Higher Different Degrees Of Substitution Research Articles

OSA modified porous starch acts as an efficient carrier for loading and sustainedly releasing naringin

To select an efficient carrier for loading and sustainedly releasing naringin (NAR), complexes of porous starch (PS) and NAR (PS-NAR) as well as those of octenyl succinic anhydride (OSA) esterified PS and NAR (OSAPS-NAR) with different degree of substitution (DS) were prepared by an ultrasonic method with an ethanol solution. The micro-morphological features, structural and thermal properties of complexes and their constituents were characterized, and in vitro release rate and kinetic of NAR from complexes were investigated. The findings revealed that NAR was successfully loaded in PS/OSAPS in an amorphous form, and the NAR's loading efficiency improved as DS increased, reaching 86.85 % at DS 0.0427. NAR cumulative release rate from the complexes in simulated digestion fluids was much higher than that of free (unloaded) NAR, but decreased as DS increased. NAR's in vitro release from complexes mainly depended on the carrier rather than NAR itself, and OSAPS with higher DS had stronger protection and slower release effect on NAR. The results would provide a new means for starch-based carrier construction to develop an efficient delivery and sustainedly releasing system for NAR, thus broadening the application ranges both for modified starch and citrus flavonoids such as NAR.

Improving the emulsifying capacity of brewers' spent grain arabinoxylan by carboxymethylation

Arabinoxylan derived from brewers' spent grain was carboxymethylated, and the emulsifying capacity of carboxymethylated arabinoxylans (CMAX) with different degrees of substitution (DS) was investigated. Results showed that carboxymethylation greatly enhanced the emulsifying capacity and emulsion stability of CMAX compared to the initial arabinoxylan. CMAX developed decreased ζ-potential, higher hydrophilicity, and improved interfacial adsorption capacity. Consequently, the denser and stronger interface on the oil droplet was formed, and the stabilizing mechanism was altered. Moreover, CMAX with lower DS could effectively stabilize emulsions during storage at a concentration of 0.5 % and pH between 6 and 7. Higher DS, however, led to poorer emulsion stability and greater flocculation as a result of the fragile interface formed by excess intermolecular ionic force. The research found CMAX potential in emulsion stabilizing and further applications in food processing.

Effect of sulfated/carboxylated cellulose nanocrystals with different degrees of substitution on the morphology and electrochemical performance of polypyrrole electrodes

As a result of different extraction methods, CNCs bear different surface groups with different degrees of substitution (DS), which may affect the electrode properties when incorporated as the reinforcing template in conducting polymer electrodes. After depositing polypyrrole (PPy) electrodes with different CNCs as dopants, we found that the PPy/CNCs electrode structure and electrochemical performance were sensitive to the DS of CNCs sulfate groups, while variation in the DS of carboxylates did not have any significant effect. PPy/CNCs electrodes deposited with carboxylated CNCs and a low sulfate group DS showed a porous and interconnected structure, while PPy/CNCs electrodes deposited with carboxylated CNCs with a high sulfate DS had a dense structure. Higher areal capacitance, higher rate capability, and smaller resistance were achieved with PPy/CNCs electrodes deposited using CNCs bearing carboxylates and a low DS of sulfate groups on CNCs. Cycling studies showed that porous electrodes reduced their charge storage capacity over 3000 cycles, however, dense PPy electrodes prepared using high-sulfate DS CNCs increased their charge storage capacity by 715% (from 0.15 to 1.07 F cm−2) over the first 1200 cycles showing opening of the structure and better electrolyte perfusion. This capacitance then stayed constant for at least another 1700 cycles.

Construction of butyric acid modified porous starch for stabilizing pickering emulsions: Encapsulation of paclitaxel

In this study, butyric acid (BA) modified porous starch (PS) was fabricated to stabilize Pickering emulsions and probe its application for encapsulating paclitaxel. BA modified PS with different degree of substitution (DS) were synthesized by esterification successfully. The structural properties were determined by N2 adsorption, SEM, 1H NMR, FT-IR and XRD analysis, confirming the porosity and ester linkages. Besides, BA-PS was used as stabilizers to produce Pickering emulsions encapsulating paclitaxel. Properties of emulsions, including emulsification index, particle size and microstructure, were evaluated. Findings indicated that emulsions produced by BA-PS with higher DS had the smaller particle size and better stability. After encapsulating paclitaxel, encapsulation efficiency, retention rate and release performance during digestion were further characterized. The results demonstrated that the emulsifying and sustained release capacity were significantly improved using higher substituted BA-PS as stabilizers. As emulsifiers, BA-PS thus has a potential application in food industry.

