Advancing fluorescence imaging: enhanced control of cyanine dye-doped silica nanoparticles

BACKGROUND

Silica nanoparticles (SNPs) have immense potential in biomedical research, particularly in drug delivery and imaging applications, owing to their stability and minimal interactions with biological entities such as tissues or cells.

RESULTS

With synthesized and characterized cyanine-dye-doped fluorescent SNPs (CSNPs) using cyanine 3.5, 5.5, and 7 (Cy3.5, Cy5.5, and Cy7). Through systematic analysis, we discerned variations in the surface charge and fluorescence properties of the nanoparticles contingent on the encapsulated dye-(3-aminopropyl)triethoxysilane conjugate, while their size and shape remained constant. The fluorescence emission spectra exhibited a redshift correlated with increasing dye concentration, which was attributed to cascade energy transfer and self-quenching effects. Additionally, the fluorescence signal intensity showed a linear relationship with the particle concentration, particularly at lower dye equivalents, indicating a robust performance suitable for imaging applications. In vitro assessments revealed negligible cytotoxicity and efficient cellular uptake of the nanoparticles, enabling long-term tracking and imaging. Validation through in vivo imaging in mice underscored the versatility and efficacy of CSNPs, showing single-switching imaging capabilities and linear signal enhancement within subcutaneous tissue environment.

CONCLUSIONS

This study provides valuable insights for designing fluorescence imaging and optimizing nanoparticle-based applications in biomedical research, with potential implications for targeted drug delivery and in vivo imaging of tissue structures and organs.

Recent Breakthroughs in Using Quantum Dots for Cancer Imaging and Drug Delivery Purposes

Cancer is one of the leading causes of death worldwide. Because each person's cancer may be unique, diagnosing and treating cancer is challenging. Advances in nanomedicine have made it possible to detect tumors and quickly investigate tumor cells at a cellular level in contrast to prior diagnostic techniques. Quantum dots (QDs) are functional nanoparticles reported to be useful for diagnosis. QDs are semiconducting tiny nanocrystals, 2-10 nm in diameter, with exceptional and useful optoelectronic properties that can be tailored to sensitively report on their environment. This review highlights these exceptional semiconducting QDs and their properties and synthesis methods when used in cancer diagnostics. The conjugation of reporting or binding molecules to the QD surface is discussed. This review summarizes the most recent advances in using QDs for in vitro imaging, in vivo imaging, and targeted drug delivery platforms in cancer applications.

Drug-Delivery Silver Nanoparticles: A New Perspective for Phenindione as an Anticoagulant

Anticoagulants prevent the blood from developing the coagulation process, which is the primary cause of death in thromboembolic illnesses. Phenindione (PID) is a well-known anticoagulant that is rarely employed because it totally prevents coagulation, which can be a life-threatening complication. The goal of the current study is to synthesize drug-loaded Ag NPs to slow down the coagulation process. Methods: A rapid synthesis and stabilization of silver nanoparticles as drug-delivery systems for phenindione (PID) were applied for the first time. Results: Several methods are used to determine the size of the resulting Ag NPs. Additionally, the drug-release capabilities of Ag NPs were established. Density functional theory (DFT) calculations were performed for the first time to indicate the nature of the interaction between PID and nanostructures. DFT findings supported that galactose-loaded nanostructure could be a proper delivery system for phenindione. The drug-loaded Ag NPs were characterized in vitro for their antimicrobial, cytotoxic, and anticoagulant activities, and ex vivo for spasmolytic activity. The obtained data confirmed the drug-release experiments. Drug-loaded Ag NPs showed that prothrombin time (PT, sec) and activated partial thromboplastin time (APTT, sec) are approximately 1.5 times longer than the normal values, while PID itself stopped coagulation at all. This can make the PID-loaded Ag NPs better therapeutic anticoagulants. PID was compared to PID-loaded Ag NPs in antimicrobial, spasmolytic activity, and cytotoxicity. All the experiments confirmed the drug-release results.

Drug-Loaded Silver Nanoparticles-A Tool for Delivery of a Mebeverine Precursor in Inflammatory Bowel Diseases Treatment

Chronic, multifactorial illnesses of the gastrointestinal tract include inflammatory bowel diseases. One of the greatest methods for regulated medicine administration in a particular region of inflammation is the nanoparticle system. Silver nanoparticles (Ag NPs) have been utilized as drug delivery systems in the pharmaceutical industry. The goal of the current study is to synthesize drug-loaded Ag NPs using a previously described 3-methyl-1-phenylbutan-2-amine, as a mebeverine precursor (MP). Methods: A green, galactose-assisted method for the rapid synthesis and stabilization of Ag NPs as a drug-delivery system is presented. Galactose was used as a reducing and capping agent forming a thin layer encasing the nanoparticles. Results: The structure, size distribution, zeta potential, surface charge, and the role of the capping agent of drug-loaded Ag NPs were discussed. The drug release of the MP-loaded Ag NPs was also investigated. The Ag NPs indicated a very good drug release between 80 and 85%. Based on the preliminary results, Ag NPs might be a promising medication delivery system for MP and a useful treatment option for inflammatory bowel disease. Therefore, future research into the potential medical applications of the produced Ag NPs is necessary.

