Bioresponsive particles

Abstract

Shielding enzymes are made by modifying the enzyme surface with silica precursors and then depositing silica to a desired thickness while retaining biological activity of the enzyme.

Claims

1. A method of making hybrid enzyme-silica nanoparticles (HES-NPs), comprising the steps of: a) reacting acryloyl groups of acrylic compounds with amine groups of enzymes to covalently decorate the enzymes with enone groups; b) coupling silyl amines to the enone groups to covalently decorate the enzymes with silyl groups, forming silica-modified enzymes; c) growing siloxane scaffolds around the silica-modified enzymes, wherein the silyl groups seed the growth of the siloxane scaffolds to form the hybrid enzyme-silica nanoparticles, with each of the nanoparticles comprising a nanoporous silica shell encapsulating a plurality of the silica-modified enzymes; and d) isolating the hybrid enzyme-silica nanoparticles.

2. The method of claim 1, wherein the acrylic compounds comprises an acryloyl group and a N-hydroxysuccinimide group.

3. The method of claim 1, wherein the silyl amines are 3-aminopropyl trimethoxysilane (APTMS) or 3-aminopropyl triethoxysilane (APTES).

4. The method of claim 2, wherein the silyl amines are 3-aminopropyl trimethoxysilane (APTMS) or 3-aminopropyl triethoxysilane (APTES).

5. The method of claim 1, wherein the enzymes are selected from catalase, superoxide dismutase, asparaginase, methioninase, carboxypeptidase G2 and luciferase.

6. The method of claim 4, wherein the enzymes are selected from catalase, superoxide dismutase, asparaginase, methioninase, carboxypeptidase G2 and luciferase.

7. The method of claim 1, wherein the shell is spherical and has a porosity that allows free access to small molecule substrates of the enzymes, while excluding proteases, antibodies and immune cells.

8. The method of claim 1, wherein step (c) comprises contacting the silica-modified enzymes with tetraethoxysilane under surfactant-free aqueous conditions and hydrolyzing silane groups to start the growth of the siloxane scaffolds.

9. The method of claim 1, wherein step (c) comprises contacting the silica-modified enzymes with tetraethoxysilane under reverse emulsion conditions and hydrolyzing silane groups to start the growth of the siloxane scaffolds.

10. The method of claim 1, wherein the nanoparticles are of average size 20-50 nm-diameter.

11. The method of claim 1, wherein the nanoparticles are conjugated with targeting groups comprising peptides or antibodies to target cancer cells.

12. The method of claim 1, wherein the enzymes are selected from catalase, superoxide dismutase, asparaginase, methioninase, carboxypeptidase G2 and luciferase.

13. The method of claim 7, wherein: the acrylic compounds comprise an acryloyl group and a N-hydroxysuccinimide group; and the silyl amines are 3-aminopropyl trimethoxysilane (APTMS) or 3-aminopropyl triethoxysilane (APTES).

14. The method of claim 7, wherein: the acrylic compounds comprises an acryloyl group and a N-hydroxysuccinimide group; the silyl amines are 3-aminopropyl trimethoxysilane (APTMS) or 3-aminopropyl triethoxysilane (APTES); and the enzymes are selected from catalase, superoxide dismutase, asparaginase, methioninase, carboxypeptidase G2 and luciferase.

15. The method of claim 1, further comprising the step of administering the nanoparticles to a person in need thereof.

16. The method of claim 1, further comprising the steps of administering the nanoparticles to a person in need thereof, the enzyme in the hybrid enzyme-silica nanoparticle is catalase.

17. The method of claim 1, further comprising the step of administering the nanoparticles to a person in need thereof, wherein the nanoparticles provide a bioresponsive ultrasound contrast agent, and imaging the patient by ultrasound.

18. The method of claim 1, further comprising the step of administering the nanoparticles to a person in need thereof, wherein the person has or is at demonstrable risk of reperfusion injury and the enzyme in the hybrid enzyme-silica nanoparticle is catalase, effective to scavenge reactive oxygen species (ROS).

