SEARCH · PubMed Health

Results for “nanoparticles”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources

PubMed1999

Spleen capture of nanoparticles: influence of animal species and surface characteristics.

PURPOSE: To investigate the influence of animal species and nanoparticle surface characteristics on the intrasplenic distribution of polystyrene nanoparticles. METHODS: Two types of fluorescent polystyrene nanoparticles (Estapor and Fluoresbrite), plain or coated, were used in mice and rats. First, a fluorimetric method was developed for nanoparticle tissue quantification. Then, intrasplenic distribution of plain or coated nanoparticles was studied using histological examination and image analysis. Finally, the role of direct interactions between nanoparticles and spleen capturing cells was assessed by in vitro binding assays, using incubation of thick spleen slices with polystyrene nanoparticles. RESULTS: The two types of polystyrene nanoparticles showed different levels of trapping: Fluoresbrite nanoparticles were more efficiently trapped by the spleen than Estapor nanoparticles, both in mice and rats. In mice, most of the injected nanoparticles were localized in the marginal zone of the spleen, involving a special population of capturing cells, while in rats, the predominant capture occured in the red pulp. In mice, coated nanoparticles were localized both in the marginal zone and in the red pulp, whereas the coating did not seem to change the intrasplenic distribution of the nanoparticles in rats. CONCLUSIONS: These complementary approaches showed different uptake pathways of nanoparticles, according to their surface characteristics and the rodent species used.

Animals↗

PubMed2004

Critical determinants in PLGA/PLA nanoparticle-mediated gene expression.

PURPOSE: The aim of the study was to determine the critical determinants in nanoparticle-mediated gene transfection. It was hypothesized that different formulation parameters could affect the nanoparticle characteristics and hence its gene transfection. METHODS: Nanoparticles encapsulating plasmid DNA encoding for firefly luciferase were formulated using polylactide (PLA) and poly (D,L-lactide-co-glycolide) (PLGA) polymers of different compositions and molecular weights. A multiple-emulsion solvent-evaporation method with polyvinyl alcohol (PVA) as an emulsifier was used to formulate DNA-loaded nanoparticles. Gene expression of nanoparticles was determined in breast cancer (MCF-7) and prostate cancer (PC-3) cell lines. RESULTS: Nanoparticles formulated using PLGA polymer demonstrated greater gene transfection than those formulated using PLA polymer, and this was attributed to the higher DNA release from PLGA nanoparticles. Higher-molecular-weight PLGA resulted in the formation of nanoparticles with higher DNA loading, which demonstrated higher gene expression than those formulated with lower-molecular-weight PLGA. In addition, the nanoparticles with lower amount of surface-associated PVA demonstrated higher gene transfection in both the cell lines. Higher gene transfection with these nanoparticles was attributed to their higher intracellular uptake and cytoplasmic levels. Further study demonstrated that the molecular weight and the degree of hydrolyzation of PVA used as an emulsifier also affect the gene expression of nanoparticles. CONCLUSIONS: Results thus demonstrate that the DNA loading in nanoparticles and its release, and the surface-associated PVA influencing the intracellular uptake and endolysosomal escape of nanoparticles, are some of the critical determinants in nanoparticle-mediated gene transfection.

Animals↗

PubMed2004

Biodistribution and targeting potential of poly(ethylene glycol)-modified gelatin nanoparticles in subcutaneous murine tumor model.

