E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Special Issue "Chitins and Chitosans"

Quicklinks

A special issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: closed (31 March 2013)

Special Issue Editor

Guest Editor
Prof. Dr. Rong-Nan Huang (Website)

Insect Toxicology Laboratory, Department of Entomology, National Taiwan University, No. 27, Lane 113, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
Phone: 886-2-33665570
Interests: tissue engineering; bioinescticide

Special Issue Information

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs).

Published Papers (16 papers)

View options order results:
result details:
Displaying articles 1-16
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle The Effect of Chitin Size, Shape, Source and Purification Method on Immune Recognition
Molecules 2014, 19(4), 4433-4451; doi:10.3390/molecules19044433
Received: 3 March 2014 / Revised: 24 March 2014 / Accepted: 4 April 2014 / Published: 10 April 2014
Cited by 8 | PDF Full-text (1047 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The animal immune response to chitin is not well understood and needs to be investigated further. However, this is a challenging topic to study because of the technical difficulties in purifying chitin, and because this material usually comes associated with contaminating components [...] Read more.
The animal immune response to chitin is not well understood and needs to be investigated further. However, this is a challenging topic to study because of the technical difficulties in purifying chitin, and because this material usually comes associated with contaminating components that can activate the immune system. In this study, improvements to previously described purification protocols were investigated for chitin obtained from different sources, including commercial shellfish, Candida albicans yeast and hyphal cell walls, as well as cell walls of the filamentous fungi Aspergillus fumigatus and Mucor circinelloides. The immune response to these different chitin preparations was tested using human peripheral blood mononuclear cells. In agreement with previous literature, small chitin particles of an average size of 0.2 µm were not immunogenic. On the other hand, bigger chitin particles induced in some cases a pro-inflammatory response. The results of this work suggest that not only the purity and size of the chitin particles, but also their shape can influence immune recognition. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Elaboration of Stable and Antibody Functionalized Positively Charged Colloids by Polyelectrolyte Complexation between Chitosan and Hyaluronic Acid
Molecules 2013, 18(7), 8563-8578; doi:10.3390/molecules18078563
Received: 23 May 2013 / Revised: 11 July 2013 / Accepted: 15 July 2013 / Published: 19 July 2013
Cited by 17 | PDF Full-text (1164 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we describe the elaboration of multifunctional positively charged polyelectrolyte complex (PEC) nanoparticles, designed to be stable at physiological salt concentration and pH, for effective targeted delivery. These nanoparticles were obtained by charge neutralization between chitosan (CS) as polycation and [...] Read more.
In this study, we describe the elaboration of multifunctional positively charged polyelectrolyte complex (PEC) nanoparticles, designed to be stable at physiological salt concentration and pH, for effective targeted delivery. These nanoparticles were obtained by charge neutralization between chitosan (CS) as polycation and hyaluronic acid (HA) as polyanion. We showed that the course of the complexation process and the physico-chemical properties of the resulting colloids were impacted by (i) internal parameters such as the Degree of Acetylation (DA, i.e., the molar ration of acetyl glucosamine residues) and molar mass of CS, the HA molar mass and (ii) external parameters like the charge mixing ratio and the polymer concentrations. As a result, nonstoichiometric colloidal PECs were obtained in water or PBS (pH 7.4) and remained stable over one month. The polymer interactions were characterized by thermal analysis (DSC and TGA) and the morphology was studied by scanning electron microscopy. A model antibody, anti-ovalbumine (OVA) immunoglobulin A (IgA) was sorbed on the particle surface in water and PBS quantitatively in 4 h. The CS-HA/IgA nanoparticles average size was between 425–665 nm with a positive zeta potential. These results pointed out that CS-HA can be effective carriers for use in targeted drug delivery. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Characterization of Protein and Peptide Binding to Nanogels Formed by Differently Charged Chitosan Derivatives
Molecules 2013, 18(7), 7848-7864; doi:10.3390/molecules18077848
Received: 25 April 2013 / Revised: 17 June 2013 / Accepted: 26 June 2013 / Published: 3 July 2013
Cited by 10 | PDF Full-text (1960 KB) | HTML Full-text | XML Full-text
Abstract
Chitosan (Chi) is a natural biodegradable cationic polymer with remarkable potency as a vehicle for drug or vaccine delivery. Chi possesses multiple groups, which can be used both for Chi derivatization and for particle formation. The aim of this work was to [...] Read more.
