On the Mechanism of Genipin Binding to Primary Amines in Lactose-Modified Chitosan at Neutral pH

The present manuscript deals with the elucidation of the mechanism of genipin binding by primary amines at neutral pH. UV-VIS and CD measurements both in the presence of oxygen and in oxygen-depleted conditions, combined with computational analyses, led to propose a novel mechanism for the formation of genipin derivatives. The indications collected with chiral and achiral primary amines allowed interpreting the genipin binding to a lactose-modified chitosan (CTL or Chitlac), which is soluble at all pH values. Two types of reaction and their kinetics were found in the presence of oxygen: (i) an interchain reticulation, which involves two genipin molecules and two polysaccharide chains, and (ii) a binding of one genipin molecule to the polymer chain without chain-chain reticulation. The latter evolves in additional interchain cross-links, leading to the formation of the well-known blue iridoid-derivatives.

Enhancement of the permeability and activities of epigallocatechin gallate by quaternary ammonium chitosan/fucoidan nanoparticles

Epigallocatechin gallate (EGCG) has many biological functions; however, the use of EGCG in biomedical and food industries was limited due to its poor oral absorption and high susceptibility to degradation. In this study, a mucoadhesive quaternary chitosan was synthesized and combined with fucoidan (FD) (or depolymerized lower molecular weight fucoidan, LMWF) to prepare EGCG-loaded nanoparticles, which extended EGCG release over 300 min and enhanced the transepithelial permeation of EGCG using Caco-2 cells as a model for intestinal absorption. The nanoparticls protected EGCG against degradation in phosphate buffer (pH 6.8) and the remaining EGCG was 1.7-folds higher than the control (EGCG alone). The additive effects of EGCG combined with FD or LMWF in the nanoparticles increased the DPPH radical scavenging activity and the enzyme inhibitory activity against α-amylase (2.82-4.92 fold increase) and α-glucosidase (1.35-1.67 fold increase), while quaternary chitosan helped to enhance the antibacterial effect of EGCG.

Unraveling the Structural Landscape of Chitosan-Based Heparan Sulfate Mimics Binding to Growth Factors: Deciphering Structural Determinants for Optimal Activity

Chitosan sulfates have demonstrated the ability to mimic heparan sulfate (HS) function. In this context, it is crucial to understand how the specific structural properties of HS domains determine their functionalities and biological activities. In this study, several HS-mimicking chitosans have been prepared to mimic the structure of HS domains that have proved to be functionally significant in cell processes. The results presented herein are in concordance with the hypothesis that sulfated chitosan-growth factor (GF) interactions are controlled by a combination of two effects: the electrostatic interactions and the conformational adaptation of the polysaccharide. Thus, we found that highly charged O-sulfated S-CS and S-DCS polysaccharides with a low degree of contraction interacted more strongly with GFs than N-sulfated N-DCS, with a higher degree of contraction and a low charge. Finally, the evidence gathered suggests that N-DCS would be able to bind to an allosteric zone and is likely to enhance GF signaling activity. This is because the bound protein remains able to bind to its cognate receptor, promoting an effect on cell proliferation as has been shown for PC12 cells. However, S-CS and S-DCS would sequester the protein, decreasing the GF signaling activity by depleting the protein or locally blocking its active site.

Ionotropic Gelation of Chitosan for Next-Generation Composite Proton Conducting Flat Structures

(1) Background: Ionotropic gelation of cost-effective and eco-friendly biopolymer chitosan (Chit) is a novel and promising approach to the one-step synthesis of proton-conducting fuel cell bio-membranes.The method discovered by the author in 2011 and subsequently drowned among very few papers. This work aimed to relaunch this method through clear and effective communication of new unpublished results emphasizing the key aspects of this topic for successful dissemination of the results and significant future developments. (2) Methods and results: The mechanism of in-situ ionotropic gelation of Chit on an alumina substrate by phosphotungtate anions (PWA3-) was discussed and analyzed. The study sheds light on the effect of prolonged post-treatment in phosphotungstic acid (PWA) solution on the obtained chitosan/phosphotungstate (Chit-PWA) flat structures. Methods used included combined structural (XRD), thermal-gravimetric (DTG), electrochemical (in-situ EIS), compositional (EDX),morphological analysis (SEM), as well as the performances in a low temperature H2/O2 fuel cell(4) Conclusions: This contribution discloses novel possibilities aimed at increasing the impact of ionotropic gelation of chitosan on the scientific community working on the synthesis of novel proton conductive bio-composite membranes and structures.

