Designed sponges based on chitosan and cyclodextrin polymer for a local release of ciprofloxacin in diabetic foot infections.

Diabetic foot infections are the most common complications requiring hospitalisation of patients with diabetes. They often result in amputation to extremities and are associated with high morbi-mortality rates, especially when bone is infected. Treatment of these complications is based on surgical procedures, nursing care and systemic antibiotic therapy for several weeks, with a significant risk of relapse. Due to low blood flow and damage caused by diabetic foot infection, blood supply is decreased, causing low antibiotic diffusion in the infected site and an increase of possible bacterial resistance, making this type of infection particularly difficult to treat. In this context, the aim of this work was to develop a medical device for local antibiotic release. The device is a lyophilized physical hydrogel, i.e a sponge based on two oppositely charged polyelectrolytes (chitosan and poly(cyclodextrin citrate)). Cyclodextrins, via inclusion complexes, increase drug bioavailability and allow an extended release. Using local release administration increases concentrations in the wound without risk of toxicity to the body and prevents the emergence of resistant bacteria. The hydrogel was characterised by rheology. After freeze-drying, a curing process was implemented. The swelling rate and cell viability were evaluated, and finally, the sponge was impregnated with a ciprofloxacin solution to evaluate its drug release profile and its antibacterial activity.

Cyclodextrin modified PLLA parietal reinforcement implant with prolonged antibacterial activity.

The use of textile meshes in hernia repair is widespread in visceral surgery. Though, mesh infection is a complication that may prolong the patient recovery period and consequently presents an impact on public health economy. Such concern can be avoided thanks to a local and extended antibiotic release on the operative site. In recent developments, poly-l-lactic acid (PLLA) has been used in complement of polyethyleneterephthalate (Dacron®) (PET) or polypropylene (PP) yarns in the manufacture of semi-resorbable parietal implants. The goal of the present study consisted in assigning drug reservoir properties and prolonged antibacterial effect to a 100% PLLA knit through its functionalization with a cyclodextrin polymer (polyCD) and activation with ciprofloxacin. The study focused i) on the control of degree of polyCD functionalization of the PLLA support and on its physical and biological characterization by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC) and cell viability, ii) on the understanding of drug/meshes interaction using mathematic model and iii) on the correlation between drug release studies in phosphate buffer saline (PBS) and microbiological evaluation of meshes and release medium against E. coli and S. aureus. All above mentioned tests highlighted the contribution of polyCD on the improved performances of the resulting antibacterial implantable material. STATEMENT OF SIGNIFICANCE: 1. We managed for the first time, with well-defined parameters in terms of temperature and time of treatment, to functionalize a bio-absorbable synthetic material to improve drug sorption and drug release properties without affecting its mechanical properties. 2. We analyzed for the first time the degradation of our coating products by mass spectroscopy to show that only citrate and cyclodextrin residues (and glucose units) without any cytotoxicity are formed. 3. We managed to improve the mechanical properties of the PLA with the cyclodextrin polymer to form a composite. The assembly (cyclodextrin polymer and PLLA) remains biodegradable.

Visceral mesh modified with cyclodextrin for the local sustained delivery of ropivacaine.

The aim of the study was to develop a polyester visceral implant modified with a cyclodextrin polymer for the local and prolonged delivery of ropivacaine to reduce post operatory pain. Therefore, we applied a coating of an inguinal mesh with a crosslinked polymer of hydroxypropyl-ß-cyclodextrin (HPßCD) whose specific host-guest complex forming properties were expected to improve the adsorption capacity of the implant toward anesthetic, and then to release it within a sustained period. The modification reaction of the textile with cyclodextrin was explored through the study of the influence of the pad/dry/cure process parameters and the resulting implant (PET-CD) was characterized by solid state NMR and SEM. Besides, the inclusion complex between ropivacaine and CD was studied by NMR and capillary electrophoresis in PBS medium. Finally, ropivacaine sorption test showed that a maximum of 30 mg/g of ropivacaine could be adsorbed on the functionalized samples. In dynamic batch tests in PBS at pH 7.4, the release could be observed up to 6h. The cytocompatibility of the PET-CD loaded with ropivacaine was also studied and reached 65% cell vitality after 6 days.

