Kun Na

Polymeric micelle for tumor pH and folate-mediated targeting.

Novel pH-sensitive polymeric mixed micelles composed of poly(L-histidine) (polyHis; M(w) 5000)/PEG (M(n) 2000) and poly(L-lactic acid) (PLLA) (M(n) 3000)/PEG (M(n) 2000) block copolymers with or without folate conjugation were prepared by diafiltration. The micelles were investigated for pH-dependent drug release, folate receptor-mediated internalization and cytotoxicity using MCF-7 cells in vitro. The polyHis/PEG micelles showed accelerated adriamycin release as the pH decreased from 8.0. When the cumulative release for 24 h was plotted as a function of pH, the gradual transition in release rate appeared in a pH range from 8.0 to 6.8. In order to tailor the triggering pH of the polymeric micelles to the more acidic extracellular pH of tumors, while improving the micelle stability at pH 7.4, the PLLA/PEG block copolymer was blended with polyHis/PEG to form mixed micelles. Blending shifted the triggering pH to a lower value. Depending on the amount of PLLA/PEG, the mixed micelles were destabilized in the pH range of 7.2-6.6 (triggering pH for adriamycin release). When the mixed micelles were conjugated with folic acid, the in vitro results demonstrated that the micelles were more effective in tumor cell kill due to accelerated drug release and folate receptor-mediated tumor uptake. In addition, after internalization polyHis was found to be effective for cytosolic ADR delivery by virtue of fusogenic activity. This approach is expected to be useful for treatment of solid tumors in vivo.

Poly(l-histidine)–PEG block copolymer micelles and pH-induced destabilization

Poly(L-histidine)-poly(ethylene glycol) diblock copolymers (polyHis-b-PEG) were prepared and used for the construction of polymeric micelles responding to local pH changes in the body. PolyHis was synthesized by ring opening polymerization of L-histidine N-carboxyanhydride, the imidazole amine group of which was protected by the dinitrophenyl group. The resulting polymer (M(n): 5,000 g/mole) was coupled to poly(ethylene glycol) (M(n): 2,000 g/mole) via an amide linkage using the dicyclohexyl carbodiimide and N-hydroxysuccinimide-mediated reaction. The block copolymer in dimethyl sulfoxide formed polymeric micelles on diafiltration against a borate buffer at pH 8. Dynamic light scattering and atomic force microscopy showed the micelles were spherical, diameter approximately 114 nm, with a unimodal distribution. The critical micelle concentration (CMC) at pH 8.0 was 2.3 mg/l. The CMC increased markedly on decreasing the pH of the diafiltration medium below 7.2. Micelles prepared at pH 8.0 were gradually destabilized below pH 7.4, as evidenced by a slight increase in light transmittance, an alteration in size distribution, and a decrease in the pyrene fluorescence intensity. It was concluded that the ionization of the polyHis block forming the micelle core determined the pH-dependent CMC and stability. After further optimization of the pH-sensitivity, pH-sensitive micelles are expected to have application for solid tumor treatment, exploiting the fact that most solid tumors have an acidic extracellular pH.

Theranostic Probe Based on Lanthanide-Doped Nanoparticles for Simultaneous In Vivo Dual-Modal Imaging and Photodynamic Therapy

Dual-modal in vivo tumor imaging and photodynamic therapy using hexagonal NaYF(4):Yb,Er/NaGdF(4) core-shell upconverting nanoparticles combined with a photosensitizer, chlorin e6, is reported. Tumors can be clearly observed not only in the upconversion luminescence image but also in the magnetic resonance image. In vivo photodynamic therapy by systemic administration is demonstrated under 980 nm irradiation.

Adriamycin loaded pullulan acetate/sulfonamide conjugate nanoparticles responding to tumor pH: pH-dependent cell interaction, internalization and cytotoxicity in vitro

