Technical Field

The invention relates to provision of flurbiprofen nanosuspensions using polymeric stabilizers and surfactants by wet milling (ball milling) technique.

Declaration of Support of the Scientific and Technological Research Council of Turkey (TUBITAK)

This invention was supported by TUBITAK with the project no. SBAG -117S149.

State of the Art

Today, pain and inflammation are the most frequent disorders encountered, and these disorders are among the major problems which the clinical medicine tries to solve. Accordingly, analgesic and anti-inflammatory drugs, especially non-steroidal anti inflammatory drugs, are the most used group of drugs. Aspirin is a prototype of these group of drugs, and a subgroup thereof which is most commonly used after aspirin is propionic acid derivatives. The active ingredient, flurbiprofen (FB), is in this group, and it has been proven in vitro and in vivo that it is more effective for prostaglandin inhibition and thus, for analgesic and anti-inflammatory efficiency as compared to indomethacin, ibuprofen and aspirin. Further, FB has been found to be effective in many disorders such as acute gout, migraine headache, osteoarthritis, soft tissue injuries, rheumatoid arthritis, sunburns, and postoperative ocular inflammation. However, there are some problems for obtaining the desired outcomes as its solubility is low (BCS class II). A low solubility limits the dissolution rate, absorption and therefore the bioavailability of the active ingredient, as well as the studies for the development of formulation. Today, there are many approaches for increasing the water solubility, such as solid dispersion, complexation with cyclodextrin, micronization, preparation of a prodrug or salt form, etc. These applications are not possible to be applied to all molecules, and also saturation solubility cannot be increased using the micronization method. Therefore, there is a need for novel approaches.

Nanocrystals are defined as a crystalline active pharmaceutical ingredient with a nano sized particle size. The nanocrystals of a drug consist almost entirely of an active pharmaceutical ingredient, and accordingly the problem of low loading efficiency as in the drug delivery systems is eliminated. The crystalline nature of the active ingredient is maintained, and they are stable systems as the agglomeration of the active ingredient is prevented using a stabilizer. Further, the saturation solubility, dissolution rates, and thus, bioavailability are increased as the drugs of BCS class II and IV, i.e., the drugs with low solubility, and the lipophilic substances are nano-sized. The particles of 1000-10.000 nm are obtained using the micronization method, and the bioavailability is increased depending on an increase both in the surface area and the dissolution rate. However, the particles below 1000 nm are obtained using the nanocrystal technology, and an increase in the bioavailability depends both on an increase in the surface area and in the saturation solubility. The nanocrystals may be administered in oral, parenteral, ophthalmic, or pulmonary route. The advantages of the nanosuspensions are generally as follows: they increase the oral bioavailability, act rapidly, and improve the dose proportionality, wherein their dose may be reduced due to a high bioavailability, the toxicity is decreased as no organic solvent is used for the development thereof, wherein the nanosuspensions are suitable for sterilization by filtration, the stability may be increased with the lyophilized powders thereof, wherein they are suitable for all dosage forms, targeting may be achieved, they are easy to be produced and administered, and the scaling-up process is easy to apply. The nanocrystal technology may reduce the difference in bioavailability in the fasted and fed states observed for lipophilic drugs with a low water solubility. For dermal administration, the solubility issue may be eliminated as the particles are nano sized with nanosuspensions, so a better penetration into the skin may be achieved and stable systems are obtained as the crystalline structure is maintained. Accordingly, the dermal bioavailability may be increased. To this end, suitable carrier gel formulations have been prepared in order to improve the applicability of the nanosuspension formulations prepared to the skin.

Polymeric substances, and/or surfactants are used as a stabilizer for forming nanocrystals. The selection of the type and concentration of the stabilizer is very important as this affects the particle size of the final product and protects the nanocrystals against aggregation, sedimentation and crystal growth. The polymers, and/or surfactants protect the surface by providing an electrostatic stabilization, or by creating a steric barrier on the nanocrystals. PVP (polyvinylpyrrolidone), hydroxymethylcellulose (HMC), hydroxypropylmethylcellulose (HPMC), and polyvinyl alcohol (PVA) are the most commonly used polymers as a stabilizer. The most commonly used surfactants are poloxamer 188, vitamin E TPGS, Tween 80, and sodium lauryl sulfate. The ratio of drug/stabilizer is important in the nanosuspension formulations. Drug nanocrystals may be prepared by various methods. These are precipitation, milling, homogenization, and a combination thereof. In the preparation of a nanocrystal, there are two main approaches: the bottom-up and the top-down technology.

