Modified Chitosan Derivatives Research Articles

Modified chitosan with different phenolic acids: Characterization, physicochemical properties, and biological activity

This study synthesized five phenolic acid-chitosan copolymers utilizing the carbodiimide-mediated chemical crosslinking reaction. Comprehensive evaluations were conducted on their structural attributes, physicochemical properties, and biological activities. Fourier transform infrared confirmed successful grafting of phenolic acids onto chitosan via amide linkages. Additionally, ultraviolet–visible absorption spectroscopy and proton nuclear magnetic resonance analyses revealed novel absorption peaks between 200 and 400 nm and 6.0–8.0 ppm, respectively, attributable to the incorporated phenolic acids. Notably, the chitosan-gentisate acid copolymer exhibited significantly enhanced biological activity (p < 0.05) compared to pure chitosan and the other four conjugates, attributed to its highest grafting degree of approximately 295.93 mg/g. These modified chitosan derivatives effectively preserved the quality of sea bass (Lateolabrax japonicus) during refrigerated storage, extending its shelf-life by up to 9 days, 7 days, and 4 days relative to control, chitosan, and gentisate acid groups.

Therapeutic applications of sustainable new chitosan derivatives and its nanocomposites: Fabrication and characterization

Chitosan (CS) is a biologically active biopolymer used in different medical applications due to its biodegradability, biocompatibility, and nontoxicity. Nanotechnology is an exciting and quick developing field in medical applications. Nanoparticles have shown great potential in the treatment of cancer and inflammation. In the present work modification of chitosan and its (Ag, Au, or ZnO) nanocomposites by N-aminophthalimide (NAP) occurred through the reaction with epichlorohydrin (ECH) as a crosslinker in the presence or absence of glutaraldehyde (GA) under different reaction conditions using microwave irradiation to give modified chitosan derivatives CS-2, CS-6, and their nanocomposites. Modified chitosan derivatives were characterized using different tools. CS-2 and CS-6 derivatives displayed enhancement of thermal stability and crystallinity compared to chitosan. Additionally, CS-2, CS-6, and their nanocomposites exhibited improvements in antitumor activity against HeLa cancer cells and enzymatic inhibitory against trypsin and α-chymotrypsin enzymes compared to chitosan. However, CS-2 revealed the highest cell growth inhibition% toward HeLa cells (89.02 ± 1.46 %) and the enzymatic inhibitory toward α-chymotrypsin enzyme (17.13 ± 1.59 %). Furthermore, CS-Au-2 showed the highest enzymatic inhibitory against trypsin enzyme (28.14 ± 1.76 %). These results suggested that the new chitosan derivatives CS-2, CS-6, and their nanocomposites could be a platform for medical applications against HeLa cells, trypsin, and α-chymotrypsin enzymes.

Optimization, Kinetics, and Isotherm Studies of Methyl Thioninium Chloride Removal from Simulated Solutions Using Chitosan Derivatives.

Methylene blue (MB) dye or methyl thioninium chloride is one of the hazardous cationic dyes that are discharged into the textile effluent causing a highly negative environmental impact. The present work targets the investigation of the adsorption performance of some chitosan-modified products toward the MB dye from simulated solutions. The claimed chitosan derivatives were prepared, characterized, and applied for the removal of lead and copper cations from an aqueous medium in a previous work. These include: N,O-carboxymethyl chitosan (N,O-CM/Cs), chitosan grafted with glutaraldehyde (Cs/GA), chitosan cross-linked with GA/epichlorohydrin (Cs/GA/ECH), and chitosan cross-linked with glutaraldehyde/methylene bis(acrylamide) (Cs/GA/MBA). The modified chitosan derivatives in this study displayed outstanding mechanical qualities, exceptional reusability, and a significant amount of adsorption capacity. The ability of prepared Cs derivatives to eradicate MB was as follows: N,O-CM/Cs (95.1 mg/g) < Cs/GA (120.1 mg/g) < Cs/GA/ECH (220.1 mg/g) < Cs/GA/MBA (270.0 mg/g). The swelling performance of the prepared sorbents was verified under different experimental conditions, and the data revealed that the maximum swelling was attained at pH = 9, temperature 55 °C, and after 24 h. The produced Cs derivatives showed exceptional reusability by maintaining higher adsorption effectiveness throughout five cycles. The MB dye was adsorbed onto the modified derivatives according to pseudo-second-order kinetics and the Langmuir model. Moreover, the adsorption process was monitored via atomic force microscopy to verify the differences between the dye-free and dye-loaded adsorbents.

