Compatible Ternary Blends of Chitosan/poly(vinyl alcohol)/poly(lactic acid) Produced by Oil-in-Water Emulsion Processing

Ternary compatible blends of chitosan, poly(vinyl alcohol), and poly(lactic acid) were prepared by an oil-in-water (O/W) emulsion process. Solutions of chitosan in aqueous acetic acid, poly(vinyl alcohol) (PVA) in water, and poly(lactic acid) (PLA) in chloroform were blended with a high shear mixer. PVA was used as an emulsifier to stabilize the emulsion and to reduce the interfacial tension between the solid polymers in the blends-produced. It proved to work very well because the emulsions were stable for periods of days or weeks and compatible blends were obtained When PVA was added. This effect was attributed to a synergistic effect of PVA and chitosan because the binary blends PVA/PLA and chitosan/PLA were completely incompatible; The blends were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), stress strain tests, and Fourier transform infrared spectroscopy (FTIR). The results indicated that despite the fact that the system contained distinct phases some degree of molecular miscibility occurred when the three components were present in the blend.

Moisture sorption isotherm characteristics of freeze-dried D-limonene emulsions in modified chitosan and maltodextrin

This article reports on modified chitosan as an alternative substance for protecting loss of volatile compounds during freeze drying. Moisture sorption isotherms of freeze-dried D-limonene emulsions in modified chitosan were determined at 15, 25, and 35 degrees C. The data were adjusted to the GAB model. Maltodextrin was used in a parallel experiment. Flavor released from microcapsules was measured. The monolayer humidity, the sorption heat, the diffusivity coefficients, and the surface area of freeze-dried D-limonene emulsions were determined.

Preparation and characterization of chitosan-treated alginate microparticles incorporating all-trans retinoic acid

Chitosan treated alginate microparticles were prepared with the purpose of incorporating all-trans retinoic acid (ATRA) using an inexpensive, simple and fast method, enhancing dermal localization and sustaining the release of ATRA into the skin. Microparticles characterization, drug-polymer interaction, release profile and in vitro skin retention were investigated. Microparticles presented spherical shape and drug loading capacity of 47%. The drug content of these microparticles was affected by ATRA concentration and by the solvent used and it was more weakly affected by chitosan concentration. The release of ATRA was also affected by chitosan concentration. Microparticles prepared with 0.4% chitosan (w/w) resulted in drug release with a more sustained profile. The results of in vitro retention studies showed that chitosan treated alginate microparticles decreased the drug retention in the stratum corneum (SC), where occur the skin irritation, but maintained the ATRA concentration in the deeper skin layers, where occur the pathologies treated with ATRA. Then, the microparticles developed in this work can be a good candidate to improve the topical therapy with retinoid.

Chitosan microparticles for sustaining the topical delivery of minoxidil sulphate

Given the hypothesis that microparticles can penetrate the skin barrier along the transfollicular route, this work aimed to obtain and characterise chitosan microparticles loaded with minoxidil sulphate (MXS) and to study their ability to sustain the release of the drug, attempting a further application utilising them in a targeted delivery system for the topical treatment of alopecia. Chitosan microparticles, containing different proportions of MXS/polymer, were prepared by spray drying and were characterised by yield, encapsulation efficiency, size and morphology. Microparticles selected for further studies showed high encapsulation efficiency (similar to 82%), a mean diameter of 3.0 mu m and a spherical morphology without porosities. When suspended in an ethanol/water solution, chitosan microparticles underwent instantaneous swelling, increasing their mean diameter by 90%. Release studies revealed that the chitosan microparticles were able to sustain about three times the release rate of MXS. This feature, combined with suitable size, confers to these microparticles the potential to target and improve topical therapy of alopecia with minoxidil.

A poloxamer/chitosan in situ forming gel with prolonged retention time for ocular delivery

The aim of the present work was to obtain an ophthalmic delivery system with improved mechanical and mucoadhesive properties that could provide prolonged retention time for the treatment of ocular diseases. For this, an in situ forming gel comprised of the combination of a thermosetting polymer, poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO, poloxamer), with a mucoadhesive agent (chitosan) was developed. Different polymer ratios were evaluated by oscillatory rheology, texture and mucoadhesive profiles. Scintigraphy studies in humans were conduced to verify the retention time of the formulations developed. The results showed that chitosan improves the mechanical strength and texture properties of poloxamer formulations and also confers mucoadhesive properties in a concentration-dependent manner. After a 10-min instillation of the poloxamer/chitosan 16:1 formulation in human eyes, 50-60% of the gel was still in contact with the cornea surface, which represents a fourfold increased retention in comparison with a conventional solution. Therefore, the developed formulation presented adequate mechanical and sensorial properties and remained in contact with the eye surface for a prolonged time. In conclusion, the in situ forming gel comprised of poloxamer/chitosan is a promising tool for the topical treatment of ocular diseases. (C) 2010 Elsevier B.V. All rights reserved.

