Patent Publication Number: US-2021161807-A1

Title: Implantable device for localized drug delivery, uses and manufacturing method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage Application of International Patent Application No. PCT/IB2019/052748, having an International Filing Date of Apr. 4, 2019, which claims the benefit of priority to Italian Patent Application No. 102018000004220, filed Apr. 5, 2018, the entire contents of which are hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally refers to an implantable device for localized drug delivery. More specifically, the invention refers to an implantable device for localized drug delivery that has been developed primarily for the treatment of tumors, even more specifically, brain tumors. 
     BACKGROUND OF THE INVENTION 
     Malignant gliomas account for almost 50% of all brain tumors in adults, with over 70,000 new cases diagnosed each year. The current standard of care for this kind of aggressive brain tumor involves surgery to remove the main malignant mass from the brain, followed by chemotherapy and radiation therapy. Despite this intense therapeutic intervention, the overall survival of patients diagnosed with glioma is generally less than 20 months. Such an unfavorable prognosis is associated with the highly infiltrating nature of glioma cells, which cannot be completely removed after surgery, eventually leading to recurrences. Furthermore, a sufficient release of therapeutic agents to the brain is limited by the presence and complexity of the blood-brain barrier (BBB). 
     For these reasons, polymeric implants have been proposed for localized chemotherapy, which are implanted directly into the surgical site and release their therapeutic content locally. The object of this approach is the pharmacological removal of the residual tumor cells. Among these implants, the Gliadel® wafer is the most effective and widely used. Gliadel® is a cylindrical polymer wafer loaded with carmustine, a drug that interferes with DNA synthesis and stops cell proliferation. This device is described in U.S. Pat. No. 8,895,597, which concerns a device for the intracranial release of chemotherapy for gliomas, or other types of tumors, more preferably, after surgical resection. The matrix of the implantable device is made of natural or synthetic biodegradable polymers. For this purpose, the preferred polymers are polyanhydrides and polyhydroxy acids, in particular poly(lactic acid-glycolic acid) copolymers. The matrix may be prepared in the form of microparticles (e.g. microbeads, microcapsules or nanoparticles), discs and wafers. In particular, wafers are the commercially available solution. Gliadel® is deposited directly in the resection cavity, where it slowly releases the chemotherapeutic active ingredient. However, this device only slightly improves the survival rate of patients, mainly due to the short release time (about  2  weeks) and the shallow penetration of therapeutic molecules in the brain tissue. Moreover, its effectiveness is still controversial among doctors. The studies carried out have failed to clearly demonstrate whether there is a benefit to the overall survival of patients. Moreover, based on meta-analysis studies, Gliadel® appears to be beneficial in patients with newly diagnosed glioma, but not in patients that have demonstrated recurrent glioma. Some clinical studies have also shown toxic side effects that, together with limited survival improvements, exclude the use of Gliadel® in new clinical studies. 
     SUMMARY OF THE INVENTION 
     One purpose of the present invention is thus to provide a localized drug delivery system that has been proven to be effective and that satisfies the shortcomings of the prior art technique outlined above. 
     These and other objects are achieved by the implantable device for localized delivery of one or more pharmaceutical active ingredients having the features described and claimed herein. 
     Further beneficial features of the implantable device of the present invention are also described. 
     The following is a detailed description of the implantable device according to the invention, as well as of the procedure for the manufacture thereof, which is a second aspect of the invention. A third aspect of the invention concerns the therapeutic applications of the implantable device according to the invention. 
