Fabrication Of Label-Free Optical Probes And Multimodal Imaging Probe

The detection of biomarkers is an effective method for early diagnosis of disease, and it is significant for the prevention and control of disease, and monitoring the development process of disease. The detection of biomarkers is also valuable in the aspects of clinical trials and intervention treatment evaluation. Due to simple preparation and convenient detection process, label-free optical probes have a great potential in clinical applications for the detection of biomarkers. In vivo imaging is widely used in clinical medicine, which could "see" the disease development and the distribution of targets in vivo, playing an important role in the clinical diagnosis and medical research. The design of imaging probes plays a key role in the development of imaging. Biomarker detection and in vivo imaging complement each other and together to form the basis of clinical diagnosis and research. The thesis of the article aims on two aspects:On the one hand:to broaden the application of label-free methods in a variety of spectroscopic methods, and fabricate various optical biosensors for detecting biological molecular based on fluorescent detection, colorimetric assay and resonance light scattering methods; On the other hand, to solve the problems in the preparation of imaging probe using obtained methods, a novel dual modal imaging probe was fabricated and applied in vivo imaging.(1) A simple, rapid, sensitive and selective RLS bioassay for detecting Hey based on Hcy-involved assembly of PEI-capped Ag-nanoclusters. Hey may act as a bridge to link the Ag cores and hyperbranched PEI due to the strong affinity of SH to Ag and the interaction between the amino groups of PEI can interact with the carboxyl groups of Hey, leading to assembling of the Ag-nanoclusters. The resultant adjoining nanoclusters can interact with one another, giving rise to the oscillation coupling of individual nanoclusters and enhancing the RLS signal. As Hey has stronger reducing ability than Cys and GSH, the proposed bioassay allows discriminating Hey from Cys, GSH and other amino acids with a detection limit of42nM, and permits detecting trace Hey in biological liquid.(2) A simple and efficient colorimetric method for the naked-eye detection and quantification of histidine in biological fluids was developed based on an indicator-displacement assay (IDA) and the Ni2+-histidine affinity pair. In this IDA approach, a commercially available dye, murexide, was used as the indicator and the selective detection of histidine was achieved based on the competition between indicator and histidine for the binding with Ni2+. The competition of histidine with murexide for Ni2+resulted in an obvious color change of the solution from yellow to purple, and the permitted naked-eye detection of trace histidine. The detection limit of the developed bioassay was0.4μM with a linear range from2to30μM. The relative standard deviation for11replicate detections of8μM histidine was2.0%. The developed bioassay allows the rapid, sensitive and selective detection of histidine in urine samples with recoveries from97to105%, and does not need complicated sample pretreatment.(3) A label-free NIR fluorescent assay was developed for selective determination of DNase I activity based on malachite green (MG)/G-quadruplexes. In the presence of Na+or K+, single stranded DNA (ssDNA) is able to form a G-quadruplex structure, thus to increase the rigidity of MG structure and result in a remarkable NIR fluorescence. As DNase I is capable of cleaving all types of DNA indiscriminately to release nucleotide products, the G-quadruplexes are cleaved into oligonucleotides in the presence of DNase I. As a result, the rigidity of MG structure is reduced, and the NIR fluorescence of the solution decreases with increase of DNase I activity, providing a useful platform for low-cost, label-free and convenient detection of DNase I activity. Under the optimum conditions, the proposed label-free NIR fluorescent assay gave a detection limit of1u mL-1, and a relative standard deviation of3.2%for eleven replicate detections of50umL-1DNase I. The proposed assay was applied to the determination of DNase I activity in spiked human urine samples with recoveries from99.1to109.0%.(4) One-pot biomineralization synthesis of Gd2O3/Au hybrid nanoprobe was developed and applied for dual-modal imaging (near infrared (NIR) fluorescence imaging and MRI) in vivo. Bovine serum albumin (BSA) was used as the template in the biomineralization synthesis as it is plenty of active chemical groups including carboxyl groups in aspartic and glutamate residues and35potential thiol groups, and thus widely used as the template for biomineralization synthesis of nanomaterials. The fabricated BSA-Gd2O3/Au nanoprobe showed excellent chemical stability, excellent biocompatibility, intense NIR fluorescence and good MRI ability. The dual-modal imaging potential of the prepared multifunctional nanoprobe was demonstrated by successful NIR fluorescent blood pool imaging. Further modification with RGD peptide enabled the nanoprobe for targeted tumor imaging in vivo.