Showing papers in "Journal of Biomaterials Science-polymer Edition in 1994"

Poly(vinyl alcohol) hydrogels as soft contact lens material

Abstract: A new type of soft contact lens was developed from the poly(vinyl alchol) (PVA) hydrogel prepared by a low temperature crystallization technique using a water-dimethyl sulfoxide mixed solvent. The PVA contact lens materials had a water content of 78% and a tensile strength of 50 kg/cm2, five times as strong as that of commercial poly(2-hydroxyethyl methacrylate) soft contact lens. The amount of proteins adsorbed to the PVA soft hydrogel material was half to one thirtieth of that of conventional soft contact lenses. Histological and scanning electron microscopic observation of rabbit eyes which had worn the PVA soft contact lens for 12 weeks showed no difference in corneal epithelium and cell arrangement in the corneal epithelium from the non-wearing eyes.

Growth of human cells on plasma polymers: putative role of amine and amide groups.

Abstract: The attachment and growth of human endothelial cells and fibroblasts was studied on polymer surfaces fabricated by the polymerization of volatile amine and amide compounds in a low pressure gas plasma, and by the treatment of various surfaces in ammonia plasmas, which served to increase the nitrogen content of the surface layers. Infrared spectra showed the presence of amide groups, including those cases where the volatile compound ('monomer') did not contain oxygen. The performance of the surfaces in cell attachment correlated with the surface hydrophilicity and the nitrogen content, although for the latter a fair degree of scatter indicated that a more complex relationship applies. All these surfaces supported the attachment and growth of human cells. Generally, amide plasma polymers were best but the individual monomer and the plasma parameters also played a role. From comparisons of the various surfaces, it is suggested that the amide group is the main promoter of cell attachment in nitrogen-containing plasma surfaces.

Attachment of human bone cells to tissue culture polystyrene and to unmodified polystyrene: the effect of surface chemistry upon initial cell attachment.

Abstract: Cell culture studies have often been used in the determination of the suitability of biomaterials as surfaces for the attachment and growth of cells. For such studies of surfaces for potential use in bone implants, cells derived from bone may be maintained in culture on tissue culture polystyrene (TCPS). We have determined the contribution that serum fibronectin (FN) or vitronectin (VN) make to the attachment and spreading of cells cultured from explanted human bone (bone-derived cells) during the first 90 min following seeding on culture surfaces. The attachment of bone-derived cells to TCPS was simulated two-fold by the addition of 10% (v/v) fetal bovine serum (FBS) to the seeding culture medium. The roles of FN and VN were determined by selective removal of the FN or VN from the FBS prior to addition to the culture medium. FBS from which the VN had been removed did not have this stimulatory activity. In contrast, the attachment of bone-derived cells onto TCPS from medium containing FN-depleted serum (w...

A study on the in vitro degradation of poly(lactic acid).

Abstract: The in vitro degradation of samples of L- and D,L-lactic acid polymers, P(L)LA and P(DL)LA respectively, having different molecular weights, morphology and/or geometry, has been studied through the determination of viscometric molecular weight, mass and mechanical properties as function of the immersion time in Ringer solution at 37 degrees C. In particular have been compared the degradation kinetics of P(L)LA, amorphous and crystalline, and of P(L)LA and P(DL)LA having different molecular weight and sample geometry. From the molecular weight versus the degradation time data, a degradation rate has been defined, as the derivative of the function best fitting the data, normalized to the molecular weight of the polymer at each time. The behavior of the degradation rate curves, plotted against the degradation time, has been interpreted and compared with relation to the initial physical and geometrical characteristics of the PLA samples.

A polymeric drug delivery system for the simultaneous delivery of drugs activatable by enzymes and/or light.

Abstract: Three water soluble copolymers based on N-(2-hydroxypropyl)methacrylamide were prepared. Copolymer I contains adriamycin, a chemotherapeutic agent, attached via enzymatically degradable oligopeptide (glycylphenylalanylleucylglycine; G-F-L-G) side chains. The other two copolymers contained the photosensitizer, meso-chlorin e6 monoethylene diamine disodium salt (Mce6). In Copolymer II, the chlorin is attached via the degradable G-F-L-G sequence, and it was bound by the nondegradable glycyl spacer in Copolymer III. Initially, the copolymers were characterized separately in vitro and in vivo. Combinations of the copolymer bound chemotherapeutic agent and each of the copolymer bound photosensitizers were then assessed for antitumor effect in vivo. Localization/retention studies (A/J mice; Neuro 2A neuroblastoma solid tumor) were performed with the two copolymers containing Mce6 as well as the free drug. Results of these experiments demonstrated a very different tumor uptake profile for the two copolymers. Whil...