Inhibitory Potential of Chitosan Derivatives against Severe Acute Respiratory Syndrome Coronavirus 2: An In Silico Prospective

The present work was designed to investigate the antiviral potential of novel monomeric and oligomeric chitosan derivatives through in silico approaches. The goal was to identify potent broad-spectrum antiviral compounds as promising drug candidates against severe acute respiratory syndrome coronavirus 2 and understand their mode of action. Chitosan biopolymer and its derivatives were virtually screened against the spike glycoprotein and human angiotensin-converting enzyme 2 (ACE2) receptor of novel coronavirus-19. Hydroxypropyl trimethyl ammonium chloride chitosan (HTCC), a polymeric chitosan, has been reported to interact with the corona viral spike (S) protein and blocks its interaction with the ACE2 receptor. The enhancement of antiviral activity relies on better biocompatibility, structural correlations, variation in the degree of deacetylation, and molecular weight of modified chitosan derivatives. The chitosan derivatives constructively interact with viral S protein. Among the chitosan derivatives, N-carboxymethyl chitosan (NCMC) displayed efficient binding affinity. Comparing NCMC to mHTCC, monomeric chitosan, for their interaction with the S protein, receptor binding domain site, and ACE2 receptor, NCMC displayed better binding affinity of &amp;minus;7.9, &amp;minus;6.3, and &amp;minus;7.4 with binding energies of &amp;minus;6.2, &amp;minus;4.8, and &amp;minus;5.5 kcal/mol, respectively. Furthermore, through flexible docking, the interactions of the S protein with ACE2 receptor and ligand mHTCC-S protein complex and NCMC-S protein complex with ACE2 receptor were calculated, showing an efficient reduction of binding energy from &amp;minus;901.2 kJ/mol to &amp;minus;765.06 kJ/mol and &amp;minus;814.72 kJ/mol, respectively. This points to the decrease binding affinity of the viral S protein for the ACE2 receptor in the presence of NCMC/mHTCC. For the first time, the computational study envisages the antiviral efficiency of NCMC, mHTCC, and biocompatible chitosan derivatives as a preventive intervention against COVID-19.

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.

Chitosan Derivatives as Carriers for Drug Delivery and Biomedical Applications.

Over the past few decades, chitosan (CS) has gained the attention of researchers investigating newer biomaterial-based carriers for drugs in pharmaceutical and biomedical research. Combined with its nontoxic behavior, biodegradability, and biocompatibility, chitosan has found widespread applications in the fields of drug delivery, tissue engineering, and cosmetics. As a novel drug carrier, chitosan is regarded as one of the promising biomaterials in the pharmaceutical industry. The extensive use of this cationic biopolysaccharide in the delivery of therapeutic agents has brought a few limitations of chitosan into the limelight. Various chemical modifications of chitosan can minimize these limitations and improve the efficacy of chitosan as a drug carrier. The effectiveness of several chemically modified chitosan derivatives, including trimethyl chitosan, thiolated chitosan, PEGylated chitosan, and other chitosan derivatives, has been investigated by many researchers for the controlled and target specific delivery of therapeutics. The chemically modified chitosan derivatives exhibited greater importance in the current scenario on drug delivery due to their solubility in wide range of media along with their interaction with pharmaceutically active ingredients. Chitosan derivatives have also attracted attention in several biomedical fields, including wound healing, hyperthermia therapy, tissue engineering, and bioadhesives. The present review narrates the sources and common physicochemical properties of chitosan, including several important synthetic modifications to obtain chemically modified chitosans and their applications in target-specific drug delivery, along with several biomedical applications.

Dual functional quaternary chitosans with thermoresponsive behavior: structure-activity relationships in antibacterial activity and biocompatibility.

