Yusi Lai

A Novel Poly(l-glutamic acid) Dendrimer Based Drug Delivery System with Both pH-Sensitive and Targeting Functions

The functionalization of pH-sensitiveness and cellular targeting is a promising strategy to fabricate drug delivery systems with high efficiency, high selectivity and low toxicity. In this paper, a poly(l-glutamic acid) dendrimer based drug delivery system with both pH-sensitive and targeting functions is reported. Poly(l-glutamic acid) dendrimers with a polyhedral oligomeric silsesquioxane (POSS) nanocubic core were synthesized. Its globular morphology and compact structure with multiple peripheral functional groups made it suitable for drug delivery. The OAS-G(3)-Glu dendrimer was conjugated with doxorubicin via pH-sensitive hydrazine bonds and targeting moiety (biotin). The cellular internalization and antitumor effects of the conjugates was evaluated in vitro. Both DLS and TEM results indicated that the conjugates aggregated into nanoparticles with diameters around 50 nm. The release rates of doxorubicin at pH 5.0 were much faster than those at pH 7.0 due to the acid cleavage of the hydrazine bonds. The internalization study revealed that the cellular uptake of the biotin modified conjugates was mainly through receptor-mediated endocytosis. These results indicate that our poly(l-glutamic acid) dendrimers with OAS core are promising vectors for fabricating smart and targeting drug delivery systems.

Capsid-like supramolecular dendritic systems as pH-responsive nanocarriers for drug penetration and site-specific delivery

UNLABELLED Supramolecular dendritic systems emerge as a promising new-generation bioinspired nanoplatform for nanomedicine. Herein, we report capsid-like mimics self-assembled from peptide dendrimers and functionalized peptides to enhance drug penetration and site-specific delivery for tumor therapy. These drug-loaded supramolecular dendritic systems are endowed with capsid-like component and nanostructure by a facile supramolecular approach. As expected, the drug-loaded capsid-like nanocarriers show some desirable advantages for antitumor drug delivery: a) well-defined nanostructure to improve drug location at tumor site, b) capsid-like architecture to enhance drug penetration, c) high internalization, pH-controlled release and nuclear delivery to jointly achieve site-specific delivery. Based on these merits, the drug-loaded capsid nanocarriers provide efficient tumor suppression to 4T1 tumor bearing BALB/c mice and decrease the DOX-induced toxicity during treatment course. FROM THE CLINICAL EDITOR Dendrimers have been tested in many clinical trials as nanocarriers, without great success due to many limitations. Here, the authors attempted to address these issues by developing supramolecular dendritic systems, which mimic capsids in viruses. Both in-vitro and in-vivo studies showed promising results. This work should provide a platform for further development of dendrimer-based nanocarriers for drug delivery.

Anti-tumor drug delivery of pH-sensitive poly(ethylene glycol)-poly(L-histidine-)-poly(L-lactide) nanoparticles.

pH-sensitive poly(ethylene glycol)-poly(L-histidine)-poly(L-lactide) (PEG-PH-PLLA) nanoparticles were prepared and used as carriers for anti-tumor drug delivery. The morphology and properties of the nanoparticles such as pH sensitivity, zeta potential and mean diameters were investigated. The cytotoxicity of PEG-PH-PLLA nanoparticles was evaluated. Doxorubicin (DOX) was encapsulated in the nanoparticles to explore the release profile. The drug-loaded nanoparticles were incubated with HepG2 cells to study the in vitro anti-tumor effect. The results showed the sizes of both blank nanoparticles and drug-loaded nanoparticles in pH 7.4 were smaller than those of nanoparticles in pH 5.0, and the mean diameter of drug-loaded nanoparticles was much bigger than that of blank nanoparticles. The PEG-PH-PLLA nanoparticles were nontoxic to both NIH 3T3 fibroblasts and HepG2 cells. The release profile showed that the release of DOX in pH 5.0 was much faster than that in pH 7.4. The in vitro experiments demonstrated that the anti-tumor effect of drug-loaded nanoparticles was preferable to free doxorubicin. The pH-sensitive PEG-PH-PLLA nanoparticles are promising carriers for anti-tumor drug delivery.

