Grafted Carboxymethyl Chitosan Research Articles

Preparation of pH-sensitive carboxymethyl chitosan nanoparticles loaded with ginsenoside Rb1 and evaluation of drug release in vitro

Oral absorption of ginsenoside Rb1 (Rb1) is often hindered by the gastrointestinal tract. Carboxymethyl chitosan deoxycholic acid loaded with ginsenoside Rb1 nanoparticles (CMDA@Rb1-NPs), were prepared as a delivery system using a self-assembly technique with amphipathic deoxycholic acid grafted carboxymethyl chitosan as the carrier, which improved the stability and embedding rate of Rb1. In addition, the CMDA@Rb1-NPs was encapsulated with sodium alginate by ion crosslinking method with additional layer (CMDAlg@Rb1-NPs). Scanning electron microscopy showed that the nanoparticles were spherical, evenly distributed, smooth and without obvious adhesion. By evaluating drug loading, entrapment efficiency, the encapsulation efficiency of Rb1 increased from 60.07 % to 72.14 % after grafting deoxycholic acid improvement and optimization. In vitro release results showed that the cumulative release of Rb1 by CMDAlg-NPs showed a pH dependent effect, which was <10 % in simulated gastric juice with pH 1.2, completely released with pH 7.4 for about 48 h. In addition, Rb1 and CMDAlg@Rb1-NPs had inhibitory effects on A549 cells, and the inhibitory effect of CMDAlg@Rb1-NPs was better. Therefore, all results indicated that CMDA/Alg@Rb1 nanoparticles might be a novel drug delivery system to improve the stability and embedding rate of Rb1, and has the potential to be applied in oral pharmaceutical preparations.

Protamine-grafted carboxymethyl chitosan based hydrogel with adhesive and long-term antibacterial properties for hemostasis and skin wound healing

In this study, we developed a tissue-adhesive and long-term antibacterial hydrogel consisting of protamine (PRTM) grafted carboxymethyl chitosan (CMC) (PCMC), catechol groups modified CMC (DCMC), and oxidized hyaluronic acid (OHA), named DCMC-OHA-PCMC. According to the antibacterial experiments, the PCMC-treated groups showed obvious and long-lasting inhibition zones against E. coli (and S. aureus), and the corresponding diameters varied from 10.1 mm (and 15.3 mm) on day 1 to 9.8 mm (and 15.3 mm) on day 7. The DCMC-OHA-PCMC hydrogel treated groups also exhibited durable antibacterial ability against E. coli (and S. aureus), and the antibacterial rates changed from 99.3 ± 0.21 % (and 99.6 ± 0.36 %) on day 1 to 76.2 ± 1.74 % (and 84.2 ± 1.11 %) on day 5. Apart from good mechanical and tissue adhesion properties, the hydrogel had excellent hemostatic ability mainly because of the grafted positive-charged PRTM. As the animal assay results showed, the hydrogel was conducive to promoting the deposition of new collagen (0.84 ± 0.03), the regeneration of epidermis (98.91 ± 6.99 μm) and wound closure in the process of wound repairing. In conclusion, the presented outcomes underline the prospective potential of the multifunctional CMC-based hydrogel for applications in wound dressings.

Preparation and evaluation of a novel chlorine dioxide preservative based on citric acid grafted carboxymethyl chitosan

Instrument-free chlorine dioxide (ClO2) preservative for fruit and vegetable has gained great attention due to its convenience and safety. In this study, a series of carboxymethyl chitosan (CMC) with citric acid (CA) substituents were synthesized, characterized, and further used to prepare a novel ClO2 slow-releasing preservative for longan. UV–Vis and FT-IR spectra revealed that CMC-CA#1–3 were successfully prepared. Further potentiometric titration showed that the mass ratios of CA grafted in CMC-CA#1–3 were 0.18:1, 0.42:1, and 0.42:1, respectively. The composition and concentration of ClO2 slow-releasing preservative were optimized, and the best formulation was as follows: NaClO2:CMC-CA#2:Na2SO4:starch = 3:2:1:1. The maximum ClO2 release time of this preservative reached >240 h at 5–25 °C, and the maximum release rate always occurred at 12–36 h. Longan treated with 0.15–1.2 g ClO2 preservative had significantly (p < 0.05) higher L* and a* values but lower respiration rate and total microbial colony counts than the CK group (0 g ClO2 preservative). After 17 days of storage, longan treated with 0.3 g ClO2 preservative had the highest L* value of 47.47 and lowest respiration rate of 34.42 mg·kg−1·h−1, showing the best pericarp color and pulp quality. This study provided a safe, effective, and simple solution for longan preservation.

