Coupling gold nanoparticles to silica nanoparticles through disulfide bonds for glutathione detection

Mesoporous silica-supported platinum nanocatalysts for colorimetric detection of glucose, cholesterol, and C-reactive protein

Noble metal nanoparticles decorated on a catalyst support with a large specific surface area can exhibit enhanced catalytic activity. To this end, a synthetic method to heterogeneously and evenly nucleate platinum nanoparticles (Pt NPs) onto mesoporous silica nanoparticles (MSNs) is developed. The obtained Pt NP-modified MSNs (Pt-MSNs) are characterized as a thin layer of 3 nm-sized Pt NPs densely assembled on the MSN surface, by which the throughput of the peroxidase-like activity of Pt-MSNs is greatly improved. The utility of Pt-MSNs in colorimetric detection of analytes is validated for two different assay schemes. Firstly, colloidally dispersed Pt-MSNs are employed as a peroxidase-mimic in a two-step cascade reaction to quantitate glucose/cholesterol based on the amount of H2O2 produced by glucose/cholesterol oxidase. Secondly, detection of C-reactive protein (CRP) is conducted on a solid substrate by adopting a sandwich immunoassay format. Detection limits are estimated to be 20 μM, 55 μM, and 3.9 pM for glucose, cholesterol, and CRP, respectively.

Fabrication and application of glutathione biosensing SPCE strips with gold nanoparticle modification

Glutathione (GSH) is a major antioxidant in organisms. An alteration in GSH concentration has been implicated in a number of pathological conditions. Therefore, GSH sensing has become a critical issue. In this study, a disposable strip used for tyrosinase-modified electrochemical testing was fabricated for the detection of GSH levels in vivo. The system is based on tyrosinase as a biorecognition element and a screen-printed carbon electrode (SPCE) as an amperometric transducer. On the tyrosinase-SPCE strips, the oxidation reaction from catechol to o-quinone was catalyzed by tyrosinase. The tyrosinase-SPCE strips were modified with gold nanoparticles (AuNPs). In the presence of AuNPs of 25 nm diameter, the cathodic peak current of cyclic voltammetry (CV) was significantly enhanced by 5.2 fold. Under optimized conditions (250 μM catechol, 50 mM phosphate buffer, and pH 6.5), the linear response of the tyrosinase-SPCE strips ranged from 31.25 to 500 μM GSH, with a detection limit of approximately 35 μM (S/N > 3). The tyrosinase-SPCE strips have been used to detect real samples of plasma and tissue homogenates in a mouse experiment. The mice were orally administrated with N-acetylcysteine (NAC) 100 mg kg-1 once a day for 7 days; the plasma GSH significantly enhanced 2.8 fold as compared with saline-treated mice (1123 vs. 480 μM μg-1 protein). NAC administration also could alleviate the adverse effect of GSH reduction in the mice treated with doxorubicin.

A smartphone-based fluorospectrophotometer and ratiometric fluorescence nanoprobe for on-site quantitation of pesticide residue

Cost-effective and user-friendly quantitation at points-of-need plays an important role in food safety inspection, environmental monitoring, and biomedical analysis. This study reports a stand-alone smartphone-based fluorospectrophotometer (the SBS) installed with a custom-designed application (the SBS-App) for on-site quantitation of pesticide using a ratiometric sensing scheme. The SBS can collect fluorescence emission spectra in the wavelength range of 380-760 nm within 5 s. A ratiometric fluorescence probe is facilely prepared by directly mixing the blue-emissive carbon nanodots (the Fe3+-specific fluorometric indicator) and red-emissive quantum dots (the internal standard) at a ratio of 11.6 (w/w). Based on the acetylcholinesterase/choline oxidase dual enzyme-mediated cascade catalytic reactions of Fe2+/Fe3+ transformation, a ratiometric fluorescence sensing scheme is developed. The practicability of the SBS is validated by on-site quantitation of chlorpyrifos in apple and cabbage with a comparable accuracy to the GC-MS method, offering a scalable solution to establish a cost-effective surveillance system for pesticide pollution.