PURPOSE: In order to develop a safe and effective systemically-administered biodegradable nanoparticle delivery system for solid tumors, the comparative biodistribution profiles of gelatin and poly(ethylene-glycol)(PEG)-modified (PEGylated) gelatin nanoparticles was examined in subcutaneous Lewis lung carcinoma (LLC)-bearing female C57BL/6J mice. METHODS: Type-B gelatin and PEGylated gelatin nanoparticles were radiolabeled ((125)I) for the in vivo biodistribution studies after intravenous (i.v.) administration through the tail vein in LLC-bearing mice. At various time intervals, the mice were sacrificed and blood, tumor, and major organs harvested for analysis of radioactivity corresponding to the localization of the nanoparticles. Percent recovered dose was determined and normalized to the weight of the fluid or tissue sample. Non-compartmental pharmacokinetic analysis was performed to determine the long-circulating property and preferential tumor targeting potential of PEGylated gelatin nanoparticles in vivo. RESULTS: From the radioactivity in plasma and various organs collected, it was evident that the majority of PEGylated nanoparticles were present either in the blood pool or taken up by the tumor mass and liver. For instance, after 3 h, the concentrations of PEGylated gelatin nanoparticles was almost 2-fold higher in the blood pool than the control gelatin nanoparticles. PEGylated gelatin nanoparticles remained in the blood pool for a longer period of time due to the steric repulsion effect of the PEG chains as compared to the gelatin nanoparticles. In addition, approximately 4-5% of the recovered dose of PEGylated gelatin nanoparticles was present in the tumor mass for up to 12 h. The plasma and the tumor half-lives, the mean residence time, and the area-under-the-curve of the PEGylated gelatin nanoparticles were significantly higher than those for the gelatin nanoparticles. CONCLUSIONS: The results of this study show that PEGylated gelatin nanoparticles do possess long circulating properties and can preferentially distribute in the tumor mass after systemic delivery.

Animals↗

PubMed2004

Pegylated poly(lactide) and poly(lactide-co-glycolide) nanoparticles: preparation, properties and possible applications in drug delivery.

The preparation, properties and potential applications in drug delivery of biocompatible and biodegradable PLA-PEG and PLGA-PEG nanoparticles are discussed. PLA-PEG and PLGA-PEG nanoparticles have been produced by emulsification-solvent evaporation, solvent displacement and salting out methods. The nanoparticles can be stored as freeze-dried powders, but an adequate amount of a suitable lyoprotectant should be added prior lyophilisation to prevent nanoparticle aggregation and retain nanoparticle redispersibility. The nanoparticles have a core-shell structure with a PLA core and a PEG coating. Their basic colloidal properties and degradation depend on copolymer composition. The PLA-PEG and PLGA-PEG nanoparticles exhibit prolonged blood circulation following intravenous administration to animals. The composition of the nanoparticles determine their biodistribution properties, probably through its effects on the effectiveness of the PEG steric barrier and the size of the nanoparticles. The ability of the PLA-PEG and PLGA-PEG nanoparticles to evade rapid phagocytocis has extended the range of sites within the body that the nanoparticles can reach, which has significant implications with regard to their application in controlled drug delivery and targeting. The PLA-PEG and PLGA-PEG nanoparticles can be loaded with a variety of bioactive agents achieving satisfactory loading, especially in the case of hydrophobic drugs. The nanoparticles have been investigated for the treatment of infectious diseases and cancer, the intravenous and mucosal delivery of proteins, and oligonucleotide and gene delivery. The results have been encouraging and PLA-PEG and PLGA-PEG nanoparticle formulations, improving the therapeutic potential of both established and new drugs, may be expected to be available in the near future.

Animals↗

PubMed2004

Influence of polymerization technique and experimental variables on the particle properties and release kinetics of methotrexate from poly(butylcyanoacrylate) nanoparticles.

Poly(butylcyanoacrylate) nanoparticles were prepared by dispersion polymerization (DP) and emulsion polymerization (EP) of n-butyl cyanoacrylate monomer. The particles were characterized by infrared spectroscopy, differential scanning calorimetry, X-ray diffractometry and transmission electron microscopy. Particle properties such as size and zeta potential were determined for nanoparticles prepared by DP and EP techniques and compared. EP technique resulted in a low particle size compared to the DP. A high zeta potential was observed for nanoparticles prepared by the DP method. Incorporation of methotrexate resulted in a decrease in zeta potential in both types of nanoparticles, the decrease being greater in DP nanoparticles. Effect of experimental variables such as monomer concentration, polymerization time and temperature on drug entrapment and particle size was studied. Both types of nanoparticles showed an increase in drug entrapment with increased monomer concentrations. Variable polymerization time did not influence the drug entrapment of EP nanoparticles. Polymerization at 60 +/- 2 degrees C resulted in a decrease of drug entrapment and a great increase in the particle size of both types of nanoparticles. In vitro drug release studies showed a comparatively high release of methotrexate from DP nanoparticles suggesting the channelizing effect of dextran chains incorporated into nanoparticles during polymerization. Though the release profiles of nanoparticles appeared similar, a significant difference in release rates was found for DP and EP nanoparticles in 0.1 mol L(-1) HCl and pH 7.4 phosphate buffer (p < 0.01). Drug release data indicate that the release of methotrexate from DP and EP nanoparticles followed Fickian diffusion in 0.1 mol L(-1) HCl, while the mechanism was found anomalous in pH 7.4 phosphate buffer. An effort was also made to critically correlate the properties of nanoparticles synthesized by the above two techniques, and emphasize the importance of these characteristics in targeted drug delivery.