New biomaterials through surface segregation phenomenon: New quaternary ammonium compounds as antibacterial agents

Abstract: Five new trisiloxane quaternary ammonium compounds were synthesized from hydro-trisiloxane with allyl glycidyl ether to yield the epoxy function. Various amines were then reacted to yield trisiloxane amines which were further reacted to methyl substitute or oxidize the β-carbons in order to provide thermal stability. These new compounds were employed as melt additives in a nonwoven polypropylene fiber extrusion process to produce, through surface segregation, a new biomaterial with antibacterial properties.

Poly(ethylene oxide) star molecules: synthesis, characterization, and applications in medicine and biology.

Abstract: Festschrift remark-It was an honor to be invited to honor Allan Hoffman on the occasion of his 60th birthday. It seems like yesterday that Allan and I shared an office in old Building 12 on the M.I.T. campus. At that time Allan had lost a bout with a snow covered mountain while on skis, and consequently moved about awkwardly in our already small room on crutches with a heavy cast. Despite these impediments, he carried on his classroom activities with typical energy. It was even earlier that at M.I.T., under the supervision of Ed Gilliland and myself, he carried out his doctoral research on the radiation grafting of styrene to polyethylene. Both he and I have dabbled in radiation chemistry on and off since then-he far more than I. Neither of us at that epoch had much idea about biomaterials or medical applications of materials-at least I did not-perhaps Allan had it in the back of his mind. The University of Washington, Seattle, is recognized as one of the great centers of biomedical engineering in the wor...

Controlled release of TGF-β1 from a biodegradable matrix for bone regeneration

Abstract: Although bone has a remarkable capacity for regenerative growth, there are many clinical situations in which the bony repair process is impaired. TGF-beta 1 is a 25 kD homodimeric protein which modulates the growth and differentiation of many cell types. The ability of TGF-beta 1 to promote bone formation suggests that it may have potential as a therapeutic agent in disease of bone loss. However, there still exists a need for an effective method of delivering TGF-beta 1 to the site of an osseous defect for the promotion of bone healing. This paper describes a novel biodegradable controlled release system for TGF-beta 1 comprised of poly (DL-lactic-co-glycolic acid) (PLPG) and demineralized bone matrix (DBM). The amount and activity of TGF-beta 1 released was determined using several methods including 125I-labeled TGF-beta 1 as a tracer, an enzyme linked immunosorbent assay (ELISA) and a growth inhibitory assay (GIA). Protein was released from the devices for time periods of more than 600 h. The amount of TGF-beta 1 released was directly proportional to both the TGF-beta 1 loading and the weight percent of DBM in the device. The release kinetics could be further controlled by applying polymeric coatings of varying porosity to the devices. The GIA indicated that between 80 and 90% of the TGF-beta 1 released from the delivery system retained its bioactivity. The PLPG and DBM existed in phase separated domains within the device as determined by differential scanning calorimetry. Scanning electron microscopy suggested that the devices were sufficiently porous to allow bone ingrowth.

In vitro activation of human macrophages by alginate-polylysine microcapsules.

Abstract: Microencapsulated islets of Langerhans have been proposed as a bioartificial pancreas. However, foreign body reaction with fibrosis has been observed around implanted microcapsules. Since macrophages are present in this reaction and interleukin-1 (IL-1), a cytokine released by activated macrophages, may induce fibrosis, we tested the capacity of alginate-polylysine microcapsules to activate macrophages. Human monocytes were isolated from whole blood of healthy donors by a Ficoll density gradient and adherence to a plastic support. Monocytes were cultured for 24 h with: (1) alginate-polylysine microcapsules; (2) lipopolysaccharide (LPS) (positive control group); and (3) alone (negative control group). Monocyte activation was evaluated by measuring the secretion of IL-1 beta and the production of intracellular IL-1 alpha and IL-1 beta. Macrophages characterization was performed by immunocytological subtyping. IL-1 beta release and intracellular IL-1 beta and IL-1 alpha production were significantly higher when macrophages were cultured with alginate-polylysine microcapsules than when macrophages were cultured alone. In conclusion, macrophages are activated in vitro by alginate-polylysine microcapsules. This effect may be involved in the fibrosis observed in vivo around implanted microcapsules. In addition, interleukin-1, released during macrophage activation, may cross the microcapsule membrane and impair islet function.

