Comparison of DNA-Gold Nanoparticle Conjugation Methods: Application in Lateral Flow Nucleic Acid Biosensors.

Lateral flow nucleic acid biosensors (LFNABs) have attracted extensive attention due to their rapid turnaround time, low cost, and results that are visible to the naked eye. One of the key steps to develop LFNABs is to prepare DNA-gold nanoparticle (DNA-AuNP) conjugates, which affect the sensitivity of LFNABs significantly. To date, various conjugation methods-including the salt-aging method, microwave-assisted dry heating method, freeze-thaw method, low-pH method, and butanol dehydration method-have been reported to prepare DNA-AuNP conjugates. In this study, we conducted a comparative analysis of the analytical performances of LFNABs prepared with the above five conjugation methods, and we found that the butanol dehydration method gave the lowest detection limit. After systematic optimization, the LFNAB prepared with the butanol dehydration method had a detection limit of 5 pM for single-strand DNA, which is 100 times lower than that of the salt-aging method. The as-prepared LFNAB was applied to detect miRNA-21 in human serum, with satisfactory results. The butanol dehydration method thus offers a rapid conjugation approach to prepare DNA-AuNP conjugates for LFNABs, and it can also be extended to other types of DNA biosensors and biomedical applications.

Spatial characteristics and coupling coordination between carbon emission efficiency and industrial structure in three metropolitan areas of Jiangsu Province, China.

It is of great practical significance to study the spatial characteristics of carbon emission efficiency, industrial structure, their coupling and coordination relationship for China's green development and industrial structure transformation in the new era. From the perspective of coupling, coordination and space, this paper analyzes and summarizes the spatial characteristics of carbon emission efficiency and industrial structure of 19 cities in three metropolitan areas of Jiangsu Province during 2009-2019 and their coupling and coordination relationship. The carbon emission efficiency in this study is represented by the carbon emission economic efficiency index and carbon emission social efficiency index. The results show that (a) the high-emission centers in the three metropolitan areas developed from "three centers" in 2009 to "five centers" in 2019. The continuous high-energy consumption of the secondary industry and the growth of the economic aggregate of the third industry kept the regional high carbon dioxide emissions. (b) The average value of carbon emission economic efficiency in 19 cities continued to increase, indicating that the contribution rate of the same amount of carbon emissions to economic income gradually increased; the growth range of carbon emission economic efficiency index is greater than that of carbon emission social efficiency index, indicating that carbon emission has a more significant effect on the improvement of regional economic development than on the improvement of public service level and residents' living quality. (d) The solidification degree of carbon emission efficiency is greater than that of the industrial structure (solidification degree carbon emission social efficiency > carbon emission economic efficiency > industrial structure). The high-grade industrial structure in Xuzhou metropolitan area is closely related to the improvement of carbon emission economic efficiency and carbon emission social efficiency, and both are in moderate antagonism. The rationalizing industrial structure in Nanjing metropolitan area is closely related to the improvement of carbon emission economic efficiency, which is in high coordination run-in. The concentration degree of industrial structure in Suzhou-Wuxi-Changzhou metropolitan area is closely related to the improvement of carbon emission economic efficiency and carbon emission social efficiency, which are in polar coordination coupling and high coordination run-in, respectively. The proposed coupling path of carbon emission efficiency-industrial structure can not only alleviate the dynamic disharmony in different cities but also effectively improve the coupling degree in cities.

Highly selective and sensitive colorimetric detection for glyphosate based on ß-CD@DNA-CuNCs enzyme mimics.

A colorimetric assay based on an enzyme-inhibition strategy is promising for the on-site detection of pesticide residues. However, very few works of pesticide detection were reported based on the inhibition toward nanozymes although nanozymes have demonstrated many advantages in sensing various targets. Herein, a facile colorimetric detection for Glyp was developed based on ß-CD@DNA-CuNCs enzyme mimics. The ß-CD@DNA-CuNCs with high peroxidase-like activity was synthesized using random DNA double strands as template and ß-CD as surface ligand. ß-CD@DNA-CuNCs could catalyze the H2O2-3,3',5,5'-tetramethylbenzidine (TMB) system. The oxidation product OxTMB with a blue color and presented a large absorption signal at 652 nm. However, Glyp could destroy the synergic effect between redox doublet (Cu2+/Cu+) on the ß-CD@DNA-CuNCs surface, resulting in the inhibition of the peroxidase-like activity. Colorimetric detection for Glyp could be established by detecting the changes of absorption signal at 652 nm. The linear range was 0.02-2 µg/mL and the detection limit was 0.85 ng/mL (3δ/s). The method was applied in measuring Glyp spiked in lake water and various food samples. This method had rapidness, high sensitivity, and selectivity advantages, indicating the high application potential in monitoring Glyp residue in food.

Kruppel like factor 16 promotes lung adenocarcinoma progression by upregulating lamin B2.

Lung cancer is one of the most common causes of cancer-related death. In the past decade, the treatment and diagnosis of lung cancer have progressed significantly in early efforts to promote the survival of lung cancer patients. Kruppel like factor 16 (KLF16) is a zinc finger transcription factor that regulates a diverse array of developmental events and cellular processes. KLF16 is involved in the progression of various cancer types. However, the role of KLF16 in the development of lung cancer remains unknown. In this study, KLF16 was overexpressed in lung cancer samples. KLF16 downregulation inhibited lung cancer cell proliferation and migration. Conversely, KLF16 overexpression promoted lung cancer cell growth and invasion. Mechanistically, the expression level LMNB2 was suppressed by KLF16 knockdown and was promoted by KLF16 overexpression. The overall survival of patients with high LMNB2 levels was poor. Luciferase assays showed that KLF16 promoted the transcription activity of LMNB2 gene. Concomitantly, the expression level of LMNB2 was also higher in lung adenocarcinoma (LUAD) than in normal tissues, and its knockdown or overexpression can reverse the effect of KLF16 overexpression or knockdown on lung cancer cell proliferation, migration, and even tumorigenesis, indicating that LMNB2 also functions as an oncogene. In conclusion, KLF16 can be used as a potential therapeutic and preventive biomarker in lung cancer treatment and prognosis by actively regulating the expression of LMNB2.

