Functionalization of chitosan polymer and their applications

Valorization of fishery industry waste: Chitosan extraction and its application in the industry

Waste from the fishing industry is disposed of in soils and oceans, causing environmental damage. However, it is also a source of valuable compounds such as chitin. Although chitin is the second most abundant polymer in nature, its use in industry is limited due to the lack of standardized and scalable extraction methods and its poor solubility. The deacetylation process increases its potential applications by enabling the recovery of chitosan, which is soluble in dilute acidic solutions. Chitosan is a polymer of great importance due to its biocompatible and bioactive properties, which include antimicrobial and antioxidant capabilities. Chitin extraction and its deacetylation to obtain chitosan are typically performed using chemical processes that involve large amounts of strongly acidic and alkaline solutions. To reduce the environmental impact of this process, extraction methods based on biotechnological tools, such as fermentation and chitin deacetylase, as well as emerging technologies, have been proposed. These extraction methods have demonstrated the potential to reduce or even avoid using strong solvents and shorten extraction time, thereby reducing costs. Nevertheless, it is important to address existing gaps in this area, such as the requirements for large-scale implementation and the determination of the stoichiometric ratios for each process. This review highlights the use of biotechnological tools and emerging technologies for chitin extraction and chitosan production. These approaches truly minimize environmental impact, reduce the use of strong solvents, and shorten extraction time. They are a reliable alternative to fishery waste valorization, lowering costs; however, addressing the critical gaps for their large-scale implementation remains challenging.

Application of Nanoparticles for Immunotherapy of Allergic Rhinitis

Allergen Immunotherapy (AIT) is the only etiological therapeutic method available for allergic rhinitis (AR). Currently, several options for AIT in the market, such as subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT), have different routes of administration. These traditional methods have achieved encouraging outcomes in clinic. However, the side effects associated with these methods have raised the need for innovative approaches for AIT that improve safety, shorten the course of treatment and increase local drug concentration. Nanoparticles (NPs) are particles ranging in size from 1 to 100 nm, which have been hired as potential adjuvants for AIT. NPs can be employed as agents for modulating immune responses in AR or/and carriers for loading proteins, peptides or DNA molecules. This review focuses on different kinds of nanoparticle delivery systems, including chitosan nanoparticles, exosomes, metal nanoparticles, and viral nanoparticles. We summarized the advantages and limitations of NPs for the treatment of allergic rhinitis. Overall, NPs are expected to be a therapeutic option for AR, which requires more in-depth studies and long-term therapeutic validation.

Functionalized chitosan-inspired (nano)materials containing sulfonic acid groups: Synthesis and application

Nature-inspired chitosan (CS) materials show a high potential for the design/fabrication of sustainable heterogeneous (nano)materials with extraordinary structural/physical features, such as superior biodegradability/biocompatibility, simplicity of chemical modification, environmental safety, high availability, cost-effectiveness, high electrochemical activity, good film-forming ability, and antioxidant, antimicrobial/antibacterial, and anticoagulant activities. Industrialization and growth of industrial wastes or by-products induce an increasing demand for the development of clean, low-cost, and renewable natural systems to minimize or eliminate the utilization of environmentally toxic compounds. The preparation of novel heterogeneous functionalized polysaccharide-inspired bio(nano)materials via chemical modifications of natural CS to improve its physicochemical/biochemical properties has recently become tremendously attractive for many researchers. The most abundantly available and cost-effective functionalized CS-inspired (nano)materials are considerably valuable in terms of the economic aspects of production of (nano)catalysts, (nano)hydrogels, (nano)composite/blend membranes, and thus their commercialization. In this respect, the preparation of functionalized CS-inspired (nano)materials containing -SO3H groups has been represented as a valid alternative to the homogenous unmodified biomaterials for various applications. Sulfonated derivatives of CS-inspired (nano)materials may possess huge surface areas, catalytic activity, adsorption, and biological/biomedical properties. This review article is aimed at the investigation of different methods and potential applications of sulfonated CS-inspired (nano)materials in catalysis, fuel cells, adsorption of ions, membranes, and biological applications.