     The implantable device according to the invention, which will hereinafter be referred to for brevity as “μMESH device”, allows the localized delivery of a wide variety of therapeutic agents, possibly incorporated in nanoparticles. The particular chemical characteristics and the micrometric geometry of the μMESH device also allow a better integration of the same device with the surrounding tissue after implantation. Although the μMESH device may be used for the localized treatment of various diseases, such as cancer, diabetes and cardiovascular diseases, it is particularly beneficial in the treatment of brain tumors, such as glioblastoma multiforme (GMB). In this field, the implantation of the μMESH device in the surgically resected tumor area may in effect lead to stopping the recurrence of the tumor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of the sequential steps in the manufacturing method of an embodiment of the device of the invention; 
         FIGS. 2A and 2B  show images of the device of the invention obtained by scanning electron microscopy (left) and fluorescence microscopy (right); 
         FIG. 3  shows the comparative loading and delivery profiles of a chemotherapeutic drug obtained with the device of the invention (square points) and with a similar device (FLAT) but in the form of a flat wafer (round points); 
         FIG. 4  shows the comparative images (in the left column the device of the invention, in the right column the FLAT device in the shape of a flat wafer) of the interaction between tissue and device, obtained by different microscopic techniques: 3D confocal microscopy (A), SEM (B), optical microscopy (C) and TEM microscopy (D); 
         FIG. 5  shows comparative images (first row μMESH device, middle row polypropylene grid, bottom row Premilene® device) of the relationship between each of these devices and a tumor spheroid, detected by fluorescence microscopy (first two columns) and SEM (last two columns); 
         FIG. 6  shows the comparative temporal interaction of the device of the invention (top line) and the flat wafer-shaped FLAT device (bottom line) with tumor spheroids over a 24-hour period; 
         FIG. 7  shows two comparative graphs wherein (A) shows the percentage of growth of tumor cells relative to treatment days and (B) shows the cell radius relative to treatment days; 
         FIG. 8  shows the results of the local μMESH implantation in the treatment of an orthotopic mouse model of glioblastoma multiforme. 
     
    
    
     DETAILED DESCRIPTION 
     Further features and advantages of the invention will become apparent from the detailed description that follows, provided by way of non-limiting example. 
     In this description, the following terms are used with the meaning specified below. 
     “Biodegradable”, with reference to a material, means that said material is able to be metabolized naturally and in a non-harmful way. 
     “Biocompatible”, with reference to a material, means that said material has no toxic or harmful effects on biological functions. 
     “Net” or “grid” interchangeably refers to the general shape of a polymer matrix of micrometric “meshes” or “cells” defining respective through holes. 
     The phrase “thickness of the polymer matrix” is used to indicate the size of the polymer matrix along a direction parallel to the axis of the holes. 
     The expression “size of the through holes” means: in the case of circular holes, the diameter of the hole itself; in the case of holes in the shape of regular polygons, the diameter of the inscribed circumference; and in the case of rectangular holes, the minor axis of the inscribed ellipse. 
     This dimension is measured in a direction perpendicular to the axis of the hole and in the plane of the hole itself. 
     As mentioned above, the present invention concerns an implantable device for the localized delivery of one or more active pharmaceutical ingredients, the device comprising a polymer matrix having a general net or grid shape, comprising a plurality of micrometric meshes, or micrometric cells, having a predefined geometric shape. All the micrometric meshes of the grid have the same geometric shape and define respective through holes. 
     The polymer matrix of the μMESH device consists of one or more biodegradable and biocompatible polymers, which may be natural or synthetic. The polymer matrix also includes one or more pharmaceutical active ingredients. 
     Polymers suitable for producing the biodegradable and biocompatible polymer matrix of the implantable device of the invention are, by way of non-limiting example, poly(lactic-co-glycolic acid) (PLGA), polyethylene glycol (PEG), hyaluronic acid (HA), chitosan, polymethyl methacrylate (PMMA), polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL) and combinations thereof. Preferably, the polymer matrix consists of or comprises PLGA. 
     In a preferred embodiment, the polymer matrix is supported on a polymeric support layer consisting of one or more biodegradable and biocompatible polymers. By way of non-limiting example, polymers suitable for making the support layer are polyvinyl alcohol (PVA), gelatin, chitosan, N-(2-hydroxypropyl) methacrylamide (HPMA), hydroxypropyl methylcellulose (HPMC), poly(lactic-co-glycolic acid) (PLGA), polyethylene glycol (PEG), hyaluronic acid (HA), chitosan, polymethyl methacrylate (PMMA), polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL) and combinations thereof. Preferably, the support layer consists of or comprises polyvinyl alcohol (PVA). 
     The active pharmaceutical ingredients suitable for use in the μMESH device of the invention are any substance that may provide a therapeutic effect on a disease, such as anti-tumor agents (taxane, agent of the anthracycline family), protease inhibitors, reverse transcriptase inhibitors, biomolecules (RNA, antibodies, peptides), iron oxide nanoparticles, gold nanoparticles, quantum dots, solid lipid nanoparticles, polymer nanoparticles and nanoparticles loaded with drugs or biomolecules. The μMESH device of the invention may also encapsulate anti-bacterial, anti-viral and anti-fungal agents, a vaccine, an agent active against anti-autoimmune diseases, a psychotherapeutic agent, a cardiovascular active ingredient, a blood modifier, a gastrointestinal active ingredient, an active agent against respiratory diseases, an anti-arthritic agent, an active agent against diabetes, an anticonvulsant, a bone metabolism regulator, an active agent against multiple sclerosis, a hormone, an active agent on the urinary tract, an immunosuppressant, an ophthalmic product, a sedative, an active ingredient for the treatment of a sexual dysfunction, an anesthetic, an active agent against migraine, an active ingredient against infertility, a weight control product and any combination thereof. 