Facile preparation of polyphenol-crosslinked chitosan-based hydrogels for cutaneous wound repair

The design and facile preparation of the smart hydrogel wound dressings with inherent excellent antioxidant and antibacterial capacity to effectively promote wound healing processes is highly desirable in clinical applications. Herein, a series of multifunctional hydrogels were prepared by the dynamic Schiff base and boronate ester crosslinking among phenylboronic acid (PBA) grafted carboxymethyl chitosan (CMCS), polyphenols and Cu2+-crosslinked polyphenol nanoparticles (CuNPs). The dynamic crosslinking bonds endowed hydrogels with excellent self-healing and degradable properties. Three polyphenols including tannic acid (TA), oligomeric proanthocyanidins (OPC) and (−)-epigallocatechin-3-O-gallate (EGCG) contributed to the outstanding antibacterial and antioxidant abilities of these hydrogels. The tissue adhesive capacity of hydrogels gave them good hemostatic effect. Through a full-thickness skin defect model of mice, these biocompatible hydrogels could accelerate wound healing processes by promoting granulation tissue formation, collagen deposition, M2 macrophage polarization and cytokine secretion, demonstrating that these natural-derived hydrogels with inherent physiological properties and low-cost preparation approaches could be promising dressing materials.

Enzymatic one-pot preparation of carboxylmethyl chitosan-based hydrogel with inherent antioxidant and antibacterial properties for accelerating wound healing

Facile preparation of multifunctional hydrogel wound dressings with inherent versatile properties is highly desirable in practical healthcare. Here, a biocompatible hydrogel was designed and fabricated via mild enzymatic crosslinking and polymerization. We first designed an enzymatic system containing horseradish peroxidase (HRP), H2O2, and the macromolecular initiator—acetoacetyl polyvinyl alcohol (PVA-ACAC), which can generate active PVA-ACAC carbon radicals via HRP-mediated oxidation by H2O2. Trimethylammonium chloride (Q), methacryloyl (MA) and phenol (Ph)-grafted carboxymethyl chitosan (Ph-QCMCS-MA) was then synthesized. HRP catalyzes the oxidation of phenol groups to achieve the fast phenol crosslinking, and PVA-ACAC carbon radicals initiate the polymerization of MA groups simultaneously, finally obtaining the target PPQM gel. The quaternary ammonium and phenol groups endow the PPQM gel with excellent antibacterial and antioxidant properties, respectively. This multifunctional hydrogel, which has additional adhesive and hemostatic properties, could promote wound healing processes in an in vivo full-thickness skin defect experiment by reducing the generation of pro-inflammatory cytokines (IL-6) and upregulating anti-inflammatory factors (IL-10) and angiogenesis-related cytokines (VEGF and α-SMA). As a result, it could be used as competitive wound dressings.

Synthesis and characterization of protocatechuic acid grafted carboxymethyl chitosan with oxidized sodium alginate hydrogel through the Schiff's base reaction

Excessive accumulation of free radicals is closely related to the occurrence and development of various neurodegenerative diseases. In this study, a novel protocatechuic acid grafted carboxymethyl chitosan with oxidized sodium alginate (PCA-g-CMCS/OSA) hydrogel was developed to maintain the oxidation-antioxidation balance activities. By optimizing the pH-soluble range (pH > 6.4) of CMCS, PCA was grafted onto CMCS skeleton via EDC/NHS, and then conjugated with aldehyde group of OSA to form Schiff's base hydrogel at physiological temperature. The gelation time can be adjusted rapidly within 1–3 min by controlling the content of OSA. The shaped hydrogel exhibited porous network structure with high porosity (>90 %), swelling ratio (2000–3000 %) and rheological property, which is beneficial to cell growth and proliferation. The conjugates preserved excellent DPPH and ABTS radicals scavenging abilities and adequate biodegradability within 5 weeks. Moreover, with the release of PCA monomer due to degradation of the PCA-g-CMCS/OSA, the hydrogel also exhibited excellent biocompatibility and protective effect on H2O2-induced oxidative damage in PC12 cells. These results suggested that the PCA-g-CMCS/OSA hydrogel would appear to be a more attractive candidate for potential biomedical applications such as antioxidant drug release and tissue engineering implant material.

