Synthesis and characterization of lactobionic acid grafted pegylated chitosan and nanoparticle complex application

A series of chemical modifications of chitosan were conducted by grafting a hydrophilic methoxy poly(ethylene glycol) (MPEG) and a target sugar molecule lactobionic acid (LA). The MPEG was grafted onto C6-OH position of chitosan, and the grafting degree was reduced for chitosan with high degree of depolymerization. The lactobionic acid was proposed to graft onto C2-NH₂ position of chitosan. The LA grafting ratio was dependent on pegylation degree of chitosan, where the flexibility and shielding effect of MPEG hindered LA grafting onto chitosan. The lactobionic acid grafted pegylated chitosan, DADP-CS-(O-MPEG)-(N-LA), successfully provoked DNA condensation into nanoparticle complexes due to electrostatic compaction. The presence of MPEG on DADP-CS-(O-MPEG)-(N-LA) played an important role on preventing nanoparticle aggregation.     

Grafting of poly(triethylene glycol dimethacrylate) onto chitosan by ceric ion initiation

Grafting of poly(triethylene glycol dimethacrylate) (poly(TriEGDMA)), onto chitosan by ceric ion initiation has been investigated. The grafting conditions were optimized by studying the effect of monomer and initiator concentrations as well as time and temperature. Products with lower grafting yields (90–261%) were water and acid soluble. Those with higher grafting yields (350–868%) were insoluble, indicating a cross linked structure. Chitosan-graft- poly(TriEGDMA) products had a lower thermal stability than chitosan as revealed by DSC analysis. C-13 NMR and FTIR analyses suggested a grafting mechanism that proceeds via oxidation and chain scission of chitosan. The products are degraded by the enzymes lysozyme, lipase and α-amylase–protease.     

Grafting reaction of living polymer cations with amino groups on chitosan powder

The grafting of polymers having controlled molecular weight and narrow molecular weight distribution onto chitosan powder by the termination of living polymer cation with amino groups on chitosan powder was investigated in heterogeneous system. The amino groups of chitosan powder successfully reacted with living poly(isobutyl vinyl ether) [poly(IBVE)] and poly(2-methyl-2-oxazoline) [poly(MeOZO)] cation with controlled molecular weight and narrow molecular weight distribution to give the corresponding polymer-grafted chitosan powders. The percentage of poly(MeOZO) grafting gradually increased and reached 24.5% after 4 days. The solubility of poly(MeOZO)-grafted chitosan in water increased with an increase in the amount of grafted polymer. It was suggested that grafting reaction of living polymer cation with chitosan powder proceeds from surface amino groups to inner amino groups of the powder with progress of the reaction. The mole number of grafted polymer chain on chitosan powder decreased with an increase in the molecular weight of the living polymer cation because the steric hindrance of functional groups of chitosan powder increased with the increasing molecular weight of living polymer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1883–1889, 1998     

Preparation and characteristics of chitosan-g-PDMS copolymer

Summary Chitosan-g-poly(dimethyl siloxane) (PDMS) copolymer was prepared by grafting PDMS prepolymer onto chitosan. PDMS prepolymer was prepared by ionic ring opening polymerization of octamethylcyclotrisiloxane (D₄) using n-buthyl-lithium (BuLi). The tensile strength and elongation of chitosan-g-PDMS copolymer were mostly constant regardless of PDMS prepolymer grafting %. While critical surface energy of chitosan is about 32 dyne/cm, that of chitosan-g-PDMS copolymer was a little decreased to 25∼29 dyne/cm by grafting PDMS onto chitosan. Received: 17 July 1998/Revised version: 5 October 1998/Accepted: 2 November 1998     

