Chitosan gallate as a novel potential polysaccharide antioxidant: an EPR study

Hybrids of Gallic Acid@SiO2 and {Hyaluronic-Acid Counterpats}@SiO2 against Hydroxyl (●OH) Radicals Studied by EPR: A Comparative Study vs Their Antioxidant Hydrogen Atom Transfer Activity

Hydrogen atom transfer (HAT) and single electron transfer (SET) are two fundamental pathways for antiradical/antioxidant processes; however, a systematic in-tandem operational evaluation of the same system is lacking. Herein, we present a comparative study of the HAT and SET processes applied to a library of well-characterized hybrid materials SiO2@GA, SiO2@GLA, SiO2@GLAM, and the doubly hybrid material {GLA@SiO2@GLAM}. Hydroxyl radicals (•OH), produced by a Fenton system, react via the single electron transfer (SET) pathway and hydrogen atom transfer, through oxygen- and carbon-atoms, respectively, while the stable-radical DPPH via the HAT pathway through oxygen-atoms. Electron paramagnetic resonance spectroscopy (EPR), eminently suited for in situ detection and quantification of free radicals, was used as a state-of-the-art tool to monitor •OH using the spin-trapping-EPR method. We found that the SiO2@GA hybrid exhibited the highest SET •OH-scavenging activity i.e., [2.7 mol of •OH per mol of grafted GA]. Then, SiO2@GLA, SiO2@GLAM, and GLA@SiO2@GLAM can scavenge 1.2, 1.3, and 0.57 mol of •OH per mol of anchored organic, respectively. The HAT efficiency for SiO2@GA was [2.0 mol of DPPH per mol of grafted GA], while SiO2@GLA, SiO2@GLAM, and GLA@SiO2@GLAM exhibited a HAT efficiency of 1.1 DPPH moles per mol of anchored organic. The data are analyzed based on the molecular structure of the organics and their -R-OH moieties. Accordingly, based on the present data we suggest that for hydroxyl (•OH) radicals, the mechanisms involved are SET from an oxygen atom and HAT from a carbon atom. In contrast, for DPPH radicals, the HAT mechanism is exclusively operating and involves hydrogen atom abstraction from OH groups.

Prolonged Microcystis restraint through allelochemicals sustained-release microspheres regulated by carbon material (CM-AC@SM): Optimal formulation, characterization, effects and synergistic inhibition mechanisms

The Microcystis blooms have caused serious damage to aquatic ecosystems. Microspheres containing allelochemicals with sustained-release properties have the potential to function as a cost-effective and environmentally friendly algaecide against M. aeruginosa. In the current investigation, we successfully optimized the synthesis of allelochemicals sustained-release microspheres regulated by carbon material (CM-AC@SM), which demonstrated a high embedding rate (90.17 %) and loading rate (0.65 %), with an accumulative release rate of 53.27 % on day 30. To investigate the sustained-release mechanism of CM-AC@SM, the sustained-release process of allelochemicals was determined using the Folin-Phenol method and the immersion behavior of the CM-AC@SM was characterized through SEM and XPS. Results showed that allelochemicals were released in the delayed-dissolution mode. In addition, to elucidate the synergistic mechanism of CM-AC@SM towards the inhibition of M. aeruginosa, this study comprehensively assessed the effects of allelochemicals, carbon material and CM-AC@SM on the morphology, antioxidant system activity and photosynthetic activity of M. aeruginosa. The findings indicated that allelochemicals and carbon material induced intracellular protein and nucleic acid leakage by increasing cell membrane permeability, disrupted the extracellular and intracellular morphology of algae, triggered peroxidative damage and restrained antioxidant system activity by stimulating the generation of reactive oxygen species. Simultaneously, the activity of photosystem II was inhibited by allelochemicals and carbon material, substantiated by the reduction in Fv/Fo and Fv/Fm ratios. Hence, CM-AC@SM shows promise in inhibiting M. aeruginosa, offering an efficient approach for the future large-scale control of harmful algal blooms (HABs).

Double-network polyphenol chitosan hydrogels with instant aldehyde-β-cyclodextrin-based structure as potential for treating bacterially infected wounds

Treatment of multiple bacterial infected wounds by eliminating bacteria and promoting tissue regeneration remains a clinical challenge. Herein, dual-network hydrogels (CS-GA/A-β-CD) with snap-structure were designed to achieve curcumin immobilization, using gallic acid-grafted chitosan (CS-GA) and aldehyde-β-cyclodextrin (A-β-CD) crosslinked. A-β-CD were able to achieve rapid dissolution (≥222.35 mg/mL H2O), and helped CS-GA/A-β-CD achieve rapid gelation (≤66.23 s). By adjusting the ratio of aldehyde groups of A-β-CD, mechanical properties and drug release can be controlled. CS-GA/A-β-CD/Cur exhibited excellent antimicrobial properties against S. aureus, E. coli, and P. aeruginosa. In vivo experiments demonstrated that CS-GA/A-β-CD/Cur achieved acute bacterial infection wound healing after 20th days, proving its great potential for wound dressing.

