FITC Doped Rattle-Type Silica Colloidal Particle-Based Ratiometric Fluorescent Sensor for Biosensing and Imaging of Superoxide Anion

Surface-Induced Conformational Changes of α-Synuclein on Silica Nanoparticles of Varying Sizes Corresponding to Protein Structural Domains: Insights from Enhanced Sampling MD Simulations

Protein-nanoparticle interactions are crucial in a diverse array of biotechnology and biomedical applications. Variations in nanoparticle sizes can adjust surface interactions with proteins and biomolecules, thereby influencing their conformation and functionality. To achieve precise control over the nanoparticle sizes corresponding to the dimensions of protein structural domains (∼nm) and establish the relationship between nanoparticle curvature and protein conformational changes, we conduct well-tempered metadynamics simulations to explore the secondary structure changes and thermodynamic characteristics of α-synuclein (αS), an intrinsically disordered protein (IDP), adsorbed onto silicon dioxide (SiO2) nanoparticles of varying sizes (diameter, d = 0.5-2.5 nm). The analysis of αS's conformational landscapes and structural probabilities reveals that intermediate-sized SiO2 nanoparticles (d = 1.2-1.4 nm) effectively stabilize the native intrinsically disordered conformations of αS (with domain sizes of 1-2 nm). In contrast, excessively large or small SiO2 nanoparticles significantly enhance the likelihood of forming intramolecular β-sheet domains within αS chains, a process that is critical for subsequent aggregation of αS. This study is of significance to the development of nanoparticles that stabilize desired protein conformations, which may pave the way for in vivo penetration and distribution of nanoparticles as well as biomedicine therapeutic interventions aimed at targeting αS aggregation.

Design of magnetic polyethyleneimine-fluorescein isothiocyanate composites toward efficient enrichment of phosphopeptides

Phosphoproteins maintain the normal metabolic activity of the organisms. Direct phosphopeptides detection is difficult to be realized by mass spectroscopy (MS) due to the low ionization efficiency, low abundance of phosphopeptides and interferences of complicated biological fluids. In the present work, a magnetic composite material was prepared by combining polyethyleneimine (PEI) and fluorescein isothiocyanate (FITC) focusing on phosphopeptides enrichment. Fourier-transform infrared spectroscopy, thermogravimetry analysis, X-ray photoemission spectroscopy, X-ray diffraction and UV-vis spectrometry measurement results confirmed the successful synthesis of Fe3O4@PEI@FITC material. FITC was facilely connected with PEI, and the two motifs endowed the efficient enrichment capacity of phosphopeptides by simple regulation of pH. The Fe3O4@PEI@FITC material was applied to the detection of phosphopeptides from real samples, implying that it can serve as an applicable platform for phosphoproteomics analysis.

Cancer Cell-Selective Inhibition of Migration by Styrenic Catiomer Emulsions

Cancer metastasis remains the most formidable cause of mortality and morbidity in cancer patients. Developing an effective and economical method toward cancer antimetastatic strategy demands immediate attention in anticancer therapy. Herein, we followed a cost-effective greener method for preparing a small family of amphiphilic catiomers with varied styrene content (45, 63, and 83%), which revealed the unique potential of promoting normal cell migration while retarding cancer metastasis. The styrenic polymers formed micellar self-assembly in aqueous phase and exhibited a cationic charge. Polymers were quite nontoxic up to 200 μg/mL concentration toward human embryonic kidney cell HEK293 as well as human, triple negative breast cancer cell MDAMB-231, mouse melanoma cell B16F10, and human oral squamous carcinoma cell FaDu. Confocal imaging and fluorescence activated cell sorting (FACS) showed effective incorporation of polymers within cells. Interestingly, the polymer-treated HEK293 cells underwent prominent wound healing in scratch assay. However, the as-synthesized polymer-treated cancer cells resisted migration as analyzed from the scratch assay. A mechanistic study using immunoblotting assay established upregulation of migratory proteins vimentin and TGF-β and downregulation of E-cadherin in normal HEK293 cells. Remarkably, this trend was completely reversed in cancer cell MDAMB-231. This study describes the extraordinary potential of styrenic catiomers as wound healers for normal cells while inhibiting cancer metastasis.

