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Quantum-sized gold nanoclusters (AuNCs) are emerging as theranostic agents-those that combine diagnostics and therapeutic properties-given their ultrasmall size

We introduce xanthate-functionalized poly(cyclic imino ethers)s (PCIEs), specifically poly(2-ethyl-2-oxazoline) and poly(2-ethyl-2-oxazine) given their stealth characteristics, as an attractive alternative to conventional thiol-based ligands for the synthesis of highly monodisperse and fluorescent gold nanoclusters (AuNCs). The xanthate in the PCIEs interacts with Au ions, acting as a well-controlled template for the direct formation of PCIE-AuNCs. This method yields red-emitting AuNCs with a narrow emission peak (λem = 645 nm), good quantum yield (4.3-4.8%), long fluorescence decay time (∼722-844 ns), and unprecedented product yield (>98%). The PCIE-AuNCs exhibit long-term colloidal stability, biocompatibility, and antifouling properties, enabling a prolonged blood circulation, lower nonspecific accumulation in major organs, and better renal clearance when compared with AuNCs without polymer coating. The advances made here in the synthesis of metal nanoclusters using xanthate-functionalized PCIEs could propel the production of highly monodisperse, biocompatible, and renally clearable nanoprobes in large-scale for different theranostic applications.

Since delivering drugs to an entire tumoral region leads to high therapeutic efficacy and good prognosis, achieving deep tumoral penetration of drugs is a major issue in cancer treatment. In this regard, conventional nanomedicines (50 nm) have shown limitations in cancer therapy, primarily attributed to the heterogeneous distribution of drugs because of the physiological barrier of the tumor interstitial space. To address this issue, we prepared transformable hybrid nanoparticles (TNPs) consisting of a pH-responsive nanocarrier (PEG-PBAE) and doxorubicin (DOX)-conjugated ultrasmall (3 nm) gold nanoparticles (nanosatellites). It has been shown that PEG-PBAE can serve as a reservoir for nanosatellites and release them in mildly acidic conditions (pH 6.5), mimicking the tumor microenvironment. When DOX-loaded TNPs (DOX-TNPs) were intravenously injected into tumor-bearing mice, they successfully accumulated and dissociated at the extracellular level of the tumor, leading to the disclosure of nanosatellites and free DOX. While the free DOX accumulated in tumor tissue near blood vessels, the deeply diffused nanosatellites were taken up by the tumor cell, followed by the release of DOX via cleavage of pH-responsive ester linkages in the nanosatellites at the intracellular level. Consequently, the DOX-TNPs effectively suppressed tumor growth through improved tumor penetration of DOX, suggesting their promising potential as a cancer nanomedicine.Deep tumor penetration of anticancer drug is an important issue for high therapeutic efficacy. If the drugs cannot reach cancer cells in a sufficient concentration, their effectiveness will be limited. In this regard, conventional nanomedicine showed only modest therapeutic efficacy since they cannot deliver their payloads to the deep site of tumor tissue. This heterogeneous distribution of the drug is primarily attributed to the physiological barriers of the tumor microenvironment, including a dense extracellular matrix. To surmount this challenge, we developed tumor acidity-triggered transformable nanoparticles. By encapsulating doxorubicin-conjugated ultrasmall gold nanosatellites into the nanoparticles, the drug was not significantly bound to genetic materials, resulting in its minimal sequestration near the vasculature and deep tumor penetration. Our strategy could resolve not only the poor penetration issue of the drug but also its restricted tumor accumulation, suggesting the potential as an effective nanotherapeutics.

Reactive oxygen species (ROS)-sensitive imaging can be used to distinguish ROS-rich diseased tissues from normal tissues. Herein, we developed a selective H2O2 concentration-dependent on-off gold nanoprobe and demonstrated its in vitro fluorescence imaging application using activated macrophages cells. The nanoprobe was prepared by covalent conjugation of polyethylene glycol and fluorescein dyes on gold nanoparticle surface through a H2O2-sensitive diselenide linker. The nanoprobes were well-dispersed in aqueous solution and inactive in H2O2-deficient conditions, ascribed to fluorescence resonance energy transfer between dye and gold nanoparticles. Once the nanoprobe was exposed to an H2O2-rich environment, it was quickly activated by diselenide bond dissociation, leading to fluorophore release from its surfaces. Overall, gold nanoprobe with the diselenide linker might be a potential candidate for ROS imaging.