Assessment of Chitosan/Gelatin Blend Enriched with Natural Antioxidants for Antioxidant Packaging of Fish Oil

In this research, bio-based films were developed using polyelectrolyte complexes derived from chitosan and gelatin for packaging fish oil. To further enhance the antioxidant functionality, the films were enriched with gallic acid and orange essential oils, either individually or in combination. Initially, the films were characterized for their physico-chemical, optical, surface, and barrier properties. Subsequently, the phenolic compounds and antioxidant capacity of the films were assessed. Finally, the films were tested as antioxidant cover lids for packaging fish oil, which was then stored at ambient temperature for 30 days, with periodical monitoring of oil oxidation parameters. This study revealed that the inclusion of gallic acid-induced possible crosslinking effects, as evidenced by changes in moisture content, solubility, and liquid absorption. Additionally, shifts in the FTIR spectral bands suggested the binding of gallic acid and/or phenols in orange essential oils to CSGEL polymer chains, with noticeable alterations in film coloration. Notably, films containing gallic acid exhibited enhanced UV barrier properties crucial for preserving UV-degradable food compounds. Moreover, formulations with gallic acid demonstrated decreased water vapor permeability, while samples containing orange essential oils had lower CO2 permeability levels. Importantly, formulations containing both gallic acid and essential oils showed a synergistic effect and a significant antioxidant capacity, with remarkable DPPH inhibition rates of up to 88%. During the 30-day storage period, fish oil experienced progressive oxidation, as indicated by an increase in the K232 value in control samples. However, films incorporating gallic acid or orange essential oils as active antioxidants, even used as indirect food contact, effectively delayed the oxidation, highlighting their protective benefits. This study underscores the potential of sustainable bio-based films as natural antioxidant packaging for edible fish oil or fresh fish, offering a promising tool for enhancing food preservation while reducing its waste.

Development of cellulose nanowhisker-gallic acid antioxidant bioconjugate via covalent conjugation and supramolecular interactions: A comparative study

A new supramolecular antioxidant bioconjugate based on cellulose nanowhisker (CNW) and gallic acid (GA) was developed by grafting β-CD on the surface of CNW and then employing host- guest chemistry to involve GA. Our challenge was to explore the effect of supramolecular conjugation of antioxidant molecules versus their covalent binding on the CNW backbone on the antioxidant activity. The synthesis of these products was confirmed using Fourier transform infrared (FT-IR) and differential scanning calorimetry (DSC) analyses. The antioxidant activity of gallic acid (GA) containing products, both products including its non-covalent interactions with CNW-g-β-CD and covalent bonding with CNW were experimentally evaluated using DPPH test. Theoretical calculations using Gaussian software and the density functional theory (DFT) method were also performed. The results showed that GA's antioxidant activity increased in non-covalent conjugated form. Hydrogen atom transfer (HAT) was used to predict the antioxidant activity of GA in computational methods. These findings not only expand our understanding of the structure-activity relationships in antioxidant systems but also provide valuable insights that can aid in the design and development of novel biopolymer-based antioxidants with improved properties.

Fe3+-induced coordination cross-linking gallic acid-carboxymethyl cellulose self-healing hydrogel

Self-healing hydrogel is a promising soft material for applications in wound dressings, drug delivery, tissue engineering, biomimetic electronic skin, and wearable electronic devices. However, it is a challenge to fabricate the self-healing hydrogels without external stimuli. Inspired by mussel, the metal-catechol complexes were introduced into the hydrogel systems to prepare the mussel-inspired hydrogels by regulating the gelation kinetics of Fe3+ crosslinkers with gallic acid (GA) in this research. The amine-functionalized carboxymethyl cellulose (CMC) was grafted with GA and then chelated with Fe3+ to form a multi-response system. The crosslinking of carboxymethyl cellulose-ethylenediamine-gallic acid (CEG) hydrogel was controlled by adjusting the pH to affect the iron coordination chemistry, which could enhance the self-healing properties and mechanical strength of hydrogels. In addition, the CEG hydrogel exhibited great antibacterial and antioxidant properties. And the CEG hydrogel could strongly adhere to the skin tissue. The adhesion strength of CEG hydrogel on pigskin was 11.44 kPa, which is higher than that of commercial wound dressings (∼5 kPa). Moreover, the thixotropy of the CEG hydrogel was confirmed with rheological test. In summary, it has great potential in the application field of wound dressing.