Synthesis of carboxylated poly(NIPAAm) oligomers and their application to form thermo-reversible polymer-enzyme conjugates

Abstract: A thermo-reversible poly(N-isopropylacrylamide) poly(NIPAAm) oligomer with a carboxyl functional end group has been synthesized by radical polymerization using β-mercaptopropionic acid as a chain transfer reagent. This polymer has been conjugated to an enzyme, β-D-glucosidase, to form a thermo-reversible water soluble-insoluble polymer-enzyme conjugate. This conjugate can be used for separation, recovery and recycle of an enzyme simply by applying small temperature changes to the reaction medium. In contrast to the random polymer-enzyme conjugates reported in the literature, in this study the enzyme is coupled to each polymer chain by a single end attachment. These preliminary studies show that the conjugated enzyme exhibits very high retention of activity ( > 90%) compared to the native enzyme and shows improved thermal stability.

Poly-DL-lactic acid: polyethylene glycol block copolymers. The influence of polyethylene glycol on the degradation of poly-DL-lactic acid.

Abstract: ABA block copolymers of polyethylene glycol and poly-DL-lactic acid were prepared by ring-opening polymerization of DL-dilactide with α,ω-dihydroxy polyethylene glycol, n, 1000 or 2000. The morphol...

Patterned neuronal attachment and outgrowth on surface modified, electrically charged fluoropolymer substrates.

Abstract: Fluorinated ethylenepropylene copolymer (FEP) and polyvinylidene fluoride (PVDF) can generate static and transient electrical charges, respectively, after bulk molecular rearrangements induced by electrical charging techniques. Neurons cultured on electrically active FEP and PVDF show increased levels of nerve fiber outgrowth compared to electrically neutral material. The purpose of the present study was to determine if the addition of charged surface groups to the surfaces of FEP and PVDF would modify the influence of bulk electrical charges on cultured neurons. Mouse neuroblastoma (Nb2a) cells were cultured on electrically charged and uncharged FEP and PVDF substrates with covalently modified surfaces containing hydroxyl (OH) and amine (NH2) groups. Surface chemical modification was performed on the entire surface or in discrete striped regions. Nb2a cells cultured on electrically active FEP and PVDF showed greater levels of differentiation than cells on electrically neutral substrates. The presence of ...

Molecular surface tailoring of biomaterials via pulsed RF plasma discharges

Abstract: A pulsed RF plasma glow discharge is employed to demonstrate molecular level controllability of surface film deposits. Molecular composition of plasma deposited films is shown to vary in a significant manner with the RF duty cycle. Three fluorocarbon monomers are used to illustrate the process. All three exhibit a trend towards increased surface CF2 content with decreasing pulsed RF duty cycle, including exclusion of oxygen. Significant variations in carbon-fluorine surface functionalities are obtained over a controllable range of film thickness. Film growth rate measurements reveal the occurrence of surface reactions during significant portions of the off portion of the duty cycle. Albumin adsorption on fluorocarbon-treated PET films is unchanged from PET controls for a 100-fold range of bulk concentrations and 60-fold range of adsorption times. However, increased retention of albumin is observed following incubation with protein-denaturing sodium dodecyl sulfate solution, the retention decreasing with i...

Preparation of DNA-carrying affinity latex and purification of transcription factors with the latex

Abstract: We have developed DNA-carrying latex particles for the separation and purification of transcription factors. These particles consist of styrene (St), glycidyl methacrylate (GMA) and divinylbenzene (DVB). It was confirmed that the ethanolamine-treated surface of these particles suffered no nonspecific adsorption of proteins. To the latex particles sequence-specific DNA oligomers were immobilized via covalent coupling. A transcription factor, E4TF3, was efficiently purified to homogeneity using the latext particles. In contrast, the purification using DNA-carrying Sepharose gel yielded poor results. Compared to DNA-carrying Sepharose gel, the latex particles exhibited several times higher efficiency in the purification of E4TF3 from the crude nuclear extract.

Dextran permeation through poly(N-isopropylacrylamide) hydrogels.