Innovative biopolyelectrolytes-based technologies for wastewater treatment

Developing eco-friendly, cost-effective, and efficient methods for treating water pollutants has become paramount in recent years. Biopolyelectrolytes (BPEs), comprising natural polymers like chitosan, alginate, and cellulose, have emerged as versatile tools in this pursuit. This review offers a comprehensive exploration of the diverse roles of BPEs in combating water contamination, spanning coagulation-flocculation, adsorption, and filtration membrane techniques. With ionizable functional groups, BPEs exhibit promise in removing heavy metals, dyes, and various pollutants. Studies showcase the efficacy of chitosan, alginate, and pectin in achieving notable removal rates. BPEs efficiently adsorb heavy metal ions, dyes, and pesticides, leveraging robust adsorption capacity and exceptional mechanical properties. Furthermore, BPEs play a pivotal role in filtration membrane techniques, offering efficient separation systems with high removal rates and low energy consumption. Despite challenges related to production costs and property variability, their environmentally friendly, biodegradable, renewable, and recyclable nature positions BPEs as compelling candidates for sustainable water treatment technologies. This review delves deeper into BPEs' modification and integration with other materials; these natural polymers hold substantial promise in revolutionizing the landscape of water treatment technologies, offering eco-conscious solutions to address the pressing global issue of water pollution.

Recent Applications of Chitosan and Its Derivatives in Antibacterial, Anticancer, Wound Healing, and Tissue Engineering Fields

Chitosan, a versatile biopolymer derived from chitin, has garnered significant attention in various biomedical applications due to its unique properties, such as biocompatibility, biodegradability, and mucoadhesiveness. This review provides an overview of the diverse applications of chitosan and its derivatives in the antibacterial, anticancer, wound healing, and tissue engineering fields. In antibacterial applications, chitosan exhibits potent antimicrobial properties by disrupting microbial membranes and DNA, making it a promising natural preservative and agent against bacterial infections. Its role in cancer therapy involves the development of chitosan-based nanocarriers for targeted drug delivery, enhancing therapeutic efficacy while minimising side effects. Chitosan also plays a crucial role in wound healing by promoting cell proliferation, angiogenesis, and regulating inflammatory responses. Additionally, chitosan serves as a multifunctional scaffold in tissue engineering, facilitating the regeneration of diverse tissues such as cartilage, bone, and neural tissue by promoting cell adhesion and proliferation. The extensive range of applications for chitosan in pharmaceutical and biomedical sciences is not only highlighted by the comprehensive scope of this review, but it also establishes it as a fundamental component for forthcoming research in biomedicine.

The Chemical Modification to Improve Solubility of Chitosan and Its Derivatives Application, Preparation Method, Toxicity as a Nanoparticles

Chitosan is a functional polymer in the pharmaceutical field, including for nanoparticle drug delivery systems. Chitosan-based nanoparticles are a promising carrier for a wide range of therapeutic agents and can be administered in various routes. Solubility is the main problem for its production and utilization in large-scale industries. Chitosan modifications have been employed to enhance its solubility, including chemical modification. Many reviews have reported the chemical modification but have not focused on the specific characteristics obtained. This review focused on the modification to improve chitosan solubility. Additionally, this review also focused on the application of chitosan derivatives in nanoparticle drug delivery systems since very few similar reviews have been reported. The specific method for chitosan derivative-based nanoparticles was also reported and the latest report of chitosan, chitosan derivative, and chitosan toxicity were also described.

Extraction and characterization of Chitosan from Shell of Borassus flabellifer and their antibacterial and antioxidant applications

Chitosan is a bio-polymer made up of repeating units of N-acetyl glucosamine and glucosamine joined together by (1-4)-glycosidic linkages. Various bioresources have been used to develop bioactive materials that have a wide range of applications in different fields, including industry and medicine. Borassus flabellifer is a well-known source of chitin in the sub-Indian continent and is used in digestion, pharmaceuticals, and other applications. Chitin can be extracted from B. flabellifer fruit shells through demineralization and deproteinization and then converted into chitosan through deacetylation. This study aimed to investigate the biological activity of chitosan extracted from B. flabellifer fruit shells and to analyze its molecular structure using FT-IR analysis. Results showed the presence of NH, OH, and CO stretching, indicating the presence of various functional groups in chitosan. Scanning electron microscopic study revealed the topography of the chitosan. Well-diffusion and MIC tests showed that chitosan exhibited activity against E. coli and S. aureus. The chitosan extract also exhibited potential antioxidant polymer by scavenging free radicals.

Enhancing Soil Resilience: Bacterial Alginate Hydrogel vs. Algal Alginate in Mitigating Agricultural Challenges