Mussel-Inspired Carboxymethyl Chitosan Hydrogel Coating of Titanium Alloy with Antibacterial and Bioactive Properties.

Infection-related titanium implant failure rates remain exceedingly high in the clinic. Functional surface coating represents a very promising strategy to improve the antibacterial and bioactive properties of titanium alloy implants. Here, we describe a novel bioactive surface coating that consists of a mussel-inspired carboxymethyl chitosan hydrogel loaded with silver nanoparticles (AgNPs) to enhance the bioactive properties of the titanium alloy. The preparation of hydrogel is based on gallic acid grafted carboxymethyl chitosan (CMCS-GA) catalyzed by DMTMM (4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride). To build a firm bonding between the hydrogel and titanium alloy plate, a polydopamine layer was introduced onto the surface of the titanium alloy. With HRP/H2O2 catalysis, CMCS-GA can simply form a firm gel layer on the titanium alloy plate through the catechol groups. The surface properties of titanium alloy were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and water contact angle. Silver nanoparticles were loaded into the gel layer by in situ reduction to enhance the antibacterial properties. In vitro antibacterial and cell viability experiments showed that the AgNPs-loaded Ti-gel possesses excellent antibacterial properties and did not affect the proliferation of rabbit mesenchymal stem cells (MSCs).

Fabrication and characterization of β-cyclodextrin-epichlorohydrin grafted carboxymethyl chitosan for improving the stability of Cyanidin-3-glucoside

Cyanidin-3-glucoside (C3G), an anthocyanin constituent of fruits and vegetables. It has been proven to possess numerous health benefits with no side effects. However, the poor stability of C3G is an intractable property that limits its application. Hence, the aim of this study is to improve the stability of C3G through the formation of well dispersed nanoparticles. In this study, C3G loaded β-CD-EP-CMC nanoparticles exhibited nearly spherical with good disperse and homogeneous morphology. Results also indicated that the nanoparticles formation of grafting of C3G to β-CD-EP-CMC could significantly improve the stability of C3G to against thermal or light degradation. Collectively, current results strongly aligned with the prospective purpose that the grafting of C3G to β-CD-EP-CMC nanoparticles could be treated as an effective approach for improving the stability. This study opens a new avenue for the utilization and development of novel wall materials β-CD-EP-CMC in C3G associated nutraceutical.

1-MT grafted carboxymethyl chitosan and its nanoparticles: Preparation, characterization and evaluation

This work aims to synthesize two novel 1-MT (1-Methyl-DL-tryptophan) grafted CMCS (carboxymethyl chitosan) polymer prodrugs CMCS-amido-1-MT and CMCS-ester-1-MT, and to further manufacture their nanoparticles for potential biomedical applications. The polymeric prodrugs are prepared by three-step chemical synthesis. The chemical structure of drugs is confirmed by FTIR and 1H-NMR. The drug loadings of the CMCS-amido-1-MT NPs and CMCS-ester-1-MT NPs are 11.43% and 10.18%, respectively. The surface morphology of the nanoparticles is spherical or nearly spherical, while the surface is smooth and the size distribution is uniform. The average particle size is both about 200 nm, while the polydispersity index is both about 0.15. The nanoparticles have a negative charge on the surface. The particle size and its distribution change little, when the two nanoparticles are tested in the simulated blood pH environment for 7 days. However, only the CMCS-ester-1-MT nanoparticles are pH-sensitive. The cell toxicity of the CMCS-ester-1-MT nanoparticles and the original drug are both in a dose- and time-dependent manner, while the nanoparticles enter cells by endocytosis. In ECA109 cells, the CMCS-ester-1-MT nanoparticles and the original drug both induce the apoptosis. CMCS-ester-1-MT NPs can activate the ATF4/CHOP pathway in endoplasmic reticulum stress, and achieve cancer suppression through mitochondrial-related apoptosis.

