Variable Degree Of Substitution Research Articles

Reactive Nanoparticles Derived from Polysaccharide Phenyl Carbonates.

Polysaccharide (PS) based nanoparticles (NP) are of great interest for biomedical applications. A key challenge in this regard is the functionalization of these nanomaterials. The aim of the present work was the development of reactive PS-NP that can be coupled with an amino group containing compounds under mild aqueous conditions. A series of cellulose phenyl carbonates (CPC) and xylan phenyl carbonates (XPC) with variable degrees of substitution (DS) was obtained by homogeneous synthesis. The preparation of PS-NP by self-assembling of these hydrophobic derivatives was studied comprehensively. While CPC mostly formed macroscopic aggregates, XPC formed well-defined spherical NP with diameters around 100 to 200 nm that showed a pronounced long-term stability in water against both particle aggregation as well as cleavage of phenyl carbonate moieties. Using an amino group functionalized dye it was demonstrated that the novel XPC-NP are reactive towards amines. A simple coupling procedure was established that enables direct functionalization of the reactive NP in an aqueous dispersion. Finally, it was demonstrated that dye functionalized XPC-NP are non-cytotoxic and can be employed in advanced biomedical applications.

Green synthesis and characterization of carboxymethyl guar gum: Application in textile printing technology

AbstractThis study focusses on the synthesis of carboxymethyl guar gum (CMG) via monochloroacetic acid under alkaline conditions. The reaction conditions were also optimized during the course of experiment. Guar derivative with variable degree of substitution (DS) were prepared and were confirmed by Fourier transform infrared (FTIR) spectroscopy. The DS was determined quantitatively by titration method for each derivative. The synthesized guar gum derivatives, being the natural thickners, have been used in textile printing technology. Substituted guar gum has been proved environmental friendly thickener as compared to synthetic thickeners. Penetration properties, fixation ability, colour fastness, levelness and fabric handling was compared with alginate thickener (commercially available). Guar gum thickeners showed enhanced properties versus alginate thickener and can be used as an alternative to synthetic thickeners in view of its green, non-hazardous and economical derivatives. Guar gum is the outstanding natural thickener, stabilizer, gelling agent and could possibly be used in various industrial units including food, cosmetic, textile, oil fracturing and mining.

Physicochemical and disintegrant properties of sodium Carboxymethyl starch derived from Borassus aethiopum (Arecaceae) shoot

Sodium carboxymethyl starch (CMS) samples synthesized from an under-utilized shoot of Borassus aethiopum were characterized and compared with a commercial brand, sodium starch glycolate. Effects of carboxylation on the physicochemical properties of the samples were examined by FTIR, XRD and SEM techniques. The rheological, micromeritics and disintegrant properties of the samples were also examined. The CMS samples had variable degree of substitution (DS) with the lowest DS (0.11) comparable to sodium starch glycolate in terms of desirable micromeritics, rheological and disintegrant properties. FTIR and XRD established modification of the native starch by showing an intense band around 1588 cm−1 to 1608 cm−1 and reduction in the peak intensities for the CMS samples respectively. CMS with variable DS and desirable micromeritics and rheological properties for potential applications as excipients in biopolymer industries could be obtained from Borassus aethiopum shoots.

Deconstruction of Nordic hardwood in switchable ionic liquids and acylation of the dissolved cellulose

Nordic hardwood (Betula pendula) was fractionated in a batch autoclave equipped with a custom-made SpinChem® rotating bed reactor, at 120°C using CO2 and CS2-based switchable ionic liquids systems. Analyses of the non-dissolved wood after treatment showed that 64wt% of hemicelluloses and 70wt% of lignin were removed from the native wood. Long processing periods or successive short-time treatments using fresh SILs further decreased the amount of hemicelluloses and lignin in the non-dissolved fraction to 12 and 15wt%, respectively. The cellulose-rich fraction was partially dissolved in an organic superbase and an ionic liquid system for further derivatization. Homogeneous acylation of the dissolved cellulose in the presence or absence of catalyst resulted in cellulose acetates with variable degree of substitution (DS), depending on the treatment conditions. By varying the reaction conditions, the cellulose acetate with the desired DS could be obtained under mild conditions.

