Cysteine-Induced Chirality Evolution of Molybdenum Disulfide Nanodots from a Bottom-Up Strategy.

The transfer of chirality from molecules to synthesized nanomaterials has recently attracted significant attention. Although most studies have focused on graphene and plasmonic metal nanostructures, layered transition metal dichalcogenides (TMDs), particularly MoS2, have recently garnered considerable attention due to their semiconducting and electrocatalytic characteristics. Herein, we report a new approach for the synthesis of chiral molybdenum sulfide nanomaterials based on a bottom-up synthesis method in the presence of chiral cysteine enantiomers. In the synthesis process, molybdenum trioxide and sodium hydrosulfide serve as molybdenum and sulfur sources, respectively. In addition, ascorbic acid acts as a reducing agent, resulting in the formation of zero-dimensional MoS2 nanodots. Moreover, the addition of cysteine enantiomers to the growth solutions contributes to the chirality evolution of the MoS2 nanostructures. The chirality is attributed to the cysteine enantiomer-induced preferential folding of the MoS2 planes. The growth mechanism and chiral structure of the nanomaterials are confirmed through a series of characterization techniques. This work combines chirality with the bottom-up synthesis of MoS2 nanodots, thereby expanding the synthetic methods for chiral nanomaterials. This simple synthesis approach provides new insights for the construction of other chiral TMD nanomaterials with emerging structures and properties. More significantly, the as-formed MoS2 nanodots exhibited highly defect-rich structures and chiroptical performance, thereby inspiring a high potential for emerging optical and electronic applications.

Electrophoretic Microplate Protein Identification Based on Gold Staining of Molybdenum Disulfide Hydrogels.

Numerous high-performance nanotechnologies have been developed, but their practical applications are largely restricted by the nanomaterials' low stabilities and high operation complexity in aqueous substrates. Herein, we develop a simple and high-reliability hydrogel-based nanotechnology based on the in situ formation of Au nanoparticles in molybdenum disulfide (MoS2)-doped agarose (MoS2/AG) hydrogels for electrophoresis-integrated microplate protein recognition. After the incubation of MoS2/AG hydrogels in HAuCl4 solutions, MoS2 nanosheets spontaneously reduce Au ions, and the hydrogels are remarkably stained with the color of as-synthetic plasmonic Au hybrid nanomaterials (Au staining). Proteins can precisely mediate the morphologies and optical properties of Au/MoS2 heterostructures in the hydrogels. Consequently, Au staining-based protein recognition is exhibited, and hydrogels ensure the comparable stabilities and sensitivities of protein analysis. In comparison to the fluorescence imaging and dye staining, enhanced sensitivity and recognition performances of proteins are implemented by Au staining. In Au staining, exfoliated MoS2 semiconductors directly guide the oriented growth of plasmonic Au nanostructures in the presence of formaldehyde, showing environment-friendly features. The Au-stained hydrogels merge the synthesis and recognition applications of plasmonic Au nanomaterials. Significantly, the one-step incubation of the electrophoretic hydrogels leads to high simplicity of operation, largely challenging those multiple-step Ag staining routes which were performed with high complexity and formaldehyde toxicity. Due to its toxic-free, simple, and sensitive merits, the Au staining integrated with electrophoresis-based separation and microplate-based high-throughput measurements exhibits highly promising and improved practicality of those developing nanotechnologies and largely facilitates in-depth understanding of biological information.

White light powered antimicrobial nanoagents for triple photothermal, chemodynamic and photodynamic based sterilization.

Antibacterial nanoagents have been increasingly developed due to their favorable biocompatibility, cost-effective raw materials, and alternative chemical or optical properties. Nevertheless, there is still a pressing need for antibacterial nanoagents that exhibit outstanding bacteria-binding capabilities and high antibacterial efficiency. In this study, we constructed a multifunctional cascade bioreactor (GCDCO) as a novel antibacterial agent. This involved incorporating carbon dots (CDs), cobalt sulfide quantum dots (CoSx QDs), and glucose oxidase (GOx) to enhance bacterial inhibition under sunlight irradiation. The GCDCO demonstrated highly efficient antibacterial capabilities attributed to its favorable photothermal properties, photodynamic activity, as well as the synergistic effects of hyperthermia, glucose-augmented chemodynamic action, and additional photodynamic activity. Within this cascade bioreactor, CDs played the role of a photosensitizer for photodynamic therapy (PDT), capable of generating ˙O2- even under solar light irradiation. The CoSx QDs not only functioned as a catalytic component to decompose hydrogen peroxide (H2O2) and generate hydroxyl radicals (˙OH), but they also served as heat generators to enhance the Fenton-like catalysis process. Furthermore, GOx was incorporated into this cascade bioreactor to internally supply H2O2 by consuming glucose for a Fenton-like reaction. As a result, GCDCO could generate a substantial amount of reactive oxygen species (ROS), leading to a significant synergistic effect that greatly induced bacterial death. Furthermore, the in vitro antibacterial experiment revealed that GCDCO displayed notably enhanced antibacterial activity against E. coli (99+ %) when combined with glucose under simulated sunlight, surpassing the efficacy of the individual components. This underscores its remarkable efficiency in combating bacterial growth. Taken together, our GCDCO demonstrates significant potential for use in the routine treatment of skin infections among diabetic patients.

