1.
A novel fluorescent biosensor based on dendritic DNA nanostructure in combination with ligase reaction for ultrasensitive detection of DNA methylation.
Zhang, S, Huang, J, Lu, J, Liu, M, Li, Y, Fang, L, Huang, H, Huang, J, Mo, F, Zheng, J
Journal of nanobiotechnology. 2019;(1):121
Abstract
BACKGROUND DNA methylation detection is indispensable for the diagnosis and prognosis of various diseases including malignancies. Hence, it is crucial to develop a simple, sensitive, and specific detection strategy. METHODS A novel fluorescent biosensor was developed based on a simple dual signal amplification strategy using functional dendritic DNA nanostructure and signal-enriching polystyrene microbeads in combination with ligase detection reaction (LDR). Dendritic DNA self-assembled from Y-DNA and X-DNA through enzyme-free DNA catalysis of a hairpin structure, which was prevented from unwinding at high temperature by adding psoralen. Then dendritic DNA polymer labeled with fluorescent dye Cy5 was ligated with reporter probe into a conjugate. Avidin-labeled polystyrene microbeads were specifically bound to biotin-labeled capture probe, and hybridized with target sequence and dendritic DNA. LDR was triggered by adding Taq ligase. When methylated cytosine existed, the capture probe and reporter probe labeled with fluorescent dye perfectly matched the target sequence, forming a stable duplex to generate a fluorescence signal. However, after bisulfite treatment, unmethylated cytosine was converted into uracil, resulting in a single base mismatch. No fluorescence signal was detected due to the absence of duplex. RESULTS The obtained dendritic DNA polymer had a large volume. This method was time-saving and low-cost. Under the optimal experimental conditions using avidin-labeled polystyrene microbeads, the fluorescence signal was amplified more obviously, and DNA methylation was quantified ultrasensitively and selectively. The detection range of this sensor was 10-15 to 10-7 M, and the limit of detection reached as low as 0.4 fM. The constructed biosensor was also successfully used to analyze actual samples. CONCLUSION This strategy has ultrasensitivity and high specificity for DNA methylation quantification, without requiring complex processes such as PCR and enzymatic digestion, which is thus of great value in tumor diagnosis and biomedical research.
2.
The effect of an oral anti-oxidant, N-Acetyl-cysteine, on inflammatory and oxidative markers in pulmonary sarcoidosis.
Hamzeh, N, Li, L, Barkes, B, Huang, J, Canono, B, Gillespie, M, Maier, L, Day, B
Respiratory medicine. 2016;:106-11
Abstract
BACKGROUND Oxidative stress (OS) has been shown to play a role in the pathogenesis of sarcoidosis and previous studies have shown that anti-oxidants can reduce markers of oxidative stress and inflammation in the peripheral blood of sarcoidosis subjects. We investigated the effect of N-Acetyl-Cysteine (NAC) on oxidative stress and inflammatory markers in the lungs of sarcoidosis patients. METHODS We randomized 11 sarcoidosis subjects to active therapy and 3 to placebo for 8 weeks in a double blinded study. Bronchoscopy with bronchoalveolar lavage was performed pre and post therapy. Our primary endpoint was TNF-α production from stimulated and unstimulated BAL cells. Secondary outcomes included measures of oxidative stress (GSH, 8-OHdG) levels in the BAL. In-vitro studies were also performed to assess the effect of NAC on lipopolysaccharide stimulated BAL cell production of TNF-α. RESULTS Eight subjects in the active group and 2 in the placebo group completed the study protocol. Eight weeks of oral NAC did not have a significant impact on TNF-α levels from BAL cells in-vivo in spite of a 59% increase in BAL GSH levels. Our in vitro studies showed a significant decline in TNF-α production from LPS stimulated BAL cells treated with 5 and 10 mM of NAC. CONCLUSIONS Oral NAC increased GSH levels but failed to suppress in-vivo TNF-α production in contrast to effects in-vitro. Anti-oxidant therapy may still play a role in the management of sarcoidosis but therapy with better bioavailability or potency is needed to suppress the lung inflammatory response.