A novel injectable tissue adhesive based on oxidized dextran and chitosan.

A surgical adhesive that can be used in different surgical situations with or without sutures is a surgeons' dream and yet none has been able to fulfill many such demanding requirements. It was therefore a major challenge to develop an adhesive biomaterial that stops bleeding and bond tissues well, which at the same time is non-toxic, biocompatible and yet biodegradable, economically viable and appealing to the surgeon in terms of the simplicity of application in complex surgical situations. With this aim, we developed an in situ setting adhesive based on biopolymers such as chitosan and dextran. Dextran was oxidized using periodate to generate aldehyde functions on the biopolymer and then reacted with chitosan hydrochloride. Gelation occurred instantaneously upon mixing these components and the resulting gel showed good tissue adhesive properties with negligible cytotoxicity and minimal swelling in phosphate buffered saline (PBS). Rheology analysis confirmed the gelation process by demonstrating storage modulus having value higher than loss modulus. Adhesive strength was in the range 200-400gf/cm2 which is about 4-5 times more than that of fibrin glue at comparable setting times. The adhesive showed burst strength in the range of 400-410mm of Hg which should make the same suitable as a sealant for controlling bleeding in many surgical situations even at high blood pressure. Efficacy of the adhesive as a hemostat was demonstrated in a rabbit liver injury model. Histological features after two weeks were comparable to that of commercially available BioGlue®. The adhesive also demonstrated its efficacy as a drug delivery vehicle. The present adhesive could function without the many toxicity and biocompatibility issues associated with such products. STATEMENT OF SIGNIFICANCE: Though there are many tissue adhesives available in market, none are free of shortcomings. The newly developed surgical adhesive is a 2-component adhesive system based on time-tested, naturally occurring polysaccharides such as chitosan and dextran which are both biocompatible and biodegradable. Simple polymer modification has been carried out on both polysaccharides so that when aqueous solutions of both are mixed, the solutions gel in less than 10s and forms an adhesive that seals a variety of incisions. The strength of the adhesive is over 5-times the strength of commercially available Fibrin glue and is more tissue compliant than BioGlue®. This adhesive biomaterial showed excellent tissue bonding, was hemostatic, biocompatible and biodegradable. The significance of this work lies on the features of the developed tissue adhesive that it stops bleeding, bond the tissues well, can act as a drug delivery vehicle and would appeal to the surgeon in terms of the simplicity of application in complex surgical situations. There is no need for special delivery systems for application of this adhesive. The two-component adhesive can be applied one over the other using syringes. There is also no need for light curing with UV or visible light and the gelation between the two components spontaneously takes place on application leading to excellent tissue bonding.

Tunable delivery of niflumic acid from resorbable embolization microspheres for uterine fibroid embolization.

Uterine arteries embolization (UAE) is a recent technique that aims, by means of particles injected percutaneously, to stifle fibroids (leiomyomas). This treatment is non-invasive, compared with uterine ablation, but generates pelvic pain for a few days. A strategy to reduce the post-embolization pain would be to use calibrated embolization microspheres preloaded with a non-steroidal inflammatory drug (NSAID). In this study, we first compared four drugs, all active at low concentration on cyclooxygenase-2, i.e. ketoprofen, sodium diclofenac, flurbiprofen and niflumic acid (NFA), for their capacity to be loaded on resorbable embolization microspheres (REM) 500-700µm. NFA had the highest capacity of loading (5mg/mL) on resorbable microspheres. Then, we evaluated in vitro the NFA release profiles from REM having various degradation times of one, two or five days. NFA release was biphasic, with an initial burst (about 60% of the loading) followed by a sustained release that correlated significantly to REM's hydrolysis (rho=0.761, p<0.0001). For each group of beads, the size distribution was not modified by the loading of NFA and their delivery through microcatheter was not impaired by the drug. NFA eluted from REM inhibited the synthesis of prostaglandin E2 from rabbit uterus explants. In summary, NFA is loadable on REM in significant amount and its delivery can be tuned according to the degradation rate of REM to provide an antalgic effect for a few days after UAE.

Anti-angiogenic drug delivery from hydrophilic resorbable embolization microspheres: an in vitro study with sunitinib and bevacizumab.

