High Performance Particle Sizer Research Articles

The effect of nanoemulsified methionine and cysteine on the in vitro expression of casein in bovine mammary epithelial cells.

ObjectiveDairy cattle nutrient requirement systems acknowledge amino acid (AAs) requirements in aggregate as metabolizable protein (MP) and assume fixed efficiencies of MP used for milk protein. Regulation of mammary protein synthesis may be associated with AA input and milk protein output. The aim of this study was to evaluate the effect of nanoemulsified methionine and cysteine on the in-vitro expression of milk protein (casein) in bovine mammary epithelial cells (MAC-T cells).MethodsMethionine and cysteine were nonionized using Lipoid S 75 by high-speed homogenizer. The nanoemulsified AA particle size and polydispersity index were determined by dynamic light scattering correlation spectroscopy using a high-performance particle sizer instrument. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed to determine the cytotoxicity effect of AAs with and without nanoionization at various concentrations (100 to 500 μg/mL) in mammary epithelial cells. MAC-T cells were subjected to 100% of free AA and nanoemulsified AA concentration in Dulbecco’s modified Eagle medium/nutrient mixture F-12 (DMEM/F12) for the analysis of milk protein (casein) expression by the quantitative reverse transcription polymerase chain reaction method.ResultsThe AA-treated cells showed that cell viability tended to decrease (80%) in proportion to the concentration before nanogenesis, but cell viability increased as much as 90% after nanogenesis. The analysis of the expression of genetic markers related to milk protein indicated that; αs2-casein increased 2-fold, κ-casein increased 5-fold, and the amount of unchanged β-casein expression was nearly doubled in the nanoemulsified methionine-treated group when compared with the free-nanoemulsified methionine-supplemented group. On the contrary, the non-emulsified cysteine-administered group showed higher expression of genetic markers related to milk protein αs2-casein, κ-casein, and β-casein, but all the genetic markers related to milk protein decreased significantly after nanoemulsification.ConclusionDetailed knowledge of factors, such nanogenesis of methionine, associated with increasing cysteine and decreasing production of genetic markers related to milk protein (casein) will help guide future recommendations to producers for maximizing milk yield with a high level of milk protein casein.

Synthesis and characterization of amphiphilic poly(ɛ-caprolactone)-b-polyphosphoester diblock copolymers bearing multifunctional pendant groups

A series of parent block copolyesters poly(ɛ-caprolactone)-block-poly[2-(2-oxo-1, 3, 2-dioxaphospholoyloxy)ethyl acrylate] (PCL-b-POPEA) with different block lengths have been synthesized by ring-opening polymerization (ROP) and four kinds of mercaptans were then used in the postpolymerization modification via Michael-type addition reaction, resulting in several block copolyesters with various functionalities (e.g., hydroxyl, carboxyl, amine, and amino acid) in their pendant groups. The chemical structures of these block copolymers were characterized by FT-IR, NMR spectroscopy and GPC analysis. The self-assembly behaviors of PCL-b-POPEA have been studied by fluorescence probe technique, transmission electron microscopy (TEM) and high-performance particle size (HPPS) instrument. In vitro cytotoxicity test indicated that the block copolymers possess good biocompatibility. Initial in vitro drug loading and release studies using Doxorubicin (DOX) as a model drug demonstrated a faster release in the presence of phosphodiesterase I as compared to the system without enzyme. Moreover, it was found that DOX-loaded nanoparticles displayed higher inhibition to KB cell proliferation in comparison with free DOX. Therefore, the combination of ROP and Michael-type addition reaction provides a general access to various types of multifunctional and biodegradable materials.

Sorption of toluene by humic acids derived from lake sediment and mountain soil at different pH

Contamination of soil and groundwater with BTEX compounds (benzene, toluene, ethylbenzene, and xylene) depends on the sorption behavior of these compounds by soil organic matter (SOM) and humic acids (HAs). In this study sorption of toluene by HAs extracted from lake sediment and mountain soil was investigated. HA suspensions were adjusted to pH 4.00, 6.00, or 8.00 and made to the concentration of 200 mg L −1. Each HA suspension or solution was subjected to particle size analysis using high performance particle sizer (HPPS). The particle size of HA from lake sediment was around 1000–1200 nm while that from mountain soil was 220–320 nm at suspension pH 4.00. Kinetic studies showed that sorption of toluene by the two HAs followed pseudo-first-order and mainly pseudo-zero-order kinetics. At suspension pH 4.00, the sorption of toluene by the two HAs was best described by Langmuir and Temkin adsorption isotherm models. Further, sorption of toluene by the lake sediment HA was significantly greater than that by mountain soil HA. It was thus suggested that the lake sediment HA with larger particle size may develop beneficially chemical conformation for sorption of toluene and related compounds in soil and associated environments.

