Cui Tang

Effects of particle size and surface charge on cellular uptake and biodistribution of polymeric nanoparticles.

To elucidate the effects of particle size and surface charge on cellular uptake and biodistribution of polymeric nanoparticles (NPs), rhodamine B (RhB) labeled carboxymethyl chitosan grafted NPs (RhB-CMCNP) and chitosan hydrochloride grafted NPs (RhB-CHNP) were developed as the model negatively and positively charged polymeric NPs, respectively. These NPs owned well defined particle sizes (150-500 nm) and Zeta potentials (-40 mV - +35 mV). FITC labeled protamine sulfate (FITC-PS) loaded RhB-CMCNP and camptothecin (CPT) loaded RhB-CHNP with high encapsulation efficiency were prepared. The fluorescence stability in plasma and towards I(-) was investigated, and the result indicated it was sufficient for qualitative and quantitative analysis. NPs with high surface charge and large particle size were phagocytized more efficiently by murine macrophage. Slight particle size and surface charge differences and different cell lines had significant implications in the cellular uptake of NPs, and various mechanisms were involved in the uptake process. In vivo biodistribution suggested that NPs with slight negative charges and particle size of 150 nm were tended to accumulate in tumor more efficiently. These results could serve as a guideline in the rational design of drug nanocarriers with maximized therapeutic efficacy and predictable in vivo properties, in which the control of particle size and surface charge was of significance.

Drug permeability and mucoadhesion properties of thiolated trimethyl chitosan nanoparticles in oral insulin delivery

Trimethyl chitosan-cysteine conjugate (TMC-Cys) was synthesized in an attempt to combine the mucoadhesion and the permeation enhancing effects of TMC and thiolated polymers related to different mechanisms for oral absorption. TMC-Cys with various molecular weights (30, 200, and 500 kDa) and quaternization degrees (15 and 30%) was allowed to form polyelectrolyte nanoparticles with insulin through self-assembly, which demonstrated particle size of 100-200 nm, zeta potential of +12 to +18 mV, and high encapsulation efficiency. TMC-Cys/insulin nanoparticles (TMC-Cys NP) showed a 2.1-4.7-fold increase in mucoadhesion compared to TMC/insulin nanoparticles (TMC NP), which might be partly attributed to disulfide formation between TMC-Cys and mucin as evidenced by DSC measurement. Compared to insulin solution and TMC NP, TMC-Cys NP induced increased insulin transport through rat intestine by 3.3-11.7 and 1.7-2.6 folds, promoted Caco-2 cell internalization by 7.5-12.7 and 1.7-3.0 folds, and augmented uptake in Peyers patches by 14.7-20.9 and 1.7-5.0 folds, respectively. Such results were further confirmed by in vivo experiment with the optimal TMC-Cys NP. Biocompatibility assessment revealed lack of toxicity of TMC-Cys NP. Therefore, self-assembled nanoparticles between TMC-Cys and protein drugs could be an effective and safe oral delivery system.

Effects of hydrophobic and hydrophilic modifications on gene delivery of amphiphilic chitosan based nanocarriers

The structure-activity relationships between hydrophobic and hydrophilic modification on chitosan and resultant physicochemical properties along with performances in dealing with critical gene delivery barriers were investigated through amphiphilic linoleic acid(LA) and poly (β-malic acid) (PMLA) double grafted chitosan (LMC)/plasmid DNA (pDNA) nanocomplexes. LMC polymers with various LA and PMLA substitution degrees were synthesized and their hydrophilicity/hydrophobicity was characterized. Compared to chitosan, LMC nanoparticles retained the pDNA binding ability at pH 5.5 when they formed nanocomplexes with pDNA encoding enhanced green fluorescence protein (pEGFP) and the resultant complexes showed diameters below 300 nm. Hydrophobic LA and hydrophilic PMLA substitution contributed to suppressed non-specific adsorption, reduced interactions inside LMC/pDNA nanocomplexes, and enhanced pDNA dissociation. However, enzymatic degradation resistance, cell adsorption, and cellular uptake through clathrin-mediated pathway were promoted by hydrophobic LA grafting while being inhibited by hydrophilic PMLA substitution. In vitro transfection assay suggested the optimal LMC/pEGFP nanocomplexes mediated an 8.0-fold improved transfection compared to chitosan/pEGFP nanocomplexes. The 4.2-fold and 2.2-fold higher intramuscular gene expression in mice compared to chitosan/pEGFP and polyethyleneimine (PEI)/pEGFP nanocomplexes further demonstrated the superiority of LMC/pDNA nanocomplexes. Therefore, amphiphilic chitosan derivates with appropriate combination of hydrophobic and hydrophilic modification would be promising gene delivery nanocarriers.

