Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-05-16
2004-03-30
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C424S450000, C424S451000, C524S205000, C524S210000
Reexamination Certificate
active
06713533
ABSTRACT:
The invention relates to nanocapsules having a size of between 50 nm and 10 &mgr;m in diameter, the coat layer of which consists of at least two different polymers P1 and P2 crosslinked with each other, with a lipid layer optionally being present underneath said coat layer. The nanocapsules of the invention are produced by covalent crosslinking of at least two different water-soluble polymers P1 and P2 on the surface of liposomes, said liposomes optionally being dissolved subsequent to crosslinking. The nanocapsules according to the invention are capable of carrying biologically active compounds.
Nanocapsules or nanoglobules are particulate structures ranging in size between 50 nm and 10 &mgr;m, wherein a coat layer separates an inner space from the exterior medium. This property distinguishes nanocapsules from nanospheres; the latter have a uniform cross-section. Structures of similar design are also known in larger dimensions and are then referred to as microcapsules. Liposomes and viral capsides are other related structures of said nanocapsules.
In the preparation of nanocapsules, such methods can be used with advantage, wherein crosslinking reactions are carried out on phase boundary surfaces. The potential benefit of such particles crucially depends on the coat layer used and the preparation method. Well-known coat layers according to prior art are those made up of crosslinked proteins or interfacial polymers, particularly of acrylic acid derivatives.
Coat layers consisting entirely or partially of proteins are of special interest, because they can be designed so as to be biocompatible and degradable. The proteins used in building up are structure-forming, but may also be activity-bearing. Such particles are suitable for the inclusion of foreign substances and in binding other components to the surface. Owing to the natural variety of employable proteins, the surface properties are highly variable and can be adapted to meet various requirements.
Membranes of surface layer (S-layer) proteins have been described in EP 0,154,620). Such membranes are formed by recrystallization of S-layer proteins in free solution or at the surface of liposomes.
In the latter event, previous inclusion of macromolecules is possible, the liposomes undergoing substantial stabilization as a result of establishing the membrane (Kupcu, S., Sara, M., and Sleytr, U. B., Biochem. Biophys. Acta, 1235 (2), 263-269 (1995)). A flat-crystalline build-up of the membranes results in structures having a regular arrangement of homogeneous pores which can be used with advantage in ultrafiltration.
A likewise regular arrangement of chemical groups on the surface results in a highly homogeneous distribution when binding other macromolecules, which is advantageous for use in detection systems. In the event of membranes of S-layer proteins, their immunogenicity may have a limiting effect as to the use in biological systems. S-layer proteins give rise to a strong immune response and are therefore used as adjuvants (U.S. Pat. No. 5,043,158). Moreover, the S-Layer proteins are not activity-bearing themselves.
The U.S. Pat. Nos. 5,498,421; 5,635,207; 5,650,156; 5,665,383; 5,639,473; as well as U.S. Pat. No. 5,512,268 describe the preparation and utilization of hollow spheres ranging in size up to 10 &mgr;m, wherein a coat layer is formed at the phase boundary to a non-water-miscible core. Said coat layer is stabilized by disulfide bridges and can be formed of proteins, particularly of hemoglobin or albumin or other thiol-containing polymers. Emulsification of the non-miscible phase is effected using strong ultrasound. During this process, hydrogen peroxide is formed among other things, resulting in oxidative crosslinking of the coat components.
Particles prepared from hemoglobin are capable of absorbing and releasing oxygen, but with a different Hill coefficient as compared to natural hemoglobin. They can be used as blood substitute.
In other uses, gases or contrast agents are entrapped in the particles and employed in medical imaging methods. In still other uses, the enveloping of biologically active substances has been described, provided, they can be dissolved or emulsified in the internal phase without loss of activity. For enveloping hydrophilic macromolecules such as proteins or nucleic acids, this method therefore is suitable to only a limited extent.
Further nanometer range hollow spheres can be prepared by repeated deposition of polyelectrolytes onto colloidally dissolved particles (Caruso, F., Caruso, R. A., and Möhwald, H. (1998) Science 282, 1111-1113). In an example, exceedingly small silica particles are deposited in alternation with poly(diallyldimethylammonium chloride) onto a polystyrene matrix. This matrix can be removed subsequently using calcination or solvents, so that the hollow spheres remain.
The use of liposomes and nanocapsules in the inclusion of biologically active compounds, such as pharmaceutical formulations, is well-known. They are capable of conveying their cargo to the site of action, or release it over a prolonged period of time. The surrounding membrane is capable of protecting the entrapped active substance from degradation or inactivation.
The nature of the entrapped active substance, particularly its solubility and molecular weight can be varied within wide ranges. In addition, owing to their immunological compatibility, liposomes are particularly suitable systems for enveloping pharmaceutically active substances.
Specially designed liposomes can be used to introduce nucleic acids into mammal cells. In an advantageous variant of this technique, lipid-nucleic acid complexes are generated using cationic lipids, and the cells to be treated are transfected with same. The transfection is simple, but proceeds with low efficiency and in a non-specific fashion. In another embodiment, pH-sensitive liposomes are incorporated in the target cells on the endocytotic route. In the acidic compartment of the endosomes, they undergo fusion with the surrounding membrane, conveying their cargo into the interior of the cell on this route. Using this method, even proteins and other active substances can be transported into the interior of the cell.
Liposomes can also be used as detection systems with high signal amplification (U.S. Pat. No. 4,622,294). The signal amplification in this case is achieved as a result of the large number of entrapped enzyme molecules relative to the detected species. One disadvantage in using conventional liposomes is their sensitivity to detergents employed in various uses for suppressing non-specific interactions.
The well-known hollow spheres suffer from the following drawbacks:
The hollow spheres based on the use of S-layers have an aqueous inner space and a well-defined permeability of the coat layer. The potential of enveloping hydrophilic macromolecules is present. However, the restriction of usable compounds to S-layer proteins is disadvantageous. They do not bear activity and exhibit an antigenic effect. The method according to U.S. Pat. No. 5,498,421 and the other above-mentioned documents produces a functional coat layer of proteins at a phase boundary. The system has only limited suitability for entrapping hydrophilic macromolecules. The components of the coat layer are crosslinked with each other in a highly rigid fashion, thereby altering the properties of the hemoglobin being used. Components useful to build up the coat are restricted to such polymers having a plurality of thiol functions and attaching to the phase boundary surfaces being employed.
One disadvantage of conventional liposome systems is their low mechanical and in vivo stability. The particles are incorporated by macrophages of the reticulo-endothelial system within a short time, thereby being removed from the circulation.
It was therefore the object of the invention to provide nanocapsules that would not involve the above-mentioned drawbacks.
According to the invention, this is achieved by means of nanocapsules which have a size of between 50 nm and 10 &mgr;m in diameter and are produced on t
Cain Edward J.
Collard & Roe P.C.
Novosom AG
LandOfFree
Nanocapsules and method of production thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Nanocapsules and method of production thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nanocapsules and method of production thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3287632