19. The method of claim 1, further comprising the step of administering the nanoparticles to a person in need thereof, wherein: the person has leukemia and the enzyme is asparaginase and/or methioninase, effective to deplete asparagine and/or methioninase, or the person has cancer and the enzyme is methioninase, effective to deplete methionine in combination with or without chemotherapy; or the person has a hypoxic solid tumor and the enzyme is catalase, effective to oxygenate solid tumors for radiosensitization; or the person has a hypoxic solid tumor and the enzyme is catalase, the method further comprises the step of infusing H.sub.2O.sub.2 to the person, effective to oxygenate the solid tumors for radiosensitization.

20. The method of claim 1, further comprising the step of administering the nanoparticles to a person in need thereof, wherein the person is administered a prodrug prior to, concomitant with, or after administration of the nanoparticles, and the enzyme is prodrug converting enzyme, effective to convert the prodrug to a therapeutic drug.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1. Schematic representation of the preparation of hybrid enzyme-silica nanoparticles using catalase as a model enzyme (CAT-HES-NP).

(2) FIG. 2. Representative TEM images of LIES-NP produced under aqueous (left) or reverse emulsion (right) conditions.

(3) FIG. 3. Schematic representation of the preparation of hybrid asparaginase-silica nanoparticles using one-pot reverse emulsion conditions (ASNase-HES-NP).

(4) FIG. 4. Representative TEM image of ASNase-HES-NP produced under one-pot reverse emulsion conditions.

(5) FIG. 5. Representative characterization of HES-NP obtained by aqueous conditions with nanoparticle tracking analysis (NTA) and intensity-weighted dynamic light scattering (DLS) size distribution.

(6) FIG. 6A. Activity of free catalase and CAT-HES-NP after incubation at 37° C. for 16 h with or without proteinase K.

(7) FIG. 6B. Activity of free asparaginase and ASNase-HES-NP after incubation at 37° C. for 26 h with or without cathepsin B.

(8) FIG. 7A. Biodistribution of .sup.89Zr-CAT-HES-NP in tumor-bearing mice expressed as percent injected dose per gram of tissue.

(9) FIG. 7B. Passive tumor uptake of .sup.89Zr-CAT-HES-NP relative to blood and muscle over time.

(10) FIG. 8. Creatinine levels 24 hours post-AKI with three doses of CAT-HES-NP.

DESCRIPTION OF PARTICULAR EMBODIMENTS OF THE INVENTION

(11) We disclose a novel hybrid approach to shielding enzymes. We first modify the enzyme surface with silica precursors and then proceed to deposit silica to a desired thickness while retaining its biological activity. An advantage of this approach is that we can control final nanoparticle size and desired enzyme activity per particle by incorporating one or more or different enzyme molecules to optimize delivery and efficacy. Unlike passive trapping of enzymes in hollow silica spheres that utilize templates ≥100 nanometers, our nanoparticles can be made as small as 20-50 nanometer to achieve optimal delivery and enzyme activity. In an embodiment we exemplify the method with catalase as a model enzyme because it can be used to detect tissues in oxidative stress using ultrasound imaging, can be used as an anti-oxidant, and its activity is easily measured using commercial assay kits. In another embodiment example, we used our method to encapsulate catalase and also to encapsulate asparaginase. Our novel approach is not enzyme-specific and can be applied to any enzymes. Other exemplary enzymes include but are not limited to superoxide dismutase, methioninase, carboxypeptidase G2 and luciferase.

(12) The invention provides a method for coating enzymes in nanoporous silica that allows free access to small molecules substrates, but not larger molecules such as antibodies or immune cells to be used as a treatment or imaging tool without interacting with the immune system. This approach extends the enzyme's activity in vivo and limits or prevents immune reactions.

