|Title of Invention||
A METHOD FOR PREPARING NANOPARTICLES COMPRISING A POLYMER
|Abstract||Method for preparing nanoparticles containing a polymer stages consisting of: a) preparing a complex of at least one active ingredient with at least one compound able to complex the latter, in solution in an aqueous or non-aqueous solvent, b) gradually adding at least one monomer of the polymer in the solution obtained at stage (a), and c) conducting polymerization, for example anionic or inducible by other agents, in particular photochemical agents, of this monomer optionally in the presence of one or more surfactant and/or stabilizing agents.|
|Full Text||FORM 2
THE PATENT ACT 1970 (39 of 1970)
The Patents Rules, 2003 PROVISIONAL / COMPLETE SPECIFICATION (See Section 10, and rule 13)
A METHOD FOR PREPARING NANOPARTICLES COMPRISING A POLYMER
BIOALLIANCE PHARMA (S.A.) of 67, RUE VERGNIAUD, F-75013 PARIS, FRANCE, FRENCH COMPANY
The following specification particularly describes the nature of the invention and the manner in which it is to be performed :-
NANOPARTICLES COMPRISING AT LEAST ONE POLYMER AND AT LEAST ONE COMPOUND ABLE TO COMPLEX ONE OR MORE ACTIVE
The invention concerns the delivery of active ingredients used, in particular, in the area of preventive, curative or diagnostic medicinal products and also concerns the improvement in their therapeutic index (improvement in the benefit/risk ratio).
Its more particular purpose concerns new nanoparticles containing at least one active ingredient.
The prime objective sought by the development of new delivery or release systems for active ingredients is the controlled delivery of an active agent, especially a pharmacological agent, to its site of action at optimum rate and therapeutic dose (I). The improvement in the therapeutic index may be obtained by modulating the distribution of the active ingredient inthe body. The association of the active ingredient with a delivery system enables, in particular, its specific delivery to the site of action or its controlled release after targeting the action site. By reducing the amount of active ingredient in the compartments in which its presence is not desired, it is possible to increase the efficacy of said active ingredient, to reduce its toxic side effects and even to modify or restore its activity.
The colloidal delivery systems for active ingredients include liposomes, microemulsions, nanocapsules, nanospheres, microparticles and nanoparticles. Nanoparticles offer the advantages of targeting modulation of distribution and flexible formulation and have a polymer structure which may be designed and produced in a manner that is adapted to the desired objective. They have proved to be particularly promising for obtaining an improved therapeutic index as defined above owing to their ability to ensure controlled release, specific delivery to the action site or targeted delivery allowing both an increase in efficacy and a reduction in toxic side effects on other organs.
This type of administration requires the use of biodegradable polymers. Among these po!y(alkyl cyanoacrylates) are of special interest since their bioerosion is seen to occur rapidly in comparison with other biodegradable polymers and takes place during periods of time that are compatible with therapeutic or diagnostic applications.
Despite these characteristics of interest, the active ingredient content capacity of nanoparticles of poly(alkylcyanoacrylates), expressed in quantity of active ingredient associated with a mass unit of polymer, is often limited, especially when the active ingredient is only scarely soluble in water since the production of nanoparticles uses polymerization techniques in an aqueous medium. This considerable limitation of the active ingredient content capacity is especially observed with hydrophobic, amphiphilic and/or insoluble active ingredients.
The relatively low ability of conventional nanoparticles to carry an adequate quantity of active ingredients from the administration site to the target site in the body often risks leading to the necessary administration of considerable quantities of polymers.
Poly(alkyl cyanoacrylates) are used to produce nanoparticles as vectors of active ingredients (3). However, for the above-mentioned reasons, the low vector loads obtained,especially with hydrophobic, amphiphilic and/or water insoluble active ingredients, restrict their therapeutic use.
In surprising manner, it has now been found that it is possilbe to widen the scope of use of polymers, in particular poly(alkylcyanoacrylates), by associating with them one or more compounds able to complex active ingredients and thereby to obtain new nanoparticles having original properties.
The subject of the invention is therefore nanoparticles containing at least one active ingredient, characterized in that they comprise the association of at least one polymer, preferably a poly(alkylcyanoacrylate), in which the alkyl group, linear or branched, comprises 1 to 12 carbon atoms, and of at least one compound able to complex said active ingredient.
The compound able to complex the active ingredient according to the invention is preferably chosen from among the cyclical oligosaccharides, in particular from among the cyclodextrins which may be neutral or charged, native (cyclodextrins α β, γ, 8, e), branched or polymerized, or even chemically modified for example by substitution of one or more hydroxypropyls by groups such as alkyls, aryls, arylalkyls, glycosides, or by etherification, esterification with alcohols or aliphatic acids. Among the above groups, particular preference is given to those
chosen from hydroxypropyl, methylm, sulfobutylether groups.
In unexpected manner, the presence of a compound able to complex the active ingredient in the association of the invention enables the active ingredient, even if it is hydrophobic, amphophilic and/or insoluble, to penetrate inside the polymer structure resulting from the association of the polymer of polymers and said compound or compounds able to complex the active ingredient, with an encapsulation yield within this structure that is significantly increased compared with the prior art, a yield which appears to be related to the equilibrium between firstly the solubilisation resulting from the use of compounds able to complex the active ingredient, and secondly the affinity of the active ingredient for the new polymer structure, which brings substantial progress at therapeutic and industrial levels. Also, the nanoparticles also stabilize the complex formed between said compound(s) and said polymer(s) owing to the solid nature of the nanoparticles.