Glycosylated-Chitosan Derivatives: A Systematic Review

Chitosan derivatives, and more specifically, glycosylated derivatives, are nowadays attracting much attention within the scientific community due to the fact that this set of engineered polysaccharides finds application in different sectors, spanning from food to the biomedical field. Overcoming chitosan (physical) limitations or grafting biological relevant molecules, to mention a few, represent two cardinal strategies to modify parent biopolymer; thereby, synthetizing high added value polysaccharides. The present review is focused on the introduction of oligosaccharide side chains on the backbone of chitosan. The synthetic aspects and the effect on physical-chemical properties of such modifications are discussed. Finally, examples of potential applications in biomaterials design and drug delivery of these novel modified chitosans are disclosed.

Facile fabrication of wood-inspired aerogel from chitosan for efficient removal of oil from Water

Aerogels that derived from biomass have long been attractive as absorbents for oil clean-up. However, it remains a significant challenge to prepare fully bio-based oil absorbents that combines fast oil/water separation capacity, adequate mechanical robustness and easy recyclability through green and facile strategy. Inspired by the fascinating structure of wood, here we report a highly porous and anisotropic bio-based aerogel by taking advantage of the directional freezing technology, followed by a freeze-drying and silylation process. Due to the directional growth of ice crystals along the vertical direction, a special spring like morphology was obtained, which is mainly composed of well aligned low-tortuosity channels that seamlessly connected to bottom layer. Superior mechanical properties that allow for high mechanical compressing and fast elastic recovery were consequently acquired. Moreover, the silylated CS aerogel displays a rather high oil absorption capacity of 63 g g^-1, together with excellent recyclability via simple hand squeezing. By virtue of such hierarchical morphology, a device that could continuously separate oil from water was successfully designed. Given the natural abundance of raw material as well as the easy processability, this work would lay solid foundation for further fabrication of bio-based oil absorbents toward low-cost, high-performance and large-scale commodities.

Cationic chitosan derivatives as potential antifungals: A review of structural optimization and applications

The increasing resistance of pathogen fungi poses a global public concern. There are several limitations in current antifungals, including few available fungicides, severe toxicity of some fungicides, and drug resistance. Therefore, there is an urgent need to develop new antifungals with novel targets. Chitosan has been recognized as a potential antifungal substance due to its good biocompatibility, biodegradability, non-toxicity, and availability in abundance, but its applications are hampered by the low charge density results in low solubility at physiological pH. It is believed that enhancing the positive charge density of chitosan may be the most effective approach to improve both its solubility and antifungal activity. Hence, this review mainly focuses on the structural optimization strategy of cationic chitosan and the potential antifungal applications. This review also assesses and comments on the challenges, shortcomings, and prospect of cationic chitosan derivatives as antifungal therapy.

Preparation And Antibacterial Effects Of Carboxymethyl Chitosan-Modified Photo-Responsive Camellia Sapogenin Derivative Cationic Liposomes

BACKGROUND

Bacterial resistance to antibiotics is a persistent and intractable problem. The sapogenin isolated from the seeds of Camellia oleifera can inhibit antibiotic-resistant bacteria after structural modification.

PURPOSE

This study aims to improve sapogenin's antibacterial activity and avoid bacterial resistance based on nano-preparation with photo responsiveness.

METHODS

The liposome shell material of carboxymethyl chitosan-phosphatidyl ethanolamine (CMC-PE) was prepared using amidation reaction, and photo-responsive cationic (PCC) liposomes containing Camellia sapogenin derivative (CSD) and photosensitizer pheophorbide-a were prepared by film dispersion method. Encapsulation efficiency, drug loading, zeta potential, particle size distribution, morphology and stability of the PCC liposomes were determined by HPLC, particle size analyzer, transmission electron microscopy (TEM) and fluorescence microscopy. Photo-responsive release of CSD in the PCC liposomes was determined by laser (0.5 mW/cm2) at 665 nm. Antibacterial activity of the PCC liposomes with or without irradiation was analyzed by MIC50, MBC, MBIC50, and bacterial morphology to evaluate the antibacterial effects on amoxicillin resistant Escherichia coli and Staphylococcus aureus.

