Poly Nanoparticles Research Articles

Complex-mediated growth mechanism of silver nanoparticles–poly(vinyl alcohol) composite nanofibers

In this study, a complex-mediated synthetic growth method was used to embed silver (Ag) nanoparticles in poly(vinyl alcohol) (PVAI) nanofibers in an aqueous solution. Azobisisobutyronitrile (AIBN) played a pivotal role in the preparation of the Ag–PVAI nanofibers, via its cyano groups. AIBN was used to assemble the Ag ions to form Ag complexes in the early stages of the reaction. As the reaction temperature approached 60 °C, AIBN decomposed via breakage of its C–N bonds, and thus the Ag compounds became disassembled. During this stage, Ag nanoparticles were aligned with a PVAI assistant, which acted as a gelator and stabilizer for the formation of fibrous nanostructures under magnetic stirring conditions. As a result, PVAI nanofibers (diameter: ca. 35 nm) were synthesized, with Ag nanoparticles (diameter: ca. 8 nm) embedded compactly in the inner part of the fiber. The formation of Ag–PVAI composite nanofibers was systematically investigated with field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Additionally, we performed several control experiments and proposed a plausible mechanism for the synthesis of Ag–PVAI composite nanofibers.

Electrochemical synthesis of silver nanoparticles in poly(vinyl alcohol) solution

In this work silver/poly(vinyl alcohol), Ag/PVA, colloid dispersions were obtained by electrochemical reduction of Ag+ ions. The electrochemical synthesis of silver nanoparticles in the aqueous solutions of 5 and 10 wt. % PVA, containing 0.1 M KNO3 and 3.9 mM AgNO3, was performed at constant current density of 25 mA cm-2, and during synthesis time of 10 min. The presence of silver nanoparticles was confirmed by UV-vis spectroscopy. Cyclic voltammetry analysis and FTIR spectroscopy indicated the interactions between silver nanoparticles and PVA molecules. TEM analysis confirmed spherical shape of the obtained silver nanoparticles, with the mean diameter of 15 ? 9 nm.

Preparation of Poly-(Methyl vinyl ether-co-maleic Anhydride) Nanoparticles by Solution-Enhanced Dispersion by Supercritical CO2

The supercritical CO2-based technologies have been widely used in the formation of drug and/or polymer particles for biomedical applications. In this study, nanoparticles of poly-(methyl vinyl ether-co-maleic anhydride) (PVM/MA) were successfully fabricated by a process of solution-enhanced dispersion by supercritical CO2 (SEDS). A 23 factorial experiment was designed to investigate and identify the significance of the processing parameters (concentration, flow and solvent/nonsolvent) for the surface morphology, particle size, and particle size distribution of the products. The effect of the concentration of PVM/MA was found to be dominant in the results regarding particle size. Decreasing the initial solution concentration of PVM/MA decreased the particle size significantly. After optimization, the resulting PVM/MA nanoparticles exhibited a good spherical shape, a smooth surface, and a narrow particle size distribution. Fourier transform infrared spectroscopy (FTIR) spectra demonstrated that the chemical composition of PVM/MA was not altered during the SEDS process and that the SEDS process was therefore a typical physical process. The absolute value of zeta potential of the obtained PVM/MA nanoparticles was larger than 40 mV, indicating the samples’ stability in aqueous suspension. Analysis of thermogravimetry-differential scanning calorimetry (TG-DSC) revealed that the effect of the SEDS process on the thermostability of PVM/MA was negligible. The results of gas chromatography (GC) analysis confirmed that the SEDS process could efficiently remove the organic residue.

