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.

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.

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.

Vascular prostheses with controlled release of antibiotics Part 1: Surface modification with cyclodextrins of PET prostheses.

Vascular prostheses were functionalised with the aim to obtain a slow release of antibiotics in order to reduce postoperative infections. The original process that we present in this paper is based on the use of a family of cage molecules named cyclodextrins (CD). These compounds have the ability to form reversible inclusion complexes with drugs such as antibiotics. The aim of this work was to graft CD onto the prosthesis, so that an antibiotic can be bound on it by this inclusion phenomenon, and then be progressively released over a prolonged period by a complex dissociation mechanism. This paper presents the first part of this research program and concerns mainly the study of the functionalization parameters. It presents surface characterization results of the modified prostheses. The PET prostheses were immersed into a solution containing a cross linking agent, cyclodextrins (beta-CD, gamma-CD, HP-beta-CD and HP-gamma-CD) and a catalyst and were padded. Grafting occurred by the mean of a thermofixation step at a temperature comprised between 140 and 180 degrees C. It was observed that the support was permanently modified when the CD polymer that coated the fibres resisted to the final washing process. Grafting rates of 12 wt% in CD polymer could be reached. It was also observed that the fibre coating reaction induced an increase of the permeability of the grafts.

Improved drug delivery properties of PVDF membranes functionalized with beta-cyclodextrin--application to guided tissue regeneration in periodontology.

The purpose of this study was to develop a membrane for guided tissue regeneration applicable in periodontology that could release antimicrobial agent during the healing period. Our strategy consisted to graft beta-cyclodextrin (beta-CD), a molecule that is known to form inclusion complexes with a large variety of drugs, onto PVDF membranes. Grafting occurred by using citric acid that provoked a crosslinking reaction of beta-CD, and the resulting polymer was imprisoned into the porous structure of the PVDF membrane. The reaction produced a weight increase of the membrane, the range of which depended on the temperature and on the time of curing applied in the process. The biological behavior of the membranes evaluated by proliferation and vitality tests showed good proliferation and improved activity of L132 epithelial cells on the raw and on the grafted membranes. Doxycyclin (DOX) and chlorhexidine (CHX) were used as antimicrobial agents. Their inclusion into the beta-CD cavity in aqueous solutions was confirmed by NMR spectroscopy. After the impregnation of the membranes with DOX and CHX, their release was studied in vitro in batch type experiments and measured by UV spectrophotometry. Low amounts of DOX and CHX were delivered from the raw membranes within the first few hours of tests. Grafted membranes, however, delivered DOX and CHX in larger quantities within 24 h and 10 days respectively.

Vascular PET prostheses surface modification with cyclodextrin coating: development of a new drug delivery system.

PURPOSE: Cyclodextrins (CDs) are torus shaped cyclic oligosaccharides with a hydrophobic internal cavity and a hydrophilic external surface. We performed and analysed an antibiotic binding on Dacron (polyethyleneterephtalate, PET) vascular grafts, previously coated with CDs based polymers. METHODS: The CDs coating process was based on the pad-dry-cure method patented in our laboratory. The Dacron prostheses were immersed into a solution containing a polycarboxylic acid, a cyclodextrin and a catalyst, and placed into a thermofixation oven before impregnation with an antibiotic solution (Vancomycin). Biocompatibility tests were performed with L132 human epithelial cells. The antibiotic release in an aqueous medium was assessed by batch type experiments using UV spectroscopy. RESULTS: Viability tests confirmed that the CDs polymers coating the Dacron fibers were not toxic towards L132 cell. Cell proliferation was similar on coated and uncoated grafts. A linear release of Vancomycin was observed over 50 days. CONCLUSION: Our results demonstrate the feasibility of coating CDs onto vascular Dacron grafts. Biological tests show no toxicity of the different cyclodextrins coated. A linear release of antibiotics was depicted over 50 days, demonstrating that cyclodextrin grafting was an efficient drug delivery system.

Uptake of heavy metals from synthetic aqueous solutions using modified PEI-silica gels.

The decontamination of synthetic Pb(II), Zn(II), Cd(II), Ni(II) solutions was investigated, using silica gels chemically modified with poly(ethyleneimine) (PEI) as sorbents. Two families of sorbents, i.e. silica/PEI and crosslinked silica/PEI, were prepared and characterized. Then the removal of metal ions from synthetic aqueous solutions was studied by static tests. They revealed that the sorption capacities depend on the pH, the initial concentration and to some extent on the nature of the metal. The recovery of the metal cations from the saturated sorbents was possible with diluted acid, only for the crosslinked supports. In this case, the regeneration and reuse without sorption decrease, was demonstrated. The presence of other cations (as Na(+), Ca(2+)) and metals does not affect the sorption capacities.

Allylamine-beta-cyclodextrin copolymer. A novel chiral selector for capillary electrophoresis.