Abstract: The permeation of macromolecules such as fluoroescein-labeled dextran fractions through thermally reversible hydrogels has been investigated. A permeation model has been formulated, which takes into account hydrogel porosity and tortuosity as well as the combined effect of a geometric restraint for a relatively large solute molecule at a pore entrance and the friction between solute molecules moving through the pores and pore walls. Based on this model, we have estimated the tortuosity and average pore size of a swollen hydrogel, poly(N-isopropylacrylamide) [poly(NIPAAm)] and a swollen heterogel, poly(N-isopropylacrylamide-co-vinyl-terminated dimethylsiloxane) [poly(NIPAAm-co-VTPDMS)]. The permeation data for dextran molecules up to the size of 43.5 A in radius show good agreement with the values predicted from the model.

Monosize microbeads based on polystyrene and their modified forms for some selected medical and biological applications

Abstract: Polymeric particles are produced by different polymerization techniques. Phase inversion (dispersion) polymerization is one of the recent techniques to obtain monosize polymeric microbeads in the size range of 1-50 microns. The size and monodispersity of these microbeads can be adjusted by using several solvent systems (e.g., alcohol-water mixtures) with different polarities and by changing the type and amount of monomer, initiator and stabilizer. Surfaces of these microbeads can be further modified by different techniques including coating with different copolymers. Monosize polymeric microbeads are widely used in medical and biological applications as carriers, such as in immunoassays and cell separation, in site-specific drug delivery systems, in nuclear medicine for diagnostic imaging, in studying the phagocytic process, in affinity separation of biological entities, etc. Here, some important aspects of the production of monosize microbeads based on polystyrene and their modified forms are briefly discussed, and some selected medical and biological applications are summarized.

Design, synthesis, and pr eliminary characterization of tyrosine-containing polyarylates: New biomaterials for medical applications

Abstract: Five structurally related, aliphatic polyarylates were synthesized from tyrosine-derived diphenols and diacids. The diphenols were a homologous series of three desaminotyrosyl-tyrosine alkyl esters (ethyl, hexyl, octyl) which had previously been used in the synthesis of mechanically strong and tissue-compatible polycarbonates. The diacids (succinic acid, adipic acid, sebacic acid) were selected among compounds that were known to be of low systemic toxicity. By using different diacids as comonomers, the flexibility of the polymer backbone could be varied while the desaminotyrosyl-tyrosine alkyl esters provided pendent chains of various length. Some of the thermal and mechanical properties of the five polymers could be correlated to their chemical structure: the glass transition temperature decreased from 53 to 13°C, and the tensile modulus (measured at room temperature) decreased from 1500 to about 3 MPa when the length of the aliphatic diacid in the polymer backbone and/or the length of the alkyl ester pe...

Ultrasonically enhanced transdermal drug delivery. Experimental approaches to elucidate the mechanism

Abstract: The effect of therapeutic range ultrasound on skin permeability was studied in vitro. Permeating molecule ionization state, pH, ultrasound duration, reversibility of the enhancement phenomenon, and skin structural alterations were evaluated. It was found that ultrasound affects the permeability of both ionized and unionized molecules. No irreversible structural alterations due to the ultrasound exposure were detected in the stratum corneum. Ultrasound enhancing mechanism was discussed.

Electro-driven chemomechanical polymer gel as an intelligent soft material

Abstract: Weakly crosslinked poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) gel was synthesized and the chemomechanical behaviors in the presence of N-alkylpyridinium chloride (CnPyCl n = 4, 12, 16) were studied. The principle of this behavior is based upon an electrokinetic molecular assembly reaction of surfactant molecules on the polymer gel caused by both electrostatic and hydrophobic interactions. Under an electric field PAMPS gel underwent significant and quick bending and the response could be controlled effectively by changing the alkyl chain length of the surfactant molecule, the salt concentration, and the current applied. The results allow us to consider that cooperative complex formation between PAMPS gel and CnPyCl is responsible for this effective chemomechanical behavior.

pH, salt, and buffer dependent swelling in ionizable copolymer gels: Tests of the ideal Donnan equilibrium theory

Abstract: We present results of equilibrium swelling studies of the ionizable copolymer gel, methyl methacrylate/N,N-dimethylaminoethyl methacrylate 70/30 mol%, in buffered and unbuffered electrolyte solutions. The experimental conditions were designed to demonstrate the sensitivity of swelling in ionized gels to the electrolyte composition of the external solution. In general, gel swelling as a function of solution ionic strength is shown to be highly nonmonotonic and is particularly sensitive to the valence and concentrations of ions present in solution. A rigorous test of ideal Donnan equilibrium theory shows that the latter is unable to explain all the data in a self-consistent manner. However, a heuristic procedure based on the ideal Donnan theory can predict qualitatively the observed trends. While not quantitative, this heuristic approach provides considerable insight into the mechanisms underlying the swelling behavior under various solution conditions. Possible causes of nonideal behavior are discussed, an...