A Strategy for Synthesis of Magnetic Nanoparticles with "Well-Defined" Polymers via Reversible Addition Fragmentation Chain Transfer Polymerization Under Ultrasonic Irradiation

The controlled graft modification of Fe3O4 magnetic nanoparticles has been achieved by reversible addition fragmentation chain transfer (RAFT) polymerization under ultrasonic irradiation. The nanoparticles of Fe3O4 were first prepared by a chemical co-precipitation method, and reacted with 3-aminopropyltriethoxylsilane (KH550), and subsequently with S-1-dodecyl-S'-(alpha,alpha'-dimethyl-alpha'-acetic acid) trithiocarbonate (DDACT) to serve as RAFT agent. The graft polymerization of methyl acrylate was carried out under ultrasonic irradiation (28 KHz, 60 W). The first-order kinetics and the polymers with narrow molecular weight distributions suggested the polymerization proceeded via RAFT process. The resultant products were characterized by Fourier transform infrared spectrometer (FT-IR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), high performance particle sizer (HPPS) and Gouy magnetic balance. The resultant products with good paramagnetism could be well modified with the "well-defined" polymers via RAFT polymerization under ultrasonic irradiation, thereby providing a new method to well modify magnetic nanoparticles.

Relationship between surface structure and morphology of Fe 3O 4/silica composite nanospheres and nucleic acid extraction

Fe 3O 4/silica composite nanospheres with different surface structure and morphology were synthesized by changing reaction conditions. As-synthesized nanospheres were characterized by high performance particle sizer (HPPS), transmission electron microscopy (TEM), nitrogen adsorption and thermogravimetry (TGA). Besides thoroughly characterization, the particles were used for DNA extraction. We found that the particle surface structure and morphology affected the nucleic acid extraction efficiency. When comparing different samples with the same silanol density (10 18), the one with a surface area of 60.37 m 2/g extracted DNA most effectively. Also, with increasing silanol density per surface area, DNA extraction efficiency increased.

Synthesis and self-assembly behaviors of three-armed amphiphilic block copolymers via RAFT polymerization

The novel trifunctional reversible addition–fragmentation chain transfer (RAFT) agent, tris(1-phenylethyl) 1,3,5-triazine-2,4,6-triyl trithiocarbonate (TTA), was synthesized and used to prepare the three-armed polystyrene (PS3) via RAFT polymerization of styrene (St) in bulk with thermal initiation. The polymerization kinetic plot was first order and the molecular weights of polymers increased with the monomer conversions with narrow molecular weight distributions (Mw/Mn≤1.23). The number of arms of the star PS was analyzed by gel permeation chromatography (GPC), ultraviolet visible (UV–vis) and fluorescence spectra. Furthermore, poly(styrene-b-N-isopropylacrylamide)3 (PS-b-PNIPAAM)3, the three-armed amphiphilic thermosensitive block copolymer, with controlled molecular weight and well-defined structure was also successfully prepared via RAFT chain extension method using the three-armed PS obtained as the macro-RAFT agent and N-isopropylacrylamide as the second monomer. The copolymers obtained were characterized by GPC and 1H nuclear magnetic resonance (NMR) spectra. The self-assembly behaviors of the three-armed amphiphilic block copolymers (PS-b-PNIPAAM)3 in mixed solution (DMF/CH3OH) were also investigated by high performance particle sizer (HPPS) and transmission electron microscopy (TEM). Interestingly, the lower critical solution temperature (LCST) of aqueous solutions of the three-armed amphiphilic block copolymers (PS-b-PNIPAAM)3 decreased with the increase of relative length of PS in the block copolymers.

