Biomedical subjects

C A van Blitterswijk

Publications and source records attributed to C A van Blitterswijk.

At least 19 recordsLinked to original sources

PubMed2001

Bone induction by porous glass ceramic made from Bioglass (45S5).

Porous glass ceramic, which was prepared from Bioglass powder (45S5, U.S. Biomaterials) by foaming with diluted H(2)O(2) solution and sintering at 1000 degrees C for 2 h, was implanted as cylinders (5 mm in diameter and 6 mm in length) in thigh muscles of dogs for 3 months. Histological observation was made on thin un-decalcified sections. Bone formation was histologically found in pores of all implants (X16) retrieved from 16 dogs. The bone tissue was also identified with backscattered scanning electron microscopy observation (BSE) and energy dispersive X-ray microanalysis (EDX). This is the first report of bone induction in soft tissues of animals by glass ceramic that has long been recognized as a bioactive (osteoconductive) biomaterial. The present results justify the impetus to investigate the osteoinductivity of calcium phosphate-based biomaterials, to study the mechanism of bone induction (osteoinduction) by calcium phosphate-based biomaterials, to develop osteoinductive calcium phosphate-based biomaterials, and to examine the relation between osteoinduction and osteoconduction.

Animals↗

PubMed2001

The different behaviors of skeletal muscle cells and chondrocytes on PEGT/PBT block copolymers are related to the surface properties of the substrate.

The attachment, proliferation, morphology, and differentiation of two cell types-skeletal muscle cells and chondrocytes-were investigated on different compositions of poly(ethylene glycol) and poly(butylene terephthalate) segmented block copolymers. Four weight percentages (40, 55, 60, and 70%) and two different molecular weights (300 and 1000 Da) of poly(ethylene glycol) were tested. Varying the weight percentage and molecular weight of poly(ethylene glycol) resulted in different behaviors for skeletal muscle cells and chondrocytes. The attachment of skeletal muscle was the highest (similar to tissue culture polystyrene) when copolymers containing 55 wt % of poly(ethylene glycol) were used, regardless of the poly(ethylene glycol) molecular weight. Maximum proliferation and differentiation of skeletal muscle cells was achieved when copolymers containing 55 wt % and 300 Da molecular weight of poly(ethylene glycol) were used. In contrast, the weight percentage and molecular weight of poly(ethylene glycol) had no significant effect on chondrocyte attachment and proliferation; the attached chondrocytes retained a differentiated phenotype only when a 70 wt % of poly(ethylene glycol) was used. Cell behavior was correlated with the surface properties of the copolymer films, as indicated by contact-angle measurements. These results suggest that an optimized wt % and molecular weight of poly(ethylene glycol) will be useful depending on the specific cell type.

Animals↗

PubMed2001

Osteoclastic resorption of biomimetic calcium phosphate coatings in vitro.

A new biomimetic method for coating metal implants enables the fast formation of dense and homogeneous calcium phosphate coatings. Titanium alloy (Ti6Al4V) disks were coated with a thin, carbonated, amorphous calcium phosphate (ACP) by immersion in a saturated solution of calcium, phosphate, magnesium, and carbonate. The ACP-coated disks then were processed further by incubation in calcium phosphate solutions to produce either crystalline carbonated apatite (CA) or octacalcium phosphate (OCP). The resorption behavior of these three biomimetic coatings was studied using osteoclast-enriched mouse bone-marrow cell cultures for 7 days. Cell-mediated degradation was observed for both carbonated apatite and octacalcium phosphate coatings. Numerous resorption lacunae characteristic of osteoclastic resorption were found on carbonated apatite after cell culture. The results showed that carbonated apatite coatings are resorbed by osteoclasts in a manner consistent with normal osteoclastic resorption. Osteoclasts also degraded the octacalcium phosphate coatings but not by classical pit formation.

Alloys↗

PubMed2001

Biocompatibility testing of novel starch-based materials with potential application in orthopaedic surgery: a preliminary study.

