Albumen Transport to Bruch's Membrane and RPE by Choriocapillaris Caveolae.

PURPOSE: The choriocapillaris (CC), the capillary network of the choroid, is positioned adjacent to Bruch's membrane (BM) and the RPE. The aim of this study was to clarify the mechanism(s) for transport of serum albumen from CC lumen to RPE. METHODS: Alexa647 conjugated to BSA (BSA-A647) or PBS was administrated via the femoral vein to young and aged wild-type (WT; C57BL/6J) mice and Caveolin-1 knockout mice (Cav1(-/-)). Mice were perfused with PBS and killed at 30 minutes, 1 hour, and 4 hours after injection. Eyecups were cryopreserved, and cryosections were analyzed on a Zeiss 710 confocal microscope. Bovine serum albumin conjugated to gold nanoparticles (BSA-GNP) was administrated through the left common carotid artery. Mice were perfused with PBS and killed at 30 minutes after injection. Eyecups were embedded after fixation, and 70-nm-thick sections were analyzed on a Hitachi H7600 transmission electron microscope. RESULTS: In eyes of WT young mice, BSA-A647 was transported to the RPE at 30 minutes and diffused to the photoreceptor layer by 1 hour. In contrast, most BSA-A647 was found in the CC in Cav1(-/-) eyes. The majority of BSA-GNP found in the CC of young WT mice was on the luminal side in caveolae at 30 minutes after injection. In aged WT mice, BSA-GNPs were found in defective tight junctions between endothelial cells and appeared trapped at the diaphragm of fenestrations. CONCLUSIONS: Normally, CC carefully regulates transport system of BSA from lumen to BM by caveolae-mediated transcytosis; however, endothelium cells of aged control WT mice have leaky tight junctions and lacked regulated BSA transport.

Enhanced stability and knockdown efficiency of poly(ethylene glycol)-b-polyphosphoramidate/siRNA micellar nanoparticles by co-condensation with sodium triphosphate.

PURPOSE: Polyelectrolyte complex nanoparticles are a promising vehicle for siRNA delivery but suffer from low stability under physiological conditions. An effective stabilization method is essential for the success of polycationic nanoparticle-mediated siRNA delivery. In this study, sodium triphosphate (TPP), an ionic crosslinking agent, is used to stabilize siRNA-containing nanoparticles by co-condensation. METHODS: siRNA and TPP were co-encapsulated into a block copolymer, poly(ethylene glycol)-b-polyphosphoramidate (PEG-b-PPA), to form ternary nanoparticles. Physicochemical characterization was performed by dynamic light scattering and gel electrophoresis. Gene silencing efficiency in cell lines was assessed by dual luciferase assay system. RESULTS: The PEG-b-PPA/siRNA/TPP ternary nanoparticles exhibited high uniformity with smaller size (80-100 nm) compared with PEG-b-PPA/siRNA nanoparticles and showed increased stability in physiological ionic strength and serum-containing medium, due to the stabilization effect from ionic crosslinks between negatively charged TPP and cationic PPA segment. Transfection and gene silencing efficiency of the TPP-crosslinked nanoparticles were markedly improved over PEG-b-PPA/siRNA complexes in serum-containing medium. No significant difference in cell viability was observed between nanoparticles prepared with and without TPP co-condensation. CONCLUSIONS: These results demonstrated the effectiveness of TPP co-condensation in compacting polycation/siRNA nanoparticles, improving nanoparticle stability and enhancing the transfection and knockdown efficiency in serum-containing medium.

Polyion complex stability and gene silencing efficiency with a siRNA-grafted polymer delivery system.

An siRNA-grafted polymer through disulfide linkage was prepared to improve the physicochemical properties and transfection efficacies of the polyion complexes (PICs) as a nanocarrier of siRNA. The siRNA-grafted polymer formed stable PICs due to its larger numbers and higher density of anionic charges compared with monomeric siRNA, leading to effective internalization by cultured cells. Following the endosomal escape of the PIC, the disulfide linkage of the siRNA-grafted polymer allowed efficient siRNA release from the PIC under intracellular reductive conditions. Consequently, the PIC from the siRNA-grafted polymer showed a potent gene silencing effect without cytotoxicity or immunogenicity, demonstrating a promising feature of the siRNA-grafted polymer to construct the PIC-based nanocarrier for in vivo siRNA delivery.