Development of New Alkylated Carrageenan Derivatives: Physicochemical, Rheological, and Emulsification Properties Assessment

In this research, amphiphilic derivatives of kappa carrageenan (KC) were synthesized by hydrophobic modification with an alkyl halide (1-Octyl chloride). Three hydrophobic polymers with different degrees of substitution (DS) were obtained by the Williamson etherification reaction in an alkaline medium. The effect of the molar ratio (R = reagent/polymer) on the DS was investigated at different ratios (1, 2, and 3). The KC derivatives (KCRs) were characterized by different techniques such as FT-IR, 1H-NMR, X-ray Diffraction, Scanning electron microscopy, and a rheological assessment. The FT-IR and 1HNMR analyses confirmed the binding of the hydrophobic groups onto the KC molecule. The degrees of substitution calculated by 1H-NMR demonstrated that the derivative KCR3 (0.68) presented a higher degree of substitution compared to KCR1(0.45) and KCR2 (0.53). The XRD and SEM analyses revealed that the alkaline etherification conditions did not alter the morphological and crystallographic properties, as well as the rheological behavior of the obtained derivatives. The amphiphilic character of the KCRs was investigated using a conductivity method which revealed that the molecular aggregation occurred above the critical aggregation concentration (CAC). Decreasing CAC values of 0.15% (KCR1), 0.11% (KCR2) and 0.08% (KCR3)with the degree of substitution (DS) were found. Furthermore, KCR’s derivatives greatly improved the stability of oil/water emulsions as the droplet size decreased with increasing DS. The derivative (KCR3) with higher DS, showed a greater amphiphilic character, and improved emulsifying power.

Tartary Buckwheat Starch Modified with Octenyl Succinic Anhydride for Stabilization of Pickering Nanoemulsions.

In this study, Tartary buckwheat starch was modified to different degrees of substitution (DS) with octenyl succinate anhydride (OS-TBS) in order to explore its potential for stabilizing Pickering nanoemulsions. OS-TBS was prepared by reacting Tartary buckwheat starch with 3, 5 or 7% (w/v) octenyl succinate in an alkaline aqueous solution at pH 8.5. Fourier-transform infrared spectroscopy gave peaks at 1726 cm-1 (C=O) and 1573 cm-1 (RCOO-), indicating the formation of OS-TBS. We further studied the physicochemical properties of the modified starch as well as its emulsification capacity. As the DS with octenyl succinate anhydride increased, the amylose content and gelatinization temperature of the OS-TBS decreased, while its solubility increased. In contrast to the original Tartary buckwheat starch, OS-TBS showed higher surface hydrophobicity, and its particles were more uniform in size and its emulsification stability was better. Higher DS with octenyl succinate led to better emulsification. OS-TBS efficiently stabilized O/W Pickering nanoemulsions and the average particle size of the emulsion was maintained at 300-400 nm for nanodroplets. Taken together, these results suggest that OS-TBS might serve as an excellent stabilizer for nanoscale Pickering emulsions. This study may suggest and expand the use of Tartary buckwheat starch in nanoscale Pickering emulsions in various industrial processes.

Structural changes of butyrylated lotus seed starch and its impact on the gut microbiota of rat in vitro fermentation

Starch acylated with short-chain fatty acids (SCFAs), as type 4 resistant starch, can transport specific SCFAs to the colon and promote intestinal health. The objective was to investigate the effect of butyrylated lotus seed starches (LSBs) with different degrees of substitution (DS) on gut microbiota and butyrate production in vitro fermentation and to construct the relationship with its structural changes. The results of substrate structure change showed that the amorphous region of LSBs hydrolyzed firstly, the content of the subcrystalline region increased, and the molecular weight decreased. LSBs with higher DS had better fermentation characteristics, and more butyric acid production. A certain abundance of beneficial gut microbiota was significantly promoted. The Lotus seed resistant starch (LRS) group produced butyrate mainly by promoting the proliferation of Romboutsia. LSBs with low and medium DS mainly produced butyric acid by promoting Clostridium. LSBs with high DS produced butyric acid by promoting Lactobacillus, and Ruminococcaceae, by inhibiting Enterococcus, and Bacteroides. The study clarified the mechanism of butyric acid production was LSB's targeting the gut microbiota, which provided a scientific basis for the development of new prebiotics with high butyric acid production.

