Rate controlled drug delivery system
- 1. Rate controlled drug delivery system Presented By : Facilitated To: Nagond Mukund m Dr. Anita Desai M.Pharm 1st year HOD and Professor Dept. of Pharmaceutics Dept. of Pharmaceutics HSKCOP, BAGALKOT. HSKCOP, BAGALKOT
- 2. Contents • Definition • Types of RCDDS • Classification
- 3. WHAT IS CONTROLLED RELEASE? The term "Controlled release" has become associated with those systems from which therapeutic agents may be automatically delivered at predefined rates over a long period of time. WHAT IS CONTROLLED RELEASE FORMULATIONS? These are the formulations which delivers the drug at a predetermined rate, for locally or systematically , for a specified period of time. Example : GITS - Prazosin (mini press) Morphine sulphate ( Roxonal SR)
- 4. • Types of RCDD Further Classified into: a)Dissolution controlled DDS b)Diffusion controlled DDs c)Erosion controlled DDS d)Combination of dissolution, diffusion, and erosion controlled DDS a)Dissolution controlled DDS: • These systems are those where the limiting phenomenon responsible for imparting the controlled release characteristics to the DDS is either A)Slow dissolution rate of the drug: The drug present in this system may be • Drug with inherently slow dissolution rate: Example: Griseofulvin, digoxin and nifedipine. • Drug that transforms into a slow dissolving form on contact with GI fluids Example: Ferrous sulphate
- 6. B)Slow dissolution rate of the reservoir membrane or matrix: The drug present in such a system may be the one having high aqueous solubility & dissolution rate. Example: pentoxifylline and metformin. The challenge in designing such systems lies in controlling the drug dissolution rate by employing either or combination by following techniques: • Embedment in slowly dissolving , degrading or erodible matrix. The matrix in addition may have low porosity or poor wettability. • Encapsulation or coating with slow dissolving, degrading or erodible substances. In this approach, the rate of dissolution fluid penetration or wettability of the reservoir system are controlled.
- 7. b)Diffusion controlled DDS: • The system where the rate controlling step is not the dissolution rate of drug or release controlling element, but diffusion of dissolved drug molecule through the rate controlling element. The rate controlling element in such system is thus insoluble, non-erodible & non degradable. Porous matrix controlled systems:
- 8. Porous membrane controlled systems: c)Erosion controlled DDs: • It is defined as physical degradation of a polymer/wax matrix or coating as a result of degradation and characterized by material loss from the polymer generally in the physical state. The pH change due to osmotic pressure(exerted by dissolved drug/excipients) or by hydrodynamic pressure(exerted by excipients that imbibe water & swell) that causes fragmentation.
- 9. • 1.Surface erosion: also called heterogeneous erosion • 2.Bulk erosion: also known as homogeneous erosion
- 10. d)Dissolution, Diffusion or erosion controlled DDS: • The rate of drug is controlled by drug or polymer dissolution, drug diffusion or polymer erosion i.e, this system is a combination of two or more systems.
- 11. CLASSIFICATION: Depending upon the sophistication of the technology in use controlled release delivery system can be classified into these fallowing three types 1)Rate preprogrammed drug delivery system 2)Activation-modulated drug delivery system 3)Feedback-regulated drug delivery system All these three types of controlled release drug delivery system consist of the following structural features 1) Drug reservoir compartment 2) Rate controlling element 3) Energy source
- 13. Controlled release system Dissolution controlled Diffusion and Dissolution controlled Diffusion controlled Water penetration controlled Chemically controlledHydrogels Ion exchange resin Encapsulation Matrix Matrix Reservoir Reservoir and Monolithic Osmotically controlled Swelling controlled Erodible systems Drug covalently linked with polymer Chemically controlled Swelling controlled Diffusion controlled Cation exchange Anion exchange Shematic structure of various classes of Controlled Release System
- 14. 1)Rate preprogrammed drug delivery system These type of controlled release drug delivery systems the release of drug molecules from the delivery systems has been preprogrammed at specific rate profiles. This was done by system design, which controls the molecular diffusion of drug molecule in/or across the barrier medium within or surrounding the delivery system These systems can be further divided as fallows: • Polymer Membrane Permeation-Controlled DDS • Polymer Matrix Diffusion-Controlled DDS • Microreservoir Partition-Controlled DDS
- 15. A. Polymer Membrane Permeation-Controlled DDS The drug reservoir is totally encapsulated in a shallow-compartment molded from a drug impermeable metallic plastic laminate and a rate controlling polymeric membrane which may be micro-porous and non- porous. The rate of drug release from this type of TDDS,can be tailored by varying the composition of polymer permeability coefficient ,thickness of the rate limiting membrane ,and adhesive . e.g.: nitroglycerine releasing transdermal systems for once a day medication in angina pectoris
- 16. 1.TDDS 2.IUD
- 17. 3.Norplant subdermal implant 4.Ocusert system
- 18. B. Polymer Matrix Diffusion-Controlled DDS Prepared by homogenously dispersing the drug particles with a liquid polymer or a highly viscous base polymer followed by cross linking of the polymer chains or homogenously blending the drug solids with a rubbery polymer at an elevated temperature. It can be prepared by dissolving the drug and the polymer in a common solvent followed by solvent evaporation in a mould at an elevated temperature or in a vacuum. It is then pasted on to an occlusive base plate in a compartment fabricated from a drug impermeable plastic backing, the adhesive polymer is then spread along the circumference to form a strip of adhesive rim around the medicated disc. E.g.: nitroglycerine releasing transdermal system(Nitro- Dur II) for therapy of angina pectoris.
