Reaction of chitosan with genipin and its fluorogenic attributes for potential microcapsule membrane characterization

Abstract

This study investigates the fluorogenic characteristics of the chitosan-genipin reaction for applications in microencapsulation research. Results showed that the chitosan-genipin reaction generated a colored and fluorescent product, with optimal excitation and emission wavelengths at 369 and 470 nm, respectively. Furthermore, it was found that reaction conditions affected the fluorescence intensity of the product. Mixture at the ratio of 4:1 (chitosan: genipin by weight) fluoresced the most. It also fluoresced stronger if the reaction occurred at higher temperature, with the intensity of 10.4 x 10(5) CPS at 37 degrees C, 5.9 x 10(5) CPS at 20 degrees C, and 2.5 x 10(5) CPS at 4 degrees C. As well, the fluorescence of the mixture developed gradually over time, attaining the emission maxima of 2.9 x 10(5), 7.6 x 10(5), and 10.0 x 10(5) CPS in 1, 6, and 18 h, respectively. Chitosan-coated alginate microcapsules were prepared without prior labeling, to which subsequent genipin treatment was applied in order to examine the potential of using genipin in microcapsule characterization. Chitosan bound to the alginate beads interacted with genipin, from which the resultant fluorescent signals allowed for clear visualization of the chitosan coating under confocal laser scanning microscopy. The relative fluorescence intensity across the chitosan membrane was found to be considerably higher than the controls (175 vs. 50). The membrane thickness measured was 29.2 +/- 7.3 microm. These findings demonstrate a convenient and effective way of characterizing chitosan-based microcapsules using genipin as a fluorogenic marker, a technique that will be useful in microcapsule research and other biomedical applications.

The dramatic effect of small pH changes on the properties of chitosan hydrogels crosslinked with genipin

“…We discovered that the pH value has a much greater effect on hydrogel's properties than anticipated, and even changes as small as half a pH unit dramatically alter properties such as rigidity and color. Furthermore, we observed that even after the hydrogels became blue, which according to previous reports is indicative of formation of a hydrogel (Chen et al, 2005), their rigidity continued increasing over time. Samples of several polymer and crosslinker concentrations that were left to cure for more than 48 h exhibited an apparent phase separation and extraction of the water.…”

Fabrication of porous chitosan scaffolds for soft tissue engineering using dense gas CO2

“…The crosslinking degree has been shown to be correlated to colour intensity [48,49]; the measurement of colour intensity was processed using Image J software [50]. As shown in Fig.…”

Graphene oxide-reinforced biodegradable genipin-cross-linked chitosan fluorescent biocomposite film and its cytocompatibility

“…38 It appears that a large conjugated system, possibly the π-π* conjugation, is formed by this reaction, thus resulting in the fluorescence in the cross-linked CS. 39 In our study, genipin was added after the GO sheets were blended into the CS solution. Both the GO and the genipin could react with primary amine group, therefore, there would have been a lesser amount of primary amine groups available for genipin after the addition of GO.…”