Acetylation modification improved the physicochemical properties of xyloglucan from tamarind seeds

Acetylation modification was conducted to improve the water-solubility and solution properties of xyloglucan from tamarind seeds (TSX). Three acetylated TSX with different degree of substitution (DS) were successfully prepared, and their structure and molecular parameters were investigated by FT-IR, NMR, and high-performance size exclusion chromatography (HPSEC). Further, the effects of acetylation on the thermal stability, solubility, and rheological properties of TSX were studied. Results showed that acetyl groups were mainly substituted at the O-6 position of terminal galactose with DS of 0.2, 0.47, and 0.36 for AC-2, AC-5, and AC-10, respectively. HPSEC analysis indicated that molecular weight of acetylated derivatives decreased slightly, and the solution conformation became more flexible as the DS increase. By comparing with TSX, the thermal stability, water-solubility, solution transmittance, and ζ-potential of acetylated TSX were significantly improved as the DS increase. In addition, rheological studies demonstrated that acetylation reduced the shear viscosity, but high DS of acetylation could induce the weak gelling property of TSX. In conclusion, acetylation modification could be applied to improve the physicochemical properties of TSX and promote its further application in food and pharmaceutical industries.

Freely Moldable Modified Starch as a Sustainable and Recyclable Plastic.

Efficiently preparing a starch-based plastic with moisture insensitivity and toughness is a challenge to improve the high-value utilization of polysaccharide resources. Herein, a sustainable, recyclable starch-based plastic was prepared in a facile and eco-friendly way. First, starch acetoacetate (SAA) with different degrees of substitution (DSs) was synthesized by transesterification. Then, the SAA film was obtained through a solvent-free hot-pressing method. Notably, SAA with different DSs exhibited various glass transition temperatures (109-140 °C), and SAA with high DS (>0.84) was insoluble even after boiling in water for 1 h. Also, the maximum fracture strength of SAA film up to 15.5 MPa and a maximum elongation at break up to 30% were reached . In addition, the starch-based plastic film retained the original mechanical properties after three cycles of hot processing. In consideration of the facile preparation process, this protocol provided a new avenue for developing sustainable and recyclable starch-based plastics.

Tailoring nanofibrillated cellulose through sonication and its potential use in molded pulp packaging

Nanofibrillated cellulose (NFC) was systematically tailored by ultrasonic-assisted esterification with lactic acid at different amplitudes and times, which led to modified NFC (mNFC) with different degrees of substitution (DS), between 0.21 and 0.55, as confirmed by titration, FTIR, and C13 NMR. A partial fragmentation and decrease in crystallinity of mNFC were revealed by TEM and XRD. To form molded pulp sheets, 5 wt% mNFC was added into a bagasse (BG) pulp slurry, then partially dewatered before hot-pressed. mNFC worked effectively as self-retention aid, partly solving the issue of drainage during sheet forming as commonly observed from unmodified NFC. The BG/mNFC (DS 0.55) sheet exhibited an enhancement in tensile properties. Water resistance and barrier performance of the current sheets were also evidently increased. The results suggested that the higher DS on mNFC can improve water resistance and mechanical properties, simultaneously overcoming drainage challenges in processing of molded pulp products.

Preparation and Characterization of Carboxymethylated and Cross-Linked Enset Starch as a Disintegrant in Tablets

