Hyaluronan-based hydrogel delivering glucose to mesenchymal stem cells intended to treat osteoarthritis.

Mesenchymal stem cell (MSC) therapy shows promise in regenerative medicine. For osteoarthritis (OA), MSCs delivered to the joint have a temporal window in which they can secrete growth factors and extracellular matrix molecules, contributing to cartilage regeneration and cell proliferation. However, upon injection in the non-vascularized joint, MSCs lacking energy supply, starve and die too quickly to efficiently deliver enough of these factors. To feed injected MSCs, we developed a hyaluronic acid (HA) derivative, where glucose is covalently bound to hyaluronic acid. To achieve this, the glucose moiety in 4-aminophenyl-ß-D-glucopyranoside was linked to the HA backbone through amidation. The hydrogel was able to deliver glucose in a controlled manner using a trigger system based on hydrolysis catalyzed by endogenous ß-glucosidase. This led to glucose release from the hyaluronic acid backbone inside the cell. Indeed, our hydrogel proved to rescue starvation and cell mortality in a glucose-free medium. Our approach of adding a nutrient to the polymer backbone in hydrogels opens new avenues to deliver stem cells in poorly vascularized, nutrient-deficient environments, such as osteoarthritic joints, and for other regenerative therapies.

Hypoxic glioblastoma-cell-derived extracellular vesicles impair cGAS-STING activity in macrophages.

BACKGROUND: Solid tumors such as glioblastoma (GBM) exhibit hypoxic zones that are associated with poor prognosis and immunosuppression through multiple cell intrinsic mechanisms. However, release of extracellular vesicles (EVs) has the potential to transmit molecular cargos between cells. If hypoxic cancer cells use EVs to suppress functions of macrophages under adequate oxygenation, this could be an important underlying mechanism contributing to the immunosuppressive and immunologically cold tumor microenvironment of tumors such as GBM. METHODS: EVs were isolated by differential ultracentrifugation from GBM cell culture supernatant. EVs were thoroughly characterized by transmission and cryo-electron microscopy, nanoparticle tracking analysis (NTA), and EV marker expression by Western blot and fluorescent NTA. EV uptake by macrophage cells was observed using confocal microscopy. The transfer of miR-25/93 as an EV cargo to macrophages was confirmed by miRNA real-time qPCR. The impact of miR-25/93 on the polarization of recipient macrophages was shown by transcriptional analysis, cytokine secretion and functional assays using co-cultured T cells. RESULTS: We show that indirect effects of hypoxia can have immunosuppressive consequences through an EV and microRNA dependent mechanism active in both murine and human tumor and immune cells. Hypoxia enhanced EV release from GBM cells and upregulated expression of miR-25/93 both in cells and in EV cargos. Hypoxic GBM-derived EVs were taken up by macrophages and the miR-25/93 cargo was transferred, leading to impaired cGAS-STING pathway activation revealed by reduced type I IFN expression and secretion by macrophages. The EV-treated macrophages downregulated expression of M1 polarization-associated genes Cxcl9, Cxcl10 and Il12b, and had reduced capacity to attract activated T cells and to reactivate them to release IFN-γ, key components of an efficacious anti-tumor immune response. CONCLUSIONS: Our findings suggest a mechanism by which immunosuppressive consequences of hypoxia mediated via miRNA-25/93 can be exported from hypoxic GBM cells to normoxic macrophages via EVs, thereby contributing to more widespread T-cell mediated immunosuppression in the tumor microenvironment.

Explosomes: A new modality for DEB-TACE local delivery of sorafenib: In vivo proof of sustained release.

