Drug delivery systems provide multiple advantages to existing drugs as well as new drugs; the main advantage resides in improving the safety of drugs by decreasing the side effects, increasing the efficacy, enhancing the drug performance, which leads to increased patient compliance.
Various formulations with liposomes have allowed the development of a new class of delivery vehicles called cochleates. These are stable, lipid based delivery formulations whose structure and properties are very different from liposomes. Liposomes are composed of lipid bilayer membranes with aqueous space bounded by the lipid bilayer 1. This lipid bilayer is susceptible to attack by harsh environment conditions like pH, lipase degradation 2 and temperature 3. Cochleates protects the entrapped molecules from harsh environmental conditions. They are stable to lyophilization and can be reconstituted with liquid prior to administration 2. Cochleate is most versatile technology for the delivery of a wide range of drugs 4 and fragile molecules such as proteins and peptides 5. They were invented by Papahadjopoulos in 1975 as an intermediate in the preparation of large unilamellar vesicles 6. Cochleates are calcium-phospholipid structures composed of naturally occurring materials that “wrap” around the drug or nutrient being introduced into the body 7.
Nanocochleates consists of a purified soy based phospholipid that contains atleast about 75% by weight of lipid which can be phosphotidyl serine (PS), dioleoylphosphatidylserine (DOPS), phosphatidic acid (PA), phosphatidylinositol (PI), phosphatidyl glycerol (PG) and /or a mixture of one or more of these lipids with other lipids. Additionally or alternatively, the lipid can include phosphatidylcholine (PC), phosphatidylethanolamine (PE), diphosphotidylglycerol (DPG), dioleoyl phosphatidic acid (DOPA), distearoyl phosphatidylserine (DSPS), and dimyristoyl phosphatidylserine (DMPS), dipalmitoyl phosphatidylgycerol (DPPG) 7. A multivalent cation, which can be Zn+2 or Ca+2 or Mg+2 or Ba+2 and a drug, which can be protein, peptide, polynucleotide, antiviral agent, anesthetic, anticancer agent, immunosuppressant, steroidal anti inflammatory agent, non steroidal anti inflammatory agents, tranquilizer, nutritional supplement, herbal product, vitamin and/or vasodilatory agent 4.
Unique structure of cochleates consists of a large, continuous solid-lipid bilayer sheet rolled up in a spiral, with no internal aqueous space, which was determined by scanning electron microscopy 8. Ca+2 ions maintain the cochleate in its rolled form, bridging each successive layer, through ionic interaction 2. One of the calcium ion’s two positive charges interact with a single negative charge on a phospholipid head group in one bilayer and other with a phospholipid in the opposing bilayer as shown in Figure 1 7.
Nanocochleates can be stored in cation-containing buffer, or as lyophilized powder at room temperature. Cochleate preparations were found to be stable for one year as a lyophilized powder at room temperature and for two year at 4ºC 9. Nanocochleates offers various advantages and are as follows:
a. They are produced easily and safely, with ease of observing under microscope 6,
b. Limited permeability to oxygen prevents oxidation of lipids, which imparts stability to nanocochleates.
c. Stability of lyophilized cochleates provides ease of shipping and storage prior to administration 6,
d. Hydrophobic or amphiphilic, molecules and tissue impermeable drugs can be delivered via cochleates 9,
e. The unique structure and properties of cochleates make them an ideal candidate for oral and systemic delivery of sensitive material including peptide and nucleic acid drugs ,
f. These are used to mediate and enhance the oral bioavailability of a broad spectrum of important but difficult to formulate bioactives, including compounds with poor water solubility, protein and peptide drugs, and large hydrophilic molecules 10,
g. Cochleates can be produced as defined formulations which composed of predetermined amounts and ratios of drugs or antigens.
h. Lipids used in cochleates are also having nutritional value and having effect on enhancing the brain functions in elderly people e.g. phosphatidylserine 4,
i. High concentration of calcium used in cochleates is also an essential mineral 11,
j. Bilayer structure of the nanocochleates provides protection for associated, or “encochleated,” molecules from harsh environmental conditions, enzymes and also protect from digestion in the stomach 8,
k. Lipid matrix-based subunit vaccines can be used to produce custom-deigned vaccines that elicit desired immune responses targeted to specific parts of the pathogen that are relevant to protection 2,
l. There are certain risks associated with the administration of the live vaccines, or with vectors containing transforming sequences. These vaccines may lead to life threatening infections in immunocompromised individuals or reversion to wild type infectivity which poses a danger to even healthy people. As cochleates are non-living subunit formulations the risks associated with the delivery of vaccines are less 11.
Methods of preparation:
Following methods are used for the preparation of the Nanocochleates; general schematic representation of formation of cochleates is given in figure 2.