Anti-angiogenic (AA) drugs are proposed as novel agents for targeted therapies in hepatocellular carcinoma (HCC). Loading of AA drugs into drug delivery systems for local delivery would reduce their side effects. The present study investigated the loading and the delivery of two AA drugs, sunitinib and bevacizumab, from one day-resorbable embolization microspheres (REM). REM were prepared with 10 or 20% of methacrylic acid (MA) as active drug binding monomer. Sterilized beads (100-300 µm) were analyzed for cytotoxicity, AA loading and in vitro release. REM modified with MA were not cytotoxic and extemporaneous drug loading was significantly higher on REM containing 20% of MA. The drug release in saline buffer was sustained for several hours before complete REM degradation. MA content had low effect on drug release profile. When eluted from REM, sunitinib and bevacizumab reduced viability of tumoral VX2 cells, and proliferation of human endothelial cells, respectively. Deliverability of REM via microcatheter was not impaired by the loaded drugs. As conclusion, the loading values of sunitinib and bevacizumab on REM were close to those achieved for cytotoxic drugs onto non-degradable MS used in chemoembolization of HCC. Transcatheter delivery to liver tumors of anti-angiogenics could be achieved with REM.

Poly(ethylene glycol) methacrylate hydrolyzable microspheres for transient vascular embolization.

Poly(ethylene glycol) methacrylate (PEGMA) hydrolyzable microspheres intended for biomedical applications were readily prepared from poly(lactide-co-glycolide) (PLGA)-poly(ethylene glycol) (PEG)-PLGA crosslinker and PEGMA as a monomer using a suspension polymerization process. Additional co-monomers, methacrylic acid and 2-methylene-1,3-dioxepane (MDO), were incorporated into the initial formulation to improve the properties of the microspheres. All synthesized microspheres were spherical in shape, calibrated in the 300-500 µm range, swelled in phosphate-buffered saline (PBS) and easily injectable through a microcatheter. Hydrolytic degradation experiments performed in PBS at 37 °C showed that all of the formulations tested were totally degraded in less than 2 days. The resulting degradation products were a mixture of low-molecular-weight compounds (PEG, lactic and glycolic acids) and water-soluble polymethacrylate chains having molecular weights below the threshold for renal filtration of 50 kg mol(-1) for the microspheres containing MDO. Both the microspheres and the degradation products were determined to exhibit minimal cytotoxicity against L929 fibroblasts. Additionally, in vivo implantation in a subcutaneous rabbit model supported the in vitro results of a rapid degradation rate of microspheres and provided only a mild and transient inflammatory reaction comparable to that of the control group.

Synthesis of hydrophilic intra-articular microspheres conjugated to ibuprofen and evaluation of anti-inflammatory activity on articular explants.

The main limitation of current microspheres for intra-articular delivery of non-steroidal anti-inflammatory drugs (NSAIDs) is a significant initial burst release, which prevents a long-term drug delivery. In order to get a sustained delivery of NSAIDs without burst, hydrogel degradable microspheres were prepared by co-polymerization of a methacrylic derivative of ibuprofen with oligo(ethylene-glycol) methacrylate and poly(PLGA-PEG) dimethacrylate as degradable crosslinker. Microspheres (40-100 µm) gave a low yield of ibuprofen release in saline buffer (≈2% after 3 months). Mass spectrometry analysis confirmed that intact ibuprofen was regenerated indicating that ester hydrolysis occurred at the carboxylic acid position of ibuprofen. Dialysis of release medium followed by alkaline hydrolysis show that in saline buffer ester hydrolysis occurred at other positions in the polymer matrix leading to the release of water-soluble polymers (>6-8000 Da) conjugated with ibuprofen showing that degradation and drug release are simultaneous. By considering the free and conjugated ibuprofen, 13% of the drug is released in 3 months. In vitro, ibuprofen-loaded MS inhibited the synthesis of prostaglandin E2 in articular cartilage and capsule explants challenged with lipopolysaccharides. Covalent attachment of ibuprofen to PEG-hydrogel MS suppresses the burst release and allows a slow drug delivery for months and the cyclooxygenase-inhibition property of regenerated ibuprofen is preserved.