Investigation of Galactosylated Low Molecular Weight Chitosan-Coated Liposomes for Cancer Specific Drug Delivery

Purpose: To assess the hepatocyte targeting potential of galactosylated low molecular weight chitosan (Gal-LMWCs)-coated liposomes bearing doxorubicin hydrochloride (DOX).Methods: Chitosan (CS) was depolymerized and lactobionic acid (LA) containing a galactose group was coupled with low molecular weight chitosan (LMWC) using carbodiimide chemistry. Two types of galactosylated polymers with variable degree of substitution were synthesized. Liposomes were prepared using film casting method, coated with the synthesized polymers and characterized for vesicle shape and size, polydispersity, zeta potential, drug entrapment, coating efficiency, in vitro drug release and cytotoxicity on human hepatoma cell line (HepG2).Results: Coating efficiency was greater for the polymer with a lower degree of substitution. The liposomes formed were spherical in shape with a size range of 110 - 160 nm, drug entrapment of 92.14 - 96.37 % and zeta potential of 20.6 - 29.4 mV. Gal-LMWC(s)-coated liposomes exhibited a maximum of 65 % in vitro drug release in 24 h in a sustained fashion. The 50 % inhibitory concentration (IC50) values for liposomal formulations and drug solution were 2.81 and 5.98 μg/ml, respectively.Conclusion: Gal-LMWC (s) coated liposomes containing DOX that demonstrate targetability to human hepatocellular carcinoma cell line (in vitro) have been successfully developed.Keywords: Targeted delivery, Doxorubicin, Galactosylated, Chitosan, Hepatocellular, Carcinoma, Nanoparticles

Sulfated modification, characterization and antitumor activities of Radix hedysari polysaccharide

Sulfated modification of a polysaccharide obtained from Radix hedysari (RHP) was studied. Four sulfated derivatives (RHPS) with variable degrees of substitution (DS) were obtained by the chlorosulfonic acid method with ionic liquids (ILs) as solvent and 4-dimethylaminopyridine (DMAP) as catalyst. The structures of RHPS were characterized by FT-IR spectra and 13C NMR spectra, and the results indicated that the sulfated groups were modified mainly at the C-6 position and C-2 position. Four kinds of RHPS showed different DS ranging from 0.63 to 1.45, and different weight-average molecular mass (Mw) ranging from 60.8 to 71.1kDa with a little degradation. Compared with RHP, all of RHPS exhibited obvious antitumor activity on A549 cells and BGC-823 cells in vitro. However, they had no obvious influence on HEK293 cells, which indicated that they had low toxicity to normal cells. Flow cytometric studies indicated that the treatment of RHPS against A549 cells and BGC-823 cells could mediate the cell-cycle arrest in the G1 phase.

Phosphorylated modification and in vitro antioxidant activity of Radix Hedysari polysaccharide

Phosphorylated modification of a polysaccharide obtained from Radix Hedysari (RHP) was studied. Three phosphorylated polysaccharides (RHPP) with variable degrees of substitution (DS(p)) were obtained with 4-dimethylaminopyridine (DMAP) and N, N' Dicyclocarbodiimide (DCC) as catalyst. The structures of RHPP were characterized by FT-IR spectra and (13)C NMR spectra. Depending on different reaction time, RHPP showed different DS(p) ranging from 0.30 to 0.66, and different Mw ranging from 86.6 to 89.7KDa. Compared with RHP, RHPP exhibited superior antioxidant activities in vitro, which indicated that phosphorylated modification could enhance antioxidant activities of RHP. Furthermore, it was obvious that the DS(p) had a significant effect on the antioxidant activity.

Sulphated modification of a polysaccharide obtained from fresh persimmon (Diospyros kaki L.) fruit and antioxidant activities of the sulphated derivatives

Free radicals and other reactive oxygen species (ROS) are believed to play significant roles in ageing as well as in a number of degenerative or pathological diseases. This paper reports the preparation, characterisation and potential antioxidant activity of a type of chemically sulphated polysaccharide isolated from fresh persimmon (Diospyros kaki L.) fruit. Three sulphated derivatives with variable degrees of substitution (0.8, 1.7 and 2.5) were obtained by the chlorosulphonic acid–pyridine method. The sulphated derivatives all showed dose-dependent reducing power and free radical scavenging effect of 1,1-dipheny-l-2-picrylhydrazyl, superoxide anion and hydroxyl. Our results showed that the sulphated modification of polysaccharides significantly increased their antioxidant activities and may be an effective way to prepare these valuable derivatives.