Multifunctional mesoporous silica nanoparticles for biomedical applications

Mesoporous silica nanoparticles (MSNs) are recognized as a prime example of nanotechnology applied in the biomedical field, due to their easily tunable structure and composition, diverse surface functionalization properties, and excellent biocompatibility. Over the past two decades, researchers have developed a wide variety of MSNs-based nanoplatforms through careful design and controlled preparation techniques, demonstrating their adaptability to various biomedical application scenarios. With the continuous breakthroughs of MSNs in the fields of biosensing, disease diagnosis and treatment, tissue engineering, etc., MSNs are gradually moving from basic research to clinical trials. In this review, we provide a detailed summary of MSNs in the biomedical field, beginning with a comprehensive overview of their development history. We then discuss the types of MSNs-based nanostructured architectures, as well as the classification of MSNs-based nanocomposites according to the elements existed in various inorganic functional components. Subsequently, we summarize the primary purposes of surface-functionalized modifications of MSNs. In the following, we discuss the biomedical applications of MSNs, and highlight the MSNs-based targeted therapeutic modalities currently developed. Given the importance of clinical translation, we also summarize the progress of MSNs in clinical trials. Finally, we take a perspective on the future direction and remaining challenges of MSNs in the biomedical field.

Ultrathin C3N4 nanosheets-based oxidase-like 2D fluorescence nanozyme for dual-mode detection of organophosphorus pesticides

Engineering efficient dual-mode portable sensor with built-in cross reference correction is of great significance for onsite reliable and precise detection of organophosphorus pesticides (OPs) and evading the false-positive outputs, especially in emergency case. Currently, most nanozyme-based sensors for OPs monitoring primarily replied on the peroxidase-like activity, which involved unstable and toxic H₂O₂. In this scenario, a hybrid oxidase-like 2D fluorescence nanozyme (PtPdNPs@g-C₃N₄) was yielded by in situ growing PtPdNPs in the ultrathin two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) nanosheet. When acetylcholinesterase (AChE) hydrolyzed acetylthiocholine (ATCh) to thiocholine (TCh), it ablated O₂^-• from the dissolved O₂ catalyzed by PtPdNPs@g-C₃N₄'s oxidase-like activity, hampering the oxidation of o-phenylenediamine (OPD) into 2,3-diaminophenothiazine (DAP). Consequently, with the increasing concentration of OPs which inhibited the blocking effect by inactivating AChE, the produced DAP caused an apparent color change and a dual-color ratiometric fluorescence change in the response system. Through integrating into a smartphone, a H₂O₂-free 2D nanozyme-based onsite colorimetric and fluorescence dual-mode visual imaging sensor for OPs was proposed with acceptable results in real samples, which holds vast promise for further development of commercial point-of-care testing platform in early warning and controlling of OPs pollution for safeguarding environmental health and food safety.

Modification of a SOCT-ISC type triphenylamine-BODIPY photosensitizer by a multipolar dendrimer design for photodynamic therapy and two-photon fluorescence imaging

In this study, a series of multipolar triphenylamine-BODIPY photosensitizers T-BDP_n (n = 1, 2, 3) was synthesized. Compared with T-BDP₁ of D-A configuration, the multipolar T-BDP₃ dendrimer have higher singlet oxygen efficiency (44%), better fluorescence quantum yield (7.45%), and could be used in the simulated photodynamic therapy in A-549 cells and two-photon fluorescence imaging in zebrafish. The theoretical calculation and fs-transient absorption spectra indicated that the reason of its higher singlet oxygen efficiency was that the multipolar T-BDP₃ dendrimer could generate more nearly degenerate charge transfer (CT) states and triplet states, which could further increase the possibility of spin-orbit charge-transfer intersystem crossing (SOCT-ISC) process. In the simulated photodynamic therapy of A-549 cells, T-BDP₃ shows good cytocompatibility, great phototoxicity with its IC₅₀ value of 3.17 μM, and could kill cancer cells effectively with the dosage of 5 μM under 10 min irradiation in the AO/EB double-staining experiment. In the fluorescence imaging of zebrafish, the experiment results indicate that T-BDP₃ could generate superoxide radical (O₂˙^-) in the body of zebrafish and could be applied to the two-photon fluorescence imaging under 800 nm excitation. The above experiment results shown that the multipolar dendrimer design was an effective approach to improve the key parameters of SOCT-ISC-type BODIPY photosensitizer and was ready for further two-photon photodynamic therapy in organisms.

