A magnetically powered nanomachine with a DNA clutch

Understanding Electron Beam-Induced Chemical Polymerization Processes of Small Organic Molecules Using Operando Liquid-Phase Transmission Electron Microscopy

Electron beams evolved as important tools for modern technologies that construct and analyze nanoscale architectures. While electron-matter interactions at atomic and macro scales are well-studied, a knowledge gap persists at the molecular to nano level─the scale most relevant to the latest technologies. Here, we employ operando liquid-phase transmission electron microscopy supported by density functional theory calculations and a mathematical random search algorithm to rationalize and quantify electron beam-induced processes at the molecular level. By examining a series of small organic molecules, we identify critical physical and chemical parameters that dictate polymerization rates under continuous electron beam irradiation. Our findings offer a deeper understanding of electron beam-induced reactions, enabling the prediction of molecular reactivities from a classical chemistry perspective. These insights apply equally to other soft matter systems and, thus, are of fundamental interest to scientists and engineers who use electron beams to analyze or to manipulate nanoscale matter.

A DNA-Based Plasmonic Nano-Ruler

DNA is an exceptional building block for the fabrication of dynamic supramolecular systems with switchable geometries. Here, a self-assembled, tunable plasmonic-fluorescent nanostructure was developed. A precise sliding motion mechanism was operated through the control of strand displacement reactions, shifting two single-strand DNA (ssDNA) rails connected by a ssDNA quasi-ring structure. The system was reconfigured as a nano-mechanical structure, generating six discrete configurations, and setting specific distances between a tethered gold nanoparticle (AuNP) and a fluorophore, Sulfo-Cyanine3 (Cy3). Each configuration produced a distinct fluorescence emission intensity via plasmonic quenching/enhancement effects, and therefore the structure behaved as a nano-ruler. To optimize the system, the reversible distance-dependent fluorescence quenching or enhancement phenomena were investigated by testing AuNPs with diameters of 5, 10, and 15 nm, yielding the best performances with 10 nm AuNPs. Furthermore, a geometric model of the system was produced, confirming the observed results. The fluorophore-plasmonic surface positioning, conferred by the DNA ruler, led to a finite state nano-machine with six alternative signal outputs. This mechanism, working as a fluorescent reporter, could find application in a multiple-responsive detection system of single-strand nucleic acids, such as viruses or microRNAs.

Dual-Ligand Assisted Anisotropic Assembly for the Construction of NIR-II Light-Propelled Mesoporous Nanomotors

The advent of autonomous nanomotors presents exciting opportunities for nanodrug delivery. However, significant potential remains for enhancing the asymmetry of nanomotors and advancing the development of second near-infrared (NIR-II) light-propelled nanomotors capable of operating within deep tissues. Herein, we developed a dual-ligand assisted anisotropic assembly strategy that enables precise regulation of the interfacial energy between selenium (Se) nanoparticle and periodic mesoporous organosilica (PMO). This strategy facilitates the controllable anisotropic growth of PMO on the Se nanoparticle, leading to the formation of Se&PMO Janus nanohybrids. The exposure ratio of the Se subunit within the Janus nanohybrids can be finely tuned from 0% to 75%. Leveraging the transformability of the Se subunit, a variety of functional MxSe&PMO Janus nanocomposites (MxSe denotes metal selenide) were further derived. As a proof of concept, CuSe&PMO Janus nanohybrids, with NIR-II photothermal properties, were employed as NIR-II light-driven nanomotors. By precisely controlling the exposure ratio of the CuSe subunit within the Janus nanostructure, these CuSe&PMO nanomotors achieved optimal self-propulsion, thus enhancing cellular uptake and promoting deep tumor penetration. Furthermore, the high loading capacity and hydrophobic framework of the PMO subunit enabled the incorporation of hydrophobic disulfiram, thereby significantly boosting the efficacy of synergistic active-motion photothermal therapy.

Advances, Challenges, and Opportunities in Plasmonic Nanogap-Enhanced Raman Scattering with Nanoparticles

Surface-enhanced Raman scattering has been widely used for molecular/material characterization and chemical and biological sensing and imaging applications. In particular, plasmonic nanogap-enhanced Raman scattering (NERS) is based on the highly localized electric field formed within the nanogap between closely spaced metallic surfaces to more strongly amplify Raman signals than the cases with molecules on metal surfaces. Nanoparticle-based NERS offers extraordinarily strong Raman signals and a plethora of opportunities in sensing, imaging and many different types of biomedical applications. Despite its potential, several challenges still remain for NERS to be widely useful in real-world applications. This Perspective introduces various plasmonic nanogap configurations with nanoparticles, discusses key advances and critical challenges while addressing possible misunderstandings in this field, and provides future directions for NERS to generate stronger, more uniform, and stable signals over a large number of structures for practical applications.

Recent advances in the development of tumor microenvironment-activatable nanomotors for deep tumor penetration

Cancer represents a significant threat to human health, with the use of traditional chemotherapy drugs being limited by their harsh side effects. Tumor-targeted nanocarriers have emerged as a promising solution to this problem, as they can deliver drugs directly to the tumor site, improving drug effectiveness and reducing adverse effects. However, the efficacy of most nanomedicines is hindered by poor penetration into solid tumors. Nanomotors, capable of converting various forms of energy into mechanical energy for self-propelled movement, offer a potential solution for enhancing drug delivery to deep tumor regions. External force-driven nanomotors, such as those powered by magnetic fields or ultrasound, provide precise control but often necessitate bulky and costly external equipment. Bio-driven nanomotors, propelled by sperm, macrophages, or bacteria, utilize biological molecules for self-propulsion and are well-suited to the physiological environment. However, they are constrained by limited lifespan, inadequate speed, and potential immune responses. To address these issues, nanomotors have been engineered to propel themselves forward by catalyzing intrinsic "fuel" in the tumor microenvironment. This mechanism facilitates their penetration through biological barriers, allowing them to reach deep tumor regions for targeted drug delivery. In this regard, this article provides a review of tumor microenvironment-activatable nanomotors (fueled by hydrogen peroxide, urea, arginine), and discusses their prospects and challenges in clinical translation, aiming to offer new insights for safe, efficient, and precise treatment in cancer therapy.