Modification, characterization and structure–anticoagulant activity relationships of persimmon polysaccharides

Six chemical sulfated polysaccharide derivatives (PFP-S) with variable degree of substitution (DS) and molecular weights (Mw) were prepared from the fresh persimmon fruits by chlorosulfonic acid-pyridine and ultrasonic degradation methods, and the effectiveness of the reaction was monitored by the DS, FT-IR and ζ-potential analysis. The sulfation modification might cause advanced structure change to the samples, the SEM of PFP-S exhibited a polyphasic convoluted structure. Results of anticoagulant activities showed that PFP-S could prolong activated partial thromboplastin time (APTT) and thrombin time (TT), but not prothrombin time (PT), and the anticoagulant activity improved with the increasing DS and decreasing Mw.

Development and In Vitro Characterization of Galactosylated Low Molecular Weight Chitosan Nanoparticles Bearing Doxorubicin

The aim of the present research was to evaluate the potential of galactosylated low molecular weight chitosan (Gal-LMWC) nanoparticles bearing positively charged anticancer, doxorubicin (DOX) for hepatocyte targeting. The chitosan from crab shell was depolymerized, and the lactobionic acid was coupled with LMWC using carbodiimide chemistry. The depolymerized and galactosylated polymers were characterized. Two types of Gal-LMWC(s) with variable degree of substitution were employed to prepare the nanoparticles using ionotropic gelation with pentasodium tripolyphosphate anions. Factors affecting nanoparticles formation were discussed. The nanoparticles were characterized by transmission electron microscopy and photon correlation spectroscopy and found to be spherical in the size range 106-320 nm. Relatively higher percent DOX entrapment was obtained for Gal-LMWC(s) nanoparticles than for LMWC nanoparticles. A further increase in drug entrapment was found with nanoparticles prepared by Gal-LMWC with higher degree of substitution. A hypothesis which correlates the ionic concentration of DOX in nanoparticles preparation medium and percent DOX entrapment in cationic polymer has been proposed to explain the enhanced DOX entrapment. In-vitro drug release study demonstrated an initial burst release followed by a sustained release. The targeting potential of the prepared nanoparticles was assessed by in vitro cytotoxicity study using the human hepatocellular carcinoma cell line (HepG(2)) expressing the ASGP receptors on their surfaces. The enthusiastic results showed the feasibility of Gal-LMWC(s) to entrap the cationic DOX and targeting potential of developed Gal-LMWC(s) nanoparticles to HepG(2) cell line.

Scanning Probe Microscopy Method for Nanosuspension Stabilizer Selection

An atomic force microscopy (AFM) method was successfully developed and utilized for investigating the interaction of polymeric stabilizers with ibuprofen to determine their suitability for the preparation and stabilization of ibuprofen nanosuspensions. Images obtained clearly showed that HPMC and HPC interacted strongly with the ibuprofen resulting in extensive surface adsorption, confirming their suitability for ibuprofen nanosuspension preparation. In addition, differences in the morphology of the adsorbed HPMC and HPC molecules were observed, which may be attributed to their variable degree of substitution. Consistent with their poor performance in stabilizing the ibuprofen nanosuspensions, images obtained with PVP and Poloxamer's depicted inadequate adsorption on the ibuprofen surface. Careful analysis of the AFM images and the ibuprofen crystal structure gave valuable insight into the success of top-down processing for the preparation of nanosuspensions as compared to bottom-up processing. On the basis of the relationship observed between nanosuspension stability and adsorption characteristics of specific polymers, such AFM studies can aid in the selection of suitable nanosuspension stabilizers. This method provides the basis for a scientific rationale for nanosuspension stabilizer selection rather than the trial and error method which is currently practiced.

Sulfation of a polysaccharide obtained from Phellinus ribis and potential biological activities of the sulfated derivatives

The paper reports the preparation, characterization and potential biological activities of a chemically sulfated polysaccharide isolated from Phellinus ribis. Four sulfated derivatives (PRP-SI–IV) with variable degrees of substitution were obtained by the chlorosulfonic acid method, without degradation of the polysaccharide (PRP). The sulfate groups were not regularly distributed along the polysaccharide chain with a multiple substitution pattern as determined by 13C NMR. The sulfated derivatives except for PRP-SI showed significant inhibition effects on HepG2 cells in comparison with the native non-sulfated polysaccharide (PRP). All sulfated derivatives could block new angiogenic vessel formation in zebrafish assay, however, the effects were less than PRP.

