Traian Chirila - Academia.edu (original) (raw)
Papers by Traian Chirila
Fibroin is the main polypeptidic component of the silk fibre generated by the larvae of the domes... more Fibroin is the main polypeptidic component of the silk fibre generated by the larvae of the domesticated silk moth (Bombyx mori), and it has been extensively studied as a biomaterial with applications in tissue engineering and regenerative medicine. Due to their inherent practical advantages, the hydrogels constitute the preferred format for the B. mori silk fibroin (BMSF) biomaterials, which can conveniently be obtained by crosslinking processes. While the physically or chemically crosslinked BMSF hydrogels have been frequently described, the self-crosslinking of BMSF solutions induced by the catalytic effect of the enzyme horseradish peroxidase (HRP) has been barely reported. Following a previous preliminary study, where we demonstrated the advantages of using this enzyme for crosslinking BMSF, in the present work we investigated factors (amount of enzyme, initial fibroin concentration) that may affect the gelation. The measurement of dynamic moduli resulting from application of an oscillatory shear stress in a rheometer was our method to estimate the gelation time and to investigate the influence of certain factors on the process of crosslinking. It was found that both a higher initial concentration of the BMSF solution and a higher amount of the catalyst HRP induced a significant reduction of the gelation time.
Polymer Preprints American Chemical Society Division of Polymer Chemistry, 2004
Journal of Applied Polymer Science
The internal morphologies for a series of heterogeneous PHEMA and P[HEMA-co-MeO-PEGMA] [PHEMA ¼ p... more The internal morphologies for a series of heterogeneous PHEMA and P[HEMA-co-MeO-PEGMA] [PHEMA ¼ poly(2-hydroxyethyl methacrylate), MeO-PEGMA ¼ poly(ethylene glycol) methyl ether methacrylate] hydrogels were characterized by scanning electron microscopy (SEM) in conjunction with a sample drying procedure, and by laser scanning confocal microscopy (LSCM) without prior drying. Compared to SEM, LSCM was far simpler and more rapid technique for imaging hydrogels. LSCM also allowed the native hydrated morphology of the hydrogels to be characterized, whereas SEM could only characterize the morphol-ogy of samples in their dehydrated state. No dehydration method used in this study preserved the true native morphology, but plunge freezing/freeze drying was the most suitable method that best preserved the native morphology for all hydrogel compositions. Refri-gerated freezing/freeze-drying and critical point drying introduced significant morphological artifacts, the severity of the artifacts b...
Australian Journal of Chemistry
Activators regenerated by electron-transfer atom-transfer radical polymerization, catalyzed by tr... more Activators regenerated by electron-transfer atom-transfer radical polymerization, catalyzed by tris(2-pyridylmethyl)amine/ CuBr 2 and Na{Cu(Gly 3)}, was used to synthesize poly(2-hydroxyethyl methacrylate) sponges from 80 : 20 H 2 O/ 2-hydroxyethyl methacrylate mixtures. Polymerization-induced phase separations resulted in sponges having morphologies based on agglomerated polymer droplets. During the synthesis of poly(2-hydroxyethyl methacrylate) sponges, first-order kinetics were observed up to a maximum of ,50 % conversion regardless of the catalyst used. The morphologies of the sponges were dependent on the rate of polymerization, slower polymerization rates resulting in polymers with larger morphological features (pores and polymer droplets).
A monomer that contained the RGD ligand motif was synthesized and copolymerized with 2-hydroxyeth... more A monomer that contained the RGD ligand motif was synthesized and copolymerized with 2-hydroxyethyl methacrylate using polymerization-induced phase separation methods to form poly(2-hydroxyethyl methacrylate)-based hydrogel sponges. The sponges had morphologies of aggregated polymer droplets and interconnected pores, the pores having dimensions in the order of 10μm typical of PHEMA sponges. RGD-containing moieties appeared to be evenly distributed through the polymer droplets. Compared to PHEMA sponges that were not functionalized with RGD, the new sponges containing RGD allowed greater invasion by human corneal epithelial cells, by advancing the attachment of cells to the surface of the polymer droplets.
