Low molecular weight chitosan-g-l-phenylalanine: Preparation, characterization, and complex formation with DNA

A Strategical Improvement in the Performance of CO2/N2 Gas Permeation via Conjugation of L-Tyrosine onto Chitosan Membrane

Rubbery polymeric membranes, containing amine carriers, have received much attention in CO₂ separation because of their easy fabrication, low cost, and excellent separation performance. The present study focuses on the versatile aspects of covalent conjugation of L-tyrosine (Tyr) onto the high molecular weight chitosan (CS) accomplished by using carbodiimide as a coupling agent for CO₂/N₂ separation. The fabricated membrane was subjected to FTIR, XRD, TGA, AFM, FESEM, and moisture retention tests to examine the thermal and physicochemical properties. The defect-free dense layer of tyrosine-conjugated-chitosan, with active layer thickness within the range of ~600 nm, was cast and employed for mixed gas (CO₂/N₂) separation study in the temperature range of 25-115 °C in both dry and swollen conditions and compared to that of a neat CS membrane. An enhancement in the thermal stability and amorphousness was displayed by TGA and XRD spectra, respectively, for the prepared membranes. The fabricated membrane showed reasonably good CO₂ permeance of around 103 GPU and CO₂/N₂ selectivity of 32 by maintaining a sweep/feed moisture flow rate of 0.05/0.03 mL/min, respectively, an operating temperature of 85 °C, and a feed pressure of 32 psi. The composite membrane demonstrated high permeance because of the chemical grafting compared to the bare chitosan. Additionally, the excellent moisture retention capacity of the fabricated membrane accelerates high CO₂ uptake by amine carriers, owing to the reversible zwitterion reaction. All the features make this membrane a potential membrane material for CO₂ capture.

Characterization of Different Salt Forms of Chitooligosaccharides and Their Effects on Nitric Oxide Secretion by Macrophages

In this paper, chitooligosaccharides in different salt forms, such as chitooligosaccharide lactate, citrate, adipate, etc., were prepared by the microwave method. They were characterized by SEM, FTIR, NMR, etc., and the nitric oxide (NO) expression was determined in RAW 264.7 cells. The results showed that pure chitooligosaccharide was an irregular spherical shape with rough surface, and its different salt type products are amorphous solid with different honeycomb sizes. In addition to the characteristic absorption peaks of chitooligosaccharides, in FTIR, the characteristic absorption of carboxyl group, methylene group, and aromatic group in corresponding acid appeared. The characteristic absorption peaks of carbon in carboxyl group, hydrogen and carbon in methyl, methylene group, and aromatic group in corresponding acid also appeared in NMR. Therefore, the sugar ring structure and linking mode of chitooligosaccharides did not change after salt formation of chitooligosaccharides. Different salt chitooligosaccharides are completely different in promoting NO secretion by macrophages, and pure chitooligosaccharides are the best.

Dual stimuli-responsive saccharide core based nanocarrier for efficient Birc5-shRNA delivery

Stimuli-responsive delivery systems show great promise in meeting the requirements of several delivery stages to achieve satisfactory gene transfection.

Hydrophobic amino acids grafted onto chitosan: a novel amphiphilic chitosan nanocarrier for hydrophobic drugs

OBJECTIVE

The objective of this study is to develop a novel biocompatible amphiphilic drug delivery for hydrophobic drugs, chitosan (CS) was grafted to a series of hydrophobic amino acids including l-alanine (A), l-proline (P), and l-tryptophan (W) by carbodiimide mediated coupling reaction.

MATERIALS AND METHODS

Chemical characteristics of the modified polymers were determined and confirmed by FT-IR, ¹H NMR, and UV-vis spectroscopy and the degree of substitution was quantified by elemental analysis. The modified polymers were used to form amphiphilic chitosan nanocarriers (ACNs) by the conventional self-assembly method using ultrasound technique. The morphology and the size of ACNs were analyzed by scanning electron microscope (SEM) and Dynamic light scattering (DLS).

RESULTS AND DISCUSSION

The sizes of spherical ACNs analyzed by SEM were obviously smaller than those of determined by DLS. The ACNs effectively surrounded the hydrophobic model drug, letrozole (LTZ), and demonstrated different encapsulation efficiencies (EE), loading capacities (LC), and controlled drug release profiles. The characteristics of ACNs and the mechanism of drug encapsulation were confirmed by molecular modeling method. The modeling of the structures of LTZ, profiles of A, P, and W grafted onto CS and the wrapping process around LTZ was performed by quantum mechanics (QM) methods. There was a good agreement between the experimental and theoretical results. The cell viability was also evaluated in two cell lines compared with free drug by MTT assay.

