Bioadhesive polymer

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BHAGAVAN MAHAVIR COLLEGE OF PHARMACY BIOADHESIVE POLYMERS PRESENTED BY: Kathiriya Julee M.Pharm Sem - II Pharmaceutics 1

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Contents Introduction Definition of Bioadhesive/Mucoadhesive Polymer? Drug Absorption and mechanisms Theories of bioadhesion Characteristics of Bio/mucoadhesive Polymers Classification of polymer Types of formulations Conclusion 2

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Adhesion as a process is simply defined as the ‘‘fixing” of two surfaces to eachother. There are many different terminological subsets of adhesion depending upon the environment in which the process occurs. When adhesion occurs in a biological setting it is often termed ‘‘bioadhesion”, furthermore if this adhesion occurs on mucosal membranes it is termed ‘‘mucoadhesion”. Bioadhesion can be defined as the binding of a natural or synthetic polymer to a biological substrate . When this substrate is a mucous layer , term is known as mucoadhesion is often used. Introduction: 3

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What is a bioadhesive polymer?  A polymer is a substance formed by the linkage of a large number of small molecules known as monomers.  A bioadhesive polymer is a synthetic or natural polymer which binds to biological substrates such as mucosal membranes . Such polymers are sometimes referred to as biological ‘glues’ because they are incorporated into drugs to enable the drugs to bind to their target tissues. History: Bioadhesive drug delivery formulations were introduced in 1947 when gum tragacanth was mixed with dental adhesive powder. The aim was to deliver Penicillin into the oral mucosa. This later became Orabase ® , a formulation used to treat mouth ulcers. This product is available as a paste which will stick to the wet surfaces of the mouth and form a protective film over the mouth ulcer. Orabase paste contains polymers such as gelatin, pectin and carboxymethylcellulose . 4

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Some examples of Orabase products are shown below 5

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Role of polymers in Bioadhesion : [mechanism] most research has described bioadhesive bond formation as a three step process. Step 1 : Wetting and swelling of polymer Step 2 : Interpenetration between the polymer chains and the mucosal membrane Bioadhesive polymer chains Mucus polymer chains Continue… … 6

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Step 3 : Formation of chemical bonds between the entangled chains 7

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Theories of bioadhesion ( 1) Electronic theory: - According to this theory, electron transfer occurs upon contact of an adhesive polymer with a mucous glycoprotein due to difference in their electronic structure. This results in formation of electrical double layer at the interface. (2) Adsorption theory: - After an initial contact between two surfaces, the material adheres because of surface forces acting between the atoms in the two surfaces. (3) Wetting theory: - Predominantly applicable to liquid bioadhesive systems. The thermodynamic work of adhesion is a function of surface tension of the surface in contact as well as interfacial tension. The interfacial energy is responsible for the contact between the two surfaces and adhesive strength. (4) Fracture theory: - It attempts to relate the difficulty of separation of two surfaces after adhesion. (5) Diffusion theory: - The polymer chains and mucus mix to a sufficient depth to create a semipermant adhesive bond. 8

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They are water soluble and water insoluble polymers which are swellable networks jointed by crosslinking agents. Characteristics of an ideal polymer …..  Degradation products should be non toxic and non absorbable from g.i.t  Non irritant to mucous membrane.  Form a strong non covalent bond with mucin epithelial cell surfaces.  Should adhere quickly to moist tissue and should possess site specificity.  Allow easy incorporation of the drug and offer no hindrance to its release.  Polymer must not decompose on storage or during shelf life of dosage form.  Cost effective 9

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Characteristics of Bioadhesive polymers In order for polymers to adhere to mucosal surfaces or epithelial cell they must ideally possess certain characteristics: Flexibility - The flexibility of bioadhesive polymers is important because it controls the extent of the interpenetration between the polymers and mucosal/epithelial surfaces. Hydrophilicity – Polymers that are hydrophilic in nature are able to form strong adhesive bonds with mucosal membranes because the mucus layer contains large amounts of water. Hydrogen bonding – Hydrogen bonding between the entangled polymer chains forms strong adhesive bonds, therefore the presence of hydrogen bond – forming groups such as OH and COOH groups are vital in large quantities. High molecular weig ht – Polymers with a high molecular weight are desirable because they provide more available bonding sites. Surface tensions – Surface tensions are needed to spread the bioadhesive polymer into the mucosal layer epithelial surface . 10

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Classification of polymers based on their criterias : Criteria Categories Examples Source Semi-natural/natural Synthetic Agarose , chitosan , gelatin Hyaluronic acid Various gums (guar, xanthan , gellan , carragenan , pectin, and sodium alginate). Cellulose derivatives [CMC, thiolated CMC , sodium CMC, HEC, HPC, HPMC, MC, methylhydroxyethylcellulose ] 11

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Criteria Categories Examples Aqueous solubility Water-soluble Water-insoluble CP, HEC, HPC (waterb38 8C), HPMC (cold water), PAA, sodium CMC, sodium alginate Chitosan (soluble in dilute aqueous acids), EC Continue….. 12

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Criteria Categories Examples Charges Cationic Anionic Chitosan (soluble in dilute aqueous acids), EC, PC Charge Cationic Aminodextran , chitosan , dimethylaminoethyl (DEAE)- dextran , trimethylated Chitosan Chitosan -EDTA, CP, CMC, pectin, PAA, PC, sodium alginate, sodium CMC, xanthan gum Continue….. 13