Do hydrogels contain different classes of water

Abstract: in the first part of this article calorimetric studies on poly (hydroxy ethyl methacrylate) (PHEMA) are presented. In the past the irregular melting curves in this type of experiment have been interpreted as evidence for the existence of different types of water in these gels. The studies presented here demonstrate that the occurrence of a glass transition in the freezing hydrogels may be responsible for this irregular melting behavior, and that this behavior is not (necessarily) an indication for the existence of different types of water. In the second part results are shown of measurements of the mobility of water in hydrogels, made by relaxation NMR. These results indicate that very rapid interchange occurs between the water molecules, and they support the conclusion that the calorimetric data mentioned above are not indicative for the existence of different classes of water in hydrogels. These results are compared with data from other fields of science, especially from fundamental freeze drying studie...

Activated, N-substituted acrylamide polymers for antibody coupling: application to a novel membrane-based immunoassay.

Abstract: A room-temperature-precipitable, activated terpolymer consisting of N-isopropylacrylamide (NIPAAm)/N n-butylacrylamide(nBAAm)/N acryloxysuccinimide(NASI) (LCST = 7-13°C) at a monomer feed ratio of 60:40:2.5, respectively, was prepared and conjugated to an antibody. The conjugate was evaluated in a novel cellulose acetate (CA) membrane-based immunoassay which utilizes the especially strong physical attachment of the polymer to CA to bind and concentrate the polymer attached protein onto the membrane. When compared in the CA membrane immunoassay to the antibody-poly(NIPAAm) conjugate prepared via anhydrous copolymerization of NIPAAm and NASI at the monomer feed ratio of 40 : 1, respectively, the performance of the NIPAAm/nBAAm/NASI terpolymer was superior to that of the NIPAAm/NASI copolymer (LCST = 32°C) when the studies were carried out at room temperature. However, the terpolymer and copolymer gave equivalent performance when the assay mixture was heated to 45°C. These results indicate the importance of ...

Characterization of extractable species from poly(etherurethane urea) (PEUU) elastomers

Abstract: Methanol extracts of four poly(etherurethane urea) (PEUU) materials were analyzed using Gel Permeation Chromatography (GPC). The additives in the materials were Santowhite® powder at 1 wt% and Methacrol® 2138 F at 5 wt% loading levels. One-to-two wt% of the original PEUU films was extractable with methanol. The extractables consisted of a low molecular weight (Mw) PEUU polymer, an MDI-rich oligomer, the additives Santowhite® (SW) powder and Methacrol® 2138 F, and aniline. The low Mw PEUU polymer had a Mw of 12 000 relative to polystyrene, and the MDI-rich oligomer had a Mw of 1000 relative to polystyrene. Quantitation of all extracted species was achieved using GPC; the use of dual-detectors on the GPC made it possible to determine the soft-to-hard composition of the PEUU extracts as a function of molecular weight.

Temperature-dependent absorption/desorption behavior of lower critical solution temperature (LCST) polymers on various substrates.

Abstract: We have been studying adsorption and retention (resistance to desorption) behavior of temperature sensitive LCST polymers on different substrates as a function of temperature. According to our studies with Poly 64 (a copolymer of 60% (mol) NIPAAm and 40% (mol) NnBAAm, LCST = 8.5 degrees C in water), the copolymer retention depends on the rinse temperature. When the rinse temperature is above the LCST, the polymer adheres well to most surfaces. On the contrary, at rinse temperatures below the LCST, most of the adsorbed polymer is easily rinsed off. These studies are relevant to our work on the thermally reversible adsorption of LCST polymers conjugated to peptides and proteins, such as affinity ligands, for uses in immunoassays and affinity separations. The interaction between the LCST polymer and most hydrophobic polymer surfaces is mainly due to hydrophobic interactions, and the critical surface tension (gamma c) and the solubility parameter (delta) of the solid polymer substrate are the most important factors which influence the LCST polymer adsorption and retention. The critical surface tension appears to correlate best with the LCST polymer adsorption levels on different substrates, while the solubility parameter correlates best with the retention of the adsorbed polymer. According to our preliminary study, n-butyl groups probably interact more strongly with the substrates than isopropyl groups because of the greater hydrophobic surface area of the former groups.