RESULTS

Size distribution, zeta potential, encapsulation efficiency and drug loading of the PCC liposomes were 189.23 ± 2.12 nm, 18.80 ± 1.57 mV, 83.52 ± 1.53% and 2.83 ± 0.05%, respectively. The PCC liposomes had higher storage stability and gastrointestinal stability, and no obvious hemolytic toxicity to rabbit red blood cells and no cytotoxicity after incubation with Hela cells. The photosensitizer pheophorbide-a was uniformly dispersed in the phospholipid layer of the PCC liposomes and increased the CSD release after irradiation. The PCC liposomes could bind to bacteria and impaired their morphology and structure, and had significant bactericidal effect on amoxicillin resistant E. coli and S. aureus.

CONCLUSION

The photo-responsive PCC liposomes are efficient antibacterial agents for avoidance of bacterial resistance against antibiotics.

Synthesis of N,O-Carboxymethyated chitosan and its application in the development of acyclovir loaded nanoparticles

Objective of the study was to perform a physico-chemical modification of low molecular weight chitosan (CTS) followed by its use in the formulation of nanoparticles carrier of Acyclovir (ACY). Modified polymer was used to develop ACY loaded nanoparticles in order to achieve optimal response and to minimize toxic effects of ACY. CTS were dissolved in varying concentrations of potassium hydroxide solution to synthesize N, O-carboxymethylated chitosan (N,O-CMC). Synthesized derivative was further processed with different concentrations of TPP (0.3%, 0.5% and 1%) and ACY to prepare nanoparticles. N,O-CMC and prepared formulations were characterized by Fourier transform infrared spectroscopy (FTIR). Furthermore, scanning electron microscopy (SEM) was done to observe the surface morphology, zeta size and zeta potential for particle size analysis, in vitro dissolution to find out the release pattern and kinetic modeling was done to observe the release mechanism and pattern of the drug. Result of FTIR was evidence of polymer modification when compared with chitosan which was the parent standard polymer as well as compatibility of the ingredients. Results of zeta size analysis have confirmed that the particles are of nanosized (109-125nm). Good controlled 98.77% over release of 24 h of formulation B observed in phosphate buffer of intestinal pH. Higuchi model with Fickian diffusion was dominating due to the formation of N, O-CMC complex which created smooth surface. All the results were significant and within the p value of 0.001. Conclusively, the modification of the CTS was in nanoparticle showed good sustained release.

Vitamin E succinate-grafted-chitosan/chitosan oligosaccharide mixed micelles loaded with C-DMSA for Hg2+ detection and detoxification in rat liver

AIM

To determine whether the use of a mixed polymeric micelle delivery system based on vitamin E succinate (VES)-grafted-chitosan oligosaccharide (CSO)/VES-grafted-chitosan (CS) mixed micelles (VES-g-CSO/VES-g-CS MM) enhances the delivery of C-DMSA, a theranostic fluorescent probe, for Hg2+ detection and detoxification in vitro and in vivo.

METHODS

Mixed micelles self-assembled from two polymers, VES-g-CSO and VES-g-CS, were used to load C-DMSA and afforded C-DMSA@VES-g-CSO/VES-g-CS MM for cell and in vivo applications. Fluorescence microscopy was used to assess C-DMSA cellular uptake and Hg2+ detection in L929 cells. C-DMSA@VES-g-CSO/VES-g-CS MM was then administered intravenously. Hg2+ detection was assessed by fluorescence microscopy in terms of bio-distribution while detoxification efficacy in Hg2+-poisoned rat models was evaluated in terms of mercury contents in blood and in liver.

RESULTS

The C-DMSA loaded mixed micelles, C-DMSA@VES-g-CSO/VES-g-CS MM, significantly enhanced cellular uptake and detoxification efficacy of C-DMSA in Hg2+ pretreated human L929 cells. Evidence from the reduction of liver coefficient, mercury contents in liver and blood, alanine transaminase and aspartate transaminase activities in Hg2+ poisoned SD rats treated with the mixed micelles strongly supported that the micelles were effective for Hg2+ detoxification in vivo. Furthermore, ex vivo fluorescence imaging experiments also supported enhanced Hg2+ detection in rat liver.

CONCLUSION

The mixed polymeric micelle delivery system could significantly enhance cell uptake and efficacy of a theranostic probe for Hg2+ detection and detoxification treatment in vitro and in vivo. Moreover, this nanoparticle drug delivery system could achieve targeted detection and detoxification in liver.

