Doxorubicin‐Conjugated Immuno‐Nanoparticles for Intracellular Anticancer Drug Delivery

A polymeric nanoparticle comprised of surface furan groups is used to bind, by Diels–Alder (DA) coupling chemistry, both targeting anti‐human epidermal growth factor receptor 2 (anti‐HER2) antibodies and chemotherapeutic doxorubicin (DOX) for targeted, intracellular delivery of DOX. In this new approach for delivery, where both chemotherapeutic and targeting ligand are attached, for the first time, to the surface of the delivery vehicle, the nuclear localization of DOX in HER2‐overexpressing breast cancer SKBR‐3 cells is demonstrated, as determined by confocal laser scanning microscopy. Flow cytometric analysis shows that the conjugated DOX maintains its biological function and induces similar apoptotic progression in SKBR‐3 cells as free DOX. The viable cell counts of SKBR‐3 cancer cells following incubation with different nanoparticle formulations demonstrates that the combined DOX and anti‐HER2 nanoparticle is more efficacious than the nanoparticle formulation with either DOX or anti‐HER2 alone. While free DOX shows similar cytotoxicity against both cancerous SKBR‐3 cells and healthy HMEC‐1 cells, the combined DOX‐anti‐HER2 nanoparticle is significantly more cytotoxic against SKBR‐3 cells than HMEC‐1 cells, suggesting the benefit of nanoparticle‐conjugated DOX for cell type‐specific targeting. The DOX‐conjugated immuno‐nanoparticle represents an entirely new method for localized co‐delivery of chemotherapeutics and antibodies.     

Magnetic‐Core/Porous‐Shell CoFe2O4/SiO2 Composite Nanoparticles as Immobilized Affinity Supports for Clinical Immunoassays

This study demonstrates a novel approach towards the development of advanced protein assay systems based on physically functionalized, magnetic‐core/porous‐shell CoFe₂O₄/SiO₂ composite nanoparticles. The preparation, characterization, and measurement of the relevant properties of the protein assay system is discussed, and the system is used for the detection of cancer antigen 15‐3 (CA 15‐3, used as a model here) in clinical immunoassays. The protein assay system, based on nanometer‐sized magnetic cores and silica shells, shows good adsorption properties for the selective attachment of CA 15‐3 antibodies specific to CA 15‐3. The core/shell nanostructures exhibit good magnetic properties, which enables their integration into a quartz crystal microbalance (QCM) detection cell with the help of a permanent magnet. Under optimal conditions, the resulting immunoassay system presents a good QCM response for the detection of CA 15‐3, and allows the detection of CA 15‐3 at concentrations as low as 1.5 U mL^–1 (U: units). Importantly, the proposed protein assay system can be extended to the detection of other antigens and biological compounds.     

Responsive Macroscopic Materials From Self‐Assembled Cross‐Linked SiO2‐PNIPAAm Core/Shell Structures

A way to obtain macroscopic responsive materials from silicon‐oxide polymer core/shell microstructures is presented. The microparticles are composed of a 60 nm SiO₂‐core with a random copolymer corona of the temperature responsive poly‐N‐isopropylacrylamide (PNIPAAm) and the UV‐cross‐linkable 2‐(dimethyl maleinimido)‐N‐ethyl‐acrylamide. The particles shrink upon heating and form a stable gel in both water and tetrahydrofuran (THF) at 3–5 wt% particle content. Cross‐linking the aqueous gel results in shrinkage when the temperature is increased above the lower critical solution temperature and it regains its original size upon cooling. By freeze drying with subsequent UV irradiation, thin stable layers are prepared. Stable fibers are produced by extruding a THF gel into water and subsequent UV irradiation, harnessing the cononsolvency effect of PNIPAAm in water/THF mixtures. The temperature responsiveness translates to the macroscopic materials as both films and fibers show the same collapsing behavior as the microcore/shell particle. The collapse and re‐swelling of the materials is related to the expelling and re‐uptake of water, which is used to incorporate gold nanoparticles into the materials by a simple heating/cooling cycle. This allows for future applications, as various functional particles (antibacterial, fluorescence, catalysis, etc.) can easily be incorporated in these systems.     