A. Hydrogel method (Figure 3):
Formation of the cochleates is multi-step process. In hydrogel method initially the small unilamellar drug loaded liposomes were prepared, which were added to polymer A (Which may be dextran, polyethylene glycol, etc.). The dispersion of two was then added to another polymer B (which may be polyvinylpyrrolidone, polyvinylalcohol, Ficoll, polyvinyl methyl ether, etc.). The two polymers were immiscible in each other. Immiscibility of the polymers leads to formation of an aqueous two-phase system.
The cationic cross-linking of the polymers was achieved by adding a solution of cation salt to the two-phase system, such that the cation diffuses into second polymer and then into the particles comprised of liposomes/polymer A allowing the formation of small-sized cochleates 6. The formed cochleates were then washed to remove polymer, which might be re-suspended into a physiological buffer or any appropriate pharmaceutical vehicle or lyophilized.
B.Trapping method 12:
This method involves the formation of phosphatidylserine liposomes followed by dropwise addition of a solution of CaCl2. Liposomes can be generated by either addition of water to phospholipid powder or by adding the water phase to a phospholipid film.
C.Liposomes before cochleates(LC) dialysis method 11, 12:
In this method mixture of lipid and detergent were used as the starting material and the removal of detergent was done by double dialysis. The mixture was dialyzed initially with buffer and followed by calcium chloride solutions leads to formation of cochleates. This method was suitable for the encapsulation of hydrophobic material or drugs containing hydrophobic regions such as membrane proteins. In this method intermediate liposome formed were small in size and hence resulted in formation of small cochleates.
Mixture of phosphatidylserine and cholesterol (9:1 wt ratio) in extraction buffer and non-ionic detergent was mixed with a pre-selected concentration of polynucleotide. The resulting solution was vortexed for 5 minutes. The solution was dialyzed overnight using a mixture of dialysate and buffer in ratio 1:200 without divalent cations, followed by three additional changes of buffer leads to the formation of small protein lipid vesicles. The vesicles were converted to a cochleate precipitate, either by the direct addition of Ca2+ ions, or by dialysis against two changes of buffer containing 3 mM Ca2+ ions, followed by buffer containing 6 mM Ca2+ 11.
D.Direct calcium (DC) dialysis method 11, 12:
Unlike LC method this method dose not involves the intermediate liposome formation and the cochleates formed were large in size. The mixture of lipid and detergent was directly dialyzed against calcium chloride solution. In this method a competition between the removal of detergent from the detergent/lipid/drug micelles and the condensation of bilayers by calcium, results in needle shaped large dimensional structures.
Mixture of phosphatidylserine and cholesterol (9:1 wt ratio) in extraction buffer and non-ionic detergent was mixed with a pre-selected concentration of polynucleotide and the solution was vortexed for 5 minutes. The clear, colorless solution which resulted was dialyzed at room temperature against three changes (minimum 4 hours per change) of buffer (2 mM TES N-Tris[hydroxymethyl]-methyl-2 aminoethane sulfonic acid, 2 mM L-histidine, 100 mM NaCl, pH 7.4) containing 3 mM CaCl2. The final dialysis routinely used is 6 mM Ca2+, although 3 mM Ca2+ is sufficient and other concentrations may be compatible with cochleate formation. The ratio of dialysate to buffer for each change was a minimum of 1:100. The resulting white calcium-phospholipid precipitates have been termed DC cochleates. When examined by light microscopy, the suspension contains numerous particulate structures up to several microns in diameter, as well as needle-like structures 11.
E.Binary aqueous-aqueous emulsion system 12:
In this method small liposomes were formed by either high pH or by film method, and then the liposomes are mixed with a polymer, such as dextran. The dextran/liposome phase is then injected into a second, non-miscible, polymer (i.e. PEG). The calcium was then added and diffused slowly from one phase to another forming nanocochleates, after which the gel is washed out. The nanocochleates proved to promote oral delivery of injectable drugs. By this method the cochleates formed are of particle size less than 1000 nm.
1.BiogeodeTM Nanocochleates have the ability to stabilize and protect an extended range of micronutrients and the potential to increase the nutritional value of processed foods 7.
2.Nanocochleates have been used to deliver proteins, peptides and DNA for vaccine and gene therapy applications.
3.Nanocochleates showed potential to deliver Amphotericin B, a potential antifungal agent, orally and parentally having a good safety profile with reduced cost of treatment 13. The prepared cochleates of amphotericin B showed improved stability and efficacy at low doses. They showed improved patient compliance
Delmas et. al. investigated benefits of cochleates containing Amphotericin by using orally administered doses ranging from 0 to 40 mg/kg of body weight/day for 14 days in a murine model of systemic aspergillosis. The administration of oral doses of CAMB (20 and 40 mg/kg/day) resulted in a survival rate of 70% and a reduction in colony counts of more than 2 logs in lungs, livers, and kidneys. Orally administered CAMB shows promise for the treatment of aspergillosis 13.
