Synthesis, characterization and properties of chitosan modified with poly(ethylene glycol)-polydimethylsiloxane amphiphilic block copolymers

Synthesis of poly(ethylene glycol)-polydimethylsiloxane amphiphilic block copolymers is discussed herein. Siloxane prepolymer was first prepared via acid-catalyzed ring-opening polymerization of octamethylcyclotetrasiloxane (D₄) to form polydimethylsiloxane (PDMS) prepolymers. It was subsequently functionalized with hydroxy functional groups at both terminals. The hydroxy-terminated PDMS can readily react with acid-terminated poly(ethylene glycol) (PEG diacid) to give PEG-PDMS block copolymers without using any solvent. The PEG diacid was prepared from hydroxy-terminated PEG through the ring-opening reaction of succinic anhydride. Their chemical structures and molecular weights were characterized using ¹H NMR, FTIR and GPC, and thermal properties were determined by DSC. The PEG-PDMS copolymer was incorporated into chitosan in order that PDMS provided surface modification and PEG provided good water swelling properties to chitosan. Critical surface energy and swelling behavior of the modified chitosan as a function of the copolymer compositions and contents were investigated.     

Smart carboxymethylchitosan hydrogels that have thermo‐ and pH‐responsive properties

Thermo‐responsive poly(N‐isopropylacrylamide) (poly(NIPAAm)) and pH‐responsive poly(N,N′‐diethylaminoethyl methacrylate) (poly(DEAEMA)) polymers were grafted to carboxymethylchitosan (CMC) via radical polymerization to form highly water swellable hydrogels with dual responsive properties. Ratios of CMC, NIPAAm to DEAEMA used in the reactions were finely adjusted such that the thermo and pH responsiveness of the hydrogels was retained. Scanning electron microscopy (SEM) indicated the formation of an internal porous structure for the swollen CMC hydrogels upon incorporation of poly(NIPAAm) and poly(DEAEMA). Effect of temperature and pH changes on water swelling properties of the hydrogels was investigated. It was found that the water swelling of the hydrogels was enhanced when the solution pH was under basic conditions (pH 11) or the temperature was below its lower critical solution temperature (LCST). These responsive properties can be used to regulate releasing rate of an entrapped drug from the hydrogels, a model drug, indomethacin was used to demonstrate the release. These smart and nontoxic CMC‐based hydrogels show great potential for use in controlled drug release applications with controllable on‐off switch properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41505.     

Synthesis of water dispersible magnetite nanoparticles in the presence of hydrophilic polymers

Water dispersible magnetite nanoparticles (Fe₃O₄) were synthesized by thermal decomposition of iron (III) acetylacetonate (Fe(acac)₃) in the presence of carboxylic acid-terminated poly(ethylene glycol) (mPEG acid), poly(vinyl alcohol) and NH₂-containing polyether. Crystal structure was investigated using X-ray diffractometry (XRD) and it showed that the as-synthesized particles had high crystallinity with distinct lattices. Particle size of the nanoparticles was investigated using XRD (15.32 nm), transmission electron microscopy (18.8 nm) and photo correlation spectroscopy (32 nm) techniques. Vibrating sample magnetometry indicated that magnetite nanoparticles exhibited superparamagnetic behavior at room temperature. Influence of each functional group on magnetic properties of the particles was also examined. These magnetite nanoparticles remained dispersible in aqueous dispersions with only 5% particles aggregating after 1 month of preparing.     

Magnetic core-bilayer shell nanoparticle: A novel vehicle for entrapmentof poorly water-soluble drugs

We are herein reporting a synthesis of indomethacin-loaded bilayer-surface magnetite nanoparticles and their releasing behavior. The particles were first stabilized with oleic acid as a primary surfactant, followed by poly(ethylene glycol) methyl ether-poly(?-caprolactone) (mPEG-PCL) amphiphilic block copolymer as a secondary surfactant to form nanoparticles with hydrophobic inner shell and hydrophilic corona. mPEG-PCL copolymers with systematically varied molecular weights of each block (2000-2000, 2000-10,000, 5000-5000 and 5000-10,000 g/mol, respectively) were synthesized via a ring-opening polymerization of ?-caprolactone using mPEG as a macroinitiator. The particles were 9 nm in diameter and exhibited superparamagnetic behavior at room temperature with saturation magnetization (M_s) about 35 emu/g magnetite. Percent of magnetite and the copolymers in the complexes were determined via thermogravimetric analysis (TGA). The effect of mPEG and PCL block lengths in the copolymer-magnetite complex on the properties of the particles, e.g. particle size, magnetic properties, stability in water, drug entrapping and loading efficiency and its releasing behavior were investigated. This novel magnetic nanocomplex might be suitable for use as an efficient drug delivery vehicle with tunable drug-released properties.     

