Multifunctional nanobeads based on quantum dots and magnetic nanoparticles: synthesis and cancer cell targeting and sorting

Capturing Cancer: Emerging Microfluidic Technologies for the Capture and Characterization of Circulating Tumor Cells

Circulating tumor cells (CTCs) escape from primary or metastatic lesions and enter into circulation, carrying significant information of cancer progression and metastasis. Capture of CTCs from the bloodstream and the characterization of these cells hold great significance for the detection, characterization, and monitoring of cancer. Despite the urgent need from clinics, it remains a major challenge to capture and retain these rare cells from human blood with high specificity and yield. Recent exciting advances in micro/nanotechnology, microfluidics, and materials science have enable versatile, robust, and efficient cell isolation and processing through the development of new micro/nanoengineered devices and biomaterials. This review provides a summary of recent progress along this direction, with a focus on emerging methods for CTC capture and processing, and their application in cancer research. Furthermore, classical as well as emerging cellular characterization methods are reviewed to reveal the role of CTCs in cancer progression and metastasis, and hypotheses are proposed in regard to the potential emerging research directions most desired in CTC-related cancer research.

Surface Complexation-Based Biocompatible Magnetofluorescent Nanoprobe for Targeted Cellular Imaging

We report the synthesis of a magnetofluorescent biocompatible nanoprobe-following room temperature complexation reaction between Fe3O4-ZnS nanocomposite and 8-hydroxyquinoline (HQ). The composite nanoprobe exhibited high luminescence quantum yield, low rate of photobleaching, reasonable excited-state lifetime, luminescence stability especially in human blood serum, superparamagnetism and no apparent cytotoxicity. Moreover, the nanoprobe could be used for spatio-controlled cell labeling in the presence of an external magnetic field. The ease of synthesis and cell labeling in vitro make it a suitable candidate for targeted bioimaging applications.

Inorganic nanomaterials for bioimaging, targeted drug delivery and therapeutics

Inorganic nanomaterials including gold nanoparticles, mesoporous silica nanoparticles, graphene, magnetic nanoparticles, quantum dots and layered double hydroxides have become one of the most active research fields in biochemistry, biotechnology and biomedicine. Benefiting from the facile synthesis/modification, intrinsically physicochemical properties and good biocompatibility, inorganic nanomaterials have shown great potential in bioimaging, targeted drug delivery and cancer therapies. This Feature Article summarizes recent progress on various inorganic nanocarriers, including the background, synthesis, modification, cytotoxicity, physicochemical properties as well as their applications in biomedicine.

Biodegradable nano-films for capture and non-invasive release of circulating tumor cells

Selective isolation and purification of circulating tumor cells (CTCs) from whole blood is an important capability for both clinical medicine and biological research. Current techniques to perform this task place the isolated cells under excessive stresses that reduce cell viability, and potentially induce phenotype change, therefore losing valuable information about the isolated cells. We present a biodegradable nano-film coating on the surface of a microfluidic chip, which can be used to effectively capture as well as non-invasively release cancer cell lines such as PC-3, LNCaP, DU 145, H1650 and H1975. We have applied layer-by-layer (LbL) assembly to create a library of ultrathin coatings using a broad range of materials through complementary interactions. By developing an LbL nano-film coating with an affinity-based cell-capture surface that is capable of selectively isolating cancer cells from whole blood, and that can be rapidly degraded on command, we are able to gently isolate cancer cells and recover them without compromising cell viability or proliferative potential. Our approach has the capability to overcome practical hurdles and provide viable cancer cells for downstream analyses, such as live cell imaging, single cell genomics, and in vitro cell culture of recovered cells. Furthermore, CTCs from cancer patients were also captured, identified, and successfully released using the LbL-modified microchips.

Inorganic nanovehicle for potential targeted drug delivery to tumor cells, tumor optical imaging

In this work, an inorganic multifunctional nanovehicle was tailored as a carrier to deliver anticancer drug for tumor optical imaging and therapy. The nanovehicle could be used as a dually targeted drug nanovehicle by bonded magnetical (passive) and folic acid (active) targeting capabilities. In addition, it was developed using rhodamine 6G (R6G) as a fluorescence reagent, and an α-zirconium phosphate nanoplatform (Zr(HPO4)2·H2O, abbreviated as α-ZrP) as the anticancer drug nanovehicle. The novel drug-release system was designed and fabricated by intercalation of α-ZrP with magnetic Fe3O4 nanoparticles and anticancer drug 5-fluorouracil (5-FU), followed by reacting with a folate acid-chitosan-rhodamine6G (FA-CHI-R6G) complex, and then α-ZrP intercalated with Fe3O4 nanoparticles and 5-fluorouracil (5-FU) was successfully encapsulated into chitosan (CHI). The resultant multifunctional drug delivery system was characterized by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, photoluminescence spectra, magnetometry, fluorescence microscopy imaging studies and other characterization methods. Simultaneously, the drug release in vitro on the obtained nanocomposites that exhibited a sustained release behavior was carried out in buffer solution at 37 °C, which demonstrated clearly that the nanocomposites shown a sustained release behavior. Meanwhile, cell culture experiments also indicated that the drug-release system had the potential to be used as an dually targeted drug nanovehicle into the tumor cells.