Cationically modified chitosan derivatives exhibit a range of appealing characteristics, with a particular emphasis on their antimicrobial potential across a broad spectrum of biomedical applications. This study aimed to delve deeper into quaternary chitosan (QC) derivatives. Through the synthesis of both homogeneously and heterogeneously dual-quaternized chitosan (DQC), utilizing AETMAC ([2-(acryloyloxy)ethyl]-trimethylammonium chloride) and GTMAC (glycidyl trimethylammonium chloride), a permanent charge was established, spanning a wide pH range. We assessed structural differences, the type of quaternary functional group, molecular weight (Mw), and charge density. Intriguingly, an upper critical solution temperature (UCST) behavior was observed in AETMAC-functionalized QC. To our knowledge, it is a novel discovery in cationically functionalized chitosan. These materials demonstrated excellent antimicrobial efficacy against model test organisms E. coli and P. syringae. Furthermore, we detected concentration-dependent cytotoxicity in NIH-3T3 fibroblasts. Striking a balance between antimicrobial activity and cytotoxicity becomes a crucial factor in application feasibility. AETMAC-functionalized chitosan emerges as the top performer in terms of overall antibacterial effectiveness, possibly owing to factors like molecular weight, charge characteristics, and variations in the quaternary linker. Quaternary chitosan derivatives, with their excellent antibacterial attributes, hold significant promise as antibacterial or sanitizing agents, as well as across a broad spectrum of biomedical and environmental contexts.

New thiadiazole modified chitosan derivative to control the growth of human pathogenic microbes and cancer cell lines

The emergence of multidrug-resistant microbes and the propagation of cancer cells are global health issues. The unique properties of chitosan and its derivatives make it an important candidate for therapeutic applications. Herein, a new thiadiazole derivative, 4-((5-(butylthio)-1,3,4-thiadiazol-2-yl) amino)-4-oxo butanoic acid (BuTD-COOH) was synthesized and used to modify the chitosan through amide linkages, forming a new thiadiazole chitosan derivative (BuTD-CH). The formation of thiadiazole and the chitosan derivative was confirmed by FT-IR, 1H/13C-NMR, GC–MS, TGA, Elemental analysis, and XPS. The BuTD-CH showed a high antimicrobial effect against human pathogens Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, and Candida albicans with low MIC values of 25–50 μg ml−1 compared to unmodified chitosan. The in-vitro cytotoxicity of BuTD-CH was evaluated against two cancer cell lines (MCF-7 and HepG2) and one normal cell (HFB4) using the MTT method. The newly synthesized derivatives showed high efficacy against cancerous cells and targeted them at low concentrations (IC50 was 178.9 ± 9.1 and 147.8 ± 10.5 μg ml−1 for MCF-7 and HepG2, respectively) compared with normal HFB4 cells (IC50 was 335.7 ± 11.4 μg ml−1). Thus, low concentrations of newly synthesized BuTD-CH could be safely used as an antimicrobial and pharmacological agent for inhibiting the growth of human pathogenic microbes and hepatocellular and adenocarcinoma therapy.

Current Advances in Chitosan Nanoparticles Based Oral Drug Delivery for Colorectal Cancer Treatment.

As per the WHO, colorectal cancer (CRC) caused around 935,173 deaths worldwide in 2020 in both sexes and at all ages. The available anticancer therapies including chemotherapy, radiotherapy and anticancer drugs are all associated with limited therapeutic efficacy, adverse effects and low chances. This has urged to emerge several novel therapeutic agents as potential therapies for CRC including synthetic and natural materials. Orally administrable and targeted drug delivery systems are attractive strategies for CRC therapy as they minimize the side effects, enhance the efficacy of anticancer drugs. Nevertheless, oral drug delivery till today faces several challenges like poor drug solubility, stability, and permeability. Various oral nano-based approaches and targeted drug delivery systems have been developed recently, as a result of the ability of nanoparticles to control the release of the encapsulant, drug targeting and reduce the number of dosages administered. The unique physicochemical properties of chitosan polymer assist to overcome oral drug delivery barriers and target the colon tumour cells. Chitosan-based nanocarriers offered additional improvements by enhancing the stability, targeting and bioavailability of several anti-colorectal cancer agents. Modified chitosan derivatives also facilitated CRC targeting through strengthening the protection of encapsulant against acidic and enzyme degradation of gastrointestinal track (GIT). This review aims to provide an overview of CRC pathology, therapy and the barriers against oral drug delivery. It also emphasizes the role of nanotechnology in oral drug targeted delivery system and the growing interest towards chitosan and its derivatives. The present review summarizes the relevant works to date that have studied the potential applications of chitosan-based nanocarrier towards CRC treatment.