A simplified fluorescent lateral flow assay for melamine based on aggregation induced emission of gold nanoclusters.

A novel lateral flow assay (LFA) was developed based on the aggregation induced emission (AIE) of gold nanoclusters (AuNCs) for the detection of melamine. We compared the interaction between melamine and AuNCs prepared with 6-Aza-2-thiothymine (ATT) and its four structural analogs as ligands and found that the ATT-AuNCs showed the best AIE induced by melamine. Then the ATT-AuNCs were directly immobilized on the test line of LFA strips as reporters. The sensing platform exhibited a linear response to melamine from 1 to 100 µM (R2 = 0.997) with a detection limit of 217 nM. Moreover, this LFA strip could discriminate 1.0 µM melamine clearly by the naked eyes within 3 min. The recoveries of 91.6-101.5% were attained in milk and baby formula samples. This strip inherited the superior characteristics of low background interference of aggregation-induced fluorescence recognition and LFA technology, thus effectively avoiding the use of antibodies, aptamers, and other biological elements.

Mesoporous silica-loaded gold nanocluster with enhanced fluorescence and ratiometric fluorescent detection of thiram in foods.

A core-shell QDs@mSiO2@y-AuNCs nanoprobe was prepared, and a new ratiometric fluorescent sensor for thiram detection was developed. The mechanism of thiram sensing was investigated using FTIR, surface-enhanced Raman, XPS spectra, etc. The sensing of thiram was mainly ascribed to the formation of Au-S bonds between thiram and Au atoms on y-AuNCs surface, resulting in the dissociation of 11-MUA ligand from the y-AuNCs surface and the charge transfer between thiram and y-AuNCs. In the ratiometric fluorescence detection of thiram based on QDs@mSiO2@y-AuNCs, a linear range of 0.5-60 ng/mL was obtained with a LOD of 0.19 ng/mL. Compared with the fluorescence detection based on y-AuNCs, the ratiometric fluorescence detection of thiram demonstrated 3-fold enhanced sensitivity. The improvement was ascribed to two aspects: the fluorescence emission of y-AuNCs was enhanced after they were loaded onto the QDs@mSiO2 nanoparticles; the ratiometric detection mode provided more precise sensing. The detection of thiram can be completed immediately after mixing the nanoprobe with thiram. Good recoveries of thiram in apple and pear samples were achieved. All the above results demonstrated the high potential of this method in practical applications.

A Fluorescent Detection for Paraquat Based on ß-CDs-Enhanced Fluorescent Gold Nanoclusters.

In this report, a fluorescent sensing method for paraquat based on gold nanoclusters (AuNCs) is proposed. It was found that paraquat could quench both glutathione-capped AuNCs (GSH-AuNCs) and ß-cyclodextrin-modified GSH-AuNCs (GSH/ß-CDs-AuNCs). The modification of ß-CDs on the surface of GSH-AuNCs obviously enhanced the fluorescence intensity of GSH-AuNCs and improved the sensitivity of paraquat sensing more than 4-fold. This sensibilization was ascribed to the obvious fluorescence intensity enhancement of GSH-AuNCs by ß-CDs and the "host-guest" interaction between paraquat and ß-CDs. The fluorescence quenching was mainly due to the photoinduced energy transfer (PET) between GSH/ß-CDs-AuNCs and paraquat. With the optimized ß-CDs modification of the GSH-AuNC surfaces and under buffer conditions, the fluorescent detection for paraquat demonstrated a linear response in the range of 5.0-350 ng/mL with a detection limit of 1.2 ng/mL. The fluorescent method also showed high selectivity toward common pesticides. The interference from metal ions could be easily masked by ethylene diamine tetraacetic acid (EDTA). This method was applied to the measurement of paraquat-spiked water samples and good recoveries (93.6-103.8%) were obtained. The above results indicate that host molecule modification of fluorescent metal NC surfaces has high potential in the development of robust fluorescent sensors.

Quantitative analysis of free fatty acids in gout by disposable paper-array plate based MALDI MS.

The quantitative determination of small molecules by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI TOF MS) was always challenging, due to low sensitivity and interferences of matrix and other contaminants on sample plates. Here we report a disposable paper-array (PA) plate in MALDI TOF MS analysis for quantitative analysis of serum free fatty acids (FFAs) with less interference and higher sensitivity, compared with conventional stainless steel (SS) plate. The disposable PA plate was low cost and environmentally friendly. In particular, it was more sensitive in FFAs detection with ~8-34-fold sensitivity increase for eight FFAs as compared to SS plate. Eight serum FFAs in gout patients were investigated using this disposable PA plate. The quantitative results showed good linearity of all eight FFAs between 0.1 and 2.5 mM with correlation coefficients between 0.994 and 0.999 and limits of detection (LODs) between 8.6 and 104.2 µM. Mann-Whitney U test, principal component analysis (PCA) and random forest categorizer allowed the clear separation of gout patients from healthy controls, according to eight FFAs levels in serum detected by disposable PA plate based MALDI TOF MS.