Dyeing and antibacterial activation with methylene blue of a cyclodextrin modified polyester vascular graft.

The aim of this study was to develop an antiseptic and blue dyed polyester (PET) vascular graft in order to reach two distinct properties: (i) the prevention of postoperative infections, (ii) the improvement of the graft compatibility with the coelioscopy surgical technique. This work consisted of dyeing a vascular prosthesis with methylene blue (MB) which is known as a cationic dye with antiseptic properties. Therefore, the functionalization of the PET fibers of the prosthesis with a cyclodextrin-citric acid polymer (PolyCD) was achieved in order to improve its sorption capacity. The NMR experiments demonstrated that a 1:2 complex occurred between hydroxypropyl ß-cyclodextrin (HP-ßCD) and MB. Kinetic and sorption isotherm studies showed that an impregnation of the polyCD modified prosthesis (PET-CD) in a 1 g L(-1) of MB solution for 150 min was sufficient to reach the saturation of the device. Results proved that the adsorption mechanism followed the Langmuir model and a maximum of 20 mg g(-1) of MB on the graft. A sustained release of MB in batch tests was observed in PBS and in vitro microbiological assays displayed a prolongation of the bactericidal effect of PET-CD whose extent varied with the amount of MB preliminarily adsorbed onto the PET-CD.

Validating the poly-cyclodextrins based local drug delivery system on plasma-sprayed hydroxyapatite coated orthopedic implant with toluidine blue O.

Local antibiotics delivery is an efficient solution to reduce the risk of infections associated with orthopedic implant. This study aims to functionalize plasma-sprayed hydroxyapatite coated titanium (Ti-HA) hip joint implant material with cyclodextrins-polymer (polyCD)-based local drug delivery system for loading therapeutic molecules (e.g. antibiotics), to offer a sustainable drug delivery. The process of polyCD coating on Ti-HA material was optimized with the help of model guest molecule - toluidine blue O (TBO) for evaluating the efficacy of polyCD system. The obtained results clearly showed that polyCD's treatment can firmly coat on the Ti-HA material under the optimized processing parameters concerning the type of CD, thermal treatment temperature and duration. PolyCD system has been proven to have a high capacity of TBO adsorption and long release duration. In vitro study also showed non-cytotoxicity of polyCD functionalized samples to osteoblastic cells. Trial study with gentamicin revealed very promising potential of polyCD system for sustained delivery of antibiotics. To conclude, the study substantiates the prospective flexibility of drug choice when applying polyCD treated implants including antibiotics, antimitotic agents or other therapeutical molecules. One or more drugs can be loaded, thus synergism and multi-factorial effects are feasible.

Comparative study of vascular prostheses coated with polycyclodextrins for controlled ciprofloxacin release.

A textile polyester vascular graft was modified with cyclodextrins to obtain a new implant capable of releasing antibiotics (here ciprofloxacin, CFX) over prolonged time periods and thereby reducing the risk of post-operative infections. In this study, we compared samples modified with native and modified cyclodextrins, presenting different cavity sizes (ß or γ cyclodextrins) and different substituent groups (hydroxypropyl and methyl). Drug release was measured in water, phosphate buffer pH 7.4 and blood plasma. The inclusion of CFX in the cyclodextrins cavities was observed in solution by two-dimensional (1)H NMR spectroscopy and confirmed by (1)F NMR measurements. Grafts modification with all cyclodextrins induced an increase of their sorption capacity towards CFX whose extent depended on the nature of the cyclodextrin: a 4-fold and 10-fold increase was observed in the cases of hydroxypropyl cyclodextrins and methylated ß-cyclodextrin, respectively. Depending on the type of release medium and nature of CD, different CFX release kinetics were obtained. The discussion highlighted not only the role of the host guest complexation, but also that of the electrostatic interactions that occur between the anionic crosslinks of the cyclodextrins polymers, and CFX that presents a zwitterionic character. The microbiological assessment confirmed sustained CFX release in human plasma and demonstrated antibacterial efficiency of CD modified prostheses against Staphylococcus aureus and Escherichia coli for at least 24 h (compared to 4 h in the case of virgin grafts).

