Qiming Kan

Large amino acid transporter 1 mediated glutamate modified docetaxel-loaded liposomes for glioma targeting.

The therapeutic outcome of glioma treatment is rigorously limited by blood-brain barrier (BBB) and infiltrating growth of glioma. To tackle the dilemma, more and more attentions were focused on developing nutrient transporters-mediated dual-targeted drug delivery system, in one side for BBB penetration, another for intracranial glioma targeting. Herein, Large amino acid transporter 1 (LAT1), overexpressed both on BBB and glioma cells, was selected as a target. Docetaxel-loaded glutamate-d-α-tocopherol polyethylene glycol 1000 succinate copolymer (Glu-TPGS) functionalized LAT1-targeting liposomes (DTX-TGL) were applied to enhance the BBB penetration and glioma therapy. The in vivo results of the fluorescent image indicated that TGL possessed an effective BBB penetration than that of unmodified ones in mice. The LAT1 targeting effcicacy and cell cytotoxicity of TGL were investigated in C6 glioma cells. Compared with unmodified liposomes, a significant higher cellular uptake and cell cytotoxicity was found in TGL treated group. Our results indicated that LAT1-targeting docetaxel-loaded liposome paves up a new direction using LAT1 transporter as a good target in designing brain glioma-targeting nanosystems.

Targeting tumor highly-expressed LAT1 transporter with amino acid-modified nanoparticles: Toward a novel active targeting strategy in breast cancer therapy

Designing active targeting nanocarriers with increased cellular accumulation of chemotherapeutic agents is a promising strategy in cancer therapy. Herein, we report a novel active targeting strategy based on the large amino acid transporter 1 (LAT1) overexpressed in a variety of cancers. Glutamate was conjugated to polyoxyethylene stearate as a targeting ligand to achieve LAT1-targeting PLGA nanoparticles. The targeting efficiency of nanoparticles was investigated in HeLa and MCF-7 cells. Significant increase in cellular uptake and cytotoxicity was observed in LAT1-targeting nanoparticles compared to the unmodified ones. More interestingly, the internalized LAT1 together with targeting nanoparticles could recycle back to the cell membrane within 3 h, guaranteeing sufficient transporters on cell membrane for continuous cellular uptake. The LAT1 targeting nanoparticles exhibited better tumor accumulation and antitumor effects. These results suggested that the overexpressed LAT1 on cancer cells holds a great potential to be a high-efficiency target for the rational design of active-targeting nanosystems.

Disulfide Bond-Driven Oxidation- and Reduction-Responsive Prodrug Nanoassemblies for Cancer Therapy

Disulfide bonds have been widely used to develop reduction-responsive drug-delivery systems (DDS) for cancer therapy. We propose that disulfide bonds might be also used as an oxidation-responsive linkage just like thioether bonds, which can be oxidized to hydrophilic sulfoxide or sulphone in the presence of oxidation stimuli. To test our hypothesis, we design three novel paclitaxel-citronellol conjugates linked via different lengths of disulfide-bond-containing carbon chain. The prodrugs can self-assemble into uniform-size nanoparticles with impressively high drug loading (>55%). As expected, the disulfide-bond-bridged prodrug nanoparticles show redox dual-responsive drug release. More interestingly, the position of disulfide bonds in the carbon chain linkage has profound impacts on the redox dual responsiveness, thereby affecting the drug release, cytotoxicity, pharmacokinetics, biodistribution, and in vivo antitumor efficacy of prodrug nanoassemblies. The redox dual-responsive mechanism is elucidated, and how the position of disulfide bonds in the carbon chain affects the redox dual responsiveness and antitumor efficiency of prodrug nanoassemblies is also clarified. Our findings give new insight into the stimuli responsiveness of disulfide bonds and provide a good foundation for the development of novel redox dual-responsive DDS for cancer therapy.

Bioresponsive albumin-conjugated paclitaxel prodrugs for cancer therapy

Abstract The efficacy of traditional chemotherapy often suffers from rapid clearance and off-target toxicity. Drug delivery systems and controlled release are applied to improve the therapeutic efficiencies of small-molecule drugs. In this work, two novel oxidative/reductive (Ox/Re) -sensitive and one non-sensitive Paclitaxel (PTX) prodrugs were synthesized with a maleimide group, which rapidly conjugates with albumin in vivo. Albumin serves as a good vehicle to deliver more prodrug to tumors due to the enhanced permeation and retention (EPR) effect. PTX was then released from the prodrugs in glutathione(GSH)/ reactive oxygen species(ROS)-rich tumor microenvironments. This bioresponsive prodrug strategy demonstrates potent chemotherapeutic efficiency in vivo and may be utilized in clinical cancer therapy.

