Three-dimensional duck’s feet collagen/PLGA scaffold for chondrification: role of pore size and porosity

Abstract

An ideal tissue-engineered scaffold must provide sufficient porosity to allow free movement of cells, nutrients, and oxygen for proper cell growth and further maintenance. Owing to variation in pore sizes and shapes of as-fabricated scaffold, the amount of oxygen available for the cells attached to the scaffold and transfer of by-products and excrement will be different, which ultimately results in cell activity. Thus, optimizing pore size and porosity of a scaffold for a specific tissue regeneration are one of the key highlights, which should be considered while designing a scaffold as well as choosing a specific cell type. In this study, three-dimensional (3D) scaffolds based on blends of duck’s feet collagen (DC) and poly (lactic-co-glycolic acid) (PLGA) with different pore sizes i.e. 90–180, 180–250, 250–355 and 355–425 μm were prepared using solvent casting/salt leaching approach and examined its effects on chondrification. The morphological analysis of the as-fabricated scaffolds was performed using SEM for studying porosity and pore size. The cell proliferation and gene expression were investigated after culturing costal chondrocytes on each scaffolds using 3-(4, 5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) assay and qRT-PCR. Histological staining of in vivo implants was performed in nude mice as models. The biological evaluation showed a pore-size dependent chondrification at different time points. Especially, the 355–425 μm DC/PLGA scaffold showed a highest positive impact on maintenance of cell proliferation, costal chondrocyte phenotype and increased glycosaminoglycan accumulation than the other groups. These results indicated that DC/PLGA scaffolds with pore size ranging from 250 to 425 μm can be considered as highly-suitable constructs for enhanced chondrification.     

Novel transparent collagen film patch derived from duck’s feet for tympanic membrane perforation

Abstract

To increase healing rate of tympanic membrane (TM) perforations, patching procedure has been commonly conducted. Biocompatible, biodegradable patching materials which is not limited across cultures is needed. The authors evaluated the effectiveness of novel transparent duck’s feet collagen film (DCF) patch in acute traumatic TM perforation. This procedure was compared with spontaneous healing and paper patching. Cell proliferation features were observed in paper and DCF patches. Forty-eight TMs of 24 rats were used for animal experiment, perforations were made on each TMs, and divided into three groups according to treatment modality. Sixteen were spontaneously healed, 16 were paper patched and 16 were DCF patched. The gross and histological healing results were analyzed. Both paper and DCF patch showed no cytotoxicity, but cell proliferations were more active in DCF than paper in early stage. In animal study, the healing of TM perforations were completed within 14 days in all three groups, but found to be faster in DCF patch group than paper patch or spontaneous healing group. The DCF patches were transparent and size of DCF patches were gradually decreased, so there were no need to remove the DCF patches to check the wound status or after the completion of healing. According to this result, authors concluded that DCF patch is transparent, biocompatible and biodegradable material, and can induce fast healing in acute traumatic TM perforations.     

Nature-derived epigallocatechin gallate/duck’s feet collagen/hydroxyapatite composite sponges for enhanced bone tissue regeneration

Abstract

Scaffolds mimicking structural and chemical characteristics of the native bone tissues are critical for bone tissue engineering. Herein, we have developed and characterized epigallocatechin gallate/duck’s feet collagen/hydroxyapatite (EGCG/DC/HAp) composite sponges that enhanced the bone tissue regeneration. The three-dimensional composite sponges were synthesized by loading various amounts (i.e. 1, 5 and 10 μM) of EGCG to duck feet derived collagen followed by freeze-drying and then coating with hydroxyapatite. Several measuremental techniques were employed to examine the properties of the as-fabricated composite sponges including morphology and structure, porosity, compressive strength, etc. and as well compared with pristine duck feet derived collagen. SEM observations of EGCG/DC/HAp sponges showed the formation of a highly porous collagen matrix with EGCG embodiment. The porosity and pore size of sponges were found to increase by high EGCG content. The compressive strength was calculated as 3.54 ± 0.04, 3.63 ± 0.03, 3.89 ± 0.05, 4.047 ± 0.05 MPa for 1, 5 and 10 μM EGCG/DC/HAp sponges, respectively. Osteoblast-like cell (BMSCs isolated from rabbit) culture and in vivo experiments with EGCG/DC/HAp sponges implanted in nude mouse followed by histological staining showed enhanced cell internalization and attachment, cell proliferation, alkaline phosphatase expressions, indicating that EGCG/DC/HAp sponges have ahigh biocompatibility. Moreover, highEGCG content in the EGCG/DC/HAp sponges have led to increased cellular behavior. Collectively, the 5 μM of EGCG/DC/HAp sponges were suggested as the potential candidates for bone tissue regeneration.     