Through the invention, it is now possible to load nanoparticles, for example of poly(alkylcyanoacrylate) type, not only with hydrophilic active ingredients but also with hydrophobic, amphophilic and/or insoluble active ingredients.
The association of a polymer with a compound able to complex the active ingredient brings the possibility of creating new fixation sites for the active ingredient which are not apparent with polymers used alone. The creation of these new sites, in particular a hydrophobic cavity, with compounds able to complex active ingredients makes it possible to increase the content load of active ingredienet while maintaining its capacity for controlled and delayed release which is non-existent when compounds able to complex are used alone.
The prior art describes the preparation of cyanoacrylate-containing polymers in which the alkylcyanoacrylates are associated with dextran during the preparation stage (Egea M. A. et al., Farmaco, 1994, 49, 211-17). In this method, however, dextran is conventionally used as a stabilizing agent and does not permit complexing of an active molecule. Also, dextran is a linear polysaccharide with high molecular weight and it is threrefore fundamentally different from the cyclodextrins which have a low molecular weight and are able to complex other molecules. Therefore, the nanoparticles according to the present invention offer original
modulation of their size,
increased encapsulation of active molecules, especially hydrophobic, amphiphilic and/or insoluble molecules,
optional absence of stabilizer such as dextran.
US Patent 5 641 515 ( No Indian Patent available) also described the encapsulation of insulin with a polycyanoacrylate polymer. This encapsulation is based on the formation of covalent bonds between insulin and the polymer, which is different from the nanoparticle-based complexing of the present invention. The nanoparticles of the invention are based on the ability of a molecule of an active ingredient to combine itself with one or more cyclodextrin molecules through the creation of low-energy chemical bonds, that are hence non-covalent, such as to form an inclusion complex. The existence of this complex results from the formation of an equilibrium between a) the free forms of the active ingredient and cyclodextrin and b) the inclusion complex. It is quantitatively characterized by its stability constant. In the meaning of the present invention, the term complexation exclusively describes this latter phenomenon. Therefore, the complexation of the active ingredient is implemented not only during the preparation of the nanoparticles but also in the prepared nanoparticles, in which it represents a means of associating a greater quantity of active ingredient.
It is helpful to recall that in general the association of an active ingredient with nanoparticles may result from simple dispersion of the active ingredient in crystal form in the particle-foaming polymer, from solubility of the active ingredient in the polymer, from adsorption bringing into action secondary chemical bonds (low-energy), or finally from a covalent bond (high-energy) with the particle-forming polymer.
In this respect, it is appropriate to point out that the preparation of nanoparticles requires polymerization of the monomers of alkylcyanoacrylates dispersed in aqueous phase. Synthesis of the poly(alkylcyanoacrylate) then enables formation of the nanoparticles. Generally, this is conducted in the presence of the active ingredients to be encapsulated. It may therefore, in some cases, lead to the non-desired development of covalent chemical bonds between the
active ingredient and the formed polymer. This phenomenon has been reported for peptides (Grangier J.I., J. Controlled Rel., 15, 3-13, 1991) or other molecules (vinblastin, V. Guise et al, Pharma. Res., 7, 736-741, 1990).
The present invention remedies this disadvantage since, by masking the potentially reactive chemical groups,the complexation of the active ingredient during the preparation of the nanoparticles of the invention makes it possible to protect said active ingredient against the chemical reactions that are necessary for the formation of the particle. Therefore, the active ingredient is advantageously associated in non-covalent manner with the particle.
Also, the association of the active ingredient with nanoparticles is generally conducted in an acid aqueous medium. For some active ingredients, however, that are unstable under these conditions, there is a resulting risk of chemical degradation likely to lead to the non-desired encapsulation of hydrolysis derivatives which is, moreover, detrimental to obtaining a high encapsulation level of the active ingredient. On the other hand, in the present invention, the complexation of active ingredients with cyclodextrins makes it possible to overcome these disadvantages as it enables the active ingredients to be protected against the outside reaction medium.
As examples of active ingredients which may enter into the composition of the nanoparticles of the invention, mention may be made of anticancer and antisense substances, antivirals, antibiotics, proteins, polypeptides, polynucleotides, antisense nucleotides, vaccinating substances, immunomodulators, steroids, analgesics, antimorphinics, antifungals, antiparasitics. Among the latter,the invention gives particular consideration to taxol or one of its derivatives, doxorubicin or one of its derivatives, platinum derivatives.
The active ingredient is generally present in a quantity of 0.01 to 300mg/g of nanoparticles.
The proportion of compound able to complex the active ingredient is in general from 0.1 to 70% by weight.
The proportion of active ingredient and the proportion of compound able to complex are independent from one another.
The invention evidently also relates to pharmaceutical or diagnostic compositions comprising the nanoparticles of the invention and at least one vehicle that is pharmaceutically acceptable and compatible.
A further purpose of the invention is the preparation of the previously described nanoparticles.
A first method of preparing nanoparticles containing a polymer, more particularly a poly(alkylcyanoacrylate) as defined above, is characterized in that it comprises the stages consisting of:
a) preparing a complex of at least one active ingredient with at least one compound able to complex the latter, in solution in an aqueous or non-aqueous solvent,
b) gradually adding at least one monomer of the polymer, more particularly the alkylcyanoacrylate monomer, in the solution obtained at stage (a), and
c) conducting polymerization, preferably anionic, but also inducible by other, especially photochemical, agents of this monomer, optionally in the presence of one or more surfactant and/or stabilising agents.