Chitosan (Chi) is a natural biodegradable cationic polymer with remarkable potency as a vehicle for drug or vaccine delivery. Chi possesses multiple groups, which can be used both for Chi derivatization and for particle formation. The aim of this work was to produce stable nanosized range Chi gels (nanogels, NGs) with different charge and to study the driving forces of complex formation between Chi NGs and proteins or peptides. Positively charged NGs of 150 nm in diameter were prepared from hexanoyl chitosan (HC) by the ionotropic gelation method while negatively charged NGs of 190 nm were obtained from succinoyl Chi (SC) by a Ca2+ coacervation approach. NGs were loaded with a panel of proteins or peptides with different weights and charges. We show that NGs preferentially formed complexes with oppositely charged molecules, especially peptides, as was demonstrated by gel-electrophoresis, confocal microscopy and HPLC. Complex formation was accompanied by a change in zeta-potential and decrease in size. We concluded that complex formation between Chi NGs and peptide/proteins is mediated mostly by electrostatic interactions. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Eudragit® L100/N-Trimethylchitosan Chloride Microspheres for Oral Insulin Delivery
Molecules 2013, 18(6), 6734-6747; doi:10.3390/molecules18066734
Received: 3 April 2013 / Revised: 29 May 2013 / Accepted: 31 May 2013 / Published: 7 June 2013
Cited by 8 | PDF Full-text (641 KB) | HTML Full-text | XML Full-text
Abstract
Effective oral delivery of protein and peptide drugs remains an active topic in scientific research. In this study, matrix type microspheres were prepared with Eudragit® L100 containing N-trimethylchitosan chloride to improve the permeation of insulin across the intestinal epithelium via [...] Read more.
Effective oral delivery of protein and peptide drugs remains an active topic in scientific research. In this study, matrix type microspheres were prepared with Eudragit® L100 containing N-trimethylchitosan chloride to improve the permeation of insulin across the intestinal epithelium via the paracellular pathway. Insulin loaded microspheres were initially formulated in accordance with a factorial design (23) and manufactured by means of a single water-in-oil emulsification/evaporation method. Based on external and internal morphology two microsphere formulations were selected from the initial formulations for further investigation in terms of particle size, dissolution behaviour and in vitro insulin transport across excised rat intestinal tissue. The initial eight microsphere formulations exhibited drug loading capacities ranging from 27.9–52.4% with different shapes and internal structures. The two selected microsphere formulations had average particle sizes of 157.3 ± 31.74 µm and 135.7 ± 41.05 µm, respectively, and mean dissolution time values for insulin release of 34.47 and 42.63 min, respectively. In vitro transport of insulin across excised rat intestinal tissue from the two selected microsphere formulations was 10.67–fold and 9.68–fold higher than the control group (insulin alone). The microsphere delivery system prepared from Eudragit® L100 containing N-trimethylchitosan chloride is therefore a promising candidate for effective oral insulin delivery. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle One-Step Biofunctionalization of Quantum Dots with Chitosan and N-palmitoyl Chitosan for Potential Biomedical Applications
Molecules 2013, 18(6), 6550-6572; doi:10.3390/molecules18066550
Received: 23 April 2013 / Revised: 27 May 2013 / Accepted: 29 May 2013 / Published: 4 June 2013
Cited by 17 | PDF Full-text (1847 KB) | HTML Full-text | XML Full-text
Abstract
Carbohydrates and derivatives (such as glycolipids, glycoproteins) are of critical importance for cell structure, metabolism and functions. The effects of carbohydrate and lipid metabolic imbalances most often cause health disorders and diseases. In this study, new carbohydrate-based nanobioconjugates were designed and synthesized [...] Read more.
Carbohydrates and derivatives (such as glycolipids, glycoproteins) are of critical importance for cell structure, metabolism and functions. The effects of carbohydrate and lipid metabolic imbalances most often cause health disorders and diseases. In this study, new carbohydrate-based nanobioconjugates were designed and synthesized at room temperature using a single-step aqueous route combining chitosan and acyl-modified chitosan with fluorescent inorganic nanoparticles. N-palmitoyl chitosan (C-Pal) was prepared aiming at altering the lipophilic behavior of chitosan (CHI), but also retaining its reasonable water solubility for potential biomedical applications. CHI and C-Pal were used for producing biofunctionalized CdS quantum dots (QDs) as colloidal water dispersions. Fourier transform infrared spectroscopy (FTIR), thermal analysis (TG/DSC), surface contact angle (SCA), and degree of swelling (DS) in phosphate buffer were used to characterize the carbohydrates. Additionally, UV-Visible spectroscopy (UV-Vis), photoluminescence spectroscopy (PL), dynamic light scattering (DLS), scanning and transmission electron microscopy (SEM/TEM) were used to evaluate the precursors and nanobioconjugates produced. The FTIR spectra associated with the thermal analysis results have undoubtedly indicated the presence of N-palmitoyl groups “grafted” to the chitosan chain (C-Pal) which significantly altered its behavior towards water swelling and surface contact angle as compared to the unmodified chitosan. Furthermore, the results have evidenced that both CHI and C-Pal performed as capping ligands on nucleating and stabilizing colloidal CdS QDs with estimated average size below 3.5 nm and fluorescent activity in the visible range of the spectra. Therefore, an innovative “one-step” process was developed via room temperature aqueous colloidal chemistry for producing biofunctionalized quantum dots using water soluble carbohydrates tailored with amphiphilic behavior offering potential applications as fluorescent biomarkers in the investigation of glycoconjugates for the nutrition, biology, pharmaceutical, and medicine fields. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Figures

