POROUS MATERIAL FOR THE DETECTION OF CANDIDA ALBICANS, DIAGNOSTIC METHOD USING SAME AND PREPARATION METHOD THEREOF

Abstract

Specifically, the invention describes obtaining a new porous material prepared to recognise DNA of the pathogenic microorganism Candida albicans, as well as the use thereof in a quick and highly sensitive in vitro diagnostic method.

Claims

1. A porous material for detecting Candida albicans, which comprises an indicator species in the inner pores and at least one DNA sequence anchored on the outer surface thereof which is complementary to a fragment of the Candida albicans genome, wherein the complementary DNA sequence blocks the release of the indicator species from the inner pores of the support.

2. The porous material, according to claim 1, wherein the complementary DNA sequence is bonded to the outer surface of the support by means of a neutral organic group and a bonding oligonucleotide.

3. The porous material, according to claim 2, wherein the neutral organic group is selected from carboxylic acid (—COOH), alcohol (—OH), aldehyde (—CHO), alkene, alkyne, amine (—NH.sub.2 or —NR′R″), amide (—C(O)NR′R″), azide (—N.sub.3), ketone (—C═O), ester (—COOR′), ether (R′—O—R″), halogen, imine (RR′C═NR″), isocyanate (—NCO), isothiocyanate (—N═C═S), nitrile (—C≡N), nitro (—NO.sub.2) or thiol (—SH).

4. The porous material, according to claim 3, wherein the bonding oligonucleotide is oligonucleotide O1 (SEQ No. 1).

5. The porous material, according to claim 4, wherein oligonucleotide O1 (SEQ No. 1) is hybridised with oligonucleotide O2 (SEQ No. 2).

6. The porous material, according to claim 1, wherein the complementary DNA sequence is bonded to the outer surface of the support by means of a cationic group.

7. The porous material, according to claim 6, wherein the cationic organic group is selected from amines, guanidine groups (H—N═(NHR)NH2), phosphonium (PH.sub.4.sup.+) or quaternary ammonium (NR.sub.4.sup.+).

8. The porous material, according to claim 7, wherein the complementary DNA sequence is oligonucleotide O3 (SEQ No. 3).

9. The porous material, according to claim 1, characterised in that it consists of mesoporous silicon dioxide with a specific surface of between 200-1400 m.sup.2 g.sup.−1.

10. The porous material, according to claim 1, characterised in that it consists of a film or plate made of nanoporous anodised alumina.

11. An in vitro diagnostic method for detecting Candida albicans which comprises: a) putting the porous material of claim 1 in contact with the DNA sample to be analysed, in an aqueous solution, b) incubating the mixture of step a) so as to produce the hybridisation reaction, c) measuring the amount of indicator species released into the aqueous phase of the mixture.

12. A method for preparing the porous material of claim 1, characterised in that it comprises the following steps: a) Preparing a support made of porous silicon dioxide or nanoporous anodised alumina, b) Introducing the indicator species into the inner pores of the substrate prepared in step a), c) Functionalising the loaded substrate obtained in step b) by bonding a neutral or cationic organic group to the surface of said substrate, d) If necessary, derivatising the substrate with a bonding oligonucleotide bonded to the neutral organic group, e) Adding a DNA sequence which is complementary to a fragment of the Candida albicans genome to the porous inorganic support obtained in step c) or d).

13. The method for preparing the porous material according to claim 12, characterised in that a DNA sequence that is hybridised with the DNA sequence which is complementary to a fragment of the genome of Candida albicans is added to the support obtained in step e).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0074] FIG. 1 shows the diagram of material S1. In this case, the porous material is loaded with the indicator species (dye/fluorophore) and functionalised with a neutral organic group. FIG. 2 shows the diagram of material S2. In this case, the porous material is loaded with the indicator species (dye/fluorophore), functionalised with a neutral organic group, and wherein oligonucleotide O1 (SEQ No. 1) is covalently anchored by means of a urea functional group.