A second method of preparing the nanoparticles of the invention, forming an alternative to the first above method, consists of firstly preparing nanoparticles containing a polymer, more particularly poly(alkylcyanoacrylates),and a compound able to complex an active ingredient, also called "blank nanoparticles", then associating the active ingredient with said blank nanoparticles. More particularly, this method comprises the stages consisting of:
a) preparing a solution of at least one compound able to complex an active ingredient in an aqueous or nonaqueous solvent,
b) gradually adding at least one monomer of the polymer, more particularly the alkylcyanoacrylate monomer, to the solution of stage (a),and
c) conducting polymerization, preferably anionic but also inducible by other agents, in particular photochemical agents, of this monomer, optionally in the presence of one or more surfactant and/or stabilising agents.
d) after controlling and optionally purifying the nanoparticles obtained at stage(c), incubating said particles in a solution of the active ingredient in an aqueous or non¬aqueous solvent.
As in the first method, the association of the active ingredient with the blank nanoparticles is dependent upon the quantity of cyclodextrins associated with the nanoparticles. This second method offers two advantages:
it avoids having to conduct purification stages on the nanoparticles loaded with active ingredient, which may lead to active ingredient losses,
it enables a system to be produced which may be extemporaneously loaded with active ingredient, for example when the active ingredient is very unstable in solution.
The invention therefore also relates to blank nanoparticles, that is to say non-loaded, obtained after stages (a) to (c) in the second above-described method. Also, these blank particles are of therapeutic interest owing to the activity of the cyclodextrins especially in the area of cancer treatment (Grosse P. Y., et al., British Journal of Cancer, 78 : 9, 1165-1169, 1998).
During stages (a) and (b) of the first method of the invention, the solvent is advantageously chosen such that, while maintaining conditions propitious to polymerization of the polymers, of (poly)alkylcyanoacrylates in particular, the solubility of the active ingredient and of the compound able to complex is maximum in the medium defined by this solvent. Advantageously said solvent is preferably chosen from among aqueous or hydroalcoholic solvents. The solvent is chosen in the manner described for stages (a) (b) and, (d) of the
second method of the invention.
The presence of a surfactant or stabilising agent is necessary to prepare the nanoparticles of the prior art. As is shown in the following examples, such agents are no longer necessary for the present invention. The compound able to complex the active ingredient, such as cyclodextrins, paradoxically have a sufficient stabilising effect for the surfactant agent usually used to be omitted. On an industrial scale this represents a notable savings..Also it is observed that poly (alkylcyanoacrylate) stabilizes the complex made up of the active ingredient and the compound able to complex the active ingredient.
However, if the method of the invention entails the use of a stabilising and/or surfactant agent, preference is given to a dextran or a poloxamer.
According to one preferred embodiment of the invention, the potentialities of the cyclodextrins vis-a- vis the active ingredients allow new properties to be added to the particles. The presence of cyclodextrins in the particles enables stabilisation of the active ingredients which would be unstable in solution, or even the masking of some unfavorable characteristics of the active ingredients such as an irritant action.
The production methods for nanoparticles known to date have shortcomings concerning the possibilities of size adjustment of the nanoparticles. In unexpected and remarkable manner, with the method of the invention it is possible to adjust nanoparticle size directly during their production with no special additional stage.
As is shown in the following examples, the size of the nanoparticles of the invention is essentially related to the concentration of the compound able to complex the active ingredient. For cyclodextrins, this size can be varied over a very wide range from 300 to less than 50 nm. Through the invention therefore, using simple preliminary tests, it is possible to adjust nanoparticle size in the compositions of the invention, especially pharmaceutical compositions, depending upon the special desired effect. In theory, having choice of size it is subsequently possible, if so desired, to overcome some physical obstacles to the distribution of nanoparticles in the body, or to prevent capture of the nanoparticles of the composition by the
reticuloendothelial system. It also enables new targeting of organs.
Consequently, at stage (a) of the method of the invention the proportion of compound able to complex the active ingredient is generally, from 0.1 to 70% by weight in re\lation to said active ingredient. As indicated above, the choice of concentration of the compound able to complex the active ingredient makes it possible to vary the size of the nanoparticles obtained with the method of the invention. Nanoparticles with a size of between 40 and 300 nm can be obtained.
Studies on the release of the compound able to complex the active ingredient and release of the active ingredient show that the release curve of the compound able to complex the active ingredient is very rapid and that release is close to 100 %, while release of the active ingredient comprises a first rapid stage followed by a slower second stage due to bioerosion, conventionally described in respect of poly(alkylcyanoacrylates).
In active ingredient release tests, the use of esterases which deteriorate the nanoparticles shows the active ingredient is largely contained in nanoparticle matrix network, which is of importance the viewpoint of expected activity (4).
The different tests conducted on a range of steroids, from the most hydrophilic (hydrocortisone) to the most hydrophobic (progesterone) have shown that vary varied active ingredients may be contained in the nanoparticles of the invention at high concentrations depending upon their physico-chemical characteristics such as their degree of hydrophobicity in particular.
