Two-dimensional substrate assisted SERS immunosensor for accurate detection of carcinoembryonic antigen.

Accurate and sensitive detection of carcinoembryonic antigen (CEA) is essential for the detection of various diseases in healthcare and the medical field. Currently, due to the high false negative rate of CEA assay in clinical setting and its use as a common indicator for early cancer screening, a novel CEA detection method with high sensitivity, increased specificity and the lower cost has become a clinical challenge. Here, a facile sandwich type immunosensor based on surface-enhanced Raman scattering (SERS) was presented including 4-mercaptobenzonitrile (4MBN) labeled gold core-silver shell nanoparticles (Au@4MBN@Ag NPs) as SERS tag and 4-mercaptophenylboronic acid (4-MPBA) functionalized two-dimensional (2D) silver nanoparticle film (Ag FM) as SERS capture substrate for CEA detection. A linearity of 10-9-10-14M was observed with high sensitivity and excellent selectivity for the detection of CEA. Additionally, the spiking experiment yielded 105.33-127.00% recovery with variation coefficients below 10% demonstrating high assay accuracy and precision. The immunosensor we proposed here is a promising approach to quantify CEA in liquid biopsy samples with high sensitivity, which could be further developed for early cancer screening.

Early detection of lung cancer via biointerference-free, target microRNA-triggered core-satellite nanocomposites.

MicroRNAs (miRNAs) are emerging as essential liquid biopsy markers for early cancer detection. Currently, the clinical applications of miRNAs are lagging behind due to their high sequence similarity and rarity. Herein, we propose biointerference-free, target-triggered core-satellite nanocomposites for ultrasensitive surface-enhanced Raman spectroscopy (SERS) detection of lung cancer-related miRNA-21. Through the hybridization-based recognition effect, we observe an enormous SERS signal enhancement caused by miRNA-21-triggered assembly of core-satellite nanocomposites. This enables the sensitive detection of miRNA-21 down to the 0.1 fM level in a linear range of 10 fM to 1 nM. The use of a biointerference-free reporter further allows quantitative and direct detection of miRNA-21 from complex plasma samples, without RNA pre-extraction. As a proof of principle, we measure the level of plasma miRNA-21 in 20 lung cancer patients and 10 healthy participants. Significantly higher levels of miRNA-21 are determined in lung cancer patients than in healthy participants, with clear lower expression in stage I (n = 10) than in stage III-IV (n = 10) lung cancer patients. We, therefore, believe that this proposed strategy will have high clinical potential for sensitive quantification of miRNA markers in liquid biopsy samples and act as a complementary method for the early detection of lung cancer.

Sensitive and Selective Detection of Clenbuterol in Meat Samples by a Graphene Quantum Dot Fluorescent Probe Based on Cationic-Etherified Starch.

The use of clenbuterol (CLB) in large quantities in feedstuffs worldwide is illegal and potentially dangerous for human health. In this study, we directly prepared nitrogen-doped graphene quantum dots (N-GQDs) by a one-step method using cationic-etherified starch as raw material without pollution, which has the advantages of simple, green, and rapid synthesis of N-GQDs and high doping efficiency of nitrogen elements, compared with the traditional nitrogen doping method of reacting nitrogen source raw material with quantum dots. The N-GQDs synthesized by cationic etherification starch with different substitution degrees (DSs) exhibit good blue-green photoluminescence, good fluorescence stability, and water solubility. By comparing the fluorescence emission intensity of the two methods, the N-GQDs prepared by this method have higher fluorescence emission intensity and good fluorescence stability. Based on the static quenching mechanism between CLB and N-GQDs, a fluorescent probe was designed to detect CLB, which exhibited a wide linear range in the concentration range of 5 × 10-10~5 × 10-7 M (R2 = 0.9879) with a limit of detection (LOD) of 2.083 × 10-13 M. More excitingly, the N-GQDs fluorescent probe exhibited a satisfactory high selectivity. Meanwhile, it can be used for the detection of CLB in chicken and beef, and good recoveries were obtained. In summary, the strategic approach in this paper has potential applications in the detection of risky substances in the field of food safety.

Interference-free SERS tags for ultrasensitive quantitative detection of tyrosinase in human serum based on magnetic bead separation.

Tyrosinase (TYR) expression and activity determine the rate and yield of melanin production. Studies have shown that TYR is a potential biomarker for melanoma and highly sensitive detection of TYR benefits early diagnosis of melanoma-related diseases. In this study, we developed a method that combines surface-enhanced Raman scattering (SERS) and sandwich-type immunity for sensitive detection of TYR, in which 4-mercaptobenzonitrile (4 MB) embedded between the Au core and Au shell (Au4MB @ Au) core-shell structure was employed as a SERS probe for quantitative detection of TYR while the magnetic bead serves as a capture substrate. Our results demonstrated that under magnetic separation, the specific SERS signal obtained is highly correlated with TYR concentrations. Furthermore, the combination of magnetic beads and Au4MB @ Au core-shell structure significantly improved the sensitivity of the sensing platform, resulting in detection limits of 0.45 ng mL-1. More importantly, the detection and analysis of TYR concentration in human serum samples showed good accuracy and an excellent recovery rate. Accuracy of the system was investigated from % recovery of spiked TYR standard solutions and found to be in the range of 90-104%, which further verified the feasibility and reliability of our method applied in a complex environment. We anticipate this SERS-based immunoassay method to be applied to TYR detection in the clinical setting and to be extended to other promising related fields.

Highly sensitive detection of tryptophan (Trp) in serum based on diazo-reaction coupling with Surface-Enhanced Raman Scattering and colorimetric assay.

Tryptophan plays an important role in the metabolic pathway and tryptophan metabolism is abnormal in tumor tissues. Therefore, Trp and its metabolites in body fluids can be used as tumor markers for cancer monitoring. However, the traditional tryptophan detection method has many shortcomings, such as low sensitivity, time-consuming and so on, which is difficult to meet the clinical needs. Herein, a rapidly, sensitive and reliable method for indirectly detecting Tryptophan (Trp) in serum was proposed by combining diazo-coupling reaction mechanism with surface-enhanced Raman scattering (SERS). The limit of detection (LOD) of Trp can be as low as 20 nM, which is much lower than existing detection methods. In addition, because of obvious change in color in diazo-coupling reaction, a colorimetric detection was applied for convenient determination of Trp in the concentration ranged from 3 × 10-5 - 10-3 M. Furthermore, with the support of good results by SERS assay, the presented method was successfully carried out for the determination of Trp in serum that came from healthy people and colorectal cancer patients. Comparing the difference of Trp content in serum between the two groups, it was found that tryptophan metabolism disorder exists in colorectal cancer patients, which suggested that the accurate detection of tryptophan content may provide important reference for the pathogenesis, prediction and prevention of colorectal cancer.