Abstract
Nutraceutical formulations based on probiotic microorganisms have gained significant attention over the past decade due to their beneficial properties on human health. Yeasts offer some advantages over other probiotic organisms, such as immunomodulatory properties, anticancer effects and effective suppression of pathogens. However, one of the main challenges for their oral administration is ensuring that cell viability remains high enough for a sustained therapeutic effect while avoiding possible substrate inhibition issues as they transit through the gastrointestinal (GI) tract. Here, we propose addressing these issues using a probiotic yeast encapsulation strategy, Kluyveromyces lactis, based on gelatin hydrogels doubly cross-linked with graphene oxide (GO) and glutaraldehyde to form highly resistant nanocomposite encapsulates. GO was selected here as a reinforcement agent due to its unique properties, including superior solubility and dispersibility in water and other solvents, high biocompatibility, antimicrobial activity, and response to electrical fields in its reduced form. Finally, GO has been reported to enhance the mechanical properties of several materials, including natural and synthetic polymers and ceramics. The synthesized GO-gelatin nanocomposite hydrogels were characterized in morphological, swelling, mechanical, thermal, and rheological properties and their ability to maintain probiotic cell viability. The obtained nanocomposites exhibited larger pore sizes for successful cell entrapment and proliferation, tunable degradation rates, pH-dependent swelling ratio, and higher mechanical stability and integrity in simulated GI media and during bioreactor operation. These results encourage us to consider the application of the obtained nanocomposites to not only formulate high-performance nutraceuticals but to extend it to tissue engineering, bioadhesives, smart coatings, controlled release systems, and bioproduction of highly added value metabolites.
Highlights
graphene oxide (GO) was characterized by Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) to confirm the synthesis and the oxidation level
FTIR spectrum of GO exhibits several peaks related to the oxidative functional groups, namely O-H stretching vibrations at 3420 cm−1, C=O stretching vibrations in the range of 1720–1740 cm−1, C=C from unoxidized sp2 CC
An important observation that after 24 h in aqueous solution, none of the GO hydrogels showed structural stability is that after 24 h in aqueous solution, none of the GO hydrogels showed structural stability failure or observable changes in their macrostructure. These findings failure or observable changes in their macrostructure. These findings strongly suggest that GO hydrogels are likely to offer better tolerance to the transit along strongly suggest that GO hydrogels are likely to offer better tolerance to the transit along the GI tract compared with the pristine ones
Summary
Nutraceuticals, which generally are poorly soluble in water, have low bioavailability by this route of administration [4] This is the case of whole cells, including lactic acid bacteria (LAB), Bifidobacteria, Escherichia coli Nissle 1917, and beneficial molecules such as bivalent fusion protein r-BL with recombinant protein UOmp, Garcinia mangostana L. ethanolic extract, and insulin [5,6,7,8,9,10,11].
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