Highly Thiolated Dendritic Mesoporous Silica Nanoparticles with High-Content Gold as Nanozymes: The Nano-Gold Size Matters

Incorporation of ultrafine TiO2/CdS heterojunction in dendritic porphyrins mesoporous silica nanospheres for efficient photocatalytic oxidation of styrene

In this paper, a novel host-guest assembly strategy is developed to incorporate TiO2 nanoparticles and CdS quantum dots (CdS QDs) into the photoactive dendritic porphyrins mesoporous silica nanospheres (DPMSN) channels for establishing heterojunctions nanoreactors (designated as DPMSTNC). The well-defined dendritic architecture facilitates the high dispersion of TiO2/CdS heterojunctions within the DPMSN matrix, effectively maximizing the interfacial contact area between the heterojunction components and the cobalt porphyrin framework. Crucially, the synergistic interplay of cobalt porphyrins incorporated in the silica framework and the ultra-small TiO2/CdS heterojunction in the dendritic channels promotes efficient charge transfer and separation in the nanoreactor. The optimized DPMSTNC nanoreactor exhibits excellent catalytic performance with a conversion of 96.0 % and a selectivity of 92.0 % in styrene oxidation, which significantly surpasses that of single-component catalysts and simple composite heterostructure catalysts. This nanoreactor design strategy, which combines spatially confined heterojunctions with photoactive porous frameworks, provides a novel and versatile platform for developing high-efficiency photocatalytic systems through precise nanoarchitectural control.

Targeted self-assembled anti-NFκB AuNCs-aptamer nanoplatform for precise theranostics via tailored follicle regeneration

NFκB is a vital transcription factor for the regulation of hair follicle cycle. As a therapeutic target, NFκB is specifically blocked by RNA aptamer with negligible side effects, but the targeted transmembrane transport of anti-NFκB aptamer remains a challenge due to its negative charge under physiological conditions. In this study, taking advantage of the depilation-induced oxidative stress microenvironment (OSM), it was confirmed for the first time that self-assembled gold nanoclusters and aptamer (AuNCs-Aptamer) complexes formed in the skin and enhanced the therapeutic effect of anti-NFκB aptamer drugs, effectively blocking the NFκB-mediated inflammatory response and inhibiting hair follicle regeneration. The hematoxylin-eosin (HE) staining of tissue section and hematology analysis demonstrated that OSM-responsive self-assembled AuNCs-Aptamer caused no toxicity to the living organism. Moreover, self-assembly occurred only in the oxidative stress-injured skin cells rather than the normal cells, which revealed that this self-assembly was a targeted, safe and effective therapy for hypertrichosis.

Nanozymes as Antibacterial Agents: New Concerns in Design and Enhancement Strategies

Nanozymes exhibiting natural enzyme-mimicking catalytic activities as antibacterial agents present several advantages, including high stability, low cost, broad-spectrum antibacterial activity, ease of preparation and storage, and minimal bacterial resistance. Consequently, they have attracted significant attention in recent years. However, the rapid expansion of antimicrobial nanozyme research has resulted in pioneering reviews that do not comprehensively address emerging concerns and enhancement strategies within this field. This paper first summarizes the factors influencing the intrinsic activity of nanozymes; subsequently, we outline new research considerations for designing antibacterial nanozymes with enhanced functionality and biosafety features such as degradable, imageable, targeted, and bacterial-binding nanozymes as well as those capable of selectively targeting pathogenic bacteria while sparing normal cells and probiotics. Furthermore, we review novel enhancement strategies involving external physical stimuli (light or ultrasound), the introduction of extrinsic small molecules, and self-supplying H2O2 to enhance the activity of antibacterial nanozymes under physiological conditions characterized by low concentrations of H2O2 and O2. Additionally, we present non-redox nanozymes that operate independently of highly toxic reactive oxygen species (ROS) alongside those designed to combat less common pathogenic bacteria. Finally, we discuss current issues, challenges faced in the field, and future prospects for antibacterial nanozymes.