Enbucrilate↗

PubMed2005

Effects of particle size and surface coating on cellular uptake of polymeric nanoparticles for oral delivery of anticancer drugs.

This study evaluated cellular uptake of polymeric nanoparticles by using Caco-2 cells, a human colon adenocarcinoma cell line, as an in vitro model with the aim to apply nanoparticles of biodegradable polymers for oral chemotherapy. The feasibility was demonstrated by showing the localization and quantification of the cell uptake of fluorescent polystyrene nanoparticles of standard size and poly(lactic-co-glycolic acid) (PLGA) nanoparticles coated with polyvinyl alcohol (PVA) or vitamin E TPGS. Coumarin-6 loaded PLGA nanoparticles were prepared by a modified solvent extraction/evaporation method and characterized by laser light scattering for size and size distribution, scanning electron microscopy (SEM) for surface morphology, zeta-potential for surface charge, and spectrofluorometry for fluorescent molecule release from the nanoparticles. The effects of particle size and particle surface coating on the cellular uptake of the nanoparticles were quantified by spectrofluorometric measurement. Cellular uptake of vitamin E TPGS-coated PLGA nanoparticles showed 1.4 folds higher than that of PVA-coated PLGA nanoparticles and 4-6 folds higher than that of nude polystyrene nanoparticles. Images of confocal laser scanning microscopy, cryo-SEM and transmission electron microscopy clearly evidenced the internalization of nanoparticles by the Caco-2 cells, showing that surface modification of PLGA nanoparticles with vitamin E TPGS notably improved the cellular uptake. It is highly feasible for nanoparticles of biodegradable polymers to be applied to promote oral chemotherapy.

Administration, Oral↗

PubMed2004

Preparation and antibacterial activity of chitosan nanoparticles.

Chitosan nanoparticles, such as those prepared in this study, may exhibit potential antibacterial activity as their unique character. The purpose of this study was to evaluate the in vitro antibacterial activity of chitosan nanoparticles and copper-loaded nanoparticles against various microorganisms. Chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions. Copper ions were adsorbed onto the chitosan nanoparticles mainly by ion-exchange resins and surface chelation to form copper-loaded nanoparticles. The physicochemical properties of the nanoparticles were determined by size and zeta potential analysis, atomic force microscopy (AFM), FTIR analysis, and XRD pattern. The antibacterial activity of chitosan nanoparticles and copper-loaded nanoparticles against E. coli, S. choleraesuis, S. typhimurium, and S. aureus was evaluated by calculation of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Results show that chitosan nanoparticles and copper-loaded nanoparticles could inhibit the growth of various bacteria tested. Their MIC values were less than 0.25 microg/mL, and the MBC values of nanoparticles reached 1 microg/mL. AFM revealed that the exposure of S. choleraesuis to the chitosan nanoparticles led to the disruption of cell membranes and the leakage of cytoplasm.

Anti-Bacterial Agents↗

PubMed2004

Poly(lactic acid) nanoparticles labeled with biologically active Neutravidin for active targeting.

