Functional mesoporous silica nanoparticles (MSNs) for highly controllable drug release and synergistic therapy.

Synergistic therapy involving two or more therapeutic agents with different anticancer mechanisms represents a promising approach to eradicate chemotherapy-refractory cancers. However, the preparation of a synergistic therapy platform generally involves complicated procedures to encapsulate different therapeutic agents and thereby increases the purification difficulty. In this work, we reported a simple but robust strategy to prepare a highly controllable drug delivery system (DDS) for synergistic cancer therapy. To construct this robust DDS, mesoporous silica nanoparticles (MSNs) were employed as a nanoplatform to encapsulate anticancer drug doxorubicin (DOX). After using a tumor-targeting cellular membrane-penetrating peptide (TCPP) and a mitochondria-targeting therapeutic peptide (TPP) to seal the surface pores via disulfide bonds, these newly developed MSNs can target cancer cells, penetrate cell membrane and rapidly release anticancer drug and mitochondria-targeted peptide in cytoplasm, inducing a remarkable synergistic anticancer effect. The new design concept reported here will promote the development of targeted and smart DDSs for synergistic cancer therapy.

Smart and hyper-fast responsive polyprodrug nanoplatform for targeted cancer therapy.

The rapid development and clinical trials of biodegradable nanoparticles (NPs) are heavily hindered by many factors, including poor drug loading, low drug concentration at disease sites, lack of active targeting function, etc. Herein, we developed a new smart and hype-responsive polyprodrug platform with five key elements (i.e. chemically incorporated drug molecules in backbone, stimuli-responsive bond, hyper-fast chain-breakage ability, hydrophilic segment and targeting ligand). Using 10-hydroxycamptothecin (HCPT) as model drug, we designed and prepared an exemplified redox-responsive amphiphilic polyprodrug via polycondensation and "click" chemistry. This polymer is composed of a hydrophobic HCPT-based polyprodrug, a hydrophilic poly(ethylene oxide) (PEG) chain and a tumor-targeting RGD tail. Employing nanoprecipitation technique, small-sized NPs (<70 nm) can be obtained. The in vitro and in vivo results prove that this newly developed nanoplatform has the following unique characteristics: 1) high and constant drug loading (>36 wt.%), 2) excellent tumor-targeting performance, 3) hyper-fast redox-responsive drug release (around 70% accumulative release within 2 h), 4) long blood circulation and 5) significant inhibition of tumor growth without side effects.

Fabrication of Alginate/Calcium Carbonate Hybrid Microparticles for Synergistic Drug Delivery.

A hybrid drug delivery system coloaded with different drugs for synergistic drug delivery was developed. Alginate/calcium carbonate (CaCO3) hybrid microparticles (MPs) were fabricated via a facile coprecipitation method under mild conditions without using any organic solvent and surfactant. Due to the incorporation of negatively charged alginate chains onto the surface, the obtained hybrid MPs with spherical morphology showed good colloidal stability in an aqueous solution. An antitumor drug (doxorubicin, DOX) and a drug resistance reversal agent (verapamil, VP) were coloaded in the hybrid MPs simultaneously to obtain dual-drug-loaded MPs (DOX/VP/MP). Due to the presence of inorganic CaCO3 (∼54 wt%), the drugs could be loaded in the hybrid MPs with high encapsulation efficiency and the drug release could be effectively sustained. The cell growth inhibition of the drug-loaded MPs was evaluated in HeLa cells. An in vitro study showed DOX/VP/MP exhibited higher cell growth inhibition as compared with DOX monodrug-loaded MPs (DOX/MP). These results suggest the hybrid MPs can potentially be used as a synergistic drug delivery platform for cancer chemotherapy.

Activable Cell-Penetrating Peptide Conjugated Prodrug for Tumor Targeted Drug Delivery.

In this paper, an activable cell-penetrating peptide (CR8G3PK6, ACPP) with a shielding group of 2,3-dimethylmaleic anhydride (DMA) was conjugated with antitumor drug doxorubicin (DOX) to construct a novel prodrug (DOX-ACPP-DMA) for tumor targeted drug delivery. The shielding group of DMA linked to the primary amines of K6 through the amide bond was used to block the cell-penetrating function of the polycationic CPP (R8) through intramolecular electrostatic attraction at physiological pH 7.4. At tumor extracellular pH 6.8, the hydrolysis of DMA led to charge reversal, activating the pristine function of CPP for improved cellular uptake by tumor cells. Confocal laser scanning microscopy (CLSM) and flow cytometry studies revealed that the cellular uptake of DOX-ACPP-DMA was significantly enhanced after acid-triggered activation in both HeLa and COS7 cells. After cell internalization, the overexpressed intracellular proteases would further trigger drug release in cells. Both in vitro and in vivo investigations showed that the peptidic prodrug exhibited significant tumor growth inhibition and demonstrated great potential for tumor therapy.