Size-dependent absorption mechanism of polymeric nanoparticles for oral delivery of protein drugs

Polymeric nanoparticles have been widely applied to oral delivery of protein drugs, however, few studies focused on the systematical elucidation of the size-dependent oral absorption mechanism with well-defined polymeric nanoparticles. Rhodamine B labeled carboxylated chitosan grafted nanoparticles (RhB-CCNP) with different particle sizes (300, 600, and 1000 nm) and similar Zeta potentials (-35 mV) were developed. FITC labeled bovine serum albumin (FITC-BSA) was encapsulated into RhB-CCNP to form drug loaded polymeric nanoparticles (RhB-CCNP-BSA). RhB-CCNP-BSA with uniform particle size and similar surface charge possessed desired structural stability in simulated physiological environment to substantially guarantee the validation of elucidation on size-dependent absorption mechanisms of polymeric nanoparticles using in vitro, in situ, and ex vivo models. RhB-CCNP-BSA with smaller sizes (300 nm) demonstrated elevated intestinal absorption, as mechanistically evidenced by higher mucoadhesion in rat ileum, release amount of the payload into the mucus layer, Caco-2 cell internalization, transport across Caco-2 cell monolayers and rat ileum, and systemic biodistribution after oral gavage. Peyers patches could play a role in the mucoadhesion of nanoparticles, resulting in their close association with the intestinal absorption of nanoparticles. These results provided guidelines for the rational design of oral nanocarriers for protein drugs in terms of particle size.

Preparation, characterization, and oral delivery of insulin loaded carboxylated chitosan grafted poly(methyl methacrylate) nanoparticles.

To improve the efficiency of insulin via oral administration, pH-sensitive carboxylated chitosan grafted poly(methyl methacrylate) nanoparticles (CCGN) were prepared. CCGN were characterized by (1)H NMR, dynamic light scattering, zeta potential, and transmission electron microscopy, and the hypoglycemic effect of insulin loaded CCGN via the oral route was evaluated in normal and diabetic rats. CCGN exhibited a homogeneous morphology and a spherical shape with core-shell structure. They were aggregated in simulated gastric fluid while separated in simulated intestinal fluid. Insulin was mainly located in the shell of the CCGN via hydrogen bonding, electrostatic interaction, and Van der Waals force. Insulin release from the CCGN exhibited a pH-sensitive property in that it had a slow release rate at pH 2.0 and a fast release rate at pH 6.8 and 7.4. The pharmacological bioavailability after oral administration of insulin loaded CCGN at a dose of 25 IU/kg was found to be 9.7%. Besides, CCGN showed desirable tissue and blood compatibility. Therefore, the CCGN would be a promising delivery carrier for protein drugs via the oral route.

Hyaluronic acid coated poly(butyl cyanoacrylate) nanoparticles as anticancer drug carriers.

The hyaluronic acid (HA) coated poly(butyl cyanoacrylate) (PBCA) nanoparticles were synthesized through radical polymerization of butyl cyanoarylate (BCA) initiated by cerium ions in the presence of HA. The chemical coupling between HA and PBCA was demonstrated by FTIR, (1)H NMR and X-ray diffraction. The sizes of the nanoparticles with different HA/BCA ratios were 291-325 nm at cerium concentration of 0.8 mmol/L and HA molecular weight of 18,000 Da. Paclitaxel (PTX), a model anticancer drug, was encapsulated in negatively charged nanoparticles with a maximal encapsulation efficiency of 90%. In vitro release demonstrated that HA modification could effectively reduce the initial burst release in the first 10h and provide a sustained release in the subsequent 188 h. As evidenced by the hemolysis assay and MTT assay, HA coating could significantly reduce the cytotoxicity. Cellular uptake indicated that uptake of HA-PBCA nanoparticles by Sarcoma-180 (S-180) cells was 9.5-fold higher than that of PBCA nanoparticles. PTX-loaded HA-PBCA nanoparticles were more potent in tumor growth suppression than PTX-loaded PBCA nanoparticles or PTX injection following intravenous administration to S-180 tumor bearing mice. Therefore, the HA-PBCA nanoparticles could be an effective and safe vehicle for systemic administration of hydrophobic anticancer drugs.

Thiolated trimethyl chitosan nanocomplexes as gene carriers with high in vitro and in vivo transfection efficiency

Trimethyl chitosan-cysteine conjugate (TMC-Cys) was evaluated as non-viral gene carriers to combine the advantages of TMC and thiolated chitosan. TMC-Cys with various molecular weights (30, 100, and 200 kDa) and quaternization degrees (15 and 30%) was allowed to form polyelectrolyte nanocomplexes with plasmid encoding enhanced green fluorescence protein (pEGFP), which demonstrated preferable diameters of below 200 nm and zeta potentials of +15 to +20 mV. Cell binding and uptake of TMC-Cys/pEGFP nanocomplexes (TMC-Cys NC) were enhanced 2.4-3.0 and 1.4-3.0 folds, respectively, compared to TMC/pEGFP nanocomplexes (TMC NC). pEGFP could be easily released from TMC-Cys NC at the intracellular glutathione concentration, which promoted its nuclear transport and accumulation. Consequently, TMC-Cys NC showed a 1.4 to 3.2-fold increase in the transfection efficiency in HEK293 cells as compared to TMC NC and the optimal TMC-Cys(100,30) NC showed a 1.5-fold enhancement than Lipofectamine2000. Such results were further confirmed by in vivo transfection with a 2.3-fold and 4.1-fold higher transfection efficiency of TMC-Cys(100,30) NC than TMC(100,30) NC and Lipofectamine2000, respectively. Therefore, TMC-Cys/DNA nanocomplexes could be a promising gene delivery system with in vitro and in vivo superiority to Lipofectamine2000.