Nanostructured magnetic nanocomposites as MRI contrast agents

Magnetic resonance imaging (MRI) has become an integral part of modern clinical imaging due to its non-invasiveness and versatility in providing tissue and organ images with high spatial resolution. With the current MRI advancement, MRI imaging probes with suitable biocompatibility, good colloidal stability, enhanced relaxometric properties and advanced functionalities are highly demanded. As such, MRI contrast agents (CAs) have been an extensive research and development area. In the recent years, different inorganic-based nanoprobes comprising inorganic magnetic nanoparticles (MNPs) with an organic functional coating have been engineered to obtain a suitable contrast enhancement effect. For biomedical applications, the organic functional coating is critical to improve colloidal stability and biocompatibility. Simultaneously, it also provides a building block for generating a higher dimensional secondary structure. In this review, the combinatorial design approach by a self-assembling pre-formed hydrophobic inorganic MNPs core (from non-polar thermolysis synthesis) into various functional organic coatings (e.g. ligands, amphiphilic polymers and graphene oxide) to form water soluble nanocomposites will be discussed. The resultant magnetic ensembles were classified based on their dimensionality, namely, 0-D, 1-D, 2-D and 3-D structures. This classification provides further insight into their subsequent potential use as MRI CAs. Special attention will be dedicated towards the correlation between the spatial distribution and the associated MRI applications, which include (i) coating optimization-induced MR relaxivity enhancement, (ii) aggregation-induced MR relaxivity enhancement, (iii) off-resonance saturation imaging (ORS), (iv) magnetically-induced off-resonance imaging (ORI), (v) dual-modalities MR imaging and (vi) multifunctional nanoprobes.

Mesoscale assemblies of iron oxide nanocubes as heat mediators and image contrast agents

Iron oxide nanocubes (IONCs) represent one of the most promising iron-based nanoparticles for both magnetic resonance image (MRI) and magnetically mediated hyperthermia (MMH). Here, we have set a protocol to control the aggregation of magnetically interacting IONCs within a polymeric matrix in a so-called magnetic nanobead (MNB) having mesoscale size (200 nm). By the comparison with individual coated nanocubes, we elucidate the effect of the aggregation on the specific adsorption rates (SAR) and on the T1 and T2 relaxation times. We found that while SAR values decrease as IONCs are aggregated into MNBs but still keeping significant SAR values (200 W/g at 300 kHz), relaxation times show very interesting properties with outstanding values of r2/r1 ratio for the MNBs with respect to single IONCs.

Fabrication of mono-dispersed silica-coated quantum dot-assembled magnetic nanoparticles

Quantum dots-embedded silica nanoparticles with an iron oxide NP core were prepared and exhibited super-paramagnetic and highly fluorescent properties.

Folic acid-targeted magnetic Tb-doped CeF3fluorescent nanoparticles as bimodal probes for cellular fluorescence and magnetic resonance imaging

Folic acid-targeted magnetic Tb-doped CeF₃nanoparticles were fabricated for cellular MRI and fluorescence dual mode imaging simultaneously.

Multifunctional core–shell polymer–inorganic hybrid nanofibers prepared via block copolymer self-assembly

A simple approach for fabricating multifunctional core–shell nanofibers via self-assembly of block copolymer has been demonstrated. The approach is versatile and could easily be extended to a range of targeted combination of nanoparticles.

Fabrication of MnFe2O4-CuInS2/ZnS Magnetofluorescent Nanocomposites and Their Characterization

Magnetofluorescent nanocomposites (MFNCs) providing a single nanoscale platform with multimodal properties are gaining momentum in biological manipulation, biomedical imaging and therapy. In this work, we report the preparation of MFNCs integrating MnFe₂O₄ magnetic nanoparticles (MNPs), CuInS₂/ZnS quantum dots (QDs) and poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PEG-PLGA) in a tetrahydrofuran (THF)/water solvent system. Through sonication and quick solvent displacement, multiple nanoparticles of each type are co-encapsulated within the hydrophobic core of PEG-PLGA micelles. The developed fabrication process is simple and fast. Moreover, due to the low toxicity of CuInS₂/ZnS QDs, the fabrication process is environmentally benign. The fabricated MFNCs were further characterized regarding their fundamental physical, chemical and biological properties. Results reveal that the MFNCs possess high (Mn + Fe) recovery rates, and the optical properties and magnetic relaxivity of the MFNCs are sensitive to the MNP:QD mass ratios in the fabrication. Furthermore, the MFNCs present excellent stability in aqueous solutions, minimal cytotoxicity, and capability for bioconjugation. This study opens an avenue for the MFNCs to be employed in broad biological or biomedical applications.