(13) General procedure for the preparation and characterization of hybrid enzyme-silica nanoparticles (HES-NP):

(14) Preparation of HES-NP

(15) Enzyme (i.e., catalase, superoxide dismutase, asparaginase, methioninase, etc.) (36 mg) was dissolved in sodium carbonate buffer (7.2 mL, 20 mM, pH 9.15) and a solution of N-acryloxysuccinimide (36 mg, in DMSO (72 μL) was added. The resulting mixture was stirred for 1 hour at room temperature and was purified by spin filtration in Amicon spin filters (Molecular weight Cutoff=10 kDa) at 4,000 g for 10 min. The filtrate was discarded, and the retentate was washed with water and spin filtered again at 4,000 g for 10 more minutes to yield the enone-modified enzyme (FIG. 1, step a). The purified enone-modified enzyme (3 mL, 12 mg/mL) was diluted down to a concentration of 1.5 mg/mL in 1M phosphate buffer pH 6.0 and water. (3-aminopropyl) trimethoxysilane (96 μL) was then added the resulting mixture was stirred for 1 hour at room temperature and purified by spin filtration in Amicon spin filters (Molecular weight Cutoff=10 kDa) at 4,000 g for 10 min. The filtrate was discarded, and the retentate was washed with water and spin filtered again at 4,000 g for 10 more minutes to yield the silica-modified enzyme (FIG. 1. Step b).

(16) Before particle formulations, the silica-modified enzyme was filtered through a syringe filter (0.2 μm) to remove large aggregates. The silica-modified enzyme was then formulated into particles using two different formulations. The first method (aqueous conditions) yields nanoparticles around 100 nm or around 200 nm, and the second method (reverse emulsion) yield ultrasmall nanoparticles around 50 mm.

(17) A] Aqueous Conditions

(18) Tetraethoxysilane (240 μL) was added to the silica-modified enzyme solution in water (1.5 mg/mL, 2 mL). The resulting mixture was stirred vigorously for 10 minutes and ammonium hydroxide (7.2 μL of 28% NH.sub.4OH solution) was added to hydrolyze silane groups and start the silica particle growth. The resulting emulsion was stirred vigorously for 2 hours at room temperature particles were collected by high speed centrifugation at 20,000 g for 15 minutes. After this time, supernatant was discarded and pellets were redispersed in water (4 mL) for a second wash and centrifugation. The supernatant was discarded a second time and pelleted particles were dispersed in water for storage and characterization.

(19) B] Reverse Emulsion Conditions

(20) Tetraethoxysilane (142 μL) was added to the silica-modified enzyme solution (1.5 mg/mL, 500 μL) under reverse emulsion conditions with decane (oil phase, 28.409 mL), IGEPAL® CO-520 (surfactant, 2.318 mL) n-hexanol (co-surfactant, 784 μL). The resulting mixture was stirred vigorously for 10 minutes and ammonium hydroxide (71 μL of 28% NH.sub.4OH solution) was added to hydrolyze silane groups and start the silica particle growth. The resulting emulsion was stirred vigorously overnight at room temperature and ethanol (16 mL) was added to remove surfactants and precipitate the particles. The resulting bottom layer was extracted and submitted to high speed centrifugation at 20,000 g for 15 minutes. After this time, supernatant was discarded and pellets were redispersed in water (4 mL) for a second wash and centrifugation. The supernatant was discarded a second time and pelleted particles were dispersed in water for storage and characterization.

(21) One-Pot Preparation of ASNase-HES-NP

(22) ASNase-HES-NPs were prepared without surface functionalization (FIG. 3). Tetraethoxysilane (242 μL) was added to the enzyme solution (1 mg/mL, 500 μL) under reverse emulsion conditions with decane (oil phase, 28.409 mL), IGEPAL® CO-520 (surfactant, 2.318 mL), and n-hexanol (co-surfactant, 784 μL). The resulting mixture was stirred vigorously for 10 minutes and ammonium hydroxide (71 μL of 28% NH4OH solution) was added to hydrolyze silane groups and start the silica particle growth. The resulting emulsion was stirred vigorously overnight at room temperature and ethanol (10 mL) was added to remove surfactants and precipitate the particles. The resulting bottom layer was extracted and submitted to high speed centrifugation at 20,000 g for 15 minutes at 4° C. After this time, the supernatant was discarded, and pellets were redispersed in water (4 mL) for a second wash and centrifugation. The supernatant was discarded a second time and pelleted particles were dispersed in water for storage and characterization.