Characterization and in-vitro bioactivity evaluation of paclitaxel-loaded polyester nanoparticles

Paclitaxel, an antimicrotubular agent used in the treatment of ovarian and breast cancer, was encapsulated in nanoparticles of poly(DL-lactide-co-glycolide) and poly(ε-caprolactone) polymers using the double emulsion-solvent evaporation technique. The morphology, size distribution, drug encapsulation efficiency, thermal degradation and in-vitro drug release profile were characterized. High-performance liquid chromatography was used to determine the drug encapsulation efficiency and in-vitro drug release profile. MCF-7 breast cancer cells were used to evaluate the cytotoxicity (MTT assay), the cellular uptake and the cell cycle. The particle size was in the range of 200-400 nm. Poly(lactide-co-glycolide) nanoparticles showed more effective cellular uptake compared with those of poly(ε-caprolactone). Unloaded nanoparticles were found to be cytocompatible on MCF-7 cells and paclitaxel formulations showed efficacy in killing MCF-7 cells. Paclitaxel-loaded nanoparticles induced the release of the drug-blocking cells in the G2/M phase. Paclitaxel-loaded nanoparticles may be considered a promising drug delivery system in the evaluation of an in-vivo model.

Dispersion of polymer-decorated hydroxyapatite nanoparticles in poly(ethylene oxide) at low grafting densities

In this research, hydroxyapatite nanoparticles sparsely coated with tethered poly(ethylene oxide) (PEO) chains were added to a bulk PEO matrix of greater molecular weight. The nanoparticles were found to be dispersed homogeneously when the particle concentration was high. Two different low-aspect ratio shaped particles were used, spherical and needle, and had similar dispersion behavior in this matrix. Characterization results indicated that the homogeneous dispersion achieved here at higher particle loadings was a kinetically trapped condition and an interfacial zone had developed at the grafted polymer/matrix polymer interface. Additionally at a critical nanoparticle loading related to specific values of the nanoparticle surface area and interparticle spacing, the crystallite size and amount of crystallinity in the PEO matrix began to decrease as opposed to the level of nanoparticle dispersion. Overall, these results provide a strategy for incorporating relatively high loadings of nanoparticles into these matrices without large scale phase segregation.

Embedded Silica Nanoparticles in Poly(Caprolactone) Nanofibrous Scaffolds Enhanced Osteogenic Potential for Bone Tissue Engineering

Poly(caprolactone) (PCL) has been frequently considered for bone tissue engineering because of its excellent biocompatibility. A drawback, however, of PCL is its inadequate mechanical strength for bone tissue engineering and its inadequate bioactivity to promote bone tissue regeneration from mesenchymal stem cells. To correct this deficiency, this work investigates the addition of nanoparticles of silica (nSiO(2)) to the scaffold to take advantage of the known bioactivity of silica as an osteogenic material and also to improve the mechanical properties through nanoscale reinforcement of the PCL fibers. The nanocomposite scaffolds and the pristine PCL scaffolds were evaluated physicochemically, mechanically, and biologically in the presence of human mesenchymal stem cells (hMSCs). The results indicated that, when the nanoparticles of size approximately 10 nm (concentrations of 0.5% and 1% w/v) were embedded within, or attached to, the PCL nanofibers, there was a substantial increase in scaffold strength, protein adsorption, and osteogenic differentiation of hMSCs. These nSiO(2) nanoparticles, when directly added to the cells evidently pointed to ingestion of these particles by the cells followed by cell death. The polymer nanofibers appeared to protect the cells by preventing ingestion of the silica nanoparticles, while at the same time adequately exposing them on fiber surfaces for their desired bioactivity.

Utilizing insulating nanoparticles as the spacer in laminated flexible polymer solar cells for improved mechanical stability

Roll-to-roll lamination is one promising technique to produce large-area organic electronic devices such as solar cells with a large through output. One challenge in this process is the frequent electric point shorting of the cathode and anode by the excess or concentrated applied stress from many possible sources. In this paper, we report a method to avoid electric point shorting by incorporating insulating and hard barium titanate (BaTiO3) nanoparticles (NPs) into the active layer to work as a spacer. It has been demonstrated that the incorporated BaTiO3 NPs in poly(3-hexylthiophene):[6,6]-phenyl-c-61-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction solar cells cause no deleterious effect to the power conversion process of this type of solar cell. The resulting laminated devices with NPs in the active layer display the same efficiency as the devices without NPs, while the laminated devices with NPs can sustain a ten times higher lamination stress of over 6 MPa. The flexible polymer solar cell device with incorporated NPs shows a much smaller survivable curvature radius of 4 mm, while a regular flexible device can only sustain a bending curvature radius of 8 mm before fracture.