Enzyme-induced and tumor-targeted drug delivery system based on multifunctional mesoporous silica nanoparticles.

Functional mesoporous silica particles have attracted growing research interest for controlled drug delivery in targeted cancer therapy. For the purpose of efficient targeting tumor cells and reducing the adverse effect of antitumor drug doxorubicin (DOX), biocompatible and enzyme-responsive mesoporous silica nanoparticles (MSNs) with tumor specificity were desired. To construct these functional MSNs, the classic rotaxane structure formed between alkoxysilane tether and α-cyclodextrin (α-CD) was employed to anchor onto the orifices of MSNs as gatekeeper in this work. After subsequent modification by multifunctional peptide (azido-GFLGR7RGDS with tumor-targeting, membrane-penetrating, and cathepsin B-responsive functions) to stabilize the gatekeeper, the resulting functional MSNs showed a strong ability to load and seal DOX in their nanopores. When incubating these DOX-loaded MSNs with tumor and normal cells, the nanoparticles could efficiently employ their surface-encoded RGDS and continuous seven arginine (R7) sequences to target tumor cells, penetrate the cell membrane, and enter tumor cells. Because cathepsin B overexpressed in late endosomes and lysosomes of tumor cells could specifically hydrolyze GFLG sequences of the nanovalves, the DOX-loaded MSNs showed an "off-on" drug release behavior that ∼80% loaded DOX could be released within 24 h and thus showed a high rate of apoptosis. Furthermore, in vitro cellular experiments indicated that DOX-loaded MSNs (DOX@MSN-GFLGR7RGDS/α-CD) had high growth inhibition toward αvß3-positive HeLa cancerous cells. The research might offer a practical way for designing the tumor-targeted and enzyme-induced drug delivery system for cancer therapy.

Complementary hydrogen bonding interaction triggered co-assembly of an amphiphilic peptide and an anti-tumor drug.

We report a new tumor-targeting amphiphilic peptide that can form complementary hydrogen bonds with anti-tumor drug methotrexate (MTX), leading to reversible self-assembled morphology transition from loose micelles to densely packed nanorods or nanofibers. The MTX loaded nanorods can target tumor cells and show more than 2-fold higher cytotoxicity (IC50 = 0.38 mg L(-1)) than that towards normal cells (IC50 = 0.89 mg L(-1)).

Cancer-targeted functional gold nanoparticles for apoptosis induction and real-time imaging based on FRET.

A versatile gold nanoparticle-based multifunctional RB-DEVD-AuNP-DTP has been developed to induce the targeted apoptosis of cancer cells and image in real time the progress of the apoptosis. The multifunctional nanoparticles were demonstrated to have the ability to initiate mitochondria-dependent apoptosis and activate caspase-3 for real-time imaging of the progression of apoptosis.

pH responsive micelle self-assembled from a new amphiphilic peptide as anti-tumor drug carrier.

An acid-responsive amphiphilic peptide that contains KKGRGDS sequence in hydrophilic head and VVVVVV sequence in hydrophobic tail was designed and prepared. In neutral or basic medium, this amphiphilic peptide can self-assemble into micelles through hydrogen bonding and hydrophobic interactions. If changing the solution pH to an acidic environment, the electrostatic repulsion interaction among the ionized lysine (K) residues will prevent the self-assembly of the amphiphilic peptide, leading to the dissociation of micelles. The anti-tumor drug of doxorubicin (DOX) was chosen and loaded into the self-assembled micelles of the amphiphilic peptide to investigate the influence of external pH change on the drug release behavior. As expected, the micelles show a sustained DOX release in neutral medium (pH 7.0) but fast release behavior in acidic medium (pH 5.0). When incubating these DOX-loaded micelles with HeLa and COS7 cells, due to the over-expression of integrins on cancer cells, the micelles can efficiently use the tumor-targeting function of RGD sequence to deliver the drug into HeLa cells. Combined with the low cytotoxicity of the amphiphilic peptide against both HeLa and COS7 cells, the amphiphilic peptide reported in this work may be promising in clinical application for targeted drug delivery.

Multi-functional envelope-type nanoparticles assembled from amphiphilic peptidic prodrug with improved anti-tumor activity.

A novel multifunctional amphiphilic peptidic prodrug was reported here by conjugating the antitumor drug of doxorubicin (DOX) to the hydrophobic tail of a designed peptide-amphiphile (PA), in which the hydrophilic peptide headgroup comprises a glycine-arginine-glycine-aspartic acid-serine (GRGDS) sequence and octaarginine (R8) sequence. Because of the amphiphilic nature, this peptidic prodrug can spontaneously self-assemble into spherical multifunctional envelop-type nanoparticles (MENPs) with the functional peptide sequences gathered on surface. By means of the multifunctions of RGD-mediated tumor targeting, R8-mediated membrane penetration and intracellular protease-mediated hydrolyzing peptide bonds, the MENPs could targeted deliver doxorubicin (DOX) to tumor cells, showing improved antitumor activity both in vitro and in vivo with much reduced side effects.