Fabrication and characterization of chitosan–collagen crosslinked membranes for corneal tissue engineering

This article describes a chitosan–collagen composite membrane as corneal tissue-engineering biomaterials. The membrane was prepared by dissolving the chitosan into collagen with the weight ratio of 0, 15, 30, 45, 60, and 100%, followed by crosslinked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. Mechanical properties, contact angles, and optical transmittance were determined and compared between chitosan membrane and crosslinking composite membrane. As a result, the optical transparency and mechanical strength of the chitosan–collagen membranes were significantly better than that of the sample of chitosan. In addition, in vitro cell culture studies revealed that the collagen has no negative effect on the cell morphology, viability, and proliferation and possess good biocompatibility. Overall, the dendrimer crosslinked chitosan–collagen composite membranes showed promising properties that suggest that these might be suitable biomaterials for corneal tissue-engineering applications.     

Acceleration of wound healing by a porous collagen/silk fibroin scaffold carrying zinc oxide nanoparticles北大核心

BACKGROUND: Anti-infective ability determine the success or failure of skin grafting. It is one of the commonly used methods to enhance the anti-infective ability of implants by compounding antibacterial materials with scaffolds. OBJECTIVE:To investigate the effect of porous collagen/silk fibroin scaffolds carrying zinc oxide nanoparticles against infection and inflammation, and to evaluate its effect on wound healing. METHODS: Thirty-two Sprague-Dawley rats with a full-thickness wound on the back skin were randomly divided into two groups. In experimental groiup, porous collagen/silk fibroin scaffolds containing zinc oxide nanoparticles were implanted, while only collagen/silk fibroin scaffolds were implanted in control group. Wound healing was compared between the two groups by measuring residual wound area at 1, 2, 4, 8 weeks post implantation. Hematoxylin-eosin and interleukin 6 immumohistochemical staining were performed at 1, 2, 4 weeks post implantation to observe wound morphology and inflammatory reactions. Meanwhile, expression of interleukin 6 and interleukin 1β was detected by real-time PCR. RESULTS AND CONCLUSION: (1) At 2, 4, 8 weeks post implantation, significantly increased healing rate was observed in the experiment group compared with the control group (P<0.05). (2) Findings from the hematoxylin-eosin staining showed that obvious inflammatory cell infiltration was observed in the control group, but less inflammation with vigorous growth of granulation tissues on the wound surface occurred in the experimental group at 1 week after implantation. Then, the wound repair was basically completed in the experimental group presenting with complete and compact epidermal tissue structure, while scar formation with no skin cover was found in the control group at 4 weeks after implantation. (3) Findings from the interleukin 6 immumohistochemical staining showed that there was interleukin 6 positive expression in both two groups to different extents; at 4 weeks after implantation, the expression of interleukin 6 was remarkably reduced in the control group, but it was still a strong positive expression, while week positive expression of interleukin 6 was observed in the experimental group. (4) Compared with the control group, the mRNA expression of interleukin 6 and interleukin 1β was both lower in the experimental group at 1, 2, 4 weeks after implantation, but there was a significant difference between the two groups at 1 and 2 weeks after implantation (P<0.05). Overall, the porous collagen/silk fibroin scaffold carrying zinc oxide nanoparticles can effectively reduce inflammations following skin injury, and accelerate skin wound healing. © 2018, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved.     

