Redispersion Of Nanoparticles Research Articles

Redispersity/Solubility of Nanopowder in Solvents

Because of the high surface energy, nanoparticles show strong tendency to agglomeration or aggregation during preparations and applications, which thus greatly deteriorate their performance. Investigations have proven that redispersible nanoparticles can exhibit enhanced performances or be used in new technical applications as compared with the non-redispersible nanoparticles. The redispersity or solubility of particles is defined as their ability for re-forming colloid-like suspension after they are redispersed in solvent. The redispersity/solubility of particles can be obtained by establishing compatibility between particles and solvent through various techniques. In this review, we will give summary descriptions about related methods and their mechanism for the fabrication of redispersible or soluble particles. Also, outlook for the development and applications in this area will be given.

Recovery and redispersion of gold nanoparticles using the self-assembly of a pH sensitive zwitterionic amphiphile.

The pH-responsive self-assembly of zwitterionic amphiphile C16CA was expanded to the recovery of gold (Au) nanoparticles for environmentally friendly chemistry applications. Multilayered lamellae at pH ∼ 4 were successfully incorporated into nanoparticles by dispersion. Redispersion of nanoparticles was achieved under basic conditions by the transition of self-assembly.

Novel Spray-Dried Genipin-Crosslinked Casein Nanoparticles for Prolonged Release of Alfuzosin Hydrochloride

To propose a simple method for the development of genipin-crosslinked casein micelles as a new delivery platform for prolonged release of alfuzosin hydrochloride. Crosslinked casein micelles entrapping alfuzosin were transformed into solid redispersible nanoparticles via spray-drying technique with no need for drying adjuvants based on the stabilizing effect of casein. The nanoparticles displayed high production yields (86.99-94.63% w/w) with a reasonable drug incorporation efficiency ranged from 92.86 to 97.75%. The nanoparticles were readily reconstituted in aqueous solution with a particle size range of 122.1-260.0nm and a zeta potential range of -21.6 to -36.6mV indicating a good colloidal stability. No drug crystals were detectable in the scanning electron micrographs revealing successful encapsulation of alfuzosin into casein nanoparticles which was confirmed by differential scanning calorimetry. The nanoparticles succeeded in prolonging the drug release that could be controlled by modulating the genipin crosslinking degree. The release data showed a good fit into Higuchi release kinetics with non-Fickian type of drug diffusion. These results demonstrated that genipin-crosslinking combined with spray-drying technique could be used as a promising tool to develop solid redispersible casein nanoparticles with sustained drug release properties.

Design of an inhalable dry powder formulation of DOTAP-modified PLGA nanoparticles loaded with siRNA

Matrix systems based on biocompatible and biodegradable polymers like the United States Food and Drug Administration (FDA)-approved polymer poly(DL-lactide-co-glycolide acid) (PLGA) are promising for the delivery of small interfering RNA (siRNA) due to favorable safety profiles, sustained release properties and improved colloidal stability, as compared to polyplexes. The purpose of this study was to design a dry powder formulation based on cationic lipid-modified PLGA nanoparticles intended for treatment of severe lung diseases by pulmonary delivery of siRNA. The cationic lipid dioleoyltrimethylammoniumpropane (DOTAP) was incorporated into the PLGA matrix to potentiate the gene silencing efficiency. The gene knock-down level in vitro was positively correlated to the weight ratio of DOTAP in the particles, and 73% silencing was achieved in the presence of 10% (v/v) serum at 25% (w/w) DOTAP. Optimal properties were found for nanoparticles modified with 15% (w/w) DOTAP, which reduced the gene expression with 54%. This formulation was spray-dried with mannitol into nanocomposite microparticles of an aerodynamic size appropriate for lung deposition. The spray-drying process did not affect the physicochemical properties of the readily re-dispersible nanoparticles, and most importantly, the in vitro gene silencing activity was preserved during spray-drying. The siRNA content in the powder was similar to the theoretical loading and the siRNA was intact, suggesting that the siRNA is preserved during the spray-drying process. Finally, X-ray powder diffraction analysis demonstrated that mannitol remained in a crystalline state upon spray-drying with PLGA nanoparticles suggesting that the sugar excipient might exert its stabilizing effect by sterical inhibition of the interactions between adjacent nanoparticles. This study demonstrates that spray-drying is an excellent technique for engineering dry powder formulations of siRNA nanoparticles, which might enable the local delivery of biologically active siRNA directly to the lung tissue.

Functionalization of Polymer Nanoparticles by Thiol−Ene Addition

Syndiotactic 1,2-polybutadiene nanoparticles (volume average diameter 13 nm) were functionalized in aqueous dispersion by free radical mercaptan addition. By appropriate choice of both water-soluble radical initiator and mercaptan concentration, nanoparticles with a degree of functionalization of up to 85% were prepared using 3-mercaptopropionic acid methyl ester and 3-mercaptopropionic acid. Only a minor portion of double bonds formed cycles instead of the desired thiol−ene addition products. The composition and structure of the nanoparticles were elucidated by combination of elemental analysis, NMR, IR, DLS, and TEM. Highly hydrophilic mercaptans (3-mercaptopropanesulfonic acid sodium salts), in contrast, only reacted with surface accessible double bonds to afford stable and redispersible nanoparticles solely stabilized with covalently bound moieties on their surface. Analogous grafting of the tripeptide glutathione was demonstrated.