The basic principle of the bottom-up technology is to dissolve the active ingredient in a solvent, and then to add this solution to another solvent which is miscible with the solvent, but does not dissolve the active ingredient, thereby obtaining a nanocrystal by adding a stabilizer and evaporating the solvent. Today, there is no commercial product developed by this method. This method is a simple and cost-efficient method but has many drawbacks, in that it is not suitable for the active ingredients which do not dissolve in any solvent, use of an organic solvent is needed, it is not suitable for scaling-up, and an extra processing is required to standardize the particle size. The ratio of surface area/volume and thus, the bioavailability of the drug nanocrystals are increased as the particle size of which is decreased from 10000 nm to 100 nm due to the top-down technology. Milling method is commonly used for this purpose. There are many studies on milling method which is performed by applying a mechanical force, while this method may cause a stability problem for the substances which are not resistant to the mechanical pressure and heat. Various mills are used for reducing the particle size to the sizes of micrometer and nanometer, however the most commonly used mills for the milling are ball mills.

In the method of ball mill, the active ingredient is in a dispersed form in a dispersion medium comprising a stabilizer, and the dispersion formed is placed in a milling chamber. The balls of an appropriate quality, number and size are placed in the chamber, and the device is operated upon adjusting the rotational speed. The size of the particles is reduced due to the mechanical energy provided by the balls rotating in the chamber. In this method, the chamber should be made of stainless steel, porcelain, or a rigid material in order to eliminate the debris caused by wearing. The balls are generally made of porcelain, glass, zirconium oxide, chromium, agate, or materials produced from special polymers. As a result of this method, the size of the particles in the nanosuspensions vary depending on the number and size (diameter) of the balls used, and the milling speed (rotational speed of the milling chamber). On the other hand, it should be noticed that the number of the balls constitute the 30-50% of the volume of the milling chamber, and that during milling the rotational speed of the chamber should not be too low or high, and the size of the balls should not be too small or large. Nanocrystals have a medical importance as they are easy to manufacture and improve the biopharmaceutical properties of the substances with low water solubility.

Commercial examples are Emend®, Rapamune ^® , Tricor ^® , Triglide ^® , Megace ^® , and Tricor ^® .

In the light of above, there is a need for FB nanocrystals in order to increase the solubility of the FB which is an active ingredient with a low solubility, to reduce the side effects thereof, to specifically provide analgesic and anti-inflammatory effects on the desired site, and to extend the time and the impact area.

Description of the Invention

FB nanocrystals have been developed in order to increase the solubility of the FB which is an active ingredient with a low solubility, to reduce the side effects thereof, to specifically provide an analgesic and anti-inflammatory effect on the desired site, and to extend the time and the impact area of the effect. In the ball milling process, the balls of an appropriate quality, amount and size are placed in the chamber of the device, a pre treated coarse mixture of the suspension is also placed in the chamber, and the device is operated upon adjusting the rotational speed. The size of the particles is reduced due to the mechanical energy provided by the balls rotating in the chamber.

A nanosuspension formulation of Flurbiprofen with a very low solubility is characterized by comprising PVP K30 (Povidon K30) or hydroxypropyl methylcellulose with a low viscosity (HPMC) as a polymeric stabilizer, and Plantacare 2000 (lauryl glicoside) or Tween 80 (Polysorbate 80) as a surfactant, in order to increase the solubility and bioavailability thereof.

The Flurbiprofen content of the nanosuspension formulations prepared is 0.5-10% w/v, preferably the ratio of Flurbiprofen is 4% w/v.

The ratio of Flurbiprofen in a Flurbiprofen containing nanosuspension is 1-5% w/v by weight, preferably 4% w/v by weight. Hydroxypropyl methylcellulose (HPMC) used as a polymeric stabilizer has a viscosity of 3 cps.

The ratio of flurbiprofen: HPMC in the flurbiprofen containing nanosuspensions is in the range of 1:8-8: 1 by weight. Preferably, it is 4:1 by weight.

The ratio of flurbiprofen :P VP K30 in the flurbiprofen containing nanosuspensions is 1:8- 8:1 by weight. Preferably, it is 4:1 by weight.

