glucose as a continuous energy source to achieve self-powered operation of medical equipment.

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