DE4308146C2 - Modified metal oxide layers as carriers of active ingredients and reagents - Google Patents

Description

The invention relates to modified metal oxide layers which are used as carriers of active ingredients and reagents in analytics, sensors, medical diagnostics and therapy, microbiology, cosmetics and Pest control can be used as well as where a timed delivery of reagents zien to the environment is desired.

Characteristic of the known prior art

In addition to inorganic solids such as glass, metal are present as carriers of active substances and reagents all natural (paper, gelatin) or synthetic organic polymers known.

These carriers have a number of specific disadvantages, e.g. B. low loading capacity (glass, metal), low mechanical stability (paper, gelatin), little or no transparency (metal, paper), microbiological gisch vulnerable (natural polymers), incompatibility with organic solvents (gelatin, hydrophilic Polymers), low penetration capacity for aqueous reagents and ecological problems (hydro phobic polymers).

They are versatile and ecologically harmless carriers for active substances and reagents therefore on metal oxide layers that by sol-gel technology from the solution or by physical or chemi cal vapor deposition from the gas phase applied to any carrier and during or after Layer formation process can be loaded with active ingredients and reagents. Such metal oxide Layers have the advantage that they are microbiologically resistant and largely resistant to changes in pH are inert. Metal oxide layers produced by sol-gel technology have therefore already been used successfully Immobilization of enzymes and for the production of biosensors and chemical sensors, cf. SPIE Proc. Ser. 1758, 456 (1992); ACS Symp. Ser. 499, 384 (1992) and EP 0 439 318 A2 (1991); Appl.-No. 91 300 458.6 from January 22, 1991.

A major disadvantage of the unmodified metal oxide matrix, however, is that in the case of incorporation tion of active ingredients or reagents in the rigid metal oxide matrix under complex chemical reactions Involvement of multiple components can be greatly delayed or completely suppressed, which is practical Severely limits applicability.

Metal oxide layers as carriers for active ingredients or reagents are also known from DE-OS 40 20 406, the porous, hydro describes lysis-stabilized silicon dioxide as a carrier material. JP-A-5-31357 describes the use of aluminum oxide as Adsorbent for active ingredients known.

Aim of the invention

The aim of the present invention is to add metal oxide layers by adding a penetrier by means of modification so that incorporated or adsorbed active ingredients or reagents have a higher reactivity vity compared to the unmodified metal oxide layers. The function of the penetrant consists in either increasing the porosity of the metal oxide layer by extractive or thermal removal increase and thus the reaction possibilities with incorporated or adsorbed active ingredients or reagents zien to improve or as an insoluble additive to change the solid structure of the metal oxides so that the Carrier behavior towards active ingredients and reagents is improved.

State the nature of the invention

The invention has for its object suitable carriers by modifying metal oxide layers for active ingredients and reagents.

According to the invention, the object is achieved in that the layers during the manufacturing process so-called penetrants are added, which are either removed again and thereby the metal oxide Make the matrix more porous or by remaining in the layer to a changed solid structure of the Metal oxides result, resulting in changed carrier properties for active substances and reagents (e.g. adsorption ability to penetrability for reagents) result.

The metal oxide layers modified according to the invention can be used as carriers of active substances and reagents be used in areas where a close interaction with the environment is necessary or a high level Reactivity of active substances and reagents in or on the metal oxide matrix is required (microbiology, medical diagnostics and therapy. Cosmetics pest control as well as in analysis and sensor technology). For this purpose, the active ingredients and reagents can be in or on the during or after the layer formation process modified metal oxide layer can be fixed. Advantages of the layers obtained in this way are higher stability of the Active substances or reagents and their reaction products, higher reactivity and better reproducibility of reaction processes. Another advantage is that due to the high porosity and improved Adsorption capacity of the modified metal oxide layers the diffusion of applied reagents in lateral Neighboring areas are largely suppressed.

The sol-gel process or the physical process can be used to produce the modified metal oxide layers or chemical vapor deposition can be used. In the case of the sol-gel technique are preferred SiO2, Al2O3, TiO2 and mixtures thereof are used. As shown in Example 1 / IV, the mixtures can also from metal oxides and alkylated metal oxides (e.g. by joint hydrolysis of tetraalkoxysilanes and Trialkoxy-alkylsilanes) exist. In the case of metal oxides produced by vacuum deposition, there are practically no restrictions on the type of metal oxide. For those at very high temperatures  evaporable metal oxides, it is often advantageous to use the corresponding lower-order metal oxides in Ge evaporate in the presence of a certain oxygen partial pressure (reactive evaporation).