The current medical practice in treating Hepatocellular carcinoma (HCC) using Drug Eluting Transarterial chemoembolization (DEB-TACE) technique is limited only to hydrophilic ionizable drugs, that can be attached ionically to the oppositely charged beads. This limitation has forced physicians to subscribe the more hydrophobic, first treatment option drugs, like sorafenib systemically via the oral route, thus flooding the patient system with a very powerful, non-specific, multiple-receptor tyrosine kinase inhibitor that is associated with notorious side effects. In this paper, a new modality is introduced, where highly charged, drug loaded liposomes are added to oppositely charged DEBs in a manner causing them to "explode" and the drug is eventually attached to the beads in the lipid patches covering their surfaces; therefore we call them "Explosomes". After fully describing the preparation process and in vitro characterization, this manuscript delves into an in vivo pharmacokinetic study over 50 New Zealand rabbits, where explosomal loading is challenged vs oral as well as current practice of emulsifying sorafenib in lipiodol. Over 14 days of follow up, and compared to other groups, explosomal loading of SRF on embolic beads proved to cause a slower release pattern with longer Tmax, lower Cmax and less washout to general circulation in healthy animals. This treatment modality opens a new untapped door for local sustained delivery of hydrophobic drugs in catheterized organs.

Bioadhesive Perivascular Microparticle-Gel Drug Delivery System for Intimal Hyperplasia Prevention: In Vitro Evaluation and Preliminary Biocompatibility Assessment.

Intimal hyperplasia (IH) is an undesirable pathology occurring after peripheral or coronary bypass surgery. It involves the proliferation and migration of vascular smooth muscle cells, leading to a reduction in the diameter of the vascular lumen, which can lead to stenosis and graft failure. Topically applied atorvastatin (ATV) has been shown to slow down this process. To be effective, the drug delivery system should remain at the perivascular site for 5-8 weeks, corresponding to the progression of IH, and be capable of releasing an initial dose of the drug followed by a sustained release. Ideally, bioadhesion would anchor the gel to the application site. To meet these needs, we encapsulated ATV in a 2-component system: a hyaluronic acid-dopamine bioadhesive gel for rapid release and biodegradable microparticles for sustained release. The system was characterized by scanning electron microscopy, rheology, bioadhesion on porcine arteries, and a release profile. The rheological properties were adequate for perivascular application, and we demonstrated superior bioadhesion and cohesion compared to the control HA formulations. The release profile showed a burst, generated by free ATV, followed by sustained release over 8 weeks. A preliminary evaluation of subcutaneous biocompatibility in rats showed good tolerance of the gel. These results offer new perspectives on the perivascular application towards an effective solution for the prevention of IH.

Synthesis, Formulation and Characterization of Immunotherapeutic Glycosylated Dendrimer/cGAMP Complexes for CD206 Targeted Delivery to M2 Macrophages in Cold Tumors.

Anti-tumor responses can be achieved via the stimulation of the immune system, a therapeutic approach called cancer immunotherapy. Many solid tumor types are characterized by the presence of immune-suppressive tumor-associated macrophage (TAMs) cells within the tumor microenvironment (TME). Moreover, TAM infiltration is strongly associated with poor survival in solid cancer patients and hence a low responsiveness to cancer immunotherapy. Therefore, 2'3' Cyclic GMP-AMP (2'3' cGAMP) was employed for its ability to shift macrophages from pro-tumoral M2-like macrophages (TAM) to anti-tumoral M1. However, cGAMP transfection within macrophages is limited by the molecule's negative charge, poor stability and lack of targeting. To circumvent these barriers, we designed nanocarriers based on poly(amidoamine) dendrimers (PAMAM) grafted with D-glucuronic acid (Glu) for M2 mannose-mediated endocytosis. Two carriers were synthesized based on different dendrimers and complexed with cGAMP at different ratios. Orthogonal techniques were employed for synthesis (NMR, ninhydrin, and gravimetry), size (DLS, NTA, and AF4-DLS), charge (DLS and NTA), complexation (HPLC-UV and AF4-UV) and biocompatibility and toxicity (primary cells and hen egg chorioallantoic membrane model) evaluations in order to evaluate the best cGAMP carrier. The best formulation was selected for its low toxicity, biocompatibility, monodispersed distribution, affinity towards CD206 and ability to increase M1 (STAT1 and NOS2) and decrease M2 marker (MRC1) expression in macrophages.