Photoluminescent silica nanostructures and nanohybrids

The complicated photophysics of wide variety of defects existing in silica (SiO2) layer of nanometer thickness determines wide spread photoluminescence bands of Si/SiO2 based system as well as SiO2 nanoparticles (NPs) for their applications in photovoltaic and optoelectronic devices. This review attempts to summarize different photophysical processes in pure SiO2 NPs. Moreover, these NPs also act as scaffolds for various guest molecules to perform their specific functions. Guest fluorophore molecules when trapped inside pores of SiO2 NPs exhibit a different photodynamics than free state, which opens up several important applications of hybrid SiO2 NPs in artificial photosynthesis, sensing, biology and optical fiber.

Fulvic acid-like substance-Ca(II) complexes improved the utilization of calcium in rice: Chelating and absorption mechanism

Water-soluble chelated calcium has been widely used in agriculture as a fertilizer to improve the absorption and utilization of calcium by plants. This paper prepared a new organic mineral fertilizer, based on fulvic acid-like substance chelated calcium (PFA-Ca²⁺ complex), using optimal parameters (i.e., pH, time, temperature, and Ca²⁺ concentration) to achieve a high chelation efficiency. The absorption, utilization, and distribution of the PFA-Ca²⁺ complex in rice roots were analyzed using laser scanning confocal microscopy (LSCM). Our results demonstrated that the optimal PFA-Ca²⁺ complex chelating efficiency (87%) was achieved at an initial Ca²⁺ concentration of 0.1 mol L^-1, an equilibration time of 120 min, a pH of 5.0, and a temperature of 40 °C. The chelating reaction of a fulvic acid-like substance with Ca²⁺ primarily occurred on phenol hydroxyl, alcohol hydroxyl, and carboxyl groups. The PFA-Ca²⁺ complex was primarily enriched in the roots' pericycle, cortical, and epidermis cells, in both chelating and non-chelating forms. To our knowledge, this is the first report investigating how the PFA-Ca²⁺complex affects transformation in plants, which has significant implications for research on plant nutrition and nutrient distribution.

Synthesis of Silica Nanoparticles with Physical Encapsulation of Near-Infrared Fluorescent Dyes and Their Tannic Acid Coating

This study reports a novel method for the synthesis of silica nanoparticles (NPs) encapsulating near-infrared (NIR) fluorescent dyes through physical adsorption. Although a NIR cationic fluorescent dye, oxazine 725 (OXA), has no chemical bonding moiety toward silica NPs such as the triethoxysilyl group, the dyes were successfully incorporated into silica NPs without denaturation under the mild reaction conditions. Next, tannic acid (TA) molecules were coated in the presence of Fe³⁺ on the particle surface for the functionalization of silica NPs encapsulating OXA (OXA@SiO₂ NPs). The TA coating on the surface of OXA@SiO₂ NPs was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. The TA coating significantly contributed to the resistance improvement against photobleaching and leakage of the dyes in the NPs. Furthermore, the obtained TA-coated silica NPs encapsulating OXAs (OXA@SiO₂@TA NPs) were used for the fluorescence imaging of African green monkey kidney (COS-7) cells, and it was shown that the fluorescence originated from OXA@SiO₂@TA NPs was clearly observed in the COS-7 cells.

