Mucoadhesive Microspheres as carriers in Drug Delivery: a Review

Microspheres constitute an important part of novel drug delivery system by virtue of their small size and efficient carrier capacity. Due to their short residence time, bioadhesive characteristics can be coupled to microspheres to develop mucoadhesive microspheres. Bioadhesion can be defined as the state in which two materials, at least one of which is biological in nature, are held together for a prolonged time period by means of interfacial forces. Microspheres are the carrier linked drug delivery system in which particle size is ranges from 1-1000 μm range in diameter having a core of drug and entirely outer layers of polymer as coating material. Mucoadhesive microspheres have advantages like efficient absorption and enhanced bioavailability of the drugs due to a high surface to volume ratio, a much more intimate contact with the mucus layer, controlled and sustained release of drug from dosage form and specific targeting of drugs to the absorption site. The present study aims to provide an overview of various aspects of mucoadhesive microsphere based on various polymers, methodology of preparation of mucoadhesive microspheres, method of evaluation and their applications in drug delivery. *Corresponding author, Mailing address: Hemlata Kaurav E-mail: [email protected] Article History:-----------------------Date of Submission: 26-03-2012 Date of Acceptance: 09-04-2012 Conflict of Interest: NIL Source of Support: NONE R e v i e w P a p e r C o v e r e d i n I n d e x C o p e r n i c u s w i t h I C V a l u e 4 .6 8 f o r 2 0 1 0 Int. J. Drug Dev. & Res., April-June 2012, 4 (2): 21-34 Covered in Scopus & Embase, Elsevier 21 circulation of body. However oral administration of most of the drugs in conventional dosage forms has short-term limitations due to their inability to restrain and localize the system at gastro-intestinal tract. Microspheres constitute an important part of these particulate drug delivery systems by virtue of their small size and efficient carrier capacity. Microspheres are the carrier linked drug delivery system in which particle size is ranges from 1-1000 μm range in diameter having a core of drug and entirely outer layers of polymer as coating material. However, the success of these microspheres is limited due to their short residence time at site of absorption. It would, therefore be advantageous to have means for providing an intimate contact of the drug delivery system with the absorbing membrane. This can be achieved by coupling bioadhesion characteristics to microspheres and developing “mucoadhesive microspheres”. Mucoadhesive microspheres have advantages like efficient absorption and enhanced bioavailability of the drugs due to a high surface to volume ratio, a much more intimate contact with the mucus layer and specific targeting of drugs to the absorption site [2]. Mucoadhesion and microspheres Mucoadhesion or bioadhesion can be defined as the state in which two materials, at least one of which is biological in nature, are held together for a prolonged time period by means of interfacial forces. In biological systems, bioadhesion can be classified into 3 types. • Type 1, adhesion between two biological phases, for example, platelet aggregation and wound healing. • Type 2, adhesion of a biological phase to an artificial substrate, for example tissue, cell adhesion to culture dishes and biofilm formation on prosthetic devices and inserts. • Type 3, adhesion of an artificial substance to a biological substrate, for example, adhesion of synthetic hydrogels to soft tissues For drug delivery purpose, the term “bioadhesion” implies attachment of a drug carrier system to a specific biological location. The biological surface can be epithelial tissue or the mucus coat on the surface of a tissue. If adhesive attachment is to a mucous coat, the phenomenon is referred to as “Mucoadhesion”. Mucoadhesion is defined as the interaction between a mucin surface and a synthetic or natural polymer [3]. Mucoadhesion has been widely promoted as a way of achieving site-specific drug delivery through the incorporation of mucoadhesive hydrophilic polymers within pharmaceutical formulations such as “microspheres” along with the active pharmaceutical ingredient (API). Microspheres are defined as spherical particles having size less than 200μm and made up of polymer matrix in which therapeutic substance is dispersed throughout the matrix at the molecular or macroscopic level. The rationale of developing mucoadhesive microsphere drug delivery system lies behind the fact that the formulation will be ‘held’ on a biological surface for localized drug delivery. The API will be released close to the site of action with a consequent enhancement of bioavailability [4]. Mucoadhesive microspheres include microparticles and microcapsules (having a core of drug) of 11000μm in diameter and consisting either entirely of a Mucoadhesive polymer or having an outer coating of it, respectively. Microspheres, in general, have the potential to be used for targeted and controlled release drug delivery; but coupling of bioadhesive properties to microspheres has additional advantages e.g. efficient absorption and bioavailability of the drugs due to high surface to volume ratio, a much more intimate contact with the mucous layer, specific targeting of drugs to the absorption site. Bioadhesive microspheres can be tailored to adhere to any R e v i e w P a p e r C o v e r e d i n I n d e x C o p e r n i c u s w i t h I C V a l u e 4 .6 8 f o r 2 0 1 0 Hemlata Kaurav et al: Mucoadhesive Microspheres as carriers in Drug Delivery: A Review