In this study, NeutrAvidin was covalently bound to the surface of poly(DL-lactic acid) (PLA) nanoparticles, with the aim of attaching targeting compounds, such as proteins, to their surface. Sulfhydryl groups were first introduced on the surface of PLA nanoparticles through a carbodiimide reaction. NeutrAvidin was then bound to the thiolated nanoparticles via a bifunctional cross-linker, which offers two binding sites, one for primary amine groups and one for thiol functions. The amount of sulfhydryl groups obtained on the surface of the nanoparticles was determined. The NeutrAvidin -labeled nanoparticles were evaluated with respect to particle size, protein concentration and biotin binding capacity. The concentration of thiol functions on the surface of nanoparticles was 105 +/- 15 mmol/mol PLA. The quantification of NeutrAvidin coupled to the nanoparticles revealed that a significant amount of the protein was covalently bound to the nanoparticles. The concentration of NeutrAvidin bound to the nanoparticles could be controlled by varying the amount of protein during the coupling reaction. The maximum concentration of NeutrAvidin attached to the particles was 6 mmol per mol of PLA. The specific activity of NeutrAvidin bound to the nanoparticles was also evaluated and results revealed that the protein maintained the capacity to bind biotin. The activity of the NAR-labeled nanoparticles was lower than expected, due to the undesired aggregation of the native NeutrAvidin. Altogether, the results suggest that other proteins, such as antibodies could be coupled to the nanoparticles for active targeting. Furthermore, PLA nanoparticles bearing NeutrAvidin are interesting candidates for active targeting with biotinylated antibodies using the biotin-avidin interaction in a two step procedure.

Avidin↗

PubMed2004

Formulation and characterization of spray-dried powders containing nanoparticles for aerosol delivery to the lung.

Spray-drying is a common practice of powder preparation for a wide range of drugs. Spray-dried powders can be used to deliver particles to the lungs via a dry powder inhaler (DPI). The present study investigated the feasibility of developing a platform for aerosol delivery of nanoparticles. Lactose was used as the excipient and spray-dried with two different types of nanoparticles: gelatin and polybutylcyanoacrylate nanoparticles. Results showed that some carrier particles were hollow while others had a continuous matrix. Gelatin nanoparticles were incorporated throughout the matrix and sometimes accumulated at one end of the lactose. Polycyanoacrylate nanoparticles mostly clustered in different spots within the lactose carriers. The mean sizes of both nanoparticle types were characterized at two different times: before they were spray-dried and after they were redissolved from the spray-dried powders. Both nanoparticle types remained in the nano-range size after spray-drying. The mean nanoparticle sizes were increased by approximately 30% after spray-drying, though this increase was statistically significant only for the gelatin nanoparticles. Dispersion of the powder with an in-house passive dry powder inhaler and subsequent cascade impaction measurements showed that incorporation of the nanoparticles did not affect the fine particle fraction (FPF) or mass median aerodynamic diameter (MMAD) of the powders. FPF was approximately 40% while MMAD was 3.0+/-0.2 microm, indicating the present formulations yield aerosols of a suitable particle size for efficient lung delivery of nanoparticles. The present work demonstrates that nanoparticles can be delivered to the lungs via carrier particles that dissolve after coming in contact with the aqueous environment of the lung epithelium. This opens the way for new drug-targeting strategies using nanoparticles for pulmonary delivery of drugs and diagnostics.

Aerosols↗

PubMed2004

Mechanism of growth of colloidal silver nanoparticles stabilized by polyvinyl pyrrolidone in gamma-irradiated silver nitrate solution.

Silver nanoparticles were prepared by using polyvinyl pyrrolidone (PVP) as a stabilizer and gamma-irradiation. Transmission electron microscopy (TEM) results showed that both the amount and the molecular weight of PVP in the irradiated solution considerably affect the average size of the silver nanoparticles. The average size of the silver nanoparticles decreases with increasing the amount of PVP in the solution, but increases with increasing its molecular weight. Further, TEM showed that the silver nanoparticles become disassembled into smaller nanoparticles after dilution with distilled water and sonication. Since the processes of dilution and sonication are not expected to result in chemical reactions or to split the silver nanoparticles, we conclude that each silver nanoparticle prepared by [Formula: see text] -irradiation consists of several smaller nanoparticles surrounded by PVP. Thus, based on these observations, we propose a three-step mechanism for the growth of the silver nanoparticles under the conditions considered here. In the first step, the silver ions interact with PVP, then in the second step the silver ions that are exposed to gamma-irradiation are reduced to silver atoms; nearby silver atoms then aggregate at close range. These aggregates are the primary nanoparticles. Finally, these primary nanoparticles coalesce with other nearby primary nanoparticles or interact with PVP to form larger aggregates which are the secondary (final) nanoparticles.