Intra-articular fate of degradable poly(ethyleneglycol)-hydrogel microspheres as carriers for sustained drug delivery.

A novel degradable microsphere (MS) for intra-articular drug delivery, composed of a polyethylene glycol (PEG) core containing degradable regions made of short poly-(lactic-co-glycolic acid) (PLGA) sequences - named PEG-hydrogel MS - was injected into the cavity of sheep shoulder joint, and compared to non-degradable MS devoid of hydrolysable crosslinker in terms of location, degradation and inflammation. One week after intra-articular injection both groups of MS were localized beneath the synovial lining of the synovial fringes located at bottom of the shoulder joint, while a fraction of particles remained in synovial fluid. Histological analyses made one and 4 weeks after intra-articular injection showed cell proliferation around the non-degradable MS entrapped within the synovium. By contrast, degradable PEG-hydrogel MS were surrounded by few cells. The degradation of degradable PEG-hydrogel MS within the synovium was slow and was not fully complete after four weeks. Our findings indicate that the tissue entrapment of MS below the synovial lining was independent of the material degradability, while degradable PEG-hydrogel MS are less inflammatory than the non-degradable one. Degradable PEG-hydrogel MS offer several advantages over the non-degradable MS as carriers for a sustained drug delivery in synovial tissue according to the low intensity of inflammatory reaction triggered in synovium.

Elasticity and viscoelasticity of embolization microspheres.

The present study investigates the mechanical properties of three embolization microspheres (E-ms): tris-acryl gelatin microspheres (TG-ms), acrylamido polyvinyl alcohol microspheres (APVA-ms), and polyphosphazene-coated polymethylmethacrylate microspheres (PP-PMMA-ms). Compression and relaxation tests were performed on monolayers of particles and their Young's moduli and relaxation half times (RHTs) were determined. The elasticity of E-ms was evaluated by applying Hertz theory with the assumptions of incompressibility and a Poisson's ratio of 0.5. The Young's moduli of TG-ms, APVA-ms, and PP-PMMA-ms were 39.6±5.05 kPa, 18.8±4.00 kPa, and 13.6±1.98 kPa, respectively. The RHTs of TG-ms, APVA-ms, and PP-PMMA-ms were 52.3±5.56 s, 59.1±8.16 s, and 31.0±7.01 s, respectively. TG-ms have a high rigidity and deform slightly under a sustained compression since they have a high elasticity. PP-PMMA-ms are soft and deform a lot under sustained compression. They are more viscous than the other two microspheres. APVA-ms have intermediate material properties, having the same low rigidity as PP-PMMA-ms and being more elastic than TG-ms.

Influence of degradation on inflammatory profile of polyphosphazene coated PMMA and trisacryl gelatin microspheres in a sheep uterine artery embolization model.

Embolization with microspheres is widely applied to treat uterine fibroids. However, the foreign body reaction that could result from the degradation of the microspheres remains to be evaluated to adequately appreciate the tissular tolerance to such biomaterials. We compared herein the in situ degradation of PMMA microspheres coated with polyphosphazene (PMMA-PPms) and trisacryl gelatin microspheres (TGms) and we thoroughly investigated the induced local inflammatory responses, at 1 and 4 weeks after uterine artery embolization in sheep, by using immunohistochemistry and microarray analyses. PMMA-PPms underwent an acute and partial degradation that was associated with the early recruitment of phagocytic cells (CD172a+ and MHCII+), and with the up-regulated expression of genes involved in the movement of phagocytes (ALOX5AP, CXCL2, CXCL5, IL8, PTGS2, YARS). By contrast, TGms were not degraded and triggered a different inflammation profile including the recruitment of FBR Giant Cells and T-lymphocytes (CD4+) and the increased expression of genes involved in lymphocyte activation (CXCL10, IL2RG, IRAK4, MALT1). Our results indicate that, in contrast to a non-degradable microsphere such as TGms which is associated to a poorly inflammatory foreign body reaction that rapidly resolves, PMMA-PPms, which is partially degradable, rapidly recruits and activates inflammatory phagocytes, thus delaying the resolution of the foreign body reaction.