For example the progesterone used as a model in the following examples has very low water-solubility (0.01 mg/ml) which, in conventional emulsion-in-water polymerization methods, can only lead to obtaining a very low active ingredient content that is of no practical advantage. Therefore this content is low when preparation techniques of the prior art are used. In particularly surprising and interesting manner, this content is more than 50 times higher in the nanoparticles of the invention. The invention therefore gives access to hydrophobic, amphiphilic and/or insoluble active ingredients and hence to a change in their therapeutic
A further purpose of the invention is therefore the use of the above-described methods to produce a medicinal product having targeted effect and an improved therapeutic index.
Other advantages and characteristics of the invention will become apparent with the description of the following examples which refer to the appended drawings in which :
Figure 1 shows the variations in particle size, or granulometry, and in the zeta potential (average of three tests ± SD) of nanoparticles of poly(isobutylcyanoacrylate) (PIBCA) prepared in the presence of 2-hydroxypropyl-P-cyclodextrin (HPpCD) in relation to the initial concentration of (HPpCD).
Figure 2 shows the variations in granulometry and zeta potential (average of three tests ± SD) of PIBCA nanoparticles prepared in the presence of the progesterone complex: 2-hydroxypropyl-β-cyclodextrin (HPpCD), relative to the initial concentration of HPpCD.
Figure 3 shows the variations in HPPCD content (average of three tests ± SD) of PIBCA nanoparticles prepared in the presence of HPpCD, in relation to the initial concentration of HPpCD.
Figure 4 shows the variations in HPPCD content (average of three tests ± SD) of PIBCA nanoparticles prepared in the presence of the progesterone : HPpCD complex, in relation to the initial concentration of HBpCD.
Figure 5 shows the variations in progesterone content (average of three tests ± SD) of PIBCA/HPPCD nanoparticles, in relation to the initial concentration of HPpCD.
Figure 6 shows the influence of particle size on the release rate of progesterone in alkaline borate buffer (ABB) (pH 8.4) from PIBCA/HPpCD nanoparticles.
Figure 7 shows the influence of the constitution of the release medium on the release rate of progesterone in ABB medium (pH 8.4), from PIBCA/HPβCD nanoparticles.
A: ABB :PEG 400 (80:20) B: ABB .PEG400(60:40)
Figure 8 shows the influence of the presence of esterase-type enzymes on the release rate of progesterone in ABB medium (pH 8.4) from PIBCA/HPJ}CD nanoparticles.
A : release medium with esterase 25 IU B : release medium with esterase 100 IU
Figure 9 shows the release rate of HPβCD in ABB medium at 37°C.
Figure 10 shows the tracings of differential scanning calorimetry (DSC) obtained with a rate of temperature rise of 10°C/min.
In the following examples isobutylcyanoacrylate, hydrocortisone, prednisolone and danazol, progesterone and esterases (19 IU/ml) were obtained from Sigma Chemicals (ST. Louis, Mo, USA), spironolactone, testosterone, megestrol acetate were obtained respectively from Sophartex, Besin-Iscovesco and Upjohn, a-, (3- and y- cyclodextrins, 2-hydroxypropyl-α-, 2-hydroxypropyl-β- and 2-hydroxypropyl-Y-cyclodextrins, with average MS values of respectively 0.9, 0.6 and 0.6 were obtained from Wacker Chemie GmbH (Munich, Germany) and sulfobutyl β-cyclodextrin ether (hereinafter SBEβ(CD) was obtained from CyDex L. C. (Overland Park, Kansas, USA). Poloxamer 188 (Lutrol F68®) was a donation from BASF (Ludwigshafen, Germany) .The other chemical products and solvents are of analytical and HPLC grade.
EXAMPLE 1 : Preparation of nanoparticles in the presence of different cvclodextrins and
The nanoparticles are prepared by anionic polymerization (2) of 100 μl isobutylcyanoacrylate
in 10 ml 0.01 M hydrochloric acid (pH 2.0) containing 1 % w/v poloxamer 188 and in the
presence of 5 mg/ml α-, β-, γ~, 2-hydroxypropyl-a-, 2-hydroxypropyl-p- or 2-hydroxypropyl-y-cyclodextrin or sulfobutyl p-cyclodextrin ether. The cyclodextrin solution is magnetically stirred (lOOOr/min) at ambient temperature and the monomer is added drop by drop. After stirring for 6 hours, the suspension is filtered through a 2.0 urn prefilter (Millex AP 500®) and then further characterized.
EXAMPLE 2 : Preparation of nanoparticles in the presence of different cvclodextrins. The nanoparticles are prepared by anionic polymerization (2) of 100μ1 isobutylcyanoacrylate in 10 ml 0.01 M hydrochloric acid (pH 2.0) in the presence of 5 mg/ml of a-, p-, y-, 2-hydroxypropyl-a-, 2-hydroxypropyl-p or 2-hydroxypropyl-Y-cyclodextrin or sulfobutyl p-cyclodextrin ether. The cyclodextrin solution is magnetically stirred (lOOOr/min) at ambient temperature and the monomer is added drop by drop. After stirring for 6 hours, the suspension is filtered through a 2.0 mm prefilter (Millex AP 500® and then further characterized.
EXAMPLE 3: Preparation of progesterone / hydroxypropvl-β-cyclodextrin (HPpCD)
The progesterone/HPβCD complexes are prepared by mixing 3.615 g HPPCD with 3.0 g
progesterone in 150 ml water under magnetic stirring for 24 hours at ambient temperature.
Afterwards, the mixture is filtered (0.45 μm). The HPβCD and progesterone are titrated in the
filtered solution before being used for the preparation of progesterone-containing
EXAMPLE 4: Preparation of nanoparticles of (polylisobutvlcvanoacrvlate/ HPpCD fPIBCA/ HPflCD) containing progesterone.
