Abstract:
The present invention refers to a ceramic nanosystem constructed for releasing medications in a controlled manner, in the treatment of human beings and animals presenting an organic deficiency which requires the application of said medications. The present invention further refers to the method for preparing said nanosystem, in the form of a ceramic matrix, and also to the method of incorporating a drug to said ceramic matrix, forming a tablet.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This Application claims benefit under 35 USC 119(a) to Brazil Patent Application No. PI 0906820-1, filed Dec. 21, 2009 
       FIELD OF THE INVENTION 
       [0002]    The present invention refers to a ceramic nanosystem constructed for releasing medications in a controlled manner, in the treatment of human beings and animals presenting an organic deficiency which requires the application of said medications. The present invention further refers to the method for preparing said nanosystem, in the form of a ceramic matrix, and also to the method of incorporating a drug to said ceramic matrix, forming a tablet. 
       BACKGROUND OF THE INVENTION 
       [0003]    Many of the drugs employed in the treatment of several diseases are indiscriminately distributed in several organs and tissues after administration thereof, which can cause inactivation of said drugs or undesirable effects not related to the pathological process. Besides, as a consequence of this wide distribution, for achieving the therapeutic concentration required in a certain organ or part of the organism, it is necessary to administer large amounts of the therapeutic agent. 
         [0004]    Aiming at overcoming these drawbacks, there have been developed new drug-carrier systems to rationalize the medication therapy, leading to the reduction of the dose and of the undesired side effects, as well as stimulating the patient to adhere to the treatment. 
         [0005]    The drug vectorization, based on Paul Ehrlich&#39;s the theory about the ability of tiny particles in carrying active molecules to the specific action sites, has been considered one of the major biopharmaceutical research lines of the last decades, taking part in a wide-range area, denominated nanotechnology, which quickly emerged in Brazil and in the world,. It is a consensus that the use of nanostructured colloidal systems, such as the liposomes, nanoemulsions and polymeric nanoparticles, is an alternative which aims to alter the biodistribution of drugs after administration thereof by different routes. The vector-oriented release system delivers, selectively, the drug to its action site, in order to offer the maximum therapeutic activity, prevent the degradation or inactivation during the transit until the target site, and protect the body from adverse reactions due to the inappropriate distribution (BANKER and RHODES, 1996). 
         [0006]    Many pathologies present potential for treatment through drug vectorization such as, for example, parasite infections in cells of the endothelial reticulum system, diseases that affect the central nervous system, tumors, and the like. Specifically for cancer, the increase of the vascular permeability of the tumor tissue enables extravasation of the drug carriers presenting between 10 and 700 nanometers of diameter. This increase of the capillary permeability results from the poor formation of the neo-vasculature of the tumor tissues, which present gaps between the endothelial cells. 
         [0007]    Thus, the application of the vectorized transport systems has potential to improve, for example, the chemotherapy of neoplasias. The effective use of said systems would, not only reduce the chemotherapeutic agent dose for a given degree of therapeutic answer, but also improve the opportunities for some cells which are typically resistant to certain drugs. Moreover, the chemotherapy application via these systems could reduce the complexity of the surgical manipulation, minimizing the severity of the cancer extension and/or reducing the residual volume. Alternatively, the use of these systems, after the tumor has been reduced through surgery and/or radiation therapy, allows enhancing the probability of effectively eradicating the residual cancerous cells (GUPTA, 1990). 
         [0008]    Another application of said technology might be noted in the international publication WO 2008/069561, which refers to a metal oxide hollow nanocapsule capable of carrying a drug adsorbed in its structure. 
         [0009]    This prior art solution requires the provision of a nanocapsule surrounding the drug to be released in a predetermined organic medium, through the wall of the shell defined by said hollow nanocapsule. In this case, the drug is not incorporated in the metal oxide matrix itself, but enclosed in its interior. 
         [0010]    The construction of the hollow nanocapsule requires specific and complex procedures, which demand sophisticated equipment and lead to high production costs. 
         [0011]    Besides the above-cited drawback, the solution described in the international patent application mentioned above also requires that the metal oxide nanocapsule be surrounded by a silica coating to keep the drug contained in the interior of the nanocapsule, until the latter reaches the region of the organism able to remove the silica coating and allow the drug to be controllably and progressively released through the surrounding wall of the nanocapsule containing the drug. 