Designing of modified ion-imprinted chitosan particles for selective removal of mercury (II) ions

Ion-imprinting methodology was utilized in the fabrication of mercury ion-imprinted sorbent derived from modified chitosan derivatives. The Schiff base ligand was first derived from 4-amino-3-hydroxybenzoic acid and 2-pyridinecarboxaldehyde (HPB) and then incorporated with chitosan via amide bonds. The obtained modified chitosan polymeric ligand (PBCS) was combined with Hg(II) ions to produce the corresponding polymeric complex and the imprinting was then achieved upon the glutaraldehyde cross-linking and eliminating the incorporated Hg(II) ions to finally have the Hg(II) ion-imprinted sorbent material (Hg-PBCS). The materials have been investigated using various techniques such as NMR and FTIR and the obtained sorbent was examined to evaluate its selective affinity to capture the target Hg(II) ions. The developed Hg-PBCS sorbent exhibited a higher tendency toward the targeted Hg(II) ions compared to the control non-imprinted sorbent particle (NI-PBCS) with a maximum capacity of 315 mg/g. Also, the sorbent displayed relatively rapid adsorption kinetics that best correlated with the pseudo-second-order model.

Preparation of Cationic Amphiphilic Nanoparticles with Modified Chitosan Derivatives for Doxorubicin Delivery

Polymeric micelle-like nanoparticles have demonstrated effectiveness for the delivery of some poorly soluble or hydrophobic anticancer drugs. In this study, a hydrophobic moiety, deoxycholic acid (DCA) was first bonded on a polysaccharide, chitosan (CS), for the preparation of amphiphilic chitosan (CS-DCA), which was further modified with a cationic glycidyltrimethylammounium chloride (GTMAC) to form a novel soluble chitosan derivative (HT-CS-DCA). The cationic amphiphilic HT-CS-DCA was easily self-assembled to micelle-like nanoparticles about 200 nm with narrow size distribution (PDI 0.08–0.18). The zeta potential of nanoparticles was in the range of 14 to 24 mV, indicating higher positive charges. Then, doxorubicin (DOX), an anticancer drug with poor solubility, was entrapped into HT-CS-DCA nanoparticles. The DOX release test was performed in PBS (pH 7.4) at 37 °C, and the results showed that there was no significant burst release in the first two hours, and the cumulative release increased steadily and slowly in the following hours. HT-CS-DCA nanoparticles loaded with DOX could easily enter into MCF-7 cells, as observed by a confocal microscope. As a result, DOX-loaded HT-CS-DCA nanoparticles demonstrated a significant inhibition activity on MCF-7 growth without obvious cellular toxicity in comparison with blank nanoparticles. Therefore, the anticancer efficacy of these cationic HT-CS-DCA nanoparticles showed great promise for the delivery of DOX in cancer therapy.

EMULSIFICATION PARAMETERS STUDY ON MICELLES FORMATION FROM HYDROPHOBICALLY MODIFIED CHITOSAN

A series of N,O-acylated chitosan derivatives were emulsified with different fatty acids. Hydrophobically modified chitosan derivatives were expected to exhibit self-assembly behaviour resulting in micelle formation. Several parameters of the oil-in-water emulsification process were investigated: mixing method, speed and duration, volume oil phase and addition of modifiers. Their influence on micellar Z-average diameter, size distribution and Zeta potential was analysed based on dynamic light scattering measurements. There were various relations between the hydrodynamic behaviour of chitosan derivatives, their chemical structure and the process parameters. Additionally, the obtained micelles could serve as active compound carriers because they encapsulated two model substances, namely ibuprofen and α-tocopherol.

Synthesis, characterization, and antimicrobial activity of novel N-acetyl,N’-chitosanacetohydrazide and its metal complexes

A new modified chitosan derivative (N-acetyl,N’-chitosanacetohydrazide, ACsAH) and its cobalt(II), nickel(II), manganese(II), and copper(II) complexes were successfully prepared. Their structures were proven using elemental analysis, FTIR, 1H-NMR and electronic spectroscopy, magnetic moment, and molar conductance. An octahedral stereochemistry for all the synthesized ACsAH–metal complexes was proposed. Their activity against the tested microbes can be arranged as follows: ACsAH–Mn(II) complex > ACsAH–Co(II) complex > ACsAH–Ni(II) complex > ACsAH–Cu(II) complex > ACsAH > chitosan. The ACsAH–Mn(II) complex exhibited a greater potency in inhibition of the growth of some of the tested microbes than that of the used standard drugs.