The solution of the progesterone/HPpCD complex obtained as described in example 3 is diluted to obtain concentrations of 2.5, 5.0, 7.5, 10.0, 12.5, 15.0 and 20.0 mg/ml of HPpCD in the polymerization medium. The nanoparticles are prepared as in example 1, in the absence or presence of 1% (w/v) of polyxamer 188.
EXAMPLE 5 (reference) : Preparation of nanoparticles of polv(isobutvlcyanoacrvlate) containing progesterone with no HPβCD
Nanoparticles of poly(isobutylcyanoacrylate) are prepared in the absence of cyclodextrin in the polymerization medium, to act as reference. The progesterone-containing nanoparticles are prepared by dissolving the active ingredient in diluted hydrochloric acid (pH 2.0) in the presence of 1% (w/v) of poloxamer 188 (approximately 60 μg/ml), corresponding to maximum solubility in this medium). The polymerization process is implemented as described in example 1.
EXAMPLE 6: Titration of progresterone and HPftCD in the nanoparticles obtained. The different suspensions of nanoparticles are centrifuged at 82 000 g for 30 to 40 min at 25°C (Beckmanm, L5-65 Ultracentrifuge, 70.1 Ti type rotor) and re-suspended in 5 ml distilled water, the suspensions are finally freeze-dried (Christ HED Freeze Drier, Germany).
To titrate the progesterone content in the nanoparticles, the freeze-dried products are diluted in acetonitrile of HPLC grade and the solutions are analyzed by high performance liquied chromatography (HPLC). The HPLC system consists of a 510 solvent delivery unit (Waters-Saint-Quentin-en-Yvelines, France), a WISP 712 automatic sampler, a column Nova-Pak C18 4 μm column (250 x 4.6 mm), a 486 absorbency detector which operates at 245 nm and is interfaced with a 746 data module. The flow rate is 1.0 ml/min and the mobile phase is made up of water and acetonitrile (40:60) for which the retention time is approximately 12 min. The results are expressed as an average of three titrations.
For quantification of HP|3CD, the freeze-dried nanoparticles are hydrolyzed with 0.2 M NaOH for 12 hours, the pH is adjusted to 7.0 (±0.5) and the HPpCD is quantified by spectrophotometric titration of the discoloring of phenolphthalein solutions in the presence of HPPCD. Phenolphthalein forms stable, colorless inclusion complexes with cyclodextrins (CD) (5). consequently, the color intensity of a phenolphthalein solution in alkaline borate buffer decreases in proportion to the quantity of CD in solution.
Reference solutions are prepared by diluting mother solutions of CD in alkaline borate buffer solution with pH 10.0 containing 2% ethanol solution of 0.006 M phenolphthalein. The reference curves (X = 550 nm) are linear for CD concentrations ranging from 1 to 100 μg/ml. To the samples are added 4 parts buffer solution containing phenolphthalein and they are then tested directly.
EXAMPLE 7 : Characterization of the nanoparticles .
Granulomere distribution, average size and polydispersity of the nanoparticles are estimated by laser light difiusion using an NS Coulter Nanosizer (Coultronics, Margency, France). The samples are dispersed in MilliQ water (resistivity > 18 MQ, Millipore, Saint-Quentin-en-Yvelines, France). Each analysis lasts 200 s. The temperature is 20°C and the analysis angle is 90°. The zeta potential of the particles in suspension in MilliQ water is determined by Doppler laser velocimetry (Zetasizer 4, Malvern, England).
RESULTS OF EXAMPLE 1 to 7.
The characteristics of the particles prepared in the presence of 5 mg/ml of different cyclodextrins and 1% poloxamer 188 (average of 3 repeated preparations + SD) are grouped in table I below.
CD = cyclodextrin HP = hydroxypropyl SBE = sulfobutyl ether
Particle size, zeta potential, cyclodextrin content and stability (values not given) are influenced by the nature of the cyclodexrin.
The quantity of the different cyclodextrins bonded to the particles lies in the range of 20 to 35% (w/w) of total particle weight.
The nanoparticles formulated with HPpCD offer the most interest as they have an average granulometry of less than 100 nm and a zeta potential close to zero mV. Also, HPPCD offers very extensive solubility in the polymerization medium and excellent tolerability. It also enables the encapsulation of numerous substances. Consequently, additional studies were conducted on HPpCD.
In the presence of HPpCD in the polymerization medium, the addition of the poloxamer 188 surfactant agent is not essential for the production of nanopartilcles.
Firstly, as shown in Figure 1, the size and zeta potential of the particles are not modified by the presence of poloxamer 188.