     In a preferred embodiment, the pharmaceutical active ingredient is a chemotherapy such as Docetaxel (DTXL), Paclitaxel, Taxotere, Vorinostat, Irinotecan, Topotecan, Metotrexate, Carboplatin, Cisplatin, Oxaliplatin, Vinblastine, Vincristine, Carmustine, Temozolomide (TMZ), Doxorubicin, Daunorubicin or any combination thereof. 
     The selected active ingredient may be appropriately incorporated into the polymer matrix in a form suitable for obtaining a prolonged release of the main active ingredient itself, without affecting the pharmacological activity thereof. For example, the Docetaxel incorporated in the polymer matrix in the form of powder is released up to 60 days after implantation. Longer release times may be easily achieved by incorporating the active ingredient, instead of in the form of powder, in its co-crystalline form. This solid form reduces the rate of dissolution, which is a necessary prerequisite for subsequent diffusion into the space surrounding the implanted device, reducing the general release profile. 
     The chemotherapy active ingredient may also be incorporated into the polymer matrix in combination with another active ingredient with a different therapeutic purpose, such as a biomolecule, an anti-inflammatory active ingredient, a cytokine, an anti-proliferative active ingredient, a chemokine to modulate the migratory processes of immune cells, an active ingredient stimulating the immune system, an anti-fungal agent or an anti-bacterial agent. Alternatively, the additional active ingredient may be incorporated into the polymeric support layer. Particularly preferred examples of active ingredients to be used in combination with a chemotherapy are diclofenac, celecoxib, curcumin, ibuprofen, indomethacin, acetylsalicylic acid, zoledronic acid. 
     In a further embodiment, the active ingredient incorporated in the polymer matrix and/or polymer support layer is conjugated with or included in a nanoparticle. By way of non-limiting example, iron oxide nanoparticles, gold nanoparticles, quantum dots, micelles, liposomes, solid lipid nanoparticles, polymeric nanoparticles are cited. These nanoparticles may be loaded with any one of the aforementioned active ingredients and the combinations thereof. 
     As mentioned above, the polymer matrix of the μMESH device has a general net or grid shape and comprises a plurality of micrometric meshes, or micrometric cells, which have a predefined geometric shape. All the micrometric meshes of the grid have the same geometric shape and define respective through holes. 
     By way of non-limiting example, the meshes of the grid may be substantially round, substantially square or another regular polygon shape, or substantially rectangular in shape. The preferred shape is square. 
     The micrometric size of the meshes is particularly advantageous as it allows the growth of the cells present in the implant site of the device and their proliferation around it. 
     The thickness of the polymer matrix is preferably in the range of 1 μm to 500 μm, more preferably in the range of 2 to 100 μm, and even more preferably in the range of 3 to 10 μm. Where the meshes are substantially square, the distance separating adjacent through holes is in the range of 1 μm to 100 μm, more preferably in the range of 2 to 50 μm, and even more preferably in the range of 3 to 10 μm. 
     In a particularly preferred embodiment, the micrometric meshes are all substantially square in shape; the longitudinal and transverse dimensions of the through hole of each mesh are both 20 μm; the thickness of the polymer matrix is 5 μm and the distance separating adjacent through holes is 3 μm. 
     The expression “distance separating adjacent holes” is used to indicate a distance relative to a direction perpendicular to the axis of the holes, i.e. along a plane of development of the polymeric matrix. 
     The surface of the polymer matrix is easily adjusted and modified during the manufacturing process to achieve the desired surface properties. The μMESH device has preferably a surface zeta potential in the range of −60 mV to +20 mV, which reflects values found in biological molecules, and which may be adapted by modifying the end groups (such as COOH or NH 2 ), or their ratio, on the constituent polymer(s). In this case, the end groups are conjugated, preferably by covalent binding, to specific molecules, adapted to support the binding of the μMESH device to the surrounding cells. For example, in at least one portion of a surface of the μMESH device, the end groups of the polymer(s) forming its polymer matrix are conjugated to a biomolecule chosen from nucleic acids, polypeptides, glycoproteins, carbohydrates, lipids, and combinations thereof. More specifically, by way of example, these biomolecules are chosen from natural or synthetic ligands for a cell surface receptor, such as a growth factor, hormones, LDL, transferrin, antibodies, antibody fragments, and single-chain antibodies. 