Targeted Delivery of Sunitinib by MUC-1 Aptamer-Capped Magnetic Mesoporous Silica Nanoparticles

Magnetic mesoporous silica nanoparticles (MMSNPs) are being widely investigated as multifunctional novel drug delivery systems (DDSs) and play an important role in targeted therapy. Here, magnetic cores were synthesized using the thermal decomposition method. Further, to improve the biocompatibility and pharmacokinetic behavior, mesoporous silica was synthesized using the sol-gel process to coat the magnetic cores. Subsequently, sunitinib (SUN) was loaded into the MMSNPs, and the particles were armed with amine-modified mucin 1 (MUC-1) aptamers. The MMSNPs were characterized using FT-IR, TEM, SEM, electrophoresis gel, DLS, and EDX. MTT assay, flow cytometry analysis, ROS assessment, and mitochondrial membrane potential analysis evaluated the nanoparticles' biological impacts. The physicochemical analysis revealed that the engineered MMSNPs have a smooth surface and spherical shape with an average size of 97.6 nm. The biological in vitro analysis confirmed the highest impacts of the targeted MMSNPs in MUC-1 overexpressing cells (OVCAR-3) compared to the MUC-1 negative MDA-MB-231 cells. In conclusion, the synthesized MMSNP-SUN-MUC-1 nanosystem serves as a unique multifunctional targeted delivery system to combat the MUC-1 overexpressing ovarian cancer cells.

Immobilization of Glucose Oxidase on Glutathione Capped CdTe Quantum Dots for Bioenergy Generation

An efficient immobilization of Glucose oxidase (GOx) on an appropriate substrate is one of the main challenges of developing fuel cells that allow energy to be obtained from renewable substrates such as carbohydrates in physiological environments. The research importance of biofuel cells relies on their experimental robustness and high compatibility with biological organisms such as tissues or the bloodstream with the aim of obtaining electrical energy even from living systems. In this work, we report the use of 5,10,15,20 tetrakis (1-methyl-4-pyridinium) porphyrin and glutathione capped CdTe Quantum dots (GSH-CdTeQD) as a support matrix for the immobilization of GOx on carbon surfaces. Fluorescent GSH-CdTeQD particles were synthesized and their characterization by UV-Vis spectrophotometry showed a particle size between 5–7 nm, which was confirmed by DLS and TEM measurements. Graphite and Toray paper electrodes were modified by a drop coating of porphyrin, GSH-CdTeQD and GOx, and their electrochemical activity toward glucose oxidation was evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Additionally, GOx modified electrode activity was explored by scanning electrochemical microscopy, finding that near to 70% of the surface was covered with active enzyme. The modified electrodes showed a glucose sensitivity of 0.58 ± 0.01 μA/mM and an apparent Michaelis constant of 7.8 mM. The addition of BSA blocking protein maintained the current response of common interferent molecules such as ascorbic acid (AA) with less than a 5% of interference percentage. Finally, the complex electrodes were employed as anodes in a microfluidic biofuel cell (μBFC) in order to evaluate the performance in energy production. The enzymatic anodes used in the μBFC allowed us to obtain a current density of 7.53 mAcm−2 at the maximum power density of 2.30 mWcm−2; an open circuit potential of 0.57 V was observed in the biofuel cell. The results obtained suggest that the support matrix porphyrin and GSH-CdTeQD is appropriate to immobilize GOx while preserving the enzyme’s catalytic activity. The reported electrode arrangement is a viable option for bioenergy production and/or glucose quantification.

Carbon Quantum Dots from Amino Acids Revisited: Survey of Renewable Precursors toward High Quantum-Yield Blue and Green Fluorescence