A photo-activated targeting chemotherapy using glutathione sensitive camptothecin-loaded polymeric micelles.

PURPOSE: A novel photo-activated targeted chemotherapy was developed by photochemical internalization (PCI) of glutathione-sensitive polymeric micelles incorporating camptothecin (CPT) prepared from thiolated CPT (CPT-DP) and thiolated poly(ethylene glycol)-b-poly(glutamic acid) (PEG-b-P(Glu-DP)) METHODS: PEG-b-P(Glu-DP) and CPT-DP were synthesized and characterized by (1)H-NMR and gel permeation chromatography, and then mixed to prepare CPT-loaded polymeric micelles (CPT/m). The CPT release from the micelle was studied by reverse phase liquid chromatography. The PCI-activated cytotoxicity of CPT/m against HeLa cells was studied in combination with a non-toxic concentration of dendrimer phthalocyanine-loaded micelles (DPc/m) as the photosensitizer. RESULTS: The diameter of CPT/m was 96 nm and the drug loading was 20% (w/w). CPT was slowly released under the conditions reproducing the extracellular or endosomal environments. However, under the reductive conditions mimicking the cytosol, CPT was rapidly released achieving approximately 90% of the drug release after 24 h. The cytotoxicity of CPT/m was drastically increased on photoirradiation, whereas the CPT/m were not cytotoxic without PCI. CONCLUSIONS: The CPT/m released the drug responding to reductive conditions. The PCI-induced endosomal escape exposed CPT/m to the cytosol triggering the drug release. Thus, CPT/m in combination with DPc/m will behave as smart nanocarriers activated only at photoirradiated tissues.

Polyplexes from poly(aspartamide) bearing 1,2-diaminoethane side chains induce pH-selective, endosomal membrane destabilization with amplified transfection and negligible cytotoxicity.

Polyplexes assembled from poly(aspartamide) derivatives bearing 1,2-diaminoethane side chains, [PAsp(DET)] display amplified in vitro and in vivo transfection activity with minimal cytotoxicity. To elucidate the molecular mechanisms involved in this unique function of PAsp(DET) polyplexes, the physicochemical and biological properties of PAsp(DET) were thoroughly evaluated with a control bearing 1,3-diaminopropane side chains, PAsp(DPT). Between PAsp(DET) and PAsp(DPT) polyplexes, we observed negligible physicochemical differences in particle size and zeta-potential. However, the one methylene variation between 1,2-diaminoethane and 1,3-diaminopropane drastically altered the transfection profiles. In sharp contrast to the constantly high transfection efficacy of PAsp(DET) polyplexes, even in regions of excess polycation to plasmid DNA (pDNA) (high N/P ratio), PAsp(DPT) polyplexes showed a significant drop in the transfection efficacy at high N/P ratios due to the progressively increased cytotoxicity with N/P ratio. The high cytotoxicity of PAsp(DPT) was closely correlated to its strong destabilization effect on cellular membrane estimated by hemolysis, leakage assay of cytoplasmic enzyme (LDH assay), and confocal laser scanning microscopic observation. Interestingly, PAsp(DET) revealed minimal membrane destabilization at physiological pH, yet there was significant enhancement in the membrane destabilization at the acidic pH mimicking the late endosomal compartment (pH approximately 5). Apparently, the pH-selective membrane destabilization profile of PAsp(DET) corresponded to a protonation change in the flanking diamine unit, i.e., the monoprotonated gauche form at physiological pH and diprotonated anti form at acidic pH. These significant results suggest that the protonated charge state of 1,2-diaminoethane may play a substantial role in the endosomal disruption. Moreover, this novel approach for endosomal disruption neither perturbs the membranes of cytoplasmic vesicles nor organelles at physiological pH. Thus, PAsp(DET) polyplexes, residing in late endosomal or lysosomal states, smoothly exit into the cytoplasm for successful transfection without compromising cell viability.