Pharmaceutics and Formulation - Literature review Example

? Development of polysaccharides vehicles for oral delivery of a model protein certain anionic polysaccharides such as alginate, gellan gum and pectin can be crossed under milk conditions to produce gel beads in which pharmacologically active molecules can be encapsulated. literature review. Name: Introduction: Polysaccharides are polymers which are made up of simple sugars as the building blocks and have many applications as they have variable and versatile complex structures that are not found in other polymer classes (Tommasina et al, 2007).For example they can be used as stabilizers, suspending agents, gelling agents, emulsifiers and also as structuring agents. Examples of these polysaccharides are Xanthan, xyloglucan, chitasan, pectin, alginate, guar gum, pullulan and also gellan gum. These substances are capable of forming hydrogels. Hydrogels have a 3 dimensional structure and hydrophilic networks which are capable of imbibing large amounts of water and are analogous to biological tissues (Patil et al., 2010) Pectins are naturally occurring polysaccharides and are important structural components of plant cell walls. They are methylated esters of polygalacturonic acids which are found in higher concentrations in the middle lamella of cells. Commercially, they are extracted from citrus peels, mango waste and sugar beet waste. This polysaccharide is made up of D- galacturonic acid units which are joined in chains by means of ? (1-4) glycosidic linkages. These uronic acids have carboxyl groups and some of them occur naturally as methyl esters .Part of pectin backbone is made up of rhomnase, a natural sugar in which arabinose, galactose and xylose can be linked as side chains. Polygalacturonic acid chains are also partially esterified with methyl groups. The ratio of esterified Gal A groups to total Gal A groups is called De and is depended on tissue, species and maturity. Based on De, we can have high methoxyl pectins (Hm) and low methoxyl pectins (Lm). Hm pectins require a minimum amount of solution solids and PH within 3 so as to form gels. They often contain dispersion agent such as dextrose to prevent lumping. The LM pectins are not PH sensitive and forms gels independent of sugar and also requires the presence of controlled amount of calcium and divalent cations for gellation (Pornsak, n.d).They have been used in industries as thickening, gelling agents and in drug delivery systems. They show perfect biocompatibility, specific PH responses and can be used without any limitation as they are not toxic. They are also thought to lower blood cholesterol level, reduce or slow down glucose absorption and enhance excretion of toxic divalent metals (Tommasina et al., 2007).Pectin polysaccharides are anionic polyelectrolytes as they bind to oppositely charged surfaces thus associating with oppositely charged molecules and they can therefore be used as a polymeric coat in drug encapsulation. Pectin forms cross links through calcium bridges ((Muhiddonov et al., 2004).This cross linking can be physical chemical or effected through a combination of the two as acid insoluble gels show potential for enzymatic degradation in the colon by pectinases secreted by colonic bacterial. Alginates are naturally occurring polysaccharides, biodegradable, non toxic and can be obtained from marine brown algae as well as from certain bacterial and have both monomeric and polymeric structures. The monomeric units of alginate ?-L gluronate and ?-D manuronate are C5 epimers of each other. Alginate is organized as either homopolymeric G blocks, polygluronate poly (G) blocks and homopolymeric M blocks. All these blocks can be present in a single alginate molecule. The arrangement of the monomers in the block structure and size of alginate formed is very important as it affects both gel forming ability and viscosity of polymer. The poly (G) blocks forms ‘buckled’ chain conformation which binds calcium ions avidly thus producing firm but brittle gels. Those regions containing MM and MG blocks do not discriminate between binding of calcium and other metals and forms elastic gels. Poly (M) blocks forms extended ribbons conformation while M and G blocks forms kinks and disrupted ribbons (Thiong et al., 2000). Alginates froms acid insolubles gels through ionotropic gelation in which bioactive substances such as enzymes, proteins, vaccines can be encapsulated. Alginate also has re-swelling ability which allows acid sensitive drugs to be incorporated in the gel.