Reusable magnetic nanocluster coated with poly(acrylic acid) and its adsorption with an antibody and an antigen

The synthesis of negatively charged magnetite nanoclusters grafted with poly(acrylic acid) (PAA) and their application as reusable nanosupports for adsorption with antibodies and antigens are presented in this article. They were facilely prepared via the free‐radical polymerization of PAA in the presence of functionalized magnetite nanoparticles to obtain highly negative charged nanoclusters with a high magnetic responsiveness and good dispersibility and stability in water. According to transmission electron microscopy, the sizes of the nanoclusters ranged between 200 and 500 nm, without large aggregation visually observed in water. The hydrodynamic size of the nanocluster consistently increased with increasing pH of the dispersion; this indicated its pH‐responsive properties, which was due to the repulsion of the anionic carboxylate groups in the structure. This nanocluster was successfully used as an efficient and reusable support for adsorption with anti–horseradish peroxidase antibody. It preserved higher than a 97% adsorption ability of the antibody after eight reuse cycles; this signified the potential of this novel nanocluster as a reusable support in the magnetic separation applications of other bioentities. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46160.     

Poly(acrylic acid)-grafted magnetic nanoparticle for conjugation with folic acid

Poly(acrylic acid) (poly(AA))-grafted magnetite nanoparticles (MNPs) prepared via surface-initiated atom transfer radical polymerization (ATRP) of t-butyl acrylate, followed by acid-catalyzed deprotection of t-butyl groups, is herein presented. In addition to serve as both steric and electrostatic stabilizers, poly(AA) grafted on MNP surface also served as a platform for conjugating folic acid, a cancer cell targeting agent. Fourier transform infrared spectroscopy (FTIR) was used to monitor the reaction progress in each step of the syntheses. The particle size was 8 nm in diameter without significant aggregation during the preparation process. Photocorrelation spectroscopy (PCS) indicated that, as increasing pH of the dispersions, their hydrodynamic diameter was decreased and negatively charge surface was obtained. According to thermogravimetric analysis (TGA), up to 14 wt% of folic acid (about 400 molecules of folic acid per particle) was bound to the surface-modified MNPs. This novel nanocomplex is hypothetically viable to efficiently graft other affinity molecules on their surfaces and thus might be suitable for use as an efficient drug delivery vehicle particularly for cancer treatment.     

Multiplex mass spectrometric genotyping of single nucleotide polymorphisms employing pyrrolidinyl peptide nucleic acid in combination with ion-exchange capture

A new ion-exchange capture technique is introduced for label-free sample preparation in single nucleotide polymorphism (SNP) genotyping. The DNA sample is hybridized with a new pyrrolidinyl peptide nucleic acid (PNA) probe and treated with a strong anion exchanger. The complementary PNA.DNA hybrid is selectively captured by the anion exchanger in the presence of noncomplementary or unhybridized PNA, allowing direct detection of the hybridization event on the anion exchanger by MALDI-TOF mass spectrometry after simple washing. The high specificity of the pyrrolidinyl PNA allows simultaneous multiplex SNP typing to be carried out at room temperature without the need for enzyme treatment or heating. Exemplary applications of this technique, in the identification of meat species in feedstuffs and in multiplex SNP typing of the human IL-10 gene promoter region are demonstrated, clearly suggesting the potential for much broader applications.     

Azlactone functionalization of magnetic nanoparticles using ATRP and their bioconjugation

Surface modification of magnetite nanoparticle (MNP) with poly(poly(ethylene glycol) methyl ether methacrylate-stat-2-vinyl-4,4-dimethylazlactone) copolymers (Poly(PEGMA-stat-VDM)) via atom transfer radical polymerization (ATRP) and its application to anchor thymine peptide nucleic acid (PNA) monomer are reported. ATRP of PEGMA and VDM was first performed in a solution system to optimize the reaction condition and the optimal condition was then applied in the surface-initiated ATRP of MNP. Fourier transform infrared spectroscopy (FTIR) indicated the presence of the copolymer in the MNP complexes. After immobilization of thymine PNA monomer, thermogravimetric analysis (TGA) results indicated that there were 4 wt% of the PNA monomer in the complex (1.2 μmol/g complex). The existence of the PNA monomer in the complex was also confirmed via FTIR and vibrating sample magnetometry (VSM). The MNP complex with active surface might be efficiently used as magnetically guidable nanosolid support for PNA oligomers and other molecules containing affinity functional groups.