Secondly, the concentration of HPPCD has a considerable influence on size and zeta potential. An increase in HPpCD concentration from 0 to 12.5 mg/ml leads to a reduction in particle size from 300 nm to less than 50 nm. Also, the zeta potential of the particles gradually decreases from strongly negative values (-40 mV) to a surface potential close to 0 mV. These trends are generally maintained when the nanoparticles are prepared in the presence of progesterone as shown in Figure 2. Compared with the particles not containing progesterone, the zeta potential is slightly negative in the HPpCD concentration range being studied. Also, in the absence of poloxamer 188 a rapid increase is observed in nanoparticle size, up to 450 nm, followed by a rapid decrease when the HPpCD concentration is greater than 10 mg/ml. This phenomenon does not occur in the presence of poloxamer 188. The addition of HPPCD to the polymerization medium leads to the association of large quantities of HPpCD with the nanoparticles, as is shown in Figure 3. The quantity of HPpCD associated with the particles continuously increases and may reach 60% of particle weight. When the initial masses of HPβCD and isobutylcyanoacrylate in the polymerization medium are equal, the quantity of HPβCD associated with the particles is approximately 35%. Also, the association of HPpCD with the particles is not influenced by the presence of poloxamer 188. The HPpCD content of the nanoparticles is not considerably affected by the presence of progesterone in the polymerization medium, as is shown in Figure 4. The progesterone content of the particles increases in spectacular fashion when the particles are prepared in the presence of HPpCD. The progesterone content, in the absence of HPβCD is 0.79 μg/mg of particles, and it gradually increases until it is multiplied by 50, which corresponds to 45 μg/mg of particles, as
is shown in Figure 5. There are no significant difference between the particles prepared with or without poloxamer 188.
The characteristics of the nanoparticles used in following examples 8 to 10 are described in Table II below:
a = initial HPβCD concentration in the polymerization medium (mg/ml) b= μg of HPβCD per mg of nanoparticles c = μg of progesterone per mg of nanoparticles
EXAMPLE 8 : In vitro release of progesterone from nanoparticles of PIBCA/ HPpCD
A weighted quantity of freeze-dried nanoparticles (containing 1% (w/v) of glucose) is placed
ina bottle containing 15 ml of alkaline borate buffer solution (ABB) (pH 8.4) or of ABB
containing esterases (25 and 100 ITJ) or of ABB/poly(ethyleneglycol) 400 (PEG) at 20 and
40% (v/v). The samples are magnetically stirred at 200 r/min and 37°C, and taken at
predetermined intervals. The suspensions are contrifuged at 82 000 g for 30 minutes at 20°C,
then the progesterone content of the supernatant is determined for all media and the HPPCD
content for the PEG media. The progesterone content is determined using HPLC as described
above with injection of 100μl for the samples incubated in ABB media and 20 μl for the PEG
All the tests are conducted under conditions such that the active ingredient concentration during the release stage ismaintained below 10% saturation.
EXAMPLE 9 : In vitro release of HPpCD from nanoparticles of PIBCA/ HPβCD. Study of the release of HPPCD is conducted as for progesterone in ABB medium with quantification of the CD content after ultracentrifuging, by complexation with phenolphthalein as described above. The CD concentration at 100% release is aproximately 100 fig/ml.
EXAMPLE 10: Differential scanning calorimetrv (DSO
DSC studies are conducted using a Perkin Elmer DSC-7 differential scanning calorimeter. The temperature is calibrated using the melting transition point of indium. Samples weighing approximately 4 mg are placed in aluminium capsules and heated from 0 to 250°C at an investigation rate of 10°C/min.
RESULTS OF EXAMPLES 8 to 10
Figure 6 in the appended drawings shows the release curve of progesterone from combined PIBCA/HPpCD nanoparticles in ABB (pH 8.4). In this graph a bi-phase release curve can be seen with initial rapid release (scattering effect) during the first hour for both tested formulations (approximately 10 and 34% of nanoparticles of 150 and 70 nm respectively). This rapid release could be attributed to the fraction of progesterone which is adsorbed or weakly bonded to the large surface generated by the formation of nanoparticles rather than to the progesterone/CD complex incorporated in the polymer network. The second phase corresponds to slower exponential release with approximately 35 and 62% of progesterone released from nanoparticles of 150 and 70 nm respectively. This slower release phase may be the result of simple outward-moving diffusion of progesterone from the nanoparticles, or of penetration of the release solution into the nanoparticles with dissolution of the progesterone followed by its outgoing diffusion.
In vitro studies show that different factors may affect the release of active ingredients from colloidal systems. These factors include particle size and morphology, active ingredient content and its solubility (6, 7, 8). In accordance with observations made in previous work, the smallest nanoparticles (70 nm) with a higher active ingredient content (24 μg/mg) give faster release than larger particles (170 nm) with a lower progesterone content (10.5 μg/mg). Average size and active ingredient content of the nanoparticles are the major factors for rate of release with a reduction in the rapid phase for the larger-sized particles.
Figure 7 shows the release curves for progesterone from nanoparticles of PIBCA/HPβCD in the presence of PEG 400 (20 and 40%) as a solubilising agent. The use of this type of medium makes it possible to reduce the volume of release medium, and consequently the concentration of active ingredient for improved detection (9). In this type of case, in which non-aqueous
solvents or solubilising agents are used, it is possible to obtain information on the release machanism. As shown in Figure 7, the release curve is not identical for these two media, which means that release is strongly influenced by PEG concentration. Consequently, the release of progesterone must be determined by penetration of the solvent into the polymer matrix, with dissolution and outside diffusion of the active ingredient from the nanoparticles. On the contrary, when the release of active ingredient results from mere diffusion across the polymer matrix, the composition of the release solvent cannot influence release of the active ingredient (10).
The method for preparing nanoparticles which consists of adding the monomer to an aqueous solution of surfactant agent and of stirring to obtaining micelles (2) can determine the distribution of the active ingredient in the micelles during the polymerization stage.
The rapid release observed in figures 6 and 7 suggests that the surface of the particles was enriched with progesterone during the polymerization stage. Also, a high proportion of active of active ingredient may have been trapped in the polymer network which could have highly porous inner structure (II). This could account for the increase in release rate when the PEG concentration increases (Figure 7), with the PEG penetrating inside the structure at different rates depending upon the constitution of the release medium, and then modifying diffusion of the active ingredient towards the outside.