Starch and modified starches have been commonly employed as excipient in pharmaceutical industry. The use of non-modified or “native” starch, However, is mostly confined due to limitation in several physicochemical properties. Cross-linked sodium carboxymethyl starch which is also known as sodium starch glycolate is extensively used in fast dissolving tablets to disperse the drugs within short span of time. In this study, enset starch was carboxymethylated and subsequently cross-linked. Carboxymethyl enset starch (CMES) was obtained by reacting enset starch and monochloroacetic acid (MCA) in the presence of sodium hydroxide. CMESs having different degree of substitution (DS) were cross-linked at variousconcentrations (2.5, 5 and 10% w/w) of sodium hexametaphosphate (SHMP) to provide sodium starch glycolate of enset starch (SSG-E). The fourier transform infrared (FTIR) spectra confirmed the presence of carboxymethylated group in the modified starch granules with new band at 1608.52 cm-1. This dually modified enset starch (SSG-E) was evaluated as a potential disintegrant in paracetamol tablets in comparison with commercially available sodium starch glycolate, Disegel. Carboxymethylation was significantly influenced by reaction medium, reaction temperature and reaction time (p < 0.05). CMES with higher DS (0.437 ± 0.03) exhibited higher peak viscosity than CMES with lower DS (0.224 ± 0.01). Despite exhibiting greater swelling power, CMES showed significantly lower pasting viscosity compared to the native starch (p < 0.05). At 2.5% SHMP, the dually modified starch (SSG-E) exhibited significant increase in swelling but its rate of water-uptake was lower than that of Disegel. As the SHMP concentration wasincreased from 2.5 to 5%, the swelling power decreased significantly (p < 0.05). When the concentration was increased to 10% the swelling power increased significantly (p < 0.05). At 2.5% SHMP concentration SSG-E showed a viscosity comparable to that of CMES. As the concentration of SHMP increased to 5 and to 10% w/w, significant decrease in viscosity (p < 0.05) was observed. Compared to the native enset starch (NES), the solubility of SSG-E was more than 4-fold, but its viscosity was much lower than that of CMESs. The SSG-E exhibited lower moisture sorption than CMES but higher sorption than NES. SSG-E showed good flowability, superior swelling power and solubility than NES. The disintegration time (DT) of paracetamol tablets containing SSG-E as a disintegrant was comparable to those tablets with similar concentration of Disegel. At 4% SSG-E, paracetamol tablets exhibited DT less than 1 min.
 Keywords: carboxymethylation, degree of cross-linking, enset starch, paracetamol tablets, sodium starch glycolate

Marine collagen peptide grafted carboxymethyl chitosan: Optimization preparation and coagulation evaluation

Uncontrolled bleeding has always been a sudden accident, which is the main cause of casualties in war trauma, emergency events and surgical operations. Rapid hemostatic materials can effectively reduce casualties and save lives. In this paper, marine collagen peptide grafted carboxymethyl chitosan (CMCS-MCP) was synthesized by 1-ethyl-(dimethylaminopropyl) carbodiimide (EDC)-mediated coupling reaction. To obtain CMCS-MCP conjugates with different degrees of substitution (DS), the reaction conditions were investigated by single-factor tests and optimized by response surface methodology. And the sponges of CMCS-MCP were prepared by freeze-thaw cycling and freeze-drying and characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), and X-ray diffraction (XRD). To evaluate the hemostatic properties of CMCS-MCP sponges, in vitro and in vivo hemostasis tests were carried out. The results showed that the optimum preparation conditions were the mass ratio of MCP to CMCS (MMCP/MCMCS) 6:1, reaction temperature 41 °C, and reaction time 16 h. And under which the DS of 58.86% was obtained. Structure analysis showed that MCP had been successfully grafted onto the CMCS molecular chain, and the CMCS-MCP sponges were of high porosity. In vitro and in vivo hemostasis tests showed that the CMCS-MCP sponges had significant procoagulant activities, especially the one with high DS of 58.86%. The hemostasis mechanism may be that the synergistic effects of MCP and CMCS accelerated coagulation through multiple approaches. The CMCS-MCP sponges give a new insight into biomedical hemostasis materials.

Preparation and properties of hydrophobic films based on acetylated broken-rice starch nanocrystals for slow protein delivery

Native and acetylated broken-rice starches (nanocrystals) with different degrees of substitution (DS) and their corresponding films were individually prepared, and the drug release profiles, weight loss, solubility and dispersion and surface morphology were comparatively studied. Bovine serum albumin (BSA) was used as a model drug. Acetylated native starch (ANS) DS 2.58, acetylated starch nanocrystals (ASN) DS 0.98, ASN DS 1.86, and ASN DS 2.72 were observed to be very soluble in chloroform. BSA was released rapidly from the native rice starch (NS) and ANS DS 2.58 films. ASN with high DS significantly slowed down the release of BSA from films, the percentages of BSA released from film ASN DS 2.72 only reached to 13% after 3.5 weeks release, and the release data followed Korsmeyer-Peppas equation. Further studies reveal that the particle size of ASN DS 2.72 was smallest, and the weight loss of ASN DS 2.72 film was lowest. The results demonstrate that acetylation and nanometer particle form of rice starch film can effectively retard protein drug release, and the prepared films based on ASN with high DS from broken rice may be suitable for the controlled protein delivery.

