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Abstract
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In this study, the process of manufacturing nanohydrogels containing papain and how to release it was investigated. Chitosan
nanohydrogels and chitosan–polyethylene glycol hybrid nanohydrogels were used to entrapment of papain as a protein
model. In order to evaluate and confirm different properties of nanohydrogels such as size, shape, the rate of swelling and
flexibility, different methods was used. The maximum amount of papain entrapment was observed in 0.75% concentration
of chitosan and 1% concentration of sodium Tripolyphosphate (TPP) as linker. The results of scanning electron microscope
(SEM) and X-ray diffraction (XRD) patterns showed that nanohydrogels containing papain on a nano scale are very porous
and swollen. Differential scanning calorimetry (DSC) thermograms analysis showed that nanohydrogels have relatively good
water absorption capacity. Also, by adding polyethylene glycol to chitosan, the melting temperature of hybrid nanohydrogels
decreased and this can be a reason for the formation of flexible structures in these nanohydrogels. In chitosan nanohydrogels,
the highest release rate of papain was observed at pH lower than 7 and high temperatures, but by adding polyethylene glycol to
the chitosan, in addition to increasing papain release, a proper and continuous release of papain was observed at temperature
and pH close to physiological conditions, especially at low ratios of polyethylene glycol. According to the present results,
hybrid nanohydrogels can have a good potential in protein delivery systems in terms of structure and release.
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