The ratio of flurbiprofen: Tween 80 in the flurbiprofen containing nanosuspensions is 1:4- 4:1 by weight. Preferably, it is 1:4 by weight.

The ratio of flurbiprofen: Plantacare in the flurbiprofen containing nanosuspensions is 1 :4- 4:1 by weight. Preferably, it is 2.5:1 or 4:1 by weight.

The FB containing nanosuspensions according to the invention are characterized in that it is obtained by optimizing the process parameters of the ball milling method, it comprises PVP, Tween 80, Plantacare 2000 and HPMC with a low viscosity as a stabilizer and it comprises these stabilizers at different ratios. It may comprise mannitol, etc. as a cryoprotectant.

The particle size in the nanosuspension formulation is in the range of 200-800 nm.

The flurbiprofen nanosuspensions were prepared using the ball milling method which has a high reproducibility, is more suitable for scaling-up, and provides more stable systems, when compared to the other methods. The process parameters of the ball mill were evaluated using the different formulation parameters, and an optimal formulation was determined. The measurements of particle size, polydispersity index and zeta potential were performed for the formulations obtained, and the characterization studies were performed for the lyophilized powder thereof using scanning electron microscope, X-ray powder diffraction, differential scanning calorimetry and fourier transform infrared. Further, solubility studies were performed for the nanosuspensions and the results were compared to coarse flurbiprofen powder and physical mixture (a mixture of Flurbiprofen and an excipient). The process parameters of the ball milling method are the volume of the ball, the size of the ball and the speed and time of the milling. Before a field of design is formed for the optimization of the process parameters, the most appropriate milling speed and the optimum milling time were determined by testing the different milling speeds and times. A full factorial design of 3 ³ (3 replicates) were performed in order to prepare the nanosuspensions at different times using zirconium balls of different sizes and volumes at a given milling speed. At the end of the milling process, spherical homogenous systems of 200-300 nm in size were obtained. The zeta potential value was found to be around -30 mV. A 7-fold increase in solubility was observed with this optimum formulation developed by the ball milling method as compared to the coarse powder. These methods give an opportunity for high-speed production and do not require use of an organic solvent.

A process for obtaining a flurbiprofen nanosuspension, wherein it comprises the following steps: a. preparing an aqueous solution of a polymeric stabilizer (HPMC or PVP) and a surfactant (Plantacare or Tween 80), b. dispersing and wetting flurbiprofen in this stabilizing solution, c. subjecting the coarse suspensions to a pre-milling process using a highspeed homogenizer (Ultraturrax), d. optimizing the homogenization time and speed of the Ultraturrax method, e. optimizing the parameters of the milling time, milling speed, and volume and size of the balls of the ball milling method, f. lyophilizing the obtained nanosuspensions

The homogenization speed of the Ultraturrax method is in the range of 5000-26000 rpm, preferably 10000 rpm. The homogenization time is in the range of 1-60 minutes, preferably 10 minutes.

The milling time of the ball milling process is in the range of 1-8 hours, preferably 1 hour. The milling speed is in the range of 100-600 rpm, preferably 500 rpm. The size of the ball is in the range of 0.1-2 mm, preferably 0.5 mm. The volume of the ball is in the range of 1 mL - 45 mL, preferably 25 mi ,. The volume of the formulation for the ball milling process is 1 mL - 45 mL, preferably 10 mL. The particle size of the formulation produced is in the range of 200-1000 nm, preferably 200-800 nm.

The particle size distribution of the formulation produced by the ball milling process is in the range of 0.1-0.99.

The zeta potential value of the formulation produced by the ball milling process is in the range of (-3Q)-(+30) mV. The zeta potential value is around -30 mV.

In order to determine the formulation parameters before the ball milling method, a high-pressure homogenization method may be used for the following process parameters which provide the optimization of the homogenization pressure for the high-pressure homogenizati on (HPH) technique and the optimization of both the formulation parameters and the homogenization cycle under a certain pressure.

The homogenization pressure of the HPH process is in the range of 5000-30000 psi, preferably 30000 psi.

The homogenization cycle of the HPH process is in the range of 1-40 passes. The homogenization cycle of the HPH process is 25 or 30 passes.

In case of the HPH process, the particle size of the formulation produced is in the range of 200-1000 nm, preferably 600-700 nm.

The particle size distribution of the formulation produced by the HPH process is in the range of 0.1-0.99.