Benzoxazine-grafted-chitosan biopolymer films with inherent disulfide linkage: Antimicrobial properties

Synthesis and fabrication of naturally sourced biopolymers, especially chitosan, grafted with renewable small molecules have recently attracted attention as efficient antimicrobial agents and are highly desired for sustainable material development. Advantageous inherent functionalities in biobased benzoxazine extend the possibility of crosslinking with chitosan which holds immense potential. Herein, a low-temperature, greener facile methodology is adopted for the covalent confinement of benzoxazine monomers bearing aldehyde and disulfide linkages within chitosan to form benzoxazine-grafted-chitosan copolymer films. The association of benzoxazine as Schiff base, hydrogen bonding, and ring-opened structures enabled the exfoliation of chitosan galleries, and such host-guest mediated interactions demonstrated outstanding properties like hydrophobicity, good thermal, and solution stability due to the synergistic effects. Furthermore, the structures empowered excellent bactericidal properties against both E. coli and S. aureus as investigated by GSH loss, live/dead fluorescence microscopy, and morphological alteration on the cell surface by SEM. The work provides the benefits of disulfide-linked benzoxazines on chitosan, offering a promising avenue for general and eco-friendly usage in wound-healing and packaging material.

Fabrication of Novel Omeprazole-Based Chitosan Coated Nanoemulgel Formulation for Potential Anti-Microbia; In Vitro and Ex Vivo Characterizations

Infectious diseases remain inevitable factors for high mortality and morbidity rate in the modern world to date. Repurposing is a novel approach to drug development has become an intriguing research topic in the literature. Omeprazole is one of the top ten proton pump inhibitors prescribed in the USA. The literature suggests that no reports based on omeprazole anti-microbial actions have been discovered to date. This study entails the potential of omeprazole to treat skin and soft tissue infections based on the literature's evident anti-microbial effects. To get a skin-friendly formulation, a chitosan-coated omeprazole-loaded nanoemulgel formulation was fabricated using olive oil, carbopol 940, Tween 80, Span 80, and triethanolamine by high-speed homogenization technique. The optimized formulation was physicochemically characterized for zeta potential, size distribution, pH, drug content, entrapment efficiency, viscosity, spreadability, extrudability, in-vitro drug release, ex-vivo permeation analysis, and minimum inhibitory concentration determination. The FTIR analysis indicated that there was no incompatibility between the drug and formulation excipients. The optimized formulation exhibited particle size, PDI, zeta potential, drug content, and entrapment efficiency of 369.7 ± 8.77 nm, 0.316, -15.3 ± 6.7 mV, 90.92 ± 1.37% and 78.23 ± 3.76%, respectively. In-vitro release and ex-vivo permeation data of optimized formulation showed 82.16% and 72.21 ± 1.71 μg/cm², respectively. The results of minimum inhibitory concentration (1.25 mg/mL) against selected bacterial strains were satisfactory, suggesting a successful treatment approach for the topical application of omeprazole to treat microbial infections. Furthermore, chitosan coating synergistically increases the antibacterial activity of the drug.

A Gallic Acid-Doped Polypyrrole Coating with Anticorrosion and Antibacterial Properties on Magnesium Alloy

Magnesium (Mg) and its alloys exhibit great potential as biomedical implants due to their excellent biological performance and mechanical properties. However, their clinical applications are limited by their rapid corrosion rate in physiological media and the risk of implant-associated infections. Herein, a multifunctional polypyrrole/gallic acid (PPy/GA) coating was deposited on an AZ31 Mg alloy substrate by electrochemical polymerization to enhance simultaneously the corrosion resistance and antibacterial properties of the Mg alloy. Electrochemical and in vitro immersion tests demonstrated that the anticorrosion performance of the Mg alloy was significantly improved with the PPy/GA coating. The thiazolyl blue tetrazolium bromide (MTT) assay and live-dead staining of L929 cells indicated the acceptable cytocompatibility of the PPy/GA coating. In vitro antibacterial tests revealed a remarkable enhancement in the antibacterial activity of the PPy/GA-coated Mg alloy compared with the PPy-coated material and the bare Mg alloy.