( Patil et al., 2010).Alginates have also been demonstrated to have very important muco-adhesive characteristics (Junginger, 1991).These qualities can increase time of contact between the absorption epithelium and alginate microbeads/ microsphere thus enhancing the uptake of the encapsulated biologically active molecule (Bowersock et al.,1994).Various studies have shown that the biodegradable alginate microspheres/ microbeads show variable release kinetics .Lim and Sun, (n.d) have shown that alginate has low toxicity and low immunogenicity and is therefore safer to use .This polymer is also inexpensive and readily available. Gellan gum is actually an exopolysaccharide of bacteria which is formed through aerobic fermentation of Sphingomonas elodea (Tommasina et al., 2007).It is a straight chain heteropolysacharide made of repeating units of 4 monosacharides which are glucose, glucoronic acid and rhamnose and has one carboxyl group in the repeating units. In addition to this, it has an acetyl group (C6) and a glyceryl group (C2) on its glucose residue immediately after its fermentation production. Inorganic ions are also present. Gellan gum and other microgels are being used in making of jellies, fillings, jams and in puddings. Gellan gel can be made by lowering the PH but because the gel which is obtained through this method has a tendency to have lower clarity and because of this, inorganic ions are used (Omoto, Uno and Asai, 1999). For the last years, research has been directed towards designing of better oral delivery systems for pharmacologically active molecules and encapsulation is one such method. This technology has a number of advantages as it protects the biological active molecules from acidic and proteolytic conditions in the gastrointestinal tract after oral administration. (Lemoine, et al., 1998).It should also be considered that some drugs requires slow release and this is provided by use of polyscharide gels.Encapsulation also ensures improved stability of the drug formulation and helps in proper time release (Gibbs et al.,1999).It is therefore important that, GIT physiological variability be considered in the formulation of grugs that have narrow therapeutic index as GIT environment is characterized by PH flactuations, enzyme changes especially in fed and fasting conditions, factors which affects the solubility of certain drugs and consequently affecting their absorption. Absorption of orally administered drugs is also faced with challenges such as the hdrophilicity of drugs, high molecular mass and their vulnerability to stomach proteolytic enzymes.Encapsulation overcomes all these delivery problems (Parisa et al, 2004).The use of Alginate, pectin and gellan gu offers an opportunity to formulate drugs for oral delivery and are widely used. This research is justified from the from the point of view that there are drawbacks in oral delivery sytems due to the physiologuical characteristics of GIT and thus the use of these polysaccharides can help in developing new formulations and thus circumvent these problems offered by GIT. Again, due to availability of technology and the availability of these polysacharide materials, this research is also justified from the feassibility point of view.In addition to these, Alginate, pectin and gellan gum have many desirable characteristics which makes them to be exploited as good tools of oral drug formulations. For instance they are biodegradable, non-toxic , available and biocompartible. Broad objective / Aim The broad objective of this study is to detemine the technical feasibility of delivering pharmacological active molecules such as protein encapsulated in Alginate, gellan gum and pectin. Specific objectives The specific objectives of this study may include. 1. To investigate the encapsulation efficiency and the release of a model protein drug from these three polysaccharide gels. 2. To determine the effects of encapsulation, molecular weight, the biological activity of the entrapped pharmacologically active molecule. 3. To determine the effects of the molecular weight of the three polysaccharide gels on the release profie of the pharmacologically active molecules. 4. To prepare alginate,gellan gum and pectin microbeads through emulsfication interface reaction techniques and to evaluate the influence of preparation precedures, encapsulation method and type of gel on the physiological properties of drug encapsulated microbeads. 5. To evaluate the effects of various divalent cations on the encapsulation effieciency. Hypothesis. 1. Alginate, gellan and pectin polysachride gels could be good tools for delivering pharmacologically active molecules such as proteins through the oral route and consequently enhance the drug bioavailability and stability in the hostile GIT through protection and slow release. 