DNA Triplex and Quadruplex Assembled Nanosensors for Correlating K + and pH in Lysosomes

Spatially Selective Monitoring of Subcellular Enzyme Dynamics in Response to Mitochondria-Targeted Photodynamic Therapy

Tracking spatial and temporal dynamics of bioactive molecules such as enzymes responding to therapeutic treatment is highly important for understanding of the related functions. However, in situ molecular imaging at subcellular level during photodynamic therapy (PDT) has been hampered by the limitations of existing methods. Herein, we present a multifunctional nanoplatform (termed as UR-HAPT) that is able to simultaneously monitor subcellular dynamics of human apurinic/apyrimidinic endonuclease 1 (APE1) during the near-infrared (NIR) light-mediated PDT. UR-HAPT was constructed by the combination of an upconversion nanoparticle-based PDT design and a mitochondria-targeting strategy with an APE1-responsive DNA reporter. Benefiting from the gain-of-function approach, activatable mitochondrial accumulation of APE1 in response to the oxidative stress was observed during the NIR light-triggered, mitochondria-targeted PDT process. We envision that this nanoplatform can be applicable to screen and evaluate potential enzyme inhibitors to improve the PDT efficacy.

Near-Infrared Light-Activatable Spherical Nucleic Acids for Conditional Control of Protein Activity

Optical control of protein activity represents a promising strategy for precise modulation of biological processes. We report rationally designed, aptamer-based spherical nucleic acids (SNAs) capable of noninvasive and programmable regulation of target protein activity by deep-tissue-penetrable near-infrared (NIR) light. The photoresponsive SNAs are constructed by integrating activatable aptamer modules onto the surface of upconversion nanoparticles. The SNAs remain inert but can be remotely reverted by NIR light irradiation to capture the target protein and thus function as an enzyme inhibitor, while introduction of antidote DNA could further reverse their inhibition functions. Furthermore, we demonstrate the potential of the SNAs as controllable anticoagulants for the NIR light-triggered regulation of thrombin function. Ultimately, the availability of diverse aptamers would allow the design to regulate the activities of various proteins in a programmable manner.

trans Single-Stranded DNA Cleavage via CRISPR/Cas14a1 Activated by Target RNA without Destruction

As a CRISPR-Cas system (clustered regularly interspaced short palindromic repeats and CRISPR associated proteins), Cas14a1 can cis/trans cleave single-stranded DNA (ssDNA). Here, we describe an unreported capacity of Cas14a1: RNA can trigger the trans ssDNA cleavage. This Cas14a1-based RNA-activated detection platform (Amplification, Transcription, Cas14a1-based RNA-activated trans ssDNA cleavage, ATCas-RNA) has an outstanding specificity for the detection of target RNAs with point mutation resolution, which is better than that of the Cas14a1-based ssDNA-activation. Using ATCas-RNA via a fluorophore quencher-labeled ssDNA reporter (FQ), we were able to detect 1 aM pathogenic nucleic acid within 1 h, and achieve 100 % accuracy with 25 milk samples. This platform can serve as a new tool for high-efficiency nucleic acid diagnostics. Importantly, this work can expand our understanding of Cas14a1 and inspire further mechanisms and applications of Class-2 Cas systems.

Ratiometric G-Quadruplex Assay for Robust Lead Detection in Food Samples

Lead (Pb²⁺) pollution is a serious food safety issue, rapid detection of Pb²⁺ residual in food is vital to guarantee food quality and safety. Here we proposed ratiometric aptamer probes, allowing robust Pb²⁺ supervision in food samples. Pb²⁺ specific aptamer can bolster a transition of G-quadruplex structural response to Pb²⁺; this process can be monitored by N-methyl mesoporphyrin IX (NMM), which is highly specific to G-quadruplex. Particularly, the utilization of G-quadruplex specific dye and terminal-labeled fluorophore allowed to endue ratiometric signal outputs towards Pb²⁺, dramatically increase the robustness for lead detection. The ratiometric G-quadruplex assay allowed a facile and one-pot Pb²⁺ detection at room temperature using a single-stranded DNA aptamer. We demonstrated its feasibility for detecting lead pollution in fresh eggs and tap water samples. The ratiometric G-quadruplex design is expected to be used for on-site Pb²⁺ testing associated with food safety.