•A novel universal signal amplification (USA) probe-based ECL assay was established.•The assay was used to detect pathogenic bacteria.•The usage of capture probes improved the specificity and sensitivity of the assay.•Ru(bpy)32 +-labeled USA probe can be used in detection of different target genes.A novel universal signal amplification (USA) probe-based electrochemiluminescence (ECL) assay for sensitive detection of pathogenic bacteria was developed. In this assay, a series of capture probes (CPs) containing two distinctly functional parts were carefully designed. One part was used to specifically recognize different regions of single-stranded (ss) target DNA in order to improve the accuracy and specificity of the assay. The other part was used to hybridize with USA probe so as to amplify the ECL signal and thus improve the sensitivity of the assay. Furthermore, the USA probe can be used to detect different target genes due to its universal sequence so as to reduce the cost of the assay. The method was applied to detect Staphylococcus aureus (S. aureus). The experimental results showed that the detection limit was 100 fM of asymmetric PCR products. The method holds great promise in pathogenic bacteria detection due to its accuracy, specificity, sensitivity and low-cost.

•An isothermal enzyme-free amplification and label-free graphene oxide (GO)-based SYBR Green I fluorescence switch platform for the detection of microRNA is developed.•The method consists of a target-triggered enzyme-free amplification (EFA) of microRNA by circulatory interactions of two hairpin probes and a convenient and rapid GO-based SYBR Green I fluorescent switch platform as the signal giving-out component.•The method is isothermal and label-free and does not use any enzyme. It holds great promise in microRNA detection due to its convenience, rapidness, sensitivity and specificity.•To the best of our knowledge, it is the first reported isothermal enzyme-free amplification combined with label-free fluorescence platform for the detection of miRNA.MicroRNAs (miRNAs) are a kind of small molecules that involve in many important life activities. They have higher expression levels in many kinds of cancers. In this study, we developed an isothermal enzyme-free amplification (EFA) and label-free graphene oxide (GO)-based SYBR Green I fluorescence platform for detection of miRNA. MiRNA-21 was used as an example to demonstrate the feasibility of the method. Results show that the sensitivity of miRNA-21 is 1 pM, and the linearity range is from 1 pM to 1 nM. The method can specifically discriminate miRNA-21 from miRNA-210 and miRNA-214. Three tumor cell lines of A549, HepG2 and MCF7 were detected by the method. The sensitivities of them were 102 cells, 103 cells and 103 cells respectively. Clinical tumor samples were also tested by this method, and 29 of 40 samples gave out positive signals. The method holds great promise in miRNA detection due to its convenience, rapidness, inexpensive and specificity.