Nanomaterial-based Novel Biosensor For The Determination Of D-dimer

As the cardiovascular and cerebrovascular diseases and other organs thrombotic diseases become increasing threat to human life, it is particularly important to diagnose and treat thrombotic disease. D-dimer is a kind of metabolites from cross linked fibrin under the effect of fibrous enzyme that reflects the specificity of the state of blood coagulation and fibrous in the body. Hence, it can be used as the tumor-specific markers by judging whether the body is occurring secondary fibrous protein dissolved overactive. Traditionally, three D-dimer analysis assays are presently available in clinical diagnosis, including enzyme-linked immunosorbent assays(ELISA), whole blood agglutination assays, and latex agglutination assays. In these analysis assays, whole blood agglutination assay tests display a high specificity, but it has a low sensitivity. Latex agglutination assays are relatively cheap and rapid, however, they also have a low sensitivity and specificity for determination. The assay of ELISA displays the high sensitivity. The conventional ELISA-test is well established, reproducible and shows sufficient sensitivity. In spite of this, it is known that the response signal of all photometric assays is influenced by the colour of medium and its composition. Moreover, the ELISA test involves several steps, hence it is time-consuming.The development of clinical laboratory medicine accompanies with the emerging of new technologies. Biosensor technology is the multi-disciplinary and cross product of medicine, electrochemistry, thermal, optical and electronic technology. Thus, it is listed as one of the five clinical inspection technologies in the 21 st century due to its outstanding characteristics such as high selectivity, fast analysis speed, simple operation, low cost, etc. Graphene and its derivatives graphene oxide(GO) have been greatly used in biomedical field. As GO surface contains carboxyl group, epoxy group, hydroxyl group, it owns outstanding characteristics of large surface area, good biocompatibility.In this work, the topic of distribution of D-dimer positive patients in clinical departments and its clinical significance is discussed firstly. Further, D-dimer is detected by GO-assisted surface plasmon resonance(SPR) biosensor and gold nanoparticles-GO based surface acoustic wave(SAW) biosensor respectively. Thus, the sensitive and specific protein assay is constructed. The aims are directed to the determination of protein and the application in clinical laboratory by the GO-assisted biosensor. The main contents are consisted of the following parts: I The distribution and clinical significance of D-dimer positive patientsThe investigation of the distribution and clinical significance of D-dimer positive patients:the departments of ICU, cardiology, respiratory medicine, orthopedics, general surgery, liver disease, neurosurgery, obstetrics and gynecology, oncology patients total positive rate was 44.1%; Both 200 D-dimer positive value and negative value were analyzed, the positive value was significantly higher than the negative value; at the same time. The cases of positive value in diffuse intravascular coagulation, deep vein thrombosis pulmonary embolism, heart cerebrovascular disease, liver disease, malignant tumor were counted, respectively. The valuable determination of plasma D-dimer in clinical application was proved. II Graphene oxide-assisted surface plasmon resonance biosensor for the determination of D-dimer.GO-assisted SPR biosensor for the determination of D-dimer was investigated. GO was conjugated onto the surface of the SPR chip surface via electrostatic interaction after the chip surface was activated with cysteamine. Subsequently, anti-D-dimer was covalently immobilized on the chip surface through binding between carboxylic groups on the GO surface and amine groups on the protein surface. Finally, the different concentrations of D-dimer were detected by the SPR biosensor via protein-protein interaction. The optimal concentration of GO was found to be 2 mg/mL. Meanwhile, this biosensor presented a response to D-dimer in the concentration range of 10-150 ng/mL, and limit of detection(LOD) of the developed biosensor was determined to be as low as 5.08 ng/mL. In addition, addition of albumin from human serum(HSA) to the anti-D-dimer-modified SPR chip revealed a negligible response, indicating a satisfactory immunological specificity. Furthermore, D-dimer detection was successfully conducted in different concentrations of human plasma. These results suggest that the GO-assisted SPR biosensor could be exploited for point-of-care diagnosis in the clinical laboratory. Ш Gold nanoparticles-graphene oxide based surface acoustic wave biosensor for the determination of D-dimer.Gold nanoparticles-GO based SAW biosensor for the determination of D-dimer was investigated. First, the different phases due to the reaction of antigen- antibody were compared, in which gold nanoparticles-GO and GO were modified, respectively. It was proved that the signal was more amplified by gold nanoparticles-GO composite modified SAW biosensor than the GO modified SAW biosensor. The kinetic analysis by SAW’s Fitmaster software showed that linear regression analysis of the correlation coefficient was 0.984, and KD =0.02 nM. It was proved that this biosensor had the high sensitivity and high affinity. The specificity was confirmed by analyzing the different phase caused by D-dimer, HAS, PBS, and BNP, respectively, showing the high specificity of the biosensor.