Ultrasonication-assisted one-step self-assembly preparation of biocompatible fluorescent-magnetic nanobeads for rare cancer cell detection

Multifunctional nanomaterials simultaneously possessing attractive properties, such as strong fluorescent intensity, excellent superparamagnetic behavior, easy modification and good biocompatibility, are always desired in a wide range of applications. In this work, we present a facile ultrasonication-assisted one-step self-assembly strategy for the fabrication of smart fluorescent-magnetic nanobeads (FMNBs) without using a matrix. Via one-step ultrasonication, organic-soluble superparamagnetic nanoparticles (MNPs) and quantum dots (QDs) were automatically encapsulated by amphiphilic (2-hydroxyl-3-dodecanoxyl) propylcarboxymethylchitosans (HDP-CMCHSs) through hydrophobic interaction to form hydrophilic FMNBs, presenting a good QD fluorescent property and a strong MNP magnetic response. The outer surface of the FMNBs was derived from natural biopolymer chitosans, enabling FMNBs with good biocompatibility and convenience for biological modification. As-prepared FMNBs can be easily modified with streptavidin, facilitating bioconjugation with biotin-labeled human epidermal growth factor (hEGF). hEGF-functionalized FMNBs are able to specifically recognize and capture rare target cells spiked in white blood cells, and the recovered cells can be further cultured for a long time. All of these excellent properties make nanobeads promising for circulating tumor cell (CTC) detection.

SERS-fluorescence joint spectral encoded magnetic nanoprobes for multiplex cancer cell separation

A new kind of cancer cell separation method is demonstrated, using surface-enhanced Raman scattering (SERS) and fluorescence dual-encoded magnetic nanoprobes. The designed nanoprobes can realize SERS-fluorescence joint spectral encoding (SFJSE) and greatly improve the multiplexing ability. The nanoprobes have four main components, that is, the magnetic core, SERS generator, fluorescent agent, and targeting antibody. These components are assembled with a multi-layered structure to form the nanoprobes. Specifically, silica-coated magnetic nanobeads (MBs) are used as the inner core. Au core-Ag shell nanorods (Au@Ag NRs) are employed as the SERS generators and attached on the silica-coated MBs. After burying these Au@Ag NRs with another silica layer, CdTe quantum dots (QDs), that is, the fluorescent agent, are anchored onto the silica layer. Finally, antibodies are covalently linked to CdTe QDs. SFJSE is fulfilled by using different Raman molecules and QDs with different emission wavelengths. By utilizing four human cancer cell lines and one normal cell line as the model cells, the nanoprobes can specifically and simultaneously separate target cancer cells from the normal ones. This SFJSE-based method greatly facilitates the multiplex, rapid, and accurate cancer cell separation, and has a prosperous potential in high-throughput analysis and cancer diagnosis.

Magneto-fluorescent core-shell supernanoparticles

Magneto-fluorescent particles have been recognized as an emerging class of materials that exhibit great potential in advanced applications. However, synthesizing such magneto-fluorescent nanomaterials that simultaneously exhibit uniform and tunable sizes, high magnetic content loading, maximized fluorophore coverage at the surface, and a versatile surface functionality has proven challenging. Here we report a simple approach for co-assembling magnetic nanoparticles with fluorescent quantum dots to form colloidal magneto-fluorescent supernanoparticles. Importantly, these supernanoparticles exhibit a superstructure consisting of a close packed magnetic nanoparticle “core” which is fully surrounded by a “shell” of fluorescent quantum dots. A thin layer of silica-coating provides high colloidal stability and biocompatiblity and a versatile surface functionality. We demonstrate that after surface pegylation, these silica-coated magneto-fluorescent supernanoparticles can be magnetically manipulated inside living cells while being optically tracked. Moreover, our silica-coated magneto-fluorescent supernanoparticles can also serve as an in vivo multi-photon and magnetic resonance dual-modal imaging probe.

A magnetic nanogel based on O-carboxymethylchitosan for antitumor drug delivery: synthesis, characterization and in vitro drug release

This paper studied the synthesis, characterization and use of the magnetic chitosan nanogel for carrying meleimidic compounds. The hydrogel polymer was prepared using O-carboxymethylchitosan, which was crosslinked with epichlorohydrin for subsequent incorporation of iron oxide magnetic nanoparticles. The characterization revealed that the magnetic material comprises about 10% of the hydrogel. This material is comprised of magnetite and maghemite and exhibits ferro-ferrimagnetic behavior. The average particle size is 4.2 nm. There was high incorporation efficiency of maleimides in the magnetic nanogel. The release was of sustained character and there was a greater release when an external magnetic field was applied. The mathematical model that best explained the process of drug release by the magnetic hydrogel was that of Peppas-Sahlin. The magnetic nanogel proved to be an excellent candidate for use in drug-delivery systems.

Colloidal assemblies of oriented maghemite nanocrystals and their NMR relaxometric properties

¹H-NMR relaxometric experiments over an extended frequency range show that ferrimagnetic colloidal nanoclusters exhibit enhanced transverse relaxivity, r₂.

Folate–PEG functionalized silica CdTe quantum dots as fluorescent probes for cancer cell imaging

CdTe@SiO₂–NH–CO–PEG−folate nanoparticles were successfully prepared and demonstrated tumor cell specific targeting through folate receptors via folate mediated endocytosis.