Design of pH-responsive nanoparticles of terpolymer of poly(methacrylic acid), polysorbate 80 and starch for delivery of doxorubicin

This work focused on the design of new pH-responsive nanoparticles for controlled delivery of anticancer drug doxorubicin (Dox). Nanoparticles of poly(methacrylic acid)-polysorbate 80-grafted starch (PMAA-PS 80-g-St) were synthesized by using a one-pot method that enabled simultaneous grafting of PMAA and PS 80 onto starch and nanoparticle formation in an aqueous medium. The particles were characterized by FTIR, 1H NMR, TEM, DLS, and potentiometric titration. Dox loading and in vitro release from the nanoparticles were investigated. The FTIR and 1H NMR confirmed the chemical composition of the graft terpolymer. The nanoparticles were relatively spherical with narrow size distribution and porous morphology. They exhibited pH-dependent swelling in a physiological pH range. The particle size and magnitude of phase transition were dependent on polymer composition and formulation parameters such as concentrations of surfactant and cross-linking agent and total monomer concentration. The nanoparticles with optimized compositions showed high loading capacity for Dox and sustained Dox release. The results suggest that the new pH-responsive terpolymer nanoparticles are useful in controlled drug delivery.

PH-Responsive Dispersion and Electrostatic-Driven Self-Assembly of Poly(acrylic acid) Grafted Carbon Black

The dispersion and self-assembly behavior of inorganic-polymer hybrid nanoparticles is a key point in the applications of these outstanding novel materials. In this work, the pH-responsive properties of core-shell nanoparticles of poly(acrylic acid) grafted carbon black (CB-g-PAA) dispersed in water were characterized by dynamic light scattering. The immobilized PAA chains were shown to control the level of CB-PAA nanoparticles dispersion in aqueous mixtures. The electrostatic-driven self-assembly of these hybrid particles, induced by cationic surfactant hexadecyltrimethylammonium bromide (CTAB) and star polyelectrolyte HPC-star-poly(2-(dimethy ethyl ammonium iodide) ethyl methacrylate) (HPC-star-poly(DMEAIEMA)), as the counter species was also characterized.

Polymer nanoparticles encapsulating siRNA for treatment of HSV-2 genital infection

Effective, low-cost, and safe treatments for sexually transmitted viral infections are urgently needed. Here, we show for the first time that intravaginal administration with nanoparticles of poly(lactic-co-glycolic acid) (PLGA) encapsulating short interfering RNA (siRNA) molecules is effective for prevention of genital HSV-2 infections in mice. PLGA nanoparticles (NPs) were designed to interfere with HSV-2 infection by siRNA-mediated knockdown of nectin, a host cell protein. NPs were characterized in vitro to determine the optimal formulation based on siRNA loading, controlled release profile, and mRNA knockdown. Mice inoculated intravaginally with a lethal dose of HSV-2, and treated with PLGA NPs, showed increased survival from ~9days (in untreated mice) to >28days (in PLGA NP treated mice) — the longest survival ever observed with siRNA treatment in this mouse model. This work provides proof-of-concept that topical administration of NPs containing siRNA against a pathologically relevant host cell target can knockdown the gene in tissue and improve survival after HSV-2 infection. Furthermore, this system provides a safe delivery platform that employs materials that are already approved by the FDA and can be modified to enhance delivery of other microbicides.