Effect of the iontophoresis of a chitosan gel on doxorubicin skin penetration and cytotoxicity

The aim of this work was to investigate doxorubicin (DOX) percutaneous absorption and retention in the skin following iontophoresis. The convective flow contribution to the overall electrotransport of DOX was also elucidated for a non-ionic hyd roxyethylcellulose gel and a cationic chitosan gel. Moreover, the cytotoxicity of DOX and its formulations, with and without low electrical current, was verified. It was observed that iontophoresis of DOX significantly increased the skin permeation and retention of the drug. In addition, the electroosmotic flow was dramatically reduced when DOX was added to the non-ionic gel, thereby indicating that the drug interacted with negative charges in the skin. Interestingly, electroosmosis was also significantly reduced when the iontophoresis was performed in the presence of the chitosan gel, but in the absence of DOX. Consequently, the transport of an electroosmotic marker from this gel almost disappeared when the positively charged drug was added to the cationic gel. These results indicated that chitosan appeared to interact with negative charges in the skin. Hence, this carrier not only reduced electroosmotic flow, but also released DOX from ionic interactions with these sites and improved its diffusion to deeper skin layers. The application of the low electrical current directly to melanoma cells increased DOX cytotoxicity by nearly three-fold, which was probably due to membrane permeation. (c) 2008 Elsevier B.V. All rights reserved.

Chitosan as a Bioadhesive Agent Between Porphyrins and Phospholipids in a Biomembrane Model

Porphyrins are currently used in photodynamic therapy as photosensitizers. In this paper we studied the interaction of two charged porphyrins, 5, 10, 15, 20-mesotetrakis(N-metyl-4-pyridyl) porphyrin, (TMPyP/chloride salt) cationic, and 5, 10, 15, 20-meso-tetrakis(sulfonatophenyl) porphyrin, (TPPS(4)/sodium salt) anionic, nanoassembled in phospholipid Langmuir monolayers and Langmuir-Blodgett films. Furthermore, we used chitosan to mediate the interaction between the porphyrins and the model membrane, aiming to understand the role of the polysaccharide in a molecular level. The effect of the interaction of the photosensitizers on the fluidity of the lipid monolayer was investigated by using dilatational surface elasticity. We also used photoluminescence (PL) spectroscopy to identify the porphyrins adsorbed in the phospholipid films. We observed an expansion of the monolayer promoted by the adsorption of the porphyrins into the lipid-air interface which was more pronounced in the case of TMPyP, as a consequence of a strong electrostatic interaction with the anionic monolayer. The chitosan promoted a higher adsorption of the porphyrins on the phospholipid monolayers and enabled the porphyrin to stay in its monomeric form (as confirmed by PL spectroscopy), thus demonstrating that chitosan can be pointed out as a potential photosensitizer delivery system in photodynamic therapy.

Jacobsen catalyst immobilized on chitosan membrane as interface catalyst in organic/aqueous system for alkene oxidation

The Jacobsen catalyst, Mn(salen), was immobilized in chitosan membrane. The obtained Mn(salen)-Chit was characterized by thermogravimetric analysis (TC), differential thermal analysis (DTA), differential scanning calorimetry (DSC), infrared spectroscopy (FT-IR), degree of N-acetylation by (1)H NMR, and UV-vis spectroscopy. The UV-vis absorption spectrum of the encapsulated catalyst displayed the typical bands of the Jacobsen catalyst, and the FT-IR presented an absorption band characteristic of the imines present in the Jacobsen catalyst. The chitosan membranes were available, in a biphasic system, as a catalytic barrier between two different phases: an organic substrate phase (cyclooctene or styrene) and an aqueous solution of either m-CPBA, t-BuOOH or H(2)O(2), and dismissing the need for phase transfer agents and leading to better product yields compared with the catalyst in homogeneous medium. This new catalyst did not leach from the support and was reused many times, leading to high turnover frequencies. (C) 2009 Elsevier B.V. All rights reserved.

Evaluation of Maxillary Alveolar Reconstruction Using a Resorbable Collagen Sponge with Recombinant Human Bone Morphogenetic Protein-2 in Cleft Lip and Palate Patients

Introduction: A resorbable collagen matrix with recombinant human bone morphogenetic protein (rhBMP-2) was compared with traditional iliac crest bone graft for the closure of alveolar defects during secondary dental eruption. Methods: Sixteen patients with unilateral cleft lip and palate, aged 8 to 12 years, were selected and randomly assigned to group 1 (rhBMP-2) or group 2 (iliac crest bone graft). Computed tomography was performed to assess both groups preoperatively and at months 6 and 12 postoperatively. Bone height and defect volume were calculated through Osirix Dicom Viewer (Pixmeo, Apple Inc.). Overall morbidity was recorded. Results: Preoperative and follow-up examinations revealed progressive alveolar bone union in all patients. For group 1, final completion of the defect with a 65.0% mean bone height was detected 12 months postoperatively. For group 2, final completion of the defect with an 83.8% mean bone height was detected 6 months postoperatively. Dental eruption routinely occurred in both groups. Clinical complications included significant swelling in three group 1 patients (37.5%) and significant donor-site pain in seven group 2 patients (87.5%). Conclusions: For this select group of patients with immature skeleton, rhBMP-2 therapy resulted in satisfactory bone healing and reduced morbidity compared with traditional iliac crest bone grafting.