Photo-induced programmable degradation of carboxymethyl chitosan-based hydrogels

Hydrogels are widely used in the biomedical field, due to their high similarity to native extracellular matrix (ECM). Most responsive hydrogels could only passively receive stimuli and independently change their properties. In this study, a photosensitive o-nitrobenzyl (NB) ester linker of polyethylene glycol (PEG) with maleimido (Mal) as terminal groups (PEG-NB-Mal) and a 5-methylfurfuryl (mF) grafted carboxymethyl chitosan (CMCS) derivative (CMCS-mF) were synthesized and used to prepare functional hydrogels via Diels-Alder (DA) reactions. The hydrogel exhibited programmable degradation properties after sequential exposure to UV light and acid treatments. It can maintain high integrity upon the single stimuli, the cascade acid and UV light treatments or the cascade UV light and alkaline treatments. Moreover, the hydrogel exhibited well controlled release profile of rhodamine B (RB). In summary, such CMCS-based hydrogels show great potential in biomedical applications. In addition, the usage of photo-induced cascade reaction in sequential degradation hydrogels can be extended to design other types of programmable smart materials.

Preparation, characterization and antioxidant activity of protocatechuic acid grafted carboxymethyl chitosan and its hydrogel

In this study, protocatechuic acid (PCA) was grafted onto carboxymethyl chitosan (CMCS) via EDC/NHS to improve the antioxidant effect. The grafting ratio of PCA-g-CMCS conjugates could be controlled by adjusting the pH value and feed ratio of raw materials. The conjugates exhibited similar pH sensitivity to CMCS and showed dramatic enhancements of DPPH and ABTS radicals scavenging activities, total antioxidant capacity, reducing power, and Fe2+-chelating activity. Three-dimensional porous PCA-g-CMCS hydrogel was prepared by lyophilization and secondary cross-linking. The shaped hydrogel preserved its antioxidant activity, and the sustained release of PCA-containing degraded fragment from biodegradable hydrogel could be achieved with the aid of lysozyme in vitro (15 days). PCA-g-CMCS hydrogel also showed excellent biocompatibility and protective effect on H2O2-induced oxidative damage in SH-SY5Y cells. These results suggested that PCA-g-CMCS conjugates and its hydrogel would appear to be a promising oxidation-resistant material for applications such as drug release and tissue engineering.

Carboxymethyl-chitosan-modified carbon nanotubes have sensitive CO2-responsive dispersion in water

In this study, we grafted carboxymethyl chitosan (CMC) onto carbon nanotubes (CNTs), demonstrating that the CMC-grafted CNTs (CNT-g-CMCs) can disperse or aggregate in water in response to the bubbling of CO2. The CO2-switchable dispersion and aggregation of CNT-g-CMCs depend on the relative amounts of COOH to NH2 in CMC. With similar amounts of COOH and NH2 in CMC, the CNT-g-CMCs are well dispersed in water at pH 10 and exhibit no phase changes in response to the bubbling of CO2. With a higher amount of COOH than NH2 in CMC, the CNT-g-CMC dispersion in water at pH 10 becomes sensitively aggregated in response to 1 min of CO2 bubbling, but reverts to good dispersion with bubbling of N2 after 10 min. This newly developed CNT-g-CMC system with a novel CO2-responsive amphiphilic feature provides an environmentally friendly way of dispersing or aggregating CNTs in an aqueous solution without using acids and bases.

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.

Carboxymethyl β-cyclodextrin grafted carboxymethyl chitosan hydrogel-based microparticles for oral insulin delivery

This study was aimed at utilizing polysaccharides for the development of effective hydrogel microparticles for oral insulin delivery that has a controlled, and sustained release to enhance paracellular transcellular absorption. Carboxymethyl β-cyclodextrin grafted carboxymethyl chitosan hydrogels (CMCD-g-CMCs) were prepared from carboxymethyl β-cyclodextrin (CMCD) and carboxymethyl chitosan (CMC) using a water-soluble carbodiimide as a crosslinker in the presence of N-hydroxysuccinimide. After synthesis, the hydrogel structures were determined via FT-IR and XRD analyses. The porous structure of hydrogels was confirmed by SEM observations and swelling behaviours. The insulin release behaviours were found to betriggered by pH in vitro. Results showed that insulin was successfully retained inside the hydrogels in the gastric environment and slowly released following passage to intestinal conditions. The stability of the secondary structure of insulin was studied by dichroism circular (CD) and fluorescence (FL) spectrophotometer measurement. There was no significant difference in the secondary structure between the native and released insulin. In vitro studies revealed that the hydrogel microparticles exhibited non-cytotoxicity and were transported across the Caco-2 cell monolayers mainly via the paracellular pathway. In order to examine the effectiveness of hydrogel-based sustained release microparticles in delivering insulin in vivo, we administered different insulin-loaded hydrogel microparticles to diabetic mice. In these studies, we found that the insulin-loaded hydrogel microparticles provided a significant and sustained (ranging from 6 h to 12 h) reduction in the blood glucose levels of diabetic mice compared with subcutaneous injection. Overall, these findings demonstrate that CMCD-g-CMCs may be a promising protein carrier for use in oral drug delivery.