Carbon quantum dots (CQDs) were synthesized via a green, one-step hydrothermal method. As CQD precursors, nine amino acids of different structural descriptors (negatively/positively charged in water, polar, hydrophobic, sulfur-containing, and other/complex ones) were surveyed: Asp, Cys, Gly, His, Leu, Lys, Phe, Pro, and Ser. The reactions were performed in an autoclave in the presence of citric acid at 180 °C for 24 h and yielded core-shell CQDs. CQDs were comprehensively characterized by transmission electron microscopy, dynamic light scattering, Raman, UV/Vis, infrared, X-ray photoelectron spectroscopy, and fluorescence spectroscopy. At the excitation wavelength of λ_ex = 350 nm, Cys-, Phe-, Leu-, and Lys-based CQDs displayed the highest quantum yield blue fluorescence-90 ± 5, 90 ± 4, 87 ± 5, and 67 ± 3%, respectively-superior to the conventional fluorescent dyes. Strikingly, for Lys- and Phe-CQDs, dissimilar trends in the excitation-emission wavelength relationships were identified, that is, constantly strong red shifts versus excitation wavelength-independent emission. Cys- and Lys-CQDs were water-dispersible toward the narrow unimodal distribution of hydrodynamic diameters-0.6 and 2.5 nm, respectively. Additionally, Lys- and Cys-CQDs, with high absolute zeta potential values, formed stable aqueous colloids in a broad range of pH (2, 7, and 12). The results constitute important premises for water-based applications of CQDs, such as bioimaging or photocatalysis.

Mitigation Effects and Associated Mechanisms of Environmentally Relevant Thiols on the Phytotoxicity of Molybdenum Disulfide Nanosheets

Thorough investigations of the environmental fate and risks are necessary for the safe application of engineered nanomaterials. Nevertheless, the current understanding of potential transformations of MoS₂ (an intensively studied two-dimensional nanosheet) upon interactions with ubiquitous environmentally relevant thiols (ERTs) in water is limited. This study revealed that two ERTs, l-cysteine and mercaptoacetic acid, could modify MoS₂ by covalently grafting thiol groups on S atoms of 1T phases, improving the colloidal persistence and chemical stability of MoS₂. Compared with the pristine form, MoS₂-thiols with higher dispersity exhibited significantly mitigated envelopment and ultrastructural damage to microalgae. MoS₂-triggered growth inhibition, upregulation of reactive oxygen species, photosynthetic injury, and metabolic perturbation in algae were remarkably attenuated by ERTs. The diminished capability for MoS₂ to generate reactive intermediates and glutathione oxidation driven by ERTs caused the weakness of oxidative stress and negative effects. Additionally, molecular dynamics simulations demonstrated that ERTs altered the extent of the influence of MoS₂ on the secondary structures and functions of adsorbed intracellular proteins, which also contributed to the lower phytotoxicity of MoS₂. Our findings provide evidence for the crucial role of specific organic ligands in the risk of MoS₂ in aquatic environments.

Ratiometric Fluorescent Biosensor Based on Forster Resonance Energy Transfer between Carbon Dots and Acridine Orange for miRNA Analysis

The expression level of miRNA is highly correlated with the pathological process of malignant tumors. Therefore, the abnormal expression of miRNA in serum is considered as reliable evidence for the existence of tumor cells. Here, a ratiometric fluorescent biosensor based on the Forster resonance energy transfer between fluorophores is proposed for detecting colorectal cancer-specific miRNA (miR-92a-3p). The miRNA in serum was first isolated by carboxyl-modified SiO2 microspheres. Then, the addition of miRNA to the detection system resulted in the distance change between the donor acridine orange (AO) and the acceptor fluorescent carbon dots (CDs), which made the fluorescence signal change. The physicochemical properties, especially the fluorescence characteristics of CDs and AO, which enabled the ratiometric fluorescence detection, were comprehensively studied. The ratiometric fluorescent biosensor could detect miRNA in the concentration range of 1-9 nM and showed a detection limit of 0.14 nM. Moreover, the ratiometric fluorescent biosensor exhibited high selectivity for the target miRNA. The validity of the ratiometric fluorescent biosensor was also verified using the serum sample, demonstrating its potential for enzyme-free miRNA analysis.