Combination of mesenchymal stem cells and bioactive molecules in hydrogels for osteoarthritis treatment.

Osteoarthritis (OA) is a chronic and inflammatory disease with no effective regenerative treatments to date. The therapeutic potential of mesenchymal stem cells (MSCs) remains to be fully explored. Intra-articular injection of these cells promotes cartilage protection and regeneration by paracrine signaling and differentiation into chondrocytes. However, joints display a harsh avascular environment for these cells upon injection. This phenomenon prompted researchers to develop suitable injectable materials or systems for MSCs to enhance their function and survival. Among them, hydrogels can absorb a large amount of water and maintain their 3D structure but also allow incorporation of bioactive agents or small molecules in their matrix that maximize the action of MSCs. These materials possess advantageous cartilage-like features such as collagen or hyaluronic acid moieties that interact with MSC receptors, thereby promoting cell adhesion. This review provides an up-to-date overview of the progress and opportunities of MSCs entrapped into hydrogels, combined with bioactive/small molecules to improve the therapeutic effects in OA treatment.

Evaluating intimal hyperplasia under clinical conditions.

OBJECTIVES: Open arterial revascularization using venous segments is frequently associated with the development of intimal hyperplasia (IH), leading to severe restenosis and graft failure. The lack of treatment to prevent this pathology is a major problem. Therefore, we generated a new porcine model, which closely mimics the clinical development of human IH, to test the therapeutic potential of candidate drugs. METHODS: A patch of jugular vein was sutured to the right common carotid artery of pigs, to expose the vein to haemodynamic conditions of the arterial bed. Four weeks after surgery, the operated vessels which received no further treatment (the control group) were compared with (i) contralateral, non-operated vessels (the healthy group); (ii) vessels of pigs that received a perivascular application of a drug-free microparticle gel (the placebo group) and (iii) vessels of pigs that perioperatively received the same gel loaded with 10-mg atorvastatin (the atorvastatin group). RESULTS: When compared with non-operated vessels, all operated segments displayed a sizable IH which was thicker in the venous patch than in the host artery. These alterations were associated with a thickening of the intima layer of both vessels in the absence of inflammation. The intima/media ratio has been significantly increased by 2000-fold in the vein patches. Perivascular application of atorvastatin did not prevent IH formation. However, the drug increased the adventitial neovascularization in the operated vessels. CONCLUSIONS: The novel porcine model allows for monitoring IH formation under haemodynamic conditions which mimic clinical situations. It should facilitate the screening of innovative treatments to prevent restenosis.

Hydrogels in three-dimensional dendritic cell (MUTZ-3) culture as a scaffold to mimic human immuno competent subcutaneous tissue.

The objective of this study was to develop a 3D cell culture model of the human subcutaneous tissue, allowing the prediction of the immunogenicity of subcutaneously injected therapeutic proteins. Several hydrogels were evaluated as scaffolds to mimic the human subcutaneous tissue in vitro. Cytocompatibility of the hydrogels with the human myelomonocytic cell line (MUTZ-3) was investigated, as well as their influence on cellular phenotype changes. Elastic Young's moduli in compression of the hydrogels were measured by a texture analyser and compared to ex vivo human samples. MUTZ-3 cells were differentiated into dendritic cells before embedding in hydrogels. Agarose at various concentrations (0.5%, 0.35% and 0.25% w/v), Geltrex® matrix and HyStem™ scaffold (1% w/v) displayed a wide range of elastic Young's moduli from 560 kPa to 49 kPa, compared to the reference value of 23 kPa obtained for human tissue. With the exception of HyStem™, good cytocompatibility of hydrogels was shown at the concentrations tested. An optimal combination of MUTZ-3 cells with 0.25% agarose or Geltrex® is suggested.