Sunflower pollen-derived microcapsules adsorb light and bacteria for enhanced antimicrobial photothermal therapy.

Bacterial infection is one of the most serious clinical complications, with life-threatening outcomes. Nature-inspired biomaterials offer appealing microscale and nanoscale architectures that are often hard to fabricate by traditional technologies. Inspired by the light-harvesting nature, we engineered sulfuric acid-treated sunflower sporopollenin exine-derived microcapsules (HSECs) to capture light and bacteria for antimicrobial photothermal therapy. Sulfuric acid-treated HSECs show a greatly enhanced photothermal performance and a strong bacteria-capturing ability against Gram-positive bacteria. This is attributed to the hierarchical micro/nanostructure and surface chemistry alteration of HSECs. To test the potential for clinical application, an in situ bacteria-capturing, near-infrared (NIR) light-triggered hydrogel made of HSECs and curdlan is applied in photothermal therapy for infected skin wounds. HSECs and curdlan suspension that spread on bacteria-infected skin wounds of mice first capture the local bacteria and then form hydrogels on the wound upon NIR light stimulation. The combination shows a superior antibacterial efficiency of 98.4% compared to NIR therapy alone and achieved a wound healing ratio of 89.4%. The current study suggests that the bacteria-capturing ability and photothermal properties make HSECs an excellent platform for the phototherapy of bacteria-infected diseases. Future work that can fully take advantage of the hierarchical micro/nanostructure of HSECs for multiple biomedical applications is highly promising and desirable.

Mercury-Mediated Epitaxial Accumulation of Au Atoms for Stained Hydrogel-Improved On-Site Mercury Monitoring.

Trivalent Au ions are easily reduced to be zerovalent atoms by coexisting reductant reagents, resulting in the subsequent accumulation of Au atoms and formation of plasmonic nanostructures. In the absence of stabilizers or presence of weak stabilizers, aggregative growth of Au nanoparticles (NPs) always occurs, and unregular multidimensional Au materials are consequently constructed. Herein, the addition of nanomole-level mercury ions can efficiently prevent the epitaxial accumulation of Au atoms, and separated Au NPs with mediated morphologies and superior plasmonic characteristics are obtained. Experimental results and theoretical simulation demonstrate the Hg-concentration-reliant formation of plasmonic nanostructures with their mediated sizes and shapes in the presence of weak reductants. Moreover, the sensitive plasmonic responses of reaction systems exhibit selectivity comparable to that of Hg species. As a concept of proof, polymeric carbon dots (CDs) were used as the initial reductant, and the reactions between trivalent Au and CDs were studies. Significantly, Hg atoms prevent the epitaxial accumulation of Au atoms, and plasmonic NPs with decreased sizes were in situ synthesized, corresponding to varied surface plasmonic resonance absorption performance of the CD-induced hybrids. Moreover, with the integration of sensing substrates of CD-doped hydrogels, superior response stabilities, analysis selectivity, and sensitivity of Hg2+ ions were achieved on the basis of the mercury-mediated in situ chemical reactions between trivalent Au ions and reductant CDs. Consequently, a high-performance sensing strategy with the use of Au NP-staining hydrogels (nanostaining hydrogels) was exhibited. In addition to Hg sensing, the nanostaining hydrogels facilitated by doping of emerging materials and advanced chem/biostrategies can be developed as high-performance on-site monitoring routes to various pollutant species.

An intelligent "chemical tongue" for high-order monitoring ATP-related physiological phosphates and ATP hydrolysis through diverse transduction principles.