Graft modification of carboxymethyl chitosan with styrene and its biological applications

BackgroundCarboxymethyl chitosan (CMCh) is a water-soluble chitosan derivative and it has been widely used in biomedical applications due to its unique properties. Modification of CMCh by graft copolymerization with different monomers is done in order to enhance its applications.ResultsGraft copolymerization of styrene (S) onto CMCh using ammonium persulfate (APS) as initiator was successfully done with optimization of grafting parameters. The new materials were prepared in nano size. The antibacterial activities against Streptococcus pneumonia (RCMB 010010), Staphylococcus aureus (RCMB 010028) as Gram-positive and Escherichia coli (RCMB 010052) as Gram-negative bacteria and antifungal activity against Aspergillus fumigates (RCMB 02568), Candida albicans (RCMB 05036), Syncephalastrum racemosum (RCMB 05922), and Geotricum candidum (RCMB 05097) were examined using the diffusion agar technique. Also, the cytotoxicity effect against mammalian cell lines (MCF-7cells (human breast cancer) and HTC-116 (colon carcinoma)) was evaluated.ConclusionsThe obtained data proved that grafted carboxymethyl chitosan with styrene (CMCh-g-S) shows better antimicrobial activities, while parent carboxymethyl chitosan showed higher activity than new grafted materials. Also the nano scaled grafted CMCh showed higher activities than grafted carboxymetyl chitosan in macro scale.

Optimisation of orthophosphate and turbidity removal using an amphoteric chitosan-based flocculant–ferric chloride coagulant system

Environmental contextThe fate and build-up of phosphate nutrients in aquatic environments is an urgent environmental problem affecting global water security. This study, guided by a statistical design method, optimises the flocculation properties of a biopolymer for removing orthophosphate from water. This improved technology has potential widespread applications for removal of orthophosphate from water and wastewater treatment systems. AbstractA coagulation-flocculation process was employed to remove turbidity (Ti) and orthophosphate (Pi) in aqueous media using a ferric chloride (FeCl3) and a grafted carboxymethyl chitosan (CMC) flocculant system. The amphoteric CMC-CTA flocculant was synthesised by grafting 3-chloro-2-hydroxypropyl trimethylammonium chloride (CTA) onto the biopolymer backbone of CMC. Here, CMC-CTA denotes the covalent grafting of CTA onto CMC. Optimisation of the variables for Pi and Ti removal was conducted using a jar test system based on the experimental design obtained from the response surface methodology (RSM). The Box–Behnken design was used to evaluate the individual and interactive effects of four independent variables: CMC-CTA dosage, FeCl3 dosage, pH and settling time. The RSM analysis showed that the experimental data followed a quadratic polynomial model with the following optimal conditions: [CMC-CTA]=3.0mgL−1, [FeCl3]=10.0mgL−1, pH 6.8 and settling time=35min. Optimum conditions led to a Pi removal of 96.4% and turbidity removal of 96.7% based on the RSM optimisation, in good agreement with experimental results with an initial concentration of 30.0mg PiL−1. The coagulation-flocculation process is characterised by a combination of electrostatic charge neutralisation, polymer bridging and a polymer adsorption mechanism.

ε-Poly(L-lysine)-based Hydrogels with Fast-acting and Prolonged Antibacterial Activities

Bacterial infections and the associated morbidity and mortality due to bacterial pathogens in wounds and medical implants have been increasing as most of current coatings cannot fulfill all the requirements including excellent intrinsically antibacterial activity, low cytotoxicity, and favorable physical properties. Herein, we present a kind of antibacterial hydrogel based on e-poly(L-lysine) (EPL) grafted carboxymethyl chitosan (CMC-g-EPL) as the inherently antibacterial matrix and the surplus EPL as highly efficient antimicrobial agent. Such hydrogels possess tunable swelling abilities with water absorption percentages of 800%-2000% and modulus varying from 10 kPa to 100 kPa, and exhibit two-stage excellent antibacterial behavior. First, the free EPL can be released from the hydrogel network for quick and highly efficient bacteria killing with 99.99% of efficacy; second, the grafted EPL endows hydrogel matrix with prolonged intrinsically antibacterial activity, especially when most of free EPL is released from the hydrogel. Overall, we provide a new insight for preparing highly effective antibacterial hydrogels.