Dual-targeting pro-apoptotic peptide for programmed cancer cell death via specific mitochondria damage.

Mitochondria are vital organelles to eukaryotic cells. Damage to mitochondria will cause irreversible cell death or apoptosis. In this report, we aim at programmed cancer cell death via specific mitochondrial damage. Herein, a functionalized pro-apoptotic peptide demonstrates a dual-targeting capability using folic acid (FA) (targeting agent I) and triphenylphosphonium (TPP) cation (targeting agent II). FA is a cancer-targeting agent, which can increase the cellular uptake of the pro-apoptotic peptide via receptor-mediated endocytosis. And the TPP cation is the mitochondrial targeting agent, which specifically delivers the pro-apoptotic peptide to its particular subcellular mitochondria after internalized by cancer cells. Then the pro-apoptotic peptide accumulates in mitochondria and causes its serious damage. This dual-targeting strategy has the potential to effectively transport the pro-apoptotic peptide to targeted cancer cell mitochondria, inducing mitochondrial dysfunction and triggering the mitochondria-dependent apoptosis to efficiently eliminate cancer cells.

In situ recognition of cell-surface glycans and targeted imaging of cancer cells.

Fluorescent sensors capable of recognizing cancer-associated glycans, such as sialyl Lewis X (sLe(x)) tetrasaccharide, have great potential for cancer diagnosis and therapy. Studies on water-soluble and biocompatible sensors for in situ recognition of cancer-associated glycans in live cells and targeted imaging of cancer cells are very limited at present. Here we report boronic acid-functionalized peptide-based fluorescent sensors (BPFSs) for in situ recognition and differentiation of cancer-associated glycans, as well as targeted imaging of cancer cells. By screening BPFSs with different structures, it was demonstrated that BPFS1 with a FRGDF peptide could recognize cell-surface glycan of sLe(x) with high specificity and thereafter fluorescently label and discriminate cancer cells through the cooperation with the specific recognition between RGD and integrins. The newly developed peptide-based sensor will find great potential as a fluorescent probe for cancer diagnosis.

Therapeutic nanomedicine based on dual-intelligent functionalized gold nanoparticles for cancer imaging and therapy in vivo.

A novel strategy to construct a therapeutic system based on functionalized AuNPs which can specifically respond to tumor microenvironment was reported. In the therapeutic system, doxorubicin was conjugated to AuNPs via thiol-Au bond by using a peptide substrate, CPLGLAGG, which can be specifically cleaved by the protease. In vivo study shows that after injection of the functionalized AuNPs to the tumor-bearing mice, the over-expressed protease of MMP-2 in tumor tissue and intracellular GSH can lead to the rapid release of the anti-tumor drug (doxorubicin) from the functionalized AuNPs to inhibit tumor growth and realize fluorescently imaging simultaneously. The functionalized AuNPs with tumor-triggered drug release property can further improve the efficacy and reduce side effects significantly.

Photo-switched self-assembly of a gemini α-helical peptide into supramolecular architectures.

An azobenzene-linked symmetrical gemini α-helical peptide was designed and prepared to realize the light-switched self-assembly. With the reversible molecular structure transition between Z- and U-structures, the morphology of the self-assembled gemini α-helical peptide can reversibly change between nanofibers and nanospheres in acidic medium, and between nanospheres and vesicles in basic medium.

A new anti-cancer strategy of damaging mitochondria by pro-apoptotic peptide functionalized gold nanoparticles.

Gold nanoparticles functionalized with pro-apoptotic peptide (PAP-AuNPs) were fabricated, which were able to lead to programmed cell-death by damaging mitochondria.

Evaluation of RGD peptide hydrogel in the posterior segment of the rabbit eye.

The aim of this study was to evaluate the biocompatibility and biodegradability of RGD peptide hydrogel in the posterior segment of the eye as a biomaterial potentially useful for sustained drug delivery systems. RGD peptide hydrogel was injected into the vitreous cavity and suprachoroidal space of rabbit eyes. Clinical follow-up and histological observation were performed up to four weeks. The biodegradability was also evaluated by the lifetime of the hydrogel which was defined by ophthalmoscopic observation or ultrasonography. The results showed that RGD peptide hydrogel was well tolerated in the vitreous cavity and suprachoroidal space, and disappeared from the injection sites progressively. As for suprachoroidal injection, the hydrogel was clearly identified by ultrasound echography and was confirmed innoxious to the retinal vessels by fluorescein angiography. Histological observations showed that the structures of retina, choroid and other tissues around the injection site remained normal after the injection. The lifetime of the hydrogel was 25.7 ± 2.65 days and 14.3 ± 3.3 days in the vitreous cavity and suprachoroidal space, respectively. The results obtained demonstrated that RGD peptide hydrogel, which showed excellent biocompatibility and favorable biodegradability in the posterior segment of rabbit eyes, appears to be a promising biomaterial to deliver drugs focally to the choroid and the retina.