The cytotoxicity of adriamycin (ADR)-loaded and pH-sensitive nanoparticles made of pullulan acetate (PA) and sulfonamide (sulfadimethoxine; SDM) (PA/SDM) conjugate to a breast tumor cell line (MCF-7) was investigated to test the feasibility of the nanoparticles in targeting acidic tumor extracellular pH (pH(e)). At pH 6.8, ADR loaded PA/SDM nanoparticles showed cytotoxicity in the cell culture experiment, comparable to that of free ADR at the same ADR concentrations, while the relative cytotoxicity at pH 7.4 was low at the tested concentration range. This pronounced cytotoxicity of the nanoparticles at low pH was attributed to the accelerated release of ADR triggered by pH, enhanced interaction with cells, and internalization. At pH 6.8 and 6.4, the PA/SDM nanoparticles aggressively bounded to MCF-7 cells, probably due to interactions of the cells with hydrophobized nanoparticle surfaces caused by SDM deionization. A confocal laser microscopic study revealed intracellular localization of the drug-loaded nanoparticles. Based on these findings, the pH-sensitive nanoparticles deserve further investigation with an in vivo animal model as a targeted carrier of pH(e).

Self-Assembled Hydrogel Nanoparticles Responsive to Tumor Extracellular pH from Pullulan Derivative/Sulfonamide Conjugate: Characterization, Aggregation, and Adriamycin Release in Vitro

AbstractPurpose. To investigate some physicochemical properties of self-assembled hydrogel nanoparticles of pullulan acetate (PA) and sulfonamide conjugates, as a potential tumor targeting drug carrier responsive to tumor extracellular pH. Methods. A new class of pH-responsive polymers was synthesized by conjugating a sulfonamide, sulfadimethoxine (SDM), to succinylated pullulan acetate (coohPA). The polymers formed self-assembled PA/SDM hydrogel nanoparticles in aqueous media, which was confirmed by fluorometry and field emission-scanning electron microscopy. The pH-dependent behavior of the nanoparticles was examined by measuring transmittance, particle size and zeta potential. Adriamycin (ADR) was tested for loading into and release from the nanoparticles at various pHs. Results. The mean diameters of all PA/SDM nanoparticles tested were <70 nm, with a unimodal size distribution. The critical aggregation concentrations at pH 9.0 were as low as 3.16 μg/mL. The nanoparticles showed good stability at pH 7.4, but shrank and aggregated below pH 7.0. The ADR release rate from the PA/SDM nanoparticles was pH-dependent around physiological pH and significantly enhanced below a pH of 6.8. Conclusions. The pH-responsive PA/SDM nanoparticles may provide some advantages for targeted anti-cancer drug delivery due to the particle aggregation and enhanced drug release rates at tumor pH.

Self-quenching polysaccharide-based nanogels of pullulan/folate-photosensitizer conjugates for photodynamic therapy

Self-quenching polysaccharide-based nanogels synthesized from pullulan/folate-pheophorbide-a (Pheo-A) conjugates were investigated for their potential to reduce photosensitizer (PS) phototoxicity in normal tissue and to enhance the efficacy of tumor treatment. While the nanogels showed photoactive properties including fluorescence and singlet oxygen generation in organic solvent (DMF), these properties were suppressed in PBS due to the self-quenching of photosensitizer moieties similar to the fluorescence resonance energy transfer (FRET) effect. When the PFP2 nanogel was co-incubated with esterase or HeLa cancer cells, its photoactivity was restored. These results demonstrate that the nanogel was internalized in cancer cells by folate receptor-mediated endocytosis and was then disintegrated by various enzymes in the lysosome, leading to restoration of photoactivity. In an in vivo study, free Pheo-A showed fluorescence immediately after injection; however, nanogel fluorescence was detected 30 min after injection, increased significantly over 12 h, and was maintained beyond 3 weeks. The phototoxic properties of the nanogel were similar to those of free Pheo-A, resulting in an IC(50) < 0.25 and apoptic cell death. Based on these results, we suggest that self-quenching PFP nanogels can be used to design new photodynamic therapies with minimal unfavorable phototoxicity.

Self-assembled hydrogel nanoparticles from curdlan derivatives: characterization, anti-cancer drug release and interaction with a hepatoma cell line (HepG2).