There are two active principles for modifying the metal oxide layers using penetrants costume:

1. Addition of soluble compounds during layer production

The metal oxide matrix is then made more porous and modified in such a way that the mobility and reactivity of incorporated active substances and reagents is increased and the accessibility by external reactants is improved. An instructive example can be seen in Figure 1. It shows how the diffusion of the water-soluble azo dye azo carmine from an SiO ₂ layer is changed by the addition of different low molecular weight penetrants.

Practically all substances which dissolve in solvents in which the Metal oxides are practically insoluble. If you put the metal oxides (preferably silicon, aluminum or Titanium oxide or mixtures thereof) according to the sol-gel process, the penetrants should be well in Dissolve water or alcohols because they are added to the generally aqueous-alcoholic metal oxide sols. Here metal salts or onium salts, mono- and disaccharides, acid amides, or soluble heterocytes clen are used that detached from the metal oxide layer before or during use or be removed thermally.

If you produce the metal oxide layers by physical or chemical vapor deposition, this has to be done Co-vaporized penetrants can be vaporized without decomposition. Metal halides are preferred or use any, non-decomposable evaporable, low molecular weight substances for their extraction from the Metal oxide layer also aprotic organic solvents can be used.

2. Layer additives that lead to a changed solid structure of the metal oxides

These substances remain in the metal oxide layer and change the carrier behavior by adding them against active ingredients and reagents.

This is achieved in the case of metal oxide layers which are produced by the sol-gel process through the addition of high molecular weight water-soluble substances, which diffuse due to their swelling ability Promote reagents in and out of the metal oxide matrix. Suitable compounds are water-soluble polymers like gelatin. Polyvinylpyrrolidone, polysaccharides and their derivatives, polyalcohols and polyethers, salts of Polycabonic acids and polysulfonic acids or polymeric onium salts. In the case of polyhydroxyl-containing Ver chemical incorporation into the metal oxide gel matrix by polycondensation (inorganic / organic hybrid gel).

In general, it was found that in the case of the modified metal oxide Layers the addition of polymer latices and wetting agents to improve the layer quality and often also contributes to improved penetrability of the metal oxide layer.

In the case of metal oxides produced by physical or chemical vapor deposition, one is Modification by steamed poorly soluble substances such as other metal oxides, metal sulfides, metal complexes xe or dye pigments possible, which leads to a drastic disruption and expansion of the metal oxide lattice lead and thus also change the carrier properties for active ingredients and reagents.

It is advantageous in all variants that any layer support such as paper, fleece, polymer film, glass or Metal can be used. In addition, the modified metal oxide layers can be used as a coating or serve as a layer support itself if the layer thickness is sufficient. In case of use in multi-component gene analytical or diagnostic test materials as in the glucose detection described in Example 1, in which 2 enzymes and 1 detection reagent are connected by complicated subsequent reactions (1. glucose oxide se supplies hydrogen peroxide with glucose, 2. peroxidase provides one with hydrogen peroxide and o-tolidine blue dye), the modified metal oxide layers offer numerous advantageous variants. In addition to the It is possible to incorporate all reactants into the modified metal oxide matrix speed to separate the system advantageous in which z. B. the detection reagent (o-tolidine) built into the metal oxide is while the enzymes are adsorbed on the oxide surface or already as a thin layer on the Carrier (e.g. adsorbed on paper). Other suitable variants are the complex reak tion mixture to adsorb on the modified metal oxide surface or the modified metal oxide Use layers as a protective coating.

From the tables in Example 1 it can be seen that the use of penetrants causes an increased reactivity in the metal oxide matrix. In addition, such additives influence the diffusion behavior in the layer as documented in Figure 1. This property predestines the modified metal oxide layers as carriers of active ingredients and reagents for their time-controlled release to the environment (as so-called retarder active ingredients or reagents). Example 5 documents the effect of how the availability of the known pharmaceutical active ingredient nifedipine can be varied within wide limits by means of different penetrants. This property can also be used without problems for other therapeutic agents with different geometrical shapes (granules, coated tablets, tablets) in order to control the bioavailability.

The possibility of simultaneous loading with active ingredients and dyes offers in particular in Cosmetics the possibility to combine the effect of coloring and body care.

The reagents and techniques given below are typical examples of those available de invention are suitable.  

Embodiments example 1 Use of modified metal oxide layers for analytical glucose determination (glucose sensor) (I) Introduction of all reactants into the modified metal oxide matrix Preparation of a SiO ₂ sol (solution A)

50 ml of tetraethoxysilane are stirred with 200 ml of ethanol and 100 ml of 0.01 mol of hydrochloric acid for 12 hours. After standing Any white precipitate present is filtered off overnight. The solution thus obtained is several Weeks stable.