Multifunctional Nanoparticles Composed of A Poly( dl‐lactide‐coglycolide) Core and A Paramagnetic Liposome Shell for Simultaneous Magnetic Resonance Imaging and Targeted Therapeutics

A multifunctional nanoscale platform that is self‐assembled from a hydrophobic poly( dl ‐lactide‐coglycolide)(PLGA) core and a hydrophilic paramagnetic‐folate‐coated PEGylated lipid shell (PFPL; PEG=polyethylene glycol) is designed for simultaneous magnetic resonance imaging (MRI) and targeted therapeutics. The nanocomplex has a well‐defined core‐shell structure which is studied using confocal laser scanning microscopy (CLSM). The paramagnetic diethylenetriaminepentaacetic acid‐gadolinium (DTPA‐Gd) chelated to the shell layer exhibits significantly higher spin–lattice relaxivity (r₁) than the clinically used small‐molecular‐weight MRI contrast agent Magnevist^®. The PLGA core serves as a nanocontainer to load and release the hydrophobic drugs. From a drug‐release study, it is found that the modification of the PLGA core with a polymeric liposome shell can be a useful tool for reducing the drug‐release rate. Cellular uptake of folate nanocomplex is found to be higher than that of non‐folate‐nanocomplex due to the folate‐binding effect on the cell membrane. This work indicates that the multifunctional platform with combined characteristics applicable to MRI and drug delivery may have great potential in cancer chemotherapy and diagnosis.     

Hybrids of Magnetic Nanoparticles with Double‐Hydrophilic Core/Shell Cylindrical Polymer Brushes and Their Alignment in a Magnetic Field

The synthesis of double‐hydrophilic core/shell cylindrical polymer brushes (CPBs), their hybrids with magnetite nanoparticles, and the directed alignment of these magnetic hybrid cylinders by a magnetic field are demonstrated. Consecutive grafting from a polyinitiator poly(2‐(2‐bromoisobutyryloxy)ethyl methacrylate) (PBIEM) of tert‐butyl methacrylate (tBMA) and oligo(ethylene glycol) methacrylate (OEGMA) using atom‐transfer radical polymerization (ATRP) and further de‐protection yields core/shell CPBs with poly(methacrylic acid) (PMAA) as the core and POEGMA as the shell, which is evidenced by ¹H NMR, gel permeation chromatography (GPC), and dynamic and static light scattering (DLS and SLS). The resulting core/shell brush is well soluble in water and shows a pH responsiveness because of its weak polyelectrolyte core. Pearl‐necklace structures are observed by cryogenic transmission electron microscopy (cryo‐TEM) at pH 4, while at pH 7, these structures disappear owing to the ionization of the core. A similar morphology is also found for the polychelate of the core/shell CPBs with Fe³⁺ ions. Superparamagnetic magnetite nanoparticles have also been prepared and introduced into the core of the brushes. The hybrid material retains the superparamagnetic property of the magnetite nanoparticles, which is verified by superconducting quantum interference device (SQUID) magnetization measurements. Large‐scale alignment of the hybrid cylinders in relatively low magnetic fields (40–300 mT) can easily be performed when deposited on a surface. which is clearly revealed by the atomic force microscopy (AFM) and TEM measurements.     

Biocompatible,Luminescent Silver@Phenol Formaldehyde Resin Core/Shell Nanospheres: Large‐Scale Synthesis and Application for In Vivo Bioimaging

Biocompatible and green luminescent monodisperse silver/phenol formaldehyde resin core/shell spheres with controllable sizes, in the range of 180 to 1000 nm, and interesting architectures (centric, eccentric, and coenocytic core/shell spheres) have been synthesized by a facile one‐step hydrothermal approach. These spheres can be used as bioimaging labels for human lung cancer H1299 cells. The results demonstrate that the nanoparticles can be internalized into cells and exhibit no cytotoxic effects, showing that such novel biocompatible core/shell structures can potentially be used as in vivo bioimaging labels. This facile one‐pot polymerization and encapsulation technique may provide a useful tool to synthesize other core/shell particles that have potential application in biotechnology.     