         [0012]    The provision of the silica coating is fundamental to prevent undesired aggregations to the nanocapsule wall, which aggregations, without the provision of the coating, require the use of aqueous dispersions containing electrostatic stabilizers, surfactants, polymers, such as steric stabilizers and polymer modelers. 
         [0013]    These aspects make it even more costly and complex the use of metal oxide nanocapsules encapsulating the drugs to be released. 
       SUMMARY OF THE INVENTION 
       [0014]    As a function of the drawbacks pointed above, the present invention has the object of providing a nanoceramic matrix, presenting a large specific area with controlled porosity and which is simple to produce at a relatively reduced cost. Through also simple and cost-effective methods, the present matrix can incorporate and retain, directly in its structure and without being surrounded by any external capsule, a large quantity of a pharmaceutical composition to be controllably released from the structure of the nanoceramic matrix to the human or animal organism to be treated. 
         [0015]    According to a first aspect of the invention, said ceramic matrix comprises a structure formed by pseudoboehmite/γ-alumina nanoparticles, presenting a specific area of 250-300 m 2 /gram. 
         [0016]    Further, according to a second aspect of the invention, said ceramic matrix of pseudoboehmite/γ-alumina nanoparticles is used to produce a tablet, by mixing it, in an amount from 50% to 60% of the total tablet weight, with a pharmaceutical composition, generally comprising a drug defined by acyclovir or atenolol to complete the total tablet weight and which will be controllably released in a human or animal organism. 
         [0017]    According to a third aspect of the invention, it is further provided a method for obtaining said ceramic matrix, comprising the production of pseudoboehmite/γ-alumina nanoparticles through the steps of: 
         [0018]    mixing an aluminium nitrate solution or aluminium chloride solution with a poly(vinyl alcohol) solution, forming a precursor solution; 
         [0019]    dripping the precursor solution in an ammonium hydroxide solution, forming a gel; 
         [0020]    ageing the gel, filtering and drying it at about 70° C. for approximately 24 hours; and 
         [0021]    calcining the gel, at about 500° C. to obtain a pseudoboehmite/γ-alumina presenting a specific area of 250-300 m 2 /gram. 
         [0022]    The invention also refers to a method for producing a tablet, comprising, in a first phase, the production of a ceramic matrix of pseudoboehmite/γ-alumina nanoparticles, through the steps of: 
         [0023]    mixing an aqueous aluminium nitrate solution or aqueous aluminium chloride solution (14% m) with a poly(vinyl alcohol) solution (8% m in water), forming a precursor solution; 
         [0024]    dripping the precursor solution in an ammonium hydroxide solution (28% m), forming a gel; 
         [0025]    ageing the gel, filtering and drying it at about 70° C. for approximately 24 hours; and 
         [0026]    calcining the gel, at about 500° C. to obtain the ceramic matrix of pseudoboehmite/γ-alumina presenting a specific area of 250-300 m 2 /gram; and 
         [0027]    In a second phase, mixing the ceramic matrix of pseudoboehmite/γ-alumina, in an amount from 50% to 60% of the total tablet weight, with a pharmaceutical composition, in an amount to complement the total tablet weight, which will be controllably released in a human or animal organism. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    As described above, the invention includes the provision of a ceramic matrix having a structure formed by pseudoboehmite/γ-alumina nanoparticles, presenting a specific area of 250-300 m 2 /gram. 
         [0029]    This large specific area of the ceramic matrix of pseudoboehmite/γ-alumina nanoparticles allows said matrix to incorporate, in small material volumes, usually defined in tablets to be ingested by the human being or animal, a large quantity of one or more drugs, generally provided with pharmaceutical compositions, incorporating a pharmaceutically acceptable filler and also at least one flow adjusting element and a lubricant agent which facilitates the final compression of the mixture defined by the ceramic matrix and pharmaceutical composition, for forming a tablet. 
         [0030]    Thus, the invention allows obtaining a tablet comprising a ceramic matrix formed by pseudoboehmite/γ-alumina nanoparticles, presenting a specific area of 250-300 mg 2 /g and defining 50% to 60% of the total tablet weight; and a pharmaceutical composition, incorporated in said matrix, in a quantity completing the total tablet weight and to be controllably released in a human or animal organism, through the structural collapse of the tablet and the progressive release of the drug in relation to the pseudoboehmite/γ-alumina nanoparticles. 
