Surface modification of polymeric biomaterials: Utilization of cyclodextrins for blood compatibility improvement

Fluorination of PVC medical devices to prevent plasticizers migration

Medical devices (MD) are often made of plasticized polyvinylchloride (PVC). However, plasticizers may leach out into infused solutions and expose the patients to a toxic risk. The aim of the present work is to fluorinate plasticized PVC tubular MDs to create a barrier layer on their internal surface, and to study the impact of such a chemical treatment on the migration of the plasticizers. Following fluorination by pure molecular fluorine, the physico-chemical characterization of these modified MDs was carried out using various spectroscopic and microscopic techniques or tensile tests, evidencing the formation of covalent C-F bonds on the surface of the treated samples without modification of their mechanical and optical properties. The migration of plasticizers from fluorinated MDs was assessed using gas chromatography coupled with mass spectrometry and was found considerably decreased in comparison with the pristine MDs. After 24 h, the amount of tri-octyltrimellitate plasticizer (TOTM) detected in migrates from fluorinated MDs was even lower than the limit of quantification. Complementary cytotoxicity assays were performed according to the ISO EN 10993-5 standard, showing that the new fluorinated material does not cause a cytotoxic effect on L929 cells.

Chemically cross-linked and grafted cyclodextrin hydrogels: from nanostructures to drug-eluting medical devices

The unique ability of cyclodextrins (CDs) to form inclusion complexes can be transmitted to polymeric networks in which CDs are chemically grafted or cross-linked. Combination of CDs and hydrogels in a single material leads to synergic properties: the hydrophilic network enhances biocompatibility and prevents dilution in the physiological medium increasing the stability of the inclusion complexes, while CDs finely tune the mechanical features and the stimuli-responsiveness and provide affinity-based regulation of drug loading and release. Therefore, CD-functionalized materials are opening new perspectives in pharmacotherapy, emerging as advanced delivery systems (DDS) for hydrophobic and hydrophilic drugs to be administered via almost any route. Medical devices (catheters, prosthesis, vascular grafts, bone implants) can also benefit from surface grafting or thermofixation of CDs. The present review focuses on the approaches tested to synthesize nano- to macro-size covalently cross-linked CD networks: i) direct cross-linking through condensation with di- or multifunctional reagents, ii) copolymerization of CD derivatives with acrylic/vinyl monomers, and iii) grafting of CDs to preformed medical devices. Examples of the advantages of having the CDs chemically bound among themselves and to substrates are provided and their applicability in therapeutics discussed.

The effect of betacyclodextrin and hydroxypropyl betacyclodextrin incorporation into plasticized poly(vinyl chloride) on its compatibility with human U937 cells

Di (2-ethyl hexyl) phthalate (DEHP) is one of the main plasticizers used in poly(vinyl chloride) (PVC) medical devices and is currently the only one listed for use in the European Pharmacopoeia Monograph. It leaches out of PVC when the material is in contact with lipophilic media, for example, blood and certain nutritional feeds. Consequently, concerns have been expressed since in certain animal species, DEHP has been shown to exhibit both carcinogenic and reproductive toxic effects. Incorporation of beta cyclodextrin (BCD) and hydroxypropyl betacyclodectrin (HPBCD) into plasticized materials has been reported to decrease the leaching of DEHP. We have investigated whether this results in improved in vitro biocompatibility by measuring the responses of U937 cells to plasticized PVC in the presence and absence of added BCD or HPBCD. Growth and viability of the U937 cells, as well as tumor necrosis factor-α (TNF-α) production in contact with these materials revealed no significant difference between unmodified plasticized PVC materials and those containing BCD or HPBCD. Lipopolysaccharide (LPS) was used to elicit TNF-α production, and the response of cells to LPS in the presence of the PVC materials was evaluated. When PVC was modified by addition of HPBCD there was a significant reduction in the TNF-α production in response to LPS. Modification of plasticized PVC biomaterials by adding cyclodextrins did not significantly improve their biocompatibility. However, the HPBCD modified plasticized PVC materials caused a reduction in the production in TNF-α induced by LPS which may have implications for the inflammatory potential of these biomaterials.

Functionalization of acrylic hydrogels with alpha-, beta- or gamma-cyclodextrin modulates protein adsorption and antifungal delivery

Poly(hydroxyethyl methacrylate) (pHEMA) hydrogels were functionalized with pendant alpha-, beta- and gamma-cyclodextrins (CD) with the aim of improving the biocompatibility and increasing the ability to host drug molecules. Pendant alpha-, beta- and gamma-CDs did not affect swelling of the hydrogels but slightly decreased the water contact angle. Protein deposition was notably dependent on the nature of the CD, due to their different affinities for hydrophobic moieties of proteins. Lysozyme and albumin sorption was hindered by gamma-CD. Functionalization with beta-CD also reduced protein sorption, although less so, while alpha-CD decreased lysozyme deposition but enhanced albumin sorption compared with control pHEMA hydrogels. Loading of the hydrogels with miconazole was carried out by immersion in drug suspension followed by autoclaving. Functionalization with gamma-CD doubled the affinity of the network for the drug and resulted in the highest amount loaded (up to 170 mgg(-1)). Sustained delivery was observed for several days. Some miconazole-loaded hydrogels completely prevented Candida albicans biofilm formation as assayed in an in vitro microbiological test.

Development of PMMA membranes functionalized with hydroxypropyl-beta-cyclodextrins for controlled drug delivery using a supercritical CO(2)-assisted technology

Cyclodextrin-containing polymers have proved themselves to be useful for controlled release. Herein we describe the preparation of membranes of poly(methylmethacrylate) (PMMA) containing hydroxypropyl-beta-cyclodextrins (HP-beta-CDs) using a supercritical CO(2)-assisted phase inversion method, for potential application as drug delivery devices. Results are reported on the membrane preparation, physical properties, and drug elution profile of a model drug. The polymeric membranes were obtained with HP-beta-CD contents ranging from 0 to 33.4 wt%, by changing the composition of the casting solution, and were further impregnated with ibuprofen using supercritical carbon dioxide (scCO(2)) in batch mode. The influence of the membrane functionalization in the controlled release of ibuprofen was studied by performing in vitro experiments in buffer solution pH at 7.4. The release of the anti-inflammatory drug could be tuned by varying the cyclodextrin content on the membranes.