Propelling gold nanozymes: catalytic activity and biosensing applications

Recently, gold nanomaterials have been rapidly developed owing to their high stability, good biocompatibility, and multifunctionality. The unique catalytic activity of gold nanomaterials has driven the emergence of the concept for a "gold nanozyme." Understanding the characteristics of gold nanozymes is crucial for improving their catalytic performance as well as expanding their applications. In this review, we provide an overview of the intrinsic enzyme-like activities of gold nanozymes, including peroxidase-, catalase-, superoxide dismutase-, and glucose oxidase-like activities, and the catalytic mechanisms involved. In addition, strategies for modulating the catalytic activity of gold nanozymes and their applications in biosensing were discussed in detail. Moreover, we highlight the current challenges of gold nanozymes and look forward to attracting more attention for propelling the developments in this field.

Ceria nanoparticles immobilized with self-assembling peptide for biocatalytic applications

Peptide-based artificial enzymes exhibit structure and catalytic mechanisms comparable to natural enzymes but they suffer from limited reusability due to their existence in homogenous solutions. Immobilization of self-assembling peptides on the surface of nanoparticles can be used to overcome limitations associated with artificial enzymes. A high, local density of peptides can be obtained on nanoparticles to exert cooperative or synergistic effects, resulting in an accelerated rate of reaction, distinct catalytic properties, and excellent biocompatibility. In this work, we have immobilized a branched, self-assembled, and nanofibrous catalytic peptide, (C12-SHD)2KK(Alloc)-NH2, onto thiolated ceria nanoparticles to generate a heterogeneous catalyst with an enhanced number of catalytic sites. This artificial enzyme mimics the activities of esterase, phosphatase, and haloperoxidase enzymes and the catalytic efficiency remains nearly unaltered when reused. The enzyme-mimicking property is investigated for pesticide detection, bone regeneration, and antibiofouling applications. Overall, this work presents a facile approach to develop a multifunctional heterogeneous biocatalyst that addresses the challenges associated with unstable peptide-based homogeneous catalysts and, thus, shows a strong potential for industrial applications.

Insights into emulsion synthesis of self-assembled suprastructures formed by Janus silica particles with -NH2/-SH surface groups

Spherical particles with tunable anisotropic structures enabled by multiple surface functionalities have garnered interest for their potential applications in adsorption technologies. The presence of diverse functional groups in the surface layer, exhibiting varying acidity and hydrophilicity, can lead to unique characteristics in terms of surface structure and behaviour. In this study, the particles were synthesised using a two-step approach involving surface functionalisation of previously synthesised SiO2 Stöber particles. This was achieved by employing 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminopropyltrimethoxysilane (APTMS) in a toluene-in-water emulsion. The resulting particles were found to be nonporous, with a specific surface area of 8 m2 g-1. Their sizes were determined to be up to 350 nm through photon cross-correlation spectroscopy. Moreover, the particles exhibited a high net content of functional groups (both amino and mercapto) of 2 mmol g-1. The organisation of the particles during synthesis was observed through SEM images, providing insights into their structural characteristics. Additionally, the study of Eu(iii), Au(iii), and Ag(i) ions and fluorescein adsorption demonstrated varying interactions on the surface, highlighting the potential applications and versatility of these functionalised particles.

Transition-Metal-Based Nanozymes: Synthesis, Mechanisms of Therapeutic Action, and Applications in Cancer Treatment

Cancer, as one of the leading causes of death worldwide, drives the advancement of cutting-edge technologies for cancer treatment. Transition-metal-based nanozymes emerge as promising therapeutic nanodrugs that provide a reference for cancer therapy. In this review, we present recent breakthrough nanozymes for cancer treatment. First, we comprehensively outline the preparation strategies involved in creating transition-metal-based nanozymes, including hydrothermal method, solvothermal method, chemical reduction method, biomimetic mineralization method, and sol-gel method. Subsequently, we elucidate the catalytic mechanisms (catalase (CAT)-like activities), peroxidase (POD)-like activities), oxidase (OXD)-like activities) and superoxide dismutase (SOD)-like activities) of transition-metal-based nanozymes along with their activity regulation strategies such as morphology control, size manipulation, modulation, composition adjustment and surface modification under environmental stimulation. Furthermore, we elaborate on the diverse applications of transition-metal-based nanozymes in anticancer therapies encompassing radiotherapy (RT), chemodynamic therapy (CDT), photodynamic therapy (PDT), photothermal therapy (PTT), sonodynamic therapy (SDT), immunotherapy, and synergistic therapy. Finally, the challenges faced by transition-metal-based nanozymes are discussed alongside future research directions. The purpose of this review is to offer scientific guidance that will enhance the clinical applications of nanozymes based on transition metals.