Fabrication and characterization of biomimetic collagen–apatite scaffolds with tunable structures for bone tissue engineering

The objective of the current study is to prepare a biomimetic collagen–apatite scaffold for improved bone repair and regeneration. A novel bottom–up approach has been developed, which combines a biomimetic self-assembly method with a controllable freeze-casting technology. In this study, the mineralized collagen fibers were generated using a simple one-step co-precipitation method which involved collagen self-assembly and in situ apatite precipitation in a collagen-containing modified simulated body fluid (m-SBF). The precipitates were then subjected to controllable freeze casting, forming scaffolds with either an isotropic equiaxed structure or a unidirectional lamellar structure. These scaffolds were comprised of collagen fibers and poorly crystalline bone-like carbonated apatite nanoparticles. The mineral content in the scaffold could be tailored in the range 0–54 wt.% by simply adjusting the collagen content in the m-SBF. Further, the mechanisms of the formation of both the equiaxed and the lamellar scaffolds were investigated, and freezing regimes for equiaxed and lamellar solidification were established. Finally, the bone-forming capability of such prepared scaffolds was evaluated in vivo in a mouse calvarial defect model. It was confirmed that the scaffolds well support new bone formation.     

Fabrication and characterization of chitosan/OGP coated porous poly(ε-caprolactone) scaffold for bone tissue engineering

As one of the stimulators on bone formation, osteogenic growth peptide (OGP) improves both proliferation and differentiation of the bone cells in vitro and in vivo. The aim of this work was the preparation of three dimensional porous poly(ε-caprolactone) (PCL) scaffold with high porosity, well interpore connectivity, and then its surface was modified by using chitosan (CS)/OGP coating for application in bone regeneration. In present study, the properties of porous PCL and CS/OGP coated PCL scaffold, including the microstructure, water absorption, porosity, hydrophilicity, mechanical properties, and biocompatibility in vitro were investigated. Results showed that the PCL and CS/OGP-PCL scaffold with an interconnected network structure have a porosity of more than 91.5, 80.8%, respectively. The CS/OGP-PCL scaffold exhibited better hydrophilicity and mechanical properties than that of uncoated PCL scaffold. Moreover, the results of cell culture test showed that CS/OGP coating could stimulate the proliferation and growth of osteoblast cells on CS/OGP-PCL scaffold. These finding suggested that the surface modification could be a effective method on enhancing cell adhesion to synthetic polymer-based scaffolds in tissue engineering application and the developed porous CS/OGP-PCL scaffold should be considered as alternative biomaterials for bone regeneration.     

Structure–property effects of novel bioresorbable hybrid structures with controlled release of analgesic drugs for wound healing applications

Over the last decades, wound dressings have developed from the traditional gauze dressing to tissue-engineered scaffolds. A wound dressing should ideally maintain a moist environment at the wound surface, allow gas exchange, act as a barrier to micro-organisms and remove excess exudates. In order to provide these characteristics, we developed and studied bioresorbable hybrid structures which combine a synthetic porous drug-loaded top layer with a spongy collagen sublayer. The top layer, prepared using the freeze-drying of inverted emulsions technique, was loaded with the analgesic drugs ibuprofen or bupivacaine, for controlled release to the wound site. Our investigation focused on the effects of the emulsion’s parameters on the microstructure and on the resulting drug-release profile, as well as on the physical and mechanical properties. The structure of the semi-occlusive top layer enables control over vapor transmission, in addition to strongly affecting the drug release profile. Release of the analgesic drugs lasted from several days to more than 100 days. Higher organic:aqueous phase ratios and polymer contents reduced the burst release of both drugs and prolonged their release due to a lower porosity. The addition of reinforcing fibers to this layer improved the mechanical properties. Good binding of the two components, PDLGA and collagen, was achieved due to our special method of preparation, which enables a third interfacial layer in which both materials are mixed to create an “interphase”. These new PDLGA/collagen structures demonstrated a promising potential for use in various wound healing applications.     

Fabrication and characterization of poly(γ-glutamic acid)-graft-chondroitin sulfate/polycaprolactone porous scaffolds for cartilage tissue engineering