Preparation of the enzyme solution (solution B)

500 mg glucose oxidase (GOD; 220 units / mg) and 300 mg peroxidase (POD; 202 units / mg lyophilisate) are dissolved in 50 ml water.

Preparation of a detection reagent solution (solution C)

1 g of o-tolidine is dissolved in 50 ml of n-propanol. (In principle, other indicators suitable for H ₂ O ₂ detection can also be used).

proof

Solutions with a glucose concentration are placed side by side on the test strips as described below of 20, 50, 200 and 2000 mg / 100 ml of water. Here, quantities proportional to concentration are formed of a stable blue charge-transfer complex that allows a semi-quantitative determination of glucose. To the The time t (E) at a concentration of 200 mg glucose / Determines 100 ml of water, which is necessary to achieve complete dye formation.

Layer production

5 ml of solution A are mixed with 2.5 ml of B and C, 0.2 ml of wetting agent and, if necessary, the added specified and coated with paper, cellulose acetate film and glass and 12 hours at the Air dried.

Table 1

(II) Use of modified metal oxide layers as a coating Layer production

Cotton fleece is soaked with a solution of B and C (1: 1) and dried. After 12 hours it will be like this treated fleece with a solution of (A), to which penetrants were added, coated and after 12 hours. tested analogously (I) with glucose solution.  

Table 2

(III) Separate reaction layers Layer production

Modified reagent solution D: 2.5 g of o-tolidine are dissolved in 50 ml of ethanol and mixed with 50 ml of SiO ₂ solution A.

10 ml of solution D are mixed with a penetrant, poured onto paper or cellulose acetate film and air dried for 12 hours.

The layers containing the encapsulated detection reagent o-tolidin are either in enzyme for 5 seconds solution B immersed (variant A: adsorbed enzyme) or coated with a mixture of 5 ml B and 5 ml A. (Variant B: enzyme incorporated in metal oxide). After drying overnight, the layers become analog (I) tested with glucose solution.

Table 3

(IV) Adsorbed reagents on modified metal oxide layers (A) Sol-gel layers Layer production

5 ml of solution A are mixed with 2 ml of the additives shown in the table below. The solution will be Pour onto cellulose acetate film and dry overnight.

The slide is split:
Part of the film is washed for 30 minutes, dried and then immersed in a mixture of the enzyme solution b and the detection reagent C (1: 1) for 10 minutes and air-dried overnight (variant A). The other part of the film is immersed directly in a mixture of B and C (1: 1) for 10 minutes without watering and air-dried overnight (variant B).

The layers were then tested analogously to (I) with glucose solution.

Table 4

Production of the metal oxide brine

The stated amounts of metal oxide precursors are stirred with 40 ml of ethanol and 20 ml of 0.01 mol of hydrochloric acid for 5 hours and filtered. 5 ml of filtrate are diluted with 2 ml of water or diluted with 2 ml of 10% solution of saccharin-Na (S) or 5% cellulose sulfate (C) and applied to film. Further processing takes place as indicated above:

5 ml tetraethoxysilane + 5 g aluminum triisopropylate (Solution E) 7 ml tetraethoxysilane + 3 ml triethoxymethylsilane (Solution F) 6 g tetraethyl orthotitanate (Solution G) 5 g tetraethyl orthotitanate + 1 g boric acid (Solution H) 5 g aluminum triisopropylate (Solution I)

Table 5

(B) layers by physical or chemical vapor deposition Layer production

The metal oxides are deposited in a high vacuum evaporation plant B 30.2 (HVD Dresden) on cellulose acetate film (F) or a glass carrier (G) at a pressure of p <1.3.10 ^-3 mbar.

The facility is with one Electron beam evaporator (for the metal oxides, molybdenum boats) and for thermal cover vaporization of admixtures with additional evaporator sources, which can be controlled separately, and layer thickness measurements and tempering devices and offers the possibility of adding oxygen in the case reactive evaporation. The prepared metal oxide layers are described in the following:

Table 6

exam

Layers 1-16 are 3 min. immersed in a mixture of solutions B and C (1: 1) and left overnight on the Air dried; then it is tested analogously (I) with glucose solution.

Example 2 Use of modified metal oxide layers for analytical protein determination

Solution A SiO ₂ sol analogous to Example 1/1 Solution B 15 g tartaric acid, 2 g citric acid, 5 g glycocoll are in 100 ml dist. Water dissolved Solution C. 180 mg of bromophenol blue are dissolved in 100 ml of water.