[0075] FIG. 3 shows the diagram of material S3. In this case, the porous material is loaded with a dye/fluorophore and functionalised with oligonucleotide O1 (SEQ No. 1) whereon oligonucleotide O2 (SEQ No. 2) is hybridised.

[0076] FIG. 4 shows the diagram of material S4. In this case, the porous material is loaded with a dye/fluorophore and the outer surface is functionalised with a cationic organic group.

[0077] FIG. 5 shows the diagram of material S5. In this case, the porous material is loaded with a dye/fluorophore and functionalised with oligonucleotide O3 (SEQ No. 3).

[0078] FIG. 6 shows: [0079] I) X-ray powder diffractogram for: a) non-calcined MSNs, b) calcined MSNs, c) S1 (which is equal to S4), d) material S2, and e) material S3 (equal to S5). [0080] II) Transmission Electron Microscopy images for: A) calcined MSNs and B) material S3, S5 showing the spherical morphology typical of nanoparticles.

[0081] FIG. 7 shows Field Emission Scanning Electron Microscope (FESEM) images of: [0082] a) non-functionalised porous alumina, and [0083] b) oligonucleotide-functionalised porous alumina (which can be anchored on the support by means of covalent bonds (S8) or electrostatic interactions (S10). In both images, the disordered pore system of the inorganic matrix can be observed.

[0084] FIG. 8 (a and b) shows the functional diagram of materials S3 and S5 in the presence of genomic DNA of Candida albicans.

[0085] FIG. 9 shows the dye/fluorophore release curves (measured by means of typical fluorescence emission of Rhodamine B at 575 nm exciting at 555 nm) from inside the pores of materials S3 (a) and S5 (b) in the absence (I) and presence (II) of genomic DNA of Candida albicans.

[0086] FIG. 10 shows the dye/fluorophore release curves (measured by means of typical fluorescence emission of Rhodamine B at 575 nm exciting at 555 nm) from inside the pores of materials S8 (a) and S10 (b) in the absence (I) and presence (II) of genomic DNA of Candida albicans.

[0087] FIG. 11 shows the fluorescence (measured at 575 nm) of Rhodamine B released from material S8 in the presence of genomic DNA of Candida albicans in real samples from infected patients (A Cerebrospinal fluid, B Peritoneal fluid).

[0088] FIG. 12 shows the selectivity of material S8. The fluorescence intensity of Rhodamine B released from S8 in the presence of different pathogens and other strains of Candida is shown.

[0089] The present invention will be additionally illustrated by the following examples. The examples are provided for illustrative purposes and do not limit the scope of the invention in any way.

MATERIALS AND INSTRUMENTATION

[0090] A magnetic stirrer and normal glass and plastic material were used to prepare the porous materials. A Hettich Rotina 35 centrifuge was used to separate the materials when these were in suspension. All the reagents used to prepare the materials were used as received from the commercial firms without any additional purification.

[0091] The materials obtained were characterised by means of X-ray Powder Diffraction, Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM), N.sub.2 adsorption-desorption isotherms, particle size by means of Dynamic Light Scattering (DLS), Fourier-Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis and fluorescence spectroscopy. An Advance D8 diffractometer was used in the measurement of X-ray Powder Diffraction, using CuKα radiation (Philips, Amsterdam, the Netherlands). The TEM images were obtained using a CM10 100 kV microscope (Philips). The FESEM images were obtained using an ULTRA 55 microscope (Zeiss). An automatic ASAP 2010 adsorption analyser (Micrometrics, Norcross, Ga., USA) was used in the measurement of nitrogen adsorption-desorption isotherms.