Mapping of drug distribution in the rabbit liver tumor model by complementary fluorescence and mass spectrometry imaging.

This study describes the use of fluorescence imaging and mass spectrometry imaging, for imaging the anti-angiogenic drug sunitinib, used to treat liver cancer. These techniques allowed for the assessment of local delivery of the unlabeled therapeutic drug. More specifically, the spatial distribution of the drug and its metabolites after local administration was investigated, and drug levels in tumor and liver tissue over time were quantified. For this purpose, sunitinib-eluting microspheres were locoregionally injected into the tumor feeding arteries of rabbits bearing liver tumors. In adjacent areas of tumor and non-targeted contralateral liver tissue, sunitinib distribution was mapped around beads in occluded vessels 7, 12, 13 and 14days after embolization by means of the two imaging methods. Presence of sunitinib metabolites was assessed by mass spectrometry imaging. Sunitinib was found around microspheres in the tumor at day 7, 12, and 13. The drug was retained by the necrotic tumor tissue, resulting in homogeneously distributed and high levels of up to 40µg/g tissue in a 1.5mm radius around the beads. The drug was almost completely eliminated from the contralateral liver tissue. Several of the drug's metabolites, including its primary active metabolite SU12662, were detected in the tumor tissue over 13days. Sunitinib diffused from the beads and was retained at high, therapeutic levels during 13days. This was confirmed independently by complementary fluorescence and mass spectrometry imaging, which served as tools to confirm effective drug delivery after hepatic transarterial administration in situ. Compound: Sunitinib: PubChem CID 5329102.

Drug-eluting embolic microspheres for local drug delivery - State of the art.

Embolic microspheres or beads used in transarterial chemoembolization are an established treatment method for hepatocellular carcinoma patients. The occlusion of the tumor-feeding vessels by intra-arterial injection of the beads results in tumor necrosis and shrinkage. In this short review, we describe the utility of using these beads as devices for local drug delivery. We review the latest advances in the development of non-biodegradable and biodegradable drug-eluting beads for transarterial chemoembolization. Their capability to load different drugs, such as chemotherapeutics and anti-angiogenic compounds with different physicochemical properties, like charge and hydrophilicity/hydrophobicity, are discussed. We specifically address controlled and sustained drug release from the microspheres, and the resulting in vivo pharmacokinetics in the plasma vs. drug distribution in the targeted tissue.

Perivascular medical devices and drug delivery systems: Making the right choices.

Perivascular medical devices and perivascular drug delivery systems are conceived for local application around a blood vessel during open vascular surgery. These systems provide mechanical support and/or pharmacological activity for the prevention of intimal hyperplasia following vessel injury. Despite abundant reports in the literature and numerous clinical trials, no efficient perivascular treatment is available. In this review, the existing perivascular medical devices and perivascular drug delivery systems, such as polymeric gels, meshes, sheaths, wraps, matrices, and metal meshes, are jointly evaluated. The key criteria for the design of an ideal perivascular system are identified. Perivascular treatments should have mechanical specifications that ensure system localization, prolonged retention and adequate vascular constriction. From the data gathered, it appears that a drug is necessary to increase the efficacy of these systems. As such, the release kinetics of pharmacological agents should match the development of the pathology. A successful perivascular system must combine these optimized pharmacological and mechanical properties to be efficient.

Antitumoral Effect of Sunitinib-eluting Beads in the Rabbit VX2 Tumor Model.