N-辛基-O-聚乙二醇壳聚糖衍生物的制备与表征

以自然界富有的天然壳聚糖为原料,在其分子结构的2位—NH2上引入部分疏水性辛基,并对其余的—NH2进行有效保护;然后在3,6位的—OH上引入亲水性聚乙二醇基团,合成了具有两亲性的N-辛基-O-聚乙二醇壳聚糖衍生物。通过FTIR,1HNMR和元素分析对衍生物的分子结构和N-位、O-位取代度进行了表征。该壳聚糖衍生物具有两亲性,水溶性好,且分子结构中保留了可用于后续交联反应的活性—NH2,在制备两亲性壳聚糖微球型药物载体领域具有潜在的应用价值。     

Temperature/pH‐sensitive comb‐type graft hydrogels composed of chitosan and poly(N‐isopropylacrylamide)

Comb‐type graft hydrogels, composed of chitosan and poly(N‐isopropylacrylamide) (PNIPAAm), were prepared to manifest rapid temperature and pH sensitivity. Instead of directly grafting the NIPAAm monomer onto the chitosan chain, semitelechelic PNIPAAm with carboxyl end group was synthesized by radical polymerization using 3‐mercaptopropionic acid as the chain‐transfer agent, and was grafted onto chitosan having amino groups. The comb‐type hydrogels were prepared with two different graft yields and grafting regions, such as surface‐ and bulk‐grafting, and then compared with a chitosan hydrogel. The synthesis of telechelic PNIPAAm and the formation of amide group were confirmed by using FTIR spectroscopy and gel permeation chromatography. Results from the water state and thermal stability revealed that the introduction of the PNIPAAm side chain disturbed the ordered arrangement of the chitosan molecule, resulting in an increase in the equilibrium water content. Comb‐type graft hydrogels showed rapid temperature and pH sensitivity because of the free‐ended PNIPAAm attached to the chitosan main chain and the chitosan amino group itself, respectively. In particular, the surface graft hydrogel maintained its dimension at low pH, although the chitosan main chain was not crosslinked, whereas chitosan and bulk graft hydrogel were dissolved as a result of the coating effect of pH‐independent PNIPAAm. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2612–2620, 2004     

Grafting of poly(3‐hydroxyalkanoate) and linoleic acid onto chitosan

Poly(3‐hydroxy octanoate) (PHO), poly(3‐hydroxy butyrate‐co‐3‐hydroxyvalerate) (PHBV), and linoleic acid were grafted onto chitosan via condensation reactions between carboxylic acids and amine groups. Unreacted PHAs and linoleic acid were eliminated via chloroform extraction and for elimination of unreacted chitosan were used 2 wt % of HOAc solution. The pure chitosan graft copolymers were isolated and then characterized by FTIR, ¹³C‐NMR (in solid state), DSC, and TGA. Microbial polyester percentage grafted onto chitosan backbone was varying from 7 to 52 wt % as a function of molecular weight of PHAs, namely as a function of steric effect. Solubility tests were also performed. Graft copolymers were soluble, partially soluble or insoluble in 2 wt % of HOAc depending on the amount of free primary amine groups on chitosan backbone or degree of grafting percent. Thermal analysis of PHO‐g‐Chitosan graft copolymers indicated that the plastizer effect of PHO by means that they showed melting transitions T_ms at 80, 100, and 113°C or a broad T_ms between 60.5–124.5°C and 75–125°C while pure chitosan showed a sharp T_m at 123°C. In comparison of the solubility and thermal properties of graft copolymers, linoleic acid derivatives of chitosan were used. Thus, the grafting of poly(3‐hydroxyalkanoate) and linoleic acid onto chitosan decrease the thermal stability of chitosan backbone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:81–89, 2007     

N-vinyl pyrrolidone-assisted free radical functionalization of glycidyl methacrylate onto styrene-b-(ethylene-co-butylene)-b-styrene

N-vinyl pyrrolidone (NVP)-assisted free radical functionalization of glycidyl methacrylate (GMA) onto styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) was investigated to attempt to overcome the low grafting reactivity of GMA and the low efficiency of the styrene (St)-assisted functionalization method. By using the optimal amount of NVP, the degree of GMA grafting was increased by at least 7.5 and 2.5-fold when compared to GMA alone and the St-assisted grafting procedure, respectively. Also, no apparent cross-linking or degradation reactions of SEBS were observed. It was proposed that NVP reacted first with SEBS macroradicals, and then the resulting NVP-macroradicals copolymerized with GMA to produce high degrees of grafting of both GMA and NVP onto SEBS.     

