Nanoparticle-polymer mixtures

We have discovered a novel protein immobilization method, i.e., a Three-Dimensional Nanostructured Protein Hydrogel (3-D NPH), which is composed of protein-reactive polymer hybrid nanoparticles to detect protein-protein interactions. The 3-D NPH can be easily prepared by spotting a protein/reactive polymer mixture on a substrate. The resulting 3-D NPH is characterized by large amounts of immobilized proteins and a novel porous structure. 

Figure 6 The main broad avenues of nanoparticle production. Comminution or size reduction (say by high-pressure homogenization or critical solution technology), precipitation methods by salting out or other solvency changes in solutions of drag-polymers mixtures and molecular assembly of amphipathic components. Methods are listed in Table 2.

SCF technologies deserve a special mention as they have been less commonly applied on a laboratory scale in the preparation of nanoparticles (73). Scheme 7 and Figures 8 and 9 summarize the approach used. A drug and polymer mixture is dissolved in an organic solvent or carbon dioxide. Under certain conditions of pressure and temperature, the liquid phase is transformed into the supercritical state as seen in Figure 8. Here the supercritical state is found at pressures >74 bar (atmospheric pressure = 1.013 bar) and at temperatures >31°C. The rapid expansion of this supercritical solution on exposure to atmospheric pressure causes the formation of microspheres or nanospheres Figure 9 on the other hand illustrates the use of a solvent, which can be formed into a... 

Besides rings, spontaneous formation of nanoparticle strip patterns has been observed on dewetting a dilute film of polymer coated nanoparticles floating on a water surface [577]. Hybridization of branched DNA trimers and Au nanoparticle DNA conjugates have been employed to produce discrete self-assembled nanoparticle dendrimers [578]. Self-assembly of triangular and hexagonal CdS nanocrystals into complex structures such as rods and arrows has been observed [579]. Furthermore, self-assembly of CdSe nanoparticle-copolymer mixtures has been observed wherein the copolymers assemble into cylindrical domains that dictate the distribution of the nanoparticles [580]. 

Numerical methods with different time- and length scales are employed and developed to investigate material properties and behaviors. Among them, molecular modeling can predict the molecular behaviors and correlate macroscopic properties of a material with various variables. The most popular techniques include molecular mechanics (MM), MD, and Monte Carlo (MC) simulation. These techniques are now routinely used to investigate the structure, dynamics, and thermodynamics of inorganic, biological, and polymer systems. They have recently been used to predict the thermodynamic and kinetic properties of nanoparticle-matrix mixtures, interfacial molecular structure and interactions, molecular dynamic properties, and mechanical properties. 

In this technique, not only pure polymers can be electrospun, but also polymers in combination with nanoparticles, as realized for example with PLGA and HA nanoparticles [61,72]. Moreover, surfactants can be added to the nanoparticle-polymer-solvent mixture to facilitate the dissolution process and overcome the different polarities of hydrophilic nanoparticles snch as HA and the hydrophobic polymer-solvent solutions such as chloroform-dissolved PLA [55]. 

Before discussing the phase behavior of ternary nanoparticle/polymer/polymer mixtures it is useful to briefly recall the fundamentals governing the phase behavior of binary polymer blends. The simplest model describing phase behavior of such... 

Phase Behavior of Ternary Nanoparticle/Polymer/Polymer Mixtures... 

The synthetic approach is very simple and does not require any special set up. In a typical room temperature reaction, 1.0 mL aqueous solution of cadmium chloride was added to 20 mL aqueous solution of soluble starch in a 50 mL one-necked round-bottom flask with constant stirring at room temperature. The pH of the solution was adjusted from 6 to 11 using 0.1 M ammonia solution. This was followed by a slow addition of 1.0 mL colourless selenide ion stock solution. The mixture was further stirred for 2 h and aged for 18 h. The resultant solution was filtered and extracted with acetone to obtain a red precipitate of CdSe nanoaprticles. The precipitate was washed several times and dried at room temperature to give a material which readily dispersed in water. The same procedure was repeated for the synthesis of PVA and PVP - capped CdSe nanoparticles by replacing the starch solution with the PVA and PVP polymers while the synthesis of elongated nanoparticles was achieved by changing the Cd Se precursor ratio from 1 1 to 1 2. The synthesis of polymer capped ZnSe nanoparticles also follows the same procedure except that ZnCb solution was used instead of CdCb solution. 

Conventional filtration cannot be applied to the separation in purification of metal nanoparticles. If the metal nanoparticles are protected by polymer, however, the membrane filter, which can cut off the pol5mer with certain molecular weight, can be used to separate the polymer protected metal nanoparticles. Free metal nanoparticles which are not protected by polymer can pass through the membrane. Ion filter like cellulose can be used to separate ionic species from the reaction mixtures. 

The acidic conditions of standard SBA-15 synthesis [35] cause the precipitation of metal nanoparticles without silica encapsulation, or the formation of amorphous silica due to the presence of the polymer used for nanoparticle synthesis. Therefore, the SBA-15 framework was synthesized under neutral condition using sodium fluoride as a hydrolysis catalyst and tetramethylorthosilicate (TMOS) as the silica precursor. Pt particles with different sizes were dispersed in the aqueous template polymer solution sodium fluoride and TMOS were added to the reaction mixture. The slurry aged at 313 K for a day, followed by an additional day at 373 K. Pt(X)/SBA-15-NE (X = 1.7, 2.9, 3.6, and 7.1nm) catalysts were obtained by ex-situ calcination (see Section 3.2). TEM images of the ordered... 

The initial transition of dissolved silicate molecules into solid nanoparticles is perhaps the least explored step in the synthesis of zeolites. One impediment to understanding this mysterious step is the poorly elucidated molecular composition of dissolved particles. The major mechanistic ideas for the formation of zeolites approach these structures differently i) many researchers believe that secondary building units (SBU) must be present to form initial nanoslabs [1,2] ii) some others prioritize the role of monomers to feed artificially introduced crystal nuclei or assume that even these nuclei form via appropriate aggregation of monomers [3] iii) silicate solutions are also frequently viewed as random mixtures of various siloxane polymers which condense first into an irregular gel configuration which can rearrange subsequently into a desired crystal nucleus at appropriate conditions [4,5],... 

In dispersion polymerization, the monomer and initiator are dissolved in the continuous phase, which acts as a nonsolvent for the developing polymer. The continuous phase can be organic, aqueous, or a mixture of miscible phases. Two methods of initiation have been employed, including gamma radiation [75] and chemical initiation by potassium perox-odisulphate [76]. As the polymer is formed, it precipitates as nanoparticles. These particles are not polymeric precipitates as in precipitation polymerization. Rather, they are swollen by a mixture of the monomer and the continuous phase [39],... 

The coprecipitation technique was based on the dropwise addition of a synthetic polymer solution, in a solvent mixture, into an aqueous protein solution under magnetic stirring. The progressive interaction between the water insoluble polymer and the protein gave rise to the microsphere formation. The glycolipid was then added as an aqueous dispersion to the nanoparticle suspension. No sedimentation was observed after several weeks of storage at room temperature. 

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