Conversion of Chitin to Defined Chitosan Oligomers: Current Status and Future Prospects

Chitin is an abundant polysaccharide primarily produced as an industrial waste stream during the processing of crustaceans. Despite the limited applications of chitin, there is interest from the medical, agrochemical, food and cosmetic industries because it can be converted into chitosan and partially acetylated chitosan oligomers (COS). These molecules have various useful properties, including antimicrobial and anti-inflammatory activities. The chemical production of COS is environmentally hazardous and it is difficult to control the degree of polymerization and acetylation. These issues can be addressed by using specific enzymes, particularly chitinases, chitosanases and chitin deacetylases, which yield better-defined chitosan and COS mixtures. In this review, we summarize recent chemical and enzymatic approaches for the production of chitosan and COS. We also discuss a design-of-experiments approach for process optimization that could help to enhance enzymatic processes in terms of product yield and product characteristics. This may allow the production of novel COS structures with unique functional properties to further expand the applications of these diverse bioactive molecules.

Novel purine thioglycoside analogs: synthesis, nanoformulation and biological evaluation in in vitro human liver and breast cancer models

Background: A series of novel pyrazolopyrimidine and pyrazololpyridine thioglycosides were synthesized and confirmed via their spectral analyses. Purpose: To evaluate the effect of these anti-metabolic compounds against proliferation of Huh-7 and Mcf-7 as in vitro models of human liver and breast cancers, respectively. Vero cells were used as an example of normal green monkey kidney cells. Methods: The most promising compound was subjected to a nanoformulation by its encapsulation into chitosan nanoparticles to increase its anti-cancerous activity. Nanoformulation was confirmed by TEM and FT-IR to ensure encapsulation and screened for their cytotoxicity against Huh-7 and Mcf-7 cells using MTT colorimetric assay and morphological examination. Genotoxic effect was performed by cellular DNA fragmentation assay. Simulated CompuSyn software (linear interaction effect) was conducted to predict the possible synergistic effect of nanocomposite as anticancerous activity. Apoptotic effect was further analyzed by detection of apoptotic proteins using ELISA assay. Results: The nano preparation was successfully prepared by encapsulation of compound 14 into chitosan nanoparticles, controlled to a size at 105 nm and zeta charges at 40.2 mV. Treatment of Huh-7 and Mcf-7 showed that compound 14 was the most cytotoxic compound on both cancer cell lines where IC50 was 24.59 (9.836 μg/mL) and 12.203 (4.8812 μg/mL) on Huh-7 and Mcf-7 respectively. But IC50 of the nano preparation was 37.19 and 30.68 μg/mL on Huh-7 and Mcf-7, respectively, indicating its aggressiveness on human breast cancer cells as confirmed by DNA fragmentation assay and theoretically by CompuSyn tool. Conclusion: A novel series of pyrazolopyrimidine thioglycosides and pyrazolopyridine thioglycosides were synthesized. Nanoformulation of compound 14 into chitosan nanoparticles demonstrated anticancer activity and can be used as a drug delivery system, but further studies are still required.

New Materials Based on Cationic Porphyrins Conjugated to Chitosan or Titanium Dioxide: Synthesis, Characterization and Antimicrobial Efficacy

The post-functionalization of 5,10,15-tris(1-methylpyridinium-4-yl)-20-(pentafluorophenyl)porphyrin tri-iodide, known as a highly efficient photosensitizer (PS) for antimicrobial photodynamic therapy (aPDT), in the presence of 3- or 4-mercaptobenzoic acid, afforded two new tricationic porphyrins with adequate carboxylic pending groups to be immobilized on chitosan or titanium oxide. The structural characterization of the newly obtained materials confirmed the success of the porphyrin immobilization on the solid supports. The photophysical properties and the antimicrobial photodynamic efficacy of the non-immobilized porphyrins and of the new conjugates were evaluated. The results showed that the position of the carboxyl group in the mercapto units or the absence of these substituents in the porphyrin core could modulate the action of the photosensitizer towards the bioluminescent Gram-negative Escherichia coli bacterium. The antimicrobial activity was also influenced by the interaction between the photosensitizer and the type of support (chitosan or titanium dioxide). The new cationic porphyrins and some of the materials were shown to be very stable in PBS and effective in the photoinactivation of E. coli bacterium. The physicochemical properties of TiO2 allowed the interaction of the PS with its surface, increasing the absorption profile of TiO2, which enables the use of visible light, inactivating the bacteria more efficiently than the corresponding PS immobilized on chitosan.