Cell-derived vesicles as a bioplatform for the encapsulation of theranostic nanomaterials

There is a great deal of interest in the development of nanoplatforms gathering versatility and multifunctionality. The strategy reported herein meets these requirements and further integrates a cell-friendly shell in a bio-inspired approach. By taking advantage of a cell mechanism of biomolecule transport using vesicles, we engineered a hybrid biogenic nanoplatform able to encapsulate a set of nanoparticles regardless of their chemistry or shape. As a proof of versatility, different types of hybrid nanovesicles were produced: magnetic, magnetic-metallic and magnetic-fluorescent vesicles, either a single component or multiple components, combining the advantageous properties of each integrant nanoparticle. These nanoparticle-loaded vesicles can be manipulated, monitored by MRI and/or fluorescence imaging methods, while acting as efficient nano-heaters. The resulting assets for targeting, imaging and therapy converge for the outline of a new generation of nanosystems merging versatility and multifunctionality into a bio-camouflaged and bio-inspired approach.

Multifunctional biodegradable polymer nanoparticles with uniform sizes: generation and in vitro anti-melanoma activity

We present a simple, yet versatile strategy for the fabrication of uniform biodegradable polymer nanoparticles (NPs) with controllable sizes by a hand-driven membrane-extrusion emulsification approach. The size and size distribution of the NPs can be easily tuned by varying the experimental parameters, including initial polymer concentration, surfactant concentration, number of extrusion passes, membrane pore size, and polymer molecular weight. Moreover, hydrophobic drugs (e.g., paclitaxel (PTX)) and inorganic NPs (e.g., quantum dots (QDs) and magnetic NPs (MNPs)) can be effectively and simultaneously encapsulated into the polymer NPs to form the multifunctional hybrid NPs through this facile route. These PTX-loaded NPs exhibit high encapsulation efficiency and drug loading density as well as excellent drug sustained release performance. As a proof of concept, the A875 cell (melanoma cell line) experiment in vitro, including cellular uptake analysis by fluorescence microscope, cytotoxicity analysis of NPs, and magnetic resonance imaging (MRI) studies, indicates that the PTX-loaded hybrid NPs produced by this technique could be potentially applied as a multifunctional delivery system for drug delivery, bio-imaging, and tumor therapy, including malignant melanoma therapy.

Advances of lab-on-a-chip in isolation, detection and post-processing of circulating tumour cells

Circulating tumour cells (CTCs) are shed by primary tumours and are found in the peripheral blood of patients with metastatic cancers. Recent studies have shown that the number of CTCs corresponds with disease severity and prognosis. Therefore, detection and further functional analysis of CTCs are important for biomedical science, early diagnosis of cancer metastasis and tracking treatment efficacy in cancer patients, especially in point-of-care applications. Over the last few years, there has been an increasing shift towards not only capturing and detecting these rare cells, but also ensuring their viability for post-processing, such as cell culture and genetic analysis. High throughput lab-on-a-chip (LOC) has been fuelled up to process and analyse heterogeneous real patient samples while gaining profound insights for cancer biology. In this review, we highlight how miniaturisation strategies together with nanotechnologies have been used to advance LOC for capturing, separating, enriching and detecting different CTCs efficiently, while meeting the challenges of cell viability, high throughput multiplex or single-cell detection and post-processing. We begin this survey with an introduction to CTC biology, followed by description of the use of various materials, microstructures and nanostructures for design of LOC to achieve miniaturisation, as well as how various CTC capture or separation strategies can enhance cell capture and enrichment efficiencies, purity and viability. The significant progress of various nanotechnologies-based detection techniques to achieve high sensitivities and low detection limits for viable CTCs and/or to enable CTC post-processing are presented and the fundamental insights are also discussed. Finally, the challenges and perspectives of the technologies are enumerated.

Fabrication of highly fluorescent graphene quantum dots using L-glutamic acid for in vitro/in vivo imaging and sensing

A facile bottom-up method for the synthesis of highly fluorescent graphene quantum dots (GQDs) has been developed using a one-step pyrolysis of a natural amino acid, L-glutamic acid, with the assistance of a simple heating mantle device. The developed GQDs showed strong blue, green and red luminescence under the irradiation of ultra-violet, blue and green light, respectively. Moreover, the GQDs emitted near-infrared (NIR) fluorescence in the range of 800-850 nm with the excitation-dependent manner. This NIR fluorescence has a large Stokes shift of 455 nm, providing significant advantage for sensitive determination and imaging of biological targets. The fluorescence properties of the GQDs, such as quantum yields, fluorescence life time, and photostability, were measured and the fluorescence quantum yield was as high as 54.5 %. The morphology and composites of the GQDs were characterized using TEM, SEM, EDS, and FT-IR. The feasibility of using the GQDs as a fluorescent biomarker was investigated through in vitro and in vivo fluorescence imaging. The results showed that the GQDs could be a promising candidate for bioimaging. Most importantly, compared to the traditional quantum dots (QDs), the GQDs is chemically inert. Thus, the potential toxicity of the intrinsic heavy metal in the traditional QDs would not be a concern for GQDs. In addition, the GQDs possessed an intrinsic peroxidase-like catalytic activity that was similar to the graphene sheets and carbon nanotubes. Coupled with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), the GQDs can be used for the sensitive detection of hydrogen peroxide with a limit of detection of 20 μM.