Anticoagulant and antimicrobial finishing of non-woven polypropylene textiles.

The aim of this work is to prepare non-woven polypropylene (PP) textile functionalized with bioactive molecules in order to improve its anticoagulation and antibacterial properties. This paper describes the optimization of the grafting process of acrylic acid (AA) on low-pressure cold-plasma pre-activated PP, the characterization of the modified substrates and the effect of these modifications on the in vitro biological response towards cells. Then, the immobilization of gentamicin (aminoglycoside antibiotic) and heparin (anticoagulation agent) has been carried out on the grafted samples by either ionic interactions or covalent linkages. Their bioactivity has been investigated and related to the nature of their interactions with the substrate. For gentamicin-immobilized AA-grafted samples, an inhibition radius and a reduction of 99% of the adhesion of Escherichia coli have been observed when gentamicin was linked by ionic interactions, allowing the release of the antibiotic. By contrast, for heparin-immobilized AA-grafted PP samples, a strong increase of the anticoagulant effect up to 35 min has been highlighted when heparin was covalently bonded on the substrate, by contact with the blood drop.

Safety, healing, and efficacy of vascular prostheses coated with hydroxypropyl-ß-cyclodextrin polymer: experimental in vitro and animal studies.

OBJECTIVES: Polyester vascular prostheses (PVPs) coated with a polymer of hydroxypropyl-ß-cyclodextrin (HPßCD) have been designed to provide an in situ reservoir for the sustained delivery of one or more bioactive molecules. The goal of this study was to assess the efficacy, the safety and the healing properties of these prostheses. METHODS: Collagen-sealed PVPs were coated with the HPßCD-based-polymer (PVP-CD) using the pad-dry-cure textile finishing method and loaded with one or two antibiotics. Appropriate control and PVP-CD samples were tested in several in vitro and animal model conditions. The study end points included haemolysis, platelet aggregation, antibacterial efficacy, polymer biodegradation, acute toxicity and chronic tolerance. RESULTS: PVP-CD proved to be compatible with human blood, since it did not induce haemolysis nor influenced ADP-mediated platelet aggregation. Sustained antimicrobial efficacy was achieved up to 7 days against susceptible bacteria when PVP-CDs were loaded with the appropriate drugs. Analysis of harvested PVP-CD from the animal model revealed that the HPßCD-based coating was still present at 1 month but had completely disappeared 6 months after implantation. All grafts were patent, well encapsulated without healing abnormalities. Clinical data, blood-sample analysis and histological examination did not evidence any signs of acute or chronic, local or systemic toxicity in the animal models. CONCLUSION: PVP-CD was proved safe and demonstrated excellent biocompatibility, healing and degradation properties. Effective antimicrobial activity was achieved with PVP-CD in conditions consistent with a sustained-release mechanism.

Selective biological response of human pulmonary microvascular endothelial cells and human pulmonary artery smooth muscle cells on cold-plasma-modified polyester vascular prostheses.