Biomacromolecules
PHEMA-peptide and P[HEMA-co-(MeO-PEGMA)]-peptide conjugate hydrogels [where PHEMA = poly(2-hydrox... more PHEMA-peptide and P[HEMA-co-(MeO-PEGMA)]-peptide conjugate hydrogels [where PHEMA = poly(2-hydroxyethyl methacrylate; PEGMA = poly(ethylene glycol) methacrylate] were readily prepared via photoinitiated free-radical polymerization in water. The PHEMA-peptide hydrogels were opaque and had a heterogeneous morphology of interconnected polymer droplets, characteristic of polymers that separate from the aqueous phase during the polymerization experiment. The P[HEMA-co-(MeO-PEGMA)]-peptide conjugates were transparent gels with a homogeneous morphology when formed in water, but when formed in aqueous NaCl solutions the P[HEMA-co-(MeO-PEGMA)]-peptide conjugates were also opaque and exhibited the heterogeneous morphology of interconnected polymer droplets. When incubated in solutions containing activated papain, P[HEMA-co-(MeO-PEGMA)]-peptide conjugates underwent degradation that was characterized by macroscopic changes to sample shape and size, sample weight, and microscopic structure. PHEM...
Cornea, 2004
To investigate in vitro the effects of selected drugs on the spoliation of poly(2-hydroxyethyl me... more To investigate in vitro the effects of selected drugs on the spoliation of poly(2-hydroxyethyl methacrylate) (PHEMA), a synthetic acrylic hydrogel currently used for the manufacture of a keratoprosthesis, AlphaCor. The experiments were carried out both in the presence of simulated aqueous humor (SAH) and in its absence. Disks of PHEMA were incubated and shaken with 9 commonly prescribed drugs at 37 degrees C in sterile conditions for 1 week. Samples were incubated either in SAH only (controls), in each drug preparation, or in each drug for 1 week followed by 1 week in SAH. The drugs selected for this study were steroids (prednisolone, dexamethasone, fluorometholone, medroxyprogesterone), antiglaucoma drugs (timolol maleate and pilocarpine), and antibiotics (chloramphenicol, cephazolin, and ciprofloxacin), as commercially available formulations. Following incubation, the PHEMA specimens were examined visually and then histologically, after staining with alizarin red for the presence of calcium in the spoliating sediments/deposits. Although only 5 of the drug formulations (dexamethasone as Maxidex, fluorometholone as FML, pilocarpine as Isopto Carpine, chloramphenicol as Chlorsig, and medroxyprogesterone as Depo-Ralovera) induced spoliation of the hydrogel in the absence of SAH, all drugs induced spoliation after postincubation in SAH, and calcium was detected in the majority of samples. The deposits on the hydrogel specimens incubated first in cephazolin (as Cefazolin-BC), pilocarpine (as Isopto Carpine), and chloramphenicol (as Chlorsig) and then in SAH did not contain calcium, despite its presence in SAH. The study appears to confirm our earlier clinical observations that topical medication may play a role in the spoliation of the hydrogel ophthalmic devices. Presence of calcium in the deposits seems to be correlated to the nature of drug. Although the incidence of spoliation in real clinical situations is much lower than suggested by this extreme-case in vitro simulation, topical therapy after implantation of AlphaCor should be carefully considered, kept to the minimum required, and additive-free where possible.