Novel Poly(p-xylylenes): Thin Films with Tailored Chemical and Optical Properties

Chemical vapor deposition polymerization is used to prepare submicron thin films of poly(p-xylylenes) with distinct chemical and optical properties. The polymers are prepared from 13 different [2.2]paracyclophanes with variable degrees of substitution and functionalities including hydroxy, methoxy, amino, triflate, or trifluoroacetyl groups. The chemical composition of the poly(p-xylylenes) is in good accordance with expected chemical structures as confirmed by X-ray photoelectron spectroscopy, microanalysis, and reflection−absorption infrared spectroscopy. For all polymers, basic optical properties, such as extraordinary and ordinary indices of refraction, are reported and reveal optical anisotropy of the coatings. Experimental data correlate well with data generated by a uniaxial Cauchy dispersion model. Furthermore, a distinct correlation between refractive indices and the electronic properties of the functional groups is observed. Similarly, optical birefringence depends on the nature of the functiona...

Biofunctional polystyrene derivatives exhibit a high affinity for the epidermal growth factor-receptor (EGF-R): Part I

Insoluble sulfamide of amino acid polystyrene derivatives interact with solubilized epidermal growth factor receptor (EGF-R). The choice of the different amino acids substituted on the polystyrene macromolecular chain is governed by the nature of the peptide involved in the binding of EGF on its receptor. This binding has a hydrophobic character with two affinity constants for EGF-R. Some of the amino acids involved in this fixation are known: Leu 44, Tyr 29, Leu 26, Ileu 23, Tyr 22, Val 19, Met 21. Therefore, statistic biofunctional polystyrene derivatives were synthesized with variable degrees of substitution by leucine and/or benzylamine or tyrosine. The random substitution may lead to complex sites that would interact with EGF-R like EGF. Indeed, among the studied copolymers, sulfamide of leucine 15% and 44% or tyrosine (35%) polystyrene derivatives exhibit a strong affinity for high and/or low affinity solubilized EGF-R and could be held as EGF-like polymers (affinity constants ranging from 2×109 to 2×1011 m −1)

Infrared and X‐Ray Analysis of Hydroxyethyl Starch

AbstractThe effect ob substituted groups in hydroxyethyl starches with variable degrees of substitution on the conformation of starch molecules was investigated by the infrared and X‐ray analysis. The highest substitution with alkoxyl groups caused the shifting of the equatorial anomeric groups of glucose units to the axial position due to strain effect in the rings of monomers. The X‐ray analysis showed that the volume of unit cell of starch was increased 4.3% with the highest substitution of corn starch. This improved the penetration of dye molecules in the coating of textiles.

Cartilage proteoglycans. Structure and heterogeneity of the protein core and the effects of specific protein modifications on the binding to hyaluronate.

Purified proteoglycans extracted from pig laryngeal cartilage in 0.15 M-NaCl and 4 M-guanidinium chloride were analysed and their amino acid compositions determined. Selective modification of amino acid residues on the protein core confirmed that binding to hyaluronate was a function of the protein core, and was dependent on disulphide bridges, intact arginine and tryptophan residues, and epsilon-amino groups of lysine. Fluorescence measurement suggested that tryptophan was not involved in direct subsite interactions with the hyaluronate. The polydispersity in size and heterogeneity in composition of the aggregating proteoglycan was compatible with a structure based on a protein core containing a globular hyaluronate-binding region and an extended region of variable length also containing a variable degree of substitution with chondroitin sulphate chains. The non-aggregated proteoglycan extracted preferentially in 0.15 M-NaCl, which was unable to bind to hyaluronate, contained less cysteine and tryptophan than did other aggregating proteoglycans and may be deficient in the hyaluronate-binding region. Its small average size and low protein and keratan sulphate contents suggest that it may be a fragment of the chondroitin sulphate-bearing region of aggregating proteoglycan produced by proteolytic cleavage of newly synthesized molecules before their secretion from the cell.