Multienzyme-Like Nanozymes: Regulation, Rational Design, and Application

Nanomaterials with more than one enzyme-like activity are termed multienzymic nanozymes, and they have received increasing attention in recent years and hold huge potential to be applied in diverse fields, especially for biosensing and therapeutics. Compared to single enzyme-like nanozymes, multienzymic nanozymes offer various unique advantages, including synergistic effects, cascaded reactions, and environmentally responsive selectivity. Nevertheless, along with these merits, the catalytic mechanism and rational design of multienzymic nanozymes are more complicated and elusive as compared to single-enzymic nanozymes. In this review, the multienzymic nanozymes classification scheme based on the numbers/types of activities, the internal and external factors regulating the multienzymatic activities, the rational design based on chemical, biomimetic, and computer-aided strategies, and recent progress in applications attributed to the advantages of multicatalytic activities are systematically discussed. Finally, current challenges and future perspectives regarding the development and application of multienzymatic nanozymes are suggested. This review aims to deepen the understanding and inspire the research in multienzymic nanozymes to a greater extent.

Engineering a hierarchically micro-/nanostructured Si@Au-based artificial enzyme with improved accessibility of active sites for enhanced catalysis

The active site accessibility and high loading of gold nanoparticles (AuNPs) are key factors affecting the catalytic activity of supported AuNP-based catalysts. However, the preparation of supported AuNP-based catalysts with highly accessible active sites still remains a challenge. Herein, sphere-on-sphere (SoS) silica microspheres with a hierarchical structure, good dispersion and high surface density of thiol groups (10 SH nm-2) are prepared and used as a platform for the growth of high-density AuNPs. The obtained hierarchical Si@Au micro-/nanostructure consisting of 0.55 μm SoS silica microspheres and 7.3 nm AuNPs (SoS-0.55@Au-7.3) is found to show excellent peroxidase-mimicking activity (Km = 0.033 mM and Vmax = 34.6 × 10-8 M s-1) with merits of high stability and good reusability. Furthermore, the as-obtained SoS-0.55@Au-7.3-based system can sensitively detect hydrogen peroxide (H2O2) with a low detection limit of 1.6 μM and a wide linear range from 2.5 μM to 1.0 mM. The high catalytic activity, excellent stability and good reusability of SoS-0.55@Au-7.3 imply its great prospects in biosensing and biomedical analysis.

Multi-Functional Applications of H-Glass Embedded with Stable Plasmonic Gold Nanoislands

Metal nanoparticles (MNPs) are synthesized using various techniques on diverse substrates that significantly impact their properties. However, among the substrate materials investigated, the major challenge is the stability of MNPs due to their poor adhesion to the substrate. Herein, it is demonstrated how a newly developed H-glass can concurrently stabilize plasmonic gold nanoislands (GNIs) and offer multifunctional applications. The GNIs on the H-glass are synthesized using a simple yet, robust thermal dewetting process. The H-glass embedded with GNIs demonstrates versatility in its applications, such as i) acting as a room temperature chemiresistive gas sensor (70% response for NO2 gas); ii) serving as substrates for surface-enhanced Raman spectroscopy for the identifications of Nile blue (dye) and picric acid (explosive) analytes down to nanomolar concentrations with enhancement factors of 4.8 × 106 and 6.1 × 105 , respectively; and iii) functioning as a nonlinear optical saturable absorber with a saturation intensity of 18.36 × 1015 W m-2 at 600 nm, and the performance characteristics are on par with those of materials reported in the existing literature. This work establishes a facile strategy to develop advanced materials by depositing metal nanoislands on glass for various functional applications.