Artificial oxygen carrier based on polysaccharides-poly(alkylcyanoacrylates) nanoparticle templates.

Biomimetic nanoparticles based on polysaccharides-poly(alkylcyanoacrylates) copolymers were initially developed in view of drug delivery. Core-shell nanoparticles covered with a sufficiently long brush of polysaccharides were shown to be very low complement activators and have the potential for long circulation times in the bloodstream. Such nanoparticles bearing haemoglobin were envisaged as potential red cell substitutes. Different core-shell nanoparticles with a brush shell made of dextran, dextran-sulphate, or heparin were prepared and haemoglobin (Hb) could be adsorbed on their surface. Benzene tetracarboxylic acid (BTCA) was used as a coupling agent for Hb to dextran-coated nanoparticles; the Hb loading capacity of the dextran nanoparticles showed a 9.3 fold increased. The coupled Hb maintained the allosteric properties of free Hb. While modification of nanoparticles by BTCA slightly increased complement activation, the further addition of Hb totally reversed this effect providing Hb-loaded nanoparticles with a very low level of complement activation. Such nanoparticles could be a suitable alternative to haemoglobin solutions in the development of a blood substitute.

An embolic gelling solution based on acrylic copolymers in ethanol for the treatment of arteriovenous malformations.

We report the preparation of an embolic agent based on specific association of an acrylic copolymer with dedicated particles formulated in ethanol. The copolymers were synthesized by radical polymerization of tertiobutylacrylamide (tBA) and 2-hydroxypropyl methacrylate (HPMA). Influences of the monomers composition, molecular weight and copolymer concentration have been evaluated on an in vitro model. Introduction of tBA units improves significantly the occlusion properties but these properties are similar whatever the molecular weight of the copolymer. As observed by viscosity studies, it seems necessary to work with a relatively high polymer concentration (C > Ce) to form a cohesive embolus. Addition of solid particles composed by a crosslinked polymer of 2-hydroxyethyl methacrylate (HEMA) and N-trishydroxymethyl methacrylamide (TRIS) in the acrylic copolymer solution has allowed to obtain an embole having an enhanced cohesion and giving a more compact structure. An in vivo evaluation has been performed by injection of this embolic agent in intercostal arteries and renal artery of sheep. There was no fragmentation of the plug during and after injection and a complete arterial occlusion by a cohesive embole. The pathological examination confirmed that there was a complete arterial occlusion by the plug and that the dedicated particles were as expected embedded in the precipitate acrylic copolymer.

Recanalization and particle exclusion after embolization of uterine arteries in sheep: a long-term study.

OBJECTIVE: To compare the long-term evolution of uterine arteries after embolization with the two most commonly used embolic agents for fibroid embolization: nonspherical polyvinyl alcohol (PVA) particles and trisacryl gelatin microspheres (TGMS). DESIGN: Prospective study. SETTING: University-based interventional radiology, pathology, and reproductive physiology units. ANIMAL(S): Two groups of 10 sheep embolized in the uterine artery. INTERVENTION(S): Embolization of the uterine artery with either 600-1000 microm nonspherical polyvinyl alcohol (PVA) particles or with 700-900 microm trisacryl gelatin microspheres (TGMS). Animals were synchronized and naturally inseminated. Animals were killed at 26 months. MAIN OUTCOME MEASURE(S): Uteri were examined pathologically for vessel size, site of occlusion, recanalization rate of vessels, and particle location within the vascular wall. RESULT(S): The PVA particles were more numerous in the vessels' lumen than the TGMS particles (13.3 +/- 20.8 vs. 2.5 +/- 2.7), were located more proximally than TGMS (97% vs. 68% in the trunk and first branches of the uterine artery), and were found almost exclusively in the intima (99.2%). In contrast, 54.4% of the TGMS particles were found in the intima, and 45.6% partially or totally excluded. The rate of recanalization was not statistically significantly different for PVA and TGMS (65.2% vs. 60.6%). CONCLUSION(S): The long-term evolution of uterine arteries was different after uterine artery embolization with PVA and TGMS because PVA particles formed large-sized aggregates that occluded proximal vessels and remained in the vessel intima. Microspheres occluded more distal vessels, and about 50% of them were partially or totally excluded from the vessel.

