Yuji Pu

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.

Functionalization of magnetic nanoparticles with peptide dendrimers

Surface functionalization of magnetic nanoparticles (MNPs) has been an exciting area of interest for researchers in biomedicine. In this paper, we introduce a new family of peptide dendritic ligands for functionalizing MNPs of superior quality. L-Lysine- and L-glutamic acid-based dendritic ligands with dopamine located at the focal points were fully designed and synthesized before the functionalization. Then ligands of different dendritic generations (G1 to G3) were immobilized on the surface of oleic-acid-coated hydrophobic MNPsvia ligand-exchange method to realize phase transfer. The two series of modified MNPs were systematically studied viaFTIR, TGA, XRD, TEM, DLS, VSM and zeta potential measurements. The modified MNPs exhibited an adjustable number of terminal functional groups and superior stability in aqueous solutions in a broad pH range. The surface existence of water-soluble polypeptide ligands promoted monodispersity of the particles and led to an increased hydrodynamic diameter under 30 nm from G1 to G3. After the ligand exchange process, the superparamagnetic behavior was successfully retained. The two series of modified MNPs exhibited approximate magnetization in the same generation, while the saturation magnetization of the MNPs decreased with increasing surface dendritic generation. MNPs functionalized with G1L-glutamic acid dendritic ligands had the highest saturation magnetization (55 emu g−1), which was larger than for the initial MNPs. This novel functionalization strategy provides a potential platform for designing and preparing highly stable ultrafine MNPs with high magnetization for biomedicinal applications.

Drug release of pH-sensitive poly(L-aspartate)-b-poly(ethylene glycol) micelles with POSS cores

Amphiphilic poly(L-aspartate)-b-poly(ethylene glycol) block copolymers were synthesized and immobilized on polyhedral oligomeric silsesquioxanes (POSS) to obtain star shaped copolymers. 1-(3-Aminopropyl) imidazole was conjugated to the pendant groups of poly(L-aspartate) segments to fabricate pH-sensitive micelles. The anticancer drug doxorubicin (DOX) was trapped in the micelles to investigate the effects of side groups on the drug release behaviors. The mean diameters of DOX loaded micelles were around 50–60 nm, which were much smaller than those of blank micelles (100–200 nm). Both the drug loading content and encapsulation efficiency of the micelles decreased with the sequence of the side group substitution of carboxyl, benzyl and imidazole. The release of DOX loaded micelles with imidazole groups was pH-dependent, and more than 90% of the loaded DOX could be released within 48 hours in a weak acidic medium (pH 5.0). The flow cytometry and confocal laser scanning microscopy results revealed that the pH-sensitive micelles exhibited better anticancer activity.

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.

Synthesis and Antibacterial Study of Sulfobetaine/Quaternary Ammonium-Modified Star-Shaped Poly[2-(dimethylamino)ethyl methacrylate]-Based Copolymers with an Inorganic Core