Multifunctional Mesoporous Silica Nanoparticles for Cancer‐Targeted and Controlled Drug Delivery

Multifunctional mesoporous silica nanoparticles are developed in order to deliver anticancer drugs to specific cancer cells in a targeted and controlled manner. The nanoparticle surface is functionalized with amino‐β‐cyclodextrin rings bridged by cleavable disulfide bonds, blocking drugs inside the mesopores of the nanoparticles. Poly(ethylene glycol) polymers, functionalized with an adamantane unit at one end and a folate unit at the other end, are immobilized onto the nanoparticle surface through strong β‐cyclodextrin/adamantane complexation. The non‐cytotoxic nanoparticles containing the folate targeting units are efficiently trapped by folate‐receptor‐rich HeLa cancer cells through receptormmediated endocytosis, while folate‐receptor‐poor human embryonic kidney 293 normal cells show much lower endocytosis towards nanoparticles under the same conditions. The nanoparticles endocytosed by the cancer cells can release loaded doxorubicin into the cells triggered by acidic endosomal pH. After the nanoparticles escape from the endosome and enter into the cytoplasm of cancer cells, the high concentration of glutathione in the cytoplasm can lead to the removal of the β‐cyclodextrin capping rings by cleaving the pre‐installed disulfide bonds, further promoting the release of doxorubicin from the drug carriers. The high drug‐delivery efficacy of the multifunctional nanoparticles is attributed to the co‐operative effects of folate‐mediated targeting and stimuli‐triggered drug release. The present delivery system capable of delivering drugs in a targeted and controlled manner provides a novel platform for the next generation of therapeutics.     

Simple and Efficient Targeted Intracellular Protein Delivery with Self‐Assembled Nanovehicles for Effective Cancer Therapy

Protein therapy offers promising prospects for the treatment of various important diseases, thus it is highly desirable to develop a robust carrier that can deliver active proteins into cells. The development of a novel protein delivery platform based on the self‐assembly of multiarmed amphiphilic cyclodextrins (CDEH) is reported. CDEH can self‐assemble into nanoparticles in aqueous solution and achieve superior encapsulation of protein (loading capacity > 30% w/w) simply by mixing with protein solution without introducing any subsequent cumbersome steps that may inactivate proteins. More importantly, CDEH nanovehicles can be easily further modified with various targeting groups based on host–guest complexation. Using saporin as a therapeutic protein, AS1411‐aptamer‐modified CDEH nanovehicles can preferentially accumulate in tumors and efficiently inhibit tumor growth in a MDA‐MB‐231 xenograft mouse model. Moreover, folate‐targeted CDEH nanovehicles can also deliver Cas9 protein and Plk1‐targeting sgRNA into Hela cells, leading to 47.1% gene deletion and 64.1% Plk1 protein reduction in HeLa tumor tissue, thereby effectively suppressing the tumor progression. All these results indicate the potential of targeted CDEH nanovehicles in intracellular protein delivery for improving protein therapeutics.     

Preparation of Near‐IR Fluorescent Nanoparticles for Fluorescence‐Anisotropy‐Based Immunoagglutination Assay in Whole Blood

A class of novel core/shell near‐IR fluorescent nanoparticles have been prepared through co‐hydrolysis of a hydrophobic silicon alkoxide, hexadecyltrimethoxysilane, and tetraethyl orthosilicate as the dye‐doped core, followed by the formation of a hydrophilic shell via hydrolysis of tetraethyl orthosilicate in a water‐in‐oil microemulsion. The co‐hydrolysis of hexadecyltrimethoxysilane and tetraethyl orthosilicate produces a highly hydrophobic core for the entrapment of a low‐cost near‐IR fluorescence dye, methylene blue. Experimental investigation of this particular core/shell nanoparticle in comparison with conventional dye‐doped silica nanoparticles demonstrates that the hydrophobic core enables the doped dye to exhibit enhanced fluorescence and show improved stability to dye leaching and exogenous quenchers. In contrast to rhodamine B doped silica nanoparticles, the near‐IR fluorescent nanoparticles also show negligible background fluorescence and low inner‐filtration interference in complex biological systems such as whole blood. This advantage is utilized for the development of an immunoagglutination assay method based on fluorescence‐anisotropy measurement for the detection of alpha fetoprotein (AFP) in whole‐blood samples. The results reveal that increase in fluorescence anisotropy is linearly correlated with AFP concentration in the range 1.9–51.9 ng mL^–1.     