Purpose To measure plasmatic sunitinib concentration (PSC) and intratumoral sunitinib concentration (ITSC) after transcatheter arterial chemoembolization (TACE) with two different sizes of sunitinib-eluting beads (SEBs) in rabbits with VX2 hepatic allografts and to investigate treatment effects on vascular endothelial growth factor receptor type 2 (VEGFR2) phosphorylation, tumor volume, and histopathologic changes. Materials and Methods The protocol was approved by the French Ethics Committee for Animal Experiments (Comité d'Ethique en Expérimentation Animale du Centre INRA de Jouy-en-Josas et AgroParisTech, or COMETHEA, approval no. 11/028). Two experiments were performed. In the first, seven animals received 0.05 mL of 100-300-µm SEBs (1.5 mg of sunitinib) in the hepatic artery, and six animals received saline injections. In the second, eight animals received 0.05 mL of 70-150-µm SEBs (1.5 mg of sunitinib), seven received 0.05 mL of 70-150-µm unloaded beads, and seven received oral sunitinib (6 mg every day). Tumor size was monitored with ultrasonography. PSC, ITSC, and phosphorylation of VEGFR2 were assessed on days 1 and 14. After the animals were sacrificed, histopathologic analysis was performed. The Kruskal-Wallis test, Mann-Whitney U test, and Fisher exact test were used to look for statistically significant differences between groups. Results Maximum PSC after TACE with 100-300-µm SEBs was 0.002 µg/mL on day 1. ITSC was 17.8 µg/g on day 1 and 0.16 µg/g on day 14. After TACE with 70-150-µm SEBs, ITSC was 40.4 µg/g on day 1 and 27.4 µg/g on day 14. Phosphorylation of VEGFR2 was inhibited until day 14 after TACE with both sizes of SEBs. The size of VX2 tumors treated with 70-150-µm SEB TACE increased less (-2%) than that of tumors treated with unloaded beads (+42%) and oral sunitinib (6 mg every day; +1853%; P = .044). Conclusion SEB TACE resulted in minimal PSC, high ITSC, and sustained VEGFR2 phosphorylation inhibition until day 14. (©) RSNA, 2016.

Sunitinib-eluting beads for chemoembolization: methods for in vitro evaluation of drug release.

Drug-eluting microspheres are used for embolization of hypervascular tumors and allow for local controlled drug release. Although the drug release from the microspheres relies on fast ion-exchange, so far only slow-releasing in vitro dissolution methods have been correlated to in vivo data. Three in vitro release methods are assessed in this study for their potential to predict slow in vivo release of sunitinib from chemoembolization spheres to the plasma, and fast local in vivo release obtained in an earlier study in rabbits. Release in an orbital shaker was slow (t50%=4.5h, 84% release) compared to fast release in USP 4 flow-through implant cells (t50%=1h, 100% release). Sunitinib release in saline from microspheres enclosed in dialysis inserts was prolonged and incomplete (t50%=9 days, 68% release) due to low drug diffusion through the dialysis membrane. The slow-release profile fitted best to low sunitinib plasma AUC following injection of sunitinib-eluting spheres. Although limited by lack of standardization, release in the orbital shaker fitted best to local in vivo sunitinib concentrations. Drug release in USP flow-through implant cells was too fast to correlate with local concentrations, although this method is preferred to discriminate between different sphere types.

Drug-eluting beads loaded with antiangiogenic agents for chemoembolization: in vitro sunitinib loading and release and in vivo pharmacokinetics in an animal model.