Erosion and tillage changes negatively the soil physical structure, which directly impacts agricultural systems and consequently food security. To mitigate these adverse modifications, different polymeric materials from synthetic and natural sources, have been used as soil conditioners to improve the hydro-mechanical behavior of affected soils. One of the most interesting and used natural polymers is the alginate hydrogel. Although commercially available alginate hydrogels are primarily sourced from algal, they can also be sourced from bacteria. The gelation capacity of these hydrogels is determined by their molecular properties, which, in turn, are influenced by the production conditions. Bacterial alginate hydrogel production offers the advantage of precise control over environmental conditions during cultivation and extraction, thereby maintaining and enhancing their molecular properties. This, in turn, results in higher molecular weight and improved gelation capacity. In this study, we compared the effects of bacterial alginate (BH) and algal alginate (AH) hydrogels over the mechanical, hydraulic, and structural behavior of coarse quartz sand as a model soil. Mechanically, it was observed that the treatment with the lowest concentration of bacteria alginate hydrogel (BH1) reached higher values of yield strength, Young's modulus (E), shear modulus (G) and strain energy (U) than those treatments with algal alginate hydrogel (AH). Furthermore, the increase in the aggregate stability could be associated with the improvement of mechanical parameters. On the other hand, a greater water retention capacity was observed in the BH treatments, as well as a greater decrease in hydraulic conductivity with respect to the AH and control treatments. All these changes could be explained by the formation of bridge-like structures between the sand particles and the hydrogel, and this alteration may result in a shift in the mechanical and wettability characteristics of the treated soils. Finally, our findings emphasize the superior impact of bacterial alginate hydrogel on enhancing the mechanical and hydraulic properties of coarse quartz sand compared to traditional algal alginate. Besides, the use of bacterial alginate hydrogel could be useful to counteract erosion and water scarcity scenarios in agricultural systems.

Quantum DFT studies on the drug delivery of favipiravir using pristine and functionalized chitosan nanoparticles

Considering the spread of the COVID-19 pandemic, finding new drugs along with the development of effective drug delivery methods can help in the treatment of this disease. For this reason, in this research work, the possibility of drug-delivery of Favipiravir (FP), one of the drugs approved in the treatment of COVID-19, by pristine chitosan (Chit) nanoparticles (NP), and functionalized chitosan nanoparticles with N-acylate, N-methyl, O-acetyl, and Oxazoline functional groups was studied using quantum mechanical DFT methods at B3LYP-D3(BJ)/6-311 + g(d,p) theoretical level in water medium. The QTAIM, NBO, DOS, frontier orbital, conceptual-DFT indices, and non-covalent interaction analysis were further implemented to investigate the possible interactions between FP and Chit NPs. The results show that the adsorption of FP on Chit NPs is done through the creation of hydrogen bonds, and the highest absorption energy of - 18.15 kcal/mol between pristine chitosan and FP. In the case of all functionalized Chit NPs, a decrease in the absorption energy is observed, which is more noticeable in the case of N-acylated and O-acetyl functionalize Chit NPs, and indicates the weakening of the van der Waals interactions for these cases. Considering the compatibility of Chit NPs with the human body and their non-toxicity, as well as the fact that factors such as pH, solubility, the ionic strength, and so on can be adjusted to control the release rate using the functionalized Chit NPs, it seems that the results of this work can be a comprehensive guide to design the drug delivery methods of FP drug using Chit NPs, to reduce the symptoms of COVID-19 disease.

Synthesis and characterization of novel chitosan derivatives (containing dipyridinium quaternary salts) with antimicrobial potential

Chitosan derivatives are versatile materials, biocompatible and biodegradable, that can be tailor-made to suit specific biomedical applications. In this study, two N-heterocyclic salts (N,N'-diphenacyl-[4,4'-dipyridinium] dibromide (DP) and N,N'-diphenacyl-1,2-bis-(4-pyridinium)ethane dibromide (DPE)) were used for chitosan functionalization to enhance its antimicrobial potential. Physico-chemical characterization of the newly synthesized derivatives (Ch-DP and Ch-DPE) was performed by elemental analysis, spectrometry (UV-Vis, FTIR), electrochemistry (OCP, CV), and electron microscopy (SEM) proving that the highest degree of functionalization was obtained for Ch-DP. The antimicrobial effect of chitosan functionalization was further tested in terms of its interaction with Listeria monocytogenes Scott A, and Staphylococcus aureus ATCC 25923, as Gram-positive bacteria and Escherichia coli ATCC 25922, as Gram-negative bacterium, respectively, showing that the Ch-DP had a good inhibitory activity compared with Ch-DPE.

Chitosan-Based Hydrogels for Infected Wound Treatment

Wound infections slow down the healing process and lead to complications such as septicemia, osteomyelitis, and even death. Although traditional methods relying on antibiotics are effective in controlling infection, they have led to the emergence of antibiotic-resistant bacteria. Hydrogels with antimicrobial function become a viable option for reducing bacterial colonization and infection while also accelerating healing processes. Chitosan is extensively developed as antibacterial wound dressings due to its unique biochemical properties and inherent antibacterial activity. In this review, the recent research progress of chitosan-based hydrogels for infected wound treatment, including the fabrication methods, antibacterial mechanisms, antibacterial performance, wound healing efficacy, etc., is summarized. A concise assessment of current limitations and future trends is presented.

