34 research outputs found
Morphology, Surface Layer Evolution, and Structure–Dye Adsorption Relationship of Porous Fe<sub>3</sub>O<sub>4</sub> MNPs Prepared by Solvothermal/Gas Generation Process
A new
system based on dimethylacetamide, ethanolamine, and azobisÂ(isobutyronitrile)
(AIBN) was employed to synthesize porous Fe<sub>3</sub>O<sub>4</sub> magnetic nanoparticles (MNPs) for the first time. The formation
mechanism, morphology, and surface layer evolution of MNPs at the
different AIBN ratios were revealed. The MNPs prepared without AIBN
showed a randomly assembled morphology with a BET surface area of
174 m<sup>2</sup>/g, which is almost the highest reported until now.
After AIBN was added, N<sub>2</sub> gas and radical were produced
by the thermal decomposition reaction. The high gas pressure enhanced
the growth and self-assembly of nanounits, leading to a microsphere
morphology. The radical caused a surface modification effect, which
led to a decline in both the specific saturation magnetization and
surface area of Fe<sub>3</sub>O<sub>4</sub> MNPs. The surface of MNPs
was fully modified when prepared at a high AIBN ratio. The methyl
orange (MO) adsorption revealed that the modification coverage and
surface composition of Fe<sub>3</sub>O<sub>4</sub> MNPs are responsible
for its adsorption capacity irrespective of the surface area. The
naked Fe<sub>3</sub>O<sub>4</sub> MNPs showed a limited adsorption
capacity, which was saturated during the synthesis process. Moreover,
the prepared MNPs(3) showed a maximum adsorption capacity of 46.7
mg/g. The surface coverage ratio revealed that its surface was almost
fully covered with dye molecules. Moreover, it has shown good acidic
stability and can be regenerated for dye adsorption applications
Surface Modification of Polyacrylonitrile Membrane by Chemical Reaction and Physical Coating: Comparison between Static and Pore-Flowing Procedures
The influences of static and pore-flowing
procedures on the surface
modification of a polyacrylonitrile (PAN) ultrafiltration membrane
through chemical reaction and physical coating were investigated in
detail. For chemical modification by ethanolamine, a membrane modified
by the pore-flowing procedure showed a higher flux and different morphology.
The reasons were explained by two effects: the pore-flowing resistance
to the random thermal motion of PAN at high temperatures and different
reaction kinetics related to the reactant concentration profile on
the interface between the membrane and reaction solution and the kinetic
property of the fluid (driving force and miscibility) and reaction
(time and rate). For physical coating modification, a dense and flat
layer via a loose and random layer was formed during the pore-flowing
process and static process, which changed the flux and antifouling
property of the membrane. The membrane prepared by dead-end filtration
showed the best trade-off between the flux and antifouling property.
Overall, the procedure kinetics plays an important role in the optimization
of membrane modification
In Situ-Forming Polyamidoamine Dendrimer Hydrogels with Tunable Properties Prepared via Aza-Michael Addition Reaction
In this work, we describe synthesis
and characterization of novel in situ-forming polyamidoamine (PAMAM)
dendrimer hydrogels (DHs) with tunable properties prepared via highly
efficient aza-Michael addition reaction. PAMAM dendrimer G5 was chosen
as the underlying core and functionalized with various degrees of
acetylation using acetic anhydride. The nucleophilic amines on the
dendrimer surface reacted with α, β-unsaturated ester
in acrylate groups of polyethylene glycol diacrylate (PEG-DA, <i>M</i><sub>n</sub> = 575 g/mol) via aza-Michael addition reaction
to form dendrimer hydrogels without the use of any catalyst. The solidification
time, rheological behavior, network structure, swelling, and degradation
properties of the hydrogel were tuned by adjusting the dendrimer surface
acetylation degree and dendrimer concentration. The DHs were shown
to be highly cytocompatible and support cell adhesion and proliferation.
We also prepared an injectable dendrimer hydrogel formulation to deliver
the anticancer drug 5-fluorouracil (5-FU) and demonstrated that the
injectable formulation efficiently inhibited tumor growth following
intratumoral injection. Taken together, this new class of dendrimer
hydrogel prepared by aza-Michael addition reaction can serve as a
safe tunable platform for drug delivery and tissue engineering
DenTimol as A Dendrimeric Timolol Analogue for Glaucoma Therapy: Synthesis and Preliminary Efficacy and Safety Assessment
In
this work, we report the synthesis and characterization of DenTimol,
a dendrimer-based polymeric timolol analog, as a glaucoma medication.
A timolol precursor (<i>S</i>)-4-[4-(oxiranylmethoxy)-1,2,5-thiadiazol-3-yl]Âmorpholine
(OTM) was reacted with the heterobifunctional amine polyethylene glycol
acetic acid (amine–PEG–acetic acid, <i>M</i><sub>n</sub> = 2000 g/mol) via a ring opening reaction of an epoxide
by an amine to form the OTM–PEG conjugate. OTM–PEG was
then coupled to an ethylenediamine (EDA) core polyamidoamine (PAMAM)
dendrimer G3 to generate DenTimol using the <i>N</i>-(3-(dimethylamino)Âpropyl)-<i>N</i>′-ethylcarbodiimide hydrochloride (EDC)/<i>N</i>-hydroxysuccinimide (NHS) coupling reaction. MALDI mass
spectrometry, <sup>1</sup>H NMR spectroscopy, and HPLC were applied
to characterize the intermediate and final products. Ex vivo corneal
permeation of DenTimol was assessed using the Franz diffusion cell
system mounted with freshly extracted rabbit cornea. The cytotoxicity
of DenTimol was assessed using the WST-1 assay. Our results show that
DenTimol is nontoxic up to an OTM equivalent concentration of 100
μM. DenTimol is efficient at crossing the cornea. About 8% of
the dendrimeric drug permeated through the cornea in 4 h. Its IOP-lowering
effect was observed in normotensive adult Brown Norway male rats.