CONCLUSION

The hydrophobic portion effects on ACNs' characteristics and the proper selection of amino acid demonstrate a promising potential for drug delivery vector.

Carbohydrate-based amphiphilic nano delivery systems for cancer therapy

Nanoparticles (NPs) are novel drug delivery systems that have been attracting more and more attention in recent years, and have been used for the treatment of cancer, infection, inflammation and other diseases. Among the numerous classes of materials employed for constructing NPs, organic polymers are outstanding due to the flexibility of design and synthesis and the ease of modification and functionalization. In particular, NP based amphiphilic polymers make a great contribution to the delivery of poorly-water soluble drugs. For example, natural, biocompatible and biodegradable products like polysaccharides are widely used as building blocks for the preparation of such drug delivery vehicles. This review will detail carbohydrate based amphiphilic polymeric systems for cancer therapy. Specifically, it focuses on the nature of the polymer employed for the preparation of targeted nanocarriers, the synthetic methods, as well as strategies for the application and evaluation of biological activity. Applications of the amphiphilic polymer systems include drug delivery, gene delivery, photosensitizer delivery, diagnostic imaging and specific ligand-assisted cellular uptake. As a result, a thorough understanding of the relationship between chemical structure and biological properties facilitate the optimal design and rational clinical application of the resulting carbohydrate based nano delivery systems for cancer therapy.

Polyamidoamine (PAMAM) dendrimers modified with short oligopeptides for early endosomal escape and enhanced gene delivery

Recently, non-viral vectors have become a popular research topic in the field of gene therapy. In this study, we conjugated short oligopeptides to polyamidoamine-generation 4 (PAMAM G4) to achieve higher transfection efficiency. Previous reports have shown that the PAMAM G4-histidine (H)-arginine (R) dendrimer enhances gene delivery by improving cell penetration and internalization mechanisms. Therefore, we synthesized PAMAM G4-H phenylalanine (F) R, PAMAM G4-FHR and PAMAM G4-FR derivatives to determine the best gene carrier with the lowest toxicity. Physicochemical studies were performed to determine mean diameters and surface charge of PAMAM derivatives/pDNA polyplexes. DNA condensation was confirmed using a gel retardation assay. Cytotoxicity and transfection efficiency were analyzed using human cervical carcinoma (HeLa) and human liver carcinoma (HepG2) cells. Similar levels of transfection were achieved in both cell lines by using gold standard transfection reagent PEI 25 kD. Therefore, our results show that these carriers are promising and may help achieve higher transfection with negligible cytotoxicity.

Antimicrobial activity of chitosan derivatives containing N-quaternized moieties in its backbone: a review

Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial activity. However, chitosan applications as a biocide are only effective in acidic medium due to its low solubility in neutral and basic conditions. Also, the positive charges carried by the protonated amine groups of chitosan (in acidic conditions) that are the driving force for its solubilization are also associated with its antimicrobial activity. Therefore, chemical modifications of chitosan are required to enhance its solubility and broaden the spectrum of its applications, including as biocide. Quaternization on the nitrogen atom of chitosan is the most used route to render water-soluble chitosan-derivatives, especially at physiological pH conditions. Recent reports in the literature demonstrate that such chitosan-derivatives present excellent antimicrobial activity due to permanent positive charge on nitrogen atoms side-bonded to the polymer backbone. This review presents some relevant work regarding the use of quaternized chitosan-derivatives obtained by different synthetic paths in applications as antimicrobial agents.

Novel self-assembled micelles based on palmitoyl-trimethyl-chitosan for efficient delivery of harmine to liver cancer

BACKGROUND

Polymeric micelles is a safe and effective delivery system, which belong to the targeted delivery system (TDS). An anticancer drug, harmine(HM) is a hydrophobic drug with much adverse effects when used for treatment of liver cancer. Chitosan (CS) is a polysaccharide and can be modified to be an amphiphilic polmer which could self-assemble into micelles and be applied for delivery of hydrophobic drugs.

OBJECTIVES

To synthesize three kinds of novel biodegradable polymers, designated as palmitoyl-trimethyl-CS (TPCS)1, TPCS2 and Lac-TPCS2, and investigate their efficiency and mechanism of delivery HM to liver tumors in vitro and in viro.

RESULTS

The self-assembled micelles presented satisfactory particle size (∼ 200 nm) and drug release characteristics in vitro. It's proved that Lac-TPCS2/HM may enter HepG2 cell through endocytosis. Antitumor experiments in vivo revealed that Lac-TPCS2/HM could significantly inhibit tumor growth and extend the lifetime of mice bearing H22 tumors after intravenous administration. Subsequently in vivo near-infrared fluorescence imaging results demonstrated a satisfactory liver tumor-targeting effect of Lac-TPCS2/HM.