Striking a Balance between Carbonate/Carbamate Linkage Bond- and Reduction-Sensitive Disulfide Bond-Bearing Linker for Tailored Controlled Release: In Situ Covalent-Albumin-Binding Gemcitabine Prodrugs Promote Bioavailability and Tumor Accumulation

To address the challenges of rapid enzyme inactivation, poor tumor targeting, and acquired drug resistance in gemcitabine (GEM) application, we report two groups of maleimide-functionalized GEM prodrugs conjugating covalently in situ with Cys-34 of blood-circulating albumin and then resulting in macromolecular prodrugs after intravenous administration. Tailored and accurate controlled release was achieved through different combinations of linkage bonds, relatively stable and labile (carbamate and carbonate, respectively), and linkers with or without insertion of a disulfide bond. Interestingly, we found that the overall advantages or disadvantages brought by a disulfide bond varied with the stability of the linkage bond. Finally, the carbonate linkage bond-bearing group, especially the one with a linker lacking a disulfide bond, stood out with remarkably increased bioavailability (21-fold greater than GEM) and efficient tumor free-GEM accumulation (8-fold of GEM), which consequently contributed to excellent in vivo antitumor efficacy.

Precisely albumin-hitchhiking tumor cell-activated reduction/oxidation-responsive docetaxel prodrugs for the hyperselective treatment of breast cancer

ABSTRACT The anticancer efficacy of chemotherapy is greatly limited by short blood circulation and poor tumor selectivity. Thus, anticancer prodrugs with prolonged systemic circulation, tumor‐specific distribution and bioactivation, could significantly strengthen the chemotherapy efficacy. Herein, we design two novel tumor cell reduction/oxidation‐responsive docetaxel (DTX) prodrugs, DTX‐maleimide conjugates with disulfide bond (DSSM) or thioether bond (DSM) linkages, to evaluate the roles of different sensitive linkages in drug release, pharmacokinetics and therapeutic efficacy. An ester bond‐linkage prodrug (DM) is utilized as a non‐sensitive control. DSSM and DSM show reduction‐ or oxidation‐sensitive release behavior, respectively, and exhibit hyperselective bioactivation and cytotoxicities between cancerous and normal cells. They could instantly hitchhike blood circulating albumin after i.v. administration with albumin‐binding half‐lives as short as 1min, resulting in prolonged systemic circulation, increased tumor accumulation. In response to the upregulated reduction/oxidation environment within tumor cells, DSSM and DSM exhibit selectively release capacity in tumor tissues, their TAITumor/Liver values are over 30‐fold greater than DM. Combining the above delivery advantages into one, DSSM and DSM achieve enhanced antitumor efficacy of DTX. Such a uniquely developed strategy, integrating high albumin‐binding capability and reduction/oxidation‐sensitive drug superselective release in tumors, has great potential to be applied in clinical cancer therapy.

Mitochondria-targeted prostate cancer therapy using a near-infrared fluorescence dye–monoamine oxidase A inhibitor conjugate

ABSTRACT Prostate cancer (PCa) is the most frequent malignant cancer among men in the USA, leading to substantial morbidity and mortality, while the existing treatments have restricted therapeutic benefits for patients with hormone‐refractory PCa (HRPC) and metastatic PCa. Recent studies show that advanced PCa exhibits an increase in the expression of monoamine oxidase A (MAOA) which is a mitochondria enzyme, and MAOA activity inhibition could restrict metastasis and extend mice survival in PCa xenografts. These findings suggest MAOA can be a potential target to treat PCa. For this reason, we identify and synthesize a near‐infrared fluorescence (NIRF) heptamethine dye–MAOA inhibitor conjugate (NIR‐INH) for simultaneous PCa imaging, targeting and therapy. The conjugate combines a NIRF dye for mitochondria targeting with the MAOA inhibitor isoniazid (INH). NIR‐INH exhibits specific targeting in PCa xenografts and markedly inhibited tumor growth. Furthermore, there is no obvious toxicity with NIR‐INH treatment, which is a remarkable superiority towards traditional chemotherapy. These results indicate that NIR‐INH has PCa targeting, imaging and high anticancer effectiveness, suggesting it is a potentially valuable image‐guided anti‐tumor strategy.