Journal of functional biomaterials, 2015
A silk protein, fibroin, was isolated from the cocoons of the domesticated silkworm (Bombyx mori)... more A silk protein, fibroin, was isolated from the cocoons of the domesticated silkworm (Bombyx mori) and cast into membranes to serve as freestanding templates for tissue-engineered corneal cell constructs to be used in ocular surface reconstruction. In this study, we sought to enhance the attachment and proliferation of corneal epithelial cells by increasing the permeability of the fibroin membranes and the topographic roughness of their surface. By mixing the fibroin solution with poly(ethylene glycol) (PEG) of molecular weight 300 Da, membranes were produced with increased permeability and with topographic patterns generated on their surface. In order to enhance their mechanical stability, some PEG-treated membranes were also crosslinked with genipin. The resulting membranes were thoroughly characterized and compared to the non-treated membranes. The PEG-treated membranes were similar in tensile strength to the non-treated ones, but their elastic modulus was higher and elongation lo...
Journal of biomaterials applications, 1999
Cross-linked gelatin gels are used as biomaterials in living tissues, either as bioadhesives or a... more Cross-linked gelatin gels are used as biomaterials in living tissues, either as bioadhesives or as devices for sustained drug release. As these applications involve surgical insertion of gels, the effect of cross-linking on mechanical properties is relevant. The effect of cross-linking on the gel water uptake is also relevant for the kinetics of drug release. Equally important is the influence of initial amounts of gelatin in the gelling solutions. We investigated the influence of cross-linking (with glutaraldehyde) and of gelatin content upon the equilibrium water content and tensile properties of resulting gels. A range of gels was prepared with gelatin contents of 10 to 40% wt, and cross-linked with 2.5 to 50% wt glutaraldehyde. The increase in gelatin content and degree of cross-linking reduced the water uptake of gels from about 60-65% wt to about 50% wt. The tensile characteristics were differentially affected. While the increase of cross-linking induced a decrease of toughnes...
Gesnerus, 1999
There has been little recognition of the French ophthalmologist Guillaume Pellier de Quengsy and ... more There has been little recognition of the French ophthalmologist Guillaume Pellier de Quengsy and his contribution to the problem of artificial cornea (keratoprosthesis). This fact that he was the first to propose such a device was seldom acknowledged, and usually as a secondary reference. Based on the examination of original texts (1789), this study demonstrates that Pellier not only proposed an essentially correct keratoprosthesis, but also suggested a porous prosthetic skirt, a revolutionary concept which is currently fundamental to artificial cornea research.
Journal of biomaterials applications, 1995
Poly(2-hydroxyethyl methacrylate) hydrogel intraocular lenses, containing adrenochrome-melanin, w... more Poly(2-hydroxyethyl methacrylate) hydrogel intraocular lenses, containing adrenochrome-melanin, were manufactured and implanted in animal eyes in order to assess the effect of melanin upon (a) biocompatibility of implants with the eye tissues, and (b) fibrous proliferation of lens epithelium responsible for the opacification of the posterior capsular membrane. An equal number of control lenses were also implanted. The animals were followed up for durations up to two years, and a detailed histopathological examination of the eyes was performed subsequent to their enucleation. The postoperative complications were minor and probably caused by surgical trauma. The study failed to give any indication of the postulated antiproliferative activity of adrenochrome-melanin since minimal capsular opacification occurred in the operated eyes, regardless of the presence of melanin.
Journal of biomaterials applications, 1997
The kinetics of controlled release of basic fibroblast growth factor (bFGF) from polymers (suture... more The kinetics of controlled release of basic fibroblast growth factor (bFGF) from polymers (sutures, polycarbonate, Hydron, and Elvax), biopolymers (alginate), and biomatrices (lens capsules), and conditions for storage of bFGF (temperature, plastic type, heparin) were evaluated in vitro. Tissue culture proliferation bioassays with 3T3 fibroblasts, showed that only lens capsules with bFGF had a sustained release of bFGF for up to three weeks. The other materials released all of the 'bound' bFGF with two hours or produced an inflammatory response in vivo. Therefore, the lens tissue had the most potential for controlled long-term delivery of bFGF in vivo. These studies emphasise the importance of in vitro analysis of release kinetics of growth factors from a range of materials as a basis for potential in vivo applications.