Near-Infrared Light-Driven Multifunctional Tubular Micromotors for Treatment of Atherosclerosis

One of the difficulties in atherosclerosis treatment is that the ablation of inflammatory macrophages, repair of vascular endothelial injury, and anti-tissue proliferation should be considered. However, there are few studies that can solve the abovementioned problems simultaneously. Herein, we present a kind of near-infrared (NIR) light-driven multifunctional mesoporous/macroporous tubular micromotor which can rapidly target the damaged blood vessels and release different drugs. Their motion effect can promote themselves to penetrate into the plaque site, and the generated heat effect caused by NIR irradiation can realize the photothermal ablation of inflammatory macrophages. Furthermore, these micromotors can rapidly release the vascular endothelial growth factor for endothelialization and slowly release paclitaxel for antiproliferation to achieve synergistic treatment of atherosclerosis. In vivo results demonstrated that the micromotors can achieve a good therapeutic effect for atherosclerosis. This kind of micro/nanomotor technology with a complex porous structure for drug loading will bring a more potential treatment platform for the disease.

Silicon-based fluorescent platforms for copper(ii) detection in water

The potential of silicon-based fluorescent platforms for the detection of trace toxic metal ions was investigated in an aqueous environment. To this aim, silicon chips were first functionalized with amino groups, and fluorescein organic dyes, used as sensing molecules, were then covalently linked to the surface via formation of thiourea groups. The obtained hybrid heterostructures exhibited high sensitivity and selectivity towards copper(ii), a limit of detection compatible with the recommended upper limits for copper in drinking water, and good reversibility using a standard metal-chelating agent. The fluorophore-analyte interaction mechanism at the basis of the reported fluorescence quenching, as well as the potential of performance improvement, were also studied. The herein presented sensing architecture allows, in principle, tailoring of the selectivity towards other metal ions by proper fluorophore selection, and provides a favorable outlook for integration of fluorescent chemosensors with silicon photonics technology.

Development of a kind of RG108-Fluorescein conjugates for detection of DNA methyltransferase 1 (DNMT1) in living cells

DNA methyltransferase 1 (DNMT1) is one of the most essential proteins in propagating DNA methylation patterns during replication. Developing methods to assess the expression level of DNMT1 will enable study of gene methylation abnormalities. Thus, a series of fluorescein-conjugated RG108 derivatives were designed and synthesized in the current study. The affinity of the derivatives with DNMT1 was evaluated using surface plasmon resonance. Permeability of the derivatives through the cytomembrane and nuclear envelope was evaluated via confocal imaging. Probe 8a was found to compete with RG108 binding to DNMT1 in the nucleus of HeLa cells, suggesting that probe 8a and RG108 share the same binding site. A HeLa cell model with 4.05-fold overexpression of DNMT1 was constructed and used to evaluate probe 8a. Probe 8a was found to be significantly increased in the nucleus of DNMT1 overexpressing cells. These results indicate that fluorescent probes derived from RG108 have the potential to be used for evaluating the expression level of DNMT1 in living cells.

Carbon quantum Dot@Silver nanocomposite-based fluorescent imaging of intracellular superoxide anion

Silver nanoparticle (Ag NP)-coated carbon quantum dot (CQD) core-shell-structured nanocomposites (CQD@Ag NCs) were developed for fluorescent imaging of intracellular superoxide anion (O₂^•-). The morphology of CQD@Ag NCs was investigated by transmission electron microscopy, and the composition was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. CQDs display blue fluorescence with excitation/emission maxima at 360/440 nm, and the fluorescence was quenched by Ag NPs in CQD@Ag NCs. In the presence of O₂^•-, Ag NPs were oxide-etched and the fluorescence of CQDs was recovered. A linearity between the relative fluorescence intensity and O₂^•- solution concentration within the range 0.6 to 1.6 μM was found, with a detection limit of 0.3 μM. Due to their high sensitivity, selectivity, and low cytotoxicity, the as-synthesized CQD@Ag NCs have been successfully applied for imaging of O₂^•- in MCF-7 cells during the whole process of autophagy induced by serum starvation. In our perception, the developed method provides a cost-effective, sensitive, and selective tool in bioimaging and monitoring of intracellular O₂^•- changes, and is promising for potential biological applications. Graphical abstract Illustration of the synthesis of carbon quantum Dot@Silver nanocomposites (CQD@Ag NCs), and CQD@Ag NCs as a "turn-on" nanoprobe for fluorescent imaging of intracellular superoxide anion.