The aim of this work was to improve the hemocompatibility and the selectivity according to cells of non-woven poly(ethylene terephthalate) (PET) membranes. Non-woven PET membranes were modified by a combined plasma-chemical process. The surface of these materials was pre-activated by cold-plasma treatment and poly(acrylic acid) (PAA) was grafted by the in situ free radical polymerization of acrylic acid (AA). The extent of this reaction and the number of carboxylic groups incorporated were evaluated by colorimetric titration using toluidine blue O. All samples were characterized by SEM, AFM and thermogravimetric analysis, and the mechanical properties of the PAA grafted sample were determined. A selective cell response was observed when human pulmonary artery smooth muscle cells (HPASMC) or human pulmonary micro vascular endothelial cells (HPMEC) were seeded on the modified surfaces. HPASMC proliferation decreased about 60%, while HPMEC proliferation was just reduced about 10%. PAA grafted samples did not present hemolytic activity and the platelet adhesion decreased about 28% on PAA grafted surfaces.

[Engineering a bone free flap for maxillofacial reconstruction: technical restrictions]. / Ingénierie d'un lambeau osseux vascularisé à destinée maxillofaciale : les limites techniques.

Vascularisation is a key for success in bone tissue engineering. Creating a functional vascular network is an important concern so as to ensure vitality in regenerated tissues. Many strategies were developed to achieve this goal. One of these is cellular growth technique by perfusion bioreactor chamber. These new technical requirements came along with improved media and chamber receptacles: bioreactors (chapter 2). Some bone tissue engineering processes already have clinical applications but for volumes limited by the lack of vascularisation. Resorbable or non-resorbable membranes are an example. They are used separately or in association with bone grafts and they protect the graft during the revascularization process. Potentiated osseous regeneration uses molecular or cellular adjuvants (BMPs and autologous stem cells) to improve osseous healing. Significant improvements were made: integration of specific sequences, which may guide and enhance cells differentiation in scaffold; nano- or micro-patterned cell containing scaffolds. Finally, some authors consider the patient body as an ideal bioreactor to induce vascularisation in large volumes of grafted tissues. "Endocultivation", i.e., cellular culture inside the human body was proven to be feasible and safe. The properties of regenerated bone in the long run remain to be assessed. The objective to reach remains the engineering of an "in vitro" osseous free flap without morbidity.

[Oro-maxillofacial bone tissue engineering combining biomaterials, stem cells, and gene therapy]. / Ingénierie du tissu osseux oro-maxillofacial par combinaison de biomatériaux, cellules souches, thérapie génique.

Improvements have been made in regenerative medicine, due to the development of tissue engineering and cellular therapy. Bone regeneration is an ambitious project, leading to many applications involving skull, maxillofacial, and orthopaedic surgery. Scaffolds, stem cells, and signals support bone tissue engineering. The scaffold physical and chemical properties promote cell invasion, guide their differentiation, and enable signal transmission. Scaffold may be inorganic or organic. Their conception was improved by the use of new techniques: self-assembled nanofibres, electrospinning, solution-phase separation, micropatterned hydrogels, bioprinting, and rapid prototyping. Cellular biology processes allow us to choose between embryonic stem cells or adult stem cells for regenerative medicine. Finally, communication between cells and their environment is essential; they use various signals to do so. The study of signals and their transmission led to the discovery and the use of Bone Morphogenetic Protein (BMP). The development of cellular therapy led to the emergence of a specific field: gene therapy. It relies on viral vectors, which include: retroviruses, adenoviruses and adeno-associated vectors (AAV). Non-viral vectors include plasmids and lipoplex. Some BMP genes have successfully been transfected. The ability to control transfected cells and the capacity to combine and transfect many genes involved in osseous healing will improve gene therapy.

Cyclodextrin and maltodextrin finishing of a polypropylene abdominal wall implant for the prolonged delivery of ciprofloxacin.