Fabrication and Evaluation of Cassava Starch Acetate Nanoparticles Loaded with Drugs of Various BCS Classes: Influence of Drug Solubility and Partition Coefficient

A successful fabrication of nanocarrier for drug delivery should yield nanoparticles (NPs) with suitable particle size and size distribution and provide high drug-loading capacity. Factors that influence these attributes include physicochemical properties of the drug, the nature of the nanocarrier, and processing variables, among others. The aim of this study was, therefore, to investigate the influence of solubility and partition coefficient of different drugs on the characteristics of starch-based NPs. Cassava starch was chemically modified by acetylation, at different degrees of substitution (DS) and characterized. The starch acetates (SAs) were then used for the preparation of drug-loaded NPs. Different model drugs: ibuprofen (BCS class II), acyclovir (BCS class III) and furosemide (BCS class IV) were incorporated into NPs using emulsification solvent evaporation technique. The effects of solubility and partition coefficient, and DS of SA on the properties of NPs, namely, size and size distribution, drug loading capacity (DL), encapsulation efficiency (EE) and in vitro release profile were investigated. The results showed that the DL and EE of ibuprofen and furosemide loaded starch acetate nanoparticles (SANPs) increased consistently with an increase in the DS of SA. On the contrary, DL and EE of acyclovir-loaded NPs decreased as DS of SA increased. Due to their poor solubility and high partition coefficient, the EEs of ibuprofen and furosemide in SANPs fabricated from SA with high DS were much greater than that of acyclovir. Furthermore, as DS of SA increased the cumulative release profile of Ibuprofen from SANPs was retarded whereas the release profile of acyclovir was enhanced. On the other hand, furosemide, the most lipophilic drug of all, exhibited lowest release profile over the study period of 8 h. In conclusion, along with the hydrophobic nature of SA, the DL, EE and drug release profile from SANPs depended on the solubility and partition coefficient of the incorporated drug molecule.

Nanocapsules of Sterculia striata acetylated polysaccharide as a potential monomeric amphotericin B delivery matrix.

Stable oil nanocapsules based on acetylated Sterculia striata polysaccharide (ASSP) were produced without the use of a surfactant, and derivatives of ASSP with four different degrees of substitution (DS) were synthesised. The data revealed that only derivatives with high DS were able to produce nanocapsules (NC), which exhibited monomodal size distribution profiles with a Z-average particle size, ζ-potential, and polydispersity index (PDI) that were dependent on ASSP DS and concentration. Nanocapsules were loaded with amphotericin B (AMB) with encapsulation efficiencies (EE%) that were dependent on drug and ASSP concentrations and DS. A maximum EE% value of 99.2% was achieved, and the loaded AMB was found to be in a monomeric form, even with a concentration one hundredfold higher than that usually observed for commercial AMB aqueous solutions. Loaded nanocapsules show an in vitro controlled release of AMB. As the monomeric AMB state decreased drug toxicity, ASSP nanocapsules loaded with AMB (NC1.68) have potential for use as a drug delivery system. AMB loaded NC 1.68 keeps its activity against 5 strains of Candida albicans tested.

Rheological and fracturing characteristics of a novel sulfonated hydroxypropyl guar gum

A series of sulfonated hydroxypropyl guar gum (SHG) samples with different degrees of substitution (DSs) were prepared, and the SHG solution and SHG fracturing fluid were prepared and analyzed. The SHG aqueous solutions with different DSs all exhibit shear thinning behavior, which is well correlated with the Ostwald-deWaele model. Owing to the electrostatic repulsion of SHG molecular chains, SHG solutions with a higher DS will exhibit weaker thixotropic performance and strong anti-salinity ability. In addition, the SHG fracturing fluids, which were formed by interactions between SHG and organic zirconium, exhibit good temperature- and shear-resistant properties, proppant suspension properties, and salt tolerance. Furthermore, SHG gel-breaking fluids show low interfacial and surface tensions, with low residue content and small core permeability damage. These results provide useful indicators for the applications of SHG in the oil field industry.

Cationic starch: Safe and economic harvesting flocculant for microalgal biomass and inhibiting E. coli growth