Mechanical behavior at nanoscale of chitosan‐coated PE surface

Chitosan coating of polyethylene (PE) was proposed as a new procedure to improve its biocompatibility and surface properties. The functionalization of the PE film surface by covalent bonding of chitosan coating and its effect on the surface mechanical properties, as surface elasticity, stiffness, and adhesion (that are important in different biological processes) were investigated by nano‐indentation, scratch, and atomic force microscopy. It has been established that chitosan grafting onto corona functionalized PE surface using various coupling agents significantly improves the surface hardness and elastic modulus although they decrease in depth of the layer. Compared to the neat PE substrate, the chitosan coated samples show significant improved friction properties and tear resistance. The surface roughness features correlate with the micro‐mechanical parameters. Therefore, the covalent immobilization of the chitosan onto PE leads to a stable coating with better mechanical performance being recommended as a promising material for medical applications and food packaging. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42344.     

N-mPEG-O-季铵化壳聚糖微球的制备及其载药性能

将聚乙二醇单甲醚（mPEG）醛化改性后,通过西佛碱反应接枝到自制的O-季铵化壳聚糖的NH2上,硼氢化钠还原制得N-mPEG接枝O-季铵化壳聚糖（QACS-mPEG）,反相悬浮法制备二乙烯基砜交联QACS-mPEG微球。用FTIR、1 H NMR、EA和SEM对产物进行表征,并且以酮洛芬为模型药物研究微球的载药性能及释放行为。结果表明,mPEG和季铵盐基团的引入提高了N-mPEG-O-季铵化壳聚糖微球的载药量,为4.31mg/mg;载药N-mPEG-O-季铵化壳聚糖微球在模拟肠液的缓释效果优于胃液,微球释药具有pH响应性。     

Homogeneous graft copolymerization of chitosan with butyl acrylate by γ‐irradiation via a 6‐O‐maleoyl‐N‐phthaloyl‐chitosan intermediate

The graft copolymerization of butyl acrylate (BA) onto chitosan was tried via a new protection‐graft‐deprotection procedure. About 6‐O‐maleoyl‐N‐phthaloyl‐chitosan was synthesized and characterized by Fourier transform infrared spectra analysis (FT‐IR) and ¹H‐NMR. Because the intermediate 6‐O‐maleoyl‐N‐phthaloyl‐chitosan was soluble in organic solvents, the graft copolymerization was carried out in a homogeneous system. Grafting was initiated by γ‐irradiation. The graft extent was dependent on the irradiation dose and the concentration of BA monomer, and copolymers with grafting above 100% were readily prepared. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 489–493, 2006     

Controlling the morphology of self-assemble chitosan through derivatization

Twenty chitosan derivatives with systematic variations in their chemical functionalities were prepared, by grafting phthaloyl groups, various cinnamoyl derivatives, and poly(ethylene oxide) moieties onto the chitosan backbones and then their self-assembled architectures were investigated. Derivatives with a high level of 2,4,5-trimethoxycinnamoyl substitution gave rod-shape and/or planar-shape architectures through solvent displacement, whilst the other derivatives gave spheres. Transformation of self-assembled architectures was also observed in derivative with an appropriate level of 2,4,5-trimethoxycinnamoyl substitution.     