Self-assembled BolA-like amphiphilic peptides as viral-mimetic gene vectors for cancer cell targeted gene delivery.

In this study, two types of BolA-like amphiphilic peptides with dual ligands comprising a tumor-targeting moiety of RGD sequence and a cell-penetrating moiety of R8 sequence are designed and synthesized as gene vectors. The BolA-structural peptide carriers can self-assemble into spherical nanoparticles with a hydrophilic core and shell, which are similar to the viral capsid and can bind plasmid DNA in an aqueous medium to form viral-mimetic complexes. It is found that the BolA-like dual ligands system exhibits significantly enhanced gene expression in both HeLa and 293T cell lines, as compared with poly(ethylenimine) PEI. These BolA-like amphiphilic peptides are promising in clinical trials of gene therapy.

A peptide nanofibrous indicator for eye-detectable cancer cell identification.

A unique peptide nanofibrous indicator (NFI) is fabricated by mixing a borono-peptide with alizarin red S, followed by subsequent binding and self-assembly. The NFI thus obtained exhibits an intense response to sialyl Lewis X tetrasaccharide, which is overexpressed in human hepatocellular carcinoma cell lines. Importantly, this NFI has the capability of specifically recognizing human hepatocellular liver carcinoma (HepG2) cells through the eye-detectable color change resulting from strong binding-induced displacement. This novel technique for cancer cell identification through direct unaided eye judgment will open up an innovative platform for cancer cell detection.

Encapsulation of an adamantane-doxorubicin prodrug in pH-responsive polysaccharide capsules for controlled release.

Supramolecular microcapsules (SMCs) with the drug-loaded wall layers for pH-controlled drug delivery were designed and prepared. By using layer-by-layer (LbL) technique, the SMCs were constructed based on the self-assembly between polyaldenhyde dextran-graft-adamantane (PAD-g-AD) and carboxymethyl dextran-graft-ß-CD (CMD-g-ß-CD) on CaCO(3) particles via host-guest interaction. Simultaneously, adamantine-modified doxorubicin (AD-Dox) was also loaded on the LbL wall via host-guest interaction. The in vitro drug release study was carried out at different pHs. Because the AD groups were linked with PAD (PAD-g-AD) or Dox (AD-Dox) by pH-cleavable hydrazone bonds, AD moieties can be removed under the weak acidic condition, leading to destruction of SMCs and release of Dox. The pH-controlled drug release can enhance the uptake by tumor cells and thus achieve improved cancer therapy efficiency.

Biological glucose metabolism regulated peptide self-assembly as a simple visual biosensor for glucose detection.

A glucose oxidase (GOx)-mediated glucose metabolism was in vitro mimicked and employed to regulate the self-assembly of peptide-based building blocks. In this new stimuli-responsive self-assembly system, two peptide-based building blocks, respectively, having aspartic acid (gelator 1) and lysine (gelator 2) residues were designed and prepared. When adding glucose and GOx to the aqueous solution of gelator 1 or the self-assembled fibrillar hydrogel of gelator 2 to construct glucose metabolism system, the metabolic product (gluconic acid) can trigger the protonation of the peptide molecules and induce the phase transitions of gelators 1 (sol-gel) and 2 (gel-sol). Because this glucose metabolism regulated peptide self-assembly is built on the oxidation of glucose, it can be used as a simple visual biosensor for glucose detection.

Facile construction of nanofibers as a functional template for surface boron coordination reaction.

A facile strategy to perform the boron coordination reaction on a template of nanofibers is developed. Peptides with phenylboronic acid tails (peptidyl boronic acids) are designed and prepared as building blocks that can self-assemble into nanofibers. After the addition of vicinal diol structural motifs to the self-assembling system, matrix-assisted laser desorption-ionization time-of-flight mass spectrometry indicates that the boron coordination reaction occurs on the template of nanofibers, which results in the increase of the width and roughness of the nanofibers as demonstrated by transmission electron microscopy and atomic force microscopy measurements. Because the surface-bound vicinal diol structural motifs have an ability to form hydrogen bonds with the peptide segments on the nanofibers, which restrain and disturb the hydrogen-bonding interaction among the nanofibers, the network structure formed based on the entanglement of nanofibers via hydrogen-bonding interaction is destroyed, which leads to a gel-sol transition. The novel concept of post-self-assembly modification demonstrated here could lead to a new technique for using self-assembled nanostructures in the emerging fields of nanoscience and nanotechnology.