Biocompatible Poly(2‐hydroxyethyl methacrylate)‐b‐poly(L‐histidine) Hybrid Materials for pH‐Sensitive Intracellular Anticancer Drug Delivery

A series of synthetic polymer bioconjugate hybrid materials consisting of poly(2‐hydroxyethyl methacrylate) (p(HEMA)) and poly(l‐ histidine) (p(His)) are synthesized by combining atom transfer radical polymerization of HEMA with ring opening polymerization of benzyl‐N‐carboxy‐L ‐histidine anhydride. The resulting biocompatible and membranolytic p(HEMA)₂₅‐b‐p(His)_n (n = 15, 25, 35, and 45) polymers are investigated for their use as pH‐sensitive drug‐carrier for tumor targeting. Doxorubicin (Dox) is encapsulated in nanosized micelles fabricated by a self‐assembly process and delivered under different pH conditions. Micelle size is characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM) observations. Dox release is investigated according to pH, demonstrating the release is sensitive to pH. Antitumor activity of the released Dox is assessed using the HCT 116 human colon carcinoma cell line. Dox released from the p(HEMA)‐b‐p(His) micelles remains biologically active and has the dose‐dependent capability to kill cancer cells at acidic pH. The p(HEMA)‐b‐p(His) hybrid materials are capable of self‐assembling into nanomicelles and effectively encapsulating the chemotherapeutic agent Dox, which allows them to serve as suitable carriers of drug molecules for tumor targeting.     

Photo‐ and pH‐Triggered Release of Anticancer Drugs from Mesoporous Silica‐Coated Pd@Ag Nanoparticles

A smart drug delivery system integrating both photothermal therapy and chemotherapy for killing cancer cells is reported. The delivery system is based on a mesoporous silica‐coated Pd@Ag nanoplates composite. The Pd@Ag nanoplate core can effectively absorb and convert near infrared (NIR) light into heat. The mesoporous silica shell is provided as the host for loading anticancer drug, doxorubicin (DOX). The mesoporous shell consists of large pores, ～10 nm in diameter, and allows the DOX loading as high as 49% in weight. DOX loaded core–shell nanoparticles exhibit a higher efficiency in killing cancer cells than free DOX. More importantly, DOX molecules are loaded in the mesopores shell through coordination bonds that are responsive to pH and heat. The release of DOX from the core‐shell delivery vehicles into cancer cells can be therefore triggered by the pH drop caused by endocytosis and also NIR irradiation. A synergistic effect of combining chemotherapy and photothermal therapy is observed in our core‐shell drug delivery system. The cell‐killing efficacy by DOX‐loaded core–shell particles under NIR irradiation is higher than the sum of chemotherapy by DOX‐loaded particles and photothermal therapy by core–shell particles without DOX.     

Design and Fabrication of Magnetically Functionalized Core/Shell Microspheres for Smart Drug Delivery

The fabrication of magnetically functionalized core/shell microspheres by using the microfluidic flow‐focusing (MFF) approach is reported. The shell of each microsphere is embedded with magnetic nanoparticles, thereby enabling the microspheres to deform under an applied magnetic field. By encapsulating a drug, for example, aspirin, inside the microspheres, the drug release of the microspheres is enhanced under the compression–extension oscillations that are induced by an AC magnetic field. This active pumping mode of drug release can be controlled by varying the frequency and magnitude of the applied magnetic field as well as the time profile of the magnetic field. UV absorption measurements of cumulative aspirin release are carried out to determine the influence of these factors. The drug release behavior is found to be significantly different depending on whether the applied field varies sinusoidally or in a step‐function manner with time.     

Efficient Luminescence from Rare‐Earth Fluoride Nanoparticles with Optically Functional Shells

Rare‐earth fluorides are a class of materials with considerable potential in optical applications. Fluoride lattices typically permit high coordination numbers for the hosted rare‐earth ions, and the high ionicity of the rare‐earth‐to‐fluorine bond leads to a wide bandgap and very low vibrational energies. These factors make rare‐earth fluorides very useful in optical applications employing vacuum ultraviolet and near‐infrared excitation. The preparation of nanometer‐sized particles has opened the door for new properties and devices if the performance of their macroscopic counterparts can be conserved in the nanometer regime. However, at small particle sizes, defect surface states and adhering water reduce the optical efficiency. These shortcomings can be reduced by applying protective shells around the luminescent cores, which can also be involved in the luminescent process.     