CONCLUSION

Three novel polymers hold great potential in the development of nanomedicine for treatment of liver tumors, in particular Lac-TPCS2 exhibits the greatest antitumor potential through active target effect.

Tunable drug-loading capability of chitosan hydrogels with varied network architectures

Advanced bioactive systems with defined macroscopic properties and spatio-temporal sequestration of extracellular biomacromolecules are highly desirable for next generation therapeutics. Here, chitosan (CT) hydrogels were prepared with neutral or negatively charged cross-linkers in order to promote selective electrostatic complexation with charged drugs. CT was functionalized with varied dicarboxylic acids, such as tartaric acid, poly(ethylene glycol) bis(carboxymethyl) ether, 1,4-phenylenediacetic acid and 5-sulfoisophthalic acid monosodium salt (PhS), whereby PhS was hypothesized to act as a simple mimetic of heparin. Attenuated total reflectance Fourier transform infrared spectroscopy showed the presence of CO amide I, N-H amide II and CO ester bands, providing evidence of covalent network formation. The cross-linker content was reversely quantified by proton nuclear magnetic resonance on partially degraded network oligomers, so that 18 mol.% PhS was exemplarily determined. Swellability (SR: 299 ± 65-1054 ± 121 wt.%), compressibility (E: 2.1 ± 0.9-9.2 ± 2.3 kPa), material morphology and drug-loading capability were successfully adjusted based on the selected network architecture. Here, hydrogel incubation with model drugs of varied electrostatic charge, i.e. allura red (AR, doubly negatively charged), methyl orange (MO, negatively charged) or methylene blue (MB, positively charged), resulted in direct hydrogel-dye electrostatic complexation. Importantly, the cationic compound, MB, showed different incorporation behaviours, depending on the electrostatic character of the selected cross-linker. In light of this tunable drug-loading capability, these CT hydrogels would be highly attractive as drug reservoirs towards e.g. the fabrication of tissue models in vitro.

Chitosan-based formulations for delivery of DNA and siRNA

Among non-viral vectors, chitosan and chitosan derivatives have been developed in vitro and in vivo for DNA and siRNA delivery systems because of their cationic charge, biodegradability and biocompatibility, as well as their mucoadhesive and permeability-enhancing properties. However, the transfection efficiency of chitosan is too low for clinical application. Studies indicated that the transfection efficiency depends on a series of chitosan-based formulation parameters, such as the Mw of chitosan, its degree of deacetylation, the charge ratio of chitosan to DNA/siRNA (N/P ratio), the chitosan salt form used, the DNA/siRNA concentration, pH, serum, additives, preparation techniques of chitosan/nucleic acid particles and routes of administration. In this paper, chitosan-based formulations for the delivery of DNA and siRNA were reviewed to facilitate the process of chitosan vector development for clinical application. In addition to formulation optimization, chitosan structure modification or additive incorporation is an effective way to improve the stability of the polyplex in biological fluids, enhance targeted cell delivery and facilitate endo-lysosomal release of the complex. In summary, the transfection efficiency of chitosan-based delivery systems can be adjusted by changing formulation-related parameters.

Comparison on in vitro characterization of fucospheres and chitosan microspheres encapsulated plasmid DNA (pGM-CSF): formulation design and release characteristics

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine used in the treatment of serious conditions resulting from chemotherapy and bone marrow transplantation such as neutropenia and aplastic anemia. Despite these effects, GM-CSF has a very short biological half-life, and it requires frequent injection during the treatment. Therefore, the cytokine production is possible in the body with plasmid-encoded GM-CSF (pGM-CSF) coding for cytokine administered to the body. However, the selection of the proper delivery system for the plasmid is important. In this study, two different delivery systems, encapsulated plasmid such as fucoidan-chitosan (fucosphere) and chitosan microspheres, were prepared and the particle physicochemical properties evaluated. Fucospheres and chitosan microspheres size ranges are 151-401 and 376-681 nm. The zeta potential values of the microspheres were changed between 8.3-17.1 mV (fucosphere) and +21.9-28.9 mV (chitosan microspheres). The encapsulation capacity of fucospheres changed between 84.2% and 94.7% depending on the chitosan molecular weight used in the formulation. In vitro plasmid DNA release from both delivery systems exhibited slower profiles of approximately 90-140 days. Integrity of released samples was checked by agarose gel electrophoresis, and any additional band was not seen. All formulations were analyzed kinetically. The calculated regression coefficients showed a higher r2 value with zero-order kinetics. In conclusion, the characterizations of the microspheres can be modulated by changing the formulation variables, and it can be concluded that fucospheres might be a potential carrier system for the controlled delivery of GM-CSF encoding plasmid DNA.