United States Patent (19) 11) Patent Number: 4,767,615 Geho et al. 45 Date of Patent: "Aug. 30, 1988 54; DENTAL THERAPY BY VESICLEDELIVERY 4,603,044 7/1986 Geho ....................................... 514/3 (75) Inventors: W. Blair Geho; Joseph Jacob; John R. OTHER PUBLICATIONS Lau, all of Wooster, Ohio Accepted Dental Therapeutics, 38th Ed., American Den 73) Assignee: Technology Unlimited, Inc., Wooster, tal Association, Chicago, Ill. 1979, p. 343. Ohio Jones et al. in Chemical Week, McGraw-Hill Inc., Jul. *) Notice: The portion of the term of this patent 30, 1986, pp. 426-5129, "Liposome Research: New Path subsequent to Jul. 29, 2003 has been for Drug Delivery'. disclaimed. Primary Examiner-Ronald W. Griffin (21) Appl. No.: 877,862 Assistant Examiner-F. T. Moezie (22 Filed: Jun. 24, 1986 Attorney, Agent, or Firm-Frijouf, Rust & Pyle 57 ABSTRACT Related U.S. Application Data A known procedure is used to prepare liposomes of 63 Continuation-in-part of Ser. No. 606,714, May 3, 1984, bipolar lipid membrane which are permeable and hence Pat. No. 4,603,044. "leak' their contents at a rate which is variable by 51) Int. Cl................................................. A61K 7/16 choice. The liposome is supplied with medication or 52 U.S. Cl. ........................................ 424/57; 424/49; cosmetic material for the oral cavity, or specifically for 424/54 the teeth and gums. The liposome is then attached to a 58) Field of Search ....................... 424/19, 21, 22, 27, molecule that has affinity for the hydroxyapatite. Thus, 424/28, 38, 49, 54, 57 the liposome will bind to oral cavity hydroxyapatite and (56) References Cited bathe the surrounding support surface with its contents for extended hours of service. U.S. PATENT DOCUMENTS 4,483,929 11/1984 Szaka ...................................... 435/7 2 Claims, 5 Drawing Sheets U.S. Patent Aug. 30, 1988 Sheet 1 of 5 4,767,615 |-9-! U.S. Patent Aug. 30, 1988 Sheet 4 of 5 4,767,615 Wash out of Vesicles Bound to Hydroxyapatite OO 90% 60%|| || || || || || NITTTTTTTTT 50% VIII 4. O N | | | | |\ | | | | | | | | W T. \ 3O% V TT N 20%.P.N. SN N 10%|| || || || NJTS) | | | | | | || FIRST SECOND THRD LEGEND; WASH WASH WASH Sample code #1 - O-G) Sample Code #2 - 4N ZN F. G. 4 U.S. Patent Aug. 30, 1988 Sheet 5 of 5 4,767,615 | | | | | | | ITTTTTT | | | | | | | | | | | | | | | To SN lo al " N N seLosen go LuIOg upM WH go u009 unrog esee easoonte-Owl log quino eAkaelruno LeoL 4,767,615 1 2 frequency sound waves, to give a dispersion of closed DENTAL THERAPY BY WESCLE DELIVERY liposomes that are quite uniform in size. There are other methods of forming such liposomes, and one specific CROSS REFERENCE TO RELATED recommended procedure is set forth in the specification APPLICATION hereinafter. This invention is a continuation-in-part of application Molecules, such as sodium fluoride for dental ther Ser. No. 606,714, filed May 3, 1984, now issued as U.S. apy, can be trapped in the aqueous compartment of Pat. No. 4,603,044. liposomes by forming them in the presence of these substances. For example, if liposomes as small as 500 A BACKGROUND OF THE INVENTION O in diameter are formed in a 0.1M glycine solution, 1. Field of the Invention Stryer states that about 2000 molecules of glycine will A chemically-structured delivery system for target be trapped in each inner aqueous compartment. This ing liposomes containing medication to the tooth struc manner of packaging oral cavity enhancement chemi ture of the oral cavity. cals is the first step of the present invention. 2. Description of Prior Art 15 The biochemistry of the polyphosphoinositides and A general background for understanding the chemi the diphosphonates as noted in the scientific literature cal process steps that go into making vesicles and lipo demonstrates that these molecules are capable of partic somes is set forth clearly in a publication "Biochemis ipating in chemical reactions that result in the formation try” by Lubert Stryer, published by W. H. Freeman and of exceptionally strong coordination complexes with Company, San Francisco, Calif., U.S.A., copyright 20 the calcium ions of the hydroxyapatite crystal over a 1981. very broad pH range. The repertoire of membrane lipids is extensive, and Stryer states they may even be bewildering, but they do SUMMARY OF THE INVENTION possess a critical common structural theme in that mem brane lipids contain both a hydrophilic and hydropho 25 Lipid vesicles, otherwise known as liposomes, are bic moiety. envelopes having, in part, a lipophilic membrane. Basi A space-filling model of a typical lipid has a general cally, the vesicle walls are composed of bipolar mole shape roughly rectangular with two fatty acid chains cules having a lipophilic end and a hydrophilic end. approximately parallel to one another and a hydrophilic These molecules are intertwined with the hydrophilic moiety pointing in the opposite direction. 