Development of gold nanoparticles-aptamer nanocomposite for multiplexed analysis of antibiotics and design of molecular logic gates

The widespread use of antibiotics caused severe problems of antibiotic residues in foodstuffs and water, posing a serious threat to public health and thus urging the development of sensitive, selective, and rapid detection methods for antibiotics. In this study, a fluorescence resonance energy transfer (FRET)-based system is developed for the multiplexed analysis of chloramphenicol (CAP) and streptomycin (Strep) with detection limits of 2.51 and 8.69μg l^-1, respectively. The FRET-based system consists of Cy3-tagged anti-CAP aptamer-conjugated gold nanoparticles (AuNPs) (referred to as AuNPs-AptCAP) and Cy5-tagged anti-Strep aptamer-conjugated AuNPs (referred to as AuNPs-AptStrep). In addition, AuNPs-AptCAP and AuNPs-AptStrep have been demonstrated to serve as signal transducers for implementing a series of logic operations such as YES, NOT, INH, OR, (2-4)-Decoder and even more complicated multi-level logic gates (OR-INH). Based on the outputs of logic operations, it could be figured out whether targeted analytes were present or not, thus enabling multiplex sensing and evaluation of pollution status. This proof of concept study might provide a new route for the enhanced sensing performance to distinguish different pollution status as well as the design of molecular mimics of logic elements to demonstrate better applicability.

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.

Synthesis of fluorescent nanoprobe with simultaneous response to intracellular pH and Zn2+ for tumor cell distinguishment

A novel dual-functional nanoprobe was designed and synthesized by facile assembly of quinoline derivative (PEIQ) and meso-tetra (4-carboxyphenyl) porphine (TCPP) via electrostatic interaction for simultaneous sensing of fluorescence of Zn²⁺ and pH. Under the single-wavelength excitation at 400 nm, this nanoprobe not only exhibits "OFF-ON" green fluorescence at 512 nm by specific PEIQ-Zn²⁺ chelation, but also presents red fluorescence enhancement at 654 nm by H⁺-triggered TCPP release. The nanoprobe demonstrated excellent sensing performance with a good linear range (Zn²⁺, 1-40 μM; pH, 5.0-8.0), low detection limit (Zn²⁺, 0.88 μM), and simultaneous response towards Zn²⁺ and pH in pure aqueous solution within 2 min. More importantly, this dual-functional nanoprobe demonstrates the capability of discerning cancerous cells from normal cells, as evidenced by the fact that cancerous HepG2 cells in tumor microenvironment exhibit substantially higher red fluorescence and significantly lower green fluorescence than normal HL-7702 cells. The simultaneous, real-time fluorescence imaging of multiple analytes in a living system could be significant for cell analysis and tracking, cancer diagnosis, and even fluorescence-guided surgery of tumors.

"Plug and Play" logic gate construction based on chemically triggered fluorescence switching of gold nanoparticles conjugated with Cy3-tagged aptamer

Gold nanoparticles (AuNPs) conjugated with Cy3-tagged aptamer which can specifically recognize chloramphenicol (CAP) (referred to as AuNPs-AptCAP) are described. CAP can trigger the configuration change of CAP binding aptamer, and thus switching the fluorescence of AuNPs-AptCAP through changing the efficiency of the fluorescence resonance energy transfer (FRET) system with Cy3 as donors and AuNPs as recipients. AuNPs-AptCAP exhibits a linear range of CAP concentrations from 26.0 to 277 μg L^-1 with a limit of detection of 8.1 μg L^-1 when Cy3 was excited at 530 nm and emission was measured at 570 nm. More importantly, AuNPs-AptCAP can be utilized as signal transducers for the build-up of a series of logic gates including YES, PASS 0, INH, NOT, PASS 1, and NAND. Utilizing the principle of a metal ion-mediated fluorescence switch together with a strong metal ion chelator, the fluorescence of AuNPs-AptCAP could be modulated by adding metal ions and EDTA sequentially. Therefore, a "Plug and Play" logic system based on AuNPs-AptCAP has been realized by simply adding other components to create new logic functions. This work highlights the advantages of simple synthesis and facile fluorescence switching properties, which will provide useful knowledge for the establishment of molecular logic systems. Graphical abstract.