     In addition, the surface of the μMESH device may be modified by adding, on one side or on both sides, other integral structural parts having the object of improving the anchorage of the device, such as pillars, needle-like structures, etc. 
     The μMESH device described above is characterized by a high degree of flexibility, allowing the device to adapt, conform, adhere and integrate to and with the surrounding tissue, without affecting the overall physico-chemical or pharmacological properties of the active ingredients incorporated therein (i.e., their incorporation and release profile). These features of the μMESH device derive from its characteristic grid shape with micrometric meshes, rather than from its surface properties. This is particularly relevant for application in the treatment of brain tumors, as inventors have shown that the close interaction between the μMESH device and the surrounding tissue promotes local recruitment of tumor cells. In particular, as will be detailed in the following examples and in particular in  FIG. 4 , the μMESH device is advantageously able to wrap around and adapt to the tumor mass; moreover, its micrometric through holes allow the cells to migrate into and around the device. The migration of cells in and around the device may be further increased by incorporating cytokines into the μMESH device, which are able to mediate the migration of tumor cells to the same device. 
     Finally, the μMESH device may be easily stored in dry conditions, preserving both the polymer and the active ingredient, and preventing the latter from being released prematurely from the device. This ensures that the features and performance of μMESH devices remain homogeneous and consistent throughout the time between manufacture and use. 
     A second aspect of the invention is the manufacturing method of the μMESH device described above. The method consists of the following steps: 
     i. providing a silicon template (wafer) having the negative of the general grid shape of the μMESH device etched on a face; 
     ii. starting from the aforesaid silicon template, obtaining a polydimethylsiloxane (PDMS) template reproducing the general grid shape of the μMESH device; 
     iii. from the aforesaid polydimethylsiloxane template, obtaining a template of one or more biodegradable and biocompatible support polymers (preferably polyvinyl alcohol (PVA)) reproducing the negative of the general grid shape of the μMESH device; 
     iv. providing a mixture comprising one or more biodegradable and biocompatible matrix polymers and one or more pharmaceutical active ingredients; 
     v. pouring the mixture of step iv) on the template of step iii) and optionally removing the template of step iii), 
     thus obtaining an implantable μMESH device according to the invention. 
     In a preferred embodiment, step i) is achieved by direct laser writing and dry etching techniques and step ii) is achieved by the replica-molding technique. 
     A further optional step is to conjugate, on at least one portion of a surface of the device matrix, the molecules or biomolecules mentioned above that will help bind the device to the surrounding cells when the device is implanted. 
     The main advantage of using the manufacturing method described above is that it is easily scalable. 
     A third aspect of the invention concerns the medical uses of the μMESH device. A preferred medical application is localized chemotherapy of tumors, in particular, but not limited to, brain tumors. 
     Brain tumors particularly suitable for treatment with the μMESH device are malignant gliomas. After surgical removal of the main tumor mass, the μMESH device is implanted at the site of the surgical resection to remove the residual tumor cells pharmacologically. The following experimental data show that the μMESH device is able to inhibit growth and induce death of residual tumor cells of glioblastoma multiforme, thus stopping recurrences. In this application, the μMESH device of the invention is even more effective than the only similar implantable device already approved by the FDA, i.e. the Gliadel®. 
     Without wishing to be bound to any one theory, it is believed that the μMESH device, once positioned in the target site, covers it and, due to its through holes of a size comparable with those of the cells, allows tumor cells to grow around it. Thus, the μMESH device may be fully integrated with the surrounding tissue, coming into close contact with the target cells and thus achieving greater effectiveness. 
     Conversely, a device without through holes (such as the implantable wafers of the prior art) may not achieve this intimate interaction with the tissues and, consequently, the growth of the tumor cells has the effect of removing or moving the device. Similarly, other devices of the prior art, such as surgical nets, which also have through holes but are larger than those of the μMESH device according to the invention, are only able to establish a superficial relationship with the cells. 