(23) Characterization of HES-NP

(24) Nanoparticles were sonicated at 10° C. for three minutes in a bath sonicator before size measurements to prevent aggregation. Transmission electron microscopy (TEM, FEI Tecnai G2 Spirit transmission electron microscope equipped with a Gatan camera operating at 120 kV with. Digital Micrograph software) was performed with negative staining (2% uranyl acetate in water) on carbon-formvar coated copper grids. TEM pictures of CAT-HES-NP were taken and showed monodisperse particles for aqueous (FIG. 2, Left) and reverse emulsion conditions (FIG. 2, Right) with sizes between 30 and 60 mm Additionally, TEM pictures of ASNase-HES-NP were taken and showed monodisperse particles with approximate sizes of 50 nm (FIG. 4).

(25) The hydrodynamic diameter of HES-NP was measured at 169.7 nm with a PdI of 0.159 by Dynamic Light Scattering (DLS, FIG. 5) (Zetasizer Z S, Malvern Instruments). HES-NP were measured with a mean diameter of 152.6 nm (StdDev=60) with a concentration of 7.6×10.sup.11 NPs/mL by Nanoparticle Tracking Analysis (NTA, ZetaView, Particle Metrix, FIG. 5). The difference in size between the real size (TEM) and the size measured by DLS is explained by the higher scattering from larger molecules increasing the overall hydrodynamic diameter of the particle population.

(26) Activity Measurements of CAT-HES-NP

(27) The enzymatic activity of CAT-HES-NP (aqueous phase) was evaluated electrochemically to detect the first-order decomposition of H.sub.2O.sub.2 using a four-channel Free Radical. Analyzer (Item #TBR4100, World Precision instruments, Sarasota, Fla.) equipped with a H.sub.2O.sub.2 macro sensor (Item #: ISO-HPO-2). A standard curve using free CAT was created by measuring the current decay rate when known concentrations of H.sub.2O.sub.2 were added. Three different free CAT concentrations were used to construct the standard activity curves, to which the activity of CAT-HES-NP was compared. Briefly, the H.sub.2O.sub.2 sensor was equilibrated in PBS (1×) with stirring at 300 rpm. H.sub.2O.sub.2 (400 μL, 1 mM) was added into the PBS solution and shortly after, an aqueous solution of CAT (20 μL, 2 mg/mL) was added. Data collection was ended when the current reached zero. This process was repeated two more times with increasing concentrations of CAT (40 μL and 60 μL). Decay linearization was performed by taking the natural log of the linear portion of the current channel to obtain sample decay rates. Activity (U/mL) was calculated from the respective CAT volumes (Equation 1).
Activity (U/mL)=[CAT baseline activity (4,500 U/mg)*Concentration of CAT solution (mg/mL)*volume (μL)]/1000/Electrolyte volume (mL)  Equation 1

(28) The decay rate (pA/s) was plotted against the corresponding activity (U/mL) to obtain the standard curve. The resulting slope of the standard curve (pA*mL/U*s) was used as the standard activity slope. The activity of CAT-HES-NP was measured in triplicate with the previously described method. From the standard curve, decay rate, and known dilution factors, the activity of the CAT-HES-NP was calculated. CAT-HES-NP have an average activity of 2,000 U/mL in 1 mg/mL (free CAT=4,500 U/mL in 1 mg/mL).