This paper describes an extensive biocompatibility evaluation of biodegradable starch-based materials aimed at orthopaedic applications as temporary bone replacement/fixation implants. For that purpose, a polymer (starch/ethylene vinyl alcohol blend, SEVA-C) and a composite of SEVA-C reinforced with hydroxyapatite (HA) particles, were evaluated in both in vitro and in vivo assays. For the in vitro analysis cell culture methods were used. The in vivo tissue reactions were evaluated in an intramuscular and intracortical bone implantation model on goats, using light and scanning electron microscopy. A computerized image analysis system was used to obtain histomorphometric data regarding bone contact and remodelling after 6 and 12 weeks of implantation. In both in vitro and in vivo models, the SEVA-C-based materials did not induce adverse reactions, which in addition to their bone-matching mechanical properties makes them promising materials for bone replacement fixation.

Animals↗

PubMed2000

Microspheres for protein delivery prepared from amphiphilic multiblock copolymers. 2. Modulation of release rate.

Amphiphilic multiblock copolymers, based on hydrophilic poly(ethylene glycol) (PEG) blocks and hydrophobic poly(butylene terephthalate) (PBT) blocks were used as matrix material for protein-loaded microspheres. The efficiency of lysozyme entrapment by a double emulsion method was found to depend on the swelling behavior of the polymers in water and decreased from 100% for polymers with a degree of swelling of less than 1.8 to 11% for PEG-PBT copolymers with a degree of swelling of 3.6. The particle size could be controlled by varying the concentration of the polymer solution used in the microsphere preparation. An increase in the polymer concentration resulted in a proportional increase in the particle size. The in vitro release profiles of the encapsulated model protein lysozyme could be precisely tailored by variation of the copolymer composition and the size of the microspheres. Both a slow continuous release of lysozyme, and a fast release which was completed within a few days could be obtained. The release behavior, attributed to a combination of diffusion and polymer degradation, could be described by a previously developed model.

Algorithms↗

PubMed2000

Microspheres for protein delivery prepared from amphiphilic multiblock copolymers. 1. Influence of preparation techniques on particle characteristics and protein delivery.

The entrapment of lysozyme in amphiphilic multiblock copolymer microspheres by emulsification and subsequent solvent removal processes was studied. The copolymers are composed of hydrophilic poly(ethylene glycol) (PEG) blocks and hydrophobic poly(butylene terephthalate) (PBT) blocks. Direct solvent extraction from a water-in-oil (w/o) emulsion in ethanol or methanol did not result in the formation of microspheres, due to massive polymer precipitation caused by rapid solvent extraction in these non-solvents. In a second process, microspheres were first prepared by a water-in-oil-in-water (w/o/w) emulsion system with 4% poly(vinyl alcohol) (PVA) as stabilizer in the external phase, followed by extraction of the remaining solvent. As non-solvents ethanol, methanol and mixtures of methanol and water were employed. However, the use of alcohols in the extraction medium resulted in microspheres which gave an incomplete lysozyme release at a non-constant rate. Complete lysozyme release was obtained from microspheres prepared by an emulsification-solvent evaporation method in PBS containing poly(vinyl pyrrolidone) (PVP) or PVA as stabilizer. PVA was most effective in stabilizing the w/o/w emulsion. Perfectly spherical microspheres were produced, with high protein entrapment efficiencies. These microspheres released lysozyme at an almost constant rate for approximately 28 days. The reproducibility of the w/o/w emulsion process was demonstrated by comparing particle characteristics and release profiles of three batches, prepared under similar conditions.

Drug Compounding↗

PubMed2000

Control of protein delivery from amphiphilic poly(ether ester) multiblock copolymers by varying their water content using emulsification techniques.

