Preparation and characterization of cyclodextrin-modified alginate hydrogel

Abstract

Alginate is commonly employed in biomedical applications such as wound healing, tissue engineering and contact lenses because of its valuable non-toxic nature and ease of gelation. Cyclodextrin (CD), with its ability to form inclusion complexes with suitable guest molecules, has optimized a wide variety of applications ranging from pharmaceuticals to foods by acting as a carrier and improving solubility and stability. This study details the preparation of CD-grafted alginate hydrogel and the methods to qualitatively and quantitively verify the successful synthesis, as well as to characterize changes in alginate hydrogel properties due to the presence of CD, its guest molecule and the manipulation of their host-guest interactions. 6-(p-Toluidino)-2- naphthalenesulfonate (TNS) is selected as the guest molecule to allow the identification of changes in fluorescence intensity. Alginate-βCD polymer was first synthesized and a set of hydrogels – (1) alginate, (2) alginate-βCD, (3) alginate TNS, (4) alginate-βCD TNS, (5) alginate soaked in TNS and (6) alginate-βCD soaked in TNS – was prepared for analysis. A series of tests were conducted to analyze the samples and characterize their biocompatibility and mechanical properties. To observe host-guest interactions between βCD and TNS, fluorescence microscopy was performed. The manipulation of βCD-TNS host-guest interactions was experimented by applying mechanical stimuli through a compression test and cell culture. Results of cell culture revealed that alginate is biocompatible and can be enhanced with the addition of an extracellular matrix. Force indentation tests performed with atomic force microscopy determined that alginate-βCD is of lower stiffness than alginate. βCD-TNS inclusion complexes in alginate-βCD TNS were positively observed from the emission of fluorescence from the entire hydrogel, unlike the scattered fluorescent TNS aggregates seen in alginate. Mechanical force inflicted on alginate-βCD soaked in TNS significantly reduced its fluorescence intensity as compared to alginate.