(29) Stability Measurements of CAT-HES-NP

(30) To confirm that enzyme-loaded silica nanoshells protect enzymes from inactivation by proteolysis, the activity of free enzyme and encapsulated enzyme was evaluated in the presence of proteinase K, a serine protease that cleaves a wide range of proteins. In this experiment, we used catalase as a model protein, as it is not expensive, allows facile observation of activity by naked eye (bubbles generated upon addition of H.sub.2O.sub.2) and quantitative measurement of the enzymatic activity using electrochemical detection. Specifically, we incubated free catalase and CAT-HES-NP overnight at 37° C. in pure water in the presence of CaCl.sub.2 (10 mM, 50 μL) and proteinase K (50 μL at 1 mg/mL). After 16 h, free catalase kept only 6% of its activity, while CAT-HES-NP kept 87% of its activity (FIG. 6A). This slight activity loss is most likely due to the degradation of catalase attached at the surface of the particle.

(31) Activity Measurements of ASNase-HES-NP

(32) The enzymatic activity of ASNase-HES-NP was measured by colorimetric detection using Nessler's assay (Sigma Aldrich, EC 3.5.1.1). Nessler's reagent is a solution of potassium tetraiodomercurate(II) (K.sub.2[HgI.sub.4]) and potassium hydroxide that changes color in the presence of ammonia. Briefly, a solution of asparagine (25 μL, 189 mM) in Tris buffer (250 μL, 50 mM, pH=8.6) and water (225 μL) was equilibrated to 37° C. Solutions of ASNase or ASNase-HES-NP were added and further incubated at 37° C. for 30 min. After 30 min, the reaction was quenched with trichloroacetic acid (25 μL, 1.5 M). The resulting solution was diluted in a 96-well plate with water and Nessler's reagent (12.5 μL) was added. After 1 min, the absorbance was measured at 436 nm at room temperature. An ammonia standard curve was prepared by plotting absorbance at 436 nm versus ammonia concentration from ammonium sulfate standards. ASNase activity was determined from the measured absorbance of the sample and the ammonia standard curve. One unit of ASNase corresponds to the liberation of 1.0 μmol of ammonia from L-asparagine per minute at pH 8.6 at 37° C. ASNase-HES-NPs formulated using one-pot reverse emulsion conditions were measured to have activity of 375 U/mL in 1 mg/mL (specific activity of ASNase used for formulations=440 U/mL in 1 mg/mL).

(33) Stability Measurements of ASNase-HES-NP

(34) To confirm that asparaginase-loaded silica nanoshells is protected from inactivation by proteolysis, the activity of free enzyme and encapsulated enzyme was evaluated in the presence of cathepsin B, a lysosomal protease that is present in leukemic cells and degrades ASNase. Specifically, free ASNase (60 μL, 1 mg/mL) and ASNase-HES-NP (60 μL, 0.5 mg/mL) were incubated for 26 h at 37° C. in the presence of sodium citrate buffer (30 μL, 10 mM, pH=5) and cathepsin. B (30 μL, 0.5 mg/mL). After 26 h, free ASNase was completely depleted while ASNase-HES-NP retained 98% survival from control (FIG. 6B)

(35) Radiolabeling CAT-HES-NP with .sup.89Zr

(36) First, CAT-HES-NP was modified with a mixture of mPEG-silane and silane-PEG-thiol for biodistribution studies. Briefly, tetraethoxysilane (240 μL) was added to the silica-modified enzyme solution in water (1.5 mg/mL, 2 mL). The resulting mixture was stirred vigorously for 10 minutes and ammonium hydroxide (7.2 μL of 28% NH.sub.4OH solution) was added to hydrolyze silane groups and start the silica particle growth. The resulting emulsion was stirred vigorously for 2 h at room temperature, then ammonium hydroxide (3.5 μL of 28% NH.sub.4OH solution) was added to increase the pH before a mixture of mPEG-silane (Creative PEGWorks, MW 2 k 250 μL, 20 mg/mL) and silane-PEG-thiol (NANOCS, MW 5 k, 200 μL, 10 mg/mL) in 95% v/v ethanol was added and stirred at room temperature for an additional 1 hour. Particles were collected by high speed centrifugation at 20,000 g for 15 minutes at 4° C. After this time, the supernatant was discarded, and pellets were redispersed in water (4 mL) for a second wash and centrifugation. The supernatant was discarded a second time and pelleted particles were dispersed in water. Then, the particles were conjugated with deferoxamine-maleimide (DFO-mal), a strong chelator to .sup.89Zr. Briefly, DFO-mal (7.1 mg, 10 mop was dissolved in DMSO (50 μL) and stirred at room temperature overnight with CAT-HES-NP (2 mg/mL, 10 mL, 10 μmol silane-PEG-thiol). After 17 hours, the particles were purified via high-speed centrifugation (20,000 g, 15 min, 4° C.) and then concentrated 5 times and dispersed in PBS 1× (10 mg/mL, 5 mM DFO-mal, 3.5×10.sup.12 NPs/mL).