For discriminating diverse analytes and monitoring a specific chemical reaction, the emerging multi-channel "chemical nose/tongue" is challenging multi-material "chemical nose/tongue". The former contributes greatly to integrating different transduction principles from a single sensing material, avoiding the need for complex design, high cost, and tedious operation involved with the latter. Therefore, this high-order sensing puts a particular emphasis on the effects of encapsulation. Herein, the plasmonic gold nanoparticles (Au NPs) are encapsulated as a core into the fluorescent guanine monophosphate-Tb3+ infinite coordination polymer nanoparticles (GMP-Tb ICPs) to obtain a core-shell nanocomposite named Au NPs@GMP-Tb ICPs. Hence, a dual-channel "chemical tongue" based on Au NPs@GMP-Tb ICPs is present to realize high-order sensing of adenosine triphosphate (ATP)-related physiological phosphates and the monitoring of ATP hydrolysis. Considering the affinity of Tb3+ towards P-O bonds, four inorganic phosphates and three nucleotide phosphates with different phosphate group numbers and steric hindrance effect directly regulate two stimulus responses (fluorescence intensity and UV-vis absorbance) of Au NPs@GMP-Tb ICPs. Robust statistical methods, such as linear discriminant analysis and hierarchical cluster analysis, are used to recognize each phosphate by the developed sensor array either in the aqueous solution or in complex media such as serum, together with efficiently monitored ATP hydrolysis at different intervals. These findings and blind test clarify that the designed "chemical tongue" guarantees interference resistance and strengthens analytical capacity, together with offering valuable insight into "lab-on-a-nanoparticle" development for monitoring specific chemical reactions.

Tracking the Growth of Chiral Plasmonic Nanocrystals at Molybdenum Disulfide Heterostructural Interfaces.

The way of accurately regulating the growth of chiral plasmonics is of great importance for exploring the chirality information and improving its potential values. Herein, cysteine enantiomers modulate the anisotropic and epitaxial growth of gold nanoplasmonics on seeds of exfoliated MoS2 nanosheets. The heterostructural Au and MoS2 hybrids induced by enantiomeric cysteine are presented with chiroptical characteristics, dendritic morphologies, and plasmonic performances. Moreover, the synthesis, condition optimization, formation mechanism, and plasmonic properties of Au and MoS2 dendritic nanostructures are studied. The chirality characteristics are identified using the circular dichroism spectra and scanning electron microscopy. Time-resolved transmission electron microscopy and UV-vis spectra of the intermediate products captured are analyzed to confirm the formation mechanism of dendritic plasmonic nanostructures at heterostructural surfaces. The specific dendritic morphologies originate from the synergistic impacts of heterostructural MoS2 interfaces and enantiomeric cysteine-induced anisotropic manipulation. Significantly, the developed synthesis strategy of chiral nanostructures at heterostructural interfaces is highly promising in promoting the understanding of the plasmonic function and crucial chirality bioinformation.

Chiral nanocrystals grown from MoS2 nanosheets enable photothermally modulated enantioselective release of antimicrobial drugs.

The transfer of the concept of chirality from molecules to synthesized nanomaterials has attracted attention amongst multidisciplinary teams. Here we demonstrate heterogeneous nucleation and anisotropic accumulation of Au nanoparticles on multilayer MoS2 planes to form chiroptically functional nanomaterials. Thiol amino acids with chiral conformations modulate asymmetric growth of gold nanoarchitectures on seeds of highly faceted Au/MoS2 heterostructures. Consequently, dendritic plasmonic nanocrystals with partial chiral morphologies are synthesized. The chirality of dendritic nanocrystals inherited from cysteine molecules refers to the structural characteristics and includes specific recognition of enantiomeric molecules. With integration of the intrinsic photothermal properties and inherited enantioselective characteristics, dendritic Au/MoS2 heterostructures exhibit chirality-dependent release of antimicrobial drugs from hydrogel substrates when activated by exogenous infrared irradiation. A three-in-one strategy involving synthesis of chiral dendritic heterostructures, enantioselective recognition, and controlled drug release system is presented, which improves nanomaterial synthetic technology and enhances our understanding of crucial chirality information.

Defect-Rich Molybdenum Sulfide Quantum Dots for Amplified Photoluminescence and Photonics-Driven Reactive Oxygen Species Generation.