Open AccessArticle A Microfluidic Chip Using Phenol Formaldehyde Resin for Uniform-Sized Polycaprolactone and Chitosan Microparticle Generation
Molecules 2013, 18(6), 6521-6531; doi:10.3390/molecules18066521
Received: 17 April 2013 / Revised: 25 May 2013 / Accepted: 29 May 2013 / Published: 3 June 2013
Cited by 6 | PDF Full-text (1997 KB) | HTML Full-text | XML Full-text
Abstract
This study develops a new solvent-compatible microfluidic chip based on phenol formaldehyde resin (PFR). In addition to its solvent-resistant characteristics, this microfluidic platform also features easy fabrication, organization, decomposition for cleaning, and reusability compared with conventional chips. Both solvent-dependent (e.g., polycaprolactone) and [...] Read more.
This study develops a new solvent-compatible microfluidic chip based on phenol formaldehyde resin (PFR). In addition to its solvent-resistant characteristics, this microfluidic platform also features easy fabrication, organization, decomposition for cleaning, and reusability compared with conventional chips. Both solvent-dependent (e.g., polycaprolactone) and nonsolvent-dependent (e.g., chitosan) microparticles were successfully prepared. The size of emulsion droplets could be easily adjusted by tuning the flow rates of the dispersed/continuous phases. After evaporation, polycaprolactone microparticles ranging from 29.3 to 62.7 μm and chitosan microparticles ranging from 215.5 to 566.3 μm were obtained with a 10% relative standard deviation in size. The proposed PFR microfluidic platform has the advantages of active control of the particle size with a narrow size distribution as well as a simple and low cost process with a high throughput. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Isocyanate-Functionalized Chitin and Chitosan as Gelling Agents of Castor Oil
Molecules 2013, 18(6), 6532-6549; doi:10.3390/molecules18066532
Received: 19 March 2013 / Revised: 29 May 2013 / Accepted: 31 May 2013 / Published: 3 June 2013
Cited by 8 | PDF Full-text (440 KB) | HTML Full-text | XML Full-text
Abstract
The main objective of this work was the incorporation of reactive isocyanate groups into chitin and chitosan in order to effectively use the products as reactive thickening agents in castor oil. The resulting gel-like dispersions could be potentially used as biodegradable lubricating [...] Read more.
The main objective of this work was the incorporation of reactive isocyanate groups into chitin and chitosan in order to effectively use the products as reactive thickening agents in castor oil. The resulting gel-like dispersions could be potentially used as biodegradable lubricating greases. Three different NCO–functionalized polymers were obtained: two of them by promoting the reaction of chitosan with 1,6-hexamethylene diisocyanate (HMDI), and the other by using chitin instead of chitosan. These polymers were characterized through 1H-NMR, FTIR and thermogravimetric analysis (TGA). Thermal and rheological behaviours of the oleogels prepared by dispersing these polymers in castor oil were studied by means of TGA and small-amplitude oscillatory shear (SAOS) measurements. The evolution and values of the linear viscoelasticity functions with frequency for –NCO–functionalized chitosan- and chitin-based oleogels are quite similar to those found for standard lubricating greases. In relation to long-term stability of these oleogels, no phase separation was observed and the values of viscoelastic functions increase significantly during the first seven days of ageing, and then remain almost constant. TGA analysis showed that the degradation temperature of the resulting oleogels is higher than that found for traditional lubricating greases. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Mercury(II) Removal with Modified Magnetic Chitosan Adsorbents
Molecules 2013, 18(6), 6193-6214; doi:10.3390/molecules18066193
Received: 6 April 2013 / Revised: 15 May 2013 / Accepted: 20 May 2013 / Published: 24 May 2013
Cited by 32 | PDF Full-text (681 KB) | HTML Full-text | XML Full-text
Abstract
Two modified chitosan derivatives were prepared in order to compare their adsorption properties for Hg(II) removal from aqueous solutions. The one chitosan adsorbent (CS) is only cross–linked with glutaraldehyde, while the other (CSm), which is magnetic, is cross-linked with glutaraldehyde and functionalized [...] Read more.
Two modified chitosan derivatives were prepared in order to compare their adsorption properties for Hg(II) removal from aqueous solutions. The one chitosan adsorbent (CS) is only cross–linked with glutaraldehyde, while the other (CSm), which is magnetic, is cross-linked with glutaraldehyde and functionalized with magnetic nanoparticles (Fe3O4). Many possible interactions between materials and Hg(II) were observed after adsorption and explained via characterization with various techniques (SEM/EDAX, FTIR, XRD, DTG, DTA, VSM, swelling tests). The adsorption evaluation was done studying various parameters as the effect of pH (optimum value 5 for adsorption and 2 for desorption), contact time (fitting to pseudo–first, –second order and Elovich equations), temperature (isotherms at 25, 45, 65 °C), in line with a brief thermodynamic analysis (ΔG0 < 0, ΔH0 > 0, ΔS0 > 0). The maximum adsorption capacity (fitting with Langmuir and Freundlich model) of CS and CSm at 25 °C was 145 and 152 mg/g, respectively. The reuse ability of the adsorbents prepared was confirmed with sequential cycles of adsorption-desorption. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Synthesis and Characterization of Oil-Chitosan Composite Spheres