Enhancing the metal ion binding characteristics and reversal of selectivity of crosslinked chitosan sorbents through functionalisation for targeted applications

In this study, we report optimised synthesis of N-carboxymethylated chitosan (CM-Cts) and its crosslinking to obtain, for the first time, glutaraldehyde crosslinked N-carboxymethylated chitosan (CM-Cts-Glu) as a metal ion sorbent. CM-Cts and CM-Cts-Glu were characterised using FTIR and solid state 13C NMR techniques. As compared to epichlorohydrin, glutaraldehyde was found to be better suited for efficient synthesis of the crosslinked functionalised sorbent. CM-Cts-Glu showed better metal ion uptake properties compared to the crosslinked chitosan (Cts-Glu). Metal ion removal by CM-Cts-Glu was studied in detail under different conditions such as different initial solution concentrations, pH, presence of complexants and competing ions. Further, sorption-desorption kinetics was studied and it was shown that complete desorption and multiple cycles of reuse without any loss in capacity was feasible. The maximum Co(II) uptake obtained for CM-Cts-Glu was found to be 265 μmol/g, while for Cts-Glu it was 10 μmol/g. Metal ion sorption by CM-Cts-Glu was found to be through chelation by the carboxylic acid functional groups present over the chitosan backbone. Utility of the CM-Cts-Glu under complexing decontamination formulations used in nuclear industry was ascertained. While Cts-Glu generally preferred iron over cobalt under complexing conditions, it was shown that the selectivity was reversed in favour of Co(II) in the functionalised sorbent, CM-Cts-Glu. N-carboxylation followed by crosslinking with glutaraldehyde was found to be a feasible approach for the generation of superior chitosan-based sorbents.

Differences in Water Dynamics between the Hydrated Chitin and Hydrated Chitosan Determined by Quasi-Elastic Neutron Scattering

Recently, it was reported that chitin and chitosan exhibited high-proton conductivity and function as an electrolyte in fuel cells. In particular, it is noteworthy that proton conductivity in the hydrated chitin becomes 30 times higher than that in the hydrated chitosan. Since higher proton conductivity is necessary for the fuel cell electrolyte, it is significantly important to clarify the key factor for the realization of higher proton conduction from a microscopic viewpoint for the future development of fuel cells. Therefore, we have measured proton dynamics in the hydrated chitin using quasi-elastic neutron scattering (QENS) from the microscopic viewpoint and compared the proton conduction mechanism between hydrated chitin and chitosan. QENS results exhibited that a part of hydrogen atoms and hydration water in chitin are mobile even at 238 K, and the mobile hydrogen atoms and their diffusion increase with increasing temperature. It was found that the diffusion constant of mobile protons is two times larger and that the residence time is two times faster in chitin than that in chitosan. In addition, it is revealed from the experimental results that the transition process of dissociable hydrogen atoms between chitin and chitosan is different. To realize proton conduction in the hydrated chitosan, the hydrogen atoms of the hydronium ions (H₃O⁺) should be transferred to another hydration water. By contrast, in hydrated chitin, the hydrogen atoms can transfer directly to the proton acceptors of neighboring chitin. It is deduced that higher proton conductivity in the hydrated chitin compared with that in the hydrated chitosan is yielded by the difference of diffusion constant and the residence time by hydrogen-atom dynamics and the location and number of proton acceptors.

Chitosan: A Potential Biopolymer in Drug Delivery and Biomedical Applications

Chitosan, a biocompatible and biodegradable polysaccharide derived from chitin, has surfaced as a material of promise for drug delivery and biomedical applications. Different chitin and chitosan extraction techniques can produce materials with unique properties, which can be further modified to enhance their bioactivities. Chitosan-based drug delivery systems have been developed for various routes of administration, including oral, ophthalmic, transdermal, nasal, and vaginal, allowing for targeted and sustained release of drugs. Additionally, chitosan has been used in numerous biomedical applications, such as bone regeneration, cartilage tissue regeneration, cardiac tissue regeneration, corneal regeneration, periodontal tissue regeneration, and wound healing. Moreover, chitosan has also been utilized in gene delivery, bioimaging, vaccination, and cosmeceutical applications. Modified chitosan derivatives have been developed to improve their biocompatibility and enhance their properties, resulting in innovative materials with promising potentials in various biomedical applications. This article summarizes the recent findings on chitosan and its application in drug delivery and biomedical science.

