Preparation Of SERS Nanoprobes And Their Application In Breast Cancer Diagnosis

Breast cancer is a malignant tumour that occurs in the epithelial tissue of the breast and has been increasing in both men and women in recent years.The detection of breast cancer includes x-rays,clinical biopsies,tumour marker tests and MRI.Early detection and treatment can significantly improve the survival rate of breast cancer patients if done in a preventative manner.Surface-enhanced Raman（SERS）is considered a powerful and promising technique for biomedical applications due to its inherent rich spectral fingerprint information,excellent detection sensitivity,and unique narrow spectral width.In recent years,various research teams at home and abroad have conducted a series of studies based on SERS for the early screening,diagnosis and prognostic treatment of tumours.Different substrate materials influence the superiority of the SERS enhancement effect.Therefore,in this paper,silver nanospheres（Ag NPs）,gold-covered silver core-shell nanoparticles（Au@MB@Ag NPs）and gold nanospheres（Au NPs）,which have better enhancement effects,were used to detect biomarkers associated with breast cancer in the oxidative state metabolic pathway of nicotinamide adenine dinucleotide.The main studies are as follows.1.The adsorption state of thymine（T）,cytosine（C）,adenine（A）and guanine（G）was studied based on Ag NPs.The changes in the binding sites of bases to Ag NPs and the adsorption status with concentration.The difference between cytosine and methylated cytosine SERS spectra was also compared and the results showed that a good distinction between the two could be achieved at 546 and 787 cm^-1.The breast cancer number one gene（BRCA1）promoter promoter fragment sequence was selected and the distinction between ssDNA1 without methylation and ssDNA2 with methylation was achieved by introducing the t-SNE algorithm.In the normal patient serum patient and methylated patient serum addition experiments,the distinction was 93.2%in the breast cancer serum addition samples and 96.3%in the normal human serum addition samples.The results showed that the differentiation of methylation rate in multiple fragments or whole genomes is a foundation for future differentiation.2.Based on the SERS technique,silver-coated gold core-shell structures（Au@MB@Ag NPs）were prepared using 4-mercaptobenzonitrile（MB）as the internal standard.The quantification was carried out using the Raman peak corresponding to the silent region of MB-CN vibrations,while avoiding competition with the site to be measured and also free from the interference of endogenous biomolecules.The prepared core-shell structure not only enhances the Raman signal,but also makes the normalisation curve data more reliable due to the presence of internal standard molecules.Furthermore,the assay in this paper demonstrates the feasibility of clinical NADH detection.Compared to previously reported results,the detection limit of NADH in complex body fluids such as serum is much lower,indicating that the proposed method has great potential for clinical application and offers the possibility of expanding the early diagnosis of breast cancer.3.Firstly,MoO_3-x with oxygen vacancies was prepared by aqueous intercalation exfoliation using commercial MoO₂ and MoO₃ as precursors.secondly,HAu Cl₄ was directly reduced to Au NPs by using MoO_3-x as a sacrificial template and electron carrier.capping with polyvinylpyrrolidone（PVP）as a stabiliser prevented the aggregation of gold colloids.In addition,the optimum ratio of MoO_3-x to HAu Cl₄ was investigated in this study to assess its performance in the SERS assay of rhodamine 6G（R6G）.The prepared Au NPs readily enabled trace detection of R6G and malachite green（MG）and were able to enhance Fluorescence of Flavin Adenine Dinucleotide（FAD）.The feasibility of this material for the detection of FAD in normal human and breast cancer patient sera has also been demonstrated.The innovative use of MoO_3-x reduction for the preparation of Au NPs in this chapter extends the purely chemical preparation of precious metals.