The development of blended biomacromolecule and polyester scaffolds can potentially be used in many tissue engineering applications. This study was to develop a poly(γ-glutamic acid)-graft-chondroitin sulfate-blend-poly(ε-caprolactone) (γ-PGA-g-CS/PCL) composite biomaterial as a scaffold for cartilage tissue engineering. Chondroitin sulfate (CS) was grafted to γ-PGA, forming a γ-PGA-g-CS copolymer with 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide (EDC) system. The γ-PGA-g-CS copolymers were then blended with PCL to yield a porous γ-PGA-g-CS/PCL scaffold by salt leaching. These blended scaffolds were characterized by ¹H NMR, ESCA, water-binding capacity, mechanical test, degradation rate and CS assay. The results showed that with γ-PGA-g-CS as a component, the water-binding capacity and the degradation rate of the scaffolds would substantially increase. During a 4 week period of culture, the mechanical stability of γ-PGA-g-CS/PCL scaffolds was raised gradually and chondrocytes were induced to function normally in vitro. Furthermore, a larger amount of secreted GAGs was present in the γ-PGA-g-CS/PCL matrices than in the control (PCL), as revealed by Alcian blue staining of the histochemical sections. Thus, γ-PGA-g-CS/PCL matrices exhibit excellent biodegradation and biocompatibility for chondrocytes and have potential in tissue engineering as temporary substitutes for articular cartilage regeneration.     

Erythropoietin improves skin wound healing and activates the TGF-β signaling pathway

We could recently report that erythropoietin (EPO) accelerates skin wound healing in mice. Now, we provide insight into the molecular mechanisms of this non-hematopoietic property of EPO analyzing the transforming growth factor (TGF)-β signaling pathway. EPO receptor was found expressed in both non-wounded and wounded skin tissue as well as in fibroblasts and keratinocytes. In saline-treated control animals, wounds exhibited a significant upregulation of TGF-β1 and of α-smooth muscle actin (α-SMA) compared with non-wounded skin. EPO treatment accelerated wound epithelialization and induced mRNA expression of TGF-β1 and α-SMA. In addition, EPO significantly enhanced phosphorylation of Smad2 and Smad3 in fibroblasts and also elevated phosphorylation of Smad3 in wound tissue. Blockade of TGF-β using a neutralizing anti-TGF-β antibody attenuated EPO-induced acceleration of wound epithelialization in vivo and markedly reversed EPO effects on mRNA expression of TGF-β1 and α-SMA. In conclusion, EPO caused activation of the Smad-dependent TGF-β signaling pathway, enhanced differentiation of myofibroblasts, and accelerated skin wound closure.     

Fabrication and characterization of Mg-doped chitosan–gelatin nanocompound coatings for titanium surface functionalization

Titanium and its alloys have been widely used in clinic and achieved great success. Due to the bio-inertness of titanium surface, challenges still exit in some compromised conditions. The present study aimed to functionalize titanium surface with magnesium (Mg)-doped chitosan/gelatin (CS/G) nanocompound coatings via electrophoretic deposition (EPD). CS/G coatings loaded with different amount of magnesium were successfully prepared on titanium substrate via EPD. Physicochemical characterization of the coatings confirmed that magnesium ions were loaded into the coatings in a dose-dependent manner. XRD results demonstrated that co-deposition of magnesium influenced the crystallinity of the coatings, and a new crystalline substance presented, namely hydrated basic magnesium carbonate. Mechanical tests showed improved tensile and shear bond strength of the magnesium-doped coatings, while the excessively high magnesium concentration could eventually decrease the bonding strength. Sustained release of magnesium ion was detected by ICP-OES within 28 days. TEM images also displayed that nanoparticles could be released from the coatings. In vitro cellular response assays demonstrated that the Mg-doped nanocompound coatings could enhance the proliferation and osteogenic differentiation of MC3T3-E1 cells compared to CS/G coatings. Therefore, it could be concluded that Mg-doped CS/G nanocompound coatings were successfully fabricated on titanium substrates via EPD. It would be a promising candidate to functionalize titanium surface with such organic–inorganic nanocompound coatings.     