Fabrication of chitosan-bis (4-formyl-2 methoxy phenyl carbonate) Schiff base nanoparticles and evaluation of their antioxidant and anticancer properties

The present study details on the mechanism of synthesis of bis (4-formyl-2 methoxy phenyl carbonate), using two green reagents dimethyl carbonate and vanillin for application as therapeutic agent. The synthesized FMPC was identified from the ¹³C nuclear magnetic resonance spectra. The novel modified Schiff base nanoparticles resulted from the crosslinking of FMPC with chitosan were confirmed by cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance spectroscopy. The incorporation of the FMPC was identified from the amorphous X-ray diffraction patterns of C-FMPC-Nps. The thermal stability of the formed nanoparticles was predicted using thermogravimetric analysis. The morphology of the nanoparticles as observed from HRTEM was found to be smooth and spherical in nature. Both FMPC and C-FMPC-Nps showed significant radical scavenging potential and anticancer property. The carbonate ester backbone and the moiety present in chitosan-FMPC-nanoparticles, underwent hydrolysis at the targeted cancer causing microenvironment to release vanillin and chitosan and enhance the anticancer activity. Both FMPC and C-FMPC-Nps exhibits a dose dependent cytotoxicity towards the different cell lines and it was tested with a commercial drug for application studies. Effective synthesis of FMPC, successful incorporation onto chitosan nanoparticles for the formation of C-FMPC-Nps. The formed Schiff base compound proves to have enhanced antioxidant and anticancer efficacy.

68Ga-radiolabeled bombesin-conjugated to trimethyl chitosan-coated superparamagnetic nanoparticles for molecular imaging: preparation, characterization and biological evaluation

INTRODUCTION

Nowadays, nanoparticles (NPs) have attracted much attention in biomedical imaging due to their unique magnetic and optical characteristics. Superparamagnetic iron oxide nanoparticles (SPIONs) are the prosperous group of NPs with the capability to apply as magnetic resonance imaging (MRI) contrast agents. Radiolabeling of targeted SPIONs with positron emitters can develop dual positron emission tomography (PET)/MRI agents to achieve better diagnosis of clinical conditions.

METHODS

In this work, N,N,N-trimethyl chitosan (TMC)-coated magnetic nanoparticles (MNPs) conjugated to S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (DOTA) as a radioisotope chelator and bombesin (BN) as a targeting peptide (DOTA-BN-TMC-MNPs) were prepared and validated using fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and powder X-ray diffraction (PXRD) tests. Final NPs were radiolabeled with gallium-68 (68Ga) and evaluated in vitro and in vivo as a potential PET/MRI probe for breast cancer (BC) detection.

RESULTS

The DOTA-BN-TMC-MNPs with a particle size between 20 and 30 nm were efficiently labeled with 68Ga (radiochemical purity higher than 98% using thin layer chromatography (TLC)). The radiolabeled NPs showed insignificant toxicity (>74% cell viability) and high affinity (IC50=8.79 µg/mL) for the gastrin-releasing peptide (GRP)-avid BC T-47D cells using competitive binding assay against 99mTc-hydrazinonicotinamide (HYNIC)-gamma-aminobutyric acid (GABA)-BN (7-14). PET and MRI showed visible uptake of NPs by T-47D tumors in xenograft mouse models.

CONCLUSION

68Ga-DOTA-BN-TMC-MNPs could be a potential diagnostic probe to detect BC using PET/MRI technique.

The Effect of Molecular Weight on the Antibacterial Activity of N,N,N-Trimethyl Chitosan (TMC)

N,N,N-trimethyl chitosan (TMC) with 93% degree of trimethylation was synthesized. TMC and the chitosan starting material were subjected to acidic hydrolysis to produce 49 different samples with a reduced average molecular weight (Mw) ranging from 2 to 144 kDa. This was done to allow the investigation of the relationship between antibacterial activity and Mw over a wide Mw range. NMR investigation showed that hydrolysis did not affect the degree of trimethylation (DSTRI) or the structure of the polymer backbone. The activity of TMC against Staphylococcus aureus (S. aureus) increased sharply with Mw until a certain Mw value (critical Mw for high activity, CMW) was reached. After the CMW, the activity was not affected by a further increase in the Mw. A similar pattern of activity was observed for chitosan. The CMW was determined to be 20 kDa for TMC and 50 kDa for chitosan.