A novel, positively charged, copolymer of allylamine and 2-hydroxy-3-methacryloyl-beta-cyclodextrin was synthesized to be used as a chiral selector in capillary electrophoresis. In the copolymer, cyclodextrin molecules are spaced from the backbone though a spacer arm which prevents sterical hindrance of the CD cavity. The self-mobility of the CD polymer in its charged form, opposite to the analytes, is the cause for the enhanced separation factor provided by this selector. Moreover, the positive charged polymer induces a reversal of electroosmotic flow which is beneficial in enantioseparations of acidic compounds as it reduces analysis time and increases peak efficiency. The ability of this copolymer to act as a CE chiral selector in the separation of 2,4-dinitrophenylamino acid enantiomers was investigated in coated and uncoated capillaries and its performance was much better then that of native beta-cyclodextrin.

Vinylpyrrolidine-beta-cyclodextrin copolymer: a novel chiral selector for capillary electrophoresis.

The synthesis and characterization of a novel polymer consisting of an alkyl backbone and pendant beta-cyclodextrin units, obtained by radical copolymerization of vinylpyrrolidone and methacryloyl-beta-cyclodextrin (PVP-beta-CD), was reported. The ability of this copolymer to act as a capillary electrophoresis (CE) chiral selector was investigated in the separation of a mixture of basic drugs. The influence of polymeric cyclodextrin concentration, temperature, and pH on the separation of the test analytes was assessed and the advantage of using the polymeric selector over native beta-cyclodextrin was demonstrated.

Molecular Conformation and Mobility of Polyamines Adsorbed on Silica Studied by Spin Labeling.

Poly(ethyleneimine) and poly(4-vinylpyridine) chains adsorbed on Nucleosil silica have been randomly labeled with nitroxide free radicals. The EPR signal is very sensitive to the molecular Brownian motion of the segments and shows generally at least two different environments: trains adsorbed on the surface with a restricted mobility, and loops and tails protruding into the solution with a fast motion. The rotational correlation times and the relative fraction of each population are given as functions of the coverage achieved and of the specific surface area of the silica for the samples in contact with methanol and sometimes water. The overall picture is consistent with a diffuse layer for the PEI and a more compact one with some heterogeneities for the P4VP. Copyright 1999 Academic Press.

Solid state NMR spectroscopy study of molecular motion in cyclomaltoheptaose (beta-cyclodextrin) crosslinked with epichlorohydrin.

Dry and hydrated insoluble cyclomaltoheptaose (beta-cyclodextrin, beta-CD) polymers have been investigated by solid state 13C NMR spectroscopy techniques such as cross polarization/magic angle spinning with dipolar decoupling (CP/MAS), magic angle spinning both with (DD-MAS) and without (MAS) dipolar decoupling and CP/MAS dipolar dephasing (dd-CP/MAS) to allow the assignment of the main 13C signals. In the solid state, the presence of water in the samples resulted in a better resolution reflecting increased mobility. Two distinct components (crosslinked beta-CD and polymerized epichlorohydrin) have been found. The molecular mobility of these two components has been analyzed in terms of relaxation parameters such as 13C spin lattice relaxation (T1) and 1H spin lattice relaxation in the rotating frame (T1 rho). The T1 values of the polymers show that the beta-CD trapped inside the polymers does not seem to undergo changes in its mobility whatever the amount of epichlorohydrin. The addition of water to beta-CD significantly increases the T1 values reflecting strong interaction between beta-CD and the solvent. The T1P values obtained reflect the homogeneous nature of the materials.

HPLC of structural isomers with cyclodextrin-poly(vinylamine)-coated silica columns, Part I: Synthesis and characterization of cyclodextrin-bonded stationary phases by NMR solid state.

Different supports for high-performance liquid chromatography are prepared by using the coating technology. These supports are based on silica beads coated with a beta-cyclodextrin-containing poly(vinylamine). Surface area, pore size distribution, and solid-state nuclear magnetic resonance are used for the characterization of these supports. The two different methods of preparation used lead to different arrangements of the polymer layers; hence, the supports have different mobility, rigidity, and accessibility of the cyclodextrin ring.

Preferential and absolute adsorption to poly[N5-(3-hydroxypropyl)-L-glutamine] in water/2-chloroethanol solvent mixtures.

Preferential adsorption to poly[N5-(3-hydroxypropyl)-L-glutamine] (PHPG) in water/2-chloroethanol solvent mixtures has been determined by measuring density increments at constant concentration and at constant chemical potential. At low alcohol concentrations, decreasing preferential adsorption of 2-chloroethanol is observed. When the organic solvent content is increased, an inversion of preferential adsorption occurs, water being preferentially adsorbed. The inversion zone parallels the conformational transition curve. As an explanation it is proposed that a competition occurs between noninteracting helicogenic 2-chloroethanol, which stabilizes hydrophobic interactions, and the hydrophilic interactions of water with PHPG. The former retains a helical structure, whereas the latter induces a helix-to-coil transition.