Journal Article↗

PubMed2005

Preparation and characterization of biodegradable nanoparticles based on poly(gamma-glutamic acid) with l-phenylalanine as a protein carrier.

The objective of the present study was to prepare nanoparticles composed of poly(gamma-glutamic acid) (gamma-PGA) and l-phenylalanine ethylester (l-PAE) in order to evaluate the possibility of using these nanoparticles as protein carriers. Novel amphiphilic graft copolymers composed of gamma-PGA as the hydrophilic backbone and l-PAE as the hydrophobic segment were successfully synthesized by grafting l-PAE to gamma-PGA using water-soluble carbodiimide (WSC). Due to their amphiphilic properties, the gamma-PGA-graft-l-PAE copolymers were able to form nanoparticles. The size of the gamma-PGA nanoparticles was measured by photon correlation spectroscopy (PCS) and showed a monodispersed size distribution with a mean diameter ranging from 150 to 200 nm. The solvents selected to prepare the gamma-PGA nanoparticles by a precipitation and dialysis method affected the particle size distribution. To evaluate the feasibility of vehicles for these proteins, we prepared protein-loaded gamma-PGA nanoparticles by surface immobilization and encapsulation methods. Ovalbumin (OVA) was used as a model protein and was immobilized onto the gamma-PGA nanoparticles or encapsulated into the inner core of these nanoparticles. Moreover, these OVA-encapsulated gamma-PGA nanoparticles could be preserved by freeze-drying process. The results of cytotoxicity tests showed that the gamma-PGA and gamma-PGA nanoparticles did not cause any relevant cell damage. It is expected that biodegradable gamma-PGA nanoparticles can immobilize proteins, peptides, plasmid DNA and drugs onto their surfaces and/or into the nanoparticles. These nanoparticles are potentially useful in pharmaceutical and biomedical applications.

Cell Proliferation↗

PubMedDate not supplied

Engineering tumor-targeted gadolinium hexanedione nanoparticles for potential application in neutron capture therapy.

Microemulsions (oil-in-water) have been employed as templates to engineer nanoparticles containing high concentrations of gadolinium for potential application in neutron capture therapy of tumors. Gadolinium hexanedione (GdH), synthesized by complexation of Gd(3+) with 2,4-hexanedione, was used as the nanoparticle matrix alone or in combination with either emulsifying wax or PEG-400 monostearate. Solid nanoparticles (<125 nm size) were obtained by simple cooling of the microemulsions prepared at 60 degrees C to room temperature in one vessel. The feasibility of tumor targeting via folate receptors was studied. A folate ligand was synthesized by chemically linking folic acid to distearoylphosphatidylethanolamine (DSPE) via a poly(ethylene glycol) (PEG; MW 3350) spacer. To obtain folate-coated nanoparticles, the folate ligand (0.75% w/w to 15% w/w) was added to either the microemulsion templates at 60 degrees C or nanoparticle suspensions at 25 degrees C. Efficiencies of folate ligand attachment/adsorption to nanoparticle formulations were monitored by gel permeation chromatography. Cell uptake studies were carried out in KB cells (human nasopharyngeal epidermal carcinoma cell line), known to overexpress folate receptors. The uptake of folate-coated nanoparticles was about 10-fold higher than uncoated nanoparticles after 30 min at 37 degrees C. The uptake of folate-coated nanoparticles at 4 degrees C was 20-fold lower than the uptake at 37 degrees C and comparable to the uptake of uncoated nanoparticles at 37 degrees C. Folate-mediated endocytosis was further verified by the inhibition of folate-coated nanoparticles uptake by free folic acid. It was observed that folate-coated nanoparticles uptake decreased to approximately 2% of its initial value with the coincubation of 0.001 mM of free folic acid. The results suggested that these tumor-targeted nanoparticles containing high concentrations of Gd may have potential for neutron capture therapy.