Design aspects of poly(alkylcyanoacrylate) nanoparticles for drug delivery.

Poly(alkylcyanoacrylate) (PACA) nanoparticles were first developed 25 years ago taking advantage of the in vivo degradation potential of the polymer and of its good acceptance by living tissues. Since then, various PACA nanoparticles were designed including nanospheres, oil-containing and water-containing nanocapsules. This made possible the in vivo delivery of many types of drugs including those presenting serious challenging delivery problems. PACA nanoparticles were proven to improve treatments of severe diseases like cancer, infections and metabolic disease. For instance, they can transport drugs across barriers allowing delivery of therapeutic doses in difficult tissues to reach including in the brain or in multidrug resistant cells. This review gives an update on the more recent developments and achievements on design aspects of PACA nanoparticles as delivery systems for various drugs to be administered in vivo by different routes of administration.

MR imaging detection of superparamagnetic iron oxide loaded tris-acryl embolization microspheres.

PURPOSE: To assess by magnetic resonance (MR) imaging the detectability of superparamagnetic iron oxide (SPIO)-labeled microspheres (MSs) in vitro on gelose, ex vivo in kidneys from embolized sheep, and in vivo in kidneys from embolized pigs. MATERIALS AND METHODS: With various sizes of SPIO-labeled MSs, common neck and pelvic spin-echo and gradient-echo sequences were acquired on a 1.5-T MR unit. SPIO-labeled MSs of four sizes were embedded in a hydrogel as single MSs or in multiple units, or multiplets. Detection rate on MR imaging was assessed according to the real size and number of MSs. SPIO-loaded and unloaded MSs of four sizes were injected into eight sheep kidneys, which underwent MR and pathologic examinations. For each size, the location of MSs in renal vasculature was determined and compared according to the technique used. Kidneys were embolized in pigs with various amounts of MSs in three sizes. MR was performed immediately after embolization and SPIO-labeled MS detection was assessed according to size, organ, and amount injected. Results SPIO-labeled MSs provide a low signal intensity on T1-weighted sequences, without distortion. In vitro, 28% of 100-300-microm single MSs were detected and more than 80% were detected for larger sizes. MS multiplets were all detected in all sizes. Ex vivo, all sizes of MSs were detected by MR imaging in kidneys, whereas control MSs were not observed. Histologic analysis showed that there was no difference in vascular distribution between SPIO-labeled MS and control MSs, and therefore for each caliber (P > .05). Arterial location of SPIO-labeled MSs was the same on MR imaging and histologic analysis. In vivo, SPIO-labeled MS were detected in the kidney vasculature when volumes greater than 1 mL of 100-300-microm or 500-700-microm MSs were injected. Volumes lower than 1 mL SPIO-labeled MSs were hardly detected in kidneys, regardless of MS size. Conclusions SPIO-labeled MSs are detected by MR imaging with common gradient-echo sequences in vitro in gelose and ex vivo and in vivo in kidneys. SPIO-labeled MSs could allow better control of embolization and thereby enhance efficacy and safety of the procedure.

Enhancing the tolerance of poly(isobutylcyanoacrylate) nanoparticles with a modular surface design.

Polymer nanoparticles are designed as nanovehicles to carry drugs in the body in a controlled manner increasing the concentration of the biologically active substance in the diseased organs and cells. The safety and biocompatibility of these nanosystems are those of the many properties that nanoparticles must meet to be used in vivo. Here we show that the cytotoxicity profile of poly(isobutylcyanoacrylate) (PIBCA) nanoparticles is affected by the way the nanosystems were produced and by the design of their surface. It was found that the tolerance of PIBCA nanoparticles by cells could be improved up to 100-fold by coating their surface with polysaccharides and haemoglobin.

Bioadhesive properties of poly(alkylcyanoacrylate) nanoparticles coated with polysaccharide.