Cationized starch-based flocculation processes are the subject of increasing attention because of their non-toxicity, biodegradability and relatively low price synthesized. The study aimed to evaluate the flocculability of different cationic starches using different concentrations of glycidyltrimethylammonium chloride (GTAC) with different degree of substitution (DS) ranged from 0.13 to 0.57. Cationized starch were characterized using Fourier Transform Infrared (FTIR), scanning electron microscopy (SEM) and toxicity checked using experimental animal procedure. They were used in comparison with aluminum sulphate for harvesting microalgal biomass collected from high rate algal pond (HRAP) at Zenin wastewater treatment plant (WWTP), Giza, Egypt. Jar test showed that gradual increase of aluminum sulphate doses (50–400 mg/L) has reduced algal suspension consequently turbidity with accompanied pH decrease from 8.6 to 6.6. Cationic starch with low DS has shown efficiency as flocculants by reducing turbidity of algal suspension from 110 to ≈2 NTU by gradual increase from 10 to 60 mg/L without change in pH value. Fecal coliforms and E. coli were inhibited from 9.6 × 102 and 8.4 × 10 CFU/ml to non-detectable count. Cationic starch with high DS (0.57) has the least effect of algae harvesting and turbidity reduction that 40 NTU after increase the dose to 60 mg/L. Results showed that 10 mg of cationic starch (DS = 0.13) has achieved the same flocculation efficiency of 100 mg of aluminum sulphate. In conclusion, further investigation is required to increase the degree of substitution of cationic starch, consequently the flocculation efficiency might be improved.

Synthesis, thermal properties and cell-compatibility of photocrosslinked cinnamoyl-modified hydroxypropyl cellulose

Biocompatibility of cinnamoyl-modified carbohydrate materials is not well-known, while they are attracting attention as a photoreactive material. In order to investigate biocompatible properties of cinnamoyl-modified carbohydrate, hydroxypropyl cellulose (HPC) was reacted with cinnamoyl chloride to yield cinnamoyl-modified HPC (HPC-C) for a cell proliferation test. HPC-Cs with three different degrees of substitution (DS) were prepared by changing a feed ratio of cinnamoyl chloride to HPC. The DS of the products ranged from 1.3 to 3.0 per one hydroxylpropyl anhydroglucose unit. Thermal analysis using DSC and TGA showed that the HPC-C with higher DS has a glass transition temperature and higher thermal stability. Ultraviolet (UV) light was irradiated on the HPC-C thin films, and changes in the UV–vis spectrum of the films were examined. In the course of UV irradiation, the absorbance at 280 nm was reduced. Fibroblast cells were cultured on the photocrosslinked HPC-C films, and cell growth was examined. The cell proliferation test revealed that the photocrosslinked HPC-C films have good compatibility with fibroblast cells.

Homogeneous synthesis and characterization of chitosan ethers prepared in aqueous alkali/urea solutions

The etherification of chitosan dissolved in aqueous LiOH/KOH/urea solutions was conducted for the first time. The structure and solution properties of the chitosan ethers were characterized using FT-IR, NMR, SEC-LLS, elemental analysis, and ζ-potential measurement. Chitosan ethers with different degrees of substitution (DSs) were obtained by adjusting the molar ratio of the etherifying agent to N-acetylglucosamine unit (AGU) of chitosan. The total DS for methyl chitosan (MCh) increased from 1.17 to 2.25, and trimethyl chitosan (TMCh) was obtained with DSN-trimethyl as high as 0.48. The total DS for carboxymethyl chitosan (CMCh) was in the range 0.75–1.45. Both N-substitution and O-substitution were observed, and the OH groups at C-6 displayed relative higher reactivity than the OH groups at C-3. In comparison with the traditional methods and solvents, aqueous alkali/urea solutions proved to be a stable and more homogeneous medium for preparing chitosan ethers with higher DS through a one-step reaction.

N-[4-(N,N,N-trimethylammonium)benzyl]chitosan chloride: Synthesis, interaction with DNA and evaluation of transfection efficiency

А novel cationic chitosan derivative, N-[4-(N,N,N-trimethylammonium)benzyl]chitosan chloride (TMAB-CS), with different degrees of substitution (DS) was synthesized by a chemoselective interaction of 4-formyl-N,N,N-trimethylanilinium iodide with chitosan amino groups using a reductive amination method. Several factors (pH, reactant ratio, reaction time, and chitosan structure) were studied for their effects on the DS of the resulting TMAB-CS. The obtained derivatives were characterized by 1H NMR and FTIR spectroscopy. Turbidimetric titration showed enhanced solubility over a wide pH range even for low-substituted TMAB-CS. TMAB-CS provided strong DS-dependent binding of plasmid DNA. Dynamic light scattering measurements revealed the formation of stable polyplexes with hydrodynamic diameters of 200–300nm and ζ-potential of 20–30mV. TMAB-CS with relatively low DS (25%) demonstrated more pronounced transfection efficiency (up to 2000 cell/cm2) of plasmid DNA into the HEK293 cell line promoted by free TMAB-CS. The positive effects of lower DS can be related to a better polyplex dissociation within the cell. The cytotoxicity of TMAB-CS was comparable to that of the initial chitosan at concentrations up to 300ng/μL, even at high DS.