Drug Delivery Systems↗

PubMedDate not supplied

A nanoparticle-based model delivery system to guide the rational design of gene delivery to the liver. 2. In vitro and in vivo uptake results.

In Part 1 of our work (1), four nanoparticles were synthesized specifically for the purpose of identifying design constraints to guide next generation gene delivery to the liver. The four nanoparticles are Gal-50 and Gal-140 (galactosylated 50 and 140 nm nanoparticles) and MeO-50 and MeO-140 (methoxy-terminated 50 and 140 nm nanoparticles). All four particles have the same surface charge, and Gal-50 and Gal-140 have the same surface galactose density (ca. 25-30 pmol/cm2). Here, the hepatocyte uptake in vitro and hepatic distribution in vivo of these four nanoparticles is investigated. With freshly isolated hepatocytes, Gal-50 nanoparticles are taken up to a greater extent than are MeO-50, and both 50 nm beads are taken up to a much greater extent than either of the 140 nm nanoparticles. In mice, about 90% of the in vivo dose of Gal-140 nanoparticles is found within the liver 20 min after tail-vein injection. TEM and immunohistochemistry images confirm that Gal-140 nanoparticles are primarily internalized by Kupffer cells, though isolated examples of a few Gal-140 in hepatocytes are also observed. Gal-50 nanoparticles are overwhelmingly found in vesicles throughout the cytoplasm of hepatocytes, with only isolated examples of Kupffer cell uptake 20 min after tail vein injections in mice. Despite similar surface charge and ligand density, 50 nm nanoparticles are primarily found in hepatocytes while 140 nm nanoparticles are primarily observed in Kupffer cells. These results clearly show that slightly anionic, galactose-PEGylated nanoparticles with 25-30 pmol/cm2 galactose should be about 50 nm in diameter to preferentially target hepatocytes while they should be about 140 nm in diameter to selectively target Kupffer cells.

Animals↗

PubMedDate not supplied

Nanoparticle-mediated wild-type p53 gene delivery results in sustained antiproliferative activity in breast cancer cells.

Gene expression with nonviral vectors is usually transient and lasts for only a few days. Therefore, repeated injection of the expression vector is required to maintain a therapeutic protein concentration in the target tissue. Biodegradable nanoparticles (approximately 200 nm diameter) formulated using a biocompatible polymer, poly(D,L-lactide-co-glycolide) (PLGA), have the potential for sustained gene delivery. Our hypothesis is that nanoparticle-mediated gene delivery would result in sustained gene expression, and hence better efficacy with a therapeutic gene. In this study, we have determined the antiproliferative activity of wild-type (wt) p53 gene-loaded nanoparticles in a breast cancer cell line. Nanoparticles containing plasmid DNA were formulated using a multiple-emulsion-solvent evaporation technique. To understand the mechanism of sustained gene expression with nanoparticles, we monitored the intracellular trafficking of both the nanoparticles and the nanoparticle-entrapped DNA, and also determined p53 mRNA levels over a period of time. Cells transfected with wt-p53 DNA-loaded nanoparticles demonstrated a sustained and significantly greater antiproliferative effect than those with naked wt-p53 DNA or wt-p53 DNA complexed with a commercially available transfecting agent (Lipofectamine). Cells transfected with wt-p53 DNA-loaded nanoparticles demonstrated sustained p53 mRNA levels compared to cells which were transfected with naked wt-p53 DNA or the wt-p53 DNA-Lipofectamine complex, thus explaining the sustained antiproliferative activity of nanoparticles. Studies with fluorescently labeled DNA using confocal microscopy and quantitative analyses using a microplate reader demonstrated sustained intracellular localization of DNA with nanoparticles, suggesting the slow release of DNA from nanoparticles localized inside the cells. Cells which were transfected with naked DNA demonstrated transient intracellular DNA retention. In conclusion, nanoparticle-mediated wt-p53 gene delivery results in sustained antiproliferative activity, which could be therapeutically beneficial in cancer treatment.