A Virus‐Mimicking pH‐Responsive Acetalated Dextran‐Based Membrane‐Active Polymeric Nanoparticle for Intracellular Delivery of Antitumor Therapeutics

Achieving cellular internalization and endosomal escape remains a major challenge for many antitumor therapeutics, especially macromolecular drugs. Viral drug carriers are reported for efficient intracellular delivery, but with limited choices of payloads. In this study, a novel polymeric nanoparticle (ADMAP) is developed, resembling the structure and functional features of a virus. ADMAP is synthesized by grafting endosomolytic poly(lauryl methacrylate‐co‐methacrylic acid) on acetalated dextran. The endosomolytic polymer mimics the capsid protein for endosomal escape, and acetalated dextran resembles the viral core for accommodating payloads. After polymer synthesis, the subsequent controlled nanoprecipitation on a microfluidic device yields uniform nanoparticles with high encapsulation efficiency. At late endosomal pH (5.0), the ADMAP particles successfully destabilize endosomal membranes and release the drug payloads synergistically, resulting in a greater therapeutic efficacy compared with that of free anticancer drugs. Further conjugation of a tumor‐penetrating peptide enhances the antitumor efficacy toward 3D spheroids and finally leads to spheroid disintegration. The unique structure along with the synergistic endosomal escape and drug release make ADMAP nanoparticles favorable for intracellular delivery of antitumor therapeutics.     

The Active‐Core/Active‐Shell Approach: A Strategy to Enhance the Upconversion Luminescence in Lanthanide‐Doped Nanoparticles

Nanoparticles of NaGdF₄ doped with trivalent erbium (Er³⁺) and ytterbium (Yb³⁺) are prepared by a modified thermal decomposition synthesis from trifluoroacetate precursors in 1‐octadecene and oleic acid. The nanoparticles emit visible upconverted luminescence on excitation with near‐infrared light. To minimize quenching of this luminescence by surface defects and surface‐associated ligands, the nanoparticles are coated with a shell of NaGdF₄. The intensity of the upconversion luminescence is compared for nanoparticles that were coated with an undoped shell (inert shell) and similar particles coated with a Yb³⁺‐doped shell (active shell). Luminescence is also measured for nanoparticles lacking the shell (core only), and doped with Yb³⁺ at levels corresponding to the doped and undoped core/shell materials respectively. Upconversion luminescence was more intense for the core/shell materials than for the uncoated nanoparticles, and is greatest for the materials having the “active” doped shell. Increasing the Yb³⁺ concentration in the “core‐only” nanoparticles decreases the upconversion luminescence intensity. The processes responsible for the upconversion are presented and the potential advantages of “active‐core”/“active‐shell” nanoparticles are discussed.     

Uniform Rattle‐type Hollow Magnetic Mesoporous Spheres as Drug Delivery Carriers and their Sustained‐Release Property

A novel kind of rattle‐type hollow magnetic mesoporous sphere (HMMS) with Fe₃O₄ particles encapsulated in the cores of mesoporous silica microspheres has been successfully fabricated by sol–gel reactions on hematite particles followed by cavity generation with hydrothermal treatment and H₂ reduction. Such a structure has the merits of both enhanced drug‐loading capacity and a significant magnetization strength. The prepared HMMSs realize a relatively high storage capacity up to 302 mg g^?1 when ibuprofen is used as a model drug, and the IBU–HMMS system has a sustained‐release property, which follows a Fick's law.     

Self‐Assembly of a Micelle Structure from Graft and Diblock Copolymers: An Example of Overcoming the Limitations of Polyions in Drug Delivery

A novel mixed micelle with a multifunctional core and shell is successfully prepared from a graft copolymer, poly(N‐isopropyl acrylamide‐co‐methacrylic acid)‐g‐poly(d,l ‐lactide) (P(NIPAAm‐co‐MAAc)‐g‐PLA) and two diblock copolymers, poly(ethylene glycol)‐b‐poly(d,l ‐lactide) and poly (2‐ethyl‐2‐oxazoline)‐b‐poly(d,l ‐lactide). This nanostructure completely screens the highly negative charges of the graft copolymer and exhibits multifunctionality because it has a specialized core/shell structure. An example of this micelle structure used in intracellular drug delivery demonstrates a strong relationship between drug release and the functionality of the mixed micelle. Additionally, the efficiency of the screening feature is also displayed in the cytotoxicities; mixed micelles exhibit higher drug activity and lower material cytotoxicity than micelles from P(NIPAAm‐co‐MAAc)‐g‐PLA ([NIPAAm]/[MAAc]/[PLA] = 84:5.9:2.5 mol/mol) copolymer. This study not only presents a new micelle structure generated using a graft–diblock copolymer system, but also elucidates concepts upon which the preparation of a multifunctional micelle from a graft copolymer with a single (or many) diblock copolymer(s) can be based for applications in drug delivery.