Electrochemical and surface analyses of X70 steel corrosion in simulated acid pickling medium: Effect of poly (N-vinyl imidazole) grafted carboxymethyl chitosan additive

In this work, water-soluble poly (N-vinyl imidazole) grafted carboxymethyl chitosan composite (CMCh-g-PVI) has been synthesized from chitosan, characterized and deployed as a corrosion inhibitor for API X70 in 1 M HCl. CMCh-g-PVI composite significantly reduced the corrosion of X70 steel when compared with equimolar concentration of chitosan and carboxymethyl chitosan in the same medium due to the formation of stable protective polymeric films on the metal surface. This was confirmed by means of scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. In depth electrochemical corrosion study was conducted after chloride treatment using potentiodynamic polarization and electrochemical impedance spectroscopic techniques on precleaned substrates. This polymer composite may have a future as an efficient ingredient in corrosion inhibitor formulations for metal surface treatments.

Synthesis and In Vitro Characterization of Carboxymethyl Chitosan-CBA-Doxorubicin Conjugate Nanoparticles as pH-Sensitive Drug Delivery Systems

Compared to the conventional anti-cancer drugs, the nano-drug delivery systems (NDDS) shows a comparatively ideal therapeutic efficacy ascribing their high tumor-target capacity and efficient drug release ability. In this study, a novel macromolecular prodrug conjugate was designed and developed that is passively triggered by the acidic environment of the tumor cells and can release doxorubicin (Dox). The susceptibility of the system to the acidic environment is due to the acid volatile Schiff base covalent bond between grafted carboxymethyl chitosan (CMCs) and Dox. The chemical structure of the finalized system was characterized by 1H-NMR spectroscopy. Because of the hydrophobicity of the Dox and the hydrophilicity of the CMCs, the amphipathic polymeric drug conjugates can self-assemble into the nanoparticles in aqueous solution. The morphology and size of the nanoparticles were observed with TEM (transmission electron microscopy) and DLS (dynamic light scattering). The in vitro drug release studies demonstrated that the drug release rate of the prodrug were visibly higher in acidic conditions (pH 5.0) compared to higher pHs like 6.5 and 7.4. DLS results showed that the mean size of the prodrug nanoparticles increased as the pH of the solution decreased from 7.4 to 6.5 and 5.0. Furthermore, the cell counting kit-8 (CCK-8) assays showed that the polymeric drug nanoparticles had a cytotoxic effect on SKOV3 ovarian cancer cells while the segments of the DDS revealed comparatively lower cytotoxic effect. Moreover, confocal laser scanning microscopy (CLSM) showed that the prodrug could efficiently deliver and release Dox in the nuclei of the cancer cells while this was not observed for the Dox pure drug. These results proved that the carboxymethyl chitosan-CBA-Doxorubicin NPs have superior stabilities, low toxicities, proper sizes, and enhanced curable efficiency for in vitro controlled release. Thus, this pH-sensitive prodrug could be a potential treatment for cancer therapy in the near future.

Preparation, characterization and antioxidant activity of silk peptides grafted carboxymethyl chitosan

Free radicals are closely related to the occurrence and development of aging, cancer and inflammation, the ability to scavenge free radicals is an important indicator of the antioxidant activity. In this study, we prepared a water soluble, free radical scavenging and biocompatible copolymer for regenerative therapy. Carboxymethyl chitosan (CMC) was modified with silk peptide (SP) by microbial transglutaminase (MTGase), FT-IR and NMR spectroscopy were used to confirm the successful grafting of SP to CMC. The degree of substitution was determined by ultraviolet spectrophotometry. In vitro antioxidant activity assays demonstrated that, within the scope of study the highest scavenging activity of DPPH was 24.86%, 91% of hydroxyl radical and 36.8% of H2O2. Finally, no relevant cytotoxicity against NIH-3T3 mouse fibroblasts was found for the copolymers. Briefly, our results suggested the potential application of CMC-SP as an antioxidant for regenerative therapy.