Enhancement of fibroblastic proliferation on chitosan surfaces by immobilized epidermal growth factor

Strategy for Conjugating Oligopeptides to Mesoporous Silica Nanoparticles Using Diazirine-Based Heterobifunctional Linkers

Successful strategies for the attachment of oligopeptides to mesoporous silica with pores large enough to load biomolecules should utilize the high surface area of pores to provide an accessible, protective environment. A two-step oligopeptide functionalization strategy is examined here using diazirine-based heterobifunctional linkers. Mesoporous silica nanoparticles (MSNPs) with average pore diameter of ~8 nm and surface area of ~730 m²/g were synthesized and amine-functionalized. Tetrapeptides Gly-Gly-Gly-Gly (GGGG) and Arg-Ser-Ser-Val (RSSV), and a peptide comprised of four copies of RSSV (4RSSV), were covalently attached via their N-terminus to the amine groups on the particle surface by a heterobifunctional linker, sulfo-succinimidyl 6-(4,4′-azipentanamido)hexanoate (sulfo-NHS-LC-diazirine, or SNLD). SNLD consists of an amine-reactive NHS ester group and UV-activable diazirine group, providing precise control over the sequence of attachment steps. Attachment efficiency of RSSV was measured using fluorescein isothiocyanate (FITC)-tagged RSSV (RSSV-FITC). TGA analysis shows similar efficiency (0.29, 0.31 and 0.26 mol peptide/mol amine, respectively) for 4G, RSSV and 4RSSV, suggesting a generalizable method of peptide conjugation. The technique developed here for the conjugation of peptides to MSNPs provides for their attachment in pores and can be translated to selective peptide-based separation and concentration of therapeutics from aqueous process and waste streams.

Epithelial Growth Factor-Anchored on Polycaprolactone/6-deoxy-6-amino-β-cyclodextrin Nanofibers: In Vitro and In Vivo Evaluation

Polycaprolactone (PCL) is a well-known FDA approved biomaterial for tissue engineering. However, its hydrophobic properties limit its use for skin wound healing which makes its functionalization necessary. In this work, we present the fabrication and evaluation of PCL nanofibers by the electrospinning technique, as well as PCL functionalized with 6-deoxy-6-amino-β-cyclodextrin (aminated nanofibers). Afterwards, epithelial growth factor (EGF) was anchored onto hydrophilic PCL/deoxy-6-amino-β-cyclodextrin. The characterization of the three electrospun fibers was made by means of field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR); Confocal-Raman Spectroscopy were used for elucidated the chemical structure, the hydrophilicity was determined by Contact Angle (CA). In vitro cell proliferation test was made by seeding embryonic fibroblast cell line (3T3) onto the electrospun mats and in vivo studies in a murine model were conducted to prove its effectivity as skin wound healing material. The in vitro studies showed that aminated nanofibers without and with EGF had 100 and 150% more cell proliferation of 3T3 cells against the PCL alone, respectively. In vivo results showed that skin wound healing in a murine model was accelerated by the incorporation of the EGF. In addition, the EGF had favorable effects in epidermal cell proliferation. The study demonstrates that a protein of high biological interest like EGF can be attached covalently to the surface of a synthetic material enriched with amino groups. This kind of biomaterial has a great potential for applications in skin regeneration and wound healing.

Chitosan as a Wound Dressing Starting Material: Antimicrobial Properties and Mode of Action

Fighting bacterial resistance is one of the concerns in modern days, as antibiotics remain the main resource of bacterial control. Data shows that for every antibiotic developed, there is a microorganism that becomes resistant to it. Natural polymers, as the source of antibacterial agents, offer a new way to fight bacterial infection. The advantage over conventional synthetic antibiotics is that natural antimicrobial agents are biocompatible, non-toxic, and inexpensive. Chitosan is one of the natural polymers that represent a very promising source for the development of antimicrobial agents. In addition, chitosan is biodegradable, non-toxic, and most importantly, promotes wound healing, features that makes it suitable as a starting material for wound dressings. This paper reviews the antimicrobial properties of chitosan and describes the mechanisms of action toward microbial cells as well as the interactions with mammalian cells in terms of wound healing process. Finally, the applications of chitosan as a wound-dressing material are discussed along with the current status of chitosan-based wound dressings existing on the market.