The zeta potential value of the formulation produced by the HPH process is in the range of (-30)-(+30) mV. The zeta potential value is around -30 mV.

The flurbiprofen nanosuspension obtained is used for obtaining dosage forms administered dermally or orally. For oral administration, the dosage forms such as tablet, capsule, etc. comprise flurbiprofen nanosuspension. For dermal administration, a gel formulation is obtained from the flurbiprofen nanosuspension using a suitable gel agent. For obtaining a gel formulation, an agent is used as a gel forming agent, which is selected from 1-5% w/v of chitosan, 0.5-5% w/v of polycarbophil (Noveon AA-1), 1-20% w/v of HPMC K100 LV, 1,5% w/v methyl cellulose, 1,5% w/v carboxymethylcellulose, 1-5% w/v carbopol 934, 1-5% w/v of carbopol 940 and 1-20% w/v of pluronic F-127. Another embodiment of the gel formulation comprises aerosilin (2-10% w/w), liquid paraffin (30% v/v) and olive oil (68.5% v/v). Example 1

Obtaining of a Flurbiprofen nanosuspension using ball milling technique, optimization of process parameters, and preparation of suitable gel formulations

For obtaining nanosuspensions using the ball milling method, the formulation parameters, the ball diameter and the ball volume are kept constant, and a milling process was performed at milling speeds in the range of 300-500 rpm for 1-8 hours. According to these results, the upper limit of the optimal milling speed and milling time was determined. Subsequently, a full factorial design of 3 ³ (3 replicates) is performed with these process parameters using the ball diameter, the ball volume and the milling time. At the end of the study carried out with the balls of different sizes in the range of 0.1-2 mm such that the volume of the ball is 5-25 mL, the data obtained by measuring the particle size, PDI and ZP values were statistically assessed. In addition, other characterization studies were also performed. Characterization of nanosuspensions:

Particle size (PS) and polxdispersilx index (PDI): The particle size and distribution (PDI) are the most parameters for assesing the efficiency and stability of the nanosuspensions. The mean particle size and distribution of the nanosuspensions prepared using method parameters, and types and ratios of stabilizers were measured by Malvem-Zetasizer. Zeta potential (ZP): The zeta potential is a parameter which indicates the electrical charge on a surface of a colloidal system, and thus the physical stability thereof. The zeta potential of nanosuspensions which are prepared using the method parameters, and types and ratios of stabilizers was measured by Malvem-Zetasizer. Morphological analysis: The morphological features of the FB nanosuspensions, which were found to be optimal using the ball milling method, of the physical mixture, and of the coarse mixture thereof as well as the marked differences between the particles thereof were viewed by SEM.

Fourier Transform Infrared Spectroscopy (FT-IR): The spectra were examined in order to asses the effect of the methods, method parameters and stabilizers which were used on the chemical structure of the physical mixtures and the nanosuspensions.

Differential Scanning Calorimetry ( DSC): This was used to asses the effect of the methods, method parameters and stabilizers which were used on the internal structure of the physical mixtures and the nanosuspensions.

X-ra diffraction (XRD): This was used to determine the possible changes in the internal structure of the FB nanosuspensions which were prepared using the method parameters, and the types and ratios of the stabilizers. In addition, XRD method was used to reveal the crystal/amorphous structures of the nanoparticles and different polymorphic phases of the polymers.

Solubility studies: These solubility studies were performed to determine the increase in water solubility of the prepared nanosuspensions compared to the coarse powder and physical mixture.

Preparation of Nanosuspension Gel Formulations

Chitosan gel formulation containing nanosuspension

First, glacial acetic acid (1% v/v) was added to half the required amount of the nanosuspension in order to prepare a chitosan gel. The required amount of chitosan (2% w/v) was weighted, added to the glacial acetic acid solution, and mixed gently. Upon swelling, the rest of the nanosuspension was added and stirred at 500 rpm at room temperature until it became homogenous.

Polycarbophil gel formulation containing nano suspension Polycarbophil (Noveon AA-1) (5% w/v) was dispersed in the nanosuspension and stirred at 800 rpm for 60 minutes. Then, it was neutralized by adding 10% NaOH dropwise. It was mixed until a transparent appearance was obtained.

Oleogel formulation containing nano suspension

Tween 80 (1 mL) was added onto the oil phase obtained by mixing aerosilin (8.5% w/w), liquid paraffin (30% v/v) and olive oil (68.5% v/v) at 150 rpm for 5 minutes. Then, a homogenous oleogel was obtained by adding the nanosuspension as water phase.