     The μMESH device may also be used to treat other diseases, for which a controlled localized release of the active ingredient is promising, such as atherosclerosis and diabetes. 
     For example, in the treatment of atherosclerosis, a μMESH device incorporating antiproliferative and anti-inflammatory agents is placed along the affected vessel through the use of a catheter or similar device, thus adhering to the vessel walls and continuously releasing antiproliferative and anti-inflammatory agents to destroy atherosclerotic plaque and prevent the formation of new lesions. In the treatment of diabetes, a μMESH device incorporating anti-diabetes agents is placed along the affected vessel through the use of a catheter or similar device, thus adhering to the vessel walls and releasing the anti-diabetes agents in a manner dependent on the concentration of glucose. 
     The following experimental examples are given for illustrative purposes only. Therein, reference is made to the accompanying drawings. 
     EXAMPLES 
     1. Manufacturing Method 
       FIG. 1  is a schematic representation of the steps in the manufacturing method of the μMESH device of the invention; 
     The μMESH device was obtained by using sequential steps for template replication. For the creation of the grid on a silicon substrate, a photopolymerizing resist was homogeneously distributed on a silicon wafer. The direct laser writing technique was used to imprint the grid pattern on the silicon. The desired thickness of the micrometric structures was then obtained by dry etching, namely Reactive Ion Etching, with consecutive steps (standard plus passivation) of the Bosch method. The silicon template was then coated with polydimethylsiloxane (PDMS), with a ratio of 1:10 between the crosslinking agent and the elastomer and polymerized in a 60° C. oven for 4 hours. Subsequently, the PDMS template was replicated in polyvinyl alcohol (PVA), resulting in an identical replica of the original pattern of the silicon template, pouring a 3.5% w/v PVA solution over the PDMS and letting all the water evaporate. Then, a polymeric paste, consisting of PLGA and the active ingredient chosen to be incorporated in the device, was spread on the template, after the latter was removed from the PDMS. Finally, the μMESH device was cut into pieces of the desired size (in this case, 5×5 mm) and stored until use. 
     In this embodiment, the PVA replica acts as a loadable sacrificial layer, the thickness of which may be easily modulated in the manufacturing method. The thickness of the PVA layer directly affects its rate of dissolution and, therefore, the rate of release of any agent (molecules or nanoparticles) dispersed therein. 
     To obtain the FLAT device used in the comparative studies, an identical protocol was used, but a smooth silicon substrate was used instead of the grid pattern template used to make the μMESH device of the invention. 
     2. Microscopic Characterization 
       FIG. 2  shows the microscopic characterization of μMESH. Representative images of the grid are shown, obtained by scanning electron microscopy (left) and fluorescence microscopy (right). 
     3. Incorporation and Release Profiles 
       FIG. 3  shows the incorporation and release profiles. In particular, a side-by-side comparison of the incorporation (left) of the active ingredient docetaxel (DTXL) and its release (right) from the μMESH device of the invention and the FLAT device for comparison is visible. The smooth FLAT device, is made of the same materials as the μMESH device (grid-shaped) and has the same overall dimensions. 
     Different amounts of docetaxel (DTXL), specifically 5, 25, 50 and 75 μg, were mixed into the polymeric paste and then incorporated into the μMESH, resulting in DTXL-μMESH. Three samples of DTXL-μMESH for each condition were dissolved in acetonitrile/water (1:1, v/v) and analyzed by high-performance liquid chromatography (HPLC). DTXL was eluted in water+0.1% (v/v) trifluoroacetic acid (TFA) and acetonitrile+0.1% (v/v) TFA, in a ratio of 47:53 v/v, under isocratic conditions, at a flow rate of 1.0 ml/min. 
     The good linear correlation between the amount of active ingredient mixed in the polymeric paste and the amount actually incorporated is a very important feature of the device, because it allows to finely adjust the amount of active ingredient incorporated in the device. 
     To study the release profile, the μMESH device and the FLAT counterpart thereof were incubated in 1 ml of phosphate buffered saline (PBS), to mimic and maximize the volume of liquid to which the devices may be exposed in a local application. At different times, the solution was centrifuged at 5000 rpm for 10 min and the supernatant was analyzed using the protocol described above. The results are expressed as a percentage of the cumulative release over time of three samples for each type of device. 