Bioinspired hot-spot engineering strategy towards ultrasensitive SERS sandwich biosensor for bacterial detection

Surface-enhanced Raman spectroscopy (SERS) sandwich biosensors have received tremendous attention in early diagnosis of bacterial infections. However, efficiently engineering nanoscale plasmonic hots pots (HS) towards ultrasensitive SERS detection still remains challenging. Herein, we propose a bioinspired synergistic HS engineering strategy to construct ultrasensitive SERS sandwich bacterial sensor (named USSB), by coupling bioinspired signal module and plasmonic enrichment module to synergistically boost the number and intensity of HS. The bioinspired signal module is based on dendritic mesoporous silica nanocarrier (DMSN) loaded with plasmonic nanoparticles and SERS tag, while magnetic Fe3O4 nanoparticles coated with Au shell are employed in plasmonic enrichment module. We demonstrate that DMSN effectively shrank nanogaps between plasmonic nanoparticles to improve HS intensity. Meanwhile, plasmonic enrichment module contributed to plenty of additional HS inside and outside individual "sandwich". Ascribing to the boosted number and intensity of HS, the constructed USSB sensor exhibits ultrahigh detection sensitivity (7 CFU/mL) and selectivity towards model pathogenic bacteria of Staphylococcus aureus. Remarkably, the USSB sensor enables fast and accurate bacterial detection in real blood samples of septic mice, achieving early diagnosis of bacterial sepsis. The proposed bioinspired synergistic HS engineering strategy opens up a new direction for constructing ultrasensitive SERS sandwich biosensors, and may promote their advancing applications in the early diagnosis and prognosis of devastating diseases.

Platinum Palladium Bimetallic Nanozymes Stabilized with Vancomycin for the Sensitive Colorimetric Determination of L-cysteine

Many diseases in the human body are related to the level of L-cysteine. Therefore, it is crucial to establish an efficient, simple and sensitive platform for L-cysteine detection. In this work, we synthesized platinum palladium bimetallic nanoparticles (Van-Ptm/Pdn NPs) using vancomycin hydrochloride (Van) as a stabilizer, which exhibited high oxidase-like catalytic activity. In addition, the catalytic kinetics of the Van-Pt1/Pd1 NPs followed the typical Michaelis-Menten equation, exhibiting a strong affinity for 3,3',5,5'-tetramethylbenzidine substrates. More importantly, we developed a simple and effective strategy for the sensitive colorimetric detection of L-cysteine using biocompatible Van-Pt1/Pd1 NPs. The detection limit was low, at 0.07 μM, which was lower than the values for many previously reported enzyme-like detection systems. The colorimetric method of the L-cysteine assay had good selectivity. The established method for the detection of L-cysteine showed promise for biomedical analysis.

Thiol-Functionalized, Antioxidant, and Osteogenic Mesoporous Silica Nanoparticles for Osteoporosis

Osteoporosis is a chronic bone disorder characterized by decreased bone mass, leading to brittle bones and fractures. Oxidative stress has been identified as the most profound trigger for the initiation and progression of osteoporosis. Current treatment strategies do not induce new bone formation and fail to address a high level of reactive oxygen species (ROS). Mesoporous silica nanoparticles (MSNs) have been explored in bone tissue regeneration owing to their inherent osteogenic property, but they lack antioxidant and cell adhesion properties, required in such applications. We have developed thiolated, bioactive mesoporous silica nanoparticles (MSN-SH) to address this challenge. MSNs were fabricated using the Stöber method, and 11% of the surface was functionalized post-synthesis with thiol groups using MPTMS to obtain MSN-SH. The particle size measured by the dynamic light scattering technique was found to be around 300 nm. The surface morphology was investigated using HR-TEM, and their physical and chemical properties were characterized using various spectroscopic techniques. They exhibited more than 90% antioxidant activity, neutralized ROS formed in cells, and provided protection against ROS-induced cell damage. The cell viability assay in murine osteoblast precursor cells (MC3T3) showed that MSN-SH is cell-proliferative in nature with 140% cell viability. Osteogenic potential was evaluated by measuring the ALP activities, calcium deposition, and gene expression levels of osteogenic markers, such as RUNX2, ALP, OCN, and OPN, and results revealed that MSN-SH increases calcium deposition and induces osteogenesis through upregulation of osteogenic genes and markers without the involvement of any osteogenic supplements. Besides promoting osteogenesis, MSN-SH was found to inhibit osteoclastogenesis. The nanomaterial was found to be regenerative in nature, and it stimulated migration of osteoblast cells and caused a complete wound closure within 48 h. We were able to achieve a multifunctional nanomaterial by simply modifying the surface. MSNs have been explored for bone tissue engineering/osteoporosis as a composite system incorporating metals, like gold and cerium, or as a nanocarrier loaded with growth factors or active drugs. This study offers a simple and economical method to enhance the existing properties of MSNs and impart new activities by a single-step surface modification. It can be concluded that MSN-SH holds promise as a complementary and alternate treatment for osteoporosis along with the standardized therapy.