- 20. C. Microreservoir Partition-Controlled DDS Drug reservoir is formed by first suspending the drug solids in an aqueous solution of a water soluble liquid polymer and then dispersing the drug suspension homogenously in a lipophilic polymer such as silicone elastomers by high dispersion technique. E.g.: nitroglycerine releasing transdermal system (Nitro disc) for once a day therapy for angina pectoris.
- 21. 2)Activation-modulated drug delivery system In this group of controlled-release drug delivery systems the release of drug molecules from the delivery systems is activated by some physical, chemical or biochemical processes and/or facilitated by the energy supplied externally.
- 22. Activation modulated drug delivery systems(DDS) can be classified into the following categories: 1. Physical means a. osmotic pressure activated DDS b. hydrodynamic pressure activated DDS c .vapor activated DDS d. mechanically activated DDS e. magnetically activated DDS f. sonophoresis activated DDS g. iontophoresis activated DDS h. hydration-activated DDS 2. Chemical means a. pH-activated DDS b. ion-activated DDS c. hydrolysis-activated DDS 3. Biochemical means a enzyme activated DDS b. biochemical-activated DDS
- 23. Hydrodynamic pressure activated DDS • These are identical to osmotic systems which releases drug at zero order rate. It differs from osmotic system in that a hydrodynamic pressure generating agent, which is typically a water swellable hydrocolloid such as HPMC, which is contained in one compartment & drug solution is present in another collapsible reservoir. The hydrocolloid imbibes water & swells to generate hydrodynamic pressure that pushes the drug reservoir compartment & thus it forces the drug through an orifice at slow and uniform rate.
- 25. Mechanically activated drug delivery systems • In this type of activation-controlled drug delivery system the drug reservoir is a solution formulation retained in a container equipped with mechanically activated pumping system. • The volume of solution delivered is controllable as small as 10-100μl. • The volume of solution delivered is independent of the force and duration of activation applied as well as the solution volume in the container. • Example is the development of the metered-dose nebulizer • for the intranasal administration of a precision dose of buserelin, which is a synthetic analog of luteinizing hormone releasing hormone (LHRH) and insulin.
- 27. Magnetically activated DDS • In this system a tiny doughnut shaped magnet is positioned in the centre of a hemispherical shaped biocompatible polymer matrix containing dispersed drug and then coating the external surface of the medicated polymer matrix. When the magnet is activated to vibrate by an external electromagnetic field, it releases the drug at a zero order rate by diffusion process.
- 28. Vapor activated DDS • pumping compartment & the drug solution compartment are separated by a freely movable partition. The pumping compartment contains a liquefied compressed gas that vaporizes at body temperature and creates vapour pressure. Example: the development of infusion pumps of heparin in anticoagulant therapy, of insulin in the control of diabetes and of morphine for patients suffering from the intensive pain of a terminal cancer.
- 29. Ph-Activated drug delivery systems • This type of DDS permits targeting the delivery of a drug only in the region with a selected pH range. • Intestinal pH activated DDS • It is fabricated by coating the drug containing core with a pH sensitive polymer combination. • A gastric fluid labile drug is protected by encapsulating it inside a polymer membrane that resist the degradative action of gastric ph. such as the combination of ethyl cellulose and HMC phthalate. • The drug is release by drug dissolution and pore channel diffusion mechanism.