Characterizing the Impact of Chitosan on the Nucleation and Crystal Growth of Ritonavir from Supersaturated Solutions

The addition of polymeric materials is often used to delay nucleation or crystal growth and maintain the high supersaturation of amorphous drugs. Therefore, this study aimed to investigate the impact of chitosan on the supersaturation behavior of drugs with a low recrystallization tendency and elucidate the mechanism of its crystallization inhibition in an aqueous solution. It was carried out using ritonavir (RTV) as a model of poorly water-soluble drugs categorized as class III of Taylor's classification, while chitosan was used as a polymer, and hypromellose (HPMC) was used for comparison. The inhibition of the nucleation and crystal growth of RTV by chitosan was examined by measuring the induction time. The interactions of RTV with chitosan and HPMC were evaluated by NMR measurements, FT-IR, and an in silico analysis. The results showed that the solubilities of amorphous RTV with and without HPMC were quite similar, while the amorphous solubility was significantly increased by the chitosan addition due to the solubilization effect. In the absence of the polymer, RTV started to precipitate after 30 min, indicating that it is a slow crystallizer. Chitosan and HPMC effectively inhibited the nucleation of RTV, as reflected by a 48-64-fold enhancement in the induction time. Furthermore, NMR, FT-IR, and in silico analysis demonstrated that the hydrogen bond interaction between the amine group of RTV and a proton of chitosan, as well as the carbonyl group of RTV and a proton of HPMC, was observed. This indicated that the hydrogen bond interaction between RTV and chitosan as well as HPMC can contribute to the crystallization inhibition and maintenance of RTV in a supersaturated state. Therefore, the addition of chitosan can delay nucleation, which is crucial for stabilizing supersaturated drug solutions, specifically for a drug with a low crystallization tendency.

Heteropolysaccharides in sustainable corrosion inhibition: 4E (Energy, Economy, Ecology, and Effectivity) dimensions

Carbohydrate polymers (polysaccharides) and their derivatives are widely utilized in sustainable corrosion inhibition (SCI) because of their various fascinating properties including multiple adsorption sites, high solubility and high efficiency. Contrary to traditional synthetic polymer-based corrosion inhibitors, polysaccharides are related to the 4E dimension, which stands for Energy, Economy, Ecology, and Effectivity. Furthermore, they are relatively more environmentally benign, biodegradable, and non-bioaccumulative. The current review describes the SCI features of various heteropolysaccharides, including gum Arabic (GA), glycosaminoglycans (chondroitin-4-sulfate (CS), hyaluronic acid (HA), heparin, etc.), pectin, alginates, and agar for the first time. They demonstrate impressive anticorrosive activity for different metals and alloys in a variety of corrosive electrolytes. Through their adsorption at the metal/electrolyte interface, heteropolysaccharides function by producing a corrosion-protective film. In general, their adsorption follows the Langmuir isotherm model. In their molecular structures, heteropolysaccharides contain several polar functional groups like -OH, -NH₂, -COCH₃, -CH₂OH, cyclic and bridging O, -CH₂SO₃H, -SO₃OH, -COOH, -NHCOCH₃, -OHOR, etc. that serve as adsorption centers when they bind to metallic surfaces.

Modification and Functionalization of Polymers for Targeting to Bone Cancer and Bone Regeneration

Bone is one of the most complex, inaccessible body structures, responsible for calcium storage and haematopoiesis. The second highest cause of death across the world is cancer. Amongst all the types of cancers, bone cancer treatment modalities are limited due to the structural complexity and inaccessibility of bones. The worldwide incidence of bone diseases and bone defects due to cancer, infection, trauma, age-related bone degeneration is increasing. Currently different conventional therapies are available for bone cancer such as chemotherapy, surgery and radiotherapy, but they have several disadvantages associated with them. Nanomedicine is being extensively researched as viable therapeutics to mitigate drug resistance in cancer therapy and promote bone regeneration. Several natural polymers such as chitosan, dextran, alginate, hyaluronic acid, and synthetic polymers like polyglycolic acid, poly(lactic-co-glycolic acid), polycaprolactone are investigated for their application in nanomedicine for bone cancer treatment and bone regeneration. Nanocarriers have shown promising results in preclinical experimental studies. However, they still face a major drawback of inadequate targetability. The paper summarizes the status of research and the progress made so far in modifications and functionalization of natural polymers for improving their site specificity and targeting for effective treatment of bone cancer and enhancing bone regeneration.