Preparation of bioactive and antimicrobial PLGA membranes by magainin II/EGF functionalization

Development of dual functional materials that are capable of both reducing bacterial interaction and encouraging host tissue integration has gained importance in design of biomaterials. In this study, we prepared a bilayer poly (lactide co-glycolide) fibrous membrane with antibacterial and bioactive properties by electrospinning. The antibacterial layer was produced by covalent immobilization of antimicrobial peptide, Magainin II. The bioactive layer incorporating epidermal growth factor (EGF) molecules was subsequently electrospun on the antibacterial layer. The membranes were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy and fluorescence microscopy. EGF release was detected by enzyme-linked immunosorbent assay. The antibacterial activity was tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The ability to support tissue cell integration was detected by using L-929 mouse fibroblasts. The dual functional membranes established enhanced antibacterial properties and increased tissue cell compatibility. This combined approach suggests a promising strategy for wound dressings, vascular grafts and dental membranes as well as catheters and fixation devices.

Surface functionalization of nanoporous alumina with bone morphogenetic protein 2 for inducing osteogenic differentiation of mesenchymal stem cells

Many studies have demonstrated the possibility to regulate cellular behavior by manipulating the specific characteristics of biomaterials including the physical features and chemical properties. To investigate the synergistic effect of chemical factors and surface topography on the growth behavior of mesenchymal stem cells (MSCs), bone morphorgenic protein 2 (BMP2) was immobilized onto porous alumina substrates with different pore sizes. The BMP2-immobilized alumina substrates were characterized with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Growth behavior and osteogenic differentiation of MSCs cultured on the different substrates were investigated. Cell adhesion and morphological changes were observed with SEM, and the results showed that the BMP2-immobilized alumina substrate was able to promote adhesion and spreading of MSCs. MTT assay and immunofluorescence staining of integrin β1 revealed that the BMP2-immobilized alumina substrates were favorable for cell growth. To evaluate the differentiation of MSCs, osteoblastic differentiation markers, such as alkaline phosphatase (ALP) activity and mineralization, were investigated. Compared with those of untreated alumina substrates, significantly higher ALP activities and mineralization were detected in cells cultured on BMP2-immobilized alumina substrates. The results suggested that surface functionalization of nanoporous alumina substrates with BMP2 was beneficial for cell growth and osteogenic differentiation. With the approach of immobilizing growth factors onto material substrates, it provided a new insight to exploit novel biofunctional materials for tissue engineering.

Antifibrotic role of captopril after ureteral injury

OBJECTIVES

To evaluate the antifibrotic role of captopril during ureteral scarring in a New Zealand rabbit model.

MATERIALS AND METHODS

The tissue expression and the fluctuation of EGF, TGF-β, FN, Col Ia1, Col Ia2 and Col III of the impaired ureter and the contralateral normal ureter were investigated by RT-PCR. The histological changes of the specimens were studied. When the sensitive markers had been selected, 10 New Zealand rabbits were randomly assigned to a captopril group and a control group. The specimens were harvested 2 weeks after the injury and then the histological examination and RT-PCR were performed.

RESULTS

By RT-PCR screening, EGF, TGF-β, FN, Col Ia1 and Col Ia2 were found to be significantly related to ureteral scarring (p < 0.05) confirmed by histological examination. The peak level of EGF, TGF-β and Col Ia1 appeared at 2 weeks after the injury, while for Fn and Col Ia2 it was at 3 and 4 weeks after the injury. An obvious reduction of fibrotic scarring was observed in the captopril group. The expression of EGF, Fn and Col Ia2 in the captopril group was significantly lower than in the control group (p < 0.05) after the treatment.

CONCLUSIONS

EGF, TGF-β, Col Ia1, Col Ia2 and FN seemed to have an important role in the ureteral scarring after injury. Captopril might partially inhibit the fibrotic process by blocking the EGF, Col Ia2 and FN pathway so that it could be a promising treatment after ureteral injury.