Plasmon-Emitter Hybrid Nanostructures of Gold Nanorod-Quantum Dots with Regulated Energy Transfer as a Universal Nano-Sensor for One-step Biomarker Detection

Recently, biosensing based on weak coupling in plasmon-emitter hybrid nanostructures exhibits the merits of simplicity and high sensitivity, and attracts increasing attention as an emerging nano-sensor. In this study, we propose an innovative plasmon-regulated fluorescence resonance energy transfer (plasmon-regulated FRET) sensing strategy based on a plasmon-emitter hybrid nanostructure of gold nanorod-quantum dots (Au NR-QDs) by partially modifying QDs onto the surfaces of Au NRs. The Au NR-QDs showed good sensitivity and reversibility against refractive index change. We successfully employed the Au NR-QDs to fabricate nano-sensors for detecting a cancer biomarker of alpha fetoprotein with a limit of detection of 0.30 ng/mL, which displays that the sensitivity of the Au NR-QDs nano-sensor was effectively improved compared with the Au NRs based plasmonic sensing. Additionally, to demonstrate the universality of the plasmon-regulated FRET sensing strategy, another plasmon-emitter hybrid nano-sensor of Au nano-prism-quantum dots (Au NP-QDs) were constructed and applied for detecting a myocardial infarction biomarker of cardiac troponin I. It was first reported that the change of absorption spectra of plasmonic structure in a plasmon-emitter hybrid nanostructure was employed for analytes detection. The plasmon-regulated FRET sensing strategy described herein has potential utility to develop general sensing platforms for chemical and biological analysis.

Magnetic resonance energy transfer for in vivo glutathione susceptibility weighted imaging

Glutathione (GSH) plays a vital role in maintaining biological redox homeostasis. Accordingly, accurate imaging of glutathione in vivo is of great significance. Herein, we propose a magnetic resonance energy transfer (MRET) strategy based on a distance-dependent magnetic exchange coupling effect (MECE), which can realize GSH detection within tumors in vivo by susceptibility weighted imaging (SWI). Fe₃O₄ nanoparticles (NPs) and CoFe₂O₄ NPs linked with cystamine (Fe₃O₄-S-S-CoFe₂O₄) have been successfully designed as SWI nanoprobes. After the disulfide bonds are broken by excess GSH in the tumor, the increase in the distance between Fe₃O₄ NPs and CoFe₂O₄ NPs will induce a decrease of MECE and magnetic susceptibility. As a result, the changes in the SWI signals are used for tumor GSH detection in vivo. Experimental results in vitro and in vivo demonstrate that the Fe₃O₄-S-S-CoFe₂O₄ SWI nanoprobe can sensitively detect concentrations of GSH in tumors. Hence, this strategy not only improves the sensitivity of the GSH response in SWI but also provides a powerful basis for the design of other responsive functional MRI nanoprobes.

A Janus upconverting nanoplatform with biodegradability for glutathione depletion, near-infrared light induced photodynamic therapy and accelerated excretion

The major limitations of photodynamic therapy (PDT) are the poor tissue penetration of excitation light and the neutralization of reactive oxygen species (ROS) generated by overexpressed glutathione (GSH) in cancer cells.

Disulfide bond-based self-crosslinked carbon-dots for turn-on fluorescence imaging of GSH in living cells

A self-quenched nanoprobe built on a disulfide bond-based crosslink of carbon-dots has been constructed for intracellular GSH sensing.

Label-Free Optical Biochemical Sensors via Liquid-Cladding-Induced Modulation of Waveguide Modes

We demonstrated modulation of the waveguide mode mismatch via liquid cladding of the controllable refractive index for label-free quantitative detection of concentration of chemical or biological substances. A multimode optical fiber with its core exposed was used as the sensor head with the suitable chemical modification of its surface. Injected analyte liquid itself formed the liquid cladding for the waveguide. We found that modulation of the concentration of analyte injected enables a degree of the waveguide mode mismatch to be controlled, resulting in sensitive change in optical power transmission, which was utilized for its real-time quantitative assay. We applied the device to quantitating concentration of glycerol and bovine serum albumin (BSA) solutions. We obtained experimentally the limit of detection (LOD) of glycerol concentration, 0.001% (volume ratio), corresponding to the resolvable index resolution of ∼1.02 × 10^-6 RIU (refractive index unit). The presented sensors also exhibited reasonably good reproducibility. In BSA detection, the sensor device response was sensitive to change in the refractive indices not only of liquid bulk but also of layers just above the sensing surface with higher sensitivity, providing the LOD experimentally as ∼3.7 ng/mL (mass coverage of ∼30 pg/mm²). A theoretical model was also presented to invoke both mode mismatch modulation and evanescent field absorption for understanding of the transmission change, offering a theoretical background for designing the sensor head structure for a given analyte. Interestingly, the device sensing length played little role in the important sensor characteristics such as sensitivity, unlike most of the waveguide-based sensors. This unraveled the possibility of realizing a highly simple structured label-free sensor for point-of-care testing in a real-time manner via an optical waveguide with liquid cladding. This required neither metal nor dielectric coating but still produced sensitivity comparable to those of other types of label-free sensors such as plasmonic fiber ones.