Transition metal dichalcogenide (TMD) quantum dots (QDs) with defects have attracted interesting chemistry due to the contribution of vacancies to their unique optical, physical, catalytic, and electrical properties. Engineering defined defects into molybdenum sulfide (MoS2 ) QDs is challenging. Herein, by applying a mild biomineralization-assisted bottom-up strategy, blue photoluminescent MoS2 QDs (B-QDs) with a high density of defects are fabricated. The two-stage synthesis begins with a bottom-up synthesis of original MoS2 QDs (O-QDs) through chemical reactions of Mo and sulfide ions, followed by alkaline etching that creates high sulfur-vacancy defects to eventually form B-QDs. Alkaline etching significantly increases the photoluminescence (PL) and photo-oxidation. An increase in defect density is shown to bring about increased active sites and decreased bandgap energy; which is further validated with density functional theory calculations. There is strengthened binding affinity between QDs and O2 due to lower gap energy (∆EST ) between S1 and T1 , accompanied with improved intersystem crossing (ISC) efficiency. Lowered gap energy contributes to assist e- -h+ pair formation and the strengthened binding affinity between QDs and 3 O2 . Defect engineering unravels another dimension of material properties control and can bring fresh new applications to otherwise well characterized TMD nanomaterials.

Plasmonic Gold Nanoparticles Stain Hydrogels for the Portable and High-Throughput Monitoring of Mercury Ions.

The hybrid of l-cysteine and agarose can reduce HAuCl4 and support the rapid growth of plasmonic gold nanoparticles (Au NPs) in the hydrogel phase. The l-cysteine-doped agarose hydrogel (C-AGH) not only offers the substrate the capacity to reduce Au(III) ions but also stabilizes and precisely modulates the in situ grown Au NPs with high repeatability, easy operation, and anti-interference performance. Herein, before the incubation of HAuCl4, the improved hydrogel is preincubated in the aqueous solution containing mercury ions, and the cysteine can specifically conjugate with mercury via the thiol groups. Subsequently, the responsive allochroic bands from dark blue to red can be identified in the solid hydrogel after the incubation of HAuCl4, which is attributed to the formation of regulated Au-Hg nanoamalgams. As a proof-of-concept, toxic Hg2+ ions are exploited as targets for constructing novel sensing assays based on the improved C-AGH protocol. Based on naked-eye recognition, Hg2+ could be rapidly and simply measured. Additionally, the high-throughput and trace analysis with a low limit of detection (3.7 nM) is performed using a microplate reader. On the basis of the filtering technique and remodeling of hydrogels, C-AGH working as the filtering membrane can even achieve the integration of enrichment and measurement with enhanced sensitivity. Significantly, the strategy of using an allochroic hydrogel with the staining of Au NPs can promote the rapid and primary assessment of water quality in environmental analysis.

Mercury ion-engineering Au plasmonics on MoS2 layers for absorption-shifted optical sensors.

Semiconducting MoS2 layers offer the electrons, reducing conjugated Au(I) to Au atoms, and sebsequently serve as desirable substrates for supporting the interfacial growths of gold nanostructures. Au-covering MoS2 heterostructures perform morphology-varied optical characteristics, and the surface engineering of MoS2 involved by Hg2+ ions results in the differential growths of nanostructures and morphological diversities. Naked-eye colorimetric responses to mercury ions, with a low limit of detection of 1.27 nM, are achieved based on the in situ grown heterostructures.

Aggregation-induced responses (AIR) of 2D-derived layered nanostructures enable emerging colorimetric and fluorescence sensors.

Layered nanostructures (LNs), including two-dimensional nanosheets, nanoflakes, and planar nanodots, show large surface-to-volume ratios, unique optical properties, and desired interfacial activities. LNs are highly promising as alternative probes and platforms due to numerous merits, e.g. signal amplification, improved recognition ability, and anti-interference capacity, for emerging sensing applications. Significantly, when stimuli-responsive aggregation occurs, the modified LNs show engineered morphologies, attractive optical absorption and fluorescence characteristics, which are remarkably programmable. On the basis of the altered aggregation behaviours of LNs, as well as their modulated physical and chemical characteristics, a series of novel sensing assays exhibiting enhanced sensitivity, simple operation, multiple functions, and improved anti-interference capacity are reported, contributing to both point-of-care testing and high-throughput measurements. Herein, the aggregation-induced response sensing strategies of LNs are comprehensively summarized with the classification of materials and variation of aggregated routes aiming at understanding dimension-dependent features, expanding nanoscale biosensor applications, and addressing key issues in disease diagnosis and environmental analysis.

Multifunctional Binding Strategy on Nonconjugated Polymer Nanoparticles for Ratiometric Detection and Effective Removal of Mercury Ions.