Molecules 2013, 18(5), 5749-5760; doi:10.3390/molecules18055749
Received: 1 April 2013 / Revised: 29 April 2013 / Accepted: 9 May 2013 / Published: 16 May 2013
Cited by 5 | PDF Full-text (968 KB) | HTML Full-text | XML Full-text
Abstract
Oil-chitosan composite spheres were synthesized by encapsulation of sunflower seed oil in chitosan droplets, dropping into NaOH solution and in situ solidification. Hydrophilic materials (i.e., iron oxide nanoparticles) and lipophilic materials (i.e., rhodamine B or epirubicin) could be [...] Read more.
Oil-chitosan composite spheres were synthesized by encapsulation of sunflower seed oil in chitosan droplets, dropping into NaOH solution and in situ solidification. Hydrophilic materials (i.e., iron oxide nanoparticles) and lipophilic materials (i.e., rhodamine B or epirubicin) could be encapsulated simultaneously in the spheres in a one step process. The diameters of the prepared spheres were 2.48 ± 0.11 mm (pure chitosan spheres), 2.31 ± 0.08 mm (oil-chitosan composites), 1.49 ± 0.15 mm (iron-oxide embedded oil-chitosan composites), and 1.69 ± 0.1 mm (epirubicin and iron oxide encapsulated oil-chitosan composites), respectively. Due to their superparamagnetic properties, the iron-oxide embedded oil-chitosan composites could be guided by a magnet. A lipophilic drug (epirubicin) could be loaded in the spheres with encapsulation rate measured to be 72.25%. The lipophilic fluorescent dye rhodamine B was also loadable in the spheres with red fluorescence being observed under a fluorescence microscope. We have developed a novel approach to an in situ process for fabricating oil-chitosan composite spheres with dual encapsulation properties, which are potential multifunctional drug carriers. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Optimization and Characterization of Chitosan Films for Transdermal Delivery of Ondansetron
Molecules 2013, 18(5), 5455-5471; doi:10.3390/molecules18055455
Received: 1 April 2013 / Revised: 2 May 2013 / Accepted: 6 May 2013 / Published: 10 May 2013
Cited by 11 | PDF Full-text (406 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this study was to develop novel transdermal films of ondansetron HCl with high molecular weight chitosan as matrix polymer and 2-(2-ethoxy-ethoxy) ethanol (Transcutol®) as plasticizer. In this context, firstly the physicochemical properties of gels used to formulate [...] Read more.
The aim of this study was to develop novel transdermal films of ondansetron HCl with high molecular weight chitosan as matrix polymer and 2-(2-ethoxy-ethoxy) ethanol (Transcutol®) as plasticizer. In this context, firstly the physicochemical properties of gels used to formulate transdermal films were characterized and, physicochemical properties and bioadhesiveness of the transdermal films prepared with chitosan gels were assessed. The impact of three different types of terpenes, namely limonene, nerolidol and eucalyptol on in vitro skin permeation of ondansetron from transdermal films were also examined. ATR-FTIR measurements were performed to investigate the effects of the chitosan film formulations on in vitro conformational order of stratum corneum intercellular lipids after 24 h permeation study. The results showed that the chitosan gels consisting of Transcutol® as plasticizer and terpenes as penetration enhancer may be used to prepare transdermal films of ondansetron due to the good mechanical properties and bioadhesiveness of the transdermal films. Eucalyptol (1%) showed higher permeation enhancer effect than the other terpenes and control. ATR-FTIR data confirmed that finding in which eucalyptol induced a blue shift in the both CH2 asymmetric and symmetric absorbance peak positions indicating increased lipid fluidity of stratum corneum. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Hydrophobic Effect of Amphiphilic Derivatives of Chitosan on the Antifungal Activity against Aspergillus flavus and Aspergillus parasiticus
Molecules 2013, 18(4), 4437-4450; doi:10.3390/molecules18044437
Received: 19 February 2013 / Revised: 20 March 2013 / Accepted: 9 April 2013 / Published: 15 April 2013
Cited by 5 | PDF Full-text (528 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Low molecular weight amphiphilic derivatives of chitosan were synthesized, characterized and their antifungal activities against Aspergillus flavus and Aspergillus parasiticus were tested. The derivatives were synthesized using as starting material a deacetylated chitosan sample in a two step process: the reaction with [...] Read more.