     4. Microscopic Characterization of the Tissue-device Interaction 
     Empty μMESH and FLAT devices were placed on top of a PDMS coated well to maintain the correct culture conditions for tumor spheroids (i.e. in a nonadherent state). After attaching the devices, to prevent them from floating in the wells, the spheroids were placed over them and were left to grow in a suitable culture medium. In this specific case, U-87 MG cells, a representative model of glioblastoma, were chosen for spheroid formation and the devices were pre-coated with myelin (1 mg/ml in PBS) to mimic the neuronal tissue. 
       FIG. 4  shows the integration of the tissue with the μMESH device and the FLAT wafer. In particular, this figure shows images obtained by 3D confocal microscopy (A); images obtained by SEM microscopy (B); images obtained by optical microscopy of TEM sections (C); and images obtained by TEM microscopy (D), showing the close interactions between the spheroids and the μMESH device, in contrast to the weak interaction of the FLAT wafer. The scale bar is 100 μm for all images, except for TEM images wherein the scale bar is 2 μm. The white arrows indicate the μMESH device inside the spheroid in the case of the μMESH device, or the flat side in the case of cells treated with the FLAT device. 
     5. Comparison Between the μMESH Device and Other Devices 
     Two grid devices were compared with the μMESH device. The first is a polypropylene grid with a rectangular structure, with a mesh thickness of approximately 250 μm, with holes approximately 400 μm wide and 800 μm high. The second is a surgical grid, Premilene®, with mesh thicknesses of approximately 160 μm and non-identical holes, with dimensions of approximately 600-700 μm. These dimensions are representative of the dimensions of grid-shaped devices found on the market and are very different from the characteristic dimensions of the μMESH device. The three devices were put in contact with U87-MG tumor spheroids and their relationship therewith was evaluated over time. The ratio of Premilene® to the spheroid always remains superficial and unchanged over time, unlike what happens with the μMESH device. Such behavior is similar to that of the aforementioned FLAT device. Only the μMESH device is clearly immersed in the spheroid, as confirmed by the SEM images. The interaction of the polypropylene grid with the spheroid, on the other hand, is so weak that it cannot resist the preparation steps of the sample for electron microscopy. 
       FIG. 5  illustrates, by means of fluorescence microscopy (first two columns) and electron microscopy (last two columns), the interaction between a tumor spheroid and the three aforesaid devices, at the beginning and after 96 hours from the deposition of the spheroid. Fluorescence microscopy images show how, over time, only the device of the invention changes and conforms to the spheroid (the scale bar represents 250 μm fluorescence microscopy in all images). SEM images of the same devices over 96 hours show that only Premilene® and μMESH establish an interaction with the spheroid, although in the first case it is only superficial, while in the second case, portions of the device of the invention that come out of the inside of the spheroid are clearly visible. This clearly demonstrates the intimate relationship established in this case between the spheroid and the μMESH device. 
     6. Anti-cancer Effectiveness 
     DTXL-μMESH and DTXL-FLAT loaded with DTXL at a concentration of 100 nM were used to evaluate anti-tumor efficacy. The same experimental conditions used for the study of the spheroid-device interaction were used. At each observed time, the spheroids were detected and their size (in terms of area of the equatorial section and respective radius) was quantified. 
       FIG. 6  shows the behavior of the tumor over time with respect to its interaction with the μMESH device (upper row) or the FLAT device (lower row). The physical interaction of μMESH with tumor spheroids shows the tendency of the device to be dragged into the spheroids, providing very close interaction with the tumor, while the FLAT device does not produce this effect. 
       FIG. 7  shows the profile of tumor growth following treatment with μMESH and FLAT devices. In particular, on the left is observable the effectiveness of DTXL-μMESH in slowing tumor growth over the period of time considered, compared with the FLAT wafer, at the same concentration and for the same time interval. On the right, the value of the mean radius on day 0 and day 14 of the spheroids treated with DTXL-μMESH or DTXL-FLAT is represented. The increased anti-tumor effectiveness of the DTXL-μMESH device is evident. 
       FIG. 8  shows the growth profile of the tumor in the brains of mice treated with the DTXL-μMESH device. Human glioblastoma multiforme cells, luciferase-positive (U87-MG Luc + ) mice were implanted orthotopically into the mice, as shown schematically at the top of the image. The response to treatment, which began on day 10, was measured through bioluminescence analysis, as reported in the lower image. Mice treated with DTXL-μMESH (#6, #8 and #9) show higher overall survival (about 2 times) relative to untreated mice (#3, #4 and #5).