Cobalt chromium alloy with immobilized BMP peptide for enhanced bone growth

Cobalt chromium (CoCr) alloys are widely used in orthopedic practice, however, lack of integration into the bone for long-term survival often occurs, leading to implant failure. Revision surgery to address such a failure involves increased risks, complications, and costs. Advances to enhancement of bone-implant interactions would improve implant longevity and long-term results. Therefore, we investigated the effects of BMP peptide covalently grafted to CoCr alloy on osteogenesis. The BMP peptide was derived from the knuckle epitope of bone morphogenic protein-2 (BMP-2) and was conjugated via a cysteine amino acid at the N-terminus. X-ray photoelectron spectroscopy and o-phthaldialdehyde were used to verify successful grafting at various stages of surface functionalization. Surface topography was evaluated from the surface profile determined by atomic force microscopy. Osteoblastic cells (MC3T3-E1) were seeded on the substrates, and the effects of BMP peptide on osteogenic differentiation were evaluated by measuring alkaline phosphatase (ALP) activity and calcium mineral deposition. The functionalized surfaces showed a twofold increase in ALP activity after 2 weeks incubation and a fourfold increase in calcium content after 3 weeks incubation compared to the pristine substrate. These findings are potentially useful in the development of improved CoCr implants for use in orthopedic applications.

Study on the Cytotoxicity In Vitro of Composite Materials Based on Poly(L-Lactide-Co-Glycolide) and Bioactive Glass

The effect of poly(L-lactide-co-glycolide)/bioactive glass (PLGA/BG) on cell attachment, proliferation and differentiation of L929 fibroblastic cells was investigated. The results ofin-vitrocytotoxicity test indicated that the cells cultured in extract of PLGA/BG and on the surface of composite showed normal growth and proliferation. The cell proliferation and alkaline phosphatase (ALP) activity of fibroblast were significantly improved after 3 and 7 days of culture on PLGA/BG films in comparison with PLGA films. It can be concluded that the addition of bioactive glass into PLGA stimulates the proliferation and differentiation of fibroblastic cells. Therefore, PLGA/BG composites have a promising biological response as a potential biomaterial in medical field.

Biodegradable and synthetic membranes for the expansion and functional differentiation of rat embryonic liver cells

The insufficient availability of donor organs for orthotopic liver transplantation worldwide has urgently increased the requirement for new therapies for acute and chronic liver disease. The creation of an unlimited source of donor cells for hepatocyte transplantation therapy and pharmaceutical applications may be the isolation and expansion of liver progenitor cells or stem cells. Here we report the expansion and functional differentiation of rat embryonic liver cells on biodegradable and synthetic polymeric membranes in comparison with traditional substrates, such as collagen and polystyrene culture dishes. Membranes prepared from chitosan and modified polyetheretherketone were used for the culture of liver progenitor cells derived from rat embryonic liver. Cells proliferated, with a significant increase in their number within 8-11 days. The cells displayed functional differentiation showing urea synthesis, albumin production and diazepam biotransformation on all substrates investigated. In particular, on a chitosan membrane liver-specific functions were expressed at significantly higher levels for prolonged times compared with other synthetic membranes, utilizing traditional substrates (collagen and PSCD) as references. These results demonstrate that chitosan membranes offer cells favourable conditions to promote the expansion and functional differentiation of embryonic liver cells that could be effectively used in liver tissue engineering and in pharmaceutical applications.

Bioactivity of immobilized EGF on self-assembled monolayers: optimization of the immobilization process

Last trends in Biomaterials focus the mimic of cellular environments capable to control cellular responses. Epidermal growth factor (EGF) is a pleiotropic cytokine known to regulate cell proliferation, differentiation, and death. This study aims to optimize the immobilization of EGF on 11-mercapto-1-undecyl-tetra(ethylene)glycol (EG4)-self-assembled monolayers (SAMs) and to establish a new model surface to study EGF-mediated signaling. Gold substrates were modified with a monolayer of EG4 and N,N'-carbonyldiimidazole (CDI) was used to activate hydroxyl terminated groups of EG4-SAMs. EGF was then immobilized on activated EG4-SAMs at pH 7.4, 4 degrees C, and 100 rpm. Different immobilization reaction times were tested as well as different CDI concentrations to optimize the reaction conditions and obtain a range of immobilized EGF concentrations on the surfaces. Surface characterization of EGF-SAMs was performed using radiolabeling, water contact angle measurements, X-ray photoelectron spectroscopy, and ELISA. Phosphorylation of EGFR on BT-20 breast cancer cell line by EGF-SAMs was tested by immunostaining. EGF was successfully immobilized on EG4-SAMs, at 4 degrees C and pH 7.4 in a range of concentrations from 3.6 +/- 0.8 to 17.6 +/- 1.5 ng/cm(2). The concentration of EGF increases with immobilization time and with the CDI concentration reaching the maximum for surfaces activated with 30 mg/mL of CDI after 48 h. The bioactivity of EGF-SAMs was confirmed by immunostaining of phospho-EGFR of BT-20 cells. This study described EGF immobilization on EG4-SAMs at different concentrations, which could be important surface models to study specific protein interactions at the molecular level evolving EGF-family of proteins.

