Polymer nanoparticles that can sharply sense and detect biological signals in cells are promising candidates for biomedical and theranostic nanomaterials. However, the response ability of current polymer assemblies poorly matches the requirement of trace concentration level (10 −6 ~ 10 −9 mol/L) of cellular biosignals due to their linear signal input-to-function output mode, which impedes their practical applications in vivo. Here we report a kind of nanobowl system with pH-tunable invaginated morphology that can nonlinearly amplify the response abilities toward biosignals by modulating the surface concavity. Compared to conventional spherical nanoparticles, nonspherical nanobowls with a specific concave structure reduce the critical response threshold of polymers by up to 5 orders of magnitude, from millimole to nanomole level, covering most of biosignal concentration windows. Moreover, we find that this nonlinear signal gain effect is originated from the collective impact of a single signal on transitioning the polymer chain aggregation state of individual assemblies, rather than just altering a certain unit or chain. This nonlinear signal-to-response mechanism is potential to solve the tricky problems of probing and sensing endogenous signals with trace physiological concentration.
An Yaqian,Yu Zhiqi,Liu Di,Han Lirong,Zhang Xian,Xin Xuelian,Li Cuiping
The detection of methyltransferase (MTase) activity is of great significance in methylation-related disease diagnosis and drug screening. Herein, a HpaII-assisted and linear amplification-enhanced exponential amplification strategy is proposed for sensitive and label-free detection of M.SssI MTase activity. The P1 probe contains self-complementary sequence 5′-CTAGCCGGCTAG-3′ at 3′-terminal. After denaturation and annealing, P1 probes hybridize with itself to generate P1 duplexes. M.SssI MTase induces methylation of cytosine at 5′-CG-3′ in P1 duplexes, and thus, HpaII fails to cleave at 5′-CCGG-3′ due to methylation sensitivity, leaving P1 duplex intact. Then, these intact P1 duplexes are extended along 3′-terminal through Vent (exo − ) DNA polymerase to generate dsDNA, which is recognized and nicked at the recognition sites by Nt.BstNBI, releasing two copies of primer X. Primer X hybridizes with X′ at the amplification template T1 (X′-Y′-X′) and then serves as primers to trigger the exponential amplification reaction (EXPAR). The point of inflection (POI) values of real-time fluorescence curves is linearly correlated with the logarithm of M.SssI MTase concentration in the range of 0.125 \(-\) 8 U mL −1 with a low detection limit of 0.034 U mL −1 . In the absence of M.SssI, P1 duplexes are cut by HpaII and separated into ssDNA under the executed temperature of EXPAR and thus unable to trigger the amplification. The strategy provides good selectivity against other types of MTases and protein and is able to detect M.SssI activity in human serum. Furthermore, the analytical method has the generality and can be extended to the analysis of other types of DNA MTases. Graphical Abstract
危险品化学品经营许可证（带存储）