Time-Resolved Fluorescence Detection of Superoxide Anions Based on an Enzyme-Integrated Lanthanide Coordination Polymer Composite

In this work, we proposed a new strategy of fabricating time-resolved fluorescent nanoprobes by using an enzyme-integrated lanthanide coordination polymer (CP) composite for the detection of superoxide anions (O₂^•-). This CP composite was constructed with terbium ions (Tb³⁺) as a metal node, adenosine triphosphate (ATP) as a bridge ligand, and carboxyphenylboronic acid (CPBA) as a sensitizer in which superoxide dismutase (SOD) was encapsulated by a self-adaptive inclusion process. The as-prepared SOD@ATP/Tb-CPBA displays both catalytic and fluorescence properties. Benefiting from the shielding effect of ATP/Tb CP, greatly enhanced catalytic activity and stability against harsh environments can be obtained in the loaded SOD. Meanwhile, the loaded SOD can remove the water molecules on the coordination sphere of Tb³⁺, leading to a significant increase in the fluorescence intensity and lifetime of SOD@ATP/Tb-CPBA. However, upon the addition of O₂^•-, the fluorescence of SOD@ATP/Tb-CPBA was quenched significantly. This is because SOD can convert O₂^•- into H₂O₂ to induce the deboronation of CPBA, resulting in an intramolecular charge transfer process. On this basis, by taking advantage of Tb³⁺ in long lifetime emission, a time-resolved fluorescence method was developed for the detection of O₂^•-, and satisfactory results have been achieved in both buffered aqueous solutions and serum samples. We believe that the presented study will open up a new avenue to develop enzyme-involved fluorescent nanoprobes.

Dynamic Detection of Endogenous Hydroxyl Radicals at Single-Cell Level with Individual Ag-Au Nanocages

Hydroxyl radicals (•OH) are a type of short-lived radical which is the most aggressive reactive oxygen species due to its high reactivity to biomolecules. Dynamic measurement of •OH level in living cells is critical for understanding cell physiology and pathology. In this manuscript, we prepare individual Ag-Au@PEG/RGD nanocages for in situ determination of endogenous •OH at single-cell level, whose spectral shift rate correlate to the •OH concentration. The high-selective response to •OH relies on the specific oxidization of the conjugated PEG/RGD outside and the silver etching inside the nanocages that resulted in a significant LSPR signal and scattered color changes. The spectral red-shift rate of LSPR has a linear relationship with the logarithm of •OH concentration in range of 100 pM to 1 μM, suitable for the measurement of endogenous •OH. Thus, the individual nanocages were successfully used to monitor the dynamic intracellular •OH level of single tumor cells under oxidative stress. This strategy has great potential in promoting •OH mediated cell homeostasis and injury research.

Nanosilica: Recent Progress in Synthesis, Functionalization, Biocompatibility, and Biomedical Applications

Silica nanoparticles (Si-NPs) are widely explored in biomedical applications due to their high surface area, excellent biocompatibility, and tunable pore size. The silica surface can be readily functionalized for wide range of applications such as cellular imaging, biosensing, and targeted drug delivery. This comprehensive review discusses different synthesis methodologies of Si-NPs and their surface functionalization with various functional groups. Nanosilica functionalization methods are discussed in detail, emphasizing their suitability for targeted drug delivery, cancer therapy, bioimaging, and biosensing. The toxicity assessment of nanosilica is also critically reviewed to get a clear focus before employing them for nanomedicine.