Study on the biocomposites with poly(ethylene glycol) dimethacrylate and surfaced‐grafted hydroxyapatite nanoparticles

AbstractIn composites of hydroxyapatite (HA) nanoparticles with a polymer matrix, the aggregation of nanoparticles would induce structural defects. In order to improve the dispersibility of HA nanoparticles in poly(ethylene glycol) dimethacrylate (PEGDMA) matrix and enhance mechanical properties of the HA/PEGDMA composite as potential bone substitute material, surface‐grafted HA nanoparticles with poly(ethylene glycol) monomethacrylate (PEGMA) were prepared, and crosslinked with PEGDMA under UV light to form a composite. The structure of HA‐g‐PEGMA was characterized by X‐ray diffraction (XRD) and thermal gravimetric analysis (TGA). The dispersibility of HA‐g‐PEGMA nanoparticles in poly(PEGDMA) was evaluated by SEM. The mechanical properties of the composites were investigated by compressive test. The dispersibility of HA‐g‐PEGMA nanoparticles in poly(PEGDMA) matrix was better than the bare HA. At a 1 wt % content of loading, the strength of composites increased by 14%, and the modulus increased by 9%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

A novel delivery system of doxorubicin with high load and pH-responsive release from the nanoparticles of poly (α,β-aspartic acid) derivative

A poly (amino acid)-based amphiphilic copolymer was utilized to fabricate a better micellar drug delivery system (DDS) with improved compatibility and sustained release of doxorubicin (DOX). First, poly (ethylene glycol) monomethyl ether (mPEG) and DOX were conjugated onto polyasparihyazide (PAHy), prepared by hydrazinolysis of the poly (succinimide) (PSI), to afford an amphiphilic polymer [PEG-hyd-P (AHy-hyd-DOX)] with acid-liable hydrazone bonds. The DOX, chemically conjugated to the PAHy, was designed to supply hydrophobic segments. PEGs were also grafted to the polymer via hydrazone bonds to supply hydrophiphilic segments and prolong its lifetime in blood circulation. Free DOX molecules could be entrapped into the nanoparticles fabricated by such an amphiphilic polymer (PEG-hyd-P (AHy-hyd-DOX)), via hydrophobic interaction and π–π stacking between the conjugated and free DOX molecules to obtain a pH responsive drug delivery system with high DOX loaded. The drug loading capacity, drug release behavior, and morphology of the micelles were investigated. The biological activity of micelles was evaluated in vitro. The drug loading capacity was intensively augmented by adjusting the feed ratio, and the maximum loading capacity was as high as 38%. Besides, the DOX-loaded system exhibited pH-dependent drug release profiles in vitro. The cumulative release of DOX was much faster at pH 5.0 than that at pH 7.4. The DOX-loaded system kept highly antitumor activity for a long time, compared with free DOX. This easy-prepared DDS, with features of biocompatibility, biodegradability, high drug loading capacity and pH-responsiveness, was a promising controlled release delivery system for DOX.

Supercritical carbon dioxide assisted dispersion and distribution of silica nanoparticles in polymers

Creating well-dispersed polymer nanocomposites is an important part of controlling composite properties. Nanoparticles have been shown to improve among others electrical, thermal, mechanical, and barrier properties of polymers if they can be dispersed and distributed within the polymer matrix effectively. In the current study, supercritical carbon dioxide is used to disperse and distribute silica nanoparticles in poly(methyl methacrylate), PMMA. It was found that processing silica/PMMA nanocomposite system with supercritical carbon dioxide led to drastic improvement of the dispersion and distribution of silica nanoparticles in PMMA. The state of dispersion and distribution was found to strongly depend on the carbon dioxide saturation pressure – the greater the saturation pressure was, the better the dispersion and distribution became. The dispersion and distribution of silica nanoparticles were quantified via radial distribution function (RDF), which was constructed from transmission electron micrographs. In addition, the non-bonded attraction and cohesive energy between almost-touching nanoparticles were calculated using the Hamaker theory and results were compared with the internal pressure of expanding pores.