Electro-spinning of PLGA/PCL blends for tissue engineering and their biocompatibility

In this study, an electro-spun co-polymer PLGA/PCL blend was fabricated using various percentages of PLGA in the blend PLGA/PCL solutions. The PLGA/PCL ratios used to fabricate the electrospun fibrous mats were reflected in the FT-IR (Fourier Transform Infrared Spectroscopy) data. Experimental results from the MTT assay showed that the biocompatibility of the electro-spun co-polymer increased at increasing percentages of PLGA. In vitro cells adhesion and proliferation of fibroblast cells on electro-spun mats were characterized by SEM morphology. In addition, we found that increasing PLGA concentrations affected the mechanical properties of electro-spun membranes and increased the biocompatibility of PLGA/PCL electro-spun fibrous mats.

Biocompatible Bacterial Cellulose Composites for Biomedical Application

This paper reports bacterial cellulose composites made by blending chitosan, poly(ethylene glycol) (PEG), and gelatin for potential biomedical application of tissue-engineering scaffold and wound-dressing material. The bacterial cellulose composites were successfully prepared by immersing a wet bacterial cellulose pellicle into chitosan, PEG, or gelatin solutions followed by freeze-drying. The products look like a foam structure. Scanning electron microscopy images show that chitosan molecules penetrated into bacterial cellulose forming a multilayer and a well interconnected porous network structure with a large aspect surface. The morphology of the bacterial cellulose/gelatin scaffold indicates that the gelatin molecules could penetrate well between the individual nanofibers of the bacterial cellulose. Cell adhesion studies for these composites were carried out using 3T3 fibroblast cells. They showed much better biocompatibility than pure bacterial cellulose. Preparation and material characterization of these composites are explained.

Gene expression profile on chitosan/rhBMP-2 films: A novel osteoinductive coating for implantable materials

This study focusses on the gene expression profile related to a new rhBMP-2 carrier material, chitosan film. This film could be suitable for use as an osteoinductive coating of commercially available titanium implants. The developed material was characterized, biocompatibility was tested and the cellular response was extensively characterized by transcriptional expression studies. Finally, in vivo studies were carried out to confirm the osteoinductivity of the developed coating. Results show good material properties for cell adhesion and proliferation. Presented data show cellular differentiation to the osteoblastic phenotype due to rhBMP-2, with a 90% common transcriptional response between the control rhBMP-2 treatment and the developed chitosan/rhBMP-2 film. The growing surface also had an influence on the observed cellular response and was quantified as 7% of the total. These results indicate that both the growth factor and the material induce a cell response, but this is mainly driven by the osteoinductor factor. In vivo, new bone formation and early vascularization was observed around chitosan/rhBMP-2 coated titanium pieces implanted in mouse muscle. In contrast, control implants did not induce this reaction. This work, therefore, shows both in vitro and in vivo that chitosan/rhBMP-2 film is a promising osteoinductive coating for titanium implantable materials.

Evaluation of RGD- or EGF-immobilized chitosan scaffolds for chondrogenic activity

Chitosan scaffolds were prepared by freeze-drying method and modified with Arg-Gly-Asp (RGD) sequence of fibronectin or epidermal growth factor (EGF) by covalent immobilization. The results obtained from FTIR-ATR, fluorescence visualization and quantitative measurements showed that biosignal molecules, RGD and EGF, were successfully immobilized on chitosan scaffolds. ATDC5 murine chondrogenic cells were seeded on both type of scaffolds, chitosan-RGD and chitosan-EGF, and cultured for 28 days in stationary conditions. According to the results of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) test, considerable increase in cell proliferation was only detected on chitosan-EGF scaffolds. Biochemical analysis of the chondrocyte seeded scaffolds showed that glycosaminoglycan (GAG) and deoxyribonucleic acid (DNA) content of the scaffolds increases with time. In conclusion, EGF-modified chitosan scaffolds (containing 1.83 microg EGF/3 mg dry scaffold) have been proposed to promote chondrogenesis and to have potential for reticular cartilage regeneration.