Modified chitosan. I. Optimized cerium ammonium nitrate‐induced synthesis of chitosan‐graft‐polyacrylonitrile

Chitin was extracted from shrimp shells and then deacetylated to obtain chitosan. The degree of deacetylation of the chitosan was determined to be 0.76 using pH‐metric titration. A large number of cyanide functional groups were introduced onto chitosan by grafting with polyacrylonitrile as an efficient way of modification. The graft copolymerization reactions were carried out under argon atmosphere in a homogeneous aqueous phase (containing a small portion of acetic acid) by using ceric ammonium nitrate as an initiator. Evidence of grafting was obtained by comparing FTIR spectra of chitosan and the graft copolymer as well as solubility characteristics of the products. The synthetic conditions were systematically optimized through studying the influential factors, including temperature and concentrations of the initiator, acrylonitrile monomer (AN), acetic acid, and chitosan. The effect of individual factors was investigated by calculating and monitoring the variations of the grafting parameters [i.e., grafting ratio (Gr), grafting efficiency (Ge), add‐on value (Ad), homopolymer content (Hp), and total conversion (Ct)]. Under optimum conditions, the grafting parameters were achieved as 535, 98, 81, 2, and 102%, respectively. A mechanism for the free‐radical grafting was proposed. As empirical rates of polymerization and graft copolymerization were plotted against [AN] and [Ce⁴⁺]^1/2, the experimental kinetic data displayed a good match to a reported rate statement. The overall activation energy for the graft copolymerization was determined to be 44.9 kJ/mol. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2048–2054, 2003     

A study on cytocompatible poly(chitosan-g-l-lactic acid)

A novel cytocompatible graft copolymer of chitosan and l-lactic acid (CL) was prepared by grafting l-lactic acid onto the amino groups in chitosan without a catalyst. The structures of the CL graft copolymers were characterized by FTIR, ¹³C-NMR and X-ray measurements. Degree of substitution and side-chain length were evaluated from salicylaldehyde and elemental analysis. The tensile strength and water uptake of the CL copolymers films were investigated as a function of feed ratio of LA/CS. The influence of pH on the swelling behavior of the copolymer films was determined and interpreted. Fibroblast culture was performed to evaluate cell proliferation on the copolymers films. The results showed that the cell growth rate on the copolymers films is faster than chitosan obviously.     

Graft-copolymerization of methylacrylic acid onto hydroxypropyl chitosan

Summary In order to study the graft modification of chitosan derivatives, hydroxypropyl chitosan (HPCTS) was prepared and characterized by FTIR, ¹H NMR, and elemental analysis Methylacrylic acid (MAA) was grafted onto HPCTS in an aqueous solution using ammonium persuffate (APS) as an initiator. Evidence of grafting was obtained by comparison of FTIR spectra of HPCTS and the grafted copolymer as well as solubility characteristics of the products. Variations of grafting percentage and grafting efficiency with reaction time, temperature, concentraton of initiator and monomer had been investigated. Received: 25 Febuary 2002/Revised version: 7 July 2002/Accepted: 12 July 2002     

Surface grafting of polymers onto aramid powder: graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface of aramid powder

The radical graft polymerization of vinyl monomers onto the surface of aramid powder, i.e., poly(p-phenylene terephthalamide) powder, initiated by azo groups introduced onto the surface was investigated. The introduction of azo groups onto the aramid surface was achieved by the reaction of surface acyl chloride groups, which were introduced by the treatment of aramid powder with adipoyl dichloride, with 2,2′-azobis[2-(2-imidazolyn-2-yl)propane] in the presence of pyridine: the amount of azo groups thus introduced onto the surface was determined to be 0.57 mmol/g by elemental analysis. It was found that the polymerizations of methyl methacrylate (MMA) and styrene were successfully initiated by the azo groups on the surface and that the corresponding polymers were grafted onto the surface. The percentage of surface grafting of polystyrene and poly(methyl methacrylate) (PMMA) increased up to 37.6 and 26.5%, respectively. Thermogravimetric analysis of polymer surface-grafted aramid powder confirmed that the grafting of polymers is limited on the surface. The polymerization rate was found to bear a first-order dependence on the concentration of aramid powder having azo groups. This suggests that in graft polymerization, unimolecular termination preferentially proceeds.     