HPMC gel formulation containing nano suspension

HPMC K100 LV (5%) was weighted, and dispersed in the nanosuspension, coarse suspension or physical mixture, and stirred at 500 rpm at room temperature for 60 minutes until a homogenous gel was obtained.

Characterization of the carrier gels

Evaluation of the physical appearance

The physical appearance, homogenity at room temperature and color of the nanosuspensions prepared within a carrier gel and empty carrier gels were examined. pH determination

The pH values of the nanosuspensions prepared in a carrier gel and the empty carrier gels were determined using a pH meter and a neutralization process was performed. Triethanolamine and 0.1 M HC1 were used for the neutralization (Argenziano et al., 2017).

Viscosity determination

The viscosities of the the nanosuspensions prepared in a carrier gel and the empty carrier gels were measured using a rotational viscometer (Brookfield, USA). The measurement of the shear stresses formed under the different shear rate conditions (decreasing from 100 to 0 and increasing from 0 to 100) was performed on the formulations prepared using a spindle no. 42. Each measurement was repeated three times and the mean values were calculated. Further, the flow properties of the gels were determined by plotting the shear rate versus the shear stress. Studies for in vitro release from the carrier gels and ex vivo skin permeation In order to determine the optimal gel type, studies were carried out for permeation through a membrane and a rat skin at 37°C. Gels containing 6.25 mg of FB were weighted and placed in a donor compartment. The nanosuspension containing HPMC gel, chitosan gel, polycarbophil gel and oleogel were placed in the donor compartment and sampling was performed at certain time points (0.25, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24 and 40 hours). The samples were analysed using HPLC, and HPMC was determined to be the optimal carrier gel. In order to increase the amount of FB permating through the skin of the determined optimum carrier gel formulation, the release studies were repeated by adding Transcutol to the donor compartment as a permeation enhancer and the optimum gel formulation was compared to the gel formulations prepared with coarse powder suspension and physical mixture of FB. The samples were analysed using HPLC by sampling at certain time points (0.25, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24 and 48 hours), and at the end of each release study, lag time (T _L ), flux (Js), permeability coefficient (Kp), and the amount of FB permeated through the skin were calculated. In addition, the amount of FB remaining on the skin was also calculated and the difference between the results obtained was evaluated statistically (p<0.05; n= 3).

RESULTS At the end of these studies, the formulation parameters and the process parameters of the ball milling method were determined. The particle size, PDI and ZP values of the optimum nanosuspensions prepared by the ball milling method with these parameters were found to be 200-300 nm, 0.1-0.2 and around -30 mV, respectively. Morphological analysis

While the coarse powder of Flurbiprofen had irregular particles in macrometer size (Figure 1A), the Plantacare 2000 was adsorbed onto the surface of FB coarse powder in the physical mixture (Figure IB). It was observed that the nanosuspensions obtained by ball milling had a more spherical and homogeneous appearance (Figure 1 C-D).

Differential Scanning Calorimetry (DSC)

DSC measurements were performed in order to assess the possible polymorphic change of the active ingredient FB and no change was observed in the melting point of FB by means of preparing the optimum nanosuspension. The melting point was found to be 114.9°C. Given the DSC thermogram of the physical mixture, no incompatibility was observed between Flurbiprofen and Plantacare 2000. In addition, any polymorphic change was not determined as well (Figure 2).

X-ray powder diffraction (XRPD)

XRPD measurements were performed in order to determine whether the substances and methods which were used during the preparation of the nanosuspension had an effect on the crystalline structure of FB. Finally, the ball milling method and lyophilization process were observed not to have any effect on the internal crystalline structure of FB (Figure

3).

Fourier Transform Infrared Spectroscopy (FT-IR)

The effect of the methods, method parameters and stabilizers which were used on the chemical structure of the physical mixtures and nanosuspansions prepared was examined using FTIR and no difference was shown between the spectrum thereof (Figure 4).

Solubility studies

The solubility studies were performed in order to determine an increase in the solubilities of the nanosuspensions prepared using the ball millig method as compared to the coarse powder and physical mixtures. As seen in table 1, the solubility of FB and was increased 4 times with the physical mixture, while the water solubility of FB was increased 7 times with the nanosuspensions prepared using the ball milling method.