Developing a multifunctional platform for the selective detection and effective removal of toxic ions is a major challenge when addressing heavy metal contamination in environmental science. Herein, novel nonconjugated polymer nanoparticles (PNPs) called mercaptosuccinic acid-thiosemicarbazide PNPs (MT-PNPs) with appealing fluorescence and stability are synthesized via facile one-step hydrothermal treatment for attractive sensing and simultaneous removal of mercury(II). Interestingly, aggregation-induced fluorescence switch-off and scattering enhancement are found upon the addition of Hg2+, rendering MT-PNPs as a ratiometric sensor for selective and accurate Hg2+ monitoring. A wide linear range (0.1-1471 µM) and a low detection limit (95 nM) are obtained. This dual-signal opposite responses triggered by Hg2+ originate from the formation of MT-PNP-Hg2+ congeries via the multisite binding between S,N,O-containing groups of MT-PNPs and mercury. Meanwhile, target-induced aggregation renders an effective Hg2+ separation from contaminative aqueous media by MT-PNPs, which exhibits a satisfactory absorption efficiency of 90.42% within 50 min. Upon the simple Na2S treatment, the MT-PNPs can be regenerated and reused. This work thus delivers an applicable method for the ratiometric detection and effective removal of mercury with the novel nonconjugated PNPs, offering potential in tackling the problem of heavy metal ion pollution for environmental monitoring and remediation.

Layered MoS2 defect-driven in situ synthesis of plasmonic gold nanocrystals visualizes the planar size and interfacial diversity.

Current defect theories significantly guide broad research progress, whereas the recognition of defect status remains challenging. Herein, MoS2 defect type, density and exposed state are visually identified with a reagent indicator of HAuCl4. Mo-terminated defects spontaneously reduce [AuCl4]- anions and oxidized Mo species are dissociated. Consequently, MoS2 edges guide the epitaxial branch of Au nanocrystals (NCs), followed by sequential growths at their planar defects. The size-evolution processes of LaMer growth and planar packages of the aggregative growth of Au/MoS2 nanoseeds result in the occupation of Au atomic layers on heterostructures. Consequently, shell-core hybrids are presented with localized surface plasmon resonance characteristics. The mechanism is systematically explored via the discriminated performance of plasmonic characteristics of Au nanostructures on semiconducting MoS2 substrates. With plasmonic identification, defect-associated size and interfacial diversities of MoS2 are visually information-rich. Tunable morphologies and synergistic optical characteristics of plasmonic semiconductor heterostructures inspire many more applications through the edge and planar defects intrinsic in layered MoS2.

Assembling Defined DNA Nanostructure with Nitrogen-Enriched Carbon Dots for Theranostic Cancer Applications.

DNA nanostructures as scaffolds for drug delivery, biosensing, and bioimaging are hindered by its vulnerability in physiological settings, less favorable of incorporating arbitrary guest molecules and other desirable functionalities. Noncanonical self-assembly of DNA nanostructures with small molecules in an alternative system is an attractive strategy to expand their applications in multidisciplinary fields and is rarely explored. This work reports a nitrogen-enriched carbon dots (NCDs)-mediated DNA nanostructure self-assembly strategy. Given the excellent photoluminescence and photodynamic properties of NCDs, the obtained DNA/NCDs nanocomplex holds great potential for bioimaging and anticancer therapy. NCDs can mediate DNA nanoprism (NPNCD ) self-assembly isothermally at a large temperature and pH range in a magnesium-free manner. To explore the suitability of NPNCD in potential biomedical applications, the cytotoxicity and cellular uptake efficiency of NPNCD are evaluated. NPNCD with KRAS siRNA (NPNCD K) is further conjugated for KRAS-mutated nonsmall cell lung cancer therapy. The NPNCD K shows excellent gene knockdown efficiency and anticancer effect in vitro. The current study suggests that conjugating NCDs with programmable DNA nanostructures is a powerful strategy to endow DNA nanostructures with new functionalities, and NPNCD may be a potential theranostic platform with further fine-tuned properties of CDs such as near-red fluorescence or photothermal activities.

Toxicity of Two-Dimensional Layered Materials and Their Heterostructures.

Two-dimensional layered materials (2D LMs) are taking the scientific world by storm. Graphene epitomizes 2D LMs with many interesting properties and corresponding applications. Following the footsteps of graphene, many other types of 2D LMs such as transition metal dichalcogenides, black phosphorus, and graphitic-phase C3N4 nanosheets are emerging to be equally interesting as graphene and its derivatives. Some of these applications such as nanomedicine do have a high probability of human exposure. This review focuses on the biological and toxicity effects of 2D LMs and their associated mechanisms linking their chemistries to their biological end points. This review aims to help researchers to predict and mitigate any toxic effects. With understanding, redesign of newer and safer 2D LMs becomes possible.