Activation of Pt/SnO 2 catalyst for catalytic oxidation of volatile organic compounds

The catalytic combustion of toluene over tin oxide-supported metal catalysts (Pt/SnO 2, Pd/SnO 2, Ru/SnO 2, and Rh/SnO 2) was studied. As a result, the Pt/SnO 2 catalyst exhibited the highest activity. The activity of Pt/SnO 2 catalyst is expected to originate from the strong chemical interaction between platinum and tin oxide. The correlation between the nano-structure and catalytic activity in the oxidation of ethyl acetate was investigated for the Pt/SnO 2 catalysts treated under a reducing or an oxidative atmosphere. For the transmission electron microscopy image of the as-calcined Pt/SnO 2 catalyst, the fine particles composed of platinum species was highly dispersed on the surface of SnO 2 support. After the reduction treatment at 400 °C, the peculiar core–shell structure was formed. It is noted that the particles with this structure disappeared by the reoxidation treatment in air, and the redispersion of nano-particles was confirmed. The particles with the core–shell structure were observed again after the second reduction treatment for the reoxidized catalyst. The catalytic activities of ethyl acetate combustion over Pt/SnO 2 catalysts were deteriorated and activated, corresponding to the nano-structural changes induced by the reduction–oxidation treatments.

Cryoprotectants for freeze drying of drug nano-suspensions: Effect of freezing rate

Drug nanoparticles are often prepared in a liquid medium, and a drying method such as freeze drying is used to convert them to an oral solid dosage form. When the dried form is reconstituted in an aqueous system, it may be redispersed to achieve its original particle size. The redispersibility of dried nanoparticles depends on the parameters of the freeze drying process. In this study, an apparatus with a freezing rate gradient was used to systematically investigate the effect of cryoprotectants on the redispersibility of nanoparticles as a function of freezing rate. Sucrose, lactose, mannitol, and polyethylene glycol were used as cryoprotectants for a naproxen nano-suspension. A fast freezing rate and a high cryoprotectant concentration were generally favored. However, under certain conditions, a slower freezing rate resulted in better redispersibility. This is probably because slow freezing can produce a more cryo-concentrated liquid phase, and the concentrated cryoprotectant in the liquid phase can more effectively protect the nanoparticles. An irreversible aggregation map was constructed as a function of the freezing rate and the cryoprotectant concentration, and shows both the favorable and unfavorable effects of cryoprotectants. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4808–4817, 2009

Direct Synthesis of Nanocrystalline Silver from the Reaction Between Silver Carboxylates and <I>n</I>-Trioctylphosphine

Neat n-Trioctylphosphine (TOP) has been used for the first ever time for reduction of silver nitrate and silver carboxylates (citrate, oleate, and myristate) under mild thermal reaction conditions. UV-visible absorption measurements of re-dispersible silver particles that were obtained by reduction of silver myristrate (product-IV) and silver nitrate (product-I) showed surface plasmon resonance absorption peak at 400 nm. The powder XRD pattern of fcc zero-valent silver resulted in diameters in the range of about 25-30 nm. TEM analysis showed particle diameter similar to that was observed by the XRD. FTIR spectroscopy revealed that the organics from the carboxylate group are retained by the nano-particles in case of product-IV however, presence of TOP is observed in product-I. It is found that when silver nitrate is reduced by TOP, spherical silver nano-particles with poor redispersity are formed but extended heating results in formation of long silver rods of micrometer size however, the re-dispersible nano-particles are easily formed when silver carboxylates are reduced by TOP.

Freeze-Drying of Composite Core-Shell Nanoparticles

ABSTRACTThe effects of four sugars (glucose, saccharose, maltose, trehalose) and one surfactant (Poloxamer 188), on the freeze-drying of poly(isobutylcyanoacrylate) (PIBCA), poly(ε-caprolactone)-poly(ethylene glycol) (PCL-PEG), and novel core (mainly PIBCA)-shell (principally PEG) composite nanoparticles (CNP) obtained by co-precipitation were investigated. The efficiency of the additives against the adverse effect of freeze-drying on the redispersibility of the nanoparticles was evaluated, based on the visual appearance of the nanoparticle suspensions (Tyndall effect and aggregation), and on the determination of the mean diameter ratio of the nanoparticles before and after freeze-drying. The results indicated that the addition of both sugars and surfactant was essential for the good redispersion of freeze-dried nanoparticles displaying hydrophobic (PIBCA) or hydrophilic (PCL-PEG and CNP) surfaces.

Processing of Transparent Conducting Coatings Made With Redispersible Crystalline Nanoparticles

The present paper describes recent developments in the employment of ITO (In2O3:Sn) nanoparticles for the preparation of transparent conducting coatings and discusses capabilities and limits of this approach, especially for applications in display and smart window technology. Meanwhile, redispersible nanoparticles of ITO, which shows the best electrical properties among the transparent coating oxides (TCOs), can be produced reproducibly on an industrial scale and various products are on the market.