Magnetic Cu/Fe3O4@FeOOH with intrinsic HRP-like activity at nearly neutral pH for one-step biosensing

The convenience of colorimetric sensors is useful for practical applications. In this work, we constructed a novel colorimetric sensor with magnetic separation ability that can be operated in nearly neutral conditions and achieve one-step detection of metabolites. Magnetic Cu doped Fe₃O₄@FeOOH magnetic nanocomposite (Cu/Fe₃O₄@FeOOH) with an oxygen vacancy was prepared by a one-step self-assembly hydrothermal method, and fully characterized by different methods. The oxygen vacancy generated by the incorporation of Cu²⁺ cations into the Fe₃O₄@FeOOH structure was confirmed to be a vital reactive site for enhancing the catalytic activity, which opens up a new way of designing highly efficient enzyme mimics. Benefiting from its inherent horseradish-peroxidase-like activity, a simple and selective enzyme-based colorimetric sensor was developed for one-step detection of H₂O₂ and cholesterol, and 3,3',5,5'-tetramethylbenzidine was catalyzed by H₂O₂ to generate a colored product of oxidized 3,3',5,5'-tetramethylbenzidine for signaling. H₂O₂ and cholesterol can be linearly detected in the same range from 0.01 to 0.4 mmol L^-1 with detection limits of 0.0075 mmol L^-1 and 0.0082 mmol L^-1, respectively. The proposed colorimetric sensor has satisfactory reusability, accuracy, and practicability in human serum samples, indicating its potential application for the detection of different metabolites in the fields of life science and analytical science. Graphical abstract.

An ultrasensitive electrochemical sensor based on cotton carbon fiber composites for the determination of superoxide anion release from cells

A sensor is described for determination of superoxide anion (O₂˙^-). The electrode consists of nitrogen-doped cotton carbon fiber (NCFs) modified with silver nanoparticles (AgNPs) which have excellent catalytic capability. The resulting sensor, best operated at working potentials around -0.5 V (vs. SCE), can detect O₂˙^- over an extraordinarily wide range that covers 10 orders of magnitude, and the detection limit is 2.32 ± 0.07 fM. The electrode enables the release of O₂˙^- from living cells under normal or under oxidative stress conditions to be determined. The ability to scavenge the superoxide anions of antioxidants was also investigated. In the authors' perception, the method represents a viable tool for studying diseases related to oxidative stress. Graphical abstract Schematic presentation of the construction of an electrochemical sensor based on Nitrogen-doped cotton carbon fiber and silver nanoparticles. It can be used for the direct detection of superoxide anions released from Glioma cells (U87) under normal or under oxidative stress conditions.

A functionalized UiO-66 MOF for turn-on fluorescence sensing of superoxide in water and efficient catalysis for Knoevenagel condensation

A MOF based sensor is reported for specific, rapid, and sensitive sensing of O₂^·− and effective and recyclable catalysis of Knoevenagel condensation.

Two aggregation-induced emission (AIE)-active reaction-type probes: for real-time detecting and imaging of superoxide anions

Two AIE-active reaction-type probes: one probe, two channels, at the same & different cell locations for superoxide anion.

Multifunctional Yolk-Shell Mesoporous Silica Obtained via Selectively Etching the Shell: A Therapeutic Nanoplatform for Cancer Therapy

Herein, we fabricated a new yolk-shell-structured mesoporous silica nanoparticle (YMSN) with multifunctionalities of fluorescence imaging, photothermal therapy (PTT), and drug delivery by using a fluorescein isothiocyanate-doped silica nanoparticle partially covered by patchy gold as the core. Different from the conventional selective etching procedure, the multifunctional silica core is left intact, and the alkali etching mainly occurs in a hexadecyl trimethyl ammonium bromide/silica hybrid layer, which leads to the formation of the void space in YMSNs. In addition, the utilization of patchy gold as the PTT agent can avoid the shield against the outer irradiation on the core. Results show that the as-prepared YMSNs have a good biocompatibility in the concentration of 0-1000 μg·mL^-1 and a high doxorubicin-loading capability (8.04 wt %). In vitro and in vivo antitumor experiments reveal that the resulting YMSNs can be utilized for chemo- and photothermic combination therapy as well as optical imaging.

