Entrapment ability and release profile of corticosteroids from starch‐based microparticles

Abstract

Abstract:We previously described the synthesis of starchbased microparticles that were shown to be bioactive (when combined with Bioactive Glass 45S5) and noncytotoxic. To further assess their potential for biomedical applications such as controlled release, three corticosteroids with a similar basic structure-dexamethasone (DEX), 16␣-methylprednisonole (MP), and 16␣-methylprednisolone acetate (MPA)-were used as models for the entrapment and release of bioactive agents. DEX, MP, and MPA were entrapped into starch-based microparticles at 10% wt/wt of the starch-based polymer and the loading efficiencies, as well as the release profiles, were evaluated. Differences were found for the loading efficiencies of the three corticosteroids, with DEX and MPA being the most successfully loaded (82 and 84%, respectively), followed by MP (51%). These differences might be explained based on the differential distribution of the molecules within the matrix of the microparticles. Furthermore, a differential burst release was observed in the first 24 h for all corticosteroids with DEX and MP being more pronounced (around 25%), whereas only 12% of MPA was released during the same time period. Whereas the water uptake profile can account for this first stage burst release, the subsequent slower release stage was mainly attributed to degradation of the microparticle network. Differences in the release profiles can be explained based on the structure of the molecule, because MPA, a more bulky and hydrophobic molecule, is released at a slower rate compared with DEX and MP. In this work, it is shown that these carriers were able to sustain a controlled release of the entrapped corticosteroids over 30 days, which confirms the potential of these systems to be used as carriers for the delivery of bioactive agents.

Preparation and characterization of starch-poly-ε-caprolactone microparticles incorporating bioactive agents for drug delivery and tissue engineering applications

“…Iodine-potassium solution (Lugol) is a well-known and useful solution for chemically identifying the presence of starch molecules [31]. The amylose present in the starch molecule has a helical secondary structure [52], where substances such as iodine can lodge, forming a complex as an inclusion compound.…”

“…For instance, starch microparticles using soluble potato starch have been developed and proposed for the release of a nonsteroidal anti-inflammatory drug [21]. Moreover, a blend of starch and polylactic acid have been used for the encapsulation of steroids, growth factors and bioactive glass in a microparticle system [31][32][33]. These studies showed that the starch-polylactic acid microparticles are suitable carriers for the controlled release of bioactive agents for bone tissue engineering applications.…”

Materials in particulate form for tissue engineering. 1. Basic concepts

“…Dextrans are being actively investigated for sustained delivery of therapeutic and imaging agents, particularly for injectables and colon-specific DDSs. Starch-based polymers have been proposed by Reis and Cunha (1995) as materials with potential for biomedical applications, particularly as scaffolds for bone tissue engineering applications (Gomes et al, 2001(Gomes et al, , 2002, bone cements (Espigares et al, 2002;Boesel et al, 2003) and recently as drug delivery systems Silva et al, 2005). These materials have been shown to be biocompatible in vitro (Mendes et al, 2001;Marques et al, 2002), and to possess a good in vivo performance (Mendes et al, 2003;Salgado et al, 2005).…”

Materials in particulate form for tissue engineering. 2. Applications in bone

“…In vitro, dexamethasone has been employed as a differentiation agent for bone marrow cells to progress into the osteoblastic lineage (Maniatopoulos et al, 1988). Within this last role, strategies employing the incorporation of dexamethasone in polymeric materials to be used as carriers for the differentiation of cells into the osteoblastic lineage have been described in the literature (Silva et al, 2005), which confers on dexamethasone a highlighted role in bone TE approaches.…”