- 31. • In the stomach the coating membrane resists the action of gastric fluid (ph < 3) and the drug ,molecules are thus protected from acid degradation. • After gastric emptying the drug delivery system travels to the small intestine and the intestinal fluid activates the erosion of the intestinal fluid-soluble HMC phthalate component from the coating membrane. • By adjusting the ratio of the intestinal fluid soluble polymer to the intestinal fluid insoluble polymer, the membrane permeability of a drug can be regulated as desired.
- 32. Sonophoresis activated DDS • This type of activation-controlled drug delivery systems utilizes ultrasonic energy to activate (or trigger) the delivery of drugs from a polymeric drug delivery device. • The system can be fabricated from either a nondegradable polymer, or a bioerodible polymer.
- 33. Iontophoresis activated DDS • This type of activation-controlled drug delivery systems uses electrical current. • For activate and to modulate the diffusion of a charged drug molecule across a biological membrane, like the skin. • The iontophoresis-facilitated skin permeation rate of a charged molecule.
- 34. Osmotic activated drug delivery system • Osmosis can be defined as the net movement of water across a selectively permeable membrane driven by a difference in osmotic pressure across the membrane. • It is driven by a difference in solute concentrations across the membrane that allows passage of water, but rejects most solute molecules or ions. • Osmotic pressure created by osmogen is used as driving force for these systems to release the drug in controlled manner. • Osmotic pump offers many advantages over other controlled drug delivery systems, that is, they are easy to formulate. simple in operation. improved patient compliance with reduced dosing frequency and more consistence.
- 35. prolonged therapeutic effect with uniform blood concentration. inexpensive and their production scale up is easy. • Osmotic drug-delivery systems suitable for oral administration typically consist of a compressed tablet core that is coated with a semipermeable membrane coating. • This coating has one or more delivery ports through which a solution or suspension of the drug is released over time. • The core consists of a drug formulation that contains an osmotic agent and a water swellable polymer. • The rate at which the core absorbs water depends on the osmotic pressure generated by the core components and the permeability of the membrane coating. • As the core absorbs water, it expands in volume, which pushes the drug solution or suspension out of the tablet through one or more delivery ports.
- 36. • Materials used in formulation of osmotic system: 1. semipermeable membrane 2. hydrophilic and hydrophobic polymers 3.wicking agents 4. solubilizing agents 5.osmogens 6.surfactants 7.coating solvents 8. plasticizers 9. pore forming agents
- 37. 1. Semipermeable membrane: • Cellulose acetate is a commonly employed semipermeable polymer for the preparation of osmotic pumps. • It is available in different acetyl content grades. Particularly, acetyl content of 32% and 38% is widely used. • Some of the polymers that can be used for above purpose include cellulose esters such as cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose acetate butyrate, and cellulose ethers like ethyl cellulose. • Apart from cellulose derivatives, some other polymers such as agar acetate, amylose triacetate, betaglucan acetate, poly(vinyl methyl) ether copolymers, poly(orthoesters), poly acetals and selectively permeable poly(glycolic acid), poly(lactic acid) derivatives, and Eudragits can be used as semipermeable film-forming materials
- 38. 2. hydrophilic and hydrophobic polymers • These polymers are used in the formulation development of osmotic systems for making drug containing matrix core. • The highly water soluble compounds can be coentrapped in hydrophobic matrices and moderately water soluble compounds can be coentrapped in hydrophilic matrices to obtain more controlled release. • The polymers are of either swellable or nonswellable nature. Mostly, swellable polymers are used for the pumps containing moderately water-soluble drugs. • Ionic hydrogels such as sodium carboxymethyl cellulose are preferably used because of their osmogenic nature. • Hydrophilic polymers such as hydroxy ethyl cellulose, carboxy methylcellulose, hydroxy propyl methylcellulose, highmolecular- weight poly(vinyl pyrrolidone), and • hydrophobic polymers such as ethyl cellulose and wax materials can be used for this purpose.