Recent advances on formation mechanism and functionality of chitosan-based conjugates and their application in o/w emulsion systems: A review

Chitosan is very attractive in the food industry due to its good biocompatibility and high biodegradability. In particular, it can be used as a preferred material for the fabrication of stabilizers in emulsion-based foods. However, poor solubility and antioxidant activity limit its wide application. The functionality of chitosan can be extended by forming chitosan-based conjugates, which can be used to modulate the characteristics of the oil-water interface, thereby improving the stability and performance of the o/w emulsions. This review highlights the recent progress of chitosan-based conjugates, focusing on the classification, formation mechanism and functional properties, and the applications of these conjugates in o/w emulsions are summarized. Lastly, the promising research trends and challenges of chitosan-based conjugates and their emulsion systems in this field are also discussed. This review will provide a theoretical basis for the wide application of chitosan-based conjugates in emulsion systems.

The Effect of Combining Post-Harvest Calcium Nanoparticles with a Salicylic Acid Treatment on Cucumber Tissue Breakdown via Enzyme Activity during Shelf Life

In the present study, an experiment was carried out on the postharvest of cucumber fruit during a 14-day shelf life. The aim was to assess the impact of calcium nanoparticles (CaNPs) blended with different concentrations of salicylic acid (SA) on the shelf life of cucumbers during the seasons of 2018 and 2019. The investigation further monitored the influences of CaNPs-SA on some physical properties of cucumber, including the percentage weight loss, color, and fruit firmness. In addition, chemical properties, such as total soluble solids (SSC%), total acidity (TA%), total soluble sugars, and chlorophyll pigmentation of the fruit skin, were assessed during a 14-day shelf lifeCell wall degradation enzymes (CWEAs) such as polygalacturonase (PG), cel-lulase (CEL), xylanase (XYL), and pectinase (PT) were also researched. In addition, the generation rates of H₂O₂ and O₂^•− were calculated, as well as the reduction of DPPH. The lipid peroxidation (malondialdehyde, MDA) and cell membrane permeability (IL%) of cell wall composites were also determined. CaNPs-SA at 2 mM suppressed CWEAs, preserved fruit quality, reduced weight loss throughout the shelf-life period, and reduced the percent leakage value. At this concentration, we also found the lowest levels of MDA and the highest levels of DPPH.

Antioxidant Properties and Aldehyde Reactivity of PD-L1 Targeted Aryl-Pyrazolone Anticancer Agents

Small molecules targeting the PD-1/PD-L1 checkpoint are actively searched to complement the anticancer arsenal. Different molecular scaffolds have been reported, including phenyl-pyrazolone derivatives which potently inhibit binding of PD-L1 to PD-1. These molecules are structurally close to antioxidant drug edaravone (EDA) used to treat amyotrophic lateral sclerosis. For this reason, we investigated the capacity of five PD-L1-binding phenyl-pyrazolone compounds (1–5) to scavenge the formation of oxygen free radicals using electron spin resonance spectroscopy with DPPH/DMPO probes. In addition, the reactivity of the compounds toward the oxidized base 5-formyluracil (5fU) was assessed using chromatography coupled to mass spectrometry and photodiode array detectors. The data revealed that the phenyl-pyrazolone derivatives display antioxidant properties and exhibit a variable reactivity toward 5fU. Compound 2 with a N-dichlorophenyl-pyrazolone moiety cumulates the three properties, being a potent PD-L1 binder, a robust antioxidant and an aldehyde-reactive compound. On the opposite, the adamantane derivative 5 is a potent PD-L1 binding with a reduced antioxidant potential and no aldehyde reactivity. The nature of the substituent on the phenyl-pyrazolone core modulates the antioxidant capacity and reactivity toward aromatic aldehydes. The molecular signature of the compound can be adapted at will, to confer additional properties to these PD-L1 binders.

Investigation of the Antioxidant Properties of the Quaternized Chitosan Modified with a Gallic Acid Residue Using Peroxidase that Produces Reactive Oxygen Species

Chitosan modified with a (2-hydroxy-3-trimethylammonium) propyl group and gallic acid residue, or quaternized chitosan with gallic acid (QCG), was synthesized. Antioxidant properties of the produced QCG have been investigated. Peroxidase in combination with NADH and salicyl hydroxamate (SHAM) caused consumption of oxygen and production of H2O2 in aqueous solution as a result of O2 reduction in the peroxidase-oxidase reactions. The rates of O2 consumption and H2O2 generation were reduced in the presence of QCG. The antioxidant propyl gallate (PG) and superoxide dismutase (SOD) had the same effect, but not the quaternized chitosan (QC) without gallic acid. The effect of chitosan derivatives on the production of reactive oxygen species (ROS) in the cells of pea leaf epidermis and on the cell death detected by the destruction of cell nuclei, was investigated. QCG, QC, and SOD had no effect, while PG decreased the rate of ROS generation in the cells of the epidermis, which was induced by NADH with SHAM or by menadione. QCG and QC prevented destruction of the guard cell nuclei in the pea leaf epidermis that was caused by NADH with SHAM or by KCN. SOD had no effect on the destruction of nuclei, while the effect of PG depended on the inducer of the cell death. Suppression of the destruction of guard cell nuclei by chitosan derivatives was associated not with their antioxidant effect, but with the disruption of the plasma membrane of the cells. The results obtained have shown that QCG exhibits antioxidant properties in solutions, but does not prevent generation of ROS in the plant cells. The mechanism of antioxidant effect of QCG is similar to that of PG and SOD.

