High Sensitive Electrochemiluminescence Biosensor Based on Ru(phen) 3 2+ ‐loaded Double Strand DNA as Signal Tags use to Detect DNA Methyltransferase Activity

Detection of methyltransferase activity and inhibitor screening based on rGO-mediated silver enhancement signal amplification strategy

DNA methylation refers to the chemical modification process of obtaining a methyl group by the covalent bonding of a specific base in DNA sequence with S-adenosyl methionine (SAM) as a methyl donor under the catalysis of methyltransferase (MTase), which is related to the occurrence of multiple diseases. Therefore, the detection of MTase activity is of great significance for disease diagnosis and drug screening. Because reduced graphene oxide (rGO) has a unique planar structure and remarkable catalytic performance, it is not clear whether rGO can rapidly catalyze silver deposition as an effective way of signal amplification. However, in this study, we were pleasantly surprised to find that using H₂O₂ as a reducing agent, rGO can rapidly catalyze silver deposition, and its catalytic efficiency of silver deposition is significantly better than that of GO. Therefore, based on further verifying the mechanism of catalytic properties of rGO, we constructed a novel electrochemical biosensor (rGO/silver biosensor) for the detection of dam MTase activity, which has high selectivity and sensitivity to MTase in the range of 0.1 U/mL to 10.0 U/mL, and the detection limit is as low as 0.07 U/mL. Besides, this study also used Gentamicin and 5-Fluorouracil as inhibitor models, confirming that the biosensor has a good application prospect in the high-throughput screening of dam MTase inhibitors.

Electrochemiluminescence biosensor for DNA adenine methylation methyltransferase based on CRISPR/Cas12a trans-cleavage-induced dual signal enhancement

In this work, an electrochemiluminescence (ECL) biosensor with dual signal enhancement was constructed and used for DNA adenine methylation methyltransferase (Dam MTase) detection. At present of Dam MTase, restriction endonuclease (DPnI) cleaves hairpin DNA (HP) and releases the HP stem end as a single strand that can activate CRISPR/Cas12a trans-cleavage activity. Assisted by trans-cleavage, the distance between the signal quenching factor ferrocene (Fc) and the ECL signal unit increased, and the repulsion between the signal unit and the Indium Tin Oxides (ITO) electrode decreased. The above results resulted in an enhanced ECL signal. ECL intensity has a good linear relationship with the logarithm of Dam MTase concentration in the range of 5-70 U/mL with a detection limit of 23.4 mU/mL. The proposed biosensor was successfully utilized to detect of Dam MTase in serum samples.

Simple Detection of DNA Methyltransferase with an Integrated Padlock Probe

DNA methyltransferases (MTases) can be regarded as biomarkers, as demonstrated by many studies on genetic diseases. Many researchers have developed biosensors to detect the activity of DNA MTases, and nucleic acid amplification, which need other probe assistance, is often used to improve the sensitivity of DNA MTases. However, there is no integrated probe that incorporates substrates and template and primer for detecting DNA MTases activity. Herein, we first designed a padlock probe (PP) to detect DNA MTases, which combines target detection with rolling circle amplification (RCA) without purification or other probe assistance. As the substrate of MTase, the PP was methylated and defended against HpaII, lambda exonuclease, and ExoI cleavage, as well as digestion, by adding MTase and the undestroyed PP started RCA. Thus, the fluorescent signal was capable of being rapidly detected after adding SYBR^TM Gold to the RCA products. This method has a detection limit of approximately 0.0404 U/mL, and the linear range was 0.5–110 U/mL for M.SssI. Moreover, complex biological environment assays present prospects for possible application in intricacy environments. In addition, the designed detection system can also screen drugs or inhibitors for MTases.

Plasmonic Au nanocube enhanced SERS biosensor based on heated electrode and strand displacement amplification for highly sensitive detection of Dam methyltransferase activity

In this work, a novel "turn-on" mode Au nanocubes (AuNCs) enhanced surface-enhanced Raman scattering (SERS) biosensing platform coupled with heated Au electrode (HAuE) and strand displacement amplification (SDA) strategy was proposed for highly sensitive detection of DNA adenine methylation (Dam) Methyltransferase (MTase) activity. The Dam MTase and DpnI enzyme activities were significantly increased by elevating the HAuE surface temperature, resulting in the rapid production of template DNA for later SDA. During the SDA process, the released single-stranded DNA (ssDNA) could be amplified exponentially, and its concentration was positively related to the Dam MTase activity. The plasmonic AuNCs in SERS tags could provide significant SERS enhancement due to their "lightning rod" effect resulting from the sharp feature of the edges and corners of AuNCs. Because of these factors, the proposed biosensors exhibited high sensitivity in detecting the Dam MTase activity. The limit of detection was estimated to be 8.65 × 10^-5 U mL^-1, which was lower than that in most of the sensors for detection of Dam MTase activity in the literature. This SERS biosensor could also be used to screen inhibitors of Dam MTase and had the potential for detecting Dam MTase activity in real biological samples.