Quantum Dot Transfer from the Organic Phase to Acrylic Monomers for the Controlled Integration of Single-Photon Sources by Photopolymerization

This paper reports on a new strategy for obtaining homogeneous dispersion of grafted quantum dots (QDs) in a photopolymer matrix and their use for the integration of single-photon sources by two-photon polymerization (TPP) with nanoscale precision. The method is based on phase transfer of QDs from organic solvents to an acrylic matrix. The detailed protocol is described, and the corresponding mechanism is investigated and revealed. The phase transfer is done by ligand exchange through the introduction of mono-2-(methacryloyloxy) ethyl succinate (MES) that replaces oleic acid (OA). Infrared (IR) measurements show the replacement of OA on the QD surface by MES after ligand exchange. This allows QDs to move from the hexane phase to the pentaerythritol triacrylate (PETA) phase. The QDs that are homogeneously dispersed in the photopolymer without any clusterization do not show any significant broadening in their photoluminescence spectra even after more than 3 years. The ability of the hybrid photopolymer to create micro- and nanostructures by two-photon polymerization is demonstrated. The homogeneity of emission from 2D and 3D microstructures is confirmed by confocal photoluminescence microscopy. The fabrication and integration of a single-photon source in a spatially controlled manner by TPP is achieved and confirmed by auto-correlation measurements.

Au@Cu2O Core-Shell and Au@Cu2Se Yolk-Shell Nanocrystals as Promising Photocatalysts in Photoelectrochemical Water Splitting and Photocatalytic Hydrogen Production

In this work, we demonstrated the practical use of Au@Cu₂O core-shell and Au@Cu₂Se yolk-shell nanocrystals as photocatalysts in photoelectrochemical (PEC) water splitting and photocatalytic hydrogen (H₂) production. The samples were prepared by conducting a sequential ion-exchange reaction on a Au@Cu₂O core-shell nanocrystal template. Au@Cu₂O and Au@Cu₂Se displayed enhanced charge separation as the Au core and yolk can attract photoexcited electrons from the Cu₂O and Cu₂Se shells. The localized surface plasmon resonance (LSPR) of Au, on the other hand, can facilitate additional charge carrier generation for Cu₂O and Cu₂Se. Finite-difference time-domain simulations were carried out to explore the amplification of the localized electromagnetic field induced by the LSPR of Au. The charge transfer dynamics and band alignment of the samples were examined with time-resolved photoluminescence and ultraviolet photoelectron spectroscopy. As a result of the improved interfacial charge transfer, Au@Cu₂O and Au@Cu₂Se exhibited a substantially larger photocurrent of water reduction and higher photocatalytic activity of H₂ production than the corresponding pure counterpart samples. Incident photon-to-current efficiency measurements were conducted to evaluate the contribution of the plasmonic effect of Au to the enhanced photoactivity. Relative to Au@Cu₂O, Au@Cu₂Se was more suited for PEC water splitting and photocatalytic H₂ production by virtue of the structural advantages of yolk-shell architectures. The demonstrations from the present work may shed light on the rational design of sophisticated metal-semiconductor yolk-shell nanocrystals, especially those comprising metal selenides, for superior photocatalytic applications.

Fluorescent Nanoparticles for Super-Resolution Imaging

Super-resolution imaging techniques that overcome the diffraction limit of light have gained wide popularity for visualizing cellular structures with nanometric resolution. Following the pace of hardware developments, the availability of new fluorescent probes with superior properties is becoming ever more important. In this context, fluorescent nanoparticles (NPs) have attracted increasing attention as bright and photostable probes that address many shortcomings of traditional fluorescent probes. The use of NPs for super-resolution imaging is a recent development and this provides the focus for the current review. We give an overview of different super-resolution methods and discuss their demands on the properties of fluorescent NPs. We then review in detail the features, strengths, and weaknesses of each NP class to support these applications and provide examples from their utilization in various biological systems. Moreover, we provide an outlook on the future of the field and opportunities in material science for the development of probes for multiplexed subcellular imaging with nanometric resolution.