Breast Neoplasms↗

PubMed2003

Surfactant-free, biodegradable nanoparticles for aerosol therapy based on the branched polyesters, DEAPA-PVAL-g-PLGA.

PURPOSE: This study describes the development of surfactant-free, biodegradable nanoparticle systems with varying physicochemical properties and their suitability for pulmonary application via nebulization. METHODS: Nanoparticle suspensions were formulated from the branched polyester, diethylaminopropyl amine-poly(vinyl alcohol)-grafted-poly(lactide-co-glycolide) (DEAPA-PVAL-g-PLGA) alone, as well as with increasing amounts of carboxymethyl cellulose (CMC). Particle size, zeta potential, turbidity, and morphology (atomic force microscopy) were characterized. Three formulations were chosen for further study: Cationic nanoparticles without CMC, cationic nanoparticles with CMC, and anionic nanoparticles with an excess of CMC. Nanoparticle degradation was characterized, as well as stability during nebulization. Nanoparticle-cell interactions were investigated and quantified using confocal laser scanning microscopy and fluorescence spectrometry. RESULTS: Nanoparticles ranged in size from 70-250 nm and displayed zeta potentials of +58.9 to -46.6 mV. Anionic nanoparticles showed the highest stability during nebulization. The degradation rate of each nanoparticle formulation decreased with increasing amounts of CMC. Cell association was highest among cationic nanoparticles (57% and 30%, respectively), although these were not internalized. Despite a lower rate of cell association (3%), anionic nanoparticles were internalized by A549 cells. CONCLUSIONS: Surfactant-free nanoparticles from DEAPA-PVAL-g-PLGA are versatile drug delivery systems; however, only the anionic formulations investigated were proven suitable for aerosol therapy.

Aerosols↗

PubMed2002

Gadolinium-loaded nanoparticles engineered from microemulsion templates.

Microemulsions (oil-in-water) have been used as templates to engineer stable emulsifying wax and Brij 72 (polyoxyl 2 stearyl ether) nanoparticles. The technique is simple, reproducible, and amenable to large-scale production of stable nanoparticles having diameters below 100 nm. Investigation of the process variables showed that the amount of surfactant used in the preparation of microemulsion templates had the greatest influence on the microemulsion window, as well as the properties and stability of the cured nanoparticles. Emulsifying wax and Brij 72 nanoparticles (2 mg/mL) made with 3 mM polyoxyl 20 stearyl ether and 2.3mM polysorbate 80, respectively, were the most stable based on retention of nanoparticle size over time. Gadolinium acetylacetonate (GdAcAc), a potential anticancer agent for neutron capture therapy (NCT), was entrapped in stable nanoparticles. The apparent water solubility of GdAcAc was increased more than 2000-fold by entrapment into nanoparticles. The entrapment efficiency of GdAcAc was about 100% for emulsifying wax nanoparticles and 86% for Brij 72 nanoparticles, as determined by gel permeation chromatography (GPC). Elution profiles were obtained with light scattering (counts per second) to detect nanoparticles and ultraviolet (UV) absorption of GdAcAc at 288 nm. Challenges of these cured nanoparticles in biologically relevant media such as 10% fetal bovine serum, 10 mM phosphate-buffered saline, 150 mM NaCl, and 10% lactose at 37 degrees C for 60 min demonstrated that these nanoparticles are stable. The ease of preparation of these very small and stable nanoparticles, and the ability to entrap lipophilic drugs such as GdAcAc with high efficiency, suggested that these systems may have potential in cell targeting, especially for specific delivery to tumor cells for NCT.

Capsules↗

PubMed2006

Multifunctional conjugation of proteins on/into bio-nanoparticles prepared by amphiphilic poly(gamma-glutamic acid).