A Self-Healing Gel Polymer Electrolyte, Based on a Macromolecule Cross-Linked Chitosan for Flexible Supercapacitors

Gel polymer electrolytes with a satisfied ionic conductivity have attracted interest in flexible energy storage technologies, such as supercapacitors and rechargeable batteries. However, the poor mechanical strength inhibits its widespread application. One of the most significant ways to avoid the drawbacks of the gel polymer electrolytes without compromising their ion transportation capabilities is to create a self-healing structure with the cross-linking segment. Herein, a new kind of macromolecule chemical cross-linked network ionic gel polymer electrolyte (MCIGPE) with superior electrochemical characteristics, a high flexibility, and an excellent self-healing ability were designed, based on chitosan and dibenzaldehyde-terminated poly (ethylene glycol) (PEGDA) via dynamic imine bonds. The ionic conductivity of the MCIGPE-65 can achieve 2.75 × 10^-2 S cm^-1. A symmetric all-solid-state supercapacitor employing carbon cloth as current collectors, activated a carbon film as electrodes, and MCIGPE-65 as a gel polymer electrolyte exhibits a high specific capacitance of 51.1 F g^-1 at 1 A g^-1, and the energy density of 7.1 Wh kg^-1 at a power density of 500.2 W kg^-1. This research proves the enormous potential of incorporating, environmentally and economically, chitosan into gel polymer electrolytes for supercapacitors.

Synthesis and characterization of functionalized modified PVC-chitosan as antimicrobial polymeric biomaterial

Amino acetic acid modified poly(vinyl chloride), MPVC, was obtained by chemical modification of PVC using glycine methyl ester. MPVC was used as a precursor to prepare some functionalized MPVC conjugates to be used in biomedical applications. MPVC-Cs was prepared by the chemical reaction of MPVC with chitosan as a natural polymer in absence and presence of epichlorohydrin (Ech) as a crosslinking agent. Further chemical modification was performed by the reaction of MPVC with Cs and salicylic acid in the absence in presence of Ech via one-pot reaction. The chemical structure of the formed MPVC, MPVC-Cs, MPVC-Cs/POH, MPVC-Cs/SA and MPVC-Cs/POH/SA was confirmed by the FTIR spectroscopic analysis, scanning electron microscopy, and thermogravimetric analysis (TGA). The antibacterial activity of the prepared MPVC and its conjugates was investigated against two Gram +ve bacteria (Staphylococcus aurous and Listeria monocytogenes) and (Escherichia coli and Salmonella typhi) as Gram −ve bacteria in addition to the Catondida albicans as yeast. Minimum inhibition concentration (MIC) was also determined for the prepared materials.

Adsorption of flexible proteins in the 'wrong side' of the isoelectric point: Casein macropeptide as a model system

We analyze the conditions of the adsorption of a flexible peptide onto a charged substrate in the 'wrong side' of the isoelectric point (WSIP), i.e. when surface and peptide charges have the same sign. As a model system, we focus on the casein macropeptide (CMP), both in the aglycosylated (aCMP) and fully glycosydated (gCMP) forms. We model the substrate as a uniformly charged plane while CMP is treated as a bead-and-spring model including electrostatic interactions, excluded volume effects and acid/base equilibria. Adsorption coverage, aminoacid charges and concentration profiles are computed by means of Monte Carlo simulations at fixed pH and salt concentration. We conclude that for different reasons the CMP can be adsorbed to both positively and negatively charged surfaces in the WSIP. For negatively charged surfaces, WSIP adsorption is due to the patchy distribution of charges: the peptide is attached to the surface by the positively charged end of the chain, while the repulsion of the surface for the negatively charged tail is screened by the small ions of the added salt. This effect increases with salt concentration. Conversely, a positively charged substrate induces strong charge regulation of the peptide: the acidic groups are deprotonated, and the peptide becomes negatively charged. This effect is stronger at low salt concentrations and it is more intense for gCMP than for aCMP, due to the presence of the additional sialic groups in gCMP.

Structural characterization and anti-inflammatory properties of green synthesized chitosan/compound K‑gold nanoparticles

Ginsenoside compound K (CK) has been shown to exhibit anti-inflammatory properties. In this study, to encourage biomedical applications of biosynthesized gold nanoparticles (AuNPs) with anti-inflammatory effects, AuNPs loaded with ginsenoside compound K were prepared using a self-assembly technique with chitosan as the carrier. Optimal conditions for chitosan-ginsenoside CK‑gold nanoparticles (CS-CK-AuNPs) formation were monitored using UV-Vis absorption spectroscopy. The physicochemical characterization of CS-CK-AuNPs was performed using FE-TEM, FE-SEM, XRD, DLS, FTIR and NMR techniques. In the stability test, CS-CK-AuNPs did not show any significant changes up to 4 weeks. Fluorescence imaging demonstrated that CS-CK-AuNPs promoted cellular uptake in vitro, but did not exhibit significant cytotoxicity at concentrations below 40 μg/mL. Additionally, the CS-CK-AuNPs inhibited NO production, and reduced the expression and secretion of inflammatory cytokines (IL-1β, IL-6, and TNF-α) via inhibition of the nuclear factor-kappaB (NF-κB) pathway in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Thus, CS-CK-AuNPs are novel candidates for developing anti-inflammatory agent. This study also confirms the superiority of chitosan AuNPs as oral delivery vehicles for inflammation-related diseases.