Nanodots of transition metal (Mo and W) disulfides grown on NiNi Prussian blue analogue nanoplates for efficient hydrogen production.

Lowering the dimension of transition metal dichalcogenides is an efficient approach to expose more S-edge-sites. Here, zero-dimensional MoS2 and WS2 nanodots are successfully prepared with the assistance of a template of NiNi Prussian blue analogue nanoplates. The novel hybrids exhibit highly efficient and stable catalytic ability for the hydrogen evolution reaction.

Layered Aggregation with Steric Effect: Morphology-Homogeneous Semiconductor MoS2 as an Alternative 2D Probe for Visual Immunoassay.

Liquid-phase exfoliation routes unavoidably generate 2D nanostructures with inhomogeneous morphologies. Herein, thickness-dependent sorting of exfoliated nanostructures is achieved via a treatment of differential-zone centrifugation in the surfactant aqueous phase. With this approach, homogeneous MoS2 nanosheets are obtained, and due to the intrinsic semiconducting characteristics, those 2D nanosheets are endowed with desired optical properties, rivaling classic gold nanoparticles in sensing applications. Furthermore, MoS2 nanosheets with high uniformity and chemical inertness are coupled with proteins, exhibiting high performance in stability and anti-interferences for bioanalysis. As a consequence of aggregation-induced steric effect, distinguishing running shifts of antibody-anchored conjugates in gel electrophoresis are visually responsive to those specific antigens. This assay enables the easy and fast monitoring of tumor biomarkers just according to "naked-eye" identification of band location in electrophoresis results, which are presented by an alternative visual probe of 2D MoS2 -protein conjugates. The developed visual immunoassay with the synergistic effect of gel electrophoresis techniques and 2D semiconductors pushes significant progress in "home-made" tests for disease early diagnosis.

Emerging 0D Transition-Metal Dichalcogenides for Sensors, Biomedicine, and Clean Energy.

Following research on two-dimensional (2D) transition metal dichalcogenides (TMDs), zero-dimensional (0D) TMDs nanostructures have also garnered some attention due to their unique properties; exploitable for new applications. The 0D TMDs nanostructures stand distinct from their larger 2D TMDs cousins in terms of their general structure and properties. 0D TMDs possess higher bandgaps, ultra-small sizes, high surface-to-volume ratios with more active edge sites per unit mass. So far, reported 0D TMDs can be mainly classified as quantum dots, nanodots, nanoparticles, and small nanoflakes. All exhibited diverse applications in various fields due to their unique and excellent properties. Of significance, through exploiting inherent characteristics of 0D TMDs materials, enhanced catalytic, biomedical, and photoluminescence applications can be realized through this exciting sub-class of TMDs. Herein, we comprehensively review the properties and synthesis methods of 0D TMDs nanostructures and focus on their potential applications in sensor, biomedicine, and energy fields. This article aims to educate potential adopters of these excitingly new nanomaterials as well as to inspire and promote the development of more impactful applications. Especially in this rapidly evolving field, this review may be a good resource of critical insights and in-depth comparisons between the 0D and 2D TMDs.

Directing Assembly and Disassembly of 2D MoS2 Nanosheets with DNA for Drug Delivery.

Layer-by-layer (LbL) self-assembled stacked Testudo-like MoS2 superstructures carrying cancer drugs are formed from nanosheets controllably assembled with sequence-based DNA oligonucleotides. These superstructures can disassemble autonomously in response to cancer cells' heightened ATP metabolism. First, we functionalize MoS2 nanosheets (MoS2-NS) nanostructures with DNA oligonucleotides having thiol-terminated groups (DNA/MoS2-NS) via strong binding to sulfur atom defect vacancies on MoS2 surfaces. The driving force to assemble into a higher-order DNA/MoS2-NS superstructure is guided by a linker aptamer that induced interlayer assembly. In the presence of target ATP molecules, these multilayer superstructures disassembled as a consequence of stronger binding of ATP molecules with the linking aptamers. This design plays a dual role of protection and delivery by LbL stacked MoS2-NS similar in concept to a Greek Testudo. These superstructures present a protective armor-like shell of MoS2-NS, which still remains responsive to small and infiltrating ATP molecules diffusing through the protective MoS2-NS, contributing to an enhanced stimuli-responsive drug release system for targeted chemotherapy.