[0092] The samples were degasified at 120° C. in a vacuum overnight. The specific surface was calculated based on the adsorption data obtained in the low-pressure range using the Brunauer-Emmett-Teller (BET) model..sup.32 Pore size was determined following the Barret-Joyner-Halenda (BJH) method..sup.33 The distribution of the particle size of the different solids was obtained using a Zetasizer Nano unit (Malvern Instruments, Malvern, UK). For these measurements, the samples were dispersed in deionised water. Data analysis was based on the Mie Theory, using refractive indices of 1.33 and 1.45 for the dispersant and for the nanoparticles, respectively. An adsorption value of 0.001 was used for all the samples. All the measurements were made in triplicate.

[0093] The infrared spectra were obtained using a Bruker TENSOR II spectrophotometer with Platinum ATR. Thermogravimetric analysis was carried out using a TGA/SDTA 851e balance (Mettler Toledo, Columbus, Ohio, USA) using an oxidising atmosphere (air, 80 ml/min) with a temperature program which consisted of a gradient of 393-1273 K at 10° C./min, followed by an isotherm at 1273 K for 30 min. The fluorescence measurements were made in a Felix 32 Analysis version 1.2 fluorimeter (Build 56, Photon Technology International, Birmingham, N.J., USA).

EXAMPLES OF EMBODIMENT

Example 1: Synthesis of Mesoporous Silicon Nanoparticles (MSNs)

[0094] Mesoporous silicon nanoparticles (MSNs) were synthesised using a surfactant (hexadecyltrimethylammonium bromide, CTABr) and a source of silicon (tetraethoxysilane, TEOS). To this end, the CTABr (1.00 g, 2.74 mmol) was first dissolved in 480 ml of deionised water. Next, NaOH (2.00 M, 3.50 ml) was added to the previous solution and the temperature was adjusted to 80° C. Next, TEOS was added (5.00 ml, 25.7 mmol) drop by drop to the previous solution. The mixture was kept under stirring for 2 hours, obtaining a white precipitate. The resulting powder was centrifuged and washed with deionised water. Finally, the solid was dried at 60° C. To prepare the final porous support, the material was calcined at 550° C. using an oxidising atmosphere for 5 hours in order to remove the surfactant.

Example 2: Synthesis of Material S1

[0095] 200 μg of calcined MSNs (50-150 nm in diameter, 1,200 m.sup.2/g of total surface) were suspended in a solution containing 766.4 mg (0.16 mmol) of Rhodamine B in 10 ml of acetonitrile, leaving the mixture under stirring at room temperature for 24 hours. Next, 247 μl (1 mmol) of (3-propyl isocyanate) triethoxysilane were added and left to react at room temperature for 5.5 hours. Next, the mixture was vacuum filtered, washed with acetonitrile and dried in a heater at 65° C. The solid obtained was characterised using thermogravimetry, TEM and X-ray Powder Diffraction techniques and identified as material S1. FIG. 1 shows the mesoporous inorganic matrix (1) obtained, which is loaded with a dye/fluorophore (Rhodamine B) (2) and functionalised with a neutral organic group.

Example 3: Synthesis of Material S2

[0096] 1 mg of material S1 was suspended in 700 μl of an acetonitrile solution with Rhodamine B (1 mM), adding oligonucleotide O1 (SEQ No. 1) (NH.sub.2—(CH.sub.2).sub.6-5′-AAA AAA CCC-3′) in a concentration of 1 nmol/mg of solid. 2 μl of triethylamine were added to this mixture and left under stirring at room temperature for 3 hours. Next, the suspension was centrifuged for 2 min at 12,000 rpm and the liquid was separated, washing the solid with 1 ml of an aqueous buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM). This suspension was separated again by centrifugation, thus obtaining material S2. FIG. 2 shows the solid obtained, which was characterised by using thermogravimetry, TEM and X-ray Powder Diffraction techniques. As shown in said FIG. 2, the porous material (1) is loaded with a dye/fluorophore (Rhodamine B) (2) and functionalised with oligonucleotide O1 (SEQ No. 1) (3), which is covalently anchored by means of a urea functional group. The concentration of oligonucleotide O1 in material S2 is 1 nmoles/mg of solid.