Cationic lipid-coated PEI/DNA polyplexes with improved efficiency and reduced cytotoxicity for gene delivery into mesenchymal stem cells

Background Effective gene transfection without serum deprivation is a prerequisite for successful stem cell-based gene therapy. Polyethylenimine (PEI) is an efficient nonviral gene vector, but its application has been hindered by serum sensitivity and severe cytotoxicity. Methods To solve this problem, a new family of lipopolyplexes was developed by coating PEI/DNA polyplexes with three serum-resistant cationic lipids, namely, lysinylated, histidylated, and arginylated cholesterol. The physical properties, transfection efficiency, cellular uptake, subcellular distribution, and cytotoxicity of the lipopolyplexes was investigated. Results The outer coat composed of lysinylated or histidylated cholesterol remarkably improved the transfection efficiency of the polyplex with a low PEI/DNA ratio of 2 in the presence of serum. The resulting lysinylated and histidylated cholesterol lipopolyplexes were even more efficient than the best performing polyplex with a high PEI/DNA ratio of 10. Results from cellular uptake and subcellular distribution studies suggest that their higher transfection efficiency may result from accelerated DNA nuclear localization. The superiority of the lipopolyplexes over the best performing polyplex was also confirmed by delivering the therapeutic gene, hVEGF165. Equally importantly, the lipid coating removed the necessity of introducing excess free PEI chains into the transfection solution for higher efficiency, generating lipopolyplexes with no signs of cytotoxicity. Conclusion Noncovalent modification of polyplexes with lysinylated and histidylated cholesterol lipids can simultaneously improve efficiency and reduce the toxicity of gene delivery under serum conditions, showing great promise for genetic modification of bone marrow stem cells.

Nanoparticles generated by PEG-Chrysin conjugates for efficient anticancer drug delivery.

Nanoparticle-based drug delivery systems promise the safety and efficacy of anticancer drugs. Herein, we presented a facile approach to fabricate novel nanoparticles generated by PEG-Chrysin conjugates for the delivery of anticancer drug doxorubicin. Chrysin was immobilized on the terminal group of methoxy poly(ethylene glycol) (mPEG) to form mPEG-Chrysin conjugate. The conjugates were self-assembled into nanoparticles. Doxorubicin (DOX) was loaded in the nanoparticles. The self-assembly, drug release profiles, interactions between nanoparticle and drug, cellular uptake and in vitro anticancer activity of the DOX loaded nanoparticles were investigated. The results showed that the mean diameters of drug loaded nanoparticles were below 200 nm. Strong π-π stacking interaction was tested within the drug loaded nanoparticles. The drug release rate was closely related to the chain length of PEG, shorter PEG chain resulted faster release. The mPEG-Chrysin conjugate was non-toxic to both 3T3 fibroblasts and HepG2 cancer cells. The cellular uptake measurements demonstrated that the mPEG1000-Chrysin nanoparticles exhibited higher capability in endocytosis. The IC50 of drug loaded mPEG1000-Chrysin nanoparticles was 4.4 μg/mL, which was much lower than that of drug loaded mPEG2000-Chrysin nanoparticles (6.8 μg/mL). These nanoparticles provided a new strategy for fabricating antitumor drug delivery systems.

Stabilization of pH-Sensitive mPEG–PH–PLA Nanoparticles by Stereocomplexation Between Enantiomeric Polylactides

Methoxy poly(ethylene glycol)-poly(L-histidine)-poly(lactide) (mPEG(45)-PH(30)-PLA(82)) triblock copolymers self-assemble into nanoparticles by sterocomplexation. The properties of the stereocomplex nanoparticles including morphology, stability, and biocompatibility are investigated. The results reveal that the stereocomplexation between PLLA and PDLA segments could prevent the aggregation of the nanoparticles when the pH value is around 6.8. The mean diameter of the stereocomplex nanoparticles is stabilized at about 100 nm when the pH values are changed from 7.9 to 5.0. The cytotoxicity of the stereocomplex nanoparticles is evaluated, and the results demonstrate that the stereocomplexation could decrease the cytotoxicity of the PDLA segments.

Ultrasound accelerated gelation of novel L-lysine based hydrogelators

We reported a novel hydrogelator with L-lysine as a linker to connect 7-carboxyl methoxycoumarin and hydrazine as lipophilic and water-soluble moieties. Ultrasound accelerated the gelation and induced homogenous self-assembly of fibrils into entangled 3D networks. The hydrogel exhibits great potential for future biomedical applications.