Barley β-glucan resist oxidative stress of Caenorhabditis elegans via daf-2/daf-16 pathway

β-glucan is an important functional active component with relatively high content in barley. It is reported to possess various biological activities, including anti-oxidative stress, but its mechanism of action remains obscure. In the current study, C. elegans was used as an in vivo animal model to explore its anti-oxidative stress mechanism. We found that both RBG (raw barley β-glucan) and FBG (fermented barley β-glucan) could significantly reduce the ROS level in C. elegans under oxidative emergency conditions. In addition, both FBG and RBG had positive effects on SOD and CAT enzyme activity, and FBG treatment obviously reduced the MDA content in nematodes under oxidative stress. Moreover, FBG and RBG pretreatment could extend the median lifespan of C. elegans under oxidative stress. The CB1370 and CF1038 mutants further confirmed that daf-2 and daf-16 were necessary for FBG or RBG to participate in anti-oxidative stress, and the RT-PCR results also evidenced that β-glucans resist oxidative stress in C. elegans partially through the daf-2/daf-16 pathway. In summary, barley β-glucan has high potential to defense oxidative stress as a natural polysaccharide.

Bombesin Peptide Conjugated Water-Soluble Chitosan Gallate-A New Nanopharmaceutical Architecture for the Rapid One-Pot Synthesis of Prostate Tumor Targeted Gold Nanoparticles

PURPOSE

We report herein bombesin peptide conjugated water-soluble chitosan gallate as a template for rapid one-pot synthesis of gold nanoparticles (AuNPs) with capabilities to target receptors on prostate cancer cells.

METHODS

Water-soluble chitosan (WCS), anchored with gallic acid (GA) and LyslLys3 (1,4,7,10-tetraazacyclo dodecane-1,4,7,10-tetraacetic acid) bombesin 1-14 (DBBN) peptide, provides a tumor targeting nanomedicine agent. WCS nanoplatforms provide attractive strategies with built-in capabilities to reduce gold (III) to gold nanoparticles with stabilizing and tumor-targeting capabilities. WCS-GA-DBBN encapsulation around gold nanoparticles affords optimum in vitro stability.

RESULTS

The DBBN content in the WCS-GA-DBBN sample was ~27%w/w. The antioxidant activities of WCS-GA and WCS-GA-DBBN nanocolloids were enhanced by 12 times as compared to the nascent WCS. AuNPs with a desirable hydrodynamic diameter range of 40-60 nm have been efficiently synthesized using WCS-GA and WCS-GA-DBBN platforms. The AuNPs were stable over 4 days after preparation and ~3 days after subjecting to all relevant biological fluids. The AuNPs capped with WCS-GA-DBBN peptide exhibited superior cellular internalization into prostate tumor (PC-3) cells with evidence of receptor mediated endocytosis.

CONCLUSION

The AuNPs capped with WCS-GA-DBBN exhibited selective affinity toward prostate cancer cells. AuNPs conjugated with WCS-GA-DBBN serve as a new generation of theranostic agents for treating various neoplastic diseases, thus opening-up new applications in oncology.

Insertion of gallic acid onto chitosan promotes the differentiation of osteoblasts from murine bone marrow-derived mesenchymal stem cells

Chitosan, a naturally occurring biodegradable and biocompatible polymer, has found use as a food additive, nutraceuticals, and functional foods in recent years. In this study, gallic acid-g-chitosan (GAC) was prepared by the insertion of GA onto plain chitosan (PC) via free radical-mediated grafting and its osteogenic effects were investigated in murine bone marrow-derived mesenchymal stem cells (mBMMSCs). Structural characterization of PC and GAC was performed using ¹H NMR and FT-IR spectroscopy. The amount of GA successfully grafted onto PC was 111 mg GA/g GAC via the Folin-Ciocalteu's method. While PC and GAC promoted the increase in alkaline phosphatase activity and mineralization, GAC increased these factors significantly more than PC, indicating that the grafting of GA onto chitosan increased its osteogenic potential. Mechanistic study revealed that GAC activated Wnt1 and Wnt3a mRNA and protein expression as well as increased the translocation of β-catenin into the nucleus and upregulated the expression of β-catenin targeted genes including Runx2, osterix, type I collagen and cyclin D1. In addition, DKK-1, a Wnt antagonist, decreased GAC-mediated osteoblast differentiation in mBMMSCs through blocking the Wnt/β-catenin signaling pathway.