Electrochemical screening of single nucleotide polymorphisms with significantly enhanced discrimination factor by an amplified ratiometric sensor

The detection of single nucleotide polymorphisms (SNPs) is of great clinical significance to the diagnosis of various genetic diseases and cancers. In this work, the development of an ultrasensitive ratiometric electrochemical sensor for screening SNP with a significantly enhanced discrimination factor is reported. The ferrocene (Fc) and methylene blue (MB) dual-tagged triple helix complex (THC) probes are self-assembled on the gold electrode to construct the sensing interface. The addition of the mutant p53 gene causes the disassembly of the THC probes with the release of the Fc-tagged sequence and the folding of the MB-labeled sequence into a hairpin structure, causing the change in the current response ratio of MB to Fc for monitoring the mutant p53 gene. Such ratio is dramatically enhanced by the toehold-mediated displacement reaction-assisted target recycling amplification with the presence of an assistance hairpin sequence. With the significant signal amplification and the advantageous specificity of the THC probes, sub-femtomolar detection limit and a highly enhanced SNP discrimination factor for the mutant p53 gene can be obtained. Besides, the proof-of-demonstration application of the sensor for diluted real samples has been verified, offering such sensor new opportunities for monitoring various genetic related diseases.

Yolk-Shell Nanostructures: Design, Synthesis, and Biomedical Applications

Yolk-shell nanostructures (YSNs) composed of a core within a hollow cavity surrounded by a porous outer shell have received tremendous research interest owing to their unique structural features, fascinating physicochemical properties, and widespread potential applications. Here, a comprehensive overview of the design, synthesis, and biomedical applications of YSNs is presented. The synthetic strategies toward YSNs are divided into four categories, including hard-templating, soft-templating, self-templating, and multimethod combination synthesis. For the hard- or soft-templating strategies, different types of rigid or vesicle templates are used for making YSNs. For the self-templating strategy, a number of unconventional synthetic methods without additional templates are introduced. For the multimethod combination strategy, various methods are applied together to produce YSNs that cannot be obtained directly by only a single method. The biomedical applications of YSNs including biosensing, bioimaging, drug/gene delivery, and cancer therapy are discussed in detail. Moreover, the potential superiority of YSNs for these applications is also highlighted. Finally, some perspectives on the future research and development of YSNs are provided.

Construction of an ultrasensitive non-enzymatic sensor to investigate the dynamic process of superoxide anion release from living cells

In this work, a novel non-enzymatic superoxide anion (O₂•^-) sensor was constructed based on Ag nanoparticles (NPs) / poly (amidoamine) (PAMAM) dendrimers and used to investigate the dynamic process of O₂•^- release from living cells. The AgNPs/PAMAM nanohybrids were characterized by transmission electron microscopy (TEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated electrode exhibited excellent catalytic activity toward the reaction of O₂•^- with a super low detection limit (LOD) of 2.530 × 10^-13M (S/N = 3) and wide linear range of 8 orders of magnitude. It could fulfill the requirement of real-time measurement O₂•^- released from living cells. Furthermore, zymosan was chosen as the stimulant to induce O₂•^- generation from cancer cells (rat adrenal medulla pheochromocytoma cell (PC12)). The electrochemical experiment results indicated that the levels of intracellular O₂•^- depended on the amount of Zymosan. A large amount of O₂•^- generated in the living cells by added heavy stimulant could damage cells seriously. More importantly, a vitro simulation experiment confirmed the role of superoxide dismutase (SOD) for the first time because it could maintain the O₂•^- concentration at a normal physiological range. These findings are of great significance for evaluating the metabolic processes of O₂•^- in the biological system, and this work has the tremendous potential application in clinical diagnostics to assess oxidative stress.