Despite a very substantial increase in the release rate obtained with the addition of PEG to the release medium, the release of progesterone does not attain 100% (it is approximately 75 and 82% respectively with 40%PEG).
On the contrary, the presence of esterase-type enzymes in the release medium leads to faster release than in a release solution not containing esterases, and the quantity of released progesterone is very close to 100% for the two tested formulations and for both enzyme concentrations (Figure 8). These facts could suggest that the progesterone molecules are, at least in part, trapped in molecular state in the polymer matrix of the nanoparticle of the invention and/or are bound to the isobutylcyanoacrylate network (12). The use of esterase-type enzymes in the release medium leads to degradation or dissolution of the polymer chains
of the poly(cyanoacrylate) nanoparticles. In this case, the active ingredients immobilized in the matrix are released by gradual degradation of the matrix.
The bioerosion caused by hydrolysis of the ester bond of the PIBCA side chains is the mechanism which enables significant acceleration in the release of progesterone, which tallies with the results reported by other authors (12, 13). At times, studies on the release of active ingredients in media containing esterases do not lead to 100% release of the incorporated active ingredient (12, 14, 15). It is suggested that there then exists the possibility of a bond between the PIBCA chains and the molecules of the active ingredient (12, 14). The release curves of cyclodextrin from nanoparticles shown in Figure 9, show a very rapid release, very close to 100% during the first hour, which demonstrates that these molecules are not chemically bound to the polymer but most probably are simply adsorbed or trapped in the polymer.
The DSC tracings of samples containing HPPCD show a wide endothermic transition, reproducible in the 30 to 90°C range with initial temperatures lying within this range (Figure 10 a, c and d). This asymmetrical peak has been attributed to the removal of water. The samples containing progesterone (physical mixture and progesterone alone) show a marked endothermic peak at approximately 130°C, which corresponds to the melting transition point of progesterone in crystalline form (Figure 10 b and C). The HPPCD : progesterone complex only shows endothermic transition in the above-described 30 to 90°C range, with disappearance of the melting transition of thecrystalline form of progesterone (Figure 10 d) which suggests that the active ingredient is dispersed in the molecular state within the cavity of the cyclodextrin molecules.In the same form, samples of PIBCA.HPβCD particles containing progesterone do not show any marked endothermic peak which, in this case, is replaced by a wide endothermic transition in the range 130 to 170°C (Figure 10 e and f). This phenomenon suggests that the progesterone is in the molecular state, either dissolved in the polymer or included in the cyclodextrins associated with the nanoparticles of the invention. In this form, all the results relating to the release of cyclodextrin and progesterone in the different media and the DSC curves, plus the data in the literature indicate that the morphology of the nanoparticles could be represented by a polymer nucleus containing a fraction of active ingredient in the molecular state, with a surface enriched with cyclodextrin : progesterone
complexes. This structure could account for the bi-phase release of progesterone with a first rapid phase perhaps due to desorption of the cyclodextrin : progesterone complex from the surface, and a second very slow phase entailing the outside diffusion of the progesterone across the polymer network.
EXAMPLE 11 : Preparation of nanoparticles of poly(isobutylcyanoacrylate) / HPβCD containing various active ingredients.
Complexes of prednisolone, spironolactone, testoterone,progesterone, danazol and megestrol acetate were obtained by mixing 300 mg HPβCD with 15 mg steroids in 15 ml water at 37°C for 72 hours under magnestic stirring. The suspensions were filtered (0.45 mm) and the cyclodextrin and active ingredient concentrations were determined as in example 12 below. Nanoparticles of poly(isobutylcyanoacrylate)/ HPβCD are prepared as in example 1 by adding a solution of formed complexes containing lOmg/ml HPpCD in a 1% w/v solution of poloxamer.
EXAMPLE 12 (referenced : Preparation of nanoparticles of poly(isobutylcvanoacrylate) containing various active ingredients.
Solutions of hydrocortisone, prednisolone, spironolactone, testoterone, progesterone, danazol and megestrol acetate at concentrations corresponding to the saturation concentration in Poloxamer 188 (1% w/v) were separately added to the polymerization media. Nanoparticles of poly(isobutylcyanoacrylate) containing various active ingredients were then prepared as in example 1 but in the absence of HPPCD.
EXAMPLE 13 : Titration of hydrocortisone, prednisolone, spironolactone, testoterone, progesterone, danazol. megestrol acetate and HPβCD.
The HPβCD was also titrated as in example 6.
EXAMPLE 14 : Size and zeta potential characteristics of nanoparticles prepared according to the invention in the presence or absence of Poloxamer 188.
The nanoparticles prepared according to example 11 and example 12 were characterized as in example 7. The size of the steroid-containing particles was generally smaller and close to approximately 100 nm when the nanoparticles of the invention were prepared in the absence of Poloxamer 188 and only in the presence of HPβCD suggesting that the load contents are masked by the cyclodextrin molecules localised on the surface of the particles.