Cationic polymethacrylates are interesting candidates for bacterial disinfectants since they can be made in large-scale by various well-established polymerization techniques such as atom transfer radical polymerization (ATRP). However, they are usually toxic or ineffective in serum and various strategies to improve their biocompatibility or nonfouling property have often resulted in compromised bactericidal activity. Also, star-shaped polymers are less explored than linear polymers for application as antibacterial compounds. In this paper, star polymers with poly[2-(dimethylamino)ethyl methacrylate] (PDMA) as the arms and polyhedral oligomeric silsesquioxane (POSS) as the core (POSS-g-PDMA) were successfully synthesized by ATRP. The minimum inhibition concentrations (MICs) of the synthesized POSS-g-PDMA are in the range of 10-20 μg/mL. POSS-g-PDMA was further modified by various hydrophilization strategies in attempting to reduce hemolysis. With quaternization of POSS-g-PDMA, the antibacterial activities of the obtained quaternary polymers are almost unchanged and the copolymers become relatively nonhemolytic. We also copolymerized sulfobetaine (SB) with POSS-g-PDMA to obtain random and block PDMA-co-PSB arm structures, where the PDMA and poly(sulfobetaine) were the cationic and zwitterionic blocks, respectively. The random cationic-zwitterionic POSS-g-(PDMA-r-PSB) copolymers showed poor antibacterial activity, while the block POSS-g-(PDMA-b-PSB) copolymers retained the antibacterial and hemolytic activity of the pristine POSS-g-PDMA. Further, the block copolymers of POSS-g-(PDMA-b-PSB) showed enhanced antifouling property and serum stability as seen by their nanoparticle size stability in the presence of serum and reduced red blood cell aggregation; the POSS-g-(PDMA-b-PSB) also somewhat retained its MIC in blood unlike the quaternized or random zwitterionic copolymers. The antibacterial kinetics study showed that Escherichia coli can be killed within 30 min by both random and block copolymers of POSS-g-(PDMA-co-PSB). Finally, our POSS star polymers showed low toxicity to zebrafish embryo and could be potentially used in aquaculture antibacterial applications.

A reactive oxygen species–responsive prodrug micelle with efficient cellular uptake and excellent bioavailability

Stimuli-responsive polymeric drug delivery systems are of great interest in anticancer research. Here, a reactive oxygen species (ROS)-responsive prodrug was prepared by thioketal linkage of poly(ethylene glycol) (PEG) and the anticancer drug doxorubicin (DOX). The ROS-responsive property of the prodrug was confirmed by dynamic light scattering and 1H NMR. The prodrug was then used as a drug carrier to further load DOX, to form a DOX-loaded prodrug micelle, which showed dual ROS and pH-responsive release behaviors. The prodrug micelle exhibited rapid intracellular uptake. Interestingly, the in vitro anticancer activity of the ROS-responsive prodrug micelle was better than that of the DOX-loaded prodrug micelle because of its faster cellular uptake and better bioavailability. However, both the ROS-responsive prodrug and drug-loaded prodrug micelles showed better anticancer efficacy than a non-responsive DOX-loaded poly(ethylene glycol)-block-polycaprolactone (PEG2k-PCL5k) micelle. Consistent results were obtained in in vivo animal experiments as the antitumor efficacy of the prodrug micelle was superior to that of the DOX-loaded prodrug micelle. Both micelles showed negligible systemic toxicity in vivo.

Using Diphenylphosphoryl Azide (DPPA) for the Facile Synthesis of Biodegradable Antiseptic Random Copolypeptides

A facile method has been developed for the large-scale synthesis of random copolypeptides composed of multiple (i.e., cationic, hydrophobic, and hydrophilic) amino acids and their relative ratios have been optimized for broad-spectrum antibacterial effect. The copolypeptides obtained have measured compositions close to the design ratios in spite of the differing reactivities of the different amino acids. An optimized random copolypeptide of lysine, leucine, and serine (denoted as KLS-3) mimicking the composition of LL-37 host defense peptide gives broad spectrum antibacterial activity against clinically relevant Gram-negative and Gram-positive bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO1) with minimum inhibitory concentrations (MICs) of 32-64 μg mL-1 , as well as good MICs against multidrug resistant Gram-negative bacteria of Escherichia coli EC 958 (64 μg mL-1 ) and Klebseilla pneumoniae PTR3 (128 μg mL-1 ). This method can be applied to the facile large-scale copolymerization of multiple amino acids, including unnatural amino acids, to make effective antibacterial copolypeptides.