Ultrasound-assisted fast encapsulation of metal microparticles in SiO2 via an interface-confined sol-gel method

Although the traditional Stoˇber process-based methods are widely used for encapsulation of metal nanoparticles in SiO2, these time-consuming methods are not effective for coating metal microparticles with a uniform SiO2 layer of desired thickness. Herein, an ultrasound-assisted, interface-confined sol-gel method is proposed for fast encapsulation of metal microparticles in SiO2, and the encapsulation of Sn microparticles is chosen as an example to illustrate its feasibility. The proposed method involves covering metal microparticles with liquid films that contain water, alcohol, surfactant (Span-80) and catalyst (NH4F) and then ultrasonically dispersing these particles into cyclohexane, where tetraethylorthosilicate (TEOS) is added. To ensure the hydrolysis-condensation reactions of TEOS occurring at the particle-cyclohexane interface so that the formed SiO2 is coated on the particles, the microparticles should be well dispersed into cyclohexane with the liquid films being not broken away from their surfaces. It is found that the assistance of probe sonication and the addition of surfactant are crucial to achievement of a good dispersion of metal microparticles in cyclohexane. And using high-viscosity alcohol (namely glycerol), controlling the volume ratio of water to alcohol and the amount of water, and choosing a suitable ultrasonic power are essential for preventing the formation of free SiO2 (namely SiO2 that is not coated on the particles), which is a result that the liquid films escape from the particle surfaces under ultrasonic cavitation. Our results have also revealed that the thickness of SiO2 layer can be adjusted by changing the reaction time or the total amount of water. In particular, the thickness of SiO2 layer can be easily raised by simply repeating the encapsulation procedure. Compared with the traditional Stoˇber process-based methods, the proposed method is time-saving (reaction time: about 30 min vs. more than 12 h) and extremely effective for coating microparticles with a continuous, uniform SiO2 layer of desired thickness.

Determination of trace aflatoxin M1 (AFM1) residue in milk by an immunochromatographic assay based on (PEI/PSS)4 red silica nanoparticles

Aflatoxin M1 (AFM1) residues in milk pose a major threat to human health, so there is an urgent need for a simple, rapid, and sensitive method for the determination of trace AFM1 in milk. In this study, a competitive immunochromatographic assay (ICA), using visual (PEI/PSS)₄ red silica nanoparticles (SiNPs) as signal amplification probes, was used for the highly sensitive detection of AFM1. The (PEI/PSS)₄ red SiNPs were used to label AFM1 monoclonal antibody (mAb) to prepare ICA for the detection of AFM1. After exploring the optimal conditions of mAb and immunoprobe dosage conditions, the lowest visual detection limit (VDL) of AFM1 in phosphate-buffered saline with Tween 20 (PBST, 10 mM, pH 7.4, containing 1% BSA, 3% sucrose, 1% trehalose, and 0.5% Tween 20) can reach 0.1 pg/mL. The intuitive visually visible value of AFM1 in both PBST and milk was 10 pg/mL. The results showed that the immunochromatographic system based on high chroma color (PEI/PSS)₄ red SiNPs has high sensitivity and broad application prospects for the detection of trace AFM1 residues in milk. The high chroma (PEI/PSS)₄ red SiNPs are expected to be a convenient biomarker for improving the sensitivity of immune chromatography bands. Graphical abstract The schematic diagram shows the detection principle. In this work, in the competitive experiment, (PEI/PSS)₄ red SiNPs were selected as visual labeling materials, and the specific antibody combined with the labeled material was selected as an immune probe. The AFM1-BSA antigen coupled with the macromolecular BSA was fixed on the T line of the nitrocellulose (NC) membrane. The AFM1 in sample solution competes with AFM1-BSA for the specific binding site of immune probe. The detection sensitivity of this method for AFM1 is obtained by judging the change of the red signal intensity produced by the positive sample, compared with the color at the T line of the negative sample.

Multifunctional ZnO/SiO2 Core/Shell Nanoparticles for Bioimaging and Drug Delivery Application

Semiconducting nanoparticles with luminescent properties are used as detection probes and drug carriers in in-vitro and in-vivo analysis. ZnO nanoparticles, due to its biocompatibility and low cost, have shown potential application in bioimaging and drug delivery. Thus, ZnO/SiO₂ core/shell nanoparticle was synthesised by wet chemical method for fluorescent probing and drug delivery application. The synthesised core/shell nanomaterial was characterized using XRD, FTIR, UV-VIS spectroscopy, Raman spectroscopy, TEM and PL analysis. The silicon shell enhances the photoluminescence and aqueous stability of the pure ZnO nanoparticles. The porous surface of the shell acts as a carrier for sustained release of curcumin. The synthesized core/shell particle shows high cell viability, hemocompatibility and promising florescent property. Graphical Abstract.

