Zhuxian Zhou

Fusogenic Reactive Oxygen Species Triggered Charge‐Reversal Vector for Effective Gene Delivery

A novel fusogenic lipidic polyplex (FLPP) vector is designed to fuse with cell membranes, mimicking viropexis, and eject the polyplex into the cytosol, where the cationic polymer is subsequently oxidized by intracellular reactive oxygen species and converts to being negatively charged, efficiently releasing the DNA. The vector delivering suicide gene achieves significantly better inhibition of tumor growth than doxorubicin.

Linear-dendritic drug conjugates forming long-circulating nanorods for cancer-drug delivery

Elongated micelles have many desirable characteristics for cancer-drug delivery, but they are difficult to obtain since amphiphilic polymers form such nanostructures only within narrow composition ranges depending on their own structures. Herein, we demonstrated a facile fabrication of different nanostructures via drug content-controlled self-assembly of amphiphilic linear-dendritic drug conjugates - using the number of the conjugated hydrophobic drug molecule camptothecin (CPT) to tailor the hydrophobicity of amphiphilic PEG-block-dendritic polylysine-CPT (PEG-xCPT) conjugates and thereby control their self-assembled nanostructures - nanospheres or nanorods of different diameters and lengths. The shape and size of the nanostructures were found to strongly affect their in vitro and in vivo properties, particularly the blood clearance kinetics, biodistribution and tumor targeting. The nanorods with medium lengths (<500 nm) had a much longer blood circulation and faster cellular uptake than the nanospheres or long nanorods. Thus, polymeric nanorods with proper lengths may be ideal nanocarriers capable of uniting the opposite requirements in cancer-drug delivery.

Charge-reversal polyamidoamine dendrimer for cascade nuclear drug delivery.

AIMS Polyamidoamine (PAMAM) dendrimers with primary amine termini have been extensively explored as drug and gene carriers owing to their unique properties, but their amine-carried cationic charges cause nonspecific cellular uptakes, systemic toxicity and other severe problems in in vivo applications. METHOD In this article, we report a charge-reversal approach that latently deactivates PAMAMs primary amines to negatively charged acid-labile amides in order to inhibit its nonspecific interaction with cells, but regenerates the active PAMAM once in acidic environments. RESULTS A cascade cancer cell nuclear drug delivery was achieved using the latently amidized PAMAM as the carrier conjugated with folic acid as the targeting group and a DNA-toxin drug camptothecin. The conjugate had low nonspecific interactions with cells, but easily entered cancer cells overexpressing folate receptors via receptor-mediated endocytosis. Subsequently, the endocytosed conjugate was transferred to acidic lysosomes, wherein the active PAMAM carrier was regenerated, escaped from the lysosome and then entered the nucleus for drug release. CONCLUSION This reversible deactivation/activation makes PAMAM dendrimers useful nanocarriers for in vivo cancer cell nuclear-targeted drug delivery.

Rational Design of Cancer Nanomedicine: Nanoproperty Integration and Synchronization

Current cancer nanomedicines can only mitigate adverse effects but fail to enhance therapeutic efficacies of anticancer drugs. Rational design of next-generation cancer nanomedicines should aim to enhance their therapeutic efficacies. Taking this into account, this review first analyzes the typical cancer-drug-delivery process of an intravenously administered nanomedicine and concludes that the delivery involves a five-step CAPIR cascade and that high efficiency at every step is critical to guarantee high overall therapeutic efficiency. Further analysis shows that the nanoproperties needed in each step for a nanomedicine to maximize its efficiency are different and even opposing in different steps, particularly what the authors call the PEG, surface-charge, size and stability dilemmas. To resolve those dilemmas in order to integrate all needed nanoproperties into one nanomedicine, stability, surface and size nanoproperty transitions (3S transitions for short) are proposed and the reported strategies to realize these transitions are comprehensively summarized. Examples of nanomedicines capable of the 3S transitions are discussed, as are future research directions to design high-performance cancer nanomedicines and their clinical translations.

MRI detection of breast cancer micrometastases with a fibronectin-targeting contrast agent

Metastasis is the primary cause of death in breast cancer patients. Early detection of high-risk breast cancer, including micrometastasis, is critical in tailoring appropriate and effective interventional therapies. Increased fibronectin expression, a hallmark of epithelial-to-mesenchymal transition, is associated with high-risk breast cancer and metastasis. We have previously developed a penta-peptide CREKA (Cys-Arg-Glu-Lys-Ala)-targeted gadolinium-based magnetic resonance imaging (MRI) contrast agent, CREKA-Tris(Gd-DOTA)3 (Gd-DOTA (4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecyl gadolinium), which binds to fibrin–fibronectin complexes that are abundant in the tumour microenvironment of fast-growing breast cancer. Here we assess the capability of CREKA-Tris(Gd-DOTA)3 to detect micrometastasis with MRI in co-registration with high-resolution fluorescence cryo-imaging in female mice bearing metastatic 4T1 breast tumours. We find that CREKA-Tris(Gd-DOTA)3 provides robust contrast enhancement in the metastatic tumours and enables the detection of micrometastases of size <0.5 mm, extending the detection limit of the current clinical imaging modalities. These results demonstrate that molecular MRI with CREKA-Tris(Gd-DOTA)3 may facilitate early detection of high-risk breast cancer and micrometastasis in the clinic.