Drug‐release behavior of chitosan‐g‐poly(vinyl alcohol) copolymer matrix

Chitosan‐g‐poly(vinyl alcohol) (PVA) copolymers with different grafting percent were prepared by grafting water‐soluble PVA onto chitosan. The drug‐release behavior was studied using the chitosan‐g‐PVA copolymer matrix containing prednisolone in a drug‐delivery system under various conditions. The relationship between the amount of the released drug and the square root of time was linear. From this result, the drug‐release behavior through the chitosan‐g‐PVA copolymer matrix is shown to be consistent with Higuchi's diffusion model. The drug‐release apparent constant (K_H) was slightly decreased at pH 1.2, but increased at pH 7.4 and 10 according to the increasing PVA grafting percent. Also, K_H was decreased by heat treatment and crosslinking. The drug release behavior of the chitosan‐g‐PVA copolymer matrix was able to be controlled by the PVA grafting percent, heat treatment, or crosslinking and was also less affected by the pH values than was the chitosan matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 458–464, 1999     

Grafting onto wool

Summary In order to ascertain the role of -SH groups in graft copolymerization of vinyl monomers onto Himachali wool fiber, an attempt has been made to graft copolymerize ethylacrylate (EA) onto reduced wool, in the presence of cerie sulfate (CS) as redox initiator in aqueous medium. Reduction of wool was carried out with thioglycolic acid (TGA) in aqueous solution. Percentage of grafting and percent efficiency were determined as functions of (a) Concentration of initiator (CS), (b) Concentration of monomer (EA), (c) Concentration of Sulfuric acid, (d) Time and (e) Temperature. Reduction of wool does not promote grafting of EA. The unreduced wool during ceric ion-initiated grafting of EA was reported earlier from this laboratory to produce more grafting. In ceric ion-initiated grafting of vinyl monomer onto wool, -SH groups do not play significant role. A plausible mechanism of grafting of EA onto reduced wool in the presence of ceric ion initiator has been suggested.     

Nanocomposites Based on Chitosan-Graft-Poly(N-Vinyl-2-Pyrrolidone): Synthesis,Characterization, and Biological Activity

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange between Na⁺-MMT and N-octyl-N-vinyl-2-pyrrolidonium bromide. Chitosan graft copolymer nanocomposites were synthesized by grafting N-vinyl-2-pyrrolidone onto chitosan in aqueous acetic acid in the presence of OMMT using free radical polymerization. The chemical structures were verified by FTIR. Scanning electron microscopy showed a surface roughness for chitosan graft nanocomposites. Wide-angle X-ray diffraction confirmed the intercalation of grafted chitosan chains between OMMT galleries. Thermogravimetric analysis indicated that the thermal stability of grafted chitosan was enhanced by OMMT incorporation. Preliminary studies showed that the nanocomposites exhibited antimicrobial activity compared with chitosan graft copolymer.     

Regiospecific Grafting of Chitosan Oligomers Brushes onto Silicon Wafers

The functionalization of surfaces using chitosan oligomers is of great interest for a wide range of applications in biomaterial and biomedical fields, as chitosan oligomers can provide various functional properties including biocompatibility, wetting, adhesion, and antibacterial activity. In this study, an innovative process for the regiospecific chemical grafting of reducing-end-modified chitosan oligomers brushes onto silicon wafers is described. Chitosan oligomers (COS) with well-defined structural parameters (average DP ~19 and DA ~0%) and bearing a 2,5-anhydro-d-mannofuranose (amf) unit at the reducing end were obtained via nitrous acid depolymerization of chitosan. After a silanization step where silicon wafers were modified with aromatic amine derivatives, grafting conditions were studied to optimize the reductive amination between aldehydes of amf-terminated COS and aromatic amines of silicon wafers. Functionalized surfaces were fully characterized by AFM, ATR-FTIR, ellipsometry, contact angle measurement, and ToF-SIMS techniques. Smooth surfaces were obtained with a COS layer about 3 nm thick and contact angle values between 72° and 76°. Furthermore, it was shown that the addition of the reducing agent NaBH₃CN could positively improve the COS grafting density and/or led to a better stability of the covalent grafting to hydrolysis. Finally, this study also showed that this grafting process is also efficient for chitosan oligomers of higher DA (i.e., ~21%).