Low molecular weight amphiphilic derivatives of chitosan were synthesized, characterized and their antifungal activities against Aspergillus flavus and Aspergillus parasiticus were tested. The derivatives were synthesized using as starting material a deacetylated chitosan sample in a two step process: the reaction with propyltrimethyl-ammonium bromide (Pr), followed by reductive amination with dodecyl aldehyde. Aiming to evaluate the effect of the hydrophobic modification of the derivatives on the antifungal activity against the pathogens, the degree of substitution (DS1) by Pr groups was kept constant and the proportion of dodecyl (Dod) groups was varied from 7 to 29% (DS2). The derivatives were characterized by 1H-NMR and FTIR and their antifungal activities against the pathogens were tested by the radial growth of the colony and minimum inhibitory concentration (MIC) methods. The derivatives substituted with only Pr groups exhibited modest inhibition against A. flavus and A. parasiticus, like that obtained with deacetylated chitosan. Results revealed that the amphiphilic derivatives grafted with Dod groups exhibited increasing inhibition indexes, depending on polymer concentration and hydrophobic content. At 0.6 g/L, all amphiphilic derivatives having from 7.0 to 29% of Dod groups completely inhibited fungal growth and the MIC values were found to decrease from 4.0 g/L for deacetylated chitosan to 0.25–0.50 g/L for the derivatives. These new derivatives open up the possibility of new applications and avenues to develop effective biofungicides based on chitosan. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Fibrous Polymeric Composites Based on Alginate Fibres and Fibres Made of Poly-ε-caprolactone and Dibutyryl Chitin for Use in Regenerative Medicine
Molecules 2013, 18(3), 3118-3136; doi:10.3390/molecules18033118
Received: 20 December 2012 / Revised: 24 January 2013 / Accepted: 25 February 2013 / Published: 8 March 2013
Cited by 5 | PDF Full-text (919 KB) | HTML Full-text | XML Full-text
Abstract
This work concerns the production of fibrous composite materials based on biodegradable polymers such as alginate, dibutyryl chitin (DBC) and poly-ε-caprolactone (PCL). For the production of fibres from these polymers, various spinning methods were used in order to obtain composite materials of [...] Read more.
This work concerns the production of fibrous composite materials based on biodegradable polymers such as alginate, dibutyryl chitin (DBC) and poly-ε-caprolactone (PCL). For the production of fibres from these polymers, various spinning methods were used in order to obtain composite materials of different composition and structure. In the case of alginate fibres containing the nanoadditive tricalcium phosphate (TCP), the traditional method of forming fibres wet from solution was used. However in the case of the other two polymers the electrospinning method was used. Two model systems were tested for biocompatibility. The physicochemical and basic biological tests carried out show that the submicron fibres produced using PCL and DBC have good biocompatibility. The proposed hybrid systems composed of micrometric fibres (zinc and calcium alginates containing TCP) and submicron fibres (DBC and PCL) meet the requirements of regenerative medicine. The biomimetic fibre system, the presence of TCP nanoadditive, and the use of polymers with different resorption times provide a framework with specific properties on which bone cells are able to settle and proliferate. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessArticle Chitosan Rate of Uptake in HEK293 Cells is Influenced by Soluble versus Microparticle State and Enhanced by Serum-Induced Cell Metabolism and Lactate-Based Media Acidification
Molecules 2013, 18(1), 1015-1035; doi:10.3390/molecules18011015
Received: 16 November 2012 / Revised: 30 December 2012 / Accepted: 7 January 2013 / Published: 15 January 2013
Cited by 5 | PDF Full-text (2589 KB)
Abstract
Chitosan is a biocompatible polysaccharide composed of glucosamine and N-acetylglucosamine. The polymer has a unique behavior of fluctuating between soluble chains at pH 6 and insoluble microparticles at pH 7. The purpose of this study was to test the hypothesis that [...] Read more.
Chitosan is a biocompatible polysaccharide composed of glucosamine and N-acetylglucosamine. The polymer has a unique behavior of fluctuating between soluble chains at pH 6 and insoluble microparticles at pH 7. The purpose of this study was to test the hypothesis that chitosan structure, solubility state, and serum influence the rate of cell uptake. Chitosans with 80% and 95% degree of deacetylation (medium and low viscosity) were tagged with rhodamine and analyzed for particle size, media solubility, and uptake by HEK293 epithelial cells using live confocal microscopy and flow cytometry. In media pH 7.4 with or without 10% serum, chitosans fully precipitated into 0.5 to 1.4 µm diameter microparticles with a slight negative charge. During 24 h of culture in serum-free medium, chitosan particles remained extracellular. In cultures with serum, particles were taken up into intracellular vesicles in a serum dose-dependent manner. Opsonization of chitosan with serum, or replacement of serum by epidermal growth factor (EGF) failed to mediate serum-free chitosan particle uptake. Serum stimulated cells to acidify the media, partly by lactate generation. Media acidified to pH 6.5 by 7 mM lactate maintained 50% of chitosan in the soluble fraction, and led to minor uniform serum-free uptake in small vesicles. Conclusion: Media acidification mediates minor in vitro uptake of non-biofouled soluble chitosan chains, while serum-biofouled insoluble chitosan microparticles require sustained serum exposure to generate energy required for macropinocytosis. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Figures