Table III below indicates the quantity of medicinal substance loaded by nanoparticles of poly(alkylcyanoacrylate) or nanoparticles of poly(alkylcyanoacrylate) and hydroxypropyl-β-cyclodextrin, and the corresponding cyclodextrin content (average of 3 values). Table III
Sample CD Drug load
PIBCA hydrocortisone (HD) - 2.19
PE - 0.12
spironolactone (SP) - 7.65
testosterone (TE) - 2.27
megestrol acetate (AM) - 0.25
danazol (DA) - 0.34
progesterone (PO) - 0.79
PIBCA/HPβCD HD 15.3
RESULTS OF EXAMPLES 11 to 14 : Increase in the steroid content of nanoparticles according to the invention.
The values of steroid contents expressed in absolute value for the nanoparticles of the invention or the reference particles are grouped together in Table IV (average of three preparations). Calculation of the increase values in particle loads shows that the increase in content can reach 129 times for prednisolone.
Steroids Content of
(mmole/g) Content of
particles (mmole/g) Increase in
Hydrocortisone 6.04 42.21 7.0
Prednisolone 0.33 43.00 129.2
Spironolactone 18.36 127.23 6.9
Testoterone 7.87 67.6 8.6
Megestrol acetate 0.65 3.64 5.6
Danazol 1.01 33.19 32.9
Progesterone 2.51 69.60 27.7
1) J. Kreuter, Colloidal Drug Delivery System, Marcel Decker, New York, 1994, 219-342.
2) Patents EP-B-0 007 895 (US-A-4 329 332 & US-A-4 489 055) and EP-B-0 064 967 (US-A-4 913 908).
3) C. Cuvier et al., Biochem. Pharmacol., 44, 509-517 (1992).
4) AC de Verdiere et al., British Journal of Cancer 76 (2), 198-205 (1997).
5) M. Vikmon, Proceed. First International Symposium on Cyclodextrins, Budapest, 1981, 69-74.
6) E. Allemann et al„ Pharm. Res., 10, 1732-1737 (1993).
7) J-C Leroux et al., J. Control. Rel., 39, 339-350 (1996).
8) N. Erden et al., International Journal of Pharmaceutics, 137, 57-66 (1996).
9) J-P. Benoit et al., Microspheres and Drug Therapy, Pharmaceutical, Immunological and Medical Aspects, Elsevier, Amsterdam, 1984, 91-102.
10) C. Washington, Int. J. Pharm., 58, 1-12 (1990).
11) P. Couvreur et al., J. Pharm, Sci., 68, 1521-1524 (1979).
12) F.Fawaz et al., International Journal of Pharmaceutics, 154, 191 -203 (1997).
13) J. L. Grangier et al., J. Control. Rel., 15, 3-13(1991).
14) Ch. Tasset et al., J. Control. Rel., 33, 23-30 (1995).
15. B. Seijo et al., Int. J. Pharm., 62, 1-7 (1990).
1 Method for preparing nanoparticles containing a polymer stages consisting of:
a) preparing a complex of at least one active ingredient with at least one compound able to complex the latter, in solution in an aqueous or non-aqueous solvent,
b) gradually adding at least one monomer of the polymer in the solution obtained at stage (a), and
c) conducting polymerization, for example anionic or inducible by other agents, in particular photochemical agents, of this monomer optionally in the presence of one or more surfactant and/or stabilizing agents.
2. Method for preparing nanoparticles containing a polymer according to claim 1 comprises the
stages consisting of:
(a) -preparing nanoparticles containing a polymer, more particularly a poly (alkylcyanoacrylate), and a compound able to complex an active ingredient.
(b) - associating the active ingredient with said nanoparticles.
3. Method for preparing nanoparticles containing a polymer according to claim 1 and 2,
characterized in it, comprises the stages consisting of:
(a) - preparing a solution of at least one compound able to complex an active ingredient in an aqueous or non-aqueous solvent,
(b) - gradually adding at least one monomer of the polymer, more particularly an alkylcyanoacrylate monomer, to the solution of stage(a), and
c) conducting polymerization, preferably anionic but also inducible by other agents, especially photochemial agents, of this monomer, optionally in the presence of one or more surfactant and/or stabilising agents,
d) after control and optional purification of the nanoparticles obtained at stage (c), incubating said particles in a solution of active ingredient in an aqueous or non-aqueous solvent.
4. Method for preparing nanoparticles containing a poly(alkylcyanoacrylate) according to any of the claims 1 to 3, characterized in it, at stage (b) at least one alkylcyanoacrylate monomer is gradually added.
5. Method according to any of claims 1 to 4, characterized in that at stages (a), (b) and (d), the solvent is advantageously chosen such that, while maintaining the conditions propitious to polymerization of the polymers, especially poly(alkylcyanoacrylates), the solubility of the active ingredient and of the compound able to complex the latter is maximum in the medium defined by this solvent.
6. Method according to any of claims 1 to 5, characterized in that stage (c) is conducted with no surfactant and/or stabilizing agent.
7. Method according to any of claims 1 to 6, characterized in that at stage (a) the proportion of compound able to complex the active ingredient is in general from 0.1 to 70% by weight relative to said active ingredient.
Dated this 21st day of August, 2000.
HIRAL CHANDRAKANT JOSHI
AGENT FOR BIOAPPLIANCE PHARMA (S.A.)
|Indian Patent Application Number||IN/PCT/2000/00312/MUM|
|PG Journal Number||32/2007|
|Date of Filing||21-Aug-2000|
|Name of Patentee||BIOALLIANCE PHARMA(S.A.)|
|Applicant Address||67,RUE VERGNIAUD, F-75013 PARIS, FRANCE|
|PCT International Classification Number||A61K 47/48|
|PCT International Application Number||N/A|
|PCT International Filing date||1999-02-24|