Improved performance of collagen scaffolds crosslinked by Traut’s reagent and Sulfo-SMCC

Collagen scaffolds are frequently employed for applications in regenerative medicine. In previous studies, we affirmed that Traut’s reagent (2-Iminothiolane hydrochloride) and Sulfo-SMCC (4-(N-Maleimidomethyl) cyclohexane-1-carboxylic acid 3-sulpho-N-hydroxysuccinimide ester sodium salt) could covalently bind growth factors on collagen scaffolds. We also observed that crosslinking formed within the collagen scaffolds with excess dosage of Sulfo-SMCC, which improved the biological performance of collagen scaffolds together with growth factors. In order to evaluate changes in capacity caused by crosslinking, Traut’s reagent and adjusted different concentrations of Sulfo-SMCC (0.263, 1.315, 2.63 and 5.26 mM) were used to construct collagen scaffolds with differing extents of crosslinking in this study. The results demonstrated that resistance of collagen scaffolds to enzymatic digestion, cellularization and vascularization in vivo were enhanced by the crosslinking procedure. The cell culture studies indicated that the crosslinking procedure did not influence biocompatibility. Moreover, there were no statistical differences in the degradation rate, cellularization or vascularization among 1.315, 2.63 and 5.26 mM crosslinked groups. These results demonstrated that crosslinking collagen scaffolds with an appropriate amount of Traut’s reagent and Sulfo-SMCC was an effective and safe method to modify naturally derived collagen scaffolds with notable potential uses in tissue regeneration.     

Natalizumab for the treatment of Crohn’s disease

Primary Sjögren’s syndrome (pSS) is a chronic autoimmune disorder characterized by immune-mediated destruction of the salivary and lacrimal glands with unknown etiology. Due to recent research utilizing human subjects as well as laboratory animal models, our understanding of the pathophysiological and immunological mechanisms of pSS has made great strides. As a consequence, targeted, immune-based therapies are gaining increased attention as the ideal way to conquer autoimmune diseases like pSS. Currently, however, there is no effective treatment to target specific immunological events or effector immune cells in the pathogenesis of pSS (discussed in other reviews of the current issue). Here, we summarize our current understanding and knowledge of the roles of monocytes/macrophages in the pathogenesis of pSS. Human studies, especially utilizing salivary gland biopsies, demonstrate the infiltration of macrophages and its correlation with disease severity. Moreover, animal model studies have shown the functional involvement of macrophages in promoting the ocular component of pSS.     

Vedolizumab for the treatment of Crohn’s disease

Introduction: Crohn’s disease (CD) is an immune-mediated condition characterized by inflammation of the gut tissue, associated with progressive damage of the affected intestinal tract and possible complications. A treat-to-target approach is strongly advocated, consisting of early and aggressive inflammatory control. However, a great proportion of affected subjects lack response or are intolerant to conventional therapy. Even though the first-line biologic therapy targeting tumor necrosis factor-alfa (TNF-α) is associated with improvement of inflammation in some patients, others do not respond at first or lose response over time. These findings brought about the possibility of different mechanisms being involved in perpetuating the chronic inflammatory state. Novel drugs targeting different inflammatory pathways have been studied in CD, specifically addressed to leucocyte trafficking.

Areas covered: We aim to review the relevant data available in the literature and briefly summarize the efficacy and safety profile of vedolizumab in the treatment of CD.

Expert commentary: Vedolizumab has shown, from pivotal and real-life data, significant clinical benefit among CD patients, in addition to a singular safety profile. Future studies will provide helpful data concerning its use in special situations.     

Effects of fibrin pad hemostat on the wound healing process in vivo and in vitro

Fibrin Pad is a hemostatic pad designed to control surgical-related bleeding. It consists of a fully absorbable composite matrix scaffold coated with human-derived active biologics that immediately form a fibrin clot upon contact with targeted bleeding surfaces. Studies were conducted to investigate the effect of Fibrin Pad and its biologics-free composite matrix component (Matrix) on the wound healing process in in vitro and in vivo models. Fibrin Pad was evaluated in solid organ, soft tissue defects, and subcutaneous tissues. Immunocompromised rodents were used to avoid xeno-mediated responses. Extracts created from both materials were evaluated for biological activity using in vitro cell culture assays. Neither Fibrin Pad nor Matrix alone showed any inhibition of the wound healing of treated defect sites. An apparent accelerated healing was noted in the soft tissue and subcutaneous tissue defects with Fibrin Pad as compared to Matrix. Both materials showed desirable properties associated with tissue scaffolds. The in vitro study results show that Fibrin Pad extract can induce dose-dependent increases in fibroblast proliferation and migration. These studies confirm that the biologic components of Fibrin Pad can enhance wound healing processes in in vitro assays and fully support wound healing at the site of in vivo application.     