Esterase‐Activated Charge‐Reversal Polymer for Fibroblast‐Exempt Cancer Gene Therapy

Selective gene expression in tumors via responsive dissociation of polyplexes triggered by intracellular signals is demonstrated. An esterase-responsive charge-reversal polymer mediates selective gene expression in the cancer cells high in esterases over fibroblasts low in esterase activity. Its gene therapy with the TRAIL suicide gene effectively induces apoptosis of HeLa cells but does not activate fibroblasts to secrete WNT16B, enabling potent cancer gene therapy with few side effects.

Molecularly Precise Dendrimer–Drug Conjugates with Tunable Drug Release for Cancer Therapy

The structural preciseness of dendrimers makes them perfect drug delivery carriers, particularly in the form of dendrimer-drug conjugates. Current dendrimer-drug conjugates are synthesized by anchoring drug and functional moieties onto the dendrimer peripheral surface. However, functional groups exhibiting the same reactivity make it impossible to precisely control the number and the position of the functional groups and drug molecules anchored to the dendrimer surface. This structural heterogeneity causes variable pharmacokinetics, preventing such conjugates to be translational. Furthermore, the highly hydrophobic drug molecules anchored on the dendrimer periphery can interact with blood components and alter the pharmacokinetic behavior. To address these problems, we herein report molecularly precise dendrimer-drug conjugates with drug moieties buried inside the dendrimers. Surprisingly, the drug release rates of these conjugates were tailorable by the dendrimer generation, surface chemistry, and acidity.

Peptide targeted tripod macrocyclic Gd(III) chelates for cancer molecular MRI.

Rational design and develop of targeted contrast agents binding to cancer-related proteins will achieve more accurate cancer diagnosis and prognosis by magnetic resonance (MR) imaging. CREKA is a tumor-homing pentapeptide (Cys-Arg-Glu-Lys-Ala) specifically homes to fibrin-fibronectin complexes abundantly expressed in tumor microenvironment. In this study, we developed and evaluated a CREKA peptide targeted multiplexed Gd-MR probe (CREKA-Tris-Gd(DOTA)3) for MR imaging of breast tumors. CREKA and azide bearing Gd(III) was attached to a maleimide-functional trialkyne scaffold via thiol-maleimide and azide-alkyne click chemistry, respectively. CREKA-Tris-Gd(DOTA)3 has a well-defined structure with a molecular weight of 2914 Da. The T1 relaxivity of CREKA-Tris-Gd(DOTA)3 is 8.06 mM(-1) s(-1) per Gd (24.18 mM(-1) s(-1) per molecule) at room temperature and 3 T. Fluorescence imaging showed high binding specificity of CREKA to a 4T1 breast tumor model in mice while it was not found for the scrambled CREKA (CERAK). The CREKA peptide-targeted contrast agent resulted in greater contrast enhancement than the corresponding CERAK agent and the commercialized contrast agent ProHance(®) in tumor at a dose of 0.1 mmol Gd/kg in female athymic mice bearing 4T1 breast carcinoma xenograft. This small molecular contrast agent was easily excreted from body after imaging indicated low toxicity. The targeted MRI contrast agent has a potential for specific cancer molecular imaging with MRI.

Degradable Dual pH‐ and Temperature‐Responsive Photoluminescent Dendrimers

Poly(β-aminoester) dendrimers have been prepared. These systems represent the first degradable dual pH- and temperature-responsive dendrimers displaying photoluminescence. The pH/temperature sensitivities are interrelated; the lower critical solution temperature of the dendrimer decreases as the pH of the solution is increased. The sensitivities are mainly due to phase changes of the surface groups with changes in pH or temperature. These dual-responsive dendrimers are very useful in drug delivery. They may be loaded with a hydrophobic drug at low temperature without using organic solvents. The loaded drug is released very slowly and steadily at 37 °C and physiological pH, but can be quickly released at acidic pH, for example the lysosomal pH (pH 4-5), for intracellular drug release. These dendrimers also display strong photoluminescence, which can be exploited for monitoring drug loading and release. Thus, poly(β-aminoester) dendrimers constitute ideal drug carriers since their thermal sensitivity allows the loading of drugs without using organic solvents, their pH sensitivity permits fast intracellular drug release, and their photoluminescence provides a means of monitoring drug loading and release.

Linear polyethyleneimine-based charge-reversal nanoparticles for nuclear-targeted drug delivery

Cationic polymer polyethyleneimine (PEI) can carry DNA across the cell membrane and enter the nucleus, and thus can be a very useful carrier for nuclear drug delivery; however, its highly positive charges make it toxic and not applicable for systemic drug delivery. Here, well-defined linear PEI (Mn = 1000 or 1500 or 2000)-block-polycaprolactone (Mn = 2000) (LPEI–PCL) was synthesized and used to fabricate a pH-triggered charge-reversal nanoparticle to solve this problem. LPEIs secondary amines are amidized as acid-labile β-carboxylic amides (LPEI/amide–PCL). LPEI/amide–PCL formed negatively charged nanoparticles with very low toxicity and low interaction with cells. Once in an acidic environment, the amides hydrolyze to regenerate the amine groups, producing LPEI–PCL nanoparticles carrying cationic charges. The LPEI–PCL escapes from the lysosomes and traverses into the nucleus. Folic-acid targeting groups are introduced to render the nanoparticles cancer-cell targeting capability. The nanoparticles efficiently enter folate-receptor overexpressing cancer cells and traverse to their nuclei. The DOX loaded in the carrier shows much improved cytotoxicity to cancer cells.