Fibroin is the main polypeptidic component of the silk fibre generated by the larvae of the domes... more Fibroin is the main polypeptidic component of the silk fibre generated by the larvae of the domesticated silk moth (Bombyx mori), and it has been extensively studied as a biomaterial with applications in tissue engineering and regenerative medicine. Due to their inherent practical advantages, the hydrogels constitute the preferred format for the B. mori silk fibroin (BMSF) biomaterials, which can conveniently be obtained by crosslinking processes. While the physically or chemically crosslinked BMSF hydrogels have been frequently described, the self-crosslinking of BMSF solutions induced by the catalytic effect of the enzyme horseradish peroxidase (HRP) has been barely reported. Following a previous preliminary study, where we demonstrated the advantages of using this enzyme for crosslinking BMSF, in the present work we investigated factors (amount of enzyme, initial fibroin concentration) that may affect the gelation. The measurement of dynamic moduli resulting from application of an oscillatory shear stress in a rheometer was our method to estimate the gelation time and to investigate the influence of certain factors on the process of crosslinking. It was found that both a higher initial concentration of the BMSF solution and a higher amount of the catalyst HRP induced a significant reduction of the gelation time.
Polymer Preprints American Chemical Society Division of Polymer Chemistry, 2004
Journal of Applied Polymer Science
The internal morphologies for a series of heterogeneous PHEMA and P[HEMA-co-MeO-PEGMA] [PHEMA ¼ p... more The internal morphologies for a series of heterogeneous PHEMA and P[HEMA-co-MeO-PEGMA] [PHEMA ¼ poly(2-hydroxyethyl methacrylate), MeO-PEGMA ¼ poly(ethylene glycol) methyl ether methacrylate] hydrogels were characterized by scanning electron microscopy (SEM) in conjunction with a sample drying procedure, and by laser scanning confocal microscopy (LSCM) without prior drying. Compared to SEM, LSCM was far simpler and more rapid technique for imaging hydrogels. LSCM also allowed the native hydrated morphology of the hydrogels to be characterized, whereas SEM could only characterize the morphol-ogy of samples in their dehydrated state. No dehydration method used in this study preserved the true native morphology, but plunge freezing/freeze drying was the most suitable method that best preserved the native morphology for all hydrogel compositions. Refri-gerated freezing/freeze-drying and critical point drying introduced significant morphological artifacts, the severity of the artifacts b...
Australian Journal of Chemistry
Activators regenerated by electron-transfer atom-transfer radical polymerization, catalyzed by tr... more Activators regenerated by electron-transfer atom-transfer radical polymerization, catalyzed by tris(2-pyridylmethyl)amine/ CuBr 2 and Na{Cu(Gly 3)}, was used to synthesize poly(2-hydroxyethyl methacrylate) sponges from 80 : 20 H 2 O/ 2-hydroxyethyl methacrylate mixtures. Polymerization-induced phase separations resulted in sponges having morphologies based on agglomerated polymer droplets. During the synthesis of poly(2-hydroxyethyl methacrylate) sponges, first-order kinetics were observed up to a maximum of ,50 % conversion regardless of the catalyst used. The morphologies of the sponges were dependent on the rate of polymerization, slower polymerization rates resulting in polymers with larger morphological features (pores and polymer droplets).
A monomer that contained the RGD ligand motif was synthesized and copolymerized with 2-hydroxyeth... more A monomer that contained the RGD ligand motif was synthesized and copolymerized with 2-hydroxyethyl methacrylate using polymerization-induced phase separation methods to form poly(2-hydroxyethyl methacrylate)-based hydrogel sponges. The sponges had morphologies of aggregated polymer droplets and interconnected pores, the pores having dimensions in the order of 10μm typical of PHEMA sponges. RGD-containing moieties appeared to be evenly distributed through the polymer droplets. Compared to PHEMA sponges that were not functionalized with RGD, the new sponges containing RGD allowed greater invasion by human corneal epithelial cells, by advancing the attachment of cells to the surface of the polymer droplets.