Development of bioadhesive nanoparticles is of great interest to improve drug absorption through the intestinal barrier. Various Polysaccharide-coated poly(alkylcyanoacrylate) nanoparticles were prepared. The bioadhesive properties of the nanoparticles coated with dextran or chitosan in end-on or side-on conformation were evaluated with an ex-vivo adsorption experiment on rat intestine. Results show that diffusion of nanoparticles in mucus layer was governed by the nanoparticle diameter and isotherms of adsorption were influenced by the nature of polysaccharide used. High amount of nanoparticles coated with chitosan can be entrapped in the mucus layer even at low nanoparticle concentration in suspension. When nanoparticle concentration increased, a pseudo-plateau was reached. In the case of dextran-coated nanoparticles, linear increase of adsorption was observed and no saturation phenomenon was highlighted over the range of nanoparticle concentration used in this study. These results suggested that interactions involved in bioadhesion mechanism depended on the nature of polysaccharide. Electrostatic interactions are enhanced between chitosan-coated nanoparticles and glycoproteins of mucus leading to a saturated adsorption phenomenon whereas dextran-coated nanoparticles interacted by non-electrostatic interactions with mucus resulting in a non-saturated phenomenon. Polysaccharides grafted at the nanoparticle surface in the brush conformation appeared more favorable to promote interactions of nanoparticles with glycoproteins of mucus in comparison with the more compact loop conformation of polysaccharide chains.

Complement activation by core-shell poly(isobutylcyanoacrylate)-polysaccharide nanoparticles: influences of surface morphology, length, and type of polysaccharide.

PURPOSE: Biodistribution of intravenously administered nanoparticles depends on opsonization. The aim of this study was the evaluation of complement activation induced by nanoparticles coated with different polysaccharides. Influences of size and configuration of dextran, dextran sulfate, or chitosan bound onto nanoparticles were investigated. METHOD: Core-shell nanoparticles were prepared by redox radical or anionic polymerization of isobutylcyanoacrylate in the presence of polysaccharides. Conversion of C3 into C3b in serum incubated with nanoparticles was evaluated. RESULTS: Cleavage of C3 increased with size of dextran bound in "loops" configuration, whereas it decreased when dextran was bound in "brush." It was explained by an increasing steric repulsive effect of the brush, inducing poor accessibility to OH groups. The same trend was observed for chitosan-coated nanoparticles. Nanoparticles coated with a brush of chitosan activated the complement system lesser than nanoparticles coated with a brush of dextran. This was explained by an improved repelling effect. Dextran-sulfate-coated nanoparticles induced a low cleavage of C3 whereas it strongly enhanced protein adsorption. CONCLUSION: Complement activation was highly sensitive to surface features of the nanoparticles. Type of polysaccharide, configuration on the surface, and accessibility to reactive functions along chains are critical parameters for complement activation.

Properties of polysaccharides grafted on nanoparticles investigated by EPR.

The in vivo fate of nanoparticles developed as drug delivery systems is influenced by the surface characteristics of the colloidal particles. In the present work, surface characteristics of a series of poly(isobutylcyanoacrylate) nanoparticles prepared by redox radical emulsion polymerization with polysaccharides of different molecular weight and nature were characterized by EPR. To this aim, a spin label was grafted on the polysaccharide chains after synthesis of the nanoparticles. The percentage of label showing fast movements was evaluated from EPR spectra which were analyzed according to the Kivelson theory. The results showed that mobility depended on temperature, type, and molecular weight of the polysaccharides. Differences between nanoparticles appeared with low-molecular-weight polysaccharides, while over a defined molecular weight which depended on the nature of the polysaccharide, the spin label behaved almost the same way in the different types of nanoparticles. Paradoxically, the percentage of fast moving label was the highest when linked to the shortest chitosan, which was the most rigid polysaccharide tested in this study. Thus, it was concluded that the apparent mobility of the polysaccharide evaluated by the EPR method depended on the capacity of the polysaccharide chains to fold making possible hydrophobic interactions between the label and the nanoparticle core. The transition between the unfolded-folded regiment depended on the molecular weight and on the nature of the polysaccharide. Results of this study may be useful to improve the understanding of the nanoparticle interactions with blood proteins and complement which in turn influence the in vivo fate of nanoparticles used as drug delivery systems.

Interactions of blood proteins with poly(isobutylcyanoacrylate) nanoparticles decorated with a polysaccharidic brush.