The aim of this work was to develop a polypropylene (PP) artificial abdominal wall implant for the prolonged release of ciprofloxacin (CFX). This sustained release effect was obtained by functionalization of the textile mesh with citric acid and hydroxypropyl-γ-cyclodextrin (HPγCD) or maltodextrin (MD). In both cases the textile finishing reaction yielded a cyclo- or malto-dextrin crosslinked polymer coating the fibers. The modified supports were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry and scanning electron microscopy. The sorption capacities and the kinetics of CFX release were studied by batch tests coupled with spectrophotometric assays. Microbiological assays were carried out on Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli, while proliferation and viability tests used fibroblasts. The main results were as follows. (i) Due to the differences between the range of temperature of thermal degradation of the (cyclo)dextrins polymers and of the PP fibers TGA was a reliable method for quantifying the degree of functionalization of the textiles. (ii) Both modified supports showed improved sorption/desorption capacities for CFX, compared with the virgin mesh. The HPγCD-finished support showed an increased sorption capacity and a lower release rate of CFX compared with the MD modified support. (iii) Microbiological assays confirmed the latter result, with greater sustained antibacterial activity of the HPγCD treated support. These experiments have demonstrated the role of the cyclodextrin cavity in interactions with CFX: the antibiotic was not only adsorbed via hydrogen and acid-base interactions with the polyCTR-HPγCD network, but also via host-guest complexation. (iv) Biological tests revealed a slight decrease in fibroblast proliferation after 6 days on the modified supports, but cell viability tests showed that this was not due to toxicity of the (cyclo)dextrin polymer coatings.

Methyl-ß-cyclodextrin modified vascular prosthesis: Influence of the modification level on the drug delivery properties in different media.

A textile polyester vascular graft was modified with methyl-ß-cyclodextrin (MeßCD) to obtain a new implant capable of releasing antibiotics directly in situ at the site of operation over a prolonged period and thereby prevent post-operative infections. We investigated the influence of the curing parameters (time and temperature) that allow control of the degree of functionalization (DF) of the support by MeßCD. The inclusion of ciprofloxacin (CFX) in the MeßCD cavity was observed in solution by two-dimensional (1)H NMR spectroscopy. The amount of CFX loaded on the modified graft increased with DF. Depending on the release medium (water, phosphate-buffered saline, or human plasma) and the DF of the prostheses, different kinetic profiles of release of CFX were obtained. The sustained release of CFX in human plasma was shown by microbiological assays that indicated prolonged antimicrobial activity against Staphylococcus aureus and Escherichia coli. Viability tests demonstrated the non-toxicity of MeßCD to an epithelial cell line (HPMEC), although a decrease in endothelial cell number was observed on the functionalized prosthesis, probably due to the roughness of the coating and also to the nature of the MeßCD polymer present on the surface of the fibers.

Bone implants modified with cyclodextrin: study of drug release in bulk fluid and into agarose gel.

The aim of this work was to better understand the importance of the type of experimental setup used to monitor antibiotic release from functionalized hydroxyapatite implants. Microporous hydroxyapatite discs were prepared by sintering and subsequently functionalized with hydroxypropyl-ß-cyclodextrin (HPßCD) polymer crosslinked with butanetetracarboxylic acid. On one hand, polymerization was performed within the implant after its impregnation with the monomers (CD-HA-M implant). On the other hand, a pre-synthesized HPßCD polymer was loaded and fixed onto the HA discs (CD-HA-P implant). Both types of implants were soaked with ciprofloxacin hydrochloride or vancomycin hydrochloride solution and dried at 37°C. The DSC study highlighted that the cyclodextrin polymer could interfere with both drugs, due to the carboxylic groups carried by the crosslinks. Drug release was measured into phosphate buffered saline pH 7.4 in agitated vials, or into agarose gels to more realistically mimic in vivo conditions. Importantly, in all cases, drug release into agarose gels was much slower than into well-agitated phosphate buffer. Non-functionalized discs displayed faster drug release because no complex could be formed and/or due to the absence of the HPßCD polymer network hindering drug diffusion within the implant pores. In the case of ciprofloxacin hydrochloride, drug release from the CD-HA-M implants was faster than drug release from the CD-HA-P implants due to the different polymer structures resulting in different complexation strengths, whereas in the case of vancomycin hydrochloride the release patterns were similar because vancomycin hydrochloride was not included into the cyclodextrin. The agarose gel method seems more biorelevant and discriminatory than the vial method for drug release measurements from bone implants.