Application of Nanozymes in Environmental Monitoring, Management, and Protection

Nanozymes are nanomaterials with enzyme-like activity, possessing the unique properties of nanomaterials and natural enzyme-like catalytic functions. Nanozymes are catalytically active, stable, tunable, recyclable, and versatile. Therefore, increasing attention has been paid in the fields of environmental science and life sciences. In this review, we focused on the most recent applications of nanozymes for environmental monitoring, environmental management, and environmental protection. We firstly introduce the tuning catalytic activity of nanozymes according to some crucial factors such as size and shape, composition and doping, and surface coating. Then, the application of nanozymes in environmental fields are introduced in detail. Nanozymes can not only be used to detect inorganic ions, molecules, organics, and foodborne pathogenic bacteria but are also involved in the degradation of phenolic compounds, dyes, and antibiotics. The capability of nanozymes was also reported for assisting air purification, constructing biofuel cells, and application in marine antibacterial fouling removal. Finally, the current challenges and future trends of nanozymes toward environmental fields are proposed and discussed.

Dendrimer-Modified Silica Nanoparticles for Efficient Enrichment of Low-Concentration Peptides

Peptide profiling based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is of particular interest as it can provide physiologically and pathologically related information of the bio-samples. Due to the complexity of real biological samples, MALDI-TOF MS-based peptide mapping methods rely strongly on particular enrichment methods to improve the signal intensity. This paper introduces third-generation dendrimer-modified SBA-15 with the surface functionalization of amino and carboxyl group, respectively (denoted as SBA-15/G3-NH₂ and SBA-15/G3-COOH), for the efficient capture of low-abundance peptides. The enrichment ability of the nanocomposites was evaluated by standard peptides digests and real biological samples. The synthesized nanocomposites incorporated the benefit of dendrimers and mesoporous silica nanomaterial SBA-15, showing enhanced peptide enrichment ability. Therefore, this work may provide a new class of nanomaterials for peptide mapping from biological samples.

Nanoarchitectured prototypes of mesoporous silica nanoparticles for innovative biomedical applications

Despite exceptional morphological and physicochemical attributes, mesoporous silica nanoparticles (MSNs) are often employed as carriers or vectors. Moreover, these conventional MSNs often suffer from various limitations in biomedicine, such as reduced drug encapsulation efficacy, deprived compatibility, and poor degradability, resulting in poor therapeutic outcomes. To address these limitations, several modifications have been corroborated to fabricating hierarchically-engineered MSNs in terms of tuning the pore sizes, modifying the surfaces, and engineering of siliceous networks. Interestingly, the further advancements of engineered MSNs lead to the generation of highly complex and nature-mimicking structures, such as Janus-type, multi-podal, and flower-like architectures, as well as streamlined tadpole-like nanomotors. In this review, we present explicit discussions relevant to these advanced hierarchical architectures in different fields of biomedicine, including drug delivery, bioimaging, tissue engineering, and miscellaneous applications, such as photoluminescence, artificial enzymes, peptide enrichment, DNA detection, and biosensing, among others. Initially, we give a brief overview of diverse, innovative stimuli-responsive (pH, light, ultrasound, and thermos)- and targeted drug delivery strategies, along with discussions on recent advancements in cancer immune therapy and applicability of advanced MSNs in other ailments related to cardiac, vascular, and nervous systems, as well as diabetes. Then, we provide initiatives taken so far in clinical translation of various silica-based materials and their scope towards clinical translation. Finally, we summarize the review with interesting perspectives on lessons learned in exploring the biomedical applications of advanced MSNs and further requirements to be explored.