New sustainable chemically modified chitosan derivatives for different applications: Synthesis and characterization

The functionalization of chitosan (CS) by terephthaloyl chloride (TPC), glutaraldehyde (GA), and 4(4-(ethyl carbamoyl) benzoyl chloride) benzene sulfonamide was performed under different reaction conditions to yield the new hydrogels (I, II, III) respectively. However, hydrogel (I-NPs) was prepared from reaction of chitosan with (TPC) via ionic gelation technique using sodium tripolyphosphate (TPP) as a cross-linker. Moreover, hydrogel (I) was loaded (Au, Ag and ZnO) nanoparticles to give the nanoformulations (I-Au NPs, I-Ag NPs and I-ZnO NPs) respectively. Structural and morphological analysis of the new chitosan derivatives hydrogels and NPs formulations were characterized by FTIR, elemental analysis, TGA, DSC, XRD, SEM and TEM. From swelling study, chitosan derivatives hydrogels revealed higher swelling degree compared to (CS) with increasing time, temperature and pH values which reached maximum at pH 7 then decreased at pH 10. In addition, the maximum sorption capacities of Congo Red (CR) in aqueous solution were in the range 81–88%. Moreover, adsorption equilibrium isotherm results displayed favorable Langmuir model than Freundlich model. Furthermore, chitosan derivatives hydrogels showed broad spectrum antimicrobial activities against Gram-negative bacteria, Gram-positive bacteria and fungi with the inhibition zone diameter ranged from 13 to 25 mm compared to (CS) hydrogel which revealed inhibition zone diameter ranged from 11 to 16 mm, especially the nano formulation hydrogel (I-Ag NPs) showed the highest antimicrobial activity. The results were promising suggesting that the new modified chitosan derivatives could be potential for dye removal and as antimicrobial agents.

Recent Advances in the Synthesis, Properties, and Applications of Modified Chitosan Derivatives: Challenges and Opportunities.

Chitosan is a very well-known biocompatible and biodegradable polysaccharide consisting of β-(1-4)-linked glucosamine units, derived from the deacetylation of chitin. This unique biopolymer consists of primary amines as well as hydrophilic hydroxyl groups along with the chitosan backbone and has exceptional properties and wide applications. Numerous articles have been devoted to the preparation and properties of chitosan-based biomaterials, which have been demonstrated as beads, films, fibers (2D-scaffolds), gels, sponges (3D-scaffolds), and wound-healing materials. The unusual adsorption capacity of chitosan cross-linked polymer is demonstrated by trapping cations, anions, organic dyes, and pharmaceutical ingredients from wastewater. The most striking manifestations of flexibility in the preparation of these adsorbents have been critically reviewed, and their sorption efficiencies compared. Notably, these materials are also used as drug delivery carriers. Further, various metal-loaded chitosan-based nanocomposite materials have been used efficiently in organic catalytic reactions. As per the rich literature survey, such chitosan-based materials warrant further research due to their abundance, eco-friendliness, and effectiveness towards commercialization. The biotechnological aspects of chitosan may lead to promising low-cost materials and by-products of industrial and agricultural significance. The constant demand for potential adsorbents for the removal of pollutants, can be met by fine-tuning the structural properties of chitosan with appropriate cross-linkers or additives.

A zwitterionic serine modified chitosan derivative for improving protein stability and activity

A zwitterionic phosphoryldiserine (PDS)- chitosan conjugate was synthesized via Atherton-Todd reaction, and its degree of substitution of PDS and structure were characterized by 1H and 31P NMR spectra, ICP, FTIR and XRD. Thermal analysis confirmed that there existed the freezing bound water surrounding PDS-chitosan due to the introduction of zwitterionic PDS groups onto chitosan backbone. In vitro cytotoxicity and hemolysis assay demonstrated that PDS-chitosan had excellent cell compatibility. UV adsorption and fluorescence spectra revealed that the model protein, bovine serum albumin (BSA) tended to keep its native conformation and showed better thermal stability in aqueous media in the presence of PDS-chitosan. We also found that the esterase-like activity of BSA could be enhanced by low concentration of PDS-chitosan (CBSA = 0.33 mg/mL, CPDS-chitosan = 0.0625 and 0.125 mg/mL, pH = 7.4, T = 25 °C). The results indicated that zwitterionic PDS-chitosan showed great potential for maintaining protein function in biomedical applications.

Crab vs. Mushroom: A Review of Crustacean and Fungal Chitin in Wound Treatment.