Chemical, biological and microbiological evaluation of cyclodextrin finished polyamide inguinal meshes.

This study describes the use of cyclodextrins (CDs) as a finishing agent of polyamide (PA) fibers used in order to obtain inguinal meshes with improved antibiotic delivery properties. The finishing process involved polymerization between citric acid and CDs, which yielded a cross-linked polymer that physically adhered to the surface of PA fibers. This permanent functionalization was characterized by evaluating the damping property with a polar liquid (glycerol) via the drop contact angle method for various rates of modification of the fabrics. The biological and microbiological effects of the PA, which were functionalized with hydroxypropylated derivate of gamma-CD (HP-gamma-CDs) and charged with ciprofloxacin (CFX), were evaluated by cell culture assays. We observed a good adhesion and proliferation of fibroblastic cells (NIH3T3) after 3 and 6 days and no detectable toxicity of the modified substrate. The in vitro antibacterial activity of the HP-gamma-CD grafted PA fabrics charged with CFX against the bacteria Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli was greatly superior to that of the virgin sample within a 24h batch experiment in human blood plasma medium. In conclusion, these results from our study offer an insight into the efficient performance of CDs as drug delivery systems for multiple applications in the fields of biomaterials and medical textiles.

Biological behaviour of an endothelial cell line (HPMEC) on vascular prostheses grafted with hydroxypropylgamma-cyclodextrine (HPgamma-CD) and hydroxypropylbeta-cyclodextrine (HPbeta-CD).

The cytocompatibility of cyclodextrins (CDs) grafting on vascular polyester (PET) prostheses for further loading with biomolecules was investigated in this study. Viability tests demonstrated no toxicity of HP-CDs and PolyHP-CDs at 4,000 mg/l with survival rates of 80 to 96%. Proliferation tests using the human pulmonary microvascular endothelial cell line (HPMEC-ST1) revealed an excellent biocompatibility for Melinex (Film form of PET). For Polythese and Polymaille, a good proliferation rate was observed at 3 days (60-80%) but decreased at 6 days (56-73%). For all CD-grafted samples, low proliferation rates were observed after 6 days (35-38%). Vitality tests revealed excellent functional capacities of HPMEC cells after 3 and 6 days for all samples. Adhesion kinetics tests showed a similar adhesion of HPMEC cells on control and Melinex. A low adhesion was observed on Polythese and especially on Polymaille compared to control. After CD grafting, the cell adhesion was decreased. The woven or knitted architecture and CD grafting were the most likely causes of this weak adhesion. The adhesion kinetic test was confirmed by SEM observations and immunocytochemistry. The low proliferation of HPMEC on virgin prostheses and especially on grafted prostheses was not due to a cytotoxic effect, but to the physical surface characteristics of the prostheses.

Antibacterial activation of hydroxyapatite (HA) with controlled porosity by different antibiotics.

In order to prevent the increasing frequency of per-operative infections, bioceramics can be loaded with anti-bacterial agents, which will release with respect to their chemical characteristics. A novel hydroxyapatite (HA) was elaborated with specific internal porosities for using as a bone-bioactive antibiotic (ATB) carrier material. UV spectrophotometry and bacteria inhibition tests were performed for testing the ATB adsorption and the microbiological effectiveness after loading with different antibiotics. The impregnation time, ATB impregnating concentration, impregnation condition and other factors, which might influence the ATB loading effect, were studied by exposure to different releasing solvents and different pathogenic bacteria: Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli. It clearly showed that the facility of ATB loading on this porous HA is even possible just under simple non-vacuum impregnation conditions in a not-so-long impregnating interval. The results also showed that, for all three types of ATB (vancomycin, ciprofloxacin and gentamicin), adsorbed amount on the micro-porous HA were hugely higher than that on dense HA. The micro-porosity of test HA had also significantly prolonged the release time of antibiotics even under mimic physiological conditions. Furthermore, it also has primarily proved by a pilot test that the antibacterial efficiency of crude micro-porous HA could be further significantly improved by other methods of functionalization such as cold plasma technique.