(37) CAT-HES-NPs were radiolabeled with .sup.89Zr (half-life=3.3 days). Briefly, .sup.89Zr oxalate (1.416 mCi) was added to CAT-HES-NP and stirred at 650 rpm for 2 h at 37° C. After 2 h, the particles were purified by spin filtration in. Amicon spin filters (Molecular weight Cutoff=10 kDa) and centrifuged at 4,000 g for 10 min. The retentate and filtrate activity was measured, and the filtrate was discarded. Pentetic acid (200 μL, 50 mM, pH=7) was added to the retentate to remove free .sup.89Zr and then the spin filters were centrifuged. The retentate and filtrate activity was measured at this time and the filtrate was discarded. Then, PBS (1×, 400 μL) was added to the retentate and the spin filters were centrifuged. The filtrate activity was measured and then discarded. This process was repeated with PBS (1×). Finally, the radiolabeled particles were recovered by inverting the spin filters and centrifuging at 1,000 g for 2 min. The recovered particles were diluted to reach 100 μCi/mL. Three standards (9 μCi) were kept aside for decay corrections. The radiostability of the particles were assessed in fresh rat plasma and PBS (1×) using the previously described procedure. Radiolabeled CAT-HES-NP was radiostable up to 7 days in plasma and PBS (1×).

(38) Biodistribution of .sup.89Zr-CAT-HES-NP in Tumor-Bearing Mice

(39) Nude mice were injected with 1×10.sup.6 MC-38 tumor cells in the flank and tumors were allowed to grow for 10 days. After 10 days, tumor-bearing mice were intravenously injected in the tail vein with .sup.89Zr-CAT-HES-NPs (10 μL, 10±1 μCi) and were sacrificed at 30 min (N=4), 24 h (N=4), 48 h (N=5), and 7 d (N=4). The animals were dissected, organs were removed and weighed, and radioactivity in each organ and tumor was measured with a gamma counter. The percent injected dose per gram of tissue (% ID/g) over time showed preferential accumulation in the lung, liver, spleen, kidneys, and bone marrow (FIG. 7A). The particle accumulation in the tumor relative to blood and muscle increased over time, demonstrating passive tumor uptake (FIG. 7B)

(40) Acute Kidney Injury (AM) Model with CAT-HES-NP

(41) An in vivo AKI model was carried out in female Sprague Dawley rats to assess the potential of scavenging reactive oxygen species by CAT-HES-NP in the event of ischemic reperfusion, ultimately providing a protective effect for the kidney. Nephrectomies were performed in the right kidney 7 days prior to the AKI as the presence of both kidneys could normalize the serum blood urea nitrogen (BUN) and creatinine (Cr) values used to assess renal function. Blood and urine samples were collected for baseline values, then CAT-HES-NP was administered intravenously via tail vein 5 min before AKI was produced in the left renal artery by occlusion for 60 min. This experiment included 5 groups: saline as a positive control (N=2), sham as a negative control (N=1), and 3 treatment groups (377, 754, and 1508 U) with N=3 each. Blood and urine samples were collected at 24 hours post-AKI to assess recovery. CAT-HES-NPs in PBS (1×) were sonicated for at least 5 min to minimize aggregation before injection. The resulting Cr levels 24 hours post-AKE suggests a protective effect with a positive dose response (FIG. 8).

(42) It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein, including citations therein, are hereby incorporated by reference in their entirety for all purposes.