New Zinc-Based Active Chitosan Films: Physicochemical Characterization, Antioxidant, and Antimicrobial Properties

The improvement of the antioxidant and antimicrobial activities of chitosan (CS) films can be realized by incorporating transition metal complexes as active components. In this context, bioactive films were prepared by embedding a newly synthesized acylpyrazolonate Zn(II) complex, [Zn(Q^PhtBu)₂(MeOH)₂], into the eco-friendly biopolymer CS matrix. Homogeneous, amorphous, flexible, and transparent CS@Zn_n films were obtained through the solvent casting method in dilute acidic solution, using different weight ratios of the Zn(II) complex to CS and characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR), Raman, and scanning electron microscopy (SEM) techniques. The X-ray single-crystal analysis of [Zn(Q^PhtBu)₂(MeOH)₂] and the evaluation of its intermolecular interactions with a protonated glucosamine fragment through hydrogen bond propensity (HBP) calculations are reported. The effects of the different contents of the [Zn(Q^PhtBu)₂(MeOH)₂] complex on the CS biological proprieties have been evaluated, proving that the new CS@Zn_n films show an improved antioxidant activity, tested according to the DPPH method, with respect to pure CS, related to the concentration of the incorporated Zn(II) complex. Finally, the CS@Zn_n films were tried out as antimicrobial agents, showing an increase in antimicrobial activity against Gram-positive bacteria (Staphylococcus aureus) with respect to pure CS, when detected by the agar disk-diffusion method.

Chitosan - Rosmarinic acid conjugates with antioxidant, anti-inflammatory and photoprotective properties

Rosmarinic acid is an attractive candidate for skin applications because of its antioxidant, anti-inflammatory, and photoprotective functions, however, its poor bioavailability hampers its therapeutic outcome. In this context, synthesis of polymer conjugates is an alternative to enlarge its applications. This work describes the synthesis of novel water-soluble chitosan - rosmarinic acid conjugates (CSRA) that have great potential for skin applications. Chitosan was functionalized with different contents of rosmarinic acid as confirmed by ATR-FTIR, 1H NMR and UV spectroscopies. CSRA conjugates presented three-fold radical scavenger capacity compared to the free phenolic compound. Films were prepared by solvent-casting procedure and the biological activity of the lixiviates was studied in vitro. Results revealed that lixiviates reduced activation of inflamed macrophages, improved antibacterial capacity against E. coli with respect to native chitosan and free rosmarinic acid, and also attenuated UVB-induced cellular damage and reactive oxygen species production in fibroblasts and keratinocytes.

Heparanized chitosans: towards the third generation of chitinous biomaterials

The functionalization of chitosans is an emerging research area in the design of solutions for a wide range of biomedical applications. In particular, the modification of chitosans to incorporate sulfate groups has generated great interest since they show structural similarity to heparin and heparan sulfates. Most of the biomedical applications of heparan sulfates are derived from their ability to bind different growth factors and other proteins, as through these interactions they can modulate the cellular response. This review aims to summarize the most recent advances in the synthesis, and structural and physicochemical characterization of heparanized chitosan, a remarkably interesting family of polysaccharides that have demonstrated the ability to mimic heparan sulfates as ligands for different proteins, thereby exerting their biological activity by mimicking the function of these glycosaminoglycans.

Factors Influencing the Antibacterial Activity of Chitosan and Chitosan Modified by Functionalization

The biomedical and therapeutic importance of chitosan and chitosan derivatives is the subject of interdisciplinary research. In this analysis, we intended to consolidate some of the recent discoveries regarding the potential of chitosan and its derivatives to be used for biomedical and other purposes. Why chitosan? Because chitosan is a natural biopolymer that can be obtained from one of the most abundant polysaccharides in nature, which is chitin. Compared to other biopolymers, chitosan presents some advantages, such as accessibility, biocompatibility, biodegradability, and no toxicity, expressing significant antibacterial potential. In addition, through chemical processes, a high number of chitosan derivatives can be obtained with many possibilities for use. The presence of several types of functional groups in the structure of the polymer and the fact that it has cationic properties are determinant for the increased reactive properties of chitosan. We analyzed the intrinsic properties of chitosan in relation to its source: the molecular mass, the degree of deacetylation, and polymerization. We also studied the most important extrinsic factors responsible for different properties of chitosan, such as the type of bacteria on which chitosan is active. In addition, some chitosan derivatives obtained by functionalization and some complexes formed by chitosan with various metallic ions were studied. The present research can be extended in order to analyze many other factors than those mentioned. Further in this paper were discussed the most important factors that influence the antibacterial effect of chitosan and its derivatives. The aim was to demonstrate that the bactericidal effect of chitosan depends on a number of very complex factors, their knowledge being essential to explain the role of each of them for the bactericidal activity of this biopolymer.