Protein-containing films and microspheres, based on poly(ethylene glycol)-poly(butylene terephthalate) (PEG-PBT) multiblock copolymers, were prepared from water-in-oil (w/o) emulsions. The properties of the matrices could be controlled by the water-to-polymer ratio (w/p) in the w/o emulsion. A linear increase in water uptake of the matrices was observed with increasing emulsion w/p. This could be explained by an increase in the number of dispersed water-rich domains in the polymer matrix. At low volume fraction of the dispersed phase (epsilon), lysozyme release was mainly dependent on the permeability of the swollen polymer bulk. Above a critical volume fraction (the percolation threshold epsilon(c)), the dispersed water-rich phase formed an interconnected network, which largely enhanced the permeability of the matrix. Determination of the permeability of PEG-PBT matrices for vitamin B(12) as a function of epsilon confirmed the formation of such an interconnected network. This interconnected network could be used to achieve controlled release of a large protein (bovine serum albumin, BSA) from PEG-PBT films and microspheres. Due to its hydrodynamic diameter, BSA was screened by the polymer network when epsilon was low. However above epsilon(c), the fraction released BSA increased with increasing volume fraction of the dispersed phase. A very rapid BSA release could be obtained, with the majority of the incorporated BSA released within 1 day, as well as a slow and continuous release, lasting for over 150 days. When BSA-containing microspheres were prepared with a volume fraction just below the percolation threshold, a delayed release was observed. This was attributed to the effect of polymer degradation on matrix permeability.

Drug Delivery Systems↗

PubMed2000

Use of bone-bonding hydrogel copolymers in bone: an in vitro and in vivo study of expanding PEO-PBT copolymers in goat femora.

Polyactive(R) [polyethylene oxide-polybuthylene terephtalate (PEO-PBT)] refers to a group of copolymers with bone-bonding properties. In reference to these properties, PEO-PBT copolymers are currently being investigated for their possible use in orthopedic surgery and dentistry. PEO-PBT copolymers exhibit hydrogel behavior. When swelling in fluid is prohibited by mechanical confinement, the copolymers exert a swelling pressure on surrounding structures. In the first part of this study, these swelling pressures were measured in vitro. Polymers with different ratios of PEO-PBT exerted a swelling pressure of more than 2 MPa when tested in fluid between the cross-heads of a Hounsfield test-bench. In the second part of the study, the biocompatibility of PEO-PBT 55-45 and the effect of continuous intramedullary pressure of these copolymers on bone was investigated. Large cylinders of dry PEO-PBT 55-45 were implanted with a tight fit in the distal part of goat femora. Preswollen cylinders of PEO-PBT implanted in the opposite femur served as a control. Although it was assumed that the pressure of dry PEO-PBT on the bone would reach more than 2 MPa with press-fit insertion, no immediate hazardous effects of the expanding polymer were noticed within the first days postoperatively. The goats were sacrificed after 3, 9, and 25 weeks. Histological examination showed good implant-bone contact at different follow-up times in the distal femora with the dry implanted implants. The femora in which the preswollen cylinders had been implanted showed a thin layer of soft tissue between the PEO-PBT implant and bone. The swelling pressure exerted by dry press-fit implanted PEO-PBT implants is an important factor in creating a strong interface bond between PEO-PBT and bone.

Animals↗

PubMed2000

Zero-order release of lysozyme from poly(ethylene glycol)/poly(butylene terephthalate) matrices.

Protein release from a series of biodegradable poly(ether ester) multiblock copolymers, based on poly(ethylene glycol) (PEG) and poly(butylene terephthalate) (PBT) was investigated. Lysozyme-containing PEG/PBT films and microspheres were prepared using an emulsion technique. Proteins were effectively encapsulated and dense polymer matrices were formed. The swelling in water of PEG/PBT films reached equilibrium within 3 days. The degree of swelling increased with increasing PEG content and with increasing molecular weight of the PEG segment. The release rate of lysozyme from PEG/PBT films could be tailored very precisely by controlling the copolymer composition. Release rates increased with increasing PEG/PBT weight ratio and increasing molecular weight of the PEG segment. For films prepared from block copolymers with PEG blocks of 4000 g/mol, first-order lysozyme release was observed. For matrices prepared from polymers with PEG segments of 1000 and 600 g/mol, the lysozyme release profile followed near zero-order kinetics. A mathematical description of the release mechanism was developed which takes into account the effect of polymer hydrolytic degradation on solute diffusion. The model was found to be consistent with the experimental observations. Finally, determination of the activity of released protein showed that lysozyme was not damaged during the formulation, storage and release periods.