Following in Situ the Degradation of Mesoporous Silica in Biorelevant Conditions: At Last, a Good Comprehension of the Structure Influence

Mesoporous silica nanoparticles (MSNs) have seen a fast development as drug delivery carriers thanks to their tunable porosity and high loading capacity. The employ of MSNs in biomedical applications requires a good understanding of their degradation behavior both to control drug release and to assess possible toxicity issues on human health. In this work, we study mesoporous silica degradation in biologically relevant conditions through in situ ellipsometry on model mesoporous nanoparticle or continuous thin films, in buffer solution and in media containing proteins. In order to shed light on the structure/dissolution relationship, we performed dissolution experiments far from soluble silicate species saturation. Via a complete decorrelation of dissolution and diffusion contributions, we proved unambiguously that surface area of silica vectors is the main parameter influencing dissolution kinetics, while thermal treatment and open mesoporous network architecture have a minor impact. As a logical consequence of our dissolution model, we proved that the dissolution lag-time can be promoted by selective blocking of the mesopores that limits the access to the mesoporous internal surface. This study was broadened by studying the impact of the organosilanes in the silica structure, of the presence of residual structuring agents, and of the chemical composition of the dissolution medium. The presence of albumin at blood concentration was found affecting drastically the dissolution kinetics of the mesoporous structure, acting as a diffusion barrier. Globally, we could identify the main factors affecting mesoporous silica materials degradation and proved that we can tune their structure and composition for adjusting dissolution kinetics in order to achieve efficient drug delivery.

Flow-controlled synthesis of gold nanoparticles in a biphasic system with inline liquid–liquid separation

4-Dimethylaminopyridine-stabilised gold nanoparticles are synthesised in a biphasic flow reactor system using organic/aqueous membrane separators and gas-permeable tubing.

CsPbX3/SiOx (X = Cl, Br, I) monoliths prepared via a novel sol-gel route starting from Cs4PbX6 nanocrystals

We developed a facile synthesis of nanocomposite powders of CsPbX₃ nanocrystals (NCs) embedded in silica. The synthesis starts from colloidal Cs₄PbX₆ NCs that are mixed with tetraethyl orthosilicate in the presence of nitric acid, which triggers the sol-gel reaction yielding the formation of SiO_x and the conversion of starting NCs into CsPbX₃ ones. The overall reaction delivers CsPbX₃ NCs encased in a silica matrix. The resulting CsPbX₃/SiO_x nano-composite powders exhibited enhanced moisture and thermal stability in air. Also, when mixing different CsPbX₃/SiO_x samples having diverse anion compositions, no interparticle anion exchange processes were observed, which is a further indication that the silica matrix acts as a robust barrier surrounding the NCs. Finallly, we used these composites as down-converter phosphors on top of a blue light-emitting diode (LED), delivering nearly ideal white light emission with the Commission Internationale de l'Eclairage (CIE) color coordinates (0.32, 0.33).

Characterization of the Ligand Exchange Reactions on CdSe/ZnS QDs by Capillary Electrophoresis

The continuous development of semiconductor quantum dots (QDs) in biochemical research has attracted special attention, and surface functionalizing becomes more important to optimize their performance. Ligand exchange reactions are commonly used to modify the surface of QDs for their biomedical applications. However, the kinetics of ligand exchange for semiconductor QDs remain fully unexplored. Here, we describe a simple and rapid method to characterize the ligand exchange reactions on CdSe/ZnS QDs by capillary electrophoresis (CE). The results of ultraviolet-visible absorption spectra, fluorescence spectra, and Fourier transform infrared spectroscopy indicated the successful implementation of the ligand exchange process. The dynamics of ligand exchange of OA-coated CdSe/ZnS QDs with 4-mercaptobenzoic acid was monitored by CE, and the observed ligand exchange trends were fitted with logistic functions. When the ligand exchange reactions reached equilibrium, the ligand density of QDs can be quantified by CE. It is anticipated that CE will be a new powerful technique for quantitative analysis of the ligand exchange reactions on the surface of QDs.