Collagen and Elastic Content of Abdominal Skin After Surgical Weight Loss

Collapsed skin folds after bariatric weight loss are often managed by plastic procedures, but changes in dermal composition and architecture have rarely been documented. Given the potential consequences on surgical outcome, a prospective histochemical study was designed. The hypothesis was that a deranged dermal fiber pattern would accompany major changes in adipose tissue. Female surgical candidates undergoing postbariatric abdominoplasty (n = 40) and never obese women submitted to control procedures (n = 40) were submitted to double abdominal biopsy, respectively in the epigastrium and hypogastrium. Histomorphometric assessment of collagen and elastic fibers was executed by the Image Analyzer System (Kontron Electronic 300, Zeiss, Germany). Depletion of collagen, but not of elastic fibers, in cases with massive weight loss was confirmed. Changes were somewhat more severe in epigastrium (P = 0.001) than hypogastrium (P = 0.007). Correlation with age did not occur. (1) Patients displayed lax, soft skin lacking sufficient collagen fiber network. (2) Elastic fiber content was not damaged, and was even moderately increased in epigastrium; (3) Preoperative obesity negatively correlated with hypogastric collagen concentration; (4) Future studies should pinpoint the roles of obesity, and especially of massive weight loss, on dermal architecture and response to surgery.

Pentoxifylline modifies three-dimensional collagen lattice model contraction and expression of collagen types I and III by human fibroblasts derived from post-burn hypertrophic scars and from normal skin

Fibroblasts are thought to be partially responsible for the persisting contractile forces that result in burn contractures. Using a monolayer cell culture and fibroblast populated collagen lattice (FPCL) three-dimensional model we subjected hypertrophic scar and non-cicatricial fibroblasts to the antifibrogenic agent pentoxifylline (PTF - 1 mg/mL) in order to reduce proliferation, collagen types I and III synthesis and model contraction. Fibroblasts were isolated from post-burn hypertrophic scars (HSHF) and non-scarred skin (NHF). Cells were grown in monolayers or incorporated into FPCL`s and exposed to PTF. In monolayer, cell number proliferation was reduced (46.35% in HSHF group and 37.73% in NHF group, p < 0.0001). PTF selectively inhibited collagen III synthesis in the HSHF group while inhibition was more evident to type I collagen synthesis in the NHF group. PTF also reduced contraction in both (HSHF and NHF) FPCL. (C) 2009 Elsevier Ltd and ISBI. All rights reserved.

The remodeling of collagen fibers in rats ankles submitted to immobilization and muscle stretch protocol

To evaluate the remodeling of collagen fibers in the articular cartilage of rat ankles, with and without immobilization, after application of muscle stretching protocol. Twenty three Wistar rats were divided into four groups: immobilized (I), n = 6; immobilized and stretched (IS), n = 6; stretched (S), n = 6 and control (C), n = 5. The animals in groups I and IS were submitted to immobilization. After the period of immobilization, the animals in groups IS and S were submitted to a muscle stretching protocol. At the end of the experiment, the animals were euthanized and the joints removed, processed and stained with Picrosirius red. The analysis was carried out using a polarized light microscope. The density of collagen fibers were quantified according to the intensity of birefringence displayed. By way of statistical analyses, the right and left hind limbs of the different groups were compared based on the total density of collagen fibers, the density of thick collagen fibers and the density of thin collagen fibers. Immobilization promoted a reduction in density of the thin fibers and of total collagen. The muscle stretching protocol after immobilization promoted a reduction in density of the total collagen and of the thick fibers, but the density of the thin fibers showed the same values as control. The collagen fibers were remodeled by the different stimuli. Immobilization was harmful to the collagen fibers and the muscle stretching protocol only recovered the thin collagen fibers.