Multi-shell structured fluorescent-magnetic nanoprobe for target cell imaging and on-chip sorting

In this paper, we have developed a core-triple-shell structured multi-functional nanoprobe Fe3O4/SiO2/CdSeTe@ZnS-SiO2/polydopamine with strong fluorescence and a fast magnetic response for specifically recognizing, fluorescently labeling, and magnetically sorting target tumor cells on a microfluidic chip. The outer polydopamine layer not only effectively alleviated the quenching effect of the interlayer quantum dots but also provided a convenient and versatile functional interface to readily conjugate with the recognizing model molecules of aptamer KH1C12 with amine, thiol, or carboxyl groups. Moreover, the polydopamine isolation and PEG decoration equipped the as-fabricated nanoprobes with little cytotoxicity and nonspecific affinity, leading to the effective and specific profiling of the protein epitopes expressed on the target tumor cells. Taking advantage of the magnetic property and specific recognition, the modified nanoprobe was utilized to label and isolate HL-60 cells from a homogeneous cell mixture of HL-60 and K562 cells on a microfluidic chip. Combining with the high throughput of the microfluidic chip, 1.0 × 10(4) HL-60 cells were readily separated from 2.0 × 10(4) cells in only 10 min with 98% separation efficiency, markedly improved in comparison with conventional strategies. This study presents an innovative strategy for developing highly integrated nanoprobes of strong fluorescence and magnetic controllability, opening up a promising probe-based avenue for biological imaging and separation.

Cancer therapy and fluorescence imaging using the active release of doxorubicin from MSPs/Ni-LDH folate targeting nanoparticles

Hierarchical structured nanomaterials with diverse functionality, such as magnetic susceptibility, stimuli-responsiveness, environmental sensing and biocompatibility, are highly sought after for biomedicine and biodetection alike. In this study, we designed and fabricated a new kind of multifunctional core/shell nanospheres as biodegradable targeted drug carriers, the controlled drug release progress and therapeutic effect were monitored in-situ by the fluorescent state of the cells. Firstly, the core/shell nanospheres with biodegradability were synthesized using magnetic supraparticles (MSPs) as core and the layered double hydroxide (LDH) as shell via a hydrothermal route, the reaction parameters were well investigated to obtain the desired structure of the LDH shell. The anti-cancer drug doxorubicin was modified with carboxyl group (DOX-COOH) and loaded in the shell of MSPs/LDH nanospheres via an anion-exchange intercalation. To endow the nanospheres with tumor-targeting capability, IDA (iminodiacetic acid)-modified folate was successfully immobilized onto the surface of LDH shell using chelating interaction. These nanospheres behaved as multifunctional carriers for targeted delivery of anti-cancer drug, doxorubicin (DOX), within Hela cells and thus, these nano-drugs exhibited clear cytotoxicity and inhibition toward Hela cells as compared to normal cell-lines of HEK 293T cells. Interestingly, after the internalization of these nano-drugs, there was a sharp contrast in illumination between the tumorous Hela cells and the normal HEK 293T cells, the acidic cytoplasm of Hela cell stimulated DOX-COOH in LDH shell quickly degraded into positive-charged DOX, and then rapidly escaped from the positive-charged intercalation of LDH shell by strong repulsive interaction, the released DOX rapidly lit up the whole tumor cells in a short time, but only very weak light was found in HEK 293T cells.

Multifunctional PEGylated nanoclusters for biomedical applications

A simple and versatile synthesis method to form water soluble multifunctional nanoclusters using polyethylene glycol (PEG) functionalized poly(maleic anhydride-alt-1-octadecene) amphiphilic brush copolymers (PMAO-g-PEG) was presented. Simply by tuning the core size and the initial nanocrystal concentration, manganese ferrite nanoparticles (MFNPs) were used to demonstrate the versatility of tuning the loading amount of the nanoclusters. The resultant nanoclusters were found to have a well-controlled spherical shape. When Zn-doped AgInS2 quantum dots (AIZS QDs) were loaded together with the MFNP nanocrystals, bi-functional nanoclusters with fluorescent and magnetic behaviors were obtained. Such bi-functional nanoclusters were also successfully demonstrated for cellular bio-imaging. Moreover, the presence of another type of nanocrystals together with MFNPs was found to have a negligible effect on the overall properties of the nanoclusters as demonstrated by the MR relaxivity test. From the time-dependent colloidal stability test, it was found that the presence of the PEG chain grafted onto PMAO was able to reduce protein adsorption onto the nanocluster surface. An in vitro study on NIH/3T3 demonstrated the biocompatibility of the nanoclusters. Such biocompatible and colloidally stable nanoclusters with an approximate size of 80-120 nm were suitable for both MRI and cell labeling applications.