A novel micelle of coumarin derivative monoend-functionalized PEG for anti-tumor drug delivery: in vitro and in vivo study

In this paper, a novel micelle for anti-tumor drug delivery was reported. Two 7-carboxymethoxy coumarin molecules were immobilized on the terminal group of a methoxy poly(ethylene glycol) chain via l-lysine as linker. The amphiphilic 7-carboxymethoxy coumarin monoend-functionalized methoxy poly(ethylene glycol) (mPEG-Lys-DCOU) chains were self-assembled micelles. Anti-tumor drug doxorubicin was loaded in the mPEG-Lys-DCOU micelles and the release profile was studied. The cytotoxicity of mPEG-Lys-DCOU was evaluated by NIH 3T3 fibroblasts. The drug-loaded micelles were incubated with HepG2 tumor cells to investigate the in vitro anti-tumor effect. The in vivo inhibition efficacy of drug-loaded micelles was carried out on 4T1 breast cancer animal model. The results showed that both hydrophobic and π-π stacking interactions within mPEG-Lys-DCOU amphiphiles were contributed to the self-assembly. Both blank and drug loaded micelles were monodisperse nanoparticles with the average diameters around 300 nm. The release profile exhibited certain pH dependence. The drug release rate at pH = 5.5 was much faster than that at pH = 7.4. mPEG-Lys-DCOU amphiphiles were non-toxic to NIH 3T3 fibroblasts. Both in vitro and in vivo studies demonstrated that the inhibition efficacy of drug-loaded micelles were comparable to that of doxorubicin hydrochloride. mPEG-Lys-DCOU micelles are promising carriers for anti-tumor drug delivery.

Oral delivery of camptothecin using cyclodextrin/poly(anhydride) nanoparticles.

Camptothecin (CPT), a molecule that shows powerful anticancer activity, is still not used in clinic due to its high hydrophobicity and poor active forms stability. In order to solve these drawbacks, the combination between poly(anhydride) nanoparticles and cyclodextrins was evaluated. CPT-loaded nanoparticles, prepared in the presence of 2-hydroxypropyl-β-cyclodextrin, (HPCD-NP) displayed a mean size close to 170nm and a payload of 50μg per mg (25 times higher than the one of the control nanoparticles). CPT was not released from nanoparticles under gastric conditions. However, under intestinal conditions, about 50% of the drug content was released as a burst, whereas the remained drug was released following a zero-order kinetic. Pharmacokinetic studies revealed that the CPT plasma levels, from orally administered nanoparticles, were high and sustained up to 48h. The CPT oral bioavailability was 7-fold higher than the value obtained with the control, whereas its clearance was significantly lower than for the aqueous suspension. These observations may be directly related to a prolonged residence time of nanoparticles in close contact with the intestinal epithelium, the presence of the cyclodextrin that decreases the CPT transformation into its inactive form and the generation of an acidic microenvironment during the degradation of the poly(anhydride) that would prevent the transformation of the active lactone into the inactive carboxylate conformation.

Anticancer drug delivery of PEG based micelles with small lipophilic moieties.

Herein, we reported a new type of self-assembly micelles based on amphiphilic polymers of cinnamate and coumarin derivatives modified PEG for drug delivery applications. Lipophilic cinnamic acid (CIN) and 7-carboxyl methoxycoumarin (COU) were immobilized on the terminal groups of poly(ethylene glycol) (PEG) to prepare amphiphiles. The amphiphiles self-assembled into micelles. The amphiphiles and micelles were characterized by (1)H NMR, FT-IR, DLS and TEM. Doxorubicin (DOX) was used as a model drug to investigate the lipophilic moieties effects on the drug release behaviors. The DOX loaded micelles were incubated with HepG2 liver cancer cells to study the in vitro anticancer activities. The results showed that DOX could be encapsulated in the micelles efficiently. The mean diameter of the drug loaded micelles was around 100 nm. Drug release profile revealed that the release rate of DOX loaded COU-PEG-COU micelles was significantly slower than that of CIN-PEG-CIN micelles. The DOX loaded micelles could be internalized in HepG2 cells. Both CLSM and flow cytometry results showed that the DOX loaded CIN-PEG-CIN micelles exhibited better anticancer efficacy.