Trop2, a transmembrane glycoprotein, has emerged as a biomarker for targeted cancer therapy since it is overexpressed in 80% of triple negative breast cancer (TNBC) patients. For the site-specific delivery of the anticancer drug into TNBC, anti-Trop2 antibody-conjugated nanoparticles (ST-NPs) were prepared as the potential nanocarrier, composed of carboxymethyl dextran (CMD) derivatives with bioreducible disulfide bonds. Owing to its amphiphilicity, the CMD derivatives were self-assembled into nano-sized particles in an aqueous condition. Doxorubicin (DOX), chosen as a model anticancer drug, was effectively encapsulated into the nanoparticles. DOX-loaded ST-NPs (DOX-ST-NPs) rapidly released DOX in the presence of 10mM glutathione (GSH), whereas the DOX release is significantly retarded in the physiological condition (PBS, pH 7.4). Confocal microscopic images and flow cytometry analysis demonstrated that DOX-ST-NPs were selectively taken up by MDA-MB-231 as the representative Trop2-expressing TNBC cells. Consequently, DOX-ST-NPs exhibited higher toxicity to Trop2-positive MDA-MB-231 cancer cells, compared to DOX-loaded control nanoparticles without the disulfide bond or anti-Trop2 antibody. Overall, ST-NPs might be a promising carrier of DOX for targeted TNBC therapy.

Conventional cancer targeting with nanoparticles has been based on the assumed enhanced permeability and retention (EPR) effect. The data obtained in clinical trials to date, however, have rarely supported the presence of such an effect. To address this challenge, we formulated intracellular nitric oxide-generating nanoparticles (NO-NPs) for the tumor site-specific delivery of NO, a well-known vasodilator, with the intention of boosting EPR. These nanoparticles are self-assembled under aqueous conditions from amphiphilic copolymers of poly(ethylene glycol) and nitrated dextran, which possesses inherent NO release properties in the reductive environment of cancer cells. After systemic administration of the NO-NPs, we quantitatively assessed and visualized increased tumor blood flow as well as enhanced vascular permeability than could be achieved without NO. Additionally, we prepared doxorubicin (DOX)-encapsulated NO-NPs and demonstrated consequential improvement in therapeutic efficacy over the control groups with considerably improved DOX intratumoral accumulation. Overall, this proof of concept study implies a high potency of the NO-NPs as an EPR enhancer to achieve better clinical outcomes.

The cell-free approach to foreignizing tumor cells with non-self antigens has received increasing attention as a method to induce cytotoxic T lymphocyte (CTL)-mediated immunological rejection of tumors, because the clinical translation of the conventional CTL-based cancer immunotherapies has been limited by a complicated manufacturing process and autotransplantation. In this study, we prepared matrix metalloproteinase 9 (MMP9)-responsive polymeric conjugates consisting of PEGylated hyaluronic acid (HA) as the targeting moiety and ovalbumin (OVA) as the model foreign antigen. The MMP9-cleavable linker was introduced between PEG and the HA backbone to facilitate the detachment of the PEG corona from the conjugate at the tumor site. From the in vitro cellular uptake study, it was revealed that the conjugate was effectively taken up by the CD44-expressing TC-1 cancer cells in the presence of MMP9 via receptor-mediated endocytosis. When the conjugate was systemically administered into the tumor-bearing mice with endogenous OVA-specific CTLs, the tumor growth was markedly inhibited, which was attributed to the significant antigen presentation on the tumor cells. Overall, the MMP9-responsive conjugates bearing foreign antigens might have the potential as an alternative to CTL-based cancer immunotherapeutics.