A novel biomaterial: poly(dimethylsiloxane)-polyamide multiblock copolymer I. Synthesis and evaluation of blood compatibility.

Abstract: Aramid-silicone resins (PASs) consisting of aromatic polyamide (aramid) and poly(dimethylsiloxane) (PDMS) segments were synthesized by low temperature solution polycondensation. For the evaluation of blood compatibility in vitro, two kinds of experiments were carried out. One was the thromboxane B2(TXB2) release test from platelets attaching to PAS and Biomer®. The other was the observation of the platelet adhesion on the surfaces of PAS by scanning electron microscopy (SEM). The results indicated that PAS was bio-inert in vitro. The surface chemical composition of PAS films was investigated by means of electron probe micro analysis (EPMA), X-ray photoelectron spectroscopy (XPS), and dynamic contact angle measurements. The relationship between blood compatibility and surface composition of PAS is discussed.

Fibroblast attachment to Arg-Gly-Asp peptide-immobilized poly(γ-methyl L-glutamate)

Abstract: The attachment of MRC-5 human fibroblasts was investigated on poly(γ-methyl L-glutamate) (PMLG), and upon cell adhesion peptides Arg-Gly-Asp-Ser (RGDS)- and Gly-Arg-Gly-Asp-Ser (GRGDS)-immobilized ...

Synthesis and nonthrombogenicity of fluoroalkyl polyetherurethanes.

Abstract: New polyetherurethanes carrying fluoroalkyl substituents in the side chains were synthesized from N,N-di(hydroxyethyl)heptadecafluorooctyl-sulfonamide (a chain extender), 4,4'-disocyanatodiphenylmethane, and poly(tetramethylene glycol). Various kinds of polyetherurethanes having different tensile properties were prepared by changing the content of fluoroalkyl chain extender or the molecular weight of poly(tetramethylene glycol). The surface of a film made from the fluoroalkyl polyetherurethane was strongly water-repulsive. The in vitro thrombus formation on the fluoroalkyl polyetherurethanes was reduced by increasing the content of chain extender for the same molecular weight of poly(tetramethylene glycol). Protein adsorption, platelet adhesion, and platelet activation on the fluoroalkyl polyetherurethanes were also investigated.

The bone-cement interface: Histological observations on the interface of cemented arthroplasties within the immediate and late phases

Abstract: Undecalcified specimens of cemented arthroplasties obtained during the early and late phases were studied. On the tenth postoperative day, there was excellent interlocking of the cement with the soft and hard tissues of the bone: there was no necrosis of the bed of the implant: a neutrophilic and macrophagic inflammatory response, where present, was mild and focal. Samples of the bone-cement interface of well fixed components obtained (at autopsy or by biopsy) many years after implantation revealed a thin and quiescent fibrous interfacial membrane alternating with bone and osteoid (that is, segmental osseointegration) or a cartilaginous layer abutting on the cement. It is concluded that, firstly, modern cementation techniques are not associated with extensive necrosis of the underlying bone in the immediate postoperative period; secondly, monomeric and polymeric methylmethacrylate as such is not toxic to the tissues; and, thirdly, acrylic cement is osseointegrated when motion at the interface is at its minimum.

Fibroblast contraction of collagen matrices with and without covalently bound hyaluronan.

Abstract: Hyaluronan, which is found in high concentrations in fetal tissues, has been suggested to play a major role in preventing scar formation in fetal wounds. We have developed a floating collagen fibrillar matrix (CFM) made out of reconstituted type I collagen for the purpose of evaluating the ability of hyaluronan to inhibit the fibroblast induced contraction of the matrix. When hyaluronan is covalently bound to collagen it appears to better support fibroblast proliferation and matrices are less contractible by these cells than when hyaluronan interacts only ionically. When hyaluronan is bridged between collagen fibrils by a network of extensive covalent crosslinks, contractibility by fibroblasts is abolished. These modified collagen matrices may prove to be very useful in the development of bioprostheses and implants.

Effect of polyurethane surface chemistry on its lipid sorption behavior.

Abstract: The relationships among surface, bulk properties and lipid sorption behaviors of segmented polyurethanes (SPUs) with various polyol soft segments were investigated. The polyols used in this study w...