PURPOSE: The combination of embolic beads with a multitargeted tyrosine kinase inhibitor that inhibits tumor vessel growth is suggested as an alternative and improvement to the current standard doxorubicin-eluting beads for use in transarterial chemoembolization. This study demonstrates the in vitro loading and release kinetics of sunitinib using commercially available embolization microspheres and evaluates the in vitro biologic efficacy on cell cultures and the resulting in vivo pharmacokinetics profiles in an animal model. MATERIALS AND METHODS: DC Bead microspheres, 70-150 µm and 100-300 µm (Biocompatibles Ltd., Farnham, United Kingdom), were loaded by immersion in sunitinib solution. Drug release was measured in saline in a USP-approved flow-through apparatus and quantified by spectrophotometry. Activity after release was confirmed in cell culture. For pharmacokinetics and in vivo toxicity evaluation, New Zealand white rabbits received sunitinib either by intraarterial injection of 100-300 µm sized beads or per os. Plasma and liver tissue drug concentrations were assessed by liquid chromatography-tandem mass spectroscopy. RESULTS: Sunitinib loading on beads was close to complete and homogeneous. A total release of 80% in saline was measured, with similar fast-release profiles for both sphere sizes. After embolization, drug plasma levels remained below the therapeutic threshold (< 50 ng/mL), but high concentrations at 6 hours (14.9 µg/g) and 24 hours (3.4 µg/g) were found in the liver tissue. CONCLUSIONS: DC Bead microspheres of two sizes were efficiently loaded with sunitinib and displayed a fast and almost complete release in saline. High liver drug concentrations and low systemic levels indicated the potential of sunitinib-eluting beads for use in embolization.

Comparative study of chemoembolization loadable beads: in vitro drug release and physical properties of DC bead and hepasphere loaded with doxorubicin and irinotecan.

PURPOSE: To characterize in vitro the loadability, physical properties, and release of irinotecan and doxorubicin from two commercially available embolization microspheres. MATERIALS AND METHODS: DC Bead (500-700 microm) and Hepasphere (400-600 microm) microspheres were loaded with either doxorubicin or irinotecan solutions. Drug amount was quantified with spectrophotometry, bead elasticity was measured under compression, and bead size and loading homogeneity were assessed with microscopy image analysis. Drug release was measured over 1-week periods in saline by using a pharmacopeia flow-through method. RESULTS: Almost complete drug loading was obtained for both microsphere types and drugs. Doxorubicin-loaded DC Beads maintained their spherical shape throughout the release. In contrast, Hepaspheres showed less homogeneous doxorubicin loading and, after release, some fractured microspheres. Incomplete doxorubicin release was observed in saline over 1 week (27% +/- 2 for DC beads and 18% +/- 7 for Hepaspheres; P = .013). About 75% of this amount was released within 2.2 hours for both beads. For irinotecan, complete release was obtained for both types of beads, in a sustained manner over 2-3 hours for DC Beads, and in a significantly faster manner as a 7-minute burst for Hepaspheres. CONCLUSIONS: The two drug-eluting microspheres could be efficiently loaded with both drugs. Incomplete doxorubicin release was attributed to strong drug-bead ionic interactions. Weaker interactions were observed with irinotecan, which led to faster drug release.

The in vivo performance of magnetic particle-loaded injectable, in situ gelling, carriers for the delivery of local hyperthermia.

We investigated the use of in situ implant formation that incorporates superparamagnetic iron oxide nanoparticles (SPIONs) as a form of minimally invasive treatment of cancer lesions by magnetically induced local hyperthermia. We developed injectable formulations that form gels entrapping magnetic particles into a tumor. We used SPIONs embedded in silica microparticles to favor syringeability and incorporated the highest proportion possible to allow large heating capacities. Hydrogel, single-solvent organogel and cosolvent (low-toxicity hydrophilic solvent) organogel formulations were injected into human cancer tumors xenografted in mice. The thermoreversible hydrogels (poloxamer, chitosan), which accommodated 20% w/v of the magnetic microparticles, proved to be inadequate. Alginate hydrogels, however, incorporated 10% w/v of the magnetic microparticles, and the external gelation led to strong implants localizing to the tumor periphery, whereas internal gelation failed in situ. The organogel formulations, which consisted of precipitating polymers dissolved in single organic solvents, displayed various microstructures. A 8% poly(ethylene-vinyl alcohol) in DMSO containing 40% w/v of magnetic microparticles formed the most suitable implants in terms of tumor casting and heat delivery. Importantly, it is of great clinical interest to develop cosolvent formulations with up to 20% w/v of magnetic microparticles that show reduced toxicity and centered tumor implantation.