Precursor Heterogeneity Driven Mo-Te Nanoparticle Structural Diversification for Cancer Photo-Theranostics

Chemical reactions between homogeneous precursors are typically used to synthesize monodisperse nanoparticles with well-controlled size and morphology. It is difficult to predict the evolved nanostructures when using two heterogeneous precursors. In this study, three types of Mo-Te nanoparticles shaped like leaves, spindles, and rice grains (denoted respectively as nanoleaf, nanospindle, and nanorice) were obtained from dextrose-mediated proton-coupled electron transfer reaction between the solid polyoxomolybdate (POM) and the ionic tellurite anion as precursors. All produced nanoparticles had excellent optical absorption in the ultraviolet(UV)-visible(Vis)-near-infrared(NIR) regions, with only slight deviations among them. After confirming nanoparticles' photothermal conversion and photocatalytic activity at multiple wavelengths, the Mo-Te nanorice was tested as a potential agent for cancer treatment due to its minimum toxicity, excellent colloidal stability, and intrinsic anticancer effect. Excellent treatment efficacy and clearance were confirmed in vitro and in vivo. Due to their photoacoustic imaging capability, the injection of pristine nanoparticles could also realize phototheranostics without using additional drugs, probes, or photosensitizers.

Recent Advances in Synthetic and Natural Biomaterials-Based Therapy for Bone Defects

Synthetic and natural biomaterials are a promising alternative for the treatment of critical-sized bone defects. Several parameters such as their porosity, surface, and mechanical properties are extensively pointed out as key points to recapitulate the bone microenvironment. Many biomaterials with this pursuit are employed to provide a matrix, which can supply the specific environment and architecture for an adequate bone growth. Nevertheless, some queries remain unanswered. This review discusses the recent advances achieved by some synthetic and natural biomaterials to mimic the native structure of bone and the manufacturing technology applied to obtain biomaterial candidates. The focus of this review is placed in the recent advances in the development of biomaterial-based therapy for bone defects in different types of bone. In this context, this review gives an overview of the potentialities of synthetic and natural biomaterials: polyurethanes, polyesters, hyaluronic acid, collagen, titanium, and silica as successful candidates for the treatment of bone defects.

A pH-Responsive Persistent Luminescence Nanozyme for Selective Imaging and Killing of Helicobacter pylori and Common Resistant Bacteria

Helicobacter pylori (H. pylori) infection is implicated in the etiology of many diseases. H. pylori eradication by antibiotic therapy is limited by the extreme acidic environment in the stomach, the undesired side effect of intestinal commensal bacteria, and the development of drug resistance. Here, we report a pH-responsive persistent luminescence (PL) nanozyme (MSPLNP-Au-CB) for in vivo imaging and inactivation of H. pylori. This PL nanozyme is composed of mesoporous silica (MS)-coated persistent luminescence nanoparticles (MSPLNP), Au nanoparticles (AuNP), and chitosan-benzeneboronic acid (CB), taking advantage of the long PL of PLNP to realize autofluorescence-free imaging, the pH-activated oxidase- and peroxidase-like nanozyme activity of AuNP, and the bacterial binding capacity of CB. The MSPLNP-Au-CB nanozyme can resist the corrosion of gastric acid and exhibit pH-activated dual nanozyme activity to catalyze bactericidal reactive oxygen species generation. This multifunctional nanozyme enables targeted imaging and activated deactivation of H. pylori under extreme gastric acid conditions as well as methicillin-resistant Staphylococcus aureus in common slightly acidic environments, while it has no side effects on the commensal bacteria and normal cells in normal physiological environments. This work provides a promising PL nanozyme platform for bioimaging and therapy of bacterial infection under harsh conditions.

Dendritic Mesoporous Nanoparticles: Structure, Synthesis and Properties

Recently, a new family of "dendritic" mesoporous silica nanoparticles has attracted great interest with widespread applications. Despite a large number of publications (>800), the terminology of "dendritic" is ambiguous. Understanding what possible "dendritic structures" are, their formation mechanisms and the underlying structure-property relationship is fundamentally important. With the advance of characterization techniques such as electron tomography, two types of tree branch-like and flower-like structures can be distinguished, both described as "dendritic" in literature. In this review, we start with the definition of "dendritic", then provide critical analysis of reported dendritic silica nanoparticles according to their structural classification. We also update the understandings of the formation mechanisms of two types of "dendritic" nanoparticles, with a focus on how to control different structural parameters. Various applications of dendritic mesoporous nanoparticles are also reviewed with a focus in biomedical field, providing new insights into the structure-property relationship in this family of nanomaterials.