Tumor Acidic Microenvironment Targeted Drug Delivery Based on pHLIP-Modified Mesoporous Organosilica Nanoparticles

Enhancing the tumor-targeting delivery of chemotherapeutic drugs is important yet challenging for improving therapeutic efficacy and reducing the side effects. Here, we first construct a drug delivery system for targeting tumor acidic microenvironment by modification of pH (low) insertion peptide (pHLIP) on mesoporous organosilica nanoparticles (MONs). The MONs has thioether-bridged framework, uniform diameter (60 nm), good biocompatibility, and high doxorubicin (DOX) loading capacity (334 mg/g). The DOX loaded in the pHLIP modified MONs can be released responsive to glutathione and low pH circumstance, ensuring the chemotherapeutic drug exerts higher cytotoxic effects to cancer cells than normal cells because of high intracellular GSH of tumor cells and low pH of tumor microenvironment. Moreover, the engineered MONs exhibit higher cellular uptake in pH 6.5 medium by MDA-MB-231 and MCF-7 cells than the particles decorated with polyethylene glycol (PEG). Importantly, the pHLIP-mosaic MONs with DOX displays better cytotoxic effects against the breast cancer cells in pH 6.5 medium than pH 7.4 medium. The in vivo experiments demonstrate that the pHLIP modified MONs are accumulated in the orthotopic breast cancer via targeting to acidic tumor microenvironment while no serious pathogenic effects was observed. After loading DOX, the pHLIP-modified MONs display better therapeutic effects than the control groups on the growth of MCF-7 breast cancers, showing promise for enhancing chemotherapy.

Portable aptamer biosensor of platelet-derived growth factor-BB using a personal glucose meter with triply amplified

Sensitive and rapid detection of platelet-derived growth factor BB (PDGF-BB), a cancer-related protein, could help early diagnosis, treatment, and prognosis of cancers. Although some methods have been developed to detect PDGF-BB, few can provide quantitative results using an affordable and portable device that is suitable for home use or field application. In this work, we report the first use of a portable kind of personal glucose meter (PGM) combining a catalytic and molecular beacon (CAMB) system with a cation exchange reaction (CX reaction) for ultrasensitive PDGF-BB assay. It realized the amplification of the detection in three ways, including greater aptamer payload on nanoparticles, CX reaction releasing thousands of Zn²⁺ and the cycle by the catalyzing cleavage of 8-17 DNAzyme. In the process, with the addition of PDGF-BB into the aptasensor, the specific recognition between aptamer and protein was initiated resulting in the combination of ZnS NNC for further CX reaction to release thousands of Zn²⁺, which could cleave the substrate DNA in the CAMB system realizing multiple cycle. The cleaved DNA fragment was designed with invertase-labeled could convert sucrose into glucose which could be detected and quantified by PGM accompanying with the change of color of the control window from yellow to green. The enhanced signal of the PGM has a relationship with the concentration of PDGF-BB in the range of 3.16×10^-16M to 3.16×10^-12M, and the detection limit is 0.11fM. Moreover, the catalytic and cleavage activities of 8-17 DNAzyme can be achieved in solution; thus, no enzyme immobilization is needed for detection. The triply amplified strategy showed high selectivity, stability, and applicability for detecting the desired protein.

A MnO2 nanosheet-assisted GSH detection platform using an iridium(iii) complex as a switch-on luminescent probe

A rapid and sensitive detection platform for GSH has been constructed by combining a MnO₂ nanosheet with a luminescent iridium(iii) complex [Ir(Cl-phq)₂(Cl-phen)]⁺. The MnO₂ nanosheet was prepared by using a facile one-step approach and was characterized by TEM. The luminescence intensity of the detection platform responded linearly with the GSH concentration from 1 to 200 μM (R² = 0.9951), and the detection limit for GSH was 0.13 μM. More importantly, practical application of the detection platform for visualizing the intracellular GSH distribution in living zebrafish has also been demonstrated.