Example 4: Synthesis of Material S3

[0097] 100 μg of material S2 were suspended in 297.5 μl of an aqueous buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM), containing oligonucleotide O2 (SEQ No. 2) (5′-TTT TGG GGG GTT GAG AAG GAT CTT TCC ATT GAT GGG GTT TT-3′) in a concentration of 2.50×10.sup.−6 nmol/mg of solid, and left under stirring at room temperature for 2 hours. Next, the suspension was centrifuged for 2 min at 12,000 rpm and the liquid was separated, washing the solid with 500 μg of the aqueous buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM). This suspension was separated again by centrifugation, thus obtaining material S3. FIG. 3 shows the diagram of material S3, which was characterised by using thermogravimetry, TEM and X-ray Powder Diffraction techniques. As mentioned earlier, this material S3 was prepared using material S2 loaded with a dye/fluorophore (Rhodamine B) (2) and functionalised with oligonucleotide O1 (SEQ No. 1((3), whereon oligonucleotide O2 hybridises (SEQ No. 2: 5′-TTT TGG GGG GTT GAG AAG GAT CTT TCC ATT GAT GGG GTT TT-3′) (4). As a consequence of the hybridisation, given the three-dimensional structure and conformation of the hybridised oligonucleotides O1-O2, the pores of the support made of porous material become blocked. The concentration of oligonucleotide O2 in solid S3 is 2.5×10.sup.−6 nmoles/mg of solid.

Example 5: Synthesis of Material S4

[0098] 200 μg of calcined MSNs (50-150 nm in diameter, 1200 m.sup.2/g of total area), obtained in example 1, were suspended in a solution containing 766.4 mg (0.16 mmol) of Rhodamine B in 10 ml of acetonitrile, leaving the mixture under stirring at room temperature for 24 hours. Next, 293 μl (1.25 mmol) of (3-aminopropyl) triethoxysilane were added and left to react at room temperature for 5.5 hours. Next, the mixture was vacuum filtered, washed with acetonitrile and dried in a heater at 65° C. The solid obtained was characterised by using thermogravimetry and elemental analysis techniques and identified as S4. FIG. 4 shows material S4, wherein it can be observed that said porous material is formed by a porous inorganic silicon matrix (1), of the family MCM-41, loaded with a dye/fluorophore (Rhodamine B) (2) and with the outer surface functionalised with a cationic organic group (7), such as 3-aminopropyl) triethoxysilane.

Example 6: Synthesis of Material S5

[0099] 500 μg of material S4 were suspended in 500 μl of an aqueous buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM) containing oligonucleotide O3 (SEQ No. 3: 5′-TTG AGA AGG ATC TTT CCA TTG ATG-3′) in a concentration of 2.00×10.sup.−6 nmol/mg of solid) and left under stirring at 37° C. for 30 min. Next, the suspension was centrifuged for 2 min at 12,000 rpm and the liquid was separated, washing the solid with 1 ml of the aqueous buffer solution. This suspension was separated again by centrifugation, thus obtaining material S5, which was characterised by using thermogravimetry, TEM and X-ray Powder Diffraction techniques. FIG. 5 shows material S4 (1), which is loaded with a dye/fluorophore such as Rhodamine B (2), and wherein the pores are blocked by adding oligonucleotide O3 (SEQ No. 3: 5′-TTG AGA AGG ATC TTT CCA TTG ATG-3′) (5), giving rise to said material S5. The concentration of oligonucleotide O3 in solid S5 is 2.00×10.sup.−6 nmoles/mg of solid.