Covalently mucoadhesive amphiphilic prodrug of 5-fluorouracil for enhanced permeation and improved oral absorption

Abstract5-Fluorouracil (5-FU) is one of the important antitumor drugs and is widely used to treat various types of cancers. However, its administration is limited to intravenous route due to poor oral bioavailability. Herein, we hypothesized that the maleimide group-containing 5-FU prodrug (EMC-5-FU) could improve the intestinal mucoadhesion because the maleimide end group can covalently target thiol residues of mucin glycoprotein covering the intestinal enterocytes. In vitro bioadhesion results showed that EMC-5-FU exhibited good affinity to the cysteine-rich subdomains of mucin and NMR studies successfully verified the covalent attachment of EMC-5-FU to mucin. The intestinal perfusion study indicated that the intestinal bioadhesion and membrane permeability are greatly enhanced for EMC-5-FU, in comparison with 5-FU. Mucoadhesion investigations on rat intestine intuitively confirmed increased intestinal retention of 5-FU through maleimide-mediated mucoadhesion. Moreover, AUC0-24h of the total 5-FU level for EMC-5-FU solution was 2.65-fold higher compared with 5-FU solution. Our study further suggested that the amphiphilic prodrug EMC-5-FU with good mucoadhesion is a promising delivery strategy form to overcome multiple barriers of oral absorption.

Dipeptide-modified nanoparticles to facilitate oral docetaxel delivery: new insights into PepT1-mediated targeting strategy

Abstract Oligopeptide transporter 1 (PepT1) has been a striking prodrug-designing target. However, the underlying mechanism of PepT1 as a target to facilitate the oral absorption of nanoparticles (NPs) remains unclear. Herein, we modify Poly (lactic-co-glycolic acid) (PLGA) NPs with the conjugates of dipeptides (L-valine-valine, L-valine-phenylalanine) and polyoxyethylene (PEG Mw: 1000, 2000) stearate to facilitate oral delivery of docetaxel (DTX) to investigate the oral absorption mechanism and regulatory effects on PepT1 of the dipeptide-modified NPs. The cellular uptake of the dipeptide-modified NPs is more efficient than that of the unmodified NPs in the stably transfected hPepT1- Hela cells and Caco-2 cells, suggesting the involvement of PepT1 in the endocytosis of NPs. The internalization of the dipeptide-modified NPs is proved to be a proton-dependent process. Moreover, the L-valine-valine modified NPs with shorter PEG chain exhibit distinct advantages in terms of intestinal permeability and oral absorption, resulting in significantly improved oral bioavailability of DTX. In summary, PepT1 could serve as a desirable target for oral nanoparticulate drug delivery and the dipeptide-modified NPs represent a promising nanoplatform to facilitate oral delivery of hydrophobic drugs with low bioavailability.

Insight into the preformed albumin corona on in vitro and in vivo performances of albumin-selective nanoparticles

Preformed albumin corona of albumin-nonselective nanoparticles (NPs) is widely exploited to inhibit the unavoidable protein adsorption upon intravenous administration. However, very few studies have concerned the preformed albumin corona of albumin-selective NPs. Herein, we report a novel type of albumin-selective NPs by decorating 6-maleimidocaproyl polyethylene glycol stearate (SA) onto PLGA NPs (SP NPs) surface, taking albumin-nonselective PLGA NPs as control. PLGA NPs and SP NPs were prepared by emulsion-solvent evaporation method and the resultant NPs were in spherical shape with an average diameter around 180 nm. The corresponding albumin-coating PLGA NPs (PLGA@BSA NPs) and albumin-coating SP NPs (SP@BSA NPs) were formulated by incubating SP NPs or PLGA NPs with bovine serum albumin solution, respectively. The impact of albumin corona on particle characteristics, stability, photothermal effect, cytotoxicity, cell uptake, spheroid penetration and pharmacokinetics was investigated. In line with previous findings of preformed albumin coating, PLGA@BSA NPs exhibited higher stability, cytotoxicity, cell internalization and spheroid penetration performances in vitro, and longer blood circulation time in vivo than those of albumin-nonselective PLGA NPs, but albumin-selective SP NPs is capable of achieving a comparable in vitro and in vivo performances with both SP@BSA NPs and PLGA@BSA NPs. Our results demonstrate that SA decorated albumin-selective NPs pave a versatile avenue for optimizing nanoparticulate delivery without preformed albumin corona.