Table 1. Solubility results of FB coarse powder, physical mixture and nanosuspension prepared by the ball milling method (mean ± S.D.)

Consequently, the Flurbiprofen containing nanosuspension is characterized in that: a) a pre-milling process is applied using Ultraturrax before the ball milling method, b) the process parameters of Ultraturrax is optimized, c) the lower and upper limits of the milling speed and time are determined with the ball milling method, d) the optimum process parameters are determined using the different volume and

5 size of the ball, milling time and milling speed.

Evaluation of the Results of the Gel Formulation

Evaluation of Physical Appearance

The physical appearance, homogenity at room temperature and color of the 0 nanosuspension prepared within a carrier gel were examined. Empty and nanosuspension- containing gels with a homogenous appearance were obtained. The empty chitosan, HPMC and polycarbophil gels had a clear appearance, while an empty oleogel was white. All nanosuspension-containing gels were white and had a homogenous appearance. 5 pH determination

The pH measurements were provided in Table 2 for the empty and flurbiprofen nanosuspension (FB-NS)-containing gel systems. The pH value of the gel systems prepared using HPMC was around a neutral pH, whereas the pH values of the others were neutralized using triethanolamine, and the studies were continued. 0

Table 2. Results of pH measurements of the empty and FB -NS -containing gel systems (mean±S.D., n=3) 5 Viscosity Determination

The results of the viscosities of the gel systems prepared are provided in Table 3. The lowest viscosity values were observed in HPMC and chitosan gels among the nanosuspension-containing gels, while the highest viscosity was observed in polycarbophil gel. Graphics of the shear stresses formed under the different share rate 0 conditions (decreasing from 100 to 0 and increasing from 0 to 100) are seen. All gel systems were determined to show a non-newtonian flow behavior. A pseudoplastic flow was observed in HPMC gels with and without NS, while a plastic flow was observed in all other gels. Table 3. Results of viscosity determinations of all gel systems at 10 rpm (Shear rate: 20 sec. ^_1 ) (mean ± S.D., n = 3)

Evaluation of Studies for In Vitro Release from the Carrier Gels and Ex Vivo Skin Permeation

In vitro and ex vivo release studies were performed using a dialysis membare and rat abdominal skin at 37°C for 40 hours in order to determine the optimum type of the carrier gel. The release studies were carried out for different types of FB -NS -containing carrier gels (Chitosan, Polycarbophil, HPMC gel abd Oleogel). The best release profile was observed in nanosuspension-containing HPMC gel (HPMC-NS gel) and a similar release profile was obtained with a nanosuspension (NS) which was not placed in a gel. The release profiles of FB from different types of NS -containing carrier gels were examined using dorsal skin of a rat. Among the carrier gels, the best release profile was observed in HPMC gel. The permeability coefficient, flux and amount of cumulatively permeated FB which were calculated according to the release profiles obtained using a dialysis membrane and rat skin are shown in Table 4. The amounf of FB permeated through the skin and the flux value were determined to be higher in HPMC gel as compared to the other gel systems. Table 5 shows the amounts of FB remaining on the skin as a result of an ex vivo skin permeation study performed using different carrier gels for 40 hours. The highest amount was observed in HPMC gel.

Table 4. Permeability coefficient (cp), flux (J) and amount of FB permeated at the end of 40 hours (mean ± S.D., n=3)

Table 5. The amount of FB remaining on the skin at the end of the 40 hours in ex vivo skin permeation studies through carrier gels (mean ± S.D., n = 3)

Industrial Aplicability of the Invention The flurbiprofen nanosuspension, the solubility and physical stability of which are increased, is used in a liquid or lyophilized form in a suitable gel formulation for dermally or in solid dosage forms (tablet, capsule, orodispersible tablet, etc.) for orally administration.

Description of the Figures

Figure 1 represents SEM images of FB. A- Coarse powder (mag. 2.000x), B- Physical mixture (mag. 2.000x), C- Nanosuspension (mag. 20.000x), D- Nanosuspension (mag. 50.000x).

Figure 2 represents a DSC thermogram of FB coarse powder, physical mixture and nanosuspension.

Figure 3 represents XRD results of FB coarse powder (A), physical mixture (B) and lyophilized nanosuspension (C).

Figure 4 represents FT-IR results of FB coarse powder (top), physical mixture (middle) and lyophilized nanosuspension (bottom).