TGF-β1-treated ADSCs-CM promotes expression of type I collagen and MMP-1, migration of human skin fibroblasts, and wound healing in vitro and in vivo

Conditioned medium from adipose-derived stem cells (ADSCs) stimulates both collagen synthesis and migration of dermal fibroblasts. However, it is still unknown whether conditioned media from tumor growth factor (TGF)-β1-treated ADSCs (TGF-β1-treated ADSCs-CM) induces increased expression of type I collagen, matrix metalloproteinase-1 (MMP-1), and migration as well as cell cycle regulatory proteins in fibroblasts, compared to non-treated ADSCs-CM. Our data showed that TGF-β1-treated ADSCs-CM promoted effectively the proliferation and migration of human skin fibroblasts, compared to non-treated ADSCs-CM. In addition the expression of MMP-1 were markedly increased by treatment of TGF-β1-treated ADSCs-CM in fibroblasts, compared to non-treated ADSCs-CM. Expression of type I collagen protein were slightly increased by treatment of TGF-β1-treated ADSCs-CM in fibroblasts. The expression of cell cycle regulators of G1/S phase transition were not markedly altered by treatment of TGF-β1-treated ADSCs-CM. Finally, artificial wounds were made using a 4-mm punch biopsy in hairless mice and TGF-β1-treated ADSCs-CM were injected into the wound area. The injection of TGF-β1-treated ADSCs-CM promoted the wound healing process in hairless mice. Taken together, our data indicated that TGF-β1-treated ADSCs-CM induced up-regulation of type I collagen and MMP-1, promoted the migration of skin fibroblasts, and thereby promoted the wound healing process in vivo. Our data indicate that TGF-β1-treated ADSCs-CM will be a component for a wound healing accelerating agent.     

Application of gentamicin-collagen sponge shortened wound healing time after minor amputations in diabetic patients – a prospective,randomised trial

Introduction

Diabetic foot infections are frequently polymicrobial. The lower tissue concentration of systemically administered antibiotics in diabetic patients was reported. Collatamp^®EG (Syntacoll GmbH Saal/Donau, Germany) is a bioabsorbable, gentamicin impregnated collagen spongeused for local treatment. The aim of this randomized trial was to assess influence of gentamicin-collagen sponge applied to a wound on surgical outcomes after minor amputations in diabetic patients.

Material and methods

Fifty diabetic patients indicated for minor amputation in 2009 at our surgery department were included in the study. Patients were pre-operatively randomised into two groups. Twenty-five patients in group A were treated with gentamicin impregnated collagen sponge applied into wound peri-operatively while 25 patients in group B had minor amputation without gentamicin sponge.

Results

There was no significant difference in the demographic data, procedures performed, diabetes duration and peripheral vascular disease severity between the groups. The median glycosylated haemoglobin was 6.0% (range: 4.6–9.5%) in group A and 6.2% (range: 4.0–8.4%) in control group B (non-significant). Median TcPO₂ level was 44 (range: 13–67) in group A and 48 (range: 11–69) in control group B (non-significant). The median of wound healing duration in group A was 3.0 weeks (range: 1.7–17.1 weeks) compared to 4.9 weeks (range: 2.6–20.0 weeks) in control group B. This was with a statistically significant difference (p < 0.05).

Conclusions

Application of gentamicin impregnated collagen sponge shortened wound healing duration after minor amputations in diabetic patients by almost 2 weeks.     

Adalimumab for the treatment of pediatric Crohn’s disease

Inflammatory bowel diseases are characterized by a chronic relapsing course, high morbidity and impaired quality of life. Their incidence is rising, and about 25% of cases are diagnosed in pediatric age. Anti-TNF-α antibodies, such as infliximab and adalimumab (ADA), are usually administered in patients refractory to conventional therapies. However, increasing evidence suggests that they can be introduced earlier in the course of the disease, especially in patients with aggressive and extensive disease since diagnosis. ADA is a fully human anti-TNF-α antibody recently approved for pediatric Crohn’s disease not only in patients unresponsive to infliximab, but also as a first-line anti-TNF-α therapy. In this review, we aim to summarize the current knowledge on the use of ADA in pediatric Crohn’s disease and to discuss open issues regarding safety as well as future perspectives.