Although sonodynamic therapy (SDT) has emerged as a potential alternative to conventional photodynamic therapy, the low quantum yield of the sonosensitizer such as TiO2 nanoparticles (NPs) is still a major concern. Here, we have developed hydrophilized Au-TiO2 nanocomposites (HAu-TiO2 NCs) as sonosensitizers for improved SDT. The physicochemical properties of HAu-TiO2 NCs were thoroughly studied and compared with their counterparts without gold deposition. Upon exposure of HAu-TiO2 NCs to ultrasound, a large quantity of reactive oxygen species (ROS) were generated, leading to complete suppression of tumor growth after their systemic administration in vivo. Overall, it was evident that the composites of gold with TiO2 NPs significantly augmented the levels of ROS generation, implying their potential as SDT agents for cancer therapy.

Hypoxia is a condition found in various intractable diseases. Here, we report self-assembled nanoparticles which can selectively release the hydrophobic agents under hypoxic conditions. For the preparation of hypoxia-responsive nanoparticles (HR-NPs), a hydrophobically modified 2-nitroimidazole derivative was conjugated to the backbone of the carboxymethyl dextran (CM-Dex). Doxorubicin (DOX), a model drug, was effectively encapsulated into the HR-NPs. The HR-NPs released DOX in a sustained manner under the normoxic condition (physiological condition), whereas the drug release rate remarkably increased under the hypoxic condition. From in vitro cytotoxicity tests, it was found the DOX-loaded HR-NPs showed higher toxicity to hypoxic cells than to normoxic cells. Microscopic observation showed that the HR-NPs could effectively deliver DOX into SCC7 cells under hypoxic conditions. In vivo biodistribution study demonstrated that HR-NPs were selectively accumulated at the hypoxic tumor tissues. As consequence, drug-loaded HR-NPs exhibited high anti-tumor activity in vivo. Overall, the HR-NPs might have a potential as nanocarriers for drug delivery to treat hypoxia-associated diseases.

In recent years, hyaluronic acid (HA) has attracted significant interest in development of drug delivery systems because of its intrinsic physicochemical and biological properties, including water solubility, viscoeleasticity, non-immunogenicity, biocompatibility, and biodegradability. In addition, HA has the ability to selectively bind specific receptors on the disease-related cells such as cancer cells and activated macrophages, followed by receptor-mediated endocytosis. Owing to these unique features, HA has been extensively used for development of the targetable carriers to deliver the therapeutic and imaging agents. In this review, we discuss the recent progress in various HA-based conjugates for cancer therapy and imaging, in which the active agents are covalently conjugated or physically encapsulated.

To minimize the premature drug release of nanocarriers, we have developed chemically cross-linked bioreducible polymersomes (CLPMs) that can specifically release the drug inside cancer cells. Polymersomes were prepared using poly(ethylene glycol)-b-poly(lysine)-b-poly(caprolactone), a biocompatible triblock copolymer. To chemically cross-link the polymersomes, the primary amine of the triblock copolymer was reacted with a disulfide-containing cross-linker. Doxorubicin (DOX) was chosen as a model anti-cancer drug, and was effectively encapsulated into the CLPMs. The drug-loaded polymersomes greatly retarded the release of DOX under physiological conditions (pH 7.4), whereas the release rate of DOX increased remarkably in the presence of 10 mM glutathione, mimicking an intracellular environment. Microscopic observation showed that DOX-loaded CLPMs could effectively deliver the drug into an intracellular level of SCC7 cancer cells, leading to high cytotoxicity. These observations suggest that CLPMs are promising nanocarriers for intracellular DOX delivery.

Polysialic acid (PSA), a natural hydrophilic polysaccharide, is a potential alternative to poly(ethylene glycol) as the hydrophilic constituent of the polymeric amphiphiles for biomedical applications. In this study, amphiphilic block copolymers were prepared based on PSA as the hydrophilic block and polycaprolactone (PCL) as the hydrophobic block. The block copolymers formed micelles with spherical shapes in an aqueous environment. The average sizes of the nanoparticles were in the range of 270-390 nm, depending on the block length of PCL. The zeta potential values of the micelles were approximately -20 mV due to the negatively charged carboxylic acids of PSA. The nanoparticles showed good stability for five days in a physiological solution (pH 7.4), and had low critical micelle concentration values (1.68-8.54 microg/ml). The in-vitro cytotoxicity tests confirmed that the PSA-PCL micelles had little cytotoxicity. All these results suggest that the PSA-PCL block copolymers can form nano-sized micelles with high stability and low toxicity, implying their high potential for biomedical application.