A reactive oxygen species (ROS)-responsive low molecular weight gel co-loaded with doxorubicin and Zn(II) phthalocyanine tetrasulfonic acid for combined chemo-photodynamic therapy

Low molecular weight gels (LMWGs) have significant advantages in drug delivery such as high drug loading capacity, in situ delivery of drug to the lesion site, sustaining drug release with excellent bioavailability, and minimized side effects. Here, we synthesized a reactive oxygen species (ROS)-responsive gelator to prepare an injectable gel. An anticancer drug, doxorubicin hydrochloride (DOX), and a photosensitizer, Zn(ii) phthalocyanine tetrasulfonic acid (ZnPCS4), were loaded into the gel for combined chemo-photodynamic therapy. The ROS-responsive gelator was characterized by proton nuclear magnetic resonance (1H NMR) and the morphology of gels was investigated by scanning electron microscopy (SEM). The rheological properties and destruction-recovery capability of both blank and drug-loaded gels were studied. The cytotoxicity of LMWGs against 3T3 fibroblasts and 4T1 breast cancer cells was tested. The in vitro drug release of both drugs was studied and the in vivo anticancer activities of DOX-ZnPCS4-coloaded LMWGs were investigated in tumor-bearing mice. The results revealed that the injectable ROS-responsive DOX-ZnPCS4-coloaded LMWGs exhibited excellent anti-tumor efficacy by a synergistic therapy.

Hierarchical nanocomposites of graphene oxide and PEGylated protoporphyrin as carriers to load doxorubicin hydrochloride for trimodal synergistic therapy

Multimodal and synergistic therapy of cancer has appeared as one of the most promising strategies in treating cancer. Here, we report a supramolecular hierarchical nanocomposite for combination photodynamic, photothermal, and chemotherapy. Graphene oxide (GO, photothermal agent for photothermal therapy, PTT), protoporphyrin IX (PpIX, photosensitizer for photodynamic therapy, PDT), and hydrophilic anticancer drug doxorubicin hydrochloride (DOX·HCl, therapeutic for chemotherapy) are involved in hierarchical self-assembled nanocomposites via supramolecular interactions. PEGylated PpIX (PEG-PpIX) is prepared to improve the stability of GO in physiological conditions. The nanocomposite GO(PEG-PpIX) is non-cytotoxic in the dark and phototoxic with light irradiation to exhibit efficient PTT and PDT effects. The drug loading content of the nanocomposite DOX/GO(PEG-PpIX) is as high as 15.9% and the drug release shows a pH-dependent profile. The combined PDT, PTT, and chemotherapy shows an excellent in vivo antitumor effect and side effect reduction. This work presents a facile yet robust strategy to fabricate a nanocomposite for multimodal synergistic therapy.

Tumor-pH-Sensitive PLLA-Based Microsphere with Acid Cleavable Acetal Bonds on the Backbone for Efficient Localized Chemotherapy

Nanoparticle- and microsphere-based drug delivery systems (DDSs) have attracted wide attention in cancer therapy; those DDSs that are responsive to tumor environment can selectively identify tumor and normal tissues and therefore have shown enhanced anticancer efficacy and alleviated systemic toxicity. Here, tumor-pH-sensitive polymeric microspheres, which are prepared by multiblock poly(l-lactide) with pH-sensitive acetal bonds in the backbone, are employed to efficiently load water-soluble anticancer drug doxorubicin hydrochloride (DOX·HCl, drug loading content: ∼10%). The pH-sensitive DOX-loaded hollow microspheres were in the size range 2-10 μm and exhibited acid-accelerated degradation of polymer matrix and drug release, and thereby efficient in vitro cancer cell inhibition. The microspheres were further intratumorally injected into breast-tumor-bearing mice, and the in vivo anticancer experiment showed that pH-sensitive DOX-loaded microsphere showed better antitumor efficiency and prolonged life-span than its counterpart that does not have pH-responsive property. Moreover, negligible organ toxicity, especially cardiotoxicity that generally exists in DOX-involved chemotherapy where DOX is administrated by intravenous injection, was observed for DOX-loaded microspheres. Hence, tumor-pH-sensitive polymeric microspheres have appeared to be a simple and efficient platform for delivering hydrophilic anticancer drug with excellent anticancer efficacy and low systemic toxicity.