Open AccessArticle Tripolyphosphate Cross-Linked Macromolecular Composites for the Growth of Shape- and Size-Controlled Apatites
Molecules 2013, 18(1), 27-40; doi:10.3390/molecules18010027
Received: 8 November 2012 / Revised: 26 November 2012 / Accepted: 10 December 2012 / Published: 20 December 2012
Cited by 6 | PDF Full-text (1048 KB)
Abstract
Bioactive composites that enable the formation of calcium phosphates have received increased attention over the last decade, in the development of osteoconductive biomaterials for orthopaedic applications. In this work, tripolyphosphate (TPP)-cross-linked chitosan/gelatin composites (TPP-CG) were prepared for the growth of shape- and [...] Read more.
Bioactive composites that enable the formation of calcium phosphates have received increased attention over the last decade, in the development of osteoconductive biomaterials for orthopaedic applications. In this work, tripolyphosphate (TPP)-cross-linked chitosan/gelatin composites (TPP-CG) were prepared for the growth of shape- and size-controlled calcium phosphates on/in the composites. The mineralization pattern of the composites, after soaking in the Ca(OH)2 aqueous solution, clearly demonstrated oriented, needle-like nanocrystallites of calcium phosphates in the matrix with especially high Ca/P molar ratio (3.98) as detected by energy dispersive X-ray spectroscopy (EDX) analysis. Subsequent to mineralization in a simulated body fluid (SBF), the mineralized composites showed micro-scaled spherical aggregates deposited on the surface and granule-like nanocrystallites grew in the matrix. The Ca/P molar ratio (1.72) and X-ray diffraction pattern of the nanocrystallites grown in the composites were similar to those of hydroxyapatite (HAp). Osteoblastic differentiation of ROS cells cultured on the mineralized composites allowed an enhanced expression of the chosen osteogenic marker (alkaline phosphatase, ALPase). These results indicated that the composites mineralized with micro- and nano-scaled calcium phosphates with various structural features make them attractive for bone tissue engineering applications. Full article
(This article belongs to the Special Issue Chitins and Chitosans)