Example 7: Synthesis of the Support Made of Nanoporous Anodised Alumina

[0100] The mesoporous alumina plates were synthesised by electrochemical anodisation using high purity aluminium plates (99.99%). Prior to anodisation, the aluminium plates were electropolished in a mixture of ethanol and perchloric acid (4:1, v/v) at 20 V for 4 min to remove the roughness of the surface of the metal. Next, they were washed with abundant water and ethanol, and finally air-dried to remove any trace of the acid. The electropolished plates were anodised with the corresponding electrolyte using a two-step anodisation process..sup.9,10 The first anodisation was carried out for 20 hours at 40 V with oxalic acid and at 10 V with sulfuric acid. Electrolyte temperature was 2° C. in both cases. The resulting material is a nanostructured porous alumina plate with disordered pores, some of which are interconnected. This initial alumina plate was dissolved by means of a mixture of phosphoric acid (0.4 M) and chromic acid (0.2 M) at 70° C. for 3 hours, obtaining an aluminium plate with a marked surface. The second anodisation was carried out under the same voltage and temperature conditions as the first, obtaining a nanostructured porous alumina layer with non-interconnected pores. Pore distribution is ordered or disordered depending on whether the electrolyte used is oxalic acid or sulfuric acid, respectively, as shown in FIG. 7 a and b, respectively.

Example 8: Synthesis of Material S6

[0101] A porous alumina plate approximately 2 cm in diameter and with a pore depth of 8 μm was immersed in a solution containing 766.4 mg (0.16 mmol) of Rhodamine B in 10 ml of acetonitrile, leaving the mixture under stirring at room temperature for 24 hours. Next, 247 μl (1 mmol) of (3-propyl isocyanate) triethoxysilane were added and left to react at room temperature for 5.5 hours. Next, the plate was removed and allowed to dry. Once dry, the plate was divided into 8 pieces approximately 2 mm in diameter. In this way, material S6 was obtained, which was characterised using the thermogravimetry technique. Material S6 is similar to material S1 but, as mentioned earlier, porous alumina was used to obtain it instead of mesoporous silicon.

Example 9: Synthesis of Material S7

[0102] Material S6 was immersed in 700 μl of an acetonitrile solution with Rhodamine B (1 mM), adding oligonucleotide O1 (NH.sub.2—(CH.sub.2).sub.6-5′-AAA AAA CCC CCC-3′) in a concentration of 1 nmol/plate. 2 μl of triethylamine were added to this mixture and left under stirring at room temperature for 3 hours. Next, the material was removed and allowed to dry at room temperature, thus obtaining material S7, which was characterised using the thermogravimetry technique. Material S7 is similar to material S2 but, as mentioned earlier, porous alumina was used to obtain it instead of mesoporous silicon.

Example 10: Synthesis of Material S8

[0103] Material S7 was immersed in 297.5 μl of an aqueous buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM), containing oligonucleotide O2 (5′-TTT TGG GGG GTT GAG AAG GAT CTT TCC ATT GAT GGG GTT TT-3′) in a concentration of 2.50×10.sup.−6 nmol/mg of solid, and left under stirring at room temperature for 2 h. Next, it was washed with a few drops of the aqueous buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM) and allowed to dry at room temperature, thus obtaining material S8, which was characterised using the thermogravimetry the FESEM techniques. Material S8 is similar to material S3 but, as mentioned earlier, porous alumina was used to obtain it instead of mesoporous silicon.

Example 11: Synthesis of Material S9

[0104] A porous alumina plate approximately 2 cm in diameter and with a pore depth of 8 μm was immersed in a solution containing 766.4 mg (0.16 mmol) of Rhodamine B in 10 ml of acetonitrile, leaving the mixture under stirring at room temperature for 24 hours. Next, 293 μl (1.25 mmol) of (3-aminopropyl) triethoxysilane were added and left to react at room temperature for 5.5 hours. Next, the plate was removed and allowed to dry. Once dry, the plate was divided into 8 pieces approximately 2 mm in diameter. In this way, material S9 was obtained, which was characterised using the thermogravimetry technique.