Functionalization of PVDF membranes with carbohydrate derivates for the controlled delivery of chlorhexidin.

Maltodextrin (MX) was fixed onto PVDF membranes in order to create a drug delivery Guided Tissue Regeneration (GTR) device with controlled drug delivery properties. PVDF microporous membranes were treated by a mixture of MX and citric acid, resulting to an 18 wt% increase of the supports. MX grafted membrane could capture 103 mg/g chlorhexidin digluconate (DigCHX) instead of 1mg/g for a virgin membrane. A neutralization step was performed before the biological tests. Viability tests confirmed the non-toxicity of the MX polymer coating after neutralisation. In vitro release test in human plasma, and microbiological tests showed that membranes grafted with MX were more performing compared to virgin and beta-CD grafted membranes. The antimicrobial activity was effective during more than 72 h.

Biological and physico-chemical assessment of hydroxyapatite (HA) with different porosity.

HA with specific internal porosities was loaded with different antibiotics (ATBs) and then tested on its microbiological effectiveness. The HA purity was controlled with X-ray diffraction, IR and Raman spectrometry. Varying the sintering temperature and/or adding graphite and PMMA as porogenous agents lead to obtained micro- and meso-porosities. The biological tests concerned cell viability, proliferation and morphology (SEM), and the cytochemical staining of actin and vinculin. The micro- and meso-porous HA samples had an internal pore size of 1-10 microm and 10-50 microm, respectively. X-ray diffraction and FTIR confirmed the high purity of the HA. The cell viability tests with L132 cells confirmed the excellent cytocompatibility of HA, the graphite powder and the ATB vancomycine. Proliferation rate was assessed with MC3T3-E1 osteoblasts. All HA samples produced a higher proliferation than the controls; the micro-porous HA inducing the highest cell growth. The ATB impregnated HA also stimulated cell proliferation but in lower extend. Cytochemical staining of osteoblasts revealed a well-developed cytoskeleton with strong stress fibres. Labelling of the focal adhesion contacts with anti-vinculin showed a less developed adhesion process in the cells on the different HA substrates. It was possible to realize a highly pure hydroxyapatite with different but controlled porosities by varying the sintering temperature and/or addition of a porogenous agents. This purity and the micro-porosity stimulate significantly cell growth.

Vascular prostheses with controlled release of antibiotics Part 2. In vitro biological evaluation of vascular prostheses treated by cyclodextrins.

Viability tests by the colony forming method show no toxicity for all CDs (beta-CD, gamma-CD, HPbeta-CD and HPgamma-CD) and their associated polymer. A survival rate of 100% is observed for all CDs at high concentration 400 ppm. Proliferation tests revealed a low proliferation of L132 cells on grafted vascular prostheses and untreated prostheses and good proliferation on Melinex (film form of PET). A proliferation of 17% is observed after 3 days of incubation and decrease at 4% after 6 days on prostheses. Melinex exhibits a proliferation rate as the controls. Vitality tests confirm proliferation tests and show a good vitality of cells even for low cell amounts. From these experiments it becomes obvious that the decreasing proliferation rate is not a cytotoxic effect but is due to the chemical and/or physical surface characteristics. A similar result is obtained for cell adhesion kinetics between grafted vascular prostheses and control. After 2 h adhesion, a lower adhesion is observed on untreated prostheses. Theses results were confirmed by immunochemistry and morphology tests. This cell adhesion inhibiting effect of the PET prostheses contributes to a better "survival" of vascular prostheses without secondary obstruction or stenosis.