Glycyrrhizin-modified O-carboxymethyl chitosan nanoparticles as drug vehicles targeting hepatocellular carcinoma.

Here we describe the O-carboxymethyl chitosan nanoparticles (CMCNP) modified by glycyrrhizin (GL) with various substitution degrees as hepatocellular carcinoma (HCC)-targeted delivery vehicles, which could efficiently deliver paclitaxel (PTX) into HCC. The resultant CMCNP-GL exhibited spherical in shape and high stability in plasma with fixed negative charged (~-30 mV) and a size range of 100-205 nm. PTX was loaded into CMCNP-GL with a maximal encapsulation efficiency of 83.7% and performed a biphasic release. CMCNP-GL promoted liver cancer SMMC-7721 cell internalization by approximate 10.0-fold as compared to unmodified CMCNP. Within 72 h, the IC(50) of PTX/CMCNP-GL, PTX/CMCNP, and PTX injection was 2.7-3.2, 8.1, and 13.5 μg/mL, respectively. Biodistribution experiments revealed that PTX/CMCNP-GL exerted significantly superior targeting to tumor than PTX/CMCNP. The in vivo tumor inhibition ratio of PTX/CMCNP-GL was 87.5%, showing remarkably higher than that of PTX/CMCNP (64.0%) and PTX injection (34.5%). CMCNP-GL with different substitution degrees possessed similar targeting property and therapeutic efficacy. Furthermore, toxicity studies suggested that blank CMCNP-GL had no systemic or hepatic toxicity.

Multifunctional polymeric nanoparticles for oral delivery of TNF-α siRNA to macrophages

Oral delivery of therapeutic siRNA is an appealing strategy for the treatment of many diseases, however poses numerous challenges to escort siRNA from the site of administration to the cytoplasm of the target cells. Mannose-modified trimethyl chitosan-cysteine (MTC) conjugate nanoparticles (NPs) were developed via ionic gelation and performed as highly effective polymeric vehicles for oral delivery of TNF-α siRNA. The chitosan backbone as well as trimethyl, thiol, and mannose groups of MTC NPs could be activated at proper time and location to overcome the extracellular and intracellular barriers to oral siRNA delivery, thereby promoting gene silencing efficiency. MTC NPs effectively improved siRNA integrity in physiological environment, enhanced siRNA permeation across the intestinal epithelium, facilitated siRNA uptake by macrophages through clathrin-independent endocytosis, and promoted cytoplasmic siRNA release. At equivalent TNF-α siRNA dose, MTC NPs notably outperformed Lipofectamine2000 in terms of in vitro knockdown of TNF-α production in macrophages. Orally delivered MTC NPs containing low amount of TNF-α siRNA (3.75 nm/kg) inhibited TNF-α production in macrophages in vivo, which protected mice with acute hepatic injury from inflammation-induced liver damage and lethality. This study could provide broad insights into the rational design of oral siRNA vehicles for the treatment of inflammatory diseases.

Dual-targeting and pH/redox-responsive multi-layered nanocomplexes for smart co-delivery of doxorubicin and siRNA.

Multi-layered nanocomplexes (MLNs) were designed here to provide smart co-delivery of doxorubicin (DOX) and vascular endothelial growth factor (VEGF) siRNA. The electrostatically self-assembled MLNs were constructed by TAT peptide modified mesoporous silica nanoparticles (TAT-MSN) as the cationic core for DOX loading, poly(allylamine hydrochloride)-citraconic anhydride (PAH-Cit) as the anionic inner layer, and galactose-modified trimethyl chitosan-cysteine (GTC) conjugate as the cationic outer layer to encapsulate siRNA. Their strong stability at pH 7.4 and 6.5 protected siRNA from degradation in the blood and tumor microenvironment. Galactose ligands on the GTC outer layers effectively facilitated the internalization of MLNs through receptor-mediated endocytosis. Afterwards, the endosomal/lysosomal acidity (pH 5.0) triggered the charge reversal of PAH-Cit, thereby inducing the disassembly of MLNs and their escape to the cytosol. Cytoplasmic glutathione further accelerated siRNA release through cleaving disulfide bonds in GTC layers, leading to high silencing efficiencies. Meanwhile, the exposed DOX-loaded cores were transported into the nuclei by virtue of TAT peptide and exhibited sustained release thereafter. As a result, potent antitumor efficacies of MLNs were noted following intravenous injection at a low dose with no apparent toxicity detected. Therefore, MLNs served as an effective and safe vector to maximize synergistic effect of chemodrugs and therapeutic genes.