Theranostic magnetic nanoparticles for efficient capture and in situ chemotherapy of circulating tumor cells

Cancer is considered to be the leading factor which threatens human lives nowadays, and 90% of cancer-related deaths are attributed to the metastasis of cancer. Thus an effective and simultaneous separation and therapeutic method for circulating tumor cells is crucial for improving the diagnosis, prognosis, and treatment of cancer. Here, we report the design of theranostic magnetic nanoparticles conjugated with the targeting peptide SP94 and the anticancer drug doxorubicin (DOX) (symbolized as Fe₃O₄-DOX/SP94) for the targeted isolation of the human hepatocellular carcinoma cell line (HepG2), followed by the in situ chemotherapy of cancer cells upon capture. It was found that the capture efficiencies of 400 μg Fe₃O₄-DOX/SP94 for HepG2 cells and human embryonic kidney transformed 293 cells (293T) were around 75% and 5% respectively after 15 min incubation. Furthermore, it is worth mentioning that DOX was covalently conjugated via pH-sensitive hydrazone bonds, and the in vitro release studies demonstrated that DOX was released much faster at pH 5.0 than at pH 7.4. According to the in vitro cytotoxicity assays, significantly reduced cell viability was observed in HepG2 cells when the concentration of Fe₃O₄-DOX/SP94 nanoparticles was 300 μg mL^-1. Such a rapid and facile approach has considerable potential for the targeted capture as well as effective chemotherapy of circulating tumor cells, in an attempt to improve the curative effects against metastatic diseases.

One-pot solvothermal synthesis of highly water-dispersible size-tunable functionalized magnetite nanocrystal clusters for lipase immobilization

A facile one-pot synthesis of highly water-dispersible size-tunable magnetite (Fe3O4) nanocrystal clusters (MNCs) end-functionalized with amino or carboxyl groups by a modified solvothermal reduction reaction has been developed. Dopamine and 3,4-dihydroxyhydroxycinnamic acid were used for the first time as both a surfactant and interparticle linker in a polylol process for economical and environment-friendly purposes. Morphology, chemical composition, and magnetic properties of the prepared particles were investigated by several methods, including FESEM, TEM, XRD, XPS, Raman, FTIR, TGA, zeta potential, and VSM. The sizes of the particles could be easily tuned over a wide range from 175 to 500 nm by varying the surfactant concentration. Moreover, ethylene glycol/diethylene glycol (EG/DEG) solvent mixtures with different ratios could be used as reductants to obtain the particles with smaller sizes. The XRD data demonstrated that the surfactants restrained the crystal growth of the grains. The nanoparticles showed superior magnetic properties and high colloidal stability in water. The cytotoxicity results indicated the feasibility of using the synthesized nanocrystals in biology-related fields. To estimate the applicability of the obtained MNCs in biotechnology, Candida rugosa lipase was selected for the enzyme immobilization process. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with the free enzyme. This novel strategy would simplify the reaction protocol and improve the efficiency of materials functionalization, thus offering new potential applications in biotechnology and organocatalysis.

Controlled release of doxorubicin loaded within magnetic thermo-responsive nanocarriers under magnetic and thermal actuation in a microfluidic channel

We report a procedure to grow thermo-responsive polymer shells at the surface of magnetic nanocarriers made of multiple iron oxide superparamagnetic nanoparticles embedded in poly(maleic anhydride-alt-1-ocatadecene) polymer nanobeads. Depending on the comonomers and on their relative composition, tunable phase transition temperatures in the range between 26 and 47 °C under physiological conditions could be achieved. Using a suitable microfluidic platform combining magnetic nanostructures and channels mimicking capillaries of the circulatory system, we demonstrate that thermo-responsive nanobeads are suitable for localized drug delivery with combined thermal and magnetic activation. Below the critical temperature nanobeads are stable in suspension, retain their cargo, and cannot be easily trapped by magnetic fields. Increasing the temperature above the critical temperature causes the aggregation of nanobeads, forming clusters with a magnetic moment high enough to permit their capture by suitable magnetic gradients in close proximity to the targeted zone. At the same time the polymer swelling activates drug release, with characteristic times on the order of one hour for flow rates of the same order as those of blood in capillaries.

Magnetic anisotropy considerations in magnetic force microscopy studies of single superparamagnetic nanoparticles

In recent years, superparamagnetic nanoparticles (SPNs) have become increasingly important in applications ranging from solid state memory devices to biomedical diagnostic and therapeutic tools. However, detection and characterization of the small and unstable magnetic moment of an SPN at the single particle level remains a challenge. Further, depending on their physical shape, crystalline structure or orientation, SPNs may also possess magnetic anisotropy, which can govern the extent to which their magnetic moments can align with an externally applied magnetic field. Here, we demonstrate how we can exploit the magnetic anisotropy of SPNs to enable uniform, highly-sensitive detection of single SPNs using magnetic force microscopy (MFM) in ambient air. Superconducting quantum interference device magnetometry and analytical transmission electron microscopy techniques are utilized to characterize the collective magnetic behavior, morphology and composition of the SPNs. Our results show how the consideration of magnetic anisotropy can enhance the ability of MFM to detect single SPNs at ambient room temperature with high force sensitivity and spatial resolution.