Self-assembled hydrogel nanoparticles were synthesized from carboxymethylated (CM)-curdlan, substituted with a sulfonylurea (SU) as a hydrophobic moiety for self-assembly. The degree of SU substitution was 2.4, 5.6, or 7.2 SU groups per hundred anhydroglucose units of curdlan. The physicochemical properties of the self-assembled hydrogel nanoparticles (DS 2.4, DS 5.6, and DS 7.2) in aqueous media were characterized by dynamic light scattering, transmission electron microscopy, and fluorescence spectroscopy. The mean diameter of all samples was less than 300 nm with a unimodal size distribution. The critical aggregation concentrations (CAC) of self-assembled hydrogel nanoparticles in distilled water were 4.2 x 10(-2), 3.1 x 10(-2) and 1.9 x 10(-2) mg/ml for DS 2.4, 5.6 and 7.2, respectively. The loading and release of all-trans retinoic acid (ATRA) was studied. The ATRA loading efficiencies and loading contents of CM-curdlan/SU nanoparticles increased as the degree of SU substitution increased. The ATRA release rate was controlled by the degree of substitution and drug-loading. For specific interaction with a hepatic carcinoma cell line (HepG2), CM-curdlan was additionally conjugated with lactobionic acid (LBA; galactose moiety) (5.5 LBA molecules per hundred glucose units). HepG2 was strongly luminated by ligand-receptor interactions with fluorescence-labeled LBA/CM-curdlan/SU hydrogel nanoparticles. The luminescence was not observed for other control cases. It is concluded that LBA/CM-curdlan/SU hydrogel nanoparticles are a useful drug carrier for the treatment of liver cancer, because of the potential immunological enhancement activities of CM-curdlan in the body, the ligand-receptor mediated specific interactions, and the controlled release of the anti-cancer drug.

Multiple‐Interaction Ligands Inspired by Mussel Adhesive Protein: Synthesis of Highly Stable and Biocompatible Nanoparticles

Theprerequisiteforthesuccessfulbiomedicaluseofnanoparticles is their colloidal stability in harsh biologicalenvironments. One main approach to render nanoparticleswater-dispersible is replacing the hydrophobic cappingligands with hydrophilic ones that harbor anchoring groupssuch as carboxylic acids, thiols, phosphines, and amines;

A cancer-recognizable MRI contrast agents using pH-responsive polymeric micelle.

A cancer-recognizable MRI contrast agents (CR-CAs) has been developed using pH-responsive polymeric micelles. The CR-CAs with pH sensitivity were self-assembled based on well-defined amphiphilic block copolymers, consisting of methoxy poly(ethylene glycol)-b-poly(L-histidine) (PEG-p(L-His)) and methoxy poly(ethylene glycol)-b-poly(L-lactic acid)-diethylenetriaminopentaacetic acid dianhydride-gadolinium chelate (PEG-p(L-LA)-DTPA-Gd). The CR-CAs have a spherical shape with a uniform size of ~40 nm at physiological pH (pH 7.4). However, in acidic tumoral environment (pH 6.5), the CR-CAs were destabilized due to the protonation of the imidazole groups of p(L-His) blocks, causing them to break apart into positively charged water-soluble polymers. As a result, the CR-CAs exhibit highly effective T1 MR contrast enhancement in the tumor region, which enabled the detection of small tumors of ~3 mm(3 )in vivo at 1.5 T within a few minutes.

Hyaluronic acid-conjugated graphene oxide/photosensitizer nanohybrids for cancer targeted photodynamic therapy

Hyaluronic acid (HA)-graphene oxide (GO) conjugates, with a high loading of photosensitizers (PS; Ce6), were developed as a cancer cell targeted and photoactivity switchable nanoplatform for photodynamic therapy (PDT). HA-GO conjugates with size below 100 nm were first prepared by the chemical conjugation between ADH-modified HA and fractionated GO sheets with size relevant for drug delivery. Before evaluating the drug delivery efficacies, their chemical structure, morphology, and biocompatibility were characterized by 1H NMR, UV, TGA, AFM, DLS and MTT assays. The physical adsorption of Ce6 onto HA-GO nanocarriers was mainly due to the π-π stacking as well as hydrophobic interactions. It was demonstrated by CLSM and FACS that the cellular internalization of the HA-GO/Ce6 nanohybrids was much more effective when compared with free Ce6, which was also found to be significantly influenced by the co-treatment with an excess amount of HA polymers, illustrating their active targeting to HA receptors overexpressed on cancer cells. The photoactivity of Ce6 adsorbed on HA-GO nanocarriers was mostly quenched in aqueous solution to ensure biocompatibility, but was quickly recovered after the release of Ce6 from HA-GO nanocarriers upon cellular uptake. As a result, the PDT efficiency of the HA-GO/Ce6 nanohybrids was remarkably improved ∼10 times more than that of free Ce6, as well demonstrated in both MTT and LIVE/DEAD assays.