Example 12: Synthesis of Material S10

[0105] Material S9 was immersed in 297.5 μl of an aqueous buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM) containing oligonucleotide O3 (5′-TTG AGA AGG ATC TTT CCA TTG ATG-3′) in a concentration of 2.00×10.sup.−6 nmoles/plate) and left under stirring at 37° C. for 30 min. Next, it was washed with a few drops of the aqueous buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM) and allowed to dry at room temperature, thus obtaining solid S10, which was characterised using the thermogravimetry the FESEM techniques.

Example 13: Characterisation of the Materials Obtained

[0106] The synthesised materials were characterised using standard methods. FIG. 6 shows the characterisation carried out on the different materials obtained. It specifically shows the X-ray powder diffractogram for: a) non-calcined MSNs, b) calcined MSNs, c) material S1 (which is equal to S4), d) material S2, and e) material S3 (equal to S5), and II) shows Transmission Electron Microscopy images for: A) calcined MSNs and B) material S3, S5 showing the spherical morphology typical of nanoparticles. The non-calcined MSNs support shows the 4 typical reflections of MCM-41-type materials corresponding to the directions in the plane (100), (110), (200) and (210). A displacement of the peak (100) can be observed in the diffractogram of calcined MSNs, corresponding to a cell contraction of approximately 7 A. Lastly, in the following diffractograms (S1, S2, S3, materials S4 and S5), the peak intensity value (100) proves that the process of filling the pores with the indicator species, in these cases the dye/fluorophore, and the functionalisation of the surface of the mesoporous solid do not destroy the three-dimensional structure of the MSNs material. The spherical morphology of the materials prepared can be visualised through Transmission Electron Microscopy (see also FIG. 6). The corresponding organic matter content (3-propyl isocyanate, 3-aminopropyl, Rhodamine B and oligonucleotides) present in the different materials was determined by means of thermogravimetric analysis. The values obtained in mmol/mg of SiO.sub.2 are shown in Tables 1 and 2.

TABLE-US-00003 TABLE 1 3-propyl isocyanate Rhodamine B O1 O2 S1 3.05 × 10.sup.−2 9.84 × 10.sup.−1 — — S2 3.05 × 10.sup.−2 3.16 × 10.sup.−1 3.18 × 10.sup.−2 — S3 3.05 × 10.sup.−2 3.17 × 10.sup.−2 3.18 × 10.sup.−2 5.04 × 10.sup.−5

TABLE-US-00004 TABLE 2 3-aminopropyl Rhodamine B O3 S4 1.23 × 10.sup.−1 4.44 × 10.sup.−4 — S5 1.23 × 10.sup.−1 3.79 × 10.sup.−4 3.32 × 10.sup.−4

[0107] The synthesised solids S6-S10 were characterised using the usual techniques for this type of systems. FIG. 7 shows the FESEM (Field Emission Scanning Electron Microscopy) image for the initial support made of nanoporous anodised alumina and for solid S8. The corresponding organic matter content (3-propyl isocyanate, 3-aminopropyl, Rhodamine B and oligonucleotides) present in the different materials was determined by means of thermogravimetric analysis. The values obtained in mmol/mg AlO.sub.2 are shown in Tables 3 and 4.

TABLE-US-00005 TABLE 3 3-propyl isocyanate Rhodamine B O1 O2 S6 1.1 × 10.sup.−2 6.7 × 10.sup.−1 S7 1.1 × 10.sup.−2  25 × 10.sup.−1 1.0 × 10.sup.−1 S8 1.1 × 10.sup.−2 2.4 × 10.sup.−1 1.0 × 10.sup.−1 1.1 × 10.sup.−1

TABLE-US-00006 TABLE 4 3-aminopropyl Rhodamine B O3 S9 1.2 × 10.sup.−1 5.47 × 10.sup.−2 — S10 1.2 × 10.sup.−1 3.79 × 10.sup.−2 4.52 × 10.sup.−2