The carboxymethyl dextran-y-cyclodextrin (CMD-yCD) conjugate was prepared as the carrier for the delivery of the poorly water-soluble anticancer drug, doxorubicin (DOX). The conjugate could form self-assembled nanoparticles (315 nm in diameter) in an aqueous solution, which might be due to the hydrogen bonding among yCD molecules in the conjugate. DOX was effectively encapsulated into CMD-yCD nanoparticles (CMD-NPs) by the emulsion method. In particular, regardless of the feed amount of DOX, its loading efficiencies were always greater than 70%. CMD-NPs released DOX in a sustained manner, owing to the inclusion complex formation between DOX and yCD. When Cy5.5-labeled CMD-NPs were treated with SCC7 cancer cells, strong fluorescence signals were observed at the cytosol, indicating effective intracellular uptake. In addition, DOX-loaded CMD-NPs exhibited dose-dependent cytotoxicity to SCC7 cancer cells. However, the empty nanoparticles did not show toxicity to the cells, implying their high biocompatibility. Overall, these results suggest that the CMD-gammaCD conjugate could be a useful carrier for the delivery of DOX.

Although sonodynamic therapy (SDT) has emerged as a potential alternative to conventional photodynamic therapy, the low quantum yield of the sonosensitizer such as TiO

Stimuli-responsive micelles have emerged as the drug carrier for cancer therapy since they can exclusively release the drug via their structural changes in response to the specific stimuli of the target site. Herein, we developed the in situ diselenide-crosslinked micelles (DCMs), which are responsive to the abnormal ROS levels of tumoral region, as anticancer drug carriers. The DCMs were spontaneously derived from selenol-bearing triblock copolymers consisting of polyethylene glycol (PEG) and polypeptide derivatives. During micelle formation, doxorubicine (DOX) was effectively encapsulated in the hydrophobic core, and diselenide crosslinks were formed in the shell. The DCMs maintained their structural integrity, at least for 6 days in physiological conditions, even in the presence of destabilizing agents. However, ROS-rich conditions triggered rapid release of DOX from the DOX-encapsulating DCMs (DOX-DCMs) because the hydrophobic diselenide bond was cleaved into hydrophilic selenic acid derivatives. Interestingly, after their systemic administration into the tumor-bearing mice, DOX-DCMs delivered significantly more drug to tumors (1.69-fold and 3.73-fold higher amount compared with their non-crosslinked counterparts and free drug, respectively) and effectively suppressed tumor growth. Overall, our data indicate that DCMs have great potential as drug carriers for anticancer therapy.

The non-invasive photodynamic therapy has been limited to treat superficial tumours, primarily ascribed to poor tissue penetration of light as the energy source. Herein, we designed a long-circulating hydrophilized titanium dioxide nanoparticle (HTiO2 NP) that can be activated by ultrasound to generate reactive oxygen species (ROS). When administered systemically to mice, HTiO2 NPs effectively suppressed the growth of superficial tumours after ultrasound treatments. In tumour tissue, the levels of proinflammatory cytokines were elevated several fold and intense vascular damage was observed. Notably, ultrasound treatments with HTiO2 NPs also suppressed the growth of deeply located liver tumours at least 15-fold, compared to animals without ultrasound treatments. This study provides the first demonstration of the feasibility of using HTiO2 NPs as sensitizers for sonodynamic therapy in vivo.

Overproduction of hydrogen peroxide is involved in the pathogenesis of inflammatory diseases such as cancer and arthritis. To image hydrogen peroxide via chemiluminescence resonance energy transfer in the near-infrared wavelength range, we prepared quantum dots functionalized with a luminol derivative.