Chitin and its derivative chitosan are popular constituents in wound-treatment technologies due to their nanoscale fibrous morphology and attractive biomedical properties that accelerate healing and reduce scarring. These abundant natural polymers found in arthropod exoskeletons and fungal cell walls affect almost every phase of the healing process, acting as hemostatic and antibacterial agents that also support cell proliferation and attachment. However, key differences exist in the structure, properties, processing, and associated polymers of fungal and arthropod chitin, affecting their respective application to wound treatment. High purity crustacean-derived chitin and chitosan have been widely investigated for wound-treatment applications, with research incorporating chemically modified chitosan derivatives and advanced nanocomposite dressings utilizing biocompatible additives, such as natural polysaccharides, mineral clays, and metal nanoparticles used to achieve excellent mechanical and biomedical properties. Conversely, fungi-derived chitin is covalently decorated with β-glucan and has received less research interest despite its mass production potential, simple extraction process, variations in chitin and associated polymer content, and the established healing properties of fungal exopolysaccharides. This review investigates the proven biomedical properties of both fungal- and crustacean-derived chitin and chitosan, their healing mechanisms, and their potential to advance modern wound-treatment methods through further research and practical application.

Recent Advances in the Application of Chitosan and Chitosan Derivatives as Bio Supported Catalyst in the Cross Coupling Reactions

The present review article surveys an outline on the most recent efforts and exciting developments (between 2010-2018 years) in the application of chitosan and modified chitosan derivatives as bio support for metal immobilization in the cross coupling reactions. The procedures incorporated in this review comprise metal nanoparticles (Pd, Ni, Cu, Au, Co) or metal ions immobilization on non-modified chitosan, porous chitosan microspheres, chitosan hybrid with other organic and inorganic polymers and functionalized chitosan with different ligands such as amine, amide, thiourea, amino acid, carbene and Schiff base derivatives. Also, in each case, the catalytic efficiency was described in various cross coupling reactions.

Fatty acid and quaternary ammonium modified chitosan nanoparticles for insulin delivery.

Liver is the major organ where insulin performs its physiological function. In this study, lauric acid and oleic acid were respectively conjugated to quaternized chitosan, and the fatty acid modified chitosan derivatives were used as the carriers to deliver the loaded insulin to liver. The nanoparticles with sizes of about 280 nm were fabricated via the electrostatic and hydrophobic interactions between insulin and the chitosan derivative. Both of insulin loading efficiency and loading capacity of the chitosan derivatives were higher than 98%. The surface hydrophobicity of the nanoparticles increased with the increases of fatty acid hydrophobicity and also fatty acid substitution degree of the chitosan derivative. The nanoparticles with higher surface hydrophobicity displayed higher hepatocyte absorption, more accumulation in the liver and better antidiabetic efficacy. Compared with free insulin treatment group, the relative pharmacological availabilities were 233% and 311% for the groups treated with the nanoparticles having lauric acid and oleic acid, respectively, after subcutaneous injection into diabetic mice. This study demonstrates that the nanoparticles fabricated from fatty acid modified polymer are an effective liver-targeted delivery system of insulin.

Novel aminohydrazide cross-linked chitosan filled with multi-walled carbon nanotubes as antimicrobial agents

Four chemically modified chitosan derivatives 1–4 were designed and synthesized via a series of four reactions; first by reaction with benzaldehyde to protect its amino groups (Derivative 1), second by reaction with epichlorohydrine (Derivative 2), third by reaction with aminobenzhydrazide (Derivative 3), and forth by removing of benzaldehyde to restore the free amino groups on the chitosan (Derivative 4). Two multi-walled carbon nanotube (MWCNT) biocomposites based on Derivative 4 were also prepared. The structure of the prepared derivatives and MWCNT composites was elucidated using elemental analyses, FTIR, XRD, SEM and TEM. The modified chitosan derivatives and MWCNT composites showed better antimicrobial activities than that of chitosan against Enterococcus faecalis, Staphylococcus epidermidis, Escherichia coli, Aspergillus niger, Cryptococcus neoformans and Candida tropicalis as judged by their higher inhibition zone diameters using the agar well diffusion technique. These derivatives and MWCNT composites are more potent against Gram-positive bacteria than against Gram-negative bacteria. The MWCNT composites displayed comparable or even better antimicrobial activities than the reference bactericides or fungicides. Thus, structural modification of chitosan through combination with functionalized moieties and MWCNTs in one system was taken as a way to achieve promising templates for antimicrobial agents and to be appropriate candidates for medical applications.