10 ml of solution A, 2 ml of solution B and 3 ml of solution C are mixed. 5 ml of this mixture are mixed with 1 ml Sorbitol or 1 ml mannitol mixed and coated with filter paper. After drying overnight, the Treatment with a solution of 3, 10 and 30 mg of human serum albumin / 10 ml of water a concentration pending change in color from yellow-green (3), light green (10) to blue-green (30 mg protein / 10 ml).

The color gradation is reproducible and more intense than with commercial test papers, e.g. B. to Detection of protein in urine can be used.

Example 3 Use of modified metal oxide layers for hemoglobin detection

• a) 1 g of o-tolidine is dissolved in 20 ml of ethanol while warm and mixed with 20 ml of SiO ₂ sols (solution A) / example 1. A cellulose acetate film is coated with this solution (solution K). After drying overnight, the film is coated with a mixture of 1 ml of 10% aqueous hydrogen peroxide-urea solution and 5 ml of solution A and air-dried.
  Treatment with a 0.5% aqueous hemoglobin solution gives a blue color after 90 seconds.
• b) If 2 ml of a 20% sorbitol solution are added to the solution K, a blue color results after 60 seconds exercise.
• c) 5 ml of SiO ₂ sols (solution A / example 1) are mixed with 2 ml of 20% sorbitol and 2 ml of 10% aqueous hydrogen peroxide-urea solution, coated on film and dried.

Treatment of the colorless film with a 0.5% aqueous hemoglobin solution gives after 40 sec a blue color.

Example 4 Use of modified metal oxide layers for pH indicators

5 ml of a 0.2% solution of nitrite yellow in water are mixed with 5 ml of SiO ₂ sol (solution A in Example 1 / I) and with 4 ml of sorbitol or mannitol. The solutions are applied to paper and dried overnight.

The papers impregnated in this way show in the envelope area between pH 5.5. . . 7 a good fine tuning of the Color shades between yellow (below pH 5.5) and blue (pH 7). In comparison to metal oxide-free test papers, that is Leakage of the color stain is greatly reduced, which improves the visual evaluation.

Example 5 Use of modified metal oxide layers for controlled drug release (I) Nifedipine release from modified sol-gel layers

1 g of nifedipine (active ingredient of Adalat® retard, 1,4-dihydro-2,6-dimethyl-4- (2-nitrophenyl) pyridine-3,5-dicarboxylic acid dimethyl ester) is heated with 25 ml of 50% acetic acid dissolved and mixed with 20 ml of SiO ₂ sol (solution A in Example 1 / I). 5 ml of this mixture are mixed with 2 ml of (a) water, (b) 20% sorbitol solution, (c) 10% saccharin-Na solution and 20% ammonium sulfate solution. These solutions are used to coat 3 × 28 cm ² cellulose strips and to air dry them overnight. 60 cm ^{2 of} the strip are divided into strips and extracted with 25 ml of 50% acetic acid at room temperature. The time course of the release of the yellow-colored nifedipine was monitored spectrophotometrically in the extraction solution. Figure 2 shows that the time release of the active ingredient can be controlled within wide limits by adding different penetrants.

(II) Nifedipine release from evaporated metal oxide layers

The following layers were produced by high vacuum evaporation:

• 1. 100 nm nifedipine on polyester film
• 2. 100 nm nifedipine with 260 nm SiO ₂ coating
• 3. 100 nm nifedipine with modified SiO ₂ NaF coating (320 nm; SiO ₂ : NaF = 60: 40 vol.%)
• 4. Mixing layer 100 nm nifedipine + 300 nm SiO ₂ ; steamed.

The layers are extracted analogously to (I) with 50% acetic acid at room temperature and the release of nifedipine is monitored spectrophotometrically as a function of time. Figure 3 shows the retarding effect when adding SiO ₂ or using a modified SiO ₂ coating.

(III) Nifedipine release from modified tablets

The pure active ingredient cores were obtained from commercially available prolonged-release tablets (Adelat retard) by swelling in water and rubbing off. The cores were brushed with SiO ₂ sol (solution A) or immersed in 5 ml of this solution, which was mixed with 2 ml of water or 2 ml of 10% saccharin solution or 2 ml of 20% sorbitol solution. After drying, the tablets were placed in a stirred 50% acetic acid and the release of nifedipine as a function of time was determined by the increase in extinction at 370 nm. The curves obtained in this way can be seen in Figure 4. The release of the active ingredient can be controlled within wide limits by modifying the SiO ₂ matrix.