Synthesis of urea-functionalized chitosan derivatives for potential antifungal and antioxidant applications

In the current study, five novel urea-functionalized chitosan derivatives were synthesized via condensation reactions of chloroacetyl chitosan (CTCS) with urea groups bearing nitrogen-containing heterocycles. In order to identify the structure characteristics of chitosan derivatives, FT-IR, ¹H NMR spectroscopy, and elemental analysis were carried out. The antifungal activity of the derivatives against four species of phytopathogen (Fusarium oxysporum f. sp. niveum, Phomopsis asparagus, Fusarium oxysporum f. sp. cucumebrium Owen, and Botrytis cinerea) was evaluated. Furthermore, the antioxidant activity of chitosan derivatives was tested by hydroxyl-radical scavenging and superoxide-radical scavenging assays. The results indicated that chitosan derivatives bearing urea groups displayed superior bioactivity compared with chitosan. Besides, L929 cells were adopted for cytotoxicity test of chitosan and synthesized samples by CCK-8 assay and all samples showed decreased cytotoxicity. These results suggested that the novel urea-functionalized chitosan derivatives could be an ideal biomaterial for antifungal and antioxidant applications.

Spreading of Cell Aggregates on Zwitterion-Modified Chitosan Films

The sulfobetaine (SB) moiety, which comprises a quaternary ammonium group linked to a negatively charged sulfonate ester, is known to impart nonfouling properties to interfaces coated with polysulfobetaines or grafted with SB-polymeric brushes. Increasingly, evidence emerges that the SB group is, overall, a better antifouling group than the phosphorylcholine (PC) moiety extensively used in the past. We report here the synthesis of a series of SB-modified chitosans (CH-SB) carrying between 20 and 40 mol % SB per monosaccharide unit. Chitosan (CH) itself is a naturally derived copolymer of glucosamine and N-acetyl-glucosamine linked with a β-1,4 bond. Analysis by quartz crystal microbalance with dissipation (QCM-D) indicates that CH-SB films (thickness ∼ 20 nm) resist adsorption of bovine serum albumin (BSA) with increasing efficiency as the SB content of the polymer augments (surface coverage ∼ 15 μg cm^-2 for films of CH with 40 mol % SB). The cell adhesivity of CH-SB films coated on glass was assessed by determining the spreading dynamics of CT26 cell aggregates. When placed on chitosan films, known to be cell-adhesive, the CT26 cell aggregates spread by forming a cell monolayer around them. The spreading of CT26 cell aggregates on zwitterion-modified chitosans films is thwarted remarkably. In the cases of CH-SB30 and CH-SB40 films, only a few isolated cells escape from the aggregates. The extent of aggregate spreading, quantified based on the theory of liquid wetting, provides a simple in vitro assay of the nonfouling properties of substrates toward specific cell lines. This assay can be adopted to test and compare the fouling characteristics of substrates very different from the chemical viewpoint.

An Antifouling Hydrogel Containing Silver Nanoparticles for Modulating the Therapeutic Immune Response in Chronic Wound Healing

Patients with diabetic wounds have deficient local and systemic cellular immunity. Herein, a new silver nanoparticle-containing hydrogel with antifouling properties was developed for enhancing the immune response in diabetic wound healing. The antifouling property was obtained by adjusting the composition of cationic chitosan and anionic dextran to approach zero charge. Furthermore, this hybrid hydrogel showed long-lasting and broad-spectrum antibacterial activity. Rapid wound contraction was observed after the treatment with the hydrogel, which suggested its superior healing activity to promote fibroblast migration, granulation tissue formation, and angiogenesis. The upregulation of CD68+ and CD3+ expression levels demonstrated that the hydrogel could trigger immune responses in the treatment of wound healing. These results show that this antifouling hybrid hydrogel as a wound dressing provided a promising strategy for the treatment of diabetic ulcers.