Dual-Ratiometric Fluorescent Nanoprobe for Visualizing the Dynamic Process of pH and Superoxide Anion Changes in Autophagy and Apoptosis

Autophagy and apoptosis are closely associated with various pathological and physiological processes in cell cycles. Investigating the dynamic changes of intracellular active molecules in autophagy and apoptosis is of great significance for clarifying their inter-relationship and regulating mechanism in many diseases. In this study, we develop a dual-ratiometric fluorescent nanoprobe for quantitatively differentiating the dynamic process of superoxide anion (O₂^•-) and pH changes in autophagy and apoptosis in HeLa cells. A rhodamine B-loaded mesoporous silica core was used as the reference, and fluorescence probes for pH and O₂^•- measurement were doped in the outer layer shell of SiO₂. Then, chitosan and triphenylphosphonium were modified on the surface of SiO₂. The experimental results showed that the nanoprobe is able to simultaneously and precisely visualize the changes of mitochondrial O₂^•- and pH in HeLa cells. The kinetics data revealed that the changes of pH and O₂^•- during autophagy and apoptosis in HeLa cells were significantly different. The pH value was decreased at the early stage of apoptosis and autophagy, whereas the O₂^•- level was enhanced at the early stage of apoptosis and almost unchanged at the initial stage of autophagy. At the late stage of apoptosis and autophagy, the concentration of O₂^•- was increased, whereas the pH was decreased at the late stage of autophagy and almost unchanged at the late stage of apoptosis. We hope that the present results provide useful information for studying the effects of O₂^•- and pH in autophagy and apoptosis in various pathological conditions and diseases.

pH and Urea Estimation in Urine Samples using Single Fluorophore and Ratiometric Fluorescent Biosensors

Kidney diseases remain often undiagnosed due to inefficient screening methods available at patient's disposal. Early diagnosis and effective management of kidney problems can best be addressed by the development of biosensors for commonly occurring clinical biomarkers. Here we report the development of single fluorophore and dual fluorophore ratiometric biosensors based on alginate microspheres for pH and urea analysis in urine samples. A facile method of air driven atomization was used for developing these polymeric fluorophore and enzyme based biosensors. Ratiometric biosensors were developed using layer-by-layer coating of polyelectrolyte conjugated to reference fluorophores. Biosensing studies using these biosensors showed that samples in pathophysiological range can be measured having pH range of 4-8 and urea levels between 0-50 mM. Testing of urine samples using these biosensors showed that both pH and urea detection can be accurately performed without interference. Thus, we believe that FITC-Dextran and FITC-Dextran/RuBpy based pH and urea biosensors show a great potential to be translated as a point of care device for pH and urea biosensing in early detection and continuous monitoring of kidney diseases.

New findings of silica nanoparticles induced ER autophagy in human colon cancer cell

Nanoparticle-induced autophagy has been extensively studied, however, real time information about the endoplasmic reticulum involved autophagic process (ER autophagy) induced by nanomaterials remains unknown. In this work, silica nanoparticles (SNPs) were synthesized with characteristics of low toxicity, good biocompatibility and excellent water dispersibility to treat cells. Results show that either low concentration (10 μg/mL) or high concentration (200 μg/mL) of SNPs could increase the quantity of processing from microtubule-associated protein 1-light chain 3-I (LC3-I) to the other variant of LC3 (LC3-II). Interestingly, the level of autophagy induced by the SNPs is associated with the treated time but not the concentrations of SNPs. Importantly, for the first time, SNP accumulation in ER was discovered through co-localization analysis, which incurs ER autophagy. These new findings about SNPs-induced ER autophagy could open an effective way for securely designing silica-based nanoparticles and enable us to know more about ER autophagy.

A Ratiomeric Fluorescent Sensor for Zn2+ Based on N,N'-Di(quinolin-8-yl)oxalamide

A new ratiometric fluorescent sensor (DQO) based on N,N'-Di(quinolin-8-yl) oxalamide has been designed and synthesized for selective detection of Zn²⁺. The fluorescence ratio (I _{536 nm}/I _{450 nm}) of DQO was enhanced 10-fold when Zn²⁺ was present in a buffer aqueous solution at pH 8.66. The sensor showed linear response toward Zn²⁺ in the concentration range 0-15 μM, and the detection limit was calculated to be 2.4 μM. A Job's plot implied the formation of a DQO/Zn²⁺ complex with 1:1 stoichiometry, and the apparent association constant of DQO/Zn²⁺ complex was computed to be 1.5 × 10⁴ M^-1.