Biomacromolecules
PHEMA-peptide and P[HEMA-co-(MeO-PEGMA)]-peptide conjugate hydrogels [where PHEMA = poly(2-hydrox... more PHEMA-peptide and P[HEMA-co-(MeO-PEGMA)]-peptide conjugate hydrogels [where PHEMA = poly(2-hydroxyethyl methacrylate; PEGMA = poly(ethylene glycol) methacrylate] were readily prepared via photoinitiated free-radical polymerization in water. The PHEMA-peptide hydrogels were opaque and had a heterogeneous morphology of interconnected polymer droplets, characteristic of polymers that separate from the aqueous phase during the polymerization experiment. The P[HEMA-co-(MeO-PEGMA)]-peptide conjugates were transparent gels with a homogeneous morphology when formed in water, but when formed in aqueous NaCl solutions the P[HEMA-co-(MeO-PEGMA)]-peptide conjugates were also opaque and exhibited the heterogeneous morphology of interconnected polymer droplets. When incubated in solutions containing activated papain, P[HEMA-co-(MeO-PEGMA)]-peptide conjugates underwent degradation that was characterized by macroscopic changes to sample shape and size, sample weight, and microscopic structure. PHEM...
Cornea, 2004
To investigate in vitro the effects of selected drugs on the spoliation of poly(2-hydroxyethyl me... more To investigate in vitro the effects of selected drugs on the spoliation of poly(2-hydroxyethyl methacrylate) (PHEMA), a synthetic acrylic hydrogel currently used for the manufacture of a keratoprosthesis, AlphaCor. The experiments were carried out both in the presence of simulated aqueous humor (SAH) and in its absence. Disks of PHEMA were incubated and shaken with 9 commonly prescribed drugs at 37 degrees C in sterile conditions for 1 week. Samples were incubated either in SAH only (controls), in each drug preparation, or in each drug for 1 week followed by 1 week in SAH. The drugs selected for this study were steroids (prednisolone, dexamethasone, fluorometholone, medroxyprogesterone), antiglaucoma drugs (timolol maleate and pilocarpine), and antibiotics (chloramphenicol, cephazolin, and ciprofloxacin), as commercially available formulations. Following incubation, the PHEMA specimens were examined visually and then histologically, after staining with alizarin red for the presence of calcium in the spoliating sediments/deposits. Although only 5 of the drug formulations (dexamethasone as Maxidex, fluorometholone as FML, pilocarpine as Isopto Carpine, chloramphenicol as Chlorsig, and medroxyprogesterone as Depo-Ralovera) induced spoliation of the hydrogel in the absence of SAH, all drugs induced spoliation after postincubation in SAH, and calcium was detected in the majority of samples. The deposits on the hydrogel specimens incubated first in cephazolin (as Cefazolin-BC), pilocarpine (as Isopto Carpine), and chloramphenicol (as Chlorsig) and then in SAH did not contain calcium, despite its presence in SAH. The study appears to confirm our earlier clinical observations that topical medication may play a role in the spoliation of the hydrogel ophthalmic devices. Presence of calcium in the deposits seems to be correlated to the nature of drug. Although the incidence of spoliation in real clinical situations is much lower than suggested by this extreme-case in vitro simulation, topical therapy after implantation of AlphaCor should be carefully considered, kept to the minimum required, and additive-free where possible.