The Role of Ligands in the Chemical Synthesis and Applications of Inorganic Nanoparticles

The design of nanoparticles is critical for their efficient use in many applications ranging from biomedicine to sensing and energy. While shape and size are responsible for the properties of the inorganic nanoparticle core, the choice of ligands is of utmost importance for the colloidal stability and function of the nanoparticles. Moreover, the selection of ligands employed in nanoparticle synthesis can determine their final size and shape. Ligands added after nanoparticle synthesis infer both new properties as well as provide enhanced colloidal stability. In this article, we provide a comprehensive review on the role of the ligands with respect to the nanoparticle morphology, stability, and function. We analyze the interaction of nanoparticle surface and ligands with different chemical groups, the types of bonding, the final dispersibility of ligand-coated nanoparticles in complex media, their reactivity, and their performance in biomedicine, photodetectors, photovoltaic devices, light-emitting devices, sensors, memory devices, thermoelectric applications, and catalysis.

Ultrastable Luminescent Organic-Inorganic Perovskite Quantum Dots via Surface Engineering: Coordination of Methylammonium Bromide and Covalent Silica Encapsulation

Encapsulation of luminescent perovskite quantum dots (QDs) into a solid matrix has been approved to be an efficient way to improve their stability. In this work, we reported a green encapsulation method to produce ultrastable CH₃NH₃PbBr₃ QDs incorporated into the SiO₂ matrix. Specifically, fresh-prepared CH₃NH₃PbBr₃ QDs were covalently embedded into silica by an aqueous sol-gel method assisted with CH₃NH₃Br, which not only effectively inhibited the water-driven degradation of QDs through surface coordination, but also strongly stabilized the QDs in solid powder via concentration gradient. As far as we know, this silica encapsulation of perovskite QDs in aqueous environments is reported for the first time. Luminescent properties of perovskite QDs during the course of gelation as well as in resulting composite powder were investigated using steady-state and time-resolved spectroscopies, and a 2 wt % QD-doped sample treated with 11.5 mM of CH₃NH₃Br was demonstrated to be the optimal phosphor. The green-emissive phosphor had a PLQY of 60.3% and a full width at half maxima of ∼25 nm, exhibiting ultrahigh stability tested by cycle heating (120 °C), continuous heating (80 °C, 60 h), and light irradiation (450 nm light, 350 h). The phosphor was readily blended with polymers and applied as a color-converting layer on blue light-emitting diodes.

Time-Dependent Growth of Silica Shells on CdTe Quantum Dots

The purpose of this study is to investigate the time dependent growth of silica shells on CdTe quantum dots to get their optimum thicknesses for practical applications. The core/shell structured silica-coated CdTe quantum dots (CdTe/SiO₂ QDs) were synthesized by the Ströber process, which used CdTe QDs co-stabilized by mercaptopropionic acid. The coating procedure used silane primer (3-mercaptopropyltrimethoxysilane) in order to make the quantum dots (QDs) surface vitreophilic. The total size of QDs was dependent on both the time of silica shell growth in the presence of sodium silicate, and on the presence of ethanol during this growth. The size of particles was monitored during the first 72 h using two principally different methods: Dynamic Light Scattering (DLS), and Scanning Electron Microscopy (SEM). The data obtained by both methods were compared and reasons for differences discussed. Without ethanol precipitation, the silica shell thickness grew slowly and increased the nanoparticle total size from approximately 23 nm up to almost 30 nm (DLS data), and up to almost 60 nm (SEM data) in three days. During the same time period but in the presence of ethanol, the size of CdTe/SiO₂ QDs increased more significantly: up to 115 nm (DLS data) and up to 83 nm (SEM data). The variances occurring between silica shell thicknesses caused by different methods of silica growth, as well as by different evaluation methods, were discussed.

Silica nanoparticle stability in biological media revisited

The stability of silica nanostructure in the core-silica shell nanomaterials is critical to understanding the activity of these nanomaterials since the exposure of core materials due to the poor stability of silica may cause misinterpretation of experiments, but unfortunately reports on the stability of silica have been inconsistent. Here, we show that luminescent silver nanodots (AgNDs) can be used to monitor the stability of silica nanostructures. Though relatively stable in water and phosphate buffered saline, silica nanoparticles are eroded by biological media, leading to the exposure of AgNDs from AgND@SiO₂ nanoparticles and the quenching of nanodot luminescence. Our results reveal that a synergistic effect of organic compounds, particularly the amino groups, accelerates the erosion. Our work indicates that silica nanostructures are vulnerable to cellular medium and it may be possible to tune the release of drug molecules from silica-based drug delivery vehicles through controlled erosion.