Drug Stability↗

PubMed2000

Amphiphilic poly(ether ester amide) multiblock copolymers as biodegradable matrices for the controlled release of proteins.

Amphiphilic poly(ether ester amide) (PEEA) multiblock copolymers were synthesized by polycondensation in the melt from hydrophilic poly(ethylene glycol) (PEG), 1,4-dihydroxybutane and short bisester-bisamide blocks. These amide blocks were prepared by reaction of 1,4-diaminobutane with dimethyl adipate in the melt. A range of multiblock copolymers were prepared, with PEG contents varying from 23-66 wt %. The intrinsic viscosity of the PEEA polymers varied from 0.58-0.78. Differential scanning calorimetry showed melting transitions for the PEG blocks and for the amide-ester blocks, suggesting a phase separated structure. Both the melting temperature and the crystallinity of the hard amide-ester segments decreased with increasing PEG content of the polymers. The equilibrium swelling ratio in phosphate buffered saline (PBS) increased with increasing amount of PEG in the polymers and varied from 1.7 to 3.7, whereas the polymer that contained 66 wt % PEG was soluble in PBS. During incubation of PEEA films in PBS, weight loss and a continuous decrease in the resulting inherent polymer viscosity was observed. The rate of degradation increased with increasing PEG content. The composition of the remaining matrices did not change during degradation. A preliminary investigation of the protein release characteristics of these PEEA copolymers showed that release of the model protein lysozyme was proportional to the square root of time. The release rate was found to increase with increasing degree of swelling of the polymers.

Biocompatible Materials↗

PubMed2000

Effects of five different barrier materials on postsurgical adhesion formation in the rat.

Postsurgical adhesion formation is a significant clinical problem within every surgical specialism. Due to the problems that adhesions cause, a wide variety of adjunctive treatments to prevent the formation and reformation of adhesions have been proposed. One of the modalities that has been studied extensively and that has been showing the most promising results is the so-called barrier method. The purpose of the present study was to compare the efficacy of five of these barrier materials in the prevention of postsurgical adhesion formation in a standardized rat adhesion model. It was concluded that no beneficial effect of Ringer's lactate on adhesion formation was seen. Significant reductions (P < 0.0001) in adhesion percentages compared to control animals were seen with Polyactive((TM)), PRECLUDE Peritoneal Membrane((TM)), Seprafilm((TM)) and Tissucol((TM)), but only PRECLUDE Peritoneal Membrane and Seprafilm significantly reduced adhesions (P < 0.01) when the barrier-treated peritoneal defects were compared with contralateral control-side peritoneal defects. The results of our study suggest that Seprafilm and PRECLUDE Peritoneal Membrane are superior to Tissucol and Polyactive in preventing adhesion formation. When Polyactive was still attached to the site of application during the second laparotomy, similar results to Seprafilm and PRECLUDE Peritoneal Membrane were seen. Future studies on the efficacy of a material to decrease adhesion formation should always include a comparison of several control materials in the same model. Our study indicates that Seprafilm or PRECLUDE Peritoneal Membrane might be used as standards of control.

Analysis of Variance↗

PubMed1999

A controlled release system for proteins based on poly(ether ester) block-copolymers: polymer network characterization.

The properties of a series of multiblock copolymers, based on hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(butylene terephthalate) (PBT) blocks were investigated with respect to their application as a matrix for controlled release of proteins. The degree of swelling, Q, of the copolymers increased with increasing PEG content and with increasing molecular weight of the PEG segment. Within the composition range tested, Q varied from 1.26 for polymers with PEG segments of 600 g/mol and a PBT content of 60 weight.% up to 3.64 for polymers with PEG segments of 4000 g/mol and a PEG/PBT weight ratio of 80:20. Equilibrium stress (compression)-strain measurements were performed in order to estimate mesh sizes. The mesh size of the copolymers ranged from 38 to 93 A, which was experimentally confirmed by diffusion of vitamin B(12) (hydrodynamic diameter d(h)=16.6 A), lysozyme (d(h)=41 A) and bovine serum albumin (d(h)=72 A). The in vitro degradation of PEG/PBT copolymers with a PEG block length of 1000 g/mol and PEG/PBT weight ratios of 70:30, 60:40 and 40:60 was studied. Matrices with increasing PEG contents exhibited a faster weight loss in phosphate-buffered saline (pH 7.4) at 37 degrees C. Over a degradation period of 54 days, M(n) decreased by about 35-45%, while the composition of the matrices, determined by NMR, remained almost constant.