Collagen is reduced and disrupted in human aneurysms and dissections of ascending aorta

In ascending aorta aneurysms, there is an enlargement of the whole vessel, whereas aortic dissections (ADs) are characterized by the cleavage of the wall into 2 sheets at the external half. We searched if alterations in collagen could be related to these diseases. Sections of aortas from 14 case patients with acute dissections, 10 case patients with aneurysms, and 9 control subjects were stained with picrosirius. Slides were analyzed under polarized microscopy to evaluate the structure of collagen fibers. The proportion of collagen was calculated in each half of the medial layer by color detection in a computerized image analysis system. Collagen appearance under polarized light was consistent with collagenolysis. The mean collagen proportions at the inner and outer halves, respectively, were 0.50 +/- 0.13 and 0.40 +/- 0.08 in the control group, 0.20 +/- 0.10 and 0.18 +/- 0.12 in the AD group, and 0.33 +/- 0.12 and 0.19 +/- 0.12 in the aneurysm group. The AD (P < .01) and control (P = .04) groups had less collagen at the external half, no difference was found in the aneurysm group (P = .71). In both halves, there was less collagen in the case patients than in the control subjects (all P < .01), but at the internal half, the decrease was significantly greater in the case patients with aneurysms than in those with dissections (P = .03; at the external half, P = .99). Aortic dissections and aneurysms show a decrease in collagen content that could be related to a weakness of the wall underlying the diseases, but the locations of the decrease differ: in dissections, it is situated mostly at the external portion of the media (site of cleavage), whereas in aneurysms, it is more diffuse, consistent with the global enlargement. (c) 2008 Elsevier Inc. All rights reserved.

Influence of Suture on Peripheral Nerve Regeneration and Collagen Production at the Site of Neurorrhaphy: An Experimental Study

BACKGROUND: Restoration of nerve continuity and effective maintenance of coaptation are considered fundamental principles of end-to-end peripheral nerve repair. OBJECTIVE: To evaluate the influence of the number of stitches on axonal regeneration and collagen production after neurorrhaphy. METHODS: Thirty male Wistar rats were equally divided into 3 groups and were all operated on with the right sciatic nerve exposed. In 2 groups, the nerve was sectioned and repaired by means of 3 (group B) or 6 (group C) epineurium sutures with 100 monofilament nylon. One group (group A) was used as a control. Each animal from groups B and C underwent electrophysiological evaluation with motor action potential recordings before nerve section and again at an 8-week interval after neurorrhaphy. Nerve biopsy specimens were used for histomorphometric assessment of axonal regeneration and quantification of collagen at the repair site. RESULTS: Animals from group C had significantly lower motor action potential conduction velocities compared with control animals (P = .02), and no significant difference was seen between groups B and C. Parameters obtained from morphometric evaluation were not significantly different between these 2 groups. Type I collagen and III collagen in the epineurium were significantly higher in group C than in either the control group (P = .001 and P = .003) or group B (P = .01 and P = .02). No differences were identified for collagen I and III in the endoneurium. CONCLUSION: Using 6 sutures for nerve repair is associated with worse electrophysiological outcomes and higher amounts of type I and III collagen in the epineurium compared with control. Neurorraphy with 6 stitches is also related to a significant increase in epineurium collagen I and III compared with 3-stitch neurorraphy.

Collagen V and vascular injury promote lung architectural changes in systemic sclerosis

Background: Systemic sclerosis (SSc) is a multisystem disorder characterized by inflammation, fibrosis and vascular damage. The aim of this study was to evaluate the interactions between basement membrane disruption, endothelial injury and collagen V deposition on the vascular wall, as well as their association with pulmonary function tests in patients with SSc. Method: The endothelial apoptosis was assessed by TUNEL and electron microscopy, and quantified through the point-counting technique. To evaluate basement membrane integrity, laminin immunostaining and electron microscopy were used. Immunofluorescence and morphometric analysis were used to determine the amount of collagen V in the vascular walls in 23 open lung biopsies of patients with SSc without pulmonary hypertension. Normal lung tissue was obtained from five individuals who had died of traumatic injuries. Results: The apoptosis index in SSc was higher in the endothelial cells (13.83 +/- 6.83) when compared with the control (2.51 +/- 2.06) group (P < 0.001) and confirmed by electron microscopy. We observed an important disruption of the basement membrane on the vascular wall shown by discontinuous laminin immunostaining and electron microscopy. An increase in collagen V on the vascular wall of the SSc group was observed (45.28 +/- 13.21), when compared with control group (22.90 +/- 4.13, P < 0.001), and this difference was statistically significant. An inverse correlation was found between vital capacity, forced vital capacity, forced expiratory volume in 1 s, vascular collagen V and endothelial apoptosis (P < 0.05). Conclusions: We conclude that the endothelial apoptosis and vascular collagen V interaction reinforce the vascular pathway in the SSc pathogenesis. Further studies are needed to determine whether this relationship is causal or consequential. Please cite this paper as: Parra ER, Aguiar AC Jr, Teodoro WR, de Souza R, Yoshinari NH and Capelozzi VL. Collagen V and vascular injury promote lung architectural changes in systemic sclerosis. The Clinical Respiratory Journal 2009; 3: 135-142.