30 ends forming inner and outer walls with the lipophilic It is common practice to use a short hand illustration ends sandwiched therebetween. which has been adopted to represent these membrane This invention employes vesicles whose membrane is lipids. The hydrophilic unit called the polar head group permeable and contain entrapped chemicals useful for is represented by a circle and the hydrocarbon tails are oral cavity enhancement, such as fluorides, antiplaque represented by lines which may be straight or wavy. 35 materials and breath fresheners. Permeability is usually The polar head groups have affinity for water and the accomplished by the use of lysolecithin as a wall mem hydrocarbon tails avoid water and seek lipid media. A brane component. A full teaching of liposomal mem bi-molecular sheet, known also as a lipid bi-layer, is the branes containing lysolecithin is contained in the 1976 favored structure for most phospholipids and glycolip addition of the Journal of Biochemistry wherein the ids in aqueous media. work of Takayuki Kitagawi, Keizo Inoue and Shoshichi The structure of a bi-molecular sheet is inherent in Nojima, department of chemistry, National Institute of the structure of lipid molecules. Their formation is a Health, Kamiosaki, Shinagawa-Ku, Tokyo, Japan, de rapid and spontaneous process in water. Hydrophobic scribing liposomes which have been prepared with lyso interaction is the major driving force for the formation lecithin, lecithin, dicetyl phosphate and cholesterol. of lipid bi-layers. It is important to the final construction 45 This report states that generally, lysolecithin incorpora of a targeted liposome that there are van der Waals tion decreases the effectiveness of the membranes as a attactive forces between the hydrocarbon tails. These barrier to glucose and made the membranes more 'os van der Waals forces favor close packing of the hydro motically fragile'. This terminology simply means that carbon tails, and also will accept the hydrocarbon moi by including lysolecithin a fault dislocation is produced ety of target molecules from an aqueous solution. 50 in the membrane wall, allowing the contents to leak Clustering of bipolar lipids is favored by the van der from the vesicle. The amount of the lysolecithin incor Waals attractive forces with the significant biological poration will decidedly influence the rate at which the consequence that they will tend to close on themselves vesicles will leak the contents. Relatively low concen so that there are no ends with exposed hydrocarbon trations of lysolecithin cause an increase in the permea chains and therefore result in the formation of a com 55 bility of the liposomes, this report states. These studies partment which is normally self sealing because a hole suggested that the induction of a change in the molecu in a bi-layer is energetically unfavorable. lar organization by lysolecithin molecules may cause However, if one of the lipid components of such a the permeability change. closed compartment has one R-group missing, there Since the work published by the National Institute of will be a fault dislocation which defeats the self sealing 60 Health in Tokyo, the manufacture of vesicles from to behavior and allows the contents of the liposome to leak tally non-leaking structure to those which quickly lose from the inner aqueous compartment. their contacts, is now fully developed and well known Therefore, as explained in the prior art and particu prior art. larly in the Stryer publication supra, liposomes are This invention provides a means whereby the perme aqueous compartments enclosed by a lipid bi-layer. 65 able liposome, with its cargo of oral cavity enhance They can be formed by suspending a suitable lipid, such ment material, anchored to tooth structure of the oral as phosphatidyl choline in an aqueous medium. This cavity in order that eating, drinking and normal saliva mixture is then sonicated, which is an agitation by high wash will not dislodge the vesicle. Keeping it in place 4,767,615 3 4. until the contents are fully expanded is the touchstone application of liquid fluoride solutions and gels, or by of this invention. incorporation such medication into toothpaste and A long chain target molecule is composed having one mouthwashes. end lipophilic and the other end characterized by the The effectiveness of such procedures is the product ability to chemisorb with the surface of hydroxyapatite of concentration and time in contact with the treated crystals. The lipophilic end is caused to penetrate the areas. The dentist uses a very high concentration of the hydrophilic wall of the liposome and form weak van fluoride medication in the liquid or gel and washes the der Waals bonds characterized as a transient attraction, area free of excess material. The dentist thereafter ob with the lipophilic membrane. The hydrophilic end of tains a high degree of effectiveness without danger of the target molecule will then project from the liposome.