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Criteria Categories Examples Potential bioadhesive forces Non-ionic Covalent Hydrogen bond Electrostatic interaction Hydroxyethyl starch, HPC, poly(ethylene oxide), PVA, PVP, scleroglucan Cyanoacrylate Acrylates [ hydroxylated methacrylate , poly( methacrylic acid)], CP, PC, PVA Chitosan Continue….. 14

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Some Examples of bioadhesive polymers: Bioadhesive polymers come from both natural and synthetic sources, some common examples are highlighted below: Acacia gum - This natural polymer is a dried gum obtained from the stem and branches of the tree Acacia senegal . It is used as a thickener in pharmaceuticals. Alginic acid – Is a natural polymer found in the cell walls of brown algae. It is widely used in the manufacture of alginate salts such as sodium alginate which is a constituent of Gaviscon liquid ® . Carbomers – Are polyacrylic acid polymers widely used in the pharmaceutical and cosmetic industries as thickening agents.. Carbomers have a huge advantage in formulation science because they adhere strongly to mucosal membranes without causing irritation, they exhibit low toxicity profiles and are compatible with many drugs. Continue….. 15

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Hydroxypropyl methylcellulose (HPMC) – This polymer is included in preparations used to moisten contact lenses and in oral gels . Sodium hyaluronate - A high molecular weight biological polymer made of repeating disaccharide units of glucuronic acid and N-acetyl-D - glucosamine. This polymer is used during intraocular surgery to protect the cornea and also acts as a tear substitute in the treatment of dry eyes. Other examples of polymers include: - pectin - polyvinylalcohol (PVA) - polyvinylpyrrolidone (PVP) - tragacanth Continue….. 16

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+++ :- Excellent ++:- Fair +:- Poor POLYMER BIOADHESIVE PROPERTY Carboxy methyl cellulose +++ Carbopol 934 +++ Polycarbophil +++ Tragacanth +++ Poly (acrylic acid / divenyl benzene) +++ Hydroxy ethyl cellulose +++ Gum karaya ++ Gelatin ++ Thermally modified starch ++ Pectin + PVP + Acacia + PEG + Psyllium + Amberlite – 200 resin + HPC + 17

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1. The eye Brand Name. Contents Uses Hypotears ® and Sno Tears® Polyvinyl alcohol Lubrication GelTears ® and Viscotears ® Polyvinyl alcohol Lubrication Pilogel ® Pilocarpine , polyacrylic acid Glaucoma Polymers in muco/bioadhesive formulations: 18

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2. The Nasal Cavity Brand Name. Contents Uses Rhinocort ® Beclomethasone dipropionate , Hydroxypropyl cellulose(HPC) nasal allergy Beconase ® Beclometasone dipropionate carboxymethyl cellulose and microcrystalline cellulose. nasal inflammation and nasal allergies associated with hayfever . Nasacort® Triamcinolone acetonide microcrystalline cellulose nasal inflammation nasal allergy 19

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3. The oral cavity 3a.The Buccal Mucosa Brand Name. Contents Uses Corlan ® Pellets Hydrocortisone succinate , Acacia mouth ulcers Daktarin ® oral gel Miconazol , pregelatinised potato starch antifungal agent Corsodyl ® Oral gel chlorhexidine gluconate Hydroxypropyl cellulose(HPC) inhibit the formation of plaque 20

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3b. The sublingual mucosa Brand Name. Active Drug Polymer used Glyceryl Trinitrate (GTN ) aerosol spray and tablet Glyceryl trinitrate , Polyvinyl alcohol ( PVA) Angina pectoris Buccastem ® Is a drug used in the treatment of nausea, vomiting and vertigo. It contains the bioadhesive agents Polyvinylpyrrolidone and Xanthan gum. Suscard ® Is a buccal tablet used in the treatment of angina. It contains the bioadhesive agent Hydroxypropyl methylcellulose (HPMC). Other Examples of Oral products 21

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CONCLUSION : Mucoadhesivepolymers may provide an important tool to improve the bioavailability of the active agent by improving the residence time at the delivery site. The various sites where mucoadhesive polymers have played an important role include buccal cavity, nasal cavity, rectal lumen, vaginal lumen and gastrointestinal tract . Development of novel mucoadhesive delivery systems are being undertaken so as to understand the various mechanism of mucoadhesion and improved permeation of active agents. Many potential mucoadhesive systems are being investigated which may find their way into the market in near future. 22

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Vyas s.p and khar .k Controlled drug delivery concept and advances,1 ,2002, pp.259-267. 2. Kaelbe D H and Moacanin J. A surface energy analysis of bioadhesion . Polym ., 18, 1977, pp. 475-481. 3. Gu J M, Robinson J R and Leung S. Binding of acrylic polymers to mucin /epithelial surfaces; Structure-property-relationship. Crit. Rev. The. Drug Car. Sys. 5, 1998, pp. 21-67. 4. Duchene D, Touchard F and Peppas N A. Pharmaceutical and medical aspects of Bioadhesive system for drug administration. Drug Dev. Ind. Pharm., 14, 1998, pp. 283-381. 5. Hollingsbee D A and Timmins P. Topical adhesive system, in Bioadhesion Possibilities and Future Trends, Gurny R and Junginger H E Eds., Wissenchaftliche verlag Gesellschaft , Stuttgart, 1990, pp. 140-164. . References : 23

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