- 39. 3.wicking agents • A wicking agent is defined as a material with the ability to draw water into the porous network of a delivery device. • The wicking agents are those agents which help to increase the contact surface area of the drug with the incoming aqueous fluid. • The use of the wicking agent helps to enhance the rate of drug released from the orifice of the drug. • A wicking agent is of either swellable or nonswellable nature . • They are characterized by having the ability to undergo physisorption with water. • Physisorption is a form of absorption in which the solvent molecules can loosely adhere to surfaces of the wicking agent via Vander Waals interactions between the surface of the wicking agent and the adsorbed molecule. • The function of the wicking agent is to carry water to surfaces inside the core of the tablet, thereby creating channels or a network of increased surface area . • The examples are colloidal silicon dioxide, PVP and Sodium lauryl sulfate.
- 40. 4. Solubilizing agents • For osmotic drug delivery system, highly water-soluble drugs would demonstrate a high release rate that would be of zero order. • Thus, many drugs with low intrinsic water solubility are poor candidates for osmotic delivery. However, it is possible to modulate the solubility of drugs within the core. • Addition of solubilizing agents into the core tablet dramatically increases the drug solubility.
- 41. 5.Osmogens • Upon penetration of biological fluid into the osmotic pump through semipermeable membrane, osmogens are dissolved in the biological fluid, which creates osmotic pressure buildup inside the pump and pushes medicament outside the pump through delivery orifice. • They include inorganic salts and carbohydrates. • Mostly, potassium chloride, sodium chloride, and mannitol used as osmogens. • Generally combinations of osmogens are used to achieve optimum osmotic pressure inside the system
- 42. 6.Surfactants • Surfactants are particularly useful when added to wall-forming material. • The surfactants act by regulating the surface energy of materials to improve their blending into the composite and maintain their integrity in the environment of use during the drug release period. • Typical surfactants such as poly oxyethylenated glyceryl recinoleate, polyoxyethylenated castor oil having ethylene oxide, glyceryl laurates, and glycerol (sorbiton oleate, stearate, or laurate) are incorporated into the formulation.
- 43. 7.Coating solvents • Solvents suitable for making polymeric solution that is used for manufacturing the wall of the osmotic device include inert inorganic and organic solvents that do not adversely harm the core and other materials. • The typical solvents include methylene chloride, acetone, methanol, ethanol, isopropyl alcohol, butyl alcohol, ethyl acetate, cyclohexane, carbon tetrachloride, and water.
- 44. 8. Plasticizers • Plasticizers, or low molecular weight diluents are added to modify the physical properties and improve film-forming characteristics of polymers. • Plasticizers can change visco elastic behavior of polymers significantly . • Plasticizers can turn a hard and brittle polymer into a softer, more pliable material, and possibly make it more resistant to mechanical stress . • PEG-600, PEG-200, triacetin (TA), dibutyl sebacate, ethylene glycol monoacetate, ethylene glycol diacetate, triethyl phosphate, and diethyl tartrate used as plasticizer in formulation of semipermeable membrane .
- 45. 9. Pore forming agents • These agents are particularly used in the pumps developed for poorly water-soluble drugs and in the development of controlled porosity or multiparticulate osmotic pumps . • These pore-forming agents cause the formation of microporous membrane. • The pore-formers can be inorganic or organic and solid or liquid in nature. For example, alkaline metal salts such as sodium chloride, sodium bromide, potassium chloride, potassium sulphate, potassium phosphate, and so forth, alkaline earth metals such as calcium chloride and calcium nitrate, carbohydrates such as sucrose, glucose, fructose, mannose, lactose, sorbitol, and mannitol, and diols and polyols such as poly hydric alcohols, polyethylene glycols, and polyvinyl pyrrolidone can be used as pore-forming agents .
- 46. Creation of Delivery Orifice • Osmotic delivery systems contain at least one delivery orifice in the membrane for drug release. • On the other hand, size of delivery orifice should not also be too large, otherwise, solute diffusion from the orifice may take place. • Optimum orifice diameter is in the range of 0.075–0.274 mm. At orifice size of 0.368 mm and above, control over the delivery rate is lost . • If the size of delivery orifice is too small, zero-order delivery will be affected because of development of hydrostatic pressure within the core. • Delivery orifices in the osmotic systems can be created with the help of a mechanical drill . • Laser drilling is one of the most commonly used techniques to create delivery orifice in the osmotic tablet.