Synthesis and characterization of amphiphilic fluorinated pentablock copolymers based on Pluronic F127

AbstractThe synthesis and self‐assembly behavior of pentablock copolymers consisting of Pluronic F127 (PEO100‐PPO65‐PEO100) and poly(2, 2, 3, 3, 4, 4, 5, 5‐octafluoropentyl methacrylate) (POFPMA) is herein described. Using the difunctional potassium alcoholate of F127, K+O–‐(PEO100‐PPO65‐PEO100)‐O–K+, as the macroinitiator, the POFPMA‐F127‐POFPMA pentablock copolymers were synthesized via oxyanion‐initiated polymerization. The chain length of POFPMA can be controlled by the original molar ratio of macroinitiator to OFPMA monomer, that is, F‐monomer. The composition and chemical structure of POFPMA‐F127‐POFPMA pentablock copolymers have been characterized by FTIR, 1HNMR, and 19F NMR spectroscopy, and gel permeation chromatography techniques. The solution behavior of POFPMA‐F127‐POFPMA copolymers was investigated by the methods of surface tension, cloud point, transmission electron microscopy, and high performance particle sizer (HPPS). The results indicate that these Pluronic F127‐based block copolymers modified with fluorinated segments possess relatively high surface activity and low cloud points, depending on various factors, such as the length of fluorinated block, the concentration of the copolymers in aqueous solution, and the adscititious inorganic salt. TEM measurements showed that the pentablock copolymers can self‐assemble in aqueous solution to form various micellar morphologies. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3029–3041, 2008

A new method of controlled grafting modification of chitosan via nitroxide-mediated polymerization using chitosan-TEMPO macroinitiator

The controlled graft modification of chitosan has first been achieved by nitroxide-mediated polymerization using chitosan-TEMPO macroinitiator. Chitosan-TEMPO macroinitiator was obtained from the 60Co γ-ray irradiation of N-phthaloylchitosan and 4-hydroxy-TEMPO in DMF under argon atmosphere. The graft copolymers were characterized by 1H nuclear magnetic resonance ( 1H NMR), Fourier transform infrared spectrometer (FT-IR), X-ray powder diffractometer (XRD) and high performance particle sizer (HPPS). The results indicate that the graft copolymers were successfully synthesized and that the graft polymerization was well controlled by the nitroxide-mediated process. The size distribution of chitosan- g-polystyrene in benzene is very narrow, which may be associated with the “well-defined” polystyrene (PSt) onto chitosan from nitroxide-mediated polymerization. This work provides a new method to prepare chitosan grafting copolymers with controlled molecular weights and “well-defined” structures.

A novel method of controlled grafting modification of chitosan via RAFT polymerization using chitosan-RAFT agent

The controlled grafting modification of chitosan has first been achieved by RAFT polymerization using chitosan-RAFT agent. The chitosan was first modified with S-1-dodecyl- S′-(α,α′-dimethyl-α′′-acetic acid)trithiocarbonate (DDACT) to serve as RAFT agent, and then the controlled grafting polymerization of acrylic acid were performed. The resultant copolymers were characterized by 1H nuclear magnetic resonance ( 1H NMR), Fourier transform infrared spectrometer (FT-IR), X-ray powder diffractometer (XRD), high performance particle sizer (HPPS), and transmission electron microscopy (TEM). The results indicate that the graft copolymers were successfully synthesized and that the grafting polymerization was a first-order reaction with respect to monomer concentration. The size distribution of chitosan -g-PAA in ethanol is very narrow, which may be associated with the grafting density and the “well-defined” PAAs onto chitosan from RAFT polymerization. TEM shows chitosan -g-PAA in dilute ethanol dispersions is roughly 80 nm in size with some aggregation. This work provides a new method to prepare chitosan grafting copolymers with controlled molecular weights and “well-defined” structures.

Synthesis of amphiphilic and thermosensitive graft copolymers with fluorescence P(St‐co‐(p‐CMS))‐g‐PNIPAAM by combination of NMP and RAFT methods