Magnetophoresis at the nanoscale: tracking the magnetic targeting efficiency of nanovectors

Aim: Most of the research efforts in magnetic targeting have been focused on the development of magnetic nanovectors, while the investigation of methods for tracking their magnetic targeting efficiency remains inappropriately addressed. We propose herein a miniaturized approach for appraising magnetophoretic mobility at the nanoscale. Materials & methods: A simple and easy-to-use chamber including a microtip as a magnetic attractor was developed to perform magnetophoretic measurement at the size scale of nano-objects, and under bright field or fluorescence microscopy. Different sets of magnetic nanocontainers were produced and their magnetophoretic mobility was investigated. Real-time observations of the Brownian motion of the nanocontainers were also carried out for simultaneous size determination. Results: Attraction of the nanocontainers at the microtip is demonstrated as a qualitative method that immediately distinguishes magnetically responsive nano-objects. The combination of the analysis of Brownian motion, together with the magnetophoretic mobility, inferred both the size, the magnetophoretic velocity and the magnetic content of the nanocontainers. Additionally, nanomagnetophoresis experiments under fluorescence microscopy provided information on the constitutive core/shell integrity of the nanocontainers and the co-internalization of a fluorescent cargo. Conclusion: This nanomagnetophoresis method represents a promising tool to estimate the feasibility of magnetic targeting in laboratory routine.

Original submitted 28 November 2011; Revised submitted 28 February 2012; Published online 18 June 2012

Tapping the potential of quantum dots for personalized oncology: current status and future perspectives

Cancer is one of the most serious health threats worldwide. Personalized oncology holds potential for future cancer care in clinical practice, where each patient could be delivered individualized medicine on the basis of key biological features of an individual tumor. One of the most urgent problems is to develop novel approaches that incorporate the increasing molecular information into the understanding of cancer biological behaviors for personalized oncology. Quantum dots are a heterogeneous class of engineered fluorescent nanoparticles with unique optical and chemical properties, which make them promising platforms for biomedical applications. With the unique optical properties, the utilization of quantum dot-based nanotechnology has been expanded into a wide variety of attractive biomedical applications for cancer diagnosis, monitoring, pathogenesis, treatment, molecular pathology and heterogeneity in combination with cancer biomarkers. Here, we focus on the clinical application of quantum dot-based nanotechnology in personalized oncology, covering topics on individualized cancer diagnosis and treatment by in vitro and in vivo molecular imaging technologies, and in-depth understanding of the biological behaviors of tumors from a nanotechnology perspective. In addition, the major challenges in translating quantum dot-based nanotechnology into clinical application and promising future directions in personalized oncology are also discussed.

Multifunctional nanoparticle-loaded spherical and wormlike micelles formed by interfacial instabilities

Hybrid spherical and wormlike amphiphilic block copolymer micelles are formed through evaporation-induced interfacial instabilities of emulsion droplets, allowing the incorporation of pre-synthesized hydrophobic inorganic nanoparticles within the micelle cores, as well as co-encapsulation of different nanoparticles. This encapsulation behavior is largely insensitive to particle surface chemistry, shape, and size, thus providing a versatile route to fabricate multifunctional micelles.

Ultrasmall biocompatible nanocomposites: a new approach using seeded emulsion polymerization for the encapsulation of nanocrystals

We report a novel approach of seeded emulsion polymerization in which nanocrystals are used as seeds. Ultrasmall biocompatible polymer-coated nanocrystal with sizes between 15 and 110 nm could be prepared in a process that avoids any treatment with high shear forces or ultrasonication. The number of nanocrystals per seed, the size of the seeds, and the shell thickness can be independently adjusted. Single encapsulated nanocrystals in ultrasmall nanobeads as well as clusters of nanocrystals can be obtained. Polysorbat-80 was used as surfactant. It consists of poly(ethylene glycol) (PEG) chains, giving the particles outstanding biofunctional characteristics such as a minimization of unspecific interactions.

Tailor-made magnetic Fe3O4@mTiO2 microspheres with a tunable mesoporous anatase shell for highly selective and effective enrichment of phosphopeptides

Selective enrichment of phosphoproteins or phosphopeptides from complex mixtures is essential for MS-based phosphoproteomics, but still remains a challenge. In this article, we described an unprecedented approach to synthesize magnetic mesoporous Fe(3)O(4)@mTiO(2) microspheres with a well-defined core/shell structure, a pure and highly crystalline TiO(2) layer, high specific surface area (167.1 m(2)/g), large pore volume (0.45 cm(3)/g), appropriate and tunable pore size (8.6-16.4 nm), and high magnetic susceptibility. We investigated the applicability of Fe(3)O(4)@mTiO(2) microspheres in a study of the selective enrichment of phosphopeptides. The experiment results demonstrated that the Fe(3)O(4)@mTiO(2) possessed remarkable selectivity for phosphopeptides even at a very low molar ratio of phosphopeptides/non-phosphopeptides (1:1000), large enrichment capacity (as high as 225 mg/g, over 10 times as that of the Fe(3)O(4)@TiO(2) microspheres), extreme sensitivity (the detection limit was at the fmol level), excellent speed (the enrichment can be completed in less than 5 min), and high recovery of phosphopeptides (as high as 93%). In addition, the high magnetic susceptibility allowed convenient separation of the target peptides by magnetic separation. These outstanding features give the Fe(3)O(4)@mTiO(2) composite microspheres high benefit for mass spectrometric analysis of phosphopeptides.