- 47. • Types of Osmotic Pumps 1) Rose-Nelson Pump 2) Higuchi-Leeper Osmotic Pump 3) Higuchi-Theeuwes Osmotic Pump 4) Elementary Osmotic Pump (EOP) 5) Push-Pull Osmotic Pump (PPOP) 6) Controlled Porosity Osmotic Pump (CPOP) 7) Liquid-Oral Osmotic (L-OROS) System 8) Sandwiched Osmotic Tablet (SOT)
- 48. 1.Rose-Nelson Pump • Rose and Nelson, the Australian scientists, were initiators of osmotic drug delivery. In 1955, they developed an implantable pump for the delivery of drugs to the sheep and cattle gut. • The Rose-Nelson implantable pump is composed of three chambers: a drug chamber, a salt chamber holding solid salt, and a water chamber. • A semipermeable membrane separates the salt from water chamber • The movement of water from the water chamber towards salt chamber is influenced by difference in osmotic pressure across the membrane. • Conceivably, volume of salt chamber increases due to water flow, which distends the latex diaphragm dividing the salt and drug chambers: eventually, the drug is pumped out of the device.
- 49. • The major problem associated with • Rose-Nelson pumps was that the osmotic action began whenever water came in contact with the semipermeable membrane. This needed pumps to be stored empty and water to be loaded prior to use.
- 50. 2.Higuchi-Leeper Osmotic Pump • The Higuchi-Leeper pump has no water chamber, and the activation of the device occurs after imbibition of the water from the surrounding environment. • Higuchi-Leeper pumps contain a rigid housing and a semi permeable membrane supported on a perforated frame; a salt chamber containing a fluid solution with an excess of solid salt. • Upon administration/implantation, surrounding biological fluid penetrates into the device through porous and semipermeable membrane and dissolves the MgSO4, creating osmotic pressure inside the device that pushes movable separator toward the drug chamber to remove drug outside the device. • It is widely employed for veterinary use.
- 51. 3. Higuchi-Theeuwes Osmotic Pump • In this device, the rigid housing consisted of a semipermeable membrane. • This membrane is strong enough to withstand the pumping pressure developed inside the device due to imbibition of water. • The drug is loaded in the device only prior to its application, which extends advantage for storage of the device for longer duration. • They are used frequently as implantable controlled release delivery systems in experimental studies requiring continuous administration of drugs.
- 52. 4. Elementary Osmotic Pump (EOP) • Elementary osmotic pump was invented by Theeuwes in 1974 . • It essentially contains an active agent having a suitable osmotic pressure; it is fabricated as a tablet coated with semi permeable membrane, usually cellulose acetate . • A small orifice is drilled through the membrane coating. • When this coated tablet is exposed to an aqueous environment, the osmotic pressure of the soluble drug inside the tablet draws water through the semi permeable coating and a saturated aqueous solution of drug is formed inside the device. • The membrane is nonextensible and the increase in volume due to imbibition of water raises the hydrostatic pressure inside the tablet, eventually leading to flow of saturated solution of active agent out of the device through a small orifice.
- 53. 5.Push-Pull Osmotic Pump (PPOP) • Push-pull osmotic pump is delivered both poorly water soluble and highly water soluble drugs at a constant rate. • This system resembles a standard bilayer coated tablet. One layer (the upper layer) contains drug in a formulation of polymeric osmotic agent, and other tablet excipients. • When the system is placed in aqueous environment, water is attracted into the tablet by an osmotic agent in both the layers. • The osmotic attraction in the drug layer pulls water into the compartment to form in situ a suspension of drug. • The osmotic agent in the nondrug layer simultaneously attracts water into that compartment, causing it to expand volumetrically, and the expansion of nondrug layer pushes the drug suspension out of the delivery orifice .
- 54. 6.Controlled Porosity Osmotic Pump (CPOP) • Controlled porosity osmotic pump (CPOP) are reliable drug delivery system and could be employed as oral drug delivery system. • CPOP consists of drug and osmogen in the core and tablet is surrounded by a semipermeable membrane containing leachable pore forming agents which in contact with aqueous environment dissolves and result in formation of micro porous membrane. • Drug release rate from CPOP depends on various factors like • Coating thickness, • Solubility of drug in tablet core, • Level of leachable pore-forming agent(s) and • The osmotic pressure difference across the membrane.
- 55. 7.Liquid-Oral Osmotic (L-OROS) System • Each of these systems includes a liquid drug layer, an osmotic engine or push layer, and a semipermeable membrane coating. • When the system is in contact with the aqueous environment, water permeates across the rate-controlling membrane and activates the osmotic layer.