Effects of Traditional Chinese Medication-Based Bioactive Compounds on Cellular and Molecular Mechanisms of Oxidative Stress

The oxidative stress reaction is the imbalance between oxidation and antioxidation in the body, resulting in excessive production of oxygen free radicals in the body that cannot be removed, leading to excessive oxidation of the body, and causing damage to cells and tissues. A large number of studies have shown that oxidative stress is involved in the pathological process of many diseases, so inhibiting oxidative stress, that is, antioxidation, is of great significance for the treatment of diseases. Studies have shown that many traditional Chinese medications contain antioxidant active bioactive compounds, but the mechanisms of those compounds are different and complicated. Therefore, by summarizing the literature on antioxidant activity of traditional Chinese medication-based bioactive compounds in recent years, our review systematically elaborates the main antioxidant bioactive compounds contained in traditional Chinese medication and their mechanisms, so as to provide references for the subsequent research.

Binary Pectin-Chitosan Composites for the Uptake of Lanthanum and Yttrium Species in Aqueous Media

Rare-earth elements such as lanthanum and yttrium have wide utility in high-tech applications such as permanent magnets and batteries. The use of biopolymers and their composites as adsorbents for La (III) and Y (III) ions were investigated as a means to increase the uptake capacity. Previous work has revealed that composite materials with covalent frameworks that contain biopolymers such as pectin and chitosan have secondary adsorption sites for enhanced adsorption. Herein, the maximum adsorption capacity of a 5:1 Pectin-Chitosan composite with La (III) and Y (III) was 22 mg/g and 23 mg/g, respectively. Pectin-Chitosan composites of variable composition were characterized by complementary methods: spectroscopy (FTIR, ¹³C solids NMR), TGA, and zeta potential. This work contributes to the design of covalent Pectin-Chitosan biopolymer frameworks for the controlled removal of La (III) and Y (III) from aqueous media.

Water-Soluble Chitosan Conjugated DOTA-Bombesin Peptide Capped Gold Nanoparticles as a Targeted Therapeutic Agent for Prostate Cancer

Introduction

Functionalization of water-soluble chitosan (WSCS) nanocolloids with, gold nanoparticles (AuNPs), and LyslLys3 (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid)-bombesin 1–14 (DOTA-BBN) peptide affords an innovative pathway to produce prostate tumor cell-specific nanomedicine agents with potential applications in molecular imaging and therapy.

Methods

The preparation involves the production and full characterization of water-soluble chitosan (WSCS), via gamma (γ) rays (80 kGy) irradiation, followed by DOTA-BBN conjugation for subsequent use as an effective template toward the synthesis of tumor cell-specific AuNPs-WSCS-DOTA-BBN.

Results

The WSCS-DOTA-BBN polymeric nanoparticles (86 ± 2.03 nm) served multiple roles as reducing and stabilizing agents in the overall template synthesis of tumor cell-targeted AuNPs. The AuNPs capped with WSCS and WSCS-DOTA-BBN exhibited average Au-core diameter of 17 ± 8 nm and 20 ± 7 nm with hydrodynamic diameters of 56 ± 1 and 67± 2 nm, respectively. The AuNPs-WSCS-DOTA-BBN showed optimum in vitro stability in biologically relevant solutions. The targeted AuNPs showed selective affinity toward GRP receptors overexpressed in prostate cancer cells (PC-3 and LNCaP).

Discussion

The AuNPs-WSCS-DOTA-BBN displayed cytotoxicity effects against PC-3 and LNCaP cancer cells, with concomitant safety toward the HAECs normal cells. The AuNPs-WSCS-DOTA-BBN showed synergistic targeting toward tumor cells with selective cytotoxicity of AuNPs towards PC-3 and LNCaP cells. Our investigations provide compelling evidence that AuNPs functionalized with WSCS-DOTA-BBN is an innovative nanomedicine approach for use in molecular imaging and therapy of GRP receptor-positive tumors. The template synthesis of AuNPs-WSCS-DOTA-BBN serves as an excellent non-radioactive surrogate for the development of the corresponding ¹⁹⁸AuNPs theragnostic nanoradiopharmaceutical for use in cancer diagnosis and therapy.