In situ reduction triggers the highly sensitive detection of pesticide by classic gold nanoparticle and quantum dots nanocomposite

Fluorescence "turn on" method is always preferable for target detection under the urgent demand to develop point-of-care portable sensors in practical applications due to its higher selectivity and less false positives. However, there is only few reports of pesticide monitoring based on this strategy so far most probably ascribed to its poor hydrophilicity and reactivity. In this work, triggered by reductant tris (2-carboxyethyl) phosphine hydrochloride (TCEP), initially fluorescence-quenched gold nanoparticles (Au NPs)-decorated quantum dots (QDs)-embedded nanobead shows obvious fluorescence "turn on" signal response to thiram with concentration response range of 0.01-20 μM and limit of detection (LOD) of 7 nM due to the target-induced dissociation of Au NPs from the surface of probe nanobead. Moreover, paper sensor has been successfully developed by immersing commercial drainage membrane in probe solution for visual detection of thiram with the ultrahigh LOD (50 nM) by the naked eye. More importantly, this work, for the first time, reported an in situ reduction strategy to improve the interaction between target and nanoprobe and thus bring obvious signal output for pesticide detection with high sensitivity, demonstrating the potential to expand the detection scope of nanomaterials.

Polythiolactone-Decorated Silica Particles: A Versatile Approach for Surface Functionalization, Catalysis and Encapsulation

The surface chemistry of colloidal silica has tremendous effects on its properties and applications. Commonly the design of silica particles is based on their de novo synthesis followed by surface functionalization leading to tailormade properties for a specific purpose. Here, the design of robust "precursor" polymer-decorated silica nano- and microparticles is demonstrated, which allows for easy post-modification by polymer embedded thiolactone chemistry. To obtain this organic-inorganic hybrid material, silica particles (SiO2 P) were functionalized via surface-initiated atom transfer radical polymerization (SI-ATRP) with poly(2-hydroxyethyl acrylate) (PHEA)-poly(thiolactone acrylamide (PThlAm) co-polymer brushes. Exploiting the versatility of thiolactone post-modification, a system was developed that could be used in three exemplary applications: 1) the straightforward molecular post-functionalization to tune the surface polarity, and therefore the dispersibility in various solvents; 2) the immobilization of metal nanoparticles into the polymer brushes via the in situ formation of free thiols that preserved catalytic activity in a model reaction; 3) the formation of redox-responsive, permeable polymer capsules by crosslinking the thiolactone moieties with cystamine dihydrochloride (CDH) followed by dissolution of the silica core.

Rational Design of Dendritic Mesoporous Silica Nanoparticles' Surface Chemistry for Quantum Dot Enrichment and an Ultrasensitive Lateral Flow Immunoassay

Lateral flow immunoassays (LFIAs) have drawn much attention in point-of-care diagnostic applications, and the development of high-performance label materials is the key. In this study, the impact of the surface chemistry of dendritic mesoporous silica nanoparticles (DMSNs) on their enrichment performance toward quantum dots (QDs) and signal amplification of the resultant DMSNs-QDs as label materials have been investigated. A series of DMSNs with controllable amino/thiol group densities have been synthesized. It is demonstrated that the amino groups are beneficial for QD fluorescence preservation, owing to the amino-based surface passivation, while the thiol groups are responsible for increasing the loading capacity of QDs due to the thiol-metal coordination. The optimized DMSNs-QDs labels with an amino density of 153 μmol g^-1 and a thiol density of 218 μmol g^-1 displayed sufficient QD fluorescence preservation (89.4%) and high QD loading capacity (1.55 g g^-1). Ultrasensitive detection of serum amyloid A (SAA) with a detection limit of 10 pg mL^-1 with the naked eye was achieved, which is 1 order of magnitude higher than that reported in the literature. This study provides insights into the development of advanced label materials and an ultrasensitive LFIA for future bioassay applications.