Compared to the undosed eye, an IOP reduction by an average of 7.3
mmHg (∼30% reduction from baseline) was observed in the eye
topically treated with DenTimol (2 × 5 μL, 0.5% w/v timolol equivalent) in less than 30 min. Daily dosing
of DenTimol for a week did not cause any irritation or toxicity as
confirmed by the histological examination of ocular tissues, including
the cornea, ciliary body, and retina
Synthesis and Characterization of Clickable Cytocompatible Poly(ethylene glycol)-Grafted Polyoxetane Brush Polymers
We report a new family of clickable polyÂ(ethylene glycol)
(PEG)-grafted
polyoxetane brush polymers as a potential modular platform for delivery
of drugs and imaging agents. 3-Ethyl-3-hydroxymethyloxetane (EHMO)
monomer reacted with propargyl benzenesulfonate in the presence of
sodium hydride to yield alkyne-substituted monomer (EAMO). Subsequently,
cationic ring-opening polymerization using boron trifluoride diethyl
etherate catalyst and 1,4-butanediol initiator produced PÂ(EAMO) homopolymer
with a DP of ∼30 (30 alkynes per chain). MethoxypolyÂ(ethylene
glycol) azide (mPEG750-azide) prepared from mPEG750 (750 g mol<sup>–1</sup>) was grafted to PÂ(EAMO) via copperÂ(I)-catalyzed alkyne–azide
cycloaddition (CuAAC) click chemistry. Water-soluble cytocompatible
PÂ(EAMO)-<i>g</i>-PEG brush polymers with controlled degrees
of PEGylation were synthesized by varying the feed molar ratio of
mPEG750-azide to alkyne (25:100, 50:100, 75:100, and 100:100). <sup>1</sup>H NMR, GPC, end-group analysis, FTIR, and DSC were applied
for polymer characterization. The utility of PÂ(EAMO)-<i>g</i>-PEG for carrying imaging agents was demonstrated by preparing fluorescently
labeled PÂ(EAMO)-<i>g</i>-PEG. 5-(Aminoacetamido)Âfluorescein
(AAF) was used as a model compound. Fluorescein-carrying PÂ(EAMO)-<i>g</i>-PEG was synthesized by click coupling bifunctional spacer
6-azidohexanoic acid (AHA) to PÂ(EAMO)-<i>g</i>-PEG and subsequently
coupling of AAF to AHA with EDC/NHS chemistry
Additional file 2: Table S2. of Integrative analysis of transcriptomics and proteomics of skeletal muscles of the Chinese indigenous Shaziling pig compared with the Yorkshire breed
GO enrichment of DEG. (XLS 77 kb
Additional file 1: Table S1. of Integrative analysis of transcriptomics and proteomics of skeletal muscles of the Chinese indigenous Shaziling pig compared with the Yorkshire breed
KEGG Pathway information of unigenes. (XLS 705 kb
Temporal dynamics of SPAD readings of labeled rice leaves under six N application rates.
<p>Each value is an average of 30 measurements. Bars indicate standard error of means. Numbers underneath bars are coefficients of variation (%) of SPAD readings obtained on the same day under the six N application rates. SPAD readings are not shown for control plants on the 45th day after full expansion (DAFE 45) because some leaves in plots without N application were dead. N1 to N6 are the same as in the legend in Fig. 1.</p
Photosynthetic photon flux density (PPFD) in relation to canopy position.
<p>Data are represented in terms of the percentage of PPFD measured at the uppermost canopy position. Measurements were taken at midday at the flag leaf and the next three leaves (2nd, 3rd, and 4th leaves) on (A) Sept. 1, 2008, and (B) Aug. 26, 2009. N1, N2, N3, N4, N5, and N6 indicate N application rates of 0, 75, 150, 225, 300, and 375 kg N ha<sup>−1</sup>, respectively.</p
Processing–Structure–Property Correlations of Polyethersulfone/Perfluorosulfonic Acid Nanofibers Fabricated via Electrospinning from Polymer–Nanoparticle Suspensions
Polyethersulfone (PES)/perfluorosulfonic acid (PFSA)
nanofiber
membranes were successfully fabricated via electrospinning method
from polymer solutions containing dispersed calcium carbonate (CaCO<sub>3</sub>) nanoparticles. ATR-FTIR spectra indicated that the nanoparticles
mainly existed on the external surface of the nanofibers and could
be removed completely by acid treatment. Surface roughness of both
the nanofibers and the nanofiber membranes increased with the CaCO<sub>3</sub> loading. Although FTIR spectra showed no special interaction
between sulfonic acid (−SO<sub>3</sub>) groups and CaCO<sub>3</sub> nanoparticles, XPS measurement demonstrated that the content
of −SO<sub>3</sub> groups on external surface of the acid-treated
nanofibers was enhanced by increasing CaCO<sub>3</sub> loading in
solution. Besides, the acid-treated nanofiber membranes were performed
in esterification reactions, and exhibited acceptable catalytic performance
due to the activity of −SO<sub>3</sub>H groups on the nanofiber
surface. More importantly, this type of membrane was very easy to
separate and recover, which made it a potential substitution for traditional
liquid acid catalysts