Gold(Core)-Lead(Shell) Nanoparticle-Loaded Titanium(IV) Oxide Prepared by Underpotential Photodeposition: Plasmonic Water Oxidation

Underpotential photodeposition of Pb yields an ultrathin shell layer on the Au(111) surface of Au nanoparticle(NP)-loaded TiO₂ (Au/TiO₂ ) with heteroepitaxial nanojunctions. The localized surface plasmon resonance of Au/TiO₂ undergoes no damping with the Pb-shell formation, and the Pb shell offers resistance to aerobic oxidation. Mesoporous films comprising the Au(core)-Pb(shell) NP-loaded TiO₂ and unmodified Au/TiO₂ were formed on fluorine-doped tin oxide (FTO) electrode. Using them as the photoanode, photoelectrochemical cells were fabricated, and the photocurrent was measured under illumination of simulated sunlight. The photocurrent for water splitting is dramatically enhanced by the Pb-shell formation. The photoelectrochemical measurements of the hot-electron lifetime and density functional theory calculations for model clusters indicate that the Pb-shell effect originates from the charge separation enhancement.

Synthesis, cytotoxicity and antitumour mechanism investigations of polyoxometalate doped silica nanospheres on breast cancer MCF-7 cells

Polyoxometalates (POMs) have shown the potential anti-bacterial, anti-viral and anti-tumor activities. In order to improve their physiological stability and antitumour activity for medical application, K2Na[AsIIIMo6O21(O2CCH2NH3)3]·6H2O doped silica nanospheres (POM@SiO2) with diameters of ~40 nm have been synthesized by the water-in-oil microemulsion method in this study. The obtained spheres were morphologically uniform nanosized and nearly monodispersed in solution. The nanoparticles had high entrapment efficiency, which was upto 46.2% by the inductively coupled plasma mass spectrometry (ICP-MS) analysis and POMs slowly released from the nanospheres both in the PH 7.4 and 5.5 phosphate buffer saline (PBS) solutions in 60 h. The in vitro MTT assays of particles on MCF-7 cell line (a human breast adenocarcinoma cell line) exhibited enhanced antitumor activity compared to that of plain polyoxometalate. The IC50 value of the POM@SiO2 nanoparticles was 40.0 μg/mL at 24 h calculated by the encapsulated POM concentration, which was much lower comparing to that of 2.0 × 104 μg/mL according to the pure POM. And the SiO2 shells showed low inhibitory effect at the corresponding concentration. Confocal images further indicated the cell morphology changes and necrosis. Flow cytometric analysis showed nanoparticles induced the apoptosis by arresting the cells in S phase and western blot analysis indicated they promoted apoptosis by inhibiting the Bcl-2 protein. Moreover, the study of interactions between human serum albumin (HSA) and the nanoparticles indicated the fluorescence quenching was static, and the nanoparticles were likely to bind to HSA and changed its conformation.

Autonomous magnetic labelling of functional mesenchymal stem cells for improved traceability and spatial control in cell therapy applications

Mesenchymal stem cells (MSCs) represent a valuable resource for regenerative medicine treatments for orthopaedic repair and beyond. Following developments in isolation, expansion and differentiation protocols, efforts to promote clinical translation of emerging cellular strategies now seek to improve cell delivery and targeting. This study shows efficient live MSC labelling using silica‐coated magnetic particles (MPs), which enables 3D tracking and guidance of stem cells. A procedure developed for the efficient and unassisted particle uptake was shown to support MSC viability and integrity, while surface marker expression and MSC differentiation capability were also maintained. In vitro, MSCs showed a progressive decrease in labelling over increasing culture time, which appeared to be linked to the dilution effect of cell division, rather than to particle release, and did not lead to detectable secondary particle uptake. Labelled MSC populations demonstrated magnetic responsiveness in vitro through directed migration in culture and, when seeded onto a scaffold, supporting MP‐based approaches to cell targeting. The potential of these silica‐coated MPs for MRI cell tracking of MSC populations was validated in 2D and in a cartilage repair model following cell delivery. These results highlight silica‐coated magnetic particles as a simple, safe and effective resource to enhance MSC targeting for therapeutic applications and improve patient outcomes. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.

An overview of chitin or chitosan/nano ceramic composite scaffolds for bone tissue engineering

Chitin and chitosan based nanocomposite scaffolds have been widely used for bone tissue engineering. These chitin and chitosan based scaffolds were reinforced with nanocomponents viz Hydroxyapatite (HAp), Bioglass ceramic (BGC), Silicon dioxide (SiO₂), Titanium dioxide (TiO₂) and Zirconium oxide (ZrO₂) to develop nanocomposite scaffolds. Plenty of works have been reported on the applications and characteristics of the nanoceramic composites however, compiling the work done in this field and presenting it in a single article is a thrust area. This review is written with an aim to fill this gap and focus on the preparations and applications of chitin or chitosan/nHAp, chitin or chitosan/nBGC, chitin or chitosan/nSiO₂, chitin or chitosan/nTiO₂ and chitin or chitosan/nZrO₂ in the field of bone tissue engineering in detail. Many reports so far exemplify the importance of ceramics in bone regeneration. The effect of nanoceramics over native ceramics in developing composites, its role in osteogenesis etc. are the gist of this review.