The present study focuses on nanoparticles composed of amphiphilic poly(gamma-glutamic acid) (gamma-PGA) as potential protein carriers. Amphiphilic graft co-polymers composed of y-PGA as the hydrophilic backbone and L-phenylalanine ethylester (L-PAE) as the hydrophobic segment were synthesized by grafting L-PAE to y-PGA using water-soluble carbodiimide (WSC). Due to their amphiphilic properties, the gamma-PGA-graft-L-PAE co-polymer formed monodispersed nanoparticles in water. The particle size of the nanoparticles composed of gamma-PGA-graft-L-PAE (gamma-PGA nanoparticles) was about 200 nm and showed a highly negative zeta potential. To evaluate their potential applications as multifunctional protein carrier, we prepared protein-entrapped gamma-PGA nanoparticles by encapsulation, covalent immobilization or physical adsorption methods. For this purpose, 11 different proteins with various molecular weights and isoelectric points (pI values) were used as model proteins. The encapsulation of the protein into the nanoparticles was observed for all tested proteins. The amount of protein covalently immobilized or adsorbed onto the nanoparticles showed different tends based on the molecular weight and pI of each protein. Positively charged proteins could be adsorbed onto the negatively charged nanoparticles by electrostatic interaction. Moreover, it was found that enzyme-encapsulated nanoparticles showed higher enzymatic activity than surface-immobilized nanoparticles. These results indicated that the enzymatic activity of the enzyme-entrapped nanoparticles was significantly affected by the conjugation method, and that encapsulation was the optimal method for the conjugation of proteins and nanoparticles. It is expected that the y-PGA nanoparticle will have great potential as multifunctional carriers in pharmaceutical and biomedical applications, such as drug and vaccine delivery systems.

Biocompatible Materials↗

PubMed2006

Construction, gene delivery, and expression of DNA tethered nanoparticles.

PURPOSE: Layered nanoparticles have the potential to deliver any number of substances to cells both in vitro and in vivo. The purpose of this study was to develop and test a relatively simple alternative to custom synthesized nanoparticles for use in multiple biological systems, with special focus on the eye. METHODS: The biotin-labeled transcriptionally active PCR products (TAP) were conjugated to gold, semiconductor nanocrystals, and magnetic nanoparticles (MNP) coated with streptavidin. The process of nanoparticle construction was monitored with gel electrophoresis. Fluorescence microscopy followed by image analysis was used to examine gene expression levels from DNA alone and tethered MNP in human hepatoma derived Huh-7 cells. Adult retinal endothelial cells from both dog (ADREC) and human (HREC) sources were transfected with nanoparticles and reporter gene expression evaluated with confocal and fluorescent microscopy. Transmission electron microscopy was used to quantify the concentration of nanoparticles in a stock solution. Nanoparticles were evaluated for transfection efficiency, determined by fluorescence microscopy cell counts. Cells treated with MNP were evaluated for increased reactive oxygen species (ROS) and necrosis with flow cytometry. RESULTS: Both 5' and 3' biotin-labeled TAP bound equally to MNP and there were no differences in functionality between the two tethering orientations. Free DNA was easily removed by the use of magnetic columns. These particles were also able to deliver genes to a human hepatoma cell line, Huh-7, but transfection efficiency was greater than TAP. The semiconductor nanocrystals and MNP had the highest transfection efficiencies. The MNP did not induce ROS formation or necrosis after 48 h of incubation. CONCLUSIONS: Once transfected, the MNP had reporter gene expression levels equivalent to TAP. The nanoparticles, however, had better transfection efficiencies than TAP. The magnetic nanoparticles were the most easily purified of all the nanoparticles tested. This strategy for bioconjugating TAP to nanoparticles is valuable because nanoparticle composition can be changed and the system optimized quickly. Since endothelial cells take up MNP, this strategy could be used to target neovascularization as occurs in proliferative retinopathies. Multiple cell types were used to test this technology and in each the nanoparticles were capable of transfection. In adult endothelial cells the MNP appeared innocuous, even at the highest doses tested with respect to ROS and necrosis. This technology has the potential to be used as more than just a vector for gene transfer, because each layer has the potential to perform its own unique function and then degrade to expose the next functional layer.

Animals↗