         [0031]    In the preferred way of carrying out the invention, the pharmaceutical composition comprises a drug, a pharmaceutically acceptable filler, a flow adjusting element and a lubricant agent used in the compression phase of the formation of the tablet. 
         [0032]    The drug used in the pharmaceutical composition is preferably defined by any of the acyclovir and atenolol compounds. In this particular case, the drug is provided in a dose of 100 mg. 
         [0033]    The pharmaceutically acceptable filler may be defined by starch, which is present in the pharmaceutical composition in an amount ranging from 20% to 30%. 
         [0034]    The flow adjusting element is generally defined by silicon dioxide, which is present in an amount which ranges from 1.5% to 2% in relation to the total weight of the pharmaceutical composition. 
         [0035]    The lubricant agent may be defined by magnesium stearate, which is present in the pharmaceutical composition in an amount ranging from 1.5% to 2%. 
         [0036]    For obtaining a ceramic matrix to be used in the preparation of the tablets, it is applied a method which comprises the production of pseudoboehmite/γ-alumina nanoparticles through the steps of: 
         [0037]    mixing an aluminium nitrate or aluminium chloride solution (14% m) with a poly(vinyl alcohol) solution (8% m in water), forming a precursor solution; 
         [0038]    dripping the precursor solution in an ammonium hydroxide solution (18% m), forming a gel; 
         [0039]    ageing the gel, filtering and drying it at about 70° C. for approximately 24 hours; and 
         [0040]    calcining the gel, at about 500° C. to obtain a ceramic matrix of pseudoboehmite/γ-alumina presenting a specific area of 250-300 m 2 /gram. 
         [0041]    For the production of a tablet using the ceramic matrix obtained by the method described above, said ceramic matrix, in a quantity from 50% to 60% of the total tablet weight, is mixed with the above-defined pharmaceutical composition, to be controllably released in a human or animal organism. 
       Preparation of the Tablets: 
       [0042]    The procedures related to the production of tablets using the acyclovir drug will be commented below. 
         [0043]    There were produced lots of acyclovir tablets adsorbed with the pseudoboehmite/γ-alumina, for conducting in-process dissolution and control tests. Another lot was made using a physical mixture of the drug and of the ceramic material, in predefined proportions. 
         [0044]    The preparation of the tablets was carried out by direct compression, through the rotating press (brand Lemaq—model Mini Express L.N.S.), according to a formulation as exemplified below: 
         [0045]    Acyclovir=quantity sufficient to form a dose of 100 mg; Starch—30% of the total tablet formulation; 
         [0046]    Colloidal silicon dioxide (Aerosil 200)=2% of the total tablet formulation; and 
         [0047]    Magnesium stearate=2% of the total tablet formulation; 
         [0048]    Pseudoboehmite/γ-alumina=50 to 60% of the total tablet formulation. 
       Procedure: 
       [0049]    Mixing the formulation components (ceramic matrix/pharmaceutical composition), except the magnesium stearate, in a V-shaped mixer (brand Lemaq—model M “V”), for at least 15 minutes. 
         [0050]    Adding the magnesium stearate and mixing for at least 5 minutes. Transferring the mixture to the press-forming machine, with the aid of a scoop. Pressing the mixture in a 10 mm punch. Proceeding to the in-process control tests (average mass, friability and hardness). 
         [0051]    According to the invention, and considering the pseudoboehmite synthesis study previously carried out at the Material Characterization Laboratory of the Universidade Presbiteriana Mackenzie (Mackenzie Presbyterian University) (CARRIO, 2007; MUNHOZ JR, 2006), pseudoboehmites were synthesized from two precursors AlCl3 and Al(NO3)3.9H2O. The samples obtained were structurally analyzed and used as a support for the production of nanoparticulate systems containing bioactive molecules. 
         [0052]    The evaluation of the systems produced as drug carriers was conducted through interaction tests, by using the techniques of UV-VIS spectrometry, scanning electron microscopy, X-ray diffraction and spectrophotometry in the infrared region. 