Vascular targeted chitosan-derived nanoparticles as docetaxel carriers for gastric cancer therapy

A gastric cancer angiogenesis marker peptide, GX1, is promising to be a desirable ligand for anti-angiogenesis targeted drug of gastric cancer treatment. In this study, GX1 was utilized to fabricate a multifunctional vascular targeting docetaxel (DCT)-loaded nanoparticle with N-deoxycholic acid glycol chitosan (DGC) as the carrier and GX1-PEG-deoxycholic acid (GPD) conjugate as the targeting ligand. The mean size of obtained GX1-DGC-DCT was 150.9 nm with a narrow size distribution and their shape was spherical with smooth surface texture. The in vitro drug release test revealed a sustained release manner and an acid pH could accelerate the release compared with the neutral pH. Furthermore, GX1-DGC-DCT showed stronger cytotoxicity against co-cultured gastric cancer cells and human umbilical vein endothelial cells (co-HUVEC) than DCT within 100 μM. In addition, GX1 efficiently enhanced the cellular uptake of nanoparticles in co-HUVEC cells as confirmed by confocal fluorescence scanning microscopy. Moreover, in vivo delivery of GX1-DGC-DCT was demonstrated to inhibit tumor growth in SGC791 tumor-bearing mice with tumor inhibition rate (TIR) of 67.05% and no weight loss of mice was observed. The anti-tumor effects were further confirmed by H&E and TUNEL analysis. Therefore, this new drug delivery system represents a potential strategy for gastric cancer therapy.

Investigation of the Effects of Molecular Parameters on the Hemostatic Properties of Chitosan

Hemorrhea is one of the major problems in war, trauma care, and surgical operation that threaten the life of the injured and patients. As a novel polymeric hemostatic agent, biodegradable chitosan can stop bleeding through a variety of approaches. In this paper, chitosan with various molecular parameters was prepared from chitin as raw material through deacetylation, oxidative degradation, hydrophilic modification, and salt formation reactions. The influence of different polymer parameters on the hemostatic effects of chitosan was investigated by in vitro coagulation time and dynamic coagulation assay. The results showed that when the molecular weights were high (10⁵⁻10⁶) and approximate, the coagulation effect of chitosan improved with a decrease of the deacetylation degree and achieved a prominent level in a moderate degree of deacetylation (68.36%). With the same degree of deacetylation, the higher the molecular weight of chitosan, the better the procoagulant effect. The substituent derivatives and acid salts of chitosan showed significant procoagulant effects, especially the acid salts of chitosan. In addition, the hemostasis mechanism of chitosan with various parameters was preliminarily explored by analyzing the plasma recalcification time (PRT). The efforts in this paper laid a basis for further study of the structure⁻activity relationship and the mechanism of chitosan hemostasis.

Polyglutamic acid-trimethyl chitosan-based intranasal peptide nano-vaccine induces potent immune responses against group A streptococcus

Peptide-based vaccines have the potential to overcome the limitations of classical vaccines; however, their use is hampered by a lack of carriers and adjuvants suitable for human use. In this study, an efficient self-adjuvanting peptide vaccine delivery system was developed based on the ionic interactions between cationic trimethyl chitosan (TMC) and a peptide antigen coupled with synthetically defined anionic α-poly-(l-glutamic acid) (PGA). The antigen, possessing a conserved B-cell epitope derived from the group A streptococcus (GAS) pathogen and a universal T-helper epitope, was conjugated to PGA using cycloaddition reaction. The produced anionic conjugate formed nanoparticles (NP-1) through interaction with cationic TMC. These NP-1 induced higher systemic and mucosal antibody titers compared to antigen adjuvanted with standard mucosal adjuvant cholera toxin B subunit or antigen mixed with TMC. The produced serum antibodies were also opsonic against clinically isolated GAS strains. Further, a reduction in bacterial burden was observed in nasal secretions, pharyngeal surface and nasopharyngeal-associated lymphoid tissue of mice immunized with NP-1 in GAS challenge studies. Thus, conjugation of defined-length anionic polymer to peptide antigen as a means of formulating ionic interaction-based nanoparticles with cationic polymer is a promising strategy for peptide antigen delivery. STATEMENT OF SIGNIFICANCE: A self-adjuvanting delivery system is required for peptide vaccines to enhance antigen delivery to immune cells and generate systemic and mucosal immunity. Herein, we developed a novel self-adjuvanting nanoparticulate delivery system for peptide antigens by combining polymer-conjugation and complexation strategies. We conjugated peptide antigen with anionic α-poly-(l-glutamic acid) that in turn, formed nanoparticles with cationic trimethyl chitosan by ionic interactions, without using external crosslinker. On intranasal administration to mice, these nanoparticles induced systemic and mucosal immunity, at low dose. Additionally, nanoparticles provided protection to vaccinated mice against group A streptococcus infection. Thus, this concept should be particularly useful in developing nanoparticles for the delivery of peptide antigens.