Example 6 Use of modified metal oxide layers in pest control

0.5 g of palmitic acid methyl ester (attractant for the bee mite) is dissolved in 5 ml of ethanol and with 15 ml of SiO ₂ sol (solution A in Example 1 / I) and 5 ml of 20% sorbitol or 10% Saccarin-Na or 20 % Ammonium sulfate solution mixed. This solution is used to impregnate filter paper or cotton fabric strips and air dry them overnight.

These strips are then watered and dried for 30 minutes. The use of these strips shows when used in beehives, a mite attracting effect comparable to that of commercial materials.

Example 7 Use of modified metal oxide layers for the local treatment of hyperkeratosis

1 g of salicylic acid are dissolved in 50 ml of SiO ₂ sol (solution A in Example 1 / I), 5 ml of 5% cellulose sulfate solution are added, gauze fabric is soaked with this solution and this is dried overnight. To remove unwanted areas of the cornea (e.g. corns), the tissue is contacted with the relevant parts of the body for 24-36 hours. The softened cornea can then be removed, if necessary by supporting a warm bath.

Example 8 Use of modified metal oxide layers as colored nail polish

3 ml of saturated aqueous azocarmine solution are mixed with 10 ml of SiO ₂ sol (solution A in Example 1 / I) and 3 ml of 5% cellulose sulfate solution. If the mixture is applied to fingernails and air-dried, a naturally shiny, mechanically stable, light red varnish coating is obtained, which can only be removed after multiple intensive hand washing.

Claims (14)

1. Modified metal oxide layer as a carrier of active ingredients and reagents, characterized in that at least one penetrant is contained in the metal oxide, with which the layer structure of the metal oxide to influence the reactivity of the active ingredients and reagents is modified. 2. Modified metal oxide layer according to claim 1, characterized, that the penetrant is selected from the group of substances is selected, the metal salts, onium salts, mono- and disac charide, acid amides, soluble heterocycles, water soluble Polymers, polyalcohols, polyethers, salts of polycarboxylic acid ren and polysulfonic acids and polymeric onium salts. 3. Modified metal oxide layer according to claim 1, characterized, that the penetrant is selected from the group of substances is chosen, the low molecular weight, vaporizable organic Substances, metal halides, metal oxides, metal sulfides, me tall complexes and dye pigments. 4. Modified metal oxide layer according to one of the preceding the claims, characterized, that they as a one-sided coating or as a closed Coating is applied to a solid substrate.   5. Modified metal oxide layer according to claim 4, characterized, that they have a coating on a known therapeutic Active ingredient forms the form of granules, dragees or a tablet. 6. Modified metal oxide layer according to one of claims 1 to 3, characterized, that it is self-supporting. 7. Modified metal oxide layer according to one of the preceding the claims, characterized, that substances are selected as active ingredients in the Microbiology, medical diagnostics and therapy, Kos Metics or pest control are used, and that substances are selected as reagents, which as analy test materials in analytics or sensor technology be applied. 8. Modified metal oxide layer according to one of the preceding claims, characterized in that the metal oxide is formed by SiO ₂ , Al ₂ O ₃ , TiO ₂ or mixtures thereof. 9. Process for the preparation of the modified metal oxide layer according to one of Claims 1 to 8, characterized, that the formation of the metal oxide layer either from the Lö solution by a sol-gel process or from the gas phase a physical or chemical vapor deposition on egg Nem substrate is carried out, each with the addition of at least one Penetrant. 10. The method according to claim 9, characterized in that the penetrant in during the sol-gel process the metal oxide matrix is introduced and from a group is selected from substances that contain metal salts, onium Salts, mono- and disaccharides, acid amides, soluble He terocycles, water-soluble polymers, polyalcohols, poly ethers, salts of polycarboxylic acids and polysulfonic acids and polymeric onium salts. 11. The method according to claim 9, characterized in that that the penetrant during vapor deposition is deposited by cover vaporization and from the group is selected from substances that have low molecular weight, ver vaporizable organic substances, metal halides, metal oxides, Metal sulfides, metal complexes and dye pigments. 12. The method according to any one of claims 9 to 11, characterized in that SiO ₂ , Al ₂ O ₃ , TiO ₂ or mixtures thereof are used as metal oxide ver. 13. The method according to claim 10, characterized in that that added polymer latices or wetting agents will. 14. Use of the modified metal oxide layer according to ei nem of claims 1 to 8 for timed delivery of active ingredients and reagents from the metal oxide layer in the environment (retarder effect), as a carrier of cosmetics active substances and dyes for coloring and body nursing or as a multi-component analytical or diagnostic test material that contains at least one compo is located in the metal oxide layer and at least one other component is arranged on the metal oxide layer.