AbstractA three‐step process, combining nitroxide‐mediated polymerization (NMP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization techniques, for synthesizing well‐defined amphiphilic and thermosensitive graft copolymers with fluorescence poly(styrene‐co‐(p‐chloromethylstyrene))‐g‐poly(N‐isopropylacrylamide) (P(St‐co‐(p‐CMS))‐g‐PNIPAAM), was conducted. Firstly, the NMP of styrene (St) and p‐chloromethylstyrene (p‐CMS) were carried out using benzoyl peroxide (BPO) as the initiator to obtain the random copolymers of P(St‐co‐(p‐CMS)). Secondly, the random copolymers were converted into macro‐RAFT agents with fluorescent carbazole as Z‐group through a simple method. Then the macro‐RAFT agents were used in the RAFT polymerization of N‐isopropylacrylamide (NIPAAM) to prepare fluorescent amphiphilic graft copolymers P(St‐co‐(p‐CMS))‐g‐PNIPAAM with controlled molecular weights and well‐defined structures. The copolymers obtained were characterized by gel permeation chromatography (GPC), 1H nuclear magnetic resonance (NMR) spectroscopy, and FT‐IR spectroscopy. The size of self‐assembly micelles of the resulting graft copolymers in deionized water was studied by high performance particle sizer (HPPS), the results showed that the Z‐average size of the micelles increased with the increase of molecular weights of PNIPAAM in side chains. The aqueous solution of the micelles prepared from P(St‐co‐(p‐CMS))‐g‐PNIPAAM using a dialysis method showed a lower critical solution temperature (LCST) at ∼ 27.5 °C, which was below the value of NIPAAM homopolymer (32 °C). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5318–5328, 2007

Chemiluminescence of luminol catalyzed by silver nanoparticles

Silver nanoparticles (AgNPs) are synthesized by chemical reduction method and characterized by UV–vis spectra, transmission electron microscopy, and high performance particle sizer. We have found that AgNPs could enhance the chemiluminescence (CL) intensity of luminol–H 2O 2 system. In this reaction, luminol intermediate is generated under alkaline condition on the surface of AgNPs in luminol–H 2O 2 system and enhances CL intensity. To validate the reaction mechanism, AgNPs are bound with thioglycolic acid (Ag–HSCH 2COOH) and then joined to BSA protein (Ag–BSA). We investigate the CL intensity in the presence of Ag–HSCH 2COOH or Ag–BSA comparing with that in the presence of AgNPs and conclude the catalytic reaction take place on the surface of AgNPs.

Brush-type amphiphilic polystyrene- g-poly(2-(dimethylamino)ethyl methacrylate)) copolymers from ATRP and their self-assembly in selective solvents

A series of well-defined brush-type amphiphilic polystyrene- g-poly(2-(dimethylamino) ethyl methacrylate)) (PS- g-PDMAEMA) copolymers were successfully synthesized via atom transfer radical polymerization (ATRP), using chloromethylated polystyrene (CMPS) as the macroinitiator. The self-assembly behavior of the resulting brush-type copolymers in deionized water and deionized water/acetone (v/v=2/3) mixture was studied by high performance particle sizer (HPPS). The results showed that the Z-average size of the micelles in deionized water increased with the increase of molecular weight of PDMAEMA, and the corresponding size was larger than that in mixed solvent of deionized water and acetone (v/v=2/3). The morphologies of the micelles self-assembled from PS- g-PDMAEMA in selective solvents were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). When the micelles were prepared in water/acetone (v/v=2/3) mixture and cast them on a glass slide at different temperatures (from 50 up to 200 °C), the transformation of the morphologies of aggregates, from needle-like solid to microcubic particles, was observed using SEM.

Synthesis of ABA triblock copolymer of poly(potassium acrylate-styrene-potassium acrylate) by atom transfer radical polymerization and the self-assembly in selective solvents

A series of well-defined ABA triblock copolymers of poly(methyl acrylate)-polystyrene-poly(methyl acrylate) (PMA- b-PS- b-PMA) with different molecular weights were synthesized using Cl-PS-Cl as macroinitiator, CuCl/ N, N, N′, N″, N″-pentamethyldiethylenetriamine (PMDETA) as catalyst system via atom transfer radical polymerization (ATRP). Amphiphilic triblock copolymer poly(potassium acrylate)-polystyrene-poly(potassium acrylate) (PKAA- b-PS- b-PKAA) was obtained by hydrolyzing PMA- b-PS- b-PMA. The self-assembly behavior of the triblock copolymers in organic solutions, which is a good solvent for the PS block and in aqueous solutions, which is a good solvent for the PKAA blocks was studied by high performance particle sizer (HPPS). The results showed that the Z-average size of the micelles obviously increases with increase in molecular weight of triblock copolymers, and the micelles in organic solutions are relatively more stable than in aqueous solutions. The effect of the length of PS block on the Z-average size of the micelles is more obvious in organic solution than in aqueous solution. The morphology of triblock copolymers PKAA- b-PS- b-PKAA in aqueous solution, which is a nearly ‘pearl-necklace’-like shape, was examined by transmission electron microscopy (TEM) at room temperature.