Gold Nanoprobe-Enabled Three-Dimensional Ozone Imaging by Optical Coherence Tomography

Ozone (O₃) would be harmful to human skin for its strong oxidizing property, especially when stratum corneum or corneal epithelium is wounded. Imaging the penetration and distribution of ozone at depth is beneficial for studying the influence of ozone on skin or eyes. Here, we introduced a facile method for three-dimensional (3D) imaging of the penetration of O₃ into the anterior chamber of an isolated crucian carp eye by using optical coherence tomography (OCT) combined with gold triangular nanoprisms (GTNPs) as the contrast agent and molecular probe. We illustrated the specific response of GTNPs to ozone and demonstrated that GTNPs can function as an efficient nanoprobe for sensing O₃. The stabilities of GTNPs in different biologic solutions, as well as the signal intensity of GTNPs on an OCT imaging system, were investigated. Visualization of 3D penetration and distribution of O₃ in the biologic tissue was proved for the first time. The quantitative analysis of O₃ diffusion in the anterior chamber of the fish eye revealed a penetration depth of 311 μm within 172 min. Due to the strong scattering, near-infrared extinction band, and easy functionalization of GTNPs, they could further serve as nanoprobes for 3D OCT or multimodal imaging of other molecules or ions in the future.

CoP Nanoparticles in Situ Grown in Three-Dimensional Hierarchical Nanoporous Carbons as Superior Electrocatalysts for Hydrogen Evolution

The development of efficient and low-cost hydrogen evolution reaction (HER) catalysts is critical for storing energy in hydrogen via water splitting but still presents great challenges. Herein, we report synthesis of three-dimensional (3-D) hierarchical nanoporous carbon (HNC) supported transition metal phosphides (TMPs) for the first time by in situ growth of CoP nanoparticles (NPs) in CaCO3 NP-templated Cinnamomum platyphyllum leaf extract-derived carbon. They were subsequently employed as a HER catalyst, showing an onset potential of 7 mV and an overpotential of 95.8 mV to achieve 10 mA cm(-2), a Tafel plot of 33 mV dec(-1), and an exchange current density of 0.1182 mA cm(-2), of which the onset overpotential and the Tafel plot are the lowest reported for non-noble-metal HER catalysts, and the overpotential to achieve 10 mA cm(-2) and the exchange current density also compare favorably to most reported HER catalysts. In addition, this catalyst exhibits excellent durability with negligible loss in current density after 2000 CV cycles ranging from +0.01 to -0.17 V vs RHE at a scan rate of 100 mV s(-1) or 22 h of chronoamperometric measurement at an overpotential of 96 mV and a high Faraday efficiency of close to 100%. This work not only creates a novel high-performance non-noble-metal HER electrocatalyst and demonstrates the great advantages of the in situ grown 3-D HNC supported TMP NPs for the electrocatalysis of HER but also offers scientific insight into the mechanism for the in situ growth of TMP and their precursor NPs, in which an ultralow reactant concentration and rich functional groups on the 3-D HNC support play critical roles.

Disulfide-bridged cleavable PEGylation in polymeric nanomedicine for controlled therapeutic delivery

PEGylation in polymeric nanomedicine has gained substantial predominance in biomedical applications due to its resistance to protein absorption, which is critically important for a therapeutic delivery system in blood circulation. The shielding layer of PEGylation, however, creates significant steric hindrance that negatively impacts cellular uptake and intracellular distribution at the target site. This unexpected effect compromises the biological efficacy of the encapsulated payload. To address this issue, one of the key strategies is to tether the disulfide bond to PEG for constructing a disulfide-bridged cleavable PEGylation. The reversible disulfide bond can be cleaved to enable selective PEG detachment. This article provides an overview on the strategy, method and progress of PEGylation nanosystem with the cleavable disulfide bond.