Review

Jump to: Research

Open AccessReview Novel Biological Activities of Allosamidins
Molecules 2013, 18(6), 6952-6968; doi:10.3390/molecules18066952
Received: 26 April 2013 / Revised: 27 May 2013 / Accepted: 7 June 2013 / Published: 13 June 2013
Cited by 3 | PDF Full-text (309 KB) | HTML Full-text | XML Full-text
Abstract
Allosamidins, which are secondary metabolites of the Streptomyces species, have chitin-mimic pseudotrisaccharide structures. They bind to catalytic centers of all family 18 chitinases and inhibit their enzymatic activity. Allosamidins have been used as chitinase inhibitors to investigate the physiological roles of chitinases [...] Read more.
Allosamidins, which are secondary metabolites of the Streptomyces species, have chitin-mimic pseudotrisaccharide structures. They bind to catalytic centers of all family 18 chitinases and inhibit their enzymatic activity. Allosamidins have been used as chitinase inhibitors to investigate the physiological roles of chitinases in a variety of organisms. Two prominent biological activities of allosamidins were discovered, where one has anti-asthmatic activity in mammals, while the other has the chitinase-production- promoting activity in allosamidin-producing Streptomyces. In this article, recent studies on the novel biological activities of allosamidins are reviewed. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Open AccessReview Chitosan for Gene Delivery and Orthopedic Tissue Engineering Applications
Molecules 2013, 18(5), 5611-5647; doi:10.3390/molecules18055611
Received: 1 April 2013 / Revised: 2 May 2013 / Accepted: 6 May 2013 / Published: 15 May 2013
Cited by 26 | PDF Full-text (1180 KB) | HTML Full-text | XML Full-text
Abstract
Gene therapy involves the introduction of foreign genetic material into cells in order exert a therapeutic effect. The application of gene therapy to the field of orthopaedic tissue engineering is extremely promising as the controlled release of therapeutic proteins such as bone [...] Read more.
Gene therapy involves the introduction of foreign genetic material into cells in order exert a therapeutic effect. The application of gene therapy to the field of orthopaedic tissue engineering is extremely promising as the controlled release of therapeutic proteins such as bone morphogenetic proteins have been shown to stimulate bone repair. However, there are a number of drawbacks associated with viral and synthetic non-viral gene delivery approaches. One natural polymer which has generated interest as a gene delivery vector is chitosan. Chitosan is biodegradable, biocompatible and non-toxic. Much of the appeal of chitosan is due to the presence of primary amine groups in its repeating units which become protonated in acidic conditions. This property makes it a promising candidate for non-viral gene delivery. Chitosan-based vectors have been shown to transfect a number of cell types including human embryonic kidney cells (HEK293) and human cervical cancer cells (HeLa). Aside from its use in gene delivery, chitosan possesses a range of properties that show promise in tissue engineering applications; it is biodegradable, biocompatible, has anti-bacterial activity, and, its cationic nature allows for electrostatic interaction with glycosaminoglycans and other proteoglycans. It can be used to make nano- and microparticles, sponges, gels, membranes and porous scaffolds. Chitosan has also been shown to enhance mineral deposition during osteogenic differentiation of MSCs in vitro. The purpose of this review is to critically discuss the use of chitosan as a gene delivery vector with emphasis on its application in orthopedic tissue engineering. Full article
(This article belongs to the Special Issue Chitins and Chitosans)
Figures

Journal Contact

MDPI AG
Molecules Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
molecules@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Molecules
Back to Top