The aim of this work was to examine the in vitro interactions of core-shell poly(isobutylcyanoacrylate)-polysaccharide nanoparticles (NP) with blood proteins. The particles were prepared by initiating the emulsion polymerization of isobutylcyanoacrylate (IBCA) in the presence of dextran 71 or 15 kDa, heparin, a blend of dextran 71 and heparin, or dextran sulphate in aqueous medium at pH 1. The mechanisms of polymerisation were redox radical (Rad) or anionic (An), resulting in differences in the spatial arrangement of the polysaccharide chains at the NP surface, i.e. "loops" and "trains" by anionic polymerization, "brush" by radical polymerization. Surface composition of NPs was determined by X-ray photo-electron spectroscopy (XPS) and surface charge by zeta potential measurements. In the presence of citrated blood plasma, efficacy of the steric repulsive effect of the NP dextran shell towards protein adsorption decreased in the order: Dex71-Rad > Dex15-Rad > Dex71-AnDex15-An. Dextran-coated NPs adsorbed ApoA-I and fibrinogen from plasma. Concerning activation of complement in serum, the effect was sharp: Dex71-Rad was a very low activator whereas Dex15-An, Dex15-Rad and Dex71-An were strong activators. In citrated plasma, the steric repulsive effects of Hep-Rad and Dex-Hep-Rad NPs were similar to Dex71-An, and Dex-Sulph-Rad NPs adsorbed twice more proteins than Hep-Rad. Hep-Rad, Dex-Hep-Rad and Dex-Sulph-Rad NPs adsorbed IgG and fibrinogen. Complement was not activated in serum in the presence of Hep-Rad and Dex-Hep-Rad and a slight adsorption of C3 was noted. C3 was completely adsorbed on Dex-Sulph-Rad. The exquisite sensitivity of blood proteins to differences in the nature and outermost structure of the polysaccharides-coated NPs is highlighted by the present results.

Heparin coated poly(alkylcyanoacrylate) nanoparticles coupled to hemoglobin: a new oxygen carrier.

A new generation of drug delivery systems based on heparin-poly(isobutylcyanoacrylate) copolymers has been developed to carry hemoglobin. These copolymers spontaneously form, in water, nanoparticles with a ciliated surface of heparin. These nanoparticles maintain the heparin antithrombotic properties and inhibit complement activation. One ml of nanoparticle suspension can be loaded with up to 2.1mg of hemoglobin, which preserves its ligand binding capacity. This work constitutes the first demonstration of hemoglobin loaded on nanoparticle surface, rather than being encapsulated. With a size of 100 nm, these drug delivery systems make suitable tools in the treatment of thrombosis oxygen deprived pathologies.

Novel polysaccharide-decorated poly(isobutyl cyanoacrylate) nanoparticles.

PURPOSE: The aim of this work was to synthesize new surface-modified nanoparticles using a radical emulsion polymerization of an alkyl cyanoacrylate. METHODS: Isobutyl cyanoacrylate was polymerized in nitric acid 0.2 M containing a polysaccharide (0.1375 g) and cerium (8 x 10(-2) M). After 1 h, the pH was adjusted to 7.0, and the nanoparticles were purified by dialysis. Nanoparticle characterization included scanning electron microscopy, quasi-elastic light scattering, zeta potential determination, measurements of the complement activation induced by different polysaccharide-coated nanoparticles and of the antithrombic activity of heparin. RESULTS: Dispersions of spherical particles were obtained using various polysaccharides. The particle diameter varied from 90 nm to several micrometers, and the zeta potential depended on the molecular weight and the nature and charge of the polysaccharide. Surface analysis performed by ESCA confirmed the presence of polysaccharides at the nanoparticle surface. The nanoparticles were very stable, and the biologic activity of the polysaccharide was preserved. Complement activation was influenced by the polysaccharide characteristics. CONCLUSIONS: A new method based on radical emulsion polymerization of isobutyl cyanoacrylate initiated by polysaccharides and cerium was developed to prepare nanoparticles. It leads, in a single step, to nanoparticles with surface properties defined by the polysaccharide. This method is a new concept for the development of biomimetic drug carriers with multiple functions.