In this paper, we explore the possibility of using ultrasmall near-infrared (NIR) gold nanoclusters (AuNCs) as novel contrast imaging agents for tumor fluorescence imaging in vivo. The fluorescence imaging signal of the tail vein administrated AuNCs in living organisms can spectrally be well distinguished from the background with maximum emission wavelength at about 710 nm, and the high photostability of AuNCs promises continuous imaging in vivo. The uptake of AuNCs by the reticuloendothelial system is relatively low in comparison with other nanoparticle-based contrast imaging agents due to their ultrasmall hydrodynamic size (∼2.7 nm). Through the body weight change analysis, the results show that the body weight of the mice administrated with AuNCs has not been changed obviously in comparison with that of the control mice injected with PBS. Furthermore, using MDA-MB-45 and Hela tumor xenograft models, in vivo and ex vivo imaging studies show that the ultrasmall NIR AuNCs are able to be highly accumulated in the tumor areas, thanks to the enhanced permeability and retention (EPR) effects. And the tumor-to-background ratio is about 15 for 6 h postinjection. The results indicate that the ultrasmall NIR AuNCs appear as very promising contrast imaging agents for in vivo fluorescence tumor imaging.

Aptamers have emerged as promising molecular probes for in vivo cancer imaging, but the reported "always-on" aptamer probes remain problematic because of high background and limited contrast. To address this problem, we designed an activatable aptamer probe (AAP) targeting membrane proteins of living cancer cells and achieved contrast-enhanced cancer visualization inside mice. The AAP displayed a quenched fluorescence in its free state and underwent a conformational alteration upon binding to target cancer cells with an activated fluorescence. As proof of concept, in vitro analysis and in vivo imaging of CCRF-CEM cancer cells were performed by using the specific aptamer, sgc8, as a demonstration. It was confirmed that the AAP could be specifically activated by target cancer cells with a dramatic fluorescence enhancement and exhibit improved sensitivity for CCRF-CEM cell analysis with the cell number of 118 detected in 200 μl binding buffer. In vivo studies demonstrated that activated fluorescence signals were obviously achieved in the CCRF-CEM tumor sites in mice. Compared to always-on aptamer probes, the AAP could substantially minimize the background signal originating from nontarget tissues, thus resulting in significantly enhanced image contrast and shortened diagnosis time to 15 min. Furthermore, because of the specific affinity of sgc8 to target cancer cells, the AAP also showed desirable specificity in differentiating CCRF-CEM tumors from Ramos tumors and nontumor areas. The design concept can be widely adapted to other cancer cell-specific aptamer probes for in vivo molecular imaging of cancer.switchable aptamer probe | in vivo imaging | activatable fluorescent molecular imaging | cancer detection | cell surface protein

Am T‐Stück angesetzt: Poly‐T‐Einzelstrang‐DNA (blau, siehe Schema) dient als Templat für die Bildung fluoreszierender Kupfernanopartikel (CuNPs, rote Kugeln). Größe und Fluoreszenz der CuNPs sind über die Länge der Poly‐T‐Sequenz einstellbar. Andere Einzelstrang‐DNAs (grün) sind keine geeigneten Template für CuNPs und können daher zum Aufbau von Nanostrukturen mit wechselnden metallierten und nichtmetallierten Bereichen genutzt werden.

Owing to its important physiological functions, especially as molecular biomarkers of diseases, RNA is an important focus of biomedicine and biochemical sensing. Signal amplification detection has been put forward because of the need for accurate identification of RNA at low expression levels, which is significant for the early diagnosis and therapy of malignant diseases. However, conventional amplification methods for RNA analysis depend on the use of enzymes, fixation of cells, and thermal cycling, which confine their performance to cell lysates or dead cells, thus the imaging of RNA in living cells remained until recently little explored. In recent years, the advance of isothermal amplification of nucleic acids has opened paths for meeting this need in living cells. This minireview tracks the development of in situ amplification assays for RNAs in living cells, and highlights the potential challenges facing this field, aiming to improve the development of in vivo isothermal amplification as well as usher in new frontiers in this fertile research area.