Animals↗

PubMed1999

Bilayered biodegradable poly(ethylene glycol)/poly(butylene terephthalate) copolymer (Polyactive) as substrate for human fibroblasts and keratinocytes.

The purpose of this study was to find an optimal polymer matrix and to optimize the culture conditions for human keratinocytes and fibroblasts for the development of a human skin substitute. For this purpose porous, dense bilayers made of a block copolymer of poly(ethylene glycol terephthalate) (PEGT) and poly(butylene terephthalate) (PBT; Polyactivetrade mark) with a PEGT/PBT weight ratio of 55/45 and a PEG molecular weight (MW) of 300, 600, 1000, or 4000 Da were used. The best performance was achieved with PEGT/PBT copolymer with MW of PEG 300 D (300PEG55PBT45). When fibroblasts were seeded into the porous underlayer and cultured for 3 weeks in medium supplemented with 100 microg/mL ascorbic acid, all pores were filled with fibroblasts and with extracellular matrix, which was judged from the presence of collagen types I, III, and IV, and laminin. When seeded onto the dense top layer of the bilayered (cell free or fibroblast populated) copolymer matrix, human keratinocytes grew out into confluent sheets. After subsequent lifting to the air-liquid interface, a multilayered epithelium with a morphology corresponding to that of the native epidermis was formed. Some differences could still be observed: the expression and localization of some differentiation specific proteins was different and close to that seen in hyperproliferative epidermis; a basal lamina and anchoring zone were absent.

Biocompatible Materials↗

PubMed1999

Incorporation of bovine serum albumin in calcium phosphate coating on titanium.

Calcium phosphate (Ca-P) and bovine serum albumin (BSA) were coprecipitated as a coating on commercially pure titanium (cpTi) with a high protein loading (15 wt %) by employing a recently developed wet-chemistry technique. It was observed that the incorporation of BSA significantly modified the morphology, composition, and crystallinity of the Ca-P coating. The Ca-P coating without BSA is a mixture of hydroxyapatite (HA) and octacalcium phosphate (OCP) with sharp-edged thin OCP crystal plates on the top layer, whereas only an HA phase was detected in the Ca-P/BSA coating. The crystal plates in the latter had a more rounded appearance. The Ca-P/BSA coatings were immersed respectively in neutral (pH 7.4) and acidic (starting pH 4.0) phosphate-buffered saline (PBS) at 37 degrees C over a 14-day period. No protein release was detected in the neutral PBS during the immersion; however, a continuous release of BSA was measured in the acidic PBS, subsequently leading to the formation of a very dense and well-adherent composite coating of BSA and Ca-P on cpTi. The present study provides the possibility to achieve a long-term effective release of biologically active proteins from a Ca-P-coated metallic implant.

Calcium Phosphates↗

PubMed1999

Biomimetic calcium phosphate coatings on Ti6AI4V: a crystal growth study of octacalcium phosphate and inhibition by Mg2+ and HCO3-.