Local moderate magnetically induced hyperthermia using an implant formed in situ in a mouse tumor model.

PURPOSE: We investigate a new heat delivery technique for the local treatment of solid tumors. The technique involves injecting a formulation that solidifies to form an implant in situ. This implant entraps superparamagnetic iron oxide nanoparticles (SPIONs) embedded in silica microbeads for magnetically induced moderate hyperthermia. Particle entrapment prevents phagocytosis and distant migration of SPIONs. The implant can be repeatedly heated by magnetic induction. METHODS: We evaluated heating and treatment efficacies by means of thermometry and survival studies in nude mice carrying subcutaneous human colocarcinomas. At day 1, we injected the formulation into the tumor. At day 2, a single 20-min hyperthermia treatment was delivered by 141-kHz magnetic induction using field strengths of 9 to 12 mT under thermometry. RESULTS: SPIONs embedded in silica microbeads were effectively confined within the implant at the injection site. Heat-induced necro-apoptosis was assessed by histology on day 3. On average, 12 mT resulted in tumor temperature of 47.8 degrees C, and over 70% tumor necrosis that correlated to the heat dose (AUC = 282 degrees C.min). In contrast, a 9-mT field strength induced tumoral temperature of 40 degrees C (AUC = 131 degrees C.min) without morphologically identifiable necrosis. Survival after treatment with 10.5 or 12 mT fields was significantly improved compared to non-implanted and implanted controls. Median survival times were 27 and 37 days versus 12 and 21 days respectively. CONCLUSION: Five of eleven mice (45%) of the 12 mT group survived one year without any tumor recurrence, holding promise for tumor therapy using magnetically induced moderate hyperthermia through injectable implants.

Cardiovascular effects of selected water-miscible solvents for pharmaceutical injections and embolization materials: a comparative hemodynamic study using a sheep model.

Generally, organic water-miscible solvents are used intravascularly (both intravenously and intra-arterially) for preparing two types of formulations, namely, pharmaceutical injections of poorly soluble drugs and precipitating liquid embolic polymeric materials for the minimally invasive treatment of aneurysms, arteriovenous malformations, or tumors, by arterial route. Although several of such solvents have been used in both drug delivery and interventional radiology, their safety profile is a concern. In particular, there is a lack of comparative investigations of their cardiovascular effects when injected intra-arterially. We selected 13 non-aqueous water-miscible solvents based on their capacity to solubilize drugs or embolic polymeric materials, and on their described use, at least diluted with water, in pharmaceutical formulations. Their in vivo hemodynamic toxicity in male adult sheep after infra-renal aorta catheterization has been estimated with respect to the arterial and venous pressures, as well as the heart rate. Saline solution was used as a control. Three different volumes (0.1, 0.5, and 1.0 mL) were infused rapidly. An increase in arterial pressure and concomitant decrease in venous pressure, which we considered as signs of a cardiovascular toxicity, were observed to a differing extent for all organic solvents. Changes in heart rate were negligible. Based on the intensity of arterial pressure change after a 1-mL infusion, a classification of the toxicity of the solvents following intra-arterial infusion is proposed: Solvents devoid of significant cardiovascular toxicity: dimethyl isosorbide (DMI), Glycofurol 75, polyethylene glycol 200 (PEG 200), diglyme. Solvents with moderate cardiovascular toxicity: tetrahydrofurfuryl alcohol (THFA), ethanol, acetone, Solketal, glycerol formal, dimethyl sulfoxide (DMSO). Solvents with marked cardiovascular toxicity: propylene glycol, ethyl lactate, N-methyl-2-pyrrolidone (NMP). Emphasis is put on the relative character of the proposed ranking and on the lack for certain solvents, at least in the open literature, of data pertaining at other forms of toxic effects (e.g., undesirable pharmacological action, carcinogenicity, teratogenicity, mutagenicity, and irritating and sensitizing properties), all factors that have to be considered when selecting a proper solvent.