       Preparation of the Pseudoboehmites 
       [0053]    As already previously cited, the used reagents are aqueous aluminium nitrate solution (Al(NO3)3.9H2O), aqueous aluminium chloride solution, aqueous ammonium hydroxide solution (NH4OH) (14% m and 28% m) and aqueous poly(vinyl alcohol) solution (8% m in water). 
         [0054]    The poly(vinyl alcohol) solution was used to increase the viscosity of the aluminium nitrate or aluminium chloride solution. 
         [0055]    The aluminium nitrate or aluminium chloride solution is mixed to the poly(vinyl alcohol) solution, forming a precursor solution which is then dripped in the ammonium hydroxide solution, forming a gel. After ageing the gel, this is filtered in a Buchner funnel and dried at 70° C. for 24 hours. 
         [0056]    For obtaining the γ-alumina, the pseudoboehmite should be calcined at 500° C. The X-ray diffraction is used to evaluate whether the γ-alumina was obtained. Depending on the result, the calcining temperature may be altered. 
         [0000]    Incorporation of the Drugs to the γ-alumina/pseudoboehmite 
         [0057]    The incorporation of the drugs to the ceramic matrix is conducted through the solubilization of the active principles in an appropriate solvent, followed by addition of the pseudoboehmite or γ-alumina. The mixture is maintained under constant agitation, at a determined temperature, during a given period of time. 
         [0058]    All the experimental conditions are optimized with the purpose of searching for a greater interaction between the molecule and the ceramic material, in a shorter time and at a lower temperature for the test. After the incorporation of the active principles, the mixture is centrifuged and the supernatant analyzed by UV-VIS spectrophotometry, for determining the quantity of molecules which interacted with the ceramic material. 
         [0059]    The dispersion is filtered and the resulting material is washed and dried to be used in posterior analytic procedures. 
       Interaction Test 
       [0060]    Scanning electron microscopy, UV-VIS spectrophotometry, X-ray diffraction and infrared spectroscopy are the techniques used to confirm the interaction of the molecules with the two types of ceramic material. 
         [0000]    Scanning Electron Microscopy: Direct Determination of the Interaction Process Between Drug/γ-alumina or Pseudoboehmite. 
         [0061]    The scanning electron microscopy (SEM) is a technique which allows analyzing, visually, the spatial distribution of the particulate matters and, therefore, aids in analyzing the drug/pseudoboehmite interaction process of the drug/γ-alumina interaction, contributing to the analysis of the uniformity of its distribution and to the homogeneity of the inorganic crystals of the ceramic materials. The SEM provides information about the diameter of the particulate materials and about the reproducibility of the synthesis conditions, thus allowing adjusting and improving these procedures. 
         [0000]    UV-VIS Spectrometry: Determination of the Adsorption of the Drug to the Pseudoboehmite/γ-alumina. 
         [0062]    The quantification of the active component to be adsorbed by the ceramic material may be evaluated through the ultraviolet UV-VIS spectrophotometry, via calibration curve of each of the substances in the appropriate solvent for the adsorption test and in the more adequate wave length for each substance. 
         [0063]    The optimization of the test conditions can be obtained by analyzing the conditions which most favor the adsorption. The parameters to be optimized are: total test time, temperature and the relation of concentration between the active principle and pseudoboehmite or γ-alumina. 
         [0064]    Through the analysis by UV-VIS, it can be determined the amount of active component which was not adsorbed by the matrix and, by comparing these data with the previously obtained calibration curve, one can indirectly find the concentration of bioactive molecules which were adsorbed by the ceramic matrix. 
         [0065]    Thus, it is possible to evaluate, for example, the pseudoboehmite/drug interaction and to know its adsorption yield. 
         [0000]    X-ray Diffraction: Determination of the Interaction Process Between Drug and Pseudoboehmite/γ-alumina 
         [0066]    It should be emphasized that an X-ray diffraction equipment provides qualitative and quantitative information about the obtained structure and about the drug/pseudoboehmite or γ-alumina nanointeractions. 
         [0000]    Absorption Spectroscopy in the Infrared Region: Determination of the Interaction Process Between Drug and Pseudoboehmite/γ-alumina 
         [0067]    The analysis by spectrophotometry in the infrared region can provide information about the adsorption mechanism, comparing the infrared spectra of the adsorbed drug and of the pure drug. It is possible to verify the absorption displacement of some groups of adsorbed drugs by influence of the ceramic material (WHITE &amp; HEM, 1983).