Multifunctional Immunoadjuvants for Use in Minimalist Nucleic Acid Vaccines

Subunit vaccines based on antigen-encoding nucleic acids have shown great promise for antigen-specific immunization against cancer and infectious diseases. Vaccines require immunostimulatory adjuvants to activate the innate immune system and trigger specific adaptive immune responses. However, the incorporation of immunoadjuvants into nonviral nucleic acid delivery systems often results in fairly complex structures that are difficult to mass-produce and characterize. In recent years, minimalist approaches have emerged to reduce the number of components used in vaccines. In these approaches, delivery materials, such as lipids and polymers, and/or pDNA/mRNA are designed to simultaneously possess several functionalities of immunostimulatory adjuvants. Such multifunctional immunoadjuvants encode antigens, encapsulate nucleic acids, and control their pharmacokinetic or cellular fate. Herein, we review a diverse class of multifunctional immunoadjuvants in nucleic acid subunit vaccines and provide a detailed description of their mechanisms of adjuvanticity and induction of specific immune responses.

Formulation of Quaternized Aminated Chitosan Nanoparticles for Efficient Encapsulation and Slow Release of Curcumin

An effective drug nanocarrier was developed on the basis of a quaternized aminated chitosan (Q-AmCs) derivative for the efficient encapsulation and slow release of the curcumin (Cur)-drug. A simple ionic gelation method was conducted to formulate Q-AmCs nanoparticles (NPs), using different ratios of sodium tripolyphosphate (TPP) as an ionic crosslinker. Various characterization tools were employed to investigate the structure, surface morphology, and thermal properties of the formulated nanoparticles. The formulated Q-AmCs NPs displayed a smaller particle size of 162 ± 9.10 nm, and higher surface positive charges, with a maximum potential of +48.3 mV, compared to native aminated chitosan (AmCs) NPs (231 ± 7.14 nm, +32.8 mV). The Cur-drug encapsulation efficiency was greatly improved and reached a maximum value of 94.4 ± 0.91%, compared to 75.0 ± 1.13% for AmCs NPs. Moreover, the in vitro Cur-release profile was investigated under the conditions of simulated gastric fluid [SGF; pH 1.2] and simulated colon fluid [SCF; pH 7.4]. For Q-AmCs NPs, the Cur-release rate was meaningfully decreased, and recorded a cumulative release value of 54.0% at pH 7.4, compared to 73.0% for AmCs NPs. The formulated nanoparticles exhibited acceptable biocompatibility and biodegradability. These findings emphasize that Q-AmCs NPs have an outstanding potential for the delivery and slow release of anticancer drugs.

Pesticide Aptasensors-State of the Art and Perspectives

Contamination by pesticides in the food chain and the environment is a worldwide problem that needs to be actively monitored to ensure safety. Unfortunately, standard pesticide analysis based on mass spectrometry takes a lot of time, money and effort. Thus, simple, reliable, cost-effective and field applicable methods for pesticide detection have been actively developed. One of the most promising technologies is an aptamer-based biosensor or so-called aptasensor. It utilizes aptamers, short single-stranded DNAs or RNAs, as pesticide recognition elements to integrate with various innovative biosensing technologies for specific and sensitive detection of pesticide residues. Several platforms for aptasensors have been dynamically established, such as colorimetry, fluorometry, electrochemistry, electrochemiluminescence (ECL) and so forth. Each platform has both advantages and disadvantages depending on the purpose of use and readiness of technology. For example, colorimetric-based aptasensors are more affordable than others because of the simplicity of fabrication and resource requirements. Electrochemical-based aptasensors have mainly shown better sensitivity than others with exceedingly low detection limits. This paper critically reviews the progression of pesticide aptasensors throughout the development process, including the selection, characterization and modification of aptamers, the conceptual frameworks of integrating aptamers and biosensors, the ASSURED (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free and deliverable to end users) criteria of different platforms and the future outlook.

Polycondensation of bis(α-diazo-1,3-dicarbonyl) compounds with dicarboxylic acids: an efficient access to functionalized alternating polyesters

We report an efficient and mild approach to functionalized alternating polyesters on the basis of O–H insertion polycondensation of bis(α-diazo-1,3-dicarbonyl) compounds with dicarboxylic acids.