Diammonium Hydrogen Citrate-Assisted Spray Pyrolysis Synthesis of Nanostructured LiCoPO4 Microspheres as High-Voltage Cathode Material for Lithium-Ion Batteries.

Nanostructured LiCoPO4 (LCP) microspheres were successfully synthesized by one-step spray pyrolysis, adding an appropriate amount of diammonium hydrogen citrate (DHC) additive to the precursor solution. Comprehensive physical characterization confirmed that the obtained LCPs exhibited a desirable orthorhombic olivine structure with nanostructured morphology and a significant increase in specific surface area. This enhancement was attributed to the dispersion effect due to the carboxyl group and the evolution of the ammonium group of DHC during the pyrolysis process. The resultant LCP delivered a high initial discharge capacity of 132 mA h g-1 with 63.3% capacity retention (vs 103 mA h g-1 and 37.1% of bare-LCP) after 50 cycles at 0.1 C using the conventional electrolyte. Moreover, the electrochemical performance showed additional enhancement when a fluorinated electrolyte was introduced, resulting in initial and 50th discharge capacities of 141 and about 100 mA h g-1, respectively, at 0.1 C.

Enzyme-Loaded Polyion Complex Vesicles as in Vivo Nanoreactors Working Sustainably under the Blood Circulation: Characterization and Functional Evaluation.

Enzyme-loaded synthetic vesicles have attracted great attention for their feasibility to exert the efficient and prolonged functionality of loaded enzymes in harsh environments, such as in vivo. However, several issues remain regarding the optimization of their structures toward practical application. Herein, we fabricated polyion complex vesicles (PICsomes) loaded with l-asparaginase (ASNase@PICsomes) and conducted a detailed characterization to ensure their utility as nanoreactors functioning under the harsh in vivo environment of the bloodstream. ASNase@PICsomes showed 100 nm-sized monodispersed vesicular structures. Fluorescence cross-correlation spectroscopy revealed essentially no empty PICsome fraction in the product, indicating the quantitative formation of ASNase@PICsomes. Furthermore, fluorescence anisotropy measurement showed that the loaded enzymes were located essentially in the inner aqueous phase of PICsomes, being successfully segregated from the external environment. ASNase@PICsomes exhibited significantly prolonged enzymatic reaction compared with free ASNase after systemic injection into mice, corroborating their functionality as in vivo nanoreactors working under the blood circulation.

Systemically Injectable Enzyme-Loaded Polyion Complex Vesicles as In Vivo Nanoreactors Functioning in Tumors.

The design and construction of nanoreactors are important for biomedical applications of enzymes, but lipid- and polymeric-vesicle-based nanoreactors have some practical limitations. We have succeeded in preparing enzyme-loaded polyion complex vesicles (PICsomes) through a facile protein-loading method. The preservation of enzyme activity was confirmed even after cross-linking of the PICsomes. The cross-linked ß-galactosidase-loaded PICsomes (ß-gal@PICsomes) selectively accumulated in the tumor tissue of mice. Moreover, a model prodrug, HMDER-ßGal, was successfully converted into a highly fluorescent product, HMDER, at the tumor site, even 4 days after administration of the ß-gal@PICsomes. Intravital confocal microscopy showed continuous production of HMDER and its distribution throughout the tumor tissues. Thus, enzyme-loaded PICsomes are useful for prodrug activation at the tumor site and could be a versatile platform for enzyme delivery in enzyme prodrug therapy.

siRNA-Loaded Polyion Complex Micelle Decorated with Charge-Conversional Polymer Tuned to Undergo Stepwise Response to Intra-Tumoral and Intra-Endosomal pHs for Exerting Enhanced RNAi Efficacy.

Small interfering RNA (siRNA) needs an efficient delivery vehicle to reach the cytoplasm of target cells for successful RNA interference (RNAi) therapy. This study aimed to develop an siRNA-loaded polyion complex (PIC) micelle equipped with a smart polymeric shell featuring tumor targetability and endosome escapability for enhanced RNAi activity in cancer cells. To this end, an acidic pH-responsive polypeptide was designed to exert a stepwise change in its charged state from negative to modestly positive and highly positive in response to slightly acidic environment of tumor (pH ∼6.7) and further lowered-pH condition of late endosomal compartments (pH ∼5.0), respectively, for selective binding to cancer cell surface and subsequent endosome disruption. This polypeptide, termed PAsp(DET-CDM/DBCO), was synthesized by introducing acid-labile carboxydimethyl maleate (CDM) and dibenzylcyclooctyne (DBCO) moieties into a polyaspartamide derivative bearing two-repeated aminoethylene side chains (PAsp(DET)). Then, PAsp(DET-CDM/DBCO) was installed on the surface of disulfide cross-linked PIC micelles prepared from cholesterol-modified siRNA (Chol-siRNA) and azide-poly(ethylene glycol)-b-poly[(3-mercaptopropylamidine)-L-lysine] (N3-PEG-b-PLys(MPA)) through the copper-free click reaction. Successful PAsp(DET-CDM/DBCO) coverage of PIC micelles was confirmed by a significant decrease in ζ-potential as well as a narrowly distributed size of 40 nm. The PAsp(DET-CDM/DBCO)-installed micelles significantly improved the gene-silencing efficiency in cultured lung cancer cells, compared with nonmodified control micelles, especially after incubation at pH 6.7. This improved silencing activity was nicely correlated with the facilitated cellular uptake of siRNA payloads at the acidic pH and the efficient endosomal escape. These results demonstrate that the acidic pH-responsive polypeptide shell is a promising design strategy for tumor-targeted siRNA delivery.

Density-tunable conjugation of cyclic RGD ligands with polyion complex vesicles for the neovascular imaging of orthotopic glioblastomas.

Introduction of ligands into 100 nm scaled hollow capsules has great potential for diagnostic and therapeutic applications in drug delivery systems. Polyethylene glycol-conjugated (PEGylated) polyion complex vesicles (PICsomes) are promising hollow nano-capsules that can survive for long periods in the blood circulation and can be used to deliver water-soluble macromolecules to target tissues. In this study, cyclic RGD (cRGD) peptide, which is specifically recognized by αVß3 and αvß5 integrins that are expressed at high levels in the neovascular system, was conjugated onto the distal end of PEG strands on PICsomes for active neovascular targeting. Density-tunable cRGD-conjugation was achieved using PICsomes with definite fraction of end-functionalized PEG, to substitute 20, 40, and 100% of PEG distal end of the PICsomes to cRGD moieties. Compared with control-PICsomes without cRGD, cRGD-PICsomes exhibited increased uptake into human umbilical vein endothelial cells. Intravital confocal laser scanning microscopy revealed that the 40%-cRGD-PICsomes accumulated mainly in the tumor neovasculature and remained in the perivascular region even after 24 h. Furthermore, we prepared superparamagnetic iron oxide (SPIO)-loaded cRGD-PICsomes for magnetic resonance imaging (MRI) and successfully visualized the neovasculature in an orthotopic glioblastoma model, which suggests that SPIO-loaded cRGD-PICsomes might be useful as a MRI contrast reagent for imaging of the tumor microenvironment, including neovascular regions that overexpress αVß3 integrins.