| Biosensing technology is a combination of biology and electronic information technology.With the continuous integration of these two technologies,the biosensor has the advantages including convenient preparation,easy operation,small size,low cost and fast and sensitive detection.It is clear that the kind of biosensor provides a new type of detection platform for basic medical research and clinical diagnosis,which is attracting great attention from the medical community.Nanomaterials play an active role in the research of biosensors due to their superior electrochemical performance,small size,large specific surface area and many surface active sites.Therefore,combination of nanomaterials and biosensor can lead two modern technologies to preparation of nanomaterial-based biosensor,which shall widely be used in biomolecule detection,disease diagnosis and other related fields.The high sensitivity and non-invasive detection of biomolecules in vivo have been the direction of many researchers,and the microelectrode sensors have a broad application prospects in biomedicine due to its small size and convenient operation.Because the acupuncture needle has the characteristics of being miniaturized,and its unique tip is easy to be penetrated into the living body,causing less damage to the body.The acupuncture needle,used as the electrodesubstrate,can be combined with nanomaterials to be prepared as the microneedle sensor,which provides a new method for the real-time monitoring of biomolecules in vivo.In this paper,an electrochemical microneedle biosensor functionalized with Au nanotubes(Au NTs)and multi-wall carbon nanotube(CNTs)is constructed,which is used for highly sensitive detection of norepinephrine and p H changes in the living locus ceruleus.The traditional acupuncture needle is selected as the microneedle sensing substrate.Firstly,Au NTs and polydopamine(PDA)are deposited on the electrode surface through a series of chemical synthesis methods,and then the CNTs are modified on the tip surface of the acupuncture needle by electrochemical deposition.The fabricated microneedle sensor is then used to perform real-time monitoring of norepinephrine released from the nucleus of the cerebral nucleus.The specific research content of this topic is mainly the following two parts:Part Ⅰ: Construction of functionalized microneedle sensors and its application in real-time monitoring norepinephrine and p HNorepinephrine(NE)is an important neurotransmitter in the body,and its content is closely related to the occurrence and the development of disease.When the metabolism of norepinephrine in the body is disordered,it will lead to various diseases such as endocrine system disorder and neurodegenerative diseases in the body.Therefore,it is of great significance to accurately and rapidly monitor NE in vivo,which is conducive to elucidate its mechanism of action in cell physiology and further exploration in clinical applications.The concentration of hydrogen ions in the body reflects the change of p H,which will lead to many cardiovascular and neurological diseases.Therefore,it is of great significance to monitor the pathological process of p H poisoning in real time.The PDA/CNTs/Au NTs functionalized microneedle sensor prepared in this study will provide a new method for the detection and diagnosis of diseases caused by norepinephrine metabolism disorder.The traditional acupuncture needle is functionalized with Au NTs,PDA and CNTs by electrochemical deposition.The surface morphology of the electrode is characterized by scanning electron microscopy(SEM)and the electrochemical cyclic voltammetry(CV)is used to investigate the electrochemical properties of the modified electrode.The experimental results show that the PDA/CNTs/Au NTs functionalized acupuncture needle sensor has obvious advantages in the catalytic reduction of NE compared with the bare electrode or CNTs and Au NTs modified electrode.It benefits from the synergistic effects between the wire and the multi-walled carbon nanotubes.And the nano-sensing platform exhibits good selectivity and stability for the detection of NE.The prepared PDA/CNTs/Au NTs sensors are used for quantitative analysisof norepinephrine solution.The results show that,the oxidation peak current of NE has a good linear relationship in the range of 0.5~50μmol/L.The detection limit is found to be 0.25 μmol/L.The changes of hydrogen ions(H~+)concentration reflect the change of p H in the body.Based on the good response of polydopamine material PDA to hydrogen ion,the experiment also investigated the response of the electrode to hydrogen ion in solution is also investigated.The open-circuit potentials were are detected recorded by changing different p H values of phosphate buffer and serum solutions with different p H values.In the range of p H 3 to 9,the corresponding open circuit potentials indecreased negatively with the increase of p H value of the solution.Both the linear relationship and a high sensitivity with a slope of 50.7 m V per p H are obtained.The potentiometric measurements is conducted to investigate the real-time response of theelectrode to hydrogen ion change.As the p H of the solution gradually decreases,the potential gradually increases,which is consistent with the results of the open circuit potential.Such a microneedle-based sensor constructed in this study provides a new method for in vivo detection.Part Ⅱ:Applications of functionalized microneedle sensors in real-time monitoring NE change in vivoThe locus nucleus-norepinephrine system plays an important role in transmitting the diffuse projection throughout the central nervous system,and the system plays a major role in arousal,attention,and stress responses if norepinephrine metabolism occurs in the body.If abnormal,there will be a series of pathological conditions.So it is great meaningful to monitor the content of norepinephrine in the locus nucleus in real time and in vivo.Based on the establishment of a normal rat model,the PDA/CNTs/Au NTs functionalized microneedle is used to real time monitor the norepinephrine in the rat blue spot nucleus by timulated with high concentration of potassium.The effects of the adrenergic receptor antagonist yohimbine and the adrenergic receptor isoproterenol on the secretion of norepinephrine in the locus coeruleus is further investigated.The change of current and voltage of the microneedle responds to the norepinephrine changes in the locus nucleus.This experiment demonstrates that the PDA/CNTs/Au NTs functionalized microneedle electrode can real-time monitor changes of norepinephrine in vivo. |
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