Biological evaluation, proposed molecular mechanism through docking and molecular dynamic simulation of derivatives of chitosan

We synthesized Schiff base and its complexes derivatives of chitosan (CS) in order to develop antibiotic compounds based on functionalized-chitosan against gram-positive and gram-negative bacteria. IR, UV-Vis, AFM, SEM, Melting point, X-ray diffraction (XRD), elemental analysis, and ¹H NMR techniques were employed to characterize the chemical structures and properties of these compounds. XRD, UV-Vis, and ¹H NMR techniques confirmed the formation of Schiff base and its functionalized-chitosan to metals. Subsequently, our antibacterial studies revealed that antibacterial activities of [Zn(Schiff base)(CS)] against S. aureus bacteria increased compared to those of their compounds. In addition, hemolysis test of CS-Schiff base-Cu(II) demonstrated better hemolytic activity than vitamin C, CS-Schiff base, CS-Schiff base-Zn(II), and CS-Schiff base-Ni(II). In a computational strategy, we carried out the optimization of compounds with molecular mechanics (MM⁺), Semi-emprical (AM1), Abinitio (STO-3G), AMBER, BIO+(CHARMM), and OPLS. Frontier orbital density distributions (HOMO and LUMO), and the optimized computational UV of the compounds were assessed. The optimized computational UV-Vis was similar to the experimental UV-Vis. We applied the docking methods to predict the DNA binding affinity, Staphylococcus aureus enoyl-acyl carrier protein reductase (ENRs), and Staphylococcus aureus enoyl-acyl carrier protein reductase (saFabI). Ultimately, the obtained data herein suggested that Schiff base is more selective toward ENRs and saFabI compared to chitosan, its complexes, and metronidazole.

Antibacterial performance of fully biobased chitosan-grafted-polybenzoxazine films: Elaboration and properties of released material

A fully biobased benzoxazine monomer, V-fa (using vanillin and furfurylamine) was grafted onto chitosan (CS) at different weight ratios (C_XV_Y) using "grafting to" benign Schiff base chemistry. Incorporation of V-fa onto CS increased the tensile strength and improved chemical resistance of the CS-graft-V-fa films. Reversible labile linkages, expansion of CS galleries and leaching out of phenolic species from biobased polymer films led to an improved antibacterial activity against Staphylococcus aureus, which is ∼125 times higher than the bare CS film, V-fa and oligomeric V-fa. The leached out species from films were analyzed extensively by NMR, FTIR, GPC, ABTS and HRMS analysis. Oxidative-stress seems to be responsible for antibacterial activity. Current work illustrates an attractive synthetic approach and the improved antibacterial performance of biobased CS-graft-poly(V-fa) films which may hold as a potential alternative for wound-healing and implant applications in future.

Synthesis and characterization of L-tyrosine-conjugated quaternary ammonium salt chitosan and their cytocompatibility as a potential tissue engineering scaffold

A novel amino acid-modified biomacromolecule was designed and synthesized as the quaternary ammonium salt chitosan grafted-tyrosine (CA-g-Tyr) suitable for biomedical applications. L-tyrosine was grafted onto the quaternary ammonium salt chitosan (CA) by N-(3-dimethylaminopropy)-N-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The chemical structure of CA-g-Tyr was confirmed by Fourier transform infrared (FTIR) spectroscopy and ¹³C-NMR. The change in the crystalline structure after the graft was characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). The surface wettability and moisturizing performance of the CA-g-Tyr were also characterized. The CA-g-Tyr film possessed good hydrophilicity, and the mechanical tensile experiments showed that the introduction of tyrosine gave CA mechanical properties more suitable for blood vessel. Cell experiments showed that the endothelial cells can adhere and proliferate better on the surface of a CA-g-Tyr film than CA. The results confirm the favorable properties and biocompatibility of CA-g-Tyr with potential applications as scaffolds for tissue engineering.

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.

Reaction Mechanisms and Structural and Physicochemical Properties of Caffeic Acid Grafted Chitosan Synthesized in Ascorbic Acid and Hydroxyl Peroxide Redox System

The ascorbic acid (AA) and hydroxyl peroxide (H₂O₂) redox pair induced free radical grafting reaction is a promising approach to conjugate phenolic groups with chitosan (CS). In order to reveal the exact mechanisms of the AA/H₂O₂ redox pair induced grafting reaction, free radicals generated in the AA/H₂O₂ redox system were compared with hydroxyl radical (^•OH) produced in the Fe²⁺/H₂O₂ redox system. Moreover, the structural and physicochemical properties of caffeic acid grafted CS (CA-g-CS) synthesized in these two redox systems were compared. Results showed that only ascorbate radical (Asc^•-) was produced in the AA/H₂O₂ system. The reaction between Asc^•- and CS produced novel carbon-centered radicals, whereas no new free radicals were detected when ^•OH reacted with CS. Thin layer chromatography, UV-vis, Fourier transform infrared, and nuclear magnetic resonance spectroscopic analyses all confirmed that CA was successfully grafted onto CS through Asc^•-. However, CA could be hardly grafted onto CS via ^•OH. CA-g-CS synthesized through Asc^•- exhibited lower thermal stability and crystallinity than the reaction product obtained through ^•OH. For the first time, our results demonstrated that the synthesis of CA-g-CS in the AA/H₂O₂ redox system was mediated by Asc^•- rather than ^•OH.