Epidermal growth factor loaded heparin-based hydrogel sheet for skin wound healing

A heparin-based hydrogel sheet composed of thiolated heparin and diacrylated poly (ethylene glycol) was prepared via photo polymerization and human epidermal growth factor (hEGF) were loaded into it for the purpose of wound healing. It showed a sustained release profile of hEGF in vitro. In order to evaluate its function on wound healing in vivo, full thickness wounds were created on the dorsal surface of mice. Application of hEGF loaded heparin-based hydrogel sheet accelerated the wound closure compared to the non-treated control group, hEGF solution, and hEGF loaded PEG hydrogel sheet. Histological and immunohistological examinations also demonstrated an advanced granulation tissue formation, capillary formation, and epithelialization in wounds treated by hEGF loaded heparin-based hydrogel compared to other groups, and no biocompatibility issue was observed. In conclusion, the delivery of hEGF using the heparin-based hydrogel could accelerate the skin wound healing process.

Electrochemiluminescent Sensing for Caspase-3 Activity Based on Ru(bpy)3(2+)-Doped Silica Nanoprobe

Caspase-3 is one of the most frequently activated cysteine proteases during the apoptosis process and has been identified as a well-established cellular marker of apoptosis. In this study, a novel approach for the sensitive determination of caspase-3 activity was proposed using electrochemiluminescence (ECL) of Ru(bpy)3(2+)-doped silica (Ru@SiO2) with tripropylamine (TPA) as coreactant. A nanocomposite containing gold nanoparticles (AuNPs), poly(dimethyldiallyl ammonium chloride) (PDDA), and multiwalled carbon nanotubes (CNTs) was fabricated as an ECL platform. The biotinylated DEVD-peptide (biotin-Gly-Asp-Gly-Asp-Glu-Val-Asp-Gly-Cys) was immobilized on the nanocomposite surface via the strong bonding interaction between AuNPs and the thiol group. Then the streptavidin-modified Ru(bpy)3(2+)-doped silica (Ru@SiO2-SA) was immobilized on the ECL platform via the specific interaction between biotin and streptavidin to generate ECL signal. Caspase-3 can specifically recognize and cleave the N-terminus of DEVD, leading to the loss of the biotin label and the decrease of ECL intensity to determine the activity of caspase-3. The results revealed a new ECL avenue for the sensitive and specific monitor of caspase-3, and the platform could be utilized to evaluate anticancer drugs.

Redox-responsive controlled DNA transfection and gene silencing based on polymer-conjugated magnetic nanoparticles

Gene or DNA transfection is a non-viral tool for therapy on gene-based diseases by delivering nucleic acids into the target cells and change gene functions or protein expressions.

A dual-mode colorimetric and fluorometric “light on” sensor for thiocyanate based on fluorescent carbon dots and unmodified gold nanoparticles

A novel, highly sensitive and selective dual-readout (colorimetric and fluorometric) sensor based on fluorescent carbon dots (CDs) and unmodified gold nanoparticles (AuNPs) for the detection of thiocyanate (SCN⁻) was proposed.

A novel dual-emission ratiometric fluorescent nanoprobe for sensing and intracellular imaging of Zn2+

The integration of unique characteristics of nanomaterials with highly specific recognition elements, such as biomolecules and organic molecules, are the foundation of many novel nanoprobes for bio/chemical sensing and imaging. In the present report, branched polyethylenimine (PEI) was grafted with 8-chloroacetyl-aminoquinoline to synthesize a water-soluble and biocompatible quinoline-based Zn(2+) probe PEIQ. Then the PEIQ was covalently conjugated to [Ru(bpy)3](2+)-encapsulated SiNPs to obtain the ratiometric fluorescence nanoprobe which exhibits a strong fluorescence emission at 600 nm and a negligible fluorescence emission at 500 nm in the absence of Zn(2+) upon a single wavelength excitation. After the addition of different amounts of Zn(2+), the fluorescence intensity at 500 nm increased continuously while the fluorescence intensity at 600 nm remained stable, thus changing the dual emission intensity ratios and displaying continuous color changes from red to green which can be clearly observed by the naked eye. The nanoprobe exhibits good water dispersivity, biocompatibility and cell permeability, high selectivity over competing metal ions, and high sensitivity with a detection limit as low as 0.5 μM. Real-time imaging of Zn(2+) in A549 cells has also been realized using this novel nanoprobe.