Example 14: Behaviour of Materials S3 and S5 in the Presence of the Genomic DNA of Candida albicans

[0108] FIG. 8a) shows the functional diagram of material S3 (1). 100 μg of material S3 were suspended in 400 μl of the buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM). 200 μl were pipetted from this suspension and 800 μl of the buffered aqueous solution were added. No release of the indicator species (dye/fluorophore) (2) was observed over time. However, upon repeating the experience in the presence of genomic DNA of Candida albicans (6) (in a concentration of 2.5×10.sup.−5 nmol/mg of solid), a release of the indicator species (dye/fluorophore) (2) was observed, as shown in FIG. 9a.

[0109] In the presence of genomic DNA of Candida albicans (2×10.sup.−5 and 4×10.sup.−6 nmoles/mg of solid for S3 (8a) and S5 (8b), respectively) in a buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM), the opening of the “molecular gates” takes place, with the ensuing release of the dye/fluorophore (2). Materials S8 and S10 behave similarly.

[0110] Similarly, FIG. 8b) shows the functional diagram of material S5. In this experiment, 500 μg of material S5 (1) were suspended in 400 μl of the buffer solution at pH 7.5 (MgCl.sub.2 37.5 mM, Tris-HCl 20 mM). Of this suspension, 200 μl were pipetted and 800 μl of the buffer solution were added without observing a release of the indicator species (dye/fluorophore) (2) over time at 37° C. (see FIG. 8B). However, upon repeating the experience in the presence of genomic DNA of Candida albicans (in a concentration of 4×10.sup.−6 nmol/mg of solid) (6), a release of the indicator species (dye/fluorophore) (2) was observed, as shown in FIG. 9b.

[0111] As observed earlier, the massive release of dye/fluorophore (Rhodamine B) is caused by the opening of the “molecular gate” upon hybridisation of the oligonucleotides (O2 and O3) situated on the different materials with the genomic DNA of Candida albicans present in the sample studied.

Example 15: Behaviour of Materials S8 and S10 in the Presence of Genomic DNA of Candida albicans

[0112] Material S8 was immersed in 1 ml of the buffer solution without observing a release of the indicator species over time at room temperature. However, upon repeating the experience in the presence of genomic DNA of Candida albicans (in a concentration of 2.5×10.sup.5 nmol/mg of solid), a release of the indicator species was observed, as shown in FIG. 10a.

[0113] Similarly, material S10 was immersed in 1 ml of the buffer solution without observing any release of the indicator species over time at 37° C., as opposed to what was observed in the presence of genomic DNA of Candida albicans (in a concentration of 4×10.sup.−6 nmol/solid). In this case, a significant release of the indicator species (dye/fluorophore) was observed, as shown in FIG. 10b.

[0114] As observed, both materials are unable to release dye/fluorophore (Rhodamine B) in the absence of genomic DNA of Candida albicans. On the contrary, a massive release of Rhodamine B is observed in the presence of genomic DNA due to the opening of the “molecular gate”, upon hybridisation of the oligonucleotides (O2 and O3) situated on the different materials with the genomic DNA provided by Candida albicans.

Example 16: Behaviour of Material S8 in the Presence of Samples Infected by Candida albicans From Infected Patients

[0115] As observed in FIG. 11, in the presence of Candida albicans in real samples of infected patients in different competitive media (cerebrospinal fluid (A) and peritoneal fluid (B)), material S8 is capable of releasing the dye/fluorophore (Rhodamine B), producing significant fluorescent intensity. On the contrary, release of Rhodamine B is not observed in the absence of Candida albicans.

Example 17: Behaviour of Material S8 in the Presence of DNA of Other Strains of Candida and of Other Infectious Pathogens

[0116] FIG. 12 shows Rhodamine B released from material S8 in the presence of different pathogens and other strains of Candida. As observed, Rhodamine B is only released in the presence of Candida albicans. This experience demonstrates the high selectivity achieved with material S8.