4.Use of cochleates in the delivery of antibacterial agents:
Cochleates would have the advantage of reducing the toxicity and improving the bactericidal activity. For aminoglycosides and linear or cyclic peptides, cochleates should allow oral administration. The proof of principle of the efficacy of anti-TB cochleates was achieved using clofazimine as an antibacterial drug model 12.
5.Nanocochleates can deliver Omega-3 fatty acids to cakes, muffins, pasta, soups and cookies without altering the product’s taste or odor 14.
6.Biodelivery Sciences International have developed nanocochleates which can be used to deliver nutrients such as vitamins, omega fatty acids more efficiently to cells, and lycopene without affecting the color and taste of food which makes the concept of super foodstuffs a reality, and these are expected to offer many different potential benefits including increased energy, improved cognitive functions, better immune function, and antiaging benefits 15.
Nanocochleates are newly emerging tailor made new drug delivery systems suitable for delivery of large number of drug molecules. The biocompatible nature makes them suitable for administration through different routes of administration. The encapsulation of drug in the lipid bilayer protects the drug from harsh environmental conditions. The development and scale up of nanocochleates could be a major breakthrough in therapy of various anomalies.
1. Elsayed MMA, Abdallah OY, Naggar VF, Khalafallah NM. Lipid vesicles for skin delivery of drugs: Reviewing three decades of research. Int. J. Pharm. 2007; 332: 1-16.
2.Susan GF, Masoumeh TK, Fan Z, Zheng W, Anthony JS, Eleonora F, Mario C, Raphael MJ. Targeting immune response induction with cochleate and liposome-based vaccines. Adv. Drug Del. Rev. 1998; 32: 273-287.
3.Gregoriadis. Liposome Technology. Boca Raton : CRC Press; 1992.
4.Tan F, Zarif L. Cochleates made with purified soy phosphatidylserine. European patent 1494690: 2005.
5. Raphael MJ, Susan GF. Stabilizing and delivery means of biological molecules. US patent 5840707: 1998.
6. Tuo J, Zarif L, Raphael MJ. Nanocochleate formulations, process of preparation and method of delivery of pharmaceutical agents. US patent 6153217: 2000.
7. Mannino D. New biogeodetm cochleates could make healthy nutrients more available in processed foods. BioDelivery Sciences International). September 30, 2003.
8.Susan GF, Raphael MJ, Patrick A, Gaofeng S, Wei CZ, Sara LK. Cochleate compositions directed against expression of proteins. US patent 20050013855: 2005.
9. Mozafari MR, Khosravi-darani K. An overview of liposome-derived Nanocarrier technologies. Nanomaterials and Nanosystems for Biomedical Applications. 2007; 7: 113-123.
10. Kharb V, Bhatia M, Dureja H, Kaushik D. Nanoparticle technology for the delivery of poorly water-soluble drugs. Pharmaceutical Technology. 2006.
11. Raphael MJ, Susan GF. Stabilizing and delivery means of biological molecules. US patent 5840707: 1998.
12.Zarif L. Elongated supramolecular assemblies in drug delivery. J. Control. Rel. 2002; 81: 7-23.
13. Delmas G, Chen WC, Tan F, Kashiwazaki R, Zarif L, Perlin DS. Efficacy of orally delivered cochleates containing amphotericin B in a murine model of aspergillosis. Antimicrobial Agents and Chemotherapy. 2002; 46: 2704-2707.
14. Etcgroup. Down on the farm-The Impact of Nano-Scale Technologies on Food and Agriculture. Available at: www.etcgroup.org. 2004.
15. Joseph T, Morrison M. Nanotechnology in agriculture and food: A nanoforum report. Institute of nanotechnology. Available at: www.nanoforum.org. 2006.
Figure 1: Bilayered structure of nanocochleates
Figure 2: Scheme of formation of cochleates
Figure 3: Hydrogel Method
Vivek Ranjan Sinha, Vinay, Anamika, and Jayant Rajaram Bhinge
Prof. V. R. Sinha
He is professor in Pharmaceutics at University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh (India). He has industrial experience of 5years in the various disciplines of manufacturing. His current areas of interest are oral site specific drug delivery, oral sustained release systems, parenteral depot systems, transdermal drug delivery systems, nanoparticles. He has expertise in the area of tablet manufacturing. He can be reached by e-mail at firstname.lastname@example.org.
He is pursuing his master’s degree in Pharmaceutics under the guidance of Prof. V. R. Sinha at University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh (India). He is currently working on analytical method validation and development of sustained release dosage forms. email@example.com
She earned her master’s from University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh (India). She is currently working as Health Analyst with Heron Health, India.
He is currently pursuing his doctorate in Pharmaceutics under the supervision of Prof. V. R. Sinha at University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh (India). His areas of research are site specific drug delivery, stability-indicating assay method development and tablet technology. He has 18 months industrial experience in product development and research department of Ranbaxy Research Laboratories.