Synthesis of Silver Nanoparticles in Poly(vinyl alcohol) Matrix in Solution and Thin Films Through Laser Irradiation

Here we communicate our experimental results on the synthesis of silver nanoparticles in solution and thin films using silver nitrate and poly vinyl alcohol (PVA) mixture at different concentrations and different laser irradiations. Detailed studies were carried out by varying pulse width, wavelength, exposure time, and energy of the laser. Formation of nanoparticles was confirmed through color change from transparent to yellow. Irradiated solutions and thin films at different concentrations showed plasmon peak in the absorption spectra. Formation of different sized nanoparticles at different energies with peak shift is observed. Transmission electron microscope (TEM) results confirmed the formation of nanoparticles with size of the particles varying from 2 to 200 nm. Formation of silver nanoparticles with hexagonal and different shapes were observed in particular with 355 nm laser irradiation. Influence of wavelength, pulse width, exposure time, and energy in the synthesis of silver nanoparticles is highlighted. Electron diffraction patten of a single nanoparticle in TEM showed polycrystallinity with cubic nature for the silver nanoparticles prepared. We also compared the linear and nonlinear absorption properties of the freshly prepared nanoparticles with nanoparticles solution left in a shelf for a long period of time.

Formation of spherical nanoparticles in poly(amic acid) films

We found for the first time the formation of spherical nanoparticles in poly(amic acid) (PAA) derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 4,4′-oxydianiline films after pre-baking. Several factors influencing the formation of spherical nanoparticles have been investigated. The molecular weights of PAA and the pre-bake temperature are important and effective parameters influencing the particle morphology. On the other hand, spherical nanoparticle formation does not depend on the film casting method. The particle size distribution after pre-baking at 100–150 °C for 5 min is rather narrow in the range of 25–45 nm and the mean particle diameter is 33 nm, which means that the resulting film is transparent and can be used as a photoresist. This observation is very important for developing photosensitive polyimides providing a deeper insight into a development process using organic solvents or aqueous base solutions.

Emulsions stabilized with organic solid particles

Biodegradable and biocompatible o/w emulsions were prepared using triglyceride oil and solid organic particles made of block copolymer nanoparticles as stabilizers (Pickering emulsions). In order to reach high concentration of internal phase, rather concentrated dispersions of nanoparticles were required. Nanoparticles of poly(caprolactone)-block-poly(ethylene oxide) (PCL-b-PEO) diblock copolymer were obtained using the “nanoprecipitation” process relying of the spontaneous emulsification upon solvent shifting. The classical “nanoprecipitation” process was improved so as to afford more concentrated suspensions of nanoparticles, and the nanoparticles were characterized by means of dynamic light scattering and 1H NMR spectroscopy. The process allowed the preparation of aqueous dispersions of PCL-b-PEO nanoparticles with 35–50nm diameter at concentrations over 5wt.%. In D2O, the PCL blocks formed a central hydrophobic core of reduced mobility, while the PEO blocks formed a hydrophilic corona layer swollen by water. O/w emulsions of medium chain triglycerides were successfully prepared using the suspensions of PCL-b-PEO nanoparticles as stabilizers. Typical droplet sizes were between 2μm and 15μm. The emulsions showed great stability upon storage and their particle size distributions did not show excess nanoparticles present in the aqueous phase as submicron nanoparticles, even when large amounts of nanoparticles with respect to oil were used. The mean droplet diameter of emulsions was controlled by the mass ratio M(oil)/M(nanoparticles). SANS and TEM experiments performed on PCL-b-PEO nanoparticles and micelle-stabilized emulsions disclosed a rearrangement of the nanoparticles at the oil/water interface due to the liquid state of the micelle core of PCL.