2. Encapsulation of the phamacologically active molecule and the molecular weight of the gels does not affect the release profles and biological activity of the encapsulated drug. 3. Divalent cations used in the encapsulation do not have any effect on the encapsulation efficiency. Methodology. Encapsulation process Techniques used includes ionotropic gelation and polyelectrolyte complexation.These techniques are important as they provide sustained release properties and ensure uniform distribution of drugs even in GIT. The formation of microbeads is done using 2 methods ie syringe droping (extruding method) and air atomization. The biomolecules are then loaded at mild conditions so as to retain their dimensional structure. ((Patil et al., 2010)).Today, in the formualtion of microbeads for encapsulaation , microfliudic systems are also widely being used other than the traditional methods of emulsification.In this study, microchannel emulsification technique will be used.This techniques has many advantages as it requires low energy input and creates desirable experimental conditions for microencapsulation of unstable substances such as proteins and peptides. Determining of encapsulation efficiency This can be done by obtaining 5mg of the pharmacologically active loaded microbeads, weighing accurately and incubating then in 0.5 ML OF EDTA 0.1 that has been prepared in phosphate buffer at 7.4 ph under magnetic stirring. The samples are the withdrawn and analyzed using Uv spectroscopy. Encapsulation efficiency is calculated by obtaining the difference between theoretical initial of the protein and the total protein recovered from the microbeads (Catarina et al, 2006).This method has been found to effective with insulin and it can be used for other proteins.This assay should be done in triplicates to ensure reproducibility. Invitro release studies A USP dissolution apparatus will be used in release profiles studies. This study requires simulated gastric fluid ph 1.2 and intestinal fluid ph 6.8 without enzymes which will be used as a dissolution media. A sample of pharmacologically loaded microbeads ie 20mg can be placed on 20ml of Hcl buffer at Ph 1.2 .After 2 hrs the microbeads can be transferred to 20ml of phosphate buffer at 6.8 ph and incubated for 2hrs.From both media, 2 ml of samples are taken at appropriate intervals and protein determined using UV spectroscopy. This assay should also be done in triplicates. Samples taken from the acidic media are centrifuged and the supernatant analyzed for the presence of protein. NB In acidic medium, the microbeads should not be able to release the proteins as they form acid gels. The microbeads should be able to protect the protein from hostile attack through retention of the protein in the polymer matrix (Catarina et al., 2006). Statistical analysis of results All data will be expressed as mean + SD and ANOVA be used to compare the means. The type of ANOVA to use will depend on the variables (both dependent and independent) you have. This test will also be used to find if there was a significant difference in the three gels in terms of delivery of the drug. Correlational analysis will be used for analysis of pharmacological and drug release kinetic parameters. References 1. Bowersock, T. H., Hogenesch, H., Park,H and Park, K (1994). Uptake of alginate by microsphere by peyer's partches. Journal of Controlled release , 21, 839-840. 2. Catarina, M. A., Antanio,J.R., Francisco,V and Adriano,S. (2006). Insulin release from alginate microsphres reiforced with Detran sulfate. CI and CEQ , 12 (1), 40-46. 3. Gibbs, B. K., Kermasha,S., Alle,I and Mulligan, C.N. (1999). Encapsulation in the food industry. International journal of food sciences and nutrition , 50 (3), 213-224. 4. Junginger, H. (1991). Mucoadhesive hydrogels. Phram Ind , 53 (11), 1056-1065. 5. Lemoine, D. W., Wauters,S., Bouched'homme and Preat, V. (1998). Preparation and characterization of alginate microspheres containing a model antigen. International journal of pharmaceutics , 176, 9-19. 6. Lim, F. A. and Sun, A. M. (n.d). Microencapsulated islets as bioartificial endocrine pancrease. Science , 210 (21), 908-910. 7. Muhiddonov, Z. K., Khalikov,D., Speaker,T and Fassihi,F. (2004). Development and characterization of different low methoxy pectin microcapsules by an emulsion interface reaction teachniqie. Journal of microencapslation , 21 (7), 729-741. 8. Omoto, T., Uno, Y and Asai, A.(1999).The latest technologies for application of gellan gum. Prog.Colloid Polym Sci, 114:123-126 9. Parisa, Y. K., Kooroush, S., Assal.M.H., Leila, M., Elatteh, N., Khosrow, B., Ahmed, R.D., and Morteza, R. (2004). Preparation and ex vivo evaluation of Tec as an absorption enhancer for poorly absorbable compounds in colon specific drug delivery. Acta pharm , 54, 339-345. 10. Patil, J. K. (2010). Ionotropic gelation and polyelectrolytic complexation. Digest journal of nanomaterials and biostructures. , 5 (1), 241-248. 11. Pornsak, S.(n.d). Chemistry of pectins and its pharmaceutical uses.A review. Retrieved on 7th Nov.2011 from http://www.journal.su.ac.th/index.php/suij/article/viewFile/48/48 12. Thiong, Y., Wong, L. , Preston and Neal, L.S .(2000).Alginate lyase: Review of major sources and enzymes characteristics structure function analysis, Biological roles and application.Annu.Rew.Microbiol.54:289-340 13. Tommasina, C., P Pietro,M., Carlotta, M and Franco,A. (2007). Polysacharide hydrogels for modified release formulations,Review. Journal of controlled release , 119, 5-2 Read More