Synthesis, Characterization, and Antifungal Activity of Pyridine-Based Triple Quaternized Chitosan Derivatives

In this study, a series of triple quaternized chitosan derivatives, including 6-O-[(2-hydroxy-3-trimethylammonium)propyl]-2-N-(1-pyridylmethyl-2-ylmethyl)-N,N-dimethyl chitosan chloride (7), 6-O-[(2-hydroxy-3-trimethylammonium)propyl]-2-N-(1-pyridylmethyl-3-yl- methyl)-N,N-dimethyl chitosan chloride (8), and 6-O-[(2-hydroxy-3-trimethylammonium)propyl]- 2-N-(1-pyridylmethyl-4-ylmethyl)-N,N-dimethyl chitosan chloride (9) were successfully designed and synthesized via reacting epoxypropyl trimethylammonium chloride with the N-pyridinium double quaternized chitosan derivatives. Detailed structural characterization was carried out using FT-IR and ¹H-NMR spectroscopy, and elemental analysis. Besides, the activity of the triple quaternized chitosan derivatives against three common plant pathogenic fungi, Watermelon fusarium, Fusarium oxysporum, and Phomopsis asparagi, was investigated in vitro. The results indicated that the triple quaternized chitosan derivatives had enhanced antifungal activity when compared to double quaternized chitosan derivatives and chitosan, especially at 1.0 mg/mL, which confirmed the theory that the higher density of positive charge contributed to the antifungal activity. Moreover, 8 with an almost 99% inhibitory index showed the better antifungal activity against Watermelon fusarium. Moreover, the cytotoxicity of the products was also evaluated in vitro on 3T3-L1 cells and all the triple quaternized chitosan derivatives exhibited low cytotoxicity. These results suggested that triple quaternized chitosan derivatives may be used as good antifungal biomaterials.

Synthesis and Evaluation of Herbal Chitosan from Ganoderma Lucidum Spore Powder for Biomedical Applications

Chitosan is an extremely valuable biopolymer and is usually obtained as a byproduct from the shells of crustaceans. In the current work, chitosan is obtained from an herbal source (Ganoderma lucidum spore powder (GLSP)) for the first time. To show this, both standard (thermochemical deacetylation, (TCD)) and emerging (ultrasound-assisted deacetylation (USAD)) methods of chitosan preparation were used. The obtained chitosan was characterized by elemental analysis, XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy) and thermogravimetric measurements. The process resulted in chitosan possessing comparable values of DD, [η] and [Formula: see text] to the commercial product. Chitosan obtained via both processes (TCD and USAD) displayed excellent biocompatibility; although the USAD prepared biopolymer exhibited significantly improved fibroblast (L929 cell) viability and enhanced antibacterial zones for both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The findings of new herbal chitosan mark key developments of natural biomaterials; marking a potential shift from conventional sea-based organisms.

Synthesis and Characterization of Poly(Vinyl Alcohol)-Chitosan-Hydroxyapatite Scaffolds: A Promising Alternative for Bone Tissue Regeneration

Scaffolds can be considered as one of the most promising treatments for bone tissue regeneration. Herein, blends of chitosan, poly(vinyl alcohol), and hydroxyapatite in different ratios were used to synthesize scaffolds via freeze-drying. Mechanical tests, FTIR, swelling and solubility degree, DSC, morphology, and cell viability were used as characterization techniques. Statistical significance of the experiments was determined using a two-way analysis of variance (ANOVA) with p < 0.05. Crosslinked and plasticized scaffolds absorbed five times more water than non-crosslinked and plasticized ones, which is an indicator of better hydrophilic features, as well as adequate resistance to water without detriment of the swelling potential. Indeed, the tested mechanical properties were notably higher for samples which were undergone to crosslinking and plasticized process. The presence of chitosan is determinant in pore formation and distribution which is an imperative for cell communication. Uniform pore size with diameters ranging from 142 to 519 µm were obtained, a range that has been described as optimal for bone tissue regeneration. Moreover, cytotoxicity was considered as negligible in the tested conditions, and viability indicates that the material might have potential as a bone regeneration system.