Assembling patchy nanorods with spheres: limitations imposed by colloidal interactions

For gold nanorods the intrinsic shape-anisotropy offers the prospect of anisotropic assembly, provided that their region-selective surface modification can be realized. Here we developed nanorods with a patchy surface chemistry, featuring positively charged molecules in the tip region and polymer molecules at the sides by careful control of molecule concentrations during ligand exchange. When these patchy nanorods are assembled with small negatively charged spherical particles, electric double layer interaction can direct the assembly of two nanospheres at the opposite ends of the nanorods. The PEG chains promote the selectivity of the procedure. As the size of the nanospheres increases, they start to shift towards the side of the nanorod due to increased van der Waals interaction. When the relative size of the nanospheres is even larger, only a single nanosphere is assembled, but instead of the tip region, they are attached to the side of the nanorods. The apparent cross-over of the region-selectivity can be interpreted in terms of colloidal interactions, i.e. the second spherical particle is excluded due to nanosphere-nanosphere electric double layer repulsion, while the large vdW attraction results in a side positioning of the single adsorbed spherical particle. The results underline the importance of absolute values of the different interaction strengths and length scales in the programmed assembly of patchy nanoscale building blocks.

Establishing the interfacial nano-structure and elemental composition of homeopathic medicines based on inorganic salts: a scientific approach

Extremely dilute systems arise in homeopathy, which uses dilution factors 10(60), 10(400) and also higher. These amounts to potencies of 30c, 200c or more, those are far beyond Avogadro's number. There is extreme skepticism among scientists about the possibility of presence of starting materials due to these high dilutions. This has led modern scientists to believe homeopathy may be at its best a placebo effect. However, our recent studies on 30c and 200c metal based homeopathic medicines clearly revealed the presence of nanoparticles of starting metals, which were found to be retained due to the manufacturing processes involved, as published earlier.(9,10) Here, we use HR-TEM and STEM techniques to study medicines arising from inorganic salts as starting materials. We show that the inorganic starting materials are present as nano-scale particles in the medicines even at 1 M potency (having a large dilution factor of 10(2000)). Thus this study has extended our physicochemical studies of metal based medicines to inorganic based medicines, and also to higher dilution. Further, we show that the particles develop a coat of silica: these particles were seen embedded in a meso-microporous silicate layer through interfacial encapsulation. Similar silicate coatings were also seen in metal based medicines. Thus, metal and inorganic salt based homeopathic medicines retain the starting material as nanoparticles encapsulated within a silicate coating. On the basis of these studies, we propose a universal microstructural hypothesis that all types of homeopathic medicines consist of silicate coated nano-structures dispersed in the solvent.

Time-gated luminescence bioimaging with new luminescent nanocolloids based on [Mo6I8(C2F5COO)6]2−metal atom clusters

Functional silica nanoparticles based on metal atom clusters for time gated luminescence biotechnology applications.

Photochemical radical thiol–ene click-based methodologies for silica and transition metal oxides materials chemical modification: a mini-review

The photochemical radical thiol–ene addition reaction (PRTEA) is a highly powerful synthetic technique for surface modification.

Bioactive hydrogel-nanosilica hybrid materials: a potential injectable scaffold for bone tissue engineering

Novel bioactive organic-inorganic hybrid materials that can serve as injectable hydrogel systems for bone tissue regeneration were obtained. The silica nanoparticles (SiNP) prepared in situ by the Stöber method were dispersed in collagen, collagen-chitosan or chitosan sols, which were then subsequently crosslinked. Laser scanning confocal microscopy studies, in which fluorescent SiNP were applied, and SEM images indicated that the nanosilica particles were distributed in the whole volume of the hydrogel matrix. In vitro studies on fibroblast cell viability indicated that the hybrid materials are biocompatible. The silica nanoparticles dispersed in the biopolymer matrix had a positive effect on cell viability. Studies on the mineralization process under simulated body fluid (SBF) conditions confirmed the bioactivity of prepared materials. SEM images revealed mineral phase formation in the majority of the hybrid materials developed. EDS analysis indicated that these mineral phases are mainly composed of calcium and phosphorus. The XRD studies confirmed that mineral phases formed during SBF incubation of hybrid materials based on collagen are bone-like apatite minerals. The silica nanoparticles added to the hydrogel at the stage of synthesis induced the occurrence of mineralization. This process occurs not only at the surface of the material but in its entire volume, which is important for the preparation of scaffolds for bone tissue engineering. The ability of these materials to undergo in situ gelation under physiological temperature and their bioactivity as well as biocompatibility make them interesting candidates for bioactive injectable systems.