Spectroscopic studies of energy transfer in fluorene co-polymer blend nanoparticles

Nanoparticles of poly(9,9-dioctylfluorene-co-bis-N,N-(4-butylphenyl)-bis-N,N-phenyl-1,4-phenylenediamine) [PFB] and poly(9,9-dioctylfluorene-co-benzothiadiazole) [F8BT] (1:1 w/w) were studied using scanned probe and single particle spectroscopy techniques. Photoluminescence (PL spectra of ∼58 and ∼100nm PFB/F8BT nanoparticles show efficient energy transfer from the PFB (donor) component to the F8BT (acceptor) component that is independent of particle size. We propose that nanoparticles are phase segregated into discrete PFB/F8BT nanodomains on the order of ∼20–40nm for both particle sizes. Pressure-dependent nanoparticle PL spectra support this assignment where lineshape maxima of each component red-shift in a similar manner due to increased interchain packing within the single nanodomains.

Size-controlled nanoparticles of poly(acrylonitrile-co-methyl methacrylate) for moisture-absorbing heat release applications

Hydrophilic and water-insoluble poly(acrylonitrile-co-methyl methacrylate) [P(AN-co-MMA)] nanoparticles were prepared to investigate their moisture-absorbing heat release effect. The nanoparticle size was controlled by varying the composition of AN and MMA. First, P(AN-co-MMA) nanoparticles were synthesized by emulsion polymerization, followed by cross-linking with hydrazine for water insolubility. Secondly, the hydrazine-cross-linked P(AN-co-MMA) nanoparticles were hydrolyzed in an aqueous NaOH solution to form hydrophilic groups. The hydrolyzed and cross-linked P(AN-co-MMA) [hc-P(AN-co-MMA)] nanoparticles had a more uniform and smaller particle size with increasing MMA content compared to the PAN nanoparticles, this is due to decreasing polar nitrile groups in the P(AN-co-MMA) with MMA content. A nanoparticle size less than 45 nm was obtained for P(AN-co-MMA) with a 20 mol% MMA content. The hc-P(AN-co-MMA) nanoparticles showed a temperature rise maximum of up to 12.9 °C in the moisture-absorbing heat release test. In addition, when the nanoparticles with 20 mol % MMA content were coated on cotton fabrics, the temperature of the fabrics increased by up to 7.8 °C at 90 % relative humidity. This demonstrates that the nanoparticles can be applied as a potential moisture-absorbing heat release material.

Effect of double growth factor release on cartilage tissue engineering

The effects of double release of insulin-like growth factor I (IGF-I) and growth factor β1 (TGF-β1) from nanoparticles on the growth of bone marrow mesenchymal stem cells and their differentiation into cartilage cells were studied on PLGA scaffolds. The release was achieved by using nanoparticles of poly(lactic acid-co-glycolic acid) (PLGA) and poly(N-isopropylacrylamide) (PNIPAM) carrying IGF-I and TGF-β1, respectively. On tissue culture polystyrene (TCPS), TGF-β1 released from PNIPAM nanoparticles was found to have a significant effect on proliferation, while IGF-I encouraged differentiation, as shown by collagen type II deposition. The study was then conducted on macroporous (pore size 200-400 µm) PLGA scaffolds. It was observed that the combination of IGF-I and TGF-β1 yielded better results in terms of collagen type II and aggrecan expression than GF-free and single GF-containing applications. It thus appears that gradual release of a combination of growth factors from nanoparticles could make a significant contribution to the quality of the engineered cartilage tissue.

Dispersion of nanoparticles in poly(vinyl chloride) grains during In situ polymerization

AbstractInorganic nanoparticles such as calcium carbonate, silica, or hydrotalcite were dispersed in vinyl chloride prior to suspension polymerization. That led to the production of poly(vinyl chloride) (PVC) composite grains with higher porosity and different internal morphology from those of commercial PVC. The PVC/composite grain sizes and their distribution were also influenced by the presence of nanofillers. The distribution of filler nanoparticles (either calcium carbonate or silica) was not uniform throughout the PVC grains. Regions of high and low filler concentration were observed. Regions of pure polymer were also observed. Reasons for that are suggested. Hydrotalcite did not remain in the PVC grains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012