The biomimetic approach for coating metal implants allows the deposition of new calcium phosphate (Ca-P) phases. Films elaborated at physiological conditions might have structures closer to bone mineral than hydroxylapatite (HA) plasma-sprayed coatings. In this study, different Ca-P coatings have been deposited through a two-step procedure. After cleaning and etching, Ti6Al4V plates were pretreated by soaking in a simulated body fluid (SBF), i.e., a solution containing inorganic components in concentration more or less similar to body fluids: a thin amorphous carbonated Ca-P layer precipitated on the metal substrate. Second, by soaking these thinly coated metal substrates in another SBF, with different concentrations, the thin amorphous carbonated Ca-P layer led to the fast precipitation of a second and thick Ca-P layer. Different SBF solutions were used in order to investigate the influence of magnesium and carbonate ions. From SBF containing only Ca2+ and HPO4(2-) ions, an octacalcium phosphate layer grew epitaxially on the substrate. When Mg2+ was added into this SBF, the coating was composed of Ca-deficient apatite crystals, while the addition of HCO3- in SBF led to the formation of a B-carbonated apatite layer. Magnesium and carbonate acted as inhibitors of crystal growth. The three phases obtained by our biomimetic process are closer to bone mineral structure than plasma-sprayed HA. Therefore, the obtained results may be particularly relevant for the development of biomimetic Ca-P coatings with optimal bioactivity.

Alloys↗

PubMed1999

Critical size defect in the goat's os ilium. A model to evaluate bone grafts and substitutes.

Bone defects and their treatment are a well known problem in orthopaedic surgery. A critical size defect is a suitable model to study bone replacement materials. This study describes a critical size defect in the goal and the evaluation of three bone fillers (particulate autograft, particulate allograft, and a polyethylene oxide/polybutylene terephthalate copolymer) in this defect. The goat allows for implantation of large implants and has a metabolic rate more comparable with that of humans than small animals. The critical size defect, located in the goat's iliac wing, is easily reproducible and allows qualitative and quantitative evaluation of bone grafts and bone graft substitutes. After 3 months of healing, the unfilled defects showed 13.5% bone in the defect, the autografted defects 36.3%, and the allografted 18.5%. The copolymer gave only 1.5% bone in the defect; this is in contrast to previous reports. The described model allows for the evaluation of bone graft substitutes before introduction into clinical practice.

Animals↗

PubMed1999

Bone induction by implants coated with cultured osteogenic bone marrow cells.

The availability of osteoinductive coatings on dental and orthopedic implants will result in an improved fixation of these devices. Those cases where implants are placed in poor-quality bone or where high failure rates are obtained are especially expected to gain from such coatings. This paper presents a novel, biological approach to obtain bioactive and osteoinductive coatings on bone-replacement implant materials. This so-called tissue engineering approach utilizes osteogenic bone marrow cells that are cultured on an implant material to form a bone-like tissue. The implant materials used herein included porous calcium phosphate scaffolds and metallic plates, the latter of which were coated with a biomimetic calcium phosphate coating to facilitate cellular attachment. Bone marrow cells were obtained from a variety of species, including humans, and were grown to facilitate cellular proliferation. The cells were subsequently seeded onto the implants and cultured for an additional week to facilitate osteogenic differentiation and extracellular matrix production. The resulting hybrid implants, encompassing the biomaterial carrier and cultured bone-like tissue, were subsequently implanted subcutaneously in nude mice for 4 weeks, followed by histological examination for de novo bone formation. The results revealed that newly formed bone was seen both in porous implants and on flat metallic surfaces. This bone tissue engineering approach, therefore, offers great potential to enhance bony healing around implants in a compromised bone bed.

Aged↗

PubMed1998

A study on the grafting reaction of isocyanates with hydroxyapatite particles.

The surface grafting reactions of a series of isocyanates with hydroxyapatite particles at different temperatures were studied by Infrared spectrophotometry (IR) and thermal gravimetric analysis (TGA). The study results show that both hexamethylene diisocyanate (HMDI) and isocyanatoethyl methacrylate (ICEM) react readily with HA while ethyl isocyanate acetate (EIA) and butyl isocyanate (BIC) have lower reactivity towards HA particles. It also has been found that the reaction of ICEM with HA follows a second-order reaction mechanism, despite the heterogeneous nature of the reaction, while the reaction of HMDI with HA does not due to the complexity of the reaction. Based on this study, it is concluded that ICEM and HMDI are suitable agents for the coupling of polymers due to their reactivity towards HA.

Bone Substitutes↗