In vitro cytotoxic effects of secondary metabolites of DEHP and its alternative plasticizers DINCH and DINP on a L929 cell line.

BACKGROUND: Phthalic acid esters are widely used to improve the plasticity of PVC in medical devices (MD). The most famous plasticizer is DEHP, whose use in medical devices has been contested by the European authorities since 2008. Several alternative plasticizers are being considered to replace DEHP, such as DEHT, TOTM, DINP or DINCH, but they are also released from the PVC throughout their life cycle and are metabolized in the same way as DEHP. OBJECTIVES: Our study focuses on the in vitro cytotoxicity of two alternative plasticizers (DINCH and DINP) contained in certain medical devices. They are likely to migrate and be transformed in vivo into the primary and secondary metabolites by a metabolism similar to that of DEHP. This preliminary study is the first to assess the in vitro cytotoxicity of oxidized metabolites of DINCH and DINP based on the EN ISO 10-993-5 standards documents. METHODS: We have studied the complete multi-step organic synthesis of secondary metabolites of DINP and DINCH and have performed cytotoxicity tests on L929 murine cells according to the EN ISO 10993-5 standard design for the biocompatibility of a MD. The tested concentrations of obtained metabolites (0.01, 0.05 and 0.1 mg/mL) covered the range likely to be found for DEHP (total metabolism) in biological fluids coming into direct contact with the MD. The concentrations tested in our study were chosen based on a complete transformation of the plasticizers released after direct contact between a MD and the patient's blood. RESULTS: Only 7-oxo-MMeOCH is cytotoxic at the highest concentration (0.1 mg/mL) after 7 days of exposure, just like 5-oxo-MEHP for the same concentration. By contrast, 7-OH-MMeOP, 7-cx-MMeOP, 7-oxo-MMeOP, 7-OH-MMeOCH and 7-cx-MMeOCH were not found to be cytotoxic. CONCLUSION: The known concentrations of these secondary metabolites in urinary samples are in the µg/L range, i.e. about 100-1000 times lower than the concentrations tested in this study. Cytotoxicity is known to be dose-dependent but it is not always the case for endocrine perturbations and the secondary metabolites could induce endocrine perturbations at very low doses.

Application of Millifluidics to Encapsulate and Support Viable Human Mesenchymal Stem Cells in a Polysaccharide Hydrogel.

Human adipose-derived stromal cells (hASCs) are widely known for their immunomodulatory and anti-inflammatory properties. This study proposes a method to protect cells during and after their injection by encapsulation in a hydrogel using a droplet millifluidics technique. A biocompatible, self-hardening biomaterial composed of silanized-hydroxypropylmethylcellulose (Si-HPMC) hydrogel was used and dispersed in an oil continuous phase. Spherical particles with a mean diameter of 200 µm could be obtained in a reproducible manner. The viability of the encapsulated hASCs in the Si-HPMC particles was 70% after 14 days in vitro, confirming that the Si-HPMC particles supported the diffusion of nutrients, vitamins, and glucose essential for survival of the encapsulated hASCs. The combination of droplet millifluidics and biomaterials is therefore a very promising method for the development of new cellular microenvironments, with the potential for applications in biomedical engineering.

Patients' exposure to PVC plasticizers from ECMO circuits.

BACKGROUND: ECMO is a therapeutic act with a high risk of exposure to diethylhexylphthalate (DEHP), plasticizer from PVC tubings. The replacement of this plasticizer with alternative compounds is recommended but the risks associated with the use of new plasticizers have not been evaluated in ECMO situations. METHODS: Ex vivo ECMO models were performed with different flow rates over 6 days to evaluate the migration of plasticizers and their potential toxic risk for patient. The release of plasticizers during ECMO was measured and compared to reference value (derived no effect level, DNEL) and to cytotoxic concentration carried out with MTT test. RESULTS: Trioctyltrimellitate (TOTM), main plasticizer present in circuit (44% w/w), is weakly released during ECMO. Concentrations are not cytotoxic and exposure doses are lower than DNEL. In contrast, DEHP doses are higher than the DNEL despite a lower presence of DEHP in the circuit (0.2%). We have shown that DEHP is not coming from the circuit but from the priming bag. Replacing this bag with a multilayer one avoids the exposure to DEHP. CONCLUSION: Our study shows that circuits made of PVC plasticized with TOTM against DEHP improves the safety of ECMO.

Polysaccharide Hydrogels Support the Long-Term Viability of Encapsulated Human Mesenchymal Stem Cells and Their Ability to Secrete Immunomodulatory Factors.

While therapeutically interesting, the injection of MSCs suffers major limitations including cell death upon injection and a massive leakage outside the injection site. We proposed to entrap MSCs within spherical particles derived from alginate, as a control, or from silanized hydroxypropyl methylcellulose (Si-HPMC). We developed water in an oil dispersion method to produce small Si-HPMC particles with an average size of about 68 µm. We evidenced a faster diffusion of fluorescein isothiocyanate-dextran in Si-HPMC particles than in alginate ones. Human adipose-derived MSCs (hASC) were encapsulated either in alginate or in Si-HPMC, and the cellularized particles were cultured for up to 1 month. Both alginate and Si-HPMC particles supported cell survival, and the average number of encapsulated hASC per alginate and Si-HPMC particle (7102 and 5100, resp.) did not significantly change. The stimulation of encapsulated hASC with proinflammatory cytokines resulted in the production of IDO, PGE2, and HGF whose concentration was always higher when cells were encapsulated in Si-HPMC particles than in alginate ones. We have demonstrated that Si-HPMC and alginate particles support hASC viability and the maintenance of their ability to secrete therapeutic factors.

In vitro cytotoxic effects of DEHP-alternative plasticizers and their primary metabolites on a L929 cell line.

Phthalic acid esters have been widely used to improve the plasticity of PVC medical devices. They carry a high exposure risk for both humans and the environment in clinical situations. Our study focuses on the cytotoxicity of alternative plasticizers. Postulated primary metabolites were synthesized, not being commercially available. Cytotoxicity assays were performed on L929 murine cells according to the ISO-EN 10993-5 standard design for the biocompatibility of medical devices. The tested concentrations of plasticizers (0.01, 0.05 and 0.1 mg/ml) covered the range likely to be found in biological fluids coming into direct contact with the medical devices. DEHP, DINP and DINCH were cytotoxic at the highest concentration (0.1 mg/ml) for 7 days of exposure. Their corresponding metabolites were found to be more cytotoxic, for the same concentration. By contrast, TOTM and its corresponding metabolite MOTM were not found to be cytotoxic. DEHA showed no cytotoxicity, but its corresponding monoester (MEHA) produced a cytotoxic effect at 0.05 mg/ml. In clinical situations, medical devices can release plasticizers, which can come into contact with patients. In vivo, the plasticizers are quickly transformed into primary metabolites. It is therefore important to measure the effects of both the plasticizers and their corresponding metabolites. Standard first-line cytotoxicity assays should be performed to ensure biocompatibility.