Synthesis of tunable and multifunctional Ni-doped near-infrared QDs for cancer cell targeting and cellular sorting

Here, we report the facile preparation of tunable magnetic Ni-doped near-infrared (NIR) quantum dots (MNIR-QDs) as an efficient probe for targeting, imaging, and cellular sorting applications. We synthesized the MNIR-QDs via a hot colloidal synthesis approach to yield monodisperse and tunable QDs. These hydrophobic QDs were structurally and compositionally characterized and further functionalized with amino-PEG and carboxyl-PEG to improve their biocompatibility. Since QDs are known to be toxic due to the presence of cadmium, we have evaluated the in vitro and in vivo toxicity of our surface-functionalized MNIR-QDs. Our results revealed that surface-functionalized MNIR-QDs did not exhibit significant toxicity at the concentrations used in the experiments and are therefore suitable for biological applications. For further in vitro applications, we covalently linked folic acid to the surface of amino-PEG-coated MNIR-QDs through NHS chemistry to target the folate receptors largely present in the HeLa cells to demonstrate the specific targeting and magnetic behavior of these MNIR-QDs. Improved specificity has been observed with treatment of HeLa cells with the folic acid-linked amino PEG-coated MNIR QDs (FA-PEG-MNIR-QDs) compared to the one without folic acid. Since the synthesized probe has magnetic property, we have also successfully demonstrated sorting between the cells which have taken up the probe with the use of a magnet. Our findings strongly suggest that these functionalized MNIR-QDs can be a potential probe for targeting, cellular sorting, and bioimaging applications.

Magnetic nanoparticles for the manipulation of proteins and cells

In the rapidly developing areas of nanobiotechnology, magnetic nanoparticles (MNPs) are one type of the most well-established nanomaterials because of their biocompatibility and the potential applications as alternative contrast enhancing agents for magnetic resonance imaging (MRI). While the development of MNPs as alternative contrast agents for MRI application has moved quickly to testing in animal models and clinical trials, other applications of biofunctional MNPs have been explored extensively at the stage of qualitative or conceptual demonstration. In this critical review, we summarize the development of two straightforward applications of biofunctional MNPs--manipulating proteins and manipulating cells--in the last five years or so and hope to provide a relatively comprehensive assessment that may help the future developments. Specifically, we start with the examination of the strategy for the surface functionalization of MNPs because the applications of MNPs essentially depend on the molecular interactions between the functional molecules on the MNPs and the intended biological targets. Then, we discuss the use of MNPs for manipulating proteins since protein interactions are critical for biological functions. Afterwards, we evaluate the development of the use of MNPs to manipulate cells because the response of MNPs to a magnetic field offers a unique way to modulate cellular behavior in a non-contact or "remote" mode (i.e. the magnet exerts force on the cells without direct contact). Finally, we provide a perspective on the future directions and challenges in the development of MNPs for these two applications. By reviewing the examples of the design and applications of biofunctional MNPs, we hope that this article will provide a reference point for the future development of MNPs that address the present challenges and lead to new opportunities in nanomedicine and nanobiotechnology (137 references).

Sensitive and rapid quantification of C-reactive protein using quantum dot-labeled microplate immunoassay

Background

High-sensitivity C-reactive protein (hs-CRP) assay is of great clinical importance in predicting risks associated with coronary heart disease. Existing hs-CRP assays either require complex operation or have low throughput and cannot be routinely implemented in rural settings due to limited laboratory resources.

Methods

We developed a novel hs-CRP assay capable of simultaneously quantifying over 90 clinical samples by using quantum dots-labeled immunoassay within a standard 96-well microplate. The specificity of the assay was enhanced by adopting two monoclonal antibodies (mAbs) that target distinct hs-CRP epitopes, serving as the coating antibody and the detection antibody, respectively. In the presence of hs-CRP antigen, the fluorescence intensity of the mAb-Ag-mAb sandwich complex captured on the microplate can be read out using a microplate reader.

Results

The proposed hs-CRP assay provides a wide analytical range of 0.001-100 mg/L with a detection limit of 0.06 (0.19) μg/L within 1.5 h. The accuracy of the proposed assay has been confirmed for low coefficient of variations (CVs), 2.27% (intra-assay) and 8.52% (inter-assay), together with recoveries of 96.7-104.2%. Bland-Altman plots of 104 clinical samples exhibited good consistency among the proposed assay, commercial high-sensitivity ELISA, and nephelometry, indicating the prospects of the newly developed hs-CRP assay as an alternative to existing hs-CRP assays.

Conclusion

The developed assay meets the needs of the rapid, sensitive and high-throughput determination of hs-CRP levels within a short time using minimal resources. In addition, the developed assay can also be used to detect and quantify other diagnostic biomarkers by immobilizing specific monoclonal antibodies.