Quality and biochemical changes of 'Hindi-Besennara' mangoes during shelf life as affected by chitosan, gallic acid and chitosan gallate

Quality and biochemical changes of 'Hindi-Besennara' mangoes in response to chitosan, gallic acid (GA) and chitosan gallate (CG) postharvest dipping were studied during 2 weeks of storage at 20 ± 2 °C and 60-70% RH. Both GA and CG lowered decay and weight loss during storage. Chitosan and GA at high level and CG at both level maintained higher membrane stability index of peel than control. Fruits treated only CG and GA at high level and chitosan at both levels retained higher acidity and vitamin C but lower pH and total soluble solids (TSS) than control. All treatments resulted with fruits with higher flesh firmness and lower TSS/acid ratio than untreated fruits. GA at both rates gave lower total phenols after 1 week of storage than control. Both levels of GA and low level of chitosan resulted with fruits with higher antioxidant capacity (lower IC50 values) after 1 week of storage than control. All treatments decreased α-amylase activity of fruit peel compared to control. CG and GA at high level and chitosan at low level increased peroxidase activity compared to control. It was concluded that CG and GA dipping delayed ripening and maintained quality of 'Hindi-Besennara' mangoes during 2 weeks of shelf life.

Microencapsulation of sardine oil: Application of vanillic acid grafted chitosan as a bio-functional wall material

Vanillic acid grafted chitosan (Va-g-Ch) was evaluated as a new antioxidant wall material for microencapsulation of polyunsaturated fatty acid rich sardine oil. A high grafting ratio of 305mg vanillic acid equivalent/g of polymer was achieved using a free radical mediated grafting reaction. Oil in water emulsion was prepared with an optimised combination of Va-g-Ch and Tween 20 (3.2:1). Sardine oil loaded microparticles (SO-M) were produced (∼75% yield) by spray drying. The average diameter and polydispersity Index (PDI) of the particles were found to be 2.3μ and 0.345. XRD spectra of SO-M showed reduction in crystallinity due to microencapsulation. After four weeks of storage, a moderate (∼12%) decrease in the EPA and DHA content and a low PV of 5.5±0.51meq/kg oil in SO-M demonstrated good oxidative stability. Satisfactory encapsulation efficiency (84±0.84%) and loading efficiency (67±0.51%) values, also demonstrated the suitability of Va-g-Ch for microencapsulation of sardine oil.

Postharvest chitosan, gallic acid and chitosan gallate treatments effects on shelf life quality, antioxidant compounds, free radical scavenging capacity and enzymes activities of 'Sukkari' bananas

The effect of postharvest chitosan, gallic acid (GA) and chitosan gallate (CG) dipping treatments at different concentrations on quality parameters, antioxidant compounds, free radical scavenging capacity (FRSC) and enzymes activities of 'Sukkari' bananas were studied during storage (ripening) at 20 ± 2 °C and 60-70% RH for 13 days. Weight loss and peel color index (the change from green to yellow) increased while, membrane stability index of peel tissues, pulp firmness and acidity decreased during storage. CG and GA treatments slowed down the changes in these parameters compared to control. Total soluble solids (TSS) concentration increased during storage and was lower at CG than other treatments. TSS/acid ratio increased during storage and showed higher value after storage than initial. This ratio was lower at 1% chitosan, 0.075% GA and CG treatments than control. Both vitamin C and total flavonoids concentrations decreased during storage and were not affected by the applied treatments. Total phenols concentration decreased during storage and was higher at acetic acid and the high rate of chitosan, GA and CG treatments than control. FRSC (DPPH IC₅₀ values) of fruit peel ranged from 2.54 to 4.19 µg phenolics concentration among the treatments. FRSC was not affected by the applied treatments but increased (lower IC₅₀ value) during shelf life. The possible relations of these biochemical changes with the activities of the enzymes α-amylase, xylanase, polygalacturonase, peroxidase and polyphenoloxidase were discussed. It is concluded that postharvest CG and GA treatments delayed ripening and maintained better quality parameters of 'Sukkari' bananas during 13 days of shelf life than control.