Enhancing hemocompatibility and the performance of Au@silica nanoparticles by coating with cRGD functionalized zein

Poor safety and effectiveness is an outstanding challenge in the preparation of drug delivery systems (DDS) for cancer treatment. The pursuit of the high curative effect will inevitably increase the risk of adverse side effects. Herein, a bio-safe DDS was constructed by combining the advantages of functional zein and Au doped mesoporous silica nanoparticles (Au@SiO₂) to achieve chemo-photothermal therapy. The cRGD functionalized zein (cRGD-Zein) was coated on the surface of Au@SiO₂ which effectively avoided premature leakage of paclitaxel and realized sustained drug release. Meanwhile, the high hemolysis rate (107%) of Au@SiO₂ had been significantly reduced to 4%. The anti-hemolysis mechanism of functionalized zein was explored to give a deeper understanding of the interaction between nanoparticles and RBCs. The results showed that the functional zein would change the protein conformation during the interaction with Au@SiO₂ to protect the RBCs from the damage of Au@SiO₂. And the release rate of hemoglobin was limited by the size of RBCs membrane cracks with approximately 40 nm in width and 470 nm in length. The cell cytotoxicity and uptake assays showed that the prepared DDS exhibited low tumour cell viability (35%) and enhanced uptake performance (99.3%). This work suggested that the prepared nanoparticles could serve as a promising carrier to achieve safe and efficacious tumour therapy.

Ratiometric fluorescence assay for L-Cysteine based on Fe-doped carbon dot nanozymes

In this work, a ratiometric fluorescence method based on nanozyme was fabricated to determine L-Cysteine. Taking silkworm feces as a carbon source, together with Fe³⁺, Fe-doped carbon dots (Fe-CDs) were synthesized through a hydrothermal method. Fe-CDs were able to oxidize the enzyme substrate o-phenylenediamine (OPD) to produce oxidized OPD (Ox-OPD) when H₂O₂ coexisted with them. Based on the fluorescence property of Fe-CDs and Ox-OPD, a dual-emission system was built. Since L-Cysteine contains reductive thiols that can inhibit the production of Ox-OPD, the addition of L-Cysteine caused a decrease in the fluorescence intensity of Ox-OPD. The results showed that the ratio of fluorescence intensities at 450 and 560 nm (I₄₅₀/I₅₆₀) varied linearly with the concentration of L-Cysteine in the range of 0.25-90 μM and the limit of detection is as low as 0.047 μM. Furthermore, using this ratiometric fluorescence system to determine L-Cysteine in serum and tap-water samples, average recoveries were evaluated to reach 98.75%-103.27% with the relative standard deviation of no more than 4.5%. Based on the fluorescence property and nanozyme-like activity, this work provides an inspiration to open a new horizon in using natural carbon source to synthesize CDs and for the application of CDs as a nanozyme.

A gold nanoparticle-intercalated mesoporous silica-based nanozyme for the selective colorimetric detection of dopamine

Highly dispersed aggregation-free gold nanoparticles intercalated into the walls of mesoporous silica (AuMS) were synthesized using thioether-functionalized silica as a nanozyme, which exhibited an excellent peroxidase mimic activity. The AuMS material was characterized via XRD, N₂ adsorption-desorption, FESEM, SEM-EDS particle mapping, TEM, and XPS. The peroxidase-like activity of the AuMS material was studied thoroughly, and the effect of pH and temperature was evaluated. The reproducibility of the peroxidase mimic activity and long-term stability of the AuMS catalyst were also studied. Furthermore, the AuMS catalyst was successfully utilized for the detection and quantification of dopamine, an important neurotransmitter, colorimetrically with a linear range of 10-80 μM and a limit of detection (LOD) value of 1.28 nM. The determination of dopamine concentration in commercially available dopamine hydrochloride injection showed high accuracy, good reproducibility, and high selectivity in the presence of uric acid, ascorbic acid, glucose, tryptophan, phenylalanine, and tyrosine.

Highly selective colorimetric determination of catechol based on the aggregation-induced oxidase–mimic activity decrease of δ-MnO2

A new determination mechanism for catechol: aggregation-induced oxidase-mimic activity decrease of δ-MnO₂.

Dendritic silica with carbon dots and gold nanoclusters for dual nanozymes

dSCS-Au NPs were established for dual nanozymes with dendritic silica spheres containing C-dots and Au NCs.