An amphiphilic diblock copolymer bearing the reduction-sensitive linker, composed of poly(ethylene glycol) (PEG) and hydrophobic poly(γ-benzyl L-glutamate) (PBLG), was prepared as the potential carrier of doxo- rubicin (DOX) via a facile synthetic method in the presence of a shell-sheddable PEG macroinitiator (PEG-SS-NH2). Owing to its amphiphilic nature, the copolymer (PEG-SS-PBLG) formed spherical micelles (137 nm in diameter) in aqueous conditions. The micelles were stable under the physiologic condition (pH 7.4) and were readily cleaved in the presence of glutathione (GSH), a tripeptide reducing the disulfide bond in the cytoplasm of the cell. DOX, chosen as a model anticancer drug, was effectively encapsulated into the hydrophobic core of the micelle with high loading efficiency (>75%). The micelle released DOX completely within 18 h at 10 mM GSH mimicking the intracellular condition, whereas only 34% of the drug was released from the micelle at 2 µM GSH. In vitro cytotoxicity tests revealed that DOX-loaded reduction-sensitive micelles are more toxic to SCC7 cells than reduction-insensitive con- trol micelles. These results suggest that PEG-SS-PBLG is the promising carrier for the intracellular delivery of DOX.

Background: Targeted cancer therapy has been extensively developed to improve the quality of treatment by reducing the systemic exposure of cytotoxic drug. Polymeric nanoparticles with conjugated targeting agents are widely investigated because they offer tunability in particle size, drug release profile and biocompatibility. Materials & methods: Here, we have prepared targeted multifunctional nanoparticles composed of a poly(lactic-co-glycolic acid) matrix, ZnS:Mn2+ quantum dots and camptothecin, and targeted them to EGF receptor overexpressing cells with a cetuximab antibody. Results: Physicochemical characterization of multifunctional nanoparticles showed stable particles with sizes of

Amphiphilic block copolymers bearing an acid-sensitive orthoester linkage, composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(γ-benzyl L-glutamate) (PBLG), were prepared as the carrier capable of selectively releasing the hydrophobic drug at the mildly acidic condition. Diblock copolymers with various lengths of PBLG were synthesized via ring opening polymerization of benzyl glutamate NCA in the presence of the acid-labile PEG as a macroinitiator. Owing to their amphiphilicities, the copolymers formed spherical micelles in aqueous conditions, and their particle sizes (22–106 nm in diameter) were dependent on the block length of PBLG. These nanoparticles were stable in the physiological buffer (pH 7.4), whereas they were readily decomposed under the acidic condition. In particular, the block copolymer with a smaller hydrophobic portion was rapidly disassembled under the acidic condition. Doxorubicin (DOX), chosen as the model anti-cancer drug, was effectively encapsulated into the hydrophobic core of the micelles using the solvent casting method. The loading efficiency depended on the hydrophobic block length of the copolymer; i.e., the longer hydrophobic block allowed for loading of larger amounts of the drug. In vitro release studies demonstrated that DOX was slowly released from the pH-sensitive micelles in the physiological buffer (pH 7.4), whereas the release rate of DOX significantly increased under the acidic condition (pH 5.0). From the in vitro cytotoxicity test, it was found that DOX-loaded pH-sensitive micelles showed higher toxicity to SCC7 cancer cells than DOX-loaded micelles without the orthoester linker. These results suggest that the amphiphilic block copolymer bearing the orthoester linkage is useful for pH-triggered delivery of the hydrophobic drug.

Nanoformulation of curcumin, (a low molecular weight hydrophobic drug) was prepared by using dextran sulphate and chitosan. The developed nanoparticles were characterized by Dynamic Light Scattering measurements (DLS), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD) and Differential Thermal Analysis (DTA). The prepared system showed an average size of 200–220 nm with a zeta potential value of −30 mV and showed ∼74% drug entrapment efficiency. In vitro drug release studies showed a controlled and pH dependent curcumin release over a period of one week. The cytocompatibility of bare nanoparticles was verified by MTT assay; cellular internalisation of curcumin loaded nanoparticles was confirmed by fluorescent imaging and quantified spectrophotometrically, anticancer activity of curcumin loaded nanoparticles was proved by MTT assay and reconfirmed by apoptosis assay (FACS). The results showed preferential killing of cancer cells compared to normal cells by the curcumin-loaded nanoparticles. Thus the developed curcumin loaded nanoformulation could be a promising candidate in cancer therapy.

