| The interaction between laser and biological tissue can produce some special effects.Due to the advantages of high spatial resolution of light signal,it is widely concerned in the field of biomedical engineering.Cochlear implant has been widely used in the treatment of severe sensorineural deafness.In order to improve the accuracy and spatial resolution of neural stimulation,the study of light stimulation of neurons in the brain is gradually carried out,and shows a good prospect of application.There are many possible working mechanisms in the stimulation of light:photothermal effect,photomechanical effect,photochemical effect or a mixture of multiple effects,which effect is the main one,what is the relationship between the effect and optical parameters,and whether it is safe.For the future application in bioelectronic devices,the relevant research has important theoretical value and practical significance.In view of the complex composition of cells and tissues,the tiny structure,the multiple effects of light are not easy to separate and so on.Therefore,it is necessary to establish a practical measurement system and method with strong pertinence and convenient operation.It is found that the photothermal effect of light on biological tissues or cells is common in literature research.In this paper,based on the micron level thermal sensor,a physical measurement system for photothermal effect of low light spots(such as suitable for auditory nerve cells)is designed and built,and the thermal effect data of multi band light signals are measured,which is convenient for cell light stimulation research to refer to.At the same time,cell electrophysiological measurement method is used Methods:a detection system was established to detect whether there was signal transduction in auditory neurons stimulated by light signals,and a comparative experiment was carried out to explore the relevant mechanisms and rules.In view of the photothermal effect,we have carried out the basic demonstration and principle analysis of a variety of temperature measurement systems.Considering that the size of auditory nerve cells is very small(usually at the micron level),and the photothermal measurement is difficult to achieve,and taking into account the high accuracy and real-time requirements of temperature measurement,we have built a set of photothermal real-time measurement system using micro nano thermal sensor.During the measurement,the pulse laser is led out by the light source and irradiated to the photothermal measurement board by the optical fiber.The 36 thermal nodes are connected with the multi-channel strobe array by the external circuit through the DuPont plug-in wire.The output voltage can be measured in real time by the connection of the nanovoltmeter and the multi-channel strobe array.The temperature rise waveform caused by the photothermal effect with time can be recorded by the computer Lab VIEW program.The system has high efficiency and accurate results.At the same time,it uses a self-designed semiconductor laser source which can generate pulse laser.Its wavelength can be from 450nm to 1065nm,covering most of the visible light range and part of the near-infrared light range,such as blue light,green light,yellow light,orange light and red light.The experimental data show that the shorter the wavelength of the pulse laser is,the better the photothermal effect is;and the longer the wavelength of the pulse laser is,the better the photothermal effect is.Based on the effect of laser on nerve tissue and cells,we designed a real-time measurement system to observe the changes of intracellular calcium concentration during nerve activity.Firstly,the specific fluorescent indicator was selected to dye the cells,and then the calcium concentration of the cells was detected in real time by the calcium imaging technology,so as to explore the signal transduction function of the auditory nerve cells stimulated by different wavelength pulse laser under the condition of ensuring the safety of the organism.The spiral ganglion cells were irradiated by three wavelengths of pulse laser,i.e.visible light(450nm)and near-infrared light(808nm,1065nm).The calcium concentration in the cells was monitored by calcium imaging instrument.It was found that the concentration of calcium in spiral ganglion cells increased significantly with blue light irradiation at about 450 nm,which further led to the change of membrane voltage,while the concentration of calcium in spiral ganglion cells did not change significantly with laser irradiation at other two bands.At the same time,it was found that the position of optical fiber also affected the selective response of spiral ganglion cells to laser wavelength.Conclusion:under the action of light signal,animal auditory nerve cells can induce signal transduction reaction,which is related to the laser wavelength.It is preliminarily confirmed that this characteristic may be related to many types of light sensitive channels widely distributed on the membrane of auditory nerve cells.In a word,this paper built a photothermal measurement system based on micro nano thermal sensor and a real-time measurement system based on the interaction between light and tissue.The former can be used not only to explore the function of nerve transduction induced by laser photothermal effect,but also to provide pulse laser for experiment under the condition of ensuring the activity of auditory nerve cells,and also to study the interaction between laser and biological tissue.The latter is a new method that we put forward at the cell level.This method can combine the blue light and near-infrared light to do further research.At the same time,this method can be used as a general research tool to develop a high-level research platform.In addition,more precise electrophysiological devices such as patch clamp can be used to further verify the band selectivity of light sensitive channels. |
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