Journal of functional biomaterials, 2015
A silk protein, fibroin, was isolated from the cocoons of the domesticated silkworm (Bombyx mori)... more A silk protein, fibroin, was isolated from the cocoons of the domesticated silkworm (Bombyx mori) and cast into membranes to serve as freestanding templates for tissue-engineered corneal cell constructs to be used in ocular surface reconstruction. In this study, we sought to enhance the attachment and proliferation of corneal epithelial cells by increasing the permeability of the fibroin membranes and the topographic roughness of their surface. By mixing the fibroin solution with poly(ethylene glycol) (PEG) of molecular weight 300 Da, membranes were produced with increased permeability and with topographic patterns generated on their surface. In order to enhance their mechanical stability, some PEG-treated membranes were also crosslinked with genipin. The resulting membranes were thoroughly characterized and compared to the non-treated membranes. The PEG-treated membranes were similar in tensile strength to the non-treated ones, but their elastic modulus was higher and elongation lo...
Journal of biomaterials applications, 1999
Cross-linked gelatin gels are used as biomaterials in living tissues, either as bioadhesives or a... more Cross-linked gelatin gels are used as biomaterials in living tissues, either as bioadhesives or as devices for sustained drug release. As these applications involve surgical insertion of gels, the effect of cross-linking on mechanical properties is relevant. The effect of cross-linking on the gel water uptake is also relevant for the kinetics of drug release. Equally important is the influence of initial amounts of gelatin in the gelling solutions. We investigated the influence of cross-linking (with glutaraldehyde) and of gelatin content upon the equilibrium water content and tensile properties of resulting gels. A range of gels was prepared with gelatin contents of 10 to 40% wt, and cross-linked with 2.5 to 50% wt glutaraldehyde. The increase in gelatin content and degree of cross-linking reduced the water uptake of gels from about 60-65% wt to about 50% wt. The tensile characteristics were differentially affected. While the increase of cross-linking induced a decrease of toughnes...
Gesnerus, 1999
There has been little recognition of the French ophthalmologist Guillaume Pellier de Quengsy and ... more There has been little recognition of the French ophthalmologist Guillaume Pellier de Quengsy and his contribution to the problem of artificial cornea (keratoprosthesis). This fact that he was the first to propose such a device was seldom acknowledged, and usually as a secondary reference. Based on the examination of original texts (1789), this study demonstrates that Pellier not only proposed an essentially correct keratoprosthesis, but also suggested a porous prosthetic skirt, a revolutionary concept which is currently fundamental to artificial cornea research.
Journal of biomaterials applications, 1995
Poly(2-hydroxyethyl methacrylate) hydrogel intraocular lenses, containing adrenochrome-melanin, w... more Poly(2-hydroxyethyl methacrylate) hydrogel intraocular lenses, containing adrenochrome-melanin, were manufactured and implanted in animal eyes in order to assess the effect of melanin upon (a) biocompatibility of implants with the eye tissues, and (b) fibrous proliferation of lens epithelium responsible for the opacification of the posterior capsular membrane. An equal number of control lenses were also implanted. The animals were followed up for durations up to two years, and a detailed histopathological examination of the eyes was performed subsequent to their enucleation. The postoperative complications were minor and probably caused by surgical trauma. The study failed to give any indication of the postulated antiproliferative activity of adrenochrome-melanin since minimal capsular opacification occurred in the operated eyes, regardless of the presence of melanin.
Journal of biomaterials applications, 1997
The kinetics of controlled release of basic fibroblast growth factor (bFGF) from polymers (suture... more The kinetics of controlled release of basic fibroblast growth factor (bFGF) from polymers (sutures, polycarbonate, Hydron, and Elvax), biopolymers (alginate), and biomatrices (lens capsules), and conditions for storage of bFGF (temperature, plastic type, heparin) were evaluated in vitro. Tissue culture proliferation bioassays with 3T3 fibroblasts, showed that only lens capsules with bFGF had a sustained release of bFGF for up to three weeks. The other materials released all of the 'bound' bFGF with two hours or produced an inflammatory response in vivo. Therefore, the lens tissue had the most potential for controlled long-term delivery of bFGF in vivo. These studies emphasise the importance of in vitro analysis of release kinetics of growth factors from a range of materials as a basis for potential in vivo applications.