The amphiphilic block copolymer, composed of hydrophilic dextran sulfate as the targeting ligand and hydrophobic polycaprolactone as the hydrophobic segment, was prepared via click chemistry to develop self-assembled nanoparticles for targeting rheumatoid arthritis.

Bioreducible carboxymethyl dextran (CMD) derivatives are synthesized by the chemical modification of CMD with lithocholic acid (LCA) through a disulfide linkage. The hydrophobic nature of LCA allows the conjugates (CMD-SS-LCAs) to form self-assembled nanoparticles in aqueous conditions. Depending on the degree of LCA substitution, the particle diameters range from 163 to 242 nm. Doxorubicin (DOX), chosen as a model anticancer drug, is effectively encapsulated into the nanoparticles with high loading efficiency (>70%). In vitro optical imaging tests reveal that the fluorescence signal of DOX quenched in the bioreducible nanoparticles is highly recovered in the presence of glutathione (GSH), a tripeptide capable of reducing disulfide bonds in the intracellular compartments. Bioreducible nanoparticles rapidly release DOX when they are incubated with 10 mm GSH, whereas the drug release is greatly retarded in physiological buffer (pH 7.4). DOX-loaded bioreducible nanoparticles exhibit higher toxicity to SCC7 cancer cells than DOX-loaded nanoparticles without the disulfide bond. Confocal laser scanning microscopy observation demonstrate that bioreducible nanoparticles can effectively deliver DOX into the nuclei of SCC7 cells. In vivo biodistribution study indicates that Cy5.5-labeled CMD-SS-LCAs selectively accumulate at tumor sites after systemic administration into tumor-bearing mice. Notably, DOX-loaded bioreducible nanoparticles exhibit higher antitumor efficacy than reduction-insensitive control nanoparticles. Overall, it is evident that bioreducible CMD-SS-LCA nanoparticles are useful as a drug carrier for cancer therapy.

Polysialic acid (PSA), a natural hydrophilic polysaccharide, is a potential alternative to poly(ethylene glycol) as the hydrophilic constituent of the polymeric amphiphiles for biomedical applications. In this study, amphiphilic block copolymers were prepared based on PSA as the hydrophilic block and polycaprolactone (PCL) as the hydrophobic block. The block copolymers formed micelles with spherical shapes in an aqueous environment. The average sizes of the nanoparticles were in the range of 270-390 nm, depending on the block length of PCL. The zeta potential values of the micelles were approximately -20 mV due to the negatively charged carboxylic acids of PSA. The nanoparticles showed good stability for five days in a physiological solution (pH 7.4), and had low critical micelle concentration values (1.68-8.54 microg/ml). The in-vitro cytotoxicity tests confirmed that the PSA-PCL micelles had little cytotoxicity. All these results suggest that the PSA-PCL block copolymers can form nano-sized micelles with high stability and low toxicity, implying their high potential for biomedical application.

Stimuli-sensitive polymersomes, composed of amphiphilic block copolymers, have emerged as a promising nanocarrier for triggered release of anticancer drugs. In this study, we synthesized a bioreducible, amphiphilic triblock copolymer based on poly(ethylene glycol)-b-poly(lysine)-b-poly(caprolactone) bearing a disulfide bond (PEG-b-PLys-SS-PCL). Owing to its unique amphiphilicity, the copolymer formed self-assembled polymersomes (256 nm diameter) under aqueous conditions. These polymersomes were stable in physiological solution (pH 7.4), whereas they readily disintegrated under a reductive environment similar to an intracellular condition. The polymersomes could simultaneously encapsulate the hydrophobic camptothecin (CPT) in their membrane and the hydrophilic doxorubicin·hydrochloride (DOX·HCl) in their aqueous cores. The polymersomes released the drugs in a sustained manner under physiological conditions (pH 7.4), whereas the drug release rates dramatically increased in a reductive environment at 10 mM glutathione. From in vitro cytotoxicity tests, it was found that dual drug-loaded polymersomes showed significantly higher cytotoxicity to SCC7 cancer cells than those with the single drug. These results suggest that the polymersomes bearing the bioreducible linker have high potential as carriers for intracellular dual-drug delivery.