This paper proposed a natural gelatin capped mesoporous silica nanoparticles (MSN@Gelatin) based pH-responsive delivery system for intracellular anticancer drug controlled release. In this system, the gelatin, a proteinaceous biopolymer derived from the processing of animal collagen, was grafted onto the MSN to form a capping layer via temperature-induced gelation and subsequent glutaraldehyde mediated cross-linking, resulting in gelatin coated MSN. At neutral pH, the gelatin capping layer could effectively prohibit the release of loaded drug molecules. However, the slightly acidic environment would lead to enhanced electrostatic repulsion between the gelatin and MSN, giving rise to uncapping and the subsequent controlled release of the entrapped drug. As a proof-of-concept, doxorubicin (DOX) was selected as the model anticancer drug. The loading and pH-responsive release experiments demonstrated that the system had excellent loading efficiency (47.3 mmol g(-1) SiO2), and almost no DOX was leaked at neutral. After being in the slightly acidic condition, the DOX release from the DOX-loaded MSN@Gelatin (DOX/MSN@Gelatin) occurred immediately. The cellular uptake and release studies using Hep-G2 hepatoma cells indicated that the DOX/MSN@Gelatin could be endocytosed and accumulated within lysosomes. Triggered by acidic endosomal pH, the intracellular release of the loaded DOX was obviously eventuated. Further cell viability results demonstrated that DOX/MSN@Gelatin exhibited dose-dependent toxicity and high killing efficacy (IC50 = 17.27 ± 0.63 μg mL(-1)), whereas the MSN@Gelatin showed negligible cytotoxicity (IC50 > 100 μg mL(-1)). This biocompatible and effective delivery system will provide great potential for developing delivery of cancer therapeutic agents.

The peroxidase‐like activity of nanozymes is promising for chemodynamic therapy by catalyzing H2O2 into .OH. However, for most nanozymes, this activity is optimal just in acidic solutions, while the pH of most physiological systems is beyond 7.0 (even >8.0 in chronic wounds) with inadequate H2O2. We herein communicate an activatable nanozyme with targeting capability to simultaneously break the local pH and H2O2 limitations under physiological conditions. As a proof of concept, aptamer‐functionalized nanozymes, glucose oxidase, and hyaluronic acid constitute an activatable nanocapsule “APGH”, which can be activated by bacteria‐secreted hyaluronidase in infected wounds. Nanozymes bind onto bacteria through aptamer recognition, and glucose oxidation tunes the local pH down and supplements H2O2 for the in‐situ generation of .OH on bacteria surfaces. The activity switching and enhanced antibacterial effect of the nanocapsule were verified in vitro and in diabetic wounds. This strategy for directly regulating local microenvironment is generally accessible for nanozymes, and significant for facilitating biological applications of nanozymes.

An intramolecular catalytic hairpin assembly is implemented on a DNA tetrahedron for mRNA imaging in living cells. The spatial confinement effect enables the acceleration of target-triggered signal generation, with excellent cell permeability and FRET signal stability.

: The infection and spread of pathogens (e.g., COVID-19) pose an enormous threat to the safety of human beings and animals all over the world. The rapid and accurate monitoring and determination of pathogens are of great significance to clinical diagnosis, food safety and environmental evaluation. In recent years, with the evolution of nanotechnology, nano-sized graphene and graphene derivatives have been frequently introduced into the construction of biosensors due to their unique physicochemical properties and biocompatibility. The combination of biomolecules with specific recognition capabilities and graphene materials provides a promising strategy to construct more stable and sensitive biosensors for the detection of pathogens. This review tracks the development of graphene biosensors for the detection of bacterial and viral pathogens, mainly including the preparation of graphene biosensors and their working mechanism. The challenges involved in this field have been discussed, and the perspective for further development has been put forward, aiming to promote the development of pathogens sensing and the contribution to epidemic prevention.