- 56. 8.Sandwiched Osmotic Tablet (SOT) • Sandwiched osmotic tablet is composed of polymeric push layer sandwiched between two drug layers with two delivery orifices. • When placed in the aqueous environment, the middle push layer containing the swelling agents' swells and the drug is released from the two orifices situated on opposite sides of the tablet; thus sandwiched osmotic tablets (SOTS) can be suitable for drugs prone to cause local irritation of the gastric mucosa.
- 57. Enzyme activated drug delivery systems • This type of activation modulated DDS depends on the enzymatic process to activate the release of the drug. • In this system the drug reservoir is either physically entrapped in microspheres or chemically bound to the polymer chains from biopolymers, such as albumins or polypeptides. • The release of drug is activated by the enzymatic hydrolysis of biopolymers by a specific enzyme in the target tissue. • Typical example of this enzyme activated DDS is the development of albumin microspheres that release 5fluorouracil in a controlled manner by protease activated biodegradation.
- 58. Feedback regulated drug delivery system • In this group of controlled-release DDS the release of drug molecules from the delivery systems is activated by triggering agent, such as a biochemical substance, in the body. • The rate of drug release is then controlled by the concentration of triggering agent detected by a sensor in the feedback-regulated mechanisms. • It is classified in to the following: 1) Bioerosion-regulated drug delivery systems 2) Bioresponsive drug delivery systems 3) Self regulating drug delivery systems
- 59. Bioerosion-regulated drug delivery systems • The feedback-regulated DDS was applied to the development of a bioerosion-regulated DDS by heller and trescony. • The system consisted of drug dispersed bioerodible matrix fabricated from poly(vinyl methyl ether) half-ester , which was coated with a half layer of immobilized urease. • In a solution of neutral pH, the polymer only erodes slowly. • In the presence of urea, urease at the surface of DDS metabolizes urea to form ammonia. • This causes the pH to increase and a rapid degradation of polymer matrix as well as the release of drug molecules.
- 60. Fig:-Cross-sectional view of a bioerosion-regulated hydrocortisone delivery system, showing the drug-dispersed monolithic bioerodible polymer matrix with surface- immobilized ureases.
- 61. Bioresponsive drug delivery systems • Bioresponsive DDS was developed by Horbett et al. • Drug reservoir is contained in a device enclosed by a bioresponsve polymeric membrane whose drug permeability is controlled by the concentration of a biochemical agent in the tissue where the system is located. • Typical example of this bioresponsive DDS is the development of a glucose-triggered insulin delivery system in which the insulin reservoir is encapsulated within a hydrogel membrane having pendent NR2 groups. • In alkaline solution the – NR2 groups are neutral and the membrane is unswollen and impermeable to insulin. • Glucose is a triggering agent, penetrates in to the membrane , it is oxidized enzymatically by the glucose oxidase entrapped in the membrane to form gluconic acid. • The –NR2 groups are protonated to form –NR2H and the hydrogel membrane then becomes swollen and permeable to insulin molecules.
- 62. Fig:-Cross-sectional view of a bioresponsive insulin delivery system, showing the glucose oxidase-entrapped hydrogel membrane constructed from amine-containing hydrophilic polymer. The mechanism of insulin release in response to the influx of glucose is also illustrated.
- 63. Self regulating drug delivery systems • This type of feedback-regulated drug delivery system depends on a reversible and competitive binding mechanism to activate and regulate the release of the drug. • In this system the drug reservoir is drug complex encapsulated within a semipermeable membrane polymeric membrane. • The release of drug is activated by the polymeric membrane of a biochemical agent from the tissue in which the system is located. • It first involves the reparation of biologically active insulin derivatives in which insulin is coupled with a sugar (maltose) and this into an insulin-sugar-lectin complex. • Complex is then encapsulated within a semipermeable membrane. • As blood glucose diffuses into the device and competitively binds at the sugar binding sites in lectin molecules. • This activates the release of bound insulin-sugar derivatives.
- 64. • Complex of glycosylated insulin-concanavalin A, which is encapsulated inside a polymer membrane. • As glucose, the triggering agent, penetrates the system, it activates the release of glycosylated insulin from the complex for controlled delivery out of the system.
- 65. • References: 1. Novel drug delivery systems by Yie W. Chein. Pg no 1 – 37 2. Osmotic drug delivery systems https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3407637/ 3. Images from Google
- 66. Thank you