Different dimensional silica materials prepared using shaped block copolymer nanoobjects as catalytic templates

A general approach for fabrication of inorganic nanoobjects of different shapes was developed by using shaped core–shell block copolymer nanoobjects as catalytic templates.

Synthesis of comb-like poly(ethyleneimine)s and their application in biomimetic silicification

In this paper, we firstly synthesized comb polymers with crystallizable poly(ethyleneimine) (PEI) side chains, and further investigated their self-assembly behavior and catalytic templating role for silicification.

Sulfonic acid-functionalized magnetic nanoparticles as a recyclable and eco-friendly catalyst for atom economical Michael addition reactions and bis indolyl methane synthesis

Sulfonic acid-functionalized magnetic nanoparticles as a recyclable and eco-friendly catalyst for atom economical Michael addition reaction and bis indolyl methane synthesis.

In situ growth of hollow gold-silver nanoshells within porous silica offers tunable plasmonic extinctions and enhanced colloidal stability

Porous silica-coated hollow gold-silver nanoshells were successfully synthesized utilizing a procedure where the porous silica shell was produced prior to the transformation of the metallic core, providing enhanced control over the structure/composition of the bimetallic hollow core. By varying the reaction time and the precise amount of gold salt solution added to a porous silica-coated silver-core template solution, composite nanoparticles were tailored to reveal a readily tunable surface plasmon resonance that could be centered across the visible and near-IR spectral regions (∼445-800 nm). Characterization by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that the synthetic methodology afforded particles having uniform composition, size, and shape. The optical properties were evaluated by absorption/extinction spectroscopy. The stability of colloidal solutions of our composite nanoparticles as a function of pH was also investigated, revealing that the nanoshells remain intact over a wide range of conditions (i.e., pH 2-10). The facile tunability, enhanced stability, and relatively small diameter of these composite particles (∼110 nm) makes them promising candidates for use in tumor ablation or as photothermal drug-delivery agents.

Bright and stable CdSe/CdS@SiO₂ nanoparticles suitable for long-term cell labeling

We report on the synthesis of luminescent CdSe/CdS@SiO2 nanoparticles and their application to cell labeling. The main novelty of these nanoparticles is the use of newly developed "flash" CdSe/CdS quantum dots (QDs), which are obtained through a new fast and efficient synthesis method recently reported. These core-shell QDs are encapsulated in silica nanoparticles through a water-in-oil microemulsion process, resulting in CdSe/CdS@SiO2 nanoparticles with good morphology and controlled architecture. The main asset of these luminescent nanoparticles is their high photoluminescent quantum yield, which is equal to that of the original CdSe/CdS QDs and remains unchanged even after several months of storage in water. Thanks to the remarkable stability of their optical property in aqueous environment and to their low levels of toxicity, the high potential of these nanoparticles for long-term cell labeling is demonstrated.

Tunable surface plasmon resonance and enhanced electrical conductivity of In doped ZnO colloidal nanocrystals

We report a new synthesis process of colloidal indium (In) doped zinc oxide (ZIO) nanocrystals by a hot injection technique. By fine tuning the synthesis we reached the same nucleation temperature for indium oxide and zinc oxide which helped us to study a dopant precursor dependent In incorporation into the ZnO matrix by using different In sources. The dopant induced shape evolution changes the hexagonal pyramid structured ZnO to a platelet like structure upon 8% In doping. The introduction of trivalent In(3+) into the ZnO lattice and consequent substitution of divalent Zn(2+) generates free electrons in the conduction band which produces a plasmonic resonance in the infrared region. The electron concentration controls plasmon frequency as well as the band gap of host ZnO. The variation of the band gap and the modification of the conduction band have been explained by the Burstein-Moss effect and Mie's theory respectively. The In dopant changes the defect chemistry of pure ZnO nanocrystals which has been studied by photoluminescence and other spectroscopic measurements. The nanocrystals are highly stable in the organic medium and can be deposited as a crack free thin film on different substrates. Careful ligand exchange and thermal annealing of the spin cast film lead to a good conductive film (720 Ω per square to 120 Ω per square) with stable inherent plasmonic absorption in the infrared and 90% transmittance in the visible region. A temperature induced metal-semiconductor transition was found for doped ZnO nanocrystals. The transition temperature shifts to a lower temperature with increase of the doping concentration.